Juniper publishers have been established with the aim of spreading quality scientific information to the research community throughout the universe. We, as Open Access publishers, strive to offer the best in class online science publications. Open Access process eliminates the barriers associated with the older publication models, thus matching up with the rapidity of the twenty-first century. Our main areas of interest lie in the fields of science, engineering and other related areas.
Vesicular compartments are responsible for an organized separation within the cell and were crucial to the generation of life and the evolution. Vesicles produced by self-assembling of amphiphilic lipids arose as a promising technology for mimicking bio-available compartments, as well as its advantages related to chemical gradients, energy storage, stimuli responsiveness, and others. After the first description of liposomes in the mid-60s, they became present in many biotechnological applications. In 2005, the FDA approved the first liposome-based drug delivery carrier, Doxil® (doxorubicin HCl liposome injection, Janssen Products, LP). Over the years, the use of an inert polymer as an adjuvant in liposome constitution was vital, and polyethylene glycol (PEG) provided improvements in biodistribution with minimal side effects [1], both of which relevant characteristics for drug delivery [2,3]. Therefore, polymersomes, comprised of amphiphilic block copolymers (BCPs), emerged as a promising alternative to liposomes [4,5]. Both present analog lamellar membrane structure. Polymer vesicles display modifications in structural features of self-assembled vesicles, and therefore show enhanced stability compared with liposomes. Moreover, the high diversity and versatility of synthetic polymers enables the modulation of physicochemical properties related to membrane thickness, composition, permeability, stimuli- responsiveness, particle morphology and size, according to the desired application [6-12]. He high stability and robustness of these structures, however, could be addressed as a disadvantage towards becoming a functional drug delivery system. For this reason, stimuli-responsive polymersomes appear as an alternative to deliver the inside content upon demand, using, for instance pH, temperature, and osmotic differences, or ultrasound as an exogenous stimulus [13,14]. Moreover, biocompatible polymersomes were already tested in vivo as drug carriers and demonstrated its great potential for therapeutic applications [15,16]
Regarding drug delivery, the existence of an aqueous core - like liposomes - enables loading of hydrophilic drugs while hydrophobic drugs can be included within their amphiphilic membranes [6-11,17]. While the concomitant use of different active principles may seem an interesting strategy for disease treatment, the interaction between the external molecule and the block copolymer branches may interfere in the morphology of the particle, which is illustrated in Figure 1. Such interference may be one of the drawbacks regarding self-assembly vesicle formation with the drug acting similarly to a blend of substances producing a worm-like micelle morphology [15].
The self-assembling or self-organization process depends on the interfacial energy related to the hydrophilic/hydrophobic interface, that tends to compensate the loss of entropy due to the polymer linkage [12]. Unfortunately, polymersomes production is not trivial. Key experimental conditions such as the nature of the solvent, type and concentration of the polymer, water disponibility, temperature and external shear forces, in addition to macromolecular parameters appear to have great influence on the self-assembling process, affecting e.g., aggregate morphology and size [1]. Predictions of aggregate morphologies were proposed based mainly on macromolecular parameters such as hydrophilic and hydrophobic balance (hydrophilic weight fraction /, for PEG hydrophobic parts), in which the increase of / seems to favor spherical or worm-like micelles, while the decrease produces hollow structures, including vesicles [15]. Nevertheless, such a prediction cannot be considered as universal, and the effective outcome depends strongly on the polymer chain structure and characteristics [1]. Moreover, even though BCPs can also self-assemble into vesicles when hydrated, commonly used preparation methods for polymersomes rely on (i) film hydratation approaches--what is somewhat inefficient or very time consuming requiring up to one month if used solely--, or (ii) bulk methods, such as the solvent-switching and double emulsion approaches--which require the use of organic solvents, often not suitable for biomedical application [9,18].
Further, the size plays an important role, especially for intravenous injection, permeability, and retention (EPR effect). For that reason, techniques well established for liposomes that improve homogeneity and size (post-formation resizing) including extrusion through polycarbonate filters, freeze- thaw cycles and/or, sonication are applied for the same intent [2,19,20]. Since the use of membrane extrusion is timeconsuming, expensive, and risky (clogging of the system is a frequent phenomenon), it is limited to the laboratory scale. This may be achieved by the use of other techniques such as sonication or freezing, but still, rely on high energy input requirements.
