General Dynamics

About: General Dynamics is a company organization based out in Fairfax, Virginia, United States. It is known for research contribution in the topics: Signal & Propellant. The organization has 5722 authors who have published 5819 publications receiving 85768 citations. The organization is also known as: GD & General Dynamics Corporation.

Scale Model Testing of a Commercial Rim-Driven Propulsor Pod

Abstract: Podded propulsion is gaining more widespread use in the marine industry and is prevalent in newer cruise ships in particular. This propulsion system can provide many advantages to the ship owner that include increased propulsion efficiency, arrangement flexibility, payload, and harbor maneuverability. A new, unique podded propulsor concept is being developed that allows optimization of each element of the system. The concept comprises a ducted, multiple-blade row propulsor with a permanent magnet, radial field motor rotor mounted on the tips of the propulsor rotor blades, and the motor stator mounted within the duct of the propulsor. This concept, designated a commercial rim-driven propulsor pod (CRDP), when compared to a conventional hub-driven pod (HDP), offers improved performance in a number of areas, including equal or improved efficiency, cavitation, and hull unsteady pressures. The combination of these CRDP performance parameters allows the ship designer much greater flexibility to provide improved ship performance as compared to that of an HDP. A CRDP is being developed to power a panamax-size cruise vessel. The paper addresses the hydrodynamic performance of that CRDP design demonstrated at 1/25th scale as tested at the Hamburg Ship Model Basin, Hamburg Germany (HSVA).

Nanosecond pulsed electric fields modulate the expression of Fas/CD95 death receptor pathway regulators in U937 and Jurkat Cells.

Abstract: In this publication, we demonstrate that exposure of Jurkat and U937 cells to nanosecond pulsed electrical fields (nsPEF) can modulate the extrinsic-mediated apoptotic pathway via the Fas/CD95 death receptor. An inherent difference in survival between these two cell lines in response to 10 ns exposures has been previously reported (Jurkat being more sensitive to nsPEF than U937), but the reason for this sensitivity difference remains unknown. We found that exposure of each cell line to 100, 10 ns pulses at 50 kV/cm caused a marked increase in expression of cFLIP (extrinsic apoptosis inhibitor) in U937 and FasL (extrinsic apoptosis activator) in Jurkat, respectively. Measurement of basal expression levels revealed an inherent difference between U937 cells, having a higher expression of cFLIP, and Jurkat cells, having a higher expression of FasL. From these data, we hypothesize that the sensitivity difference between the cells to nsPEF exposure may be directly related to expression of extrinsic apoptotic regulators. To validate this hypothesis, we used siRNA to knockdown cFLAR (coding for cFLIP protein) expression in U937, and FasL expression in Jurkat and challenged them to 100, 10 ns pulses at 150 kV/cm, a typical lethal dose. We observed that U937 survival was reduced nearly 60 % in the knockdown population while Jurkat survival improved ~40 %. These findings support the hypothesis that cell survival following 10 ns pulse exposures depends on extrinsic apoptotic regulators. Interestingly, pretreatment of U937 with a 100-pulse, 50 kV/cm exposure (to amplify cFLAR expression) significantly reduced the lethality of a 150 kV/cm, 100-pulse exposure applied 24 h later. From these data, we conclude that the observed survival differences between cells, exposed to 10 ns pulsed electric fields, is due to inherent cell biochemistry rather than the biophysics of the exposure itself. Understanding cell sensitivity to nsPEF may provide researchers/clinicians with a predicable way to control or avoid unintended cell death during nsPEF exposure.