270 research outputs found

    Thermal decoupling and the smallest subhalo mass in dark matter models with Sommerfeld-enhanced annihilation rates

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    We consider dark matter consisting of weakly interacting massive particles (WIMPs) and revisit in detail its thermal evolution in the early universe, with a particular focus on models where the annihilation rate is enhanced by the Sommerfeld effect. After chemical decoupling, or freeze-out, dark matter no longer annihilates but is still kept in local thermal equilibrium due to scattering events with the much more abundant standard model particles. During kinetic decoupling, even these processes stop to be effective, which eventually sets the scale for a small-scale cutoff in the matter density fluctuations. Afterwards, the WIMP temperature decreases more quickly than the heat bath temperature, which causes dark matter to reenter an era of annihilation if the cross-section is enhanced by the Sommerfeld effect. Here, we give a detailed and self-consistent description of these effects. As an application, we consider the phenomenology of simple leptophilic models that have been discussed in the literature and find that the relic abundance can be affected by as much two orders of magnitude or more. We also compute the mass of the smallest dark matter subhalos in these models and find it to be in the range of about 10^{-10} to 10 solar masses; even much larger cutoff values are possible if the WIMPs couple to force carriers lighter than about 100 MeV. We point out that a precise determination of the cutoff mass allows to infer new limits on the model parameters, in particular from gamma-ray observations of galaxy clusters, that are highly complementary to existing constraints from g-2 or beam dump experiments.Comment: minor changes to match published versio

    Characterization of an embedded RF-MEMS switch

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    An RF-MEMS capacitive switch for mm-wave integrated circuits, embedded in the BEOL of 0.25μm BiCMOS process, has been characterized. First, a mechanical model based on Finite-Element-Method (FEM) was developed by taking the residual stress of the thin film membrane into account. The pull-in voltage and the capacitance values obtained with the mechanical model agree very well with the measured values. Moreover, S-parameters were extracted using Electromagnetic (EM) solver. The data observed in this way also agree well with the experimental ones measured up to 110GHz. The developed RF model was applied to a transmit/receive (T/R) antenna switch design. The results proved the feasibility of using the FEM model in circuit simulations for the development of RF-MEMS switch embedded, single-chip multi-band RF ICs

    The Relationship Between Serum Adiponectin, Tumor Necrosis Factor−Alpha, Leptin Levels and Insulin Sensitivity in Childhood and Adolescent Obesity: Adiponectin is a Marker of Metabolic Syndrome

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    Objective: This study aimed (a) to investigate the relationship between the degree of obesity and serum adiponectin, tumor necrosis factor (TNF)−α, leptin, insulin levels and the lipid profile; (b) to clarify the relationship between insulin resistance/glucose tolerance and adipocytokine levels; and (c) to investigate the value of adipocytokine levels as a marker of metabolic syndrome (MS)

    The Effect of Tranexamic Acid and Tourniquet Use on Tibial Cement Penetration in Primary Total Knee Arthroplasties

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    Background: In this study, our aim was to compare the effects of tourniquet and tranexamic acid (TXA) use on tibial cement penetration in primary total knee arthroplasty (TKA) using radiograph images. In addition, we also aimed at investigating the effects of age, gender, body mass index (BMI), and bone mineral density on cement penetration. Methods: One hundred seventy patients who underwent TKA for primary osteoarthritis were retrospectively evaluated. TXA was administered to patients in group 1 (n = 96), and tourniquet application was used in patients in group 2 (n = 74). Tibial cement penetration was evaluated radiologically on a total of 4 zones: 2 anteroposterior and 2 lateral zones. In addition, age, gender, BMI, and bone mineral density were recorded in each group. Results: The mean cement penetration in the total study population was 2.34 ± 0.24 mm, with a mean of 2.33 ± 0.25 mm in the TXA group and a mean of 2.35 ± 0.24 mm in the tourniquet group (P = .453). A negative correlation was detected between BMI and anteroposterior 1 values in the total and TXA groups (P = .022 and P = .029). In the evaluation of the differences between genders, significantly higher penetration values were observed only in the females in the tourniquet group (P = .024). Conclusions: The use of TXA instead of a tourniquet does not reduce the depth of cement penetration in TKA. The clinical implications of individual-induced penetration differences may be significant for future implant survival. © 2020 The Author

    Magnetic critical behavior of two-dimensional random-bond Potts ferromagnets in confined geometries

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    We present a numerical study of 2D random-bond Potts ferromagnets. The model is studied both below and above the critical value Qc=4Q_c=4 which discriminates between second and first-order transitions in the pure system. Two geometries are considered, namely cylinders and square-shaped systems, and the critical behavior is investigated through conformal invariance techniques which were recently shown to be valid, even in the randomness-induced second-order phase transition regime Q>4. In the cylinder geometry, connectivity transfer matrix calculations provide a simple test to find the range of disorder amplitudes which is characteristic of the disordered fixed point. The scaling dimensions then follow from the exponential decay of correlations along the strip. Monte Carlo simulations of spin systems on the other hand are generally performed on systems of rectangular shape on the square lattice, but the data are then perturbed by strong surface effects. The conformal mapping of a semi-infinite system inside a square enables us to take into account boundary effects explicitly and leads to an accurate determination of the scaling dimensions. The techniques are applied to different values of Q in the range 3-64.Comment: LaTeX2e file with Revtex, revised versio

    Solid-state structure, solution-state behaviour and catalytic activity of electronically divergent C, N-chelating palladium-N-heterocyclic carbene complexes

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    A family of electronically diverse pyridyl- and picolyl-substituted imidazolium salts have been prepared and coordinated to palladium in a single step, to deliver a variety of palladium(II)–N-heterocyclic carbene (NHC) complexes. Neutral Pd(NHC)X2, cationic [Pd(NHC)2X]X and dicationic [Pd(NHC)2]X2-type complexes have been isolated and fully characterised, with single-crystal X-ray analysis revealing a variety of coordination environments around the palladium centres. The pre-formed complexes have been employed in a model Suzuki–Miyaura cross-coupling reaction to yield a sterically congested tetra-ortho-substituted biaryl product, showcasing turnover numbers comparable to Pd-PEPPSI-IPr catalyst

    Surface plasmon resonance based immunosensor for the detection of the cancer biomarker carcinoembryonic antigen

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    An immunoassay in optimised conditions with a highly sensitive surface plasmon resonance (SPR) based biosensor was developed for the detection of the cancer biomarker carcinoembryonic antigen (CEA). Different formats of the immunoassay were initially investigated on the surface of the gold sensor chip. A self- assembled monolayer (SAM) was formed on the gold chip using 11- mercaptoundecanoic acid (MUDA), before the immobilisation of the antibodies was conducted. The assay was then formed in a direct capture and a sandwich assay. In order to increase the sensor signal the CEA antigen was incubated with the detection/capture antibody before it was injected to the sensor chip surface and the results were recorded in real-time using the Biacore 3000 instrument. A detection limit of 3ngml-1 CEA was obtained with a dynamic detection range from 3ngml-1 to 400ngml-1 with correlation coefficients of 1.00 and 0.99 for the sandwich and rabbit anti-mouse (RAM) capture assay. Kinetic data analysis was performed for the standard capture test and subsequently for the developed assays and Rmax showed an increase from 215 RU for the standard capture test to 428 RU for the RAM-capture assay and 734 RU for the sandwich assay, respectively. The developed SPR immunosensor using the sandwich assay format showed high sensitivity and reproducibility for CEA detection which makes it a promising procedure for cancer biomarker analysi
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