Large decrease of fluctuations for supercooled water in hydrophobic nanoconfinement

Using Monte Carlo simulations, we study a coarse-grained model of a water layer confined in a fixed disordered matrix of hydrophobic nanoparticles at different particle concentrations c. For c=0, we find a first-order liquid-liquid phase transition (LLPT) ending in one critical point at low pressure P. For c>0, our simulations are consistent with a LLPT line ending in two critical points at low and high P. For c=25%, at high P and low temperature, we find a dramatic decrease of compressibility, thermal expansion coefficient, and specific heat. Surprisingly, the effect is present also for c as low as 2.4%. We conclude that even a small presence of hydrophobic nanoparticles can drastically suppress thermodynamic fluctuations, making the detection of the LLPT more difficult.     

Electron-transfer-mediated decay and interatomic Coulombic decay from the triply ionized states in argon dimers

We report the first observation of electron-transfer-mediated decay (ETMD) and interatomic Coulombic decay (ICD) from the triply charged states with an inner-valence vacancy, using the Ar dimer as an example. These ETMD and ICD processes, which lead to fragmentation of Ar(3+)-Ar into Ar(2+)-Ar(2+) and Ar(3+)-Ar+, respectively, are unambiguously identified by electron-ion-ion coincidence spectroscopy in which the kinetic energy of the ETMD or ICD electron and the kinetic energy release between the two fragment ions are measured in coincidence.     

Simply generated trees,B‐series and Wigner processes

We consider simply generated trees, like rooted plane trees, and consider the problem of computing generating functions of so‐called bare functionals, like the tree factorial, using B‐series from Butcher's theory. We exhibit a special class of functionals from probability theory: the associated generating functions can be seen as limiting traces of product of semi‐circular elements. © 2004 Wiley Periodicals, Inc. Random Struct. Alg. 2004     

Investigation of superconductivity in the Y−Ba−Cu−O system

Summary Experiments are performed to determine the effect of polyphasicity on YBa₂Cu₃O_7−x critical temperature. Results are obtained which show thatT _c fluctuations up to 2 K exist, depending on phase mixing.     

Bidimensional antiferromagnetism in layered NH4FeF4

Summary The compound NH₄FeF₄, characterized by layers of (FeF₆)³⁻ octahedra alternating with NH ₄ ⁺ layers, has been investigated by means of M?ssbauer spectroscopy. Experimental data, which evidentiate an antiferromagnetic order, are compared with the molecular-field model for anisotropic media. Magnetization is found orthogonal to the octahedra layers and the octahedra axes are found to be tilted by 17° with respect to the magnetization direction.

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Riassunto Il composto NH₄FeF₄, caratterizzato da strati di ottaedri (FeF₆)³⁻ alternati con strati NH ₄ ⁺ , è stato studiato con la spettroscopia M?ssbauer. I dati sperimentali, che evidenziano un ordine antiferromagnetico, sono stati interpretati col modello del campo molecolare per mezzi anisotropi. Si è trovato che la magnetizzazione è ortogonale agli strati ottaedrici e che gli assi ottaedrici sono inclinati di 17° rispetto alla direzione di magnetizzazione.

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Резюме С помощью м?ссбауэровской спектроскопии исследуется соединение NH₄FeF₄, характеризующееся слоями (FeF₆)³⁻, которые чередуются с NH ₄ ⁺ слоями. Экспериментальные данные, которые подтверждают антиферромагнитную упоряденность, сравниваются с моделью молекулярного поля для анизотропной среды. Обнаружено, что намагниченность ортогональна октаэдрическим слоям, а октаэдрические оси наклонены под углом 17° к направлению намагниченности.

     

广义Bethe树上奇偶马尔可夫链场上的若干极限性质

通过构造两个非负鞅证明了一个强极限定理,然后把它应用到本文所定义的广义Bethe树上的奇偶马尔可夫链场上,从而获得了此马氏链场上的一类强极限定理.     

Experimental and numerical study of the relaxation behavior of facial soft tissue

Challenges in computational simulation of the mechanical behavior of soft tissues and organs for clinical applications are related to the reliability of the models with respect to the anatomy, the mechanical interactions between different tissues, and the non linear (time dependent) force deformation characteristics of soft biological materials. In this paper a 3D finite element model of the face and neck, which has applications in surgical devices optimization and surgery planning, is presented. Bones, muscles, skin, fat, and superficial muscoloaponeurotic system (SMAS) were reconstructed from magnetic resonance images and their shape, constraints and interactions have been modeled according to anatomical, plastic and reconstructive surgery literature. Non linear time dependent constitutive equations are implemented in the numerical model, based on the Rubin-Bodner model. For the present calculations a simplified hyperelastic formulation has been used. The corresponding model parameters were selected according to previous work with mechanical measurements ex vivo on facial soft tissue. For determination of model parameters, in particular the ones corresponding to the time dependent behavior, an instrument for measuring the relaxation behavior of the face tissue in vivo was developed. The experimental set-up is described and results are presented for tests performed on different locations of the face (jaw, mid-face, parotid regions) and neck. The measured “long term” reaction force of the facial soft tissue is compared to numerical results. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Probing the chemical reactivity of free titanium clusters by x-ray absorption spectroscopy

Synchrotron radiation-based experimental techniques are largely employed for the characterization of the reactivity of finite size systems; in particular, x-ray absorption spectroscopy (XAS) is a suitable tool to shed light on the local electronic structure and chemical status of atoms in nano-objects, as it is very sensitive to the local bonding environment of the probed site. In supported clusters intrinsic properties and reactivity are largely distorted and obscured by the changes imposed by the growth procedure and by the influence of the substrate, so the attainability of experiments on free clusters reacting with species in the gas phase is a primary goal in the development of cluster science. In this paper we report a proof of principle of the applicability of gas phase XAS technique to titanium and titanium oxide, hydride and hydrate systems. Experiments are performed by coupling a pulsed microplasma cluster source (PMCS) with a third generation synchrotron light source, and measuring the intensity of the electron yield coming from the interaction of VUV photons with the clusters seeded in a supersonic beam.