Differences in electrophysical and gas sensing properties of flame spray synthesized Fe2O3(gamma-Fe2O3 and alpha-Fe2O3)

Nanoscaled Fe2O3 powders as candidates for gas sensing material for hydrogen detection were synthesized by the high temperature flame spray assisted combustion of ferrocene dissolved in benzene. X-ray diffraction (XRD) and selected area electron diffraction (SAED) show that the as prepared nanopowder consists of maghemite (gamma-Fe2O3) with low crystallinity. Thermal post-treatment causes a phase transformation towards hematite (alpha-Fe2O3) accompanied by an increase in the crystallinity. Upon exposure to air and hydrogen at elevated temperatures, both phases show a significant variation of conductivity and activation energy-as evidenced by impedance spectra-and thus a favorable sensor response, surpassing even that of flame-synthesized nanocrystalline tin dioxide. The conductivity has been identified as of electronic origin, affected by trap states located in the region adjacent to grain boundaries. Quantitative analysis of the impedance spectra with equivalent circuits shows that the conductivity is thermally activated and affected by the interaction of hydrogen with the sensor material. The calculated Debye screening length of gamma-Fe2O3 and alpha-Fe2O3 is about 27 nm and 16 nm, respectively, what contributes significantly to the sensitivity of the material. Gamma-Fe2O3 and alpha-Fe2O3 exhibit high sensor response towards hydrogen in a wide concentration range. Gamma-Fe2O3 shows n-type semiconducting behavior up to 573 K. Alpha-Fe2O3 shows p-type semiconducting behavior, as reflected in the dynamic changes of the resistivity. For both sensor materials, 523 K was the optimal operating temperature.     

Aseptically packaged UHPH-treated apple juice: Safety and quality parameters during storage

Ultra-high pressure homogenization (UHPH) at 300 MPa and 4 °C inlet temperature were used to preserve apple juice, and shelf-life evaluation of aseptically packaged juice was investigated. After processing Tetra Brik containers were stored at temperatures of 4, 10, 20 and 30 °C during 60 days. In this article, the effect of processing on the spoilage inactivation was evaluated after processing and during the storage trial. Non-germinated and germinated spores were found in the UHPH-treated juice, being an inactive population during storage. Patulin content was also not modified by UHPH processing, but a significant decrease was observed during storage at 30 °C (P < 0.05). Polyphenoloxidase (PPO) and pectinmethylesterase (PME) activity was not found after UHPH-processing and during storage.A kinetic study of post-processing quality loss was conducted. Vitamin C, chlorogenic acid, total polyphenols and color change were measured during storage study and were used to model the UHPH-treated apple juice shelf-life. Loss of vitamin C was correlated with the hydroxymethylfurfural (HMF) accumulation (0.59, P < 0.05). A limiting quality parameter was polyphenolic content. UHPH-treated apple juice stored at 4 °C was found to show a shelf-life for about 21 months by preserving the color characteristics of the juice with low HMF accumulation. From 15 °C changes in quality parameters were more evident.     

Identification of phenolic constituents of Cytisus multiflorus

The phenolic composition of the ethanolic extract obtained from the flowers of the medicinal plant Cytisus multiflorus has been elucidated by high performance liquid chromatography, electrospray mass spectrometry and nuclear magnetic resonance analysis. The extract was mainly composed of flavones, including the common chrysin, orientin, luteolin-5-O-glucoside, luteolin-7-O-glucoside, apigenin and apigenin-7-O-glucoside, which appeared as minor components. The major flavone in the extract was chrysin-7-O-β-d-glucopyranoside, and it also contained moderate amounts of a dihydroxyflavone isomer of chrysin, as well as of 2″-O-pentosyl-6-C-hexosyl-luteolin, 2″-O-pentosyl-8-C-hexosyl-luteolin and 6″-O-(3-hydroxy-3-methylglutaroyl)-2″-O-pentosyl-C-hexosyl-apigenin, which are not commonly found in the Fabaceae family. Other novel phenolic compounds found in the ethanolic extract of C. multiflorus comprised the flavones 2″-O-pentosyl-6-C-hexosyl-apigenin, 2″-O-pentosyl-8-C-hexosyl-apigenin and 6″-O-(3-hydroxy-3-methylglutaroyl)-2″-O-pentosyl-C-hexosyl-luteolin. The assessment of the biological activities of the main compounds of this extract are now keen, in order to determine their relevance in the beneficial properties of the plant.     

