Formation of rectifier with gold nanoclusters

Gold nanoclusters encapsulated with organic molecules are of great interest for its possible applications in the fields of molecular electronics, catalysis and medical science. Here we demonstrate that monolayer and bilayer films of thiol-capped gold nanoclusters can exhibit diode-like properties provided controlled spatial asymmetry exist between two tunnel junctions used to connect a thiol capped gold nanoclusters. Current-voltage characteristics of this rectifier were obtained from conducting probe atomic force microscopy measurements and also from conventional two probe resistance measurements. Systematic x-ray reflectivity and atomic force microscopy measurements were carried out to characterize the spatial asymmetry introduced by a monolayer of fatty acid salt gadolinium stearate used to deposit thiol-capped gold nanocluster molecules on hydrophilic SiO2-Si(001) substrate by Langmuir Blodgett technique. This information was used to explain prominent rectification observed in these nano-structured films.Comment: 13 pages, 3 figure

Supracondylar fracture of femur: our experience of treatment with locking compression plate from rural Maharashtra

Background: Surgical treatment of supracondylar or intercondylar distal femoral fractures (AO/OTA types 33-A to 33-C) remains a significant surgical challenge with significant complication rates. Supracondylar and intercondylar fractures of femur are very often difficult to treat and they are notorious for many complications. We have studied use of LCP (locking compression plate) in the treatment of metaphyseal fractures. These implants improve fracture healing, especially in osteoporotic bone due to better holding capacity. Objective wass to assess the efficacy of LCP in maintenance of post-operative distal femoral alignment and in preventing post-operative varus collapse in supracondylar fracture of femur.Methods: Prospective Longitudinal observational study Conducted at Post Graduate Institute of Swasthiyog Pratishthan, Miraj, Maharashtra involving 50 patients with supracondylar fracture. The fractures were classified as supracondylar femur fracture (AO/OTA type 33) (A- C). Fractures that were supracondylar with significant proximal fracture extension were classified as an AO/OTA type 33 fracture unless there was a separate diaphyseal fracture. Data was analysed by using SPSS 16.0 version and expressed as percentages.Results: Majority of patients were from 30-39 years age group i.e. 32%. Majority of patients were males i.e. 46 (92%). 7 (14%) patients had healing time <4 months. 24 (48%) patients had healing time between 4-6 months. 19 (38%) patients had healing time more than 6 months. To assess the overall results, we used Knee society score. In 38% of patients, we found excellent results. Good and fair results were seen in 32% and 26% of patients.Conclusion: Locking compression plate is an ideal implant for fixation of supracondylar fracture of femur 33 (A-C) especially in C3 type where articular comminution is present

A Luminous Companion to SGR 1806-20

We have obtained infrared spectra of the star suggested to be the counterpart of the soft gamma-ray repeater (SGR) 1806-20. We found strong emission lines similar to those seen in the spectra of the rare Luminous Blue Variables and B[e] stars. A He I absorption line is also seen, from which we infer a spectral type O9--B2. This classification, in combination with the minimum distance of \simgt6 kpc inferred from its extinction, makes the star one of the most luminous in the Galaxy. We infer that it is a companion to SGR 1806-20, and suggest that the presence of a companion is somehow related to the SGR phenomenon.Comment: 5 pages, AASTEX text+table and 2 PostScript figures (needs LaTeX style files aaspptwo.sty, epsf.sty and rotate.sty). In case of problems, contact [email protected]. Postscript file of complete article available on request. (Replaced because first version had one wrong reference in it

The Angular Size and Proper Motion of the Afterglow of GRB 030329

The bright, nearby (z=0.1685) gamma-ray burst of 29 March 2003 has presented us with the first opportunity to directly image the expansion of a GRB. This burst reached flux density levels at centimeter wavelengths more than 50 times brighter than any previously studied event. Here we present the results of a VLBI campaign using the VLBA, VLA, Green Bank, Effelsberg, Arecibo, and Westerbork telescopes that resolves the radio afterglow of GRB 030329 and constrains its rate of expansion. The size of the afterglow is found to be \~0.07 mas (0.2 pc) 25 days after the burst, and 0.17 mas (0.5 pc) 83 days after the burst, indicating an average velocity of 3-5 c. This expansion is consistent with expectations of the standard fireball model. We measure the projected proper motion of GRB 030329 in the sky to <0.3 mas in the 80 days following the burst. In observations taken 52 days after the burst we detect an additional compact component at a distance from the main component of 0.28 +/- 0.05 mas (0.80 pc). The presence of this component is not expected from the standard model.Comment: 12 pages including 2 figures, LaTeX. Accepted to ApJ Letters on May 14, 200

The Rapidly Fading Afterglow from the Gamma-Ray Burst of 1999 May 6

We report on the discovery of the radio afterglow from the gamma-ray burst (GRB) of 1999 May 6 (GRB 990506) using the Very Large Array (VLA). The radio afterglow was detected at early times (1.5 days), but began to fade rapidly sometime between 1 and 5 days after the burst. If we attribute the radio emission to the forward shock from an expanding fireball, then this rapid onset of the decay in the radio predicts that the corresponding optical transient began to decay between 1 and 5 minutes after the burst. This could explain why no optical transient for GRB 990506 was detected in spite of numerous searches. The cause of the unusually rapid onset of the decay for the afterglow is probably the result of an isotropically energetic fireball expanding into a low density circumburst environment. At the location of the radio afterglow we find a faint (R ~ 24 mag) host galaxy with a double morphology.Comment: in press at ApJ Letters, 13 page LaTeX document includes 2 postscript figure