Atmospheric boundary-layer across Hadley and Ferrel cells over the Indian Ocean

A Southern Ocean Pilot cruise covering the latitudes from 10 degrees N to 56 degrees S in the open Indian Ocean was carried out during January February 2004. Surface and upper air data collected during this cruise are reported here. It is shown that the broad features of the atmosphere, in particular that of temperature, follow the tropical and mid-latitude weather expected during January February in this region. However, the atmospheric boundary-layer shows large variations, both in its height and structure between tropics and high latitudes. Strong influence of the surface heat flux on boundary layer structure is clearly seen. Humidity field reveals several local maxima and minima, suggesting a laminated atmosphere with air from different sources moving almost unmixed in adjacent layers.

Missile battery placement for air defense: A dynamic programming approach

A procedure to evaluate surface-to-air missile battery placement patterns for air defense is presented. A measure of defense effectiveness is defined as a function of kill probability of the defense missiles and the nature of the surrounding terrain features. The concept of cumulative danger index is used to select the best path for a penetrating hostile aircraft for any given pattern of placement. The aircraft is assumed to be intelligent and well-informed. The path is generated using a dynamic programming methodology. The software package so developed can be used off-line to choose the best among a number of possible battery placement patterns.

Sequential Assembly of an Active RNA Polymerase Molecule at the Air-Water Interface

At the heart of understanding cellular processes lies our ability to explore the specific nature of communication between sequential information carrying biopolymers. However, the data extracted from conventional solution phase studies may not reflect the dynamics of communication between recognized partners as they occur in the crowded cellular milieu. We use the principle of immobilization of histidine-tagged biopolymers at a Ni(II)-encoded Langmuir monolayer to study sequence-specific protein-protein interactions in an artificially crowded environment The advantage of this technique lies in increasing the surface density of one of the interacting partners that allows us to study macromolecular interactions in a controlled crowded environment, but without compromising the speed of the reactions. We have taken advantage of this technique to follow the sequential assembly process of the multiprotein complex Escherichia coil RNA polymerase at the interface and also deciphered the role of one of the proteins, omega (omega), in the assembly pathway. Our reconstitution studies indicate that in the absence of molecular chaperones or other cofactors, omega (omega) plays a decisive role in refolding the largest protein beta prime (beta') and its recruitment into the multimeric assembly to reconstitute an active RNA polymerase. It was also observed that the monolayer had the ability to distinguish between sequence-specific and -nonspecific interactions despite the immobilization of one of the biomacromolecules. The technique provides a universal two-dimensional template for studying protein-ligand interactions while mimicking molecular crowding.

Responsiveness of human male volunteers to immunization with ovine follicle stimulating hormone vaccine: Results of a pilot study

A study of 140 days duration was performed to examine if human male volunteers (n = 5) respond to ovine follicle stimulating hormone (oFSH) immunization (administered adsorbed on Alugel on days 1, 20, 40 and 70) by producing antibodies capable of both binding and neutralizing bioactivity of human FSH. The kinetics of antibody production for both the immunogen (oFSH) and the cross-reactive antigen (hFSH) were essentially similar, The volunteers responded only to the first two immunizations, The boosters given on days 40 and 70 were ineffective, probably because of the presence of substantial amounts of circulating antibody to oFSH. Of the antibodies generated to oFSH, 25-45% bound hFSH with a mean binding affinity of 0.65 x 10(9) +/- 0.53 M(-1). The binding capacities at the time of high (30-80 days of immunization) and low (>110 days) titres were 346 +/- 185 and 10.5 +/- 5.8 ng hFSH/ml respectively, During the period of high titre, free serum FSH (value in normal males 1-5 ng/ml) was not monitorable, A 50 mu l aliquot of the antiserum obtained from different volunteers between days 30 and 80 and on day 140 blocked binding of I-125-labelled hFSH to its receptor by 82 +/- 9.7 and 53 +/- 12.2% respectively, The antibody produced was specific for FSH, and no significant change in the values of related glycoprotein hormones (luteinizing hormone/testosterone and thyroid stimulating hormone/thyroxine) were recorded, Seminal plasma transferrin, a marker of Sertoli cell as well as of seminiferous tubular function, showed marked reduction (30-90%) following immunization with oFSH. Considering that endogenous FSH remained neutralized for approximately one sperm cycle only (65 days), the reduction in sperm counts (30-74%) exhibited by some volunteers is encouraging, Immunization with oFSH did not result in any significant changes in haematology, serum biochemistry or hormonal profiles, There was no production of antibodies capable of interacting with non-specific tissues, It is concluded that it should be possible to obtain a sustained long-term blockade of endogenous FSH action in men by using oFSH as an immunogen, This is a prerequisite for obtaining significant reduction in the quality and quantity of spermatozoa produced, thus leading to infertility.

