On the characterization of solar cells using advanced imaging techniques

Photovoltaic (PV) cells are devices capable of producing electricity - in particular, from the abundant resource of sunlight. Solar energy (from PV cells) provides a sustainable alternative to fossil fuel energy sources such as coal and oil. PV cells are typically strung in series in PV modules to generate the current and voltage required for commercial use. However, PV cell performance can be limited by defects and degradation. Under operational conditions due to mismatch and shading, individual cells within a PV module can be forced to operate in their reverse bias regime. Depending on the severity of the reverse bias and the defects present in the cell, the longevity of the cell and/or the module can be affected. Reverse bias (assuming bypass diodes are absent) can result in localised heating that can affect the encapsulant polymer’s longevity as well as degrade the cell’s performance over time. However, under more severe reverse bias, the cell could fail, drastically affecting the performance of the module. PV cells can be characterised using various opto-electronic non-destructive techniques, this provides a set of powerful tools which allow the application of multiple such techniques to the same sample. Furthermore, this allows for an in-depth study of the device. Dark Current-Voltage (I-V) measurements, Electroluminescence (EL), Infrared (IR) thermography, Light Beam Induced Current (LBIC) measurements, and the associated techniques are all examples of such tools and are used within this study. An experimental setup was developed to perform dark I-V measurements, EL imaging, IR thermography and LBIC measurements. Part of the development of the experimental setup was the design of an enclosure in which to perform all the measurements. The enclosure minimised internal reflection, and isolated the experiment from electromagnetic radiation. Due to the complex mathematical model applied to the I-V curve, an Evolutionary Algorithm was used to determine optimal parameter values for the equation. More specifically, a Genetic Algorithm was used in the Parameter Optimisation (or Extraction) of the dark I-V parameters based upon the two-diode model for PV cells. The resulting parameters give an indication of the material and device quality. However, to determine the spatial distribution of the defects that effect the I-V response of the device, various imaging techniques were utilised. LBIC is a technique that uses a focussed light beam to raster scan across the surface of a PV cell. The local photo-induced current/voltage can then be measured and compiled into a response map. LBIC was used to determine the local current response across the device. The intensity distribution of EL signal is related to the local junction voltage and the local quantum efficiency. EL intensity imaging with a Si CCD camera was used to determine the spatial distribution of features visible both in the forward bias and in the reverse bias. The experimental setup utilised had a micron scale resolution. A voltage dependent approach was utilised to further characterise features observed. In forward bias, the local junction varies across the device due to parasitic resistances such as series and shunt resistance. At higher forward bias conditions (in the vicinity of and higher than maximum power voltage), series resistance becomes a limiting factor. Therefore, utilising a voltage dependent approach allows for the determination of a series resistance map from voltage dependent EL images. In reverse bias, localised radiative processes can be imaged. These radiative processes are related to defects in the device, such as Al stains, FeSi2 needles and avalanche breakdown. The processes are related to highly localised current flow; this causes localised heating which degrades the device. The voltage dependent Reverse Bias EL (ReBEL) imaging was also used to determine the local breakdown voltage of radiative reverse features. Dark IR thermography is a technique used in the identification of high current sites that leads to localised Joule heating, particularly in reverse bias. In this study, thermography was used to identify breakdown sites and shunts. The results of this study allow for an in-depth analysis of defects found in multi-crystalline Si PV cells using the opto-electronic techniques mentioned above. The multi-pronged approach allowed from a comparison of the various opto-electronic techniques, as well as a more in-depth characterisation of the defects than if only one technique was used

Expression of the progesterone receptor, bcl-2 and bax in clomiphene citrate treated rat uteri

