Numerical Studies on the Seismic Retrofit of Bridges Using Shape Memory Alloys

Recent earthquakes have highlighted the seismic vulnerability of bridges due to excessive movements at the joints (in simply supported deck bridges) or concentration of seismic forces in a few piers (in multi-span continuous deck bridges). Steel-based seismic restrainers and viscous shock transmitters are used to limit the joint openings in simply supported deck bridges or to redistribute the seismic force among all piers in continuous deck bridges, respectively. Currently used devices, however, have some limitations such as large dimensions, no energy dissipation, possible large residual displacements, bad control of the force transmitted to the substructure (steel restrainers), large dimensions, difficulty of installation in existing structures, need of maintenance, and sensitivity to the earthquake characteristics (viscous shock transmitters). Shape memory alloys (SMAs) with superelastic behavior show the potential to overcome the limitations involved in the current technologies. In this article, a multi-performance seismic device based on superelastic SMA wires is proposed for the seismic retrofit of multi-span simply supported and continuous deck bridges. The effectiveness of the SMA devices is assessed through a number of nonlinear time-history analyses on two bridge structures representative of existing Italian highway bridges. Results are compared to the seismic response of the bridges in the as-built configuration.     

A bacteriophage reagent for Salmonella: molecular studies on Felix 01

Felix 01 (F01) is a bacteriophage originally isolated by Felix and Callow which lyses almost all Salmonella strains and has been widely used as a diagnostic test for this genus. Molecular information about this phage is entirely lacking. In the present study, the DNA of the phage was found to be a double-stranded linear molecule of about 80 kb. 11.5 kb has been sequenced and in this region A + T content is 60%. There are relatively few restriction endonuclease cleavage sites in the native genome and clones show this is due to their absence rather than modification. A restriction map of the genome has been constructed. The ends of the molecule cannot be ligated although they contain 5' phosphates. At least 60% of the genome must encode proteins. In the sequenced portion, many open reading frames exist and these are tightly packed together. These have been examined for homology to published proteins but only 1 to 17 shows similarity to known proteins. F01 is therefore the prototype of a new phage family. On the basis of restriction sites, codon usage and the distribution of nonsense codons in the unused reading frames, a strong case can be made for natural selection that reacts to mRNA structure and function.     

Biomimetic synthesis and patterning of silver nanoparticles

The creation of nanoscale materials for advanced structures has led to a growing interest in the area of biomineralization. Numerous microorganisms are capable of synthesizing inorganic-based structures. For example, diatoms use amorphous silica as a structural material, bacteria synthesize magnetite (Fe3O4) particles and form silver nanoparticles, and yeast cells synthesize cadmium sulphide nanoparticles. The process of biomineralization and assembly of nanostructured inorganic components into hierarchical structures has led to the development of a variety of approaches that mimic the recognition and nucleation capabilities found in biomolecules for inorganic material synthesis. In this report, we describe the in vitro biosynthesis of silver nanoparticles using silver-binding peptides identified from a combinatorial phage display peptide library.     

Full geometry dependence of index contrast in photorefractive polymer composites

Detailed analysis of the relationship between the experimental geometry and the holographic contrast in photorefractive polymers is important for applications, such as angle multiplexing in holographic data storage. In this paper the field dependent photogeneration efficiency is introduced into the complete reorientational model to provide a full account of the electric field and geometrical dependence of the index contrast. The interaction of a local grating and the photorefractive grating is also considered. A simplification for acute angles between writing beams is described. Experimental verification by use of four-wave mixing and transmission ellipsometry reveals an excellent agreement between theory and measurement.     

The beginnings of vitreous materials in the Near East and Egypt

In the Near East and Egypt, vitreous materials in the form of glazed stones and faience were first produced from about the 4th millennium B.C. Subsequently, the period around 1500 BC saw major developments in the range of vitreous materials with the production of glass vessels and glazed clay objects and an extension in the range of colorants used. This paper first describes how the examination of artifacts has been used to reconstruct the processes involved in the production of these different vitreous materials. This information is then used to try to understand how the new technologies were discovered and why they were adopted.     

