8,049 research outputs found
Methods development for total organic carbon accountability
This report describes the efforts completed during the contract period beginning November 1, 1990 and ending April 30, 1991. Samples of product hygiene and potable water from WRT 3A were supplied by NASA/MSFC prior to contract award on July 24, 1990. Humidity condensate samples were supplied on August 3, 1990. During the course of this contract chemical analyses were performed on these samples to qualitatively determine specific components comprising, the measured organic carbon concentration. In addition, these samples and known standard solutions were used to identify and develop methodology useful to future comprehensive characterization of similar samples. Standard analyses including pH, conductivity, and total organic carbon (TOC) were conducted. Colorimetric and enzyme linked assays for total protein, bile acid, B-hydroxybutyric acid, methylene blue active substances (MBAS), urea nitrogen, ammonia, and glucose were also performed. Gas chromatographic procedures for non-volatile fatty acids and EPA priority pollutants were also performed. Liquid chromatography was used to screen for non-volatile, water soluble compounds not amenable to GC techniques. Methods development efforts were initiated to separate and quantitate certain chemical classes not classically analyzed in water and wastewater samples. These included carbohydrates, organic acids, and amino acids. Finally, efforts were initiated to identify useful concentration techniques to enhance detection limits and recovery of non-volatile, water soluble compounds
Regional Hydrothermal Alteration of the Leadville Limestone (Mississippian) of Central Colorado
Massive metallic-sulfide deposits were implaced in the Leadville Limestone {Mississippian) of Central Colorado less than 70 million years ago. The thermal fluids which precipitated ore at Gilman, Colorado have regionally altered the Leadville Limestone. The sequence of alteration began with the recrystallization of limestone to a dark medium~grained dolomite containing a homogeneous distribution of Fe. This Was followed by partial recrystallization of the medium-grained dolomite to coarse-clear dolomite which contains an inhomogeneous distribution of Fe. The resulting banded rock is known as zebra rock . Precipitation of Si0 2 (jasperoid) occurred next. The jaspe=oid formed prior to the deposition of sulfides (O\u27Neil, 1951) which is the final event of the hydrothermal epoch. The alteration sequence is essentially the same everywhere. The one exception is the presence of ferroan-calcite in localities outside the Leadville-Gilman hydrothermal aureole. This calcite was deposited prior to the formation of the homogen· eous ferroan-dolomite. Regional alteration of sediment by thermal fluids is herein proposed as a fundamental diagenetic process. This process may be the s.ource of ferroan-carbonate cement which. fills fractures and vugs in numerous sedimentary sequences
Mechanisms of fragmentation of Al-W granular composites under dynamic loading
Numerical simulations of Aluminum (Al) and Tungsten (W) granular composite
rings under various dynamic loading conditions caused by explosive loading were
examined. Three competing mechanisms of fragmentation were observed: a
continuum level mechanism generating large macrocracks described by the
Grady-Kipp fragmentation mechanism, a mesoscale mechanism generating voids and
microcracks near the initially unbonded Al/W interfaces due to tensile strains,
and a mesoscale jetting due to the development of large velocity gradients
between the W particles and adjacent Al. These mesoscale mechanisms can be used
to tailor the size of the fragments by selecting an appropriate initial
mesostructure for a given loading condition.Comment: 10 pages, 3 figures, submitted to AP
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Radiofrequency superconductivity applied to free-electron lasers
Low wall losses and low wakefields inherent in superconducting radiofrequency (srf) cavities make them attractive candidates for accelerators that operate efficiently at high continuous-wave (cw) gradients. Such accelerators are desirable for free-electron lasers (FELs) that extract high-power cw light from a high-average-current electron beam, or that produce ultrashort-wavelength light from a high-energy electron beam. Efficiency is a prime consideration in the former case, while high electron-beam quality is a prime consideration in the latter case. This paper summarizes the status of FEL projects involving srf accelerators. It also introduces Jefferson Lab`s srf FEL and surveys its design because it is a new machine, with commissioning having commenced in October 1997. Once commissioning is complete, this FEL should produce tunable, cw, kW-level light at 3-6 {mu}m wavelength
Controlled photon transfer between two individual nanoemitters via shared high-Q modes of a microsphere resonator
We realize controlled cavity-mediated photon transfer between two single
nanoparticles over a distance of several tens of micrometers. First, we show
how a single nanoscopic emitter attached to a near-field probe can be coupled
to high-Q whispering-gallery modes of a silica microsphere at will. Then we
demonstrate transfer of energy between this and a second nanoparticle deposited
on the sphere surface. We estimate the photon transfer efficiency to be about
six orders of magnitude higher than that via free space propagation at
comparable separations.Comment: accepted for publication in Nano Letter
Driver Accelerator Design for the 10 kW Upgrade of the Jefferson Lab IR FEL
An upgrade of the Jefferson Lab IR FEL is now under construction. It will
provide 10 kW output light power in a wavelength range of 2-10 microns. The FEL
will be driven by a modest-sized 80-210 MeV, 10 mA energy-recovering
superconducting RF (SRF) linac. Stringent phase space requirements at the
wiggler, low beam energy, and high beam current subject the design to numerous
constraints. These are imposed by the need for both transverse and longitudinal
phase space management, the potential impact of collective phenomena (space
charge, wakefields, beam break-up (BBU), and coherent synchrotron radiation
(CSR)), and interactions between the FEL and the accelerator RF system. This
report addresses these issues and presents an accelerator design solution
meeting the requirements imposed by physical phenomena and operational
necessities.Comment: submission THC03 for LINAC200
Ab initio description of nonlinear dynamics of coupled microdisk resonators with application to self-trapping dynamics
Ab initio approach is used to describe the time evolution of the amplitudes
of whispering gallery modes in a system of coupled microdisk resonators with
Kerr nonlinearity. It is shown that this system demonstrates a transition
between Josephson-like nonlinear oscillations and self-trapping behavior.