Clearly, a major drawback of this technology is the preparation step, which is time-consuming and difficult for high- throughput setups. This may be the reason why there are still no commercially available products based on polymer vesicles.
A first report discussing the value of developing industry- scale polymersome production techniques was by published Poschenrieder et al. [21] who described a fundamental study regarding polymersome production via the ethanol method in a stirred-tank reactor [21,22]. Even though it was an important contribution to the field, such an approach may not be universally used as it still depends on the BCP's characteristics. Novel microfluidic methods for polymersome preparation techniques have emerged and since then, efforts have been concentrated mainly in device parallelization for industrial applications [23]. Devices such as a tandem emulsification device provide a promising alternative.
The fact that novel protocols for scaling-up are emerging indicates that the field is moving forward. One has to keep in mind that it took almost four decades until the approval of the first FDA-approved liposomal-based drug formulation and polymersomes exist only for two decades. In order to move closer to commercialization, significant developments are necessary in the process of self-assembly either for bulk production or for microfluidic production in industrial scale. Breakthroughs in this direction are expected.
This work was funded in part by CNPq (207254/2014-1), by the Institute for Technological Research, IPT, and the Institute for Technological Research Foundation, FIPT, for infrastructure and a fellowship for B.N.M.M. The National Institute for Science and Technology in Bioanalytics - INCTBio kindly acknowledges FAPESP (grant # 2014/50867-3) and CNPq (grant # 465389/2014-7) for their support.
To
Know More About Current Trends in Biomedical Engineering & Biosciences Please
Click on:
Discrepancy in Intercollegiate Fellowship of the Royal Colleges of Surgeons (FRCS) Trauma & Orthopaedics (T&O) exit exam passing rates between trainees & career grade orthopaedic surgeons has been well established and accepted for a long time. This has been thought a consequence of the lack of access to a structured teaching program, which renders the career-grade surgeons less likely to meet the exam standards. A problem-based teaching system has been implemented. Exam pass results for trainee and career-grade surgeons published on the Joint committee of Intercollegiate Examination (JCIE) website, before and after implementing the career-grade teaching programme are extracted, analysed and percentages calculated, to explore if there was any effect and to which degree.The analysis showed an impressive improvement in career-grade surgeons’ passing rate after establishing the teaching activities, with more than doubling of the pass rate.The findings of this audit strongly call for re-exploration of the current career-grade teaching opportunities, and the introduction of a regular teaching platform.
Intercollegiate Fellowship of the Royal Colleges of Surgeons, Trauma & Orthopaedics (FRCS Tr & Orth) is a prestigious qualification and is a prerequisite for all the trauma and orthopaedic surgeons working in the UK and looking for a more senior role.It has worldwide recognition and considered to be one of the toughest exams in medicine. Success in the exam leads to the award of FRCS Tr & Orth, which is one the requirements for the award of Certificate of Eligibility for Specialist Registration (CESR) [1]. It allows the candidate to demonstrate that they have attained the standard of competence required of a newly appointed Trauma & Orthopaedic Consultant in the United Kingdom’s National Health Service. The examinations are regulated by the Joint Committee on Intercollegiate Examinations (JCIE) on behalf of the four Royal Colleges of Surgeons Great Britain and Ireland. Those aspiring to do the exam wish to accomplish recognition and career progression. However, there is no doubt that this is a potentially stressful time for surgeons to achieve this career milestone alongside a busy job and personal life. This stress is further accentuated by the expensive exam fees of around £2000 and essential revision courses, which have a significant financial bearing on the candidates.
The FRCS exam is composed of oral and clinical components which require significant presentation skills and ability to perform focused clinical examination under time constraints. The surgeons who are not in a formal training programme face additional challenges due to lack of support, deficient career advice and lack of focused clinical training. Postgraduate medical education is currently carrying a health warning because of the stress and anxiety caused to doctors [2]. Therefore, any educational process that promotes engagement, interaction and a focused approach to learning is likely to improve the success rate.It is a much-needed step in the right direction [3].
