Thermodynamics of Adiabatically Loaded Cold Bosons in the Mott Insulating Phase of One-Dimensional Optical Lattices

In this work we give a consistent picture of the thermodynamic properties of bosons in the Mott insulating phase when loaded adiabatically into one-dimensional optical lattices. We find a crucial dependence of the temperature in the optical lattice on the doping level of the Mott insulator. In the undoped case, the temperature is of the order of the large onsite Hubbard interaction. In contrast, at a finite doping level the temperature jumps almost immediately to the order of the small hopping parameter. These two situations are investigated on the one hand by considering limiting cases like the atomic limit and the case of free fermions. On the other hand, they are examined using a quasi-particle conserving continuous unitary transformation extended by an approximate thermodynamics for hardcore particles.Comment: 10 pages, 6 figure

Fabric Cooling by Water Evaporation

Clothing can provide safety and comfort for persons exposed to both cold and hot thermal environments. To assess the potential impact of clothing moisture and wetness on fabric cooling, a series of wind-tunnel tests was conducted to quantify the evaporative cooling capacity of selected fabric samples. Single-layer cotton, polyester, nylon and silk were evaluated. The results showed that onset and magnitude of evaporative cooling was determined by the amount of water contained in a fabric sample. The results also showed that an exposed skin exhibited more cooling when covered with a fabric than when it was not. The information obtained helps better understand the evaporative cooling process for fabrics and assist in the selection of garment materials that optimize worker comfort and safety

Virtual concrete specimens: discrete element simulations of the quasistatic and dynamic material behavior and failure mechanisms of concrete and mortar

A quite minimalistic approach is described which allows to generate differently shaped ensembles of densely packed spherical particles. The distributions of the particle diameters approximate realistic sieving distributions of concrete aggregates. An ad hoc approach is used in order to add cohesive interaction forces to the model which allows first plausibility tests

Temperature in One-Dimensional Bosonic Mott insulators

The Mott insulating phase of a one-dimensional bosonic gas trapped in optical lattices is described by a Bose-Hubbard model. A continuous unitary transformation is used to map this model onto an effective model conserving the number of elementary excitations. We obtain quantitative results for the kinetics and for the spectral weights of the low-energy excitations for a broad range of parameters in the insulating phase. By these results, recent Bragg spectroscopy experiments are explained. Evidence for a significant temperature of the order of the microscopic energy scales is found.Comment: 8 pages, 7 figure

Mol. Cell. Proteomics

Chemical cross-linking in combination with mass spectrometric analysis offers the potential to obtain low-resolution structural information from proteins and protein complexes. Identification of peptides connected by a cross-link provides direct evidence for the physical interaction of amino acid side chains, information that can be used for computational modeling purposes. Despite impressive advances that were made in recent years, the number of experimentally observed cross-links still falls below the number of possible contacts of cross-linkable side chains within the span of the cross-linker. Here, we propose two complementary experimental strategies to expand cross-linking data sets. First, enrichment of cross-linked peptides by size exclusion chromatography selects cross-linked peptides based on their higher molecular mass, thereby depleting the majority of unmodified peptides present in proteolytic digests of cross-linked samples. Second, we demonstrate that the use of proteases in addition to trypsin, such as Asp-N, can additionally boost the number of observable cross-linking sites. The benefits of both SEC enrichment and multiprotease digests are demonstrated on a set of model proteins and the improved workflow is applied to the characterization of the 20S proteasome from rabbit and Schizosaccharomyces pombe

Pressure Thresholds and Stiffness on the Plantar Surface of the Human Foot

The objective was to develop a methodology to assess Pressure Discomfort Thresholds (PDT), Pressure Pain Thresholds (PPT), and tissue stiffness on the plantar surface of the foot. Ten male and ten female participants volunteered for the study. Foot landmarks were used to create a standardized grid-type template of 95 points. For each test point, PPT and PDT values were obtained, and stiffness was calculated for each of the twenty participants. Cluster analyses were performed to determine the regions of similarity for the three dependent variables, PPT, PDT and stiffness. Moran’s-I-index was used to determine the spatial auto correlations. The use of k-means clustering showed five distinct clusters while the three dependent variables showed strong correlations to each other. Morisita’s similarity index was used to check the similarity of the grid among all participants. Both male and female participants showed a Morisita’s index greater than 0.7 confirming the reliability of the foot template

