Friday, July 31, 2020

Optimization of the Optical Methods of Ore Grade Analysis at Mineral Processing - Juniper Publishers

Insights in Mining Science & Technology - Juniper Publishers


Introduction

In-stream ore grade analysis is a new trend in effective control of ore benefication processes. On-line estimation of ore grade can be implemented based on continuous measurement of the mineralogical composition directly in-stream or using in-stream sampling with the following analysis. Reliable separate determination of minerals in ore is possible using modern formats of colour image recognition. The spectral characteristics of minerals in visible light are the source of information for optical spectrum-based estimation of ore mineralogical composition (Figure 1). The task of determining the grade of ore, entering processing, is to determine its similarity to the main technological types of ores [1]. The calculation of ore grade was carried out using a multi-criteria method for affiliation shares calculations. The system mathematical model provides for calculation of the incoming ore affiliation by six (or more) significant parameters (minerals contents in the ore). At the Erdenet processing plant (Mongolia), a new facility for advanced ore diagnostics, based on optical analyzer of mineral composition, was tested. The optical spectrum-based analysis system was installed above the conveyor (Figure 2) for feeding ore to the grinding operation [2]. The ore scanning on the conveyor belt is carried out continuously. Then, using the algorithm, recognition of the ore grade is carried out. For exact analysis, the special flatbed facility was developed [3]. The measurement technique involves preparing the ore sample, forming the measurement area in the form of a flat portion of the sample, illumination and capture of the images in the visible spectrum (Figure 3).
Insights in Mining Science & Technology
Insights in Mining Science & Technology
Insights in Mining Science & Technology
To calculate the required parameters of grinding and flotation, special studies were carried out on the most pronounced samples of the typical ores, and the process diagrams for their grind ing and flotation were developed. The value of the pre-set function SF for each parameter of the process was calculated as a weighted average of the parameters values for each “typical” ore type (SFi) considering the contribution of the given type in the ore’s mixture using Equation (1):
Insights in Mining Science & Technology
where γi - relative weight fraction of an ore type in the ore mixture incoming to processing. The predefined functions were used as baseline in the local systems of automatic control of grinding and flotation processes at the Erdenet processing plant. Using the procedure for ore grade determination increases the automatic control stability, as it allows a fast response to changes in the incoming ore grade. Maintaining the optimum degree of grinding and reagent consumption in the flotation provides increasing recovery of copper and molybdenum into concentrates by 0.3% and 1.1%, respectively, as well as decreasing the consumption of reagents by 2–3% [4].

   

Thursday, July 30, 2020

Employee Motivation, An Organizational Performance Improvement Strategy (A Review on Influence of Employee Motivation on Organizational Performance) - Juniper Publishers

JOJ Sciences - Juniper Publishers  

Abstract

The major aim of most organizations worldwide is to be good performer in terms of goal achievement. They lay several strategies to boost their productivity and some of these strategies touch on the mode of employment or change of human resource to become result centered. According to Hussein & Simba [1], employee’s performance fundamentally depends on employee motivation, training and development, performance appraisals, employee satisfaction, compensation, job security, organizational structure among others. It is out of such arguments that the study was informed to examine how motivating employees influence performance of organizations. The study employed document analysis as a method for gathering relevant information required by the study.

Keywords: Motivation; Employee; Organization; Performance

Introduction

The term motivation has received varied scholarly definitions. According to Baron et al. [2] motivation was driven from Latin word ‘movere’ meaning move. The act of providing people with incentives to make them act in a desired manner is considered as motivation Certo [3]. In view of Nelson [4], motivation is the process of arousing and sustaining goal-directed behavior. According to Geomani [5], motivation is a decision-making process. It is inspiring a person to accomplish a behavior which is goal-oriented. Stanley [6] perceived motivation forces that are psychological and control direction of an individual’s effort level together with his/her tenacity in obstacles. Globally, desire to become successful and have constant progress is in the mind of every organization and business owners Manzoor [7]. According Manzoor [7], many organizations are facing challenges of employee retention regardless of their sizes, technology and market focus following the competitiveness in the current era. Nevertheless, these challenges can be overcome through adoption of a strong bonding between employees and their organizations Manzoor [7]. It is articulated that employees form the most critical part of any organization hence need to influence and persuade them towards tasks fulfillment is also crucial.

Discussion

According to Hussein & Simba [1], employee’s performance fundamentally depends on employee motivation, training and development, performance appraisals, employee satisfaction, compensation, job security, organizational structure among others. Osabiya [8] acknowledged different strategies that various organizations design to compete and achieve prosperity. He asserted that employee’s motivation determines any business facet’s success. Further, he noted that the capability of drawing, holding and advancing employees that are talented are the main characteristics of a business that is successful. He considered employees as an asset with the highest significance in an organization chiefly in industries which are low-tech labour rigorous. Geomani [5] established that for an organization to grow, it must consider motivation as a significant factor in achievement of its growth. Stanley acknowledged the change and competition among companies which seek a competitive edge in today’s market hence call for employee motivation for their retention in the organization for improved performance.

In view of Neeraj [9], the values and vision of an organization, employee engagement, acknowledgement of management and appreciation after work together with inclusive leadership legitimacy are the critical factors in motivating employees for better performance. According to Stanley [6], most organizations face several challenges of which employee turnover has been identified as a universal problem around the world face. He noted that de-motivation is amongst the factors that contribute to high employee turnover. This was also affirmed by Mosley et al. [10]. A growing consensus among managers and leaders on the significance of combining effective motivation incentives to improve organizational performance was established by Cole & Kelly (2011). For organizations to meet their objectives, they must have a workforce that is motivated and works towards achieving the said objectives (Steers & Porter, 2011). Levy (2013) contended that keeping employees motivated is the greatest challenge many organizations face despite acknowledging that motivating them improves the organizational performance. Nevertheless, the organizations put efforts to identify and implement programs that prove effective in improving employee productivity Deci [10]. George & Jones (2013) posited that increase in salaries alone is not enough, other motivational factors must be considered for improved organizational performance.

In 2014, Jobber & Lee contended that a poorly motivated labour-force is costly in that it makes an organization realize lower production and performance. They established that lack of motivation is characterized by high/excessive staff turnover, frequent absenteeism, increased expenses, and a negative effect on the morale of colleagues. Al-Madi et al. [11] argued that the success of an organization largely depends on quality of her human resource irrespective of the industry within which it operates. This was also established by Deci [10]. This leaves mangers and leaders with no alternative other than striving to motivate their workforce to improve the performance of their organizations Nabi et al. [12]. Kemoh [13] asserted that motivation falls among the significant factors in an organizational behavior and human resource management.

According to Al-Madi et al. [11] employees are the real assets of any organization. Mohsen et al. [14] asserted that employees form the company’s engine. They noted a rising need of the job being done properly by the staff and the organization getting the required output from employees. Geomani [5] posited that for this to be achieved, there must be adequate motivation of employees by the management. Omollo [15] contended that it is always rewarding to a business to keep employee committed, motivated and involved in their jobs in that motivated and committed employees are more productive. According to Waiyaki [16], organizations are in a constant pressure to retain their workforce in a global and highly competitive environments. Deci [12] postulated that experienced, reliable and highly skilled employees are an asset for any organization.

