762 research outputs found
Strain bursts in plastically deforming Molybdenum micro- and nanopillars
Plastic deformation of micron and sub-micron scale specimens is characterized
by intermittent sequences of large strain bursts (dislocation avalanches) which
are separated by regions of near-elastic loading. In the present investigation
we perform a statistical characterization of strain bursts observed in
stress-controlled compressive deformation of monocrystalline Molybdenum
micropillars. We characterize the bursts in terms of the associated elongation
increments and peak deformation rates, and demonstrate that these quantities
follow power-law distributions that do not depend on specimen orientation or
stress rate. We also investigate the statistics of stress increments in between
the bursts, which are found to be Weibull distributed and exhibit a
characteristic size effect. We discuss our findings in view of observations of
deformation bursts in other materials, such as face-centered cubic and
hexagonal metals.Comment: 14 pages, 8 figures, submitted to Phil Ma
Homogeneous Gold Catalysis through Relativistic Effects: Addition of Water to Propyne
In the catalytic addition of water to propyne the Au(III) catalyst is not
stable under non-relativistic conditions and dissociates into a Au(I) compound
and Cl2. This implies that one link in the chain of events in the catalytic
cycle is broken and relativity may well be seen as the reason why Au(III)
compounds are effective catalysts.Comment: 12 pages, 3 figures, 1 tabl
Brain Edema Formation and Functional Outcome After Surgical Decompression in Murine Closed Head Injury Are Modulated by Acetazolamide Administration
Acetazolamide (ACZ), carbonic anhydrase inhibitor, has been successfully applied in
several neurosurgical conditions for diagnostic or therapeutic purposes. Furthermore,
neuroprotective and anti-edematous properties of ACZ have been postulated. However,
its use in traumatic brain injury (TBI) is limited, since ACZ-caused vasodilatation
according to the Monro-Kellie doctrine may lead to increased intracranial blood
volume / raise of intracranial pressure. We hypothesized that these negative effects
of ACZ will be reduced or prevented, if the drug is administered after already
performed decompression. To test this hypothesis, we used a mouse model of closed
head injury (CHI) and decompressive craniectomy (DC). Mice were assigned into
following experimental groups: sham, DC, CHI, CHI+ACZ, CHI+DC, and CHI+DC+ACZ
(n = 8 each group). 1d and 3d post injury, the neurological function was assessed
according to Neurological Severity Score (NSS) and Beam Balance Score (BBS). At
the same time points, brain edema was quantified by MRI investigations. Functional
impairment and edema volume were compared between groups and over time.
Among the animals without skull decompression, the group additionally treated with
acetazolamide demonstrated the most severe functional impairment. This pattern was
reversed among the mice with decompressive craniectomy: CHI+DC treated but not
CHI+DC+ACZ treated animals showed a significant neurological deficit. Accordingly,
radiological assessment revealed most severe edema formation in the CHI+DC group
while in CHI+DC+ACZ animals, volume of brain edema did not differ from DC-only
animals. In our CHI model, the response to acetazolamide treatment varies between animals with decompressive craniectomy and those without surgical treatment. Opening
the cranial vault potentially creates an opportunity for acetazolamide to exert its beneficial
effects while vasodilatation-related risks are attenuated. Therefore, we recommend
further exploration of this potentially beneficial drug in translational research projects
Cohesive energies of cubic III-V semiconductors
Cohesive energies for twelve cubic III-V semiconductors with zincblende
structure have been determined using an ab-initio scheme. Correlation
contributions, in particular, have been evaluated using the coupled-cluster
approach with single and double excitations (CCSD). This was done by means of
increments obtained for localized bond orbitals and for pairs and triples of
such bonds. Combining these results with corresponding Hartree-Fock data, we
recover about 92 \% of the experimental cohesive energies.Comment: 16 pages, 1 figure, late
, Nuclear quadrupole moment of 139La from relativistic electronic structure calculations of the electric field gradients in LaF, LaCl, LaBr and LaI
Relativistic coupled cluster theory is used to determine accurate electric field gradients in order to provide a theoretical value for the nuclear quadrupole moment of La139. Here we used the diatomic lanthanum monohalides LaF, LaCl, LaBr, and LaI as accurate nuclear quadrupole coupling constants are available from rotational spectroscopy by Rubinoff [J. Mol. Spectrosc. 218, 169 (2003)]. The resulting nuclear quadrupole moment for La139 (0.200±0.006 barn) is in excellent agreement with earlier work using atomic hyperfine spectroscopy [0.20 (1) barn]. © 2007 American Institute of Physics
Safety and Efficacy of Itraconazole Compared to Amphotericin B as Empirical Antifungal Therapy for Neutropenic Fever in Patients with Haematological Malignancy
