Effects of ion beam hydrogenation on silicon solar cell structures

A Kaufman ion source was used to hydrogenate polycrystalline silicon structures at energies from 250 to 5000 eV. This results in improvements in photovoltaic properties and in shorter hydrogenation times than have been reported by other groups using arc or plasma discharges. Single-crystal silicon samples exposed to similar hydrogenation conditions were evaluated using scanning electron microscopy, IR spectroscopy, reflectometry and ellipsometry. The thickness and other characteristics of this modified surface region vary as a function of the ion energy and the dose rate. The properties of this surface region may influence the choice of subsequent antireflective coatings that are used to provide optimum performance of these devices.     

Imaging of metal-coated biological samples by scanning tunneling microscopy

A method for imaging biological samples by scanning tunneling microscopy (STM) is presented. There are two main difficulties in imaging biological samples by STM: (1) the low conductivity of biological material and (2) finding a method of reliably depositing the sample on a flat conducting surface. The first of these difficulties was solved by coating the samples with a thin film of platinum-carbon. The deposition problem was solved by a method similar to a procedure used to deposit biological molecules onto field ion microscope (FIM) tips. STM images of bacteriophage T7 and filamentous phage fd are shown. The substrate on which the samples were absorbed was atomically flat gold. The images do not show molecular detail due to the metal coating, but the gross dimensions and morphology are correct for each type of virus. Also, the surface density of virus particles increases and decreases in the way expected when the conditions of deposition are changed. These methods allow reliable and reproducible STM imaging of biological samples.     

EPR‐Messungen in warmgehenden Anlagen

EPR measurements in heat‐working plants This paper reports about experiences of sensitization behaviour of titanium and niob stabilized steels under practice conditions at operating temperature between 340 and 600°C. Pipes, flanges, welds including heat‐affected zones are examined for sensitization with help of the e lectrochemical‐p otentiodynamic‐r eactivation‐method. Measurements were carried out on‐site during plant stoppage at different pipes with diameter between 150 to 460 mm with a set‐up measuring cell.     

Point-projection imaging of macromolecular contours

A point-projection microscope is described which uses an electric field of several volts per nanometre to generate ions from a layer of benzene condensed in high vacuum on to the apex of a cryogenically cooled field-emitter tip. Clusters of ferritin (a spherical protein molecule) embedded in the layer, have been imaged by exposing their contours during controlled field-desorption. Image contrast is high. A magnification of 2 times 10⁵ has been achieved at a spatial resolution estimated to be better than 3 nm. Three-dimensional reconstructions of cluster morphology from a series of molecular contours are in qualitative agreement with transmission-electron micrographs of the ferritin covered emitter apex. Reproducibility of the cluster contours, and TEM images of the apex before and after imaging suggest that the imaging procedure is nondestructive.     

Genome-wide association study using high-density single nucleotide polymorphism arrays and whole-genome sequences for clinical mastitis traits in dairy cattle

Mastitis is a mammary disease that frequently affects dairy cattle. Despite considerable research on the development of effective prevention and treatment strategies, mastitis continues to be a significant issue in bovine veterinary medicine. To identify major genes that affect mastitis in dairy cattle, 6 chromosomal regions on Bos taurus autosome (BTA) 6, 13, 16, 19, and 20 were selected from a genome scan for 9 mastitis phenotypes using imputed high-density single nucleotide polymorphism arrays. Association analyses using sequence-level variants for the 6 targeted regions were carried out to map causal variants using whole-genome sequence data from 3 breeds. The quantitative trait loci (QTL) discovery population comprised 4,992 progeny-tested Holstein bulls, and QTL were confirmed in 4,442 Nordic Red and 1,126 Jersey cattle. The targeted regions were imputed to the sequence level. The highest association signal for clinical mastitis was observed on BTA 6 at 88.97 Mb in Holstein cattle and was confirmed in Nordic Red cattle. The peak association region on BTA 6 contained 2 genes: vitamin D-binding protein precursor (GC) and neuropeptide FF receptor 2 (NPFFR2), which, based on known biological functions, are good candidates for affecting mastitis. However, strong linkage disequilibrium in this region prevented conclusive determination of the causal gene. A different QTL on BTA 6 located at 88.32 Mb in Holstein cattle affected mastitis. In addition, QTL on BTA 13 and 19 were confirmed to segregate in Nordic Red cattle and QTL on BTA 16 and 20 were confirmed in Jersey cattle. Although several candidate genes were identified in these targeted regions, it was not possible to identify a gene or polymorphism as the causal factor for any of these regions.     

