248 research outputs found
Photoheliograph Functional Verification Unit Test and Operations Plan, November 1967 - June 1968
Test and operations plan for functional verification unit of photoheliograph to be used with Apollo telescope moun
Use of Carbon Arc Lamps as Solar Simulation in Environmental Testing
This report covers work done by the authors on the solar simulator for the six-foot diameter space simulator presently in use at JPL. The space simulator was made by modifying an existent vacuum chamber and uses carbon arc lamps for solar simulation. All Ranger vehicles flown to date have been tested in this facility. The report also contains a series of appendixes covering various aspects of space-simulation design and use. Some of these appendixes contain detailed analyses of space-simulator design criteria. Others cover the techniques used in studying carbon-arc lamps and in applying them as solar simulation
Use of the Curtis-Godson approximation in calculations of radiant heating by inhomogeneous hot gases
Curtis-Gordon approximation in calculations of radiant heating by inhomogeneous hot gase
Of Some Theoretical Significance: Implications of Casimir Effects
In his autobiography Casimir barely mentioned the Casimir effect, but
remarked that it is "of some theortical significance." We will describe some
aspects of Casimir effects that appear to be of particular significance now,
more than half a century after Casimir's famous paper
Gedanken experiments with Casimir forces, vacuum energy, and gravity
Gedanken experiments are used to explore properties of quantum vacuum energy
that are currently challenging to explore experimentally. A constant lateral
Casimir force is predicted to exist between two overlapping finite parallel
plates at 0 K, otherwise it would be possible to extract an arbitrary amount of
energy from the quantum vacuum. A rigid unpowered object cannot be accelerated
by the quantum vacuum because of the translational symmetry of space. By
considering systems in which vacuum energy and other forms of energy are
exchanged, we demonstrate that a change {\Delta}E in vacuum energy, whether
positive or negative with respect to the free field, corresponds to an
equivalent inertial mass and equivalent gravitational mass
{\Delta}M={\Delta}E/c^2. We consider the possibility of a gravitational shield,
and show that, if it exists, the energy to operate it would have to cancel the
net energy extracted from the gravitational field, otherwise we could extract
an arbitrary amount of energy from the field.Comment: 24 pages, 3 figure
Casimir Energy For a Massive Dirac Field in One Spatial Dimension: A Direct Approach
In this paper we calculate the Casimir energy for a massive fermionic field
confined between two points in one spatial dimension, with the MIT Bag Model
boundary condition. We compute the Casimir energy directly by summing over the
allowed modes. The method that we use is based on the Boyer's method, and there
will be no need to resort to any analytic continuation techniques. We
explicitly show the graph of the Casimir energy as a function of the distance
between the points and the mass of the fermionic field. We also present a
rigorous derivation of the MIT Bag Model boundary condition.Comment: 8 Pages, 4 Figure
Casimir force on a piston
We consider a massless scalar field obeying Dirichlet boundary conditions on
the walls of a two-dimensional L x b rectangular box, divided by a movable
partition (piston) into two compartments of dimensions a x b and (L-a) x b. We
compute the Casimir force on the piston in the limit L -> infinity. Regardless
of the value of a/b, the piston is attracted to the nearest end of the box.
Asymptotic expressions for the Casimir force on the piston are derived for a <<
b and a >> b.Comment: 10 pages, 1 figure. Final version, accepted for publication in Phys.
Rev.
The validity of using ICD-9 codes and pharmacy records to identify patients with chronic obstructive pulmonary disease
Background: Administrative data is often used to identify patients with chronic obstructive pulmonary disease (COPD), yet the validity of this approach is unclear. We sought to develop a predictive model utilizing administrative data to accurately identify patients with COPD.
Methods: Sequential logistic regression models were constructed using 9573 patients with postbronchodilator spirometry at two Veterans Affairs medical centers (2003-2007). COPD was defined as: 1) FEV1/FVC <0.70, and 2) FEV1/FVC < lower limits of normal. Model inputs included age, outpatient or inpatient COPD-related ICD-9 codes, and the number of metered does inhalers (MDI) prescribed over the one year prior to and one year post spirometry. Model performance was assessed using standard criteria.
Results: 4564 of 9573 patients (47.7%) had an FEV1/FVC < 0.70. The presence of ≥1 outpatient COPD visit had a sensitivity of 76% and specificity of 67%; the AUC was 0.75 (95% CI 0.74-0.76). Adding the use of albuterol MDI increased the AUC of this model to 0.76 (95% CI 0.75-0.77) while the addition of ipratropium bromide MDI increased the AUC to 0.77 (95% CI 0.76-0.78). The best performing model included: ≥6 albuterol MDI, ≥3 ipratropium MDI, ≥1 outpatient ICD-9 code, ≥1 inpatient ICD-9 code, and age, achieving an AUC of 0.79 (95% CI 0.78-0.80).
Conclusion: Commonly used definitions of COPD in observational studies misclassify the majority of patients as having COPD. Using multiple diagnostic codes in combination with pharmacy data improves the ability to accurately identify patients with COPD.Department of Veterans Affairs, Health Services Research and Development (DHA), American Lung Association (CI- 51755-N) awarded to DHA, the American Thoracic Society Fellow Career Development AwardPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/84155/1/Cooke - ICD9 validity in COPD.pd
Chronic Obstructive Pulmonary Disease: Effects beyond the Lungs
Peter Barnes discusses the growing epidemic of chronic obstructive pulmonary disease (COPD), especially in developing countries and among nonsmokers
Normal and Lateral Casimir Forces between Deformed Plates
The Casimir force between macroscopic bodies depends strongly on their shape
and orientation. To study this geometry dependence in the case of two deformed
metal plates, we use a path integral quantization of the electromagnetic field
which properly treats the many-body nature of the interaction, going beyond the
commonly used pairwise summation (PWS) of van der Waals forces. For arbitrary
deformations we provide an analytical result for the deformation induced change
in Casimir energy, which is exact to second order in the deformation amplitude.
For the specific case of sinusoidally corrugated plates, we calculate both the
normal and the lateral Casimir forces. The deformation induced change in the
Casimir interaction of a flat and a corrugated plate shows an interesting
crossover as a function of the ratio of the mean platedistance H to the
corrugation length \lambda: For \lambda \ll H we find a slower decay \sim
H^{-4}, compared to the H^{-5} behavior predicted by PWS which we show to be
valid only for \lambda \gg H. The amplitude of the lateral force between two
corrugated plates which are out of registry is shown to have a maximum at an
optimal wavelength of \lambda \approx 2.5 H. With increasing H/\lambda \gtrsim
0.3 the PWS approach becomes a progressively worse description of the lateral
force due to many-body effects. These results may be of relevance for the
design and operation of novel microelectromechanical systems (MEMS) and other
nanoscale devices.Comment: 20 pages, 5 figure
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