A game theoretical multiple resource interaction approach to resource allocation in an air campaign

In this paper we propose a multiple resource interaction model in a game-theoretical framework to solve resource allocation problems in theater level military campaigns. An air raid campaign using SEAD aircraft and bombers against an enemy target defended by air defense units is considered as the basic platform. Conditions for the existence of saddle point in pure strategies is proved and explicit feedback strategies are obtained for a simplified model with linear attrition function limited by resource availability. An illustrative example demonstrates the key features.

Bubble size measurement in a gas-liquid ejector for a sodium chloride-air system

A high speed photographic technique has been employed to measure the Sauter mean diameter of bubbles experimentally in a gas liquid ejector using a sodium chloride-air system. The measured values are compared with the theoretically predicted maximum bubble size diameter using Sprow's correlation. Bubble size as a function of the liquid flow rate and also of its distance from the throat of the ejector has been reported in this paper. The results obtained for this non-reactive system are also compared with those obtained earlier for the air-water system.

Converging swirling liquid jets from pressure swirl atomizers: Effect of inner air pressure

Converging swirling liquid jets from pressure swirl atomizers injected into atmospheric air are studied experimentally using still and cine photographic techniques in the context of liquid-liquid coaxial swirl atomizers used in liquid rocket engines. The jet exhibits several interesting flow features in contrast to the nonswirling liquid jets (annular liquid jets) studied in the literature. The swirl motion creates multiple converging sections in the jet, which gradually collapse one after the other due to the liquid sheet breakup with increasing Weber number (We). This is clearly related to the air inside the converging jet which exhibits a peculiar variation of the pressure difference across the liquid sheet, DeltaP, with We. The variation shows a decreasing trend of DeltaP with We in an overall sense, but exhibits local maxima and minima at specific flow conditions. The number of maxima or minima observed in the curve depends on the number of converging sections seen in the jet at the lowest We. An interesting feature of this variation is that it delineates the regions of prominent jet flow features like the oscillating jet region, nonoscillating jet region, number of converging sections, and so on. Numerical predictions of the jet characteristics are obtained by modifying an existing nonswirling liquid jet model by including the swirling motion. The comparison between the experimental and numerical measurements shows that the pressure difference across the liquid sheet is important for the jet behavior and cannot be neglected in any theoretical analysis. (C) 2002 American Institute of Physics.

Comparative Analysis of Pilot-Assisted Distributed Cophasing Approaches in Wireless Sensor Networks

This paper compares and analyzes the performance of distributed cophasing techniques for uplink transmission over wireless sensor networks. We focus on a time-division duplexing approach, and exploit the channel reciprocity to reduce the channel feedback requirement. We consider periodic broadcast of known pilot symbols by the fusion center (FC), and maximum likelihood estimation of the channel by the sensor nodes for the subsequent uplink cophasing transmission. We assume carrier and phase synchronization across the participating nodes for analytical tractability. We study binary signaling over frequency-flat fading channels, and quantify the system performance such as the expected gains in the received signal-to-noise ratio (SNR) and the average probability of error at the FC, as a function of the number of sensor nodes and the pilot overhead. Our results show that a modest amount of accumulated pilot SNR is sufficient to realize a large fraction of the maximum possible beamforming gain. We also investigate the performance gains obtained by censoring transmission at the sensors based on the estimated channel state, and the benefits obtained by using maximum ratio transmission (MRT) and truncated channel inversion (TCI) at the sensors in addition to cophasing transmission. Simulation results corroborate the theoretical expressions and show the relative performance benefits offered by the various schemes.

Analytical Evaluation of Squeeze Film Forces in a CMUT With Sealed Air-Filled Cavity

The presence of vacuum inside the cavity of a capacitive micromachined ultrasonic transducer (CMUT) causes the membrane of the device (which is the main vibrating structural component) to deflect towards the substrate, thereby causing a reduction in the effective gap height. This reduction causes a drastic decrease in the pull-in voltage of the device limiting the DC bias at which the device can be operated for maximum efficiency. In addition, this initial deflection of the membrane due to atmospheric pressure, causes significant stress stiffening of the the membrane, changing the natural frequency of the device significantly from the design value. To circumvent the deleterious effects of vacuum in the sealed cavity, we investigate the possibility of using sealed CMUT cavities with air inside at ambient pressure. In order to estimate the transducer loss due to the presence of air in the sealed cavity, we evaluate the resulting damping and determine the forces acting on the vibrating membrane resulting from the compression of the trapped air film. We take into account the flexure of the top vibrating membrane instead of assuming the motion to be parallel-plate like. Towards this end, we solve the linearized Reynolds equation using the appropriate boundary conditions and show that, for a sealed CMUT cavity, the presence of air does not cause any squeeze film damping.