The effects of reverse bias on the efficiency of dye solar cells

Philosophiae Doctor - PhDDye-sensitised solar cells (DSC) have attracted much attention during the last few years due to their high efficiencies and their potentially low production costs. The technology is based on a thin layer of nano sized, high band gap (3.2 eV) TiO2 film. A Ru containing dye (from hereon called the Ru dye) is chemisorbed onto the TiO2 film. This combination acts as the working electrode. The counter electrode consists of a platinum layer which is the catalyst for the regeneration of the Iodine/Iodide electrolyte. The work that is presented here is focused on the results that were obtained during studies of the performance of the DSC under certain reverse bias conditions. When one cell in the series connection in a module is shaded, the current will pass this cell in reverse bias. In such a case the shaded cell will be subjected to a voltage in the reverse direction coming from the other lit cells in the module. This reverse voltage could permanently modify or damage the cell if it is not properly protected. Although the work is focussed on the chemical stability of the dye, various techniques were employed to determine the physical changes in the cell. It was found that a cell that was subjected to a reverse bias of 2 V for 500 min showed a 58% recovery and a cell that was subjected to 4.5 V reverse bias was irreversibly damaged. The UV-vis spectra showed a blue shift (higher energy), the Raman showed no peak at 1713 cm-1 (which indicates the absence of free carboxylate groups) and the FT-IR showed the disappearance of the NC-S absorption band at 2100 cm-1. The combined conclusion is that the - NCS ligand has been depleted and replaced with I3- ions. When measuring the impedance, the Nyquist plots showed an increase in the charge transfer resistance at the counter electrode when subjected to a reverse bias potential of 2 V. This is confirmed by the Bode plots. This indicates a partial oxidation of the Pt catalyst on the counter electrode. It can therefore be stated with confidence that the changes in the cell after being subjected to a reverse bias potential of 2 V for 500 min are changes on the -NCS bonds on the Ru dye as well as the Pt in the counter electrode.South Afric

Reduction in air pollution using the ‘basa njengo magogo’ method and the applicability to low-smoke fuels

The then Department of Minerals and Energy (DME) piloted the top-down Basa njengo Magogo alternative fire ignition method at Orange Farm dur-ing the winter of 2003. In total, 76% of households reported less smoke in their homes, while 67%reported less smoke in the streets after one month of using the method (Palmer Development Consulting, 2003). Work by Nova (Schoonraad & Swanepoel, 2003) in eMbalenhle (actual environ-mental tests) indicated up to a 60% reduction in smoke compared with the conventional method of bottom-up ignition. To support the findings of the environmental studies, the CSIR were appointed by the DME to conduct an experiment under con-trolled laboratory conditions to gather quantitative data on the reduction in particulate emissions asso-ciated with the Basa njengo Magogo method of lighting coal fires. The CSIR was further contracted to assess whether the Basa njengo Magogo technol-ogy was viable with low-smoke fuels. The experiment was conducted using traditional D-Grade coal in both the conventional bottom-up and the Basa njengo Magogo ignition techniques. Three low volatile fuels were also assessed using the Basa njengo Magogo method namely: •    Anthracite (volatile content of 10.6%) •    Anthracite (volatile content of 12%) •    Low volatile coal (volatile content of 20.8%), from Slater Coal in Dundee. All four fuels using the Basa njengo Magogo method recorded similar times of between 11 and 13 minutes from ignition to the fires reaching cook-ing temperature. The bottom-up fire for conven-tional D-Grade coal reached cooking temperature after 55 minutes.Particulate emissions from all the Basa njengo Magogo fires were similar and up to 92% lower in particulate emissions than that of the D-Grade coal in the bottom-up fire. SO2 emissions from the two D-Grade coal fires were the lowest and were identical. The highest SO2 emission resulted from the low volatile coal. The method of lighting the fire does not have a significant effect on the SO2 emissions. The Basa njengo Magogo method of ignition uses approximately 1 kg less coal to reach cooking temperature than the traditional bottom–up method. At a cost of approximately R1.00 per kilo-gram of coal, this translates into a cost savings of approximately R30 per month

Reduction in air pollution using the ‘basa njengo magogo’ method and the applicability to low-smoke fuels

