658 research outputs found
Membrane-Based Sorbent for Heavy Metal Sequestration
A process is provided for making membrane-based sorbents with enhanced binding activity that are particularly useful for heavy metal sequestration. The process includes the step of selectively hydrolyzing a polyacetylated membrane in order to deacetylate a surface layer of said membrane and expose free hydroxyl groups. This is followed by the oxidizing of the hydroxyl groups to aldehyde groups. This is then followed by the attaching of a polycarboxylic acid such as a polyamino acid, polyalkenoic acid or polypeptide to the membrane through the aldehyde groups. Preferably, the hydrolyzing step is completed under alkaline conditions and the oxidizing step is completed using an aqueous solution of sodium periodate
A comprehensive radial velocity error budget for next generation Doppler spectrometers
We describe a detailed radial velocity error budget for the NASA-NSF Extreme
Precision Doppler Spectrometer instrument concept NEID (NN-explore Exoplanet
Investigations with Doppler spectroscopy). Such an instrument performance
budget is a necessity for both identifying the variety of noise sources
currently limiting Doppler measurements, and estimating the achievable
performance of next generation exoplanet hunting Doppler spectrometers. For
these instruments, no single source of instrumental error is expected to set
the overall measurement floor. Rather, the overall instrumental measurement
precision is set by the contribution of many individual error sources. We use a
combination of numerical simulations, educated estimates based on published
materials, extrapolations of physical models, results from laboratory
measurements of spectroscopic subsystems, and informed upper limits for a
variety of error sources to identify likely sources of systematic error and
construct our global instrument performance error budget. While natively
focused on the performance of the NEID instrument, this modular performance
budget is immediately adaptable to a number of current and future instruments.
Such an approach is an important step in charting a path towards improving
Doppler measurement precisions to the levels necessary for discovering
Earth-like planets.Comment: 20 pages, 12 figures, published in Proc. of SPIE Astronomical
Telescopes + Instrumentation 201
Cosmic rays and neutrino interactions beyond the standard model
Some solutions of the hierarchy problem of particle physics can lead to
significantly increased neutrino cross sections beyond the electroweak scale.
We discuss some consequences for and constraints resulting from cosmic ray
physics.Comment: 3 latex pages, 1 postscript figure included, to appear in the TAUP 99
Proceedings, Nucl. Phys. B (Proc. Suppl.), ed. by M. Froissart, J. Dumarchez
and D. Vignau
Cosmological Constraints on Theories with Large Extra Dimensions
In theories with large extra dimensions, constraints from cosmology lead to
non-trivial lower bounds on the fundamental scale M_F, corresponding to upper
bounds on the radii of the compact extra dimensions. These constraints are
especially relevant to the case of two extra dimensions, since only if M_F is
10 TeV or less do deviations from the standard gravitational force law become
evident at distances accessible to planned sub-mm gravity experiments. By
examining the graviton decay contribution to the cosmic diffuse gamma
radiation, we derive, for the case of two extra dimensions, a conservative
bound M_F > 110 TeV, corresponding to r_2 < 5.1 times 10^-5 mm, well beyond the
reach of these experiments. We also consider the constraint coming from
graviton overclosure of the universe and derive an independent bound M_F > 6.5
h^(-1/2) TeV, or r_2 < .015 h mm.Comment: 10 pages, references adde
Solving the Hierarchy Problem with Exponentially Large Dimensions
In theories with (sets of) two large extra dimensions and supersymmetry in
the bulk, the presence of non-supersymmetric brane defects naturally induces a
logarithmic potential for the volume of the transverse dimensions. Since the
logarithm of the volume rather than the volume itself is the natural variable,
parameters of O(10) in the potential can generate an exponentially large size
for the extra dimensions. This provides a true solution to the hierarchy
problem, on the same footing as technicolor or dynamical supersymmetry
breaking. The area moduli have a Compton wavelength of about a millimeter and
mediate Yukawa interactions with gravitational strength. We present a simple
explicit example of this idea which generates two exponentially large
dimensions. In this model, the area modulus mass is in the millimeter range
even for six dimensional Planck scales as high as 100 TeV.Comment: 13 pages, 7 figures, corrected typo
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Benefits and Costs of Interventions to Improve Breast Cancer Outcomes in African American Women
Purpose Historically, African American women have experienced higher breast cancer mortality than white women, despite lower incidence. Our objective was to evaluate whether costs of increasing rates of screening or application of intensive treatment will be off-set by survival benefits for African American women.
Methods We use a stochastic simulation model of the natural history of breast cancer to evaluate the incremental societal costs and benefits of status quo versus targeted biennial screening or treatment improvements among African Americans 40 years of age and older. Main outcome measures were number of mammograms, stage, all-cause mortality, and discounted costs per life year saved (LYS).
