Structure of sticky-hard-sphere random aggregates: The viewpoint of contact coordination and tetrahedra

International audienceWe study more than 10 4 random aggregates of 10 6 monodisperse sticky hard spheres each, generated by various static algorithms. Their packing fraction varies from 0.370 up to 0.593. These aggregates are shown to be based on two types of disordered structures: random regular polytetrahedra and random aggregates, the former giving rise to δ peaks on pair distribution functions. Distortion of structural (Delaunay) tetrahedra is studied by two parameters, which show some similarities and some differences in terms of overall tendencies. Isotropy of aggregates is characterized by the nematic order parameter. The overall structure is then studied by distinguishing spheres in function of their contact coordination number (CCN). Distributions of average CCN around spheres of a given CCN value show trends that depend on packing fraction and building algorithms. The radial dependence of the average CCN turns out to be dependent upon the CCN of the central sphere and shows discontinuities that resemble those of the pair distribution function. Moreover, it is shown that structural details appear when the CCN is used as pseudochemical parameter, such as various angular distribution of bond angles, partial pair distribution functions, Ashcroft-Langreth and Bhatia-Thornton partial structure factors. These allow distinguishing aggregates with the same values of packing fraction or average tetrahedral distortion or even similar global pair distribution function, indicative of the great interest of paying attention to contact coordination numbers to study more precisely the structure of random aggregates

Serological profiles in nursery piglets colonized with Staphylococcus aureus

At present, the immune response of pigs in relation to Staphylococcus aureus carriage is poorly understood. This study aimed at investigating the dynamics of the anti-staphylococcal humoral immune response in methicillin-susceptible S. aureus (MSSA)-positive piglets and at assessing the effect of the experimental introduction of a methicillin-resistant S. aureus (MRSA) Sequence Type (ST) 398 strain. Therefore, serum samples were collected at different times from 31 weaned piglets originating from four different sows. Twenty-four out of the 31 piglets were challenged with MRSA ST398. The serum samples were analysed for IgG antibodies to 39 S. aureus antigens, using a multiplex bead-based assay (xMAP technology, Luminex Corporation). Though antibody responses showed broad inter-individual variability, serological results appeared to be clustered by litter of origin. For most antigens, an age-related response was observed with an apparent increase in antibody titres directed against staphylococcal microbial surface components recognizing adhesive matrix molecules (MSCRAMMs), which have been shown to play a role in S. aureus colonization. In most animals, antibody titres directed against staphylococcal toxins or immune-modulating proteins decreased with age, possibly reflecting absence of bacterial invasion. The introduction of MRSA ST398 did not elicit a significant humoral immune reaction. This study describes, for the first time, the humoral immune response in weaned pigs colonized with S. aureus

Classical Limit of Demagnetization in a Field Gradient

We calculate the rate of decrease of the expectation value of the transverse component of spin for spin-1/2 particles in a magnetic field with a spatial gradient, to determine the conditions under which a previous classical description is valid. A density matrix treatment is required for two reasons. The first arises because the particles initially are not in a pure state due to thermal motion. The second reason is that each particle interacts with the magnetic field and the other particles, with the latter taken to be via a 2-body central force. The equations for the 1-body Wigner distribution functions are written in a general manner, and the places where quantum mechanical effects can play a role are identified. One that may not have been considered previously concerns the momentum associated with the magnetic field gradient, which is proportional to the time integral of the gradient. Its relative magnitude compared with the important momenta in the problem is a significant parameter, and if their ratio is not small some non-classical effects contribute to the solution. Assuming the field gradient is sufficiently small, and a number of other inequalities are satisfied involving the mean wavelength, range of the force, and the mean separation between particles, we solve the integro- partial differential equations for the Wigner functions to second order in the strength of the gradient. When the same reasoning is applied to a different problem with no field gradient, but having instead a gradient to the z-component of polarization, the connection with the diffusion coefficient is established, and we find agreement with the classical result for the rate of decrease of the transverse component of magnetization.Comment: 22 pages, no figure

