Effect of aspect ratio on fire resistance of hollow core concrete floors

Previous studies have shown that the fire performance of hollowcore units is significantly affected by the end support conditions, but it has not been clear how the fire resistance of the overall floor system can be improved by providing side supports. The previous studies used beam grillage and shell elements to separately model the hollowcore units and the topping concrete slab using the platform of the non-linear finite element program SAFIR. The modelling method required a lot of computational resources and is not ideal to model a large floor area. This paper describes the effect of the side supports and the aspect ratio of the floor on the predicted fire resistance. It also compares the efficiencies of shell elements and short beam elements for finite element modelling of the topping concrete in fire conditions. The results show that integrating the topping concrete slab into the beam grillages reduces the complexity of the model and also provides satisfactory results. Side supports can increase the fire performance of hollowcore floor slabs provided that the spacing of the side supports does not greatly exceed the span length

Affine Toda model coupled to matter and the string tension in QCD2_{2}

The $sl(2)$ affine Toda model coupled to matter (ATM) is shown to describe various features, such as the spectrum and string tension, of the low-energy effective Lagrangian of QCD$_{2}$ (one flavor and $N$ colors). The corresponding string tension is computed when the dynamical quarks are in the {\sl fundamental} representation of SU(N) and in the {\sl adjoint} representation of SU(2).Comment: LaTex, 10 pages. Revised version to appear in Phys. Rev.

Effects of impurities and vortices on the low-energy spin excitations in high-Tc materials

We review a theoretical scenario for the origin of the spin-glass phase of underdoped cuprate materials. In particular it is shown how disorder in a correlated d-wave superconductor generates a magnetic phase by inducing local droplets of antiferromagnetic order which eventually merge and form a quasi-long range ordered state. When correlations are sufficiently strong, disorder is unimportant for the generation of static magnetism but plays an additional role of pinning disordered stripe configurations. We calculate the spin excitations in a disordered spin-density wave phase, and show how disorder and/or applied magnetic fields lead to a slowing down of the dynamical spin fluctuations in agreement with neutron scattering and muon spin rotation (muSR) experiments.Comment: 4 pages, 3 figures, submitted for SNS2010 conference proceeding

Defining the molecular pathology of pancreatic body and tail adenocarcinom

Background: Pancreatic ductal adenocarcinoma (PDAC) remains a dismal disease, with very little improvement in survival over the past 50 years. Recent large-scale genomic studies have improved understanding of the genomic and transcriptomic landscape of the disease, yet very little is known about molecular heterogeneity according to tumour location in the pancreas; body and tail PDACs especially tend to have a significantly worse prognosis. The aim was to investigate the molecular differences between PDAC of the head and those of the body and tail of the pancreas. Methods: Detailed correlative analysis of clinicopathological variables, including tumour location, genomic and transcriptomic data, was performed using the Australian Pancreatic Cancer Genome Initiative (APGI) cohort, part of the International Cancer Genome Consortium study. Results: Clinicopathological data were available for 518 patients recruited to the APGI, of whom 421 underwent genomic analyses; 179 of these patients underwent whole-genome and 96 RNA sequencing. Patients with tumours of the body and tail had significantly worse survival than those with pancreatic head tumours (12·1 versus 22·0 months; P = 0·001). Location in the body and tail was associated with the squamous subtype of PDAC. Body and tail PDACs enriched for gene programmes involved in tumour invasion and epithelial-to-mesenchymal transition, as well as features of poor antitumour immune response. Whether this is due to a molecular predisposition from the outset, or reflects a later time point on the tumour molecular clock, requires further investigation using well designed prospective studies in pancreatic cancer. Conclusion: PDACs of the body and tail demonstrate aggressive tumour biology that may explain worse clinical outcomes

Prospects For Identifying Dark Matter With CoGeNT

It has previously been shown that the excess of events reported by the CoGeNT collaboration could be generated by elastically scattering dark matter particles with a mass of approximately 5-15 GeV. This mass range is very similar to that required to generate the annual modulation observed by DAMA/LIBRA and the gamma rays from the region surrounding the Galactic Center identified within the data of the Fermi Gamma Ray Space Telescope. To confidently conclude that CoGeNT's excess is the result of dark matter, however, further data will likely be needed. In this paper, we make projections for the first full year of CoGeNT data, and for its planned upgrade. Not only will this body of data more accurately constrain the spectrum of nuclear recoil events, and corresponding dark matter parameter space, but will also make it possible to identify seasonal variations in the rate. In particular, if the CoGeNT excess is the product of dark matter, then one year of CoGeNT data will likely reveal an annual modulation with a significance of 2-3$\sigma$. The planned CoGeNT upgrade will not only detect such an annual modulation with high significance, but will be capable of measuring the energy spectrum of the modulation amplitude. These measurements will be essential to irrefutably confirming a dark matter origin of these events.Comment: 6 pages, 6 figure

