Exploring polymer/nanoparticle hybrid solar cells in tandem architecture

Tandem solar cells offer the possibility to significantly enhance solar cell performance through harvesting a broader part of the solar spectrum by using complementary absorbing materials. We report on tandem solar cells, with at least one polymer/nanoparticle hybrid layer as absorber material, in which the nanoparticles are prepared in situ by thermal decomposition of metal xanthates directly in the polymer matrix. In a first series, we investigated a hybrid-organic tandem solar cell, with a hybrid solar cell consisting of the silafluorene containing low band gap polymer PSiF-DBT and copper indium sulphide (CIS) nanoparticles as the bottom cell, and a low band gap polymer (PTB7)/fullerene derivative (PC61BM) organic solar cell as the top cell in order to study different recombination layers. Tandem devices with open circuit voltages nearly reaching the sum of the individual cells have been realised. The short circuit current is equal to the value of the hybrid single cell and a fill factor above 50% is obtained, leading to power conversion efficiencies of about 4.1%. Furthermore, the first results on hybrid-hybrid tandem solar cells consisting of two PSiF-DBT/CIS solar cells are presented. Although the preparation of these double hybrid devices is challenging because of the necessity of two thermal annealing steps, the resulting multilayer stack reveals smooth and homogeneous layers with sharp interfaces. The first working hybrid-hybrid tandem solar cells still exhibited 81% of the sum of the open circuit voltages of the single junction solar cells. © 2013 The Royal Society of Chemistry

Proteasome Lid Bridges Mitochondrial Stress with Cdc53/Cullin1 NEDDylation Status

Cycles of Cdc53/Cullin1 rubylation (a.k.a NEDDylation) protect ubiquitin-E3 SCF (Skp1-Cullin1-F-box protein) complexes from self-destruction and play an important role in mediating the ubiquitination of key protein substrates involved in cell cycle progression, development, and survival. Cul1 rubylation is balanced by the COP9 signalosome (CSN), a multi-subunit derubylase that shows 1:1 paralogy to the 26 S proteasome lid. The turnover of SCF substrates and their relevance to various diseases is well studied, yet, the extent by which environmental perturbations influence Cul1 rubylation/derubylation cycles per se is still unclear. In this study, we show that the level of cellular oxidation serves as a molecular switch, determining Cullin1 rubylation/derubylation ratio. We describe a mutant of the proteasome lid subunit, Rpn11 that exhibits accumulated levels of Cullin1-Rub1 conjugates, a characteristic phenotype of csn mutants. By dissecting between distinct phenotypes of rpn11 mutants, proteasome and mitochondria dysfunction, we were able to recognize the high reactive oxygen species (ROS) production during the transition of cells into mitochondrial respiration, as a checkpoint of Cullin1 rubylation in a reversible manner. Thus, the study adds the rubylation cascade to the list of cellular pathways regulated by redox homeostasis

Differential localization of LTA synthesis proteins and their interaction with the cell division machinery in Staphylococcus aureus

Lipoteichoic acid (LTA) is an important cell wall component of Gram-positive bacteria. In Staphylococcus aureus it consists of a polyglycerolphosphate-chain that is retained within the membrane via a glycolipid. Using an immunofluorescence approach, we show here that the LTA polymer is not surface exposed in S. aureus, as it can only be detected after digestion of the peptidoglycan layer. S. aureus mutants lacking LTA are enlarged and show aberrant positioning of septa, suggesting a link between LTA synthesis and the cell division process. Using a bacterial two-hybrid approach, we show that the three key LTA synthesis proteins, YpfP and LtaA, involved in glycolipid production, and LtaS, required for LTA backbone synthesis, interact with one another. All three proteins also interacted with numerous cell division and peptidoglycan synthesis proteins, suggesting the formation of a multi-enzyme complex and providing further evidence for the co-ordination of these processes. When assessed by fluorescence microscopy, YpfP and LtaA fluorescent protein fusions localized to the membrane while the LtaS enzyme accumulated at the cell division site. These data support a model whereby LTA backbone synthesis proceeds in S. aureus at the division site in co-ordination with cell division, while glycolipid synthesis takes place throughout the membrane

Flexibilisierung der Arbeitsentgelte und Beschäftigungseffekte : Ergebnisse einer Unternehmensbefragung

