Stability of the shell structure in 2D quantum dots

We study the effects of external impurities on the shell structure in semiconductor quantum dots by using a fast response-function method for solving the Kohn-Sham equations. We perform statistics of the addition energies up to 20 interacting electrons. The results show that the shell structure is generally preserved even if effects of high disorder are clear. The Coulomb interaction and the variation in ground-state spins have a strong effect on the addition-energy distributions, which in the noninteracting single-electron picture correspond to level statistics showing mixtures of Poisson and Wigner forms.Comment: 7 pages, 8 figures, submitted to Phys. Rev.

Human acclimation and acclimatization to heat: A compendium of research, 1968-1978

Abstracts and annotations of the majority of scientific works that elucidate the mechanisms of short-term acclimation to heat in men and women are presented. The compendium includes material from 1968 through 1977. Subject and author indexes are provided and additional references of preliminary research findings or work of a peripheral nature are included in a bibliography

Probabilistic Search for Object Segmentation and Recognition

The problem of searching for a model-based scene interpretation is analyzed within a probabilistic framework. Object models are formulated as generative models for range data of the scene. A new statistical criterion, the truncated object probability, is introduced to infer an optimal sequence of object hypotheses to be evaluated for their match to the data. The truncated probability is partly determined by prior knowledge of the objects and partly learned from data. Some experiments on sequence quality and object segmentation and recognition from stereo data are presented. The article recovers classic concepts from object recognition (grouping, geometric hashing, alignment) from the probabilistic perspective and adds insight into the optimal ordering of object hypotheses for evaluation. Moreover, it introduces point-relation densities, a key component of the truncated probability, as statistical models of local surface shape.Comment: 18 pages, 5 figure

A recoil detector for the measurement of antiproton-proton elastic scattering at angles close to 90∘^{\circ}

The design and construction of a recoil detector for the measurement of recoil protons of antiproton-proton elastic scattering at scattering angles close to 90$^{\circ}$ are described. The performance of the recoil detector has been tested in the laboratory with radioactive sources and at COSY with proton beams by measuring proton-proton elastic scattering. The results of laboratory tests and commissioning with beam are presented. Excellent energy resolution and proper working performance of the recoil detector validate the conceptual design of the KOALA experiment at HESR to provide the cross section data needed to achieve a precise luminosity determination at the PANDA experiment.Comment: 10 pages, 15 figure

Geometric and impurity effects on quantum rings in magnetic fields

We investigate the effects of impurities and changing ring geometry on the energetics of quantum rings under different magnetic field strengths. We show that as the magnetic field and/or the electron number are/is increased, both the quasiperiodic Aharonov-Bohm oscillations and various magnetic phases become insensitive to whether the ring is circular or square in shape. This is in qualitative agreement with experiments. However, we also find that the Aharonov-Bohm oscillation can be greatly phase-shifted by only a few impurities and can be completely obliterated by a high level of impurity density. In the many-electron calculations we use a recently developed fourth-order imaginary time projection algorithm that can exactly compute the density matrix of a free-electron in a uniform magnetic field.Comment: 8 pages, 7 figures, to appear in PR

Periodic Orbits in Polygonal Billiards

We review some properties of periodic orbit families in polygonal billiards and discuss in particular a sum rule that they obey. In addition, we provide algorithms to determine periodic orbit families and present numerical results that shed new light on the proliferation law and its variation with the genus of the invariant surface. Finally, we deal with correlations in the length spectrum and find that long orbits display Poisson fluctuations.Comment: 30 pages (Latex) including 11 figure

A novel variant of the 13C-methacetin liver function breath test that eliminates the confounding effect of individual differences in sytemic CO2 kinetics

