53,576 research outputs found
Effect of magnetostatic interactions on the hysteresis parameters of single-domain and psuedo-single domain grains
No full textFrom experiments it is known that magnetostatic interactions between grains strongly affect the magnetic behavior of samples. However, because of the difficulty in predicting the nonlinear behavior, the effect of interactions has been largely ignored from theoretical models. Instead models are often based on noninteracting assemblages. This approximation is valid for certain natural systems, but there are many cases where interactions are known to be important, for example, bacterial magnetosomes found in sedimentary rocks. Using a three-dimensional micromagnetic model, we have conducted a detailed study of the role of magnetostatic interactions on the magnetic properties of assemblages of ideal single domain (SD) grains and cubic grains between 30–250 nm in size. We quantify the contribution of interactions to hysteresis parameters and the Day plot. We show that interactions can strongly affect the magnetic characteristics of a grain assemblage. For example, assemblages of interacting SD grains can plot in the traditional multidomain (MD) area of the Day plot. For grains >100 nm in size, interactions can have the opposite effect, and can cause the hysteresis parameters to shift toward the SD region of the Day plot. In addition to varying grain size, we have also considered various anisotropies, e.g., uniaxial and cubic, and the importance of the alignment configuration of the particle assemblages, i.e., randomly distributed or aligned. It is shown that for assemblages of aligned magnetite particles, that as the interaction spacing is decreased, the SD/MD transition size increases, which may explain why some magnetotatic bacteria possess aligned grains of magnetite above the traditional transition size value of 70 nm. By aligning the anisotropies, the grains become stable SD, and having larger crystals will increase the magnetic signal
Triple-band planar dipole antenna for omnidirectional radiation
No full textThis Letter presents a compact triple-band dipole antenna that radiates omnidirectionally. The antenna is a T-shaped structure that is excited through a vertical feedline. Located under the horizontal rectangular patch are two λ/2 long meander-line stubs symmetrically interfaced to the feedline. On the bottom side of the substrate is a trident shaped ground-plane structure located under the T-shaped radiator. The proposed configuration is essentially composed of three radiating elements, which has a small footprint of 19×16 mm2 on a 0.8 mm thick substrate. Regions of enhanced impedance matching are realized between 0.5 – 2.69 GHz, 3.2 – 4.44 GHz and 4.82 – 6.6 GHz covering major portions of L, S and C-bands. It is shown by reducing the gap between the meander lines stub and rectangular patch reduces results in increased gain performance. Measured results confirm the antenna exhibits omnidirectional radiation with enhanced impedance match at 1.5, 4 and 5.4 GHz with corresponding average gain of 1.6 dBi, 3.4 dBi and 3 dBi, respectively
Measurement of the top-quark mass in all-jets events in pp collisions at = 7 TeV
No full textThe mass of the top quark is measured using a sample of candidate events with at least six jets in the final state. The sample is selected from data collected with the CMS detector in pp collisions at = 7 TeV in 2011 and corresponds to an integrated luminosity of 3.54 . The mass is reconstructed for each event employing a kinematic fit of the jets to a hypothesis. The top-quark mass is measured to be 173.49 0.69(stat.) 1.21(syst.) GeV. A combination with previously published measurements in other decay modes by CMS yields a mass of 173.54 0.33(stat.) 0.96(syst.) GeV
16 March 2009 - HRH Princess Maha Chakri Sirindhorn, Kingdom of Thailand, visiting CMS experimental area and LHC tunnel with Coordinator for external relations F. Pauss and Collaboration Spokesperson T. Virdee.
