Analysis of TOPEX laser retroreflector array characteristics

The joint U.S./French TOPEX/POSEIDON mission was successfully launched on August 10, 1992 for the study of ocean height variation using microwave altimetry. Accurate determination of the satellite orbit is paramount to the determination of the above phenomenon. To accomplish this, using laser ranging, the satellite is equipped with a laser retroreflector array (LRA) around the altimeter antennae. The goal of laser ranging is to obtain precision orbits with a radial accuracy of 13 cm to the center of mass of the satellite. This requires the laser range correction to the LRA reference be known at the sub-cm level and is quite a challenge considering the geometry of the LRA. Detailed studies were initiated by the TOPEX project office (Christensen) under the auspices of the CDP/DOSE project (Degnan) at Goddard Space Flight Center

Comparison of empirical antibiotics used with microbiological sensitivity pattern among patients admitted with urinary tract infection

Background: Symptomatic Urinary tract infection (UTI) is among the most common infection described in hospital settings. Inappropriate use of antibiotics initiated before the laboratory results of urine culture contribute to increasing resistance to antibiotics in uropathogens. Awareness of the disease, knowledge of the spectrum of antibiotics and common complication of UTI will help to reduce morbidity and mortality. This study compares common empirical antibiotics used with their  clinical outcomes and microbiological sensitivity pattern among patients admitted with UTI in a tertiary care hospital.Methods: It is a cross sectional study conducted in inpatients of Pushpagiri medical college, Thiruvalla from January 2017 – June 2018. Assuming that 50% of organisms will show sensitivity to empirical antibiotic therapy with a relative precision of 20% and alpha error of 5 %. Sample size is calculated as 100. Those patient  satisfying the inclusion criteria was recruited into the study after obtaining informed consent till the sample size attained. Symptoms on the day of admission was assessed using the questionnaire for Clinical profile. Primary outcome was matching of empirical antibiotics with culture and sensitivity pattern.  Secondary outcomes were Symptom resolution on third day with empirical antibiotics and profile organisms causing UTI.Results: Majority of the population belonged to 61-80 year of age (57%). The study population had 44 percent male and 56 females.72 percent of total population was diabetic.  The most common antibiotic used to treat empirically was piperacillin –tazobactum accounting for 47.2 percent followed by ceftriaxone  45 percent. Others contributed less than 8 percent.75 percent of empirical antibiotics matched with culture and sensitivity report in the study population.The most common organisms found was Escherichia coli (61%) followed by Klebsiella pneumonia(15 %) The most common resistant organism was E Coli followed by Klebsiella pneumonia. Esbl resistance was encountered in 28 cases and carbepenamase resistance in 2 percent cases. 27 percent of diabetic patient had resistant organism infection in urine. Symptoms  of  urinary tract infections were better resolved when empirical antibiotics used had  matched microbiological sensitivity pattern.Conclusions: After the age of 60 year UTI occurred almost equal in male and females There was only 75 percent agreement with empirical antibiotics and culture sensitivity report. Resistant organism were common in the diabetic population. Most common organism encountered in symptomatic UTI is E coli. Symptomatic resolution occurred in majority of cases where the empirical antibiotic was sensitive than compared to resistant case. Some of the resistant cases had symptomatic resolution  possibly explained by the in vivo sensitivity. As the agreement with empirical antibiotics became low, hospital antibiotic policies must reviewed and changed according to resistance pattern and type of organism that is locally prevalen

Preliminary results from the portable standard satellite laser ranging intercomparison with MOBLAS-7

Conventional Satellite Laser Ranging (SLR) instrumentation has been configured and successfully used to provide high-accuracy laboratory measurements on the LAGEOS-2 and TOPEX cube-corner arrays. The instrumentation, referred to as the Portable Standard, has also been used for field measurements of satellite ranges in tandem with MOBLAS-7. Preliminary results of the SLR measurements suggest that improved range accuracy can be achieved using this system. Results are discussed

