8,857 research outputs found
Dimensional Reduction, Hard Thermal Loops and the Renormalization Group
We study the realization of dimensional reduction and the validity of the
hard thermal loop expansion for lambda phi^4 theory at finite temperature,
using an environmentally friendly finite-temperature renormalization group with
a fiducial temperature as flow parameter. The one-loop renormalization group
allows for a consistent description of the system at low and high temperatures,
and in particular of the phase transition. The main results are that
dimensional reduction applies, apart from a range of temperatures around the
phase transition, at high temperatures (compared to the zero temperature mass)
only for sufficiently small coupling constants, while the HTL expansion is
valid below (and rather far from) the phase transition, and, again, at high
temperatures only in the case of sufficiently small coupling constants. We
emphasize that close to the critical temperature, physics is completely
dominated by thermal fluctuations that are not resummed in the hard thermal
loop approach and where universal quantities are independent of the parameters
of the fundamental four-dimensional theory.Comment: 20 pages, 13 eps figures, uses epsfig and pstrick
Chlorinated auxinsâhow does Arabidopsis thaliana deal with them?
Plant hormones have various functions in plants and play crucial roles in all developmental and differentiation stages. Auxins constitute one of the most important groups with the major representative indole-3-acetic acid (IAA). A halogenated derivate of IAA, 4-chloro-indole-3-acetic acid (4-Cl-IAA), has previously been identified in Pisum sativum and other legumes. While the enzymes responsible for the halogenation of compounds in bacteria and fungi are well studied, the metabolic pathways leading to the production of 4-Cl-IAA in plants, especially the halogenating reaction, are still unknown. Therefore, bacterial flavin-dependent tryptophan-halogenase genes were transformed into the model organism Arabidopsis thaliana. The type of chlorinated indole derivatives that could be expected was determined by incubating wild type A. thaliana with different Cl-tryptophan derivatives. We showed that, in addition to chlorinated IAA, chlorinated IAA conjugates were synthesized. Concomitantly, we found that an auxin conjugate synthetase (GH3.3 protein) from A. thaliana was able to convert chlorinated IAAs to amino acid conjugates in vitro. In addition, we showed that the production of halogenated tryptophan (Trp), indole-3-acetonitrile (IAN) and IAA is possible in transgenic A. thaliana in planta with the help of the bacterial halogenating enzymes. Furthermore, it was investigated if there is an effect (i) of exogenously applied Cl-IAA and Cl-Trp and (ii) of endogenously chlorinated substances on the growth phenotype of the plants
Rapid purification of quantum systems by measuring in a feedback-controlled unbiased basis
Rapid-purification by feedback --- specifically, reducing the mean impurity
faster than by measurement alone --- can be achieved by making the eigenbasis
of the density matrix to be unbiased relative to the measurement basis. Here we
further examine the protocol introduced by Combes and Jacobs [Phys.Rev.Lett.
{\bf 96}, 010504 (2006)] involving continuous measurement of the observable
for a -dimensional system. We rigorously re-derive the lower bound
on the achievable speed-up factor, and also an upper bound, namely
, for all feedback protocols that use measurements in unbiased bases.
Finally we extend our results to independent measurements on a register of
qubits, and derive an upper bound on the achievable speed-up factor that
scales linearly with .Comment: v2: published versio
Entanglement in a molecular three-qubit system
We study the entanglement properties of a molecular three-qubit system
described by the Heisenberg spin Hamiltonian with anisotropic exchange
interactions and including an external magnetic field. The system exhibits
first order quantum phase transitions by tuning two parameters, and , of
the Hamiltonian to specific values. The three-qubit chain is open ended so that
there are two types of pairwise entanglement : nearest-neighbour (n.n.) and
next-nearest-neighbour (n.n.n.). We calculate the ground and thermal state
concurrences, quantifying pairwise entanglement, as a function of the
parameters , and the temperature . The entanglement threshold and gap
temperatures are also determined as a function of the anisotropy parameter .
The results obtained are of relevance in understanding the entanglement
features of the recently engineered molecular --
complex which serves as a three-qubit system at sufficiently low temperatures.Comment: 9 pages, 13 figures, revtex
Perspectives of autistic adolescent girls and women on the determinants of their mental health and social and emotional well-being: A systematic review and thematic synthesis of lived experience
Autistic girls and women experience more mental health difficulties and poorer well-being than their non-autistic peers. Little emphasis has been placed on the perspectives of the girls and women within the literature. This review aims to provide an overview of the factors that impact autistic femalesâ emotional and social well-being and mental health, as described in self-report qualitative studies. The protocol for the present review was pre-registered on PROSPERO (CRD42020184983), and this article follows Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. PsycInfo, Academic Search Complete and MEDLINE were systematically searched using a pre-defined search string. This yielded 877 unique records, which were systematically screened by two reviewers, resulting in 52 eligible studies. Structured data extraction and quality appraisal were completed. The present review presents the perspectives of 973 autistic females aged 13â70+. Thematic synthesis identified three themes and nine subthemes. Our findings suggest that autistic girlsâ and womenâs experiences can be conceptualised within a social model, where biological and psychological factors (âThe Autistic Neurotypeâ) are experienced through the lens of social factors (âThe Neurotypical Worldâ and âStigmaâ), together shaping well-being and mental health outcomes.
