Lightweight Optical Wavelength Communications without a Laser in Space

We will present a model for an earth-to-low-earthorbit optical communications system. The system modeled herein is designed to offer a very lightweight, low power consumption, low data rate communications link from LEO satellites. A novel architecture for a free-space optical communications link is presented and analyzed. For the first time, a method that offers full-duplex communications on a single beam is presented. In addition, a novel data format for free-space optical communications is presented. In this system, both the laser and the downlink receiver are located on the ground. The optical elements located on the spacecraft are a simple uplink receiver and a retromodulator. In fact, the laser transmitter for the system is a semiconductor device. We will present a simple feasibility model for the LOWCAL experiment that provides an estimate of the performance capability and identifies major system tradeoffs. Assuming a laser transmitter power of - 7-dB and a communications data rate of 10-kbps, we expect link margins of 17 dB for the downlink. For the uplink, an SC-FSK format is proposed that is invisible to the downlink and provides a link margin of 20 dB

Antiulcer and Anti-inflammatory Activity of Aerial Parts Enicostemma littorale Blume

The antiulcer and in vitro anti-inflammatory activities of the aerial parts of Enicostemma littorale against aspirin, ethanol, and pyloric ligation-induced ulcers in rats and bovine serum albumin denaturation were studied. The extract (200 mg/kg and 400 mg/kg po) was administered to the overnight fasted rats, one hour prior to aspirin / alcohol / pyloric ligation challenge. The ulcer index, tissue GSH levels, and lipid peroxidation levels were estimated in all the models of ulcers and the volume of gastric secretion, acidity, and pH, were estimated in the pyloric ligation model of ulcers. Pretreatment with the extract showed a dose-dependent decrease in the ulcer index (Against Aspirin, ethanol challenge, and pyloric ligation. The prior administration of the extract also reduced the total acidity, free acidity, and volume of gastric secretion, and elevated the gastric pH. In addition, it was also observed that the extract inhibited the serum albumin denaturation in a dose-dependent manner. It may be concluded that the methanolic extract possesses antiulcer activity, and the anti-inflammatory activity of the extract may be attributed to the antioxidant potential, as reported earlier

Introduction to the issue on laser beam combining and fiber laser systems

The 27 papers in this special issue focus on laser beam combining and fiber laser systems

Resolving Coastal Ocean Eddy Activity in Surface Velocity Signatures from Wellen Radars and an Acoustic Doppler Current Profiler

A dual-station high frequency Wellen Radar (WERA), transmitting at 16.045 MHz, was deployed along the east Florida Shelf and is currently operated and maintained by the University of Miami's Rosenstiel School for Marine and Atmospheric Science. From September 2004 to June 2005, a bottom-mounted acoustic Doppler current profiler (ADCP) obtained subsurface current measurements within the radar footprint along the shelf break at 86-m depth. The RMS differences ranged from 0.1 to 0.25 ms -1 between the surface and 14 m depth indicating good data. Monthly time series analyses indicated numerous current reversals during the 9-month deployment. When utilized in conjunction with the ADCP subsurface measurements, WERA enables 3-dimensional snapshots of coastal oceanographic features. Given the high temporal and spatial resolution of the WERA system, an increased understanding can be gained in the coastal ocean regime aiding the ability of ocean models at predicting complicated features in the domain

Discharge excitation of the XeF C to A transition

Recent success in high efficiency and high energy laser extraction of tunable radiation in the blue-green C-A transition of XeF under intense, short-pulse electron beam excitation has renewed interest in the possibility of similar performance in avalanche discharges. We present preliminary results of discharge excited fluorescence studies in a variety of devices having different degrees of energy loading