Differential c-fos expression in the nucleus of the solitary tract and spinal cord following noxious gastric distention in the rat

c-Fos has been used as a marker for activity in the spinal cord following noxious somatic or visceral stimulation. Although the viscera receive dual afferent innervation, distention of hollow organs (i.e. esophagus, stomach, descending colon and rectum) induces significantly more c-Fos in second order neurons in the nucleus of the solitary tract and lumbosacral spinal cord, which receive parasympathetic afferent input (vagus, pelvic nerves), than the thoracolumbar spinal cord, which receives sympathetic afferent input (splanchnic nerves). The purpose of this study was to determine the contribution of sympathetic and parasympathetic afferent input to c-Fos expression in the nucleus of the solitary tract and spinal cord, and the influence of supraspinal pathways on Fos induction in the thoracolumbar spinal cord. Noxious gastric distention to 80 mmHg (gastric distension/80) was produced by repetitive inflation of a chronically implanted gastric balloon. Gastric distension/80 induced c-Fos throughout the nucleus of the solitary tract, with the densest labeling observed within 300 microns of the rostral pole of the area postrema. This area was analysed quantitatively following several manipulations. Gastric distension/80 induced a mean of 724 c-Fos-immunoreactive nuclei per section. Following subdiaphragmatic vagotomy plus distention (vagotomy/80), the induction of c-Fos-immunoreactive nuclei was reduced to 293 per section, while spinal transection at T2 plus distention (spinal transection/80) induced a mean of 581 nuclei per nucleus of the solitary tract section. Gastric distension/80 and vagotomy/80 induced minimal c-Fos in the T8-T10 spinal cord (50 nuclei/section), but spinal transection/80 induced 200 nuclei per section. Repetitive bolus injections of norepinephrine produced transient pressor responses mimicking the pressor response produced by gastric distension/80. This manipulation induced minimal c-Fos in the nucleus of the solitary tract and none in the spinal cord. It is concluded that noxious visceral input via parasympathetic vagal afferents, and to a lesser extent sympathetic afferents and the spinosolitary tract, contribute to gastric distention-induced c-Fos in the nucleus of the solitary tract. The induction of c-Fos in the nucleus of the solitary tract is significantly greater than in the viscerotopic segments of the spinal cord, which is partially under tonic descending inhibition, but is not subject to modulation by vagal gastric afferents. Distention pressures produced by noxious gastric distention are much greater than those produced during feeding, suggesting that c-Fos induction in the nucleus of the solitary tract to noxious distention is not associated with physiological mechanisms of feeding and satiety. The large vagal nerve-mediated induction of c-Fos in the nucleus of the solitary tract following gastric distension suggests that parasympathetic afferents contribute to the processing of noxious visceral stimuli, perhaps by contributing to the affective-emotional component of visceral pain.     

TES modeling for analysis of a video multiplexer

The transport of video images is likely to be a major application of high-speed networks of the future. These applications are capable of utilizing the high bandwidths that will become available with the advent of B-ISDN. In this paper, we propose a new methodology (called TES) for modeling the frame bitrate stream generated by compressed video sources. The main characteristic of this method is that it can model an arbitrary marginal distribution and approximate the autocorrelation structure of the random bitrate process generated by compressed frames. We present a modeling example utilizing this method, based on data from a video coding algorithm employing a layering technique. Using the source model, we develop a simulation model of a multiplexer of video sources. We show that this model can be used to address a number of design issues that arise in this class of problem. In particular, we show that for a layered video coding algorithm, it is possible to have a gain in the number of sources multiplexed at the cost of some loss of low priority packets.     

Multi purpose research reactor

At present Dhruva and Cirus reactors provide the majority of research reactor based facilities to cater to the various needs of a vast pool of researchers in the field of material sciences, physics, chemistry, bio sciences, research & development work for nuclear power plants and production of radio isotopes. With a view to further consolidate and expand the scope of research and development in nuclear and allied sciences, a new 20 MWt multi purpose research reactor is being designed. This paper describes some of the design features and safety aspects of this reactor.     