La formulación magistral: adquisición de compètencias mediante ABP y estrategias no presenciales

[cast] La formulación magistral, una de las actividades profesionales más representativas del farmacéutico, consiste en la elaboración, de acuerdo con una prescripción médica, de un medicamento personalizado, adaptado a un paciente concreto, en un compromiso profesional de solucionar un problema de salud específico. La amplia oferta de medicamentos industriales ha reducido considerablemente esta actividad, que a pesar de todo, debe considerarse una herramienta de futuro en sintonía con la tendencia personalizadora actual de la medicina y las necesidades del paciente. Los conocimientos y competencias requeridas para dicha actividad profesional se introducen actualmente en la carrera de Farmacia mediante una asignatura optativa. En el presente trabajo se presenta el planteamiento metodológico diseñado por el Grupo de Innovación Docente de Tecnología Farmacéutica (GIDTF) y el grupo e-Galenica, ambos de la Universidad de Barcelona, para esta asignatura. Dicha metodología esta basada en el Aprendizaje Basado en Problemas (ABP) incluyendo tutorías y prácticas de campo, apoyada en estrategias no presenciales como foro de debate, recursos on-line, cuestionarios y tareas de autoevaluación a través de la plataforma Moodle del Campus Virtual de la UB. Se evalúan asimismo los resultados académicos y las respuestas de los estudiantes a las encuestas realizadas en relación al sistema de impartición de la asignatura. [eng] The pharmaceutical compounding, one of the most representative professional activities of pharmacists, involves the preparation of an individualized medicine tailored to a specific patient in a professional commitment to solve a specific health problem, according to a prescription. The wide range of industrial medicine has significantly reduced this activity, which nevertheless should be considered a tool of the future in line with the current trend of personalizing medicine and patient needs. The knowledge and competences required for this professional activity are introduced to the students of Pharmacy through an optional subject. In this paper we present the ethodological approach developed for this subject by the Teaching Innovation Group of pharmaceutical Technology (GIDTF) and e-Galenica group, both from the University of Barcelona. This methodology is based on Problem-Based Learning (PBL) including tutorials and practices in other centres, supported by out of class strategies as discussion forum, online resources, self-assessment questionnaires and work through the platform Moodle of Virtual Campus UB. The academic performance and student responses to surveys in relation to the didactic methodology are also assessed

Persistence with Partial Survival

We introduce a parameter $p$, called partial survival, in the persistence of stochastic processes and show that for smooth processes the persistence exponent $\theta(p)$ changes continuously with $p$, $\theta(0)$ being the usual persistence exponent. We compute $\theta(p)$ exactly for a one-dimensional deterministic coarsening model, and approximately for the diffusion equation. Finally we develop an exact, systematic series expansion for $\theta(p)$, in powers of $\epsilon=1-p$, for a general Gaussian process with finite density of zero crossings.Comment: 5 pages, 2 figures, references added, to appear in Phys.Rev.Let

Radiation Hardness of Perovskite Solar Cells Based on Aluminum‐Doped Zinc Oxide Electrode Under Proton Irradiation

Due to their high specific power and potential to save both weight and stow volume, perovskite solar cells have gained increasing interest to be used for space applications. However, before they can be deployed into space, their resistance to ionizing radiations such as high‐energy protons must be demonstrated. In this report, we investigate the effect of 150 keV protons on the performance of perovskite solar cells based on aluminium‐doped zinc oxide (AZO) transparent conducting oxide (TCO). Record power conversion efficiency of 15% and 13.6% were obtained for cells based on AZO under AM1.5G and AM0 illumination, respectively. We demonstrate that perovskite solar cells can withstand proton irradiation up to 1013 protons.cm−2 without significant loss in efficiency. At this irradiation dose, Si or GaAs solar cells would be completely or severely degraded when exposed to 150 keV protons. From 1014 protons.cm−2, a decrease in short‐circuit current of the perovskite cells is observed, which is consistent with interfacial degradation due to deterioration of the Spiro‐OMeTAD HTL during proton irradiation. Using a combination of non‐destructive characterization techniques, results suggest that the structural and optical properties of perovskite remain intact up to high fluence levels. Although shallow trap states are induced by proton irradiation in perovskite bulk at low fluence levels, they can release charges efficiently and are not detrimental to the cell's performance. This work highlights the potential of perovskite solar cells based on AZO TCO to be used for space applications and give a deeper understanding of interfacial degradation due to proton irradiation