Many scholars have argued that employees who are motivated highly normally are characterized by high productivity. Nevertheless, Certo [10] contended that good performance does not only emanate from motivation but also other factors such as employee’s ability and skills, supplies, equipment, and time. Previous scholarly studies have noted that pressure that most organizations are constantly experiencing to retain their workforce in a highly competitive, global environment Waiyaki [16]. Deci [10] contended that the only valuable assets that any organization can be proud of is its highly skilled, reliable and experienced employees. Nabi et al. [12] acknowledged that employee’s productivity increase with its level of motivation even though this fact was refuted by Certo [10] who posited that a good performance is not because of motivation only, but also includes other factors such as ability, skills, equipment, supplies and time. One of the challenges facing most organizations is a high staff turnover irrespective of the salaries they offer Aguinis, [17]. This is a clear indication that salary is not the only motivator Waiyaki [16]. According to George & Jones (2013), the managers and supervisors should understand the need of individual employees and what motivates them instead of assuming a one-size-fits-all approach. Emeka et al. [18] compared an organization with its workforce and noted that an organization is only as strong as its workforce. Storey (2013) emphasized on the need to treat human resources with great care as they hold the productivity of any organization. Such kind of treatments are lucking in some organization even though the managers have recognized employees as invaluable assets in an organization.

Motivation of employees is perceived to have positive impact on the performance of organizations, yet many organizations have not realized this, or they have but lack the capacity to implement it Kemoh, [13]. Considering various kinds of motivation such as training, promotion, salary increment, sponsorship for further studies, improving working environment conditions, rewards and praises, many organizations have not adopted these strategies for improving organizational performance Osabiya [8]. Instead, the employees get their salaries or remunerations late, they sometimes face harassment and frustrations, they work in poor working environments and treated as slaves with their leaders, they are at times discriminated and denied promotions and denied even the sick leave, medical cover and houses allowances, in some cases they are not paid for overtime.

In some cases, the employees get dismissed from work simply because of lack of adequate skills which the organization can improve through offering trainings at some level Nguyen [18]. The leadership style in some organization has also been a major issue affection organizations performance Gachingiri [19]. In some cases, the employees get treated badly with no respect by some leaders. Motivation as a strategy to improve the performance of the organization, entails several things. Most organizations have failed just because of their lack of concerns on the welfare of employees. Motivations take various forms and not all about money or increase of salaries. This study recognizes the following as a way of employee motivation.

Training and workshops

Several employees have been dismissed from their duties just because of lack of basic knowledge on operating some simple machines. We live in a competitive world where organizations need to improve the capacities, competence and capabilities of the employees they have Tella et al. [20]. Employees training enables them to improve on their knowledge, skills, capabilities and competence. Some organizations have taken the initiative to engage their employees in various workshop and training to help boost their skills in performance. As considered the most asset of the organization, employees feel encouraged and empowered when trained and embrace the organizational goals with all their efforts. This in turn increases organizational productivity Waiyaki [16]. Some organizations have also adopted the use of bench marking where their employees are taken to other companies or organization to see by themselves and learn how various activities are undertaken. The new environment they are taken motivates them and makes the eager to learn from people who works with them in the same capacity but may be effective in their performance. The knowledge gained from this together with workshops can be transferred to the organization which sponsored them to help meet the organizational set objectives. Training empowers employees with new skills and competencies.

Good Leadership Style

The way employee is handled directly impact their commitment and performance in an organization. Some leader has adopted the character of being commanders and do not look like part of the team in an organization. They put a lot of pressure on employees and treat them with no respect despite their ages. Under such conditions, the organization should expect very little in terms of productivity Gachingiri [19]. This normally brings the difference in performance among organization set in the same region. Some may perform poorly but has skilled and able employees. Frustrations in the organization brought by poor leadership demoralizes employees and may lead to high staff turn-over. A good leader is always understanding. What should be acknowledged is that in every home an individual comes has its own stress. Employee might have their own at work places combined with others associated with family obligations. Such employees may come to work while stressed and may need a very caring and understanding leader. A leader who takes employee’s problem as his or hers and embraces an employee makes him motivated committed to his duties in the organization. This improves performance and organizational productivity Achua & Lussier (2013). The senior leadership, direct manager and employees are responsible for motivation Bhuvanaiah & Raya [21]. Kemoh [13] posited that engagement, trust, job satisfaction, achievement, values of individual and organization, acknowledgement and rewards fall among the motivational.

Improved Working Environment

Every employee needs a stress-free environment. This factor has not been considered by many organizations. In fact, some managers and leaders in the organization have slighted the issue of working environment Surjosuseno [22]. Many scholars have always advocated for a healthy and safe working conditions. Sedarmayanti [23] gave two distinct working environments which comprises physical and non-physical. He further contended that employees are motivated by a better working condition. According to him clean, secured, friendly and safe working environment motivate employee and this in turn improves the organizational performance.

Work environment is about creating conditions in which an employee can perform his/her duties comfortably Gitonga [24]. He further noted that effective application of ergonomics can help realize an equilibrium amid the task of employees’ and demands. Some employees have been exposed in a working environment which are dusty, noisy and hostile. They organizations at times do not provides protective gadgets or working gears that may protect the employees from dust and noise. Some of them work in a poorly ventilate facilities that degrade their health gradually. An employee might be discouraged while he or she thinks of such conditions and may feel like not going to work. In most cases absenteeism realized by many organizations may be associated with their poor working environment that the employees tend to fear Bushiri [25]. Hostility of the environment in this case may because of non-corporation among the employees themselves or the senior staff creating a wide gap between them and their juniors. A friend, clean, safe and healthy working environment encourages someone and shuns fear in him or her and makes him to be committed to the work. Through such commitment, an organization realizes its set objectives.

Employee Remuneration

Traditionally, work done goes with at least a token inform of wage or salary depending on the agreement between the work own and the person contracted. Many organizations look at this as the only employee motivational strategy Babagana & Dungus [26]. Advantage has been taken by some organizations that pay very low remunerations to their employee in the name of standing a chance to hire others who are jobless at a lower cost. Such mentally has not only demoralized the employees but also affected the same organization with staff turn-over. Some employees have done overtime, some are also paid in a flat rate regardless of their education qualification. Some organizations have also been characterized with delayed payment of their employees. Previous scholars have noted that appropriate and timely payment of employees motivate them and increases their commitment to work for the organization Ojeleye [27]. A good example that can be given in this case is parttime jobs that are done to the institutions like universities in Kenya where payment might delay for over three years. At this level, the employees whether temporarily contracted, does not give fully his services. An employee feels frustrated and may appear in class even once or twice in a whole semester. What is affected most is the quality of the organization’s products. In such go on in other organizations that deal with production of goods, the performance and productivity go down.

Proper Organizational Physical Facilities

Physical facilities play a very important role in an organizational productivity. Someone once put it that a bad workman quarrels with his tools. Sometimes you may find that what the employees uses in an organization does not give him easy time. Where he put to work may also be uncomfortable. An organization with poor structures, and equipment demoralizes employees as they are left with no alternative other than struggling to produce. Good physical facilities encourage and make the work easier for the employees. Poorly ventilated structures threaten employee’s health. Employee’s welfare includes all those facilities, services and benefits which are provided by employer to its staff for their comfort Sameer [28]. She further posited that employee’s welfare, safety and health are the measures that promote the efficiency of the staffs. She contended that different welfare programs provided by any organization to its workers have direct impact on the physical, health and mental efficiency alertness, morale and overall efficiency of the employees. She considered accommodations arrangements and canteen facilities as some of the welfare facilities which can be categorized to as comfort of living as well as working environment.

According to Sameer [28], the welfare facilities can be classified as Intra-mural welfare facilities which includes all the activities relating to industrial fatigue, providing safety measures to staffs like enough lighting conditions, first aid services, good layout of the plant and machinery among other. The other type of facility is the extra-mural welfare facilities which include the facilities which are provided outside the company’s boundary. They include recreations sports, better housing accommodations, educational facilities etc. The provision of these facilities is voluntary. The third type of facility is the statutory facilities which are all the welfare facilities which are passed by government of a country. It is worth noting that no company can ignore these facilities and mishandling of statutory facilities can be result toward punishable under the government Act concerned. The fourth is mutual facilities which are facilities which are usually outside the reach of statutory. These activities are voluntarily undertaken by the staffs themselves for their own interest. The other type of facilities is the voluntary facilities which are those facilities which are provided by employers voluntarily. Adapted from Sameer [28]. An organization with proper office equipment and good physical facilities motivate employees and this increase productivity and organization performance. The health facilities, educational and recreational facilities are vital for an organization. This study also noted that employees can be motivated by factors such as mentoring, counseling, coaching and assimilation.

