bluuebunny/crossref_metadata_2025 huggingface dataset:
The Role of Epithelial and Vascular-Endothelial Cadherin in the Differentiation and Maintance of Tissue Integrity
Authors: Nachtigal Petr , Gojová Andrea , Semecký Vladimír
Published: June 2019

The present review has focused on the cell adhesion molecules from the cadherin superfamily, in particular on E- and VE-cadherin. In general, cadherins are a large group of cell adhesion molecules located at intercellular junctions called adherent junctions. They play an important role in embryogenesis and morphogenesis in animals and humans due to their adhesive and cell-signalling functions. Disturbances of the expression or function of cadherins and their associated proteins called catenins are crucial for the initiation and development of many pathological states. E-cadherin is an epithelium-specific cadherin that is required for the development and maintenance of the normal function of all epithelial cells in tissues. The loss or down-regulation of E-cadherin is a key event in the process of tumour invasion and metastasis. The assessment of E-cadherin immunoreactivity may be a useful prognostic marker in some cancers, complementary to the established prognostic factors. VE-cadherin is an endothelium-specific cadherin, which plays a relevant role in vascular homeostasis. It has been demonstrated that VE-cadherin is required for normal vasculogenesis, angiogenesis, and for the maintenance of vascular integrity. Disruption of VE-cadherin-catenin complexes by some inflammatory agents such as thrombin, by inflammatory cells, or shear stress is accompanied by an increase in vascular permeabilityin vivoandin vitro.
Pneumatosis Cystoides Intestinalis - A Review
Authors: Vobořil René
Published: June 2019

Pneumatosis cystoides intestinalis is a rare disease characterized by presence of multilocular cysts in the gastrointestinal wall. Idiopatic and secondary forms of the disease can be distinguished. There are presented several theories explaining pneumatogenesis in this article. The specific and non-specific symptoms are described. Attention is drawn to the pneumoperitoneum without signs of peritoneal irritation, what is a typical complication of this disease. The suspition of pneumatosis cystoides intestinalis may be based on plain abdominal X-ray, and is usually confirmed by computer tomography or magnetic resonance imaging. The therapy can be conservative or surgical. In conclusion, although pneumatosis cystoides intestinalis is a rare disease, it may represent a problem in differential diagnosis of abdominal pain.
Long Term Effects of Low-Level Sarin Inhalation Exposure on the Spatial Memory of Rats in a T-Maze
Authors: Kassa Jiří , Koupilová Marie , Vachek Josef
Published: June 2019

To study the influence of low-level sarin exposure on cognitive functions, male albino Wistar rats were exposed to three various low concentrations of sarin (LEVEL 1–3) for 60 minutes in the inhalation chamber. Testing of cognitive functions was carried out using the T-maze evaluating learning and spatial memory. The behavior of sarin-exposed rats in the T-maze was tested several times within five weeks following sarin inhalation exposure to look for any cognitive impairments. The alteration of cognition was evaluated by using a method studying memory elicitation in response to appetitive motivation in a multiple T-maze. 2. Statistically significant, short-term deficiency in the T-maze performance was observed in rats exposed to symptomatic (LEVEL 3) as well as clinically asymptomatic concentration (LEVEL 2) of sarin. The repeated exposure of rats to clinically asymptomatic dose of sarin (LEVEL 2R) did not change the effect of lowlevel sarin exposure on spatial memory compared to the single exposure to the same dose of sarin. 3. Thus, sarin is able to influence the cognitive functions (e.g. spatial memory) even at low doses that do not cause clinically manifested intoxication following the inhalation exposure. Nevetheless, the alteration of spatial memory lasts for a short time only, in contrast with the severe sarin poisoning.
Morbidity and Mortality in Patients 70 Years of Age and Over Undergoing Isolated Coronary Artery Bypass Surgery
Authors: Žáček Pavel , Dominik Jan , Harrer Jan , Lonský Vladimír , Manďák Jiří , Kuneš Pavel , Solař Miroslav
Published: June 2019

Background and aim: Due to the constantly improving results of surgical revascularization for coronary heart disease even the elderly patients are offered more frequently this type of treatment. Since older age is a harbinger of reduced vital capacity and increased morbidity the results of coronary artery bypass grafting (CABG) in elderly as well as long-term benefit deserve a careful examination. Materials and methods: 1475 isolated CABG procedures performed between 1995 and 1997 in a university hospital cardiac surgery unit, divided in group I (age below 70, n = 1324) and group II (age 70 and over, n=151). A retrospective analysis of pre-operative, peri-operative and post-operative data. Results: Significant differences (lower BMI and BSA, advanced NYHA and CCS stage, higher prevalence of diabetes, renal dysfunction and extracardial atherosclerotic lesions) were found in elderly. CABG was performed in both groups with no differences in technique of procedure (only slightly longer duration of CPB in group II). However, there was markedly higher mortality (2.3 vs. 7.3 %, p < 0.005), incidence of NearMiss+ (18.4 vs. 36.4 %, p < 0.005) and post-operative morbidity (34.6 vs. 56.3 %, p < 0.005) in the older group, which was also expressed in a longer ICU stay and postoperative hospitalization. Conclusion: Coronary revascularization can be performed in elderly with higher but still acceptable risk. Higher mortality and associated morbidity is caused by higher preoperative prevalence of known risk factors as well as generally reduced vital capacity. Surgical procedure should not be denied to elderly population because of the age alone but a careful evaluation of an individual patient is required.
The End of Life As “Non” Death
Authors: Tarca Luigi Vero
Published: June 2019

