141 research outputs found
Record-light weight c-Si modules based on the small unit compound approach : mechanical load tests and general results
The âsmall unit compoundâ (SUC) concept allows the preparation of very light weight c-Si solar laminates utilizing thin glass or plastic materials. A main difference to the common module type is the replacement of the frame at the laminates fringe by a lattice-like structure at the rear or at the rear and front side. Due to the small distances between the mechanical supporting elements which prevent the dishing of the laminate, the stiffness of the laminate itself can be reduced to a minimum. This enables the use of thin glass or alternative materials such as polymer foils. In this paper we present results of mechanical tests with such modules and discuss general results concerning the module lay-out. The paper has a focus on glass/glass and glass/backsheet laminates with glass thicknesses of 0.8, 1.1, 1.6 and 2 mm. A 60 cell glass/backsheet module 0.8 mm front glass with a weight of as low as 6.3 kg (without junction box and cables) has been fabricated. According to our knowledge this is the lowest weight for 60-cell c-Si modules with front glass ever reported. First hail resistance tests show that these modules may surpass the IEC 61215 norm. Only slightly lower weights are possible if alternative materials are used instead of glass for the front side cover
Signature of Electron Capture in Iron-Rich Ejecta of SN 2003du
Late-time near-infrared and optical spectra are presented for the
normal-bright SN2003du. At about 300 days after the explosion, the emission
profiles of well isolated [FeII] lines (in particular that of the strong
1.644mu feature) trace out the global kinematic distribution of radioactive
material in the expanding. In SN2003du, the 1.644 mu [FeII] line shows a
flat-topped, profile, indicative of a thick but hollow-centered expanding
shell, rather than a strongly-peaked profile that would be expected from a
``center-filled'' distribution.Based on detailed models for exploding
Chandrasekhar mass white dwarfs, we show that the feature is consistent with
spherical explosion models.Our model predicts central region of non-radioactive
electron-capture elements up to 2500--3000km/s as a consequence of burning
under high density, and an extended region of 56Ni up to 9,000--10,000km/s.
Furthermore our analysis indicates that the 1.644mu [FeII] profile is not
consistent with strong mixing between the regions of electron- capture isotopes
and the 56Ni layers as is predicted by detailed 3D models for nuclear
deflagration fronts. We discuss the possibility that the flat-topped profile
could be produced as a result of an infrared catastrophe and conclude that such
an explanation is unlikely. We put our results in context to other SNeIa and
briefly discuss the implications of our result for the use of SNe Ia as
cosmological standard candles.Comment: 12 pages + 8 figures, ApJ (in press, Dec. 20, 2004) For high
resolution figures send E-mail to [email protected]
The evolution of ultraviolet emission lines from the circumstellar material surrounding SN 1987A
The presence of narrow high-temperature emission lines from nitrogen-rich gas
close to SN 1987A has been the principal observational constraint on the evolu-
tionary status of the supernova's progenitor. A new analysis of the complete
five-year set of low and high resolution IUE ultraviolet spectra of SN 1987A
(1987.2--1992.3) provide fluxes for the N V 1240, N IV] 1486, He II 1640, OIII]
1665, NIII] 1751, and CIII] 1908 lines with significantly reduced random and
systematic errors and reveals significant short-term fluctuations in the light
curves. The N V, N IV] and N III] lines turn on sequentially over 15 to 20 days
and show a progression from high to low ionization potential, implying an ioni-
zation gradient in the emitting region. The line emission turns on suddenly at
83+/-4 days after the explosion, as defined by N IV]. The N III] line reaches
peak luminosity at 399+/-15 days. A ring radius of (6.24+/-0.20)E{17} cm and
inclination of 41.0+/-3.9 is derived from these times, assuming a circular
ring. The probable role of resonant scattering in the N V light curve
introduces systematic errors that leads us to exclude this line from the timing
analysis. A new nebular analysis yields improved CNO abundance ratios
N/C=6.1+/-1.1 and N/O=1.7+/-0.5, confirming the nitrogen enrichment found in
our previous paper. From the late-time behavior of the light curves we find
that the emission origi- nates from progressively lower density gas. We
estimate the emitting mass near maximum (roughly 400 days) to be roughly
4.7E{-2} solar masses, assuming a filling factor of unity and an electron
density of 2.6E4 cm^{-3}. These results are discussed in the context of current
models for the emission and hydrodynamics of the ring.Comment: 38 pages, AASTeX v.4.0, 13 Postscript figures; ApJ, in pres
Abundances and density structure of the inner circumstellar ring around SN 1987A
We present optical spectroscopic data of the inner circumstellar ring around
SN 1987A from the Anglo-Australian Telescope (AAT) and the Very Large Telescope
(VLT) between ~1400 and ~5000 days post-explosion. We also assembled the