Historically, there has been a significant gap between the pass rate of training and career grades in the UK [4]. It is hypothesised that lack of access to structured teaching programme and the absence of exam-oriented teaching contribute towards the relatively poor outcomes.Although the complexities of surgical care have increased dramatically over the last century, the methods of delivering training have changed little. Particularly for those outside of national training programmes.In a problembased curriculum, surgeons learn by actively solving problems, rather than by passively absorbing information. Surgeons must actively participate in their own education [3].We achieve this by a creating a peer to peer interface, through a multiplatform approach to complete the curriculum, using practice exam question to start the revision process on a topic, followed by both large group interactive session and small group viva sessions based on specific topics.
In this audit, our objective was to evaluate the pass rate of career-grade surgeons undertaking the FRCS exit examination who participated, in the peer-assisted and problem-based teaching designed by a group of career-grade grade surgeons who have been successful in completing the exit exam. The results are compared with the pass rate of trainees in a national training programme.To our knowledge there has not been any similar multiplatform, peer to peer, self-directed and problembased learning programme within the UK or the world for Surgeons.
For the initial audit, we extracted exam results for trainee and career-grade surgeons published on the JCIE website for February 2016 and May 2016 [4]. These two exam sittings were prior to the start of the educational system for career-grade surgeons.Data collected included the total number of careergrade and trainees who appeared in the exam, and the total number of career-grades and trainees who passed the exam. For the purposes of this Auditthe pass rate of trainees has been used as the standards for comparison as it has been maintained at a high level over many years.To overcome some of the above challenges, we introduced surgeon-focused mentoring platform as discussed earlier and re-evaluated the pass rate in Nov 2017, Feb 2018 and April 2018.
We then compared the results after the introduction of our problem-based teaching programme, designed specifically for surgeons who are not in the national training programme.
Our problem-based teaching system includes several constituents:
i. A communication platform using Telegram® app. This became the largest community of career-grade orthopaedic surgeons in the UK preparing for the FRCS exam, with around 400 members at various stages of exam preparation, from people preparing for part 1 to people who have already passed.
ii. This allowed prospective exam candidates to correspond directly with previous successful candidates who have been through the similar experience. The successful candidates were able to give valuable advice on how to prepare for the exam, practical tips, sharing of educational materials, the recommendation of courses to attend as well as coaching. Membership in this group is free of charge, and invitation based on recommendation by existing members.
iii. Comprehensive FRCS revision notes that have been written and developed by faculty who are members of the group, specifically aiming at exam candidates. These notes were provided electronically free of charge.
iv. Introduction to a series of weekly webinars and online conferencing sessions, delivered and facilitated by keen and competent mentors. Candidates were invited to attend and were given the opportunity to interact with the presenters. Appropriate sessions have been recorded and shared with the wider audience. Once again, this facility was also provided free of charge. The only motivation for mentors is to make a positive contribution to the educational development of their colleagues.
v. The average weekly attendance was ranging from 50- 60 participants from 12 different countries.
vi. The mentors are a group of post FRCS surgeons with good knowledge of the exam and who continue to show interest in FRCS relevant education.
viii. Following the introduction of the above teaching methods, we re-audited the FRCS exam results. We collected the same above data about trainees from the JCIE website and compared those to the results of the members of our group who took part in the above coaching scheme. The results were collected by asking each member who attempted the exam to declare if they passed or failed. We also compared results with other career-grades surgeons who were not members of the coaching group. Their results were obtained from the JCIE website.
ix. Number of participants enrolled in study were naturally dictated by the number of members in group that felt ready to proceed to the exam, it was felt the by demonstrating consistent improvement in the outcome of the members from our group we can demonstrate the efficacy of this programme.As this was an observational study, the comparison of cohorts was the preferred method.
x. Personal data on participants within the group and those outside was not collected.There was no monitoring of preparedness to take the exam within group as this was felt to be outside the parameters of self-directed own pace learning.Also due to the voluntary nature of both those providing direction and teaching freely, and those participating in all capacities, the use of targets would not be helpful in maintaining the enthusiasm and0 good will of those who have passed the exam to remain and become the new mentors
The first audit results are demonstrated in the table below (Table 1). These results show a significant difference in the pass rate between trainees and career grades.To overcome some of the above challenges, we introduced surgeon-focused mentoring platform as discussed earlier and re-evaluated the pass rate in Nov 2017, Feb 2018 and April 2018.From our group 7 out of 14 passed in Nov 2017, 11 out of 15 passed in Feb 2018 and 9 out of 19 in April 2018.
