Monte Carlo simulation of sinusoidally modulated superlattice growth

The fabrication of ZnSe/ZnTe superlattices grown by the process of rotating the substrate in the presence of an inhomogeneous flux distribution instead of the successively closing and opening of source shutters is studied via Monte Carlo simulations. It is found that the concentration of each compound is sinusoidally modulated along the growth direction, caused by the uneven arrival of Se and Te atoms at a given point of the sample, and by the variation of the Te/Se ratio at that point due to the rotation of the substrate. In this way we obtain a ZnSe(1-x)Tex alloy in which the composition x varies sinusoidally along the growth direction. The period of the modulation is directly controlled by the rate of the substrate rotation. The amplitude of the compositional modulation is monotonic for small angular velocities of the substrate rotation, but is itself modulated for large angular velocities. The average amplitude of the modulation pattern decreases as the angular velocity of substrate rotation increases and the measurement position approaches the center of rotation. The simulation results are in good agreement with previously published experimental measurements on superlattices fabricated in this manner.

The Kondo effect in an artificial quantum dot molecule

Double quantum dots provide an ideal model system for studying interactions between localized impurity spins. We report on the transport properties of a series-coupled double quantum dot as electrons are added one by one onto the dots. When the many-body molecular states are formed, we observe a splitting of the Kondo resonance peak in the differential conductance. This splitting reflects the energy difference between the bonding and antibonding states formed by the coherent superposition of the Kondo states of each dot. The occurrence of the Kondo resonance and its magnetic field dependence agree with a simple interpretation of the spin status of a double quantum dot.

Comparable system-level organization of Archaea and Eukaryotes

A central and long-standing issue in evolutionary theory is the origin of the biological variation upon which natural selection acts. Some hypotheses suggest that evolutionary change represents an adaptation to the surrounding environment within the constraints of an organism's innate characteristics. Elucidation of the origin and evolutionary relationship of species has been complemented by nucleotide sequence and gene content analyses, with profound implications for recognizing life's major domains. Understanding of evolutionary relationships may be further expanded by comparing systemic higher-level organization among species. Here we employ multivariate analyses to evaluate the biochemical reaction pathways characterizing 43 species. Comparison of the information transfer pathways of Archaea and Eukaryotes indicates a close relationship between these domains. In addition, whereas eukaryotic metabolic enzymes are primarily of bacterial origin, the pathway-level organization of archaeal and eukaryotic metabolic networks is more closely related. Our analyses therefore suggest that during the symbiotic evolution of eukaryotes, incorporation of bacterial metabolic enzymes into the proto-archaeal proteome was constrained by the host's pre-existing metabolic architecture.

Parasitic computing

Reliable communication on the Internet is guaranteed by a standard set of protocols, used by all computers. Here we show that these protocols can be exploited to compute with the communication infrastructure, transforming the Internet into a distributed computer in which servers unwittingly perform computation on behalf of a remote node. In this model, which we call 'parasitic computing', one machine forces target computers to solve a piece of a complex computational problem merely by engaging them in standard communication. Consequently, the target computers are unaware that they have performed computation for the benefit of a commanding node. As experimental evidence of the principle of parasitic computing, we harness the power of several web servers across the globe, which-unknown to them-work together to solve an NP complete problem.

Inhibition of lipid peroxidation and oxidative DNA damage by Ganoderma lucidum

Reactive oxygen species (ROS), such as superoxide anions and hydroxyl radicals, are associated with carcinogenesis and other pathophysiological conditions. Therefore, elimination or inactivation of ROS or inhibition of their excess generation may be beneficial in terms of reducing the risk for cancer and other diseases. Ganoderma lucidum has been used in traditional oriental medicine and has potential antiinflammatory and antioxidant activities. In the present study, we tested the amino-polysaccharide fraction (designated as 'G009') from Ganoderma lucidum for the ability to protect against oxidative damage induced by ROS. G009 significantly inhibited iron-induced lipid peroxidation in rat brain homogenates and showed a dose-dependent inactivation of hydroxyl radicals and superoxide anions. It also reduced strand breakage in phiX174 supercoiled DNA caused by UV-induced photolysis of hydrogen peroxide and attenuated phorbol ester-induced generation of superoxide anions in differentiated human promyelocytic leukaemia (HL-60) cells. These findings suggest that G009 from Ganoderma lucidum possesses chemopreventive potential.

