1,347 research outputs found
Book Review: Physical chemistry and biology
Book Title:Â Physical chemistry and biologyPp. xiv + 367. ÂŁ4.0.0. Maidenhead, Berks.: Edward Arnold. 1968
Drought feeding studies with cattle and sheep. 2. The use of sorghum silage with and without urea as a drought fodder for cattle
Four groups each of seven maiden Hereford heifers 15-18 months old were confined in bare yards and fed a basal ration of sorghum silage with and without a urea supplement. Heifers which received ad lib. silage with urea showed normal behaviour; un-supplemented animals on ad lib. silage became lethargic, apathetic and dejected
Wormhole phase in the RST model
We show that the RST model describing the exactly soluble black hole model
can have a dynamical wormhole solution along with an appropriate boundary
condition. The necessary exotic matter which is usually negative energy density
is remarkably produced by the quantization of the infalling matter fields. Then
the asymptotic geometry in the past is two-dimensional anti-de Sitter(AdS),
which implies the exotic matter is negative. As time goes on, the wormhole
eventually evolves into the black hole and its Hawking radiation appears. The
throat of the static RST wormhole is lower-bounded but in the presence of
infalling matter it collapses to a black hole.Comment: v1. REVTeX3, 12 pages and 1 figure; v2. JHEP3, 10 pages and 1 figure,
version published in JHE
Densitometry and Thermometry of Starburst Galaxies
With a goal toward deriving the physical conditions in external galaxies, we
present a survey of formaldehyde (H2CO) and ammonia (NH3) emission and
absorption in a sample of starburst galaxies using the Green Bank Telescope. By
extending well-established techniques used to derive the spatial density in
star formation regions in our own Galaxy, we show how the relative intensity of
the 1(10)-1(11) and 2(11)-2(12) K-doublet transitions of H2CO can provide an
accurate densitometer for the active star formation environments found in
starburst galaxies (c.f. Mangum et al. 2008). Similarly, we employ the
well-established technique of using the relative intensities of the (1,1),
(2,2), and (4,4) transitions of NH3 to derive the kinetic temperature in
starburst galaxies. Our measurements of the kinetic temperature constrained
spatial density in our starburst galaxy sample represent the first mean density
measurements made toward starburst galaxies. We note a disparity between
kinetic temperature measurements derived assuming direct coupling to dust and
those derived from our NH3 measurements which points to the absolute need for
direct gas kinetic temperature measurements using an appropriate molecular
probe. Finally, our spatial density measurements point to a rough constancy to
the spatial density (10^{4.5} to 10^{5.5} cm^{-3}) in our starburst galaxy
sample. This implies that the Schmidt-Kennicutt relation between L_{IR} and
M_{dense}: (1) Is a measure of the dense gas mass reservoir available to form
stars, and (2) Is not directly dependent upon a higher average density driving
the star formation process in the most luminous starburst galaxies.Comment: 4 pages, to appear in proceedings of The 5th Zermatt ISM Symposiu
STM study of multiband superconductivity in NbSe2 using a superconducting tip
We present a method to produce superconducting tips to be used in Scanning
Tunneling Microscopy/Spectroscopy experiments. We use these tips to investigate
the evolution of the electronic density of states of NbSe2 from 0.3K up to its
critical temperature (7.2K). The use of a superconducting tip (Pb) as
ounterelectrode provides an enhancement of the different features related to
the DOS of NbSe2 in the tunneling conductance curves, along all the studied
thermal range. The analysis of the experimental results gives evidence of the
presence of multiband superconductivity in NbSe2.Comment: 5 pages, 5 figures, PDF fil
The E-ELT Multi-Object Spectrograph: latest news from MOSAIC
There are 8000 galaxies, including 1600 at z larger than 1.6, which could be
simultaneously observed in an E-ELT field of view of 40 sq. arcmin. A
considerable fraction of astrophysical discoveries require large statistical
samples, which can only be obtained with multi-object spectrographs (MOS).
MOSAIC will provide a vast discovery space, enabled by a multiplex of 200 and
spectral resolving powers of R=5000 and 20000. MOSAIC will also offer the
unique capability of more than 10 "high-definition" (multi-object adaptive
optics, MOAO) integral-field units, optimised to investigate the physics of the
sources of reionization. The combination of these modes will make MOSAIC the
world-leading MOS facility, contributing to all fields of contemporary
astronomy, from extra-solar planets, to the study of the halo of the Milky Way
and its satellites, and from resolved stellar populations in nearby galaxies
out to observations of the earliest "first-light" structures in the Universe.
It will also study the distribution of the dark and ordinary matter at all
scales and epochs of the Universe. Recent studies of critical technical issues
such as sky-background subtraction and MOAO have demonstrated that such a MOS
is feasible with state-of-the-art technology and techniques. Current studies of
the MOSAIC team include further trade-offs on the wavelength coverage, a
solution for compensating for the non-telecentric new design of the telescope,
and tests of the saturation of skylines especially in the near-IR bands. In the
2020s the E-ELT will become the world's largest optical/IR telescope, and we
argue that it has to be equipped as soon as possible with a MOS to provide the
most efficient, and likely the best way to follow-up on James Webb Space
Telescope (JWST) observations.Comment: 10 pages, 3 Figures, in Ground-based and Airborne Instrumentation for
Astronomy VI, 2016, Proc. SPI
Classical and Quantum Strings in compactified pp-waves and Godel type Universes
We consider Neveu-Schwarz pp-waves with spacetime supersymmetry. Upon
compactification of a spacelike direction, these backgrounds develop Closed
Null Curves (CNCs) and Closed Timelike Curves (CTCs), and are U-dual to
supersymmetric Godel type universes. We study classical and quantum strings in
this background, with emphasis on the strings winding around the compact
direction. We consider two types of strings: long strings stabilized by NS flux
and rotating strings which are stabilized against collapse by angular momentum.
Some of the latter strings wrap around CNCs and CTCs, and are thus a potential
source of pathology. We analyze the partition function, and in particular
discuss the effects of these string states. Although our results are not
conclusive, the partition function seems to be dramatically altered due to the
presence of CNCs and CTCs. We discuss some interpretations of our results,
including a possible sign of unitary violation.Comment: 42 pages, LaTeX, 2 figure
On Traversable Lorentzian Wormholes in the Vacuum Low Energy Effective String Theory in Einstein and Jordan Frames
Three new classes (II-IV) of solutions of the vacuum low energy effective
string theory in four dimensions are derived. Wormhole solutions are
investigated in those solutions including the class I case both in the Einstein
and in the Jordan (string) frame. It turns out that, of the eight classes of
solutions investigated (four in the Einstein frame and four in the
corresponding string frame), massive Lorentzian traversable wormholes exist in
five classes. Nontrivial massless limit exists only in class I Einstein frame
solution while none at all exists in the string frame. An investigation of test
scalar charge motion in the class I solution in the two frames is carried out
by using the Plebanski-Sawicki theorem. A curious consequence is that the
motion around the extremal zero (Keplerian) mass configuration leads, as a
result of scalar-scalar interaction, to a new hypothetical "mass" that confines
test scalar charges in bound orbits, but does not interact with neutral test
particles.Comment: 18 page
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