Rm Ph Research Articles

The influence of the magnetic field on the spectral properties of blazars

We explore the signature imprinted by dynamically relevant magnetic fields on the spectral energy distribution (SED) of blazars. It is assumed that the emission from these sources originates from the collision of cold plasma shells, whose magnetohydrodynamic evolution we compute by numerically solving Riemann problems. We compute the SEDs including the most relevant radiative processes and scan a broad parameter space that encompasses a significant fraction of the commonly accepted values of not directly measurable physical properties. We reproduce the standard double hump SED found in blazar observations for unmagnetized shells, but show that the prototype double hump structure of blazars can also be reproduced if the dynamical source of the radiation field is very ultrarelativistic both, in a kinematically sense (namely, if it has Lorentz factors \gtrsim 50) and regarding its magnetization (e.g., with flow magnetizations \sigma \simeq 0.1). A fair fraction of the {\em blazar sequence} could be explained as a consequence of shell magnetization: negligible magnetization in FSRQs, and moderate or large (and uniform) magnetization in BL Lacs. The predicted photon spectral indices (\gph) in the \gamma-ray band are above the observed values (\Gamma_{\rm ph, obs} \lesssim 2.6 for sources with redshifts 0.4\le z \le 0.6) if the magnetization of the sources is moderate (\sigma \simeq 10^{-2}).

Electromagnetic Performance of Novel Variable Flux Reluctance Machines With DC-Field Coil in Stator

In this paper, novel variable flux reluctance machines (VFRMs) with different rotor pole numbers, which employ a doubly salient structure together with field windings identically located in the stator for each phase, are investigated and compared. Different from other doubly salient machines, such as switched reluctance machines (SRM) and doubly fed doubly salient machines (DFDSM), the equation for determining the stator/rotor pole numbers, i.e., $N_{\rm r}=N_{\rm s}\pm 2k$ , is no longer limited in VFRMs. More feasible selections of rotor pole numbers can be used if the stator/rotor pole numbers can satisfy $N_{\rm r}\ne kN_{\rm ph}$ . Thus, for a 6-stator pole machine not only the rotor pole number can be selected as even numbers, such as 4- and 8-rotor poles, which are commonly used for SRM and DFDSM, but odd numbers, such as 5- and 7- rotor poles, are also feasible. The benefits of using 5- and 7-rotor poles are the cancellation of even-order harmonics together with the third-order harmonic in the flux-linkage and back-EMF. Hence, more sinusoidal back-EMF can be obtained to produce a lower torque ripple. The cancellation in 5- and 7-rotor pole machines is because the flux generated by field and armature windings can pass through the adjacent stator poles to form a shorter flux path, which can further increase their average torque. To validate the analysis, four prototype machines with different rotor pole numbers are manufactured and tested.

NIR Spectroscopy of Star-Forming Galaxies at z ∼ 1.4 with Subaru/FMOS: The Mass–Metallicity Relation

Abstract We present near-infrared spectroscopic observations of star-forming galaxies at $z$$\sim $ 1.4 with FMOS on the Subaru Telescope. We observed $K$-band selected galaxies in the SXDS/UDS fields with $K$$\leq$ 23.9 mag, 1.2 $\leq$$z_{\rm ph}$$\leq$ 1.6, $M_{*}$$\geq$ 10$^{9.5}\ M_{\odot}$, and expected F(H$\alpha $) $\geq$ 10$^{-16}\ $erg s$^{-1}\ $cm$^{-2}$; 71 objects in the sample have significant detections of H$\alpha $. For these objects, excluding possible AGNs, identified from the BPT diagram, gas-phase metallicities were obtained from the [N II] / H$\alpha $ line ratio. The sample is split into three stellar-mass bins, and the spectra are stacked in each stellar-mass bin. The mass–metallicity relation obtained at $z$$\sim $ 1.4 is located between those at $z$$\sim $ 0.8 and $z$$\sim $ 2.2. We constrain the intrinsic scatter to be $\sim $ 0.1 dex, or larger in the mass–metallicity relation at $z$$\sim $ 1.4; the scatter may be larger at higher redshifts. We found trends that the deviation from the mass–metallicity relation depends on the SFR (Star-formation rate) and the half light radius: Galaxies with higher SFR and larger half light radii show lower metallicities at a given stellar mass. One possible scenario for the trends is the infall of pristine gas accreted from IGM, or through merger events. Our data points show larger scatter than the fundamental metallicity relation (FMR) at $z$$\sim $ 0.1, and the average metallicities slightly deviate from the FMR. The compilation of the mass–metallicity relations at $z$$\sim $ 3 to $z$$\sim $ 0.1 shows that they evolve smoothly from $z$$\sim $ 3 to $z$$\sim $ 0 without changing the shape so much, except for the massive part at $z$$\sim $ 0.

