2,829 research outputs found
Temperature dependent orbital degree of freedom in a bilayer manganite by magnetic Compton scattering
We have measured temperature-dependent magnetic Compton profiles (MCPs) from
a single crystal of LaSrMnO. The MCPs, which involved
the scattering of circularly polarized x-rays, are in general related to the
momentum density of all the unpaired spins in the system. Nevertheless, we show
that when the x-ray scattering vector lies along the [110] direction, the
number of magnetic electrons of a specific symmetry, i.e. -electrons of
symmetry, yield a distinct signature in the MCP, allowing us to
monitor substantial changes in the occupancy of the states over
the investigated temperature range of 5-200K. This study indicates that
magnetic Compton scattering can provide a powerful window on the properties of
specific magnetic electrons in complex materials.Comment: 5 pages, 4 figures, to appear in Phys. Rev. Let
Computational interaction techniques for 3D selection, manipulation and navigation in immersive VR
3D interaction provides a natural interplay for HCI. Many techniques involving diverse sets of hardware and software components have been proposed, which has generated an explosion of Interaction Techniques (ITes), Interactive Tasks (ITas) and input devices, increasing thus the heterogeneity of tools in 3D User Interfaces (3DUIs). Moreover, most of those techniques are based on general formulations that fail in fully exploiting human capabilities for interaction. This is because while 3D interaction enables naturalness, it also produces complexity and limitations when using 3DUIs.
In this thesis, we aim to generate approaches that better exploit the high potential human capabilities for interaction by combining human factors, mathematical formalizations and computational methods. Our approach is focussed on the exploration of the close coupling between specific ITes and ITas while addressing common issues of 3D interactions.
We specifically focused on the stages of interaction within Basic Interaction Tasks (BITas) i.e., data input, manipulation, navigation and selection. Common limitations of these tasks are: (1) the complexity of mapping generation for input devices, (2) fatigue in mid-air object manipulation, (3) space constraints in VR navigation; and (4) low accuracy in 3D mid-air selection.
Along with two chapters of introduction and background, this thesis presents five main works. Chapter 3 focusses on the design of mid-air gesture mappings based on human tacit knowledge. Chapter 4 presents a solution to address user fatigue in mid-air object manipulation. Chapter 5 is focused on addressing space limitations in VR navigation. Chapter 6 describes an analysis and a correction method to address Drift effects involved in scale-adaptive VR navigation; and Chapter 7 presents a hybrid technique 3D/2D that allows for precise selection of virtual objects in highly dense environments (e.g., point clouds). Finally, we conclude discussing how the contributions obtained from this exploration, provide techniques and guidelines to design more natural 3DUIs
Spin moment over 10-300 K and delocalization of magnetic electrons above the Verwey transition in magnetite
In order to probe the magnetic ground state, we have carried out temperature
dependent magnetic Compton scattering experiments on an oriented single crystal
of magnetite (FeO), together with the corresponding first-principles
band theory computations to gain insight into the measurements. An accurate
value of the magnetic moment associated with unpaired spins is obtained
directly over the temperature range of 10-300K. is found to be
non-integral and to display an anomalous behavior with the direction of the
external magnetic field near the Verwey transition. These results reveal how
the magnetic properties enter the Verwey energy scale via spin-orbit coupling
and the geometrical frustration of the spinel structure, even though the Curie
temperature of magnetite is in excess of 800 K. The anisotropy of the magnetic
Compton profiles increases through the Verwey temperature and indicates
that magnetic electrons in the ground state of magnetite become delocalized on
Fe B-sites above .Comment: 5 pages, 5 figures, to appear in Journal of Physics and Chemistry of
Solid
Effect of energy density and virginiamycin supplementation in diets on growth performance and digestive function of finishing steers.
