19,609 research outputs found

    Phase Diagrams of Three-Component Attractive Ultracold Fermions in One-Dimension

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    We investigate trions, paired states and quantum phase transitions in one-dimensional SU(3) attractive fermions in external fields by means of the Bethe ansatz and the dressed energy formalism. Analytical results for the ground state energy, critical fields and complete phase diagrams are presented for weak and strong regimes. Numerical solutions of the dressed energy equations allow us to examine how the different phase boundaries modify by varying the inter-component coupling throughout the whole attractive regimes. The pure trionic phase reduces smoothly by decreasing this coupling until the weak limit is reached. In this weak regime, a pure BCS-paired phase can be sustained under certain nonlinear Zeeman splittings. Finally we confirm that the analytic expressions for the physical quantities and resulting phase diagrams are highly accurate in the weak and strong coupling regimes.Comment: 12 pages, 3 figures, revised version, accepted in New J. Phy

    Micellization in the presence of polyelectrolyte

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    We present a simple model to study micellization of amphiphiles condensed on a rodlike polyion. Although the mean field theory leads to a first order micellization transition for sufficiently strong hydrophobic interactions, the simulations show that no such thermodynamic phase transition exists. Instead, the correlations between the condensed amphiphiles can result in a structure formation very similar to micelles.Comment: 8 pages, 7 figure

    Optimum pulse shapes for stimulated Raman adiabatic passage

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    Stimulated Raman adiabatic passage (STIRAP), driven with pulses of optimum shape and delay has the potential of reaching fidelities high enough to make it suitable for fault-tolerant quantum information processing. The optimum pulse shapes are obtained upon reduction of STIRAP to effective two-state systems. We use the Dykhne-Davis-Pechukas (DDP) method to minimize nonadiabatic transitions and to maximize the fidelity of STIRAP. This results in a particular relation between the pulse shapes of the two fields driving the Raman process. The DDP-optimized version of STIRAP maintains its robustness against variations in the pulse intensities and durations, the single-photon detuning and possible losses from the intermediate state.Comment: 8 pages, 6 figures. submitted to Phys. Rev.

    An Unusual Case of Tertiary Syphilis Behaving Like Tongue Squamous Cell Carcinoma.

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    Syphilis may present with a myriad of oral manifestations in the primary, secondary, and tertiary stages, and may be confused with malignancy. Despite a rise in the incidence of syphilis, tertiary syphilis is exceedingly rare. Tertiary syphilis gummas usually affect the hard palate, while tongue involvement is very rare. A 55-year-old male with extensive smoking and alcohol use was referred for malignancy evaluation with an ulcerative mass creating a tongue cleft, and a positron emission tomography scan suggestive for malignancy. Biopsy results demonstrated no carcinoma but histology demonstrated granulomatous inflammation. Further laboratory results demonstrated elevated rapid plasma reagin titers with Treponema pallidum immunoglobulin G antibodies present. The patient was diagnosed with tertiary syphilis, received appropriate antibiotic therapy, and had healing of the tongue with a persistent cleft. Syphilis may mimic many disease processes. As such, it is important to include this disease in the differential of an unusual tongue lesion. An oral lesion may be the first sign of infection

    Modelling of hydrological response to climate change in glacierized Central Asian catchments

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    The arid lowlands of Central Asia are highly dependent on the water supplied by the Tien Shan mountains. Snow and ice storage make large contributions to current runoff, particularly in summer. Two runoff models with different temporal resolutions, HBV-ETH and OEZ, were applied in three glaciated catchments of the Tien Shan mountains. Scenario runs were produced for a climate change caused by the doubling of atmospheric CO2 as predicted by the GISS global circulation model and assuming a 50% reduction of glaciation extent, as well as a complete loss of glaciation. Agreement of the results was best for runs based on 50% glaciation loss, where both models predict an increase in spring and summer runoff compared to current levels. Scenarios for complete loss of glaciation predict an increase in spring runoff levels, followed by lower runoff levels for July and August. Model predictions differ concerning the degree of reduction of late summer runoff. These scenarios are sensitive to model simulation of basin precipitation, as well as to reduction of glaciation extent

    Calculation of compressible turbulent boundary layers with pressure gradients and heat transfer

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    Calculation of compressible turbulent boundary layers with pressure gradients and heat transfe

    Tight local approximation results for max-min linear programs

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    In a bipartite max-min LP, we are given a bipartite graph \myG = (V \cup I \cup K, E), where each agent v∈Vv \in V is adjacent to exactly one constraint i∈Ii \in I and exactly one objective k∈Kk \in K. Each agent vv controls a variable xvx_v. For each i∈Ii \in I we have a nonnegative linear constraint on the variables of adjacent agents. For each k∈Kk \in K we have a nonnegative linear objective function of the variables of adjacent agents. The task is to maximise the minimum of the objective functions. We study local algorithms where each agent vv must choose xvx_v based on input within its constant-radius neighbourhood in \myG. We show that for every ϵ>0\epsilon>0 there exists a local algorithm achieving the approximation ratio ΔI(1−1/ΔK)+ϵ{\Delta_I (1 - 1/\Delta_K)} + \epsilon. We also show that this result is the best possible -- no local algorithm can achieve the approximation ratio ΔI(1−1/ΔK){\Delta_I (1 - 1/\Delta_K)}. Here ΔI\Delta_I is the maximum degree of a vertex i∈Ii \in I, and ΔK\Delta_K is the maximum degree of a vertex k∈Kk \in K. As a methodological contribution, we introduce the technique of graph unfolding for the design of local approximation algorithms.Comment: 16 page

    Dynamics of fast pattern formation in porous silicon by laser interference

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    Patterns are fabricated on 290 nm thick nanostructured porous silicon layers by phase-mask laser interference using single pulses of an excimer laser (193 nm, 20 ns pulse duration). The dynamics of pattern formation is studied by measuring in real time the intensity of the diffraction orders 0 and 1 at 633 nm. The results show that a transient pattern is formed upon melting at intensity maxima sites within a time 1-µs) upon melting induced by homogeneous beam exposure and related to the different scenario for releasing the heat from hot regions. The diffraction efficiency of the pattern is finally controlled by a combination of laser fluence and initial thickness of the nanostructured porous silicon layer and the present results open perspectives on heat release management upon laser exposure as well as have potential for alternative routes for switching applications.Postprint (published version
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