SHORT GAMMA-RAY BURSTS: THE MASS OF THE ACCRETION DISK AND THE INITIAL RADIUS OF THE OUTFLOW

In this work we estimate the accretion-disk mass in the specific scenario of binary-neutron-star-merger with current observational data. Assuming that the outflows of short Gamma-ray Bursts (GRBs) are driven via neutrino-antineutrino annihilation we estimate the disk mass of about half of short bursts in the sample to be $\sim 0.01-0.1 M_\odot$, in agreement with that obtained in the numerical simulations. Massive disks ($\sim {\rm several} 0.1 M_\odot$) found in some other short GRBs may point to the more efficient magnetic process of energy extraction or the neutron star and black hole binary progenitor. Our results suggest that some short bursts may be really due to the coalescence of double neutron stars and are promising gravitational wave radiation sources. For future short GRBs with simultaneous gravitational-wave detections, the disk mass may be reliably inferred and the validity of our approach will be tested. We also propose a method to constrain the initial radius of a baryonic outflow where it is launched ($R_0$) without the need of identifying an ideal thermal spectrum. We then apply it to GRB 090510 and get that $R_0 \lesssim 6.5\times 10^{6}(\Gamma_{\rm ph}/2000)^{-4}$ cm, suggesting that the central engine is a black hole with a mass $< 22 M_\odot(\Gamma_{\rm ph}/2000)^{-4}$, where $\Gamma_{\rm ph}$ is the bulk Lorentz factor of the outflow at the photospheric radius.

Theoretical study of thermal conductivity in single-walled boron nitride nanotubes

We perform a theoretical investigation on the thermal conductivity of single-walled boron nitride nanotubes (SWBNT) using the kinetic theory. By fitting to the phonon spectrum of boron nitride sheet, we develop an efficient and stable Tersoff-derived interatomic potential which is suitable for the study of heat transport in sp2 structures. We work out the selection rules for the three-phonon process with the help of the helical quantum numbers $(\kappa, n)$ attributed to the symmetry group (line group) of the SWBNT. Our calculation shows that the thermal conductivity $\kappa_{\rm ph}$ diverges with length as $\kappa_{\rm ph}\propto L^{\beta}$ with exponentially decaying $\beta(T)\propto e^{-T/T_{c}}$, which results from the competition between boundary scattering and three-phonon scattering for flexure modes. We find that the two flexure modes of the SWBNT make dominant contribution to the thermal conductivity, because their zero frequency locates at $\kappa=\pm\alpha$ where $\alpha$ is the rotational angle of the screw symmetry in SWBNT.

Renormalization and Asymptotic Expansion of Dirac’s Polarized Vacuum

We perform rigorously the charge renormalization of the so-called reduced Bogoliubov-Dirac-Fock (rBDF) model. This nonlinear theory, based on the Dirac operator, describes atoms and molecules while taking into account vacuum polarization effects. We consider the total physical density ρ ph including both the external density of a nucleus and the self-consistent polarization of the Dirac sea, but no ‘real’ electron. We show that ρ ph admits an asymptotic expansion to any order in powers of the physical coupling constant α ph, provided that the ultraviolet cut-off behaves as \({\Lambda\sim e^{3\pi(1-Z_3)/2\alpha_{\rm ph}} \gg 1}\). The renormalization parameter 0 < Z 3 < 1 is defined by Z 3 = α ph/α, where α is the bare coupling constant. The coefficients of the expansion of ρ ph are independent of Z 3, as expected. The first order term gives rise to the well-known Uehling potential, whereas the higher order terms satisfy an explicit recursion relation.

