883 research outputs found

    Fluctuating local moments, itinerant electrons and the magnetocaloric effect: the compositional hypersensitivity of FeRh

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    We describe an ab-initio Disordered Local Moment Theory for materials with quenched static compositional disorder traversing first order magnetic phase transitions. It accounts quantitatively for metamagnetic changes and the magnetocaloric effect. For perfect stoichiometric B2-ordered FeRh, we calculate the transition temperature of the ferromagnetic-antiferromagnetic transition to be Tt=T_t = 495K and a maximum isothermal entropy change in 2 Tesla of ∣ΔS∣=21.1|\Delta S|= 21.1 J~K−1^{-1}~kg−1^{-1}. A large (40\%) component of ∣ΔS∣|\Delta S| is electronic. The transition results from a fine balance of competing electronic effects which is disturbed by small compositional changes - e.g. swapping just 2\% Fe of `defects' onto the Rh sublattice makes TtT_t drop by 290K. This hypersensitivity explains the narrow compositional range of the transition and impurity doping effects.Comment: 11 pages, 4 figure

    Monitoring urban green spaces in Sweden

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    In 2009, FoMA began its funding of various projects to establish a national standard for urban tree inventories in order to aid urban tree planners and professionals within green space management in conducting consistent tree inventories. A national tree inventory standard was created in 2012 (Swedish Tree Inventory Standard, STIS), which was updated in 2015. At that time call was made, encouraging the tree management organisations to upload their local data to a global database called Curio. The purpose of this evaluation has been twofold: 1) based on STIS, to present and analyse the Swedish inputs to the Curio database, and 2) to assess to which degree STIS and experiences from the Curio database can be used to include a broader perspective than urban trees, in order to also perform long-term monitoring of urban green spaces, e.g. to be used in future development of descriptions of the Swedish green sector. It is concluded, that the ambition to create a national standard for urban tree inventorying has proven to be successful, and STIS is now frequently referred to in Swedish outsourcing documents and contracts. However, in its current form, the Curio database does not provide an optimal foundation for national monitoring of urban trees. The data set is too small to be nationally representative. Envisioning total inventories and relying on municipalities to provide data is not a sustainable approach in order to ensure longitudinal monitoring with given frequencies between updates and a baseline quality of the included data. It is recommended that FoMA and SLU provide a longitudinal spatial registration coupled with an assessment of the Swedish green sectors development. It is described how this can be done based on experiences from the STIS, and the latest Green Sector Description and SCB reports on urban spatial development

    The CCFM Monte Carlo generator CASCADE 2.2.0

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    CASCADE is a full hadron level Monte Carlo event generator for ep, \gamma p and p\bar{p} and pp processes, which uses the CCFM evolution equation for the initial state cascade in a backward evolution approach supplemented with off - shell matrix elements for the hard scattering. A detailed program description is given, with emphasis on parameters the user wants to change and variables which completely specify the generated events

    Early Attachment Disruption, Inflammation, and Vulnerability for Depression in Rodent and Primate Models

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    Early experiments in nonhuman primates established the relation between disruption of filial attachment and depressive-like outcomes. Subsequent studies in rats and mice have been instrumental in linking depressive-like outcomes to disturbances in maternal behavior. Another aspect of attachment disruption, absence of the attachment object per se, may be studied more effectively in a different laboratory rodent—the guinea pig. Here, we discuss the rationale for using guinea pigs for this work. We then review guinea pig studies providing evidence for inflammatory mechanisms mediating both depressive-like behavior during separation as well as sensitization of stress responsiveness such as is thought to lead to increased vulnerability to depression at later ages. Finally, we discuss recent complementary work in adult monkeys that suggests cross-species generalizability of broad principles derived from the guinea pig experiments. Overall, the findings provide experimental support for human research implicating inflammatory mechanisms in the development of increased stress responsiveness and vulnerability to depression following attachment disruption and other forms of early-life stress. Specifically, the findings suggest inflammatory mechanisms may set in motion a cascade of underlying processes that mediate later increased stress responsiveness and, therefore, depression susceptibility

    Terahertz underdamped vibrational motion governs protein-ligand binding in solution

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    Low-frequency collective vibrational modes in proteins have been proposed as being responsible for efficiently directing biochemical reactions and biological energy transport. However, evidence of the existence of delocalized vibrational modes is scarce and proof of their involvement in biological function absent. Here we apply extremely sensitive femtosecond optical Kerr-effect spectroscopy to study the depolarized Raman spectra of lysozyme and its complex with the inhibitor triacetylchitotriose in solution. Underdamped delocalized vibrational modes in the terahertz frequency domain are identified and shown to blue-shift and strengthen upon inhibitor binding. This demonstrates that the ligand-binding coordinate in proteins is underdamped and not simply solvent-controlled as previously assumed. The presence of such underdamped delocalized modes in proteins may have significant implications for the understanding of the efficiency of ligand binding and protein–molecule interactions, and has wider implications for biochemical reactivity and biological function

    Heavy Flavour Production at Tevatron and Parton Shower Effects

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    We present hadron-level predictions from the Monte Carlo generator Cascade and numerical calculations of charm and beauty production at the Fermilab Tevatron within the framework of the kTk_T-factorization QCD approach. Our consideration is based on the CCFM-evolved unintegrated gluon densities in a proton. The performed analysis covers the total and differential cross sections of open charm and beauty quarks, BB and DD mesons (or rather muons from their semileptonic decays) and the total and differential cross sections of bbˉb \bar b di-jet hadroproduction. We study the theoretical uncertainties of our calculations and investigate the effects coming from parton showers in initial and final states. Our predictions are compared with the recent experimental data taken by the D0 and CDF collaborations. Special attention is put on the specific angular correlations between the final-state particles. We demonstrate that the final state parton shower plays a crucial role in the description of such observables. The decorrelated part of angular separations can be fully described, if the process gg∗→gggg^*\rightarrow gg is included.Comment: Fig 8,9 10 replaced, small corrections in text A discussion of the delta phi results is adde
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