633 research outputs found
OH+ in Diffuse Molecular Clouds
Near ultraviolet observations of OH+ and OH in diffuse molecular clouds
reveal a preference for different environments. The dominant absorption feature
in OH+ arises from a main component seen in CH+ (that with the highest CH+/CH
column density ratio), while OH follows CN absorption. This distinction
provides new constraints on OH chemistry in these clouds. Since CH+ detections
favor low-density gas with small fractions of molecular hydrogen, this must be
true for OH+ as well, confirming OH+ and H2O+ observations with the Herschel
Space Telescope. Our observed correspondence indicates that the cosmic ray
ionization rate derived from these measurements pertains to mainly atomic gas.
The association of OH absorption with gas rich in CN is attributed to the need
for high enough density and molecular fraction before detectable amounts are
seen. Thus, while OH+ leads to OH production, chemical arguments suggest that
their abundances are controlled by different sets of conditions and that they
coexist with different sets of observed species. Of particular note is that
non-thermal chemistry appears to play a limited role in the synthesis of OH in
diffuse molecular clouds.Comment: 15 pages, 4 figures, to appear in ApJ Letter
Boron Abundances in Diffuse Interstellar Clouds
We present a comprehensive survey of B abundances in diffuse interstellar
clouds from HST/STIS observations along 56 Galactic sight lines. Our sample is
the result of a complete search of archival STIS data for the B II resonance
line at 1362 angstroms, with each detection confirmed by the presence of
absorption from other dominant ions at the same velocity. The data probe a
range of astrophysical environments including both high-density regions of
massive star formation as well as low-density paths through the Galactic halo,
allowing us to clearly define the trend of B depletion onto interstellar grains
as a function of gas density. Many extended sight lines exhibit complex
absorption profiles that trace both local gas and gas associated with either
the Sagittarius-Carina or Perseus spiral arm. Our analysis indicates a higher
B/O ratio in the inner Sagittarius-Carina spiral arm than in the vicinity of
the Sun, which may suggest that B production in the current epoch is dominated
by a secondary process. The average gas-phase B abundance in the warm diffuse
ISM is consistent with the abundances determined for a variety of Galactic disk
stars, but is depleted by 60 percent relative to the solar system value. Our
survey also reveals sight lines with enhanced B abundances that potentially
trace recent production of B-11 either by cosmic-ray or neutrino-induced
spallation. Such sight lines will be key to discerning the relative importance
of the two production routes for B-11 synthesis.Comment: To be published in the proceedings of the IAU Symposium 268, Light
Elements in the Universe, C. Charbonnel, M. Tosi, F. Primas & C. Chiappini,
ed
Impact of Fertilizer Type, Seed Coating, and Duration of Exposure on the Germination of Orchardgrass Seed
Cool-season grasses such as orchardgrass, are important components of forage systems in transition zone states like Kentucky. To maintain dense and vigorous sods, improved cool-season grass varieties are sometimes overseeded into existing stands in late-winter or early-spring. In many cases seed is mixed with fertilizer and top-dressed onto pastures. Little data are available on the impact of fertilizer type or duration of exposure on the germination of raw and coated grass seed. The objective of this study was to evaluate the impact of two fertilizer types, muriate of potash and a blended fertilizer (urea, diammonium phosphate, and muriate of potash), and the duration of exposure (1 to 28 days) on the germination of an improved orchardgrass variety that was raw or coated. Mixing seed with the blended fertilizer resulted in a quadratic decrease in germination rate for the raw seed and coated seed. This rate of decrease was greater for the coated seed in the blended fertilizer. Combining seed with muriate of potash resulted in a linear decline in germination with the decline being similar for both the coated and raw seed. Overall, the rate of decrease was considerably less than that of the blended fertilizer. Results of this study indicate that the combination of seed coating and blended fertilizer had the most detrimental impact on orchardgrass germination
Impact of Fertilizer Type, Seeding Coating, and Duration of Exposure on the Germination of Red Clover Seed
Legumes are important components in grassland ecosystems. Red clover is one the most used legumes in the transition zones states like Kentucky. To maintain legumes in grass pastures, improved red clover varieties are often overseeded in the late-winter or early-spring. In many cases seed is mixed with fertilizer and top-dressed onto pastures. Little data are available on the impact of fertilizer type or duration of exposure on the germination of raw and coated red clover seed. The objective of this study was to evaluate the impact of two fertilizer types, muriate of potash and a blended fertilizer (urea, diammonium phosphate, and muriate of potash), and the duration of exposure (1 to 28 days) on the germination of an improved red clover variety that was raw or coated. Mixing seed with the blended fertilizer resulted in a linear decrease in germination rate for the raw seed and quadratic decrease for the coated seed. After 20 days of exposure to the blended fertilizer, the germination rate of the coated and raw seed was 0 and 60%, respectively. Combining seed with muriate of potash resulted in a linear decline in germination rate with the decline being greater for the coated seed. Overall, the rate of decrease was considerably less than that of the blended fertilizer. Results of this study indicate that seed coating enhanced the detrimental effects of fertilizer on seed germination
