Anatomy of neck configuration in fission decay

The anatomy of neck configuration in the fission decay of Uranium and Thorium isotopes is investigated in a microscopic study using Relativistic mean field theory. The study includes $^{236}U$ and $^{232}Th$ in the valley of stability and exotic neutron rich isotopes $^{250}U$, $^{256}U$, $^{260}U$, $^{240}Th$, $^{250}Th$, $^{256}Th$ likely to play important role in the r-process nucleosynthesis in stellar evolution. Following the static fission path, the neck configurations are generated and their composition in terms of the number of neutrons and protons are obtained showing the progressive rise in the neutron component with the increase of mass number. Strong correlation between the neutron multiplicity in the fission decay and the number of neutrons in the neck is seen. The maximum neutron-proton ratio is about 5 for $^{260}$U and $^{256}$Th suggestive of the break down of liquid-drop picture and inhibition of the fission decay in still heavier isotopes. Neck as precursor of a new mode of fission decay like multi-fragmentation fission may also be inferred from this study.Comment: 16 pages, 5 figures (Accepted

A rare case report on ovotesticular disorders of sex development (DSD) 46XY variant

Ovotestis refers to the histology of a gonad that contains both ovarian follicles and testicular tubular elements. Ovotesticular DSD is a rare condition characterized by mixed ovarian and testicular tissue. Majority have a 46,XX karyotype, 7% have 46,XY karyotype and 10-40% exhibit chromosomal mosaicism. Here, we report the case of a boy with a 46,XY karyotype diagnosed as ovotesticular DSD by gonadal biopsy. A 14 year-old reared as  boy presented with came with ambiguous genitalia with no palpable gonads since birth and developed progressive virilization and gynaecomastia at puberty  having curved phallus with glans, redundant prepucial skin, labia majora and hypoplastic labia minora, rudimentary vagina with small introitus was present. External urethral meatus present lower down the vestibular area above the introitus. Testicles not felt. USG - revealed definite uterus behind Urinary bladder with small intraabdominal testes. Karyotyping - 46XY Barr body present. Diagnostic laparoscopy showed   Uterus with bilateral fallopian tubes. Bilateral gonadectomy done. Histopathologic examination report revealed bilateral gonadoblastoma in testis and ovotestis. Patient underwent transperitoneal excision of Mullerian remnants. Patient was discharged with an advice of cap testosterone undecanoate and regular follow up. We highlight the importance of histological and cytogenetic investigation in DSD

Evaluation of stem rot disease in jute (Corchorus olitorius) germplasm caused by Macrophomina phaseolina (Tassi) Goid

This study was aimed to identify more sources of resistance in jute germplasm (Corchorus olitorius) against deadly disease of stem rot. Thirteen C. olitorius jute germplasm including one standard check (JRO-524) were evaluated against stem rot disease at Barrackpore, Coochbehar and Bahraich location for two consecutive years 2012-2013. Out of thirteen germplasms of jute, six germplasms OIN-853, OIN-651, OIN-154, OIN-125, OEX-27 and OIN-467, with disease rating scale (1.1-5) were found moderately resistant against the stem rot disease at Barrackpore and Bahraich location. Whereas, OIN-270, OIN-932, OIN-270, OIJ-52, OIN-270, OEX-15 and OIN-853 with disease rating scale (5.1-10.0) were found moderately susceptible at all the three location. Rest of the lines were either susceptible or highly susceptible. These germplasm lines OIN-853, OIN-651, OIN-154, OIN-125, OEX-27 and OIN-467, possessed good degree of resistance against stem rot of jute and were found moderately resistant under natural epiphytotic condition at Barrackpore and Bahraich location that would be further exploited for resistance breeding programme against this deadly disease