Taking the cue from some verses of Rilke’s Duineser Elegien, where the poet talks about the distinction between life and death, a distinction which mortals perform too rigidly, in this paper I discuss the contrast just between life and death, in order to understand the conditions under which the first truly distinguishes itself from the latter. This happens to the extent that life is also distinguished from the denial of death because otherwise, being the negation a form of necation (nex = killing, murder), the presumed denial of death would reverse in a triumph of death.In the present age this circumstance is particularly evident and significant, since humanity aims at a technological realization of im‑mortality, understood as the denial of death. To the extent that this remains a negative operation, it takes the form of the scrapping of mortals. True liberation/salvation from death presupposes that the negation itself is called into question. Only on this condition, in fact, is possible a life free from any form of necation. This freedom presupposes, inter alia, a “non” education, intended as an education to be able to freely play with the negative of death and denial.
Intercultural Dialogue and Humanities from Late Antiquity to the Middle Ages
Authors: Di Palma Enrico Maria
Published: June 2019

The aim of this articole is to discover traces of humanitas in late antique and mediaval literature. Starting from the classic meaning of this notion, the paper finds three meaningful episodes: the controversy between Ambrosius and Symmachus about the Altar of Victory, the Dialogue of a Philosopher with a Jew and a Christian by Peter Abelard and the spread of the Life of Balaam and Josaphat. Through these examples, the article builds a new idea of humanitas, free from historical restricion, a blend of literary passion, acceptance of diversity and multiculturalism.
The Cartography of Childhood. A Parcours of Philosophy for Children / Community and Cartography
Authors: Bevilacqua Silvia
Published: June 2019

The following reflections are born from some practical and theoretical trajectories undertook by the writer – already since a few years in my research scope – around philosophy for children/community and philosophical practices. The experience of some activities proposed at the Liceo Vasco/Beccaria/Govone in Mondovì during the Cespec Summer School 2017 around the issue of Humanitas in the contemporary society was recently added to these reflections. It is a theme that engaged us in several experiences of Philosophy for Community. Throughout these gatherings, we proposed a cartographic writing and philosophical approach. In particular, this contribution will explore the concept of children cartography (cartografia d’infanzia), as an occasion of translating the philosophical discourse into a map of a philosophical debate, also mutuating the concept of philosophical confluence considered by Pierpaolo Casarin. The adopted perspective is the transdisciplinary border where human geography, philosophy, and writing, as disciplinary subjects, can confound their identities and boundaries in a space of immanence in the making. Summarizing, we intend to highlight the themes, concepts, and practical propositions around some practical and theoretical research trajectories, current and future, which hold implications for all of us (and for humanity). Such practices allow again – and still – the possibility of orienting and losing oneself thanks to the Humanitas.
Sufizm w Dagestanie
Authors: Siereda Natalia
Published: June 2019

The article describes the religious situation in Daghestan, one of the north-Caucasian republics of Russia, focusing especially on the Islamic mysticism – Sufism. The introduction presents the geographical and ethnical situation of the Republic. The following chapters discuss the history of Islam in Caucasus which had started in Daghestan as well as the development of mystical brotherhoods and their profiles. The role of Islam and its mystical branch in contemporary Daghestan has been depicted in the conclusion.
Recenzja: Muhsin Maci (red.). 2017. Hatâyî Divânı. İstanbul: Türkiye Yazma Eserler Kurumu.
Authors: Erdem Cem
Published: June 2019

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Who is Responsible for Responsible Innovation? Lessons From an Investigation into Responsible Innovation in Health Comment on "What Health System Challenges Should Responsible Innovation in Health Address? Insights From an International Scoping Review"
Authors: Stahl Bernd Carsten
Published: June 2019

Responsible innovation in health (RIH) takes the ideas of responsible research and innovation (RRI) and applies them to the health sector. This comment takes its point of departure from Lehoux et al which describes a structured literature review to determine the system-level challenges that health systems in countries at different levels of human development face. This approach offers interesting insights from the perspective of RRI, but it also raises the question whether and how RRI can be steered and achieved across healthcare systems. This includes the question who, if anybody, is responsible for responsible innovation and which insights can be drawn from the systemic nature RIH.
RACISMO E SUA REPRODUTIBILIDADE: EXCLUSÃO E REPRESENTAÇÃO SOCIAL NA SOCIEDADE BRASILEIRA NA SEGUNDA METADE DO SÉCULO XX
Authors: Carneiro João Paulo
Published: June 2019

O presente artigo aborda a exclusão social da população negra no âmbito das determinações racistas (APPIAH, 1997; GUIMARÃES, 2012; MUNANGA, 2012; HALL, 2012; DOMINGUES, 2004; SKIDMORE, 2012; SANTOS, 1997) e, também, pelas determinações capitalistas e sua reprodução ideológica (IANNI, 1978; FERNANDES, 2008; GRAMSCI, 1891-1937). Para tanto, torna-se necessário uma apresentação conceitual de raça, racismo, discriminação racial, os nexos históricos, sociais e de poder no contexto da sociedade brasileira na esfera das relações étnico-raciais. No campo das políticas públicas a discussão é realizada através dos conceitos de hegemonia e ideologia gramsciana. Por fim, permanências e rupturas na construção de políticas públicas antirracistas e anti-hegemônicas.

