3,136 research outputs found
Genome-Wide Linkage Analysis of Human Auditory Cortical Activation Suggests Distinct Loci on Chromosomes 2, 3, and 8
Neural processes are explored through macroscopic neuroimaging and microscopic molecular measures, but the two levels remain primarily detached. The identification of direct links between the levels would facilitate use of imaging signals as probes of genetic function and, vice versa, access to molecular correlates of imaging measures. Neuroimaging patterns have been mapped for a few isolated genes, chosen based on their connection with a clinical disorder. Here we propose an approach that allows an unrestricted discovery of the genetic basis of a neuroimaging phenotype in the normal human brain. The essential components are a subject population that is composed of relatives and selection of a neuroimaging phenotype that is reproducible within an individual and similar between relatives but markedly variable across a population. Our present combined magnetoencephalography and genome-wide linkage study in 212 healthy siblings demonstrates that auditory cortical activation strength is highly heritable and, specifically in the right hemisphere, regulated oligogenically with linkages to chromosomes 2q37, 3p12, and 8q24. The identified regions delimit as candidate genes TRAPPC9, operating in neuronal differentiation, and ROBO1, regulating projections of thalamocortical axons. Identification of normal genetic variation underlying neurophysiological phenotypes offers a non-invasive platform for an in-depth, concerted capitalization of molecular and neuroimaging levels in exploring neural function.Peer reviewe
InGaAs-QW VECSEL emitting >1300nm via intracavity Raman conversion
We report intracavity Raman conversion of a long-wavelength InGaAs-QW VECSEL to ~1320 nm, the longest wavelength yet achieved by a VECSEL-pumped Raman laser. The setup consisted of a VECSEL capable of emitting >17W at 1180nm and tunable from 1141-1203nm and a 30-mm-long KGd(WO4)2 (KGW) Raman crystal in a coupled-cavity Raman resonator. The Raman cavity was separated from the VECSEL resonator by a tilted dichroic mirror, which steers the Raman beam to an output coupler external to the VECSEL. The spectral emission of the VECSEL, and consequently of the Raman laser, was set by a 4-mm-thick quartz birefringent filter in the VECSEL cavity. The KGW Raman laser was capable of emitting 2.5W at 1315 nm, with M2~2.7 and >4% diode-to-Stokes conversion efficiency. The Raman laser emission was tunable from 1295-1340 nm, limited by the free spectral range of the birefringent filter. Spectral broadening of the fundamental emission was observed during Raman conversion. At the maximum Raman laser output power, the total linewidth of the VECSEL spectrum was ~0:7nm FWHM. As a consequence, the Raman laser emission was also relatively broad (~0.9nm FWHM). Narrow (<0.2nm FWHM) Raman emission was obtained by inserting an additional 100 µm etalon within the VECSEL cavity. With this configuration the fundamental intracavity power clamped at its value at the Raman threshold, suggesting an enhanced effective Raman gain, but the maximum output power of the Raman laser was 1.8 W
Status report of the JYFL-ECR ion sources
"Ion beam cocktails" are mixtures of ions with near-identical charge-to-mass ratios. In conjunction with the JYFL-ECRIS, the K130-cyclotron acts as a mass analyzer: the switch from one ion to another within the same cocktail is simple and fast. In the case of the first ion beam cocktail, the oxygen and argon gases were mixed into the gas feed line. At the same time the magnesium and iron ion beams were produced using the MIVOC method. Magnesocene and ferrocene compounds were both mixed into the MIVOC chamber. This capability is especially useful in the study of single event effects (SEE) in space electronics. All gaseous elements from H to Xe can be produced. The non-gaseous elements produced so far are C, Mg, Al, Si, S, Ca, Ti, Cr, Fe, Co, Ni, Cu, Zn and Ge. A major technical modification since the construction (in 1990) of the JYFL-ECRIS was made in January 98: a negatively biased disc replaces now the first plasma stage. After a couple of months experience with the modified source the change was found to be towards a correct direction. The source is now much easier to use and the good operating conditions are well repeated. A real advantage is the new magnetic field settings which are practically the same for all kind of beams, gaseous and solids. Due to the requirements of ion beams with higher charges and heavier elements than the present JYFL-ECRIS can produce, JYFL decided to begin a design and construction project of a new ECR ion source, called as ECRIS 2. The project aims to a source that is based mainly on the design of the 14 GHz AECR-U source at the LBNL. Some modifications made into the similar source under construction at the NSCL/MSU will be utilized here. The new source will be installed horizontally in the basement of the ECRIS laboratory. It requires a new beam-line from the source to the cyclotron injection line, since the old vertically located JYFL-ECRIS will be preserved in operation. The new source is planned to be operational during the year 2000
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