43 research outputs found
Low-Loss All-Optical Zeno Switch in a Microdisk Cavity Using EIT
We present theoretical results of a low-loss all-optical switch based on
electromagnetically induced transparency and the classical Zeno effect in a
microdisk resonator. We show that a control beam can modify the atomic
absorption of the evanescent field which suppresses the cavity field buildup
and alters the path of a weak signal beam. We predict more than 35 dB of
switching contrast with less than 0.1 dB loss using just 2 micro-Watts of
control-beam power for signal beams with less than single photon intensities
inside the cavity.Comment: Updated with new references, corrected Eq 2a, and added introductory
text. 7 pages, 5 figures, 3 table
Properties of low-lying states in some high-nuclearity Mn, Fe and V clusters: Exact studies of Heisenberg models
Using an efficient numerical scheme that exploits spatial symmetries and spin
parity, we have obtained the exact low-lying eigenstates of exchange
Hamiltonians for the high nuclearity spin clusters, Mn_{12}, Fe_8 and V_{15}.
The largest calculation involves the Mn_{12} cluster which spans a Fock space
of a hundred million. Our results show that the earlier estimates of the
exchange constants need to be revised for the Mn_{12} cluster to explain the
level ordering of low-lying eigenstates. In the case of the Fe_8 cluster,
correct level ordering can be obtained which is consistent with the exchange
constants for the already known clusters with butterfly structure. In the
V_{15} cluster, we obtain an effective Hamiltonian that reproduces exactly, the
eight low-lying eigenvalues of the full Hamiltonian.Comment: Revtex, 12 pages, 16 eps figures; this is the final published versio
Optical nanofibers and spectroscopy
We review our recent progress in the production and characterization of
tapered optical fibers with a sub-wavelength diameter waist. Such fibers
exhibit a pronounced evanescent field and are therefore a useful tool for
highly sensitive evanescent wave spectroscopy of adsorbates on the fiber waist
or of the medium surrounding. We use a carefully designed flame pulling process
that allows us to realize preset fiber diameter profiles. In order to determine
the waist diameter and to verify the fiber profile, we employ scanning electron
microscope measurements and a novel accurate in situ optical method based on
harmonic generation. We use our fibers for linear and non-linear absorption and
fluorescence spectroscopy of surface-adsorbed organic molecules and investigate
their agglomeration dynamics. Furthermore, we apply our spectroscopic method to
quantum dots on the surface of the fiber waist and to caesium vapor surrounding
the fiber. Finally, towards dispersive measurements, we present our first
results on building and testing a single-fiber bi-modal interferometer.Comment: 13 pages, 18 figures. Accepted for publication in Applied Physics B.
Changes according to referee suggestions: changed title, clarification of
some points in the text, added references, replacement of Figure 13
p53 convergently activates Dux/DUX4 in embryonic stem cells and in facioscapulohumeral muscular dystrophy cell models
p53 activates Dux in mouse embryos and embryonic stem cells, as well as DUX4 in human facioscapulohumeral muscular dystrophy cell models.In mammalian embryos, proper zygotic genome activation (ZGA) underlies totipotent development. Double homeobox (DUX)-family factors participate in ZGA, and mouse Dux is required for forming cultured two-cell (2C)-like cells. Remarkably, in mouse embryonic stem cells, Dux is activated by the tumor suppressor p53, and Dux expression promotes differentiation into expanded-fate cell types. Long-read sequencing and assembly of the mouse Dux locus reveals its complex chromatin regulation including putative positive and negative feedback loops. We show that the p53-DUX/DUX4 regulatory axis is conserved in humans. Furthermore, we demonstrate that cells derived from patients with facioscapulohumeral muscular dystrophy (FSHD) activate human DUX4 during p53 signaling via a p53-binding site in a primate-specific subtelomeric long terminal repeat (LTR)10C element. In summary, our work shows that p53 activation convergently evolved to couple p53 to Dux/DUX4 activation in embryonic stem cells, embryos and cells from patients with FSHD, potentially uniting the developmental and disease regulation of DUX-family factors and identifying evidence-based therapeutic opportunities for FSHD.Molecular Technology and Informatics for Personalised Medicine and HealthFunctional Genomics of Muscle, Nerve and Brain Disorder