Palavras-chave: Racismo. Exclusão Social. Ideologia. Hegemonia.
Evaluación de los mediadores IL-1α, IL-1β y TNF-α, en fluido gingival crevicular de pacientes con periodontitis
Authors: Simone Rosamary , Escalona Laura , Ávila Maira , Fernandes Andreína , Correnti María
Published: June 2019

Objetivo. Evaluar los niveles de mediadores químicos inflamatorios como la interleucina- 1α (IL-1α), interleucina-1β (IL-1β), factor de necrosis tumoral-α (TNF-α) y los parámetros clínicos en pacientes diagnosticados con periodontitis crónica o agresiva, antes y después de la terapia periodontal no quirúrgica (TPNQ). Métodos. Se tomaron muestras de fluido gingival crevicular (FGC) en 11 pacientes diagnosticados con periodontitis y 11 controles sanos para evaluar niveles de IL-1α, IL-1β, TNF-α antes y después de la TPNQ, mediante la técnica de ELISA (Enzyme-Linked Immuno Sorbent Assay). Resultados. En el grupo con periodontitis se observó disminución significativa de los parámetros clínicos después del tratamiento (p<0,05). En FGC, IL-1β presentó los niveles más elevados, seguido de IL-1α y TNF-α. Posterior a la TPNQ, IL-1β disminuyó 17 veces su concentración e IL-1α 4 veces en relación a los valores iniciales, sin embargo, solo se observó una relación estadísticamente significativa para TNF-α. Las mayores correlaciones con los parámetros clínicos de la enfermedad periodontal se observaron para IL-1β (p<0,01), seguido por IL-1α (p<0,05) y una baja correlación con TNF-α. Conclusiones. En este trabajo, el grupo de pacientes con periodontitis presentó mayores niveles de IL-1α, IL-1β y TNF-α en FGC, siendo IL-1β la citocina más elevada. Posterior al TPNQ, se observó disminución significativa de los valores clínicos periodontales. Así mismo, las interleucinas redujeron sus valores promedios, sin alcanzar los del grupo control. Las correlaciones observadas entre los índices periodontales y los mediadores sugieren mayor correlación de IL-1β con los signos clínicos de la enfermedad periodontal.
Nonalcoholic Fatty Liver Disease and Urolithiasis. A Systematic Review and Meta-Analysis
Authors: Wijarnpreecha Karn , Lou Susan , Panjawatanan Panadeekarn , Sanguankeo Anawin , Pungpapong Surakit , Lukens Frank J , Ungprasert Patompong , Ungprasert Patompong
Published: June 2019

Background & Aims: Recent studies have suggested that nonalcoholic fatty liver disease (NAFLD) could be a predisposing factor for urolithiasis but the results have been inconsistent. This systematic review and meta-analysis was conducted with the aim to summarize all available data.Methods: A comprehensive literature review was conducted using MEDLINE and EMBASE databases through March 2018 to identify all studies that compared the risk of urolithiasis among patients with NAFLD versus those without NAFLD. Effect estimates from each study were extracted and combined together using the random-effect, generic inverse variance method of DerSimonian and Laird.Results: A total of eight studies with 238,400 participants fulfilled the eligibility criteria and were included in the meta-analysis. The risk of urolithiasis among patients with NAFLD was significantly higher than in those without NAFLD with a pooled odds ratio of 1.81 (95% confidence interval, 1.29-2.56; I2 92%).Conclusions: A significantly increased risk of urolithiasis among patients with NAFLD was observed in this meta-analysis.
Liver infarction in a patient with Clostridium Difficile colitis. A possible connection?
Authors: Mihaila Romeo Gabriel , Sandu Mariana
Published: June 2019

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The frequency and risk factors of low bone mineral density one year after liver transplantation in children: a study in Shiraz Organ Transplant Center
Authors: Dehghani Seyed Mohsen , Amirhakimi Anis , Shahramian Iraj , Bazi Ali , Hashemi Mahboobeh , Ilkhanipour Homa
Published: June 2019

Objective: Osteoporosis is a severe epiphenomenon that follows liver transplantation (LT). There is an inconsistency regarding risk factors of developing osteoporosis in LT children. In this article, we address the frequency of low bone mineral density (BMD) in LT children.

Methods: This is a prospective study performed on children aged <18 years old, referred to the Shiraz Organ Transplant Center. The study was conducted from March 2009 until March 2014. Those with at least one year passed from the transplantation were included. Lumbar and hip bone densities were checked by Dual-Energy Radiograph Absorptiometry.

