Analysis method of the angiotensin-I converting enzyme inhibitory activity based on micellar electrokinetic chromatography.

A micellar electrokinetic chromatography (MEKC) method was developed for estimating the angiotensin-I converting enzyme (ACE) inhibitory activity by separating the hippuric acid liberated in the ACE reaction mixture in the presence of an inhibitor, captopril. The hippuric acid was successfully separated and detected by MEKC with a 25 mM sodium dodecyl sulfate solution in a 25 mM phosphate-50 mM borate buffer at pH 7.0; the total analysis took about 5 min. A good linear relationship was observed between the inhibitor and the peak area of hippuric acid release. No significant difference in the ACE inhibitory activity (IC50) of captopril (an antihypertensive medicine) or autolyzed-mushrooms (functional foods) was observed between the conventional method and the MEKC method. The MEKC method was found to be a useful technique for a rapid assay of the ACE inhibitory activity.     

Carbide precipitates in solution-quenched PH13-8 Mo stainless steel: A small-angle neutron scattering investigation

This paper deals with the small-angle neutron scattering (SANS) investigation on solution-quenched PH13-8 Mo stainless steel. From the nature of the variation of the functionality of the profiles for varying specimen thickness and also from the transmission electron microscopy (TEM), it has been established that the small-angle scattering signal predominantly originates from the block-like metallic carbide precipitates in the specimen. The contribution due to double Bragg reflection is not significant in the present case. The single scattering profile has been extracted from the experimental profiles corresponding to different values of specimen thickness. In order to avoid complexity and non-uniqueness of the multi-parameter minimization for randomly oriented polydisperse block-like precipitate model, the data have been analyzed assuming randomly oriented polydisperse cylindrical particle model with a locked aspect ratio.     

A novel discrete control strategy for independent stabilization of parallel three-phase boost converters by combining space-vector modulation with variable-structure control

We propose a discrete nonlinear controller, developed in a synchronous frame, for a parallel three-phase boost converter consisting of two modules. The basic idea, however, can be extended to a system with N modules. Each of the closed-loop power-converter modules operates asynchronously without any communication with the other modules. The controller stabilizes the currents on the dq-axes and limits the flow of the pure-zero sequence current. It combines the space-vector modulation scheme with a variable-structure control, thereby keeping the switching frequency constant and achieving satisfactory dynamic performance.     

Coprocessor design for multilayer surface-mounted PCB routing

The authors present the issues involved in the design of a special-purpose processing array system, called HAM, which accelerates computationally intensive wire routing tasks. It is especially suited for double-sided surface-mounted boards, which require complex three-dimensional search operations over multiple wiring planes. The novel features of the design include a hexagonal interconnection scheme to improve workload distributions during multilayer concurrent search operations and the VLSI custom design of the processors. Particular emphasis has been placed on the demands of maze routing. A cell-address propagation scheme, which is quite different from the traditional grid-coordinate approach, is discussed. It provides rapid lookup of pertinent routing information and can be extended to any distributed memory multiprocessor system. A global pipelining scheme of cell updates and expands is discussed. Experimental results are presented relating the speedup to various criteria for two different modes of parallel wave propagation     

Long Duration Persistent Photocurrent in 3 nm Thin Doped Indium Oxide for Integrated Light Sensing and In-Sensor Neuromorphic Computation

Miniaturization and energy consumption by computational systems remain major challenges to address. Optoelectronics based synaptic and light sensing provide an exciting platform for neuromorphic processing and vision applications offering several advantages. It is highly desirable to achieve single-element image sensors that allow reception of information and execution of in-memory computing processes while maintaining memory for much longer durations without the need for frequent electrical or optical rehearsals. In this work, ultra-thin (<3 nm) doped indium oxide (In₂O₃) layers are engineered to demonstrate a monolithic two-terminal ultraviolet (UV) sensing and processing system with long optical state retention operating at 50 mV. This endows features of several conductance states within the persistent photocurrent window that are harnessed to show learning capabilities and significantly reduce the number of rehearsals. The atomically thin sheets are implemented as a focal plane array (FPA) for UV spectrum based proof-of-concept vision system capable of pattern recognition and memorization required for imaging and detection applications. This integrated light sensing and memory system is deployed to illustrate capabilities for real-time, in-sensor memorization, and recognition tasks. This study provides an important template to engineer miniaturized and low operating voltage neuromorphic platforms across the light spectrum based on application demand.     

