Search Results - (Author, Cooperation:G. Schneider)

2015-10-10

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

2015-08-14

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

0021-9673

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Chemistry and Pharmacology

Electronic Resource

2018-03-07

Institute of Physics Publishing (IOP)

1748-0221

Physics

1089-7550

AIP Digital Archive

Physics

A new stable compound in the Nd–Fe system has been identified as Nd5Fe17. The crystal structure belongs to the hexagonal space group P63/mcm, with a=2.0214(8) nm and c=1.2329(8) nm, and with 12 formula units per unit cell. This compound is a ferromagnet with Tc = 503 K and magnetization 162 emu/g at 4.2 K. Mössbauer spectra have been measured and fitted with five Fe sites, yielding an average Beff=26.5 T at room temperature, from which an average Fe moment of 1.83 Bohr magnetons is deduced. X-ray powder diagrams from magnetically aligned samples suggest basal anisotropy.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Magnetic anisotropy is a difficult topic to describe by electronic structure theory. The results of ab initio calculations for iron and nickel are disappointing, especially since these calculations require high numerical precision and are very time consuming. For iron the value of the energy is too small by a factor of 3, while for nickel the sign is wrong and the value is too small by a factor of 5. The local density approximation can be improved by adding corrections that mimic the inclusion of Hund's second rule. This is equivalent to increasing the effective spin–orbit parameter. For iron a small increase in the effective spin–orbit parameter is sufficient to reconcile theory and experiment. For nickel, this is not possible. © 2000 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

We calculate the torque on a magnetic moment with arbitrary orientation in a solid and use it to calculate the magnetocrystalline anisotropy energy (MAE) of bulk materials by integrating the torque along an angular path connecting the easy and hard magnetization directions. We apply this approach to the calculation of the MAE of elemental ferromagnets Ni and Fe using a tight-binding model with an added spin-orbit-coupling (SOC) term λSOL⋅S. The MAE for both Fe and Ni is computed for a wide range of values of the SOC strength. Our results for the MAE calculated with the torque method agree with the MAE determined from energy differences. The convergence rate as a function of k-vector needed for integrating over the Brillouin zone for the torque method is comparable to the convergence rate of conventional energy difference schemes. We compare the calculated torque as function of angle to the lowest order term in the expansion in anisotropy constants. © 1997 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

The coupled wave theory is applied to calculate the diffraction efficiency of zone plates used in high orders of diffraction. In contradiction to the existing understanding about 30%–50% of the incident intensity can be diffracted by a single high order if the line-to-space ratio of the zone structures is in the range of 0.1–0.5 and the aspect ratios are larger than 30:1. Highly efficient diffractive transmission x-ray optics with high numerical apertures and resolving power can be developed without manufacturing extremely small zones which are necessary for zone plates used in the first order. © 1997 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

In the phase Fe14R2X, where R is a lanthanide and X is either boron or carbon, or a mixture of the two, the extent of stability of the carbides and their miscibility with the borides is traced for the lighter rare-earth metals. Like the borides, the carbides are magnetically hard, but unlike them, they do not normally crystallize from the melt, and this property is exploited to produce intrinsic coercivities above 12 kOe in cast materials without the added special processing step of sintering or melt spinning. The high coercivity is related to a cellular microstructure of Fe14R2X in which the cell size is approximately 1 μm. The cell structure, which originates in a peritectoidlike transformation from primary Fe17R2, is quite stable and does not change during prolonged annealing. The coercivity is sensitive to variations in composition.

