442 research outputs found
Relativistic Proton Production During the 14 July 2000 Solar Event: The Case for Multiple Source Mechanisms
Protons accelerated to relativistic energies by transient solar and
interplanetary phenomena caused a ground-level cosmic ray enhancement on 14
July 2000, Bastille Day. Near-Earth spacecraft measured the proton flux
directly and ground-based observatories measured the secondary responses to
higher energy protons. We have modelled the arrival of these relativistic
protons at Earth using a technique which deduces the spectrum, arrival
direction and anisotropy of the high-energy protons that produce increased
responses in neutron monitors. To investigate the acceleration processes
involved we have employed theoretical shock and stochastic acceleration
spectral forms in our fits to spacecraft and neutron monitor data. During the
rising phase of the event (10:45 UT and 10:50 UT) we find that the spectrum
between 140 MeV and 4 GeV is best fitted by a shock acceleration spectrum. In
contrast, the spectrum at the peak (10:55 UT and 11:00 UT) and in the declining
phase (11:40 UT) is best fitted with a stochastic acceleration spectrum. We
propose that at least two acceleration processes were responsible for the
production of relativistic protons during the Bastille Day solar event: (1)
protons were accelerated to relativistic energies by a shock, presumably a
coronal mass ejection (CME). (2) protons were also accelerated to relativistic
energies by stochastic processes initiated by magnetohydrodynamic (MHD)
turbulence.Comment: 38 pages, 9 figures, accepted for publication in the Astrophysical
Journal, January, 200
Bright source of spectrally uncorrelated polarization-entangled photons with nearly single-mode emission
We present results of a bright polarization-entangled photon source operating
at 1552 nm via type-II collinear degenerate spontaneous parametric
down-conversion in a periodically poled potassium titanyl phosphate crystal. We
report a conservative inferred pair generation rate of 123,000 pairs/s/mW into
collection modes. Minimization of spectral and spatial entanglement was
achieved by group velocity matching the pump, signal and idler modes and
through properly focusing the pump beam. By utilizing a pair of calcite beam
displacers, we are able to overlap photons from adjacent down-conversion
processes to obtain polarization-entanglement visibility of 94.7 +/- 1.1% with
accidentals subtracted.Comment: 4 pages, 7 color figures. Revised manuscript includes the following
changes: corrected pair generation rate from 44,000/s/mW pump to 123,000/s/mW
pump; replaced Fig. 1b to enhance clarity; minor alterations to the title,
abstract and introduction; grammatical correction
A stacking-fault based microscopic model for platelets in diamond
We propose a new microscopic model for the planar defects in
diamond commonly called platelets. This model is based on the formation of a
metastable stacking fault, which can occur because of the ability of carbon to
stabilize in different bonding configurations. In our model the core of the
planar defect is basically a double layer of three-fold coordinated
carbon atoms embedded in the common diamond structure. The properties of
the model were determined using {\it ab initio} total energy calculations. All
significant experimental signatures attributed to the platelets, namely, the
lattice displacement along the direction, the asymmetry between the
and the directions, the infrared absorption peak
, and broad luminescence lines that indicate the introduction of
levels in the band gap, are naturally accounted for in our model. The model is
also very appealing from the point of view of kinetics, since naturally
occurring shearing processes will lead to the formation of the metastable
fault.Comment: 5 pages, 4 figures. Submitted for publication on August 2nd, 200
Employment loss and food insecurity - race and sex disparities in the context of COVID-19
INTRODUCTION: Applying an intersectional framework, we examined sex and racial inequality in COVID-19-related employment loss (ie, job furlough, layoff, and reduced pay) and food insecurity (ie, quality and quantity of food eaten, food worry, and receipt of free meals or groceries) among residents in Saint Louis County, Missouri.
METHODS: We used cross-sectional data from adults aged 18 or older (N = 2,146), surveyed by using landlines or cellular phones between August 12, 2020, and October 27, 2020. We calculated survey-weighted prevalence of employment loss and food insecurity for each group (Black female, Black male, White female, White male). Odds ratios for each group were estimated by using survey-weighted binary and multinomial logistic regression models.