The then Department of Minerals and Energy (DME) piloted the top-down Basa njengo Magogo alternative fire ignition method at Orange Farm dur-ing the winter of 2003. In total, 76% of households reported less smoke in their homes, while 67%reported less smoke in the streets after one month of using the method (Palmer Development Consulting, 2003). Work by Nova (Schoonraad & Swanepoel, 2003) in eMbalenhle (actual environ-mental tests) indicated up to a 60% reduction in smoke compared with the conventional method of bottom-up ignition. To support the findings of the environmental studies, the CSIR were appointed by the DME to conduct an experiment under con-trolled laboratory conditions to gather quantitative data on the reduction in particulate emissions asso-ciated with the Basa njengo Magogo method of lighting coal fires. The CSIR was further contracted to assess whether the Basa njengo Magogo technol-ogy was viable with low-smoke fuels.The experiment was conducted using traditional D-Grade coal in both the conventional bottom-up and the Basa njengo Magogo ignition techniques. Three low volatile fuels were also assessed using the Basa njengo Magogo method namely:•    Anthracite (volatile content of 10.6%)•    Anthracite (volatile content of 12%)•    Low volatile coal (volatile content of 20.8%), from Slater Coal in Dundee.All four fuels using the Basa njengo Magogo method recorded similar times of between 11 and 13 minutes from ignition to the fires reaching cook-ing temperature. The bottom-up fire for conven-tional D-Grade coal reached cooking temperature after 55 minutes.Particulate emissions from all the Basa njengo Magogo fires were similar and up to 92% lower in particulate emissions than that of the D-Grade coal in the bottom-up fire. SO2 emissions from the two D-Grade coal fires were the lowest and were identical. The highest SO2 emission resulted from the low volatile coal. The method of lighting the fire does not have a significant effect on the SO2 emissions. The Basa njengo Magogo method of ignition uses approximately 1 kg less coal to reach cooking temperature than the traditional bottom–up method. At a cost of approximately R1.00 per kilo-gram of coal, this translates into a cost savings of approximately R30 per month

Erythritol and xylitol differentially impact brain networks involved in appetite regulation in healthy volunteers

Background: There is a growing consensus that sugar consumption should be reduced and the naturally occurring, low-calorie sweeteners xylitol and erythritol are gaining popularity as substitutes, but their effect on brain circuitry regulating appetite is unknown. Aim: The study’s objective was to examine the effects of the two sweeteners on cerebral blood flow (rCBF) and resting functional connectivity in brain networks involved in appetite regulation, and test whether these effects are related to gut hormone release. Methods: The study was performed as a randomized, double-blind, placebo-controlled, cross-over trial. Twenty volunteers received intragastric (ig) loads of 50g xylitol, 75g erythritol, 75g glucose dissolved in 300mL tap water or 300mL tap water. Resting perfusion and blood oxygenation level-dependent data were acquired to assess rCBF and functional connectivity. Blood samples were collected for determination of CCK, PYY, insulin and glucose. Results: We found: (i) xylitol, but not erythritol, increased rCBF in the hypothalamus, whereas glucose had the opposite effect; (ii) graph analysis of resting functional connectivity revealed a complex pattern of similarities and differences in brain network properties following xylitol, erythritol, and glucose; (iii) erythritol and xylitol induced a rise in CCK and PYY, (iv) erythritol had no and xylitol only minimal effects on glucose and insulin. Conclusion: Xylitol and erythritol have a unique combination of properties: no calories, virtually no effect on glucose and insulin while promoting the release of gut hormones, and impacting appetite-regulating neurocircuitry consisting of both similarities and differences with glucose

Carbon nanotube-enhanced photoelectrochemical properties of metallo-octacarboxyphthalocyanines

The photoelectrochemistry of metallo-octacarboxyphthalocyanines (MOCPc, where M = Zn or Si(OH)2) integrated with MWCNTs for the development of dye-sensitized solar cells (DSSCs) is reported. The DSSC performance (obtained from the photo-chronoamperometric and photo-impedimetric data) decreased as ZnOCPc > (OH)2SiOCPc. The incorporation of the MWCNTs on the surface of the TiO2 film (MOCPc–MWCNT systems) gave higher photocurrent density than the bare MOCPc complexes. Also, from the EIS results, the MOCPc–MWCNT hybrids gave faster charge transport kinetics (approximately three times faster) compared to the bare MOCPc complexes. The electron lifetime was slightly longer (ca. 6 ms) at the ZnOCPc systems than at the (OH)2SiOCPc system (ca. 4 ms) meaning that the presence of the MWCNTs on the surface of the TiO2 film did not show any significant improvement on preventing charge recombination process