The re-audit results are summarised in the table below (Table 2). The results of the audit loop closure show significant improvement in the pass rates of non-trainee surgeons undertaking the FRCS (TR&Orth) exam after being supported by a mentoring programme, with an impressive increase from 29.3 % to 56.2 %.Chi square test on the pass rates among careergrades in and outside the group shows a statistically significant positive outcome for those is the group (p value 0.006). This shows a narrowing of the gap between trainees and careergrades. It also shows that career-grades who followed the mentoring scheme have much better chance of being successful than those who didn’t.Feedbacks collected from candidates after the interactive webinar sessions & the experience they shared following their success emphasised the fact that problem-based learning curriculum and access to the support provided, have facilitated their learning and their eventual success, even those who had not passed felt supported and felt their performance had improved.
This study provides the first review of exam performance of career-grades versus trainee orthopaedic surgeons. It focuses on current challenges and attempts to find some solutions. These findings lend support to the notion that provision of guidance, peer support and problem-based interactive sessions help career-grades surgeons to improve their likelihood of passing the exit exam and hence allow them more opportunities to advance their career should they wish to. One significant measure of the success of such a system is the extent to which participants obtain their Fellowship exam certificates.
We have assumed that language and communication skills and lack of mentoring as possible contributing factors to this discrepancy.Part of the focus of the group has been to correct this, with focus on precise use of language and the higher order thinking required for the exam. The data strongly suggests that if the career-grades are given structured mentoring and teaching but allowed to learn at their own pace and with the use of multiple platforms, the pass rate gap will be significantly narrowed.
The Standing Committee on Postgraduate Medical and Dental Education [5]described mentoring as: ‘The process whereby an experienced, highly regarded, empathic person (the mentor), guides another individual (the mentee) in the development and re-examination of their own ideas, learning, and personal and professional development. The mentor who often, but not necessarily, works in the same organisation or field as the mentee, achieves this by listening and talking in confidence to the mentee.
We have found use of the Mentors within the telegram group has provided support to many participants both in developing and guiding study but also in coping with tremendous pressure of the exam and preparation for exam,all mentors have successfully taken the exam and now we have an alumni of mentors who started with the group prior to sitting the exams, and volunteer their time in both structured and non-structured ways. Much of the dissatisfaction with conventional medical education has come about as a result of the pronounced trend of lectures. The lecture method has proven to be unsatisfactory as a principal mode of instruction. Lectures have the potential to vary widely in quality and they often attract low attendances. Thus, educators who use conventional curricula are forced to emphasise an inadequate method of instruction [3].
The non-consultant, career-grade doctors are a diverse and large part of the medical workforce and should be considered as a distinct group [6]. Although some doctors are content and fulfilled in working within their current grade. Significant numbers want to train and progress to a more senior responsibility and productivity within the profession. This would not only benefit the individuals concerned but would also help with the current medical workforce challenges. There is a good deal of support for these doctors although there is variation in this support among hospitals and deaneries across the UK.
Peer-assisted learning has many purported benefits including preparing surgeons as educators, improving communication skills and reducing faculty teaching burden and costs [7]. Another advantage of this comprehensive online mentoring approach is the low cost involved, such as saving on booking lecture rooms and providing catering, and the time saved by not having to travel long distances to attend teaching. Thus, it was possible to deliver this teaching to candidates who were geographically spread all over UK, and in fact the world[8]. This smart use of technology has ensured better attendance as location of the candidate is not a hindrance.
The limitations of this study are the small number of candidates following this mentoring problem-based teaching programme who have attempted the exam. However, we noticed increasing interest among the candidates to participate in this programme in view of improving results. We have since started introducing a one to one mentoring to those candidates who have only one last attempt left at the examination, and we will audit the outcome of this programme in due course.
To
Know More About Orthopedics and Rheumatology Open Access Journal Please Click
on:
Evaporation is major component of global water cycle and water balance of a small/large irrigation area, reservoir or lake, and a catchment. In this study, evaporation from Class-A pan (Ep) for the years from 2004 to 2013 at Tharandt, Germany is calculated and analyzed using daily and ten-minute Class-A pan water level data from automatic measuring pressure sensor instrument.
