CO2 capture by dry alkanolamines and an efficient microwave regeneration process

Removal of acidic gases such as H2S and CO2 is performed during the purification of raw natural gas, most commonly using amine gas treatment. However, this industrially entrenched method is limited by significant shortcomings including low operational capture efficiency, amine pipeline corrosion and a large energy penalty due to the sorbent regeneration process. To address these shortcomings, we have studied the use of perfluorinated silica-stabilized dry alkanolamines (DAf) for CO2 capture. Due to their micronized liquid domains, DAf display high operational CO2 capture efficiency. Further, to minimize energy requirements for sorbent regeneration, microwave-assisted regeneration of the spent DAf sorbent was also studied and shown to decrease the energy requirements by about ten times. In contrast to very recent work, our results show that the use of DAf exhibits extraordinary recyclability, with a negligible decrease in absorption capacity over at least ten absorption–regeneration cycles, indicating the potential of this material for gas treatment applications

Revealing the electroweak properties of a new scalar resonance

One or more new heavy resonances may be discovered in experiments at the CERN Large Hadron Collider. In order to determine if such a resonance is the long-awaited Higgs boson, it is essential to pin down its spin, CP, and electroweak quantum numbers. Here we describe how to determine what role a newly-discovered neutral CP-even scalar plays in electroweak symmetry breaking, by measuring its relative decay rates into pairs of electroweak vector bosons: WW, ZZ, \gamma\gamma, and Z\gamma. With the data-driven assumption that electroweak symmetry breaking respects a remnant custodial symmetry, we perform a general analysis with operators up to dimension five. Remarkably, only three pure cases and one nontrivial mixed case need to be disambiguated, which can always be done if all four decay modes to electroweak vector bosons can be observed or constrained. We exhibit interesting special cases of Higgs look-alikes with nonstandard decay patterns, including a very suppressed branching to WW or very enhanced branchings to \gamma\gamma and Z\gamma. Even if two vector boson branching fractions conform to Standard Model expectations for a Higgs doublet, measurements of the other two decay modes could unmask a Higgs imposter.Comment: 23 pages, two figures; v2: minor revision and version to appear in JHE

Structure analysis of the virtual Compton scattering amplitude at low energies

We analyze virtual Compton scattering off the nucleon at low energies in a covariant, model-independent formalism. We define a set of invariant functions which, once the irregular nucleon pole terms have been subtracted in a gauge-invariant fashion, is free of poles and kinematical zeros. The covariant treatment naturally allows one to implement the constraints due to Lorentz and gauge invariance, crossing symmetry, and the discrete symmetries. In particular, when applied to the $ep\to e'p'\gamma$ reaction, charge-conjugation symmetry in combination with nucleon crossing generates four relations among the ten originally proposed generalized polarizabilities of the nucleon.Comment: 19 pages, LaTeX2e/RevTeX, no figures, original sections IV.-VI. removed, to be discussed in a separate publication, none of the conclusions change

Rap1-mediated nuclear factor-kappaB (NF-κB) activity regulates the paracrine capacity of mesenchymal stem cells in heart repair following infarction

published_or_final_versio

A Statistical Study on Force-Freeness of Solar Magnetic Fields in the Photosphere

It is an indisputable fact that solar magnetic fields are force-free in the corona, where force free fields means that current and magnetic fields are parallel and there is no Lorentz force in the fields. While the force-free extent of photospheric magnetic fields remains open. In this paper, the statistical results about it is given. The vector magnetograms (namely, $B_{x}$, $B_{y}$ and $B_{z}$ in heliocentric coordinates) are employed, which are deduced and calibrated from Stokes spectra, observed by Solar Magnetic Field Telescope (SMFT) at Huairou Solar Observing Station (HSOS) are used. We study and calibrated 925 magnetograms calibrated by two sets of calibration coefficients, that indicate the relations between magnetic fields and the strength of Stokes spectrum and can be calculated either theoretically or empirically. The statistical results show that the majority of active region magnetic fields are not consistent with the force-free model.Comment: 10 pages, 5 figures, has been accepted by PAS

Integer Quantum Hall Effect with Realistic Boundary Condition : Exact Quantization and Breakdown

