The contribution of high frequencies to human brain activity underlying horizontal localization of natural spatial sounds

Background  

In the field of auditory neuroscience, much research has focused on the neural processes underlying human sound localization. A recent magnetoencephalography (MEG) study investigated localization-related brain activity by measuring the N1m event-related response originating in the auditory cortex. It was found that the dynamic range of the right-hemispheric N1m response, defined as the mean difference in response magnitude between contralateral and ipsilateral stimulation, reflects cortical activity related to the discrimination of horizontal sound direction. Interestingly, the results also suggested that the presence of realistic spectral information within horizontally located spatial sounds resulted in a larger right-hemispheric N1m dynamic range. Spectral cues being predominant at high frequencies, the present study further investigated the issue by removing frequencies from the spatial stimuli with low-pass filtering. This resulted in a stepwise elimination of direction-specific spectral information. Interaural time and level differences were kept constant. The original, unfiltered stimuli were broadband noise signals presented from five frontal horizontal directions and binaurally recorded for eight human subjects with miniature microphones placed in each subject's ear canals. Stimuli were presented to the subjects during MEG registration and in a behavioral listening experiment.     

Hyperfine fields and exchange interactions in BaLiFe17O27 W-type hexagonal ferrite

The temperature dependence of the hyperfine fields corresponding to ferric ions in the different sublattices of BaLiFe₁₇O₂₇ W-type hexagonal ferrite has been measured. A mean field analysis of these sublattice magnetizations has been done and a set of nearest neighbour isotropic exchange interactions has been obtained. The relative strenght of these fitted exchange values is in accordance with superexchange theory     

Etude de la détonation de mélanges pauvres H2NO2/N2O4

Calculations of the detonation reaction zone of gaseous H₂NO₂/N₂O₄ mixtures in the range of equivalence ratio Φ between 0.25 and 0.7 show that for 0.25Φ0.4 the chemical energy is released in two distinct and successive exothermic steps characterised by different chemical characteristic times. As for rich mixtures, the first exothermic step is mainly due to the reaction NO₂ + H → NO + OH, but the second one is different since it results from the exothermic decomposition of NO into N₂ and O₂. For Φ=0.3 the measured detonation velocity in a tube of 52 mm internal diameter is very much smaller than the calculated value and the mean size of the cellular structure is very much larger than the value extrapolated from data obtained with mixtures of higher but close equivalence ratio. All these results show that the detonation, though self-sustained and steady, is ‘non-ideal’, i.e. it is supported only by a part of the available chemical energy, that provided mainly by the first exothermic step. To cite this article: D. Desbordes et al., C. R. Mecanique 332 (2004).     

Crystal structures of three intermetallic phases in the Mo-Pt-Si system

The crystal structures of three ternary Mo-Pt-Si intermetallic compounds have been determined ab initio from powder X-ray diffraction data. All three structures are representative of new structure types. Both the X (MoPt₂Si₃, Pmc2₁, oP12, a=3.48438(6), b=9.1511(2), c=5.48253(8) Å) and Y (MoPt₃Si₄, Pnma, oP32, a=5.51210(9), b=3.49474(7), c=24.3090(4) Å) phases derive from PtSi (FeAs type) structure while the Z phase (ideal composition Mo₃₂Pt₂₀Si₁₆, refined composition Mo_29.9(2)Pt_21.0(3)Si_17.1(1), Cc, mC68, a=13.8868(3), b=8.0769(2), c=9.6110(2) Å, β=100.898(1)°) present similarities with the group of Frank-Kasper phases.     

Specific molecular and cellular events induced by irradiated X‐ray photoactivatable drugs raise the problem of co‐toxicities: particular consequences for anti‐cancer synchrotron therapy

Synchrotrons are capable of producing intense low‐energy X‐rays that enable the photoactivation of high‐Z elements. Photoactivation therapy (PAT) consists of loading tumors with photoactivatable drugs and thereafter irradiating them at an energy, generally close to the K‐edge of the element, that enhances the photoelectric effect. To date, three major photoactivatable elements are used in PAT: platinum (cisplatin and carboplatin), iodine (iodinated contrast agents and iododeoxyuridine) and gadolinium (motexafin gadolinium). However, the molecular and cellular events specific to PAT and the radiobiological properties of these photoactivatable drugs are still misknown. Here, it is examined how standard and synchrotron X‐rays combined with photoactivatable drugs impact on the cellular response of human endothelial cells. These findings suggest that the radiolysis products of the photoactivatable drugs may participate in the synergetic effects of PAT by increasing the severity of radiation‐induced DNA double‐strand breaks. Interestingly, subpopulation of highly damaged cells was found to be a cellular pattern specific to PAT. The data show that the efficiency of emerging anti‐cancer modalities involving synchrotron photoactivation strongly depends on the choice of photoactivatable drugs, and important series of experiments are required to secure their clinical transfer before applying to humans.     

Vacuum ultra violet absorption spectroscopy of 193 nm photoresists

193 nm photoresists which are methacrylate-based polymers are very sensitive to vacuum ultra violet (VUV) light (100 nm<λ<200 nm) generated by plasmas used for pattern transfer technologies. Upon plasma treatment the physical properties of the polymers can be deeply modified. To better understand the chemical changes involved, the absorption coefficient of a commercial 193 nm photoresist has been measured in the 120–280 nm wavelength range using a home built experimental set-up. The different contributions to the absorption were identified by also measuring the spectra of model polymers and simpler polymer chains. This knowledge was then used to identify the chemical changes in the photoresist upon heating up to 240°C.     

A density functional theory study of uranium(VI) nitrate monoamide complexes

Density functional theory calculations were performed on uranyl complexed with nitrate and monoamide ligands (L) [UO(2)(NO(3))(2)·2L]. The obtained results show that the complex stability is mainly governed by two factors: (i) the maximization of the polarizability of the coordinating ligand and (ii) the minimization of the steric hindrance effects. Furthermore, the electrostatic interaction between ligands and uranium(vi) was found to be a crucial parameter for the complex stability. These results pave the way to the definition of (quantitative) property/structure relationships for the in silico screening of monoamide ligands with improved extraction efficiency of uranium(vi) in nitrate acidic solution.