Results: From the total of 84 included children, 32 (38.1%) and 52 (61.9%) were males and females respectively. The underlying diseases included cryptogenic (32, 28.1%), biliary atresia (18, 21.4%), Wilson disease (9, 10.7%), autoimmune hepatitis (9, 10.7%), tyrosinemia (6, 7.1%), acute liver failure (5, 6%), and hypercholesterolemia (5, 6%). Overall, 53 children (63.1%) had normal BMD, while 31 (36.9%) revealed lower than normal BMD. The means of lumbar and hip z scores were -1.04+/-1.47 (median of -0.75) and -0.98+/-1.92 (median of -0.60), respectively. There was no significant association between bone density and the age of transplantation, sex, weight, height, or underlying diseases (P>0.05). None of the immunosuppressive drugs were associated with low BMD. The patients who received pulse therapy showed a significantly higher rate of low BMD respective to the patients who did not receive pulse therapy (P=0.03).

Conclusion: The frequency of low BMD is relatively high in LT children. Pulse therapy may increase the risk of low BMD and osteoporosis in LT children.
Psychological and Pedagogical Conditions of Professional Responsibility of an International Journalist in Non-Proliferation of Fake News
Authors: Romanenko Nadezhda M.
Published: June 2019

Introduction.Against the background of the mass media crisis and despite the need to increase the responsibility of international journalists in non-proliferation of “fake news”, there are no studies that regulate effective pedagogical conditions for increasing the reporters’ honesty and integrity. The purpose of the article is to present results of a study carried out at the international journalism faculty of Moscow State Institute of International Relations under the Ministry of Foreign Affairs of Russia between 2014-2018, including dedicated psychological and pedagogical conditions involving key approaches and effective technological support and diagnostic tools to measure levels of professional responsibili ty of international journalists.
Materials and Methods. The empirical base of the study comprised a multiyear observation and questionnaires for 2nd-4th-year students of the MGIMO international journalism faculty, as well as re-analysis and substantive interpretation of matters of improving quality of professional journalism.
Results. The study presents the analysis of problems of increasing professional responsibility of international journalists under conditions of commercialization of information field and mass media and effective psychological and pedagogical conditions required to improve quality of their professional training. A series of criteria and indicators related to the concept of the professional responsibility of the international journalist (civil position, moral standing and professional persistence) were defined.
Discussion and Conclusion. Specially created psychological and pedagogical conditions of education can satisfy the state order, employers and students of the journalism area, building highly professional competences of international journalist. Mechanisms and step-by-step implementation of the model may be replicated in the broad higher school practice, increasing the level of professional responsibility of international journalists. The results obtained are of interest to the administrative staff of higher educational institutions, heads of departments that continuously monitor quality of journalistic education, as well as scientists and university professors engaged in improving the quality of education of media professionals. Prospective studies of the determinants of better quality of journalist education must be focused on deepening professional competencies of graduates to ensure the creation of adequate conditions for national and foreign political elite activity.
Experience of Quantitative Analysis of Students Questionnaires on Education Quality Problems: Methodology, Models and Perspectives
Authors: Gulyaeva Tatyana I. , Kolomeychenko Alla S. , Polshakova Natalya V. , Shumetov Vadim G. , Yakovlev Aleksandr S.
Published: June 2019

Introduction. The relevance of the article is determined by the lack of scientific substantiation of existing methods of quantitative analysis of mass student questionnaires that can lead to erroneous conclusions about the quality of educational services they receive. Authors first applied the in-house probabilistic approach to the preparation of data for mass questioning of students to develop regression and factor models that adequately reflect their subjective judgments about learning quality. Our goal was to estimate the efficiency and possibility of the practical application of the authors, approach to the analysis of student questionnaire results by means of multivariate statistics by the example of the development of the quantitative estimation model of education quality and subjective well-being of student s of Orel State Agrarian University.
Materials and Methods. The suggested approach is based on the methods of parametrical multivariate statistics. The empiric basis of modeling consists of the results of questioning students of the 2nd-4th years of learning. The analytic software SPSS Base was used.
Results. At the example of the development of correlation-regressive and factor models of the subjective well-being of the students, we proved the efficiency of the suggested approach to the quantitative modeling of questionnaire results by means of multivariate statistical methods. It is shown that all the obtained correlation-regression models have high statistical characteristics of quality and adequately reflect the simulated phenomena. Of particular interest is the model structure of factors of subjective well-being of students, reflecting the process of their professional and cultural development and adaptation to the current socio-political environment.
Discussion and Conclusion. The completed study expanded the understanding of possibilities of quantitative analysis of the results of mass student questioning by simulating various aspects of their subjective wellbeing. The advantage of this method is that at modeling it allows considering the status features influence on the degree of the higher educational institution satisfaction and the obtainable education quality. The approach suggested by the authors will be useful in quality education monitoring at higher schools as well as in the educational sphere in general and for various social and economic studies.
Molekuláris citogenetikai vizsgálatok Baranya és Tolna megye plazmasejtes myelomában szenvedő betegein
Authors: Kosztolányi Szabolcs , Horváth Bálint , Hosnyánszki Diána , Kereskai László , Sziládi Erzsébet , Jáksó Pál , Alizadeh Hussain , Szuhai Károly , Alpár Donát , Kajtár Béla
Published: June 2019