Mentoring

An individual is not born with knowledge of everything. It has been noted that even after going to school we still need to be taken through various activities that improves our proficiency. We need people who are more skilled and experienced than us to help us learn more things required or expected of us. In a working environment, for instance organizations, new recruits might not be well vast with knowledge and/or skill to perform to the standards required by the organization. They need to be subjected to mentorship where they are guided and led by experienced and skilled employees. Through mentorship, employee gains skill, knowledge and competence from their mentors who know the organizational goals and standards Nyamori [29]. They get motivated to perform as their mentors. Unfortunately, some organizations have not recognized mentorship as a strategy of motivating employees and improving performance. Instead some even send away their new recruits simply because they are unable to perform basic tasks. In most cases skills and experience are gained in the field where someone interact practically with what is required of him to deliver. Those that have adopted this strategy have seen how fast their new employees adapt and perform to the standards set by the organization. Mentoring increases someone’s capability and competence to perform. Mentorship is considered tailor-made advice that is intended to improve the capability of inexperienced employee Tanoli [30].

Coaching
In view of Muriithi [31], this is a systematic and collaborative process aimed at finding solution or good result. Coaching is also done with an aim to enhance the experience of the employees. It is different from mentorship in that mentors normally engaged in the activities that they would like their mentees or juniors to learn while the coach always stands and give instructions on what to be followed. The managers and organizational leaders may become coaches through organizing seminars or workshops to build experience or capacity and competence of their employees. Having set targets in an organization, employees are oriented towards achieving this target. Some of the targets might be set higher and these might cause panic and stressful working environment to the employees. The coaches will help employee through coaching on how to reach the set targets whose capabilities of skill they have might not allow them. Coaching adds skills to perform various tasks that an employee is assigned Bwengi [32]. The employees get motivated when they can do or perform task that appear to worry or when they meet high targets set by the organizations. Coaching is considered a continuously monitored improvement process where an employee is always at the watch to perform as expected of him or her. The previous scholars noted that organizations which have adopted and embraced coaching to their employees have been able to retain their employees and have also improved their performance El Achi & Sleilati [33].

Counseling
In view of Padmasiri & Jayatilake [34] counseling of an employee is like provision of a health care intervention which is psychological. According to Matolo & Mukulu [35] poor performance of an employee may be associated with stress and demoralization. Employees who are demoralized and stressed have emotional responses and are characterized by low productivity. Challenges we meet at home in meeting family obligations may be stressful. Workplace environment may also be stressful. Working to meet the organizational set targets may also stressful. This therefore leaves the organizations with no alternative other than arranging for employee counselling. Employee counseling provides relief to the situations considered impossible to overcome. Stress is associate with dissatisfaction, lack of concentration and anxiety which in turn lowers employee’s productivity. Migwe et al. [36] noted that a stress-free employee is motivated and provides its best to the organization. They therefore advocate for organizations to adopt employee counseling as it helps relieve employees from tension and make them be focused to achieving organizational goals and set objectives. Employees should not be over tasked as they suffer exhaustion which demoralizes them.

Assimilation
Assimilation of employees has been considered a motivational factor in an organization. Some organizations do not embrace their employees with the orientation required. A recruit takes long before he or she becomes part of the team. Socializing with the staff he finds in the organization becomes a problem. The recruit become a lone range and feels isolated and alienated or stigmatized Kokemuller [37]. He operates independently without the love and concern of other employees. Assimilating new employees and making the part of the organizational team makes one feel part of that family fast and adapts to the organizational set standards. When a new employee is embraced and made feel part of the team, interaction and enquiring form others become easier Basu [6]. If this is not done, the person may feel inferior and may not ask what is required or expected of him. Operation in such fear hinder performance. It is therefore imperative for organization to embrace their new employee with love and brotherhood to enable them to adapt fast and meet organizational goals.

Conclusion

Considering document analysis that this study undertook, the researcher agrees that motivation of employee can significantly affect performance of an organization. It is true that a stressed, exhausted and demoralized hearts and/or mind are associated with poor performance while a motivated one remain focused to the organizational goals hence improved productivity and performance.


Wednesday, July 29, 2020

Importance of Psychiatric Evaluation and Patient Selection in the Field of Cosmetic Dermatology - Juniper Publishers

Dermatology & Cosmetics- Juniper Publishers

Introduction

Cosmetics is an ever-increasing component of every-day practice for dermatologists. However, as elective procedures such as neuromodulator injections, dermal fillers, and body contouring have pushed their way into most dermatology practices, little objective research has been done to identify ideal patients to undergo these procedures. It is the opinion of these authors that objective studies to evaluate the pre and post procedural psychologic well-being are essential to identify patients who may have an underlying and undisclosed psychiatric illness that is contributing to their decision-making process. This issue is further complicated by the plethora of cosmetic day-spas that offer these services without physician oversite or ethical obligation to responsibly select candidates. One example regarding the importance of patient selection is exemplified by patients with body-dysmorphic disorder (BDD) - a condition in which the subject has a fixation with one or more perceived flaws in their appearance.

Some studies have reported as high as 12% of patients seen in a dermatology clinic are afflicted with this disorder, and it is our opinion that part of the solution in managing patients such as this is through proper identification and preventing unnecessary procedures that may serve to reinforce their delusion [1]. Furthermore, the rapid growth of sensitive cosmetic procedures such as non-surgical penoplasy is a relatively new field in which previously developed procedures are being creatively applied in ways that are wholly unstudied with regards to the appropriate patient populations. We feel that in order to responsibly select patients, a simple screening tool used for pre and post procedure evaluation of their happiness and/or psychologic well-being would serve as a simple way for clinicians to help monitor their patient’s satisfaction while preventing procedures on patients who may never be satisfied. There are very few studies which use such tools, most of which only assess post-procedure scores. Of the limited studies available, some scoring systems that have been used include the Happiness Measures Scale, FACE-Q, and Derriford Appearance Scale (Litner). [2-4] Of course, without any reports of studies that evaluate the patient’s perception of their problem both before and after a cosmetic procedure, clinicians will not have a baseline in which to compare their patient’s results.

Conclusion

In summary, the field of cosmetic dermatology is growing rapidly and can be expected to continue this trend for years to come. It is the responsibility of the physician to understand what is driving their patient’s decisions and interpret if there is a psychiatric illness contributing. In order to do this, we feel there must be an objective means to measure dissatisfaction and satisfaction before and after any cosmetic procedure is pursued with emphasis on pre-procedure evaluation.

Monday, July 27, 2020

Application of Magnetized Water Irrigation for Agricultural Products - Juniper Publishers

 Horticulture & Arboriculture - Juniper Publishers

Opinion

Magnetic phenomena are common in nature. With the rapid development of magnetic biology, researches on magnetized water theory and applied technology have been carried out in many places in the world, and significant progress has been made in basic experimental materials and microscopic mechanism. There is no unified conclusion on the mechanism of magnetized water in the academic circle. However, many studies showed that the magnetic field intensity, magnetization time, raw water quality and water velocity and other factors have important influences on the physical and chemical properties of magnetized water.

Regular water can become magnetized when it passes through a magnetic field of a certain strength perpendicular to the magnetic line at a certain speed. After water is magnetized, the original structure of water is changed, which changes the physical and chemical characteristics of water molecules to some extent, such as the transformation of macromolecular clusters into individual water molecules or dimers, and the reduction of the expression tension coefficient of water molecules, thus promoting the growth and development of plants and the improvement of environment. The crystallization of minerals in the soil due the small molecules Increases permeability and solubility in cell metabolism which promotes the absorption and utilization of nutrients in soil by plants. Therefore, magnetized water irrigation provides a new way to increase crop yield and improve site environment, which not only increases the research and application in agricultural and forestry production, but also enriches the research content of biomagnetism.

