706 research outputs found
Frequency noise and intensity noise of next-generation gravitational-wave detectors with RF/DC readout schemes
The sensitivity of next-generation gravitational-wave detectors such as
Advanced LIGO and LCGT should be limited mostly by quantum noise with an
expected technical progress to reduce seismic noise and thermal noise. Those
detectors will employ the optical configuration of resonant-sideband-extraction
that can be realized with a signal-recycling mirror added to the Fabry-Perot
Michelson interferometer. While this configuration can reduce quantum noise of
the detector, it can possibly increase laser frequency noise and intensity
noise. The analysis of laser noise in the interferometer with the conventional
configuration has been done in several papers, and we shall extend the analysis
to the resonant-sideband-extraction configuration with the radiation pressure
effect included. We shall also refer to laser noise in the case we employ the
so-called DC readout scheme.Comment: An error in Fig. 10 in the published version in PRD has been
corrected in this version; an erratum has been submitted to PRD. After
correction, this figure reflects a significant difference in the ways RF and
DC readout schemes are susceptible to laser noise. In addition, the levels of
mirror loss imbalances and input laser amplitude noise have also been updated
to be more realistic for Advanced LIG
High-sensitivity optical measurement of mechanical Brownian motion
We describe an experiment in which a laser beam is sent into a high-finesse
optical cavity with a mirror coated on a mechanical resonator. We show that the
reflected light is very sensitive to small mirror displacements. We have
observed the Brownian motion of the resonator with a very high sensitivity.Comment: 4 pages, 4 figures, RevTe
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Implementation of an Ultraviolet Phototherapy Service at a National Referral Hospital in Western Kenya: Reflections on Challenges and Lessons Learned.
IntroductionIn order to manage skin conditions at a national referral hospital level in Kenya, specialized dermatology services, such as dermatologic surgery, dermatopathology, phototherapy, and sub-specialty care, should be offered, as is typically available in referral hospitals around the world. A Kenyan patient with prurigo nodularis, whose severe itch remitted after phototherapy treatment at the University of California, San Francisco (UCSF), inspired the development of a phototherapy service at Academic Model Providing Access to Healthcare (AMPATH), a partnership in Western Kenya between Moi Teaching and Referral Hospital, Moi University College of Health Sciences, and a consortium of North American academic medical centers.MethodsInitial project funds were raised through a crowdfunding campaign and fundraising events. A new narrowband ultraviolet B phototherapy unit and replacement bulbs were donated and air shipped to Eldoret, Kenya. A team of dermatologists and phototherapy nurses from UCSF conducted a 2-day training session. US-based dermatologists affiliated with AMPATH provide ongoing support through regular communication and on-site visits.ResultsEarly in implementation, challenges faced included training clinical staff with limited experience in phototherapy and improving communication between nurses and clinicians. More recent challenges include frequent rotation of specialty clinic nurses in the dermatology clinic, adaptation of phototherapy guidelines to balance patient volume with service delivery capacity, and training assessment of disease activity in darkly pigmented skin.ConclusionStrategies that have been helpful in addressing implementation challenges include: increasing on-site and remote training opportunities for clinicians and nurses, developing a tiered payment schema, educating patients to combat misconceptions about phototherapy, dynamic phototherapy referral guidelines to accommodate service delivery capacity, and prioritizing the engagement of a multidisciplinary team
Prospects for improving the sensitivity of KAGRA gravitational wave detector
KAGRA is a new gravitational wave detector which aims to begin joint observation with Advanced LIGO and Advanced Virgo from late 2019. Here, we present KAGRA's possible upgrade plans to improve the sensitivity in the decade ahead. Unlike other state-of-the-art detectors, KAGRA requires different investigations for the upgrade since it is the only detector which employs cryogenic cooling of the test mass mirrors. In this paper, investigations on the upgrade plans which can be realized by changing the input laser power, increasing the mirror mass, and injecting frequency dependent squeezed vacuum are presented. We show how each upgrade affects to the detector frequency bands and also discuss impacts on gravitational-wave science. We then propose an effective progression of upgrades based on technical feasibility and scientific scenarios
Cooling of a mirror by radiation pressure
We describe an experiment in which a mirror is cooled by the radiation
pressure of light. A high-finesse optical cavity with a mirror coated on a
mechanical resonator is used as an optomechanical sensor of the Brownian motion
of the mirror. A feedback mechanism controls this motion via the radiation
pressure of a laser beam reflected on the mirror. We have observed either a
cooling or a heating of the mirror, depending on the gain of the feedback loop.Comment: 4 pages, 6 figures, RevTe
Diagonal-unitary 2-designs and their implementations by quantum circuits
We study efficient generations of random diagonal-unitary matrices, an
ensemble of unitary matrices diagonal in a given basis with randomly
distributed phases for their eigenvalues. Despite the simple algebraic
structure, they cannot be achieved by quantum circuits composed of a few-qubit
diagonal gates. We introduce diagonal-unitary -designs and present two
quantum circuits that implement diagonal-unitary -designs with the
computational basis in -qubit systems. One is composed of single-qubit
diagonal gates and controlled-phase gates with randomized phases, which
achieves an exact diagonal-unitary -design after applying the gates on all
pairs of qubits. The number of required gates is . If the
controlled-Z gates are used instead of the controlled-phase gates, the circuit
cannot achieve an exact -design, but achieves an -approximate
-design by applying gates on randomly selected pairs of qubits. Due to the
random choice of pairs, the circuit obtains extra randomness and the required
number of gates is at most . We also provide an
application of the circuits, a protocol of generating an exact -design of
random states by combining the circuits with a simple classical procedure
requiring random classical bits.Comment: Revised, 22 pages + Appendix, 3 figures; major revision from v2;
presentation is improved in v4; v5 is a published versio
The C-terminal helical bundle of the tetrameric prokaryotic sodium channel accelerates the inactivation rate
Most tetrameric channels have cytosolic domains to regulate their functions, including channel inactivation. Here we show that the cytosolic C-terminal region of NavSulP, a prokaryotic voltage-gated sodium channel cloned from Sulfitobacter pontiacus, accelerates channel inactivation. The crystal structure of the C-terminal region of NavSulP grafted into the C-terminus of a NaK channel revealed that the NavSulP C-terminal region forms a four-helix bundle. Point mutations of the residues involved in the intersubunit interactions of the four-helix bundle destabilized the tetramer of the channel and reduced the inactivation rate. The four-helix bundle was directly connected to the inner helix of the pore domain, and a mutation increasing the rigidity of the inner helix also reduced the inactivation rate. These findings suggest that the NavSulP four-helix bundle has important roles not only in stabilizing the tetramer, but also in accelerating the inactivation rate, through promotion of the conformational change of the inner helix
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