2,079 research outputs found
Apalachee During the Brisih Occupation
According to Prof. F. H. Hodder, in the introduction to his reprint of Pittmanâs work entitled âThe Present State of the European Settlements on the Mississippi,â there are but few available biographical data pertaining to Pittman. Hodder there presents such information as he was able to collect. Apparently Pittman must have accompanied the first British detachment occupying Florida, he states that he âresided four years as an engineer in those partsâ and it is known that he left towards the close of 1768. Apparently during 1767 he was occupied in making surveys in different parts of West Florida, as records survive indicating his departure from. Pensacola for Apalachee on June 16, 1767. However the four reports here considered, submitted by Lieut. Pittman to General Haldimand bear no date. They are preserved among the Haldimand papers in the Public Archives of Canada, where they are calendared as Series B (Haldimand) Vol. 17, pp. 313-325. They are respectively numbered 313, 316, 319 and 322.
Parametric performance of circumferentially grooved heat pipes with homogeneous and graded-porosity slab wicks at cryogenic temperatures
A recently developed, potentially high-performance nonarterial wick has been extensively tested. This slab wick has an axially varying porosity which can be tailored to match the local stress imposed on the wick. The purpose of the tests was to establish the usefulness of the graded-porosity slab wick at cryogenic temperatures between 110 K and 260 K, with methane and ethane as working fluids. For comparison, a homogeneous (i.e., uniform porosity) slab wick was also tested. The tests included: (1) maximum heat pipe performance as a function of fluid inventory, (2) maximum performance as a function of operating temperature, (3) maximum performance as a function of evaporator elevation, and (4) influence of slab wick orientation on performance. The experimental data was compared with theoretical predictions obtained with the computer program GRADE
The far field diffraction pattern for corner reflectors with complex reflection coefficients
The far field diffraction pattern of a geometrically perfect corner reflector is examined analytically for normally incident monochromatic light. The states of polarization and the complex amplitudes of the emerging light are expressed through transformation matrices in terms of those of the original incident light for each sextant of the face in a single coordinate system. The analytic expression of the total diffraction pattern is obtained for a circular face. This expression consists of three component functions in addition to the basic Airy function. The coefficient of each function is expressed in terms of complex coefficients of reflectance of the reflecting surface. Some numerical results for different reflecting surfaces, including total internal reflection, are presented. The iso-intensity contours of the diffraction pattern evaluated from the analytical expressions for an uncoated solid corner reflector are also presented along with the photographs of the pattern
Validation of the Harvard Lyman-α in situ water vapor instrument: Implications for the mechanisms that control stratospheric water vapor
Building on previously published details of the laboratory calibrations of the Harvard Lyman-α photofragment fluorescence hygrometer (HWV) on the NASA ER-2 and WB-57 aircraft, we describe here the validation process for HWV, which includes laboratory calibrations and intercomparisons with other Harvard water vapor instruments at water vapor mixing ratios from 0 to 10 ppmv, followed by in-flight intercomparisons with the same Harvard hygrometers. The observed agreement exhibited in the laboratory and during intercomparisons helps corroborate the accuracy of HWV. In light of the validated accuracy of HWV, we present and evaluate a series of intercomparisons with satellite and balloon borne water vapor instruments made from the upper troposphere to the lower stratosphere in the tropics and midlatitudes. Whether on the NASA ER-2 or WB-57 aircraft, HWV has consistently measured about 1â1.5 ppmv higher than the balloon-borne NOAA/ESRL/GMD frost point hygrometer (CMDL), the NOAA Cryogenic Frost point Hygrometer (CFH), and the Microwave Limb Sounder (MLS) on the Aura satellite in regions of the atmosphere where water vapor is <10 ppmv. Comparisons in the tropics with the Halogen Occultation Experiment (HALOE) on the Upper Atmosphere Research Satellite show large variable differences near the tropopause that converge to ~10% above 460 K, with HWV higher. Results we show from the Aqua Validation and Intercomparison Experiment (AquaVIT) at the AIDA chamber in Karlsruhe do not reflect the observed in-flight differences. We illustrate that the interpretation of the results of comparisons between modeled and measured representations of the seasonal cycle of water entering the lower tropical stratosphere is dictated by which data set is used
