544 research outputs found
Gamma ray burst distances and the timescape cosmology
Gamma ray bursts can potentially be used as distance indicators, providing
the possibility of extending the Hubble diagram to redshifts ~7. Here we follow
the analysis of Schaefer (2007), with the aim of distinguishing the timescape
cosmological model from the \LambdaCDM model by means of the additional
leverage provided by GRBs in the range 2 < z < 7. We find that the timescape
model fits the GRB sample slightly better than the \LambdaCDM model, but that
the systematic uncertainties are still too little understood to distinguish the
models.Comment: 7 pages, 7 figures, revised version accepted for publication in MNRA
Practice makes perfect: a review of banking in Central and Eastern Europe
Planned economies produced many goods and services - such as cars, electricity, and machinery - that did not differ fundamentally from those available in market economies. Certainly, the quality and variety of these goods and services did not reach Western standards and there was an almost perennial mismatch between demand and supply, with an excess demand for many goods and an over-supply of others. Yet, there was a supply of cars, electricity, machinery, and the like. This cannot be said about banking services, or finance in general, as known in market economies. For sure, there were financial flows and payments. But to the extent that they accompanied investment, they largely followed real resources that had been allocated before under the central plan, which - in turn - saw no need for key banking functions such as transforming assets, managing risks, and processing information on and monitoring of borrowers. In creating market-driven banking sectors, all Central and Eastern European accession countries (CEECs) (1) encountered similar problems, notably a substantial amount of bad loans inherited from the communist past and the accumulation of new non-performing loans in the early years of transition. The latter was due to a combination of factors, in particular an inevitable lack of expertise in commercial banking, continued lending of incumbent banks to enterprises from the communist past with a doubtful future in an open economy, imprudent or fraudulent lending by a rapidly growing number of new banks, and - last but not least - weak banking sector regulation and supervision
BVRI Light Curves for 22 Type Ia Supernovae
We present 1210 Johnson/Cousins B,V,R, and I photometric observations of 22
recent type Ia supernovae (SNe Ia): SN 1993ac, SN 1993ae, SN 1994M, SN 1994S,
SN 1994T, SN 1994Q, SN 1994ae, SN 1995D, SN 1995E, SN 1995al, SN 1995ac, SN
1995ak, SN 1995bd, SN 1996C, SN 1996X, SN 1996Z, SN 1996ab, SN 1996ai, SN
1996bk, SN 1996bl, SN 1996bo, and SN 1996bv. Most of the photometry was
obtained at the Fred Lawrence Whipple Observatory (FLWO) of the
Harvard-Smithsonian Center for Astrophysics in a cooperative observing plan
aimed at improving the data base for SN Ia. The redshifts of the sample range
from =1200 to 37000 km s with a mean of =7000 km s.Comment: Accepted to the Astronomical Journal, 41 pages, 8 figure
The liquid penetration of diesel substitutes
[EN] Diesel fuel consist of several hundreds of substances on organic basis. Experimental and numerical investigations
of this multicomponent fuel are hard to interpret in detail, since the behavior of the multicomponent mixture is
complex. Physical and chemical data of this system is not available under engine relevant conditions. Instead,
fundamental research substitutes diesel with pure substances, where a big database exists.
Prior work already showed, that overall spray propagation (including vapor phase) is nearly independent on the
injected fuel. This is due to the high air entrainment at present diesel engine conditions (very high injection pressure
and dense ambient atmosphere). The high air entrainment shortly behind the nozzle exit (within the first 5 mm
penetration) creates a situation where properties of the ambient gas dominate the spray propagation resulting in
similar mass and momentum distributions even for different fuels, if the injection conditions are kept constant. On
the other hand, the liquid length is clearly different for different fuels, so that location and time of the phase change
differ with consequences on the time available for mixture formation in the gas phase. The paper describes the
liquid length as a function of the enthalpy necessary for the phase transition (given by the fuel and fuel temperature
at injection) and the injection conditions (ambient gas properties, injector design and injection pressure). We
compare two different models describing the enthalpy balance. Siebers et al. presented âModel Iâ, where mass
transfer dominates the enthalpy transfer and evaporation takes place. In our own âModel IIâ evaporation is
suppressed, resulting in a heat transfer driven enthalpy transfer without mass transport. The calculations are
validated with experimental data.
