CYTOPLASMIC PARTICLES AND AMINOACYL TRANSFERASE I ACTIVITY

It has been possible to show by electron microscopy of samples selected from sucrose gradients that particles of specific size and shape are present in supernatant fluids derived from nucleated animal and plant cells, but not in extracts from Escherichia coli. Aminoacyl transferase I activity in these same gradients sediments in two peaks representing material of approximately 5–7S and 18–20S. A rectangular particle, 100 x 145 A in size, sediments at 19S and coincides with the second peak of transferase I activity. The possibility that the rectangular particle may be a "carrier" particle associated with transferase I is discussed

A comparison of the hard-switching performance of 650V power transistors with calorimetric verification

We compare the switching losses of four equivalent silicon and wide-bandgap 650V power transistors operated in a hard-switched half-bridge configuration, switching 400V at 40A. Each transistor is mounted on an identical PCB and driven by a gate drive circuit matched to its requirements. Switching speed is maximised by a PCB design featuring very low parasitic inductance and the use of zero external gate resistance (where possible). Switching losses are measured electrically using a Double Pulse Test (DPT) method. However, high-bandwidth electrical measurements are prone to error and so we assess the gain accuracy, offset accuracy, and the bandwidth requirements of the DPT measurements, and then verify the DPT results by calorimetry. The electrical and calorimetric measurements are shown to agree to within 5%. Comprehensive plots of gate-source voltage, drain-source voltage, and source current are provided for all transistors over a junction temperature range of 50-150°C. The ratio of the total half-bridge switching losses is 1:3.2:14:31 for the GaN HEMT, SiC MOSFET, Si IGBT, and Si superjunction MOSFET, respectively

Comparison of fast switching high current power devices

New GaN and SiC wide bandgap power devices offer impressively fast switching performance compared to their traditional Silicon counterparts. However, Silicon devices have not stood still, and new generations of these devices offer excellent performance at competitive prices. This paper makes a comparative study between the latest generation of high-current SiC, GaN, Si CoolMOS and Si IGBT power switching devices, switched as fast as possible using low inductance circuit design and no external gate resistors. An analysis of the factors that determine switch edge-rate is presented, along with an overview of circuits developed by the authors to achieve accurate measurement of switching energy loss

A Close Companion Search Around L Dwarfs Using Aperture Masking Interferometry and Palomar Laser Guide Star Adaptive Optics

We present a close companion search around 16 known early L dwarfs using aperture masking interferometry with Palomar laser guide star adaptive optics (LGS AO). The use of aperture masking allows the detection of close binaries, corresponding to projected physical separations of 0.6-10.0 AU for the targets of our survey. This survey achieved median contrast limits of ΔK ~ 2.3 for separations between 1.2λ/D-4λ/D and ΔK ~ 1.4 at 2/3λ/D. We present four candidate binaries detected with moderate-to-high confidence (90%-98%). Two have projected physical separations less than 1.5 AU. This may indicate that tight-separation binaries contribute more significantly to the binary fraction than currently assumed, consistent with spectroscopic and photometric overluminosity studies. Ten targets of this survey have previously been observed with the Hubble Space Telescope as part of companion searches. We use the increased resolution of aperture masking to search for close or dim companions that would be obscured by full aperture imaging, finding two candidate binaries. This survey is the first application of aperture masking with LGS AO at Palomar. Several new techniques for the analysis of aperture masking data in the low signal-to-noise regime are explored

Prevalence of marine litter along the Indian beaches : A preliminary account on its status and composition

