Sommerfeld Radiation Condition at Threshold

We prove Besov space bounds of the resolvent at low energies in any dimension for a class of potentials that are negative and obey a virial condition with these conditions imposed at infinity only. We do not require spherical symmetry. The class of potentials includes in dimension ≥3 the attractive Coulomb potential. There are two boundary values of the resolvent at zero energy which we characterize by radiation conditions. These radiation conditions are zero energy versions of the well-known Sommerfeld radiation condition.     

Blow‐up criterion for 3D viscous‐resistive compressible magnetohydrodynamic equations

In this paper, we establish a blow‐up criterion of strong solutions for 3D viscous‐resistive compressible magnetohydrodynamic equations, which depends only on and . Our result improves the previous criterion in Lu's paper (Journal of Mathematical Analysis and Applications 2011; 379: 425–438.) for compressible magnetohydrodynamic equations by removing a stringent condition on the viscous coefficients μ > 4λ. In addition, initial vacuum states are also allowed in our cases. Copyright © 2012 John Wiley & Sons, Ltd.     

Strong water repellency effect on SiO<Subscript>2</Subscript> films processed at a nanometric scale

The present study deals with the creation of nano-rough surfaces with stable and controlled high hydrophobicity. These surfaces were obtained by combining the ion track etching technique with a simple functionalization by grafting perfluoroctyltrichlorosilane (PFOTS) molecules. Surface morphology was investigated by AFM observations which evidenced a self-affine fractal structure with a fractal dimension D_f ~ 2.6. The study of the wetting properties of these surfaces allowed to elucidate the conditions for observing a high hydrophobicity phenomenon and to predict the contact angle values for surfaces designed at a nanometric scale.     

The effect of tamper layer on the explosion dynamics of atom clusters

The behavior of small samples in very short and intense hard X-ray pulses is studied by molecular dynamics type calculations. The main emphasis is put on the effect of various tamper layers about the sample. This is discussed from the point of view of structural imaging of single particles, including not only the distortion of the structure but also the background conditions. A detailed picture is given about the Coulomb explosion, with explanation of the tampering mechanism. It is shown that a thin water layer is efficient in slowing down the distortion of the atomic structure, but it gives a significant contribution to the background.     

Argon and krypton ion-induced changes in permalloy thin films

The effects of 75-keV Ar and 100-keV Kr ion irradiations of 72-nm thin DC-sputtered permalloy (Ni₈₁Fe₁₉) films on Si(100) wafers were studied at fluences of up to 10¹⁶ ions/cm². The changes of the structural and magnetic properties were measured via X-ray diffraction, Rutherford backscattering spectroscopy, and magneto-optical Kerr effect. The irradiations increase the lattice constant and improve the crystallinity of the samples. They induce also strong changes of the magnetic polarisation and the coercive field for increasing ion fluence. The hysteresis loops suggest that, with increasing ion fluence, the reversal of the magnetisation changes gradually from rotation-dominated in the as-deposited films to domain-wall-motion dominated at the highest ion fluences. The results are compared with those obtained for Ni-, Cr-and Xe-ion irradiated permalloy films.     

Local structural analysis of In-doped Bi2Se3 topological insulator using X-ray fluorescence holography

We performed X-ray fluorescence holography measurements on an In-doped Bi₂Se₃ topological insulator and obtained an in-plane atomic image in the vicinity of In. We found that atomic images at the positions of the first nearest neighbors (NNs) are very weak whereas those at the positions of the second and the third NNs are relatively strong. On the basis of the fact that In is half of the atomic number of Bi, we attributed the origin of this feature to the clustering of the In atoms in the Bi plane. We calculated the intensity of the atomic images and confirmed that the formation of In cluster results in a decrease by 30% in the first NN atomic image intensity. However, the decrease in the magnitude is not enough to explain the experimental results, suggesting another contribution such as the lattice distortions. The effect of the lattice distortion on the atomic image intensity is discussed on the basis of the simulation including the positional fluctuation of In atoms.     