Daily Ep is first calculated at two different times; at 7 a.m. and at midnight. Because daily Ep calculated at 7 a.m. had shown less errors as it had fewer negative values (n = 43 out of a total of 2145 values) than Ep calculated at midnight (n = 84 out of a total of 1971 values); Ep calculated at 7a.m. is selected for the calculation of Ep. The correlation between Ep calculated at midnight and Ep calculated at 7a.m. was ‘very good’ (R2 = 0.87, MSE = 0.32mm d-1). Therefore, Ep calculated at midnight is used for filling as well as for correcting Ep calculated at 7 a.m. values. Accordingly, missing values of daily Ep at 7a.m. are filled using 0.908 × daily Ep at midnight values + 0.385 (Eq. 7). In Eq. 7, the cause for non-zero offset (0.385) could be instrument error. Assuming no instrument error, out of 1836 days, Epd which is the difference between 7a.m. and midnight Ep (see Figure 1) was larger than zero for 1184 days (64.5% of the days). This means out of 1836 days, for 64.5% of the days next day ‘night time’ Ep was greater than its previous day ‘night time’ Ep. Also, for at least 54 days |Epd| ≤ 1.5mm d-1 which means that the ‘night time’ daily Ep had to be ≥ 1.0mm d-1.
Figure 1: Understanding Epd which is daily Ep at 7 a.m. (‘blue’) minus daily Ep at midnight (‘red’) for day n.
Finally, 2098 daily values of Ep are calculated from March to November for the available data; however, only the summer half year (April to September, n=1702) values of Ep are mainly used for most of the analysis.
Generally, the accuracy of the self-recording ten-minute and daily water level measurements from Class-A pan at Tharandt from 2004 to 2013 can be considered as very good. However, the measurement should be carefully checked as it might have sensitivity to other than pressure or water depth difference in the pan. Hence, the sensitivity of the pressure sensor instrument at 7a.m. and at midnight for same pressure (depth of pan water) might have slight difference.
Keywords: Tharandt; Class-A pan Evaporation (Ep); Ep at 7 a.m. and at midnight, Epd
Abbrevations: Ep: Class-A Pan Evaporation (Ep); Epd: Ep at 7a.m. minus Ep at midnight; ET: Evapotranspiration; V: Water Level at 7 a.m.; P: Precipitation at 7a.m.; V’: Water Level at Midnight; RF: Precipitation at Midnight; NSE: Nash-Sutcliffe Efficiency; MAE: Mean Absolute Error; RMSE: Root Mean Square Error; RSR: RMSE-Observations Standard Deviation Ratio; MPE: Mean Percent of Error; ‘night time’: The Time between Midnight and 7 a.m.
Measured and estimated evaporation data has been in use by agricultural, hydrological, hydro meteorological, irrigation and soil and water conservation applications. Evaporation or evapotranspiration (ET) which is a major component of the global water cycle and the hydrologic budget or water balance of small or large irrigation area, reservoir or lake and a catchment is important consumer of energy. On average, across all continents about 70% of precipitation reaching the land surface evaporates; in dry regions (e.g., Australia) this ratio is higher and can reach up to 90% and in Europe to approximately 60% of the annual rainfall (Nova´k 2012 & Baumgarter and Reichel, 1975) [1,2].
Measured and estimated evaporation data has been in use by agricultural, hydrological, hydro meteorological, irrigation and soil and water conservation applications. Evaporation or evapotranspiration (ET) which is a major component of the global water cycle and the hydrologic budget or water balance of small or large irrigation area, reservoir or lake and a catchment is important consumer of energy. On average, across all continents about 70% of precipitation reaching the land surface evaporates; in dry regions (e.g., Australia) this ratio is higher and can reach up to 90% and in Europe to approximately 60% of the annual rainfall (Nova´k 2012 & Baumgarter and Reichel, 1975) [1,2].
The station is situated in-flat and grass covered area and fulfils the WMO standard for meteorological measurements. This station has special characteristics because it is situated at the bottom of a V-shaped valley and close to an asphalt road, buildings and the Weißeritz River (see Figure 2 & 3). Therefore, it has a reduced sky view factor and consequently sunshine may comparatively reaches the area late in the morning and leaves earlier in the evening resulting in lower sunshine hours. Due to high shelter effects at low level, it is expected that the wind speed at 2m (which was derived from the wind speeds at 3m and at 10m) would have been higher than real values (if actual measurement had been conducted at 2m height).
