Mögliche Beteiligung von krebserzeugenden Arbeitsstoffen an der Entstehung von Nasenkrebs bei Beschäftigten im holzverarbeitenden Gewerbe

Hexavalent chromium compounds (chromates) were the most common ingredients in stains used in furnituremaking during the first half of the century. Detailed instructions of historic handbooks indicate that especially craftsmen in small joinery/furniture shops were exposed regularly to chromate or highly chromate-contaminated wood dust while brushing of crystalline stain residues from dried wood surfaces. In the literature, chromates are reported to cause malignant tumors of the respiratory system, including nasal adenocarcinoma. Unlike exposures to wood dust itself, combined exposures to highly chromate-contaminated wood dust are supposed to be a specific cancerogenic factor for members of the riskgroup and may explain the incidence of the disease confined to this occupational environment.     

The Effects of Marination and Cooking Regimes on the Waterbinding Properties and Tenderness of Beef and Bison Top Round Roasts

ABSTRACT: The combined effect of marination and different cooking regimes on the cooking yield and palat-ability of bison and beef top round roasts was investigated. Semimembranosus (SM) muscles from beef and bison top rounds were injected with a marinade to achieve 20% extension by weight and 0.5% sodium chloride and 0.3% sodium tripolyphosphate levels and then subdivided into 4 roasts and cooked by following 4 cooking regimes: cooking at a constant temperature of 75°C (control; C); similar to the control treatment except that roasts were held at an internal temperature of 55°C for 45 min (Hold45) or 90 min (Hold90) prior to final cooking at 75°C; initial cooking at 55°C with a 5°C increase in oven temperature every hour (Step-up) until the 71°C internal temperature was achieved. Cooking yield, expressible moisture, purge, and shear force of processed roasts were determined. Marination by injection improved the yield and tenderness of beef and bison SM roasts. The cooking yield for injected samples (78%) was significantly (P < 0.05) higher compared with noninjected controls (68%). Injected SM roasts from bison had lower cooking losses than those from beef, whereas control samples from these 2 species did not differ in their cooking yields. Injected beef SM was more tender than bison SM; however, marination significantly reduced the shear force values of SM roasts for both species (i.e., shear force values of 82 N in control samples was reduced to 63 N in injected ones). The cooking regimes, Hold45, Hold90, and Step-up (which allowed a longer time at 55 to 60°C), gave products with lower ( P < 0.05) shear force values than those of the controls. Based on the cooking yield and time involved, the Hold 45 treatment performed the best.     

Determining casting defects in near-net shape casting aluminum parts by computed tomography

Three types of near-net shape casting aluminum parts were investigated by computed tomography to determine casting defects and evaluate quality. The first, second, and third parts were produced by low-pressure die casting (Al-12Si-0.8Cu-0.5Fe-0.9Mg-0.7Ni-0.2Zn alloy), die casting (A356, Al-7Si-0.3Mg), and semi-solid casting (A356, Al-7Si-0.3Mg), respectively. Unlike die casting (second part), low-pressure die casting (first part) significantly reduced the formation of casting defects (i.e., porosity) due to its smooth filling and solidification under pressure. No significant casting defect was observed in the third part, and this absence of defects indicates that semi-solid casting could produce high-quality near-net shape casting aluminum parts. Moreover, casting defects were mostly distributed along the eutectic grain boundaries. This finding reveals that refinement of eutectic grains is necessary to optimize the distribution of casting defects and reduce their size. This investigation demonstrated that computed tomography is an efficient method to determine casting defects in near-net shape casting aluminum parts.     

The use of the lectin Helix pomatia agglutinin (HPA) as a prognostic indicator and as a tool in cancer research

Progress in treatment for cancer has enabled extension of the disease-free interval, and of the quality of life for patients, but there has been very little improvement in overall survival rates. The main reason for this has been the ineffectiveness of current therapies to kill all the cancer cells once they have spread to distant sites to form metastatic deposits. One marker which has proved to be useful in identifying those cancers which have the potential to spread is the lectin Helix pomatia agglutinin (HPA). In clinical studies, HPA binding to primary tumours in tissue sections has been of prognostic value in breast, colon and gastric cancer, while no prognostic significance for HPA could be detected in tumours of the head and neck. These studies hence indicate that HPA is best suited to recognise a glycotope on adenocarcinomas. In several studies, HPA reactivity is equal or superior to other classical markers of metastatic potential. Since HPA is a marker of prognosis at the level of individual tumour cells, human tumour cell lines were screened for their HPA positivity. When transplanted into severe combined immunodeficient (scid) mice, HPA positive human breast and colon cancer cells metastasised while HPA negative cancer cell lines in general did not. In order to define HPA binding glycotopes at the molecular level, isolated cell membrane glycoproteins were exposed to labelled HPA on nitrocellulose membranes after Western blotting procedure. The majority of the isolated cell membrane glycoproteins bound HPA indicating that not a single HPA binding glycoprotein exists, which is associated with the metastatic phenotype. Functional investigations using the human/scid mouse chimeras will aid in the identification of those HPA positive glycoproteins which are functionally involved in the metastatic cascade.     

