Diffusion and Trapping on a one-dimensional lattice

The properties of a particle diffusing on a one-dimensional lattice where at each site a random barrier and a random trap act simultaneously on the particle are investigated by numerical and analytical techniques. The combined effect of disorder and traps yields a decreasing survival probability with broad distribution (log-normal). Exact enumerations, effective-medium approximation and spectral analysis are employed. This one-dimensional model shows rather rich behaviours which were previously believed to exist only in higher dimensionality. The possibility of a trapping-dominated super universal class is suggested.Comment: 20 pages, Revtex 3.0, 13 figures in compressed format using uufiles command, to appear in Phys. Rev. E, for an hard copy or problems e-mail to: [email protected]

Correlation of vulnerability and damage between artistic assets and structural elements: The DataBAES archive for the conservation planning of CH masonry buildings in seismic areas

Historical buildings in seismic hazard-prone regions need specific measures in safety protection, largely due to the presence of artistic assets and/or decorations, both movable (e.g., statues, pinnacles, etc.) and unmovable (e.g., frescoes, valuable plasters or wall paintings, mosaics, and stuccoes). A correlation of damage between structural systems and artworks is fundamental for defining limit states, which can identify the proper conditions for interventions. Nevertheless, several vulnerability aspects can be identified before a seismic event occurs, the study of which can provide the basic dataset for setting up preventive measures in conservation programs. In this paper, the vulnerability and damage conditions related to structural elements (SE) and unmovable artistic assets (AA) belonging to historical masonry buildings are analysed. Optimized survey forms for the onsite detection of either intrinsic (e.g., compositional) defects or deterioration phenomena for both materials and structure are proposed, and results are provided in a web data system (called DataBAES). This enables us to compare the current levels of vulnerability and damage of AA and SE on a scale of five increasing grades. This procedure has been validated on a series of buildings struck by earthquakes in Italy and can be used for correlations of the seismic behaviour of SE and AA in predictive analyses

Can Polarity-Inverted Surfactants Self-Assemble in Nonpolar Solvents

We investigate the self-assembly process of a surfactant with inverted polarity in water and cyclohexane using both all-atom and coarse grained hybrid particle-field molecular dynamics simulations. Unlike conventional surfactants, the molecule under study, proposed in a recent experiment, is formed by a rigid and compact hydrophobic adamantane moiety, and a long and floppy triethylene glycol tail. In water, we report the formation of stable inverted micelles with the adamantane heads grouping together into a hydrophobic core, and the tails forming hydrogen bonds with water. By contrast, microsecond simulations do not provide evidence of stable micelle formation in cyclohexane. Validating the computational results by comparison with experimental diffusion constant and small-angle X-ray scattering intensity, we show that at laboratory thermodynamic conditions the mixture resides in the supercritical region of the phase diagram, where aggregated and free surfactant states co-exist in solution. Our simulations also provide indications about how to escape this region, to produce thermodynamically stable micellar aggregates.Comment: 14 pages, 10 Figures, accepted for publication (2020

Effects of patch size and number within a simple model of patchy colloids

We report on a computer simulation and integral equation study of a simple model of patchy spheres, each of whose surfaces is decorated with two opposite attractive caps, as a function of the fraction $\chi$ of covered attractive surface. The simple model explored --- the two-patch Kern-Frenkel model --- interpolates between a square-well and a hard-sphere potential on changing the coverage $\chi$. We show that integral equation theory provides quantitative predictions in the entire explored region of temperatures and densities from the square-well limit $\chi = 1.0$ down to $\chi \approx 0.6$. For smaller $\chi$, good numerical convergence of the equations is achieved only at temperatures larger than the gas-liquid critical point, where however integral equation theory provides a complete description of the angular dependence. These results are contrasted with those for the one-patch case. We investigate the remaining region of coverage via numerical simulation and show how the gas-liquid critical point moves to smaller densities and temperatures on decreasing $\chi$. Below $\chi \approx 0.3$, crystallization prevents the possibility of observing the evolution of the line of critical points, providing the angular analog of the disappearance of the liquid as an equilibrium phase on decreasing the range for spherical potentials. Finally, we show that the stable ordered phase evolves on decreasing $\chi$ from a three-dimensional crystal of interconnected planes to a two-dimensional independent-planes structure to a one-dimensional fluid of chains when the one-bond-per-patch limit is eventually reached.Comment: 26 pages, 11 figures, J. Chem. Phys. in pres

Effect of Polydispersity and Anisotropy in Colloidal and Protein Solutions: an Integral Equation Approach