Utilitat de la determinació del DNA del virus de l'hepatitis B en serum per hibridació molecular

Mediante una técnica de hibridación molecular, utilizando como sonda DNA-VHB purificado de un plasmido recombinante, se ha examinado la presencia de DNA-VHB en el suero de 82 portadores crónicos de HBsAg(RIA) sin evidenciashade infección Delta y en 80 sujetos HBsAg negativos (40 donantes de Sangre y 40 con hepatitis crónica o cirrosis no alcohólica). Se detectó DNA-VHB en cantidades variables en los 62 portadores crónicos(57 HBeAg positivo y 5 antiHBe positivo) con transaminasas elevadas, lesiones de hepatitis crónica y presencia de HBcAg en el tejido hepático (inmunoperoxidasa). En los 8 portadores con transaminasas elevadas, antiHBe positivo, lesiones de hepatitis crónica y HBcAg ausente del higado, se detectó DNA-VHB sérico en forma intermitente. El examen fue negativo en los 11 portadores crónicos con antiHBe positivo y transaminasas normales, así como en los sujetos HBsAg negativo. La presencia de DNA-VHB en el suero se asocia a la existencia de actividad inflamatoria y refleja la actividad replicativa del VHB con mayor fidelidad que la valoración del sistema antigénico HBe. Su examen constituye un elemento sumamente útil tanto para el estudio de la historia natural de la infección crónica por el VHB como para la valoración de agentes terapéuticos

Mechanical Stability and Decohesion of Sol-Fel Hybrid Coatings on Metallic Substrates

ABSTRACT The mechanical properties and adhesion behaviour of coatings based on organically modified silanes and synthesized using sol-gel technology were assessed using nano-indentation and microtensile testing, respectively. The relationship between the film structure and its mechanical response is examined. It is shown that the mechanical properties (hardness and Young's modulus) of the coatings is influenced dramatically by the organic substituent and the presence of an oxide layer thermally grown on the substrate material prior to deposition plays an important role on the film/substrate adhesion behaviour. Keywords: Sol-gel, cracking, debonding, adhesion. INTRODUCTION The adhesion and mechanical stability of thin film coatings on substrates is increasingly becoming a key issue in device reliability as technology driven products demand smaller, thinner and more complex functional coatings. It is well known that the reliability of metallurgical protective coatings and microelectronic circuits containing multilayered thin film structures is strongly influenced by their interfacial properties, namely strength, fracture resistance and adhesion. Hence, characterizing and understanding the cracking evolution, debonding behavior and adhesion performance of thin films subject to external applied stresses is crucial when planning such applications. By using micro-mechanical in-situ tensile experiments it is possible to detect and analyze the critical conditions for cracking and debonding of the thin film Sol-gel hybrid coatings, also known as "ormosils" (organically modified silicates), up to several hundred nanometers thick are used to modify the functional behavior of the inorganic component for plastic and metal surfaces to confer wear/abrasion resistance and corrosion protection, respectively Characterization of the film cracking and debonding is achieved primarily by in-situ optical microscopy and subsequent scanning electron microscopy (SEM). Load-partial unload data from nanoindentation of the coatings on copper were used to determine the film properties and to provide data for future fracture and adhesion analyses. Implications concerning the influence of the thermal oxide layer on the interfacial adhesion behavior of the sol-gel coatings are discussed. EXPERIMENTAL Sol-gel coating solutions were prepared by adding a 0.01 M solution of HNO 3 to a mixture of the inorganic constituent tetraethylorthosilicate (TEOS) and the organic constituent glycidoxypropyltrimethoxysilane (GTMS) in ethanol. The solutions prepared were: (i) 100% TEO