Mouse Liver Compensates Loss of Sgpl1 by Secretion of Sphingolipids into Blood and Bile

Sphingosine 1 phosphate (S1P) lyase (Sgpl1) catalyses the irreversible cleavage of S1P and thereby the last step of sphingolipid degradation. Loss of Sgpl1 in humans and mice leads to accumulation of sphingolipids and multiple organ injuries. Here, we addressed the role of hepatocyte Sgpl1 for regulation of sphingolipid homoeostasis by generating mice with hepatocyte-specific deletion of Sgpl1 (Sgpl1^HepKO mice). Sgpl1^HepKO mice had normal body weight, liver weight, liver structure and liver enzymes both at the age of 8 weeks and 8 months. S1P, sphingosine and ceramides, but not glucosylceramides or sphingomyelin, were elevated by ~1.5–2-fold in liver, and this phenotype did not progress with age. Several ceramides were elevated in plasma, while plasma S1P was normal. Interestingly, S1P and glucosylceramides, but not ceramides, were elevated in bile of Sgpl1^HepKO mice. Furthermore, liver cholesterol was elevated, while LDL cholesterol decreased in 8-month-old mice. In agreement, the LDL receptor was upregulated, suggesting enhanced uptake of LDL cholesterol. Expression of peroxisome proliferator-activated receptor-γ, liver X receptor and fatty acid synthase was unaltered. These data show that mouse hepatocytes largely compensate the loss of Sgpl1 by secretion of accumulating sphingolipids in a specific manner into blood and bile, so that they can be excreted or degraded elsewhere.     

Characterising PEM Fuel Cell Performance Using a Current Distribution Measurement in Comparison with a CFD Model

The characterisation of a proton exchange membrane (PEM) fuel cell with a straight channel flow field design is performed. Spatially resolved current distribution measurements, at different air flow rates, are compared to numerical simulation results. The numerical model is validated by agreement of the measured and simulated current distribution. The test cell is segmented. It is operated at steady state conditions and the gas flow rates and cell temperature are controlled. The numerical simulation is realised with a PEM fuel cell model based on FLUENT™ computational fluid dynamics (CFD) software. It accounts for mass transport in the gaseous phase, heat transfer, electrical potential field and the electrochemical reaction. It provides three‐dimensional distributions of, e.g., current densities, reactant concentrations and temperature.     

Modelling Approach for Planar Self‐Breathing PEMFC and Comparison with Experimental Results

This paper presents a model‐based analysis of a proton exchange membrane fuel cell (PEMFC) with a planar design as the power supply for portable applications. The cell is operated with hydrogen and consists of an open cathode side allowing for passive, self‐breathing, operation. This planar fuel cell is fabricated using printed circuit board (PCB) technology. Long‐term stability of this type of fuel cell has been demonstrated. A stationary, two‐dimensional, isothermal, mathematical model of the planar fuel cell is developed. Fickian diffusion of the gaseous components (O₂, H₂, H₂O) in the gas diffusion layers and the catalyst layers is accounted for. The transport of water is considered in the gaseous phase only. The electrochemical reactions are described by the Tafel equation. The potential and current balance equations are solved separately for protons and electrons. The resulting system of partial differential equations is solved by a finite element method using FEMLAB (COMSOL Inc.) software. Three different cathode opening ratios are realized and the corresponding polarization curves are measured. The measurements are compared to numerical simulation results. The model reproduces the shape of the measured polarization curves and comparable limiting current density values, due to mass transport limitation, are obtained. The simulated distribution of gaseous water shows that an increase of the water concentration under the rib occurs. It is concluded that liquid water may condense under the rib leading to a reduction of the open pore space accessible for gas transport. Thus, a broad rib not only hinders the oxygen supply itself, but may also cause additional mass transport problems due to the condensation of water.     

Input–output invertibility and sliding mode control for close formation flying of multiple UAVs

This paper treats the question of invertibility of input–output maps and the design of a robust control system for formation flying of multiple unmanned aerial vehicles (UAVs). In close formation, the wing UAV motion is affected by the vortex of the adjacent lead aircraft. The forces produced by these vortices are complex functions of relative position coordinates of the UAVs. In this paper, these forces are treated as unknown functions. For trajectory tracking, invertibility of certain input–output maps in the wind axes system are examined. Interestingly, in the wind axes system, the system is not invertible, but in a simplified co‐ordinate system obtained from the wind axes system for which the velocity roll is zero, inverse control of separation co‐ordinates is possible. Variable structure control laws are derived for separation trajectory control of wing aircraft in the simplified wind co‐ordinate system and for the flight control of the lead aircraft. Simulation results for two UAVs are presented which show precise separation trajectory control in spite of the presence of unknown vortex forces, while the lead aircraft maneuvers. Furthermore, these results confirm that when the wing aircraft is positioned properly in the vortex of the lead aircraft, there is a reduction in the required flight power. Published in 2000 by John Wiley & Sons, Ltd.     

Porous SiOC monoliths with catalytic activity by in situ formation of Ni nanoparticles in solution-based freeze casting

Micro- and macroporous monoliths with in situ formed nickel nanoparticles were prepared for the first time by the combination of solution-based freeze casting and preceramic polymers (methyl polysiloxane). This one-step process results in macroporous monoliths composed of microporous and catalytic active nickel-containing polymer-derived ceramic. Four different complexing and cross-linking siloxanes with amino functionality were screened for their ability to create small nickel particles. TEM analysis confirmed 3-aminopropyltriethoxysilane being most efficient. High BET-specific surface areas of 344-461 m² g⁻¹ were achieved. Increased ratio of complexing groups to nickel improves the dispersion of nickel to (3.61 ± 1.49) nm. The nickel size dependence of conversion (maximum 0.49) and CH₄ selectivity (maximum 0.74) in CO₂ methanation emphasizes the importance of controlling the nickel size. The hydrophobic surface characteristic is hypothesized to be the main reason polymer-derived catalysts having better catalytic activity compared with nickel-impregnated silica. The promising catalytic activity combined with the versatile freeze casting process can prospectively address heat- and mass-transfer considerations in heterogeneous monolith catalysis.