8,222 research outputs found
Generating Polarization-Entangled Photon Pairs with Arbitrary Joint Spectrum
We present a scheme for generating polarization-entangled photons pairs with
arbitrary joint spectrum. Specifically, we describe a technique for spontaneous
parametric down-conversion in which both the center frequencies and the
bandwidths of the down-converted photons may be controlled by appropriate
manipulation of the pump pulse. The spectral control offered by this technique
permits one to choose the operating wavelengths for each photon of a pair based
on optimizations of other system parameters (loss in optical fiber, photon
counter performance, etc.). The combination of spectral control, polarization
control, and lack of group-velocity matching conditions makes this technique
particularly well-suited for a distributed quantum information processing
architecture in which integrated optical circuits are connected by spans of
optical fiber.Comment: 6 pages, 3 figure
Apollo-11 lunar sample information catalogue
The Apollo 11 mission is reviewed with emphasis on the collection of lunar samples, their geologic setting, early processing, and preliminary examination. The experience gained during five subsequent missions was applied to obtain physical-chemical data for each sample using photographic and binocular microscope techniques. Topics discussed include: binocular examination procedure; breccia clast dexrriptuons, thin section examinations procedure typical breccia in thin section, typical basalt in thin section, sample histories, and chemical and age data. An index to photographs is included
Cyanobacteria blooms cannot be controlled by effective microorganisms (EM) from mud- or Bokashi-balls
In controlled experiments, the ability of ‘‘Effective Microorganisms (EM, in the form of mudballs or Bokashi-balls)’’ was tested for clearing waters from cyanobacteria. We found suspensions of EM-mudballs up to 1 g l-1 to be ineffective in reducing cyanobacterial growth. In all controls and EM-mudball treatments up to 1 g l-1 the cyanobacterial chlorophyll-a (Chl-a) concentrations increased within 4 weeks from&120 to 325–435 lg l-1. When pieces of EM-mudballs (42.5 g) were added to 25-l lake water with cyanobacteria, no decrease of cyanobacteria as compared to untreated controls was observed. In contrast, after 4 weeks cyanobacterial Chl-a concentrations were significantly higher in EM-mudball treatments (52 lg l-1) than in controls (20 lg l-1). Only when suspensions with extremely high EM-mudball concentrations were applied (i.e., 5 and 10 g l-1), exceeding the recommended concentrations by orders of magnitude, cyanobacterial growth was inhibited and a bloom forming concentration was reduced strongly. In these high dosing treatments, the oxygen concentration dropped initially to very low levels of 1.8 g l-1. This was most probably through forcing strong light limitation on the cyanobacteria caused by the high amount of clay and subsequent high turbidity of the water. Hence, this study yields no support for the hypothesis that EM is effective in preventing cyanobacterial proliferation or in terminating blooms. We consider EM products to be ineffective because they neither permanently bind nor remove phosphorus from eutroficated systems, they have no inhibiting effect on cyanobacteria, and they could even be an extra source of nutrients
A simple and quick sensitivity analysis method for methane isotopologues detection with GOSAT-TANSO-FTS
Measurements of methane isotopologues can differentiate between different source types, be
they biogenic (e.g. marsh lands) or abiogenic (e.g. industry). Global measurements of these
isotopologues would greatly benefit the current disconnect between ‘top-down’ (knowledge from
chemistry transport models and satellite measurements) and ‘bottom-up’ (in situ measurement
inventories) methane measurements. However, current measurements of these isotopologues are
limited to a small number of in situ studies and airborne studies. In this paper we investigate the
potential for detecting the second most common isotopologue of methane (13CH4) from space using
the Japanese Greenhouse Gases Observing Satellite applying a quick and simple residual radiance
analysis technique. The method allows for a rapid analysis of spectral regions, and can be used
to teach university students or advanced school students about radiative transfer analysis. Using
this method we find limited sensitivity to 13CH4, with detections limited to total column methane
enhancements of >6%, assuming a desert surface albedo of >0.3
Vibration characteristics of ring-stiffened orthotropic shells of revolution
Computer program solves vibration modes and frequencies of thin shells of revolution having general meridional curvature and orthotropic elastic properties in order to evaluate the dynamic behavior of structures with thin shelled components
Symmetric Autocompensating Quantum Key Distribution
We present quantum key distribution schemes which are autocompensating
(require no alignment) and symmetric (Alice and Bob receive photons from a
central source) for both polarization and time-bin qubits. The primary benefit
of the symmetric configuration is that both Alice and Bob may have passive
setups (neither Alice nor Bob is required to make active changes for each run
of the protocol). We show that both the polarization and the time-bin schemes
may be implemented with existing technology. The new schemes are related to
previously described schemes by the concept of advanced waves.Comment: 4 pages, 2 figur
X-ray Lags in PDS 456 Revealed by Suzaku Observations
X-ray reverberation lags from the vicinity of supermassive black holes have
been detected in almost 30 AGN. The soft lag, which is the time delay between
the hard and soft X-ray light curves, is usually interpreted as the time
difference between the direct and reflected emission, but is alternatively
suggested to arise from the direct and scattering emission from distant clouds.
By analysing the archival Suzaku observations totalling an exposure time of ~
770 ks, we discover a soft lag of ks at Hz in
the luminous quasar PDS 456, which is the longest soft lag and lowest Fourier
frequency reported to date. In this study, we use the maximum likelihood method
to deal with non-continuous nature of the Suzaku light curves. The result
follows the mass-scaling relation for soft lags, which further supports that
soft lags originate from the innermost areas of AGN and hence are best
interpreted by the reflection scenario. Spectral analysis has been performed in
this work and we find no evidence of clumpy partial-covering absorbers. The
spectrum can be explained by a self-consistent relativistic reflection model
with warm absorbers, and spectral variations over epochs can be accounted for
by the change of the continuum, and of column density and ionization states of
the warm absorbers.Comment: accepted for publication in MNRA
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