Oscillating Superfluidity of Bosons in Optical Lattices

We follow up on a recent suggestion by C. Orzel et. al., Science, 291, 2386 (2001), whereby bosons in an optical lattice would be subjected to a sudden parameter change from the Mott to the superfluid phase. We analyze the Bose Hubbard model with a modified coherent states path integral which can escribe - both - phases. The saddle point theory yields collective oscillations of the uniform superfluid order parameter. These would be seen in time resolved interference patterns made by the released gas. We calculate the collective oscillation's damping rate by phason pair emission. In two dimensions the overdamped region largely overlaps with the quantum critical region. Measurements of critical dynamics on the Mott side are proposed.Comment: 4 pages 1 eps figures; Final version as appears in PRL. Added discussion on spontaneous generation of vortice

Employment implications of the growth of the Indigenous Australian working-age population to 2001

This paper has been specifically prepared as a submission to the review of the Aboriginal Employment Development Policy (AEDP) which is to be completed early in 1994. A critical innovative feature of the Commonwealth Government's AEDP, launched in 1986-87, is its overarching goal of attaining statistical employment equality between Indigenous and non-Indigenous Australians by the year 2000. This paper examines the nature of labour force planning and goal setting in the AEDP Statement. It then re-examines a critique of the statistical targets made by demographers Tesfaghiorghis and Gray in 1991. Using recently published 1991 Census data, the paper explores intercensal changes in the size and labour force status of the Indigenous population. The paper's main aim is to present new projections of the Indigenous population of working age to the year 2001 and to re-assess the employment creation goals that will need to be set if statistical equality is to be achieved. It is estimated that the Indigenous population of working age will exceed 200,000 by the year 2001 and that to achieve statistical equality between 6,400 and 7,400 new jobs per annum will need to be created. Both figures represent over 10 per cent of the 1991 base employment of Indigenous Australians and represent impossible targets. The paper highlights a number of statistical, methodological and conceptual issues. In particular, it emphasises that insufficient statistical data are available to make accurate projections and that a more sophisticated analytical framework is required. At the macro level, it will be essential to match the supply of Indigenous labour, in all its diversity, with regional demand. Given significant underestimation in initial AEDP goal-setting, the paper concludes that the aim of statistical equality may be both inappropriate and destined to fail and that a notion of equity that recognises diversity of both circumstances and aspirations is needed

Establishing trends in ATSIC regional council populations using census data: A cautionary note

Section 94(1) of the Aboriginal and Torres Strait Islander Act 1989 requires regional councils to 'formulate and revise from time to time a regional plan for improving the economic, social and cultural status of Aboriginal and Torres Strait Islander residents of the region'. Guidelines for the preparation of such regional plans require that councils compile a data base on the demographic composition of their council area and to consider how various social indicators may differ in the future, say in the next five years. While not explicitly stated, the guidelines thus require that some form of demographic trend analysis be undertaken for council areas so that meaningful projections of the population to be serviced may be calculated. This paper seeks to point out that limitations in official census data for Aborigines and Torres Strait Islanders draw into question the validity of trend analysis based on time series data for regional council areas. Accordingly, the meaningful application of projection techniques to estimate future population profiles using existing census data is severely restricted. Among the difficulties encountered in reconstructing council area populations are, census boundary changes over time, changes in enumeration techniques and coverage, the problems posed by self-identification and associated population growth, and, in some cases, the difficulty of matching ATSIC regional council boundaries with census geography. Following discussion of these problems, detailed figures showing changes in the size of the Aboriginal and Islander populations and labour force in each council area are presented using 1976 as the base year. As expected, geographic patterns of population and labour force change are difficult to discern and exact reasons for comparative growth or decline are impossible to determine. The paper concludes that reverse projections for regional council areas using 1991 Census data would provide a more reliable basis for establishing demographic trends. Although not entirely adequate, these reconstructions for ATSIC regional councils are the only estimates of these populations that have been undertaken to date

Hanbury Brown-Twiss Interferometry for Fractional and Integer Mott Phases

Hanbury-Brown-Twiss interferometry (HBTI) is used to study integer and fractionally filled Mott Insulator (MI) phases in period-2 optical superlattices. In contrast to the quasimomentum distribution, this second order interferometry pattern exhibits high contrast fringes in the it insulating phases. Our detailed study of HBTI suggests that this interference pattern signals the various superfluid-insulator transitions and therefore can be used as a practical method to determine the phase diagram of the system. We find that in the presence of a confining potential the insulating phases become robust as they exist for a finite range of atom numbers. Furthermore, we show that in the trapped case the HBTI interferogram signals the formation of the MI domains and probes the shell structure of the system.Comment: 13 pages, 15 figure

Phase diagram of two-component bosons on an optical lattice

We present a theoretical analysis of the phase diagram of two--component bosons on an optical lattice. A new formalism is developed which treats the effective spin interactions in the Mott and superfluid phases on the same footing. Using the new approach we chart the phase boundaries of the broken spin symmetry states up to the Mott to superfluid transition and beyond. Near the transition point, the magnitude of spin exchange can be very large, which facilitates the experimental realization of spin-ordered states. We find that spin and quantum fluctuations have a dramatic effect on the transition making it first order in extended regions of the phase diagram. For Mott states with even occupation we find that the competition between effective Heisenberg exchange and spin-dependent on--site interaction leads to an additional phase transition from a Mott insulator with no broken symmetries into a spin-ordered insulator

