Influence of surface environment on Auger peaks : The Palladium M45N45N45 transition

The fine structure of the M₄₅N₄₅N₄₅ Palladium Auger transition was investigated. The energy of the peaks and the changes of their shapes due to surface modifications, either by alloying or by oxidation are studied. It is found that the fine structure is due to the overlapping of two “band-like” transitions of the type M₄VV and M₅VV.     

Microstructure and melting in fractions of polyethylene characterized with the aid of a novel folded-chain-lamella model

Folded-chain-lamellae are considered as “cooperative units” with frozen matter flow and with a locally heterogeneous atomistic order the degree of which is reversibly regulated by surface-melting or surface crystallization. A consequent thermodynamic treatment of restricted micro-phase equilibrium in semicrystalline fractions of polyethylene of different molecular weights can be shown to deliver a characterization of such nonequilibrium states by relating additional internal variables to parameters of the microstructure (DSC-measurements, electron-micrographs, SAXS). What appears to be very satisfactory is the conclusion that the excess situation produced by noncrystallizable defects in the semicrystalline samples is clearly related to the original state of order in the melt: Approximative invariance of penetration is directly elucidating that any matter flow in the regime of the chains of sufficient length is frozen during folded-chain crystallization. Molecular-weight effects in semicrystalline fractions of polyethylene can be interpreted on these lines.     

Interaction of oxygen and hydrogen with Pd-Au alloys: An AES and XPS study

Pd-Au alloys of three different concentrations have been studied with Auger Electron Spectroscopy and Photoelectron Spectroscopy. A quantitative method shows that the decontaminated surfaces possess the same composition as the bulk. Interaction of oxygen up to 600°C with gold rich alloys (>85%) is very weak. It starts around 300°C on the other two alloys and results in a significant palladium surface enrichment. On the 60 at% Pd-Au alloy, at 500–580°C, the surface may be completely covered with PdO. A hydrogen treatment at 350°C leads to a complete reduction of the oxide without reequilibration of the surface.     

Monolayer pattern evolution via substrate strain-mediated spinodal decomposition

Investigations of octylsilane (C8H17SiH3) monolayer pattern formation on Au(111) are reported. Scanning tunneling microscopy data display the evolution of a approximately 6 nm scale pattern of interwoven features concomitant with ejection of surface Au atoms and relaxation of the Au(111) 23xsqrt[3] surface reconstruction. Numerical simulations suggest the surface dynamics are governed by a substrate strain-mediated spinodal decomposition mechanism, novel to organic monolayer formation. Collectively, the experimental and theoretical data indicate strain-inducing Si-Au bond interactions drive the pattern formation and the alkyl chains play a negligible role.     

Urine steroid profile of judo competitors affected by acute physical exercises

A heterogeneous group of 10 male and 15 female judo players are utilized in this study. The subjects complete a standardized maximal treadmill exercise test. Urine samples are collected at the pre- and postexercise stages. The urine steroids are measured using a gas chromatography-mass spectrometry instrument. In rest and after exercise, significantly higher testosterone and epitestosterone concentrations in males (p < 0.01) are found. The etiocholanolone-dehydroepiandrosterone (DHEA) ratio is significantly lower in males than females (p < 0.05). In both males and females, etiocholanolone concentration significantly decreases with the effect of exercise (p < 0.05). 11-OH etiocholanolone concentration also significantly decreases, but only in females (p < 0.05). Positive correlation is found between the changes of the etiocholanolone and epitestosterone concentration caused by exercise.     

Synthetic and natural polycationic polymer nanoparticles interact selectively with fluid-phase domains of DMPC lipid bilayers

Polycationic polymers are known to disrupt lipid bilayers. In this letter, we report the dependence of this disruption on the lipid structural phase. DMPC bilayers are exposed to two polycationic polymeric nanoparticles, PAMAM dendrimers and MSI-78. We find that regions of the bilayer that are in the gel phase are unaffected by the presence of polymers, whereas the liquid phase is disrupted.     

Some relevant parameters affecting the glass transition of supported ultra-thin polymer films

We have measured, the thickness dependence of the glass transition temperature T(g)( h), using ellipsometry at variable temperature, for poly(methyl-methacrylate) (PMMA) of various tacticity in confined geometry. We report that several factors significantly affect T(g)( h): i) polymer microstructure (stereoregularity of PMMA) related to local dynamics; ii) interfacial interactions; iii) conformation of the polymer chains. These results raise many fundamental questions on the origin of the thickness-dependent glass transition. Why and how do the interactions with the substrate significantly affect T(g)( h)? Does T(g)( h) depend on the modifications of conformational parameters of the chains (their entropy)? What is the correlation between local dynamics and T(g)( h) in thin films? The aim of this paper is to summarise these open questions, which should stimulate further investigations in the thin polymer film scientific community.     

Spectroscopic Characterization of a [C−F−C]+ Fluoronium Ion in Solution

We report the first spectroscopic evidence for a [C?F?C]⁺ fluoronium ion in solution. Extensive NMR studies (¹⁹F, ¹H, ¹³C) characterize a symmetric cage‐like species in which fluorine exhibits substantial covalent bonding to each of the two carbon atoms involved in the three‐center interaction. Experimental NMR data comport well with calculated values to lend credence to the structural assignment. As the culminating experiment, a Saunders isotopic perturbation test confirmed the symmetric structure. Congruent with the trend in other types of onium ions, the calculated charge at fluorine moves in a more positive (less negative) direction from the neutral. It is this important trend that explains in part the extraordinary historical difficulty in making theoretical predictions of fluoronium ions come true in solution, and why it takes fluorine captured in a cage to produce, finally, a stable ion and complete the historical arc of the organic halonium ion story.     

Photon production at c.m. energies of 200 and 900 GeV

We present data on photon production in non single-diffractivep \(\bar p\) -collisions at c.m. energies of 200 and 900 GeV. Besides the general properties of photon production, i.e. pseudorapidity distribution and average multiplicity, we also investigate photon-charged two-particle pseudorapidity and multiplicity correlations. We find for the average number of photons in non single-diffractivep \(\bar p\) -collisions 22.2±1.4±2.0 at 200 GeV and 41.4±2.1±3.5 at 900 GeV, where the first error is statistical and the second systematic. The analysis of photon-charged particle multiplicity correlations reveals strong positive correlations between the average number of photons and the number of simultaneously produced charged particles, as expected from FNAL and ISR studies and from our result at 546 GeV. We obtain for the correlation slope 0.95±0.08±0.11 at 200 GeV and 1.09±0.09±0.13 at 900 GeV (first error is statistical and the second systematic). The investigation of photon-charged two-particle pseudorapidity correlations shows that these correlations are of short range and compatible with the observed charged two-particle pseudorapidity correlations. These correlations and the results for the average number of photons as a function of the produced number of charged particles favour the conclusion that photon sources other than π⁰ s contribute significantly to the observed photon yield in non single-diffractivep \(\bar p\) -collisions. For example, if all photons are assumed to come from π⁰ s and η mesons, a η/π⁰ ratio of about 20% is inferred.