Mechanical squeezing of an elastomeric nanochannel device: numerical simulations and ionic current characterization

Peculiar transport phenomena appear at nanoscale, since surface effects strongly affect the behaviour of fluids. Electrostatic and steric interactions, capillary forces and entropic effects play a key role in the behaviour of fluids and biomolecules. Since these effects strongly depend on the size of the nanofluidic system, a careful characterization of the fluidic environment is necessary. Moreover, the possibility to dynamically modulate the size of nanochannels is very appealing in the field of biomolecule manipulation. Recently, we have developed a lab-on-chip made of poly(dimethylsiloxane) (PDMS). This polymeric device is based on a tuneable nanochannel able to dynamically change its dimension in order to fit the application of interest. In fact, a mechanical compression applied on the top of the elastomeric device squeezes the nanochannel, reducing the channel cross section and allowing a dynamical optimization of the nanostructures. In this paper, this squeezing process is fully characterized both numerically and experimentally. This analysis provides information on the reduction of the nanochannel dimensions induced by compression as a function of the work of adhesion and of the stiffness of the materials composing the device. Moreover, calculations demonstrate the possibility to predict the change of the nanochannel size and shape induced by the compression. The possibility to dynamically tune the channel size opens up new opportunities in biomolecular sensing or sieving and in the study of new hydrodynamics effects.     

Fix-and-Relax-Coordination for a multi-period location–allocation problem under uncertainty

A multi-period discrete facility location problem is introduced for a risk neutral strategy with uncertainty in the costs and some of the requirements along the planning horizon. A compact 0–1 formulation for the Deterministic Equivalent Model of the problem under two alternative strategies for the location decisions is presented. Furthermore, a new algorithmic matheuristic, Fix-and-Relax-Coordination, is introduced. This solution scheme is based on a specialization of the Branch-and-Fix Coordination methodology, which exploits the Nonanticipativity Constraints and uses the Twin Node Family concept. The results of an extensive computational experience allow to compare the alternative modeling strategies and assess the effectiveness of the proposed approach versus the plain use of a state-of-the-art MIP solver.     

Applicability assessment of a real-time PCR assay for the specific detection of bovine,ovine and caprine material in feedstuffs

A TaqMan real-time polymerase chain reaction (PCR) method was developed for specific detection of bovine, ovine and caprine processed animal protein (PAP) in industrial feedstuffs. The method uses species-specific primers and probes targeting short mitochondrial D-loop sequences, and a positive amplification control based on 18S rRNA gene. The applicability of the real-time PCR protocol was assessed through analysis of 126 industrial feed samples that were manufactured to reproduce rendering processes of commercial feeds destined for farmed animals. The assay successfully classified samples as positive or negative according to the ruminant composition, enabling qualitative detection of banned material in feeds at levels as low as 0.1%. Although the method provides quantitative potential, results suggest that the real quantitative capability of the assay is limited by the existing variability in terms of composition and processing treatments of the feeds, which affect the amount and quality of amplifiable DNA.     

Revision of ochratoxin a production capacity by the main species of Aspergillus section Circumdati. Aspergillus steynii revealed as the main risk of OTA contamination

Ochratoxin A (OTA) is a highly toxigenic mycotoxin commonly present in a number of diverse agroproducts. Aspergillus Section Circumdati includes some of the most important OTA-producing species: Aspergillus ochraceus, Aspergillus elegans and the recently described Aspergillus steynii and Aspergillus westerdijkiae. In this work, OTA production by several strains of these four species from diverse origins and food matrices was examined. Identification of all the strains was carried out by specific PCR assays. The strains were cultivated in CYA solid medium and OTA was measured by HLPC. This study demonstrated for the first time the high capacity of A. steynii strains to produce OTA at higher levels than A. westerdijkiae,A. ochraceus and A. elegans strains showed low levels or no production at all. In conclusion, the results of this study suggest that the occurrence of A. steynii and A. westerdijkiae might represent the major potential risk for OTA contamination due to their high production and the diversity of commodities that these species may contaminate.     

Three-dimensional optical data storage through multi-photon confocal microscopy and imaging

Three dimensional optical data storage is one of the most promising tools to respond to the always growing demand for high data storage capacity. Here, we focused a femtosecond laser source by means of a confocal microscope onto different transparent recording media. The purpose of the study is to probe the capability of the system to independently address different data layers within the storage medium achieving thus three dimensional data storage. We demonstrated the possibility to write superposed independent layers of data due to either multiphoton excitation or to local optical breakdown and the performances observed in the different types of media used are compared.     

Mixed Messages about Mixed Tenure: Do Reviews Tell the Real Story?

Mixed tenure is the predominant development and regeneration strategy and is a key component of UK housing and urban policy. It is purported to provide wide-ranging social, environmental and economic benefits to residents. While there is a large literature on mixed tenure, policy makers are likely to rely on reviews and summaries of the evidence rather than primary studies. But can they rely on such reviews? Using systematic review methods this paper critically appraises recent reviews for the evidence that mixed tenure policies and strategies have achieved any of these expected benefits. Of the six UK reviews of primary studies, most drew on less than half the available primary studies, none provided a critical appraisal of individual studies and made no comment on conflicting evidence between and within studies. While the reviews gave indications of the deficiencies of the evidence base, rather than focus on the implications of these deficiencies, four of the six reviews emphasised the positive effects of tenure mix.     

Stress–strain relationship in axial compression for concrete using recycled saturated coarse aggregate

In this work the stress–strain curve of the recycled concretes was determined by replacing different percentages of the natural coarse aggregate with recycled coarse aggregate (20%, 50% and 100%). The results made it possible to establish the differences between the stress–strain relationship of a conventional concrete and this relationship for a recycled concrete depending on the percentage of replacement. In this way, it was found that the longitudinal strain of the recycled concretes increases with the percentage of recycled coarse aggregate used.Finally, using the experimental results, an analytical expression of the stress–strain curve accounting for the percentage of replacement was developed. The verification of the proposed model equation was done by comparing it to the experimental data. The results show that the proposed model equation satisfactorily describes the effect of the recycled aggregate on the stress–strain curve.     

Psychological services to Spanish-speaking populations: A model curriculum for training competent professionals.

The competent delivery of mental health services to Spanish-speaking clients requires knowledge of Latino cultures, racial and ethnic identity development, variables that impact service delivery, and the Spanish language. We present the Psychological Services for Spanish Speaking Populations (PSSSP) program as a model for training mental health professionals to deliver services to Spanish-speaking clients. The goals for the program were to improve participants' oral and written Spanish language proficiency in work-related contexts and to improve multicultural competence in service delivery to Latino clients. Recommendations for those who wish to offer similar programs include (a) grouping trainees according to Spanish language proficiency, (b) using Spanish language instructors with expertise in teaching heritage language learners, and (c) developing criterion references or measures to assess program outcomes. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Characterization of MEMS Devices for the Study of?Superfluid Helium Films

Measurements on the mechanical properties of MEMS resonators were performed to characterize such devices at room temperature and low temperatures. Using state-of-the-art silicon integrated circuit technology, we have designed, fabricated, and manufactured resonators consisting of a pair of parallel plates with a well-defined gap whose size can be controlled with a high accuracy down to the sub-micron range. A full study of resonance properties at various pressures was performed at room temperature. We will discuss the details of design, fabrication, and operation. These studies open up a window of opportunities to look for novel phenomena in quantum fluids such as in superfluid ³He films.