2,993 research outputs found
Geometric quantum computation with NMR
The experimental realisation of the basic constituents of quantum information
processing devices, namely fault-tolerant quantum logic gates, requires
conditional quantum dynamics, in which one subsystem undergoes a coherent
evolution that depends on the quantum state of another subsystem. In
particular, the subsystem may acquire a conditional phase shift. Here we
consider a novel scenario in which this phase is of geometric rather than
dynamical origin. As the conditional geometric (Berry) phase depends only on
the geometry of the path executed it is resilient to certain types of errors,
and offers the potential of an intrinsically fault-tolerant way of performing
quantum gates. Nuclear Magnetic Resonance (NMR) has already been used to
demonstrate both simple quantum information processing and Berry's phase. Here
we report an NMR experiment which implements a conditional Berry phase, and
thus a controlled phase shift gate. This constitutes the first elementary
geometric quantum computation.Comment: Minor additions at request of referees. 4 pages revtex including 2
figures (1 eps). Nature in pres
P16-30. Induction of Tim-3 expression by the common gamma-chain cytokines IL-2, IL-7, IL-15 and IL-21
Explicit solutions for effective four- and five-loop QCD running coupling
We start with the explicit solution, in terms of the Lambert W function, of
the renormalization group equation (RGE) for the gauge coupling in the
supersymmetric Yang-Mills theory described by the well-known beta function of
Novikov et al.(NSVZ). We then construct a class of beta functions for which the
RGE can be solved in terms of the Lambert W function. These beta functions are
expressed in terms of a function which is a truncated Laurent series in the
inverse of the gauge coupling. The parameters in the Laurent series can be
adjusted so that the first coefficients of the Taylor expansion of the beta
function in the gauge coupling reproduce the four-loop or five-loop QCD (or
SQCD) beta function.Comment: 21 pages, 13 figures; in v2, minor changes in the text, two figures
added, ref.[3] (2nd entry) is new; version to appear in JHE
The information needs of people living with ankylosing spondylitis: a questionnaire survey
<p>BACKGROUND:Today, health care is patient-centred with patients more involved in medical decision making and taking an active role in managing their disease. It is important that patients are appropriately informed about their condition and that their health care needs are met. We examine the information utilisation, sources and needs of people with ankylosing spondylitis (AS).</p>
<p>METHODS: Participants in an existing AS cohort study were asked to complete a postal or online questionnaire containing closed and open-ended questions, regarding their information access and needs. Participants were stratified by age and descriptive statistics were performed using STATA 11, while thematic analysis was performed on open-ended question narratives. Qualitative data was handled in Microsoft Access and explored for emerging themes and patterns of experiences.</p>
<p>RESULTS: Despite 73% of respondents having internet access, only 49% used the internet to access information regarding AS. Even then, this was only infrequently. Only 50% of respondents reported accessing written information about AS, which was obtained mainly in specialist clinics. Women were more likely than men to access information (63% (women) 46% (men)) regardless of the source, while younger patients were more likely to use online sources. The main source of non-written information was the rheumatologist. Overall, the respondents felt there was sufficient information available, but there was a perception that the tone was often too negative. The majority (95%) of people would like to receive a regular newsletter about AS, containing positive practical and local information. Suggestions were also made for more information about AS to be made available to non-specialist medical professionals and the general public.</p>
<p>CONCLUSIONS: There appears to be sufficient information available for people with AS in the UK and this is mostly accessed by younger AS patients. Many patients, particularly men, choose not to access AS information and concerns were raised about its negative tone. Patients still rely on written and verbal information from their specialists. Future initiatives should focus on the delivery of more positive information, targeting younger participants in particular and increasing the awareness in the general population and wider non-specialist medical community.</p>
Effects of intermediate scales on renormalization group running of fermion observables in an SO(10) model
In the context of non-supersymmetric SO(10) models, we analyze the
renormalization group equations for the fermions (including neutrinos) from the
GUT energy scale down to the electroweak energy scale, explicitly taking into
account the effects of an intermediate energy scale induced by a Pati--Salam
gauge group. To determine the renormalization group running, we use a numerical
minimization procedure based on a nested sampling algorithm that randomly
generates the values of 19 model parameters at the GUT scale, evolves them, and
finally constructs the values of the physical observables and compares them to
the existing experimental data at the electroweak scale. We show that the
evolved fermion masses and mixings present sizable deviations from the values
obtained without including the effects of the intermediate scale.Comment: Comments: 20 pages, 3 figures. Final version published in JHE
The Thermal Design, Characterization, and Performance of the SPIDER Long-Duration Balloon Cryostat
We describe the SPIDER flight cryostat, which is designed to cool six
millimeter-wavelength telescopes during an Antarctic long-duration balloon
flight. The cryostat, one of the largest to have flown on a stratospheric
payload, uses liquid helium-4 to deliver cooling power to stages at 4.2 and 1.6
K. Stainless steel capillaries facilitate a high flow impedance connection
between the main liquid helium tank and a smaller superfluid tank, allowing the
latter to operate at 1.6 K as long as there is liquid in the 4.2 K main tank.