Weighted evolving networks

Many biological, ecological, and economic systems are best described by weighted networks, as the nodes interact with each other with varying strength. However, most evolving network models studied so far are binary, the link strength being either 0 or 1. In this paper we introduce and investigate the scaling properties of a class of models which assign weights to the links as the network evolves. The combined numerical and analytical approach indicates that asymptotically the total weight distribution converges to the scaling behavior of the connectivity distribution, but this convergence is hampered by strong logarithmic corrections.

Immunohistochemical analysis of CD44s and CD44v6 in endometriosis and adenomyosis : comparison with normal, hyperplastic, and malignant endometrium

The expression patterns of CD44s and CD44v6 were immunohistochemically compared with those of normal, hyperplastic and malignant endometrium. In normal endometria (n=37), endometrioses (n=46) and adenomyoses (n=20), the surface and glandular epithelial cells were negative for CD44s and CD44v6 in a proliferative pattern and positive in a secretory pattern, whereas the stroma was only positive for CD44s in both proliferative and secretory patterns. The endometrial hyperplasia (4 simple and 9 complex) had the identical patterns with normal proliferative phase of endometrium. Only one case showing complex hyperplasia with atypia was focally positive for CD44s and CD44v6 in glandular epithelia. CD44s and CD44v6 were positive in all endometrial adenocarcinomas (13), except one CD44s-negative case. In summary, the expressions of CD44s and CD44v6 in endometriosis and adenomyosis recapitulated those of normal cyclic endometrium. The expression patterns in endometrial hyperplasia were similar to those in normal proliferative endometrium, whereas the endometrial adenocarcinoma showed abnormal expressions for CD44s and CD44v6. Thus it was considered that the ectopic endometrium in endometriosis and adenomyosis was not aberrant as in endometrial carcinoma on the aspects of immunohistochemical expressions of CD44s and CD44v6.

IgE-mediated occupational asthma induced by herbal medicine, Banha (Pinellia ternata)

There have been few reported cases of occupational asthma induced by Pinellia ternata (Banha), and the mechanism responsible for this type of asthma is still undetermined. We report a case of Banha-induced occupational asthma with IgE-mediated mechanism. The patient had positive skin responses to Banha extract and Banha-specific bronchial challenge elicited an early asthmatic response. The serum-specific IgE binding to Banha extract was detectable and completely inhibited with the additions of 0.1 microg/mL of Banha extract on ELISA inhibition. Seven IgE binding components to Banha extract (6.5, 22, 24, 32, 34, and 48 kDa) were detected using SDS-PAGE and immunoblot analysis. In conclusion, the results of this study suggest that P. ternata (Banha)-derived allergens are able to cause IgE-mediated bronchoconstriction in exposed workers.

Extracellular polymeric substances in relation to nutrient removal from a sequencing batch biofilm reactor

Experimental investigations were performed to determine the possibility of simultaneous biological nitrogen and phosphorus removal during various biofilm processes in conjunction with biofilm characterisation, especially extracellular polymeric substance (EPS). Since biologial nitrogen removal requires an alternating exposure of anaerobic-anoxic-oxic conditions in the bulk liquid that surrounds the biofilm growth media, a sequencing batch reactor (SBR)-type operation was used. Various materials including expanded clay, polystyrene, polyurethane, and acrylic materials were used as the biofilm growth support medium. Simultaneous nitrogen and phosphorus removal was possible with SBR, but it was postulated that nutrient removal efficiencies varied with film thickness. Thinner biofilm promoted nitrification and phosphorus removal, but thicker biofilm enhanced denitrification and reduced phosphorus removal. EPS contents were similar regardless of support media types or biofilm configuration, but EPS contents gradually increased as the film growth continued after backwashing. EPS contents were increased with increased nitrogen removal, but it was difficult to define its relation with phosphorus removal. In addition, suspended solids removal was correlated well with the EPS content in the biofilms.

The large-scale organization of metabolic networks

In a cell or microorganism, the processes that generate mass, energy, information transfer and cell-fate specification are seamlessly integrated through a complex network of cellular constituents and reactions. However, despite the key role of these networks in sustaining cellular functions, their large-scale structure is essentially unknown. Here we present a systematic comparative mathematical analysis of the metabolic networks of 43 organisms representing all three domains of life. We show that, despite significant variation in their individual constituents and pathways, these metabolic networks have the same topological scaling properties and show striking similarities to the inherent organization of complex non-biological systems. This may indicate that metabolic organization is not only identical for all living organisms, but also complies with the design principles of robust and error-tolerant scale-free networks, and may represent a common blueprint for the large-scale organization of interactions among all cellular constituents.