The pan used for measurement of pan evaporation is a standard Class-A pan evaporimeter (see Figure 3). The readings of the water level in the pan for every 10-minute interval (V’) as well as for daily basis (V) are recorded automatically by a pressure sensor device.
Using Eq. 4 and using daily water level (V) and the corresponding precipitation at 7 a.m. (P) daily pan evaporation from Class-A pan (Ep) is calculated at 7 a.m. Similarly, Ep at midnight is calculated using 10-minute water level (V’) and daily precipitation at midnight (RF).
The change in water level for a day say d (ΔV’d) at midnight is calculated by subtracting the water level at day d at 23:59:00 hour (V’d) from the water level at previous day (day d-1) at 23:59:00 hour (V’d-1); i.e., images/IJESNR.MS.ID.555778.I001.png Δ can also be calculated by taking the sum of 144 ten-minute water level differences for each day. Both will give same result if V’ has no missing values. Similarly, The change in water level for a day say d (ΔVd) at 7 a.m. is calculated by subtracting the next day (day d+1) water level at 7 a.m. (Vd+1) from the water level at day d at 7 a.m. (V’d); i.e., images/IJESNR.MS.ID.555778.I002.png . Note that those days with missing V or V’ data are excluded in the calculation of ΔV and ΔV’.
According to Dingman [3], pan evaporation is calculated using eq. 1 below:
Where,
E pan evaporation (in mm)
P precipitation (in mm) during Δt,
V1 & V2 the storages (in mm) at the beginning and end of Δt, respectively.
According to (WMO 1994 Sec. 9.2), the amount of evaporation that has occurred between two observations of water level in the pan (E) is calculated using Eq. 2 below:
Where,
P the depth of precipitation during the period between the two measurements,
P the depth of precipitation during the period between the two measurements,
Combining Eq. 1 and Eq. 2, we get:
Modifying Eq. 3 and replacing E with Epan or Ep, we have:
Where, Ep is daily evaporation computed as the difference in Class-A pan water level on successive days, corrected for any precipitation and Δd during the period. P, Δd, V1 and V2 are as defined above. For the calculation of daily Ep, Eq. 4 is used throughout this article with Δd = 0 (because of missing Δd values). However, 41 days have information for ‘special features’ (‘Besonderheiten_Daten’) like emptying or drawing out (pumping off) some water, cleaning (e.g. using Anti-Algae chemicals) and refilling of pan (including information about confirmation of no precipitation during the refilling time); removal (fishing out) of grass, seeds, coarse dirt or suspended matter (solids) from the pan; and so forth which are excluded from the calculation of E
Note that the maximum possible value of daily Epan in mm d-1 can be set to be equal to the upper estimate of daily PET in mm d-1 (PETmax) (see Eq. 6). PETmax is estimated to be the extreme maximum value of the ratio of daily net radiation (in MJ m-2 d-1) calculated using Eq. 19 and (daily) latent heat of vaporization (in MJ kg-1) calculated using Eq. 5. It is calculated with the assumption that all the available energy provided by radiation is consumed (used for vaporization).
Where,
λ latent heat of vaporization (in MJ kg-1)
T air temperature (in °C)
Where, Ep_max is the maximum possible upper limit of Ep (in mm d-1), PETmax is the maximum possible upper limit of PET (in mm d-1), λ latent heat of vaporization (in MJ kg-1) and Rn net radiation (in MJ m-2 d-1). For the calculation of Rn refer Appendix A.
Note, however, that the estimated net radiation used in this paper is based on measurements above grass level and that the Class-A pan will have a different radiation balance. Therefore, Eq. 6 can be a suited check for PET estimations according to Haude, Wendling, and Penman and ETo but only a rough check for Ep. Ep_max resulted 7.198 ( 7.2) mm d-1.
Monthly Ep is calculated by aggregation of daily Ep values for months from April to October of each year. Note however that few days at the beginning of April and at the end of October had considerable missing daily Ep values. Hence, the average values of daily Ep for the available ten years (from 2004 to 2013) is used for filling missing daily Ep values of each year (see Table 1).
Daily values of pan evaporation from Class-A pan (Ep) were calculated at 7 a.m. and at midnight using Eq. 4. The calculation was performed for n = 2145 and 1971 days {from daily P and RF data and their corresponding fully available daily (V) and tenminutes (V’) water level data, respectively}.