EPISODIC TRANSIENT GAMMA-RAY EMISSION FROM THE MICROQUASAR CYGNUS X-1

Cygnus X-1 is the archetypal black hole (BH) binary system in our Galaxy. We report the main results of an extensive search for transient gamma-ray emission from Cygnus X-1 carried out in the energy range 100 MeV - 3 GeV by the AGILE satellite, during the period 2007 July - 2009 October. The total exposure time is about 300 days, during which the source was in the "hard" X-ray spectral state. We divided the observing intervals in 2 or 4 week periods, and searched for transient and persistent emission. We report an episode of significant transient gamma-ray emission detected on 2009, October 16 in a position compatible with Cygnus X-1 optical position. This episode, occurred during a hard spectral state of Cygnus X-1, shows that a 1-2 day time variable emission above 100 MeV can be produced during hard spectral states, having important theoretical implications for current Comptonization models for Cygnus X-1 and other microquasars. Except for this one short timescale episode, no significant gamma-ray emission was detected by AGILE. By integrating all available data we obtain a 2$\sigma$ upper limit for the total integrated flux of $F_{\gamma,U.L.} = 3 \times 10^{-8} \rm ph cm^{-2} s^{-1}$ in the energy range 100 MeV - 3 GeV. We then clearly establish the existence of a spectral cutoff in the energy range 1-100 MeV that applies to the typical hard state outside the flaring period and that confirms the historically known spectral cutoff above 1 MeV.

Evidence of Hot Spot Activity on BH Virginis

Photoelectric light curves of BH Vir in the UBVRI bands observed by Arévalo et al. in 1986 were analyzed by using the latest version of the Wilson–Devinney program and to investigate the photometric parameters and spot activity. Satisfactory fits were obtained by assuming a hot spot only on the secondary star. The results show that the temperature of the spotted region relative to the photosphere, $T_{\rm s}/T_{\rm ph}$, is 1.13$\pm$0.027. The active region tends to occur at low latitude (near 81$^{\circ}$). The results also show that the mass ratio obtained from the photoelectric light curves is $q=m_{2}/m_{1} =$ 0.971. It is close to the spectroscopic value of 0.968 obtained by Zhai et al. (1990). The photosphere temperature of the primary is $T_{1}=$ 5969$\pm$11 K. After checking of the activity pattern from 1953 to 1991, the activity cycle is estimated to be about 10 yr.

Thermoelectrical properties and optical third harmonic generation of Gd-doped PbTe

We performed the temperature measurements of transport and non-linear optical properties, particularly optical third harmonic generation of PbTe and Gd-doped PbTe to elucidate the effect of the rare earth ion doping on behavior of the thermal conductivity and the third-order non-linear optical susceptibility. The feature of Gd-doped PbTe shows the existence of small values of the low temperature resistivities, (\({10^{-6}\Omega\,\hbox{cm}}\)) and a very significant value of mobility \({\mu=1.5^{\ast}10^{6}\hbox{cm}^{2}\hbox{V}^{-1} \hbox{s}^{-1}}\). The thermal conductivity κ decreases with incorporation of the rare earth ion (Gd) in PbTe matrice. The optical third harmonic generation (THG) shows that the great contribution of the phonons observed for PbGdTe compared to the PbTe, enhances the lattice thermal conductivity of network \({(\hbox{k}_{\rm ph})}\).

Metal‐induced rearrangement of benzothiazoline ring: Synthesis and characterization of some new organoantimony(V) derivatives of N, O, and S atom containing schiff base ligands

AbstractSome new triphenylantimony(V) derivatives of Schiff bases having the composition ${\rm Ph_3 S\overline{b[SC_6 H_4 N: C(R)CH:CO}COOC H_3]}$ have been synthesized by the equimolar reactions of Ph3SbBr2 with newly synthesized benzothiazoline ligands, $\hbox{H }{\rm \overline{NC_6 H_4 SC} (R)CH:C(OH)COOCH_3}$ (where R = C6H5(H2L1), 4‐BrC6H4(H2L2), 4‐ClC6H4(H2L3), 4‐CH3‐OC6H4(H2L4), 4‐CH3C6H4(H2L5)). The reaction proceeds with the rearrangement of benzothiazoline ring. All the derivatives have been characterized by elemental analyses, molecular weight measurements and their plausible structures have been proposed on the basis of IR and NMR (1H and 13C) spectral studies. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:70–75, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20260