3 years of liraglutide versus placebo for type 2 diabetes risk reduction and weight management in individuals with prediabetes: a randomised, double-blind trial

Background: Liraglutide 3·0 mg was shown to reduce bodyweight and improve glucose metabolism after the 56-week period of this trial, one of four trials in the SCALE programme. In the 3-year assessment of the SCALE Obesity and Prediabetes trial we aimed to evaluate the proportion of individuals with prediabetes who were diagnosed with type 2 diabetes. Methods: In this randomised, double-blind, placebo-controlled trial, adults with prediabetes and a body-mass index of at least 30 kg/m2, or at least 27 kg/m2 with comorbidities, were randomised 2:1, using a telephone or web-based system, to once-daily subcutaneous liraglutide 3·0 mg or matched placebo, as an adjunct to a reduced-calorie diet and increased physical activity. Time to diabetes onset by 160 weeks was the primary outcome, evaluated in all randomised treated individuals with at least one post-baseline assessment. The trial was conducted at 191 clinical research sites in 27 countries and is registered with ClinicalTrials.gov, number NCT01272219. Findings: The study ran between June 1, 2011, and March 2, 2015. We randomly assigned 2254 patients to receive liraglutide (n=1505) or placebo (n=749). 1128 (50%) participants completed the study up to week 160, after withdrawal of 714 (47%) participants in the liraglutide group and 412 (55%) participants in the placebo group. By week 160, 26 (2%) of 1472 individuals in the liraglutide group versus 46 (6%) of 738 in the placebo group were diagnosed with diabetes while on treatment. The mean time from randomisation to diagnosis was 99 (SD 47) weeks for the 26 individuals in the liraglutide group versus 87 (47) weeks for the 46 individuals in the placebo group. Taking the different diagnosis frequencies between the treatment groups into account, the time to onset of diabetes over 160 weeks among all randomised individuals was 2·7 times longer with liraglutide than with placebo (95% CI 1·9 to 3·9, p<0·0001), corresponding with a hazard ratio of 0·21 (95% CI 0·13–0·34). Liraglutide induced greater weight loss than placebo at week 160 (–6·1 [SD 7·3] vs −1·9% [6·3]; estimated treatment difference −4·3%, 95% CI −4·9 to −3·7, p<0·0001). Serious adverse events were reported by 227 (15%) of 1501 randomised treated individuals in the liraglutide group versus 96 (13%) of 747 individuals in the placebo group. Interpretation: In this trial, we provide results for 3 years of treatment, with the limitation that withdrawn individuals were not followed up after discontinuation. Liraglutide 3·0 mg might provide health benefits in terms of reduced risk of diabetes in individuals with obesity and prediabetes. Funding: Novo Nordisk, Denmark

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

The occurrence of bleached topsoils on weakly structured subsoil horizons in the Western Cape and Mpumalanga Provinces of South Africa