A theory of integer quantum Hall effect(QHE) in realistic systems based on von Neumann lattice is presented. We show that the momentum representation is quite useful and that the quantum Hall regime(QHR), which is defined by the propagator in the momentum representation, is realized. In QHR, the Hall conductance is given by a topological invariant of the momentum space and is quantized exactly. The edge states do not modify the value and topological property of $\sigma_{xy}$ in QHR. We next compute distribution of current based on effective action and find a finite amount of current in the bulk and the edge, generally. Due to the Hall electric field in the bulk, breakdown of the QHE occurs. The critical electric field of the breakdown is proportional to $B^{3/2}$ and the proportional constant has no dependence on Landau levels in our theory, in agreement with the recent experiments.Comment: 48 pages, figures not included, some additions and revision

UV friendly T-parity in the SU(6)/Sp(6) little Higgs model

Electroweak precision tests put stringent constraints on the parameter space of little Higgs models. Tree-level exchange of TeV scale particles in a generic little Higgs model produce higher dimensional operators that make contributions to electroweak observables that are typically too large. To avoid this problem a discrete symmetry dubbed T-parity can be introduced to forbid the dangerous couplings. However, it was realized that in simple group models such as the littlest Higgs model, the implementation of T-parity in a UV completion could present some challenges. The situation is analogous to the one in QCD where the pion can easily be defined as being odd under a new $Z_2$ symmetry in the chiral Lagrangian, but this $Z_2$ is not a symmetry of the quark Lagrangian. In this paper we examine the possibility of implementing a T-parity in the low energy $SU(6)/Sp(6)$ model that might be easier to realize in the UV. In our model, the T-parity acts on the low energy non-linear sigma model field in way which is different to what was originally proposed for the Littlest Higgs, and lead to a different low energy theory. In particular, the Higgs sector of this model is a inert two Higgs doublets model with an approximate custodial symmetry. We examine the contributions of the various sectors of the model to electroweak precision data, and to the dark matter abundance.Comment: 21 pages,4 figures. Clarifications added, typos corrected and references added. Published in JHE

PCA-based lung motion model

Organ motion induced by respiration may cause clinically significant targeting errors and greatly degrade the effectiveness of conformal radiotherapy. It is therefore crucial to be able to model respiratory motion accurately. A recently proposed lung motion model based on principal component analysis (PCA) has been shown to be promising on a few patients. However, there is still a need to understand the underlying reason why it works. In this paper, we present a much deeper and detailed analysis of the PCA-based lung motion model. We provide the theoretical justification of the effectiveness of PCA in modeling lung motion. We also prove that under certain conditions, the PCA motion model is equivalent to 5D motion model, which is based on physiology and anatomy of the lung. The modeling power of PCA model was tested on clinical data and the average 3D error was found to be below 1 mm.Comment: 4 pages, 1 figure. submitted to International Conference on the use of Computers in Radiation Therapy 201

A Census of the High-Density Molecular Gas in M82

We present a three-pointing study of the molecular gas in the starburst nucleus of M82 based on 190 - 307 GHz spectra obtained with Z-Spec at the Caltech Submillimeter Observatory. We present intensity measurements, detections and upper limits, for 20 transitions, including several new detections of CS, HNC, C2H, H2CO, and CH3CCH lines. We combine our measurements with previously-published measurements at other frequencies for HCN, HNC, CS, C34S, and HCO+ in a multi-species likelihood analysis constraining gas mass, density and temperature, and the species' relative abundances. We find some 1.7 - 2.7 x 10^8 M_sun of gas with n_H2 between 1 - 6 x 10^4 cm^-3 and T > 50 K. While the mass and temperature are comparable to values inferred from mid-J CO transitions, the thermal pressure is a factor of 10 - 20 greater. The molecular interstellar medium is largely fragmented and is subject to ultraviolet irradiation from the star clusters. It is also likely subject to cosmic rays and mechanical energy input from the supernovae, and is warmer on average than the molecular gas in the massive star formation regions in the Milky Way. The typical conditions in the dense gas in M82's central kpc appear unfavorable for further star formation; if any appreciable stellar populations are currently forming, they are likely biased against low mass stars, producing a top-heavy initial mass function.Comment: 15 pages (using emulateapj.cls), 6 figures, Astrophysical Journal, in pres

Electron pumping in graphene mechanical resonators

The combination of high frequency vibrations and metallic transport in graphene makes it a unique material for nano-electromechanical devices. In this letter, we show that graphene-based nano-electromechanical devices are extremely well suited for charge pumping, due to the sensitivity of its transport coefficients to perturbations in electrostatic potential and mechanical deformations, with the potential for novel small scale devices with useful applications