Since the 1970s, magnetized water has been applied to agricultural production in countries in the world, and the research scope involves food crops, fruits and vegetables, edible fungi and poultry. The results showed that magnetized water had significant effects on soil improvement, seed germination, crop stress resistance and crop yield. Therefore, the organic combination of magnetized water treatment technology with the development and utilization of low-quality water resources and the improvement of soil quality is of great significance for the efficient utilization of magnetized water, agricultural production increment and quality improvement. Based on field experiment and laboratory test research magnetized water irrigation (such as saline water and brackish water, water containing cadmium) soil micro ecological environment, mineral nutrient transport, plant photosynthetic performance plant growth, yield and quality characteristics were studied by many researchers. The cationic dynamics of mesophyll cells, root tip meristem and elongation region were observed in real time by noninvasive micrometry. 

The characteristics of bacterial community structure in continuous cropping and cadmium-contaminated soil were analyzed by high-throughput sequencing. Soil microenvironment, yield composition and flavor nutrition of different fruits and vegetables under continuous cropping mode were determined and analyzed. The physiological and ecological responses of the difficult rooting trees were measured in real time by magnetizing devices with different magnetic field intensities. The effects of magnetized water irrigation on soil physical properties, enzyme activity, mineral nutrient content and plant biological characteristics of salinized soil and cadmium-polluted soil were also studied. Through these researches, researches try to clarify the mechanism of plant biology and physiological response to micro ecological environment after the irrigation of magnetized water. Though magnetized water irrigation has been used to improve agricultural production and many researches have done to study the mechanisms of bio-magnetism, much of it remains unknown and further researches should be done for us to learn more about bio-magnetism.

Friday, July 24, 2020

Etiological Diagnosis in Orthodontics and Interceptive Possibilities - Juniper Publishers

Orthopedic & Orthoplastic Surgery - Juniper Publishers

Abstract

The search of etiological factors is a fundamental step in the diagnosis. The success of orthodontic treatment is essentially based on the quality of the clinical observation; any cause related to malocclusion must be identified and analyzed. The acquired knowledge and clinical experience, then, will allow the best choice of the therapeutic method. The mechanisms of facial development and growth are numerous and strongly nested; thus, it is difficult to identify all the etiological factors involved in orthodontic malocclusions, but we can determine a large number among them and avoid their impact and so, many anomalies. The mistake would be to not suppress them or act late. Anomalies may appear, or become worse if they already exist, or relapse after orthodontic treatment.

Keywords: etiological factors diagnosis malocclusions orthodontic treatment

Introduction

It may be interesting to introduce by answering the question: Why the etiological diagnosis?
And the answer is that it is an essential element for orthodontic care since it allows to:
a) identify the causes involved in the appearance of malocclusions;
b) evaluate the muscular and functional environment and so the chances of stability after treatment [1].
c) analyze the evolution of the anomaly and to determine the prognosis;
d) consider etiological treatment which will consider the possibilities of prevention and interception according to age [2,3].
e) facilitate treatment with often, fewer orthodontic extractions;
f) decrease the duration of treatment and risk of relapse in the short and long term.

Etiological Factors and Orthodontic Anomalies

The orthodontic literature attaches great importance to etiopathogeny, and the various factors involved in the appearance of anomalies [4,5]. These have been the subject of multiple searches and classifications. This led to establishing general and local causes of orthodontic anomalies. Factors are considered intrinsic or extrinsic. It may be heredity, congenitalcauses, predisposing metabolic disease, nutritive deficiency, factors related to the muscular environment, the orofacial functions disorders (improper deglutition, speech defects, abnormal chewing), and the presence of harmful habits (thumb or lip sucking) [6,7] or dental causes (premature dental contact, early loss of primary teeth, trauma). It is important to note that most orthodontic anomalies [8] have multifactorial etiologies and that it is difficult to distinguish between the part that goes with predeterminism and that related to the environment. Moreover, it is recognized that neuromuscular behavior may be genetic in origin and that hereditary abnormalities may cause functional disturbances. The prognosis is naturally more reserved when a hereditary etiology is implicated. The practitioner must take this into account at the time of the therapeutic decision.

Interceptive Possibilities

While it is difficult to act on certain predetermined etiological factors, many can be improved. The goal is to prevent the onset or aggravation of abnormalities and recurrence after treatment. For this, we can use simple methods and appliances:
a. dental caries screening and endodontic care of temporary dentition to ensure the balanced development of the dentoalveolar arches;
b. maintaining the space in case of premature loss of the primary teeth to avoid the loss of space and dental crowding [9,10];
c. unlocking the occlusion to allow growth to express itself normally in case of deep bite, anterior or lateral crossbite;
d. treatment of breathings problems (buccal breathing) by the otolaryngologist and the orthodontist;
e. functional education of swallowing and chewing, suppression of harmful habits to avoid their impact in the onset of bone or dentoalveolar anomalies and prevent their recurrence after treatment [1];
f. suppression of possible obstacles (premature dental contact, hypertrophic labial frenum, short lingual frenum, supernumerary teeth, persistent temporary teeth).

Conclusion

The essential concern of the orthodontist is the success of the treatment; the etiological analysis is a crucial step in establishing the diagnosis. It is possible to avoid long and difficult care for both the patient and the practitioner by intervening early and effectively on the causes of certain orthodontic abnormalities knowing that the association; etiological treatment and treatment of the anomaly is possible. The results remain stable with a reduced risk of recurrence, the approach depends however on the patient’s cooperation and the isolated or nonisolated, primary or secondary nature of the etiology involved.


Thursday, July 23, 2020

A New Challenging Strategy in the Prevention and Management of Tumor Lysis Syndrome in Patients with Chemo-Sensitive Hematological Malignancies - Juniper Publishers

Blood Research & Transfusion - Juniper Publishers

Summary
Introduction Tumor lysis syndrome (TLS) is a metabolic derangement that results from rapid destruction of cells. It happens frequently in cancers receiving chemotherapy, particularly hematological malignancies. It can lead to death in severe cases. Tumor lysis syndrome that leads to acute renal failure requiring dialysis and/or ICU admission can be associated with a higher rate of complications and mortality.
Case Report: We present a 24-year-old male patient with Burkitt’s lymphoma. After receiving one cycle therapy, He developed severe kidney injury from TLS. We initiated renal replacement therapy soon after his admission to the ICU, with marked response to therapy. This led to early discharge from the ICU.
Conclusion: Early initiation of renal replacement therapy After TLS- AKI Can improve the severity of AKI and hasten recovery and prevent complications. This can lead to earlier discharge from the hospital and better outcomes.

Introduction
Tumor Lysis syndrome (TLS) is a serious complication of chemotherapy in rapidly progressive cancer. It presents clinically with nausea, vomiting, fatigue, acute kidney injury, seizure, arrhythmia, and even death. It is caused by the release of electrolytes from the damaged cells. Characteristic electrolyte disturbances include hyperuricemia, hyperkalemia, hyperphosphatemia, and hypocalcemia [1]. The National Comprehensive Cancer Network (NCCN) guidelines recommended prophylaxis and treatment with aggressive hydration and control of hyperuricemia with Allopurinol (xanthine oxidase inhibitor) 2-3 days prior to chemotherapy, or Rasburicase (urate oxidase) which is highly effective in prevention and treatment of TLS, it’s indicated for high-risk patient, patient with adequate hydration not possible to achieve, urgent therapy in high bulk patient, and acute kidney injury [2]. Acute Kidney Injury (AKI) may frequently complicate TLS. It is caused by precipitation of uric acid, calcium phosphate or hypoxanthine in the renal tubules [3]. It may lead to renal failure requiring renal replacement therapy (RRT) in its most severe forms.

