The Experts below are selected from a list of 3033 Experts worldwide ranked by ideXlab platform

Zach Medin - One of the best experts on this subject based on the ideXlab platform.

  • condensed surfaces of magnetic neutron stars and particle acceleration above pulsar polar caps
    40 YEARS OF PULSARS: Millisecond Pulsars Magnetars and More, 2008
    Co-Authors: Zach Medin
    Abstract:

    Recent calculations indicate that the Cohesive energy of condensed matter increases with magnetic field strength and becomes very significant at magnetar‐like fields (e.g., 10 keV at 3×1014 G for zero‐pressure condensed iron). This implies that for sufficiently strong magnetic fields and/or low temperatures, the neutron star surface may be in a condensed state with little gas or plasma above it. Such surface condensation may lead to the formation of a charge‐depleted acceleration zone (“vacuum gap”) in the magnetosphere above the stellar polar cap. Using the latest results on the Cohesive Property of magnetic condensed matter, we quantitatively determine the conditions for vacuum gap formation in magnetic neutron stars. We also study the physics of pair cascades in the (Ruderman‐Sutherland type) vacuum gap model for photon emission by accelerating electrons and positrons due to both curvature radiation and resonant/nonresonant inverse Compton scattering. Our calculations of the condition of cascade‐induce...

  • condensed surfaces of magnetic neutron stars thermal surface emission and particle acceleration above pulsar polar caps
    Monthly Notices of the Royal Astronomical Society, 2007
    Co-Authors: Zach Medin
    Abstract:

    Recent calculations indicate that the Cohesive energy of condensed matter increases with magnetic field strength and becomes very significant at magnetar-like fields (e.g. 10 keV at 3 × 10 14 G for zero-pressure condensed iron). This implies that for sufficiently strong magnetic fields and/or low temperatures, the neutron star surface may be in a condensed state with little gas or plasma above it. Such surface condensation can significantly affect the thermal emission from isolated neutron stars, and may lead to the formation of a charge-depleted acceleration zone (‘vacuum gap’) in the magnetosphere above the stellar polar cap. Using the latest results on the Cohesive Property of magnetic condensed matter, we quantitatively determine the conditions for surface condensation and vacuum gap formation in magnetic neutron stars. We find that condensation can occur if the thermal energy kT of the neutron star surface is less than about 8 per cent of its Cohesive energy Qs, and that a vacuum gap can form if Ω · Bp < 0 (i.e. the neutron star’s rotation axis and magnetic moment point in opposite directions) and kT is less than about 4 per cent of Qs. For example, at B = 3 × 10 14 G, a condensed Fe surface forms when T 10 7 K and a vacuum gap forms when T 5 × 10 6 K. Thus, vacuum gap accelerators may exist for some neutron stars. Motivated by this result, we also study the physics of pair cascades in the (Ruderman‐Sutherland type) vacuum gap model for photon emission by accelerating electrons and positrons due to both curvature radiation and resonant/non-resonant inverse-Compton scattering. Our calculations of the condition of cascade-induced vacuum breakdown and the related pulsar death line/boundary generalize previous works to the superstrong field regime. We find that inverse-Compton scatterings do not produce a sufficient number of high-energy photons in the gap (despite the fact that resonantly upscattered photons can immediately produce pairs for B 1.6 × 10 14 G) and thus do not lead to pair cascades for most neutron star parameters (spin and magnetic field). We discuss the implications of our results for the recent observations of neutron star thermal radiation as well as for the detection/non-detection of radio emission from high-B pulsars and

  • condensed surfaces of magnetic neutron stars thermal surface emission and particle acceleration above pulsar polar caps
    arXiv: Astrophysics, 2007
    Co-Authors: Zach Medin, Dong Lai
    Abstract:

    For sufficiently strong magnetic fields and/or low temperatures, the neutron star surface may be in a condensed state with little gas or plasma above it. Such surface condensation can significantly affect the thermal emission from isolated neutron stars, and may lead to the formation of a charge-depleted acceleration zone ("vacuum gap") in the magnetosphere above the stellar polar cap. Using the latest results on the Cohesive Property of magnetic condensed matter, we quantitatively determine the conditions for surface condensation and vacuum gap formation in magnetic neutron stars. We find that condensation can occur if the thermal energy kT of the neutron star surface is less than about 8% of its Cohesive energy Q_s, and that a vacuum gap can form if the neutron star's rotation axis and magnetic moment point in opposite directions and kT is less than about 4% of Q_s. Thus, vacuum gap accelerators may exist for some neutron stars. Motivated by this result, we also study the physics of pair cascades in the vacuum gap model for photon emission by accelerating electrons and positrons due to both curvature radiation and resonant/nonresonant inverse Compton scattering. Our calculations of the condition of cascade-induced vacuum breakdown and the related pulsar death line/boundary generalize previous works to the superstrong field regime. We find that inverse Compton scatterings do not produce a sufficient number of high energy photons in the gap and thus do not lead to pair cascades for most neutron star parameters. We discuss the implications of our results for the recent observations of neutron star thermal radiation as well as for the detection/non-detection of radio emission from high-B pulsars and magnetars.

  • Cohesive Property of magnetized neutron star surfaces: Computations and implications
    Advances in Space Research, 2007
    Co-Authors: Zach Medin, Dong Lai
    Abstract:

    The Cohesive energy of condensed matter in strong magnetic fields is a fundamental quantity characterizing magnetized neutron star surfaces. The Cohesive energy refers to the energy required to pull an atom out of the bulk condensed matter at zero pressure. Theoretical models of pulsar and magnetar magnetospheres depend on the Cohesive properties of the surface matter in strong magnetic fields. For example, depending on the Cohesive energy of the surface matter, an acceleration zone (“polar gap”) above the polar cap of a pulsar may or may not form. Also, condensation of the neutron star surface, if it occurs, can significantly affect thermal emission from isolated neutron stars. We describe our calculations of the Cohesive Property of matter in strong magnetic fields, and discuss the implications of our results to the recent observations of neutron star surface emission as well as to the detection/non-detection of radio emission from magnetars.

Dong Lai - One of the best experts on this subject based on the ideXlab platform.

  • condensed surfaces of magnetic neutron stars thermal surface emission and particle acceleration above pulsar polar caps
    arXiv: Astrophysics, 2007
    Co-Authors: Zach Medin, Dong Lai
    Abstract:

    For sufficiently strong magnetic fields and/or low temperatures, the neutron star surface may be in a condensed state with little gas or plasma above it. Such surface condensation can significantly affect the thermal emission from isolated neutron stars, and may lead to the formation of a charge-depleted acceleration zone ("vacuum gap") in the magnetosphere above the stellar polar cap. Using the latest results on the Cohesive Property of magnetic condensed matter, we quantitatively determine the conditions for surface condensation and vacuum gap formation in magnetic neutron stars. We find that condensation can occur if the thermal energy kT of the neutron star surface is less than about 8% of its Cohesive energy Q_s, and that a vacuum gap can form if the neutron star's rotation axis and magnetic moment point in opposite directions and kT is less than about 4% of Q_s. Thus, vacuum gap accelerators may exist for some neutron stars. Motivated by this result, we also study the physics of pair cascades in the vacuum gap model for photon emission by accelerating electrons and positrons due to both curvature radiation and resonant/nonresonant inverse Compton scattering. Our calculations of the condition of cascade-induced vacuum breakdown and the related pulsar death line/boundary generalize previous works to the superstrong field regime. We find that inverse Compton scatterings do not produce a sufficient number of high energy photons in the gap and thus do not lead to pair cascades for most neutron star parameters. We discuss the implications of our results for the recent observations of neutron star thermal radiation as well as for the detection/non-detection of radio emission from high-B pulsars and magnetars.