Manifestation of this transition in the dynamics of radiative losses is
studied.Comment: 10 pages, 5 figures, accepted for publication in Phys. Rev.
Measurement of the 0.511 MeV gamma ray line from the Galactic Center
The detection of the 0.511 MeV electron positron annihilation line coming from the Galactic Center to provide the means to estimate the rate of positron production and to test some theoretical sources of positrons is addressed. The results of the measurements of the 0.511 MeV line flux made with a gamma ray experiment on board a stratospheric balloon are presented. The detector field of view looked at the galactic longitude range -31 deg l(II) +41 deg. The observed flux is 0.0067 (+ or - 0.0005) photons 1/cm(2)5 which is in very good agreement with the expected flux when assuming that the Galactic Center is a line source emitting uniformly
A New Method for Calculating Arrival Distribution of Ultra-High Energy Cosmic Rays above 10^19 eV with Modifications by the Galactic Magnetic Field
We present a new method for calculating arrival distribution of UHECRs
including modifications by the galactic magnetic field. We perform numerical
simulations of UHE anti-protons, which are injected isotropically at the earth,
in the Galaxy and record the directions of velocities at the earth and outside
the Galaxy for all of the trajectories. We then select some of them so that the
resultant mapping of the velocity directions outside the Galaxy of the selected
trajectories corresponds to a given source location scenario, applying
Liouville's theorem. We also consider energy loss processes of UHE protons in
the intergalactic space. Applying this method to our source location scenario
which is adopted in our recent study and can explain the AGASA observation
above 4 \times 10^{19} eV, we calculate the arrival distribution of UHECRs
including lower energy (E>10^19 eV) ones. We find that our source model can
reproduce the large-scale isotropy and the small-scale anisotropy on UHECR
arrival distribution above 10^19 eV observed by the AGASA. We also demonstrate
the UHECR arrival distribution above 10^19 eV with the event number expected by
future experiments in the next few years. The interesting feature of the
resultant arrival distribution is the arrangement of the clustered events in
the order of their energies, reflecting the directions of the galactic magnetic
field. This is also pointed out by Alvarez-Muniz et al.(2002). This feature
will allow us to obtain some kind of information about the composition of
UHECRs and the magnetic field with increasing amount of data.Comment: 10 pages, 8 figures, to appear in the Astrophysical Journa
Bosons in a Lattice: Exciton-Phonon Condensate in Cu2O
We explore a nonlinear field model to describe the interplay between the
ability of excitons to be Bose-condensed and their interaction with other modes
of a crystal. We apply our consideration to the long-living para-excitons in
Cu2O. Taking into account the exciton-phonon interaction and introducing a
coherent phonon part of the moving condensate, we derive the dynamic equations
for the exciton-phonon condensate. These equations can support localized
solutions, and we discuss the conditions for the moving inhomogeneous
condensate to appear in the crystal. We calculate the condensate wave function
and energy, and a collective excitation spectrum in the semiclassical
approximation; the inside-excitations were found to follow the asymptotic
behavior of the macroscopic wave function exactly. The stability conditions of
the moving condensate are analyzed by use of Landau arguments, and Landau
critical parameters appear in the theory. Finally, we apply our model to
describe the recently observed interference and strong nonlinear interaction
between two coherent exciton-phonon packets in Cu2O.Comment: 34 pages, LaTeX, four figures (.ps) are incorporated by epsf.
Submitted to Phys. Rev.
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