Impact of environmental oxygen on nanoparticle formation and agglomeration in aluminum laser ablation plumes.

The role of ambient oxygen gas (O2) on molecular and nanoparticle formation and agglomeration was studied in laser ablation plumes. As a lab-scale surrogate to a high explosion detonation event, nanosecond laser ablation of an aluminum alloy (AA6061) target was performed in atmospheric pressure conditions. Optical emission spectroscopy and two mass spectrometry techniques were used to monitor the early to late stages of plasma generation to track the evolution of atoms, molecules, clusters, nanoparticles, and agglomerates.

Incidental Verbal Semantic Processing Recruits the Fronto-temporal Semantic Control Network.

The frontoparietal semantic network, encompassing the inferior frontal gyrus and the posterior middle temporal cortex, is considered to be involved in semantic control processes. The explicit versus implicit nature of these control processes remains however poorly understood. The present study examined this question by assessing regional brain responses to the semantic attributes of an unattended stream of auditory words while participants' top-down attentional control processes were absorbed by a demanding visual search task.

In vivo imaging of synaptic loss in Alzheimer's disease with [18F]UCB-H positron emission tomography.

Purpose: Loss of brain synapses is an early pathological feature of Alzheimer's disease. The current study assessed synaptic loss in vivo with positron emission tomography and an 18F-labelled radiotracer of the synaptic vesicle protein 2A, [18F]UCB-H.

Methods: Twenty-four patients with mild cognitive impairment or Alzheimer's disease and positive [18F]Flutemetamol amyloid-PET were compared to 19 healthy controls.

Calibration of two compact permanent magnet spectrometers for high current electron linear induction accelerators.

In this work, two compact, permanent magnet, electron spectrometers have been built to measure the electron beam energy at the Dual Axis Radiographic Hydrodynamic Test facility. Using H and OH anions, the spectrometers were calibrated at the Special Technologies Laboratory in Santa Barbara, California (USA). The spectrometers were mounted on a custom drift tube that allows the magnet assemblies to be translated, which increases the path length of the electrons traveling through the magnetic field and therefore increases the upper bound of the measurable electron kinetic energy.

The neural bases of proactive and reactive control processes in normal aging.

Introduction: Research on cognitive control suggests an age-related decline in proactive control abilities (anticipatory control), whereas reactive control (following conflict detection) seems to remain intact. As proactive and reactive control abilities are associated with specific brain networks, this study investigated age-related effects on the neural substrates associated with each kind of control.

Methods: In an event-related fMRI study, a modified version of the Stroop task was administered to groups of 20 young and 20 older healthy adults.

Relationship between grey matter integrity and executive abilities in aging.

This cross-sectional study was designed to investigate grey matter changes that occur in healthy aging and the relationship between grey matter characteristics and executive functioning. Thirty-six young adults (18-30 years old) and 43 seniors (60-75 years old) were included. A general executive score was derived from a large battery of neuropsychological tests assessing three major aspects of executive functioning (inhibition, updating and shifting).

Influence of COMT Genotype on Antero-posterior Cortical Functional Connectivity Underlying Interference Resolution.

Genetic variability related to the catechol-O-methyltransferase (COMT) gene (Val(158)Met) has received increasing attention as a possible modulator of executive functioning and its neural correlates. However, this attention has generally centered on the prefrontal cortices because of the well-known direct impact of COMT enzyme on these cerebral regions. In this study, we were interested in the modulating effect of COMT genotype on anterior and posterior brain areas underlying interference resolution during a Stroop task.

Age-related decline in cognitive control: the role of fluid intelligence and processing speed.

Background: Research on cognitive control suggests an age-related decline in proactive control abilities whereas reactive control seems to remain intact. However, the reason of the differential age effect on cognitive control efficiency is still unclear. This study investigated the potential influence of fluid intelligence and processing speed on the selective age-related decline in proactive control.

Modulating effect of COMT genotype on the brain regions underlying proactive control process during inhibition.

Introduction: Genetic variability related to the catechol-O-methyltransferase (COMT) gene (Val(158)Met polymorphism) has received increasing attention as a possible modulator of cognitive control functions.

Methods: In an event-related functional magnetic resonance imaging (fMRI) study, a modified version of the Stroop task was administered to three groups of 15 young adults according to their COMT Val(158)Met genotype [Val/Val (VV), Val/Met (VM) and Met/Met (MM)]. Based on the theory of dual mechanisms of control (Braver et al.

A design for a compact time-of-flight mass spectrometer.

The design of a prototype, compact time-of-flight (TOF) mass spectrometer is described. The system primarily consists of an ion acceleration∕focusing∕steering assembly (AFSA), an 8 cm field-free region, a 4 cm dual-stage reflectron, and a miniature microchannel plate detector. Consequently, the resulting flight length of the system is 12 cm.

Structural analysis of metal interactions with the dinucleotide duplex, dCG x dCG, using ion mobility mass spectrometry.

The metal binding properties of the dinucleotide duplex, dCG x dCG, were analyzed in the gas phase with ion mobility mass spectrometry. Both MALDI and ESI were used to generate [M(dCG x dCG)]+ complexes. The collision cross section of each complex was measured in helium using ion mobility based methods and compared to calculated cross sections of theoretical structures.

Probing shapes of bichromophoric metal-organic complexes using ion mobility mass spectrometry.

Ion mobility mass spectrometry (IM-MS) was used to probe the structures of several metal complexes carrying pendant chromophores. The three complexes investigated were the copper(II) complex Cu(DAC)2+ (DAC = 1,8-bis(9-methylanthracyl)cyclam, cyclam = 1,4,8,11-tetraazacyclotetradecane), the N-nitrosylated ligand DAC-NO, and the Roussin's red salt ester (mu-S,mu-S')-protoporphyrin-IX-bis(2-thioethyl ester)tetranitrosyldiiron (PPIX-RSE). From the IM-MS data coupled with theoretical calculations, it was found that [Cu(II)(DAC - H)]+ exists as a single conformer, with one anthracenyl group above the cyclam and the other below, similar to the crystal structure of Cu(II)(DAC)2+.

Probing the structure of gas-phase metallic clusters via ligation energetics: sequential addition of C2H4 to Agm+ (m=3-7).

A new method that utilizes ligation to probe geometries of clusters in the gas-phase has been developed. This technique bases structural assignments on thermodynamic quantities obtained for sequential ligand additions to a bare cluster. The information is obtained from temperature-dependent equilibrium data.