Assessment of metabolic changes in the striatum of a MPTP-intoxicated canine model: in vivo ¹H-MRS study of an animal model for Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the progressive loss of the dopaminergic neurons in the substantia nigra pars compacta, which projects to the striatum. We induced a selective loss of nigrostriatal dopamine neurons, by infusing the mitochondrial complex 1 inhibitor 1-methyl 4-phenyl 1,2,3,6-tetrahydropyridine (MPTP) into adult beagle dogs (N=5). Single voxel ¹H water suppressed magnetic resonance spectroscopy (¹H-MRS) at 3 T was used to assess the metabolic changes in the striatum of canine before and after MPTP intoxication. The metabolite spectra obtained from the striatum (voxel size: 2 cm³) showed a lower N-acetyl aspartate to total creatine (creatine+phosphocreatine) ratio after MPTP intoxication. There were no significant differences in other metabolite ratios such as glutamate+glutamine, choline-containing compounds (glycerophosphocholine+phophorylcholine and myo-inositol). Our findings indicated that ¹H-MRS is a sensitive, noninvasive measure of neural toxicity and biochemical alterations of the striatum in a canine model of PD, and further studies are needed to confirm brain metabolic changes in association with progression of MPTP-intoxication.     

Photoproduction ofρ- andω-mesons in the peripheral model

Photoproduction ofρ- andω-mesons on nucleons is considered. The possible matrix elements according to the peripheral model are constructed and the cross section is calculated,π,η,σ (ABC) and vector meson exchange is taken into account. The angular distribution for the decay pions of polarizedρ's is discussed with particular reference to peripheral production     

Epidemic centrality — is there an underestimated epidemic impact of network peripheral nodes?

In the study of disease spreading on empirical complex networks in SIR model, initially infected nodes can be ranked according to some measure of their epidemic impact. The highest ranked nodes, also referred to as “superspreaders”, are associated to dominant epidemic risks and therefore deserve special attention. In simulations on studied empirical complex networks, it is shown that the ranking depends on the dynamical regime of the disease spreading. A possible mechanism leading to this dependence is illustrated in an analytically tractable example. In systems where the allocation of resources to counter disease spreading to individual nodes is based on their ranking, the dynamical regime of disease spreading is frequently not known before the outbreak of the disease. Therefore, we introduce a quantity called epidemic centrality as an average over all relevant regimes of disease spreading as a basis of the ranking. A recently introduced concept of phase diagram of epidemic spreading is used as a framework in which several types of averaging are studied. The epidemic centrality is compared to structural properties of nodes such as node degree, k-cores and betweenness. There is a growing trend of epidemic centrality with degree and k-cores values, but the variation of epidemic centrality is much smaller than the variation of degree or k-cores value. It is found that the epidemic centrality of the structurally peripheral nodes is of the same order of magnitude as the epidemic centrality of the structurally central nodes. The implications of these findings for the distributions of resources to counter disease spreading are discussed.     

Baxter–Wu model in the presence of an external magnetic field

In this work we study an unusual phase transition of the Baxter–Wu model in the presence of an external magnetic field. The model is pure Baxter–Wu, which means that only three-spin interactions are taken into account. We construct a phase diagram on the temperature–field plane based mainly on the singularities of the specific heat. These singularities are more clearly observed than those of the magnetic susceptibility which are used in existing works. We establish a discontinuity in the critical exponents when the field is changed from zero to negative.     

How happy is your web browsing? A model to quantify satisfaction of an Internet user searching for desired information

We feel happy when web browsing operations provide us with necessary information; otherwise, we feel bitter. How to measure this happiness (or bitterness)? How does the profile of happiness grow and decay during the course of web browsing? We propose a probabilistic framework that models the evolution of user satisfaction, on top of his/her continuous frustration at not finding the required information. It is found that the cumulative satisfaction profile of a web-searching individual can be modeled effectively as the sum of a random number of random terms, where each term is a mutually independent random variable, originating from ‘memoryless’ Poisson flow. Evolution of satisfaction over the entire time interval of a user’s browsing was modeled using auto-correlation analysis. A utilitarian marker, a magnitude of greater than unity of which describes happy web-searching operations, and an empirical limit that connects user’s satisfaction with his frustration level—are proposed too. The presence of pertinent information in the very first page of a website and magnitude of the decay parameter of user satisfaction (frustration, irritation etc.) are found to be two key aspects that dominate the web user’s psychology. The proposed model employed different combinations of decay parameter, searching time and number of helpful websites. The obtained results are found to match the results from three real-life case studies.     