Depinning of an anisotropic interface in random media: the tilt effect

We study the tilt dependence of the pinning-depinning transition for an interface described by the anisotropic quenched Kardar-Parisi-Zhang equation in 2+1 dimensions, where the two signs of the nonlinear terms are different from each other. When the substrate is tilted by m along the positive sign direction, the critical force F(c)(m) depends on m as F(c)(m)-F(c)(0) approximately -|m|(1.9(1)). The interface velocity v near the critical force follows the scaling form v approximately |f|(straight theta)Psi(+/-)(m(2)/|f|(straight theta+straight phi)) with straight theta=0.9(1) and straight phi=0.2(1), where f identical withF-F(c)(0) and F is the driving force.

Quasi-unit-cell model for an Al-Ni-Co ideal quasicrystal based on clusters with broken tenfold symmetry

We present new evidence supporting the quasi-unit-cell description of the Al72Ni20Co8 decagonal quasicrystal which shows that the solid is composed of repeating, overlapping decagonal cluster columns with broken tenfold symmetry. We propose an atomic model which gives a significantly improved fit to electron microscopy experiments compared to a previous proposal by us and to alternative proposals with tenfold symmetric clusters.

Fracture source location in thin plates using the wavelet transform of dispersive waves

A new signal processing approach was presented for acoustic emission source location using the dispersive waves in a thin plate. For wave propagation in dispersive media, the accuracy of source location can be improved by using the arrival times of a single frequency component in the output signals at an array of sensors. The wavelet transform (WT) was used to resolve this problem. By utilizing the time-frequency data of the WT, the frequency-dependent arrival time traveling with the group velocity was shown to be easily determined. Experiments were performed using a lead break as the simulated fracture source on the surface of an aluminum plate. Two plate modes corresponding to the S(0) and A(0) Lamb waves were identified, and their group velocities were accurately measured. The source location results based on the WT method agreed well with the true locations. The WT method was also compared with the cross correlation technique, and both methods provide similar results.

Numerical test of the damping time of layer-by-layer growth on stochastic models

We perform Monte Carlo simulations on stochastic models such as the Wolf-Villain (WV) model and the Family model in a modified version to measure the mean separation l between islands in a submonolayer regime and the damping time t* of layer-by-layer growth oscillations in one dimension. The stochastic models are modified, allowing for diffusion within interval r upon deposition. It is found numerically that the mean separation and the damping time depend on the diffusion interval r, leading to the fact that the damping time is related to the mean separation as t* approximately l(4/3) for the WV model and t* approximately l(2) for the Family model. The numerical results are in excellent agreement with recent theoretical predictions.

Penile sensitivity in men with premature ejaculation

Premature ejaculation is the most prevalent form of male sexual dysfunction, but its cause has not been well established. Recent studies have indicated that in men with premature ejaculation, penile sensitivity is increased. To investigate whether penile hypersensitivity is a cause of premature ejaculation, we prospectively evaluated the penile sensitivity of 18 patients with a lifelong history of premature ejaculation from the first coital experience and 15 controls, both in the flaccid and erect state. We used an SMV-5 vibrometer (Suzuki-Matsuoka, Teknologue, Tokyo, Japan), which automatically controls stimulatory strength; its precision and reproducibility are thus higher than analogue-type biothesiometers. At the styloid process of the ulna and medial maleolus of the tibia, there was no significant statistical difference in vibratory threshold between the two groups (P > 0.05). Also we did not find significant statistical differences in sensitivity of the glans penis, dorsum of the penile shaft, or frenulum of the penis between the two groups, in either the flaccid or erect state (P > 0.05). According to our results, penile hypersensitivity, as measured by an SMV-5 vibrometer, does not appear to be a major factor contributing to premature ejaculation.

Neural solution to the correction of miss distance in gun fire control system

Multilayer perceptrons trained with the backpropagation algorithm are tested in gun fire control system for error correction and are compared to optimal algorithms based on minimum mean square error. The structure of the proposed neural controller is described and performance results are shown.

An allograft kidney showing both features of IgA nephropathy and membranous glomerulonephritis--a case report

We report a case of glomerular disease with both mesangial IgA and subepithelial IgG deposits in the allograft kidney. The patient was a 36 year-old man who had received a renal allograft 1 year previously. Fifteen days before admission, he discovered a microscopic hematuria without clinical evidences of allograft rejection. Light microscopy showed diffuse increase of mesangial matrix without mesangial cell proliferation. Capillary walls were diffusely and mildly thickened. Immunofluorescence microscopy demonstrated both granular deposits of IgA in the mesangium and IgG along the capillary walls. On electron microscopy, electron-dense deposits were identified not only in the mesangium but also on the epithelial side of the glomerular basement membrane.