231 research outputs found
Michelson interferometer with diffractively-coupled arm resonators in second-order Littrow configuration
Michelson-type laser-interferometric gravitational-wave (GW) observatories
employ very high light powers as well as transmissively- coupled Fabry-Perot
arm resonators in order to realize high measurement sensitivities. Due to the
absorption in the transmissive optics, high powers lead to thermal lensing and
hence to thermal distortions of the laser beam profile, which sets a limit on
the maximal light power employable in GW observatories. Here, we propose and
realize a Michelson-type laser interferometer with arm resonators whose
coupling components are all-reflective second-order Littrow gratings. In
principle such gratings allow high finesse values of the resonators but avoid
bulk transmission of the laser light and thus the corresponding thermal beam
distortion. The gratings used have three diffraction orders, which leads to the
creation of a second signal port. We theoretically analyze the signal response
of the proposed topology and show that it is equivalent to a conventional
Michelson-type interferometer. In our proof-of-principle experiment we
generated phase-modulation signals inside the arm resonators and detected them
simultaneously at the two signal ports. The sum signal was shown to be
equivalent to a single-output-port Michelson interferometer with
transmissively-coupled arm cavities, taking into account optical loss. The
proposed and demonstrated topology is a possible approach for future
all-reflective GW observatory designs
Unequal Mass Binary Black Hole Plunges and Gravitational Recoil
We present results from fully nonlinear simulations of unequal mass binary
black holes plunging from close separations well inside the innermost stable
circular orbit with mass ratios q = M_1/M_2 = {1,0.85,0.78,0.55,0.32}, or
equivalently, with reduced mass parameters . For each case, the initial binary orbital
parameters are chosen from the Cook-Baumgarte equal-mass ISCO configuration. We
show waveforms of the dominant l=2,3 modes and compute estimates of energy and
angular momentum radiated. For the plunges from the close separations
considered, we measure kick velocities from gravitational radiation recoil in
the range 25-82 km/s. Due to the initial close separations our kick velocity
estimates should be understood as a lower bound. The close configurations
considered are also likely to contain significant eccentricities influencing
the recoil velocity.Comment: 12 pages, 5 figures, to appear in "New Frontiers" special issue of
CQ
From one cell to the whole froth: a dynamical map
We investigate two and three-dimensional shell-structured-inflatable froths,
which can be constructed by a recursion procedure adding successive layers of
cells around a germ cell. We prove that any froth can be reduced into a system
of concentric shells. There is only a restricted set of local configurations
for which the recursive inflation transformation is not applicable. These
configurations are inclusions between successive layers and can be treated as
vertices and edges decorations of a shell-structure-inflatable skeleton. The
recursion procedure is described by a logistic map, which provides a natural
classification into Euclidean, hyperbolic and elliptic froths. Froths tiling
manifolds with different curvature can be classified simply by distinguishing
between those with a bounded or unbounded number of elements per shell, without
any a-priori knowledge on their curvature. A new result, associated with
maximal orientational entropy, is obtained on topological properties of natural
cellular systems. The topological characteristics of all experimentally known
tetrahedrally close-packed structures are retrieved.Comment: 20 Pages Tex, 11 Postscript figures, 1 Postscript tabl
Polytetrahedral Clusters
By studying the structures of clusters bound by a model potential that
favours polytetrahedral order, we find a previously unknown series of `magic
numbers' (i.e. sizes of special stability) whose polytetrahedral structures are
characterized by disclination networks that are analogous to hydrocarbons.Comment: 4 pages, 4 figure
Organometallic iridium(III) anticancer complexes with new mechanisms of action: NCI-60 screening, mitochondrial targeting, and apoptosis
Platinum complexes related to cisplatin, cis-[PtCl2(NH3)2], are successful anticancer drugs; however, other transition metal complexes offer potential for combating cisplatin resistance, decreasing side effects, and widening the spectrum of activity. Organometallic half-sandwich iridium (IrIII) complexes [Ir(Cpx)(XY)Cl]+/0 (Cpx = biphenyltetramethylcyclopentadienyl and XY = phenanthroline (1), bipyridine (2), or phenylpyridine (3)) all hydrolyze rapidly, forming monofunctional G adducts on DNA with additional intercalation of the phenyl substituents on the Cpx ring. In comparison, highly potent complex 4 (Cpx = phenyltetramethylcyclopentadienyl and XY = N,N-dimethylphenylazopyridine) does not hydrolyze. All show higher potency toward A2780 human ovarian cancer cells compared to cisplatin, with 1, 3, and 4 also demonstrating higher potency in the National Cancer Institute (NCI) NCI-60 cell-line screen. Use of the NCI COMPARE algorithm (which predicts mechanisms of action (MoAs) for emerging anticancer compounds by correlating NCI-60 patterns of sensitivity) shows that the MoA of these IrIII complexes has no correlation to cisplatin (or oxaliplatin), with 3 and 4 emerging as particularly novel compounds. Those findings by COMPARE were experimentally probed by transmission electron microscopy (TEM) of A2780 cells exposed to 1, showing mitochondrial swelling and activation of apoptosis after 24 h. Significant changes in mitochondrial membrane polarization were detected by flow cytometry, and the potency of the complexes was enhanced ca. 5× by co-administration with a low concentration (5 μM) of the γ-glutamyl cysteine synthetase inhibitor L-buthionine sulfoximine (L-BSO). These studies reveal potential polypharmacology of organometallic IrIII complexes, with MoA and cell selectivity governed by structural changes in the chelating ligands
Further Evidence for the Decay K+ to pi+ neutrino-antineutrino
Additional evidence for the rare kaon decay K+ to pi+ neutrino-antineutrino
has been found in a new data set with comparable sensitivity to the previously
reported result. One new event was observed in the pion momentum region
examined, 211<P<229 MeV/c, bringing the total for the combined data set to two.
Including all data taken, the backgrounds were estimated to contribute 0.15 pm
0.05 events. The branching ratio is B=1.57^{+1.75}_{-0.82} 10^{-10}.Comment: 10 pages, 2 figure
Search for the decay in the momentum region
We have searched for the decay in the kinematic
region with pion momentum below the peak. One event was
observed, consistent with the background estimate of . This
implies an upper limit on
(90% C.L.), consistent with the recently measured branching ratio of
, obtained using the standard model
spectrum and the kinematic region above the peak. The
same data were used to search for , where is a weakly
interacting neutral particle or system of particles with .Comment: 4 pages, 2 figure
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