arXiv subjects

A. Goswami

Publications and source records attributed to A. Goswami.

64 records · Page 4Linked to original sources

arXiv2012

Onset of deformation at $N = 112$ in Bi nuclei

The high spin states in $^{195}$Bi has been studied by $γ$-ray spectroscopic method using the $^{181}$Ta($^{20}$Ne, 6n) fusion evaporation reaction at 130 MeV. The $γγ$ coincidence data were taken using an array of 8 clover HPGe detectors. The spin and parity assignments of the excited states have been made from the measured directional correlation from oriented states (DCO) ratios and integrated polarization asymmetry (IPDCO) ratios. The results show, for the first time, the evidence of a rotational like band based on a 13/2$^+$ band head in this nucleus, indicating the onset of deformation at neutron number $N = 112$ for the Bismuth isotopes. The results obtained were found to be consistent with the prediction of the total Routhian surface calculations using Woods Saxon potential. The same calculations also predict a change in shape from oblate to triaxial in $^{195}$Bi at high rotational frequency.

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arXiv2011

Fusion of $^{6}$Li with $^{159}$Tb} at near barrier energies

Complete and incomplete fusion cross sections for $^{6}$Li+$^{159}$Tb have been measured at energies around the Coulomb barrier by the $γ$-ray method. The measurements show that the complete fusion cross sections at above-barrier energies are suppressed by $\sim$34% compared to the coupled channels calculations. A comparison of the complete fusion cross sections at above-barrier energies with the existing data of $^{11,10}$B+$^{159}$Tb and $^{7}$Li+$^{159}$Tb shows that the extent of suppression is correlated with the $α$-separation energies of the projectiles. It has been argued that the Dy isotopes produced in the reaction $^{6}$Li+$^{159}$Tb, at below-barrier energies are primarily due to the $d$-transfer to unbound states of $^{159}$Tb, while both transfer and incomplete fusion processes contribute at above-barrier energies.

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arXiv2011

Systematics of Anti magnetic rotation in even-even Cd isotopes

The lifetimes for the high spin levels of the yrast band of $^{110}$Cd has been measured. The estimated B(E2) values decrease with increase in angular momentum. This is the characteristic of Anti magnetic rotation as reported in $^{106,108}$Cd. However, alignment behavior of $^{110}$Cd is completely different from its even-even neighbors. A model based on classical particle plus rotor has been used to explore the underlying systematics and develop a self consistent picture for the observed behavior of these isotopes.

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arXiv2010

Band crossing in Shears band of $^{108}$Cd

The level lifetimes have been measured for a Shears band of $^{108}$Cd which exhibits bandcrossing. The observed level energies and B(M1) rates have been successfully described by a semi-classical geometric model based on shear mechanism. In this geometric model, the bandcrossing in Shears band has been described as the reopening of the angle between the blades of a shear.

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arXiv2009

Observation of isomeric decays and the high spin states in doubly-odd 208Fr

Neutron deficient isotopes of Francium (Z=87, N=121-123) as excited nuclei were produced in the fusion-evaporation reaction: 197Au(16O,xn)[213-x]Fr at 100 MeV. The gamma-rays from the residues were observed through the high sensitivity Germanium Clover detector array INGA. The decay of the high spin states and the isomeric states of the doubly-odd 208Fr nuclei, identified from the known sequence of ground state transitions, were observed. The half lives of the 194(2) keV isomeric transition, known from earlier observations, was measured to be 233(18) ns. A second isomeric transition at 383(2) keV and half life of 33(7) ns was also found. The measured half lives were compared with the corresponding single particle estimates, based on a the level scheme obtained from the experiment.

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arXiv2009

Enhanced orbital electron-capture nuclear decay rate in compact medium

The eigenstate energies of an atom increase under spatial confinement and this effect should also increase the electron density of the orbital electrons at the nucleus thus increasing the decay rate of an electron-capturing radioactive nucleus. We have observed that the orbital electron capture rates of 109In and 110Sn increased by (1.00+-0.17)% and (0.48+-0.25)% respectively when implanted in the small Au lattice versus large Pb lattice. These results have been understood because of the higher compression experienced by the large radioactive atoms due to the spatial confinement in the smaller Au lattice.