RESULTS: Black female residents had higher odds of being laid off, as compared with White male residents (OR = 2.61, 95% CI, 1.24-5.46). Both Black female residents (OR = 4.13, 95% CI, 2.29-7.45) and Black male residents (OR = 2.41, 95% CI, 1.15-5.07) were more likely to receive free groceries, compared with White male residents. Black female (OR = 4.25, 95% CI, 2.28-7.94) and White female residents (OR = 1.93, 95% CI, 1.04-3.60) had higher odds of sometimes worrying about food compared with White male residents. Black women also had higher odds of always or nearly always worrying about food, compared with White men (OR = 2.99, 95% CI, 1.52-5.87).
CONCLUSION: Black women faced the highest odds of employment loss and food insecurity, highlighting the disproportionate impact of COVID-19 among people with intersectional disadvantages of being both Black and female. Interventions to reduce employment loss and food insecurity can help reduce the disproportionately negative social effects among Black women
Methods and Costs to Achieve Ultra Reliable Life Support
A published Mars mission is used to explore the methods and costs to achieve ultra reliable life support. The Mars mission and its recycling life support design are described. The life support systems were made triply redundant, implying that each individual system will have fairly good reliability. Ultra reliable life support is needed for Mars and other long, distant missions. Current systems apparently have insufficient reliability. The life cycle cost of the Mars life support system is estimated. Reliability can be increased by improving the intrinsic system reliability, adding spare parts, or by providing technically diverse redundant systems. The costs of these approaches are estimated. Adding spares is least costly but may be defeated by common cause failures. Using two technically diverse systems is effective but doubles the life cycle cost. Achieving ultra reliability is worth its high cost because the penalty for failure is very high
Solar Magnetic Polarity Effect on Neutron Monitor Count Rates: Comparing Latitude Surveys and Antarctic Stations
The Galactic cosmic ray spectrum manifests pronounced variations over the
11-year sunspot cycle and more subtle variations over the 22-year solar
magnetic cycle. An important tool to study these variations is repeated
latitude surveys with neutron monitors (NMs) onboard icebreakers in conjunction
with land-based references. We revisit 13 annual latitude surveys from 1994 to
2007 using reference data from the Mawson NM instead of McMurdo NM (which
closed in 2017). We then consider two more latitude surveys (2018 and 2019)
with a monitor similar to the 3NM64 in the previous surveys but without lead
rings around the central tube, a so-called ``semi-leaded neutron monitor.'' The
new surveys extend the linear relationship among data taken at different cutoff
rigidity ranges. They also confirm the ``crossover'' measured near solar minima
during epochs of opposite solar magnetic polarity and the absence of a
crossover for epochs having the same solar magnetic polarity.Comment: Accepted for publication in Astrophys.
3-D Inlet Shock-Boundary Layer Interactions - PIV Database for the Second SBLI Workshop
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/97090/1/AIAA2012-3214.pd
Increasing the Sensitivity of ELISA using Multiplexed Electrokinetic Concentrator
We developed a novel method to increase the sensitivity of standard enzyme-linked immunosorbent assay (ELISA) using a multiplexed electrokinetic concentration chip. The poly(dimethylsiloxane) (PDMS) molecular concentrator(1) was used to trap and collect charged fluorescent product of target-bound enzyme turnover reaction of ELISA that occurred in a standard 96 well plate. Detection sensitivities of both prostate specific antigen (PSA) and CA 19-9 (a human pancreatic and gastrointestinal cancer marker) ELISAs in serum are enhanced ~100 fold with a low CV of <17%. We also integrated this method with an on-chip bead-based ELISA that lends itself toward a fully automated on-chip diagnostic device. Detection sensitivity of microfluidic bead-based CA 19-9 ELISA in serum is enhanced ~65 fold compared to the results without the electrokinetic accumulation step. This chip can be directly applied to enhance the readout sensitivity of a wide range of existing ELISA kits at concentrations below the current detection limit.National Institutes of Health (U.S.) (CA119402)National Institutes of Health (U.S.) (EB005743
1962: Abilene Christian College Bible Lectures - Full Text
THE RESTORATION PRINCIPLE”
Being the Abilene Christian College Annual Bible Lectures 1962
Price: $3.95
Published by
ABILENE CHRISTIAN COLLEGE
STUDENTS EXCHANGE
ACC Station Abilene, Texa
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