Exploring nucleoside hydrolase catalysis in silico: molecular dynamics study of enzyme-bound substrate and transition state

The mechanism of action of inosine-uridine nucleoside hydrolase has been investigated by long-term molecular dynamics (MD) simulation in TIP3P water using stochastic boundary conditions. Five MD studies have been performed with enzyme substrate complex (E.S), enzyme substrate complex with protonated His241 (EH.S), enzyme transition state complex (E.TS), enzyme transition state complex with protonated His241 (EH.TS), and His241Ala transition state complex E(H241A).TS. Special attention has been given to the role of His241, which has been considered as the general acid catalyst to assist departure of the leaving nucleobase on the basis of its location in the active site in the X-ray crystal structure (). Yet on the basis of the location in the active site, Tyr229 is closer to the aniline ring of pAPIR as compared to His241. On initiation of MD simulations, His241 does not approach the nucleobase in the structures of EH.S, E.S, EH.TS, and E.TS. In the solvated enzyme, Tyr229, which is a member of the hydrogen bonding network inosine O2'.Asp14.His241.Tyr229.inosine N7, serves as a proton source to the leaving nucleobase. The loss of significant activity of His241Ala mutant is shown to be related to the disruption of the above hydrogen bonded network and the distancing of Tyr229 from inosine N7. The structures of the enzyme complexes with substrate or TS are not visibly altered on protonation of His241, a most unusual outcome. The bell-shaped pH dependence upon pK(app)'s of 7.1 and 9.1 may be attributed to the necessity of the dissociation of Asp10 or Asp15 and the acid form of Tyr229, respectively. In TS, the residue Ile81 migrated closer, whereas Arg233 moved away from the nucleobase. The probability of ribooxocarbenium ion stabilization by Asn168 and Asp14 is discussed. The Asp14-CO(2)(-) is hydrogen bonded to the ribose 2'-OH for 96% of the MD simulation time. Nucleophilic addition of water138 to ribooxocarbenium ion is suggested to be assisted by the proton shuttle from water138 --> Asp10 --> Asp15 --> water pool. An anticorrelation motion between Tyr229-OH and Asn168-OD1 in EH.S and E.S is observed. The relationship of this anticorrelated motion to mechanism, if any, deserves further exploration, perhaps the formation of a near attack conformation.     

A Comprehensive Survey of Emergency Communication Network and Management

Wireless Personal Communications - The performance of wireless communication network is important in emergency rescue operations while ensuring optimum usage of limited wireless resources. Due to...     

Formation of bamboo-shaped carbon nanotubes on carbon black in a fluidized bed

For the first time, bamboo-shaped multiwalled carbon nanotubes, having diameter of the order of 50 nm, have been grown on carbon black in a fluidized bed in bulk amount. The activation energy for the synthesis of the product was found out to be around 33 kJ/mol in the temperature range of 700−900 °C. The carbon nanotubes were separated from the carbon black by preferential oxidation of the later, the temperature of which was determined by thermogravimetry. The transmission electron microscopy revealed different features of the nanotubes such as “Y” junction, bend, and catalyst filling inside the nanotubes. Small angle neutron scattering was performed on the nanotubes synthesized at different temperatures. The data were fitted into a suitable model in order to find out the average diameter, which decreases with increase in synthesis temperature. The Monte Carlo simulation predicts the same behavior. Based on the above observations, a possible growth mechanism has been predicted. The oscillation in carbon saturation value inside the catalyst in the fluidized bed has been indicated as the responsible factor for the bamboo-shaped structure.     

Novel pattern forming process due to the coupling of convection and phase change

We present a novel mechanism of pattern formation behind a flat interface during directional solidification of peritectic alloys. It is shown through computational modeling that irregular oscillatory thermosolutal convection can develop in the vertical Bridgman system, even with bottom seeding and bottom cooling. The coupling of the flow oscillation near the interface with solidification leads to ordered layered structures in the solidified crystal, which agree closely with earlier experimental results.