Each telescope houses a closed cycle helium-3 adsorption refrigerator that
further cools the focal planes down to 300 mK. Liquid helium vapor from the
main tank is routed through heat exchangers that cool radiation shields,
providing negative thermal feedback. The system performed successfully during a
17 day flight in the 2014-2015 Antarctic summer. The cryostat had a total hold
time of 16.8 days, with 15.9 days occurring during flight.Comment: 15 pgs, 17 fig
Stability of Spatial Optical Solitons
We present a brief overview of the basic concepts of the soliton stability
theory and discuss some characteristic examples of the instability-induced
soliton dynamics, in application to spatial optical solitons described by the
NLS-type nonlinear models and their generalizations. In particular, we
demonstrate that the soliton internal modes are responsible for the appearance
of the soliton instability, and outline an analytical approach based on a
multi-scale asymptotic technique that allows to analyze the soliton dynamics
near the marginal stability point. We also discuss some results of the rigorous
linear stability analysis of fundamental solitary waves and nonlinear impurity
modes. Finally, we demonstrate that multi-hump vector solitary waves may become
stable in some nonlinear models, and discuss the examples of stable
(1+1)-dimensional composite solitons and (2+1)-dimensional dipole-mode solitons
in a model of two incoherently interacting optical beams.Comment: 34 pages, 9 figures; to be published in: "Spatial Optical Solitons",
Eds. W. Torruellas and S. Trillo (Springer, New York
Treatment outcomes of new tuberculosis patients hospitalized in Kampala, Uganda: a prospective cohort study.
BACKGROUND: In most resource limited settings, new tuberculosis (TB) patients are usually treated as outpatients. We sought to investigate the reasons for hospitalisation and the predictors of poor treatment outcomes and mortality in a cohort of hospitalized new TB patients in Kampala, Uganda. METHODS AND FINDINGS: Ninety-six new TB patients hospitalised between 2003 and 2006 were enrolled and followed for two years. Thirty two were HIV-uninfected and 64 were HIV-infected. Among the HIV-uninfected, the commonest reasons for hospitalization were low Karnofsky score (47%) and need for diagnostic evaluation (25%). HIV-infected patients were commonly hospitalized due to low Karnofsky score (72%), concurrent illness (16%) and diagnostic evaluation (14%). Eleven HIV uninfected patients died (mortality rate 19.7 per 100 person-years) while 41 deaths occurred among the HIV-infected patients (mortality rate 46.9 per 100 person years). In all patients an unsuccessful treatment outcome (treatment failure, death during the treatment period or an unknown outcome) was associated with duration of TB symptoms, with the odds of an unsuccessful outcome decreasing with increasing duration. Among HIV-infected patients, an unsuccessful treatment outcome was also associated with male sex (P = 0.004) and age (P = 0.034). Low Karnofsky score (aHR = 8.93, 95% CI 1.88 - 42.40, P = 0.001) was the only factor significantly associated with mortality among the HIV-uninfected. Mortality among the HIV-infected was associated with the composite variable of CD4 and ART use, with patients with baseline CD4 below 200 cells/µL who were not on ART at a greater risk of death than those who were on ART, and low Karnofsky score (aHR = 2.02, 95% CI 1.02 - 4.01, P = 0.045). CONCLUSION: Poor health status is a common cause of hospitalisation for new TB patients. Mortality in this study was very high and associated with advanced HIV Disease and no use of ART
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