1,217 research outputs found
The Bulk Channel in Thermal Gauge Theories
We investigate the thermal correlator of the trace of the energy-momentum
tensor in the SU(3) Yang-Mills theory. Our goal is to constrain the spectral
function in that channel, whose low-frequency part determines the bulk
viscosity. We focus on the thermal modification of the spectral function,
. Using the operator-product expansion we give
the high-frequency behavior of this difference in terms of thermodynamic
potentials. We take into account the presence of an exact delta function
located at the origin, which had been missed in previous analyses. We then
combine the bulk sum rule and a Monte-Carlo evaluation of the Euclidean
correlator to determine the intervals of frequency where the spectral density
is enhanced or depleted by thermal effects. We find evidence that the thermal
spectral density is non-zero for frequencies below the scalar glueball mass
and is significantly depleted for .Comment: (1+25) pages, 6 figure
Installing the "magic methyl" - C-H methylation in synthesis
The selective and efficient C-H methylation of sp2 and sp3 carbon centres has become a powerful transformation in the synthetic toolbox. Due to the potential for profound changes to physicochemical properties attributed to the installation of a "Magic Methyl" group at a strategic site in a lead compound, such techniques have become highly desirable in modern drug discovery and synthesis programmes. This review will cover the diverse techniques that have been employed to enable the selective installation of the C-Me bond in a wide range of chemical structures, from simple building blocks to complex drug-like architectures
The pressure of strong coupling lattice QCD with heavy quarks, the hadron resonance gas model and the large N limit
In this paper we calculate the pressure of pure lattice Yang-Mills theories
and lattice QCD with heavy quarks by means of strong coupling expansions.
Dynamical fermions are introduced with a hopping parameter expansion, which
also allows for the incorporation of finite quark chemical potential. We show
that in leading orders the results are in full agreement with expectations from
the hadron resonance gas model, thus validating it with a first principles
calculation. For pure Yang-Mills theories we obtain the corresponding ideal
glueball gas, in QCD with heavy quarks our result equals that of an ideal gas
of mesons and baryons. Another finding is that the Yang-Mills pressure in the
large N limit is of order to the calculated orders, when the inverse
't Hooft coupling is used as expansion parameter. This property is expected in
the confined phase, where our calculations take place.Comment: 12 pages, 4 figure
Mapping coherence in measurement via full quantum tomography of a hybrid optical detector
Quantum states and measurements exhibit wave-like --- continuous, or
particle-like --- discrete, character. Hybrid discrete-continuous photonic
systems are key to investigating fundamental quantum phenomena, generating
superpositions of macroscopic states, and form essential resources for
quantum-enhanced applications, e.g. entanglement distillation and quantum
computation, as well as highly efficient optical telecommunications. Realizing
the full potential of these hybrid systems requires quantum-optical
measurements sensitive to complementary observables such as field quadrature
amplitude and photon number. However, a thorough understanding of the practical
performance of an optical detector interpolating between these two regions is
absent. Here, we report the implementation of full quantum detector tomography,
enabling the characterization of the simultaneous wave and photon-number
sensitivities of quantum-optical detectors. This yields the largest
parametrization to-date in quantum tomography experiments, requiring the
development of novel theoretical tools. Our results reveal the role of
coherence in quantum measurements and demonstrate the tunability of hybrid
quantum-optical detectors.Comment: 7 pages, 3 figure
Second law, entropy production, and reversibility in thermodynamics of information
We present a pedagogical review of the fundamental concepts in thermodynamics
of information, by focusing on the second law of thermodynamics and the entropy
production. Especially, we discuss the relationship among thermodynamic
reversibility, logical reversibility, and heat emission in the context of the
Landauer principle and clarify that these three concepts are fundamentally
distinct to each other. We also discuss thermodynamics of measurement and
feedback control by Maxwell's demon. We clarify that the demon and the second
law are indeed consistent in the measurement and the feedback processes
individually, by including the mutual information to the entropy production.Comment: 43 pages, 10 figures. As a chapter of: G. Snider et al. (eds.),
"Energy Limits in Computation: A Review of Landauer's Principle, Theory and
Experiments
Long-term follow-up on the use of vascularized fibular graft for the treatment of congenital pseudarthrosis of the tibia
<p>Abstract</p> <p>Background</p> <p>Congenital pseudoarthrosis of the tibia (CPT) is one of the most difficult conditions to treat.</p> <p>Methods</p> <p>Five girls and 3 boys with CPT were treated by vascularized fibular grafting (VFG). The average age at VFG was 7.0 years (range: 1.9–11.5 years) with an average follow-up term of 11.7 years (range: 4.9–19.6 years). Five of the children had undergone multiple operations before VFG, while the other 3 had no such history.</p> <p>Results</p> <p>Bone consolidation was obtained in all cases after an average term of 6.6 months (range: 4–10 months); this was with the first VFG in 7 cases but with the second VFG in 1 case. Complication of stress fracture and ankle pain occurred in 1 and 3 cases, respectively, only in cases undergoing multiple operations. Leg-length discrepancy was more prominent in the patients with multiple previous operations (mean: 7.5 cm), than in the cases with no prior surgery (mean: 0.7 cm).</p> <p>Conclusion</p> <p>The long-term results of VFG for CPT were excellent, especially in the cases, with no prior surgery. VFG should be considered as a primary treatment option for CPT.</p