Textual case-based reasoning for spam filtering: a comparison of feature-based and feature-free approaches

Spam filtering is a text classification task to which Case-Based Reasoning (CBR) has been successfully applied. We describe the ECUE system, which classifies emails using a feature-based form of textual CBR. Then, we describe an alternative way to compute the distances between cases in a feature-free fashion, using a distance measure based on text compression. This distance measure has the advantages of having no set-up costs and being resilient to concept drift. We report an empirical comparison, which shows the feature-free approach to be more accurate than the feature-based system. These results are fairly robust over different compression algorithms in that we find that the accuracy when using a Lempel-Ziv compressor (GZip) is approximately the same as when using a statistical compressor (PPM). We note, however, that the feature-free systems take much longer to classify emails than the feature-based system. Improvements in the classification time of both kinds of systems can be obtained by applying case base editing algorithms, which aim to remove noisy and redundant cases from a case base while maintaining, or even improving, generalisation accuracy. We report empirical results using the Competence-Based Editing (CBE) technique. We show that CBE removes more cases when we use the distance measure based on text compression (without significant changes in generalisation accuracy) than it does when we use the feature-based approach.     

Awareness of faces is modulated by their emotional meaning.

A central question in perception is how stimuli are selected for access to awareness. This study investigated the impact of emotional meaning on detection of faces using the attention blink paradigm. Experiment 1 showed that fearful faces were detected more frequently than neutral faces, and Experiment 2 revealed preferential detection of fearful faces compared with happy faces. To rule out image artifacts as a cause for these results, Experiment 3 manipulated the emotional meaning of neutral faces through fear conditioning and showed a selective increase in detection of conditioned faces. These results extend previous reports of preferential detection of emotional words or schematic objects and suggest that fear conditioning can modulate detection of formerly neutral stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Personality traits, perceived risk, and risk-reduction behaviors: A further study of smoking and radon.

Personality traits and risk perceptions were examined as predictors of changes in smoking behavior. Participants (N = 697) were part of a randomized controlled trial of interventions to reduce exposure to the combined hazard of radon and cigarette smoke. Participants with higher perceived risk at baseline for the combination of smoking and radon were more likely to have a more restrictive household smoking ban in place at 12-month follow-up (p p p     

Decision making and set shifting impairments are associated with distinct symptom dimensions in obsessive-compulsive disorder.

Obsessive- compulsive disorder (OCD) is clinically heterogeneous. The authors examined how specific OCD symptom dimensions were related to neuropsychological functions using multiple regression analyses. A total of 39 OCD patients and 40 controls completed the Iowa Gambling Task (IGT; A. Bechara, A. R. Damasio, H. Damasio, & S. W. Anderson, 1994), which is a test of decision making, and the Wisconsin Card Sorting Test (R. K. Heaton, 1981), which is a test of set shifting. OCD patients and controls showed comparable decision making. However, patients with prominent hoarding symptoms showed impaired decision making on the IGT as well as reduced skin conductance responses. OCD patients had poorer set shifting abilities than controls, and symmetry/ordering symptoms were negatively associated with set shifting. These results help explain previous inconsistent findings in neuropsychological research in OCD and support recent neuroimaging data showing dissociable neural mechanisms involved in mediating the different OCD symptom dimensions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Characterizing nicotine withdrawal in pregnant cigarette smokers.

Maternal smoking is a leading preventable cause of poor pregnancy outcomes and infant morbidity and mortality. Whereas pregnancy has been thought of as a "window of opportunity" when women are more motivated to change health behaviors such as smoking, only 20% of pregnant women quit smoking upon learning they are pregnant and remain abstinent at the end of the pregnancy. Greater understanding of possible obstacles to smoking during pregnancy, such as nicotine withdrawal, is needed. The symptoms of nicotine withdrawal have been well characterized in nonpregnant smokers, but there has been only 1 report conducted during pregnancy, and that was a retrospective study. The aim of the present study was to characterize nicotine withdrawal and craving in pregnant cigarette smokers. These data were collected as part of prospective clinical trials assessing the efficacy of voucher-based incentives to promote abstinence from cigarette smoking during pregnancy and postpartum. The authors examined results from the Minnesota Nicotine Withdrawal Scale (J. R. Hughes & D. K. Hatsukami, 1998) in 27 abstainers (reported no or very low levels of smoking, which was confirmed biochemically) and 21 smokers (smoked at >80% of their baseline smoking level) during the first 5 days of a cessation attempt. Abstainers reported more impatience, anger, and difficulty concentrating than did smokers. The results also suggest that pregnant smokers generally may have elevated baseline levels of withdrawal, which need to be considered in the design and analysis of future studies. (PsycINFO Database Record (c) 2010 APA, all rights reserved)