Electronic Resource

1468-2494

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

A multicentre study for measuring skin hydration with 349 volunteers was carried out in six different laboratories. The purpose of the study was to investigate physical-, physiological- and product-dependent parameters of three test emulsions (base, base + moisturizer and base + moisturizer + lipids) in a double-blind study. A comparison between analogous and digital sensor technology of the Corneometer CM825 was examined. Here, a clear relationship between both sensor types could be highlighted. A vital point of the study was the division of the test subjects according to their skin type. To get more objective limits for three different skin types – very dry, dry and normal skin – visual expert evaluation, self-assessment and hydration measurements were analysed by means of statistical methods. The moisture-related skin types were determined as follows: very dry skin was characterized with corneometer units below 30, dry skin between 30 and 40 and normal skin higher than 40 a.u. (arbitrary units). The efficacy of the three test emulsions was examined in relation to the mentioned skin types. Analysing the measured data of all test centres, a clear dependency of skin physiology (skin type) and product efficacy became evident. The drier the skin, the higher the increase of hydration. The product performance of the three test emulsions compared to the untreated control resulted in a significant increase of skin hydration in all measuring centres. The evaluation of a product ranking showed a good differentiation between the basic emulsion and the two other products. An increase of efficacy by adding lipids could be observed in four of six centres. The important influence of the skin type of the volunteers on the degree of product performance, as demonstrated in this study, should be especially considered when drawing up guidelines for efficacy testing.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

Diffractive transmission x-ray optics, e.g., zone plates and gratings, are well suited for x-ray microscopy and spectroscopy. X-ray optics for use at short wavelengths require high zone aspect ratios which can be obtained by alternately depositing two materials with different x-ray scattering properties on a microwire. The roughness and the diffusion inherent to this process influence the diffraction efficiency of these optics. Using coupled wave theory, it is shown that roughness and interdiffusion increase the structure height required for optimal diffraction efficiency compared to ideally smooth structure profiles. In addition, the maximum obtainable diffraction efficiency decreases with increasing root-mean-square roughness and interdiffusion. © 1998 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

High-resolution x-ray microscopy makes use of nanostructured diffractive optics such as Fresnel zone plates made of nickel. These micro zone plates are manufactured using microscopic galvanoforms and electrodeposition techniques. Copolymer galvanoforms for nickel micro zone plates were irradiated with high doses of x-ray radiation to increase the degree of cross-linking of the copolymer network; in this way, exact pattern replication in the galvanoform was obtained for zone aspect ratios of up to 8:1. Using these galvanoforms, nickel micro zone plates were produced for the soft x-ray wavelength λ=2.4 nm, with smallest zone widths of 30 nm and 40 nm, achieving first-order diffraction efficiencies of up to 13% and 20%, respectively. © 1998 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

X-ray imaging of electromigration in a passivated Cu interconnect was performed with 100-nm spatial resolution. A time sequence of 200 images, recorded with the European Synchrotron Radiation Facility x-ray microscope in 2.2 h at 4 keV photon energy, visualizes the mass flow of Cu at current densities up to 2×107 A/cm2. Due to the high penetration power through matter and the element specific image contrast, x-ray microscopy is a unique tool for time-resolved, quantitative mass transport measurements in interconnects. Model calculations predict that failures in operating microprocessors are detectable with 30 nm resolution by nanotomography. © 2001 American Institute of Physics.

Electronic Resource

1460-9568

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Excessive synchronization of neural activity in the beta frequency band (∼20 Hz) within basal ganglia circuits might contribute to the paucity and slowness of movement in Parkinson's disease (PD). Treatment with dopaminergic drugs reduces the background level of beta frequency band synchronization in the subthalamic nucleus (STN), but has not been shown to increase the proportion of beta activity that is suppressed before voluntary movement in PD. We assessed changes in the event-related desynchronization (ERD) in the beta frequency band of local field potential signals from the region of the STN in 14 patients with PD as they performed self-paced movements of a joystick before and after levodopa administration. The dopamine precursor, levodopa, increased the duration and magnitude of the premovement beta ERD, but did not alter postmovement synchronization in the beta band. Both the latency and magnitude of the beta ERD inversely correlated with the degree of motor impairment. These findings suggest that the beta ERD recorded in the STN area reflects motor-preparative processes that are at least partly dependent on dopaminergic activity within the basal ganglia.

