196,256 research outputs found
Letter, 1935 Nov. 22, Washington, D.C., to Miss Amelia M. Earhart, Rye, N.Y.
No full textLetter from Robert R. Reining, Chief of the Registration Section of the U. S. Bureau of Air Commerce, to Amelia Earhart concerning her license renewal, November 22, 193
Ab initio pseudopotential calculation of the equilibrium structure of tin monoxide
No full textWe present an ab initio pseudopotential calculation of the structural properties of stannous oxide SnO. We discuss the delicate balance of different contributions to the cohesion of this material, and compare the monoxide to the dioxide SnO2. We point out how different choices concerning the pseudopotential of tin may dramatically influence the resulting equilibrium structure of SnO, and show that the physically most appropriate choice leads to excellent agreement with experiment
First Principles simulations
No full textIn this paper we outline the major features of the “ab-initio” simulation scheme of Car and
Parrinello, focusing on the physical ideas and computational details at the basis of its efficiency
and success. We briefly review the main applications of the method. We discuss the limitations
of the standard scheme, as well as recent developments proposed in order to extend the reach
of the method. Moreover, we consider more in detail two specific subjects. First, we describe a simple improvement
(Gradient Corrections) on the basic approximation of the "ab-initio" simulation, ie the
Local Density Approximation. These corrections can be easily and efficiently included in the
Car-Parrinello code, bringing computed structural and cohesive properties significantly closer
to their experimental values. Finally, we discuss the choice of the pseudopotential, with special
attention to the possibilities and limitations of the last generation of soft pseudopotentials
Ab initio pseudopotential calculation of the equilibrium structure of tin monoxide
No full textWe present an ab initio pseudopotential calculation of the structural properties of stannous oxide SnO. We discuss the delicate balance of different contributions to the cohesion of this material, and compare the monoxide to the dioxide SnO2. We point out how different choices concerning the pseudopotential of tin may dramatically influence the resulting equilibrium structure of SnO, and show that the physically most appropriate choice leads to excellent agreement with experiment
Physiological responses of mature Quarter Horses to reining training when fed conventional and fat supplemented diets
No full textDue to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Includes bibliographical references: p. 52-55.Issued also on microfiche from Lange Micrographics.An initial experiment was conducted utilizing five mature Quarter Horses to establish baseline physiological responses to typical reining training. Heart rate and plasma lactate concentration indicated that galloping circles, spinning and stopping were anaerobic maneuvers (203 beats/min and 8.86 mmol/L, respectively). However, lactate concentrations declined before the end of exercise. The values were used to modify the SET to a degree of difficulty that would elicit anaerobiosis. In a second experiment, ten mature Quarter Horses were exercised by reining horse training in a repeated switchback experiment. Horses were fed a control (C) and a IO% fat-supplemented (F) concentrate with bermudagrass hay in a 65:3 5 ratio. Heart rate (HR), respiration rate (RR), rectal temperature (RT) and venous blood samples were taken prior to, during and following recovery from an SET which simulated reining horse training. Heart rates and plasma lactate concentrations indicated that all maneuvers except loping circles elicited anaerobiosis (208 beats/min and 11.8 mmol/L, respectively). Plasma glucose concentration fell during loping circles from resting concentrations of I 00 mg/dL to 75 mg/dL, increased throughout the remainder of the SET to 90 mg/dL and returned to resting concentrations by 30 min of recovery. Respiration rate, packed cell volume, rectal temperature and non-esterified fatty acids rose throughout the SET and peaked between the end of exercise and after I 0 min of recovery (I 3 0 breaths/min, 5 1%, 3 9.9 'C and .747 mEq/L, respectively). There was no difference in HR between treatments, but HR's were lower (P<.05) on d 28 than on d 0. There were increases (P<.05) in RR on d 28, indicative of more difficult heat dissipation due to increased ambient temperature resulting from environmental changes, but no difference between treatments was observed. A trend was observed for packed cell volume (PCV) to be higher (P<.07) on d 0, but no difference between treatments was observed. Plasma lactate concentrations were higher (P<.05) on d 0, but plasma glucose concentrations and non-esterified fatty acid concentrations did not differ between treatments or d of the SET
Physiological responses of reining horses to interval training versus conventional training procedures
