495 research outputs found
Comparing Post-Newtonian and Numerical-Relativity Precession Dynamics
Binary black-hole systems are expected to be important sources of
gravitational waves for upcoming gravitational-wave detectors. If the spins are
not colinear with each other or with the orbital angular momentum, these
systems exhibit complicated precession dynamics that are imprinted on the
gravitational waveform. We develop a new procedure to match the precession
dynamics computed by post-Newtonian (PN) theory to those of numerical binary
black-hole simulations in full general relativity. For numerical relativity NR)
simulations lasting approximately two precession cycles, we find that the PN
and NR predictions for the directions of the orbital angular momentum and the
spins agree to better than with NR during the inspiral,
increasing to near merger. Nutation of the orbital plane on the
orbital time-scale agrees well between NR and PN, whereas nutation of the spin
direction shows qualitatively different behavior in PN and NR. We also examine
how the PN equations for precession and orbital-phase evolution converge with
PN order, and we quantify the impact of various choices for handling partially
known PN terms
Ăj kĂ©ntartalmĂș szĂ©nhidrĂĄt-szĂĄrmazĂ©kok trypanosoma- ill. amöba-ellenes hatĂĄsĂĄnak vizsgĂĄlata: szerkezet-hatĂĄs összefĂŒggĂ©sek = Testing the trypanocidal, amoebicidal activity of novel S-containing sugar derivatives: structure â activity investigations.
A Trypanosoma cruzi protozoa, a Chagas betegsĂ©g kĂłrokozĂłja, Latin AmerikĂĄban Ă©vente 12-14 milliĂł ember fertĆzĂ©sĂ©Ă©rt felelĆs. A betegsĂ©g kezelĂ©sĂ©re jelenleg alkalmazott szerek hatĂĄsossĂĄga nem kielĂ©gĂtĆ, kĂŒlönösen a betegsĂ©g gyakori, krĂłnikus formĂĄja ellen. KĂsĂ©rleteket folytattunk potenciĂĄlisan tripanoszĂłma-ellenes vegyĂŒletek szintĂ©zisĂ©re; ennek sorĂĄn Ășj, multivalens aromĂĄs glikozil-diszulfidokat Ă©s nĂ©hĂĄny diglikozil-diszulfidot ĂĄllĂtottunk elĆ T.cruzi elleni tesztelĂ©s cĂ©ljĂĄra. NĂ©hĂĄny szĂĄrmazĂ©k meglepĆen hatĂĄsosnak mutatkozott sejttenyĂ©szetbĆl szĂĄrmazĂł tripomasztigotĂĄk ellen: az eddig talĂĄlt legaktĂvabb szĂĄrmazĂ©k, az 1,4-bis(Ă-D-galaktopiranozil-dithiometilĂ©n)-benzol gĂĄtlĂĄsi ĂĄllandĂłja (IC50) 8.7 ±1.21 ”M. Több, hasonlĂł kĂ©miai szerkezettel jellemzett szĂĄrmazĂ©k is hatĂĄsosnak mutatkozott ~ 15 ”M-os szinten. A tesztvegyĂŒletek citotoxikus hatĂĄsĂĄt konfluens HeLa sejttenyĂ©szeteken tanulmĂĄnyoztuk 18 ĂłrĂĄs inkubĂĄlĂĄst követĆen. Az aktĂv vegyĂŒletek mindegyike csekĂ©ly citotoxicitĂĄst mutatott. TovĂĄbbi, igen jelentĆs megfigyelĂ©s, hogy az aktĂv szĂĄrmazĂ©kok kĂ©pesek a parazita intracellulĂĄris proliferĂĄciĂłjĂĄt (amasztigota forma) is gĂĄtolni, amint ez a T.cruzi-val fertĆzött Vero-sejtekbĆl kibocsĂĄtott parazitĂĄk szĂĄmlĂĄlĂĄsa bizonyĂtotta. VĂ©lemĂ©nyĂŒnk szerint ez igen figyelemre mĂ©ltĂł eredmĂ©ny, u.i. a jelenleg alkalmazott T.cruzi elleni szerek (beznidazol, nifurtimox) nem kĂ©pesek a parazita intracellulĂĄris fĂĄzisĂĄt gĂĄtolni. | Trypanosoma cruzi is the etiologic agent of Chagas disease, an endemic parasitosis in Latin America with 12â14 million people infected. Currently available drugs for treatment of this disease are unsatisfactory, particularly in its prevalent chronic form. In a search for novel chemical structures with potential trypanocidal activity we have synthesized novel aromatic multivalent glycosyl disulfides and some diglycosyl disulfides for testing against T.cruzi. Some of the tested compounds were found remarkably efficient to kill cell culture-derived trypomastigotes; 1,4-bis(Ă-D-galactopyranosyl-dithiomethylene) benzene proved to be the most active derivative with an IC50 of 8.7 ±1.21 ”M. Other derivatives, of similar chemical structures, were further promising candidates with low IC50 values of ~ 15 ”M. The cytotoxic effects of the active and inactive compounds were evaluated after 18 h incubation with confluent HeLa cell cultures. Pleasingly, all of the active trypanocidal agents showed low cytotoxicites. Further, we observed that several of the compounds tested were also able to inhibit intracellular proliferation or parasite differentiation (amastigote form) when the number of parasites released by T.cruzi infected Vero cells was evaluated. These observations, of outstanding interest, show a remarkable effect of these compounds against the intracellular stage of T.cruzi, an activity that is missing in the currently available drugs like beznidazol and nifurtimox
Channelling study of LaSrCoO films on different substrates
The cobalt oxide system LaCoO and its Sr-doped child compounds have been
intensively studied for decades due to their intriguing magnetic and electronic
