7,617 research outputs found
The genomes and history of domestic animals
This paper reviews how mammalian genomes are utilized in modern genetics for the detection of genes and polymorphisms (mutations) within domesticated animal (mostly livestock) genomes that are related to traits of economic importance to humans. Examples are given of how genetic analysis allows to determine key genes associated with the quality and quantity of milk in cattle and key genes for meat production. Various questions are reviewed, such as how contemporary methods of genome sequencing allow to maximise the effective detection of coding and regulatory DNA polymorphisms within the genomes of major domesticated mammals (cattle, sheep and pigs) and the history of their formation from the standpoint of genetics
A constrained random-force model for weakly bending semiflexible polymers
The random-force (Larkin) model of a directed elastic string subject to
quenched random forces in the transverse directions has been a paradigm in the
statistical physics of disordered systems. In this brief note, we investigate a
modified version of the above model where the total transverse force along the
polymer contour and the related total torque, in each realization of disorder,
vanish. We discuss the merits of adding these constraints and show that they
leave the qualitative behavior in the strong stretching regime unchanged, but
they reduce the effects of the random force by significant numerical
prefactors. We also show that a transverse random force effectively makes the
filament softer to compression by inducing undulations. We calculate the
related linear compression coefficient in both the usual and the constrained
random force model.Comment: 4 pages, 1 figure, accepted for publication in PR
Transport in a Dissipative Luttinger Liquid
We study theoretically the transport through a single impurity in a
one-channel Luttinger liquid coupled to a dissipative (ohmic) bath . For
non-zero dissipation the weak link is always a relevant perturbation
which suppresses transport strongly. At zero temperature the current voltage
relation of the link is where and
denotes the compressibility. At non-zero temperature the linear
conductance is proportional to . The decay of
Friedel oscillation saturates for distance larger than
from the impurity.Comment: 4 page
Asymmetry of Nonlinear Transport and Electron Interactions in Quantum Dots
The symmetry properties of transport beyond the linear regime in chaotic
quantum dots are investigated experimentally. A component of differential
conductance that is antisymmetric in both applied source-drain bias V and
magnetic field B, absent in linear transport, is found to exhibit mesoscopic
fluctuations around a zero average. Typical values of this component allow a
measurement of the electron interaction strength.Comment: related papers at http://marcuslab.harvard.ed
Conventional and charge six superfluids from melting hexagonal Fulde-Ferrell-Larkin-Ovchinnikov phases in two dimensions
We consider defect mediated melting of Fulde-Ferrell-Larkin-Ovchinnikov
(FFLO) and pair density wave (PDW) phases in two dimensions. Examining
mean-field ground states in which the spatial oscillations of the FFLO/PDW
superfluid order parameter exhibit hexagonal lattice symmetry, we find that
thermal melting leads to a variety of novel phases. We find that a spatially
homogeneous charge six superfluid can arise from melting a hexagonal
vortex-anitvortex lattice FFLO/PDW phase. The charge six superfluid has an
order parameter corresponding to a bound state of six fermions. We further find
that a hexagonal vortex-free FFLO/PDW phase can melt to yield a conventional
(charge two) homogeneous superfluid. A key role is played by topological
defects that combine fractional vortices of the superfluid order and fractional
dislocations of the lattice order.Comment: 8 pages, 3 figure
Effect of a rotating propeller on the separation angle of attack and distortion in ducted propeller inlets
The present study represents an extension of an earlier wind tunnel experiment performed with the P&W 17-in. Advanced Ducted Propeller (ADP) Simulator operating at Mach 0.2. In order to study the effects of a rotating propeller on the inlet flow, data were obtained in the UTRC 10- by 15-Foot Large Subsonic Wind Tunnel with the same hardware and instrumentation, but with the propeller removed. These new tests were performed over a range of flow rates which duplicated flow rates in the powered simulator program. The flow through the inlet was provided by a remotely located vacuum source. A comparison of the results of this flow-through study with the previous data from the powered simulator indicated that in the conventional inlet the propeller produced an increase in the separation angle of attack between 4.0 deg at a specific flow of 22.4 lb/sec-sq ft to 2.7 deg at a higher specific flow of 33.8 lb/sec-sq ft. A similar effect on separation angle of attack was obtained by using stationary blockage rather than a propeller
