Thermoheliox: effect on the functional hemodynamics of the human brain

A kinetic study of the effect of thermoheliox (inhalation of a helium and oxygen mixture, 70 °C) on the functional hemodynamics of the human brain by functional magnetic resonance imaging was carried out. The dynamic responses of the BOLD signal were found to be biphasic. An empirical equation describing the first phase of the hemodynamic response to visual stimulus was proposed. It was shown that preliminary inhalation of thermoheliox stimulates the hemodynamic responses by slowing down the vasoconstriction.

     

Sequential chemical deposition of metal alloy jellyfish using polyaniline: redox chemistry at the metal-polymer interface

We here demonstrate for the first time the fabrication of jellyfish-like Au-Ag alloys through sequential chemical deposition on a PANI substrate. This methodology can be applied to fabricate not only nanoparticles with complex morphology but also alloys with various compositions.     

Spectral editing in proton magnetic resonance spectroscopy. Determination of GABA level in the brains of humans with ultra-high risk for schizophrenia

Russian Chemical Bulletin - The intravital level of γ-aminobutyric acid (GABA) was measured for the first time and the imbalance of the key excitatory and inhibitory neurotransmitters in the...     

Quantification of cerebral aspartate concentration <Emphasis Type="Italic">in vivo</Emphasis> using proton magnetic resonance spectroscopy

The ¹Н MRS is a unique method allowing in vivo observation of concentrations of proton-containing chemical compounds in human tissues and organs. The main problem of this technique is the signal overlap caused by the similarity of structural fragments of variousmetabolites. To separate overlapped signals, the J-modulation technique for editing spectra, based on the spin–spin interaction can be used. In this study, a method of direct observation of the lifetime aspartate concentration in local regions of the human brain, based on the MEGA-PRESS pulse sequence, is developed for the first time.     

Observation of a metastable periodic structure for the (001) surface of KTaO3 after cleaving in situ

Helium atom diffraction experiments carried out under ultrahigh vacuum conditions on a freshly cleaved (001) surface of KTaO3 reveal metastable features which decay over a period of several hours. The initial He diffraction pattern contains large scattering intensity satellite peaks very close to the specular reflection beam. As time from cleaving elapses, the satellite intensities diminish virtually to zero while the specular intensity increases, and the diffraction pattern evolves into one consistent with the (1x1) bulk termination surface. The data are compared with model calculations for scattering from a series of terraces at two heights with a distribution of terrace lengths [Surf. Sci. 384, 15 (1997)].     

Optimization of signal-to-noise ratio in the <Emphasis Type="Italic">in vivo</Emphasis><Superscript>31</Superscript>P magnetic resonance spectra of the human brain

The main problem in ³¹P magnetic resonance spectroscopy is a low signal-to-noise ratio (SNR) of spectra acquired with clinical magnetic resonance imaging (MRI) scanners. Using spin-spin phosphorus-proton (³¹P-¹H) decoupling and heteronuclear Overhauser effect and taking into account the effect of the longitudinal relaxation time T₁ on the SNR, the method for localization and excitation of the region of interest (Image Selected in vivo Spectroscopy pulse sequence) was optimized to increase the SNR in the ³¹P magnetic resonance spectra of the human brain to ~50% without increasing signal acquisition time.     

Mechanistic study of silver nanoparticle formation on conducting polymer surfaces

Conducting polymer (polyaniline) sheets are shown to be active substrates to promote the growth of nanostructured silver thin films with highly tunable morphologies. Using the spontaneous electroless deposition of silver, we show that a range of nanostructured metallic features can be controllably and reproducibly formed over large surface areas. The structural morphology of the resulting metal-polymer nanocomposite is demonstrated to be sensitive to experimental parameters such as ion concentration, temperature, and polymer processing and can range from densely packed oblate nanosheets to bulk crystalline metals. The deposition mechanisms are explained using a diffusion-limited aggregation (DLA) model to describe the semi-fractal-like growth of the metal nanostructures. We find these composite films to exhibit strong surface-enhanced Raman (SERS) activity, and the nanostructured features are optimized with respect to SERS activity using a self-assembled monolayer of mercapto-benzoic acid as a model Raman reporter. SERS enhancements are estimated to be on the order of 10(7). Through micro-Raman SERS mapping, these materials are shown to exhibit uniform SERS responses over macroscopic areas. These metal-polymer nanocomposites benefit from the underlying polymer's processability to yield SERS-active materials of almost limitless shape and size and show significant promise for future SERS-based sensing and detection schemes.