9,605 research outputs found
Chirality in Liquid Crystals: from Microscopic Origins to Macroscopic Structure
Molecular chirality leads to a wonderful variety of equilibrium structures,
from the simple cholesteric phase to the twist-grain-boundary phases, and it is
responsible for interesting and technologically important materials like
ferroelectric liquid crystals. This paper will review some recent advances in
our understanding of the connection between the chiral geometry of individual
molecules and the important phenomenological parameters that determine
macroscopic chiral structure. It will then consider chiral structure in
columnar systems and propose a new equilibrium phase consisting of a regular
lattice of twisted ropes.Comment: 20 pages with 6 epsf figure
Some solutions of linearized 5-d gravity with brane
We consider linearized 5-d gravity in the Randall-Sundrum brane world. The
class of static solutions for linearized Einstein equations is found. Also we
obtaine wave solutions describing radiation from an imaginary point source
located at the Planck distance from the brane. We analyze the fields asymptotic
behavior and peculiarities of matter sources.Comment: Latex, 8 page
Energetic electrons in the magnetosphere of Saturn
The energy spectra and angular distributions of electrons observed by Pioneer 11 as a function of radial distance in the inner magnetosphere of Saturn are reanalyzed and phase space densities are then calculated. The radial dependence of phase space density requires a distributed loss process. The loss is greatest in the region of the E ring (5.5 less than L less than 8.5) and is attributed to collisions with the ring particles in agreement with earlier work by Van Allen et al. (1980). Quantitative analysis yields the following properties of the E ring: the particle radii are in the range of 4 x 10(exp -5) to 3.2 x 10(exp -4) cm and the thickness of the ring is approximately 3 R(sub s). Between the inner edge of the E ring (5.5 R(sub s)) and the outer edge of the A ring (2.3 R(sub s)) there are more energetic electrons than can be supplied by radial diffusion from an external source. Detailed calculations show that a cosmic ray albedo neutron decay (CRAND) source in the A and B rings is a plausible source for this excess. The radial diffusion coefficient required to explain the E ring absorption and CRAND source for electrons is 1 x 10(exp -12) greater than D(sub 0) greater than 3 x 10(exp -12) R(exp 2, sub s)/s, assuming that D(sub LL) = D(sub 0)L(exp 3). As part of the reanalysis program, a method for the deconvolution of pitch angle distributions observed by simple detectors on a rotating spacecraft is developed. This process removes the instrumental response and rotational smear due to finite sampling periods and yields true angular distributions
Time variations of magnetospheric intensities of outer zone protons, alpha particles and ions (Z greater than or equal to 2)
A comprehensive study of the temporal behavior of trapped protons, alpha particles and ions (Z 2) in outer zone of the earth's magnetosphere has been made. These observations were made by the Injun V satellite during the first 21 months of operation, August 1968 to May 1970. Rapid increases in the observed number of particles followed by slower exponential decay characterize the data. Comparisons are made with the temporal behavior of interplanetary particles of the same energy observed by Explorer 35. Increases in the trapped fluxes generally correspond to enhanced interplanetary activity. The energy spectra of protons and alpha particles at L = 3 have similar shapes when compared on an energy per charge basis while the respective polar cap spectra have similar shape on an energy per nucleon basis. Apparent inward trans-L motion of energetic protons is observed. These particles are diffused inward by a process involving fluctuating electric fields. The loss of trapped low altitude protons, alpha particles and ions (Z 2) is controlled by coulombic energy loss in the atmosphere
Smectic Phases with Cubic Symmetry: The Splay Analog of the Blue Phase
We report on a construction for smectic blue phases, which have quasi-long
range smectic translational order as well as long range cubic or hexagonal
order. Our proposed structures fill space with a combination of minimal surface
patches and cylindrical tubes. We find that for the right range of material
parameters, the favorable saddle-splay energy of these structures can stabilize
them against uniform layered structures.Comment: 4 pages, 4 eps figures, RevTe
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A genome-wide association study reveals specific transferases as candidate loci for bovine milk oligosaccharides synthesis.
