19,914 research outputs found
Spectroscopic investigations of plasma properties quarterly summary report no. 2, 11 aug. - 10 nov. 1964
Performance of plasma source operated with helium - intensity and temperature profiles of source electronic instrumentation for detecting weak spectrum line
Improved chlorate candle provides concentrated oxygen source
Improved chlorate candle is used as a solid, portable source of oxygen in emergency situations. It contains sodium chlorate, iron, barium peroxide, and glass mixed in powdered form. The oxygen evolves from the decomposition of the sodium chlorate when an ignition pellet is electrically initiated
signals at LEP2 energies in the Minimal Supersymmetric Standard Model
In this paper we compare and into four-fermion production
at centre-of-mass energies typical of LEP2 and somewhat larger. The theoretical
framework considered is the Minimal Supersymmetric Standard Model. The interest
in exploiting the CERN collider at values of greater than
192 GeV could come from the discovery of Supersymmetric signals during runs at
lower energy. If these indicate that a charged Higgs boson exists in the mass
range \MH\approx95-105 GeV, then a few years of running at
GeV and nominal luminosity could make the detection of such scalars feasible,
in the purely leptonic channel and, for small
\tb's, also in the semi-hadronic(leptonic) one . Charged
Higgs bosons of the above nature cannot be produced by the beam energies
approved at present for LEP2. However, if runs beyond the so-called `192 GeV
cryogenic limit' will be approved by the CERN Council, our selection procedure
will enable us to establish the presence, or otherwise, of charged Higgs bosons
in the mentioned mass rangeComment: 30 pages, latex, epsfig, 12 postscript figures, complete paper
available at ftp://axpa.hep.phy.cam.ac.uk/stefano/cavendish_9615 and at
http://www.hep.phy.cam.ac.uk/theory/papers
Mass transfer from a fluid flowing through a porous media
A mathematical model is developed for the process of mass transfer from a
fluid flowing through a packed column. Mass loss, whether by absorption or
adsorption, may be significant. This is appropriate for example when removing
contaminants from flue gases. With small mass loss the model reduces to a
simpler form which is appropriate to describe the removal of
contaminants/pollutants from liquids. A case study is carried out for the
removal of CO2 from a gas mixture passing over activated carbon. Using the
experimental parameter values it is shown, via non-dimensionalisation, that
certain terms may be neglected from the governing equations, resulting in a
form which may be solved analytically using a travelling wave substitution.
From this all important quantities throughout the column may be described;
concentration of gaseous materials, amount of material available for mass
transfer, fluid velocity and pressure. Results are verified by comparison with
experimental data for the breakthrough curve (the amount of carbon measured at
the column outlet). The advantage of the analytical expression over a purely
numerical solution is that it can easily be used to optimise the process. In
the final section we demonstrate how the model may be further reduced when
small amounts of contaminant are removed. The model is shown to exhibit better
agreement than established models when compared to experimental data for the
removal of amoxicillin and congo red dye from water
Pupillometry, a bioengineering overview
The pupillary control system is examined using a microprocessor based integrative pupillometer. The real time software functions of the microprocessor include: data collection, stimulus generation and area to diameter conversion. Results of an analysis of linear and nonlinear phenomena are presented
QED calculation of the n=1 and n=2 energy levels in He-like ions
We perform ab initio QED calculations of energy levels for the and
states of He-like ions with the nuclear charge in the range -100.
The complete set of two-electron QED corrections is evaluated to all orders in
the parameter \aZ. Uncalculated contributions to energy levels come through
orders \alpha^3 (\aZ)^2, \alpha^2 (\aZ)^7, and higher. The calculation
presented is the first treatment for excited states of He-like ions complete
through order \alpha^2 (\aZ)^4. A significant improvement in accuracy of
theoretical predictions is achieved, especially in the high- region.Comment: 23 pages, 5 figure
Black Holes with a Generalized Gravitational Action
Microscopic black holes are sensitive to higher dimension operators in the
gravitational action. We compute the influence of these operators on the
Schwarzschild solution using perturbation theory. All (time reversal invariant)
operators of dimension six are included (dimension four operators don't alter
the Schwarzschild solution). Corrections to the relation between the Hawking
temperature and the black hole mass are found. The entropy is calculated using
the Gibbons-Hawking prescription for the Euclidean path integral and using
naive thermodynamic reasoning. These two methods agree, however, the entropy is
not equal to 1/4 the area of the horizon.Comment: plain tex(uses phyzzx.tex), 8 pages, CALT-68-185
Clustering on very small scales from a large sample of confirmed quasar pairs: Does quasar clustering track from Mpc to kpc scales?
We present the most precise estimate to date of the clustering of quasars on
very small scales, based on a sample of 47 binary quasars with magnitudes of
and proper transverse separations of \,kpc. Our
sample of binary quasars, which is about 6 times larger than any previous
spectroscopically confirmed sample on these scales, is targeted using a Kernel
Density Estimation technique (KDE) applied to Sloan Digital Sky Survey (SDSS)
imaging over most of the SDSS area. Our sample is "complete" in that all of the
KDE target pairs with \,kpc in our area
of interest have been spectroscopically confirmed from a combination of
previous surveys and our own long-slit observational campaign. We catalogue 230
candidate quasar pairs with angular separations of <8\arcsec, from which our
binary quasars were identified. We determine the projected correlation function
of quasars () in four bins of proper transverse scale over the
range \,kpc. The implied small-scale
quasar clustering amplitude from the projected correlation function, integrated
across our entire redshift range, is at \,kpc. Our sample is the first spectroscopically confirmed sample of
quasar pairs that is sufficiently large to study how quasar clustering evolves
with redshift at kpc. We find that empirical descriptions of
how quasar clustering evolves with redshift at Mpc also
adequately describe the evolution of quasar clustering at
kpc.Comment: 16 pages, 8 figures, 6 tables, Accepted for publication in MNRA
Toward the assessment of the susceptibility of a digital system to lightning upset
Accomplishments and directions for further research aimed at developing methods for assessing a candidate design of an avionic computer with respect to susceptability to lightning upset are reported. Emphasis is on fault tolerant computers. Both lightning stress and shielding are covered in a review of the electromagnetic environment. Stress characterization, system characterization, upset detection, and positive and negative design features are considered. A first cut theory of comparing candidate designs is presented including tests of comparative susceptability as well as its analysis and simulation. An approach to lightning induced transient fault effects is included
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Dendrimer-Encapsulated Nanoparticles: New Synthetic and Characterization Methods and Catalytic Applications
In this article we describe the synthesis, characterization, and applications of dendrimer-encapsulated nanoparticles (DENs). These materials are synthesized using a template approach in which metal ions are extracted into the interior of dendrimers and then subsequently reduced chemically to yield nearly size-monodisperse particles having diameters in the 1-2 nm range. Monometallic, bimetallic (alloy and core@shell), and semiconductor nanoparticles have been prepared by this route. The dendrimer component of these composites serves not only as a template for preparing the nanoparticle replica, but also as a stabilizer for the nanoparticle. In this perspective, we report on progress in the synthesis, characterization, and applications of these materials since our last review in 2005. Significant advances in the synthesis of core@shell DENs, characterization, and applications to homogeneous and heterogeneous catalysis (including electrocatalysis) are emphasized.U.S. Department of Energy, Office of Basic Energy Sciences DE-FG02-09ER16090U.S. National Science Foundation 0847957Robert A. Welch Foundation F-0032Chemistr
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