Transition from the two- to three-dimensional growth of Ge films upon deposition onto relaxed SiGe/Si(001) buffer layers

The critical thickness of the two-dimensional growth of Ge on relaxed SiGe/Si(001) buffer layers different in Ge content is studied in relation to the parameters of the layers. It is shown that the critical thickness of the two-dimensional growth of Ge on SiGe buffer layers depends on the lattice mismatch between the film and the substrate and, in addition, is heavily influenced by Ge segregation during SiGe-layer growth and by variations in the growth-surface roughness upon the deposition of strained (stretched) Si layers. It is found that the critical thickness of the two-dimensional growth of Ge directly onto SiGe buffer layers with a Ge content of x = 11–36% is smaller than that in the case of deposition onto a Si (001) substrate. The experimentally detected increase in the critical thickness of the two-dimensional growth of Ge with increasing thickness of the strained (stretched) Si layer predeposited onto the buffer layer is attributed to a decrease in the growth-surface roughness and in the amount of Ge located on the surface as a result of segregation.     

Geometry-adapted hexahedral meshes improve accuracy of finite-element-method-based EEG source analysis

Mesh generation in finite-element- (FE) method-based electroencephalography (EEG) source analysis generally influences greatly the accuracy of the results. It is thus important to determine a meshing strategy well adopted to achieve both acceptable accuracy for potential distributions and reasonable computation times and memory usage. In this paper, we propose to achieve this goal by smoothing regular hexahedral finite elements at material interfaces using a node-shift approach. We first present the underlying theory for two different techniques for modeling a current dipole in FE volume conductors, a subtraction and a direct potential method. We then evaluate regular and smoothed elements in a four-layer sphere model for both potential approaches and compare their accuracy. We finally compute and visualize potential distributions for a tangentially and a radially oriented source in the somatosensory cortex in regular and geometry-adapted three-compartment hexahedra FE volume conductor models of the human head using both the subtraction and the direct potential method. On the average, node-shifting reduces both topography and magnitude errors by more than a factor of 2 for tangential and 1.5 for radial sources for both potential approaches. Nevertheless, node-shifting has to be carried out with caution for sources located within or close to irregular hexahedra, because especially for the subtraction method extreme deformations might lead to larger overall errors. With regard to realistic volume conductor modeling, node-shifted hexahedra should thus be used for the skin and skull compartments while we would not recommend deforming elements at the grey and white matter surfaces.     

Nano structured physical vapor deposited coatings by means of picosecond laser radiation

Molding of nano structures by injection molding leads to special requirements for the tools e.g., wear resistance and as low as possible release forces of the molded components. On the other hand it is not allowed to affect the replication precision. Physical vapor deposition is one of the promising technologies for applying coatings with adapted properties like high hardness, low roughness, low Young's modulus and less adhesion to the plastics melt. Although physical vapor deposition technology allows the deposition of films on micro structures without changing the structure significantly, film deposition on nano structures and small micro structures leads to a relevant change in surface topography. For this reason direct structuring of physical vapor deposition coatings might be beneficial. In this paper structuring was done using a picoseconds ultraviolet laser, Lumera Laser "Rapid," with a master oscillator power amplifier system at 355 nm. Two different coatings were deposited by magnetron sputter ion plating physical vapor deposition technology for laser structuring tests ((Cr, Al)N, (Cr, Al,Si)N). After deposition, the coatings were analyzed by common techniques regarding hardness, Young's modulus and morphology. The structures were analyzed by scanning electron microscopy. The results show a high potential for laser structuring of coatings deposited via physical vapor deposition. Linear structures with sizes between 400 nm and 10microm were realized.     

A Study on the Feasibility of Measuring the Emissivity with the Laser-Flash Method

The laser-flash method is a fast, widely used and well established technique to measure the thermal diffusivity. Since its introduction in the 1960s, it was proposed to expand this technique to the measurement of heat capacity and emissivity. Currently, the measurement of spectral emissivity at high temperatures is connected with relatively large uncertainties, although the spectral emissivity is an essential parameter for applications, e.g., in the lamp industry and fusion research. In this work, a theoretical study is presented on the possibility of emissivity measurements using the laser-flash method. Two mathematical approaches are discussed which solve the problem, that a measured temperature rise—necessary to calculate the emissivity—itself depends on the emissivity. It is shown that both methods have a negligible arithmetic error, making them applicable to be used in future work.     

