Design and Construction of a High Pressure System for Evaluating Multiphase Twin-Screw Pumps

Twin-screw pumps are currently sold by manufacturers without adequate data predicting the pump behavior when pumping multiphase mixtures. In light of the fact that pump behavior is known to change significantly under these conditions, a new closed-loop test facility has been designed and constructed to allow for testing of twin-screw pumps at high gas volume fractions. With minimal modification, the test facility can accommodate high pressure flows and oil-based liquids for testing. The closed-loop test facility supplies air and water to the inlet of an MR-200 twin-screw pump of which the performance characteristics are desired. The flow of air and water can be regulated to give the desired inlet pressure, outlet pressure, and gas volume fraction. The resulting mixture is driven to the test pump by its inlet suction. It then passes through the pump to a gravity separator, where it is separated into discrete liquid and gas phases. Inlet pressures up to seventy-five psig can be used, and with minimal modification, up to three-hundred psig. Total flow rates of up to six-hundred-fifty gallons per minute can be accommodated. A two-hundred horsepower electric motor provides the mechanical power for the pump. The test facility includes instrumentation and data acquisition equipment to monitor the pressures and temperatures at various points in the flow loop, as well as the flow rate and motor voltage of the pump. The closed-loop facility is validated by comparing the volumetric efficiency, mechanical efficiency, and pump effectiveness results to a previous open-loop facility that was also used to test the same twin-screw pump. Suggestions are given to replace an air valve to allow for more precise control of the air supply and to add a pulsation dampener that will moderate pressure oscillations. High pressure piping and tubing must be added for testing at higher inlet pressures

Domain specific software architectures: Command and control

GTE is the Command and Control contractor for the Domain Specific Software Architectures program. The objective of this program is to develop and demonstrate an architecture-driven, component-based capability for the automated generation of command and control (C2) applications. Such a capability will significantly reduce the cost of C2 applications development and will lead to improved system quality and reliability through the use of proven architectures and components. A major focus of GTE's approach is the automated generation of application components in particular subdomains. Our initial work in this area has concentrated in the message handling subdomain; we have defined and prototyped an approach that can automate one of the most software-intensive parts of C2 systems development. This paper provides an overview of the GTE team's DSSA approach and then presents our work on automated support for message processing

Allosteric Modulation of the HIV-1 gp120-gp41 Association Site by Adjacent gp120 Variable Region 1 (V1) N-Glycans Linked to Neutralization Sensitivity

The HIV-1 gp120-gp41 complex, which mediates viral fusion and cellular entry, undergoes rapid evolution within its external glycan shield to enable escape from neutralizing antibody (NAb). Understanding how conserved protein determinants retain functionality in the context of such evolution is important for their evaluation and exploitation as potential drug and/ or vaccine targets. In this study, we examined how the conserved gp120-gp41 association site, formed by the N- and Cterminal segments of gp120 and the disulfide-bonded region (DSR) of gp41, adapts to glycan changes that are linked to neutralization sensitivity. To this end, a DSR mutant virus (K601D) with defective gp120-association was sequentially passaged in peripheral blood mononuclear cells to select suppressor mutations. We reasoned that the locations of suppressors point to structural elements that are functionally linked to the gp120-gp41 association site. In culture 1, gp120 association and viral replication was restored by loss of the conserved glycan at Asn136 in V1 (T138N mutation) inconjunction with the L494I substitution in C5 within the association site. In culture 2, replication was restored with deletion of the N139INN sequence, which ablates the overlapping Asn141-Asn142-Ser-Ser potential N-linked glycosylation sequons inV1, in conjunction with D601N in the DSR. The 136 and 142 glycan mutations appeared to exert their suppressive effects by altering the dependence of gp120-gp41 interactions on the DSR residues, Leu593, Trp596 and Lys601. The 136 and/or 142glycan mutations increased the sensitivity of HIV-1 pseudovirions to the glycan-dependent NAbs 2G12 and PG16, and also pooled IgG obtained from HIV-1-infected individuals. Thus adjacent V1 glycans allosterically modulate the distal gp120-gp41 association site. We propose that this represents a mechanism for functional adaptation of the gp120-gp41 association site to an evolving glycan shield in a setting of NAb selection