BackgroundHuman milk oligosaccharides (OS) play a key role in brain and gut microbiota development of the neonate, but the underlying biosynthetic steps of OS in the mammary gland are still largely unknown. As bovine milk contains OS with somewhat similar structures and functionalities there is increased interest in further understanding the genetic basis underlying the OS content of milk for eventual extraction and generation of value-added ingredients for infant formulas and nutraceuticals. The present study is the first to report on genetic parameter estimation as well as on a genome wide association study (GWAS) from the largest bovine milk OS dataset analyzed to date.ResultsIn total 15 different bovine milk OS were monitored. Heritabilities ranged from 0 to 0.68 in Danish Holstein and from 0 to 0.92 in Danish Jersey. The GWAS identified in total 1770 SNPs (FDR < 0.10) for five different OS in Danish Holstein and 6913 SNPs (FDR < 0.10) for 11 OS in Danish Jersey. In Danish Holstein, a major overlapping QTL was identified on BTA1 for LNH and LNT explaining 24% of the variation in these OS. The most significant SNPs were associated with B3GNT5, a gene encoding a glycosyltransferase involved in glycan synthesis. In Danish Jersey, a very strong QTL was detected for the OS with composition 2 Hex 1 HexNAc (isomer 1) on BTA11. The most significant SNP had -log10(P-value) of 52.88 (BOVINEHD1100030300) and was assigned to ABO, a gene encoding ABO blood group glycosyltransferases. This SNP has been reported to be a missense mutation and explains 56% of the OS variation. Other candidate genes of interest identified for milk OS were ALG3, B3GALNT2, LOC520336, PIGV, MAN1C1, ST6GALNAC6, GLT6D1, GALNT14, GALNT17, COLGALT2, LFNG and SIGLEC.ConclusionTo our knowledge, this is the first study documenting a solid breeding potential for bovine milk OS and a strong indication of specific candidate genes related to OS synthesis underlying this genetic influence. This new information has the potential to guide breeding strategies to achieve production of milk with higher diversity and concentration of OS and ultimately facilitate large-scale extraction of bovine milk OS
Series solutions for a static scalar potential in a Salam-Sezgin Supergravitational hybrid braneworld
The static potential for a massless scalar field shares the essential
features of the scalar gravitational mode in a tensorial perturbation analysis
about the background solution. Using the fluxbrane construction of [8] we
calculate the lowest order of the static potential of a massless scalar field
on a thin brane using series solutions to the scalar field's Klein Gordon
equation and we find that it has the same form as Newton's Law of Gravity. We
claim our method will in general provide a quick and useful check that one may
use to see if their model will recover Newton's Law to lowest order on the
brane.Comment: 5 pages, no figure
CHANCE CONSTRAINED PROGRAMMING MODELS FOR RISK-BASED ECONOMIC AND POLICY ANALYSIS OF SOIL CONSERVATION
The random nature of soil loss under alternative land-use practices should be an important consideration of soil conservation planning and analysis under risk. Chance constrained programming models can provide information on the trade-offs among pre-determined tolerance levels of soil loss, probability levels of satisfying the tolerance levels, and economic profits or losses resulting from soil conservation to soil conservation policy makers. When using chance constrained programming models, the distribution of factors being constrained must be evaluated. If random variables follow a log-normal distribution, the normality assumption, which is generally used in the chance constrained programming models, can bias the results.Risk and Uncertainty,
Direction-Dependent Polarised Primary Beams in Wide-Field Synthesis Imaging
The process of wide-field synthesis imaging is explored, with the aim of
understanding the implications of variable, polarised primary beams for
forthcoming Epoch of Reionisation experiments. These experiments seek to detect
weak signatures from redshifted 21cm emission in deep residual datasets, after
suppression and subtraction of foreground emission. Many subtraction algorithms
benefit from low side-lobes and polarisation leakage at the outset, and both of
these are intimately linked to how the polarised primary beams are handled.
Building on previous contributions from a number of authors, in which
direction-dependent corrections are incorporated into visibility gridding
kernels, we consider the special characteristics of arrays of fixed dipole
antennas operating around 100-200 MHz, looking towards instruments such as the
Square Kilometre Array (SKA) and the Hydrogen Epoch of Reionization Arrays
(HERA). We show that integrating snapshots in the image domain can help to
produce compact gridding kernels, and also reduce the need to make complicated
polarised leakage corrections during gridding. We also investigate an
alternative form for the gridding kernel that can suppress variations in the
direction-dependent weighting of gridded visibilities by 10s of dB, while
maintaining compact support.Comment: 15 pages, 4 figures. Accepted for publication in JA
Electroweak Sudakov Corrections using Effective Field Theory
Electroweak Sudakov corrections of the form alpha^n log^m s/M_{W,Z}^2 are
summed using renormalization group evolution in soft-collinear effective theory
(SCET). Results are given for the scalar, vector and tensor form-factors for
fermion and scalar particles. The formalism for including massive gauge bosons
in SCET is developed.Comment: 5 page
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