Thesis (MSc)--Stellenbosch University, 2015.ENGLISH ABSTRACT: Bleaching is a topsoil discolouration phenomenon recognised at family level within certain soil forms in the South African soil classification system. These topsoil horizons derive their name from the pale greyish colouration they exhibit in the dry state which is the result of the loss of pigmentation agents, specifically Fe oxides and organic material, from the upper part of the soil profile. In recent years, discrepancies regarding both the occurrence of bleached topsoils as part of weakly structured soil profiles in the South African soil landscape, and the description of this phenomenon in the national soil classification system, have become apparent. This has accentuated the clear lack of understanding which exists regarding the genesis of bleached topsoil horizons under weakly structured subsoil conditions in South Africa. Based on the land-use and classification significance of this soil feature, this study aimed to provide clarity on the characteristics of bleached topsoils and some of the weakly structured subsoil horizons they overlie to determine by which mechanism these bleached topsoils develop and if the pedogenetic mechanisms are similar across two regions of South Africa. Due to soil colour’s obvious importance as the only feature with which to recognise topsoil bleaching, an investigation into the measurement and expression of soil colour was also deemed to be important. A total of 26 soil profiles were sampled throughout the Western Cape (WC) and Mpumalanga provinces. Colour was visually determined in the field using a Munsell soil colour chart and also by means of a spectrophotometer in the laboratory. A wide variety of soil chemical and physical properties were also determined for each sampled horizon. For comparison’s sake, the selected soil profiles needed to represent profiles that could potentially qualify as having red/yellow-brown apedal B (ferralsols) or red/yellow neocutanic B horizons (cambisols), either with or without a perceived bleached topsoil (achromic). During sampling on the Highveld, bleaching was observed to be landscape related with bleached orthic A horizons only occurring on yellow-brown apedal B subsoil horizons at lower positions along the plinthic catenas. As a result, sampling on the Mpumalanga Highveld was conducted along catenal transects. In the WC, bleached profiles did not follow a noticeable landscape pattern and subsoils comprising both red and yellow weakly structured horizons were recorded. Soil colour investigations proved Fe oxides to be the main pigmentation agents responsible for the expression of red- and yellow colours in the sampled soils, with soil samples also becoming redder with an increase in the Fe oxide content. Discrepancies were detected in the way soil colour was registered through human perception and spectrophotometer measurements. In general, the eye perceived the soils to be brighter and more chromatic and therefore was less sensitive towards detecting bleached horizon colours. The majority of the determined chemical and physical soil properties did not differ between the Western Cape and Highveld soils and did not show any relation to the bleaching phenomenon in either of the locations. In the Western Cape, profiles tended to have a greater water dispersible clay (WDC) phase, with the bleached Western Cape profiles proving to be even more unstable than the non-bleached variants. Iron oxide characterisation indicated proportionally similar amounts of crystalline and poorly-crystalline Fe oxides were present at both locations although in general bleached topsoils tended to have greater poorly-crystalline Fe contents. This trend was more pronounced in the Highveld profiles and was deemed to be indicative of a wetter soil moisture regime and alternating cycles of Fe reduction and oxide precipitation at this location. The reported poorly-crystalline nature of the Fe oxides together with the observed landscape influences, suggest Fe reduction to be the pedogenetic process responsible for bleached topsoil horizons overlying weakly structured subsoils on the Mpumalanga Highveld. The strong association between bleaching and clay dispersibility in similar profiles of the Western Cape suggest clay eluviation to be a common pedogenetic process in these soils. The presented data is this study did not provide an explanation for how clay eluviation results in bleached soil colours and no evidence was obtained to enable conclusive statements regarding the role of Fe reduction and clay eluviation as independent or complementary processes responsible for bleaching in the Western Cape soils. For the purpose of soil classification in South Africa, the inclusion of bleached orthic A horizons as family criteria in wetter variants of the yellow-brown apedal profiles is suggested. Based on the instability of the clay phase in the Western Cape profiles, it is proposed that these red or yellow weakly structured subsoils would be better classified as neocutanic B horizons and that bleached topsoils can in some instances be indicative of a more dispersive profile.AFRIKAANSE OPSOMMING: Verbleiking is ‘n bogrondverskynsel wat erken word op familievlak