Anhaltend hohe Arbeitslosenzahlen in Deutschland werden immer wieder auch auf eine zu rigide Entgeltstruktur zurückgeführt. Diese Inflexibilität habe ihre Ursache in einem (zu) stark regulierten Arbeitsmarkt. Das deutsche Arbeitsrecht lasse Flexibilisierungen im Entgelt-bereich nicht (oder zumindest nicht hinreichend) zu. Obwohl diese Thesen von Wirtschafts-politikern und Ökonomen vertreten werden, fehlt es bislang an einer umfassenden theoretischen Aufarbeitung und empirischen Überprüfung. Die in dieser Studie vorgestellten Befragungsergebnisse liefern erstmals repräsentative Daten für rund 38v.H. aller privaten Unternehmen über deren Entgeltsysteme - politik. Damit schließt die Studie eine Forschungslücke zwischen Einzelfallstudien zur Entgeltfindung in den Unternehmen und sektoralen und gesamtwirtschaftlichen Analysen zum Zusammenhang zwischen Entgeltstrukturen und Beschäftigung. An der Umfrage haben sich 801 Unternehmen aus dem Industrie- und Dienstleistungsbereich sowie aus dem in den letzten Jahren stark wachsenden Bereich der unternehmensnahen Dienstleistungen beteiligt. Die Studie verdeutlicht das Zusammenwirken rechtlicher und ökonomischer Faktoren bei der Entgeltfindung. Hält man das Entgeltniveau in Deutschland für zu hoch, so legen die Ergebnisse die Vermutung nahe, dass vollbeschäftigungskonformere Entgeltrelationen - etwa durch eine Verlagerung der Entgeltfindung auf die betriebliche Ebene - nicht so ohne weiteres erreicht werden können. Denn Entgeltstarrheiten lassen sich nur zum Teil auf rechtliche Restriktionen zurückführen. Inflexibilitäten im Entgeltbereich haben auch ökonomische Gründe, die in der Rationalität von Arbeitgeber-Arbeitnehmer-Beziehungen liegen, wobei die Umfrageergebnisse auf verstärkte Anstrengungen zur Flexibilisierung der Entgelte in den Unternehmen hindeuten. Eine Bestandsaufnahme bestehender Vergütungssysteme zeigt, dass in den fünf untersuchten Branchen (Chemie, Metall-/Elektroindustrie/Maschinenbau, Handel, Banken und Versicherungen, unternehmensnahe Dienstleister) nur rund 39v.H. der Unternehmen Tarifverträge überhaupt anwenden. Das könnte den Weg für eine experimentelle Entgeltpolitik auf Unternehmensebene frei machen, doch wird der Tarifvertrag um so öfter angewandt, je größer die Belegschaft der einzelnen Unternehmen ist. Insgesamt arbeiten daher ca. 77v.H. aller Beschäftigten in Unternehmen, die Tarifverträge anwenden. Für die Gruppe der gering qualifizierten Arbeitnehmer stellten Tarifverträge und implizite Kontrakte wesentliche Flexibilisierungshemmnisse dar; für hochqualifizierte Arbeitnehmer stehen Personalbeschaffungs- und Einarbeitungskosten sowie betriebsspezifisches Humankapital im Vordergrund. Unternehmen scheinen auch deshalb von Entgeltsenkungen abzusehen, weil dadurch die Gefahr zunimmt, dass die jeweils besten Arbeitnehmer einer jeden Qualifikationsgruppe abwandern und dies negative Signale für die Anwerbung neuer Mitarbeiter bedeutet

Evidence of a high incidence of subclinically affected calves in a herd of cattle with fatal cases of Bovine Neonatal Pancytopenia (BNP).

BACKGROUND: Bovine Neonatal Pancytopenia (BNP) is a disease of calves characterised by bone marrow trilineage hypoplasia, mediated by ingestion of alloantibodies in colostrum. Suspected subclinical forms of BNP have been reported, suggesting that observed clinical cases may not represent the full extent of the disease. However to date there are no objective data available on the incidence of subclinical disease or its temporal distribution. This study aimed to 1) ascertain whether subclinical BNP occurs and, if so, to determine the incidence on an affected farm and 2) determine whether there is evidence of temporal clustering of BNP cases on this farm. To achieve these aims, haematological screening of calves born on the farm during one calving season was carried out, utilising blood samples collected at defined ages. These data were then analysed in comparison to data from both known BNP-free control animals and histopathologically confirmed BNP cases. An ordinal logistic regression model was used to create a composite haematology score to predict the probabilities of calves being normal, based on their haematology measurements at 10–14 days old. RESULTS: This study revealed that 15% (21 of 139) of the clinically normal calves on this farm had profoundly abnormal haematology (<5% chance of being normal) and could be defined as affected by subclinical BNP. Together with clinical BNP cases, this gave the study farm a BNP incidence of 18%. Calves with BNP were found to be distributed throughout the calving period, with no clustering, and no significant differences in the date of birth of cases or subclinical cases were found compared to the rest of the calves. This study did not find any evidence of increased mortality or increased time from birth to sale in subclinical BNP calves but, as the study only involved a single farm and adverse effects may be determined by other inter-current diseases it remains possible that subclinical BNP has a detrimental impact on the health and productivity of calves under certain circumstances. CONCLUSIONS: Subclinical BNP was found to occur at a high incidence in a herd of cattle with fatal cases of BNP