12,866 research outputs found
Evidence for a Humoral Mechanism which Prevents Growth of Dermatophytes11From the Section of Dermatology Department of medicine, The University of Chicago, Chicago, Ill. and the Department of Dermatology, Walter Reed Army Hospital, Washington, D.C.
Rapid state purification protocols for a Cooper pair box
We propose techniques for implementing two different rapid state purification
schemes, within the constraints present in a superconducting charge qubit
system. Both schemes use a continuous measurement of charge (z) measurements,
and seek to minimize the time required to purify the conditional state. Our
methods are designed to make the purification process relatively insensitive to
rotations about the x-axis, due to the Josephson tunnelling Hamiltonian. The
first proposed method, based on the scheme of Jacobs [Phys. Rev. A 67,
030301(R) (2003)] uses the measurement results to control bias (z) pulses so as
to rotate the Bloch vector onto the x-axis of the Bloch sphere. The second
proposed method, based on the scheme of Wiseman and Ralph [New J. Phys. 8, 90
(2006)] uses a simple feedback protocol which tightly rotates the Bloch vector
about an axis almost parallel with the measurement axis. We compare the
performance of these and other techniques by a number of different measures.Comment: 14 pages, 14 figures. v2: Revised version after referee comments.
Accepted for publication by Physical Review
Heat Transfer Operators Associated with Quantum Operations
Any quantum operation applied on a physical system is performed as a unitary
transformation on a larger extended system. If the extension used is a heat
bath in thermal equilibrium, the concomitant change in the state of the bath
necessarily implies a heat exchange with it. The dependence of the average heat
transferred to the bath on the initial state of the system can then be found
from the expectation value of a hermitian operator, which is named as the heat
transfer operator (HTO). The purpose of this article is the investigation of
the relation between the HTOs and the associated quantum operations. Since, any
given quantum operation on a system can be realized by different baths and
unitaries, many different HTOs are possible for each quantum operation. On the
other hand, there are also strong restrictions on the HTOs which arise from the
unitarity of the transformations. The most important of these is the Landauer
erasure principle. This article is concerned with the question of finding a
complete set of restrictions on the HTOs that are associated with a given
quantum operation. An answer to this question has been found only for a subset
of quantum operations. For erasure operations, these characterizations are
equivalent to the generalized Landauer erasure principle. For the case of
generic quantum operations however, it appears that the HTOs obey further
restrictions which cannot be obtained from the entropic restrictions of the
generalized Landauer erasure principle.Comment: A significant revision is made; 33 pages with 2 figure
Rapid and quantitative detection of homologous and non-homologous recombination events using three oligonucleotide MLPA
Embryonic stem (ES) cell technology allows modification of the mouse germline from large deletions and insertions to single nucleotide substitutions by homologous recombination. Identification of these rare events demands an accurate and fast detection method. Current methods for detection rely on Southern blotting and/or conventional PCR. Both the techniques have major drawbacks, Southern blotting is time-consuming and PCR can generate false positives. As an alternative, we here demonstrate a novel approach of Multiplex Ligation-dependent Probe Amplification (MLPA) as a quick, quantitative and reliable method for the detection of homologous, non-homologous and incomplete recombination events in ES cell clones. We have adapted MLPA to detect homologous recombinants in ES cell clones targeted with two different constructs: one introduces a single nucleotide change in the PCNA gene and the other allows for a conditional inactivation of the wild-type PCNA allele. By using MLPA probes consisting of three oligonucleotides we were able to simultaneously detect and quantify both wild-type and mutant alleles
Optimal Unravellings for Feedback Control in Linear Quantum Systems
For quantum systems with linear dynamics in phase space much of classical
feedback control theory applies. However, there are some questions that are
sensible only for the quantum case, such as: given a fixed interaction between
the system and the environment what is the optimal measurement on the
environment for a particular control problem? We show that for a broad class of
optimal (state-based) control problems (the stationary
Linear-Quadratic-Gaussian class), this question is a semi-definite program.
