Production-decay interferences at NLO in QCD for t-channel single-top production

We present a calculation of O(\alpha_s) contributions to the process of t-channel single-top production and decay, which include virtual and real corrections arising from interference of the production and decay subprocesses. The calculation is organized as a simultaneous expansion of the matrix elements in the couplings \alpha_{ew},\alpha_s and the virtuality of the intermediate top quark, (p_t^2-m_t^2)/m_t^2 ~ \Gamma_t/m_t, and extends earlier results beyond the narrow-width approximation.Comment: 33 pages, 6 Figure

An experimental investigation of the hypergolic ignition of some polymeric fuels with oxygen

Hypergolic ignition of polymeric fuels with oxyge

Heterogeneous Ignition of Metals - Model and Experiment

Spontaneous ignition temperature, ignition temperature, and transition temperature for metal-oxidizing gas system models of solid propellant rocket engine combustion processe

Cauchy horizon singularity without mass inflation

A perturbed Reissner-Nordstr\"om-de Sitter solution is used to emphasize the nature of the singularity along the Cauchy horizon of a charged spherically symmetric black hole. For these solutions, conditions may prevail under which the mass function is bounded and yet the curvature scalar $R_{\alpha\beta\gamma\delta} R^{\alpha\beta\gamma\delta}$ diverges.Comment: typeset in RevTex, 13 page

Dissipation due to tunneling two-level systems in gold nanomechanical resonators

We present measurements of the dissipation and frequency shift in nanomechanical gold resonators at temperatures down to 10 mK. The resonators were fabricated as doubly-clamped beams above a GaAs substrate and actuated magnetomotively. Measurements on beams with frequencies 7.95 MHz and 3.87 MHz revealed that from 30 mK to 500 mK the dissipation increases with temperature as $T^{0.5}$, with saturation occurring at higher temperatures. The relative frequency shift of the resonators increases logarithmically with temperature up to at least 400 mK. Similarities with the behavior of bulk amorphous solids suggest that the dissipation in our resonators is dominated by two-level systems

Brain natriuretic peptide and NT-proBNP levels reflect pulmonary artery systolic pressure in trekkers at high altitude.

Our objective was to evaluate the utility of the natriuretic peptides BNP (brain natriuretic peptide) and NT-proBNP as markers of pulmonary artery systolic pressure (PASP) in trekkers ascending to high altitude (HA). 20 participants had BNP and NT-proBNP assayed and simultaneous echocardiographic assessment of PASP performed during a trek to 5150 m. PASP increased significantly (p=0.006) with ascent from 24+/-4 to 39+/-11 mm Hg at 5150 m. At 5150 m those with a PASP>/=40 mm Hg (n=8) (versus those with PASP/=400 pg/ml) rise in NT-proBNP at 5150 m (n=4) PASP was significantly higher: 45.9+/-7.5 vs. 32.2+/-6.2 mm Hg (p=0.015). BNP and NT-proBNP may reflect elevated PASP, a central feature of high altitude pulmonary oedema, at HA

Real-space imaging of quantum Hall effect edge strips

We use dynamic scanning capacitance microscopy (DSCM) to image compressible and incompressible strips at the edge of a Hall bar in a two-dimensional electron gas (2DEG) in the quantum Hall effect (QHE) regime. This method gives access to the complex local conductance, Gts, between a sharp metallic tip scanned across the sample surface and ground, comprising the complex sample conductance. Near integer filling factors we observe a bright stripe along the sample edge in the imaginary part of Gts. The simultaneously recorded real part exhibits a sharp peak at the boundary between the sample interior and the stripe observed in the imaginary part. The features are periodic in the inverse magnetic field and consistent with compressible and incompressible strips forming at the sample edge. For currents larger than the critical current of the QHE break-down the stripes vanish sharply and a homogeneous signal is recovered, similar to zero magnetic field. Our experiments directly illustrate the formation and a variety of properties of the conceptually important QHE edge states at the physical edge of a 2DEG.Comment: 7 page

Low-temperature and high magnetic field dynamic scanning capacitance microscope

We demonstrate a dynamic scanning capacitance microscope (DSCM) that operates at large bandwidths, cryogenic temperatures and high magnetic fields. The setup is based on a non-contact atomic force microscope (AFM) with a quartz tuning fork sensor with non-optical excitation and read-out for topography, force and dissipation measurements. The metallic AFM tip forms part of an rf resonator with a transmission characteristics modulated by the sample properties and the tip-sample capacitance. The tip motion gives rise to a modulation of the capacitance at the frequency of the AFM sensor and its harmonics, which can be recorded simultaneously with the AFM data. We use an intuitive model to describe and analyze the resonator transmission and show that for most experimental conditions it is proportional to the complex tip-sample conductance, which depends on both the tip-sample capacitance and the sample resistivity. We demonstrate the performance of the DSCM on metal disks buried under a polymer layer and we discuss images recorded on a two-dimensional electron gas in the quantum Hall effect regime, i.e. at cryogenic temperatures and high magnetic fields, where we directly image the formation of compressible stripes at the physical edge of the sample

Pair Creation of Black Holes by Domain Walls

In this paper we study the production of pairs of neutral and charged black holes by domain walls, finding classical solutions and calculating their classical actions. We find that neutral black holes whose creation is mediated by Euclidean instantons must be produced mutually at rest with respect to one another, but for charged black holes a new type of instanton is possible in which after formation the two black holes accelerate away from one another. These new types of instantons are not possible in Einstein-Maxwell theory with a cosmological constant. We also find that the creation of non-orientable black hole solutions can be mediated by Euclidean instantons and that in addition if one is prepared to consider entirely Lorentzian no-boundary type contributions to the path integral then mutually accelerating pairs may be created even in the neutral case. Finally we consider the production of Kaluza-Klein monopoles both by a standard cosmological term and in the presence of a domain wall. We find that compactification is accompanied by the production of pairs of Kaluza-Klein monopoles.Comment: 22 pages (REVTeX with AMS Symbols) with 5 postscript figures attached in a single uuencoded, g-zipped, tar file at end of tex fil

Nonlinear modal coupling in a high-stress doubly-clamped nanomechanical resonator

We present results from a study of the nonlinear intermodal coupling between different flexural vibrational modes of a single high-stress, doubly-clamped silicon nitride nanomechanical beam. The measurements were carried out at 100 mK and the beam was actuated using the magnetomotive technique. We observed the nonlinear behavior of the modes individually and also measured the coupling between them by driving the beam at multiple frequencies. We demonstrate that the different modes of the resonator are coupled to each other by the displacement induced tension in the beam, which also leads to the well known Duffing nonlinearity in doubly-clamped beams.Comment: 15 pages, 7 figure