15,218 research outputs found
The thermal noise of cascaded mismatched passive two-ports in the microwave range
Thermal noise calculation of cascaded mismatched passive two-ports in microwave rang
Reduction of noise in gyro outputs
Technique is described to reduce extraneous gyro output signals by using relatively inexpensive shrouds which do not increase power comsumption. Shrouds reduce noise by minimizing mass of gas spinning with rotor, reducing Reynolds number near rotor, and inducing laminar flow
Hawking Radiation as Tunneling
We present a short and direct derivation of Hawking radiation as a tunneling
process, based on particles in a dynamical geometry. The imaginary part of the
action for the classically forbidden process is related to the Boltzmann factor
for emission at the Hawking temperature. Because the derivation respects
conservation laws, the exact spectrum is not precisely thermal. We compare and
contrast the problem of spontaneous emission of charged particles from a
charged conductor.Comment: LaTeX, 10 pages; v2. journal version, added section on relation of
black hole radiation to electric charge emission from a charged conducting
sphere; v3. restored cut referenc
Disk tracing for B[e] supergiants in the Magellanic Clouds
B[e] supergiants are evolved massive stars with a complex circumstellar
environment. A number of important emission features probe the structure and
the kinematics of the circumstellar material. In our survey of Magellanic Cloud
B[e] supergiants we focus on the [OI] and [CaII] emission lines, which we
identified in four more objects.Comment: 2 pages; 1 figure; submitted to the proceedings of the Physics of
Evolved Stars - A conference dedicated to the memory of Olivier Chesneau,
Nice, France, June 8-12, 201
Large Area Crop Inventory Experiment (LACIE). Evaluation of multitemporal data enchancements for the identification of winter wheat fields
There are no author-identified significant results in this report
Off-shell Top Quarks with One Jet at the LHC: A comprehensive analysis at NLO QCD
We present a comprehensive study of the production of top quark pairs in
association with one hard jet in the di-lepton decay channel at the LHC. Our
predictions, accurate at NLO in QCD, focus on the LHC Run II with a
center-of-mass energy of 13 TeV. All resonant and non-resonant contributions at
the perturbative order are taken into account,
including irreducible backgrounds to production, interferences and
off-shell effects of the top quark and the gauge boson. We extensively
investigate the dependence of our results upon variation of renormalisation and
factorisation scales and parton distribution functions in the quest for an
accurate estimate of the theoretical uncertainties. Additionally, we explore a
few possibilities for a dynamical scale choice with the goal of stabilizing the
perturbative convergence of the differential cross sections far away from the
threshold. Results presented here are particularly relevant for
searches of new physics as well as for precise measurements of the top-quark
fiducial cross sections and top-quark properties at the LHC.Comment: 51 pages, 36 figures, 6 tables, version to appear in JHE
Rigid invariance as derived from BRS invariance: The abelian Higgs model
Consequences of a symmetry, e.g.\ relations amongst Green functions, are
renormalization scheme independently expressed in terms of a rigid Ward
identity. The corresponding local version yields information on the respective
current. In the case of spontaneous breakdown one has to define the theory via
the BRS invariance and thus to construct rigid and current Ward identity
non-trivially in accordance with it. We performed this construction to all
orders of perturbation theory in the abelian Higgs model as a prelude to the
standard model. A technical tool of interest in itself is the use of a doublet
of external scalar ``background'' fields. The Callan-Symanzik equation has an
interesting form and follows easily once the rigid invariance is established.Comment: 33 pages, Plain Te
Chiral black hole in three-dimensional gravitational Chern-Simons
A chiral black hole can be defined from the three-dimensional pure
gravitational Chern-Simons action as an independent gravitational theory. The
third order derivative of the Cotton tensor gives a dimensional constant which
plays a role of the cosmological constant. The handedness of angular momentum
depends on the signature of the Chern-Simons coefficient. Even in the massless
black hole which corresponds to the static black hole, it has a nonvanishing
angular momentum. We also study statistical entropy and thermodynamic
stability.Comment: 6 pages, a reference added, minor changes to introductio
High maternal androstenedione levels during pregnancy in a small precocial mammal with female genital masculinisation
-Masculinisation of female genitalia is an intriguing phenomenon amongst some mammalian species and its endocrinological basis as well as its adaptive value is still heavily debated. We recently reported female genital masculinisation in Cavia magna. The closely related C. aperea, does not show such masculinisation providing an unique opportunity to investigate potential endocrinological mechanisms underlying this difference. For both species we determined plasma levels of androstenedione and testosterone in adults of both sexes, and in females during different stages of pregnancy. Consistent with the normal mammalian pattern males showed higher levels of both androgens than conspecific females. Androgen profiles during pregnancy differed significantly between C. magna and C. aperea females: during mid-pregnancy androstenedione levels were strongly elevated in the masculinised C. magna, but not in C. aperea, indicating that high levels of this androgen may be involved in the differentiation of masculinized genitalia in female C. magna, as has been suggested for the spotted hyena. In both C. magna and the spotted hyena the pups show a highly advanced state of maturation, but in contrast to the hyena female C. magna are not overly aggressive. We therefore propose that female genital masculinisation might be a side effect of early exposure to elevated levels of maternal androgens that might be selected for to speed up precocial development.
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