Beach litter are man-made objects discarded directly or indirectly. This study brings out synoptic picture of status and composition of beach litter from 254 selected beaches along the maritime States of Peninsular coast of India as well as the Union Territories of Andaman and Lakshadweep Islands from the one time observation conducted between October 2013 and January 2014 for the first time. These beaches were classified and graded with colour codes according to the levels of beach litter. Beach litter from different maritime States and the UTs showed that Odisha coast has the lowest (0.31 g/m2) quantity and Goa coast (205.75 g/m2) the highest quantity of beach debris. Archipelagic coasts of Andamans as well as Lakshadweep recorded values higher than Kerala, Tamil Nadu, Andhra Pradesh, Odisha and West Bengal. Samples of debris collected from beaches revealed that all the items were domestic and anthropogenic discards. Plastic litters such as single use carry bags and sachets of soft drinks, edible oils, detergents, beverages, cases of cosmetics, toothpaste, PET bottles, ice cream containers etc., recorded highest mean of 25.47g/m2 from Goa coast and the lowest (0.08 g/m2) from Odisha. The relative percentage of mean values of plastic (B group) items in beach debris along the Indian coast registered highest mean percentage from Maharashtra (81 %) and the lowest mean from beaches of Andhra Pradesh (7%). The two island Union Territories registered 40% (Lakshadweep) and 47% (Andamans) of plastics over the total debris, while the national average was only 14%. Available online at: www.mbai.org.in doi: 10.6024/jmbai.2017.59.1.1953-03 Out of the total 254 beaches surveyed, 51 beaches were graded as very clean with green (<1 g/m2) colour, 122 beaches were graded as Clean and depicted by blue colour. Beaches of very clean grade (<1 g/m2) were found in Kerala (17), Maharashtra (12), Tamil Nadu (2), Andhra Pradesh (4), Odisha (7) and West Bengal (3). Whereas extremely littered beaches (>100 g/m2) were found in Karnataka (13), Goa, Gujarat, and Andaman Island. With reference to the coastal population and per capita share of beach debris, Goa registered highest values (40.97 kg/head) and the Odisha coast registered the lowest values (0.005 kg/head)

Discontinuation and non-publication of surgical randomised controlled trials:observational study

Objective To determine the rate of early discontinuation and non-publication of randomised controlled trials involving patients undergoing surgery. Design Cross sectional observational study of registered and published trials. Setting Randomised controlled trials of interventions in patients undergoing a surgical procedure. Data sources The ClinicalTrials.gov database was searched for interventional trials registered between January 2008 and December 2009 using the keyword “surgery”. Recruitment status was extracted from the ClinicalTrials.gov database. A systematic search for studies published in peer reviewed journals was performed; if they were not found, results posted on the ClinicalTrials.gov results database were sought. Email queries were sent to trial investigators of discontinued and unpublished completed trials if no reason for the respective status was disclosed. Main outcome measures Trial discontinuation before completion and non-publication after completion. Logistic regression was used to determine the effect of funding source on publication status, with adjustment for intervention type and trial size. Results Of 818 registered trials found using the keyword “surgery”, 395 met the inclusion criteria. Of these, 21% (81/395) were discontinued early, most commonly owing to poor recruitment (44%, 36/81). The remaining 314 (79%) trials proceeded to completion, with a publication rate of 66% (208/314) at a median time of 4.9 (interquartile range 4.0-6.0) years from study completion to publication search. A further 6% (20/314) of studies presented results on ClinicalTrials.gov without a corresponding peer reviewed publication. Industry funding did not affect the rate of discontinuation (adjusted odds ratio 0.91, 95% confidence interval 0.54 to 1.55) but was associated with a lower odds of publication for completed trials (0.43, 0.26 to 0.72). Investigators’ email addresses for trials with an uncertain fate were identified for 71.4% (10/14) of discontinued trials and 83% (101/122) of unpublished studies. Only 43% (6/14) and 20% (25/122) replies were received. Email responses for completed trials indicated 11 trials in press, five published studies (four in non-indexed peer reviewed journals), and nine trials remaining unpublished. Conclusions One in five surgical randomised controlled trials are discontinued early, one in three completed trials remain unpublished, and investigators of unpublished studies are frequently not contactable. This represents a waste of research resources and raises ethical concerns regarding hidden clinical data and futile participation by patients with its attendant risks. To promote future efficiency and transparency, changes are proposed to research governance frameworks to overcome these concerns