Moreover, the answer also applies to Markovian (current-based) feedback.Comment: 5 pages. Version published by Phys. Rev. Let
Disparity of superconducting and pseudogap scales in low-Tc Bi-2201 cuprates
We experimentally study transport and intrinsic tunneling characteristics of
a single-layer cuprate Bi(2+x)Sr(2-y)CuO(6+delta) with a low superconducting
critical temperature Tc < 4 K. It is observed that the superconducting energy,
critical field and fluctuation temperature range are scaling down with Tc,
while the corresponding pseudogap characteristics have the same order of
magnitude as for high-Tc cuprates with 20 to 30 times higher Tc. The observed
disparity of the superconducting and pseudogap scales clearly reveals their
different origins.Comment: 5 page
A Straightforward Introduction to Continuous Quantum Measurement
We present a pedagogical treatment of the formalism of continuous quantum
measurement. Our aim is to show the reader how the equations describing such
measurements are derived and manipulated in a direct manner. We also give
elementary background material for those new to measurement theory, and
describe further various aspects of continuous measurements that should be
helpful to those wanting to use such measurements in applications.
Specifically, we use the simple and direct approach of generalized measurements
to derive the stochastic master equation describing the continuous measurements
of observables, give a tutorial on stochastic calculus, treat multiple
observers and inefficient detection, examine a general form of the measurement
master equation, and show how the master equation leads to information gain and
disturbance. To conclude, we give a detailed treatment of imaging the resonance
fluorescence from a single atom as a concrete example of how a continuous
position measurement arises in a physical system.Comment: 24 pages, 3 eps figues. To appear in Contemporary Physic
Strategies for Real-Time Position Control of a Single Atom in Cavity QED
Recent realizations of single-atom trapping and tracking in cavity QED open
the door for feedback schemes which actively stabilize the motion of a single
atom in real time. We present feedback algorithms for cooling the radial
component of motion for a single atom trapped by strong coupling to
single-photon fields in an optical cavity. Performance of various algorithms is
studied through simulations of single-atom trajectories, with full dynamical
and measurement noise included. Closed loop feedback algorithms compare
favorably to open-loop "switching" analogs, demonstrating the importance of
applying actual position information in real time. The high optical information
rate in current experiments enables real-time tracking that approaches the
standard quantum limit for broadband position measurements, suggesting that
realistic active feedback schemes may reach a regime where measurement
backaction appreciably alters the motional dynamics.Comment: 12 pages, 10 figures, submitted to J. Opt. B Quant. Semiclass. Op
Overseeing oversight: governance of quality and safety by hospital boards in the English NHS
Objectives:
To contribute towards an understanding of hospital Board composition and oversight of patient safety and health care quality in the NHS.
Methods:
A review of the theory related to hospital Board governance and two national surveys undertaken about Board management in NHS hospital trusts in England. The first was issued to 150 Trusts in 2011/12 and completed online via a dedicated web tool. A total of 145 replies were received (97% response rate). The second online survey undertaken in 2012/13 targeted individual Board members using the Board Self Assessment Questionnaire (BSAQ). A total of 334 responses were received from 165 executive and 169 non-executive board members, providing at least one response from 95 of the 144 NHS Trusts then in existence (66% response rate).
Results:
Around 42% of Boards had 10-12 members and around 51% had 13-15 members. We found no significant difference in Board size between Foundation and non Foundation trusts. Around 62% of Boards had three or fewer serving Board members with clinical backgrounds. For about two-thirds of the Trusts (63%), Board members with a clinical background comprised less than 30% of the Board members. Boards were using a wide range of hard performance metrics and soft intelligence to monitor their organisation with regard to patient safety. Hard, quantitative data were reportedly used at every Board meeting across most hospital Trusts (>80%), including a range of clinical outcomes measures, infection rates and process measures such as medication errors and readmission rates. A much smaller proportion of Trusts (57%) routinely report morbidity rates at every Board meeting. Softer intelligence, used organisationally and reported at all Board meetings, was more variably reported, with discussions with clinicians (in 89% of Trusts) and executive walk-arounds (88%) being most often reported, alongside use of patient stories (83%). However, in only about two-thirds of Trusts did Board members shadow clinicians and report back to the Board (65%). The BSAQ data showed general high or very high levels of agreement with desirable statements of practice in each of the six dimensions. Aggregate levels of agreement within each dimension ranged from 73% (interpersonal) to 85% (political).
Conclusions:
The study provides the best account to-date of English NHS Boards and their actions around health care quality and patient safety. While systematic differences between Trusts of different types were rare, there was nonetheless variation between individual Trusts on both Board composition and Board practices. These findings lay the groundwork for further empirical research exploring the dynamics, influences and impacts of Boards
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