2,233 research outputs found

    Transport Out of the Antarctic Polar Vortex from a Three-dimensional Transport Model

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    [1] A three-dimensional chemical transport model is utilized to study the transport out of the Antarctic polar vortex during the southern hemisphere spring. On average, over five consecutive years between 1993 and 1997, horizontal transport out of the vortex into the midlatitude stratosphere is smaller than vertical transport into the troposphere. However, there is significant interannual variability in the magnitude of mass exchange, which is related to year-to-year fluctuations in planetary wave activity. In 1994 the net loss of the vortex tracer mass in September is similar to that in October. However, the relative mass flux entering the midlatitude stratosphere and the troposphere differ between the two months. The ratio of horizontal transport out of the vortex to vertical transport into the troposphere is about 3:7 in September and 5:5 in October, indicating the higher permeability of the vortex in October compared to September. The September mass flux into the troposphere is larger than in October, consistent with the fact that stronger diabatic cooling occurs in September than October over Antarctica. The estimated ozone change at southern midlatitudes due to the intrusion of ozone-depleted air from high latitudes during September–October 1994 is about −0.44% per decade, which could contribute up to 10% of observed ozone decline at southern midlatitudes in spring. This amount is an underestimate of the dilution effect from high latitudes during the spring season, as it does not include the vortex breakup in late spring

    Simulating Ability: Representing Skills in Games

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    Throughout the history of games, representing the abilities of the various agents acting on behalf of the players has been a central concern. With increasingly sophisticated games emerging, these simulations have become more realistic, but the underlying mechanisms are still, to a large extent, of an ad hoc nature. This paper proposes using a logistic model from psychometrics as a unified mechanism for task resolution in simulation-oriented games

    Magnetoelastic coupling in triangular lattice antiferromagnet CuCrS2

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    CuCrS2 is a triangular lattice Heisenberg antiferromagnet with a rhombohedral crystal structure. We report on neutron and synchrotron powder diffraction results which reveal a monoclinic lattice distortion at the magnetic transition and verify a magnetoelastic coupling. CuCrS2 is therefore an interesting material to study the influence of magnetism on the relief of geometrical frustration.Comment: 6 pages, 6 figures, 1 tabl

    The potential impact of CT-MRI matching on tumor volume delineation in advanced head and neck cancer

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    To study the potential impact of the combined use of CT and MRI scans on the Gross Tumor Volume (GTV) estimation and interobserver variation. Four observers outlined the GTV in six patients with advanced head and neck cancer on CT, axial MRI, and coronal or sagittal MRI. The MRI scans were subsequently matched to the CT scan. The interobserver and interscan set variation were assessed in three dimensions. The mean CT derived volume was a factor of 1.3 larger than the mean axial MRI volume. The range in volumes was larger for the CT than for the axial MRI volumes in five of the six cases. The ratio of the scan set common (i.e., the volume common to all GTVs) and the scan set encompassing volume (i.e., the smallest volume encompassing all GTVs) was closer to one in MRI (0.3-0.6) than in CT (0.1-0.5). The rest volumes (i.e., the volume defined by one observer as GTV in one data set but not in the other data set) were never zero for CT vs. MRI nor for MRI vs. CT. In two cases the craniocaudal border was poorly recognized on the axial MRI but could be delineated with a good agreement between the observers in the coronal/sagittal MRI. MRI-derived GTVs are smaller and have less interobserver variation than CT-derived GTVs. CT and MRI are complementary in delineating the GTV. A coronal or sagittal MRI adds to a better GTV definition in the craniocaudal directio

    Giant Taro (Alocasia macrorrhiza) Root Meal with or without Coconut Oil Slurry as Source of Dietary Energy for Laying Hens

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    The effect of feeding Alocasia macrorrhiza root meal (AMRM) with or without added coconut oil slurry (COS) on egg production and egg qualities was investigated in a 20-week experiment. A control diet based on maize and 4 other diets containing 10 and 20% AMRM with or without COS were fed each to 4 replicates of 10 birds in a completely randomized design. There were no significant dietary effects on feed intake (FI) and the intake of lysine, methionine and metabolizable energy (ME). Birds fed the 20% AMRM_COS added significantly less weight during the experimental period compared to the control fed group. Body weight change (BWC) did not differ among the AMRM fed birds. Per cent hen-day and feed conversion ratio were depressed on 20% AMRM and egg weight on 10% AMRM but these depressing effects were overcome by COS addition. Egg shape index, Haugh unit and per cent shell were not affected by the diet. It is concluded that AMRM can replace 10% dietary maize without adverse effect on laying performance but 20% replacement negatively impacts on hen-day and egg weight. These adverse effects are however, overcome by treating AMRM with COS at the ratio of 9: 1. More research into higher levels of COS treated AMRM in the diet is warranted
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