10,151 research outputs found
Research on the properties of circadian systems amenable to study in space
Three areas of inquiry are reported for the Skylab Experiment S-071 whose objective was to study the circadian system of a mammal during space flight. The thermoregulatory behavior of the Perognathus longimembris, or little pocket mouse, was studied under conditions of constant dark and constant temperature in the prolonged weightless environment of Skylab. The following specific questions were studied: (1) the effects of weightlessness on circadian periodicity in the little pocket mouse; (2) stability of the free-running circadian period of body temperature of the little pocket mouse exposed to simulated launch stress; and (3) characteristics of the circadian rhythm of body temperature in the little pocket mouse. Diagrams of the electronic circuitry and hardware used in the experiment are shown and results are given in both graphical and tabular form. The methods used in the experiment are fully documented, along with conclusions and recommendations for future research
Evaluation of factors affecting sale price of performance tested bulls
The objective of this study was to partition the total variability of price received for performance tested bulls into that which is attributed to various selected criteria. The records of twelve Tennessee performance tested bull sales (six junior and six senior) were compiled. These records, collected by the University of Tennessee Extension Service from 1982 through 1987, consisted of 343 junior bulls and 250 senior bulls. An adjusted sale price was calculated using an index which consisted of standardizing feeder cattle prices, slaughter bull prices and an agricultural consumer price index to a 1987-year dollar equivalent, for both data sets. A first analysis was conducted to partition out the effects of the following four discrete variables: (1) year; (2) breed; (3) sire; and (4) preweaning management. By using the beta value estimates of these factors to adjust the data, all records were equalized to a 1987 year, British breed, artificial sire, no-creep feed management system.
In the second analysis, adjusted sale price was set to equal nine commonly available performance variables. A stepwise regression resulted in 34.06 and 50.69 percent of the total variability in the sale price explained by the performance variables in the junior and senior tests, respectively. For the junior test, adjusted 365-day weight and frame score explained 32.19 percent of the variation and were highly significant (P \u3c .001). Average daily gain on-test, off-test age, and off-test weight added a combined 1.87 percent to the explained portion of variation. In the senior test however, average daily gain on-test and frame core explained 36.60 and 11.28 percent of the variation, respectively. The effects of these two variables were also highly significant (P \u3c .001). Adjusted 205-day weight, age off-test, and weight off-test added 2.81 percent to the explained portion in sale price.
The variables age of dam, adjusted 365-day weight, weight per day of age and adjusted 365-day height in the senior test and age of dam, adjusted 205-day weight, weight per day of age and adjusted 365-day height in the junior test were not used in the forward selection procedure of the stepwise regression because they did not meet the preselected level of significance (P \u3c .10).
Conclusions may be drawn that frame score and some level of gaining performance for a specified age were important traits when considering prospective herd sires. Also, age of dam had very little effect on the choice of herd sire and, weight per day of age and adjusted 365 day height were not considered when frame score and average daily gain on-test are available to the bull buyers. However, it is important to understand that bull buyers did utilize the performance data available to them when selecting prospective herd sires from test stations
Some investigations into the numerical solution of initial value problems in ordinary differential equations
PhD ThesisIn this thesis several topics in the numerical solution
of the initial value problem in first-order ordinary diff'erentlal
equations are investigated,
Consideration is given initially to stiff differential
equations and their solution by stiffly-stable linear multistep
methods which incorporate second derivative terms. Attempts are
made to increase the size of the stability regions for these
methods both by particular choices for the third characteristic
polynomial and by the use of optimization techniques while
investigations are carried out regarding the capabilities of a
high order method.
Subsequent work is concerned with the development of
Runge-Kutta methods which include second-derivative terms and
are implicit with respect to y rather than k. Methods of
order three and four are proposed which are L-stable.
The major part of the thesis is devoted to the establishment
of recurrence relations for operators associated with linear
multistep methods which are based on a non-polynomial
representation of the theoretical solution. A complete set of
recurrence relations is developed for both implicit and
explicit multistep methods which are based on a representation
involving a polynomial part and any number of arbitrary functions.
The amount of work involved in obtaining mulc iste, :ne::l'lJds by this
technique is considered and criteria are proposed to Jecide when
this particular method of derivation should be em~loyed.
The thesis is conclud~d by using Prony's method to develop
one-step methods and multistep methods which are exponentially
adaptive and as such can be useful in obtaining solutions to
problems which are exponential in nature
Entanglement-assisted local operations and classical communications conversion in the quantum critical systems
Conversions between the ground states in quantum critical systems via
entanglement-assisted local operations and classical communications (eLOCC) are
studied. We propose a new method to reveal the different convertibility by
local operations when a quantum phase transition occurs. We have studied the
ground state local convertibility in the one dimensional transverse field Ising
model, XY model and XXZ model. It is found that the eLOCC convertibility sudden
changes at the phase transition points. In transverse field Ising model the
eLOCC convertibility between the first excited state and the ground state are
also distinct for different phases. The relation between the order of quantum
phase transitions and the local convertibility is discussed.Comment: 7 pages, 5 figures, 5 table
High-Frequency Spin Waves in YBa2Cu3O6.15
Pulsed neutron spectroscopy is used to make absolute measurements of the
dynamic magnetic susceptibility of insulating YBa2Cu3O6.15. Acoustic and
optical modes, derived from in- and out-of-phase oscillation of spins in
adjacent CuO2 planes, dominate the spectra and are observed up to 250 meV. The
optical modes appear first at 74 meV. Linear-spin-wave theory gives an
excellent description of the data and yields intra- and inter-layer exchange
constants of J_parallel =125 meV and J_perp = 11 meV respectively and a
spin-wave intensity renormalization Z_chi = 0.4.Comment: postscript, 11 pages, 4 figures, Fig.2 fixe
Thermally stable low current consuming gallium and germanium chalcogenides for consumer and automotive memory applications
The phase change technology behind rewritable optical disks and the latest generation of electronic memories has provided clear commercial and technological advances for the field of data storage, by virtue of the many well known attributes, in particular scaling, cycling endurance and speed, that chalcogenide materials offer. While the switching power and current consumption of established germanium antimony telluride based memory cells are a major factor in chip design in real world applications, often the thermal stability of the device can be a major obstacle in the path to the full commercialisation. In this work we describe our research in material discovery and characterization for the purpose of identifying more thermally stable chalcogenides for applications in PCRAM
A Comparison of the High-Frequency Magnetic Fluctuations in Insulating and Superconducting La2-xSrxCuO4
Inelastic neutron scattering performed at a spallation source is used to make
absolute measurements of the dynamic susceptibility of insulating La2CuO4 and
superconducting La2-xSrxCuO4 over the energy range 15<EN<350 meV. The effect of
Sr doping on the magnetic excitations is to cause a large broadening in
wavevector and a substantial change in the spectrum of the local spin
fluctuations. Comparison of the two compositions reveals a new energy scale of
22 meV in La1.86Sr0.14CuO4.Comment: RevTex, 7 Pages, 4 postscript figure
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