Fermi's golden rule and exponential decay as a RG fixed point

We discuss the decay of unstable states into a quasicontinuum using models of the effective Hamiltonian type. The goal is to show that exponential decay and the golden rule are exact in a suitable scaling limit, and that there is an associated renormalization group (RG) with these properties as a fixed point. The method is inspired by a limit theorem for infinitely divisible distributions in probability theory, where there is a RG with a Cauchy distribution, i.e. a Lorentz line shape, as a fixed point. Our method of solving for the spectrum is well known; it does not involve a perturbation expansion in the interaction, and needs no assumption of a weak interaction. We use random matrices for the interaction, and show that the ensemble fluctuations vanish in the scaling limit. Thus the limit is the same for every model in the ensemble with probability one.Comment: 20 pages, 1 figur

Long-Term Clinical Impact of Coronary CT Angiography in Patients With Recent Acute-Onset Chest Pain The Randomized Controlled CATCH Trial

AbstractObjectivesThe aim of the CATCH (CArdiac cT in the treatment of acute CHest pain) trial was to investigate the long-term clinical impact of a coronary computed tomographic angiography (CTA)-guided treatment strategy in patients with recent acute-onset chest pain compared to standard care.BackgroundThe prognostic implications of a coronary CTA-guided treatment strategy have not been compared in a randomized fashion to standard care in patients referred for acute-onset chest pain.MethodsPatients with acute chest pain but normal electrocardiograms and troponin values were randomized to treatment guided by either coronary CTA or standard care (bicycle exercise electrocardiogram or myocardial perfusion imaging). In the coronary CTA-guided group, a functional test was included in cases of nondiagnostic coronary CTA images or coronary stenoses of borderline severity. The primary endpoint was a composite of cardiac death, myocardial infarction (MI), hospitalization for unstable angina pectoris (UAP), late symptom-driven revascularizations, and readmission for chest pain.ResultsWe randomized 299 patients to coronary CTA-guided strategy and 301 to standard care. After inclusion, 24 patients withdrew their consent. The median (interquartile range) follow-up duration was 18.7 (range 16.8 to 20.1) months. In the coronary CTA-guided group, 30 patients (11%) had a primary endpoint versus 47 patients (16%) in the standard care group (p = 0.04; hazard ratio [HR]: 0.62 [95% confidence interval: 0.40 to 0.98]). A major adverse cardiac event (cardiac death, MI, hospitalization for UAP, and late symptom-driven revascularization) was observed in 5 patients (2 MIs, 3 UAPs) in the coronary CTA-guided group versus 14 patients (1 cardiac death, 7 MIs, 5 UAPs, 1 late symptom-driven revascularization) in the standard care group (p = 0.04; HR: 0.36 [95% CI: 0.16 to 0.95]). Differences in cardiac death and MI (8 vs. 2) were insignificant (p = 0.06).ConclusionsA coronary CTA-guided treatment strategy appears to improve clinical outcome in patients with recent acute-onset chest pain and normal electrocardiograms and troponin values compared to standard care with a functional test. (Cardiac-CT in the Treatment of Acute Chest Pain [CATCH]; NCT01534000

Spatial distribution of early red lesions is a risk factor for development of vision-threatening diabetic retinopathy

Aims/hypothesis Diabetic retinopathy is characterised by morphological lesions related to disturbances in retinal blood flow. It has previously been shown that the early development of retinal lesions temporal to the fovea may predict the development of treatment-requiring diabetic maculopathy. The aim of this study was to map accurately the area where lesions could predict progression to vision-threatening retinopathy. Methods The predictive value of the location of the earliest red lesions representing haemorrhages and/or microaneurysms was studied by comparing their occurrence in a group of individuals later developing vision-threatening diabetic retinopathy with that in a group matched with respect to diabetes type, age, sex and age of onset of diabetes mellitus who did not develop vision-threatening diabetic retinopathy during a similar observation period. Results The probability of progression to vision-threatening diabetic retinopathy was higher in a circular area temporal to the fovea, and the occurrence of the first lesions in this area was predictive of the development of vision-threatening diabetic retinopathy. The calculated peak value showed that the risk of progression was 39.5% higher than the average. There was no significant difference in the early distribution of lesions in participants later developing diabetic maculopathy or proliferative diabetic retinopathy. Conclusions/interpretation The location of early red lesions in diabetic retinopathy is predictive of whether or not individuals will later develop vision-threatening diabetic retinopathy. This evidence should be incorporated into risk models used to recommend control intervals in screening programmes for diabetic retinopathy

Wild-Type Phosphoribosylpyrophosphate Synthase (PRS) from Mycobacterium tuberculosis: A Bacterial Class II PRS?