Abstract:

Introduction: Plasma cell myeloma is a hematological malignancy with heterogeneous genomic landscape and diverse clinical course. Recurrent chromosomal and subchromosomal aberrations commonly occur in this entity and are associated with the pathogenesis and progression of the disease. The identification of these alterations aids genetic characterization, classification and prognostication of patients. Aim: Molecular cytogenetic investigations of plasma cell myeloma patients treated at the University of Pécs Clinical Center and János Balassa County Hospital of Tolna County, Szekszárd, between 2005 and 2018 were evaluated in our study. Method: 231 patients were screened for genetic aberrations using fluorescence in situ hybridization. Translocations involving the immunoglobulin heavy chain gene, losses of 1p and 17p chromosome arms, gains of 1q chromosome arm and unbalanced aberrations of chromosome 13 were investigated. Losses and gains of 1p, 1q, 5q, 12p, 13q, 16q and 17p chromosome arms were analyzed using multiplex ligation-dependent probe amplification in 42 patients. During the investigated period, 116 bone marrow karyotyping was also performed. Results: In total, 233 genetic aberrations were identified using our targeted approaches; the frequency of specific aberrations correlated with data of the recent literature. Concordance of results gained by fluorescence in situ hybridization and multiplex ligation-dependent probe amplification was 96.2% by analyzing the same chromosome arms. The latter technique revealed 21 additional genetic aberrations in 16/42 patient samples (38%) as compared to fluorescence in situ hybridization. Conclusions: Our results suggest that the combined application of the two molecular cytogenetic methods may facilitate a more detailed characterization of genetic aberrations of plasma cell myeloma patients in Hungary. Orv Hetil. 2019; 160(24): 944–951.
Az emberi halántékcsontnak a csecsemő- és kisgyermekkori cochlearis implantáció szempontjából kiemelkedően fontos dimenziói. Klinikoradiológiai vizsgálat
Authors: Perényi Ádám , Jóri József , Csanády Miklós , Rovó László
Published: June 2019

Abstract:

Introduction: Early cochlear implantation enables prelingual deaf individuals to become full members of the hearing society. Although early diagnostics are widely accessible and enable early rehabilitation, implant surgery often may be delayed due to a candidate’s young age. Aim: The authors’ objectives were to determine the anatomical parameters of the pediatric and adult temporal bone that are relevant to cochlear implantation and to ascertain the differences between them in order to assess whether the anatomical differences could influence the surgical technique and the timing of surgery. Method: Along with a survey of the literature, findings from the authors own cochlear implantees were assessed with respect to the most relevant dimensions of the internal electronic package, including the stimulating electrode of the cochlear implant, by measuring the squama of the temporal bone, the mastoid cavity and the facial recess on high resolution computed tomographic images. Results: The skull and the overlying soft tissues proved to be thinner and the mastoid cavity was less developed in children than in adults, while no significant changes were noted in the size of the facial recess. Conclusions: It is recommended to choose modern, thin implants that do not require sinking the implant package into a bone bed. Less bone work in infants and children enables excellent visualization of the round window through the underdeveloped mastoid cavity, which makes the procedure less time-consuming and minimally invasive. Indeed, a young age should alert ear surgeons to be cautious, but no higher risk of injury to important structures is predicted for young subjects than those that might occur in adults. Orv Hetil. 2019; 160(24): 936–943.
Családi disznótor, avagy a szokások nem változnak. Hagyományőrző infektológiai esetbemutatás
Authors: Dezsényi Balázs , Szabó Bálint Gergely , Danka József , Ocskay László , Bor László , Csepregi András , Babarczi Edit , Petrovicz Edina , Budai József
Published: June 2019

Abstract:

We report a case of a 41-year-old female patient presenting with watery diarrhoea and myalgia in the winter-season. Before her symptoms started she had participated in a pig slaughtering with her family. Some of the family members also became ill. On her physical examination periorbital odema and myalgia were found. Eosinophilia, hypalbuminaemia, elevated lactate dehydrogenase and creatin kinase levels were detected on laboratory investigations. The clinical picture, the laboratory findings and background epidemiological data implied the diagnosis of trichinellosis and albendazol was started. Serum gained on the 22nd post-infectious day turned out to be equivocal for trichinellosis. For this reason and because of the refractory fever a muscle-biopsy was done. Granulomatous myositis described by histology and Trichinella seropositivity from the repeated serum sample on the 62nd post-infectious day finally confirmed the diagnosis. During the course of the disease, we experienced elevation of troponin I suggesting myocarditis, but it was accompanied neither with abnormal ECG signs nor characteristic symptoms. Almost a century ago, a case report was published in Hungarian with a similar introduction. Trichinellosis in that epidemic setting led to the death of five people. Orv Hetil. 2019; 160(24): 952–957.
Framgångsrika skolor – de flesta enligt deras rektorer
Authors: Alvesson Mats
Published: June 2019