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arXiv2008

Evaluation of Cooling Solutions for Outdoor Electronics

The thermal management of an outdoor electronic enclosure can be quite challenging due to the additional thermal load from the sun and the requirement of having an air-sealed enclosure. It is essential to consider the effect of solar heating loads in the design process; otherwise, it can shorten the life expectancy of the electronic product or lead to catastrophic failure. In this paper we analyze and compare the effectiveness of different cooling techniques used for outdoor electronics. Various cooling techniques were compared like special coatings and paints on the outer surface, radiation shields, double-walled vented enclosures, fans for internal air circulation and air-to-air heat exchangers. A highly simplified, typical outdoor system was selected for this study measuring approximately 300x300x400 mm (WxLxH). Solar radiation was incident on 3 sides of the enclosure. There were 8 equally spaced PCBs inside the enclosure dissipating 12.5W each uniformly (100 watts total). A computational fluid dynamics (CFD) model of the system was built and analyzed. This was followed by building a mock-up of the system and conducting experiments to validate the CFD model. It was found that some of the simplest cooling techniques like white oil paint on the outer surface can significantly reduce the impact of solar loads. Adding internal circulation fans can also be very effective. Using air-to-air heat exchangers was found to be the most effective solution although it is more complex and costly.

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arXiv2007

Nanosilica mops up host lipids and fights baculovirus: a B. mori model

Malaria and other parasites, including virus often induce an increase in host lipids which the invaders use to their own advantage. We obtained encouraging results in our investigations on bird malaria with a new approach namely the use of nanosilica to mop up excess host lipids. While this project is continuing we have investigated another, simpler system namely silkworms which suffer from a deadly baculovirus, BmNPV. This virus decimates the infected population within 24 hours or so and no known antibiotic antidote or genetically resistant strain of silkworm3 exists. We report here a partial success, which is worth following up. Our rationale, we believe, has a broad and interdisciplinary appeal, for, this nanosilica treatment might be used together with other arsenals on all sorts of virus which take advantage of enhanced host lipids. It has not escaped our notice that Ebola and HIV also belong to this category. Nanoparticles are being preferentially harnessed, because they offer a greater surface area, circulate more easily and in lepidopteran system4 they are removed within 24 hours from the body. Lawry surmised, on cogent theoretical grounds that particles significantly smaller than micron order would be less harmful in the hemocoele. Furthermore, Hui-peng et al. pointed out that lipase treatment, the only viable option for controlling BmNPV interferes in hormonal balance and cannot be applied to pre molting stage.

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arXiv2007

Nanosilica mop up host lipids and fights baculovirus

Various types of surface functionalized nanosilica (50-60 nm size with 3-10 nm inner pore size range) have been used to kill insect pests by sucking up cuticular lipids and breaking the water barrier. We have also utilized nanosilica for mopping up host lipids induced by the malarial parasite, P. gallinaceum in poultry birds; VLDL cholesterol and serum triglycerides are brought back to the normal level with a concomitant check in parasite growth. While this work continues, we have explored another more convenient system, silkworm (Bombyx mori) that is frequently decimated by a baculovirus, NPV for which no antidote is known so far. Here, too, viral infection enhances host lipids. Eight different types of nanosilica were injected in the virus infected silkworm (batches of 10 worms) after ensuring 100% survival up to cocoon formation in control larvae (injected with the same volume of ethanol, the medium of nanosilica). Of these 8, AL60102 and AL60106, have the most marked effect on infected silkworm, both as prophylactic and pharmaceutical agents. Normal larvae injected with these nanosilica survive up to cocoon formation.

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arXiv2005

Absence of M2 Retardation in $^{35}Cl$: Evidence for Stronger Isospin-Mixing Effects in A=35 Mirror Nuclei

The lifetime of the 3163 keV, 7/2$^-$ isomeric state in $^{35}Cl$ that decays by a stretched M2 transition to the $3/2^+$ ground state, has been re-measured using the Doppler Shift Attenuation Method, by gating on the 1185 keV transition which directly feeds this state. This eliminates the uncertainties in the measurement arising from the direct feedings from the continuum. A mean life of 0.6$^{+0.5}_{-0.2}$ ps has been obtained from the present work. This is considerably smaller than the adopted value 45.3(6) ps. Implication of this major reduction in the lifetime has been pointed out.

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