Case Scenario
A 24 years old male with no significant past medical history presented to ED with gradually worsening abdominal pain for one month. His symptoms were associated with anorexia, black tarry stools, intermittent fever, sweating, vomiting, dizziness, and significant unintentional weight loss (40Ibs in 3 months). On admission, his vital signs were stable. He was anxious and clammy, and his physical exam was significant for splenomegaly. Initial blood work showed leukocytosis with a white cell count of 33.9 K/Ul, Hemoglobin was 15.3 g/dl, Platelet count was 67 K/Ul with Blast cells of 30%. The liver panel showed aspartate aminotransferase (AST) of 161 IU/l, alanine aminotransferase (ALT) of 65 IU/l, alkaline phosphatase (ALP) of 64.3 IU/l. Total bilirubin was 0.9 mg/dl. Lactate dehydrogenase (LDH) was 6000 U/l, and uric acid was 11.3 mg/dl. Urea was 14 mg/dl, and serum Creatinine was 1.24 mg/dl. Na was 139 mmol/l, K 3.9 mmol/l, and Ca was 9.6 mmol/l. An abdominal CT scan showed large ileocolic mass with enlarged lymphadenopathy at the right colic area (Figure 1). Peripheral smear showed immature cells with increase blast suggestive of acute leukemia. Biopsy of the colonic mass showed lymphoma. Flow cytometry confirmed the diagnosis of Burkitt’s lymphoma. CT head, neck, and thorax no other lymph nodes involvement (Figure 2).



Bone marrow biopsy with 400x H&E stain showed diffuse infiltrate and characterized by medium to large cells with irregular nuclear contour, prominent nucleoli, and cytoplasmic vacuoles Figure 2A. Brisk mitosis identified. B: Colon Biopsy with 400x H&E stain showed intermediate size lymphoid cells with scattered histiocytes imparting a “starry sky” pattern. The patient was diagnosed with stage IV Burkitt’s lymphoma with leukemic phase. Treatment was initiated with R Hyper- CVAD (hyper-fractionated Cyclophosphamide, Vincristine, Doxorubicin, and Dexamethasone), he received one cycle of part A, then switched other treatment regimen DA EPOCH-R (Doseadjusted Etoposide, Prednisone, Vincristine, Cyclophosphamide, Doxorubicin, and Rituximab), and prophylactic intrathecal chemotherapy (Methotrexate, Cytarabine and Hydrocortisone). On day 2 of admission, the patient developed TLS-AKI. His glomerular filtration rate (GFR) dropped to 22 ml/min/1.73 m2. and serum Creatinine increased to 4 mg/dl (Figure 3). Treatment was started with aggressive hydration, rasburicase, and allopurinol. on day 5 all of the previous measures failed, and his kidney functions were deteriorated, so renal replacement therapy (RRT) was initiated and continued for a total of 14 days. He responded well to therapy and was discharged from the hospital after 25 days of management with recommendations for outpatient follow up.

Discussion
The overall incidence of TLS was reported at 4.4%in two large multicenter studies of Non- Hodgkin lymphoma (NHL). Of these, TLS occurred in 8.4% of the patients diagnosed with Burkitt lymphoma/leukemia or B-cell acute lymphocytic leukemia (B-ALL) [4]. In a large retrospective study in the United States, the nation-wide estimate of patients admitted with TLS was 22,785. 12.8% of them developed acute kidney injury requiring dialysis (AKI-D) [5]. AKI-D patient has higher mortality (41.9% vs. 19.1%; P<0.01), and longer hospital stay than patient with AKI without dialysis requirement (19 vs. 14.9 days; P<0.01). [5] In a single-center study at Saint- Louis University Hospital in France that included 63 patients, the adjusted mortality at hospital discharge was higher in patients with TLS who developed AKI (odds ratio, 10.41; 95% confidence interval 2.01- 19.17; p=0.005). Interestingly RRT was performed in 17 patients without AKI, and in 31 patients with TLS induced AKI [6]. TLS induced AKI may decrease the probability of getting a long-term remission of the malignancy therefor prevention of development of AKI to play an essential role in the management of TLS, and consequently primary malignancy outcome [6,7]. In patients with hematological malignancies who require chemotherapy, anticipation and early recognition of TLS and intervention play a crucial role in the treatment and prevention of complications. Although RRT by self can’t prevent AKI from occurrence in a patient with TLS, we challenge early initiation of RRT could play a pivotal role in preventing complication associated with TLS, even in early stages of AKI. Further clinical trials are needed to evaluate early intervention using RRT to assess prognosis as well as mortality and morbidity in the patient with chemo-sensitive hematological malignancies who developed TLS.



Wednesday, July 22, 2020

About Climate Change - Juniper Publishers

Engineering Technology Open Access Journal -  Juniper Publishers 




Opinion

Humanity annually takes away more and more lands from nature: plowing it under crops, flooding it with hydroelectric power stations, concreting and asphalt cities and roads. The total area of such lands was 67% of the total land area of the planet by 2015. All water evaporated from such territories, at best, does not change its structure. As they came with precipitation, they returned back to the atmosphere. At worst, they are impregnated and combined with chemical elements, which then, it happens that, with a strong concentration, they fall acid rain. Evaporations from artificial areas are substantially complemented by evaporation from technological processes of industrial and municipal production. At their core, these fumes are alien to nature. Before the advent of man, such fumes did not exist. You can call them artificial fumes. Nature did not expect such a massive evaporation from washing and drying clothes, dishes, asphalt - everything that was created by man.

Historically, the interaction of the plant and animal worlds with water created atmospheric phenomena and a circuit in the nature of water itself and other substances. For millions of years, the volumes and frequency of precipitation, their places of precipitation have stabilized. The consequence of this was the formation of various zones: steppes, deserts, forests, tropics - the whole palette of geographical zones, including the comfortable climate in the inhabited man, areas. Of particular importance is the accumulation of water in the polar and mountain glaciers. It is possible that the reduction of glaciers at the poles of the Earth and in the mountains is not a result of warming, but changes in atmospheric phenomena. And the warming itself is a consequence of the decrease in the action of the “global refrigerator” - glaciers.

As industrialization develops, artificial evaporation increases in volumes and speeds. The quality of evaporation is a little-studied direction of science, but, in all likelihood, it also has some effect on the «heavenly kitchen.» Evaporations from drying asphalt and from the plant or from our breathing cannot be the same. The official hypothesis, based on carbon dioxide emissions, distracts the world community from the true cause of climate change and leads the world to a global catastrophe. If during the year 4 billion tons of carbon dioxide is released into the atmosphere, then the water of artificial evaporation alone is 2,200 billion tons. Since the beginning of the 20th century, according to UN experts, the increase in CO2 emissions has ranged from 0.5 to 5% per year. As a result, over the past hundred years, 400 billion tons of carbon dioxide has just entered the atmosphere due to the burning of fuel. ” Or 4 billion tons per year. According to http://jkg-portal.com.ua/ru/publication/one/globalna-posuha-abo-problemi-vodospozhivannja-32688. Up to 20 thousand km of cubic groundwater is extracted annually. Plus to this: http://www.kursach.com/geografiya-ekonomicheskaya-geografiya/816-referat-gidrosfera-v-sostave-biosferi/view-details.html. Plus, every year people irrevocably take approximately 2,000 cubic meters from rivers and lakes. km fresh water. Annually. All this water through sewers and evaporation goes into the atmosphere without organic changes.

They are joined by natural evaporation - in volume, perhaps even greater. Against the background of such fumes, the fight against carbon dioxide is a flea war.»Heavenly kitchen» has broken, due to changes in its components. Distribution mechanisms, schedules, dosing of precipitation by zones of the earth’s surface have disappeared. In some places, devastating floods, in others - drought and fires. These facts are known to us from reports and chronicles from the scene. Today floods in Spain, yesterday - hurricane Florence.