Application of integral equation theory to complex fluids is reviewed, with particular emphasis to the effects of polydispersity and anisotropy on their structural and thermodynamic properties. Both analytical and numerical solutions of integral equations are discussed within the context of a set of minimal potential models that have been widely used in the literature. While other popular theoretical tools, such as numerical simulations and density functional theory, are superior for quantitative and accurate predictions, we argue that integral equation theory still provides, as in simple fluids, an invaluable technique that is able to capture the main essential features of a complex system, at a much lower computational cost. In addition, it can provide a detailed description of the angular dependence in arbitrary frame, unlike numerical simulations where this information is frequently hampered by insufficient statistics. Applications to colloidal mixtures, globular proteins and patchy colloids are discussed, within a unified framework.Comment: 17 pages, 7 figures, to appear in Interdiscip. Sci. Comput. Life Sci. (2011), special issue dedicated to Prof. Lesser Blu

Prevalence of Mycobacterium avium subsp. paratuberculosis in milk and dairy cattle in Southern Italy; preliminary results

Paratuberculosis affects all ruminants worldwide. Mycobacterium avium subsp. paratuberculosis could have a role in human diseases like Crohn\u2019s. Some extra EU countries request importation of MAP-free products. Italy has not yet actualized a control program and the diffusion of the infection is still unknown in Southern Italy. The aim of this study was to evaluate the prevalence of the infection in five regions of Southern Italy. Bulk tank milk and in-line milk filters were sampled in 780 dairy cattle herds and respectively analyzed by ELISA and real time PCR. One hundred and fifty-five out of 780 herds (19.9%) were found positive by ELISA and/or real time PCR. Individual milk samples were then collected from all the producing animals of positive herds and from a selection of negative herds. The estimated prevalence varies from region to region between 2.8% and 5.5%. Our results indicate that the disease is widespread in the five regions. The observed prevalence could be underestimated

Survey on antimicrobial residues in raw milk and antimicrobial use in dairy farms in the Emilia-Romagna Region, Italy

This survey investigated the antimicrobials most commonly used in dairy herds and t antimicrobial residues most frequently detected in milk to evaluate the suitability of rapid screening tests to determine antimicrobial residues in milk. The investigation was carried out in 45 dairy herds consulting the farm administration records and in a national dairy industry collecting milk from almost all the dairy farms studied. Data were recorded on: i) treatments with drugs containing antimicrobials during the 12 months prior to the visit; ii) antimicrobial active substances present in the drugs; iii) data from routine controls to detect antimicrobial residues (52,771 samples). The antimicrobial classes most commonly used were penicillins, cephalosporins, fluoroquinolones, macrolides, sulphonamides, tetracyclines, aminoglycosides and lyncosamides; the most frequently used antimicrobial not belonging to any of the previous groups was riphaximin. Sixty-four samples collected from milk trucks yielded antimicrobial residues exceeding the detection limit of the screening test used: sulphonamide residues were the most prevalent (3.4%), followed by tetracycline (0.3%) and penicillins and cephalosporins (0.03%). The antimicrobial classes most commonly used on dairy farms are the same as the residues most frequently detected in milk. The association of several commercially available rapid test kits proved satisfactory for determination of the veterinary antimicrobial drugs most used on dairy farms but at least five kits are required. Therefore knowledge of the most frequently used veterinary drugs and periodic monitoring are required for the dairy industry to develop a targeted and effective control pla

Chlorophyll-proteins of the photosystem II antenna system.

The chlorophyll-protein complexes of purified maize photosystem II membranes were separated by a new mild gel electrophoresis system under conditions which maintained all of the major chlorophyll a/b-protein complex (LHCII) in the oligomeric form. This enabled the resolution of three chlorophyll a/b-proteins in the 26-31-kDa region which are normally obscured by monomeric LHCII. All chlorophyll a/b-proteins had unique polypeptide compositions and characteristic spectral properties. One of them (CP26) has not previously been described, and another (CP24) appeared to be identical to the connecting antenna of photosystem I (LHCI-680). Both CP24 and CP29 from maize had at least one epitope in common with the light-harvesting antennae of photosystem I, as shown by cross-reactivity with a monoclonal antibody raised against LHCI from barley thylakoids. A complex designated Chla.P2, which was capable of electron transport from diphenylcarbazide to 2,6-dichlorophenolindophenol, was isolated by nondenaturing gel electrophoresis. It lacked CP43, which therefore can be excluded as an essential component of the photosystem II reaction center core. Fractionation of octyl glucoside-solubilized photosystem II membranes in the presence and absence of Mg2+ enabled the isolation of the Chla . P2 complex and revealed the existence of a light-harvesting complex consisting of CP29, CP26, and CP24. This complex and the major light-harvesting system (LHCII) are postulated to transfer excitation energy independently to the photosystem II reaction center via CP43