4,426 research outputs found
Activation of prothrombin accompanying thrombolysis with recombinant tissue-type plasminogen activator
AbstractIncreases in thrombin activity in patients given fibrinolytic agents for acute myocardial infarction have been shown to be important in limiting the ultimate success of coronary thrombolysis. The present study was designed to determine whether increases in thrombin activity reflect, in part, activation of prothrombin accompanying thrombolysis. Plasma concentrations of prothrombin fragment 1.2, a polypeptide released when prothrombin is activated by factor Xa, were measured in 22 patients with acute myocardial infarction before and after treatment with 100 mg of recombinant tissue-type plasminogen activator (rt-PA). Concentrations of prothrombin fragment 1.2 increased from 0.83 ± 1.1 nM(mean ± SD) before rt-PA infusion to 1.5 ± 1.5 nM2 h after initiation of the infusion (p < 0.05). After a 5,000-U intravenous dose of heparin given at the end of the infusion of rt-PA, concentrations of prothrombin fragment 1.2 decreased from 1.8 ± 1.5 to 1.1 ± 0.9 nM(n = 20, p < 0.05), although values were still increased compared with concentrations before rt-PA.These results indicate that thrombin activity increases in patients given rt-PA at least in part because of activation of the coagulation system leading to activation of prothrombin. Thus, inhibition of the reactions involving coagulant proteins that lead to activation of prothrombin may be of value as conjunctive treatment to potentiate the efficacy of pharmacologic thrombolysis
Statistical Mechanics of the Hyper Vertex Cover Problem
We introduce and study a new optimization problem called Hyper Vertex Cover.
This problem is a generalization of the standard vertex cover to hypergraphs:
one seeks a configuration of particles with minimal density such that every
hyperedge of the hypergraph contains at least one particle. It can also be used
in important practical tasks, such as the Group Testing procedures where one
wants to detect defective items in a large group by pool testing. Using a
Statistical Mechanics approach based on the cavity method, we study the phase
diagram of the HVC problem, in the case of random regualr hypergraphs.
Depending on the values of the variables and tests degrees different situations
can occur: The HVC problem can be either in a replica symmetric phase, or in a
one-step replica symmetry breaking one. In these two cases, we give explicit
results on the minimal density of particles, and the structure of the phase
space. These problems are thus in some sense simpler than the original vertex
cover problem, where the need for a full replica symmetry breaking has
prevented the derivation of exact results so far. Finally, we show that
decimation procedures based on the belief propagation and the survey
propagation algorithms provide very efficient strategies to solve large
individual instances of the hyper vertex cover problem.Comment: Submitted to PR
Rapid Miocene Exhumation to the East of the Tauern Window
The Eastern Alps were substantially shaped by northward movement of the Dolomites Indenter and eastward extrusion of the orogenic wedge in front of the indenter. A resulting sinistral wrench zone runs through the western Tauern Window (TW) and continues along the Salzach-Ennstal-Mariazell-Puchberg Fault (SEMP) eastward. Low-T thermochronological studies demonstrate rapid Miocene cooling of the TW units from â„ 350 °C to below ~ 80 °C due to folding and coeval erosion. Thermochronologic ages in the Eastern Tauern Window range between 12 Ma to 22 Ma for the zircon fission track chronometer (partial annealing zone (PAZ) ~ 200 â 350°C, e.g., Tagami et al., 1996) and 5 Ma to 13 Ma for the apatite (U-Th)/He chronometer (partial retention zone (PRZ) ~ 40 â 80°C, Stockli et al., 2000). Ages for the zircon (U-Th)/He and apatite fission track chronometers fall in between.
