591 research outputs found
Mutations in SCG10 Are Not Involved in Hirschsprung Disease
Hirschsprung disease (HSCR) is a congenital malformation characterized by the absence of enteric neurons in the distal part of the colon. Several genes have been implicated in the development of this disease that together account for 20% of all cases, implying that other genes are involved. Since HSCR is frequently associated with other congenital malformations, the functional characterization of the proteins encoded by the genes involved in these syndromes can provide insights into the protein-network involved in HSCR development. Recently, we found that KBP, encoded by the gene involved in a HSCR- associated syndrome called Goldberg-Shprintzen syndrome, interacts with SCG10, a stathmin-like protein. To determine if SCG10 is involved in the etiology of HSCR, we determined SCG10 expression levels during development and screened 85 HSCR patients for SCG10 mutations. We showed that SCG10 expression increases during development but no germline mutation was found in any of these patients. In conclusion, this study shows that SCG10 is not directly implicated in HSCR development. However, an indirect involvement of SCG10 cannot be ruled out as this can be due to a secondary effect caused by its direct interactors
The Fading Optical Counterpart of GRB~970228, Six Months and One Year Later
We report on observations of the fading optical counterpart of the gamma-ray
burst GRB 970228, made with the Hubble Space Telescope STIS CCD approximately
six months after outburst and with the HST/NICMOS and Keck/NIRC approximately
one year after outburst. The unresolved counterpart is detected by STIS at
V=28.0 +/- 0.25, consistent with a continued power-law decline with exponent
-1.14 +/- 0.05. The counterpart is located within, but near the edge of, a
faint extended source with diameter ~0."8 and integrated magnitude V=25.8 +/-
0.25. A reanalysis of HST and NTT observations performed shortly after the
burst shows no evidence of proper motion of the point source or fading of the
extended emission. Only the extended source is visible in the NICMOS images
with a magnitude of H=23.3 +/- 0.1. The Keck observations find K = 22.8 +/-
0.3. Several distinct and independent means of deriving the foreground
extinction in the direction of GRB 970228 all agree with A_V = 0.75 +/- 0.2.
After adjusting for Galactic extinction, we find that the size of the observed
extended emission is consistent with that of galaxies of comparable magnitude
found in the Hubble Deep Field (HDF) and other deep HST images. Only 2% of the
sky is covered by galaxies of similar or greater surface brightness; therefore
the extended source is almost certainly the host galaxy. Additionally, we find
that the extinction-corrected V - H and V - K colors of the host are as blue as
any galaxy of comparable or brighter magnitude in the HDF. Taken in concert
with recent observations of GRB 970508, GRB 971214, and GRB 980703 our work
suggests that all four GRBs with spectroscopic identification or deep
multicolor broad-band imaging of the host lie in rapidly star-forming galaxies.Comment: 24 pages, Latex, 4 PostScript figures, to appear in the May 10 issue
of The Astrophysical Journal (Note: displayed abstract is abridged
Compact object coalescence rate estimation from short gamma-ray burst observations
Recent observational and theoretical results suggest that Short-duration
Gamma-Ray Bursts (SGRBs) are originated by the merger of compact binary systems
of two neutron stars or a neutron star and a black hole. The observation of
SGRBs with known redshifts allows astronomers to infer the merger rate of these
systems in the local universe. We use data from the SWIFT satellite to estimate
this rate to be in the range -1500 Gpcyr. This result
is consistent with earlier published results which were obtained through
alternative approaches. We estimate the number of coincident observations of
gravitational-wave signals with SGRBs in the advanced gravitational-wave
detector era. By assuming that all SGRBs are created by neutron star-neutron
star (neutron star-black hole) mergers, we estimate the expected rate of
coincident observations to be in the range to 1 ( to 3)
yr.Comment: 23 pages, 3 figures, version accepted for publicatio
SchussenAktivplus: reduction of micropollutants and of potentially pathogenic bacteria for further water quality improvement of the river Schussen, a tributary of Lake Constance, Germany
The project focuses on the efficiency of combined technologies to reduce the release of micropollutants and bacteria into surface waters via sewage treatment plants of different size and via stormwater overflow basins of different types. As a model river in a highly populated catchment area, the river Schussen and, as a control, the river Argen, two tributaries of Lake Constance, Southern Germany, are under investigation in this project. The efficiency of the different cleaning technologies is monitored by a wide range of exposure and effect analyses including chemical and microbiological techniques as well as effect studies ranging from molecules to communities
