A simple quantum gate with atom chips

We present a simple scheme for implementing an atomic phase gate using two degrees of freedom for each atom and discuss its realization with cold rubidium atoms on atom chips. We investigate the performance of this collisional phase gate and show that gate operations with high fidelity can be realized in magnetic traps that are currently available on atom chips.Comment: 7 pages, 7 figures. One missing reference added in v2. To appear in European Physical Journal

Does geothermal exploitation trigger earthquakes in Tuscany?

For the past 25 years, power production has been accompanied by a small but steady increase in seismicity near geothermal wells. A new project seeks to explore why

The core structure of presolar graphite onions

Of the ``presolar particles'' extracted from carbonaceous chondrite dissolution residues, i.e. of those particles which show isotopic evidence of solidification in the neighborhood of other stars prior to the origin of our solar system, one subset has an interesting concentric graphite-rim/graphene-core structure. We show here that single graphene sheet defects in the onion cores (e.g. cyclopentane loops) may be observable edge-on by HREM. This could allow a closer look at models for their formation, and in particular strengthen the possibility that growth of these assemblages proceeds atom-by-atom with the aid of such in-plane defects, under conditions of growth (e.g. radiation fluxes or grain temperature) which discourage the graphite layering that dominates subsequent formation of the rim.Comment: 4 pages, 7 figures, 11 refs, see also http://www.umsl.edu/~fraundor/isocore.htm

Nuclear Surveillance and Degradation of Hypomodified Initiator tRNA\u3csup\u3eMet\u3c/sup\u3e in \u3cem\u3eS. cerevisiae\u3c/em\u3e

The tRNA m1A58 methyltransferase is composed of two subunits encoded by the essential genes TRM6 and TRM61 (formerly GCD10 and GCD14). The trm6-504 mutation results in a defective m1A methyltransferase (Mtase) and a temperature-sensitive growth phenotype that is attributable to the absence of m1A58 and consequential tRNAiMet instability. We used a genetic approach to identify the genes responsible for tRNAiMet degradation in trm6 cells. Three recessive extragenic mutations that suppress trm6-504 mutant phenotypes and restore hypomodified tRNAiMet to near normal levels were identified. The wild-type allele of one suppressor, DIS3/RRP44, encodes a 3′-5′ exoribonuclease and a member of the multisubunit exosome complex. We provide evidence that a functional nuclear exosome is required for the degradation of tRNAiMet lacking m1A58. A second suppressor gene encodes Trf4p, a DNA polymerase (pol σ) with poly(A) polymerase activity. Whereas deletion of TRF4 leads to stabilization of tRNAiMet, overexpression of Trf4p destabilizes the hypomodified tRNAiMet in trm6 cells. The hypomodified, but not wild-type, pre-tRNAiMet accumulates as a polyadenylated species, whose abundance and length distribution both increase upon Trf4p overexpression. These data indicate that a tRNA surveillance pathway exists in yeast that requires Trf4p and the exosome for polyadenylation and degradation of hypomodified pre-tRNAiMet

Bibliometric Measures and Journal Characteristics of Leading Accounting and Finance Journals

This study analyzes journal quality metrics and characteristics of leading accounting and finance journals in the Academic Journal Guide. The quality metrics analyzed are Journal Citation Reports (JCR), SCImago Journal Rank (SJR), Source Normalized Impact per Paper (SNIP), and CiteScore. The characteristics analyzed are acceptance rates, issue frequency, journal longevity, number of reviewers, and review time. The findings show that accounting journal SNIP average ratings are higher, finance journal SJR ratings are higher, while the JCR measures are virtually identical. However, CiteScore measures of top-tier accounting journals are significantly higher than those of finance journals. Leading accounting journals are older and have higher acceptance rates. Leading finance journals have more issues, more referees, and longer initial reviews. The journal acceptance rate is the journal characteristic that is the most correlated with measures of journal quality. These findings could be beneficial for accounting and finance junior faculty when working towards promotion and tenure

Correlations in Bipartite Collaboration Networks

Collaboration networks are studied as an example of growing bipartite networks. These have been previously observed to have structure such as positive correlations between nearest-neighbour degrees. However, a detailed understanding of the origin of this phenomenon and the growth dynamics is lacking. Both of these are analyzed empirically and simulated using various models. A new one is presented, incorporating empirically necessary ingredients such as bipartiteness and sublinear preferential attachment. This, and a recently proposed model of team assembly both agree roughly with some empirical observations and fail in several others.Comment: 13 pages, 17 figures, 2 table, submitted to JSTAT; manuscript reorganized, figures and a table adde

Estimating flexibility preferences to resolve temporal scheduling conflicts in activity-based modelling