It is assumed that the mechanism of long-term accumulation of water in glaciers also broke down. The growth of glaciers stopped. Without reaching the poles and mountain zones of the water, snow falls not in historically given places, but in the rain in the oceans and foothill zones. The level of the oceans is growing, and the glaciers are decreasing. According to the chain of positive feedback, this growth increases in some progression. This is indicated by increasing natural disasters, their destructiveness and the prospects for flooding the continents. The future of the planet is quite alarming.

Is there salvation? Do we want to continue the human race and in general life on the planet? It is necessary to return all taken away to nature: land and water. It is urgent to prove the assumptions made here and develop a new concept of saving life on the planet. It should be based on total saving of water in production and everyday life by every enterprise, every state, every person. It is not easy to make rules about forgotten tap and the reduction of water consumption. It is necessary to radically reconsider all actions related to water. Water must make a qualitative transition from the functions of the working fluid body, the reagent to the food product - drinking and only to personal consumption - by living organisms. Everything else must be reduced. 




Tuesday, July 21, 2020

Myocardial Contraction Fraction Performance in Left Ventricular Hypertrophy - Juniper Publishers

Clinical & Medical Imaging - Juniper Publishers  

Abstract

Left ventricular hypertrophy (LVH) is a frequently diagnosed cardiac condition, which may result from physiological adaptation as well as from chronic pressure overload in various etiologies. Its differentiation has important prognostic implications for the patient. However, in clinical practice the identification of the underlying cause of disease is challenging. Myocardial contraction fraction (MCF) as an easily available parameter has the ability to offer additional diagnostic and prognostic information on LVH. The goal of this mini review is to provide a comprehensive overview of MCF performance in LVH assessed by cardiac magnetic resonance (CMR).

Keywords: Myocardial contraction fraction, Left ventricular hypertrophy, Cardiac magnetic resonance, Cardiac amyloidosis

Intrоductiоn

Left ventricular hypertrophy (LVH) is a common condition and associated with a poor cardiovascular prognosis [1,2]. Various etiologies cause LVH and their differentiation has prognostic implications for the patients. Physiological adaptation to chronic pressure overload in conditions such as aortic stenosis or arterial hypertension (AH) present the most common cause of LVH. In addition, genetically determined hypertrophic cardiomyopathy (HCM) as well as infiltrative myocardial disease, such as cardiac amyloidosis (CA), may also result in apparent LVH. In clinical practice, the non-invasive measurement of LVH assessed by two-dimensional (2D) M-mode echocardiography leads to the diagnosis of LVH. However, the echocardiographic differentiation of the underlying disease is not perennially feasible by echocardiography alone and patients are referred to cardiac magnetic resonance (CMR) for further diagnostic evaluation. CMR is the modality of choice for the quantitative assessment of ventricular mass and myocardial tissue characterization using Late gadolinium enhancement (LGE) images as well as T1 mapping with calculation of extracellular volume (ECV) [3]. Both techniques have been introduced for identification of myocardial fibrosis. Different pattern of fibrosis have been reported according to the underlying etiology [4-6]. However, the assessment of LGE as well as ECV requires the injection of contrast agents, which holds the risk of gadolinium-associated nephrogenic systemic fibrosis in patients with severe renal dysfunction. Especially, patients with CA suffer from renal failure and application of gadolinium-based contrast agents is often limited. Furthermore, tissue characterization may not represent enough information on functional abnormalities in LVH, especially subtle regional or global dysfunction for disease detection. Therefore, additional parameter for characterization of LVH are desirable. The goal of this mini review is to provide a comprehensive overview of myocardial contraction fraction (MCF) diagnostic and prognostic performance in LVH assessed by CMR.

Discussion

Introduction of myocardial contraction fraction (MCF)

MCF is an easily available quantitative marker, dictated from standard cine CMR images, without the need for contrast agents or specific post-processing software. MCF is a simple imaging parameter, reflecting the relationship between stroke volume (SV) and left ventricle (LV) mass. It is calculated by dividing LV SV (LV enddiastolic volume - LV endsystolic volume) by LV myocardial volume and multiplicated by 100. LV myocardial mass divided by the mean density of myocardium of 1.05g/ml presents LV myocardial volume (Figure 1).
MCF reference values are defined in a large cohort of an age- and gender-matched healthy population [7]. The normal MCF mean values are higher in women (155 ± 18.7 %) than in men (126.6 ± 21.2%). These data consistent with Framingham Heart Study data [8]. Furthermore, the study demonstrated an association of higher MCF values with cardiovascular events.

MCF measured by different modalities

The first description of MCF exists from King et. al. and introduces MCF as a novel marker for investigating myocardial performance in LVH [9]. The estimation of MCF, as a ratio of SV to myocardial volume, is performed by freehand contours and 3D echocardiographic LV reconstruction algorithms. Echocardiography measurements of LV mass by M-mode or 2D echocardiography based on geometric assumptions has been hampered by poor accuracy, especially when compared to CMR as the accepted gold [10]. Major advantage of CMR is accuracy and reproducibility by using 3D approach. Even 3D echocardiography shows only limited performance compared to CMR, suffering from substantial variability and underestimation [11]. CMR is considered the reference standard for LV mass measurements [12,13]. Therefore, MCF derived from CMR images may present a more accurate and reproducible parameter than from 3D echocardiography.

Diagnostic performance of MCF in LVH

In a recent published study, we could demonstrate that MCF has a good diagnostic accuracy to identify LVH and discriminate heart failure patients with CA from patients with other forms of LVH [7]. Therefore, we analyzed CMR images of a heterogenous study population consisted of patients with CA, HCM, hypertensive heart disease (HHD). The diagnostic accuracy of MCF was compared to that of left ventricular ejection fraction (LVEF) and mass index. The results demonstrated a significant reduction of MCF values in LVH. Thereby, MCF performed better than LVEF in discriminating LVH from controls. In addition, MCF outperformed standard functional marker, such as LVEF and LV mass index, in discrimination of LVH etiologies. A cut-off value for MCF < 50% was identified for patients with high probability for CA. Similar to our analysis, a study by King et al presented lower values of MCF in patients with LVH compared with normal subjects [9]. The echocardiographic MCF measurements was performed in a heterogeneous group with various pathologies and controls. The authors concluded that MCF may be useful in assessing differences in myocardial performance in other patients with LVH. In both studies the decrease in MCF indicated an abnormal LV function, although LVEF remained normal even in advanced stages because the progressive reduction in ventricular capacitance. Therefore, measurement of LVEF alone may not give a complete representation of the complex cardiac dysfunction especially in LVH.

Prognostic performance of MCF amyloidosis

After identification of MCF as a discriminator for CA, the prognostic value of MCF was studied in a separate population of systemic immunoglobulin light chain (AL) amyloidosis [14]. Seventy-four subjects with biopsy-proven AL amyloidosis and LGE pattern characteristic for CA were analyzed. The median follow-up was 41 months. The results showed a reduced transplant-free survival and higher rates of death in AL patients with lower MCF values. In addition, the determination of MCF could further risk stratify subjects with AL amyloidosis. Related results were achieved in an additional study by Tendler et al. [15]. The authors proved the prognostic value of MCF in CA in standard 2D echocardiography and concluded the superiority of MCF to LVEF in predicting overall survival among patients with AL amyloidosis. The same method for MCF calculation was utilized by Rubin et al. in 30 subjects with wild-type or mutant ATTR from the THAOS registry. The recent published data could also demonstrate superiority of MCF to LVEF in predicting mortality [16]. These few investigations existing are indicating that MCF is a relevant prognostic marker in CA.