Analysis of D.C Parameters of Short-Channel Heterostructure Double Gate Junction-Less MOSFET Circuits Considering Quantum Mechanical Effects

Silicon - In this article, the electrical behavior of short channel SiGe Heterostructure Junction-Less DG-MOSFET have been studied by incorporating the quantum mechanical effect and short channel...     

Polyamide-6,6/in situ silica hybrid nanocomposites by sol-gel technique: synthesis, characterization and properties

The organic-inorganic hybrid nanocomposites comprising of poly(iminohexamethyleneiminoadipoyl), better known as Polyamide-6,6 (abbreviated henceforth as PA66), and silica (SiO₂) were synthesized through sol-gel technique at ambient temperature. The inorganic phase was generated in situ by hydrolysis-condensation of tetraethoxysilane (TEOS) in different concentrations, under acid catalysis, in presence of the organic phase, PA66, dissolved in formic acid. Infrared (IR) spectroscopy was used to monitor the microstructural evolution of the silica phase in the PA66 matrix. Wide angle X-ray scattering (WAXS) studies showed that the crystallinity in PA66 phase decreased with increasing silica content. Atomic force microscopy (AFM) of the nanocomposite films revealed the dispersion of SiO₂ particle with dimensions of <100 nm in the form of network as well as linear structure. X-ray silicon mapping further confirmed the homogeneous dispersion of the silica phase in the bulk of the organic phase. The melting peak temperatures slightly decreased compared to neat PA66, while an improvement in thermal stability by about 20 °C was achieved with hybrid nanocomposite films, as indicated by thermogravimetric analysis (TGA). Dynamic mechanical analysis (DMA) exhibited significant improvement in storage modulus (E′) for the hybrid nanocomposites over the control specimen. An increase in Young's modulus and tensile strength of the hybrid films was also observed with an increase in silica content, indicating significant reinforcement of the matrix in the presence of nanoparticles. Some properties of the in situ prepared PA66-silica nanocomposites were compared with those of conventional composites prepared using precipitated silica as the filler by solution casting from formic acid.     

One pot synthesis of nano Ag in calcium alginate beads and its catalytic application in p‐Nitrophenol reduction with kinetic parameter estimation and model fitting

In this work, one step process of synthesis of silver nanoparticles (Agnp) embedded in insitu formed calcium alginate (CA) beads is stated. CA, formed from the reaction between sodium alginate and calcium hydroxide, acts as reducing and stabilizing agent as well as support for nanoparticles. The reaction mechanism for the formation and stabilization of Agnp is proposed where the vicinal dihydroxy groups of alginate are assumed to act as the reducing agent for Ag⁺ to Ag°. Transmission electron microscopy (TEM), x‐ray diffraction (XRD), UV‐vis spectroscopy, field emission scanning electron microscopy (FESEM), and atomic absorption spectroscopy (AAS) were used to characterize the Agnp. The formation of spherical nanoparticles with average size range of 4‐5 nm was confirmed by TEM. Catalytic activity of this nano silver‐calcium alginate (Agnp‐CA) composite was evaluated in the reduction of p‐nitrophenol. Concentrations of sodium alginate, calcium hydroxide, and AgNO₃ are found to be the parameters that critically affect the synthesis of Agnp. The efficacy of the catalyst is expressed on the basis of suitable reaction parameters. Both pseudo‐homogeneous and heterogeneous kinetic models are proposed for the reaction to find the best model and the Eley‐Riedel model is found to fit well with the experimental data. The novelty of this work is that the tandem process of CA bead formation, Agnp formation, and Agnp entrapment in CA have been transformed into a single‐step process. Moreover, elaborations of each step of the ionic mechanisms of Agnp formation and p‐NP reduction with Agnp and the establishment of a heterogeneous kinetic model for the reaction are reported for the first time here.     