Data-Driven Regionalization of Decarbonized Energy Systems for Reflecting Their Changing Topologies in Planning and Optimization
The decarbonization of energy systems has led to a fundamental change in their topology since generation is shifted to locations with favorable renewable conditions. In planning, this change is reflected by applying optimization models to regions within a country to optimize the distribution of generation units and to evaluate the resulting impact on the grid topology. This paper proposes a globally applicable framework to find a suitable regionalization for energy system models with a data-driven approach. Based on a global, spatially resolved database of demand, generation, and renewable profiles, hierarchical clustering with fine-tuning is performed. This regionalization approach is applied by modeling the resulting regions in an optimization model including a synthesized grid. In an exemplary case study, South Africa’s energy system is examined. The results show that the data-driven regionalization is beneficial compared to the common approach of using political regions. Furthermore, the results of a modeled 80% decarbonization until 2045 demonstrate that the integration of renewable energy sources fundamentally changes the role of regions within South Africa’s energy system. Thereby, the electricity exchange between regions is also impacted, leading to a different grid topology. Using clustered regions improves the understanding and analysis of regional transformations in the decarbonization process
Quantum Mechanics of Yano tensors: Dirac equation in curved spacetime
In spacetimes admitting Yano tensors the classical theory of the spinning
particle possesses enhanced worldline supersymmetry. Quantum mechanically
generators of extra supersymmetries correspond to operators that in the
classical limit commute with the Dirac operator and generate conserved
quantities. We show that the result is preserved in the full quantum theory,
that is, Yano symmetries are not anomalous. This was known for Yano tensors of
rank two, but our main result is to show that it extends to Yano tensors of
arbitrary rank. We also describe the conformal Yano equation and show that is
invariant under Hodge duality. There is a natural relationship between Yano
tensors and supergravity theories. As the simplest possible example, we show
that when the spacetime admits a Killing spinor then this generates Yano and
conformal Yano tensors. As an application, we construct Yano tensors on
maximally symmetric spaces: they are spanned by tensor products of Killing
vectors.Comment: 1+32 pages, no figures. Accepted for publication on Classical and
Quantum Gravity. New title and abstract. Some material has been moved to the
Appendix. Concrete formulas for Yano tensors on some special holonomy
manifolds have been provided. Some corrections included, bibliography
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Delay Times and Rates for Type Ia Supernovae and Thermonuclear Explosions from Double-detonation Sub-Chandrasekhar Mass Models
We present theoretical delay times and rates of thermonuclear explosions that
are thought to produce Type Ia supernovae, including the double-detonation
sub-Chandrasekhar mass model, using the population synthesis binary evolution
code StarTrack. If detonations of sub-Chandrasekhar mass carbon-oxygen white
dwarfs following a detonation in an accumulated layer of helium on the white
dwarf's surface ("double-detonation" models) are able to produce thermonuclear
explosions which are characteristically similar to those of SNe Ia, then these
sub-Chandrasekhar mass explosions may account for at least some substantial
fraction of the observed SN Ia rate. Regardless of whether all
double-detonations look like 'normal' SNe Ia, in any case the explosions are
expected to be bright and thus potentially detectable. Additionally, we find
that the delay time distribution of double-detonation sub-Chandrasekhar mass
SNe Ia can be divided into two distinct formation channels: the 'prompt'
helium-star channel with delay times <500 Myr (~10% of all sub-Chandras), and
the 'delayed' double white dwarf channel, with delay times >800 Myr spanning up
to a Hubble time (~90%). These findings coincide with recent
observationally-derived delay time distributions which have revealed that a
large number of SNe Ia are prompt with delay times <500 Myr, while a
significant fraction also have delay times spanning ~1 Gyr to a Hubble time.Comment: MNRAS Accepted: 13 pages, shortened text, now 3 figure
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