Generally daily Ep at 7 a.m. resulted in greater values than daily Ep at midnight. It also resulted in less (121) negative values whereas daily Ep at midnight resulted in more (213) negative values (see Table 2). Thus, comparatively Ep at 7 a.m. has the advantage of having a greater number of values with a smaller number of negative values which made it preferable to Ep at midnight. Therefore, Ep calculated at 7 a.m. is selected in this article. Its missing values are filled using Ep at midnight values following the description in section 3.2.
aEpd is used to denote daily Ep at 7 a.m. minus daily Ep at midnight
bout of the 1966 days for two days both Ep at 7 a.m. and Ep at midnight had equal values
cthe number in parenthesis is the number of days where both Ep at 7 a.m. and Ep at midnight had values;
dthe corresponding average value.
To evaluate the error among case A, case B, and case C of Table 2, the methods for comparison and evaluation of models which are discussed in Appendix B are applied by considering the daily Ep at midnight as observation values (i.e., x or Oi) and daily Ep at 7 a.m. as model (estimated) values (i.e., y or Pi).
For all the three cases, the p-value was 0.05 (not shown). It indicated that existence of statistically significant difference between daily Ep at 7 a.m. and daily Ep at midnight values at 5% significance level could not be concluded. In all cases, the MPE was around 7.1%; which means that Ep at 7 a.m. values were relatively larger by 7.1% as compared to Ep at midnight values (see Table 3).
For case A, three ‘goodness-of-fit’ measures (R2, NSE, and RSR) showed ‘very good’ relationship between daily Ep values at midnight and at 7 a.m. (see Table 3). However, the RMSE was comparatively the biggest. Moreover, in case A (see Table 2) daily Ep at 7 a.m. and at midnight resulted in 43 and 84 days with Ep ≤ -0.5mm d-1 and in 28 and 21 days with Ep ≥ 7.2mm d-1, respectively. Thus, comparatively, using case B or case C was better than using case A. Overall, it can be concluded that case B was the best because it had the advantage of using more values with better NSE and RSR as compared to case C.
Note that in this article the minimum possible Ep from Class-A pan for the climate condition of Germany is limited to ≥ -0.5mm d-1 in an assumption that there could be a maximum condensation of up to 0.5mm d-1. Similarly, the maximum possible Ep, as calculated using Eq. 6, is limited to ≤ 7.2mm d-1 [5-12].
Case B resulted in a regression equation (see Eq. 7and Figure 4) which is used for filling the missing values of daily Ep at 7 a.m. by using daily Ep at midnight values as given below:
In Eq. 7 a zero offset was expected; however, an offset of 0.385 had resulted. The cause for non-zero offset might be instrument error; the sensitivity of the pressure sensor instrument for same pressure (depth of pan water) at 7 a.m. and at midnight might have slight difference. Assuming no instrument error, for example for case B, out of 1836 days, Ep at 7 a.m. was larger than Ep at midnight for 1184 days (64.5% of the days). Note also that R2 = 0.87 in Eq. 7 indicates that daily Ep at 7 a.m. explains 87 % of the variability in the observed data (daily Ep at midnight values).
Therefore, out of 2145 daily values of Ep at 7 a.m. the values which are missing and were not in the range between -0.5 and 7.2mm d-1 are corrected using 1971 Ep at midnight values (Table 2). Accordingly, 24 values of Ep at 7 a.m. are filled or replaced using Eq. 7 while other 47 values are omitted and 2098 (2145 minus 47) values of Ep at 7 a.m. are used for next analyses.
As discussed in the above sections, daily Class-A pan evaporation (Ep) is calculated using daily Ep at 7 a.m. values for n = 2098 days from March/April to October/November. Accordingly, the daily Ep resulted in average, extreme maximum and extreme minimum values of approximately 2.16, 6.87 and -0.50mm d-1, respectively. Throughout the 2004 to 2013 period, it was above 6mm d-1 for only 8 days (see Figure 5).
The ten-year daily average Ep calculated from April to October (see Figure 6) was approximately between 3 and 4mm d-1 from mid of May to mid of August except for one day in July where it was around 4.28mm d-1. In the rest of the months it was between 3 and 1mm d-1 except from mid of September to October where it declined to between 1 & 0.14mm d-1.