Clomiphene citrate (CC) is a synthetic oestrogen receptor modulator that may act to promote or inhibit oestrogenic responses depending on the type of tissue or organism. CC acts as a superovulator and has been widely prescribed in the treatment of female infertility. However, pregnancy rates after CC treatment are low, possibly due to the CC causing morphological and other unidentified changes to the uterus. This study investigated the changes caused by CC on the progesterone receptor (PR), the anti-apoptotic protein, Bcl-2, and the pro-apoptotic protein, Bax. PR with its ligand, progesterone, is important for the maintenance of a pregnancy. Bcl-2 is a cell survival molecule and acts in opposition to Bax, which promotes apoptosis, which is important in allowing an attaching blastocyst to infiltrate the maternal endometrium. A high physiological dose of CC (1.25 mg) was administered to ovariectomised rats, either as a single treatment, or prior to a hormonal treatment regime characteristic of pre-implantation animals. The single CC treated animals were compared with single 5 mg progesterone (P4) treated animals and vehicle controls. The animals treated with CC in conjunction with the ovarian hormone milieu (CCPPPE treatment) were compared to PPPE treated animals or to the vehicle controls. The effects of CC, P4, PPPE and SPPPE on the morphology of the uteri were investigated by light microscopy. Expression of the PR, Bcl-2 and Bax were investigated using immunohistochemistry and enzyme linked immunosorbent (ELISA) techniques. The present study showed that CC treatment affects the microanatomy of the uterine compartments, particularly the shape of the lumen and the luminal epithelial height. The expressions of PR, Bcl-2 and Bax in the entire uterus were not significantly affected by the various treatments applied to the ovariectomised rats, as measured using ELISA. However, expression of the proteins in the various uterine compartments was altered by CC treatment. The single CC and CCPPPE treatments had an oestrogenic effect with regards to PR expression in the uteri as seen in the immunolocalisation, whereas the single P4 treatment decreased the PR expression, as expected. CC treatment caused patchiness in both Bcl-2 and Bax expression surrounding the endometrial lumen. Moreover, treatment with CC maintained expression of Bcl-2 in the luminal epithelium, whereas the expression of Bax shifted away from the luminal epithelium. This suggests that CC treatment promotes cell survival of the luminal epithelium, which may diminish the ability of the blastocyst to infiltrate the maternal tissue. CC action is both dose sensitive and has a cumulative effect with multiple treatments. Future studies would aim to separate the various uterine compartments in order to quantitatively assess the actions of CC on expression in the PR, Bcl-2 and Bax. In addition, it would be interesting to investigate how the accumulation of subsequent CC doses affects the expression of apoptotic markers, as this would be a more realistic model for human infertility treatment

The hole in holism : a critical appraisal of the "holistic development of learners" with specific reference to the emotions

The National Curriculum Statement argues that it takes all of the different components of the individual into account when attempting to educate each learner. It states that one of the goals of the National Curriculum Statement is to promote the “holistic development of learners”, and within this area to take each learner’s emotions into account. This is a bold statement that has many practical implications for the learner, the educator, and the lecturers in teacher training programmes. There appears to be very little guidance provided in the National Curriculum Statement or teacher training programmes with regards to how one should take the “holistic development of learners”, and specifically the emotions into account. For this reason, this research focuses on whether it is possible to prepare teachers to take the “whole child” into account, with particular reference to the emotional dimension of the learner. The research also focuses on whether educators in schools feel adequately prepared to look at the emotions, and what different factors come into play when attempting to look at the both the emotions and the “holistic development of learners”. In order to do this, the current research focuses on Life Orientation, since it appears to be the subject that is most able to deal with the cognitive, spiritual, physical social and emotional needs of the learners. With the purpose of achieving the abovementioned objectives, the researcher conducted a qualitative research study which involved the interviews of six Life Orientation Educators from six different public schools in the Northern Suburbs of Johannesburg; as well as three lecturers who lecture Life Orientation at the University of the Witwatersrand. The findings of this research report indicate that most of the educators and lecturers who participated in the research feel inadequately prepared to take the emotions, and the holistic development of learners, into account in the teaching /learning process. There are a number of reasons for this. First, many participants felt that both the emotions and holism are implied within the curriculum. However, the participants felt that there is not an explicit explanation for what these elements of the individual are. As a result of the lack of a coherent explanation of the different elements of the individual, the participants felt that it is difficult to teach the non-cognitive aspects of the individual. Second, because the emotions and holism are implicit rather than explicit, it was felt that there are no clear indications provided by the National Curriculum Statement, or in the Life Orientation courses or workshops on how it is possible to teach or assess the whole child, and the emotions specifically

Exposure of a 23F serotype strain of <i>Streptococcus pneumoniae</i> to cigarette smoke condensate is associated with selective upregulation of genes encoding the two-component regulatory system 11 (TCS11)

