96 research outputs found
An Abundance of K3 Fibrations from Polyhedra with Interchangeable Parts
Even a cursory inspection of the Hodge plot associated with Calabi-Yau
threefolds that are hypersurfaces in toric varieties reveals striking
structures. These patterns correspond to webs of elliptic-K3 fibrations whose
mirror images are also elliptic-K3 fibrations. Such manifolds arise from
reflexive polytopes that can be cut into two parts along slices corresponding
to the K3 fibers. Any two half-polytopes over a given slice can be combined
into a reflexive polytope. This fact, together with a remarkable relation on
the additivity of Hodge numbers, explains much of the structure of the observed
patterns.Comment: 30 pages, 15 colour figure
The Hidden Work of the Farm Homemaker
Despite women’s involvement in agricultural production, the work role of women residing in farm households has not been thoroughly examined. Data collected in 1994-1995 as part of the NIOSH-sponsored Farm Family Health and Hazard Surveillance Project were used to address task issues and health status of farm women in Kentucky. In 1996, the farm woman component of the Kentucky study was replicated in five counties in west Texas, allowing an examination of farm women in two large agricultural states. The Kentucky study employed a two-stage cluster design;the Texas study was based on a systematic quota sample of farms. Both studies selected a sample of women aged 18 years and older living in farm households. A total of 992 women in Kentucky (response rate = 85%) and 665 women in Texas completed a structured 30-min telephone interview on work roles, health status, injuries, and demographics. The results indicated that although 46.4% of the Kentucky respondents and 46.3% of the Texas respondents characterized themselves as farm homemakers, they regularly engaged in farmwork. Reported tasks included work with animals, tobacco-related chores, field irrigation, farm equipment operation, and farm management. Further, women who characterized themselves as homemakers reported rates of farm injuries that were comparable with women who classified themselves in other roles such as full agricultural partners. Role definition may influence the woman’s perception of risk on the farm, preclude participation in farm safety programs, and prevent an accurate occupational medical history. This two-state descriptive study highlights the hidden work role of the farm woman—a role that remains invisible to the farm woman herself—and emphasizes the important occupational exposures that farm women encounter
On the Classification of Quasihomogeneous Functions
We give a criterion for the existence of a non-degenerate quasihomogeneous
polynomial in a configuration, i.e. in the space of polynomials with a fixed
set of weights, and clarify the relation of this criterion to the necessary
condition derived from the formula for the Poincar\'e polynomial. We further
prove finiteness of the number of configurations for a given value of the
singularity index. For the value 3 of this index, which is of particular
interest in string theory, a constructive version of this proof implies an
algorithm for the calculation of all non-degenerate configurations.Comment: 12 page
Myrtucommulone from Myrtus communis: metabolism, permeability, and systemic exposure in rats
Nonsteroidal anti-inflammatory drug intake is associated with a high prevalence of gastrointestinal side effects, and severe cardiovascular adverse reactions challenged the initial enthusiasm in cyclooxygenase-2 inhibitors. Recently, it was shown that myrtucommulone, the active ingredient of the Mediterranean shrub Myrtus communis, dually and potently inhibits microsomal prostaglandin E₂ synthase-1 and 5-lipoxygenase, suggesting a substantial anti-inflammatory potential. However, one of the most important prerequisites for the anti-inflammatory effects in vivo is sufficient bioavailability of myrtucommulone. Therefore, the present study was aimed to determine the permeability and metabolic stability in vitro as well as the systemic exposure of myrtucommulone in rats. Permeation studies in the Caco-2 model revealed apparent permeability coefficient values of 35.9 · 10⁻⁶ cm/s at 37 °C in the apical to basolateral direction, indicating a high absorption of myrtucommulone. In a pilot rat study, average plasma levels of 258.67 ng/mL were reached 1 h after oral administration of 4 mg/kg myrtucommulone. We found that myrtucommulone undergoes extensive phase I metabolism in human and rat liver microsomes, yielding hydroxylated and bihydroxylated as well as demethylated metabolites. Physiologically-based pharmacokinetic modeling of myrtucommulone in the rat revealed rapid and extensive distribution of myrtucommulone in target tissues including plasma, skin, muscle, and brain. As the development of selective microsomal prostaglandin E₂ synthase-1 inhibitors represents an interesting alternative strategy to traditional nonsteroidal anti-inflammatory drugs and cyclooxygenase-2 inhibitors for the treatment of chronic inflammation, the present study encourages further detailed pharmacokinetic investigations on myrtucommulone
Orbital pacing of the Early Jurassic carbon cycle, black-shale formation and seabed methane seepage
