Nanofabricated atom optics: Atom chips

Abstract

Small tight trapping and guiding potentials can be created for neutral atoms moving microns above surfaces patterned with nanofabricated charged and current-carrying structures. Surfaces holding such structures form atom chips which, for coherent matter wave optics, may form the basis for a variety of novel applications and research tools, similar to integrated circuits in electronics. In this paper we describe the basic principles of atom chip experiments.     

An electronic driver for improving the open and closed loop electro-mechanical response of Dielectric Elastomer actuators

Actuators based on Dielectric Elastomers are a promising technology in robotic and mechatronic applications. The overall actuator performances are influenced by the non-linear and highly coupled electrical and mechanical behavior of the employed materials. To date, the practical electro-mechanical response and controllability of actuators based on Dielectric Elastomers are limited by the inadequacy of the employed driving circuits, which are based on voltage-regulated converters. In this paper, first a novel activation strategy is proposed for Dielectric Elastomer actuators, which is based on a custom electronic driver derived from the flyback transformer topology. Second, two closed-loop controllers employing the proposed electronic driver are presented and compared for the accurate and fast regulation of the position of Dielectric Elastomer actuators. Experimental results are reported which show that the proposed electronic driver outperforms the traditional driving circuits in terms of energy efficiency, fast open-loop actuator activation and good closed-loop actuator controllability.     

Comparative assessment of genotoxicity of mineral water packed in polyethylene terephthalate (PET) and glass bottles

The potential migration of genotoxic compounds into mineral water stored in polyethylene terephthalate (PET) bottles was evaluated by an integrated chemical/biological approach using short-term toxicity/genotoxicity tests and chemical analysis. Six commercial brands of still and carbonated mineral water bottled in PET and in glass were stored at 40 °C for 10 days in a stove according to the standard EEC total migration test (82/711/EEC), or at room temperature in the dark. After treatment, the samples were analysed using gas-chromatography/mass spectrometry (GC/MS) to detect volatile and non-volatile compounds, the Microtox^® test to evaluate potential toxicity of the samples, and three mutagenicity tests - Tradescantia and Allium cepa micronucleus tests and the Comet assay on human leukocytes - to detect their genotoxic activity.GC/MS analysis did not detect phthalates or acetaldehyde in the water samples. The Microtox^® test found no toxic effects. Mutagenicity tests detected genotoxic properties of some samples in both PET and glass bottles. Statistical analyses showed a positive association between mineral content and mutagenicity (micronuclei in A. cepa and DNA damage in human leukocytes). No clear effect of treatment and PET bottle was found. These results suggest the absence of toxic compounds migrating from PET regardless of time and conditions of storage. In conclusion, bottle material and stove treatment were not associated with the genotoxic properties of the water; the genotoxic effects detected in bottled water may be related to the characteristics of the water (minerals and CO₂ content).     

In vitro fertilisation with frozen-thawed bovine sperm sexed by flow cytometry and validated for accuracy by real-time PCR

The methodologies used for cytometric sorting of fresh spermatozoa never allowed a clear resolution of sexual chromosomes of frozen-thawed semen. To devise a novel method for the production of bovine predefined sexed embryos using frozen-thawed semen, sorting efficiency of different protocols was studied using a new quantitative real-time PCR method to verify the purity of sexed semen. To this aim, after Percoll separation, frozen-thawed samples were stained at different temperatures and concentrations of Hoechst 33342 using a short-incubation time. The concentration of Hoechst 33342 of 500 mug/ml at a temperature of 37 degrees C provided good and stable fluorescence signals. Preventing the sperm clustering by adding 0.6% BSA in the 90% Percoll fraction led to X-bearing sperms purity of 91+/-2%. Thereafter, sorted sperms were used for in vitro fertilisation (IVF). Despite the lower cleavage rates reported in the sorted groups when compared with the control groups (40 vs 48%, P<0.01), blastocyst formation in the sorted and control groups was not different (27 vs 24% of the cleaved respectively). The PCR analysis of 30 blastocysts confirmed 26 embryos to be correctly sexed (87%). Transfer of two embryos per recipient into six synchronised heifers resulted in four pregnancies. Two abortions occurred at day 60, while two pregnancies went to term delivering two female calves. In conclusion, high purity and repeatability of sorting was obtained with frozen-thawed bull semen that was subsequently used for IVF giving rise to viable embryos and offspring. In addition, real-time PCR revealed to be an optimal support for these studies, providing a rapid and reliable estimation of flow cytometric efficiency.     