available optical and near-infrared line fluxes from the literature between
~300 and ~2000 days. These line light curves were fitted with a photoionization
model to determine the density structure and the elemental abundances for the
inner ring. We found densities ranging from 1x10^3 to 3x10^4 atoms cm^-3 and a
total mass of the ionized gas of ~0.058 Msun within the inner ring. Abundances
inferred from the optical and near-infrared data were also complemented with
estimates of Lundqvist & Fransson (1996) based on ultraviolet lines. This way
we found an He/H-ratio (by number of atoms) of 0.17+-0.06 which is roughly 30%
lower than previously estimated and twice the solar and the Large Magellanic
Cloud (LMC) value. We found an N/O-ratio of 1.5+-0.7, and the total
(C+N+O)/(H+He) abundance about 1.6 times its LMC value or roughly 0.6 times the
most recent solar value. An iron abundance of 0.20+-0.11 times solar was found
which is within the range of the estimates for the LMC. We also present late
time (~5000 - 7500 days) line light curves of [O III], [Ne III], [Ne IV], [Ar
III], [Ar IV], and [Fe VII] from observations with the VLT. We compared these
with model fluxes and found that an additional 10^2 atoms cm^-3 component was
required to explain the data of the highest ionization lines. Such low density
gas is expected in the H II-region interior to the inner ring which likely
extends also to larger radii at higher latitudes (out of the ring plane). At
epochs later than ~5000 days our models underproduce the emission of most of
these lines as expected due to the contribution from the interaction of the
supernova ejecta with the ring.Comment: 17 pages, 8 figures, accepted for publication in Ap
Beurteilung bestehender Stahltragwerke : Empfehlungen zur AbschÀtzung der restnutzungsdauer
Assessment of existing steel structures: recommendations for estimation of remaining fatigue life. The growing importance of sustainability affects new markets for the construction industry; the rehabilitation and refurbishment of existing buildings and civil engineering works is getting more and more into the focus of construction activities. This also applies to bridges as well where the quality management comprising the full life of a bridge has a long tradition. For bridges in particular the enormous increase of freight-volume on roads and rails and the growing age of the bridges cause the question, whether the existing structures are still fit for use and whether or not they can be retrofitted and if so how that could be done. For decision making concerning measures for maintenance and refurbishment of a bridge or its substitution by a new bridge the value of the residual service life is very important. Therefore the bridge authorities have been cooperating for a long time to develop appropriate methods for determining the residual safety and service life of existing bridges. Also the International Technical-Scientific Organisations as the ECCS and fip as well as Standard Organisations as ISO and CEN have cared for an international exchange of views and the harmonisation of methods. For steel bridges in particular the Technical Committee 6 â Fatigue â of the ECCS has taken over the task to develop a technical guidance for the assessment of existing steel bridges on the grounds of national experiences and the present state of the art. This guidance has been prepared to serve as a basis for CEN/TC 250 â the CEN-Technical Committee responsible for the structural Eurocodes â for future further development of these Eurocodes to include the assessment and retrofitting of existing structures. The result of the development of ECCS-TC 6 is a technical- scientific report which has been published by the Commission of the EU (DG-Research â Joint Research Centre â JRC) in the frame of a cooperation agreement between the JRC and the ECCS. This report may be used as a technical recommendation as long as the revision of the Eurocodes has not been carried out. This contribution gives the main information from the JRC-ECCS report, that can be downloaded free of charge from the e-bookshop of the Commission
HST-COS Observations of Hydrogen, Helium, Carbon and Nitrogen Emission from the SN 1987A Reverse Shock
We present the most sensitive ultraviolet observations of Supernova 1987A to
date. Imaging spectroscopy from the Hubble Space Telescope-Cosmic Origins
Spectrograph shows many narrow (dv \sim 300 km/s) emission lines from the
circumstellar ring, broad (dv \sim 10 -- 20 x 10^3 km/s) emission lines from
the reverse shock, and ultraviolet continuum emission. The high signal-to-noise
(> 40 per resolution element) broad LyA emission is excited by soft X-ray and
EUV heating of mostly neutral gas in the circumstellar ring and outer supernova
debris. The ultraviolet continuum at \lambda > 1350A can be explained by HI
2-photon emission from the same region. We confirm our earlier, tentative
detection of NV \lambda 1240 emission from the reverse shock and we present the
first detections of broad HeII \lambda1640, CIV \lambda1550, and NIV]
\lambda1486 emission lines from the reverse shock. The helium abundance in the
high-velocity material is He/H = 0.14 +/- 0.06. The NV/H-alpha line ratio
requires partial ion-electron equilibration (T_{e}/T_{p} \approx 0.14 - 0.35).