The Early Jurassic (ca 201 to 174 Ma) was marked by a series of rapid perturbations in climate, the environment and global geochemical cycles, which have been linked to volcanic outgassing and the release of biogenic or thermogenic methane into the ocean–atmosphere system. The state of the global carbon cycle and prevailing climatic and environmental conditions that existed at this time are, however, poorly constrained. Here, mudrocks of the Lower Sinemurian Arietites bucklandi ammonite Biozone at coastal exposures at Kilve, Somerset, UK, have been studied. This succession includes laminated organic-rich black shales, which are present throughout the Bristol Channel Basin, and coincides with a 2 to 3‰ negative carbon-isotope excursion, distinct changes in inferred land vegetation and abundant marine prasinophytes (green algae). The event itself does not represent a single perturbation of the regional environment, but follows in a sequence of eccentricity-modulated, precession-paced perturbations that occur throughout the preceding Hettangian stage, with the periodic formation of organic-rich laminated black shales in the Bristol Channel Basin. However, the Early Sinemurian event studied herein is more extreme in nature, with sedimentary total organic carbon values of 5 to 11% persisting over about 2 m, representing ca 100 kyr, possibly in phase with short (ca 100 kyr) and long (ca 405 kyr) eccentricity forcing. The formation of methane-seep carbonate-cemented mounds took place relatively soon after the deposition of laminated black shales. Biogenic methane probably formed in response to microbial methanogenesis in the organic-rich black shale, which was subsequently channelled to the sediment–water interface approximately 5 m above the source bed, and ca 200 kyr after cessation of formation of the black shale
GUTs in Curved Spacetime: Running Gravitational Constants, Newtonian Potential and the Quantum Corrected Gravitational Equations
The running coupling constants (in particular, the gravitational one) are
studied in asymptotically free GUTs and in finite GUTs in curved spacetime,
with explicit examples. The running gravitational coupling is used to calculate
the leading quantum GUT corrections to the Newtonian potential, which turn out
to be of logarithmic form in asymptotically free GUTs. A comparison with the
effective theory for the conformal factor ---where leading quantum corrections
to the Newtonian potential are again logarithmic--- is made. A totally
asymptotically free GUT with quantum higher derivative gravity is then
constructed, using the technique of introducing renormalization group (RG)
potentials in the space of couplings. RG equations for the cosmological and
gravitational couplings in this theory are derived, and solved numerically,
showing the influence of higher-derivative quantum gravity on the Newtonian
potential. The RG-improved effective gravitational Lagrangian for
asymptotically free massive GUTs is calculated in the strong (almost constant)
curvature regime, and the non-singular De Sitter solution to the quantum
corrected gravitational equations is subsequently discussed. Finally, possible
extensions of the results here obtained are briefly outlined.Comment: LaTeX, 27 pages, 2 uu-figure
Association between single nucleotide polymorphisms in the mu opioid receptor gene (OPRM1) and self-reported responses to alcohol in American Indians
Abstract Background Variation in response to the hedonic and adverse effects of a substance is in part an inherited factor that may influence its use, abuse and dependence. The mu opioid receptor is the primary site of action for opiates and individuals with polymorphisms in this receptor appear to have variation in the CNS effects of opiates. Several studies have suggested that this receptor may also mediate some of the effects of non-opioid drugs, such as alcohol. The purpose of this study was to investigate associations between 13 single nucleotide polymorphisms in the mu opioid receptor gene (OPRM1) with self-reported responses to alcohol, an endophenotype associated with the development of alcohol dependence, in American Indians living on eight contiguous reservations. Methods Each participant gave a blood sample and completed a structured diagnostic interview. Additionally, response to alcohol was indexed using the expectation version of the subjective high assessment scale (SHAS-E). SNPs were genotyped in 251 participants and data analyses were conducted using SOLAR. Results The estimated heritability (h2) for the SHAS-E phenotypes ranged from 0.01 to 0.28. Endorsing the expectation of a more intense response on one or more of the following items from the SHAS-E: buzzed, clumsy, dizzy, drunk, effects, high, nausea, sleepy, talkative, terrible, and/or uncomfortable after imbibing 2–3 drinks was significantly associated with having at least one minor allele for at least one of 7 SNPs (p < 0.01) in the OPRM1 receptor gene. Conclusion These studies provide data to suggest that the minor allele, for most of the polymorphisms in the OPRM1 receptor gene investigated, was found to be associated with a more intense, and/or more adverse, response to alcohol, traits that are significantly correlated with lowered quantity of alcohol consumption and less susceptibility to dependence in this Indian population. These data further suggest that making conclusions on the role of the mu opiod receptor gene in the development of alcohol dependence may be limited if only one polymorphism in the gene is evaluated in isolation
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