  • Cohesive Property of magnetized neutron star surfaces: Computations and implications
    Advances in Space Research, 2007
    Co-Authors: Zach Medin, Dong Lai
    Abstract:

    The Cohesive energy of condensed matter in strong magnetic fields is a fundamental quantity characterizing magnetized neutron star surfaces. The Cohesive energy refers to the energy required to pull an atom out of the bulk condensed matter at zero pressure. Theoretical models of pulsar and magnetar magnetospheres depend on the Cohesive properties of the surface matter in strong magnetic fields. For example, depending on the Cohesive energy of the surface matter, an acceleration zone (“polar gap”) above the polar cap of a pulsar may or may not form. Also, condensation of the neutron star surface, if it occurs, can significantly affect thermal emission from isolated neutron stars. We describe our calculations of the Cohesive Property of matter in strong magnetic fields, and discuss the implications of our results to the recent observations of neutron star surface emission as well as to the detection/non-detection of radio emission from magnetars.

Wang Li-yan - One of the best experts on this subject based on the ideXlab platform.

  • Experiment of Paper Tape′s Cohesive Property of Environment-friendly Strapping Machine
    Light Industry Machinery, 2010
    Co-Authors: Wang Li-yan
    Abstract:

    The influence factors on paper tape′s cohesion of environment-friendly strapping machine are heating temperature,pressure and time preservation after adhesive thawing,as well as adhesive′s usage value.Taking note-binding for example,through single factor experiments and orthogonal experiment to obtain the optimum combined value of influence factors: heating temperature 140 ℃,pressure 70 N,time 4 s,adhesive′s usage value 0.05 g.So that adhesive has greatest Cohesive Property.The experimental data illustrate paper tape′s Cohesive Property can meet the requirements of financial department.[Ch,3 fig.4 tab.10 ref.]

Wang Liyan - One of the best experts on this subject based on the ideXlab platform.

  • experiment of paper tape s Cohesive Property of environment friendly strapping machine
    Light Industry Machinery, 2010
    Co-Authors: Wang Liyan
    Abstract:

    The influence factors on paper tape′s cohesion of environment-friendly strapping machine are heating temperature,pressure and time preservation after adhesive thawing,as well as adhesive′s usage value.Taking note-binding for example,through single factor experiments and orthogonal experiment to obtain the optimum combined value of influence factors: heating temperature 140 ℃,pressure 70 N,time 4 s,adhesive′s usage value 0.05 g.So that adhesive has greatest Cohesive Property.The experimental data illustrate paper tape′s Cohesive Property can meet the requirements of financial department.[Ch,3 fig.4 tab.10 ref.]

Hayato Tokumoto - One of the best experts on this subject based on the ideXlab platform.

  • ZnO nanoparticles effect on pollen grain germination and pollen tube elongation
    Plant Cell Tissue and Organ Culture (PCTOC), 2021
    Co-Authors: Shizue Yoshihara, Saki Hirata, Kasumi Yamamoto, Yoshino Nakajima, Kensuke Kurahashi, Hayato Tokumoto
    Abstract:

    Plant germ cells, such as pollen grains, can be affected by exposure to metal nanoparticles (NPs) that have diffused into the environment. The germination and tube elongation of pollen grain ( Lilium longiflorum ) exposed to low-solubility NPs was observed. The germination rate of pollen grain exposed to 100 mg L^−1 ZnO NP dispersion decreased significantly from controls and exposure of the other NPs. On the other hand, when pollens were exposed to ionic solutions in which particles were removed from the 100 mg L^−1 ZnO NP dispersion, the germination rates were equivalent to those in the control pollens. On the contrary, decrease of the germination rate compared to controls was small in the exposure to ZnCl_2 solution, which contained a larger amount of water-soluble Zn^2+ than ZnO NP dispersion. From these results, it was concluded that fine ZnO NP may adhere to pollens, due to the Cohesive Property of nanoparticles, and Zn^2+ dissolved at the interface may be continuously absorbed by pollens. When pollen was exposed to ZnO NP, a spot with a high Ca^2+ local concentration was observed at the tip of the pollen tube. On the contrary, simultaneous exposure to antagonistic ZnO NP and CaCl_2 resulted in no decrease in the germination rate. From the above, it is considered that upon exposure to ZnO NP, cells absorb Zn^2+ depending on the specific solubility of ZnO NP. Despite the low solubility of zinc oxide nanoparticle, pollen cell-attached particles inhibited germination and elongation of pollen tube by continuous Zn^2+ dissolution from particles and Zn^2+ absorption by the cell.