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To study 2D and 3D dosimetric values for bladder and rectum, and the influence of bladder volume on bladder dose in high dose rate (HDR) intracavitary brachytherapy (ICBT). The large patient data incorporated in this study would better represent the inherent variations in many parameters affecting dosimetry in HDR-ICBT.
Material and Methods:
We prospectively collected data for 103 consecutive cervical cancer patients (over 310 HDR fractions) undergoing CT-based HDR-ICBT at our centre. Correlation among bladder and rectum maximum volume doses and corresponding International Commission on Radiation Units and Measurement (ICRU) point doses were estimated and analysed. Impact of bladder volume on bladder maximum dose was assessed.
The ICRU point doses to bladder and rectum varied from the volumetric doses to these organs. Further, bladder volume poorly correlated with bladder maximum dose for volume variations encountered in the clinical practice at our centre.
ICRU point doses to bladder and rectum are less likely to correlate with long-term toxicities to these organs. Further, in clinical practice where inter-fraction bladder volume does not vary widely there is no correlation between bladder volume and bladder dose.
The structure and the size of the core of massive presupernova stars are determined by the electron fraction and entropy of the core during its late stages of evolution; these in turn affect the subsequent evolution during gravitational collapse and supernova explosion phases. Beta decay and electron capture on a number of neutron rich nuclei can contribute substantially towards the reduction of the entropy and possibly the electron fraction in the core. Methods for calculating the weak transition rates for a number of nuclei for which no reliable rates exist (particularly for A > 60) are outlined. The calculations are particularly suited for presupernova matter density (p = 107 - 109 g/cc) and temperature (T = 2 - 6 × 109 °K). We include besides the contributions from the ground state and the known excited states, the Gamow-Teller (GT) resonance states (e.g. for beta decay rates, the GT+ states) in the mother nucleus which are populated thermally. For the GT strength function for transitions from the ground state (as well as excited states) we use a sum rule calculated by the spectral distribution method where the centroid of the distribution is obtained from experimental data on (p,n) reactions. The contribution of the excited levels and GT+ resonances turn out to be important at high temperatures which may prevail in presupernova stellar cores.
Observation of the field strength of low frequency radio waves (164 kHz) transmitted during night hours from Tashkent and received at Ahmedabad show increased absorption around the sidereal times of the transit of the X ray stars Sco X-1 and Tau X-1. It is estimated that the ionization in the D region produced by these X-ray stars can explain the observed changes in field strength.
In this paper, we report on the growth and fabrication of thin film Si photovoltaic devices on photonic structures which were fabricated on steel and PEN and Kapton substrates. Both amorphous Si and thin film nanocrystalline Si devices were fabricated. The 2 dimensional photonic reflector structures were designed using a scattering matrix theory and consisted of appropriately designed holes/pillars which were imprinted into a polymer layer coated onto PEN, Kapton and stainless steel substrates. The photonic structures were coated with a thin layer of Ag and ZnO. Both single junction and tandem junction (amorphous/amorphous and amorphous/nanocrystalline) cells were fabricated on the photonic layers. It was observed that the greatest increase in short circuit current and efficiency in these cells due to the use of photonic reflectors was in nanocrystalline Si cells, where an increase in current approaching 30% (compared to devices fabricated on flat substrates) was obtained for thin (∼ 1 micrometer thick i layers) films of nano Si deposited on steel structures. The photonic structures (which were nanoimprinted into a polymer) were shown to stand up to temperatures as large as 300 C, thereby making such structures practical when a steel (or glass) of kapton substrate is used. Detailed measurements and discussion of quantum efficiency and device performance for various photonic back reflector structures on steel, kapton and PEN substrates will be presented in the paper.
Germanium doping of InGaAsP epitaxial layers grown by liquid phase epitaxy produces n type conduction with a net distribution coefficient KGe∼ 5×10-3. In addition, Ge doping introduces a broad band (∼0.2eV) of efficient luminescence which is red shifted with respect to the band edge. The intensity of this band grows with increasing Ge concentration. In all the samples, the integrated intensity of the broad band varies relatively less in the temperature range 15K to about 90K. At higher temperatures, the intensity falls exponentially with an activation energy of 0.05 - 0.07 eV. The emission spectra are compared with the configuration-coordinate model of the emission from a Ge related complex.
Deep level admittance spectroscopy (DLAS) of the Sn-DX centers in Alx Ga1−x As:Sn (0.2 < x < 0.6) shows three peaks SNi, SN2 and SN3. The SN3 peak is identified to be related to the dominant peak of the Sn-DX center observed in the conventional DLTS technique. The SN1 and SN2 peaks are not easily seen in DLTS. A careful analysis of the DLAS data shows that the three peaks are not due to independent (chemically distinct) defects related to Sn, but they are caused by the multiple sates of the same DX center.
Shock absorption traditionally exploits visco-elastic devices, fluid viscous dampers and friction dampers, or “soft” materials. Recent work on impulse propagation in granular assemblies suggests that it may be possible to absorb shock waves using a different variety of shock absorbers and thus unlock the possibility of building structures that are significantly more shock absorbent than is currently possible, an issue of relevance to concerns of security. These new shock absorbers are composed of granular materials and exploit the nonlinear energy propagation properties in assemblies of granular materials. They have the potential to partially recover the energy of the absorbed shock waves for useful purposes, a property that might allow one to design devices to convert the incident energy to other useful forms. The basic physics of the “tapered chain shock absorber” is briefly discussed in this work.