Safety, tolerability and efficacy of itraconazole and amphotericin B (AMB) were compared for empirical antifungal treatment of febrile neutropenic cancer patients. Patients and Methods: In an open, randomised study, 162 patients with at least 72 h of antimicrobial treatment received either intravenous followed by oral itraconazole suspension or intravenous AMB for a maximum of 28 days. Permanent discontinuation of study medication due to any adverse event was the primary safety parameter. Efficacy parameters included response and success rate for both treatment groups. Results: Significantly fewer itraconazole patients discontinued treatment due to any adverse event (22.2 vs. 56.8% AMB; p < 0.0001). The main reason for discontinuation was a rise in serum creatinine (1.2% itraconazole vs. 23.5% AMB). Renal toxicity was significantly higher and more drug-related adverse events occurred in the AMB group. Intention-to-treat (ITT) analysis showed favourable efficacy for itraconazole: response and success rate were both significantly higher than for AMB (61.7 vs. 42% and 70.4 vs. 49.3%, both p < 0.0001). Treatment failure was markedly reduced in itraconazole patients (25.9 vs. 43.2%), largely due to the better tolerability. Conclusions: Itraconazole was tolerated significantly better than conventional AMB and also showed advantages regarding efficacy. This study confirms the role of itraconazole as a useful and safe agent in empirical antifungal therapy of febrile neutropenic cancer patients.Hintergrund: Es wurden die Sicherheit, Verträglichkeit und Wirksamkeit von Itraconazol und Amphotericin B (AMB) in der antimykotischen Therapie der persistierend febrilen Neutropenie verglichen. Patienten und Methoden: In einer offenen, randomisierten Studie erhielten 162 Patienten mit mindestens 72-stündiger antibiotischer Therapie entweder Itraconazol (erst intravenös, dann oral) oder AMB (intravenös) für maximal 28 Tage. Primärer Sicherheitsparameter war die dauerhafte Unterbrechung der Studienmedikation aufgrund von Nebenwirkungen. Die Wirksamkeitsparameter umfassten die Ansprech- und Erfolgsrate für beide Behandlungsgruppen. Ergebnisse: Signifikant weniger Itraconazol-Patienten brachen die Behandlung wegen Nebenwirkungen ab (22,2 vs. 56,8% AMB; p < 0,0001). Hauptursache für Studienabbrüche war der Anstieg des Serum-Kreatinin-Spiegels (1,2% Itraconazol vs. 23,5% AMB). Nephrotoxische und weitere Nebenwirkungen traten im AMB-Studienarm signifikant häufiger auf. Intention-to-Treat (ITT)-Analysen zeigten eine bessere Wirksamkeit von Itraconazol: Ansprech- und Erfolgsrate waren signifikant höher als unter AMB (61,7 vs. 42% und 70,4 vs. 49,3%, beide p < 0,0001). Behandlungsversagen trat bei Itraconazol-Patienten merklich weniger auf (25,9 vs. 43,2%). Schlussfolgerungen: Die Verträglichkeit von Itraconazol war signifikant höher als beim herkömmlichen AMB. Itraconazol zeigte ebenfalls Vorteile in der Wirksamkeit. Diese Studie bestätigt die Rolle von Itraconazol als sinnvolles und sicheres Medikament in der empirischen antimykotischen Therapie von fiebrigen neutropenischen Tumorpatienten.Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich
Comparison of the atmosphere above the South Pole, Dome C and Dome A: first attempt
The atmospheric properties above three sites (Dome C, Dome A and the South
Pole) on the Internal Antarctic Plateau are investigated for astronomical
applications using the monthly median of the analyses from ECMWF (the European
Centre for Medium-Range Weather Forecasts). Radiosoundings extended on a yearly
time scale at the South Pole and Dome C are used to quantify the reliability of
the ECMWF analyses in the free atmosphere as well as in the boundary and
surface layers, and to characterize the median wind speed in the first 100 m
above the two sites. Thermodynamic instability properties in the free
atmosphere above the three sites are quantified with monthly median values of
the Richardson number. We find that the probability to trigger thermodynamic
instabilities above 100 m is smaller on the Internal Antarctic Plateau than on
mid-latitude sites. In spite of the generally more stable atmospheric
conditions of the Antarctic sites compared to mid-latitude sites, Dome C shows
worse thermodynamic instability conditions than those predicted above the South
Pole and Dome A above 100 m. A rank of the Antarctic sites done with respect to
the strength of the wind speed in the free atmosphere (ECMWF analyses) as well
as the wind shear in the surface layer (radiosoundings) is presented.Comment: Accepted for publishing in MNRAS. 14 pages, 10 figures. The
definitive version is available at http://www.blackwell-synergy.co
Quantum Computer with Mixed States and Four-Valued Logic
In this paper we discuss a model of quantum computer in which a state is an
operator of density matrix and gates are general quantum operations, not
necessarily unitary. A mixed state (operator of density matrix) of n two-level
quantum systems is considered as an element of 4^n-dimensional operator Hilbert
space (Liouville space). It allows to use a quantum computer model with
four-valued logic. The gates of this model are general superoperators which act
on n-ququat state. Ququat is a quantum state in a four-dimensional (operator)
Hilbert space. Unitary two-valued logic gates and quantum operations for an
n-qubit open system are considered as four-valued logic gates acting on
n-ququat. We discuss properties of quantum four-valued logic gates. In the
paper we study universality for quantum four-valued logic gates.Comment: 17 page
The 10 Meter South Pole Telescope
The South Pole Telescope (SPT) is a 10 m diameter, wide-field, offset
Gregorian telescope with a 966-pixel, multi-color, millimeter-wave, bolometer
camera. It is located at the Amundsen-Scott South Pole station in Antarctica.
The design of the SPT emphasizes careful control of spillover and scattering,
to minimize noise and false signals due to ground pickup. The key initial
project is a large-area survey at wavelengths of 3, 2 and 1.3 mm, to detect
clusters of galaxies via the Sunyaev-Zeldovich effect and to measure the
small-scale angular power spectrum of the cosmic microwave background (CMB).
The data will be used to characterize the primordial matter power spectrum and
to place constraints on the equation of state of dark energy. A
second-generation camera will measure the polarization of the CMB, potentially
leading to constraints on the neutrino mass and the energy scale of inflation.Comment: 47 pages, 14 figures, updated to match version to be published in
PASP 123 903 (May, 2011
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