Systematic Mapping of the Hubbard Model to the Generalized t-J Model

The generalized t-J model conserving the number of double occupancies is constructed from the Hubbard model at and in the vicinity of half-filling at strong coupling. The construction is realized by a self-similar continuous unitary transformation. The flow equation is closed by a truncation scheme based on the spatial range of processes. We analyze the conditions under which the t-J model can be set up and we find that it can only be defined for sufficiently large interaction. There, the parameters of the effective model are determined.Comment: 16 pages, 13 figures included. v2: Order of sections changed. Calculation and discussion of apparent gap in Section IV.A correcte

Microscopic model for Bose-Einstein condensation and quasiparticle decay

Sufficiently dimerized quantum antiferromagnets display elementary S=1 excitations, triplon quasiparticles, protected by a gap at low energies. At higher energies, the triplons may decay into two or more triplons. A strong enough magnetic field induces Bose-Einstein condensation of triplons. For both phenomena the compound IPA-CuCl3 is an excellent model system. Nevertheless no quantitative model was determined so far despite numerous studies. Recent theoretical progress allows us to analyse data of inelastic neutron scattering (INS) and of magnetic susceptibility to determine the four magnetic couplings J1=-2.3meV, J2=1.2meV, J3=2.9meV and J4=-0.3meV. These couplings determine IPA-CuCl3 as system of coupled asymmetric S=1/2 Heisenberg ladders quantitatively. The magnetic field dependence of the lowest modes in the condensed phase as well as the temperature dependence of the gap without magnetic field corroborate this microscopic model.Comment: 6 pages, 5 figure

Efficacy of Information Extraction from Bar, Line, Circular, Bubble and Radar Graphs

With the emergence of enormous amounts of data, numerous ways to visualize such data have been used. Bar, circular, line, radar and bubble graphs that are ubiquitous were investigated for their effectiveness. Fourteen participants performed four types of evaluations: between categories (cities), within categories (transport modes within a city), all categories, and a direct reading within a category from a graph. The representations were presented in random order and participants were asked to respond to sixteen questions to the best of their ability after visually scanning the related graph. There were two trials on two separate days for each participant. Eye movements were recorded using an eye tracker. Bar and line graphs show superiority over circular and radial graphs in effectiveness, efficiency, and perceived ease of use primarily due to eye saccades. The radar graph had the worst performance. “Vibration-type” fill pattern could be improved by adding colors and symbolic fills. Design guidelines are proposed for the effective representation of data so that the presentation and communication of information are effective

Evaluation of single and double-locus real-time PCR assays for methicillin-resistant Staphylococcus aureus (MRSA) surveillance

<p>Abstract</p> <p>Background</p> <p>Methicillin-resistant <it>Staphylococcus aureus </it>(MRSA) is a human pathogen, representing an infection control challenge. Conventional MRSA screening takes up to three days, therefore development of rapid detection is essential. Real time-PCR (rt-PCR) is the fastest method fulfilling this task. All currently published or commercially available rt-PCR MRSA assays relay on single or double-locus detection. Double-locus assays are based on simultaneous detection of <it>mecA </it>gene and a <it>S. aureus</it>-specific gene. Such assays cannot be applied on clinical samples, which often contain both coagulase-negative staphylococci (CoNS) and <it>S. aureus</it>, either of which can carry <it>mecA</it>. Single-locus assays are based on detection of the staphylococcal cassette chromosome <it>mec </it>(SCC<it>mec</it>) element and the <it>S. aureus</it>-specific <it>orfX </it>gene, assuming that it is equivalent to <it>mecA </it>detection.</p> <p>Findings</p> <p>Parallel evaluation of several published single and double-locus rt-PCR MRSA assays of 150 pure culture strains, followed by analysis of 460 swab-derived clinical samples which included standard identification, susceptibility testing, followed by PCR detection of staphylococcal suspected isolates and in-PCR mixed bacterial populations analysis indicated the following findings.</p> <p>Pure cultures analysis indicated that one of the single-locus assay had very high prevalence of false positives (Positive predictive value = 77.8%) and was excluded from further analysis. Analysis of 460 swab-derived samples indicated that the second single-locus assay misidentified 16 out of 219 MRSA's and 13 out of 90 methicillin-sensitive <it>S</it>. <it>aureus</it>'s (MSSA) were misidentified as MRSA's. The double-locus detection assay misidentified 55 out of 90 MSSA's. 46 MSSA containing samples were misidentified as MRSA and 9 as other than <it>S. aureus </it>ending with low positive predicted value (<85%) and very low specificity (<62%).</p> <p>Conclusion</p> <p>The results indicate that high prevalence of false-positive and false-negative reactions occurs in such assays.</p