On the resolution of the big bang singularity in isotropic Loop Quantum Cosmology

In contrast to previous work in the field, we construct the Loop Quantum Cosmology (LQC) of the flat isotropic model with a massless scalar field in the absence of higher order curvature corrections to the gravitational part of the Hamiltonian constraint. The matter part of the constraint contains the inverse triad operator which can be quantized with or without the use of a Thiemann- like procedure. With the latter choice, we show that the LQC quantization is identical to that of the standard Wheeler DeWitt theory (WDW) wherein there is no singularity resolution. We argue that the former choice leads to singularity resolution in the sense of a well defined, regular (backward) evolution through and beyond the epoch where the size of the universe vanishes. Our work along with that of the seminal work of Ashtekar, Pawlowski and Singh (APS) clarifies the role, in singularity resolution, of the three `exotic' structures in this LQC model, namely: curvature corrections, inverse triad definitions and the `polymer' nature of the kinematic representation. We also critically examine certain technical assumptions made by APS in their analysis of WDW semiclassical states and point out some problems stemming from the infrared behaviour of their wave functionsComment: 26 pages, no figure

KIF14 and E2F3 mRNA expression in human retinoblastoma and its phenotype association

Purpose: We quantified mRNA expression of candidate genes for proliferation (KIF14 and E2F3) in a large retinoblastoma tumor cohort and associated with disease phenotype. Methods: KIF14 and E2F3 mRNA expression was quantified by real time PCR in 57 retinoblastoma (RB) tumors, 3 RB cell lines, and control samples that included 4 each fetal, age-matched, adult retinas. Immunohistochemistry was done to confirm KIF14 and E2F3 protein expression in tumor cells. The mRNA expression levels were correlated with disease phenotypes including the significance of chemotherapy on tumors. Results: There was statistically significant overexpression of KIF14 and E2F3 mRNA in tumors compared with control retinas (p<0.0001). Further, E2F3 also showed a significant overexpression compared to RB cell lines (p=0.01). Immunohistochemistry confirmed KIF14 and E2F3 protein overexpression in tumor cells. KIF14 had significant mRNA overexpression with older age (p=0.01) in presenting patients and in unilateral RB patients (p=0.04). Chemotherapytreated tumors showed a significant decrease in KIF14 and E2F3 expression compared to untreated tumors (p<0.01 and 0.001, respectively). Conclusions: This report confirms significant mRNA overexpression of KIF14 and E2F3 together in a large cohort of RB tumors. The decreased expression in chemotherapy treated cases needs further validation in a large chemotherapytreated cohort

A Four-Unit-Cell Periodic Pattern of Quasiparticle States Surrounding Vortex Cores in Bi2Sr2CaCu2O8+d

Scanning tunneling microscopy is used to image the additional quasiparticle states generated by quantized vortices in the high-Tc superconductor Bi2Sr2CaCu2O8+d. They exhibit a Cu-O bond oriented 'checkerboard' pattern, with four unit cell (4a0) periodicity and a ~30 angstrom decay length. These electronic modulations may be related to the magnetic field-induced, 8a0 periodic, spin density modulations of decay length ~70 angstroms recently discovered in La1.84Sr0.16CuO4. The proposed explanation is a spin density wave localized surrounding each vortex core. General theoretical principles predict that, in the cuprates, a localized spin modulation of wavelength L should be associated with a corresponding electronic modulation of wavelength L/2, in good agreement with our observations.Comment: 10 pages, 3 figure

Dirac Quantization of Parametrized Field Theory

Parametrized field theory (PFT) is free field theory on flat spacetime in a diffeomorphism invariant disguise. It describes field evolution on arbitrary foliations of the flat spacetime instead of only the usual flat ones, by treating the `embedding variables' which describe the foliation as dynamical variables to be varied in the action in addition to the scalar field. A formal Dirac quantization turns the constraints of PFT into functional Schrodinger equations which describe evolution of quantum states from an arbitrary Cauchy slice to an infinitesimally nearby one.This formal Schrodinger picture- based quantization is unitarily equivalent to the standard Heisenberg picture based Fock quantization of the free scalar field if scalar field evolution along arbitrary foliations is unitarily implemented on the Fock space. Torre and Varadarajan (TV) showed that for generic foliations emanating from a flat initial slice in spacetimes of dimension greater than 2, evolution is not unitarily implemented, thus implying an obstruction to Dirac quantization. We construct a Dirac quantization of PFT,unitarily equivalent to the standard Fock quantization, using techniques from Loop Quantum Gravity (LQG) which are powerful enough to super-cede the no- go implications of the TV results. The key features of our quantization include an LQG type representation for the embedding variables, embedding dependent Fock spaces for the scalar field, an anomaly free representation of (a generalization of) the finite transformations generated by the constraints and group averaging techniques. The difference between 2 and higher dimensions is that in the latter, only finite gauge transformations are defined in the quantum theory, not the infinitesimal ones.Comment: 33 page

