2,447,534 research outputs found
OGLE-TR-56
In early 2003 our team announced the discovery of the second extrasolar transiting planet, around the faint star OGLE-TR-56 (V = 16.6), based on the detection of small changes in the radial velocity of the primary. The star was originally identified as a candidate by the OGLE team from the shallow and periodic dips in its brightness. We present here new precise radial velocity measurements that confirm the variation measured earlier, supporting the conclusion that the companion is indeed a planet. Additional photometric observations are also available, which combined with the spectroscopy yield improved parameters (mass and radius) for the planet
Millimagnitude Photometry for Transiting Extrasolar Planetary Candidates. V. Follow-up of 30 OGLE Transits. New Candidates
We used VLT/VIMOS images in the V band to obtain light curves of extrasolar
planetary transits OGLE-TR-111 and OGLE-TR-113, and candidate planetary
transits: OGLE-TR-82, OGLE-TR-86, OGLE-TR-91, OGLE-TR-106, OGLE-TR-109,
OGLE-TR-110, OGLE-TR-159, OGLE-TR-167, OGLE-TR-170, OGLE-TR-171. Using
difference imaging photometry, we were able to achieve millimagnitude errors in
the individual data points. We present the analysis of the data and the light
curves, by measuring transit amplitudes and ephemerides, and by calculating
geometrical parameters for some of the systems. We observed 9 OGLE objects at
the predicted transit moments. Two other transits were shifted in time by a few
hours. For another seven objects we expected to observe transits during the
VIMOS run, but they were not detected. The stars OGLE-TR-111 and OGLE-TR-113
are probably the only OGLE objects in the observed sample to host planets, with
the other objects being very likely eclipsing binaries or multiple systems. In
this paper we also report on four new transiting candidates which we have found
in the data.Comment: 11 pages, 17 figures, accepted for publication in A&
Performance Enhancement of Multiuser Time Reversal UWB Communication System
UWB communication is a recent research area for indoor propagation channels.
Time Reversal (TR) communication in UWB has shown promising results for
improving the system performance. In multiuser environment, the system
performance is significantly degraded due to the interference among different
users. TR reduces the interference caused by multiusers due to its spatial
focusing property. The performance of a multiuser TR communication system is
further improved if the TR filter is modified. In this paper, multiuser TR in
UWB communication is investigated using simple TR filter and a modified TR
filter with circular shift operation. The concept of circular shift in TR is
analytically studied. Thereafter, the channel impulse responses (CIR) of a
typical indoor laboratory environment are measured. The measured CIRs are used
to analyze the received signal peak power and signal to interference ratio
(SIR) with and without performing the circular shift operation in a multiuser
environment
The asymmetric ABAB matrix model
In this letter, it is pointed out that the two matrix model defined by the
action S=(1/2)(tr A^2+tr B^2)-(alpha_A/4) tr A^4-(alpha_B/4) tr B^4-(beta/2)
tr(AB)^2 can be solved in the large N limit using a generalization of the
solution of Kazakov and Zinn-Justin (who considered the symmetric case
alpha_A=alpha_B). This model could have useful applications to 3D Lorentzian
gravity.Comment: 7 pages, 1 figur
Categorified trace for module tensor categories over braided tensor categories
Given a braided pivotal category and a pivotal module tensor
category , we define a functor , called the associated categorified trace. By a result of
Bezrukavnikov, Finkelberg and Ostrik, the functor
comes equipped with natural isomorphisms , which we call the
traciators. This situation lends itself to a diagramatic calculus of `strings
on cylinders', where the traciator corresponds to wrapping a string around the
back of a cylinder. We show that in fact has a much
richer graphical calculus in which the tubes are allowed to branch and braid.
Given algebra objects and , we prove that
and are again algebra objects.
Moreover, provided certain mild assumptions are satisfied,
and are
semisimple whenever and are semisimple.Comment: 49 pages, many figure
Transversal Lattices
A flat of a matroid is cyclic if it is a union of circuits; such flats form a
lattice under inclusion and, up to isomorphism, all lattices can be obtained
this way. A lattice is a Tr-lattice if all matroids whose lattices of cyclic
flats are isomorphic to it are transversal. We investigate some sufficient
conditions for a lattice to be a Tr-lattice; a corollary is that distributive
lattices of dimension at most two are Tr-lattices. We give a necessary
condition: each element in a Tr-lattice has at most two covers. We also give
constructions that produce new Tr-lattices from known Tr-lattices.Comment: 12 pages; 5 figure
On spectra and Brown's spectral measures of elements in free products of matrix algebras
We compute spectra and Brown measures of some non self-adjoint operators in
(M_2(\cc), {1/2}Tr)*(M_2(\cc), {1/2}Tr), the reduced free product von Neumann
algebra of M_2(\cc) with M_2(\cc). Examples include and , where A
and B are matrices in (M_2(\cc), {1/2}Tr)*1 and 1*(M_2(\cc), {1/2}Tr),
respectively. We prove that AB is an R-diagonal operator (in the sense of Nica
and Speicher \cite{N-S1}) if and only if Tr(A)=Tr(B)=0. We show that if X=AB or
X=A+B and A,B are not scalar matrices, then the Brown measure of X is not
concentrated on a single point. By a theorem of Haagerup and Schultz
\cite{H-S1}, we obtain that if X=AB or X=A+B and , then X has
a nontrivial hyperinvariant subspace affiliated with (M_2(\cc),
{1/2}Tr)*(M_2(\cc), {1/2}Tr).Comment: final version. to appear on Math. Sca
A conserved U-rich RNA region implicated in regulation of translation in Plasmodium female gametocytes.
Translational repression (TR) plays an important role
in post-transcriptional regulation of gene expression
and embryonic development in metazoans. TR
also regulates the expression of a subset of the
cytoplasmic mRNA population during development
of fertilized female gametes of the unicellular
malaria parasite, Plasmodium spp. which results
in the formation of a polar and motile form, the
ookinete. We report the conserved and sex-specific
regulatory role of either the 3’- or 5’-UTR of a subset
of translationally repressed mRNA species as
shown by almost complete inhibition of expression
of a GFP reporter protein in the female gametocyte.
A U-rich, TR-associated element, identified previously
in the 3’-UTR of TR-associated transcripts,
played an essential role in mediating TR and a
similar region could be found in the 5’-UTR shown in
this study to be active in TR. The silencing effect of
this 5’-UTR was shown to be independent of its
position relative to its ORF, as transposition to a
location 3’ of the ORF did not affect TR. These
results demonstrate for the first time in a unicellular
organism that the 5’ or the 3’-UTR of TR-associated
transcripts play an important and conserved role in
mediating TR in female gametocytes
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