Heralded generation of entangled photon pairs
Entangled photons are a crucial resource for quantum communication and linear
optical quantum computation. Unfortunately, the applicability of many
photon-based schemes is limited due to the stochastic character of the photon
sources. Therefore, a worldwide effort has focused in overcoming the limitation
of probabilistic emission by generating two-photon entangled states conditioned
on the detection of auxiliary photons. Here we present the first heralded
generation of photon states that are maximally entangled in polarization with
linear optics and standard photon detection from spontaneous parametric
down-conversion. We utilize the down-conversion state corresponding to the
generation of three photon pairs, where the coincident detection of four
auxiliary photons unambiguously heralds the successful preparation of the
entangled state. This controlled generation of entangled photon states is a
significant step towards the applicability of a linear optics quantum network,
in particular for entanglement swapping, quantum teleportation, quantum
cryptography and scalable approaches towards photonics-based quantum computing
Quantum interference by two temporally distinguishable pulses
We report a two-photon interference effect, in which the entangled photon
pairs are generated from two laser pulses well-separated in time. In a single
pump pulse case, interference effects did not occur in our experimental scheme.
However, by introducing a second pump pulse delayed in time, quantum
interference was then observed. The visibility of the interference fringes
shows dependence on the delay time between two laser pulses. The results are
explained in terms of indistinguishability of biphoton amplitudes which
originated from two temporally separated laser pulses.Comment: two-column, 4pages, submitted to PRA, minor change
Early childhood lung function is a stronger predictor of adolescent lung function in cystic fibrosis than early Pseudomonas aeruginosa infection
Pseudomonas aeruginosa has been suggested as a major determinant of poor pulmonary outcomes in cystic fibrosis (CF), although other factors play a role. Our objective was to investigate the association of early childhood Pseudomonas infection on differences in lung function in adolescence with CF
Imperfect Detectors in Linear Optical Quantum Computers
We discuss the effects of imperfect photon detectors suffering from loss and
noise on the reliability of linear optical quantum computers. We show that for
a given detector efficiency, there is a maximum achievable success probability,
and that increasing the number of ancillary photons and detectors used for one
controlled sign flip gate beyond a critical point will decrease the probability
that the computer will function correctly. We have also performed simulations
of some small logic gates and estimate the efficiency and noise levels required
for the linear optical quantum computer to function properly.Comment: 13 pages, 5 figure
Upper cenozoic chronostratigraphy of the southwestern Amazon Basin
The lack of numerical age dates for upper Cenozoic strata of the Amazon Basin has prevented resolution of its geologic history and accurate dating of important paleofaunas. Here we present results of magnetostratigraphy and 40Ar/39Ar dating of two volcanic ash deposits from the Madre de Dios Formation of eastern Peru. The two ash ages, 9.01 ± 0.28 Ma and 3.12 ± 0.02 Ma, provide the first numerical age data necessary for accurate interpretation of late Tertiary sedimentation in Amazonia and establish approximate time constraints for the last major cycle of Cenozoic deposition within the southwestern Amazon Basin. The older ash age also provides a minimum age for numerous Amazonian paleofaunas, which allows a more definitive correlation of these paleofaunas with those in other regions of South America
Role of entanglement in two-photon imaging
The use of entangled photons in an imaging system can exhibit effects that
cannot be mimicked by any other two-photon source, whatever the strength of the
correlations between the two photons. We consider a two-photon imaging system
in which one photon is used to probe a remote (transmissive or scattering)
object, while the other serves as a reference. We discuss the role of
entanglement versus correlation in such a setting, and demonstrate that
entanglement is a prerequisite for achieving distributed quantum imaging.Comment: 15 pages, 2 figure
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