Monte Carlo Calculation of the Spin-Stiffness of the Two-Dimensional Heisenberg Model
Using a collective-mode Monte Carlo method (the Wolff-Swendsen-Wang
algorithm), we compute the spin-stiffness of the two-dimensional classical
Heisenberg model. We show that it is the relevant physical quantity to
investigate the behaviour of the model in the very low temperature range
inaccessible to previous studies based on correlation length and susceptibility
calculations.Comment: 6 pages, latex, 3 postscript figures appended, DIM preprint 93-3
Health Disparities and COVID-19 Pandemic: Increasing Clinical Research Participation among African Americans
Health disparities in African Americans is a persistent issue. Higher rates and severity of the novel coronavirus-19 [COVID-19] among African Americans only widens health disparities. Effective COVID-19 treatment options are imperative, requiring representation of African Americans in clinical research. However, low participation and under-representation of African Americans is complex in nature. This article describes health disparities, the impact of COVID-19, and participation in clinical research among African Americans. We offer strategies for researchers to enhance the inclusion of African Americans. We also offer strategies in conducting clinical research during COVID-19
Analysis and evaluation of forecasting methods and tools to predict future demand for secondary chemical-biological configuration items
As the Engineering Support Activity (ESA) for numerous consumable Chemical Biological items managed by the Defense Logistics Agency (DLA), Edgewood Chemical Biological Center (ECBC) must be able to complete reviews of all procurement packages within 15 calendar days. With such little lead time, it would be very beneficial if ECBC had the ability to forecast when DLA procurement actions will occur. This thesis presents an evaluation of the effectiveness of Simple Regression and Exponentially Weighted Moving Average (EWMA) forecasting models to predict the demand of Chemical Biological consumable items using the procurement history data for four specific items. Neither forecasting model proved effective at predicting the demand for the items due in large part to large variation in demand patterns. The inventory policies and supply issues which currently exist at an Army production site were investigated and it was recommended to consider Economic Order Quantity (EOQ) or Just-in-Time (JIT) inventory management models as possible alternatives to achieve smoother demand patterns. Additionally, recommendations were made to examine the integrity of the historical demand data as well as using a Multiple Regression forecast model with several causal effects in addition to time.http://archive.org/details/analysisndevalua1094534729Civilian, United States ArmyApproved for public release; distribution is unlimited
It Takes More Than Calcium to Neutralize Soil Acidity
Proper pH management is the foundation to a good soil fertility program. Soil pH influences nutrient availability and root growth and function. Just because an agricultural product contains calcium does not mean that it will change soil pH. The effectiveness of three calcium products in raising soil pH was compared to an untreated check in acid soils. A field trial was conducted at 16 locations across Kentucky and a laboratory incubation study was conducted at the University of Kentucky Research and Education Center. The same application rates were used for the three products, whether in field trials or laboratory incubations. The rates were 46.8 L ha-1 for the liquid calcium and 4.5 Mg ha-1 for the pelletized and ag limes. The field studies exhibited higher soil pH at 3-month and 12-month sample dates with ag lime and pelletized lime treatments than with the check and liquid calcium treatments. The lab study exhibited higher soil pH values at each sample date (1, 3, 6 and 12 month) with ag lime and pelletized lime than with check and liquid calcium. The soil pH was not improved with the addition of liquid calcium (chloride) and results of this study are supported by the chemical foundations of soil acidity neutralization reactions - calcium chloride does not neutralize acidity and calcium carbonates do
Minimally Invasive Therapies for Hepatocellular Carcinoma: Mechanisms of Local Control and Systemic Immunologic Response
Minimally invasive treatments for hepatocellular carcinoma (HCC) are a cornerstone in the management of this challenging disease. For many years, percutaneously guided ablative techniques, such as radiofrequency ablation (RFA), cryoablation, and microwave ablation (MWA), have successfully treated many different solid malignancies including HCC. Since the initial implementation of these ablative techniques, there have been many advances in the design, technique, and patient selection as well as investigation into the body’s response to treatment. The mechanisms of thermal-based ablative techniques, advantages and disadvantages of each technique, subsequent immunologic response following ablation, and advances in care that utilize combination therapy to potentiate the immunologic response creating a robust and long-term immunity to HCC are outlined in this chapter
XY checkerboard antiferromagnet in external field
Ordering by thermal fluctuations is studied for the classical XY
antiferromagnet on a checkerboard lattice in zero and finite magnetic fields by
means of analytical and Monte Carlo methods. The model exhibits a variety of
novel broken symmetries including states with nematic ordering in zero field
and with triatic order parameter at high fields.Comment: 6 page
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