Aggregation of calcium ionophore (A23187) in phospholipid vesicles

The circular dichroism studies on calcium ionophore, A23187, incorporated in Dipalmitoyl phosphatidyl choline (DPPC) vesicle showed interesting time dependent changes in the CD spectra. Analysis of the data indicated the possible aggregation of the observed dimeric structure of this molecule in non-polar solvents into a stacked dimeric pore in the phospholipid vesicle.

Low-temperature polymer precursor-based synthesis of nanocrystalline particles of lanthanum calcium manganese oxide (La0.67Ca0.33MnO3) with enhanced ferromagnetic transition temperature

We report a simple modified polymeric precursor route for the synthesis of highly crystalline and homogenous nanoparticles of lanthanum calcium manganese oxide (LCMO). The LCMO phase formation was studied by thermal analysis, x-ray powder diffraction, and infrared spectroscopy at different stages of heating. These nanocrystallites (average particle size of 30 nm) possess ferromagnetic-paramagnetic transition temperature (T-c) of 300 K, nearly 50 K higher than that of a single crystal. The Rietveld analysis of the powder x-ray diffraction data of the nanopowders reveals significant lattice contraction and reduction in unit cell anisotropy-these structural changes are correlated to the enhancement in T-c.

Implications of Energy Profile and Storage on Energy Harvesting Sensor Link Performance

Energy harvesting sensors (EHS), which harvest energy from the environment in order to sense and then communicate their measurements over a wireless link, provide the tantalizing possibility of perpetual lifetime operation of a sensor network. The wireless communication link design problem needs to be revisited for these sensors as the energy harvested can be random and small and not available when required. In this paper, we develop a simple model that captures the interactions between important parameters that govern the communication link performance of a EHS node, and analyze its outage probability for both slow fading and fast fading wireless channels. Our analysis brings out the critical importance of the energy profile and the energy storage capability on the EHS link performance. Our results show that properly tuning the transmission parameters of the EHS node and having even a small amount of energy storage capability improves the EHS link performance considerably.

Role of a PAS sensor domain in the Mycobacterium tuberculosis transcription regulator Rv1364c

The Mycobacterium tuberculosis transcriptional regulator Rv1364c regulates the activity of the stress response sigma factor sigma(F). This multi-domain protein has several components: a signaling PAS domain and an effector segment comprising of a phosphatase, a kinase and an anti-anti-sigma factor domain. Based on Small Angle X-ray Scattering (SAXS) data, Rv1364c was recently shown to be a homo-dimer and adopt an elongated conformation in solution. The PAS domain could not be modeled into the structural envelope due to poor sequence similarity with known PAS proteins. The crystal structure of the PAS domain described here provides a structural basis for the dimerization of Rv1364c. It thus appears likely that the PAS domain regulates the anti-sigma activity of Rv1364c by oligomerization. A structural comparison with other characterized PAS domains reveal several sequence and conformational features that could facilitate ligand binding - a feature which suggests that the function of Rv1364c could potentially be governed by specific cellular signals or metabolic cues. (C) 2010 Elsevier Inc. All rights reserved.

Optimal Sleep-Wake Policies for an Energy Harvesting Sensor Node

We study a sensor node with an energy harvesting source. In any slot,the sensor node is in one of two modes: Wake or Sleep. The generated energy is stored in a buffer. The sensor node senses a random field and generates a packet when it is awake. These packets are stored in a queue and transmitted in the wake mode using the energy available in the energy buffer. We obtain energy management policies which minimize a linear combination of the mean queue length and the mean data loss rate. Then, we obtain two easily implementable suboptimal policies and compare their performance to that of the optimal policy. Next, we extend the Throughput Optimal policy developed in our previous work to sensors with two modes. Via this policy, we can increase the through put substantially and stabilize the data queue by allowing the node to sleep in some slots and to drop some generated packets. This policy requires minimal statistical knowledge of the system. We also modify this policy to decrease the switching costs.

Rapid localization of damage using a circular sensor array and Lamb wave based triangulation

A damage detection and imaging methodology based on symmetry of neighborhood sensor path and similarity of signal patterns with respect to radial paths in a circular array of sensors has been developed It uses information regarding Limb wave propagation along with a triangulation scheme to rapidly locate and quantify the severity of damage without using all of the sensor data. In a plate like structure, such a scheme can be effectively employed besides full field imaging of wave scattering pattern from the damage, if present in the plate. This new scheme is validated experimentally. Hole and corrosion type damages have been detected and quantified using the proposed scheme successfully. A wavelet based cumulative damage index has been studied which shows monotonic sensitivity against the severity of the damage. which is most desired in a Structural Health Monitoring system. (C) 2010 Elsevier Ltd. All rights reserved.

Joint Power Control, Scheduling and Routing for Multihop Energy Harvesting Sensor Networks

We study wireless multihop energy harvesting sensor networks employed for random field estimation. The sensors sense the random field and generate data that is to be sent to a fusion node for estimation. Each sensor has an energy harvesting source and can operate in two modes: Wake and Sleep. We consider the problem of obtaining jointly optimal power control, routing and scheduling policies that ensure a fair utilization of network resources. This problem has a high computational complexity. Therefore, we develop a computationally efficient suboptimal approach to obtain good solutions to this problem. We study the optimal solution and performance of the suboptimal approach through some numerical examples.

