Evidence for a trigonal twist mechanism involving a phosphite ligand of Os3(CO)7,[P(OMe)3]5

The fluxional molecule Os₃(CO)₇[P(OMe)₃]₅ has been prepared from OS₃(CO)₁₂ and P(OMe)₃ by a combination of thermal and UV irradiation synthetic methods. An investigation by ³¹P and ¹³C NMR spectroscopy indicated that the mechanism of fluxionality in this compound probably involves the P(OMe)₃ ligand of the Os(CO)₃[P(OMe)₃] unit moving from one equatorial site to the other via a trigonal twist mechanism.     

Preparation of some complexes of the type (C6H5)3P[(CH3)2AsCH2CH(R)CH2As(CH3)2] M(CO)3 (M = Mo or W,R = H or C(CH3)3)

The title compounds, which contain six-membered chelate rings locked in the chair conformation, have been prepared by the reaction of (C₆H₅)₃P with the appropriate tetracarbonyl derivative in refluxing mesitylene.     

Analysis of microgram amounts of particulate material by simultaneous multiwavelength AES

A unique simultaneous emission spectrograph is utilized to perform qualitative and quantitative analysis on trace quantities of solid particulates. The atomic emission spectroscopic system consists of a direct current plasma source and an echelle spectrograph with a charge injection device detector, enabling the system to simultaneously measure the wavelength range from 220 nm to 520 nm with 0.02 nm resolution at 300 nm. Monitoring all wavelengths simultaneously allows the qualitative and quantitative determination of most major and minor constituent in a trace quantity of sample with little prior knowledge about the sample. The ability to perform qualitative and quantitative analysis on particulates is demonstrated by evaluating NBS certified coal fly ash, as well as a sample taken from the respirator air filter at an acute care unit in a hospital.Presented in part at the 1989 European Winter Conference on Plasma Spectrochemistry, Reutte, Austria     

Isolation and characterization of nongeminal cyclic methylphenylphosphazene tetramers

Heating pure samples of the cyclic phosphazenes, cis- or trans-[Me(Ph)PN](3), yielded mixtures of the cis and trans isomers of the cyclic phosphazene trimers, [Me(Ph)PN](3), and all four geometric isomers of the tetramers, [Me(Ph)PN](4). Varying the temperature and heating times changes the ratio of these components. Following the thermolysis by NMR spectroscopy indicated that only a mixture of the two isomeric trimers occurred initially. Longer heating times produced mixtures of the isomers of the tetramer. Column chromatography and solubility differences were used to separate each of the isomers of the tetramer. Spectroscopic and X-ray crystallographic studies suggest that the four different geometrical isomers of the tetramer can be described as cone, partial cone, 1,2-alternate, and 1,3-alternate by analogy to calix[4]arene.     

Heritability of Stroop and flanker performance in 12-year old children

Background  

There is great interest in appropriate phenotypes that serve as indicator of genetically transmitted frontal (dys)function, such as ADHD. Here we investigate the ability to deal with response conflict, and we ask to what extent performance variation on response interference tasks is caused by genetic variation. We tested a large sample of 12-year old monozygotic and dizygotic twins on two well-known and closely related response interference tasks; the color Stroop task and the Eriksen flanker task. Using structural equation modelling we assessed the heritability of several performance indices derived from those tasks.     

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.