The liquid length is optically accessible by Mie-Scattering imaging techniques, the complete spray evolution by
Schlieren technique. The experimental study was carried out in the high-pressure combustion vessel âOptiVePâ at
FAU. The data shown in this paper derived from measurements with dodecane injected at 1200 bar into 613 K
ambient. The ambient pressure varies from 1 â 10 MPa. A Continental research injector with a 115 ”m hole and
L/D of 6.5 was used. Nitrogen atmosphere suppressed ignition.
Increasing the ambient pressure leads to a change in the mechanism in phase transition. It switches from a mass
transfer dominated regime to a heat transfer dominated regime at high ambient pressures.Riess, S.; Weiss, L.; Rezaei, J.; Peter, A.; Wensing, M. (2017). The liquid penetration of diesel substitutes. En Ilass Europe. 28th european conference on Liquid Atomization and Spray Systems. Editorial Universitat PolitĂšcnica de ValĂšncia. 1060-113. https://doi.org/10.4995/ILASS2017.2017.4764OCS106011
Constraints on Type Ia Supernova Progenitor Companions from Early Ultraviolet Observations with Swift
We compare early ultraviolet (UV) observations of Type Ia Supernovae (SNe Ia)
with theoretical predictions for the brightness of the shock associated with
the collision between SN ejecta and a companion star. Our simple method is
independent of the intrinsic flux from the SN and treats the flux observed with
the Swift/Ultra-Violet Optical Telescope (UVOT) as conservative upper limits on
the shock brightness. Comparing this limit with the predicted flux for various
shock models, we constrain the geometry of the SN progenitor-companion system.
We find the model of a 1 M_sun red supergiant companion in Roche lobe overflow
to be excluded at a 95% confidence level for most individual SNe for all but
the most unfavorable viewing angles. For the sample of 12 SNe taken together,
the upper limits on the viewing angle are inconsistent with the expected
distribution of viewing angles for RG stars as the majority of companions with
high confidence. The separation distance constraints do allow MS companions. A
better understanding of the UV flux arising from the SN itself as well as
continued UV observations of young SNe Ia will further constrain the possible
progenitors of SNe Ia.Comment: accepted versio
Quantification of mixture composition, liquid-phase fraction and temperature in transcritical sprays
How do fuel and air mix, if a liquid fuel is injected into an environment featuring pressure and temperature that exceed the critical pressure and the critical temperature of the fuel? It is subject of current discussion on whether and if so when, the fuel/air-mixture becomes supercritical or not. We here report experimental data comprising three mixture properties that are relevant for the current debate, all spatially and temporally resolved throughout the spray and injection event: The overall composition of the fuel/air-mixture, the liquid fraction of the fuel/air-mixture, and the temperature of the liquid phase. To this end, we applied Raman spectroscopy and gave special attention to the signature of the Raman OH-band of ethanol, which we used as fuel. Its signature is connected to the development of a hydrogen bonded network between the ethanol molecules and thus extremely sensitive to thermodynamic state and temperature. Measurements were carried out in a high-pressure, high-temperature combustion vessel in a pressure range of 3â8âŻMPa and a temperature range of 573â923âŻK. For the highest set temperature we found ethanol in liquid-like mixtures that exceeded the mixture critical temperature. This is an indication of the existence of a single-phase mixing path
Near-Ultraviolet Properties of a Large Sample of Type Ia Supernovae as Observed with the Swift UVOT
We present ultraviolet (UV) and optical photometry of 26 Type Ia supernovae
(SNe~Ia) observed from March 2005 to March 2008 with the NASA {\it Swift}
Ultraviolet and Optical Telescope (UVOT). The dataset consists of 2133
individual observations, making it by far the most complete study of the UV
emission from SNe~Ia to date. Grouping the SNe into three subclasses as derived
from optical observations, we investigate the evolution of the colors of these
SNe, finding a high degree of homogeneity within the normal subclass, but
dramatic differences between that group and the subluminous and SN 2002cx-like
groups. For the normal events, the redder UV filters on UVOT (, ) show
more homogeneity than do the bluer UV filters (, ). Searching for
purely UV characteristics to determine existing optically based groupings, we
find the peak width to be a poor discriminant, but we do see a variation in the
time delay between peak emission and the late, flat phase of the light curves.