Monitoring of the Kα–Kβ Spectrum of a Micropinch in an Iron Plasma

JETP Letters - The variation of the Kα–Kβ spectrum of a micropinch in an iron plasma of a high-current vacuum spark has been studied at detection in a single discharge using a...     

A model of turbulent mixing in the A+B→0 reaction

The diffusion limited reaction A+B0 in sufficiently low dimensions results in macroscopically self-regregated systems with anomalous reaction rate laws. When the chemical mixture is embedded in a fluctuating velocity field having statistics mimicking turbulent diffusion the effects of spatial inhomogeneities are washed out and the classical global reaction rate laws in three dimensions result.     

Can an effect precede its cause? A model of a noncausal world

The world appears causal in the sense that the result of a measurement may depend on the past history of the observed system, but not on what the experimenter will do with the system after the measurement. This raises the question whether noncausality at a macroscopic level would necessarily lead to an unreasonable world. The study of a model world with axiomatically well-specified properties shows that noncausal systems can be discussed in a logically consistent manner so that noncausality might well exist in the real world as a weak, but so far overlooked, effect.     

A microscopic model for the spin-spin relaxation of Fe3+ in an amorphous Mössbauer sample

A model for the spin-spin relaxation of glassy paramagnetic substances in external magnetic fields is developed and applied to frozen aqueous solutions of Fe(NO₃)₃. In these the ferric ions are surrounded by weakly distorted octahedral complexes of water molecules. The relaxation process is characterized by several relaxation frequencies which replace the single flip frequency of earlier approaches. In contrast to the latter, they can be calculated from the microscopic properties of the sample. The only model parameter is the ligand field coupling constant D determining the relaxational behavior. A set of Mössbauer spectra, measured under various experimental conditions, is well described by a single value of the ligand field parameter D = 2.2g_B kG. Some characteristic features of the model become obvious in the spectra, e.g. the fading of certain absorption lines with increasing Fe³⁺ concentration.     

A Family of Schrödinger Operators Whose Spectrum is an Interval

By approximation, I show that the spectrum of the Schrödinger operator with potential V(n) = f (n ^ρ (mod 1)) for f continuous and \({\rho > 0, \rho \notin \mathbb{N}}\) is an interval.     

Automatic detection of the belt-like region in an image with variational PDE model

In this paper, we propose a novel method to automatically detect the belt-like object, such as highway, river, etc., in a given image based on Mumford-Shah function and the evolution of two phase curves. The method can automatically detect two curves that are the boundaries of the belt-like object. In fact, this is a partition problem and we model it as an energy minimization of a Mumford-Shah function based minimal partition problem like active contour model. With Eulerian formulation the partial differential equations (PDEs) of curve evolution are given and the two curves will stop on the desired boundary. The stop term does not depend on the gradient of the image and the initial curves can be anywhere in the image. We also give a numerical algorithm using finite differences and present various experimental results. Compared with other methods, our method can directly detect the boundaries of belt-like object as two continuous curves, even if the image is very noisy.     

Drift−diffusion model of normal glow discharge in an axial magnetic field

A two-dimensional axisymmetrical computing model is formulated with using of which the mathematical modeling of the normal glow discharge in molecular hydrogen is fulfilled in an axial magnetic field with the induction B = 0.1 T in the pressure range p = 1.25?5 Torr and the current-source electromotive force E = 1?3 kV.     

A simple model of structural disorder in III–V quaternary alloys

A model is proposed describing the bond length and bond-bending angle distributions in quaternary A³B⁵ alloys with ZB structure in quasi-continuum approximation. The model allows to consider reasonably large crystal lattice clusters employing minimum computing resources. Analytical expressions are derived for the radial distribution functions. The developed approach is applied to the analysis of available experimental data on structural disorder in III–V alloys. Employing the valence force field Keating model the deformation energy for several alloys is evaluated.     

A quark model of the meson fragmentation region in πp collisions

A model is explored in which the fragmentation region is populated by the hadronization of a string which stretches from a fast forward quark to a quark in the backward hemisphere of the p collision. This model is a part of more complicated models which have been studied elsewhere. It successfully fits observed inclusive production of ⁰-mesons, ⁰-mesons and -mesons, and agrees with the result that their production in p collisions is harder than in electron-position annihilation if: (a) the forward quark has an initial momentum which is at least 0·9 of that of the ⁰-mesons (b) gluon radiation is weaker than in electron-positron annihilation.     