Streak camera based SLR receiver for two color atmospheric measurements

To realize accurate two-color differential measurements, an image digitizing system with variable spatial resolution was designed, built, and integrated to a photon-counting picosecond streak camera, yielding a temporal scan resolution better than 300 femtosecond/pixel. The streak camera is configured to operate with 3 spatial channels; two of these support green (532 nm) and uv (355 nm) while the third accommodates reference pulses (764 nm) for real-time calibration. Critical parameters affecting differential timing accuracy such as pulse width and shape, number of received photons, streak camera/imaging system nonlinearities, dynamic range, and noise characteristics were investigated to optimize the system for accurate differential delay measurements. The streak camera output image consists of three image fields, each field is 1024 pixels along the time axis and 16 pixels across the spatial axis. Each of the image fields may be independently positioned across the spatial axis. Two of the image fields are used for the two wavelengths used in the experiment; the third window measures the temporal separation of a pair of diode laser pulses which verify the streak camera sweep speed for each data frame. The sum of the 16 pixel intensities across each of the 1024 temporal positions for the three data windows is used to extract the three waveforms. The waveform data is processed using an iterative three-point running average filter (10 to 30 iterations are used) to remove high-frequency structure. The pulse pair separations are determined using the half-max and centroid type analysis. Rigorous experimental verification has demonstrated that this simplified process provides the best measurement accuracy. To calibrate the receiver system sweep, two laser pulses with precisely known temporal separation are scanned along the full length of the sweep axis. The experimental measurements are then modeled using polynomial regression to obtain a best fit to the data. Data aggregation using normal point approach has provided accurate data fitting techniques and is found to be much more convenient than using the full rate single shot data. The systematic errors from this model have been found to be less than 3 ps for normal points

Test results from LAGEOS-2 optical characterization using pulsed lasers

The Laser Geodynamic Satellite-2 (LAGEOS-2) has undergone extensive optical testing at NASA Goddard Space Flight Center during 1989. The techniques included measuring the far field diffraction pattern using cw and pulsed lasers. In the pulsed measurement technique, response of the satellite was studied by measuring the far-field diffraction pattern (FFDP) as a function of pulsewidth, wavelength, polarization, position in the FFDP, detector/processing techniques, and satellite orientation. The purpose of the pulsed laser testing was two-fold: (1) to characterize the satellite optical response with the detector and signal processing electronics currently used in most SLR stations using the portable laser ranging standard, and (2) to characterize the satellite response for various conditions using the highest bandwidth optical detector (streak camera) available for the next generation of satellite laser ranging (SLR) technology. The portable ranging standard employed multiple measurement devices and an optical calibration scheme to eliminate range-dependent and amplitude-dependent systematics. These precautions were taken to eliminate/minimize instrumental errors and provide maximum accuracy. For LAGEOS orbit (6000 Km), ground stations are located 34 to 38 Mu radians off the axis of the return signal from the satellite; therefore, an optical mask was used to restrict the field of view (FOV) of detection to this annular region of the FFDP. The two measurement techniques were implemented using an aperture sharing scheme and complemented each other by providing mutual verification

Ecology and biodiversity of open sea cage farm at Mandapam, India

Farming of marine fin and shellfish species is an age old practice across the globe to augment the seafood demand and to supplement the rich protein food. Fin fish mariculture in India has been a recent initiative and the Central Marine Fisheries Research Institute was successful in developing captive breeding and seed production technique for cobia (Rachycentron canadum) and silver pompano (Trachinotus blochii). The open sea cages are particularly advantageous for maintaining the brood stock of potential species for captive breeding. However, the ecology of the cage farming sites is of paramount importance and should be conducive for the survival, health and growth of fishes that are farmed. In the present study, an attempt was made to understand the ecology and biodiversity of the cage farming area at Mandapam in Gulf of Mannar, south-east coast of India

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