Real-time nuclear activation detectors for measuring neutron angular distributions at the National Ignition Facility (invited).

The Real Time Nuclear Activation Detector (RTNAD) array at NIF measures the distribution of 14 MeV neutrons emitted by deuterium-tritium (DT) fueled inertial confinement fusion implosions. The uniformity of the neutron distribution is an important indication of implosion symmetry and DT shell integrity. The array consists of 48 LaBr(Ce) crystal gamma-ray spectrometers mounted outside the NIF target chamber, which continuously monitor the slow decay of the 909 keV gamma-ray line from activated Zr located in Zr cups surrounding each crystal.

Understanding the effects of neutron scattering for neutron-yield-isotropy measurements at the NIF.

Neutron-yield diagnostics at the NIF have been upgraded to include 48 detectors placed around the NIF target chamber to assess the DT-neutron-yield isotropy for inertial confinement fusion experiments. Real-time neutron-activation detectors are used to understand yield asymmetries due to Doppler shifts in the neutron energy attributed to hotspot motion, variations in the fuel and ablator areal densities, and other physics effects. In order to isolate target physics effects, we must understand the contribution due to neutron scattering associated with the different hardware configurations used for each experiment.

First on-line detection of radioactive fission isotopes produced by laser-accelerated protons.

The on-going developments in laser acceleration of protons and light ions, as well as the production of strong bursts of neutrons and multi-[Formula: see text] photons by secondary processes now provide a basis for novel high-flux nuclear physics experiments. While the maximum energy of protons resulting from Target Normal Sheath Acceleration is presently still limited to around [Formula: see text], the generated proton peak flux within the short laser-accelerated bunches can already today exceed the values achievable at the most advanced conventional accelerators by orders of magnitude. This paper consists of two parts covering the scientific motivation and relevance of such experiments and a first proof-of-principle demonstration.

Manganese(iv) oxide amendments reduce methylmercury concentrations in sediment porewater.

Manganese(iv) oxide (pyrolusite, birnessite) mineral amendments can reduce dissolved MeHg concentrations in sediment theoretically by inhibiting microbial sulfate reduction, which is a major methylation pathway in sediments. Anaerobic sediment slurry microcosms in which Hg methylation was stimulated by addition of labile organic carbon (acetate) and HgCl2 showed that manganese(iv) oxide reduced the percent MeHg in slurry porewater (filtered), by 1-2 orders of magnitude relative to controls. Sediment-water mesocosms with pyrolusite or birnessite either directly mixed into the top 5 cm or applied in a thin (5 cm) sand layer over sediment showed reductions in percent MeHg in porewater of 66-69% for pyrolusite and 81-89% for birnessite amendment.

Persistent reductions in the bioavailability of PCBs at a tidally inundated Phragmites australis marsh amended with activated carbon.

In situ amendment of sediments with highly sorbent materials like activated carbon (AC) is an increasingly viable strategy to reduce the bioavailability of persistent, sediment-associated contaminants to benthic communities. Because in situ sediment remediation is an emerging strategy, much remains to be learned about the field conditions under which amendments can be effective, the resilience of amendment materials toward extreme weather conditions, and the optimal design of engineered applications. We report the results of a multiyear, pilot-scale field investigation designed to measure the persistence and efficacy of AC amendments to reduce the bioavailability of polychlorinated biphenyls (PCBs) in an intertidal Phragmites marsh.

Biogeochemical controls on methylmercury in soils and sediments: Implications for site management.

Management of Hg-contaminated sites poses particular challenges because methylmercury (MeHg), a potent bio-accumulative neurotoxin, is formed in the environment, and concentrations are not generally predictable based solely on total Hg (THg) concentrations. In this review, we examine the state of knowledge regarding the chemical, biological, and physical controls on MeHg production and identify those most critical for contaminated site assessment and management. We provide a list of parameters to assess Hg-contaminated soils and sediments with regard to their potential to be a source of MeHg to biota and therefore a risk to humans and ecological receptors.

Note: Radiochemical measurement of fuel and ablator areal densities in cryogenic implosions at the National Ignition Facility.

A new radiochemical method for determining deuterium-tritium (DT) fuel and plastic ablator (CH) areal densities (ρR) in high-convergence, cryogenic inertial confinement fusion implosions at the National Ignition Facility is described. It is based on measuring the (198)Au/(196)Au activation ratio using the collected post-shot debris of the Au hohlraum. The Au ratio combined with the independently measured neutron down scatter ratio uniquely determines the areal densities ρR(DT) and ρR(CH) during burn in the context of a simple 1-dimensional capsule model.

Radiochemical determination of Inertial Confinement Fusion capsule compression at the National Ignition Facility.

