2,650 research outputs found
Planting Trees on Kansas Prairies
Kansas always has been and always will be essentially a prairie state. But every year brings more convincing proof that her plains need not always remain treeless. Each planting season sees new effort put forth to beautify the Western Kansas homes and divest fhe plains of their traditional bleakness
Progress of Forestry Extension in Iowa
Interest and activity in forestry for Iowa is increasing definitely. A brief summary of last year\u27s forestry extension program appears something as follows
V723 Cas (Nova Cassiopeiae 1995): MERLIN observations from 1996 to 2001
MERLIN observations of the unusually slow nova V723 Cas are presented. Nine
epochs of 6-cm data between 1996 and 2001 are mapped, showing the initial
expansion and brightening of the radio remnant, the development of structure
and the final decline. A radio light curve is presented and fitted by the
standard Hubble flow model for radio emission from novae in order to determine
the values of various physical parameters for the shell. The model is
consistent with the overall development of the radio emission. Assuming a
distance of 2.39 (+/-0.38) kpc and a shell temperature of 17000 K, the model
yields values for expansion velocity of 414 +/- 0.1 km s^-1 and shell mass of
1.13 +/- 0.04 * 10^-4 Msolar. These values are consistent with those derived
from other observations although the ejected masses are rather higher than
theoretical predictions. The structure of the shell is resolved by MERLIN and
shows that the assumption of spherical symmetry in the standard model is
unlikely to be correct.Comment: 6 pages, 6 figure
Properties of Accretion Flows Around Coalescing Supermassive Black Holes
What are the properties of accretion flows in the vicinity of coalescing
supermassive black holes (SBHs)? The answer to this question has direct
implications for the feasibility of coincident detections of electromagnetic
(EM) and gravitational wave (GW) signals from coalescences. Such detections are
considered to be the next observational grand challenge that will enable
testing general relativity in the strong, nonlinear regime and improve our
understanding of evolution and growth of these massive compact objects. In this
paper we review the properties of the environment of coalescing binaries in the
context of the circumbinary disk and hot, radiatively inefficient accretion
flow models and use them to mark the extent of the parameter space spanned by
this problem. We report the results from an ongoing, general relativistic,
hydrodynamical study of the inspiral and merger of black holes, motivated by
the latter scenario. We find that correlated EM+GW oscillations can arise
during the inspiral phase followed by the gradual rise and subsequent drop-off
in the light curve at the time of coalescence. While there are indications that
the latter EM signature is a more robust one, a detection of either signal
coincidentally with GWs would be a convincing evidence for an impending SBH
binary coalescence. The observability of an EM counterpart in the hot accretion
flow scenario depends on the details of a model. In the case of the most
massive binaries observable by the Laser Interferometer Space Antenna, upper
limits on luminosity imply that they may be identified by EM searches out to
z~0.1-1. However, given the radiatively inefficient nature of the gas flow, we
speculate that a majority of massive binaries may appear as low luminosity AGN
in the local universe.Comment: Revised version accepted to Class. Quantum Grav. for proceedings of
8th LISA Symposium. 15 pages, 3 figures, includes changes suggested in
referee report
Liverpool Telescope 2: a new robotic facility for time domain astronomy in 2020
The robotic 2m Liverpool Telescope, based on the Canary island of La Palma, has a diverse instrument suite and a strong track record in time domain science, with highlights including early time photometry and spectra of supernovae, measurements of the polarization of gamma-ray burst afterglows, and high cadence light curves of transiting extrasolar planets. In the next decade the time domain will become an increasingly prominent part of the astronomical agenda with new facilities such as LSST, SKA, CTA and Gaia, and promised detections of astrophysical gravitational wave and neutrino sources opening new windows on the transient universe. To capitalise on this exciting new era we intend to build Liverpool Telescope 2: a new robotic facility on La Palma dedicated to time domain science. The next generation of survey facilities will discover large numbers of new transient sources, but there will be a pressing need for follow-up observations for scientific exploitation, in particular spectroscopic follow-up. Liverpool Telescope 2 will have a 4-metre aperture, enabling optical/infrared spectroscopy of faint objects. Robotic telescopes are capable of rapid reaction to unpredictable phenomena, and for fast-fading transients like gamma-ray burst afterglows. This rapid reaction enables observations which would be impossible on less agile telescopes of much larger aperture. We intend Liverpool Telescope 2 to have a world-leading response time, with the aim that we will be taking data with a few tens of seconds of receipt of a trigger from a ground- or space-based transient detection facility. We outline here our scientific goals and present the results of our preliminary optical design studies. © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only