Lay abstract
Difficulties with mental health and low levels of well-being are more common among autistic girls and women than non-autistic people, but we do not fully understand why. Research does not focus enough on what autistic girls and women could tell us about this. This review aims to summarise the studies where autistic girls and women explain things that affect their mental health and well-being to help us understand how to prevent these difficulties from developing. Three research databases were searched to find possibly relevant studies. There were 877 studies found, which two researchers screened according to particular criteria. They found 52 studies that could be included in this review. One researcher evaluated the quality of these studies and extracted the key information from them. This review summarises the views of 973 autistic girls and women aged between 13 and 70+. The findings from the 52 studies were analysed, and we found many factors that affect the mental health and well-being of autistic girls and women. These factors fall into two categories: (1) difficulties living in a world not designed for autistic people and (2) the impact of stigma due to being autistic
Sustainable development as a framework for ethics and skills in higher education computing courses
The impact of sustainable development on the curriculum remains variable, and in some disciplines the inclusion is considered by some to be inappropriate or not relevant. This paper considers the ways in which sustainable development can be embedded within the curriculum, with the dual aims of showing how it can be made both relevant to students within the context of their discipline, and how sustainable development can provide a framework for developing an appreciation of the legal, social, ethical and professional (LSEP) aspects of the discipline and to develop awareness of sustainability values in students, i.e. the meaning and aspects of sustainable development. The paper focusses on a case study in embedding sustainable development within Computer Science degree programmes, where the LSEP requirements are recognised by accrediting bodies and by many employers as essential characteristics and skills in graduates. The paper will describe how sustainable development provides an overarching framework within which to explore these issues. Moreover, the paper will include some examples of how this is successful in engaging students who may otherwise struggle to appreciate the LSEP topics. The success will be demonstrated through some objective data showing the impact of this approach to students understanding and acknowledgment of sustainability and how this may be applied to other disciplines and national contexts
Fine Structure of the 1s3p ^3P_J Level in Atomic ^4He: Theory and Experiment
We report on a theoretical calculation and a new experimental determination
of the 1s3p ^3P_J fine structure intervals in atomic ^4He. The values from the
theoretical calculation of 8113.730(6) MHz and 658.801(6) MHz for the nu_{01}
and nu_{12} intervals, respectively, disagree significantly with previous
experimental results. However, the new laser spectroscopic measurement reported
here yields values of 8113.714(28) MHz and 658.810(18) MHz for these intervals.
These results show an excellent agreement with the theoretical values and
resolve the apparent discrepancy between theory and experiment.Comment: 9 pages, 3 figure
Short gamma-ray bursts within 200 Mpc
We present a systematic search for short-duration gamma-ray bursts (GRBs) in the local Universe based on 14âyr of observations with the Neil Gehrels Swift Observatory. We cross-correlate the GRB positions with the GLADE catalogue of nearby galaxies, and find no event at a distance âČ100 Mpc and four plausible candidates in the range 100âMpc âČ DââČ 200âMpc. Although affected by low statistics, this number is higher than the one expected for chance alignments to random galaxies, and possibly suggests a physical association between these bursts and nearby galaxies. By assuming a local origin, we use these events to constrain the range of properties for X-ray counterparts of neutron star mergers. Optical upper limits place tight constraints on the onset of a blue kilonova, and imply either low masses (â âČ10â3Mââ ) of lanthanide-poor ejecta or unfavorable orientations (Ξ_(obs) âł 30 deg). Finally, we derive that the all-sky rate of detectable short GRBs within 200 Mpc is 1.3^(+1.7)_(â0.8) yrâ»Âč (68 perâcent confidence interval), and discuss the implications for the GRB outflow structure. If these candidates are instead of cosmological origin, we set a upper limit of âČ2.0 yrâ»Âč (90 perâcent confidence interval) to the rate of nearby events detectable with operating gamma-ray observatories, such as Swift and Fermi
Overcoming synecdoche: why practice development and quality improvement approaches should be better integrated
Commentary on: Lavery, G. (2016) Quality improvement â rival or ally of practice development? International Practice Development Journal. Vol. 6. No. 1. Article 1
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