Micro- and macroscopic thermal expansion of stabilized aluminum titanate

The lattice expansion of aluminum titanate (AT) obtained by firing a mixture of alumina, rutile, strontium and calcium carbonate and silica was measured using neutron and laboratory X-ray diffraction. The microscopic data are compared with macroscopic measurement completed by dilatometry.A powder and a compact rod sample were compared to assess the influence of micro residual stresses locked into the solid structure at grain level, which could possibly be relieved upon grinding.Results show good correlation between neutron and X-ray diffraction techniques. They also show that a compact material behaves differently than a powder, contrary to what happens for other porous ceramics such as cordierite. The integrity factor model was used to rationalize the results and predict grain level stresses in all crystal directions and all phases (AT, Strontium aluminum silicate, alumina and residual glass). Calculation show that the AT c-axis is always under compression while all other crystal directions and phases are under tension. Those micro-stresses do not undermine the macroscopic mechanical properties of the material and confer to it its interesting properties like low thermal expansion and enhanced strain tolerance.     

A universal fluid cell for the imaging of biological specimens in the atomic force microscope

Recently, atomic force microscope (AFM) manufacturers have begun producing instruments specifically designed to image biological specimens. In most instances, they are integrated with an inverted optical microscope, which permits concurrent optical and AFM imaging. An important component of the set‐up is the imaging chamber, whose design determines the nature of the experiments that can be conducted. Many different imaging chamber designs are available, usually designed to optimize a single parameter, such as the dimensions of the substrate or the volume of fluid that can be used throughout the experiment. In this report, we present a universal fluid cell, which simultaneously optimizes all of the parameters that are important for the imaging of biological specimens in the AFM. This novel imaging chamber has been successfully tested using mammalian, plant, and microbial cells. Microsc. Res. Tech. 76:357–363, 2013. © 2013 Wiley Periodicals, Inc.     

Non-Coding RNAs in Muscle Dystrophies

ncRNAs are the most recently identified class of regulatory RNAs with vital functions in gene expression regulation and cell development. Among the variety of roles they play, their involvement in human diseases has opened new avenues of research towards the discovery and development of novel therapeutic approaches. Important data come from the field of hereditary muscle dystrophies, like Duchenne muscle dystrophy and Myotonic dystrophies, rare diseases affecting 1 in 7000–15,000 newborns and is characterized by severe to mild muscle weakness associated with cardiac involvement. Novel therapeutic approaches are now ongoing for these diseases, also based on splicing modulation. In this review we provide an overview about ncRNAs and their behavior in muscular dystrophy and explore their links with diagnosis, prognosis and treatments, highlighting the role of regulatory RNAs in these pathologies.     

Fitting genetic algorithms to distributed on-line evolution of network protocols

In this work, we introduce a framework for enabling the on-line evolution of network protocols. The proposed approach is based on the use of techniques and tools drawn from evolutionary computing research, and it enables embedding evolutionary features in the operation of network protocols. In this way, it becomes possible to build a system in which the operation of the network changes at run-time to adapt to the current conditions. As a case study, we apply the proposed framework to the evolution of forwarding schemes in intermittently connected wireless networks. Simulation results are reported to validate the ability of the proposed scheme to converge to the optimal operating point and to explore the various trade-offs deriving from its design and implementation.     

Changes of the main physical and technological properties of talc due to mechanical strain

A commercial talc was treated by planetary ball milling to evaluate the changes of the main physical and technological properties due to induced progressive mechanical stress.Firstly, a high orientation of talc platelets was obtained, secondly a progressive structural disorder of the talc and finally a re-aggregation of the particles during prolonged grinding was observed. Delamination during the initial and intermediate stages cannot be excluded.Mechanical grinding reduced the particles size and increased the specific surface area leading to enhanced absorption and cation exchange capacity during the initial and intermediate stages of grinding. The reduced lightness and brightness for prolonged grinding were attributed to the agglomeration of the particles. The mechanical treatment does not induce significant amorphization, thus preserving the main properties of talc even after prolonged grinding.     