Vet rektorer mycket om sina skolor? Säkert vet man en del om detaljer men hur mycket kunskap har man om skolans övergripande kvalitet? Har man god kunskap om skolan är framgångsrik eller inte? I denna essä redovisas resultat baserade på en enkät till svenska skolrektorer om hur bra deras skolor är, hur de vet något om detta och vad deras egna rektorsinsatser har för betydelse. Den övergripande slutsatsen är att man ofta har en dålig uppfattning om hur välfungerande den egna skolan är och troligen överskattar sina kunskaper härom och även de egna ledarskapsinsatsernas betydelse och inverkan.
Doodmenslik (W. L. van der Merwe)
Authors: Visagie Andries
Published: June 2019

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Challenges in household energisation and the poor
Authors: Lloyd Philip
Published: June 2019

While the electrification of households in South Africa since 1994 has been impressive, many of the major energy services in poor households are still met by traditional fuels such as, on the Highveld, coal; in coastal regions, paraffin; and in rural areas by wood. Their use is associated with a range of challenges, from chronic respiratory tract infections to asphyxiation by carbon monoxide to massive fires that destroy not only homes but also lives. State interventions such as the provision of Free Basic Electricity are costly and do not appear to be contributing towards any solutions. The challenges are assessed, and a range of mitigations proposed.
Design of a low voltage DC microgrid system for rural electrification in South Africa
Authors: Bokanga Gilbert M. , Raji Atanda , Kahn Mohammed T.E.
Published: June 2019

This project entails the design of a low voltage DC microgrid system for rural electrification in South Africa. Solar energy is freely available, environmental friendly and it is considered as a promising power generating source due to its availability and topological advantages for local power generation. Off-grid solar systems are perceived to be a viable means of power delivery to households in rural outlying areas in South Africa as solar panels can be used almost anywhere in the country. The design presented in this paper is based on the power demand estimation, photovoltaic panel selection, battery sizing and wire selection for the distribution system.
Voltage stability enhancement using an adaptive hysteresis controlled variable speed wind turbine driven EESG with MPPT
Authors: Jeevajothi R. , Devaraj D.
Published: June 2019

This paper investigates the enhancement in voltage stability achieved while connecting a variable speed wind turbine (VSWT) driven electrically excited synchronous generator (EESG) into power systems. The wind energy conversion system (WECS) uses an AC-DC-AC converter system with an uncontrolled rectifier, maximum power point tracking (MPPT) controlled dc-dc boost converter and adaptive hysteresis controlled voltage source converter (VSC). The MPPT controller senses the rectified voltage (VDC) and traces the maximum power point to effectively maximize the output power. With MPPT and adaptive hysteresis band current control in VSC, the DC link voltage is maintained constant under variable wind speeds and transient grid currents.The effectiveness of the proposed WECS in enhancing voltage stability is analysed on a standard IEEE 5 bus system, which includes examining the voltage magnitude, voltage collapse and reactive power injected by the systems. Simulation results show that the proposed WECS has the potential to improve the long-term voltage stability of the grid by injecting reactive power. The performance of this scheme is compared with a fixed speed squirrel cage induction generator (SCIG), a variable speed doubly-fed induction generator (DFIG) and a variable speed permanent magnet synchronous generator (PMSG).
Use of hybrid solar-wind energy generation for remote area electrification in South-Eastern Nigeria
Authors: Nnadi Damian B.N. , Odeh Charles I. , Omeje Crescent
Published: June 2019

This paper presents simulated hybridized solar-wind generation as an alternative for rural dwellers that do not have access to a conventional grid connection. Solar and wind were used as the main sources of energy with battery storage. Each power source has a DC-DC converter to control the power flow. An axial flux permanent magnet generator, which is suitable for a location with a low wind speed, was driven by the wind turbine. By using this generator, the efficiency of the system increased since certain losses were removed. The perturbation and observation method of MPPT is used to achieve maximum power extraction from the solar panel. The hybrid system was modelled in Matlab/Simulink software. A squirrel cage induction motor was used as the electrical load to the system load. The results obtained for the proposed hybrid system indicates that it can be used as an isolated power supply. By doing so, it improves the standard of living and hence, increasing total number of citizens using energy in the country.
Performance of a compression ignition engine operated with sunflower ethyl ester under different engine loads
Authors: Açıkkalp Emin , Yamık Hasan , İçingür Yakup
Published: June 2019

This study investigated the performance of a compression ignition engine operating with sunflower ethyl ester. A thermodynamic analysis, including energy and exergy analysis at different engine loads (20%, 40%, 60%, 80%, 100%), was conducted. The study calculated the first and second law efficiency, effective work, heat exergy losses and exergy destruction values at 10 different engine speeds for 5 loads. Maximum work, maximum thermal efficiency, maximum exergy efficiency and maximum volumetric efficiency are determined to be 6.45 kW, 0.26, 0.24 and 0.71 respectively. Finally, optimum operating conditions are discussed and it was determined that the engine should be operated at a lower engine speed for partial loads.
A review on protective relays’ developments and trends
Authors: Abdelmoumene Abdelkader , Bentarzi Hamid
Published: June 2019