As shown below in Figure 7, the monthly total Ep calculated from April to October had the highest value in July (103.2mm) followed by June (97.3mm), May (81.8mm) and August (77.4mm). The least value of Ep was in October (17.3mm) followed by September (42.4mm) and April (57.0mm). Figure 7 also shows that the peak value was in July for five years, in June for four years and in May for one year.
Epd (daily Ep at 7 a.m. minus daily Ep at midnight) means a next day (Day n+1) ‘night time’ Ep minus a previous day (Day n) ‘night time’ Ep (see Figure 1). Note that ‘night time’ is used in this thesis to represent the time from midnight to 7 a.m.
Like Table 3, Figure 8 & 9 graphically show that there was a general ‘good’ relationship between Ep at 7 a.m. and Ep at midnight; Epd was between ±1 mm d-1 for majority of the days. Daily Epd was > 1 and < -1mm d-1 for 107 and 14 days, respectively.
In Figure 10 the regression line shows only a slight increment in Epd. The increase was very small; from about 0.1mm to 0.4mm. That means an increase of around 0.3mm per 10 years. Moreover, R2 was too low. Thus, the trend (existence of a systematic increase or decrease) of Epd can be neglected.
If all other conditions are constant or if instrument and calculation errors are negligible, Epd shows the ‘night time’ difference of Ep (in mm d-1) between two consecutive days. Also, because:
1. there was no a systematic significant trend, shift or lag (Figure 9 and Figure 10);
2. daily Ep at 7 a.m. and at midnight have good correlation (R2 = 0.87); and
3. Epd > 1.5mm d-1 for 48 days and < -1.5mm d-1 for 6 days; it can be concluded that the ‘night time’ daily Ep had to be greater than 1.0mm d-1 for 54 days.
The accuracy of the self-recording ten-minute and daily water level measurements from Class-A pan at Tharandt from 2004 to 2013 could be considered as very good. However, the accuracy of the pressure sensor instrument which is used to automatically measure Class-A pan water level shall be carefully checked for the available daily and ten-minute measurements; it might have sensitivity to other than pressure or water depth difference in the pan. Hence, the sensitivity of the pressure sensor instrument at 7 a.m. and at midnight for same pressure (depth of pan water) might have slight difference.
Missing values of daily Ep at 7 a.m. can be filled using 0.908 × daily Ep at midnight values + 0.385 (Eq. 7). In Eq. 7, the cause for non-zero offset (0.385) could be instrument error. Assuming no instrument error, at Tharandt from 2004 to 2013, out of 1836 days, Epd was larger than zero for 1184 days (64.5% of the days). It is also concluded that the ‘night time’ daily Ep had to be ≥ 1.0mm d-1 for 54 days. The existence of ‘night time’ Ep might have made the comparison of Ep at 7 a.m. and Ep at midnight a bit complicated.
The sensitivity of the automatic Class-A pan water level measuring instrument to other than pressure (water depth difference in the pan) must be checked. If there was no measurement error and if ‘night time’ Ep is negligible, then the question: ‘Why Ep at 7 a.m. is greater than Ep at midnight for majority (65%) of the days?’ may require further study.
For every good thing, I praise GOD and GOD’S MOTHER above all. I particularly thank Virgin Mary or ‘Tsadkane Mariam’ (ፃድቃኔ ማርያም) monastery of Ethiopia for I get healings!
Very special thanks to my official supervisors Prof. Dr. Christian Bernhofer and Dr. Uta Moderow for their excellent supervision, for providing me all the needed data in advance, and for their friendly approach throughout my research. Very special thanks to Mr. Endalkachew Bekele for giving me valuable guidance and for editing the text for publishing. I also thank Mr. Thomas Pluntke, Mr. Philipp Körner and their colleague(s) for their support and for providing me meteorological data.
I also want to thank all my elementary and high school teachers especially my mathematics teachers Mrs. Abebech (‘Tiye Abebech’) and Mr. Abebe (‘Gash Abe’). I also want to use this chance to thank all kind persons who (have) supported me in my life.
Last but the best, I would like to thank my wife and my family and friends for their crucial support and for sharing love and happiness throughout my life.
To
Know More About International Journal of Environmental Sciences & Natural
Resources Please Click on:
