Making Record-efficiency SnS Solar Cells by Thermal Evaporation and Atomic Layer Deposition

Tin sulfide (SnS) is a candidate absorber material for Earth-abundant, non-toxic solar cells. SnS offers easy phase control and rapid growth by congruent thermal evaporation, and it absorbs visible light strongly. However, for a long time the record power conversion efficiency of SnS solar cells remained below 2%. Recently we demonstrated new certified record efficiencies of 4.36% using SnS deposited by atomic layer deposition, and 3.88% using thermal evaporation. Here the fabrication procedure for these record solar cells is described, and the statistical distribution of the fabrication process is reported. The standard deviation of efficiency measured on a single substrate is typically over 0.5%. All steps including substrate selection and cleaning, Mo sputtering for the rear contact (cathode), SnS deposition, annealing, surface passivation, Zn(O,S) buffer layer selection and deposition, transparent conductor (anode) deposition, and metallization are described. On each substrate we fabricate 11 individual devices, each with active area 0.25 cm². Further, a system for high throughput measurements of current-voltage curves under simulated solar light, and external quantum efficiency measurement with variable light bias is described. With this system we are able to measure full data sets on all 11 devices in an automated manner and in minimal time. These results illustrate the value of studying large sample sets, rather than focusing narrowly on the highest performing devices. Large data sets help us to distinguish and remedy individual loss mechanisms affecting our devices.     

HEPNet: A Knowledge Base Model of Human Energy Pool Network for Predicting the Energy Availability Status of an Individual

HEPNet is an electronic representation of metabolic reactions occurring within human cellular organization focusing on inflow and outflow of the energy currency ATP, GTP and other energy associated moieties. The backbone of HEPNet consists of primary bio-molecules such as carbohydrates, proteins and fats which ultimately constitute the chief source for the synthesis and obliteration of energy currencies in a cell. A series of biochemical pathways and reactions constituting the catabolism and anabolism of various metabolites are portrayed through cellular compartmentalization. The depicted pathways function synchronously toward an overarching goal of producing ATP and other energy associated moieties to bring into play a variety of cellular functions. HEPNet is manually curated with raw data from experiments and is also connected to KEGG and Reactome databases. This model has been validated by simulating it with physiological states like fasting, starvation, exercise and disease conditions like glycaemia, uremia and dihydrolipoamide dehydrogenase deficiency (DLDD). The results clearly indicate that ATP is the master regulator under different metabolic conditions and physiological states. The results also highlight that energy currencies play a minor role. However, the moiety creatine phosphate has a unique character, since it is a ready-made source of phosphoryl groups for the rapid synthesis of ATP from ADP. HEPNet provides a framework for further expanding the network diverse age groups of both the sexes, followed by the understanding of energetics in more complex metabolic pathways that are related to human disorders.     

Induction of suicidal erythrocyte death by listeriolysin from Listeria monocytogenes.

Listeriolysin, the secreted cytolysin of the facultative intracellular bacterium Listeria monocytogenes, is its major virulence factor. Previously, non-lytic concentrations of listeriolysin were shown to induce Ca2+-permeable nonselective cation channels in human embryonic kidney cells. In erythrocytes, Ca2+ entry is followed by activation of K+ channels resulting in K+-exit as well as by membrane scrambling resulting in phosphatidylserine exposure at the cell surface. Phosphatidylserine-exposing erythrocytes are recognized by macrophages, engulfed, degraded and thus cleared from circulating blood. Phosphatidylserine exposure is a key event of eryptosis, the suicidal death of erythrocytes. The present study utilized patch-clamp technique, Fluo3-fluorescence, and annexin V-binding in FACS analysis to determine the effect of listeriolysin on cell membrane conductance, cytosolic free Ca2+ concentration, and phosphatidylserine exposure, respectively. Within 30 minutes, exposure of human peripheral blood erythrocytes to low concentrations of listeriolysin (which were non-hemolytic for the majority of cells) induced a Ca2+-permeable cation conductance in the erythrocyte cell membrane, increased cytosolic Ca2+ concentration, and triggered annexin V-binding. Increase of extracellular K+ concentration blunted, but did not prevent, listeriolysin-induced annexin V-binding. In conclusion, listeriolysin triggers suicidal death of erythrocytes, an effect at least partially due to depletion of intracellular K+. Listeriolysin induced suicidal erythrocyte death could well contribute to the pathophysiology of L. monocytogenes infection.     

Serological detection and immunogold localization of cross-reactive antigens shared by Camellia sinensis and Exobasidium vexans

AIMS: Pathogenicity of Exobasidium vexans, causal agent of blister blight of tea, was studied in 30 commercially cultivated tea varieties by analysing the antigenic patterns of host and pathogen using immunological techniques. METHODS AND RESULTS: Whole plant inoculation of tea varieties with E. vexans showed that T-78 and T-17/1/54 were most susceptible and most resistant respectively. Antigen preparations from tea varieties, pathogen, nonpathogen (Fusarium oxysporum) and of nonhosts (Glycine max, Leucaena leucocephala and Oryza sativa) were compared by indirect enzyme-linked immunosorbent assay and dot-immunobinding assay using polyclonal antibodies raised against the pathogen, nonpathogen, susceptible and resistant tea varieties. Cross-reactive antigens (CRA) were found among susceptible varieties and E. vexans isolates but not in resistant varieties, nonhosts or nonpathogen. Indirect staining of antibodies using fluorescein isothiocyanate indicated CRA were concentrated mainly around epidermal and mesophyll cells in compatible host (T-78). This was substantiated by ultrastructural studies using gold-labelled antibodies through transmission electron microscopy which showed specific localization in the chloroplasts and host cytoplasm. CONCLUSION: Pathogenicity of E. vexans to different tea varieties is therefore related to the level of antigenic similarity between host and pathogen. SIGNIFICANCE AND IMPACT OF THE STUDY: Immunological methods proved to be valuable in screening commercially cultivated tea varieties against E. vexans.     