This paper presents a novel activity-based demand model that combines an optimisation framework for continuous temporal scheduling decisions (i.e. activity timings and durations) with traditional discrete choice models for non-temporal choice dimensions (i.e. activity participation, number and type of tours, and destinations). The central idea of our approach is that individuals resolve temporal scheduling conflicts that arise from overlapping activities, e.g. needing to work and desiring to shop at the same time, in order to maximise their daily utility. Flexibility parameters capture behavioural preferences that penalise deviations from desired timings. This framework has three advantages over existing activity-based modelling approaches: (i) the time conflicts between different temporal scheduling decisions including the activity sequence are treated jointly; (ii) flexibility parameters follow a utility maximisation approach; and (iii) the framework can be used to estimate and simulate a city-scale case study in reasonable time. We introduce an estimation routine that allows flexibility parameters to be estimated using real-world observations as well as a simulation routine to efficiently resolve temporal conflicts using an optimisation model. The framework is applied to the full-time workers of a synthetic population for the city of Lausanne, Switzerland. We validate the model results against reported schedules. The results demonstrate the capabilities of our approach to reproduce empirical observations in a real-world case study

Pulmonary function testing after operative stabilisation of the chest wall for flail chest

Objective: This is a prospective evaluation of chest wall integrity and pulmonary function in patients with operative stabilisation for flail chest injuries. Methods: From 1990 to 1999, 66 patients (56 men, 10 women; mean age 52.6 years) with antero-lateral flail chest (≧4 ribs fractured at ≧2 sites) underwent surgical stabilisation using reconstruction plates. Clinical assessment and pulmonary function testing were performed at 6 months following surgery. Results: Fifty-five (83%) patients had various combinations of injuries of the thorax, head, abdomen and extremities. Sixty-three (95.5%) patients underwent unilateral and 3 (4.5%) patients bilateral stabilisation with a median delay of 2.8 days (range 0-21 days) from admission. The 30-day mortality was 11% (seven of 66 patients). Immediate postoperative extubation was feasible in 31 of 66 patients (47%) and extubation within 7 days following stabilisation in 56 of 66 patients (85%). No plate dislocation was observed during the follow-up. The shoulder girdle function was intact in 51 of 57 patients (90%). Chest wall complaints were noted in 6 of 57 (11%) patients, requiring removal of implants in three cases. All patients returned to work within a mean period of 8 (range 3-16) weeks following discharge. Pulmonary function testing (n=50) at 6 months after the operation revealed a significant difference of predicted vs. recorded vital capacity (VC) and forced expiratory volume in 1s (FEV1) (P=0.04 and P=0.0001, respectively; Wilcoxon signed-rank test). The median ratio of the recorded and predicted total lung capacity (TLC) was shown to be significantly higher than 0.85 (P=0.0002; Wilcoxon signed-rank test), indicating prevention of pulmonary restriction. Conclusion: Antero-lateral flail chest injuries accompanied by respiratory insufficiency can be effectively stabilised using reconstruction plates. Early restoration of the chest wall integrity and respiratory pump function may be cost effective through the prevention of prolonged mechanical ventilation and restriction-related working incapacit

Infrared Spectroscopy of Molecular Supernova Remnants

We present Infrared Space Observatory spectroscopy of sites in the supernova remnants W28, W44, and 3C391, where blast waves are impacting molecular clouds. Atomic fine-structure lines were detected from C, N, O, Si, P, and Fe. The S(3) and S(9) lines of H2 were detected for all three remnants. The observations require both shocks into gas with moderate (~ 100 /cm3) and high (~10,000 /cm3) pre-shock densities, with the moderate density shocks producing the ionic lines and the high density shock producing the molecular lines. No single shock model can account for all of the observed lines, even at the order of magnitude level. We find that the principal coolants of radiative supernova shocks in moderate-density gas are the far-infrared continuum from dust grains surviving the shock, followed by collisionally-excited [O I] 63.2 and [Si II] 34.8 micron lines. The principal coolant of the high-density shocks is collisionally-excited H2 rotational and ro-vibrational line emission. We systematically examine the ground-state fine structure of all cosmically abundant elements, to explain the presence or lack of all atomic fine lines in our spectra in terms of the atomic structure, interstellar abundances, and a moderate-density, partially-ionized plasma. The [P II] line at 60.6 microns is the first known astronomical detection. There is one bright unidentified line in our spectra, at 74.26 microns. The presence of bright [Si II] and [Fe II] lines requires partial destruction of the dust. The required gas-phase abundance of Fe suggests 15-30% of the Fe-bearing grains were destroyed. The infrared continuum brightness requires ~1 Msun of dust survives the shock, suggesting about 1/3 of the dust mass was destroyed, in agreement with the depletion estimate and with theoretical models for dust destruction.Comment: 40 pages; 10 figures; accepted by ApJ July 11, 200