Terminal digit preference biases polyp size measurements at endoscopy, computed tomographic colonography and histopathology

BACKGROUND AND STUDY AIMS: Terminal digit preference bias for "pleasing" numbers has been described in many areas of medicine. The aim of this study was to determine whether endoscopists, radiologists, and pathologists exhibit such bias when measuring colorectal polyp diameters. METHODS: Colorectal polyp diameters measured at endoscopy, computed tomographic colonography (CTC), and histopathology were collated from a colorectal cancer screening program and two parallel multicenter randomized trials. Smoothing models were fitted to the data to estimate the expected number of polyps at 1-mm increments, assuming no systematic measurement bias. The difference between the expected and observed numbers of polyps was calculated for each terminal digit using statistical modeling. The impact of measurement bias on per-patient detection rates of polyps ≥ 10 mm was estimated for each modality. RESULTS: A total of 92 124 individual polyps were measured by endoscopy (91 670 screening and 454 from trials), 2385 polyps were measured by CTC (1664 screening, 721 trials), and 79 272 were measured by histopathology (78 783 screening, 489 trials). Clustering of polyp diameter measurements at 5-mm intervals was demonstrated for all modalities, both in the screening program and the trials. The statistical models estimated that per-patient detection rates of polyps ≥ 10 mm were over-inflated by 2.4 % for endoscopy, 3.1 % for CTC, and 3.3 % for histopathology in the screening program, with similar trends in the randomized trials. CONCLUSION: Endoscopists, radiologists, and pathologists all exhibit terminal digit preference when measuring colorectal polyps. This will bias trial data, referral rates for further testing, adenoma surveillance regimens, and comparisons between tests

Frustrated H-Induced Instability of Mo(110)

Using helium atom scattering Hulpke and L"udecke recently observed a giant phonon anomaly for the hydrogen covered W(110) and Mo(110) surfaces. An explanation which is able to account for this and other experiments is still lacking. Below we present density-functional theory calculations of the atomic and electronic structure of the clean and hydrogen-covered Mo(110) surfaces. For the full adsorbate monolayer the calculations provide evidence for a strong Fermi surface nesting instability. This explains the observed anomalies and resolves the apparent inconsistencies of different experiments.Comment: 4 pages, 2 figures, submitted to PR

Regulators of G-Protein signaling RGS10 and RGS17 regulate chemoresistance in ovarian cancer cells

<p>Abstract</p> <p>Background</p> <p>A critical therapeutic challenge in epithelial ovarian carcinoma is the development of chemoresistance among tumor cells following exposure to first line chemotherapeutics. The molecular and genetic changes that drive the development of chemoresistance are unknown, and this lack of mechanistic insight is a major obstacle in preventing and predicting the occurrence of refractory disease. We have recently shown that Regulators of G-protein Signaling (RGS) proteins negatively regulate signaling by lysophosphatidic acid (LPA), a growth factor elevated in malignant ascites fluid that triggers oncogenic growth and survival signaling in ovarian cancer cells. The goal of this study was to determine the role of RGS protein expression in ovarian cancer chemoresistance.</p> <p>Results</p> <p>In this study, we find that RGS2, RGS5, RGS10 and RGS17 transcripts are expressed at significantly lower levels in cells resistant to chemotherapy compared with parental, chemo-sensitive cells in gene expression datasets of multiple models of chemoresistance. Further, exposure of SKOV-3 cells to cytotoxic chemotherapy causes acute, persistent downregulation of RGS10 and RGS17 transcript expression. Direct inhibition of RGS10 or RGS17 expression using siRNA knock-down significantly reduces chemotherapy-induced cell toxicity. The effects of cisplatin, vincristine, and docetaxel are inhibited following RGS10 and RGS17 knock-down in cell viability assays and phosphatidyl serine externalization assays in SKOV-3 cells and MDR-HeyA8 cells. We further show that AKT activation is higher following RGS10 knock-down and RGS 10 and RGS17 overexpression blocked LPA mediated activation of AKT, suggesting that RGS proteins may blunt AKT survival pathways.</p> <p>Conclusions</p> <p>Taken together, our data suggest that chemotherapy exposure triggers loss of RGS10 and RGS17 expression in ovarian cancer cells, and that loss of expression contributes to the development of chemoresistance, possibly through amplification of endogenous AKT signals. Our results establish RGS10 and RGS17 as novel regulators of cell survival and chemoresistance in ovarian cancer cells and suggest that their reduced expression may be diagnostic of chemoresistance.</p

Transurethral and suprapubic mesh resection after Prolift® bladder perforation: a case report

Bladder perforation is a complication which can occur after a Prolift® procedure and may enhance vesicovaginal fistula formation. Different methods of management of bladder perforation caused by mesh procedures are described in the literature, and most authors advise complete excision of the mesh. In the case described in this article, we propose a combined transurethral and suprapubical approach as the optimal method for maximal tape removal, being both minimally invasive and less damaging to the vesical wall. A suprapubical catheter can be removed shortly after surgery to enable optimal tissue healing of the vesical mucosa

Dynamics of a bistable Mott insulator to superfluid phase transition in cavity optomechanics

We study the dynamics of the many-body state of ultracold bosons trapped in a bistable optical lattice in an optomechanical resonator controlled by a time-dependent input field. We focus on the dynamics of the many-body system following discontinuous jumps of the intracavity field. We identify experimentally realizable parameters for the bistable quantum phase transition between Mott insulator and superfluid.Comment: 6 pages, 5 figure