Photoconductivity in Thin Film of a-(Ge20Se80)0.90Sn0.10

Steady state and transient photoconductivity measurements have been done on thin film of a-(Ge20Se80)0.90Sn0.10 as a function of temperature and intensity. Dark conductivity (σd) and photoconductivity (\(\sigma_{\rm ph}\)) measurements show that the conduction in this glass is through an activated process having single activation energy in the temperature range 283–350 K. The intensity dependence of steady state photoconductivity (\(\sigma_{\rm ph}\)) follows a power law with intensity (F), \(\sigma_{\rm ph} \propto F^{\gamma}\), where the power γ has been found between 0.5 and 1.0, suggesting bimolecular recombination. Rise and decay of photocurrent at different temperatures and intensities show that photocurrent (Iph) rises monotonically to the steady state value and the decay of photocurrent is quite slow. A detailed analysis of photoconductive decay shows that the recombination within localized states may be predominant recombination mechanism in this glassy alloy.

Small Fermi energy, zero-point fluctuations, and nonadiabaticity inMgB2

Small Fermi energy effects are induced in MgB$_2$ by the low hole doping in the $\sigma$ bands which are characterized by a Fermi energy $E_{\rm F}^\sigma \sim 0.5$ eV. We show that, due to the particularly strong deformation potential relative to the $E_{2g}$ phonon mode, lattice fluctuations are reflected in strong fluctuations in the electronic band structure. Quantum fluctuations associated to the zero-point lattice motion are responsible for an uncertainty of the Fermi energy of the order of the Fermi energy itself, leading to the breakdown of the adiabatic principle underlying the Born-Oppenheimer approximation in MgB$_2$ even if $\omega_{\rm ph}/E_{\rm F} \sim 0.1-0.2$, where $\omega_{\rm ph}$ are the characteristic phonon frequencies. This amounts to a new nonadiabatic regime, which could be relevant to other unconventional superconductors.

Predicting intense-field photoionization of atoms and molecules from their linear photoabsorption spectra in the ionization continuum

We report a new approach to intense-field photoionization that is based on the ad hoc assumption that m photons of energy $E_{\rm ph}$ arriving within a typical electronic response time are effectively equivalent to a single photon of energy $mE_{\rm ph}$ . The heuristic model contains no adjustable parameters and unifies apparent multiphoton and field aspects. Moreover, nonsequential, suppressed and above-threshold ionization phenomena become readily understandable. Predicted ionization intensities are in satisfactory agreement with available experimental data ranging from C6H6 to Ne3 + , from femtosecond to nanosecond laser pulses, and from ultraviolet to infrared laser radiation.

Asymptotics of the hypergeometric function

AbstractAn asymptotic representation is obtained for the hypergeometric function ${\bf F}(a+\lambda,b‐\lambda,c,1/2‐1/2z)$\nopagenumbers\end as $|\lambda|\rightarrow\infty$\nopagenumbers\end with $|{\rm ph}\,\lambda|&amp;#60;\pi$\nopagenumbers\end. It is uniformly valid in the z‐plane cut in an appropriate way. Several other forms of the hypergeometric function are discussed also. Another representation which has some advantages over the conventional one is given as well. Copyright © 2001 John Wiley &amp; Sons, Ltd.

Scale- and scheme-independent extension of Padé approximants: Bjorken polarized sum rule as an example

A renormalization-scale-invariant generalization of the diagonal Pad\'e approximants (dPA), developed previously, is extended so that it becomes renormalization-scheme-invariant as well. We do this explicitly when two terms beyond the leading order (NNLO, $\sim \alpha_s^3$) are known in the truncated perturbation series (TPS). At first, the scheme dependence shows up as a dependence on the first two scheme parameters $c_2$ and $c_3$. Invariance under the change of the leading parameter $c_2$ is achieved via a variant of the principle of minimal sensitivity. The subleading parameter $c_3$ is fixed so that a scale- and scheme-invariant Borel transform of the resummation approximant gives the correct location of the leading infrared renormalon pole. The leading higher-twist contribution, or a part of it, is thus believed to be contained implicitly in the resummation. We applied the approximant to the Bjorken polarized sum rule (BjPSR) at $Q^2_{\rm ph}=5$ and $3 GeV^2$, for the most recent data and the data available until 1997, respectively, and obtained ${\alpha}_s^{\bar MS}(M_Z^2)=0.119^{+0.003}_{-0.006}$ and $0.113^{+0.004}_{-0.019}$, respectively. Very similar results are obtained with the Grunberg's effective charge method and Stevenson's TPS principle of minimal sensitivity, if we fix $c_3$-parameter in them by the aforementioned procedure. The central values for ${\alpha}_s^{\bar MS}(M_Z^2)$ increase to 0.120 (0.114) when applying dPA's, and 0.125 (0.118) when applying NNLO TPS.