The principle of dynamic liver function breath tests is founded on the administration of a 13C-labeled drug and subsequent monitoring of 13CO2 in the breath, quantified as time series delta over natural baseline 13CO2 (DOB) liberated from the drug during hepatic CYP-dependent detoxification. One confounding factor limiting the diagnostic value of such tests is that only a fraction of the liberated 13CO2 is immediately exhaled, while another fraction is taken up by body compartments from which it returns with delay to the plasma. The aims of this study were to establish a novel variant of the methacetin-based breath test LiMAx that allows to estimate and to eliminate the confounding effect of systemic 13CO2 distribution on the DOB curve and thus enables a more reliable assessment of the hepatic detoxification capacity compared with the conventional LiMAx test. We designed a new test variant (named "2DOB") consisting of two consecutive phases. Phase 1 is initiated by the intravenous administration of 13C-bicarbonate. Phase 2 starts about 30 min later with the intravenous administration of the 13C-labelled test drug. Using compartment modelling, the resulting 2-phasic DOB curve yields the rate constants for the irreversible elimination and the reversible exchange of plasma 13CO2 with body compartments (phase 1) and for the detoxification and exchange of the drug with body compartments (phase 2). We carried out the 2DOB test with the test drug 13C-methacetin in 16 subjects with chronic liver pathologies and 22 normal subjects, who also underwent the conventional LiMAx test. Individual differences in the systemic CO2 kinetics can lead to deviations up to a factor of 2 in the maximum of DOB curves (coefficient of variation CV ≈ 0.2) which, in particular, may hamper the discrimination between subjects with normal or mildly impaired detoxification capacities. The novel test revealed that a significant portion of the drug is not immediately metabolized, but transiently taken up into a storage compartment. Intriguingly, not only the hepatic detoxification rate but also the storage capacity of the drug, turned out to be indicative for a normal liver function. We thus used both parameters to define a scoring function which yielded an excellent disease classification (AUC = 0.95) and a high correlation with the MELD score (RSpearman = 0.92). The novel test variant 2DOB promises a significant improvement in the assessment of impaired hepatic detoxification capacity. The suitability of the test for the reliable characterization of the natural history of chronic liver diseases (fatty liver-fibrosis-cirrhosis) has to be assessed in further studies

CAEv–A program for computer aided evaluation

The evaluation of new reagents and instruments in clinical chemistry leads to complex studies with large volumes of data, which are difficult to handle. This paper presents the design and development of a program that supports an evaluator in the definition of a study, the generation of data structures, communication with the instrument (analyser), online and offline data capture and in the processing of the results. The program is called CAEv, and it runs on a standard PC under MS-DOS. Version 1 of the program was tested in a multicentre instrument evaluation. The concept and the necessary hardware and software are discussed. In addition, requirements for instrument/host communication are given. The application of the laboratory part of CAEv is described from the user's point of view. The design of the program allows users a high degree of flexibility in defining their own standards with regard to study protocol, and/or experiments, without loss of performance. CAEv's main advantages are a pre-programmed study protocol, easy handling of large volumes of data, an immediate validation of the experimental results and the statistical evaluation of the data

Effect of goji berry on the formation of extracellular senile plaques of Alzheimer\u27s disease

BACKGROUND: Alzheimer\u27s disease (AD) is the most common neurodegenerative disease and a major source of morbidity and mortality. Currently, no therapy nor drug can cure or modify AD progression, but recent studies suggest that nutritional compounds in certain foods can delay or prevent the onset of AD. Diets with high antioxidants is one of the examples which is believed to influence AD pathogenesis through direct effect on amyloid beta levels. Compared to other fruits and vegetables, goji berry (GB) has high levels of polyphenolic substances with antioxidant activities which have shown some positive effects on cognitive function while its mechanism on neuroprotection is yet to be explored. We investigated whether GB would decrease the quantity of amyloid beta in cell culture model of AD. OBJECTIVE: To assess the protective effects of GB against amyloid beta toxicity in M17 cells using different techniques. METHODS: Goji berry powder (GBP) at different concentrations was treated with 20 μM amyloid beta-induced neuronal cells. MTS assay (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxy-phenyl)-2-(4-sulfophenyl)-2H-tetrazolium), bicinchoninic acid (BCA) assay, Western blot analysis, enzyme-linked immunosorbent assay (ELISA) and atomic force microscopy (AFM) were performed to identify how GB affected amyloid beta. RESULTS: MTS assay indicated that GBP significantly increased cell viability up to 105% when GBP was at 1.2 μg/ mL. Western blot showed significant reduction of amyloid beta up to 20% in cells treated with 1.5 μg/ mL GBP. GBP at 1.5 μg/ mL was the most effective concentration with 17% reduction of amyloid beta in amyloid beta-induced neuronal cells compared to control (amyloid beta only) based on ELISA results. AFM images further confirmed increasing GBP concentration led to decreased aggregation of amyloid beta. CONCLUSION: GB can be a promising anti-aging agent and warrants further investigating due to its effect on reduction of amyloid beta toxicity