Scale of fermion mass generation

Unitarity of longitudinal weak vector boson scattering implies an upper bound on the scale of electroweak symmetry breaking, $\Lambda_{EWSB}\equiv \sqrt{8\pi}v\approx$ 1 TeV. Appelquist and Chanowitz have derived an analogous upper bound on the scale of fermion mass generation, proportional to $v^2/m_f$, by considering the scattering of same-helicity fermions into pairs of longitudinal weak vector bosons in a theory without a standard Higgs boson. We show that there is no upper bound, beyond that on the scale of electroweak symmetry breaking, in such a theory. This result is obtained by considering the same process, but with a large number of longitudinal weak vector bosons in the final state. We further argue that there is no scale of (Dirac) fermion mass generation in the standard model. In contrast, there is an upper bound on the scale of Majorana-neutrino mass generation, given by $\Lambda_{Maj}\equiv 4\pi v^2/m_\nu$. In general, the upper bound on the scale of fermion mass generation depends on the dimensionality of the interaction responsible for generating the fermion mass. We explore the scale of fermion mass generation in a variety of excursions from the standard model: models with fermions in nonstandard representations, a theory with higher-dimension interactions, a two-Higgs-doublet model, and models without a Higgs boson.Comment: 31 pages, 9 figures; version accepted for publication in Phys. Rev.

High-time Resolution Astrophysics and Pulsars

The discovery of pulsars in 1968 heralded an era where the temporal characteristics of detectors had to be reassessed. Up to this point detector integration times would normally be measured in minutes rather seconds and definitely not on sub-second time scales. At the start of the 21st century pulsar observations are still pushing the limits of detector telescope capabilities. Flux variations on times scales less than 1 nsec have been observed during giant radio pulses. Pulsar studies over the next 10 to 20 years will require instruments with time resolutions down to microseconds and below, high-quantum quantum efficiency, reasonable energy resolution and sensitive to circular and linear polarisation of stochastic signals. This chapter is review of temporally resolved optical observations of pulsars. It concludes with estimates of the observability of pulsars with both existing telescopes and into the ELT era.Comment: Review; 21 pages, 5 figures, 86 references. Book chapter to appear in: D.Phelan, O.Ryan & A.Shearer, eds.: High Time Resolution Astrophysics (Astrophysics and Space Science Library, Springer, 2007). The original publication will be available at http://www.springerlink.co

Advances in the treatment of mood and anxiety disorders

Mood and anxiety disorders are prevalent in all countries and cultures, which becomes obvious when standardized diagnostic and evaluation techniques are utilized. It is estimated that ~450 million people worldwide suffer from psychiatric illness. In the United States alone, epidemiologic research has identified that tens of millions of Americans suffer from major depressive disorder (MDD) annually, with many of them being in the prime of their adult lives. In addition to medical, personal, and social costs, depression is also believed to have a significant impact on work productivity. Further epidemiologic research indicates that nearly half of all individuals meeting lifetime criteria for MDD also have met criteria for a comorbid anxiety disorder. With an average age of 16 years for the onset of any lifetime anxiety disorder, anxiety disorders appear to predispose affected individuals to a substantial lifetime risk for MDD. In order to improve outcomes in depression and anxiety disorders, clinicians must enhance the entire process of recognition, diagnosis, and treatment

Experience with lifetime limits for EBR-II core components

The Experimental Breeder Reactor No. 2 (EBR-II) is operated for the US Department of Energy by Argonne National Laboratory and is located on the Idaho National Engineering Laboratory where most types of American reactor were originally tested. EBR-II is a complete electricity-producing power plant now in its twenty-fourth year of successful operation. During this long history the reactor has had several concurrent missions, such as demonstration of a closed Liquid-Metal Reactor (LMR) fuel cycle (1964-69); as a steady-state irradiation facility for fuels and materials (1970 onwards); for investigating effects of operational transients on fuel elements (from 1981); for research into the inherent safety aspects of metal-fueled LMR's (from 1983); and, most recently, for demonstration of the Integral Fast Reactor (IFR) concept using U-Pu-Zr fuels. This paper describes experience gained at EBR-II in defining lifetime limits for LMR core components, particularly fuel elements

Detecting the heavy Higgs boson at the SSC

Detection of a heavy Higgs boson (2M/sub z/ < M/sub H/ < 1 TeV) is considered. The production mechanisms and backgrounds are discussed. Their implementation in the PYTHIA and ISAJET Monte Carlo programs are checked. The decay modes H ..-->.. ZZ ..-->.. llll and H ..-->.. ZZ ..-->.. llvv are discussed in detail. The signal/background is evaluated and some relevant detector parameters are specified. Some remarks are also made concerning the requirements imposed on detectors by the decay mode H ..-->.. WW ..-->.. lv + jets. Experimental signatures for models in which there is no Higgs boson of mass less than 1 TeV are outlined. 44 refs

Crystal structure of the CRISPR RNA–guided surveillance complex from Escherichia coli

Clustered regularly interspaced short palindromic repeats (CRISPRs) are essential components of RNA-guided adaptive immune systems that protect bacteria and archaea from viruses and plasmids. In Escherichia coli, short CRISPR-derived RNAs (crRNAs) assemble into a 405-kilodalton multisubunit surveillance complex called Cascade (CRISPR-associated complex for antiviral defense). Here we present the 3.24 angstrom resolution x-ray crystal structure of Cascade. Eleven proteins and a 61-nucleotide crRNA assemble into a seahorse-shaped architecture that binds double-stranded DNA targets complementary to the crRNA-guide sequence. Conserved sequences on the 3' and 5' ends of the crRNA are anchored by proteins at opposite ends of the complex, whereas the guide sequence is displayed along a helical assembly of six interwoven subunits that present five-nucleotide segments of the crRNA in pseudo–A-form configuration. The structure of Cascade suggests a mechanism for assembly and provides insights into the mechanisms of target recognition