Study of the growth and structural properties of InMnAs dots grown on high-index surfaces by MOVPE

The growth of InMnAs quantum dots by low pressure MOVPE technique on patterned (1 0 0) GaAs substrates was studied. The patterning in the form of ridges with sidewalls having (2 1 1) and (3 1 1) facets was prepared by wet chemical etching via a GaAs/AlAs sacrificial etching mask structure. AFM studies showed that the dots formation and distribution were very similar for both types of facets under study. InMnAs dot density on the (3 1 1) plane is about 5–7 times lower in comparison to that on the (1 0 0) planar substrate. The dots on sidewalls are larger in comparison to average dots formatted on planar GaAs (1 0 0) substrate. The lateral dimensions of these dots are in the interval 100–180 nm. In addition, dot distribution along the sidewall (from top to bottom) is not uniform. A higher dot concentration was observed close to the intersection of (3 1 1) facets with concave bottom part of the valleys between ridges. Finally, no dots were grown on the (1 0 0) plane created by self-faceting on the top of the triangular ridges. This is probably a consequence of the high quality of the (1 0 0) facet formed by lateral overgrowth.     

Probabilistic Nonlocal Theory for Quasibrittle Fracture Initiation and Size Effect.?II: Application

The nonlocal probabilistic theory developed in Part I is applied in numerical studies of plain concrete beams and is compared to the existing test data on the modulus of rupture. For normal size test beams, the deterministic theory is found to dominate and give adequate predictions for the mean. But the present probabilistic theory can further provide the standard deviation and the entire probability distribution (calculated via Latin hypercube sampling). For very large beam sizes, the statistical size effect dominates and the mean prediction approaches asymptotically the classical Weibull size effect. This is contrary to structures failing only after the formation of a large crack, for which the classical Weibull size effect is asymptotically approached for very small structure sizes. Comparison to the existing test data on the modulus of rupture demonstrates good agreement with both the measured means and the scatter breadth.     

Anisotropic Magnetoresistance of GaMnAs Ferromagnetic Semiconductors

The angular dependence of the magnetoresistance has been studied for two sets of samples: annealed and hydrogenated, respectively. Different behavior of magnetoresistance anisotropy has been discussed in terms of change of scattering rate and/or introduction of strain during treatment.     

Structure analysis of trivalent glycoclusters by post-source decay matrix-assisted laser desorption/ionization mass spectrometry

Post-source decay (PSD) matrix-assisted laser desorption/ionization time-of-flight mass spectra were found to be useful for the structural elucidation of a series of tris [2-(glycosylthiourylene)ethyl]amines. The reported fragmentation behaviours of [M + H]+, [M + Na]+ and [M - H]- ions differ from each other significantly; however, they can be compared to tree pruning in every case. Whereas detailed structural information on unprotected glycoclusters is obtained from all PSD experiments, only the positive-ion mode can be used to gain relevant information about the acetylated glycoclusters.     

Enhanced hemicholinium binding and attenuated dendrite branching in cognitively impaired acetylcholinesterase-transgenic mice

In a search for behavioral, neuroanatomical, and metabolic characteristics of Alzheimer's disease that may result from cholinergic malfunction, we used transgenic mice overexpressing acetylcholinesterase (AChE) mRNA and active enzyme in brain neurons. Mapping by in situ hybridization revealed that transgenic and host AChE mRNAs were distributed similarly. In a Morris water maze working memory paradigm, adult transgenic mice did not display the characteristic improvement found in control mice either between or within test days and spent less time than control mice in the platform zone. In 5-week-old transgenic mice, the basilar dendritic trees of layer 5 pyramidal neurons from the frontoparietal cortex were essentially as developed as in age-matched controls. However, branching totally ceased after this age, whereas in control adults it continued up to at least 7 months. Therefore, dendritic arbors became smaller in adult transgenic mice than those of controls. Furthermore, the average number of spines was significantly lower on dendritic branches of 7-month-old but not 5-week-old transgenics as compared with controls. Binding of tritiated hemicholinium-3, a blocker of the high-affinity choline uptake characteristic of active cholinergic terminals, was over twofold enhanced in the brain of transgenic mice. In contrast, no differences were observed in the mRNA and ligand binding levels of several different subtypes of nicotinic and muscarinic acetylcholine receptors. These findings suggest that three different hallmarks associated with Alzheimer's disease--namely, progressive cognitive failure, cessation of dendrite branching and spine formation, and enhanced high-affinity choline uptake--are outcomes of cholinergic malfunction.     

Detection of opiates in the urine using thin-layer chromatography

The determination of opiates in urine by thin layer chromatography may be difficult for the low concentrations of opiates and their mixtures. The result of the analysis is influenced by the isolation recovery, sensitivity of detection and by the choice of the chromatographic conditions for the separation of opiate mixtures. The study of these factors resulted in several modifications of routinely used method, so that the results are reliable for the concentration of opiates in urine 1 mg/l. Nevertheless, for the analysis of opiates in drug abuse control the comparison of thin layer chromatography findings with other chromatographic methods or immunoassays is important for the improvement of the laboratory performance and for the interpretation of the results.     

Poly[N-(2-hydroxypropyl)methacrylamide]-based tissue-embedding medium compatible with MALDI mass spectrometry imaging experiments

Traditional tissue-sectioning techniques for histological samples utilize various embedding media to stabilize the tissue on a sectioning target and to provide a smooth cutting surface. Due to the ion suppression effect in MALDI ionization and number of background peaks in the low-mass region, these media are not suitable for mass spectrometry imaging (MSI) experiments. To overcome this, droplets of water are often used to mount the tissue on a sectioning target, but the ice block formed around the tissue does not provide a good support for sectioning of fragile samples. In this work, we propose a novel embedding media, compatible with MALDI ionization and MSI experiments, based on poly[N-(2-hydroxypropyl)methacrylamide] (pHPMA). Using a reversible addition-fragmentation chain transfer polymerization technique, well-defined pHPMA polymer with narrow mass distribution was prepared. Benefits of the resulted pHPMA-based embedding media were tested on different tissue samples.     

A uniform-complexity treatment of encryption and zero-knowledge

We provide a treatment of encryption and zero-knowledge in terms of uniform complexity measures. This treatment is appropriate for cryptographic settings modeled by probabilistic polynomial-time machines. Our uniform treatment allows the construction of secure encryption schemes and zero-knowledge proof systems (for allNP) using only uniform complexity assumptions. We show that uniform variants of the two definitions of security, presented in the pioneering work of Goldwasser and Micali, are in fact equivalent. Such a result was known before only for nonuniform formalization. Nonuniformity is implicit in all previous treatments of zero-knowledge in the sense that a zero-knowledge proof is required to “leak no knowledge” onall instances. For practical purposes, it suffices to require that it isinfeasible to find instances on which a zero-knowledge proof “leaks knowledge.” We show how to construct such zero-knowledge proof systems for every language inNP, using only a uniform complexity assumption. Properties of uniformly zero-knowledge proofs are investigated and their utility is demonstrated. This research was partially supported by the Fund for Basic Research Administered by the Israeli Academy of Sciences and Humanities. Revision of this work was supported by Grant No. 89-00312 from the United States-Israel Binational Science Foundation (BSF), Jerusalem, Israel.     

解读DOCSIS 2.0技术

新的应用是否需要新的技术?或者，新的技术是否会产生新的应用?在不同的情况下，这一由来已久的问题的答案也各不相同。但就有线宽带市场而言，对这两个问题的回答都是肯定的。