Conclusion

MCF calculated by CMR has a good diagnostic accuracy compared with LV mass and it presents a great prognostic marker in patients with CA. MCF is easily determined from standard cine CMR images, without the need for specific sequences, contrast agents or post-processing software. MCF remains as a routinely available clinical marker with a strong potential. However, further studies of MCF performance are required before it becomes part of clinical routine in the evaluation of LVH.


Friday, July 17, 2020

A Polymethylvinylsiloxane/Low Density Polyethylene Blending Melt: Dynamic Rheological Behavior and Relaxation Time - Juniper Publishers

Academic Journal of Polymer Science - Juniper Publishers 


Abstract

The dynamic rheological behavior of a polymethylvinylsiloxane (PMVS)/ low density polyethylene (LDPE) blending melts at 150,180 and 210 ℃ is investigated by small amplitude oscillatory shear on a rotational rheometer. LDPE has higher viscosity than PMVS at three temperatures, which affects the morphology and rheological response of the blends. The LDPE-rich blends have smaller dispersed droplets and longer relaxation time than the PMVS-rich blends. Higher temperature means less viscosity as well as dynamic modulus difference between the LDPE-rich blend and the PMVS-rich blend. Increasing temperature fastens relaxation of polymer samples thus relaxation time at higher temperature is shorter than that at low temperature. Phase separation can be shown at some weight ratio of PMVS/LDPE through the failure of time-temperature superposition principle and double peaks of relaxation time including the form relaxation time peak due to relaxation of dispersed droplets.

Keywords: Rheology; Blend; Relaxation Time; polymethylvinylsiloxane; Rheological Analysis; Viscosity; Elasticity

Abbreviations: PMVS: Polymethylvinylsiloxane; LDPE: Low Density Polyethylene; PP: Polypropylene; PA6: Polyamide 6; EPDM: Ethylene-Propylene-Diene; PCL: Polycaprolactone

Introduction
In recent years rheology of polymer blends attracts lots of researchers, and blending is an easy and convenient method to obtain new and valuable polymer materials. Most blends are immiscible, and the physical properties are affected by many factors such as weight ratios, viscosity ratio, interfacial tension [1,2] and shear strength etc. Rheological analysis is a powerful tool to relate the rheological behavior and phase structure at different environments. In dynamic shear on polymer blend, a balance between the breakup and coalescence affects the morphology and rheological response. Coalescence mainly depends on two parameters, one is the number of droplet collisions, another is the ability of the blend to drain the film of matrix phase, which is entrapped between two droplets of the dispersed phase until the critical thickness for coalescence to happen is reached [3]. Increase of concentration and droplet size of dispersed phase produces higher number of droplets collisions. Two factors affect film drainage: interfacial tension and viscosity of the matrix. Droplets with high viscosity are easy to remain spherical during flow, while droplets with low viscosity are likely to deform. Decrease of droplet coalescence will lead to smaller particle size in compatibilized blends [4]. Droplets will break when interfacial stress cannot counterbalance the shear stress anymore.

Viscosity ratio of blend’s phases affects mainly the dynamic modulus at low frequency since geometrical relaxation of the droplets of dispersed phase brings about long-time relaxation. Elasticity affects phase behavior of immiscible polymer blends besides viscosity [5-7] and a corresponding model [8] has been developed to describe elastic contribution to the interfacial tension. Rheology and morphology of a polypropylene/polyamide 6 (PP/PA6) blends compatibilized with maleic anhydride grafted polypropylene (PP-g-MAH) was investigated by Shi et al. [9]. They found the morphology of the blend was of an emulsion-in-emulsion type, i.e., PA6 particles dispersed in the PP matrix themselves contained PP or PP-g-MAH inclusions. The emulsion-in-emulsion morphology became visible when PA6 content was high, for example, the ternary blend with PP/PP-g-MAH/PA6 was 35/35/30. In our recent work [10], a polypropylene(PP)/ high density polyethylene(HDPE) blend compatibilized with an Ethylene-Propylene-Diene Monomer block copolymer(EPDM) has similar morphology and rheology. This emulsion-in-emulsion structure is in How to cite this article: Hua Y L, Ya Qian L, Chun L L, Guo L T. A Polymethylvinylsiloxane/Low Density Polyethylene Blending Melt: Dynamic Rheological 0085 Behavior and Relaxation Time. Academ J Polym Sci. 2020; 3(5): 555621. DOI: 10.19080/AJOP.2020.03.555621 fact the so-called “core-shell”. A Core-shell morphology (core of HDPE and shell of EPDM) in PP matrix for a polypropylene (PP)/ ethylene-propylene-diene (EPDM) rubber/high density polyethylene (HDPE) 70/20/10 blend was successfully predicted by minimum free energy model [11]. Also, another core-shell morphology (core: HDPE, shell: EPDM-g-MA in PA6 matrix) was observed in PA6/EPDM-g-MA/HDPE ternary blends [12].

Polymethylvinylsiloxane (PMVS) [13,14] is a material with outstanding properties and has been widely used in industries, such as thermal shielding, press pads, and weather resistance, etc. The performance and radiation crosslinking of polycaprolactone (PCL) and polymethylvinylsiloxane (PMVS) blends has been investigated by Zhu and co-workers [15]. But researches on rheological behavior on polymer blends about silicon rubber are not enough. In this paper, dynamic rheological behavior and relaxation time of a PMVS/LDPE binary blend were investigated. It was found viscosity difference between the two components and temperature affect greatly the morphology and rheological response, relaxation time of the blends. The results are interesting and useful in processing of silicon rubber materials.

Experimental

Materials and Methods

PMVS 110-2, manufactured by Jilin Jihui Industry and Commerce Co., Ltd (Jilin, China). Its mass average and number-average molar masses are Mw=570,000 g/mol and Mn =370,000g/mol, respectively. LDPE 2102TN26 is produced by Qilu Petro. Co. Ltd( Shandong China). Its mass average and number-average molar masses are Mw = 190,000 g/mol and Mn = 23,000 g/mol, respectively.

Preparation of Blends

The materials were dried at 80 ℃ for 12h in an electric blast drying oven, then were mixed in an internal mixer with the weight ratio PMVS/LDPE of 10/90, 30/70, 50/50, 70/30 and 90/10 at 150 ℃ for 30minutes. The rotating speed of the internal mixer was 30r/min. After that the samples were scraped off the internal mixer, then were cooled down at room temperature. The sample disks with diameter 25 mm and thickness 2mm for rheological measurement were prepared by molding with a laboratory press at 150 ℃ and under 10MPa for 10 min, and then cooled in the atmosphere.

Measurement

Microscopic images: Melt the blending sample at 210 ℃ between cover glasses on an electric stove and made into a piece of film, then cooled the sample film to room temperature at nitrogen atmosphere. Put the prepared film onto the objective table of a polarization microscope and observed the microscopic photos at unpolarized mode at proper magnification and save the photos on a computer. The average dispersed phase size is calculated by a software Nano Measurer 1.2.0. Rheological measurement: small amplitude oscillatory shear was applied by using a rotational rheometer MCR301 made by Anton Paar GmbH of Germany with two parallel plates. The diameter of the plate is 25mm, the gap of the two plates was 1mm. The temperature in the experiment was 150 ℃, 180 ℃ and 210 ℃, and the angular frequency was from 0.028 rad·s-1 to 300 rad·s-1 in ascending order. The measurement was under nitrogen gas to avoid the oxidization of the samples. Before the start of the measurement the samples were kept for 5min between the gap of the two plates to eliminate thermal history. The linear viscoelastic regime was determined by applying strain sweeping.

