Duality Invariant Actions and Generalised Geometry

We construct the non-linear realisation of the semi-direct product of E(11) and its first fundamental representation at lowest order and appropriate to spacetime dimensions four to seven. This leads to a non-linear realisation of the duality groups and introduces fields that depend on a generalised space which possess a generalised vielbein. We focus on the part of the generalised space on which the duality groups alone act and construct an invariant action.Comment: 59 pages (typos fixed and added comments

The ABCDEF's of Matrix Models for Supersymmetric Chern-Simons Theories

We consider N = 3 supersymmetric Chern-Simons gauge theories with product unitary and orthosymplectic groups and bifundamental and fundamental fields. We study the partition functions on an S^3 by using the Kapustin-Willett-Yaakov matrix model. The saddlepoint equations in a large N limit lead to a constraint that the long range forces between the eigenvalues must cancel; the resulting quiver theories are of affine Dynkin type. We introduce a folding/unfolding trick which lets us, at the level of the large N matrix model, (i) map quivers with orthosymplectic groups to those with unitary groups, and (ii) obtain non-simply laced quivers from the corresponding simply laced quivers using a Z_2 outer automorphism. The brane configurations of the quivers are described in string theory and the folding/unfolding is interpreted as the addition/subtraction of orientifold and orbifold planes. We also relate the U(N) quiver theories to the affine ADE quiver matrix models with a Stieltjes-Wigert type potential, and derive the generalized Seiberg duality in 2 + 1 dimensions from Seiberg duality in 3 + 1 dimensions.Comment: 30 pages, 5 figure

Towards a large-scale quantum simulator on diamond surface at room temperature

Strongly-correlated quantum many-body systems exhibits a variety of exotic phases with long-range quantum correlations, such as spin liquids and supersolids. Despite the rapid increase in computational power of modern computers, the numerical simulation of these complex systems becomes intractable even for a few dozens of particles. Feynman's idea of quantum simulators offers an innovative way to bypass this computational barrier. However, the proposed realizations of such devices either require very low temperatures (ultracold gases in optical lattices, trapped ions, superconducting devices) and considerable technological effort, or are extremely hard to scale in practice (NMR, linear optics). In this work, we propose a new architecture for a scalable quantum simulator that can operate at room temperature. It consists of strongly-interacting nuclear spins attached to the diamond surface by its direct chemical treatment, or by means of a functionalized graphene sheet. The initialization, control and read-out of this quantum simulator can be accomplished with nitrogen-vacancy centers implanted in diamond. The system can be engineered to simulate a wide variety of interesting strongly-correlated models with long-range dipole-dipole interactions. Due to the superior coherence time of nuclear spins and nitrogen-vacancy centers in diamond, our proposal offers new opportunities towards large-scale quantum simulation at room temperatures

Spacelike Singularities and Hidden Symmetries of Gravity

We review the intimate connection between (super-)gravity close to a spacelike singularity (the "BKL-limit") and the theory of Lorentzian Kac-Moody algebras. We show that in this limit the gravitational theory can be reformulated in terms of billiard motion in a region of hyperbolic space, revealing that the dynamics is completely determined by a (possibly infinite) sequence of reflections, which are elements of a Lorentzian Coxeter group. Such Coxeter groups are the Weyl groups of infinite-dimensional Kac-Moody algebras, suggesting that these algebras yield symmetries of gravitational theories. Our presentation is aimed to be a self-contained and comprehensive treatment of the subject, with all the relevant mathematical background material introduced and explained in detail. We also review attempts at making the infinite-dimensional symmetries manifest, through the construction of a geodesic sigma model based on a Lorentzian Kac-Moody algebra. An explicit example is provided for the case of the hyperbolic algebra E10, which is conjectured to be an underlying symmetry of M-theory. Illustrations of this conjecture are also discussed in the context of cosmological solutions to eleven-dimensional supergravity.Comment: 228 pages. Typos corrected. References added. Subject index added. Published versio

