On the quest for positivity in operator algebras

AbstractWe show that in every nonzero operator algebra with a contractive approximate identity (or c.a.i.), there is a nonzero operator T such that ‖I−T‖⩽1. In fact, there is a c.a.i. consisting of operators T with ‖I−2T‖⩽1. So, the numerical range of the elements of our contractive approximate identity is contained in the closed disk center 12 and radius 12. This is the necessarily weakened form of the result for C⁎-algebras, where there is always a contractive approximate identity consisting of operators with 0⩽T⩽1 – the numerical range is contained in the real interval [0,1]. So, if an operator algebra has a c.a.i., it must have operators with a “certain amount” of positivity

Cervical spine instability in rheumatoid arthritis

Atlanto-axial instability in the rheumatoid patient is discussed. Special reference is made to the importance of diagnosing this potentially lethal condition by means of routine flex ion and extension radiographs of the cervical spine. Treatment by means of occipito-C1-C2 posterolateral fusion is recommended

Chapter 15: Vulnerability of marine reptiles in the Great Barrier Reef to climate change

Marine reptiles are an important and well-documented component of the Great Barrier Reef (GBR), comprising a single species of crocodile (Crocodylidae), six species of marine turtles (five Chelonidae and one Dermochelyidae), at least 16 species of sea snakes (Hydrophiidae), one species of file snake (Acrochordidae) and one species of mangrove snake (Colubridae). Together these marine reptile species inhabit or traverse through each of the 70 bioregions identified by the Great Barrier Reef Marine Park Authority Representative Areas Program . These marine reptile species, with the exception of some of the snakes, have distributions that span large areas of the GBR. Crocodiles, marine turtles, file snakes, mangrove snakes and sea snakes all have life history traits, behaviour and physiology that are strongly influenced by temperature. All are ectothermic except for the leatherback turtle and thus their body temperatures fluctuate with environmental temperature. For egg laying species (crocodiles and turtles), the temperature of the nest determines incubation period, hatching success and hatching sex ratio. Thus as a group they are potentially vulnerable to climate change.This is Chapter 15 of Climate change and the Great Barrier Reef: a vulnerability assessment. The entire book can be found at http://hdl.handle.net/11017/13

Rotating spin-1 bosons in the lowest Landau level

We present results for the ground states of a system of spin-1 bosons in a rotating trap. We focus on the dilute, weakly interacting regime, and restrict the bosons to the quantum states in the lowest Landau level (LLL) in the plane (disc), sphere or torus geometries. We map out parts of the zero temperature phase diagram, using both exact quantum ground states and LLL mean field configurations. For the case of a spin-independent interaction we present exact quantum ground states at angular momentum $L\leq N$. For general values of the interaction parameters, we present mean field studies of general ground states at slow rotation and of lattices of vortices and skyrmions at higher rotation rates. Finally, we discuss quantum Hall liquid states at ultra-high rotation.Comment: 24 pages, 14 figures, RevTe

The UKIDSS Galactic Plane Survey

'The definitive version is available at www.blackwell-synergy.com .' Copyright Blackwell Publishing DOI: 10.1111/j.1365-2966.2008.13924.xThe UKIDSS Galactic Plane Survey (GPS) is one of the five near-infrared Public Legacy Surveys that are being undertaken by the UKIDSS consortium, using the Wide Field Camera on the United Kingdom Infrared TelescopePeer reviewe

Bounded analytic functions in the Dirichlet space

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46275/1/209_2005_Article_BF01163287.pd

An Efficient Implementation of a Quasi-polynomial Algorithm for Generating Hypergraph Transversals

Given a finite set V, and a hypergraph , the hypergraph transversal problem calls for enumerating all minimal hitting sets (transversals) for . This problem plays an important role in practical applications as many other problems were shown to be polynomially equivalent to it. Fredman and Khachiyan (1996) gave an incremental quasi-polynomial time algorithm for solving the hypergraph transversal problem [9]. In this paper, we present an efficient implementation of this algorithm. While we show that our implementation achieves the same bound on the running time as in [9], practical experience with this implementation shows that it can be substantially faster. We also show that a slight modification of the algorithm in [9] can be used to give a stronger bound on the running time

Frequent capsule switching in 'ultra-virulent' meningococci - Are we ready for a serogroup B ST-11 complex outbreak?

The meningococcal ST-11 complex (cc11) causes large invasive disease outbreaks with high case fatality rates, such as serogroup C (MenC) epidemics in industrialised nations in the 1990s and the serogroup W epidemic currently expanding globally. Glycoconjugate vaccines are available for serogroups A, C, W and Y. Broad coverage protein-based vaccines have recently been licensed against serogroup B meningococci (MenB), however, these do not afford universal MenB protection. Capsular switching from MenC to MenB among cc11 organisms is concerning because a large MenB cc11 (B:cc11) outbreak has the potential to cause significant morbidity and mortality. This study aimed to assess the potential for licensed and developmental non-capsular meningococcal vaccines to protect against B:cc11. The population structure and vaccine antigen distribution was determined for a panel of >800 geo-temporally diverse, predominantly MenC cc11 and B:cc11 genomes. The two licensed vaccines potentially protect against many but not all B:cc11 meningococci. Furthermore, strain coverage by these vaccines is often due to a single vaccine antigen and both vaccines are highly susceptible to vaccine escape owing to the apparent dispensability of key proteins used as vaccine antigens. cc11 strains with MenB and MenC capsules warrant special consideration when formulating future non-capsular meningococcal vaccines

Search for the lepton-flavor-violating decays Bs0→e±μ∓ and B0→e±μ∓

A search for the lepton-flavor-violating decays Bs0→e±μ∓ and B0→e±μ∓ is performed with a data sample, corresponding to an integrated luminosity of 1.0  fb-1 of pp collisions at √s=7  TeV, collected by the LHCb experiment. The observed number of Bs0→e±μ∓ and B0→e±μ∓ candidates is consistent with background expectations. Upper limits on the branching fractions of both decays are determined to be B(Bs0→e±μ∓)101  TeV/c2 and MLQ(B0→e±μ∓)>126  TeV/c2 at 95% C.L., and are a factor of 2 higher than the previous bounds