We find that the N/C abundance ratio in the gas crossing the reverse shock is
significantly higher than that in the circumstellar ring, a result that may be
attributed to chemical stratification in the outer envelope of the supernova
progenitor. The N/C abundance ratio may have been stratified prior to the ring
expulsion, or this result may indicate continued CNO processing in the
progenitor subsequent to the expulsion of the circumstellar ring.Comment: 12 pages, 8 figures. ApJ - accepte
Recommended from our members
Bootstrapped Biocatalysis: Biofilm-Derived Materials as Reversibly Functionalizable Multienzyme Surfaces
Cell-free biocatalysis systems offer many benefits for chemical manufacturing, but their widespread applicability is hindered by high costs associated with enzyme purification, modification, and immobilization on solid substrates, in addition to the cost of the material substrates themselves. Here we report a âbootstrappedâ biocatalysis substrate material that is produced directly in bacterial culture and is derived from biofilm matrix proteins, which self-assemble into a nanofibrous mesh. We demonstrate that this material can simultaneously purify and immobilize multiple enzymes site-specifically, and directly from crude cell lysates using a panel of genetically programmed, mutually orthogonal conjugation domains. We further demonstrate the utility of the technique in a bi- enzymatic stereoselective reduction coupled with cofactor recycling scheme. The domains allow for several cycles of selective removal and replacement of enzymes under mild conditions to regenerate the catalyst system.Engineering and Applied Science
Factor VIII/protein C ratio independently predicts liver-related events but does not indicate a hypercoagulable state in ACLD
Background & Aims: It has been suggested that the ratio of procoagulant factor VIII to anticoagulant protein C (FVIII/PC) reflects the hemostatic equilibrium. Moreover, FVIII/PC predicted decompensation/death in a small study not accounting for portal hypertension severity. We investigated (i) the prognostic value of FVIII/PC (outcome-cohort) and (ii) whether FVIII/PC reflects the hypercoagulable state (assessed by thrombomodulin-modified thrombin generation assay [TM-TGA]) or the risk of bleeding/thrombotic events in patients undergoing hepatic venous pressure gradient (HVPG) measurement during follow-up. Methods: (i) The outcome-cohort comprised 576 patients with evidence of advanced chronic liver disease (liver stiffness measurement â„10 kPa and/or HVPG â„6 mmHg). (ii) TM-TGA-cohort patients (n = 142) were recruited from the prospective VIenna CIrrhosis Study (VICIS: NCT03267615). Results: (i) FVIII/PC significantly increased across clinical stages (p <0.001) as well as HVPG (p <0.001) and MELD score (p <0.001) strata and remained independently associated with decompensation/liver-related death (adjusted hazard ratio 1.06; 95% CI 1.01â1.11; p = 0.013), even after multivariable adjustment. It was also associated with acute-on-chronic liver failure (ACLF) development (adjusted hazard ratio 1.10; 95% CI 1.02-1.19; p = 0.015) in patients with decompensated cirrhosis. (ii) FVIII/PC showed a weak positive correlation with endogenous thrombin potential (Spearman's Ï = 0.255; p = 0.002), but this association disappeared after adjusting for the severity of liver disease. FVIII/PC was not associated with the development of bleeding (p = 0.272) or thrombotic events (p = 0.269). However, FVIII/PC correlated with biomarkers of different pathophysiological mechanisms that promote liver disease progression. Conclusion: FVIII/PC provides prognostic information regarding hepatic decompensation/death and ACLF, independently of established prognostic indicators. However, this is not evidence that hypercoagulability drives disease progression, as the correlation between FVIII/PC and thrombin generation is confounded by liver disease severity and FVIII/PC was not associated with thrombosis. Therefore, FVIII/PC does not reflect coagulation and results from previous studies on FVIII/PC require re-interpretation. Clinical trial number: NCT03267615 (in part). Lay summary: A balanced coagulation system is essential for preventing bleeding episodes and blood clot formation (thrombosis). Blood of patients with advanced liver disease may have increased coagulation potential, possibly promoting the worsening of liver disease via thrombosis in the blood vessels of the liver. The ratio between the results of 2 blood tests (procoagulant factor VIII to anticoagulant protein C) has been suggested to reflect these increases in coagulation potential. Our study demonstrates, on the one hand, that this ratio is a versatile predictor of the development of complications of cirrhosis, yet on the other hand, that it is unrelated to coagulation
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