One of the most complex disciplines in electrical engineering is power system protection which requires not only the proper understanding of the different components of a power system and their behaviours but also a good knowledge and analysis of the abnormal circumstances and failures that can occur in any element of a power system. Moreover, the rapid changing and development in relays principles as well as in their technologies are additional factors that oblige those people working in the field to expand and update continuously their knowledge. In this paper, we shed light in the evolution of protective relays since the onset of electrical energy to currently. We try also to foresee the future prospects and trends in this area.
General aspects of carbon dioxide as a refrigerant
Authors: Belman-Flores J.M. , Pérez-García Vicente , Ituna-Yudonago Jean Fulbert , Rodríguez-Muñoz José Luis , Ramírez-Minguela José de Jesús
Published: June 2019

Carbon dioxide is an innocuous refrigerant for the environment. It is a substance of current interest in the refrigeration area. Its good thermodynamic and heat transfer properties have placed it in an excellent position for substituting refrigerants that contribute to global warming. This paper describes carbon dioxide as a refrigerant, the main characteristics that have made it a substance of current interest, its applications in subcritical and transcritical cycles, and a general vision of its usage at international level. Moreover, this paper presents the disadvantages of using this refrigerant and the upgrades made by the scientific community in order to improve the performance of those systems that work with this fluid. This paper is a reference for those interested in having a wider vision of frigorific technology based on carbon dioxide as a refrigerant.
A case study of climate variability effects on wind resources in South Africa
Authors: Herbst Lynette , Lalk Jörg
Published: June 2019

The wind energy sector is one of the most prominent sectors of the renewable energy industry. However, its dependence on meteorological factors subjects it to climate change. Studies analysing the impact of climate change on wind resources usually only model changes in wind speed. Two elements that have to be calculated in addition to wind speed changes are Annual Energy Production (AEP) and Power Density (PD). This is not only because of the inherent variability between wind speed and wind power generated, but also because of the relative magnitudes of change in energy potentially generated at different areas under varied wind climates. In this study, it was assumed that two separate locations would experience a 10% wind speed increase after McInnes et al. (2010). Given the two locations’ different wind speed distributions, a wind speed increase equal in magnitude is not equivalent to similar magnitudes of change in potential energy production in these areas. This paper demonstrates this fact for each of the case studies. It is of general interest to the energy field and is of value since very little literature exists in the Southern African context on climate change- or variability-effects on the (wind) energy sector. Energy output is therefore dependent not only on wind speed, but also wind turbine characteristics. The importance of including wind power curves and wind turbine generator capacity in wind resource analysis is emphasised.
Clear sky solar illuminance using visual band irradiance
Authors: Nurick A.
Published: June 2019

Solar illuminance may be quantified by applying relevant efficacy functions to available full spectrum ground irradiance. Alternatively, illuminance may be determined by applying the Photopic function to ground level irradiance spectra obtained from the terrestrial irradiance spectrum adjusted using relevant atmospheric absorption and scattering coefficients. The Photopic function has finite values in the wavelength range of 400 nm to 700 nm and is concentrated around a mean wavelength of 555 nm with irradiance at wavelengths close to 555 nm contributing to the major portion of illuminance. Calculation of ground level direct, diffuse and hence global illuminance is simplified as absorption of irradiance in the atmosphere by water vapour and uniformly mixed gases is negligible and may be ignored. It is shown that due to the small variations in the overall irradiance over wavelengths in the visible bandwidth combined with the concentration effect of the Photopic function in this wavelength range illuminance may be calculated, with good accuracy, using constant extinction functions for both direct and diffuse illuminance. Due to the concentration of illuminance by the Photopic function global illuminance data were also correlated with a simplified description of illuminance attenuation through the atmosphere based on the Beer-Lambert-Bouger Law using a single constant effective extinction coefficient which accounts for all extinction processes under clear sky conditions over the visible range of wavelengths. Constants used in extinction functions for solar irradiance due atmospheric aerosols were obtained by fitting experimental data to analytical descriptions of atmospheric extinction while published constants were used for ozone and Rayleigh scattering. The analytical descriptions of global illuminance with solar elevation were compared with experimental data collected at Johannesburg over both summer and winter clear sky conditions. Correlations of measured and calculated global illuminance data for the method based on extinction of various atmospheric components was 4.47 % and 4.49 % for the method based on the Beer-Lambert-Bouger Law, both normalised using the terrestrial illuminance constant. While measurements were made at a specific site in Gauteng, the methods used to correlate the data are general and location independent but local climatic conditions may need to be taken into account to quantify the extinction coefficients for specific areas.
Energy consumption, thermal utilization efficiency and hypericin content in drying leaves of St John’s Wort (Hypericum Perforatum)
Authors: Minaei Saeid , Chenarbon Hossein Ahmadi , Motevali Ali , Hosseini Akbar Arab
Published: June 2019