Hexagonal dielectric resonators and microcrystal lasers

We study long-lived resonances (lowest-loss modes) in hexagonally shaped dielectric resonators in order to gain insight into the physics of a class of microcrystal lasers. Numerical results on resonance positions and lifetimes, near-field intensity patterns, far-field emission patterns, and effects of rounding of corners are presented. Most features are explained by a semiclassical approximation based on pseudointegrable ray dynamics and boundary waves. The semiclassical model is also relevant for other microlasers of polygonal geometry.Comment: 12 pages, 17 figures (3 with reduced quality

Dark Matter attempts for CoGeNT and DAMA

Recently, the CoGeNT collaboration presented a positive signal for an annual modulation in their data set. In light of the long standing annual modulation signal in DAMA/LIBRA, we analyze the compatibility of both of these signal within the hypothesis of dark matter (DM) scattering on nuclei, taking into account existing experimental constraints. We consider the cases of elastic and inelastic scattering with either spin-dependent or spin-independent coupling to nucleons. We allow for isospin violating interactions as well as for light mediators. We find that there is some tension between the size of the modulation signal and the time-integrated event excess in CoGeNT, making it difficult to explain both simultaneously. Moreover, within the wide range of DM interaction models considered, we do not find a simultaneous explanation of CoGeNT and DAMA/LIBRA compatible with constraints from other experiments. However, in certain cases part of the data can be made consistent. For example, the modulation signal from CoGeNT becomes consistent with the total rate and with limits from other DM searches at 90% CL (but not with the DAMA/LIBRA signal) if DM scattering is inelastic spin-independent with just the right couplings to protons and neutrons to reduce the scattering rate on xenon. Conversely the DAMA/LIBRA signal (but not CoGeNT) can be explained by spin-dependent inelastic DM scattering.Comment: 20 pages, 9 figure

Large effects on \BsBs mixing by vector-like quarks

We calculate the contributions of the vector-like quark model to \BsBs mixing, taking into account the constraints from the decay $B\to X_s\gamma$. In this model the neutral bosons mediate flavor-changing interactions at the tree level. However, \BsBs mixing is dominated by contributions from the box diagrams with the top quark and the extra up-type quark. In sizable ranges of the model parameters, the mixing parameter $x_s$ is much different from the standard model prediction.Comment: 11 pages, 4 figures, To be published in Phys. Rev.

Localizability of Tachyonic Particles and Neutrinoless Double Beta Decay

The quantum field theory of superluminal (tachyonic) particles is plagued with a number of problems, which include the Lorentz non-invariance of the vacuum state, the ambiguous separation of the field operator into creation and annihilation operators under Lorentz transformations, and the necessity of a complex reinterpretation principle for quantum processes. Another unsolved question concerns the treatment of subluminal components of a tachyonic wave packets in the field-theoretical formalism, and the calculation of the time-ordered propagator. After a brief discussion on related problems, we conclude that rather painful choices have to be made in order to incorporate tachyonic spin-1/2 particles into field theory. We argue that the field theory needs to be formulated such as to allow for localizable tachyonic particles, even if that means that a slight unitarity violation is introduced into the S matrix, and we write down field operators with unrestricted momenta. We find that once these choices have been made, the propagator for the neutrino field can be given in a compact form, and the left-handedness of the neutrino as well as the right-handedness of the antineutrino follow naturally. Consequences for neutrinoless double beta decay and superluminal propagation of neutrinos are briefly discussed.Comment: 12 pages, 5 figure

Naturalness and Higgs Decays in the MSSM with a Singlet

The simplest extension of the supersymmetric standard model - the addition of one singlet superfield - can have a profound impact on the Higgs and its decays. We perform a general operator analysis of this scenario, focusing on the phenomenologically distinct scenarios that can arise, and not restricting the scope to the narrow framework of the NMSSM. We reexamine decays to four b quarks and four tau's, finding that they are still generally viable, but at the edge of LEP limits. We find a broad set of Higgs decay modes, some new, including those with four gluon final states, as well as more general six and eight parton final states. We find the phenomenology of these scenarios is dramatically impacted by operators typically ignored, specifically those arising from D-terms in the hidden sector, and those arising from weak-scale colored fields. In addition to sensitivity of m_Z, there are potential tunings of other aspects of the spectrum. In spite of this, these models can be very natural, with light stops and a Higgs as light as 82 GeV. These scenarios motivate further analyses of LEP data as well as studies of the detection capabilities of future colliders to the new decay channels presented.Comment: 3 figures, 1 appendix; version to appear in JHEP; typos fixed and additional references and acknowledgements adde