ELECTROPHORETIC COATINGS FOR ADVANCED MATERIALS

We have electrophoretically deposited a variety of coatings for a number of applications. We have also worked extensively with a process for electrophoretically depositing styrene acrylate polymer coatings. These coatings provide useful corrosion protection and dielectric properties for capacitors and electrical insulation. Dielectric breakdown strengths in the order of 1000 V/micrometer have been observed for capacitors with this coating as the dielectric. Various particles have also been dispersed in the electrolyte; these mixtures yield composite coatings of unusual materials such as fissile uranium in a carbon matrix. The process can also be adapted to form very thin, free-standing styrene acrylate films or pellicles. We have also explored the feasibility of depositing a variety of colloidal inorganic particles from liquid suspensions. Our results show that isopropanol works relatively well as a dispersing medium for a large number of powders. Isopropanol slurries can be used to deposit a number of uniform ceramic or glass coatings on metal substrates. Important coating considerations with regard to whether useful coatings can be deposited using this latter type of electrophoretic process include: (1) the average size, size distribution, and shape of the particles, (2) the charge assumed by the powder particles when they are dispersed in a liquid such as isopropanol, and (3) the coefficients of thermal expansion of the substrate and the coating material from the standpoint of the heat treatment or sintering required to obtain sufficient cohesion and adhesion.     

Osteogenic Potential of Mesenchymal Stem Cells from Adipose Tissue,Bone Marrow and Hair Follicle Outer Root Sheath in a 3D Crosslinked Gelatin-Based Hydrogel

Bone transplantation is regarded as the preferred therapy to treat a variety of bone defects. Autologous bone tissue is often lacking at the source, and the mesenchymal stem cells (MSCs) responsible for bone repair mechanisms are extracted by invasive procedures. This study explores the potential of autologous mesenchymal stem cells derived from the hair follicle outer root sheath (MSCORS). We demonstrated that MSCORS have a remarkable capacity to differentiate in vitro towards the osteogenic lineage. Indeed, when combined with a novel gelatin-based hydrogel called Osteogel, they provided additional osteoinductive cues in vitro that may pave the way for future application in bone regeneration. MSCORS were also compared to MSCs from adipose tissue (ADMSC) and bone marrow (BMMSC) in a 3D Osteogel model. We analyzed gel plasticity, cell phenotype, cell viability, and differentiation capacity towards the osteogenic lineage by measuring alkaline phosphatase (ALP) activity, calcium deposition, and specific gene expression. The novel injectable hydrogel filled an irregularly shaped lesion in a porcine wound model displaying high plasticity. MSCORS in Osteogel showed a higher osteo-commitment in terms of calcium deposition and expression dynamics of OCN, BMP2, and PPARG when compared to ADMSC and BMMSC, whilst displaying comparable cell viability and ALP activity. In conclusion, autologous MSCORS combined with our novel gelatin-based hydrogel displayed a high capacity for differentiation towards the osteogenic lineage and are acquired by non-invasive procedures, therefore qualifying as a suitable and expandable novel approach in the field of bone regeneration therapy.     

The behaviour of graphite, carbon black, and Li4Ti5O12 in LiBOB-based electrolytes

The film formation behaviour of lithium bis(oxalato)borate (LiBOB), a new electrolyte salt for lithium batteries, on graphite, carbon black and lithium titanate is reported. LiBOB is actively involved in the formation of the solid electrolyte interphase (SEI) at the anode. Part of this formation is an irreversible reductive reaction which takes place at potentials of around 1.75 V vs Li/Li⁺ and contributes to the irreversible capacity of anode materials in the first cycle. Carbon black interacts strongly with LiBOB-based electrolytes, which results in strong film formation and loss of electronic conductivity within the composite electrode. In LiBOB-based electrolytes the electrode kinetics increase in the order: carbon black << fine particulate graphite ~ metal powder, due to decreased film formation of the conductive additive. The influence of various solvents, surfactant additives, and potential impurities was also studied.