A comprehensive model of the railway wheelset–track interaction in curves

Train–track interaction has been extensively studied in the last 40 years at least, leading to modelling approaches that can deal satisfactorily with many dynamic problems arising at the wheel/rail interface. However, the available models are usually not considering specifically the running dynamics of the vehicle in a curve, whereas a number of train–track interaction phenomena are specific to curve negotiation.     

Combined analysis of near-threshold production of ω and φ mesons in nucleon-nucleon collisions within an effective meson-nucleon model

Vector meson ( V = ,) production in near-threshold elementary nucleon-nucleon collisions ppppV, pnpnV and pndV is studied within an effective meson-nucleon theory. It is shown that a set of effective parameters can be established to describe fairly well the available experimental data of angular distributions and the energy dependence of the total cross-sections without explicit implementation of the Okubo-Zweig-Iizuka rule violation. Isospin effects are considered in detail and compared with experimental data whenever available.     

Validation of an analytical model of Si-ring resonators for designing a 1 × 8 multiplexer in SCISSOR configuration

We numerically simulate chromatic and thermal dispersion in ring-resonator-based filters and validate the model with experimental data. A low-loss 1 × 8 multiplexer based on SCISSOR structure was designed with a bandwidth of 200GHz at ?3 dB and a crosstalk better than ?13.5 dB for each channel.     

A simple model for approximate bandgap structure calculation of all-solid photonic bandgap fibre based on an array of rings

A simple model for approximate bandgap structure calculation of all-solid photonic bandgap fibre based on an array of rings is proposed. In this model calculated are only the potential modes of a unit cell, which is a high-index ring in the low-index background for this fibre, rather than the whole cladding periodic structure based on Bloch＇s theorem to find the bandgap. Its accuracy is proved by comparing its results with the results obtained by using the accurate full-vector plane-wave method. High speed in computation is its great advantage over the other exact methods, because it only needs to find the roots of one-dimensional analytical expressions. And the results of this model, mode plots, offer an ideal environment to explore the basic properties of photonie bandgap clearly.     

A point‐defect model of structural phase transitions in the ferroelastic superconductor Y-Ba-Cu-O

A point-defect model of structural phase transitions in YBa₂Cu₃O_{6 + x} is proposed. The model treats the basal-plane oxygen atoms as point defects. The treatment parallels the work of Alefeld and coworkers on ferroelasticity due to hydrogen in metals. The model predicts that the tetragonal-to-orthorhombic phase transition should be accompanied by precipitation into regions of high and low oxygen density, as well as high and low oxygen ordering. This is in agreement with experiment, as well as with the predictions of Khachaturyan's concentration-wave model. A new feature of the present model is the prediction of two characteristic temperatures related, respectively, to Snoek-type and Gorsky-type diffusive relaxations. Practical implications of the high diffusivity of the basal-plane oxygens include the easy fabricability of a bicrystal of Y-Ba-Cu-O such that the two components of the bicrystal are rotated by 90° with respect to each other, and are separated by a non-superconducting layer. Such a bicrystal can find applications as a Josephson-tunneling device.     

Simulation of dynamic temperature evolution in an underground coal fire area based on an optimised Thermal–Hydraulic–Chemical model

Underground coal fires (UCFs) exist in almost all coal mining countries. In this paper, an optimised Thermal–Hydraulic–Chemical model, which includes variable reaction kinetics of coal and permeability variation in UCF zones, was developed for the simulation of dynamic temperature evolution of an actual UCF in Xinjiang, China. The model was also adopted in the analysis of the effect of surface coverage permeability on the temperature field, providing a theoretical reference for UCFs control. The results demonstrate that the temperature evolution included three distinct stages which were slow-heating stage, rapid-heating stage and stable-development stage. The slow-heating stage was occupied by the low-temperature oxidation of residual coal. During the rapid-heating stage, a hotspot (combustion centre) formed in residual coal zone and moved toward the air inlet side when the temperature reached a certain threshold. And before moving back into the deeper coal seam, the hotspot developed the temperature to the maximum when it got to the air inlet side. In the stable-development stage, the hotspot spread along the coal seam with the maximum temperature staying between about 800°C and 1000°C, creating elliptical temperature anomalies around the combustion centre. The simulation proved to be in good agreement with the in situ measurements. Surface covering will extinguish the UCF when the permeability of the coverage layer is lower than 10^–10?m², otherwise the fire will persist and continue to spread.