Electronic Resource

1600-0714

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Background:  Beta-catenin, an E-cadherin-associated protein involved in cell–cell adhesion and signaling, has been hypothesized to translocate to the nucleus and activate transcription in several human cancers, including oral squamous cell carcinomas (OSCC).Methods:  In the present study, we analyzed the subcellular localization of beta-catenin in cultures of human oral normal and malignant (cell lines SCC15 and SCC25) keratinocytes and in 24 frozen samples of oral squamous cell carcinomas by a double-staining technique for nucleic acids and beta-catenin. Growth potential, as assessed by cell count at different time periods, was established for normal, SCC15 and SCC25 cell lines; oral squamous cell carcinomas were classified according to the histopathological and malignancy indexes.Results:  Beta-catenin localized at the plasma membrane in the normal and SCC15 cells, not in the SCC25 cells, where it localized mostly in the perinuclear and nuclear areas. In the growth assays, SCC25 cell lines proliferated faster than in normal and SCC15 cells over a period of 6 days (cell numbers were significantly different, P 〈 0.0001). Carcinoma sections showed a combination of membranous, cytoplasmic and, in few invading epithelial islands of two tumors, nuclear localization of beta-catenin.Conclusions:  In oral squamous cell carcinomas, nuclear beta-catenin staining was observed only within invading islands of two carcinomas deep in the underlying connective tissue. On the basis of this study, we conclude that intranuclear beta-catenin does not appear to be a common finding in oral squamous cell carcinomas and that a clear association between intranuclear beta-catenin and histopathological and malignancy indexes in vivo could not be established.

Electronic Resource

1460-2695

Blackwell Publishing Journal Backfiles 1879-2005

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Both experimental and analytical investigations were conducted to study crack initiation and growth of small cracks, near-threshold growth behavior of large cracks at constant R-ratio/decreasing ΔK and constant Kmax/decreasing ΔK, respectively, for 9310 steel. The results showed that a pronounced small-crack effect was not observed even at R = −1, small cracks initiated by a slip mechanism at strong slip sites. Worst-case near-threshold testing results for large cracks under several Kmax values showed that an effect of Kmax on the near-threshold behavior does not exist in the present investigation. A worst-case near-threshold test for a large crack, i.e. constant Kmax/decreasing ΔK test, can give a conservative prediction of growth behavior of naturally initiated small cracks. Using the worst-case near-threshold data for a large crack and crack-tip constraint factor equations defined in the paper, Newman's total fatigue-life prediction method was improved. The fatigue lives predicted by the improved method were in reasonable agreement with the experiments. A three-dimensional (3D) weight function method was used to calculate stress-intensity factors for a surface crack at a notch of the present SENT specimen (with r/w = 1/8) by using a finite-element reference solution. The results were verified by limited finite-element solutions, and agreed well with those calculated by Newman's stress-intensity factor equations when the stress concentration factor of the present specimen was used in the equations.

Electronic Resource

1365-2842

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Summary To explain the breakage process of food particles in human mastication, we propose a simple fragmentation model. To verify its clinical accuracy, a mechanical test with a sieving method and a natural test food (coffee) was performed on three groups of subjects. The values obtained permitted to demonstrate that the model could predict, at least qualitatively, the general trend of the experimental data, even for a very small group (two subjects). It also shows that the choice of the yielding factors used to calculate the masticatory index (MI) is relevant.

Electronic Resource

1365-2842

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

A lot of test foods have been used during this century to evaluate the masticatory ability of human subjects. Nevertheless, none has been universally admitted. If the test food by itself is of importance, attention should also be paid to its behaviour during the chewing test procedure. Therefore, we analysed step by step coffee beans through the processing of the chewing test and a dry sieving method. The development of a compression test and a computer simulation have shown that groups of 11 coffee beans give satisfactory results and deserve to be used in mastication studies.

Electronic Resource

0006-291X

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Biology

Chemistry and Pharmacology

Physics

Electronic Resource

1476-4687

Nature Archives 1869 - 2009

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

[Auszug] Band 3 proteins rotate in the human erythrocyte membrane; rotation is almost certainly confined to an axis normal to the plane of the membrane and is characterised by a diffusion coefficient of the order of 1,000 s−1. Spectrin does not restrict rotational motion of band 3 ...

Electronic Resource