Sociodemographic differences in linkage error: An examination of four large-scale datasets
© 2018 The Author(s). Background: Record linkage is an important tool for epidemiologists and health planners. Record linkage studies will generally contain some level of residual record linkage error, where individual records are either incorrectly marked as belonging to the same individual, or incorrectly marked as belonging to separate individuals. A key question is whether errors in linkage quality are distributed evenly throughout the population, or whether certain subgroups will exhibit higher rates of error. Previous investigations of this issue have typically compared linked and un-linked records, which can conflate bias caused by record linkage error, with bias caused by missing records (data capture errors). Methods: Four large administrative datasets were individually de-duplicated, with results compared to an available 'gold-standard' benchmark, allowing us to avoid methodological issues with comparing linked and un-linked records. Results were compared by gender, age, geographic remoteness (major cities, regional or remote) and socioeconomic status. Results: Results varied between datasets, and by sociodemographic characteristic. The most consistent findings were worse linkage quality for younger individuals (seen in all four datasets) and worse linkage quality for those living in remote areas (seen in three of four datasets). The linkage quality within sociodemographic categories varied between datasets, with the associations with linkage error reversed across different datasets due to quirks of the specific data collection mechanisms and data sharing practices. Conclusions: These results suggest caution should be taken both when linking younger individuals and those in remote areas, and when analysing linked data from these subgroups. Further research is required to determine the ramifications of worse linkage quality in these subpopulations on research outcomes
Technical challenges of providing record linkage services for research
Background: Record linkage techniques are widely used to enable health researchers to gain event based longitudinal information for entire populations. The task of record linkage is increasingly being undertaken by specialised linkage units (SLUs). In addition to the complexity of undertaking probabilistic record linkage, these units face additional technical challenges in providing record linkage ‘as a service’ for research. The extent of this functionality, and approaches to solving these issues, has had little focus in the record linkage literature. Few, if any, of the record linkage packages or systems currently used by SLUs include the full range of functions required. Methods: This paper identifies and discusses some of the functions that are required or undertaken by SLUs in the provision of record linkage services. These include managing routine, on-going linkage; storing and handling changing data; handling different linkage scenarios; accommodating ever increasing datasets. Automated linkage processes are one way of ensuring consistency of results and scalability of service. Results: Alternative solutions to some of these challenges are presented. By maintaining a full history of links, and storing pairwise information, many of the challenges around handling ‘open’ records, and providing automated managed extractions are solved. A number of these solutions were implemented as part of the development of the National Linkage System (NLS) by the Centre for Data Linkage (part of the Population Health Research Network) in Australia.Conclusions: The demand for, and complexity of, linkage services are growing. This presents as a challenge to SLUs as they seek to service the varying needs of dozens of research projects annually. Linkage units need to be both flexible and scalable to meet this demand. It is hoped the solutions presented here can help mitigate these difficulties
Thermodynamics of deformed AdS model with a positive/negative quadratic correction in graviton-dilaton system
By solving the Einstein equations of the graviton coupling with a real scalar
dilaton field, we establish a general framework to self-consistently solve the
geometric background with black-hole for any given phenomenological holographic
models. In this framwork, we solve the black-hole background, the corresponding
dilaon field and the dilaton potential for the deformed AdS model with a
positive/negative quadratic correction. We systematically investigate the
thermodynamical properties of the deformed AdS model with a positive and
negative quadratic correction, respectively, and compare with lattice QCD on
the results of the equation of state, the heavy quark potential, the Polyakov
loop and the spatial Wilson loop. We find that the bulk thermodynamical
properties are not sensitive to the sign of the quadratic correction, and the
results of both deformed holographic QCD models agree well with lattice QCD
result for pure SU(3) gauge theory. However, the results from loop operators
favor a positive quadratic correction, which agree well with lattice QCD
result. Especially, the result from the Polyakov loop excludes the model with a
negative quadratic correction in the warp factor of .Comment: 26 figures,36 pages,V.3: an appendix,more equations and references
added,figures corrected,published versio
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