Results and Discussion
Material Science
Figure 1 shows microscopic images of the PMVS/LDPE blends with weight ratio 10/90, 30/70, 70/30 and 90/10, respectively. The average diameter of the dispersed droplets is 14.0μm,19.54μm,7.16μm and 3.43μm, respectively. For the LDPErich blends, such as 10/90 and 30/70, the matrix is LDPE and the dispersed phase is PMVS. For the PMVS-rich blends, such as 70/30 and 90/10 blends, LDPE is the dispersed phase and PMVS is the matrix. The viscosity of LDPE is much higher than that of PMVS, as shown in Figure 2-4. Thus, it is much easier for PMVS to breakup in LDPE matrix, and more difficult for LDPE to breakup in PMVS matrix. In another word, the more viscous discrete LDPE droplets in the 70/30 PMVS/LDPE sample are more easily to be coarsened. The balance between the breakup and coalescence affects the morphology and rheological response [16].

Figure 2-4 show the dynamic rheological behavior of the PMVS/LDPE blending melts including the pure components PMVS and LDPE at 150,180 and 210 ℃. At three temperatures LDPE has higher viscosity than PMVS, and the viscosity of the blend decreases as the weight ratio of the PMVS/LDPE increases except the 50/50 blend. All the blends exhibit shear thinning behaviors in the range of applied angular frequencies. As the temperatures increases from 150 to 210 ℃, the viscosity of the blends drops, and the viscosity of the LDPE-rich blend drops much faster than the PMVS-rich blend, as shown in Figure 2-4. For example, the 10/90(PMVS/LDPE) blend has a viscosity of 21,000Pas,9040 Pas and 5190 Pas at 0.028rad/s, while the 90/10(PMVS/LDPE) blend has a viscosity of 6690Pas, 5010 Pas and 4780 Pas, respectively. This is understandable, since LDPE is a branched polymer, and PMVS is a liner polymer, the former is more sensitive to temperature than the latter. Higher temperature means less viscosity difference between the LDPE-rich blend and the PMVS-rich blend. The dynamic modulus of the blend has similar behavior with the viscosity. Due to the shape relaxation of discrete phase in the matrix, the dynamic modulus of the blends present much more difference at lower frequency, and the difference disappears gradually at high frequency [17].

Material Science
Material Science
Material Science
It is noticed the dynamic modulus of the 50/50 and 70/30 blend at low frequency is higher than that of pure PMVS and LDPE at 180 ℃ and 210 ℃. This means these two blends are immiscible [18,19]. The storage modulus of the two blends increases because the interfacial area of the blends is changed by the relaxation and deformation of dispersed phase droplets during dynamic rheological measurement. Comparing the storage modulus curve and loss modulus curve at three temperatures as shown in Figure 2-4, it can be seen the loss modulus is higher than the storage modulus at low frequency. The storage modulus is more sensitive to interfacial tension than loss modulus at low frequency. It is worth mentioning that the PMVS used in the blends is uncured sample and can flow easily at high temperatures. Vulcanization can increase the strength of the PMVS sample as well as the blends, which is not the interest of this work [15,20].

Material Science
The Cole–Cole diagram G’’ versus G’ data at three temperatures for the 30/70,50/50 and 70/30 PMVS/LDPE blends were shown in Figure 5 respectively. It is obvious the G’’-G’ data at three temperatures overlapped well for the 30/70 blend. But for the 50/50 blend the data at low modulus somewhat dispersed. The dispersion phenomenon was more evident for the 70/30 blend. The invalidity of time-temperature superposition principle means phase separation of the blends [21]. As temperature increases, G’ value increases with a fixed G’’ (see the arrow in Figure 5c), which has a similar trend to the work of Wu and co-workers [17]. The estimated interfacial tension of PMVS/LDPE blend at 150,180 and 210 ℃ is 6.07,6.53 and 7.06mN/m respectively [22,23]. Thus, the two polymers are immiscible. It is more difficult for more viscous LDPE droplets to disperse in less viscous PMVS matrix. The 10/90 blend and 90/10 blend have similar trends with the 30/70, and the 70/30 blend respectively, which are not shown in Figure 5.

Relaxation Time

Table 1 lists the characteristic frequency and relaxation time of the blends when storage modulus(G’) equals to loss modulus (G’’). The characteristic relaxation time is the reciprocal of the characteristic frequency. Firstly, comparing the relaxation time of pure component, it is clear that relaxation time of LDPE is longer than PMVS at the same temperature. It can be acceptable since LDPE has much higher viscosity than PMVS, as seen in Figure 2-4a. As the content of PMVS increases, relaxation time of the PMVS/LDPE blends drops gradually at a fixed temperature. In another word, the LDPE-rich blend has longer relaxation time than PMVS-rich blend. As temperature increases, relaxation time of the sample decreases because polymer chains relax faster at higher temperature. The relaxation time listed in Table 1 is only some characteristic relaxation time. In fact, polymer has a relaxation time spectrum rather than one relaxation time. The weighted relaxation time spectrum of the blending melts can be obtained by using the approximation formula of dynamic modulus [24].

Material Science
Figure 6 shows the weighted relaxation time spectrum of the PMVS/LDPE blends. The shape of the spectrum curves at three temperatures are similar but with different intensities. Higher temperature corresponds to lower intensity. In order to analyze the relaxation time spectrum of the blends at different temperatures, (Table 2) lists the peak relaxation time. Basically, the LDPErich blend has longer relaxation time than PMVS-rich blend. This agrees with that shown in Table 1. The 50/50 and 70/30 blends show two peaks of relaxation time at 180 and 210 ℃. The relaxation time of the pure PMVS is about 0.13-0.18s. The relaxation time of pure LDPE is about 2.56-18.68s at different temperatures, as shown in Table 2. Some relaxation time listed in Table 2 is more than 18.68s, it is neither that of PMVS nor of LDPE. This relaxation time is the secondary peak, which corresponds to the longest form relaxation time of dispersed phase droplets due to interfacial tension. Appearance of two relaxation time peaks also means phase separation of the blends, which is accordance with the failure of time-temperature superposition principle shown in Figure 5.

Material Science
Not all the blends show the longest form of relaxation time. In the work of Shi and co-workers [25] with various PP/PA6 uncompatibilized blends and PP/PP-g-MAH/PA6 compatibilized blends, both PP and PA6 show individual relaxation time peak, and some blends show a third peak at the longest time corresponded to the form relaxation time. In the present work, PMVS/LDPE blends did not show obviously individual peak relaxation time like that [26], possibly because the two peak relaxation time merged together, even the three peaks of relaxation time including the form relaxation time merged. Relaxation time can also see from the peak of dynamic viscosity (η’’ vs ω) curve [27]. It was reported [28] interfacial force between PP and PS was affected by addition of the silica filler. Similar investigation about silica filler upon polymer blends can be found in the literature [29-30].

Material Science

Conclusion

Dynamic rheological behavior of the PMVS/LDPE blends at 150,180 and 210 ℃ is investigated through small amplitude oscillatory shear. The more viscous LDPE is more difficult to breakup in PMVS matrix, thus the LDPE-rich blends have smaller dispersed droplets than the PMVS-rich blends. Higher temperature decreases the viscosity difference between the LDPE-rich blend and the PMVS-rich blend. The 50/50 and 70/30 PMVS/LDPE blends exhibit invalidity of time-temperature superposition principle. Furthermore, the LDPE-rich blends have higher viscoelasticity and longer relaxation time than the PMVS-rich blends. The blends at higher temperature have shorter relaxation time and lower relaxation time spectrum. Some relaxation time spectrum of the PMVS/ LDPE blends show only one peak, the spectrums of the 50/50 and 70/30 PMVS/LDPE blends show a main peak and a longest form relaxation time. These cases infer the PMVS/LDPE blends are immiscible.

Comparative Reflections on the Acquisition of Language in Hearing and Deaf Children: A Case of Natural Learning of Mexican Sign Language - Juniper Publishers

Intellectual & Developmental Disabilities - Juniper Publishers Abstract Sign languages are visual and iconic languages used by Deaf c...