Cystatins as calpain inhibitors: Engineered chicken cystatin- and stefin B-kininogen domain 2 hybrids support a cystatin-like mode of interaction with the catalytic subunit of μ-calpain
Within the cystatin superfamily, only kininogen domain 2 (KD2) is able to inhibit μ- and m-calpain. In an attempt to elucidate the structural requirements of cystatins for calpain inhibition, we constructed recombinant hybrids of human stefin B (an intracellular family 1 cystatin) with KD2 and Delta L110 deletion mutants of chicken cystatin-KD2 hybrids. Substitution of the N-terminal contact region of stefin B by the corresponding KD2 sequence resulted in a calpain inhibitor of K-i = 188 nM. Deletion of L110, which forms a beta -bulge in family 1 and 2 cystatins but is lacking in KD2, improved inhibition of mu -calpain 4- to 8-fold. All engineered cystatins were temporary inhibitors of calpain due to slow substrate-like cleavage of a single peptide bond corresponding to Gly9-Ala10 in chicken cystatin. Biomolecular interaction analysis revealed that, unlike calpastatin, the cystatin-type inhibitors do not bind to the calmodulin-like domain of the small subunit of calpain, and their interaction with the mu -calpain heterodimer is completely prevented by a synthetic peptide comprising subdomain B of calpastatin domain 1. Based on these results we propose that (i) cystatin-type calpain inhibitors interact with the active site of the catalytic domain of calpain in a similar cystatin-like mode as with papain and (ii) the potential for calpain inhibition is due to specific subsites within the papain-binding regions of the general cystatin fold
The circumburst environment of a FRED GRB: study of the prompt emission and X-ray/optical afterglow of GRB 051111
We report a multi-wavelength analysis of the prompt emission and early
afterglow of GRB051111 and discuss its properties in the context of current
fireball models. The detection of GRB051111 by the Burst Alert Telescope
on-board Swift triggered early BVRi' observations with the 2-m robotic Faulkes
Telescope North in Hawaii, as well as X-ray observations with the Swift X-Ray
Telescope. The prompt gamma-ray emission shows a classical FRED profile. The
optical afterglow light curves are fitted with a broken power law, with
alpha_1=0.35 to alpha_2=1.35 and a break time around 12 minutes after the GRB.
Although contemporaneous X-ray observations were not taken, a power law
connection between the gamma-ray tail of the FRED temporal profile and the late
XRT flux decay is feasible. Alternatively, if the X-ray afterglow tracks the
optical decay, this would represent one of the first GRBs for which the
canonical steep-shallow-normal decay typical of early X-ray afterglows has been
monitored optically. We present a detailed analysis of the intrinsic
extinction, elemental abundances and spectral energy distribution. From the
absorption measured in the low X-ray band we find possible evidence for an
overabundance of some alpha elements such as oxygen, [O/Zn]=0.7+/-0.3, or,
alternatively, for a significant presence of molecular gas. The IR-to-X-ray
Spectral Energy Distribution measured at 80 minutes after the burst is
consistent with the cooling break lying between the optical and X-ray bands.
Extensive modelling of the intrinsic extinction suggests dust with big grains
or grey extinction profiles. The early optical break is due either to an energy
injection episode or, less probably, to a stratified wind environment for the
circumburst medium.Comment: accepted to A&A on Nov. 10 (14 pages, 8 figures
String amplitudes in arbitrary dimensions
We calculate gravitational dressed tachyon correlators in non critcal
dimensions. The 2D gravity part of our theory is constrained to constant
curvature. Then scaling dimensions of gravitational dressed vertex operators
are equal to their bare conformal dimensions. Considering the model as d+2
dimensional critical string we calculate poles of generalized Shapiro-Virasoro
amplitudes.Comment: 14 page
Non-perturbative renormalization of quark mass in Nf=2+1 QCD with the Schroedinger functional scheme
We present an evaluation of the quark mass renormalization factor for Nf=2+1
QCD. The Schroedinger functional scheme is employed as the intermediate scheme
to carry out non-perturbative running from the low energy region, where
renormalization of bare mass is performed on the lattice, to deep in the high
energy perturbative region, where the conversion to the renormalization group
invariant mass or the MS-bar scheme is safely carried out. For numerical
simulations we adopted the Iwasaki gauge action and non-perturbatively improved
Wilson fermion action with the clover term. Seven renormalization scales are
used to cover from low to high energy regions and three lattice spacings to
take the continuum limit at each scale. The regularization independent step
scaling function of the quark mass for the Nf=2+1 QCD is obtained in the
continuum limit. Renormalization factors for the pseudo scalar density and the
axial vector current are also evaluated for the same action and the bare
couplings as two recent large scale Nf=2+1 simulations; previous work of the
CP-PACS/JLQCD collaboration, which covered the up-down quark mass range heavier
than MeV and that of PACS-CS collaboration for much lighter
quark masses down to MeV. The quark mass renormalization factor is
used to renormalize bare PCAC masses in these simulations.Comment: 26 pages, 17 Postscript figures. Two tables are update
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