Non-equilibrium Thermodynamics of Rayleigh–Taylor Instability

Here, the fundamental problem of Rayleigh–Taylor instability (RTI) is studied by direct numerical simulation (DNS), where the two air masses at different temperatures, kept apart initially by a non-conducting horizontal interface in a 2D box, are allowed to mix. Upon removal of the partition, mixing is controlled by RTI, apart from mutual mass, momentum, and energy transfer. To accentuate the instability, the top chamber is filled with the heavier (lower temperature) air, which rests atop the chamber containing lighter air. The partition is positioned initially at mid-height of the box. As the fluid dynamical system considered is completely isolated from outside, the DNS results obtained without using Boussinesq approximation will enable one to study non-equilibrium thermodynamics of a finite reservoir undergoing strong irreversible processes. The barrier is removed impulsively, triggering baroclinic instability by non-alignment of density, and pressure gradient by ambient disturbances via the sharp discontinuity at the interface. Adopted DNS method has dispersion relation preservation properties with neutral stability and does not require any external initial perturbations. The complete inhomogeneous problem with non-periodic, no-slip boundary conditions is studied by solving compressible Navier–Stokes equation, without the Boussinesq approximation. This is important as the temperature difference between the two air masses considered is high enough (\(\Delta T = 70\) K) to invalidate Boussinesq approximation. We discuss non-equilibrium thermodynamical aspects of RTI with the help of numerical results for density, vorticity, entropy, energy, and enstrophy.     

A Formal Methodology for Detecting Managerial Vulnerabilities and Threats in an Enterprise Information System

From information security point of view, an enterprise is considered as a collection of assets and their interrelationships. These interrelationships may be built into the enterprise information infrastructure, as in the case of connection of hardware elements in network architecture, or in the installation of software or in the information assets. As a result, access to one element may enable access to another if they are connected. An enterprise may specify conditions on the access of certain assets in certain mode (read, write etc.) as policies. The interconnection of assets, along with specified policies, may lead to managerial vulnerabilities in the enterprise information system. These vulnerabilities, if exploited by threats, may cause disruption to the normal functioning of information systems. This paper presents a formal methodology for detection of managerial vulnerabilities of, and threats to, enterprise information systems in linear time.     

A recursive maximum a posteriori estimator

Kalman Filter (KF) is the optimal state estimator for linear dynamical systems in the presence of zero mean white Gaussian noise. It is a minimum mean square error (MMSE) estimator. In the present work a recursive maximum a posteriori estimator (RMAPE) has been developed from basic principles of estimation. This estimator may be used for realtime state estimation of linear dynamical systems in presence of zero mean white Gaussian noise. It is further shown here that the KF can be derived from this RMAPE algorithm, i.e. this work shows an alternative method way to derive the KF. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

Universal instability modes in internal and external flows

Two prototypical external and internal flows have been studied which display linear temporal instability followed by nonlinear saturation taking the flows to a new equilibrium state. Direct simulation results are obtained using a specific formulation and numerical methods with very high accuracy. These results are analyzed via proper orthogonal decomposition (POD), which reveal similar modes for flow past a circular cylinder and flow inside a lid-driven cavity, indicating universality of such modes. Unlike many other efforts on reduced order modeling via POD, here the emphasis has been on understanding the physical aspect of the flow instability which requires very high accuracy of the simulation. Then, the obtained POD modes are related to the instability modes (in the classical sense of defining the latter) and new generic types of instability modes are identified in the studied external and internal flows. These new modes have been reported for flow past a circular cylinder [Sengupta TK, Singh N, Suman VK. Dynamical system approach to instability of flow past a circular cylinder. J Fluid Mech 2010;656:82–115] which help one in understanding the instability sequence and the relative importance of these modes in the flow evolution starting from an impulsive start. Present comparative study, furthermore, reveals universality of such instability modes by showing their presence for the flow inside a lid-driven cavity as well. Despite seeming dissimilarities between these two flows, similarities between the instability portrait of these two flows suggest universality of such modes. From the equilibrium amplitude of vorticity time-series, we establish the presence of multiple modes and multiple bifurcation sequences for these flows in parameter space. Existing theory due to Landau and Stuart that considers only a single dominant mode and its self-interaction does not explain all these features. We invoke a multi-modal interaction model in the cited reference above, termed as Landau–Stuart–Eckhaus (LSE) equation in recognition of Eckhaus’ work in modifying the classical Stuart–Landau equation. We also show that the new instability modes do not follow either the classical Stuart–Landau or the newly proposed LSE model equations and for this reason we call these as anomalous modes. Two specific classes of anomalous modes are identified and classified in the present work. Empirical expressions for the evolution of these anomalous modes are presented and their unambiguous role during instabilities is discussed.