Supercritical fluid technology of nanoparticle coating for new ceramic materials

This work highlights, for the first time, the coating of ferroelectric nanoparticles with a chemical fluid deposition process in supercritical fluids. BaTiO3 nanoparticles of about 50 nm are coated with a shell of a few nanometers of amorphous alumina and can be recovered as a dry powder for processing. The sintering of these core-shell nanoparticles gives access to a ceramic material with very interesting ferroelectric properties, in particular, dielectric losses below 1%.     

Antioxidant activity of extracts of defatted seeds of niger (<Emphasis Type="Italic">Guizotia abyssinica</Emphasis>)

Niger (Guizotia abyssinica) seed was ground and then defatted with hexane. The meal remaining after oil extraction was tested as a source of antioxidants. Three solvent systems, A [80∶20 (vol/vol) ethanol/water], B [80∶20 (vol/vol) acetone/water], and C (water) were evaluated as extraction media. Crude extracts were examined for their antioxidant activity in a β-carotene-linoleate and a meat model system. Extract A exhibited superior antioxidant activity, compared to extracts B and C, and its composition was studied further by using column chromatography and HPLC. Four fractions (I–IV) were obtained, of which fractions III and IV showed activity in the β-carotene-linoleate model system. Fraction IV was also highly effective in scavenging the 2,2-diphenyl-1-picrylhydrazyl radical but was less active when used in a bulk oil model system. Preparative TLC showed fraction IV as consisting of two components. UV spectroscopy suggested that the major active component pressent was a chlorogenic acid-related compound. Furthermore, HPLC analysis established that chlorogenic acid was dominant in the free phenolics fraction (2.6 mg/g). Upon hydrolysis, however, a substantial amount of caffeic acid (42.8 mg/g) was released, presumably from esterified and glycosylated chlorogenic acid. Thus, niger extracts derive their antioxidant activity, at least in part, from the chlorogenic acid-related compounds.     

Recent trauma in psychiatric outpatients

Psychiatric clinic outpatients were screened for recent traumatic events, and post-traumatic symptomatology was evaluated in those reporting occurrence of one or more events within the two years prior to screening. Clear symptoms of post-traumatic stress disorder were revealed in 18% of the reporting patients, and the distribution of diagnoses was found to be different in the trauma-reporting group than it was in a comparison diagnostic group.     

Horizontal submammary skin incision for median sternotomy

Usual techniques in open-heart operations leave a vertical median skin scar. Especially for women this is rather embarassing since it looks ugly. The use of horizontal submammary skin incision for access to the heart is described here. Although obtaining the usual midsternal exposure takes some extra time, long-term results have shown the value of this approach and its benefit to the patient. The surgical technique is simple, and wound healing, in the long run, is unimpaired.     

Getting worse: Psychotherapy or no treatment—the jury should still be out.

It has been contended that patients receiving psychotherapy show significantly higher rates of deterioration than similar patients who receive no treatment. It has further been suggested that psychotherapy causes harm to some of those receiving it. These concerns are widely circulated and are likely to influence decision making at this critical time for the mental health professions. Relevant studies are reviewed with particular attention to characteristics of design. It is concluded that few studies allow for meaningful comparisons between experimental and control groups. In studies permitting such comparisons, there is no significant evidence of greater deterioration among the experimental groups. Alternative hypotheses consistent with these conclusions are presented, each with different implications for reducing the incidence of deterioration. The need for more and better research is underscored. (3 p ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Determination of Fracture Toughness in 2-D Woven SiC Matrix Composites Made by Chemical Vapor Infiltration

An approach to the R -curve behavior of 2-D woven ceramic matrix composites is proposed. This approach takes into account the presence of a process zone at the crack tip. The strain energy release rate is determined using an equivalent system of two specimens free of process zones. The process zone size is determined independently by assimilating a notch tip region to a beam of bimaterial. Compact tension specimens having different dimensions and single-edge notched beam specimens were used for the analysis. Important trends in toughening of ceramic matrix composites were anticipated.     

MEMS Scanning Calorimeter With Serpentine-Shaped Platinum Resistors for Characterizations of Microsamples

We report a new design and operation of a microelectromechanical systems (MEMS) differential scanning calorimeter (DSC) for heat-capacity measurements. The sensor consists of a 500-nm silicon nitride membrane supported by four bridges on a silicon wafer. On one side of the membrane, a serpentine-shaped platinum layer is deposited and used as both a resistive heater and a thermometer during the DSC measurement. This MEMS design can provide a self-alignment between the DSC cell and the material to be analyzed in order to prevent its deposition on the sloping side walls of the silicon frame. According to FEM calculations, the system exhibits good thermal isolation and high uniformities in the temperature field in the sensing area of the device. To evaluate the use of this calorimetric device for liquid samples, we measure the heat of vaporization of nanoliter-scale water droplets with high preciseness using the calorimeter in both scanning and heat conduction modes.     

Compound-Specific 14N/15N Analysis of Amino Acid Trimethylsilylated Derivatives from Plant Seed Proteins

Isotopic analyses of plant samples are now of considerable importance for food certification and plant physiology. In fact, the natural nitrogen isotope composition (δ¹⁵N) is extremely useful to examine metabolic pathways of N nutrition involving isotope fractionations. However, δ¹⁵N analysis of amino acids is not straightforward and involves specific derivatization procedures to yield volatile derivatives that can be analysed by gas chromatography coupled to isotope ratio mass spectrometry (GC-C-IRMS). Derivatizations other than trimethylsilylation are commonly used since they are believed to be more reliable and accurate. Their major drawback is that they are not associated with metabolite databases allowing identification of derivatives and by-products. Here, we revisit the potential of trimethylsilylated derivatives via concurrent analysis of δ¹⁵N and exact mass GC-MS of plant seed protein samples, allowing facile identification of derivatives using a database used for metabolomics. When multiple silylated derivatives of several amino acids are accounted for, there is a good agreement between theoretical and observed N mole fractions, and δ¹⁵N values are satisfactory, with little fractionation during derivatization. Overall, this technique may be suitable for compound-specific δ¹⁵N analysis, with pros and cons.     

Influence of Mechanical Surface Treatment on High-Temperature Oxidation of Pure Titanium

The excellent combination of light-weight and good mechanical properties makes titanium alloys attractive for compressor section components in gas turbine engines (temperature between 250 and 600 °C). However, above 600 °C, the formation of an unprotective oxide layer facilitates the oxygen diffusion into the alloy. In this experimental study, pure titanium was treated with mechanical surface treatment to promote better protection against oxidation at high temperature. Shot-peened and laser-shock peened specimens were compared to untreated samples in terms of oxidation behavior at high temperature. We used thermal gravimetric analysis to oxidize the samples at 700 °C for 100 h. Subsequently, XRD, optical microscopy, SEM/EDS, NRA, micro-Raman spectroscopy, and micro-hardness were used to characterize the oxide scale and the alpha-case layer formed during the high-temperature exposure. The shot-peened samples oxidized less (?45%) than the untreated and laser-shock peened samples. This behavior was attributed to the formation of a continuous nitride layer between oxide and metal.