Electronic properties and gap state defect passivation of Si SiO2 nanostructures

Bandgap control of silicon based material provides a promising way towards next generation photovoltaic devices such as tandem solar cells, what can be realized by nanostructures consisting of Si SiO2 quantum wells or superlattices. However, due to increased interface to volume ratios at reduced dimensions, charge carrier recombination and scattering at Si SiO2 interfaces might dominate the photoelectrical properties and gain critical impact on mobility lifetime products amp; 956; amp; 964; and thus internal quantum efficiencies [1]. To circumvent this drawback, the effect of hydrogen treatment on charge carrier recombination and electronic densities of states at the interface of ultrathin oxides layers is analyzed. Samples with structurally and chemically well defined interfaces were prepared by plasma oxidation of crystalline Si with atomic oxygen under ultrahigh vacuum conditions [2]. It is demonstrated, that Si SiO2 interface states can be passivated under appropriate conditions in forming gas H2 N2 and in hydrogen plasma. As a result, the photoelectrical performance of such structures is clearly improved. This is verified by i estimation of mobility lifetime products from photocurrent measurements, ii analysis of interface densities of states by means of surface photovoltage measurements SPV , and iii deducing densities of occupied states in the band gap as elucidated from UV excited constant final state yield spectroscopy CFSYS

Subsequent layer growth of supported nanoparticles by deposition of Sb4 clusters onto MoS2(0001)

The surface morphology after deposition of Sb4 clusters onto MoS2(0001) at 90 K has been studied in detail with scanning tunnelling microscopy in ultrahigh vacuum. It has been found that during the initial stage of growth two-dimensional nanoparticles are formed. With increasing coverage these nanoparticles grow layer by layer and each layer has the height of one monolayer of undissociated Sb4 clusters. The interface width (surface roughness) has been quantitatively determined as a function of total coverage. Ideal three-dimensional layer-by-layer growth has been identified for the single particles according to a Poisson distribution of exposed areas of the layers of the particles. Consequently, antimony grows on MoS2(0001) without interlayer diffusion which is suppressed by an effective step edge (Schwoebel-Ehrlich) barrier.Peer Reviewe

Comparison of environmental impacts of individual meals - Does it really make a difference to choose plant-based meals instead of meat-based ones?

More than one third of global greenhouse gas emissions (GHG) can be attributed to our food system. Limiting global warming to 1.5° or 2 °C will not be possible without reducing GHG emissions from the food system. Dietary change at the meal level is of great importance as day-to-day consumption patterns drive the global food production system. The aim of this paper was to assess the life cycle environmental impact of a sample of meals from different cuisines (chilli, lasagne, curry and teriyaki meals) and their meat-based, vegetarian, vegan, and whole-food vegan recipe variations. The environmental impacts (global warming, freshwater eutrophication, terrestrial acidification and water depletion potential) of 13 meals, made with 33 different ingredients, were estimated from cradle to plate using Life Cycle Assessment (LCA). Results showed that irrespective of the type of cuisine, the plant-based version of meals (vegan and whole-food vegan) had substantially lower environmental impacts across all impact categories than their vegetarian and meat-based versions. On average, meat-based meals had 14 times higher environmental impact, while vegetarian meals had 3 times higher environmental impact than vegan meals. Substantial reductions in the environmental impacts of meals can be achieved when animal-based ingredients (e.g., beef, cheese, pork, chicken) are replaced with whole or minimally processed plant-based ingredients (i.e., vegetables, legumes) in recipes. Swapping animal-based meals for plant-based versions, and preferably transitioning to plant-based diets, present important opportunities for mitigating climate change and safeguarding environmental sustainability

Phase entrainment of induced ventricular fibrillation: A human feasibility and proof of concept study

Cardioversion and defibrillation by a single high energy shock applied by myocardial or body surface electrodes is painful, causes long term tissue damage, and is associated with worsening long term outcomes, but is almost always required for treatment of ventricular fibrillation . As a initial step towards developing methods that can terminate ventricular arrhythmias painlessly, we aim to determine if pacing stimuli at a rate of 5/s applied via an implantable cardiac defibrillator (ICD) can modify human ventricular fibrillation. In 8 patients undergoing defibrillation testing of a new/exchanged intracardiac defibrillator, five seconds of pacing at five stimuli per second was applied during the 10-20 seconds of induced ventricular fibrillation before the defibrillation shock was automatically applied, and the cardiac electrograms recorded and analyzed. The high frequency pacing did not entrain the ventricular fibrillation, but altered the dominant frequency in all 8 patients, and modulated the phase computed via the Hilbert Transform, in four of the patients. In this pilot study we demonstrate that high frequency pacing applied via ICD electrodes during VF can alter the dominant frequency and modulate the probability density of the phase of the electrogram of the ventricular fibrillation

Interdigitated back contact silicon heterojunction solar cells Towards an industrially applicable structuring method