No full textDue to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Includes bibliographical references: p. 57-62.Eight mature Quarter Horses were used in a cross-over hics. experiment to determine the efficacy of an interval training program versus a conventional training program to enhance fitness in the reining performance horse. The two training treatments were conducted in 31-d experimental periods which were each preceded by 28-d standardizing periods. In the conventional protocol, horses were ridden 5 days per week at an aerobic level of work on d 1 and 5. Day 2, 3 and 4 of each week included an additional intense maneuver workout for 20 min to stimulate anaerobic energy systems. The interval training program was conducted 6 days per week and was designed to implement the "overload'' principle by exercising the horses to the same physiologic endpoint approaching fatigue on d 2 and 5. On interval work days, 'ton-board'' heart rate monitors were used to record heart rates through a series of anaerobic maneuver repetitions with 1 min of recovery in between repetitions. When peak and recovery heart rates became elevated over previous repetitions, fatigue was declared and the workout ended. Exercise on d 1 and 4 followed the same protocol as that used for the conventionally trained horses, and on d 3 and 6, horses were ridden at a jog for 20 min. A standardized reining exercise test (RET) which included all the reining maneuvers (circling, spinning, stopping), was administered on d 0, 28 and 31 of each experimental period. The RET was designed to work the horses at an intensity past the anaerobic threshold. Heart rate (HR), respiratory rate (RR), rectal temperature (RT) and venous blood samples were taken prior to, during and through recovery from the RET. Both training protocols resulted in significantly lower [(1M0.05)] plasma lactate concentrations at stopping and post-exercise times on d 28 when compared to d 0. However it was only following interval training that this increase in aerobic capacity response was repeated on d 31. On d 31 of the conventional protocol, plasma lactate concentrations were significantly higher during circling and spinning, and from the last stop to 2 min recovery. exceeding pre-treatment values
Electronic structure of tin oxides
No full textStannic oxide SnO2 is a technologically important material which is frequently obtained by the oxidation of SnO. The tin oxides both have a tetragonal structure which differ essentially by the insertion of an oxygen plane between two tin planes in the layered SnO crystal. In order to well understand this structural evolution, it is crucial to have a precise description of the atomic and electronic structure of the two oxides. Preliminary results of calculations performed within Density Functional Theory in the Local Density Approximation (DFT-LDA) have already shown the relation existing between the electronic and geometric configurations of the two oxides. The gap calculated for SnO2 was in good agreement with the experimental value, but the calculations did not reproduce with a very good accuracy the experimental structure of SnO. We present ab-initio (DFT-LDA) study of the electronic structure of SnO, in comparison with SnO2. The charge density distribution of each oxide is analyzed with a special emphasis on low-charge-density contributions. Particular problems in the calculation of the equilibrium structure due to the pseudopotential of tin are put into evidence. We discuss the origin of these problems, and a possible solution
Nonlocal density scheme for electronic-structure calculations
No full textAn exchange-correlation energy functional beyond the local-density approximation (LDA), based on the exchange-correlation kernel of the homogeneous electron gas and originally introduced by Kohn and Sham, is considered for electronic-structure calculations of semiconductors and atoms. Calculations are carried out for diamond, silicon, silicon carbide, and gallium arsenide. The lattice constants and gaps show a small improvement with respect to the LDA results. However, the corresponding corrections to the total energy of the isolated atoms are not large enough to yield a substantial improvement for the cohesive energy of solids, which remains hence overestimated as in the LDA. [S0163-1829(99)01940-2]
First-principles calculations of electronic excitations in clusters
No full textWe discuss an approach to calculate electronic excitations in clusters, which starts from the determination of the ground state within density functional theory and the local density approximation, and subsequently yields electronic spectra from Green's function theory. These methods, which were originally developed and used in extended systems, are shown to work well also in clusters. We discuss the theory and the computational implementation, and illustrate the performance and the physical mechanisms of this approach for the example clusters Na-4, Na-6, and SiH4. (C) 2000 John Wiley & Sons, Inc
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