in die Suid-Afrikaanse grondklassifikasiestelsel. Die benaming van hierdie verskynsel spruit voort uit die vaalgrys kleure wat hierdie bogrondhorisonte openbaar in die droëgrondtoestand, as gevolg van die verlies van grondpigmente soos Fe oksiedes en organiese materiaal uit die boonste gedeeltes van die grondprofiel. ‘n Aantal teenstrydighede aangaande beide die voorkoms van gebleikte bogronde as deel van swak gestruktureerde grondprofiele in Suid-Afrika, sowel as die beskrywing van hierdie verskynsel in die nasionale grondklassifikasiestelsel, het oor die afgelope paar jaar te voorskyn gekom. Hierdie teenstrydighede beklemtoon die beperkte kennis wat daar bestaan aangaande die pedogenetiese oorsprong van gebleikte bogronde op swak gestruktureerde ondergronde in Suid-Afrika. Weens die implikasies van hierdie bogrondverskynsel vir gebruiks- en grondklassifikasie doeleindes, beoog hierdie studie om die eienskappe van gebleikte bogronde en sommige van die swak gestruktureerde ondergronde wat hul oorlê, te bepaal, om sodoende die genetiese oorsprong van hierdie gronde onder sulke toestande te probeer verklaar. As gevolg van grondkleur se belangrikheid as die enigste eienskap wat gebruik kan word om gebleikte bogronde te identifiseer, is aspekte aangaande die meting en uitdrukking van hierdie verskynsel ook as belangrik geag. Altesaam 26 grondprofiele, verspreid oor die Wes-Kaap Provinsie en die Mpumalanga Hoëveld, is versamel. Grondkleur is eers visueel bepaal tydens veldwerk deur gebruik te maak van die Munsell grondkleurkaarte en later ook deur middel van n spektrofotometer in die laboratorium. ‘n Verskeidenheid grondchemiese en –fisiese eienskappe is ook bepaal vir elk van die versamelde horisonte. Die gekose profiele moes van so ‘n aard wees dat beide rooi/geelbruin apedale B of rooi/geel neokutaniese B horisonte ‘n klassifikasiemoontlikheid kon wees. Profiele met en sonder gebleikte bogronde is ingesluit. Tydens die versameling van grondmonsters is dit waargeneem dat verbleiking op die Hoëveld landskap-gedrewe is, met gebleikte ortiese A horisonte wat slegs voorkom op geelbruin apedale ondergronde in die laer hellingsposisies van hierdie landskap. As ‘n gevolg van hierdie waarneming, is grondversameling op die Hoëveld uitgevoer langs katena-transekte af. In die Wes-Kaap was daar geen merkbare verhouding tussen verbleiking en landskapposisie nie en die ondergronde van gebleikte profiele het bestaan uit beide rooi en geel swak gestruktureerde horisonte. Die ondersoeke na grondkleur het bewys dat Fe oksiedes die hoof grondpigment is in die rooi en geel gronde wat versamel is en dat gronde geneig was om rooier te raak soos wat die Fe inhoud van die monster toegeneem het. Verskille ten opsigte van die wyse waarop hierdie uitgedrukte kleure geregistreer word, is tussen die visuele en spektrofotometriese bepalings waargeneem. Oor die algemeen het die oog die grondkleure as helderder en meer chromaties waargeneem en gevolglik was visuele kleurbepaling minder sensitief ten opsigte van gebleikte grondkleure. Die meerderheid van die chemiese en fisiese grondeienskappe wat bepaal is, het nie verskil tussen die Wes-Kaapse en Hoëveld profiele nie en het ook geen verwantskap met verbleiking getoon in enige van die twee areas nie. Die Wes-Kaapse profiele het egter n groter waterdispergeerbare kleifraksie (WDC) getoon, met die gebleikte profiele in die area wat as nog meer onstabiel as die nie-gebleikte variante bewys is. Die grond Fe inhoud in beide die Wes-Kaap en die Hoëveld het proporsioneel dieselfde vlakke van kristallyne en swak-kristallyne Fe oksiedes bevat, met die gebleikte profiele in geheel wat meer swak-kristallyne Fe oksiedes besit het. Hierdie tendens was meer prominent in die Hoëveld bogronde en is toegeskryf aan natter grondtoestande wat variërende fases van Fe reduksie en oksidasie tot gevolg gehad het. Die swak-kristallyne Fe oksiedes tesame met waarnemings in die veld aangaande landskap en grondverhoudings, dui daarop dat Fe reduksie die meganisme is waardeur gebleikte bogronde op swak gestruktureerde ondergronde in die Hoëveld ontstaan. Die sterk verwantskap tussen verbleiking en WDC in soortgelyke profiele in die Wes-Kaap dui daarop dat klei-eluviasie 'n groot rolspeler in hierdie grondprofiele is. Daar kon egter in hierdie studie geen bewyse gevind word wat aandui hoe klei-eluviasie gebleikte grondkleure veroorsaak nie. Verder kon Fe reduksie se bydrae tot verbleiking in die Wes-Kaap gronde nie uitgesluit of vasgestel word nie. Vir grondklassifikasiedoeleindes word daar voorgestel dat gebleikte ortiese A horisonte as n familie-kriterium in die natter weergawes van die geelbruin apedale profiele ingesluit word. Verder, gegrond op die onstabiele klei fraksie in die Wes-Kaap profiele, stel ons voor dat hierdie swak gestruktureerde rooi en geel ondergronde as neokutaniese B horisonte geklassifiseer word en dat in somige gevalle, ‘n gebleikte bogrond ‘n aanduiding kan wees van ‘n meer onstabiele grondprofiel

Microwave-assisted optimization of the manganese redox states for enhanced capacity and capacity retention of LiAlxMn2-xO4 (x = 0 and 0.3) spinel materials

Please read abstract in article.CSIR and the NRFhttp://www.rsc.org/advancesam2017Chemistr