High energy emission from microquasars

The microquasar phenomenon is associated with the production of jets by X-ray binaries and, as such, may be associated with the majority of such systems. In this chapter we briefly outline the associations, definite, probable, possible, and speculative, between such jets and X-ray, gamma-ray and particle emission.Comment: Contributing chapter to the book Cosmic Gamma-Ray Sources, K.S. Cheng and G.E. Romero (eds.), to be published by Kluwer Academic Publishers, Dordrecht, 2004. (19 pages

Study of scattered radiation during fluoroscopy in hip surgery

Objetivo: Medir a intensidade da dose de radiação espalhada em diferentes posições simulando uma intervenção cirúrgica no quadril. Materiais e Métodos: Simulou-se uma intervenção cirúrgica no quadril com apoio da fluoroscopia para estudar a distribuição da radiação espalhada no bloco operatório. Para simular o paciente foi utilizado um simulador antropomórfico de corpo inteiro e para medir a radiação utilizou-se um detector específico para medir raios X. Realizaram-se incidências com um equipamento de raios X tipo arco em C móvel, em modo de escopia contínua, com a ampola a 0° (configuração 1) e a 90° (configuração 2). Os parâmetros operacionais utilizados (voltagem, corrente, tempo de exposição) foram determinados por meio de um estudo estatístico resultante da observação de cirurgias ortopédicas de quadril. Resultados: Em todas as medições observaram-se exposições mais elevadas na configuração 2. Nas medições em função da altura, observaram-se os valores máximos da taxa de dose de 1,167 (± 0,023) µSv/s e 2,278 (± 0,023) µSv/s nas configurações 1 e 2, respectivamente, correspondendo à altura do tórax dos profissionais. No estudo em torno do paciente os valores máximos registraramse na posição ocupada pelo médico cirurgião. Conclusão: Concluiu-se que a exposição à radiação dos profissionais é baixa, podendo ainda ser reduzida mediante o uso de equipamentos de proteção individualObjective: To measure the scattered radiation dose at different positions simulating hip surgery. Materials and Methods: We simulated fluoroscopy-assisted hip surgery in order to study the distribution of scattered radiation in the operating room. To simulate the patient, we used a anthropomorphic whole-body phantom, and we used an X-ray-specific detector to quantify the radiation. Radiographs were obtained with a mobile C-arm X-ray system in continuous scan mode, with the tube at 0° (configuration 1) or 90° (configuration 2). The operating parameters employed (voltage, current, and exposure time) were determined by a statistical analysis based on the observation of orthopedic surgical procedures involving the hip. Results: For all measurements, higher exposures were observed in configuration 2. In the measurements obtained as a function of height, the maximum dose rates observed were 1.167 (± 0.023) µSv/s and 2.278 (± 0.023) µSv/s in configurations 1 and 2, respectively, corresponding to the chest level of health care professionals within the operating room. Proximal to the patient, the maximum values were recorded in the position occupied by the surgeon. Conclusion: We can conclude that, in the scenario under study, health care professionals workers are exposed to low levels of radiation, and that those levels can be reduced through the use of personal protective equipmen

Cell Therapy for Cardiovascular Disease: A Comparison of Methods of Delivery

The field of myocardial regeneration utilizing novel cell-based therapies, gene transfer, and growth factors may prove to play an important role in the future management of ischemic heart disease and cardiomyopathy. Phases I and II clinical trials have been published for a variety of biologics utilizing four methods of delivery: systemic infusion, intracoronary infusion, transvenous coronary sinus, and intramyocardial. This review discusses the advantages and disadvantages of the delivery approaches above

Equal pay by gender and by nationality: a comparative analysis of Switzerland's unequal equal pay policy regimes across time

What explains the adoption of two different policies on equal pay by gender (EPG) and by nationality (EPN) in Switzerland? And why is the liberal, litigation-based, equal pay policy regime set up by the Gender Equality Act of 1996 much less effective than the neocorporatist ‘accompanying measures' to the Bilateral European Union-Switzerland Agreement on Free Movement of Persons adopted in 1999 to ensure equal pay for workers of different national origins? The formation of two different policy regimes cannot be explained by different levels of political will. Equally, different ‘varieties of capitalism' cannot explain the setup of the two different equal pay policy regimes within the very same country. Instead, our qualitative comparative analysis across time suggests that the differences can be best explained by a particular constellation of attributes, namely the use of different policy frames—i.e. ‘anti-discrimination' in the EPG and ‘unfair competition' in the EPN case—and the different setting of interest politics epitomised by the opposite stances adopted by Switzerland's employer associations in the two case