Thin SiN films deposited by plasma enhanced chemical vapor deposition (PECVD) have been analyzed by a variety of analytical techniques including Fourier Transform Infrared Spectroscopy (FTIR), X-ray reflectivity (XRR), and Rutherford Backscattering Spectrometry/Hydrogen Forward Scattering (RBS/HFS) to collect data on bonding, density and chemical composition respectively. Both tensile and compressive SiN films have been deposited and analyzed. Mechanisms of stress formation in SiN thin films are discussed. It has been found that amount of bonded hydrogen as detected by FTIR is higher for compressive films compared to tensile SiN films. Amount of bonded hydrogen in a film is correlated well with tensile stress. Effect of deposition temperature and other process parameters on stress have been studied. Exposure of SiN films to elevated temperature after deposition lead to increase in tension and degradation in compressive stress. New approaches to stress generation in thin films like creation of multilayer film structures have been delineated.
We report on the growth and properties of nanocrystalline Si superlattice solar cells. The solar cells consisted of a stack of alternating layers of amorphous and nanocrystalline Si. The thickness of each of the two layers in the superlattice structure was varied independently. It was found that when the nanocrystalline layer thickness was low, increasing the thickness of the amorphous layer in the superlattice systematically reduced the <220> grain size, while the <111> grain size remained essentially invariant. This fact shows that by interposing an amorphous layer between two nanocrystalline layers forces the nano grains to renucleate and regrow. It was also found that when the amorphous Si layer was too thick, there were significant problems with hole transport through the device. Measurements of defect densities and effective diffusion lengths showed that there was an optimum thickness of the amorphous layer (about 10 nm) for which the defect density was the lowest and the diffusion length was the highest. We also show that the absorption coefficient in nano Si depends upon the grain size and can be increased significantly by increasing the grain size.
Hoarseness of voice due to paralysis of the left recurrent laryngeal nerve caused by a dilated left atrium in mitral stenosis as discussed by Ortner, is a subject of controversy. Different authors have cited different mechanisms as explanation. A variety of cardiac problems such as primary pulmonary hypertension, ischaemic heart disease, various congenital heart disorders can all lead to paralysis of the left recurrent laryngeal nerve. Most authors believe that pressure in the pulmonary artery causes the nerve compression. In Papua New Guinea cor pulmonale and rheumatic heart disease are the commonest cardiac disorders seen. Ortner's syndrome is a rarity and has never been reported from here before. Here three different case reports are presented with mitral stenosis, primary pulmonary hypertension and combined mitral stenosis and regurgitation and the pathogenesis of hoarseness is discussed.
A. Ray, Tata Institute of Fundamental Research, Bombay 400 005, India,
T. Kar, Saha Institute of Nuclear Physics, Calcutta 700 064, India,
S. Sarkar, Saha Institute of Nuclear Physics, Calcutta 700 064, India,
S. Chakravarti, California State Polytechnic University, Pomona, CA91768, USA
The structure and the size of the core of massive presupernova stars are determined by the electron fraction and entropy of the core during its late stages of evolution; these in turn affect the subsequent evolution during gravitational collapse and supernova explosion phases. Beta decay and electron capture on a number of neutron rich nuclei can contribute substantially towards the reduction of the entropy and possibly the electron fraction in the core. Methods for calculating the weak transition rates for a number of nuclei for which no reliable rates exist (particularly for A > 60) are outlined. The calculations are particularly suited for presupernova matter density (ρ = 107 − 109 g/cc) and temperature (T = 2 − 6 × 109 °K). We include besides the contributions from the ground state and the known excited states, the Gamow-Teller (GT) resonance states (e.g. for beta decay rates, the GT+ states) in the mother nucleus which are populated thermally. For the GT strength function for transitions from the ground state (as well as excited states) we use a sum rule calculated by the spectral distribution method where the centroid of the distribution is obtained from experimental data on (p,n) reactions. The contribution of the excited levels and GT+ resonances turn out to be important at high temperatures which may prevail in presupernova stellar cores.
Presupernova Evolution of Massive Stars
Beta decay (β−) and electron (e−) capture of neutron rich nuclei play important roles in determining presupernova core structure (Nomoto et al, 1991).
The alkali syenite assemblage of Kunavaram, Khammam district, Andhra Pradesh in south-eastern India, comprises perthite syenite and nepheline syenite. The massive perthite syenite (locally grading to alaskite) is fringed on either side by foliated nepheline syenite, the latter developing composite gneisses along the contact zones with the country rocks. The syenites are essentially hypersolvus although the alkali feldspar, the dominant constituent of the rocks, shows varying degrees of unmixing and Al/Si order. The mafic constituents (e.g. sodic pyroxene, amphibole and biotite) are appreciably rich in ferrous iron. Mineralogical and chemical data suggest that the primary crystallization characteristics of the syenites were not totally obliterated during the post-magmatic history of the pluton.
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