390 research outputs found
Bending of beams of thin sections
The tendency toward economy of material and lightness of structure has long since led to the increased application of beams having large ratios of moment of area W to cross-sectional area F. This paper tries to provide an answer to how thin the beams can be
CooperativityâDriven Reactivity of a Dinuclear Copper Dimethylglyoxime Complex
In this report, we present the dinuclear copper(II) dimethylglyoxime (Hdmg) complex [Cu(Hdmg)(Hdmg)(dmg)] (1), which, in contrast to its mononuclear analogue [Cu(Hdmg)] (2), is subject to a cooperativity-driven hydrolysis. The combined Lewis acidity of both copper centers increases the electrophilicity of the carbon atom in the bridging ÎŒ-OâN=C-group of Hdmg and thus, facilitates the nucleophilic attack of H2O. This hydrolysis yields butane-2,3-dione monoxime (3) and NHOH that, depending on the solvent, is then either oxidized or reduced. In ethanol, NHOH is reduced to NH, yielding acetaldehyde as the oxidation product. In contrast, in CHCN, NHOH is oxidized by Cu to form NO and [Cu(CHCN)4]. Herein are presented the combined synthetic, theoretical, spectroscopic and spectrometric methods that indicate and establish the reaction pathway of this solvent-dependent reaction
Ultrasoft NLL Running of the Nonrelativistic O(v) QCD Quark Potential
Using the nonrelativistic effective field theory vNRQCD, we determine the
contribution to the next-to-leading logarithmic (NLL) running of the effective
quark-antiquark potential at order v (1/mk) from diagrams with one potential
and two ultrasoft loops, v being the velocity of the quarks in the c.m. frame.
The results are numerically important and complete the description of ultrasoft
next-to-next-to-leading logarithmic (NNLL) order effects in heavy quark pair
production and annihilation close to threshold.Comment: 25 pages, 7 figures, 3 tables; minor modifications, typos corrected,
references added, footnote adde
Diagnostic performance of quantitative coronary artery disease assessment using computed tomography in patients with aortic stenosis undergoing transcatheter aortic-valve implantation.
BACKGROUND
Computed tomography angiography (CTA) is a cornerstone in the pre- transcatheter aortic valve replacement (TAVI) assessment. We evaluated the diagnostic performance of CTA and coronary artery calcium score (CACS) for CAD evaluation compared to invasive coronary angiography in a cohort of TAVI patients.
METHODS
In consecutive TAVI patients without prior coronary revascularization and device implants, CAD was assessment by quantitative analysis in CTA. (a) Patients with non-evaluable segments were classified as obstructive CAD. (b) In patients with non-evaluable segments a CACS cut-off of 100 was applied for obstructive CAD. The reference standard was quantitative invasive coronary angiography (QCA, i.e.ââ„â50% stenosis).
RESULTS
100 consecutive patients were retrospectively included, age was 82.3â±â6.5 years and 30% of patients had CAD. In 16% of the patients, adequate visualization of the entire coronary tree (all 16 segments) was possible with CTA, while 84% had at least one segment which was not evaluable for CAD analysis due to impaired image quality. On a per-patient analysis, where patients with low image quality were classified as CAD, CTA showed a sensitivity of 100% (95% CI 88.4-100.0), specificity of 11.4% (95% CI 5.1-21.3), PPV of 32.6% (95% CI 30.8-34.5), NPV of 100% and diagnostic accuracy of 38% (95% CI 28.5-48.3) for obstructive CAD. When applying a combined approach of CTA (in patients with good image quality) and CACS (in patients with low image quality), the sensitivity and NPV remained at 100% and obstructive CAD could be ruled out in 20% of the TAVI patients, versus 8% using CTA alone.
CONCLUSION
In routinely acquired pre-TAVI CTA, the image quality was insufficient in a high proportion of patients for the assessment of the entire coronary artery tree. However, when adding CACS in patients with low image quality to quantitative CTA assessment in patients with good image quality, obstructive CAD could be ruled-out in 1/5 of the patients and may therefore constitute a strategy to streamline pre-procedural workup, and reduce risk, radiation and costs in selected TAVI patients without prior coronary revascularization or device implants
A lower to middle Eocene astrochronology for the Mentelle Basin (Australia) and its implications for the geologic time scale
The geologic time scale for the Cenozoic Era has been notably improved over the last decades by virtue of integrated stratigraphy, combining high-resolution astrochronologies, biostratigraphy and magnetostratigraphy with high-precision radioisotopic dates. However, the middle Eocene remains a weak link. The so-called âEocene time scale gapâ reflects the scarcity of suitable study sections with clear astronomically-forced variations in carbonate content, primarily because large parts of the oceans were starved of carbonate during the Eocene greenhouse. International Ocean Discovery Program (IODP) Expedition 369 cored a carbonate-rich sedimentary sequence of Eocene age in the Mentelle Basin (Site U1514, offshore southwest Australia). The sequence consists of nannofossil chalk and exhibits rhythmic clay content variability. Here, we show that IODP Site U1514 allows for the extraction of an astronomical signal and the construction of an Eocene astrochronology, using 3-cm resolution X-Ray fluorescence (XRF) core scans. The XRF-derived ratio between calcium and iron content (Ca/Fe) tracks the lithologic variability and serves as the basis for our U1514 astrochronology. We present a 16 million-year-long (40-56 Ma) nearly continuous history of Eocene sedimentation with variations paced by eccentricity and obliquity. We supplement the high-resolution XRF data with low-resolution bulk carbon and oxygen isotopes, recording the long-term cooling trend from the Paleocene-Eocene Thermal Maximum (PETM â ca. 56 Ma) into the middle Eocene (ca. 40 Ma). Our early Eocene astrochronology corroborates existing chronologies based on deep-sea sites and Italian land sections. For the middle Eocene, the sedimentological record at U1514 provides a single-site geochemical backbone and thus offers a further step towards a fully integrated Cenozoic geologic time scale at orbital resolution
How many general and inflammatory variables need to be fulfilled when defining sepsis due to the 2003 SCCM/ESICM/ACCP/ATS/SIS definitions in critically ill surgical patients: a retrospective observational study
Nanosilver/DCOIT-containing surface coating effectively and constantly reduces microbial load in emergency room surfaces
Background
Colonization of near-patient surfaces in hospitals plays an important role as a source of healthcare-associated infections. Routine disinfection methods only result in short-term elimination of pathogens.