Decomposition of Picolyl Radicals at High Temperature: A Mass Selective Threshold Photoelectron Spectroscopy Study

The reaction products of the picolyl radicals at high temperature were characterized by mass-selective threshold photoelectron spectroscopy in the gas phase. Aminomethylpyridines were pyrolyzed to initially produce picolyl radicals (m/z=92). At higher temperatures further thermal reaction products are generated in the pyrolysis reactor. All compounds were identified by mass-selected threshold photoelectron spectroscopy and several hitherto unexplored reactive molecules were characterized. The mechanism for several dissociation pathways was outlined in computations. The spectrum of m/z=91, resulting from hydrogen loss of picolyl, shows four isomers, two ethynyl pyrroles with adiabatic ionization energies (IE_ad) of 7.99 eV (2-ethynyl-1H-pyrrole) and 8.12 eV (3-ethynyl-1H-pyrrole), and two cyclopentadiene carbonitriles with IE′s of 9.14 eV (cyclopenta-1,3-diene-1-carbonitrile) and 9.25 eV (cyclopenta-1,4-diene-1-carbonitrile). A second consecutive hydrogen loss forms the cyanocyclopentadienyl radical with IE′s of 9.07 eV (T₀) and 9.21 eV (S₁). This compound dissociates further to acetylene and the cyanopropynyl radical (IE=9.35 eV). Furthermore, the cyclopentadienyl radical, penta-1,3-diyne, cyclopentadiene and propargyl were identified in the spectra. Computations indicate that dissociation of picolyl proceeds initially via a resonance-stabilized seven-membered ring.     

Hole Migration in Telomere-Based Oligonucleotide Anions and G-Quadruplexes

Vacuum ultraviolet photoionization of a gas-phase oligonucleotide anion leads to the formation of a valence hole. This hole migrates towards an energetically favorable site where it can weaken bonds and ultimately lead to bond cleavage. We have studied Vacuum UV photoionization of deprotonated oligonucleotides containing the human telomere sequence dTTAGGG and G-quadruplex structures consisting of four dTGGGGT single strands, stabilized by NH₄⁺ counter ions. The oligonucleotide and G-quadruplex anions were confined in a radiofrequency ion trap, interfaced with a synchrotron beamline and the photofragmentation was studied using time-of-flight mass spectrometry. Oligonucleotide 12-mers containing the 5'-TTAGGG sequence were found to predominantly break in the GGG region, whereas no selective bond cleavage region was observed for the reversed 5'-GGGATT sequence. For G-quadruplex structures, fragmentation was quenched and mostly non-dissociative single and double electron removal was observed.     

紫外辐照法合成环蕃醛

利用254 nm紫外光对[2.2]对环蕃氯仿溶液进行辐照,得到两种主要产物4-醛基-[2.2]-对环蕃和4,4'-(乙基-1,2-二取代)二苯甲醛,利用核磁共振波谱仪(NMR)和气相色谱-质谱联用(GC-MS)技术手段对产物的结构进行分析研究。 同时对反应条件进行探究,发现当氯仿和水同时存在时才能生成醛基,并由此提出了提出了可能的反应机理:通过瑞默-提曼反应使CHCl₂·自由基加成到苯环上并进一步生成醛基。     

Properties of ethylene propylene diene rubber/white and black filler composites cured by gamma radiation in presence of sorbic acid

The effect of incorporating sorbic acid (SA), an echo-friendly curing agent, and silica or carbon black (CB) filler, as well as gamma irradiation on the physico-chemical, mechanical and thermal properties of ethylene propylene diene monomer rubber (EPDM) was investigated. The results indicated that the developed composites revealed improvement in the studied parameters over the untreated samples. Filler incorporation into rubber matrix has been proven a key factor in enhancing the swelling resistance, tensile strength and thermal properties of the fabricated composites. The improvement in tensile strength and modulus was attributed to better interfacial bonding via SA. Alternatively, a comparison was established between the performance of the white and black fillers. The utmost mechanical performance was reported for the incorporated ratios 10 phr SA and 40 phr white filler into a 50 kGy irradiated composite. Meanwhile, the incorporation of CB yielded better thermally stable composites than those filled with silica at similar conditions.