The 5-phospho-α-D-ribose 1-diphosphate (PRPP) metabolite plays essential roles in several biosynthetic pathways, including histidine, tryptophan, nucleotides, and, in mycobacteria, cell wall precursors. PRPP is synthesized from α-D-ribose 5-phosphate (R5P) and ATP by the Mycobacterium tuberculosis prsA gene product, phosphoribosylpyrophosphate synthase (MtPRS). Here, we report amplification, cloning, expression and purification of wild-type MtPRS. Glutaraldehyde cross-linking results suggest that MtPRS predominates as a hexamer, presenting varied oligomeric states due to distinct ligand binding. MtPRS activity measurements were carried out by a novel coupled continuous spectrophotometric assay. MtPRS enzyme activity could be detected in the absence of Pi. ADP, GDP and UMP inhibit MtPRS activity. Steady-state kinetics results indicate that MtPRS has broad substrate specificity, being able to accept ATP, GTP, CTP, and UTP as diphosphoryl group donors. Fluorescence spectroscopy data suggest that the enzyme mechanism for purine diphosphoryl donors follows a random order of substrate addition, and for pyrimidine diphosphoryl donors follows an ordered mechanism of substrate addition in which R5P binds first to free enzyme. An ordered mechanism for product dissociation is followed by MtPRS, in which PRPP is the first product to be released followed by the nucleoside monophosphate products to yield free enzyme for the next round of catalysis. The broad specificity for diphosphoryl group donors and detection of enzyme activity in the absence of Pi would suggest that MtPRS belongs to Class II PRS proteins. On the other hand, the hexameric quaternary structure and allosteric ADP inhibition would place MtPRS in Class I PRSs. Further data are needed to classify MtPRS as belonging to a particular family of PRS proteins. The data here presented should help augment our understanding of MtPRS mode of action. Current efforts are toward experimental structure determination of MtPRS to provide a solid foundation for the rational design of specific inhibitors of this enzyme

Neutron Scattering and Its Application to Strongly Correlated Systems

Neutron scattering is a powerful probe of strongly correlated systems. It can directly detect common phenomena such as magnetic order, and can be used to determine the coupling between magnetic moments through measurements of the spin-wave dispersions. In the absence of magnetic order, one can detect diffuse scattering and dynamic correlations. Neutrons are also sensitive to the arrangement of atoms in a solid (crystal structure) and lattice dynamics (phonons). In this chapter, we provide an introduction to neutrons and neutron sources. The neutron scattering cross section is described and formulas are given for nuclear diffraction, phonon scattering, magnetic diffraction, and magnon scattering. As an experimental example, we describe measurements of antiferromagnetic order, spin dynamics, and their evolution in the La(2-x)Ba(x)CuO(4) family of high-temperature superconductors.Comment: 31 pages, chapter for "Strongly Correlated Systems: Experimental Techniques", edited by A. Avella and F. Mancin

Nonequilibrium relaxation of the two-dimensional Ising model: Series-expansion and Monte Carlo studies

We study the critical relaxation of the two-dimensional Ising model from a fully ordered configuration by series expansion in time t and by Monte Carlo simulation. Both the magnetization (m) and energy series are obtained up to 12-th order. An accurate estimate from series analysis for the dynamical critical exponent z is difficult but compatible with 2.2. We also use Monte Carlo simulation to determine an effective exponent, z_eff(t) = - {1/8} d ln t /d ln m, directly from a ratio of three-spin correlation to m. Extrapolation to t = infinity leads to an estimate z = 2.169 +/- 0.003.Comment: 9 pages including 2 figure

Essential features of responsible governance of agricultural biotechnology

Agricultural biotechnology continues to generate considerable controversy. We argue that to address this controversy, serious changes to governance are needed. The new wave of genomic tools and products (e.g., CRISPR, gene drives, RNAi, synthetic biology, and genetically modified [GM] insects and fish), provide a particularly useful opportunity to reflect on and revise agricultural biotechnology governance. In response, we present five essential features to advance more socially responsible forms of governance. In presenting these, we hope to stimulate further debate and action towards improved forms of governance, particularly as these new genomic tools and products continue to emerge

Assigning a function to a conserved archaeal metallo-β-lactamase from Haloferax volcanii

The metallo-β-lactamase family of enzymes comprises a large group of proteins with diverse functions in the metabolism of the cell. Among others, this superfamily contains proteins which are involved in DNA and RNA metabolism, acting as nucleases in e.g. repair and maturation. Many proteins have been annotated in prokaryotic genomes as being potential metallo-β-lactamases, but very often the function has not been proven. The protein HVO_2763 from Haloferax volcanii is such a potential metallo-β-lactamase. HVO_2763 has sequence similarity to the metallo-β-lactamase tRNase Z, a tRNA 3′ processing endonuclease. Here, we report the characterisation of this metallo-β-lactamase HVO_2763 in the halophilic archaeon Haloferax volcanii. Using different in vitro assays with the recombinant HVO_2763, we could show that the protein does not have tRNA 3′ processing or exonuclease activity. According to transcriptome analyses of the HVO_2763 deletion strain, expression of proteins involved in membrane transport is downregulated in the mutant. Therefore, HVO_2763 might be involved directly or indirectly in membrane transport

Search for the standard model Higgs boson in the H to ZZ to 2l 2nu channel in pp collisions at sqrt(s) = 7 TeV

A search for the standard model Higgs boson in the H to ZZ to 2l 2nu decay channel, where l = e or mu, in pp collisions at a center-of-mass energy of 7 TeV is presented. The data were collected at the LHC, with the CMS detector, and correspond to an integrated luminosity of 4.6 inverse femtobarns. No significant excess is observed above the background expectation, and upper limits are set on the Higgs boson production cross section. The presence of the standard model Higgs boson with a mass in the 270-440 GeV range is excluded at 95% confidence level.Comment: Submitted to JHE