Spin Excitation Spectrum of La1−xAx_{1-x}A_xMnO3_3

As an effective model to describe perovskite-type manganates (La,$A$)MnO$_3$, the double-exchange model on a cubic lattice is investigated. Spin excitation spectrum of the model in the ground state is studied using the spin wave approximation. Spin wave dispersion relation observed in the inelastic neutron scattering experiment of La$_{0.7}$Pb$_{0.3}$MnO$_3$ is reproduced. Effective values for the electron bandwidth as well as Hund's coupling is estimated from the data.Comment: 10 pages LaTeX including 4 PS figure

Electronic Raman scattering and photoluminescence from La0.7_{0.7}Sr0.3_{0.3}MnO3_3 exhibiting giant magnetoresistance

Raman and Photoluminescence (PL) experiments on correlated metallic La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ have been carried out using different excitation wavelengths as a function of temperature from 15 K to 300 K. Our data suggest a Raman mode centered at 1800 cm$^{-1}$ and a PL band at 2.2 eV. The intensities of the two peaks decrease with increasing temperature. The Raman mode can be attributed to a plasmon excitation whose frequency and linewidths are consistent with the measured resistivities. The PL involves intersite electronic transitions of the manganese ions.Comment: 10 pages + 4 eps figures, Revtex 3.0, figures available on reques

Zero Temperature Insulator-Metal Transition in Doped Manganites

We study the transition at T=0 from a ferromagnetic insulating to a ferromagnetic metallic phase in manganites as a function of hole doping using an effective low-energy model Hamiltonian proposed by us recently. The model incorporates the quantum nature of the dynamic Jahn-Teller(JT) phonons strongly coupled to orbitally degenerate electrons as well as strong Coulomb correlation effects and leads naturally to the coexistence of localized (JT polaronic) and band-like electronic states. We study the insulator-metal transition as a function of doping as well as of the correlation strength U and JT gain in energy E_{JT}, and find, for realistic values of parameters, a ground state phase diagram in agreement with experiments. We also discuss how several other features of manganites as well as differences in behaviour among manganites can be understood in terms of our model.Comment: To be published in Europhysics Letter

Masses of Multiquark Droplets

The mass formulae for finite lumps of strange quark matter with $u$, $d$ and $s$ quarks, and non-strange quark matter consisting of $u$ and $d$ quarks are derived in a non-relativistic potential model. The finite-size effects comprising the surface, curvature and even, the Gauss curvature were consistently obtained, which shows a converging trend. It is found that there is a possibility for the formation of metastable strangelets of large mass. The model predicts low charge to mass ratio as the characteristic signature of strange matter in agreement with the relativistic studies. This study also yields an independent estimate for the bag energy density $B$, which is in agreement with the M.I.T bag model value.Comment: 24pages + 5 figures available upon request,Latex,IP/BBSR/93-3

Important role of alkali atoms in A4C60

We show that hopping via the alkali atoms plays an important role for the t1u band of A4C60 (A=K, Rb), in strong contrast to A3C60. Thus the t1u band is broadened by more than 40 % by the presence of the alkali atoms. The difference between A4C60 and A3C60 is in particular due to the less symmetric location of the alkali atoms in A4C60.Comment: 5 pages, revtex, 2 figures, submitted to Phys. Rev. B more information at http://www.mpi-stuttgart.mpg.de/dokumente/andersen/fullerene

Effects of uniaxial strain in LaMnO_3

The effects of uniaxial strain on the structural, orbital, optical, and magnetic properties of LaMnO_3 are calculated using a general elastic energy expression, along with a tight-binding parameterization of the band theory. Tensile uniaxial strain of the order of 2 % (i.e., of the order of magnitude of those induced in thin films by lattice mismatch with substrates) is found to lead to changes in the magnetic ground state, leading to dramatic changes in the band structure and optical conductivity spectrum. The magnetostriction effect associated with the Neel transition of bulk(unstrained) LaMnO_3 is also determined. Due to the Jahn-Teller coupling, the uniform tetragonal distortion mode is softer in LaMnO_3 than in doped cubic manganates. Reasons why the observed (\pi \pi 0) orbital ordering is favored over a (\pi \pi \pi) periodicity are discussed.Comment: 9 figures, submitted in Phys. Rev.