Alterations in whole genome expression profiles following exposure of the pneumococcus (strain 172, serotype 23F) to cigarette smoke condensate (160 μg/mL) for 15 and 60 min have been determined using the TIGR4 DNA microarray chip. Exposure to CSC resulted in the significant (P &#60; 0.014–0.0006) upregulation of the genes encoding the two-component regulatory system 11 (TCS11), consisting of the sensor kinase, hk11, and its cognate response regulator, rr11, in the setting of increased biofilm formation. These effects of cigarette smoke on the pneumococcus may contribute to colonization of the airways by this microbial pathogen

Surgical complications of bacille Calmette-Guérin (BCG) infection in HIV-infected children: Time for a change in policy?

AIM: Bacille Calmette-Guérin (BCG) immunisation is well established as part of the South African national expanded programme for immunisation (EPI). The World Health Organization (WHO) currently recommends that BCG be given to all asymptomatic infants irrespective of HIV exposure at birth but does not recommend BCG vaccination for children with symptomatic HIV infection. This approach, however, has led to HIV-infected neonates who are asymptomatic at birth, developing severe vaccine-related complications. We present a surgical case series, representative of a minority of the cases in circulation, in support of a change to the timing of BCG administration to HIV-exposed neonates. METHODS: A case series of 17 HIV-infected patients with surgical complications of BCG vaccination. RESULTS: Seventeen patients are presented. The first two illustrate disseminated systemic BCG infection, resulting in BCG infection of the lymph nodes, liver, spleen and tibia, and the second with gastrointestinal involvement causing bowel obstruction. The other 15 patients represent a series of severe ulcerating lymphadenitis secondary to BCG. CONCLUSION: The risks of BCG in HIV-infected infants are significant. Current recommendations are not satisfactory, and a change in policy is required to prevent the harmful effects of this vaccine in a high-risk group of patients. We believe that there is sufficient need to adequately stratify patients and vaccinate them according to a protocol that takes impaired immunity into consideration

Measurement properties and responsiveness of the EQ-5D-Y-5L compared to the EQ-5D-Y-3L in children and adolescents receiving acute orthopaedic care

Objective The aim of this study is a head-to-head comparison of the instrument performance and responsiveness of the EQ-5D-Y-3L and the expanded English version of the EQ-5D-Y-5L in children/adolescents receiving acute orthopaedic management in South Africa. Methods Children/adolescents aged 8–15 years completed the EQ-5D-Y-5L, EQ-5D-Y-3L, self-rated health (SRH) question and PedsQL at baseline. The EQ-5D-Y-5L, EQ-5D-Y-3L and SRH question were repeated after 24 and 48 h. Performance of the EQ-5D-Y-5L and EQ-5D-Y-3L was determined by comparing feasibility (missing responses), redistribution of dimensions responses, discriminatory power, concurrent validity, and responsiveness. Results Eighty-three children/adolescents completed baseline measures and seventy-one at all three time-points. Reporting of 11111 decreased by 20% from the EQ-5D-Y-3L to the EQ-5D-Y-5L. Informativity of dimensions improved on average by 0.267 on the EQ-5D-Y-5L with similar evenness. There was a range of 11–27% inconsistent responses when moving from the EQ-5D-Y-3L to the EQ-5D-Y-5L. There was a low to moderate and significant association on the EQ-5D-Y-3L and EQ-5D-Y-5L to similar items on the PedsQL and SRH scores. Percentage change over time was greater for the EQ-5D-Y-5L (range 0–182%) than EQ-5D-Y-3L (range 0–100%) with the largest reduction for both measures between 0 and 48 h. For those who respondents who showed an improved SRH the EQ-5D-Y-5L and EQ-5D-Y-3L showed significant paired differences. Conclusion The English version of the EQ-5D-Y-5L appears to be a valid and responsive extension of the EQ-5D-Y-3L for children receiving acute orthopaedic management. The expanded levels notably reduce the ceiling effect and has greater discriminatory power. Concurrent validity of the EQ-5D-Y-3L and EQ-5D-Y-5L was low to moderate with similar PedsQL items and SRH. The EQ-5D-Y-5L generally showed greater change than the EQ-5D-Y-3L across all dimensions with the greatest change observed for 0–48 h. Responsiveness was comparable across the EQ-5D-Y-3L and EQ-5D-Y-5L for those with improved SRH. Greater sensitivity to change may be observed on comparison of utility scores, once preference-based value sets are available for the EQ-5D-Y-5L