Along the eastern margin of the TW, the extensional Katschberg Fault-System (KFS) decoupled the Gurktal Block (GB) in its hanging wall from folding. The KFS was active between 20 and 17 Ma, in the early Miocene (Scharf et al., 2016). A late reactivation phase is demonstrated by reset or partially reset zircon and apatite fission track ages within the footwall towards the fault, yielding Late Miocene to Pliocene ages (Bertrand et al., 2017). A similar younging trend is observed within the TW towards the Brenner Fault in the western TW. The GB in the hanging wall of the KFS preserves a rapid Cretaceous and Eocene cooling through the zircon fission track PAZ and rapid Oligocene to Miocene cooling through the apatite fission track PAZ (Wölfler et al., 2023).
The Niedere Tauern (NT), north of the GB and south of the SEMP line, seem to be structurally closely linked to the TW. They show a similar rapid Miocene cooling history and an intervening Cenozoic structure between the TW and the NT is missing. Published apatite fission track ages range between 14 Ma and 24 Ma (apatite PAZ ~ 60 â 100°C, Wagner et al., 1989). Published apatite (U-Th)/He ages from the southern boundary of the NT range between 6 Ma and 7 Ma, indicating a Late Miocene cooling below ~ 80 °C (Wölfler et al., 2016).
Our (U-Th)/He analysis from the interiour of the NT revealed ages of around 20 Ma to 23 Ma (zircon (U-Th)/He), and 11 Ma to 22 Ma (apatite (U-Th)/He). Published apatite fission track ages fall in between and partly overlap with our results. This demonstrates a rapid cooling pulse in the Miocene, exhuming at least the western part of the NT from ℠200 °C to below ~ 80 °C. Published AHe ages of ~ 6 Ma along the southern margin of the NT might relate to late Miocene normal faulting along the complex Murtal Fault-System (MFS). A pronounced jump towards older thermochronologic ages in the Seckauer Tauern, east of the Pöls fault and extensional structures along this fault indicate a structural decoupling of the western NT from the Seckauer Tauern.
In this contribution, we discuss the linkage between TW and N T and characterize in greater detail the exhumation history along the eastern wrench zone
Neutrino-induced deuteron disintegration experiment
Cross sections for the disintegration of the deuteron via neutral-current
(NCD) and charged-current (CCD) interactions with reactor antineutrinos are
measured to be 6.08 +/- 0.77 x 10^(-45) cm-sq and 9.83 +/- 2.04 x 10^(-45)
cm-sq per neutrino, respectively, in excellent agreement with current
calculations. Since the experimental NCD value depends upon the CCD value, if
we use the theoretical value for the CCD reaction, we obtain the improved value
of 5.98 +/- 0.54 x 10^(-45) for the NCD cross section. The neutral-current
reaction allows a unique measurement of the isovector-axial vector coupling
constant in the hadronic weak interaction (beta). In the standard model, this
constant is predicted to be exactly 1, independent of the Weinberg angle. We
measure a value of beta^2 = 1.01 +/- 0.16. Using the above improved value for
the NCD cross section, beta^2 becomes 0.99 +/- 0.10.Comment: 22pages, 9 figure
Occupational choice, number of entrepreneurs and output: theory and empirical evidence with Spanish data
This paper extends the (Lucas, Bell J Econ 9:508â523,1978) model of occupational choices by individuals with different skills, beyond the simple options of self-employment or wage-employment, by including a second choice for the self-employed. That is, an option to hire employees and so become self-employed with employees (SEWEs), or to be self-employed without employees (SEWNEs). We solve for the market equilibrium and examine the sensitivity of relative sizes of occupational groups, and of the level of productivity, to changes in the exogenous parameters. The results show that the positive (negative) association between number of SEWEs (SEWNEs) and productivity, observed in the Spanish data, can be explained, under certain conditions, as the result of cross-region and time differences in average skills. These findings point to the importance of distinguishing between SEWEs and SEWNEs in drawing valid conclusions concerning any link between entrepreneurship and economic development
Expression of Interest: The Atmospheric Neutrino Neutron Interaction Experiment (ANNIE)