Shot noise in diffusive conductors: A quantitative analysis of electron-phonon interaction effects

Using the 'drift-diffusion-Langevin' equation, we have quantitatively analyzed the effects of electron energy relaxation via their interaction with phonons, generally in presence of electron-electron interaction, on shot noise in diffusive conductors. We have found that the noise power $ S_I(\omega )$ (both at low and high observation frequencies $\omega $) drops to half of its 'mesoscopic' value only at $\beta \gtrsim 100,$ where $\beta $ is the ratio of the sample length $L$ to the energy relaxation length $l_{% {\rm ph}}$ (the latter may be much larger then the dephasing length). It means in particular that at low temperatures the shot noise may be substantial even when $L\sim 10^{-2}$ -- $10^{-1}$ cm, and the conductor is 'macroscopic' in any other respect.

Quantitative description of the chloride effect on chlorine dioxide generation from the ClO2‐HOCl reaction

AbstractThe generation of chlorine dioxide from the reaction between hypochlorous acid and chlorite with or without an initial chloride addition has been studied under slightly acidic conditions. Chloride (Cl‐), one of the products from the reaction, not only changes the reaction stoichiometry, but also alters the rate law. It was found that the formation of chlorine dioxide from the HOCI‐ClO2‐ system consists of two distinct parts, one is promoted by chloride, the other is independent of chloride. The overall kinetics of the chlorine dioxide generation from the reaction is: This model can very well predict the reaction under the following conditions: \documentclass{article}\pagestyle{empty}\begin{document}$ 273 - 303{\rm K},\left[ {ClO_2^ - } \right] = 0.001 - 0.00267\;{\rm mol}/{\rm L},\left[ {ClO_2^ - } \right]/\left[ {HOCl} \right] = 2,\;{\rm and}\;{\rm pH}\;3.86 - 4.91 $\end{document}

A Downward Collapse within the Polynomial Hierarchy

Downward collapse (also known as upward separation) refers to cases where the equality of two larger classes implies the equality of two smaller classes. We provide an unqualified downward collapse result completely within the polynomial hierarchy. In particular, we prove that, for k > 2, if ${\rm P}^{\Sigma^p_k[1]} = {\rm P}^{\Sigma^p_k[2]}$ then $\Sigma^p_k = \Pi^p_k = {\rm PH}$. We extend this to obtain a more general downward collapse result.

Comparison of chromatographic parameters of heterocyclic bases and their N-oxides in liquid-liquid partition systems

Relationships between RM values and pH of aqueous stationary phase were determined for some heterocyclic bases and their N-oxides chromatographed in partition systems of the type: organic solvent (benzene, chloroform or mixture of chloroform with cyclohexane)—aqueous buffer solution. In view of large differences in pKA values of the bases and their N-oxides, the ΔRMro(N→NO) values (change of RM during suppressed ionization, due to reaction) could only be estimated by graphical extrapolation of the chromatographic data. The ΔRMro values thus determined were in most cases in the range 2.2–2.7 RM units.

The Radiation Chemistry of Phosphine-Ammonia Mixtures in the Gas Phase

Irradiation of gaseous mixtures of ammonia and phosphine with Co-60 gamma rays yields hydrogen, red phosphorus, and nitrogen. Attempts to find other products have been unsuccessful. Hydrogen yields are larger than predicted from the assumption of an ideal mixture, in which the ammonia and phosphine decompose proportionately to the dose each absorbs, but nitrogen yields show a striking depression. This occurs even in mixtures with less than 0.1 mole percent phosphine. Phosphine appears to be acting as an efficient radical scavenger, via reactions such as ${\rm NH}_{2}\cdot +{\rm PH}_{3}\rightarrow {\rm NH}_{3}+{\rm PH}_{2}\cdot $ and ${\rm H}\cdot +{\rm PH}_{3}\rightarrow {\rm H}_{2} {\rm PH}_{2}$. The phosphino radical reacts further to yield (finally) phosphorus and hydrogen. By comparing the radiolytic decomposition of ammonia in a mixture containing a few mole percent phosphine and in the pure state, it can be shown that roughly one phosphine is removed for each ammonia that is prevented from decomp...