properties. Preparing thin LaSrCoO (LSCO) films on different
substrates allows for studies with a new type of perturbation, as the films are
subject to substrate-dependent epitaxial strain. By choosing a proper substrate
for a thin film grow, not only compressing but also tensile strain can be
applied. The consequences for the fundamental physical properties are dramatic:
while compressed films are metallic, as the bulk material, films under tensile
strain become insulating. The goal of this work is to determine the strain
tensor in LSCO films prepared on LaAlO and SrTiO substrates by pulsed
laser deposition using RBS/channelling methods. Apart from the composition and
defect structure of the samples, the depth dependence of the strain tensor, the
cell parameters, and the volume of the unit cell are also determined.
Asymmetric behaviour of the strained cell parameters is found on both
substrates. This asymmetry is rather weak in the case of LSCO film grown on
LaAlO, while stronger on SrTiO substrate. The strain is more effective
at the interface, some relaxation can be observed near to the surface
A Numerical Relativity Waveform Surrogate Model for Generically Precessing Binary Black Hole Mergers
A generic, non-eccentric binary black hole (BBH) system emits gravitational
waves (GWs) that are completely described by 7 intrinsic parameters: the black
hole spin vectors and the ratio of their masses. Simulating a BBH coalescence
by solving Einstein's equations numerically is computationally expensive,
requiring days to months of computing resources for a single set of parameter
values. Since theoretical predictions of the GWs are often needed for many
different source parameters, a fast and accurate model is essential. We present
the first surrogate model for GWs from the coalescence of BBHs including all
dimensions of the intrinsic non-eccentric parameter space. The surrogate
model, which we call NRSur7dq2, is built from the results of numerical
relativity simulations. NRSur7dq2 covers spin magnitudes up to and mass
ratios up to , includes all modes, begins about orbits
before merger, and can be evaluated in . We find the
largest NRSur7dq2 errors to be comparable to the largest errors in the
numerical relativity simulations, and more than an order of magnitude smaller
than the errors of other waveform models. Our model, and more broadly the
methods developed here, will enable studies that would otherwise require
millions of numerical relativity waveforms, such as parameter inference and
tests of general relativity with GW observations.Comment: 10 pages, 5 figures; Added report numbe
Three-Coordinate Copper(I) Amido and Aminyl Radical Complexes
Electron transfer (ET) through proteins often utilizes copper-containing active sites as efficient one-electron relays. The type-1 active sites of the blue copper proteins are prominent examples. It is generally thought that high ET rates through type-1 redox sites occur because the protein environments enforce unusual trigonally distorted coordination spheres to allow for minimal structural
reorganization during ET. Though large Cu^II/Cu^I self-exchange ET rate constants (kS) in the range observed for type-1 sites have been achieved in certain synthetic monocopper systems using geometries distinct from trigonal environments, ET studies have yet to be conducted in a synthetic system featuring isolated, trigonally disposed copper centers. The simplest such systems would contain a trigonal planar geometry.
Here we report the structural characterization of a trigonal planar system featuring formally Cu^II and Cu^I amido complexes related by a reversible one-electron redox event. We find in this system that ET is extremely rapid and is accompanied by a small degree of structural reorganization during redox. We propose that this structural rigidity in the absence of secondary coordination sphere effects results from significant covalency of the copper-amide linkages. In fact, a CuI-aminyl radical description of the formally Cu^II-amide complex may be most appropriate
Tailoring Fe/Ag Superparamagnetic Composites by Multilayer Deposition
The magnetic properties of Fe/Ag granular multilayers were examined by SQUID
magnetization and Mossbauer spectroscopy measurements. Very thin (0.2 nm)
discontinuous Fe layers show superparamagnetic properties that can be tailored
by the thickness of both the magnetic and the spacer layers. The role of
magnetic interactions was studied in novel heterostructures of
superparamagnetic and ferromagnetic layers and the specific contribution of the
ferromagnetic layers to the low field magnetic susceptibility was identified.Comment: 5 pages and 3 figure
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