Submitted for the January 2014 Fermilab Physics Advisory Committee meetingSubmitted for the January 2014 Fermilab Physics Advisory Committee meetingSubmitted for the January 2014 Fermilab Physics Advisory Committee meetingSubmitted for the January 2014 Fermilab Physics Advisory Committee meetingNeutron tagging in Gadolinium-doped water may play a significant role in reducing backgrounds from atmospheric neutrinos in next generation proton-decay searches using megaton-scale Water Cherenkov detectors. Similar techniques might also be useful in the detection of supernova neutrinos. Accurate determination of neutron tagging efficiencies will require a detailed understanding of the number of neutrons produced by neutrino interactions in water as a function of momentum transferred. We propose the Atmospheric Neutrino Neutron Interaction Experiment (ANNIE), designed to measure the neutron yield of atmospheric neutrino interactions in gadolinium-doped water. An innovative aspect of the ANNIE design is the use of precision timing to localize interaction vertices in the small fiducial volume of the detector. We propose to achieve this by using early production of LAPPDs (Large Area Picosecond Photodetectors). This experiment will be a first application of these devices demonstrating their feasibility for Water Cherenkov neutrino detectors
Majorana Neutrinos and Gravitational Oscillation
We analyze the possibility of encountering resonant transitions of high
energy Majorana neutrinos produced in Active Galactic Nuclei (AGN). We consider
gravitational, electromagnetic and matter effects and show that the latter are
ignorable. Resonant oscillations due to the gravitational interactions are
shown to occur at energies in the PeV range for magnetic moments in the
range. Coherent precession will dominate for larger magnetic
moments. The alllowed regions for gravitational resonant transitions are
obtained.Comment: 11 pages, 8 figures, Latex; requires revtex and epsf.tex submitted to
Physical Review
Expression of Interest: The Atmospheric Neutrino Neutron Interaction Experiment (ANNIE)
Neutron tagging in Gadolinium-doped water may play a significant role in
reducing backgrounds from atmospheric neutrinos in next generation proton-decay
searches using megaton-scale Water Cherenkov detectors. Similar techniques
might also be useful in the detection of supernova neutrinos. Accurate
determination of neutron tagging efficiencies will require a detailed
understanding of the number of neutrons produced by neutrino interactions in
water as a function of momentum transferred. We propose the Atmospheric
Neutrino Neutron Interaction Experiment (ANNIE), designed to measure the
neutron yield of atmospheric neutrino interactions in gadolinium-doped water.
An innovative aspect of the ANNIE design is the use of precision timing to
localize interaction vertices in the small fiducial volume of the detector. We
propose to achieve this by using early production of LAPPDs (Large Area
Picosecond Photodetectors). This experiment will be a first application of
these devices demonstrating their feasibility for Water Cherenkov neutrino
detectors.Comment: Submitted for the January 2014 Fermilab Physics Advisory Committee
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Using the weak-temperature gradient approximation to evaluate parameterizations: an example of the transition from suppressed to active convection
Two single-column models are fully coupled via the weak-temperature gradient approach. The coupled-SCM is used to simulate the transition from suppressed to active convection under the influence of an interactive
large-scale circulation. The sensitivity of this transition to the value of mixing entrainment within the convective parameterization is explored. The results from these simulations are compared with those from equivalent simulations using coupled cloud-resolving models.
Coupled-column simulations over non-uniform surface forcing are used to initialize the simulations of the transition, in which the column with suppressed convection is forced to undergo a transition to active convection by
changing the local and/or remote surface forcings. The direct contributions from the changes in surface forcing are to induce a weakening of the large-scale circulation which systematically modulates the transition. In the SCM, the contributions from the large-scale circulation are dominated by the heating effects, while in the CRM the heating and moistening effects are about equally divided.
A transition time is defined as the time when the rain rate in the dry column is halfway to the value at equilibrium after the transition. For the control value of entrainment, the order of the transition times is identical to that
obtained in the CRM, but the transition times are markedly faster. The locally forced transition is strongly delayed by a higher entrainment. A consequence is that for a 50% higher entrainment the transition times are reordered. The remotely forced transition remains fast while the locally forced transition becomes slow, compared to the CRM
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