Massive consumption of energy in the drying industry has prompted extensive research regarding various aspects of drying energy and requirements. Thermal utilization efficiency, specific energy requirement, total energy consumption and hypericin content in drying of St John’s Wort were determined using a hot-air dryer. Experiments were conducted at four air temperature levels (40, 50, 60, and 70°C), three air velocities (0.3, 0.7, and 1 m/s) and three sample thicknesses (1, 2 and 3 cm). Based on the results of data analysis, minimum and maximum levels of energy consumption were 0.56 and 3.24 kWh, respectively. The required specific energy decreased with increasing sample thickness. The minimum and maximum required specific energies were 4.41 and 17.53 for 2 cm thick and 4.28 and 13.67 for 3 cm thick layers (kWh/kg), respectively. The maximum and minimum values of thermal utilization efficiency in different treatments were found to be 14% and 72%, respectively. Hypericin content decreased with increasing temperature and increased with air velocity and product sample thickness, so that the minimum and maximum hypericin amounts were 67 and 355 ppm, respectively.
The impacts of energy prices and technological innovation on the fossil fuel-related electricity-growth nexus: An assessment of four net energy exporting countries
Authors: Qin Fei , Rasiah Rajah , Leow JiaShen
Published: June 2019

This study uses annual data from 1974 to 2011 to examine the long-run and short-run relationships between fossil fuel powered electricity consumption, economic growth, energy prices and technological innovation for four net energy exporting countries. Canada, Ecuador, Norway and South Africa are chosen as the main research background in order to investigate how the development degree and economic dependence on energy exports affect the electricity-growth nexus. Based on the results drawing from the ARDL approach and the Granger causality test, economic growth positively influences the variation in fossil fuel powered electricity consumption in both the short-run and long-run for all four countries. The reverse causality from electricity consumption to economic growth is only evident in Ecuador and Norway. The degree of dependence on energy exports is a contributory factor of explaining the causality puzzle of the electricity-growth nexus. Given the fact that technological innovation does not benefit fossil fuel powered electricity generation, this paper suggests these net energy exporting countries to replace fossil fuel with more sustainable and effective sources in the electricity generation process.
Economic implications of constant power outages on SMEs in Nigeria
Authors: Akuru Udochukwu B. , Okoro Ogbonnaya I.
Published: June 2019

This paper is concerned with the unabated epileptic power (electric) delivery which is seen to be periodic with a struggling generation capacity and losses-prone inefficient transmission network in Nigeria. Ordinarily, it should mean that only an average Nigerian suffers directly, and only, the burden of this inefficiency, whereby electricity supply to power both household and commercial appliances becomes unpredictable. Yet, further studies have revealed that there is almost no other sector that this ineptitude does not impact indirectly, especially as adverse economic consequences. GDP per Capita versus electrical energy production data for Nigeria and selected countries for the year 2004 served as input parameters which underwent research validation. Small and medium scale enterprises (SMEs) were a case study in this paper. In the end, submissions are that apart from the internal devastating effect on SMEs, constant power outages have a major connection with the recent trends of big companies closing or relocating from Nigeria. To sum up, measures were suggested for improvement.
Renewable energy investment in Nigeria: A review of the Renewable Energy Master Plan
Authors: Akuru Udochukwu B. , Okoro Ogbonnaya I.
Published: June 2019

Data for investment into renewable energy resources in Nigeria is mainly unavailable due to over reliance on conventional resources for energy generation. However, recent developments in the energy sector have portrayed gradual attention to investments in renewable energy resources. This paper reviews the Renewable Energy Master Plan (REMP) which identifies this improvement and presents a draft on how an increase in investment in renewable energy resources, which will in the long run balance the national energy equation, ensure energy security and promote sustainable development.
A comparative study of the stochastic models and harmonically coupled stochastic models in the analysis and forecasting of solar radiation data
Authors: Ranganai Edmore , Nzuza Mphiliseni B
Published: June 2019

Extra-terrestrially, there is no stochasticity in the solar irradiance, hence deterministic models are often used to model this data. At ground level, the Box-Jenkins Seasonal/Non-seasonal Autoregressive Integrated Moving Average (S/ARIMA) short memory stochastic models have been used to model such data with some degree of success. This success is attributable to its ability to capture the stochastic component of the irradiance series due to the effects of the ever-changing atmospheric conditions. However, irradiance data recorded at the earth’s surface is rarely entirely stochastic but a mixture of both deterministic and stochastic components. One plausible modelling procedure is to couple sinusoidal predictors at determined harmonic (Fourier) frequencies to capture the inherent periodicities (seasonalities) due to the diurnal cycle, with SARIMA models capturing the stochastic components. We construct such models which we term, harmonically coupled SARIMA (HCSARIMA) models and use them to empirically model the global horizontal irradiance (GHI) recorded at the earth’s surface. Comparison of the two classes of models shows that HCSARIMA models generally out-compete SARIMA models in the forecasting arena.
The inter-relationships between regulation and competition enforcement in the South African liquid fuels industry
Authors: Nair Reena Das , Mondliwa Pamela , Roberts Simon
Published: June 2019

The competition authorities have devoted considerable time and energy to investigating anticompetitive conduct in the broad area of liquid fuel, gas and related products, where regulation sets rules for firm conduct. Competition cases have included the Sasol-Engen merger, collusive arrangements in gas distribution and the pricing of bitumen for road construction projects, and alleged coordination through information exchange in diesel. Drawing on a review of these matters we assess the inter-relationships between regulation and competition enforcement. We argue that regulation can be designed to enable greater competitive rivalry, while anti-competitive conduct can also be better remedied through recognition of the role of regulation.