The expressions of Ret/PTC and p53 in normal, benign and malignant thyroid lesions

Goiter is a highly prevalent problem in the local population. Studies at HUSM have found high percentage of papillary carcinoma within this lesion. Ret/PTC is a recently discovered oncogene which is solely related to papillary carcinoma. It has been proven to play a major role in the pathogenesis of this malignant lesion. P53 gene is a well known tumour suppressor gene, usually associated with the undifferentiated thyroid carcinoma. Immunohistochemistry is able to demonstrate p53 mutation in well differentiated thyroid carcinoma. This study aims to investigate the expression of ret and p53 in the local normal, benign and malignant thyroid lesions in order to shed light on the pathogenesis of papillary carcinoma and explain the high prevalence of this condition among the nodular hyperplasia ( multinodular goiter) cases. From the records of HUSM pathology department, archival blocks from 50 follicular adenomas, 66 nodular hyperplasia cases and 53 papillary carcinoma cases were retrieved. They were studied by immunohistochemistry method for the presence of ret/PTC and p53 mutant protein within the follicular cells. Normal thyroid tissues from 74 of the cases were utilized as controls. Ret/PTC is expressed by 5.4% of normal thyroid tissue, 18% of follicular adenomas, 22.7% of nodular hyperplasia cases and 71.7% of papillary carcinomas. There is no statistically significant difference of ret expression between pure nodular hyperplasia and the ones with coexisting papillary carcinoma

Simple model for scanning tunneling spectroscopy of noble metal surfaces with adsorbed Kondo impurities

A simple model is introduced to describe conductance measurements between a scanning tunneling microscope (STM) tip and a noble metal surface with adsorbed transition metal atoms which display the Kondo effect. The model assumes a realistic parameterization of the potential created by the surface and a d3z2-r2 orbital for the description of the adsorbate. Fano lineshapes associated with the Kondo resonance are found to be sensitive to details of the adsorbate-substrate interaction. For instance, bringing the adsorbate closer to the surface leads to more asymmetric lineshapes while their dependence on the tip distance is weak. We find that it is important to use a realistic surface potential, to properly include the tunnelling matrix elements to the tip and to use substrate states which are orthogonal to the adsorbate and tip states. An application of our model to Co adsorbed on Cu explains the difference in the lineshapes observed between Cu(100) and Cu(111) surfaces.Comment: 11 pages, 8 eps figure

Implementation of Peltier Cooling in Hermetically Sealed Electronic Packaging Unit for Sub-sea Vessel

This paper presents the methodology adopted for implementation of Peltier cooling in hermetically sealed electronic packaging units used in sub-sea vessels. In sub-sea vessels, sonar front-end electronics is packaged in hermetically sealed electronic packaging units. The thermal design of the unit is a highly challenging task considering the heat dissipation of 300W from the electronics, non-availability of chilled air for cooling and IP68 sealing requirements. Cooling fans cannot be integrated, since these units are to be placed in acoustically sensitive pressure capsule area of the subsea vessel. The electronic cooling in this unit is achieved using conduction cooling with external fins. To enhance the cooling, suitable Peltier cooling (Thermo-electric cooling or TEC) module is selected and implemented with the system. Computational fluid dynamic analysis of the unit is carried-out to study the air-flow and thermal performances with Peltier cooler. The unit is realised and the estimated temperatures validated by experimental temperature measurements on the realised unit. The measured temperatures are within the safe operating limits of the electronic components and hence the cooling design of the unit is satisfactory. It is also observed that maximum temperature reduction has occurred at 1.5A current and card edge temperature of Printed circuit board lowered by 9.28 °C by implementing Peltier cooling

Studies on clustering of chilli (Capsicum annum L.) genotypes based on genetic distance

Mahalanobis' D2 statistics was used to analyse forty-five chilli (Capsicum annum L.) genotypes based on eighteen characters in order to pick out supreme potential parents for hybridization. Based on D2 values, the genotypes were divided into eleven groups with extreme divergence. Cluster I had the majority of genotypes (sixteen), whereas the fewest genotypes were identified in clusters VII, VIII, X and XI (one). Cluster XI had the greatest distance within the cluster. Clusters V and XI had the maximum generalized distance between them, followed by clusters VII and XI, clusters IV and VII, clusters IV and V and clusters II and XI. This suggests that the genotypes in these groups had more genetic variation. Following cluster VII and VIII, cluster V showed the highest cluster mean for green, dry fruit yield (846g and 95.50g) and several yield-related features. At clusters I, II and VI, no observation for high cluster means but had fair trait performance. It may be suggested to directly advance the genotypes from clusters V, VII, VII in hybridization to obtain unique recombinants