Results At the current screening rate of 76%, there is little incremental benefit associated with further increasing screening, and the costs are high: 124,217 per LYS for lay health worker and patient reminder interventions, respectively, compared with the status quo. Using reminders would cost 78,130 per LYS if targeted to women with a two-fold increase in baseline risk. If all patients received the most intensive treatment recommended, costs increase but deaths decrease, for a cost of 6,000 per breast cancer patient could be used to enhance treatment and still yield cost-effectiveness ratios of less than $75,000 per LYS.
Conclusion Except in pockets of unscreened or high-risk women, further investments in interventions to increase screening are unlikely to be an efficient use of resources. Ensuring that African American women receive intensive treatment seems to be the most cost-effective approach to decreasing the disproportionate mortality experienced by this population
A comparison of two schemes for the convective transport of chemical species in a Lagrangian global chemistry model
A Study of the Sediments of Narragansett Bay, Volume 1: The Surface Sediments of Narragansett Bay
This report is divided into two volumes. The focus of Volume I is the surface sediments of Narragansett Bay. Volume I contains a study of the surface sediments of Narragansett Bay (Chapter 1), a study of suspended sediments in the northwestern section of the Narragansett Bay System (Chapter 2), a study of the relationship between contaminant concentrations in the surface sediments and soft tissues of the hard clam, Mercenaria mercenaria in Narragansett Bay (Chapter 3), and the results of a side-scan sonar survey of the Providence River dredged channel (Chapter 4).
The focus of Volume II is a study of sediment cores from the Narragansett Bay System. Chapter 5 contains the results of geophysical (side-scan and sub-bottom sonar) that support the core studies. The results of studies of sediment cores from Narragansett Bay are contained in Chapter 6, and the results of sediment core studies from its freshwater tributaries (i.e., the Blackstone and Pawtuxet Rivers) are contained in Chapter 7.
(Text taken from report preface
Neutrinos as Source of Ultra High Energy Cosmic Rays in Extra Dimensions
If the neutrinos are to be identified with the primary source of ultra-high
energy cosmic rays(UHECR), their interaction on relic neutrinos is of great
importance in understanding their long intergalactic journey. In theories with
large compact dimensions, the exchange of a tower of massive spin-2 gravitons
(Kaluza-Klein excitations) gives extra contribution to and processes along with the opening
of a new channel for the neutrinos to annihilate with the relic cosmic neutrino
background to produce bulk gravitons in
the extra dimensions. This will affect their attenuation. We compute the
contribution of these Kaluza-Klein excitations to the above processes and find
that for parameters of the theory constrained by supernova cooling, the
contribution does indeed become the dominant contribution above GeV.Comment: 16 pages Latex2e file including 4 postscript figures. Effect of brane
fluctuation taken into accoun
APOBEC Mutagenesis Is Concordant between Tumor and Viral Genomes in HPV-Positive Head and Neck Squamous Cell Carcinoma
APOBEC is a mutagenic source in human papillomavirus (HPV)-mediated malignancies, including HPV+ oropharyngeal squamous cell carcinoma (HPV + OPSCC), and in HPV genomes. It is unknown why APOBEC mutations predominate in HPV + OPSCC, or if the APOBEC-induced mutations observed in both human cancers and HPV genomes are directly linked. We performed sequencing of host somatic exomes, transcriptomes, and HPV16 genomes from 79 HPV + OPSCC samples, quantifying APOBEC mutational burden and activity in both host and virus. APOBEC was the dominant mutational signature in somatic exomes. In viral genomes, there was a mean of five (range 0–29) mutations per genome. The mean of APOBEC mutations in viral genomes was one (range 0–5). Viral APOBEC mutations, compared to non-APOBEC mutations, were more likely to be low-variant allele fraction mutations, suggesting that APOBEC mutagenesis actively occurrs in viral genomes during infection. HPV16 APOBEC-induced mutation patterns in OPSCC were similar to those previously observed in cervical samples. Paired host and viral analyses revealed that APOBEC-enriched tumor samples had higher viral APOBEC mutation rates (p = 0.028), and APOBEC-associated RNA editing (p = 0.008), supporting the concept that APOBEC mutagenesis in host and viral genomes is directly linked and occurrs during infection. Using paired sequencing of host somatic exomes, transcriptomes, and viral genomes, we demonstrated for the first-time definitive evidence of concordance between tumor and viral APOBEC mutagenesis. This finding provides a missing link connecting APOBEC mutagenesis in host and virus and supports a common mechanism driving APOBEC dysregulation
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