No full textPhoto 1: Relations with Non-Member State E. Tsesmelis, CMS Collaboration Spokesperson T. Virdee, HRH Princess Maha Chakri Sirindhorn and Coordinator for External relations F. Pauss, in CMS experimental area. Photo 2-12: Arrival of HRH at building 160: Posy presented to HRH by E. and F. Breedon; Welcome line: Director-General R. Heuer who introduces S. Bertolucci, F. Pauss, E. Tsesmelis, A. de Roeck, R. Breedon and Protocol Officer W. Korda. Photo 13-26:Presentation by Director-General R. Heuer and Head of Education R. Landua. Photo 27-30: Welcome at CMS by Spokesperson T. Virdee Photo 31-43: LHC tunnel visit Photo 44 - 60: CMS underground area visit Photo 61-63: HRH signs the guest book in the SCX5 conference room Photo 64-69: Signature of an expression of interest between SLRI and CMS Photo 75-88: Final discussion with Coordinator for External relation F. Pauss and Director-General R. Heuer
Acoustic radiation due to scattering of T-S wave by the mean-flow distortion induced by steady local suction
No full textSubstantial sound waves can be generated by boundary-layer instability modes when the latter are scattered by a rapid mean-flow distortion. This is a rather generic mechanism and operates when an oncoming T-S wave is scattered by a steady local suction slot. This paper focuses on this problem by extending a recently developed Local Scattering Theory (Wu & Dong, J. Fluid Mech. submitted), where a so-called transmission coefficient, defined as the ratio of the T-S wave amplitude downstream of the scatter to that upstream, is introduced to characterize the effect of a local scatter on boundary-layer instability and transition. As in the earlier work, the mathematical formulation is based on triple-deck formulism, but in order to accommodate the acoustic far field, which was not considered in the paper mentioned, the unsteady terms in the upper deck, which play a leading-order role in radiation, are retained, and the influence of the radiated sound on the near-wall perturbation is included. The upper deck equation for the pressure is the Helmholtz equation rather than the Laplace equation. This leads to a modified pressure-displacement relation, which is coupled with the linearized boundary-layer equations in the lower deck. Discretization of the whole system formulates a generalized eigenvalue problem, which is solved numerically. It is found that suction suppresses oncoming T-S waves, and this effect increases with the suction velocity and the slot width. The directivity is ndependent of the flow parameters only when the Mach number is low. The intensity of the radiated sound in general increases with the frequency, the suction velocity and the width of the suction slot. Interestingly, for O(1) suction velocities, the radiated sound is very weak, indicating that the gain of stabilizing effect does not cause aeroacoustic penalty
Measuring industry-science links through inventor-author relations: A profiling method
No full textIn this pilot study we examine the performance of text-based profiling in recovering a set of validated inventor-author links. In a first step we match patents and publications solely based on their similarity in content. Next, we compare inventor and author names on the highest ranked matches for the occurrence of name matches. Finally, we compare these candidate matches with the names listed in a validated set of inventor-author names. Our text-based profile methodology performs significantly better than a random matching of patents and publications, suggesting that text-based profiling is a valuable complementary tool to the name searches used in previous studies.innovation; industry-science links; text-based profiling;
The maternal immune system during pregnancy and its influence on fetal development
No full textThe maternal immune system plays a critical role in the establishment, maintenance, and completion of a healthy pregnancy. However, the specific mechanisms utilized to achieve these goals are not well understood. Various cells and molecules of the immune system are key players in the development and function of the placenta and the fetus. Effector cells of the immune system act to promote and yet limit placental development. The T helper 1 (Th1)/T helper 2 (Th2) immune shift during pregnancy is well established. A fine balance between proinflammatory and anti-inflammatory influences is required. We herein review the evidence regarding maternal tolerance of fetal tissues and the underlying cell-mediated immune and humoral (hormones and cytokines) mechanisms. We also note the many unanswered questions in our understanding of these mechanisms. In addition, we summarize the clinical manifestations of an altered maternal immune system during pregnancy related to susceptibility to common viral, bacterial, and parasitic infections, as well as to autoimmune diseases.Peer reviewe
S-heterocyclic carbene with a disilane backbone
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Heterogeneous and tissue-specific regulation of effector T cell responses by IFN-gamma during Plasmodium berghei ANKA infection.
No full textIFN-γ and T cells are both required for the development of experimental cerebral malaria during Plasmodium berghei ANKA infection. Surprisingly, however, the role of IFN-γ in shaping the effector CD4(+) and CD8(+) T cell response during this infection has not been examined in detail. To address this, we have compared the effector T cell responses in wild-type and IFN-γ(-/-) mice during P. berghei ANKA infection. The expansion of splenic CD4(+) and CD8(+) T cells during P. berghei ANKA infection was unaffected by the absence of IFN-γ, but the contraction phase of the T cell response was significantly attenuated. Splenic T cell activation and effector function were essentially normal in IFN-γ(-/-) mice; however, the migration to, and accumulation of, effector CD4(+) and CD8(+) T cells in the lung, liver, and brain was altered in IFN-γ(-/-) mice. Interestingly, activation and accumulation of T cells in various nonlymphoid organs was differently affected by lack of IFN-γ, suggesting that IFN-γ influences T cell effector function to varying levels in different anatomical locations. Importantly, control of splenic T cell numbers during P. berghei ANKA infection depended on active IFN-γ-dependent environmental signals--leading to T cell apoptosis--rather than upon intrinsic alterations in T cell programming. To our knowledge, this is the first study to fully investigate the role of IFN-γ in modulating T cell function during P. berghei ANKA infection and reveals that IFN-γ is required for efficient contraction of the pool of activated T cells
Letter from Carl Hayden to Fred S. Breen
No full textLetter from Carl T. Hayden to Fred S. Breen concerning the expenditure of $100,000 to purchase Bright Angel Trail
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