First-Principles Calculation of the Third Virial Coefficient of Helium

Knowledge of the pair and three-body potential-energy surfaces of helium is now sufficient to allow calculation of the third density virial coefficient, C(T), with significantly smaller uncertainty than that of existing experimental data. In this work, we employ the best available pair and three-body potentials for helium and calculate C(T) with path-integral Monte Carlo (PIMC) calculations supplemented by semiclassical calculations. The values of C(T) presented extend from 24.5561 K to 10 000 K. In the important metrological range of temperatures near 273.16 K, our uncertainties are smaller than the best experimental results by approximately an order of magnitude, and the reduction in uncertainty at other temperatures is at least as great. For convenience in calculation of C(T) and its derivatives, a simple correlating equation is presented.     

Riparian Vegetation Mapping for Hydraulic Roughness Estimation Using Very High Resolution Remote Sensing Data Fusion

For detailed hydraulic modeling, accurate spatial information of riparian vegetation patterns needs to be derived in automatic fashion. We propose a supervised classification for heterogeneous riparian corridors with a low number of spectrally separate classes using data fusion of a Quickbird image and LIDAR data. The approach considers nine land cover classes including three woody riparian species, brush, cultivated areas, grassland, urban infrastructures, bare soil and water. The classical “stacked vector” approach is adopted for data fusion, while the nonparametric weighted feature-extraction method and the pixel-oriented maximum likelihood algorithm are used for feature-reduction and classification purposes, respectively. We test the approach over a 14-km stretch of the Sieve River (Tuscany Region, Italy). A one-dimensional river modeling is applied over the study reach comparing the results of a classification-derived hydraulic roughness map and a traditional ground-based approach. Despite the complex study reach, the classification method produced encouraging accuracies (OKS = 0.77) and represents a useful tool to delineate application domains of flow resistance models suited to different hydrodynamic patterns (e.g., stiff/flexible vegetation). Hydraulic modeling results showed that the remotely derived floodplain roughness parameterization captures the equivalent Manning coefficient over 20 test cross sections with uncertainty distributions described by low mean and standard deviation values.     

Nondestructive evaluation of the depth of surface-breaking cracks in concrete pipes

Surface-breaking cracks affect the material and structural properties of concrete pipes. Therefore, the nondestructive evaluation of the crack depth is important to assess the serviceability of these pipes, which are commonly used in underground infrastructure and trenchless installations (micro-tunneling). This paper presents theoretical, numerical and experimental results for the depth evaluation of surface-breaking cracks. The wall of a concrete pipe is represented as a plate in the numerical and the analytical studies. In the experiments, an ultrasonic piezoelectric transmitter is used as a source. The propagation of the ultrasonic pulse is analyzed using the wavelet transform. A newly proposed wavelet transmission coefficient (WTC) is measured using an equal spacing configuration for the crack depth evaluation in concrete pipes and concrete plates. The results from laboratory and in situ tests show good potential for the practical application of the WTC for the depth evaluation of surface-breaking cracks.     

Cyclic bond behaviour of plain bars. Part I: Experimental investigation

In recent years there has been wide use of non-linear dynamic analysis for the evaluation of existing structures in areas of high seismic risk. In the simulation of the cyclic behaviour of elements in reinforced concrete (RC) its bonding performance cannot be ignored. There are numerous numerical models developed in recent decades which can explicitly account for the slip between reinforcing bars and the surrounding concrete through the definition of the local hysteretic bond–slip relationship. As for plain bars, commonly used in reinforced concrete buildings before the 1970s, there are almost no references to hysteretic bond mechanisms.This paper describes the results of a series of monotonic and cyclic pull-out tests aimed at the assessment of the bond performances of plain round bars. Monotonic behaviour is characterized by a first ascending branch, up to the maximum bond strength; in this phase, as the slip increases, chemical–physical adhesion and micro-interlocking between the cement paste and the indentations of the bar surface progressively activate. During post-peak phase the only frictional contribute is present, gradually degrading towards a minimum value as the slip increases. The two parameters, maximum bond strength and minimum frictional bond, in spite of the high variability shown, seem to reflect well the literature indications about bond performances of plain bars. In cyclic field, where the only frictional mechanism is present, experimental results show a significant degradation of bond capacities. Hysteretic cycles show a singular shape, characterized by a reloading phase showing a slight reduction for slip values approaching zero and a subsequent increase in bond stress towards the maximum imposed slip. Bond stresses in cyclic field show a high variability, but it is generally possible to recognize a decreasing trend both with the number of cycles and with the maximum imposed slip.