Comparative antimicrobial susceptibility of aerobic and facultative bacteria from community-acquired bacteremia to ertapenem in Taiwan

<p>Abstract</p> <p>Background</p> <p>Ertapenem is a once-a-day carbapenem and has excellent activity against many gram-positive and gram-negative aerobic, facultative, and anaerobic bacteria. The susceptibility of isolates of community-acquired bacteremia to ertapenem has not been reported yet. The present study assesses the in vitro activity of ertapenem against aerobic and facultative bacterial pathogens isolated from patients with community-acquired bacteremia by determining and comparing the MICs of cefepime, cefoxitin, ceftazidime, ceftriaxone, ertapenem, piperacillin, piperacillin-tazobactam, ciprofloxacin, amikacin and gentamicin. The prevalence of extended broad spectrum β-lactamases (ESBL) producing strains of community-acquired bacteremia and their susceptibility to these antibiotics are investigated.</p> <p>Methods</p> <p>Aerobic and facultative bacteria isolated from blood obtained from hospitalized patients with community-acquired bacteremia within 48 hours of admission between August 1, 2004 and September 30, 2004 in Chang Gung Memorial Hospital at Keelung, Taiwan, were identified using standard procedures. Antimicrobial susceptibility was evaluated by Etest according to the standard guidelines provided by the manufacturer and document M100-S16 Performance Standards of the Clinical Laboratory of Standard Institute. Antimicrobial agents including cefepime, cefoxitin, ceftazidime, ceftriaxone, ertapenem, piperacillin, piperacillin-tazobactam, ciprofloxacin, amikacin and gentamicin were used against the bacterial isolates to test their MICs as determined by Etest. For <it>Staphylococcus aureus </it>isolates, MICs of oxacillin were also tested by Etest to differentiate oxacillin-sensitive and oxacillin-resistant <it>S. aureus</it>.</p> <p>Results</p> <p>Ertapenem was highly active in vitro against many aerobic and facultative bacterial pathogens commonly recovered from patients with community-acquired bacteremia (128/159, 80.5 %). Ertapenem had more potent activity than ceftriaxone, piperacillin-tazobactam, or ciprofloxacin against oxacillin-susceptible <it>S</it>. <it>aureus </it>(17/17, 100%)and was more active than any of these agents against <it>enterobacteriaceae </it>(82/82, 100%).</p> <p>Conclusion</p> <p>Based on the microbiology pattern of community-acquired bacteremia, initial empiric treatment that requires coverage of a broad spectrum of both gram-negative and gram-positive aerobic bacteria, such as ertapenem, may be justified in moderately severe cases of community-acquired bacteremia in non-immunocompromised hosts.</p

Correlated Mutations: A Hallmark of Phenotypic Amino Acid Substitutions

Point mutations resulting in the substitution of a single amino acid can cause severe functional consequences, but can also be completely harmless. Understanding what determines the phenotypical impact is important both for planning targeted mutation experiments in the laboratory and for analyzing naturally occurring mutations found in patients. Common wisdom suggests using the extent of evolutionary conservation of a residue or a sequence motif as an indicator of its functional importance and thus vulnerability in case of mutation. In this work, we put forward the hypothesis that in addition to conservation, co-evolution of residues in a protein influences the likelihood of a residue to be functionally important and thus associated with disease. While the basic idea of a relation between co-evolution and functional sites has been explored before, we have conducted the first systematic and comprehensive analysis of point mutations causing disease in humans with respect to correlated mutations. We included 14,211 distinct positions with known disease-causing point mutations in 1,153 human proteins in our analysis. Our data show that (1) correlated positions are significantly more likely to be disease-associated than expected by chance, and that (2) this signal cannot be explained by conservation patterns of individual sequence positions. Although correlated residues have primarily been used to predict contact sites, our data are in agreement with previous observations that (3) many such correlations do not relate to physical contacts between amino acid residues. Access to our analysis results are provided at http://webclu.bio.wzw.tum.de/~pagel/supplements/correlated-positions/