Use of the Nasicon/Na2SO4 couple in a solid state sensor for SOx (x=2,3)

The e.m.f. of a concentration cell for SO x (x=2,3)-O2 incorporating Nasicon as the main solid electrolyte has been measured in the temperature range 720 to 1080 K. The cell arrangement can be represented as,$$Pt, O'_2 + SO'_2 + SO'_3 \left| {Na_2 SO_4 \left\| {\left. {Nasicon} \right\|} \right.} \right.\left. {Na_2 SO_4 } \right|SO''_3 + SO''_2 + O''_2 , Pt$$ The Na2SO4 acts both as an auxiliary electrode, converting chemical potentials of SO x and O2 to equivalent sodium potentials, and as an electrolyte. The presence of Na2SO4 provides partial protection of Nasicon from chemical reaction with gas mixtures containing SO x . The open circuit e.m.f. of the cell is in close agreement with values given by the Nernst equation. For certain fixed inlet gas compositions of SO2+O2, the e.m.f. varies non-linearly with temperature. The intrinsic response time of the cell to step changes in gas composition is estimated to vary from sim2.0 ksec at 723K to sim 0.2 ksec at 1077K. The cell functions well for large differences in partial pressures of SO3(pPrimeSO 3/pprimeSO 3ap104) at the electrodes.

An SOx (x = 2, 3) sensor using ?-alumina/Na2SO4 couple

A solid-state sensor for SOx (x = 2, 3) species has been designed using ?-alumina as the solid electrolyte and Na2SO4 as the auxiliary electrode. The measured e.m.f. of the cell Pt, O?2 + SO?2 + SO?3|Na2SO4short parallel?-aluminashort parallelNa2SO4|SO?3 + SO?2 + O?2, PT in the temperature range 700 K to 1150 K agrees well with values calculated using the Nernst equation. The sodium sulphate acts both as a protective covering, preventing direct access of the gaseous SOx species to the ?-alumina electrolyte, and as an auxiliary electrode, converting chemical potentials of SOx species and O2 into an equivalent sodium potential. The open-circuit e.m.f. varies non-linearly with temperature for fixed composition of inlet gas mixtures containing SO2, O2 and Ar. The response time (t0.99) of the cell varies between 1.9 ks at 750 K and 0.06 ks at 1100 K. The e.m.f. response is faster when the partial pressure of SOx at the electrode is increased than when it is decreased.

A role for calcium in gonadotrophin-releasing hormone (GnRH) stimulated secretion of chorionic gonadotrophin by first trimester human placental minces in vitro

In vitro studies using first-trimester human placental minces have shown that stimulation of human chorionic gonadotrophin (hCG) secretion by gonadotrophin-releasing hormone (GnRH) is dependent upon the presence of extracellular calcium. Addition of GnRH to first-trimester placental minces in vitro was found to stimulate 45Ca2+ uptake into placental minces, and the process was associated with an increase in immunoreactive hCG in the medium. Addition of GnRH to placental minces preloaded with 45Ca2+ stimulated the efflux of 45Ca2+ within one minute. The calmodulin inhibitors chlorpromazine andtrifluoperazine inhibited the basal uptake and efflux of 45Ca2+ suggesting the involvement of calmodulin in the mobilization of calcium in the placenta.

A wide‐range superconductor thermal sensor for low‐temperature measurement

This paper aims at describing a low‐temperature thermal sensor based on superconductor films which can be designed to have required variation of resistance with temperature through an appropriate geometry. Further, it has been shown that the temperature range can be varied to some extent by controlling the bias current.

A Low-Complexity Algorithm for Intrusion Detection in a PIR-Based Wireless Sensor Network

We present a low-complexity algorithm for intrusion detection in the presence of clutter arising from wind-blown vegetation, using Passive Infra-Red (PIR) sensors in a Wireless Sensor Network (WSN). The algorithm is based on a combination of Haar Transform (HT) and Support-Vector-Machine (SVM) based training and was field tested in a network setting comprising of 15-20 sensing nodes. Also contained in this paper is a closed-form expression for the signal generated by an intruder moving at a constant velocity. It is shown how this expression can be exploited to determine the direction of motion information and the velocity of the intruder from the signals of three well-positioned sensors.

A New Liquid Level Sensor for Process-Control Applications

Many process-control systems are air-operated. In such an environment, it would be desirable and economical to use pneumatic sensors. Bubble-back pressure sensors perform quite satisfactorily, but in case of viscous inflammable and slurry-like liquids with a tendency to froth, this level sensor is inadequate. The method suggested in this paper utilizes a pneumatic capacitor, one boundary of which is formed by the liquid level, to modulate a fluid amplifier feedback oscillator. The absence of moving parts and economy obtained makes this method attractive for process-control applications. The system has been mathematically modeled and simulated on an IBM 360/44 digital computer. Experimental values compare fairly well with the theoretical results. For the range tested, the sensor is found to have a linear frequency variation with the liquid level Extended running in the laboratory shows that the system is very reliable. This system has been found insensitive to temperature variations of up to 15ðC.

Vapor-Pressure Of Calcium Corresponding To The Reduction Of Calcia By Aluminum

The equilibrium pressure of calcium corresponding to the reduction reaction 6CaO (s) + 2Al (l) half-arrow-right-over-half-arrow-left 3CaO.Al2O3 (s) + 3Ca (g) has been measured by Knudsen effusion - mass loss analysis in the temperature range 1190 - 1500 K. The measured vapour pressure can be expressed as a function of temperature by the relation: log p(Ca) (Pa) = -10,670/T + 9.267 The calcium generated is partially absorbed by aluminium to form an alloy. The equilibrium composition of the alloy at 1373 K was found to be 22 mol% Ca - 78 mol% Al. The measured vapour pressure is in good agreement with that computed from thermodynamic data.