We report on the investigation and comparison of two different processing approaches for interdigitated back contacted silicon heterojunction solar cells our photolithography based reference procedure and our newly developed shadow mask process. To this end, we analyse fill factor losses in different stages of the fabrication process. We find that although comparably high minority carrier lifetimes of about 4 ms can be observed for both concepts, the shadow masked solar cells suffer yet from poorly passivated emitter regions and significantly higher series resistance. Approaches for addressing the observed issues are outlined and first solar cell results with efficiencies of about 17 and 23 for shadow masked and photolithographically structured solar cells, respectively, are presente

Modulation of Allergic Sensitization and Allergic Inflammation by Staphylococcus aureus Enterotoxin B in an Ovalbumin Mouse Model

The superantigen Staphylococcus aureus (S. aureus) enterotoxin B (SEB) has been proposed a central player in the associations between S. aureus nasal colonization and the development of allergic asthma. Previously, SEB has been shown to aggravate allergic sensitization and allergic airway inflammation (AAI) in experimental mouse models. Aiming at understanding the underlying immunological mechanisms, we tested the hypothesis that intranasal (i.n.) SEB-treatment divergently modulates AAI depending on the timing and intensity of the SEB-encounter. In an ovalbumin-mediated mouse model of AAI, we treated mice i.n. with 50 ng or 500 ng SEB either together with the allergic challenge or prior to the peripheral sensitization. We observed SEB to affect different hallmark parameters of AAI depending on the timing and the dose of treatment. SEB administered i.n. together with the allergic challenge significantly modulated respiratory leukocyte accumulation, intensified lymphocyte activation and, at the higher dose, induced a strong type-1 and pro-inflammatory cytokine response and alleviated airway hyperreactivity in AAI. SEB administered i.n. prior to the allergic sensitization at the lower dose significantly boosted the specific IgE response while administration of the higher dose led to a significantly reduced recruitment of immune cells, including eosinophils, to the respiratory tract and to a significantly dampened Th-2 cytokine response without inducing a Th-1 or pro-inflammatory response. We show a remarkably versatile potential for SEB to either aggravate or alleviate different parameters of allergic sensitization and AAI. Our study thereby not only highlights the complexity of the associations between S. aureus and allergic asthma but possibly even points at prophylactic and therapeutic pathways

Nonuniform friction-area dependency for antimony oxide surfaces sliding on graphite

Cataloged from PDF version of article.We present frictional measurements involving controlled lateral manipulation of antimony nanoparticles on graphite featuring atomically smooth particle-substrate interfaces via tapping- and contact-mode atomic force microscopy. As expected from earlier studies, the power required for lateral manipulation as well as the frictional forces recorded during the manipulation events exhibit a linear dependence on the contact area over a wide size range from 2000 nm2 to 120 000 nm2. However, we observe a significant and abrupt increase in frictional force and dissipated power per contact area at a value of about 20 000 nm2, coinciding with a phase transition from amorphous to crystalline within the antimony particles. Our results suggest that variations in the structural arrangement and stoichiometry of antimony oxide at the interface between the particles and the substrate may be responsible for the observed effect. © 2013 American Physical Society

Influence of chlorine on the fate of Pb and Cu during clinkerization

The fate of heavy metals during clinkerization is of crucial significance to the utilization of solid waste as fuels and raw materials in cement kiln producing clinker. A ternary system of clinker-heavy metal-chlorine was developed that is more coincident with the condition of co-processing of solid waste in cement kiln. The main goal of this study was to investigate the relationships among chlorine, volatilization and solidification of Cu/Pb, and mineral phases of the clinker during clinkirization. The AlCl3·6H2O (chlorine source) and PbO/CuO were mixed with cement raw meal in appropriate ratios to produce co-processed clinkers. The volatilization and solidification of Pb and Cu were investigated experimentally using a combination of atomic absorption spectrometry, electron probe micro-analysis, scanning electron microscopy with energy-dispersive X-ray spectroscopy, optical microscope, thermogravimetric and X-ray diffraction quantitative analyses. The volatilization ratios of Pb and Cu increased up to 46.18% and 34.04%, respectively, with increasing AlCl3·6H2O content up to 1.6%. comparing to the cement mixtures without AlCl3·6H2O addition (Pb and Cu volatilisation ratios are 49.90% and 27.21%, respectively). Pb and Cu oxides can be transformed into Pb and Cu chlorides, that are not stable and have high vapor pressure. Pb and Cu are mainly concentrated in the interstitial phases of the clinker. The addition of AlCl3·6H2O led to increase the crystal size of alite and belite. X-ray diffraction quantitative analyses proved that the content of silicate phase increased with the corresponding content of interstitial phases decreased during clinkerization with the addition of AlCl3·6H2O, that decreased the ability of clinker to solidify Pb and Cu in the produced clinkers. This research can help to promote understanding of the fate of heavy metals during the cement kiln co-processing of solid wastes and meaningfully for energy conservation and sustainable development