Kinetics of the superconducting charge qubit in the presence of a quasiparticle
We investigate the energy and phase relaxation of a superconducting qubit
caused by a single quasiparticle. In our model, the qubit is an isolated system
consisting of a small island (Cooper-pair box) and a larger superconductor
(reservoir) connected with each other by a tunable Josephson junction. If such
system contains an odd number of electrons, then even at lowest temperatures a
single quasiparticle is present in the qubit. Tunneling of a quasiparticle
between the reservoir and the Cooper-pair box results in the relaxation of the
qubit. We derive master equations governing the evolution of the qubit
coherences and populations. We find that the kinetics of the qubit can be
characterized by two time scales - quasiparticle escape time from reservoir to
the box, , and quasiparticle relaxation time . The
former is determined by the dimensionless normal-state conductance of the
Josephson junction and one-electron level spacing in the reservoir
(), and the latter is due to electron-phonon
interaction. We find that phase coherence is damped on the time scale of
. The qubit energy relaxation depends on the ratio of the two
characteristic times, and , and also on the ratio of
temperature to the Josephson energy .Comment: 12 pages, 4 figures, final version as published in PRB, some changes,
reference adde
Chromomagnetic instability in two-flavor quark matter at nonzero temperature
We calculate the effective potential of the 2SC/g2SC phases including vector
condensates () and study the gluonic phase and the
single plane-wave Larkin-Ovchinnikov-Fulde-Ferrell state at nonzero
temperature. Our analysis is performed within the framework of the gauged
Nambu--Jona-Lasinio model. We compute potential curvatures with respect to the
vector condensates and investigate the temperature dependence of the Meissner
masses squared of gluons of color 4--7 and 8 in the neutral 2SC/g2SC phases.
The phase diagram is presented in the plane of temperature and coupling
strength. The unstable regions for gluons 4--7 and 8 are mapped out on the
phase diagram. We find that, apart from the case of strong coupling, the
2SC/g2SC phases at low temperatures are unstable against the vector
condensation until the temperature reaches tens of MeV.Comment: 10 pages, 10 figures, revisions to text, published in Phys. Rev.
Superfluid and Pseudo-Goldstone Modes in Three Flavor Crystalline Color Superconductivity
We study the bosonic excitations in the favorite cubic three flavor
crystalline LOFF phases of QCD. We calculate in the Ginzburg-Landau
approximation the masses of the eight pseudo Nambu-Goldstone Bosons (NGB)
present in the low energy theory. We also compute the decay constants of the
massless NGB Goldstones associated to superfluidity as well as those of the
eight pseudo NGB. Differently from the corresponding situation in the
Color-Flavor-Locking phase, we find that meson condensation phases are not
expected in the present scenario.Comment: 10 pages, RevTeX4 class. Section IIIA enlarged, to appear on Phys.
Rev.
Spin and Charge Josephson effects between non-uniform superconductors with coexisting helimagnetic order
We consider the spin and charge Josephson current between two non-uniform
Fulde-Ferrel-Larkin-Ovchinnikov superconductors with helimagnetic order. We
demonstrate that the presence of the helimagnetic phase generates a spin
Josephson effect and leads to additional contributions to both single-particle
and Josephson charge current. It is shown that for such systems the AC effect
differs more radically from the DC effect than in the case of a BCS
superconductor with helimagnetic order considered earlier in the literature [M.
L. Kuli\'c and I. M. Kuli\'c, Phys. Rev. B {\bf 63}, 104503 (2001)] where a
spin Josephson current has also been found. In our system the most interesting
effect occurs in the presence of an external magnetic field and in absence of
voltage, where we show that the charge Josephson current can be tuned to zero
while the spin Josephson current is non-vanishing. This provides a well
controlled mechanism to generate a spin supercurrent in absence of charge
currents.Comment: final versio
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