Relating dietary diversity and food variety scores to vegetable production and socio-economic status of women in rural Tanzania

The objective of the present study was to measure diversity in nutrition with dietary scores, and to assess their relationship to vegetable production and the socio-economic status of women in rural Tanzania. A dietary diversity score (DDS) and a food variety score (FVS) were created from data gathered with three semi-quantitative 24-h recalls performed during three non-consecutive seasons during 2006/2007. Data on vegetable production, selling and buying and socio-economic data was gathered with a semi-quantitative questionnaire. A total of 252 randomly selected women from three districts of north-eastern and central Tanzania participated. The median DDS of 6 and the mean FVS of 8.3 were low, suggesting an overall poor dietary quality, with about one third of participants having an alarmingly low DDS of only two to four food groups per day. These women consumed a very basic diet consisting mainly of cereals and vegetables. Differences among districts were pronounced while those among seasons were less distinct. The DDS and FVS were both significantly associated with ethnicity, occupation and status within the household of participants. As a more varied diet is not necessarily healthier, integration of both quantity and quality in the scores is proposed for future studies. This can be achieved, for example, by weighing food types according to their importance in the diet. As both scores are linked to the production, selling and buying of vegetables, the promotion of homestead food production may be a good way to improve dietary diversity.     

Combined high pressure and temperature induced lethal and sublethal injury of Lactococcus lactis--application of multivariate statistical analysis

It was the aim of this work to determine the combined effects of pressure, temperature, and co-solutes on Lactococcus lactis, and to detect correlations between culture-dependent and culture-independent methods for assessment of cellular viability and sublethal injury. Therefore, the pressure induced inactivation of L. lactis MG 1363 was investigated in buffer and in buffer with 1.5 M sucrose or 4 M NaCl at a pressure range of 0.1 to 500 MPa and a temperature range of 5 to 50 degrees C. The inactivation was characterised by viable cell counts, stress resistant cell counts, membrane integrity, metabolic activity, and the activity of the multi-drug-resistance transport enzyme LmrP. L. lactis was most resistant to pressure application at 20-30 degrees C. Sucrose protected towards inactivation at any temperature, NaCl provided protection at high temperatures only. By using Principal Component Analysis, correlations were detected between viable cell counts and metabolic activity as well as stress resistant cell counts and LmrP activity. In conclusion, the pressure-inactivation of L. lactis is strongly temperature dependent, baroprotection by sucrose occurs at any temperature but the baroprotective effects of NaCl is temperature dependent. Further on, a combination of two experimental methods fully describe lethal and sublethal injury of pressure treated cells. These simplification of data acquisition and model development facilitates the establishment of pressure processes in food technology.     

Immunoaffinity-chromatography purification of salbutamol in liver and HPLC-fluorometric detection at trace residue level

Summary A method combining immunoaffmity-chromatography (IAC) and high-performance liquid chromatography (HPLC) for the analysis of Salbutamol in liver with a low quantification limit of 1 g/kg has been developed. Salbutamol was extracted with 0.01 mol/L HCl and purified by IAC. The samples were analysed on a liquid Chromatograph fitted with a C₁₈ -Bondapak column. A fluorometer was used for the detection of salbutamol. Recoveries of 67–80% could be obtained.

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Immunoaffinitätschromatographische Reinigung von Salbutamol in Leber und Rückstandsbestimmung mittels HPLC und fluorimetrischer Detektion

Zusammenfassung Eine Methode, die Immunoaffinitäts-und Hochleistungsflüssigchromatographie verbindet, ist für die Analyse von Salbutamol in Leber entwickelt worden. Eine niedrige Bestimmungsgrenze von 1 g/kg Leber wurde erreicht. Salbutamol wurde mit 0,01 mol/L Salzsäure freigesetzt und durch Immunoaffinitätschromatographie gereinigt. Die Proben wurden durch Flüssigchromatographie auf einer C₁₈ -Bondapak-Säule analysiert. Ein Fluorimeter wurde für die Detektion von Salbutamol benutzt. Ausbeuten von 67 bis 80% konnten erreicht werden.

     

Serial measurement of arterial plasma progesterone levels throughout gestation and parturition in individual rats

Daily blood samples were taken from 6, chronically cannulated, fully conscious rats to measure plasma progesterone levels throughout gestation. Progesterone levels in individual rats fluctuated by up to 28 ng/ml per day, but tended to be consistently higher or lower than the group mean. The accuracy of predicting progesterone levels in individual rats from previous values was examined. Progesterone levels on day 7 of gestation were negatively correlated with foetal weights near term. There was little indication that high progesterone levels at any stage of gestation lead to increased foetal or placental weights. Progesterone levels on day 17 were positively correlated with the number of corpura lutea but there was little relationship between progesterone and either the number or total mass of the placentas. Serial blood samples taken from a second group of 6 rats at 2 hourly intervals showed that the time between the major fall in progesterone levels to below 12 ng/ml and the onset of parturition was relatively constant (varying by only 8 h) despite a 29 h range in the total length of gestation.