The UV light curves peak a few days before the band for most subclasses (as
was previously reported by Jha et al. 2006a), although the SN 2002cx-like
objects peak at a very early epoch in the UV. That group also features the
bluest emission observed among SNe~Ia. As the observational campaign is
ongoing, we discuss the critical times to observe, as determined by this study,
in order to maximize the scientific output of future observations.Comment: Accepted to Astrophysical Journa
A Mismatch in the Ultraviolet Spectra between Low-Redshift and Intermediate-Redshift Type Ia Supernovae as a Possible Systematic Uncertainty for Supernova Cosmology
We present Keck high-quality rest-frame ultraviolet (UV) through optical
spectra of 21 Type Ia supernovae (SNe Ia) in the redshift range 0.11 < z < 0.37
and a mean redshift of 0.22 that were discovered during the Sloan Digital Sky
Survey-II (SDSS-II) SN Survey. Using the broad-band photometry of the SDSS
survey, we are able to reconstruct the SN host-galaxy spectral energy
distributions (SEDs), allowing for a correction for the host-galaxy
contamination in the SN Ia spectra. Comparison of composite spectra constructed
from a subsample of 17 high-quality spectra to those created from a
low-redshift sample with otherwise similar properties shows that the Keck/SDSS
SNe Ia have, on average, extremely similar rest-frame optical spectra but show
a UV flux excess. This observation is confirmed by comparing synthesized
broad-band colors of the individual spectra, showing a difference in mean
colors at the 2.4 - 4.4 sigma level for various UV colors. We further see a
slight difference in the UV spectral shape between SNe with low-mass and
high-mass host galaxies. Additionally, we detect a relationship between the
flux ratio at 2770 and 2900 A and peak luminosity that differs from that
observed at low redshift. We find that changing the UV SED of an SN Ia within
the observed dispersion can change the inferred distance moduli by ~0.1 mag.
This effect only occurs when the data probe the rest-frame UV. We suggest that
this discrepancy could be due to differences in the host-galaxy population of
the two SN samples or to small-sample statistics.Comment: 28 pages, 21 figures, accepted by AJ, spectra are available at
http://www.cfa.harvard.edu/~rfoley/data
Genetic dissection of apoptosis and cell cycle control in response of colorectal cancer treated with preoperative radiochemotherapy
BACKGROUND: In previous analyses we identified therapy-induced upregulation of the CDK inhibitor p21(CIP/WAF-1 )and consequently decreased tumor cell proliferation or loss of Bax as adverse factors for survival in rectal cancer treated with radiochemotherapy. Here, we address the individual role of p53 and its transcriptional targets, p21(CIP/WAF-1 )and Bax, on apoptosis induced by individual components of multimodal anticancer therapy, i.e. 5-fluorouracil (5-FU), ionising γ-radiation (IR) and heat shock/hyperthermia. METHODS: We analysed tumor samples 66 patients with rectal carcinoma treated by a neoadjuvant approach with radiochemotherapy ± heat shock/hyperthermia for the expression and mutation of p53 and the expression of p21(CIP/WAF-1 )and Bax. These data were correlated with the tumor response. The functional relevance of p53, p21(CIP/WAF-1 )and Bax was investigated in isogeneic HCT116 cell mutants treated with 5-FU, IR and heat shock. RESULTS: Rectal carcinoma patients who received an optimal heat shock treatment showed a response that correlated well with Bax expression (p = 0.018). Local tumor response in the whole cohort was linked to expression of p21(CIP/WAF-1 )(p < 0.05), but not p53 expression or mutation. This dichotomy of p53 pathway components regulating response to therapy was confirmed in vitro. In isogeneic HCT116 cell mutants, loss of Bax but not p53 or p21(CIP/WAF-1 )resulted in resistance against heat shock. In contrast, loss of p21(CIP/WAF-1 )or, to a lesser extent, p53 sensitized predominantly for 5-FU and IR. CONCLUSION: These data establish a different impact of p53 pathway components on treatment responses. While chemotherapy and IR depend primarily on cell cycle control and p21, heat shock depends primarily on Bax. In contrast, p53 status poorly correlates with response. These analyses therefore provide a rational approach for dissecting the mode of action of single treatment modalities that may be employed to circumvent clinically relevant resistance mechanisms in rectal cancer
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