Search

Melting and freezing of metallic nanoparticles embedded in glass matrices usually occur at temperatures lower than for the same metal in the bulk state. In situ small-angle X-ray scattering (SAXS) measurements using a synchrotron beamline and a specially designed high-temperature chamber allowed the determination of the temperature dependence of the SAXS intensity produced by a dilute and nearly monodisperse set of spherical Pb nanoparticles, with an average radius 〈 R〉 = 16.1 nm, embedded in a homogeneous lead-borate oxide glass. The temperature dependences of the nanoparticle volume V( T) and nanoparticle radius of gyration Rg( T) derived from SAXS results exhibit clear discontinuities during the cooling and during the heating processes, thus allowing for precise determinations of the melting and freezing temperatures of the studied Pb nanoparticles. Additional features observed in both V( T) and Rg( T) curves showed that during the heating cycle the frozen Pb nanoparticles suffer a transition to a more compact phase at 433 K before melting at 580 K. The results of this work demonstrate that the melting and freezing temperatures of nanoparticles in a very diluted state - for which the X-ray diffraction technique is not sensitive enough - can be precisely determined by applying only the SAXS method. [ABSTRACT FROM AUTHOR]

Background Increasing numbers of children are at-risk for behavioural and emotional disorders, a phenomenon contributing to increased use of pharmacological interventions for paediatric clients. Adverse side effects and other risks associated with pharmacological approaches have helped fuel interest in nutritional interventions for behaviourally at-risk children. Methods The current randomized clinical trial evaluates the efficacy of a neurochemical intervention involving the glutamine and glutamate analogue L-theanine and 5-hydroxytryptophan, the precursor for serotonin, with children adopted from traumatic backgrounds. Results Results include significant increases in urinary levels of the biomarkers for serotonin and gamma-aminobutyric acid, coupled with significant decreases in parent reports of the children's behaviour problems. Conclusions While further research is needed, these initial findings are encouraging and are consistent with a growing number of studies indicating the efficacy of nutritional approaches to help behaviourally at-risk children. [ABSTRACT FROM AUTHOR]