Aim
To investigate the efficiency of a newly developed antimicrobial coating containing nanosilver in long-term reduction of bacterial burden in hospital surfaces to close the gap between routine disinfection cycles.
Methods
In this prospective, double-blinded trial, frequently touched surfaces of a routinely used treatment room in an emergency unit of a level-I hospital were treated with a surface coating (nanosilver/DCOIT-coated surface, NCS) containing nanosilver particles and another organic biocidal agent (4,5-dichloro-2-octyl-4-isothiazolin-3-one, DCOIT), whereas surfaces of another room were treated with a coating missing both the nanosilver- and DCOIT-containing ingredient and served as control. Bacterial contamination of the surfaces was examined using contact plates and liquid-based swabs daily for a total trial duration of 90 days. After incubation, total microbial counts and species were assessed.
Findings
In a total of 2880 antimicrobial samples, a significant reduction of the overall bacterial load was observed in the NCS room (median: 0.31 cfu/cm2; interquartile range: 0.00â1.13) compared with the control coated surfaces (0.69 cfu/cm2; 0.06â2.00; P 5 cfu/cm2) by 60% (odds ratio 0.38, P < 0.001). No significant difference in species distribution was detected between NCS and control group.
Conclusion
Nanosilver-/DCOIT-containing surface coating has shown efficiency for sustainable reduction of bacterial load of frequently touched surfaces in a clinical setting
Fast and Not-so-Furious: Case Study of the Fast and Faint Type IIb SN 2021bxu
We present photometric and spectroscopic observations and analysis of
SN~2021bxu (ATLAS21dov), a low-luminosity, fast-evolving Type IIb supernova
(SN). SN~2021bxu is unique, showing a large initial decline in brightness
followed by a short plateau phase. With
during the plateau, it is at the lower end of the luminosity distribution of
stripped-envelope supernovae (SE-SNe) and shows a distinct 10 day plateau
not caused by H- or He-recombination. SN~2021bxu shows line velocities which
are at least slower than typical SE-SNe. It is
photometrically and spectroscopically similar to Type IIb SNe during the
photospheric phases of evolution, with similarities to Ca-rich IIb SNe. We find
that the bolometric light curve is best described by a composite model of shock
interaction between the ejecta and an envelope of extended material, combined
with a typical SN~IIb powered by the radioactive decay of Ni. The
best-fit parameters for SN~2021bxu include a Ni mass of , an ejecta mass of
, and an ejecta
kinetic energy of . From the fits to the properties of the extended material of
Ca-rich IIb SNe we find a trend of decreasing envelope radius with increasing
envelope mass. SN~2021bxu has on the low end compared to
SE-SNe and Ca-rich SNe in the literature, demonstrating that SN~2021bxu-like
events are rare explosions in extreme areas of parameter space. The progenitor
of SN~2021bxu is likely a low mass He star with an extended envelope.Comment: 18 pages, 15 figures, submitted to MNRA
Sicherung von DĂ€mmen, Deichen und Stauanlagen : Handbuch fĂŒr Theorie und Praxis ; Vol. V - 2015
Die UniversitĂ€t Siegen beschĂ€ftigt sich seit ĂŒber 15 Jahren wissenschaftlich und im Bereich der anwendungsorientierten Forschung mit diesem Thema und hat dazu mittlerweile fĂŒnf Symposien durchgefĂŒhrt.
Mit der Veröffentlichung soll die langjĂ€hrige Tradition als etablierte wissenschaftliche Plattform mit einem Wissensaustausch auf europĂ€ischer Ebene fortgesetzt werden. Die Bearbeitung dieser Thematik erfolgt auf der Basis der bewĂ€hrten Kooperation zwischen Geotechnik und Wasserbau an der UniversitĂ€t Siegen. Aktuelle Ereignisse, wie z.B. die aus England oder Australien im Februar des Jahres 2014, machen uns aber auch deutlich, dass ein absoluter Schutz gegen Extremereignisse nicht möglich ist. Sie zeigen aber auch, dass dort wo technischer Hochwasserschutz konsequent umgesetzt wurde SchĂ€den vermieden werden konnten. Wir sind nach den Ereignissen in den vergangenen Jahren aufgefordert wissenschaftlich noch leistungsfĂ€higere und duktilere Systeme zu entwickeln. Weiter ist die Wissenschaft in der Pflicht, die Zivile Sicherheit im Hochwasser-schutz permanent zu bewerten, zu bearbeiten und ganzheitliche-interdisziplinĂ€re und lĂ€nderĂŒbergreifende Lösungen fĂŒr die Zivilgesellschaft einzufordern
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