Risk factors and outcomes of contrast-induced nephropathy in hospitalised South Africans

Background. Despite ranking third as a cause of hospital-acquired acute kidney injury (AKI), iatrogenic contrast-induced nephropathy (CIN) impacts significantly on morbidity and mortality and is associated with high hospital costs. In  sub-Saharan Africa, the rates and risk factors for CIN and patient outcomes remain unexplored.Methods. We conducted a prospective observational study at the Charlotte Maxeke Johannesburg Academic Hospital, South Africa, from 1 July 2014 to 30 July 2015. Hospitalised patients undergoing computed tomography scan contrast media administration and angiography were consecutively recruited to the study and followed up for development of AKI. CIN was defined as an increase in serum creatinine &gt;25% or an absolute increase of &gt;44 μmol/L from baseline at 48 - 72 hours post exposure to contrast media. Outcome variables were the occurrence of CIN, length of hospitalisation and in-hospital mortality.Results. We recruited 371 hospitalised patients with a mean (standard deviation) age of 49.3 (15.9). The rates of CIN, assessed using an absolute or relative increase in serum creatinine from baseline, were 4.6% and 16.4%, respectively. Anaemia was an independent predictor for the development of CIN (risk ratio (RR) 1.71, 95% confidence interval (CI) 1.01 - 2.87; p=0.04). The median serum  albumin was 34 g/L (interquartile range (IQR) 29 - 39.5) and 38 g/L (IQR 31 - 42) in the CIN and control groups, respectively (p=0.01), and showed a significant trend for CIN development (RR 1.68, 95% CI 0.96 - 2.92; p=0.06). Mortality was  significantly increased in the CIN group (22.4% v. 6.8%; p&lt;0.001), and CIN  together with anaemia increased mortality twofold (RR 2.39, 95% CI 1.20 - 4.75; p=0.01) and threefold (RR 3.32, 95% CI 1.48 - 7.43; p=0.003), respectively.Conclusions. CIN has a relatively high incidence in sub-Saharan Africa and predicts poorer clinical outcomes. The presence of CIN and anaemia positively predicted mortality. Caution should be exercised in patients with hypoalbuminaemia and anaemia undergoing contrast media administration

Workmen’s compensation for occupational hand injuries

Background. The Compensation for Occupational Injuries and Diseases Act No. 130 of 1993, as amended in 1997 (COIDA), provides payment to healthcare providers for treatment of occupational injuries in South Africa (SA). Patients and employers are often unaware of procedures for claiming, and patients then carry the burden of costs themselves. Additionally, under-billing results in a loss of income for treating hospitals. Hand injuries are common occupational injuries and form the focus of this study.Objectives. To investigate whether occupational hand injuries treated at the Martin Singer Hand Unit at Groote Schuur Hospital, Cape Town, were accurately captured and allocated correct professional fee coding and billing. Accurate capturing and billing would allow for access to the Compensation Fund and allocation of finances to improve service delivery, as well as avoid unnecessary costs to otherwise uninsured patients.Methods. All new hand injuries presenting to the hand unit at the hospital in August 2017 were sampled in a retrospective folder review. Injuries on duty (IODs) were identified and analysed further. Coding and billing were compared with independent private quotes.Results. Sixty new hand injuries presented during the month. Fifteen were IODs, but only 6 were recognised by administration. The other 9 were billed at minimum income rates and 5 of these patients also had operations, which were not billed for. A total of ZAR88 871.99 was under-billed in terms of professional fees only. The 9 incorrectly classified patients had to bear costs themselves at a median of ZAR130.00 each.Conclusions. There were large discrepancies in billing for occupational hand injuries. This resulted in costs to the patients and loss of income for the facility. Access to the Compensation Fund is vital in financing resources in the overburdened public sector. Suggestions for improvement include accessing COIDA funds in order to improve administration at the unit, so improving identification, coding and billing of occupational hand injuries.