Upgrading biomass pyrolysis gas by conversion of methane at high temperature: Experiments and modelling

Biomass gasification at temperatures below 1273 K produces gas which contains methane and too much tar for Fischer-Tropsch synthesis. The aim of this study is to investigate methane conversion at high temperature. Experimental tests were performed between 1273 and 1773 K, with a mixture of gas representative of wood pyrolysis at 1100 K (main components only: CO, CO₂, CH₄, H₂, H₂O). Two different kinetic schemes were used to predict the gas composition, and PAH molecules formation. For a residence time of 2 s in the reactor, the gas must be heated to at least 1650 K to reach a methane conversion rate of 90%. A parametric study was performed at 1453 K, by varying the initial methane, steam and hydrogen contents, so as to find out which components are the most influent on methane conversion and soot production.     

Fruit quality of Italian pomegranate (<Emphasis Type="Italic">Punica granatum</Emphasis> L.) autochthonous varieties

Pomegranate is getting an increasing attention for its health-promoting effects. Collection and characterization of plants of local sources has been performed, and five accessions have been propagated and cultivated in a collection field for extra situ investigations. Accessions differ for pomological traits and chemical composition. Three of them, MG1, MG2, and MG3, belong to typology with low-medium acidity and high sugar content, while the other two, Tordimonte A and B, belong to typology with high acidity. In the juice and in the peels’ extract of Tordimonte A accession a high level of punicalin has been found through chromatographic determinations, while the presence of punicalagin was found in the juice of accession MG1. The accessions MG1, MG2, and MG3 seem particularly suitable for direct commercialization of fruits due to the fruit traits and quality (sweet varieties), while Tordimonte A and B could be valuable for juice processing (sour varieties).     

Effects of hydrocolloids on chemical properties and cooking quality of gluten‐free spaghetti

The effects of different hydrocolloids on chemical composition and cooking quality of spaghetti based on maize and oat flours were investigated. Rheological and texture properties of the gluten‐free dough were also assessed. Amount of 2% of gellan gum, carboxymethylcellulose, pectin, agar, egg protein powder, tapioca starch, guar seed flour and chitosan were separately added to the formulation. The samples enriched with hydrocolloids generally showed a different rheological behaviour compared with the control samples. As regards chemical composition, spaghetti with chitosan showed a value of insoluble dietary fibres (8.0%) higher than the control ones (3.9%). Moreover, results highlighted that most hydrocolloids improved cooking quality and texture properties of spaghetti (adhesiveness, cooking loss, hardness), thus supporting their application in gluten‐free pasta.     

Energy Dissipation in Transient Gaseous Cavitation

The aim of the paper is to examine nonfriction energy dissipation in transient cavitating flows and to verify whether they can be attributed to thermic exchange between gas bubbles and the surrounding liquid or to gas release and solution process. A two-dimensional (2D) numerical model for liquid flow with a small amount of free gas is proposed. The results of the numerical runs are compared with experimental data of pressure head oscillations in transient cavitating flow. Both thermic exchange and gas release can explain some of the dissipation if a relaxation process is assumed. However, the 2D model, including the thermodynamics of the gaseous phase, does not seem to fully explain the observed dissipation. The 2D model with gas release allows for a good simulation of the experimental data after a suitable calibration of the model parameters.