5,876 research outputs found
Observations on North Dakota Sponges (Haplosclerina: Spongillidae) and Sisyrids (Neuroptera: Sisyridae)
Factors influencing occurrence, distribution, and ecology of sponges and sisyrids are discussed, with emphasis on northeastern North Dakota. New state records for North Dakota sponges, Eunapius Jraguis Leidy and Ephydatia fluviatilis L. and the sisyrids, Sisyra vicaria (Hagen) and Climacia areolaris (Hagen), and new county records for C. areolaris in northwestern Minnesota and Eunapius fragilis in northeastern North Dakota are reported. A rare association of the parasite, S. vicaria with the host, Ephydatia fluviatilis is also reported. Some physicochcmical relations of Eunapius fragilis found in the Forest River, North Dakota, are discussed
Preparation, testing, and delivery of low density polyimide foam panels
Plastic foams based on polyimide resins were shown to be stable at relatively high temperatures, and to possess very low flame spread and smoke generation characteristics. A system and process were developed to prepare low-density polyimide foam from a liquid formulation. The system is based on the reaction of micropulverized grade pyromellitic dianhydride with a polymeric diisocyanate. The panels produced were postcured at elevated temperatures to achieve maximum thermal and fire resistance, and incorporation of a fire retardant into the formulation was considered. The effects of a flame retardant (Flameout 5600B1) were investigated, but eliminated in preference to the postcuring approach
Association Between APOL1 Genotypes and Risk of Cardiovascular Disease in MESA (Multi-Ethnic Study of Atherosclerosis).
BACKGROUND:APOL1 genetic variants confer an increased risk for kidney disease. Their associations with cardiovascular disease (CVD) are less certain. We aimed to compare the prevalence of subclinical CVD and incidence of atherosclerotic CVD and heart failure by APOL1 genotypes among self-identified black participants of MESA (Multi-Ethnic Study of Atherosclerosis). METHODS AND RESULTS:Cross-sectional associations of APOL1 genotypes (high-risk=2 alleles; low-risk=0 or 1 allele) with coronary artery calcification, carotid-intimal media thickness, and left ventricular mass were evaluated using logistic and linear regression. Longitudinal associations of APOL1 genotypes with incident myocardial infarction, stroke, coronary heart disease, and congestive heart failure were examined using Cox regression. We adjusted for African ancestry, age, and sex. We also evaluated whether hypertension or kidney function markers explained the observed associations. Among 1746 participants with APOL1 genotyping (mean age 62 years, 55% women, mean cystatin C-based estimated glomerular filtration rate 89 mL/min per 1.73 m2, 12% with albuminuria), 12% had the high-risk genotypes. We found no difference in prevalence or severity of coronary artery calcification, carotid-intimal media thickness, or left ventricular mass by APOL1 genotypes. The APOL1 high-risk group was 82% more likely to develop incident heart failure compared with the low-risk group (95% confidence interval, 1.01-3.28). Adjusting for hypertension (hazard ratio, 1.80; 95% confidence interval, 1.00-3.24) but not markers of kidney function (hazard ratio, 1.86; 95% confidence interval, 1.03-3.35) slightly attenuated this association. The APOL1 high-risk genotypes were not significantly associated with other clinical CVD outcomes. CONCLUSIONS:Among blacks without baseline CVD, the APOL1 high-risk variants may be associated with increased risk for incident heart failure but not subclinical CVD or incident clinical atherosclerotic CVD
The Constitutive Relations and the Magnetoelectric Effect for Moving Media
In this paper the constitutive relations for moving media with homogeneous
and isotropic electric and magnetic properties are presented as the connections
between the generalized magnetization-polarization bivector and
the electromagnetic field F. Using the decompositions of F and ,
it is shown how the polarization vector P(x) and the magnetization vector M(x)
depend on E, B and two different velocity vectors, u - the bulk velocity vector
of the medium, and v - the velocity vector of the observers who measure E and B
fields. These constitutive relations with four-dimensional geometric
quantities, which correctly transform under the Lorentz transformations (LT),
are compared with Minkowski's constitutive relations with the 3-vectors and
several essential differences are pointed out. They are caused by the fact
that, contrary to the general opinion, the usual transformations of the
3-vectors , , , , etc. are
not the LT. The physical explanation is presented for the existence of the
magnetoelectric effect in moving media that essentially differs from the
traditional one.Comment: 18 pages, In Ref. [10] here, which corresponds to Ref. [18] in the
published paper in IJMPB, Z. Oziewicz's published paper is added. arXiv admin
note: text overlap with arXiv:1101.329
A general approximation of quantum graph vertex couplings by scaled Schroedinger operators on thin branched manifolds
We demonstrate that any self-adjoint coupling in a quantum graph vertex can
be approximated by a family of magnetic Schroedinger operators on a tubular
network built over the graph. If such a manifold has a boundary, Neumann
conditions are imposed at it. The procedure involves a local change of graph
topology in the vicinity of the vertex; the approximation scheme constructed on
the graph is subsequently `lifted' to the manifold. For the corresponding
operator a norm-resolvent convergence is proved, with the natural
identification map, as the tube diameters tend to zero.Comment: 19 pages, one figure; introduction amended and some references added,
to appear in CM
Ground-State of Charged Bosons Confined in a Harmonic Trap
We study a system composed of N identical charged bosons confined in a
harmonic trap. Upper and lower energy bounds are given. It is shown in the
large N limit that the ground-state energy is determined within an accuracy of
and that the mean field theory provides a reasonable result with
relative error of less than 16% for the binding energy .Comment: 15 page
Direct approach to the problem of strong local minima in Calculus of Variations
The paper introduces a general strategy for identifying strong local
minimizers of variational functionals. It is based on the idea that any
variation of the integral functional can be evaluated directly in terms of the
appropriate parameterized measures. We demonstrate our approach on a problem of
W^{1,infinity} weak-* local minima--a slight weakening of the classical notion
of strong local minima. We obtain the first quasiconvexity-based set of
sufficient conditions for W^{1,infinity} weak-* local minima.Comment: 26 pages, no figure
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