ObjectiveThis study was determined the influence of virginiamycin supplementation on growth-performance and characteristics of digestion of cattle with decreasing dietary net energy value of the diet for maintenance (NEm) from 2.22 to 2.10 Mcal/kg.MethodsEighty crossbred beef steers (298.2±6.3 kg) were used in a 152-d performance evaluation consisting of a 28-d adaptation period followed by a 124-d growing-finishing period. During the 124-d period steers were fed either a lesser energy dense (LED, 2.10 Mcal/kg NEm) or higher energy dense (HED, 2.22 Mcal/kg NEm) diet. Diets were fed with or without 28 mg/kg (dry matter [DM] basis) virginiamycin in a 2×2 factorial arrangement. Four Holstein steers (170.4±5.6 kg) with cannulas in the rumen (3.8 cm internal diameter) and proximal duodenum were used in 4×4 Latin square experiment to study treatment effects on characteristics of digestion.ResultsNeither diet energy density nor virginiamycin affected average daily gain (p>0.10). As expected, dry matter intake and gain efficiency were greater (p<0.01) for LED- than for HED-fed steers. Virginiamycin did not affect estimated net energy value of the LED diet. Virginiamycin increased estimated NE of the HED diet. During daylight hours when the temperature humidity index averaged 81.3±2.7, virginiamycin decreased (p<0.05) ruminal temperature. Virginiamycin did not influence (p>0.10) ruminal or total tract digestion. Ruminal (p = 0.02) and total tract digestion (p<0.01) of organic matter, and digestible energy (p<0.01) were greater for HED vs LED. Ruminal microbial efficiency was lower (p<0.01) for HED vs LED diets.ConclusionThe positive effect of virginiamycin on growth performance of cattle is due to increased efficiency of energy utilization, as effects of virginiamycin on characteristics of digestion were not appreciable. Under conditions of high ambient temperature virginiamycin may reduce body temperature
Second-harmonic generation microscopy analysis reveals proteoglycan decorin is necessary for proper collagen organization in prostate.
Collagen remodeling occurs in many prostate pathologies; however, the underlying structural architecture in both normal and diseased prostatic tissues is largely unexplored. Here, we use second-harmonic generation (SHG) microscopy to specifically probe the role of the proteoglycan decorin (Dcn) on collagen assembly in a wild type (wt) and Dcn null mouse (Dcn  -    /    -  ). Dcn is required for proper organization of collagen fibrils as it regulates size by forming an arch-like structure at the end of the fibril. We have utilized SHG metrics based on emission directionality (forward-backward ratio) and relative conversion efficiency, which are both related to the SHG coherence length, and found more disordered fibril organization in the Dcn  -    /    -  . We have also used image analysis readouts based on entropy, multifractal dimension, and wavelet transforms to compare the collagen fibril/fiber architecture in the two models, where all these showed that the Dcn  -    /    -   prostate comprised smaller and more disorganized collagen structures. All these SHG metrics are consistent with decreased SHG phase matching in the Dcn  -    /    -   and are further consistent with ultrastructural analysis of collagen in this model in other tissues, which show a more random distribution of fibril sizes and their packing into fibers. As Dcn is a known tumor suppressor, this work forms the basis for future studies of collagen remodeling in both malignant and benign prostate disease
A Preliminary Evaluation of Morphing Horizontal Tail Design for UAVs
Morphing structures are a relatively new aircraft technology currently being investigated for a variety of applications, from civil to military. Despite the lack of literature maturity and its
complexity, morphing wings offer significant aerodynamic benefits over a wide range of flight
conditions, enabling reduced aircraft fuel consumption and airframe noise, longer range and higher
efficiency. The aim of this study is to investigate the impact of morphing horizontal tail design on
aircraft performance and flight mechanics. This study is conducted on a 1:5 scale model of a Preceptor
N-3 Pup at its trim condition, of which the longitudinal dynamics is implemented in MATLAB.
Starting from the original horizontal tail airfoil NACA 0012 with the elevator deflected at the trim
value, this is modified by using X-Foil tool to obtain a smooth morphing airfoil trailing edge shape
with the same CLα. By comparing both configurations and their influence on the whole aircraft, the
resulting improvements are evaluated in terms of stability of the short-period mode, reduction of
parasitic drag coefficient CD0, and increased endurance at various altitude
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