Structural models of critical regions in old-type r.c. frames with smooth rebars

Structural assessment of existing reinforced concrete constructions under gravity loads and seismic actions has a high social and economical impact; actually in many European countries, most of the buildings dates back to 1960s and 1970s and cannot ensure satisfactory seismic response, since many areas have been later classified as seismic or since design has been carried out according to obsolete codes. These structures are generally reinforced with smooth bars that exhibit poor bond and need specific anchoring end details. In the present paper, some key aspects of structural models of smooth reinforcement for old-type r.c. frame analysis are reported. Results of experimental tests on smooth reinforcement and circular hook anchoring devices are also used to discuss some aspects of behavioural models of beam to column critical regions.     

Disposal of domestic sludge and sludge ash on volcanic soils

Column leaching experiments were conducted to test the ability of Chilean volcanic soils in retaining the mineral constituents and metals in sewage sludge and sludge ash that were incorporated into the soils. Small or negligible amounts of the total content of Pb, Fe, Cr, Mn, Cd, and Zn (0 to <2%), and more significant amounts of mineral constituents such as Na (7-9%), Ca (7-13%), PO4 (4-10%), and SO4 (39-46%) in the sludge and sludge ash were readily soluble. When they were incorporated on the surface layer of the soils and leached with 12 pore volumes of water over a 3 month period of time, less than 0.1% of the total amount of heavy metals and PO4 in the sludge and sludge ash were collected in the drainage water. Cation exchange selectivity, specific anion adsorption and solubility are the processes that cause the reduction of leaching. The volcanic soils were capable of retaining the mineral constituents, P, and metals in applied sewage sludge and sludge ash and gradually released them as nutrients for plant growth.     

The anti-symmetry principle for quasi-static crack propagation in Mode III

In this note we study a basic propagation criterion for quasi-static crack evolution in Mode III. Using classical techniques of complex analysis, the assumption of stable growth is expressed in terms of the parameters defining the elastic field around the tip. We explore the consequences of the local condition obtained and analyse its role as a crack propagation law. In particular, we herein extend to bounded domains a number of results previously obtained for the whole plane.     

The ideal reporting interval for an epidemic to objectively interpret the epidemiological time course

The reporting interval of infectious diseases is often determined as a time unit in the calendar regardless of the epidemiological characteristics of the disease. No guidelines have been proposed to choose the reporting interval of infectious diseases. The present study aims at translating coarsely reported epidemic data into the reproduction number and clarifying the ideal reporting interval to offer detailed insights into the time course of an epidemic. We briefly revisit the dispersibility ratio, i.e. ratio of cases in successive reporting intervals, proposed by Clare Oswald Stallybrass, detecting technical flaws in the historical studies. We derive a corrected expression for this quantity and propose simple algorithms to estimate the effective reproduction number as a function of time, adjusting the reporting interval to the generation time of a disease and demonstrating a clear relationship among the generation-time distribution, reporting interval and growth rate of an epidemic. Our exercise suggests that an ideal reporting interval is the mean generation time, so that the ratio of cases in successive intervals can yield the reproduction number. When it is impractical to report observations every mean generation time, we also present an alternative method that enables us to obtain straightforward estimates of the reproduction number for any reporting interval that suits the practical purpose of infection control.     

A microfluidic platform using molecular beacon-based temperature calibration for thermal dehybridization of surface-bound DNA

This work presents a simple microfluidic device with an integrated thin-film heater for studies of DNA hybridization kinetics and double-stranded DNA melting temperature measurements. The heating characteristics of the device were evaluated with a novel, noninvasive indirect technique using molecular beacons as temperature probes inside reaction chambers. This is the first microfluidic device in which thermal dehybridization of surface-bound oligonucleotides was performed for measurement of double-stranded DNA melting temperatures with +/- 1 degrees C precision. Surface modification and oligonucleotide immobilization were performed by continuously flowing reagents through the microchannels. The resulting reproducibility of oligonucleotide surface densities, at 9% RSD, was better than for the same modification chemistries on glass slides in unstirred reagent solutions (RSD=20%). Moreover, the surface density of immobilized DNA probe molecules could be varied controllably by changing the concentration of the reagent solution used for immobilization. Thus, excellent control of surface characteristics was made possible, something which is often difficult to achieve with larger devices. Solid-phase hybridization reactions, a fundamental aspect of microarray technologies often taking several hours in conventional systems, were reduced to minutes in this device. It was also possible to determine forward rate constants for hybridization, k. These varied from 820,000 to 72,000 M(-1) s(-1), decreasing as surface densities increased. Surface densities could therefore be optimized to obtain rapid hybridization using such an approach. Taken together, this combined microfluidic/small-volume heating approach represents a powerful tool for surface-based DNA analysis.     

Issues in the prevention of AIDS among Black and Hispanic men.

Ethnic minority men, particularly Blacks and Hispanics, make up a significant proportion of all AIDS cases in the United States, with these cases linked primarily to homosexual or bisexual behavior and intravenous (IV) drug use. Difficulties in developing successful prevention strategies include (a) limited data on the prevalence of AIDS risk behaviors among minorities, (b) limited information on successful community interventions for minority populations, and (c) problems in using social networks for AIDS prevention. Suggestions are made to include culturally appropriate information in developing communication messages and to consider culture-specific values, norms, attitudes, and expectations in designing community interventions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)