We describe a radiochemical measurement of the ratio of isotope concentrations produced in a gold hohlraum surrounding an Inertial Confinement Fusion capsule at the National Ignition Facility (NIF). We relate the ratio of the concentrations of (n,γ) and (n,2n) products in the gold hohlraum matrix to the down-scatter of neutrons in the compressed fuel and, consequently, to the fuel's areal density. The observed ratio of the concentrations of (198m+g)Au and (196g)Au is a performance signature of ablator areal density and the fuel assembly confinement time.

Childhood and current ADHD symptom dimensions are associated with more severe cannabis outcomes in college students.

Background: Numerous studies have shown that attention deficit/hyperactivity disorder (ADHD) is associated higher risk of cannabis use disorders (CUD). However, these studies are limited in that most did not: (a) differentiate the role of hyperactivity-impulsivity (HI) and inattention (IN); (b) control for associated psychopathology; and (c) consider more fine-grained CUD-related measures. Our aim was to clarify the unique and interactive contributions of inattention and hyperactivity symptoms to age of cannabis initiation and DSM-IV cannabis dependence, craving, and severity of problems related to cannabis use while statistically controlling for symptoms of comorbid psychopathology in a non-clinical sample of young adults.

Cannabis cue reactivity and craving among never, infrequent and heavy cannabis users.

Substance cue reactivity is theorized as having a significant role in addiction processes, promoting compulsive patterns of drug-seeking and drug-taking behavior. However, research extending this phenomenon to cannabis has been limited. To that end, the goal of the current work was to examine the relationship between cannabis cue reactivity and craving in a sample of 353 participants varying in self-reported cannabis use.

Alcohol effects on performance monitoring and adjustment: affect modulation and impairment of evaluative cognitive control.

Alcohol is known to impair self-regulatory control of behavior, though mechanisms for this effect remain unclear. Here, we tested the hypothesis that alcohol's reduction of negative affect (NA) is a key mechanism for such impairment. This hypothesis was tested by measuring the amplitude of the error-related negativity (ERN), a component of the event-related brain potential (ERP) posited to reflect the extent to which behavioral control failures are experienced as distressing, while participants completed a laboratory task requiring self-regulatory control.

Response Conflict and Affective Responses in the Control and Expression of Race Bias.

Models of racial attitudes traditionally have assumed that individual differences in the strength of underlying, 'implicit' associations between racial categories and stereotypical traits are the primary determinant of the expression of race bias. Thus, individual differences in performance on laboratory tasks designed to assess implicit race bias tend to be interpreted in terms of association strength. Here, we argue that such associations tell only part of the story, and probably the least interesting part.

The feasibility and effectiveness of expressive writing for rural and urban breast cancer survivors.

Purpose/objectives: To determine the feasibility and effectiveness of implementing an in-home expressive-writing intervention among breast cancer survivors living in urban and rural areas.

Design: Women who had completed radiation therapy were selected to participate in either expressive writing or a usual-care control condition.

Setting: All materials were completed in the privacy of participants' homes.

Electrophysiological evidence of alcohol-related attentional bias in social drinkers low in alcohol sensitivity.

Low sensitivity to the acute effects of alcohol is a known risk factor for alcoholism. However, little is known concerning potential information-processing routes by which this risk factor might contribute to increased drinking. We tested the hypothesis that low-sensitivity (LS) participants would show biased attention to alcohol cues, compared with their high-sensitivity (HS) counterparts.

Evidence for regulation of monomethyl mercury by nitrate in a seasonally stratified, eutrophic lake.

The accumulation of monomethyl mercury (CH3Hg+) in aquatic ecosystems is a redox sensitive process that is accelerated under sulfate-reducing conditions. While nitrate (NO3-) reduction is energetically favored over sulfate reduction, the influence of NO3 on the accumulation of CH3Hg+ has not been reported in the literature. We examined temporal and vertical patterns in redox constituents and CH3Hg+ concentrations in the hypolimnion of a dimictic lake, Onondaga Lake, prior to and following increases in NO3- inputs.

Death on the brain: effects of mortality salience on the neural correlates of ingroup and outgroup categorization.

Research has shown that thoughts of one's; own death (i.e. mortality salience; MS) increase aspects of intergroup bias.

Effects of alcohol sensitivity on P3 event-related potential reactivity to alcohol cues.

Although alcoholics and individuals at risk for alcoholism often show smaller amplitude of the P3 event-related brain potential (ERP), recent data (K. Namkoong, E. Lee, C.

Intense high-energy proton beams from Petawatt-laser irradiation of solids.

An intense collimated beam of high-energy protons is emitted normal to the rear surface of thin solid targets irradiated at 1 PW power and peak intensity 3x10(20) W cm(-2). Up to 48 J ( 12%) of the laser energy is transferred to 2x10(13) protons of energy >10 MeV. The energy spectrum exhibits a sharp high-energy cutoff as high as 58 MeV on the axis of the beam which decreases in energy with increasing off axis angle.