Calcium effect on mechanical properties of model cell walls and apple tissue

Bacterial cellulose alone, with pectin added and with both pectin and xyloglucan added were produced as models for plant cell walls. The artificial cell wall materials and natural apple tissue were treated with calcium and then subjected to tests of mechanical properties; a tension test for the artificial cell wall materials and a compression test for the apple tissue. It was found that pectin and xyloglucan had a significant effect on the mechanical properties of artificial cell wall materials, making them more extensible. A high concentration of calcium increased the failure strain and decreased the failure stress of these materials. Treatment of apple tissue with calcium had similar effects on the failure stress and the secant modulus, whereas the differences of failure strain and work to failure resulted in behaviour different from that of the artificial material.     

Turing, ciphers and quanta

Alan Turing has certainly contributed to a widespread belief that the quest for a perfect, unbreakable, cipher is a futile pursuit. The ancient art of concealing information has, in the past, been matched by the ingenuity of code-breakers, but no longer! With the advent of quantum cryptography, the hopes of would-be eavesdroppers have been dashed, perhaps for good. Moreover, recent research, building on schemes that were invented decades ago to perform quantum cryptography, shows that secure communication certified by a sufficient violation of a Bell inequality makes a seemingly insane scenario possible-devices of unknown or dubious provenance, even those that are manufactured by our enemies, can be safely used for secure communication, including key distribution. All that is needed to implement this bizarre and powerful form of cryptography is a loophole-free test of a Bell inequality, which is on the cusp of technological feasibility. We provide a brief overview of the intriguing connections between Bell inequalities and cryptography and describe how studies of quantum entanglement and the foundations of quantum theory influence the way we may protect information in the future.     

Solution blow spinning: A new method to produce micro‐ and nanofibers from polymer solutions

A solution blow spinning technique was developed using elements of both electrospinning and melt blowing technologies as an alternative method for making non‐woven webs of micro‐ and nanofibers with diameters comparable with those made by the electrospinning process with the advantage of having a fiber production rate (measured by the polymer injection rate) several times higher. The diameters of fibers produced ranged from 40 nm for poly(lactic acid) to several micrometers for poly(methyl methacrylate). This solution blow spinning method uses a syringe pump to deliver a polymer solution to an apparatus consisting of concentric nozzles whereby the polymer solution is pumped through the inner nozzle while a constant, high velocity gas flow is sustained through the outer nozzle. Analysis of the process showed that pressure difference and shearing at the gas/solution interface jettisoned multiple strands of polymer solution towards a collector. During flight, the solvent component of the strands rapidly evaporates forming a web of micro and nanofibers. The effect of injection rate, gas flow pressure, polymer concentration, working distance, and protrusion distance of the inner nozzle was investigated. Polymer type and concentration had a greater effect on fiber diameter than the other parameters tested. Injection rate, gas flow pressure, and working distance affected fiber production rate and/or fiber morphology. Fibers were easily formed into yarns of micro‐ and nanofibers or non‐woven films that could be applied directly onto biological tissue or collected in sheets on a rotating drum. Indeed, virtually any type of target could be used for fiber collection. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

DBC: a condensed representation of frequent patterns for efficient mining

Given a large set of data, a common data mining problem is to extract the frequent patterns occurring in this set. The idea presented in this paper is to extract a condensed representation of the frequent patterns called disjunction-bordered condensation (DBC), instead of extracting the whole frequent pattern collection. We show that this condensed representation can be used to regenerate all frequent patterns and their exact frequencies. Moreover, this regeneration can be performed without any access to the original data. Practical experiments show that the DBCcan be extracted very efficiently even in difficult cases and that this extraction and the regeneration of the frequent patterns is much more efficient than the direct extraction of the frequent patterns themselves. We compared the DBC with another representation of frequent patterns previously investigated in the literature called frequent closed sets. In nearly all experiments we have run, the DBC have been extracted much more efficiently than frequent closed sets. In the other cases, the extraction times are very close.