GECO--linear visualization for comparative genomics

In order to understand and interpret phylogenetic and functional relationships between multiple prokaryotic species, qualitative and quantitative data must be correlated and displayed. GECO allows linear visualization of multiple genomes using a client/server based approach by dynamically creating .png- or .pdf-formatted images. It is able to display ortholog relations calculated using BLASTCLUST by color coding ortholog representations. Irregularities on the genomic level can be identified by anomalous G/C composition. Thus, this software will enable researchers to detect horizontally transferred genes, pseudogenes and insertions/deletions in related microbial genomes. AVAILABILITY: http://bioinfo.mikrobio.med.uni-giessen.de/geco2/GecoMainServlet     

Passage through alternative hosts changes the fitness of Fusarium graminearum and Fusarium pseudograminearum

Species of the necrotrophic fungal pathogen Fusarium that cause head blight and crown rot of cereals including wheat also infect a number of alternative host plants. This raises the prospect of more damaging pathogen strains originating and persisting as highly successful saprophytes on hosts other than wheat. The immediate impact on pathogenic (aggressiveness) and saprophytic (growth rate and fecundity) behaviour of six isolates with low, moderate or high initial aggressiveness was examined in two species of Fusarium after their passage through 10 alternative plant hosts. One passage through alternative hosts significantly reduced the pathogenic fitness of most isolates, but this change was not associated with a concomitant change in their overall saprophytic behaviour. The overall weak association between aggressiveness, fecundity and growth rate both before and after passage through the alternative hosts indicate that pathogenic and saprophytic fitness traits may be independently controlled in both Fusarium species. Thus, there was no trade-off between pathogenic and saprophytic fitness in these necrotrophic plant pathogens.     

Sintering of wax for controlling release from pellets

The purpose of the present study was to investigate incorporation of hydrophobic (ie, waxy) material into pellets using a thermal sintering technique and to evaluate the pellets in vitro for controlled release. Pellets prepared by extrusion-spheronization technology were formulated with a water-soluble drug, microcrystalline cellulose, and carnauba wax. Powdered carnauba wax (4%–20%) prepared by grinding or by emulsification was studied with an attempt to retard the drug release. The inclusion of ground or emulsified carnauba wax did not sustain the release of theophylline for more than 3 hours. Matrix pellets of theophylline prepared with various concentrations of carnauba wax were sintered thermally at various times and temperatures. In vitro drug release profiles indicated an increase in drug release retardation with increasing carnauba wax concentration. Pellets prepared with ground wax showed a higher standard deviation than did those prepared with emulsified wax. There was incomplete release at the end of 12 hours for pellets prepared with 20% ground or emulsified wax. The sintering temperature and duration were optimized to allow for a sustained release lasting at least 12 hours. The optimized temperature and duration were found to be 100° and 140 seconds, respectively. The sintered pellets had a higher hydrophobicity than did the unsintered pellets. Scanning electron micrographs indicated that the carnauba wax moved internally, thereby increasing the surface area of wax within the pellets. Published: September 14, 2007     

Interaction of piroxicam with mitochondrial membrane and cytochrome c

Modulation of surface properties of biomembranes by any ligand leading to permeabilization, fusion, rupture, etc. is a fundamental requirement for many biological processes. In this work, we present the interaction of piroxicam, a long acting Non-Steroidal Anti-Inflammatory Drug (NSAID) with isolated mitochondria, membrane mimetic systems, intact cells and a mitochondrial protein cytochrome c. Dye permeabilization study on isolated mitochondria indicates that piroxicam can permeabilize mitochondrial membrane. Direct imaging by Scanning Electron Microscope (SEM) shows that piroxicam induces changes in mitochondrial membrane morphology leading to fusion and rupture. Transmission Electron Microscope (TEM) imaging of piroxicam treated DMPC vesicles and mixed micelles formed from CTAB and SDS show that causing membrane fusion is a general property of piroxicam at physiological pH. In intact cells viz., V79 Chinese Hamster lung fibroblast, piroxicam is capable of releasing cytochrome c from mitochondria into the cytosol in a dose dependent manner along with the enhancement of downstream proapoptotic event viz., increase in caspase-3 activity. We have also shown that piroxicam can reduce cytochrome c within a time frame relevant to its lifetime in blood plasma. UV-visible spectroscopy has been used to study the reaction mechanism and kinetics in detail, allowing us to propose and validate a Michaelis-Menten like reaction scheme. CD spectroscopy shows that small but significant changes occur in the structure of cytochrome c when reduced by piroxicam.