Oxidative damage and photosynthetic impairment in tropical rice cultivars upon exposure to excess iron
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Working Group 7.0 Environmental Transport and Health Effects, Chernobyl Studies Project. Progress report, October 1994 -- March 1995
This document presents the details from the working group 7.0 Chernobyl Studies Project. This working group looked at the environmental transport and health effects from the fallout due to the meltdown of Chernobylsk-4 reactor. Topics include: hydrological transport; chromosome painting dosimetry; EPR, TL and OSL dosimetry; stochastic effects; thyroid studies; and leukemia studies
Chernobyl Studies Project: Working group 7.0, Environmental transport and health effects. Progress report, March--September 1994
In April 1988, the US and the former-USSR signed a Memorandum of Cooperation (MOC) for Civilian Nuclear Reactor Safety; this MOC was a direct result of the accident at the Chernobyl Nuclear Power Plant Unit 4 and the following efforts by the two countries to implement a joint program to improve the safety of nuclear power plants and to understand the implications of environmental releases. A Joint Coordinating Committee for Civilian Nuclear Reactor Safety (JCCCNRS) was formed to implement the MOC. The JCCCNRS established many working groups; most of these were the responsibility of the Nuclear Regulatory Commission, as far as the US participation was concerned. The lone exception was Working Group 7 on Environmental Transport and Health Effects, for which the US participation was the responsibility of the US Department of Energy (DOE). The purpose of Working Group 7 was succintly stated to be, ``To develop jointly methods to project rapidly the health effects of any future nuclear reactor accident.`` To implement the work DOE then formed two subworking groups: 7.1 to address Environmental Transport and 7.2 to address Health Effects. Thus, the DOE-funded Chernobyl Studies Project began. The majority of the initial tasks for this project are completed or near completion. The focus is now turned to the issue of health effects from the Chernobyl accident. Currently, we are involved in and making progress on the case-control and co-hort studies of thyroid diseases among Belarussian children. Dosimetric aspects are a fundamental part of these studies. We are currently working to implement similar studies in Ukraine. A major part of the effort of these projects is supporting these studies, both by providing methods and applications of dose reconstruction and by providing support and equipment for the medical teams
Recommended from our members
Chernobyl Studies Project: Working group 7.0, Environmental transport and health effects. Progress report, March--September 1994
In April 1988, the US and the former-USSR signed a Memorandum of Cooperation (MOC) for Civilian Nuclear Reactor Safety; this MOC was a direct result of the accident at the Chernobyl Nuclear Power Plant Unit 4 and the following efforts by the two countries to implement a joint program to improve the safety of nuclear power plants and to understand the implications of environmental releases. A Joint Coordinating Committee for Civilian Nuclear Reactor Safety (JCCCNRS) was formed to implement the MOC. The JCCCNRS established many working groups; most of these were the responsibility of the Nuclear Regulatory Commission, as far as the US participation was concerned. The lone exception was Working Group 7 on Environmental Transport and Health Effects, for which the US participation was the responsibility of the US Department of Energy (DOE). The purpose of Working Group 7 was succintly stated to be, ``To develop jointly methods to project rapidly the health effects of any future nuclear reactor accident.`` To implement the work DOE then formed two subworking groups: 7.1 to address Environmental Transport and 7.2 to address Health Effects. Thus, the DOE-funded Chernobyl Studies Project began. The majority of the initial tasks for this project are completed or near completion. The focus is now turned to the issue of health effects from the Chernobyl accident. Currently, we are involved in and making progress on the case-control and co-hort studies of thyroid diseases among Belarussian children. Dosimetric aspects are a fundamental part of these studies. We are currently working to implement similar studies in Ukraine. A major part of the effort of these projects is supporting these studies, both by providing methods and applications of dose reconstruction and by providing support and equipment for the medical teams