Cross section for inelastic neutron scattering from 193Ir at 6 MeV.

Two samples, one of natural iridium and the other of enriched 193Ir, were irradiated with a monoenergetic neutron beam of energy 6.0 MeV at the Triangle Universities Nuclear Laboratory. The product of the 193Ir [Formula: see text] Ir reaction was determined by means of measuring X-rays following electron conversion of the isomeric state at 80.2 keV in 193Ir. The cross section for inelastic neutron scattering is reported disagreeing with the literature data.

Corn stover harvest N and energy budgets in central Iowa.

Harvesting corn stover removes N from the fields, but its effect on subsurface drainage and other N losses is uncertain. We used the Root Zone Water Quality Model (RZWQM) to examine N losses with 0 (NRR) or 50% (RR) corn residue removal within a corn and soybean rotation over a 10-yr period. In general, all simulations used the same pre-plant or post-emergence N fertilizer rate (200 kg ha-1 yr-1). Simulated annual corn yields averaged 10.7 Mg ha-1 for the post emergence applications (NRRpost and RRpost), and 9.5 and 9.4 Mg ha-1 yr-1 for NRRpre and RRpre. Average total N input during corn years was 19.3 kg N ha-1 greater for NRRpre compared to RRpre due to additional N in surface residues, but drainage N loss was only 1.1 kg N ha-1 yr-1 greater for NRRpre. Post-emergence N application with no residue removal (NRRpost) reduced average drainage N loss by 16.5 kg ha-1 yr-1 compared to pre-plant N fertilization (NRRpre). The farm-gate net energy ratio was greatest for RRpost and lowest for NRRpre (14.1 and 10.4 MJ output per MJ input) while greenhouse gas intensity was lowest for RRpost and highest for NRRpre (11.7 and 17.3 g CO2-eq. MJ-1 output). Similar to published studies, the simulations showed little difference in N2O emissions between scenarios, decreased microbial immobilization for RR compared to NRR, and small soil carbon changes over the 10-yr simulation. In contrast to several previous modeling studies, the crop yield and N lost to drain flow were nearly the same between NRR and RR without supplemental N applied to replace N removed with corn stover. These results are important to optimizing the energy and nitrogen budgets associated with corn stover harvest and for developing a sustainable bioenergy industry.

An inverse free electron laser acceleration-driven Compton scattering X-ray source.

The generation of X-rays and γ-rays based on synchrotron radiation from free electrons, emitted in magnet arrays such as undulators, forms the basis of much of modern X-ray science. This approach has the drawback of requiring very high energy, up to the multi-GeV-scale, electron beams, to obtain the required photon energy. Due to the limit in accelerating gradients in conventional particle accelerators, reaching high energy typically demands use of instruments exceeding 100's of meters in length. Compact, less costly, monochromatic X-ray sources based on very high field acceleration and very short period undulators, however, may enable diverse, paradigm-changing X-ray applications ranging from novel X-ray therapy techniques to active interrogation of sensitive materials, by making them accessible in energy reach, cost and size. Such compactness and enhanced energy reach may be obtained by an all-optical approach, which employs a laser-driven high gradient accelerator based on inverse free electron laser (IFEL), followed by a collision point for inverse Compton scattering (ICS), a scheme where a laser is used to provide undulator fields. We present an experimental proof-of-principle of this approach, where a TW-class CO2 laser pulse is split in two, with half used to accelerate a high quality electron beam up to 84 MeV through the IFEL interaction, and the other half acts as an electromagnetic undulator to generate up to 13 keV X-rays via ICS. These results demonstrate the feasibility of this scheme, which can be joined with other techniques such as laser recirculation to yield very compact photon sources, with both high peak and average brilliance, and with energies extending from the keV to MeV scale. Further, use of the IFEL acceleration with the ICS interaction produces a train of high intensity X-ray pulses, thus enabling a unique tool synchronized with a laser pulse for ultra-fast strobe, pump-probe experimental scenarios.

Pulse dilation gas Cherenkov detector for ultra-fast gamma reaction history at the NIF (invited).

The Cherenkov mechanism used in Gas Cherenkov Detectors (GCDs) is exceptionally fast. However, the temporal resolution of GCDs, such as the Gamma Reaction History diagnostic at the National Ignition Facility (NIF), has been limited by the current state-of-the-art photomultiplier tube technology to ∼100 ps. The soon-to-be deployed Pulse Dilation Photomultiplier Tube (PD-PMT) at NIF will allow for temporal resolution comparable to that of the gas cell or ∼10 ps. Enhanced resolution will contribute to the quest for ignition in a crucial way through precision measurements of reaction history and ablator areal density (ρR) history, leading to better constrained models. Features such as onset of alpha heating, shock reverberations, and burn truncation due to dynamically evolving failure modes may become visible for the first time. Test measurements of the PD-PMT at Atomic Weapons Establishment confirmed that design goals have been met. The PD-PMT provides dilation factors of 2 to 40× in 6 increments. The GCD-3 recently deployed at the NIF has been modified for coupling to a PD-PMT and will soon be making ultrafast measurements.

Progress on next generation gamma-ray Cherenkov detectors for the National Ignition Facility.

Fusion reaction history and ablator areal density measurements for Inertial Confinement Fusion experiments at the National Ignition Facility are currently conducted using the Gamma Reaction History diagnostic (GRH_6m). Future Gas Cherenkov Detectors (GCDs) will ultimately provide ∼100x more sensitivity, reduce the effective temporal response from ∼100 to ∼10 ps, and lower the energy threshold from 2.9 to 1.8 MeV, relative to GRH_6m. The first phase toward next generation GCDs consisted of inserting the existing coaxial GCD-3 detector into a reentrant well which puts it within 4 m of the implosion. Reaction history and ablator gamma measurement results from this Phase I are discussed here. These results demonstrate viability for the follow-on Phases of (II) the use of a revolutionary new pulse-dilation photomultiplier tube to improve the effective measurement bandwidth by >10x relative to current PMT technology; and (III) the design of a NIF-specific "Super" GCD which will be informed by the assessment of the radiation background environment within the well described here.

Characterization of the Mercury pulsed power x-ray source spectrum using multichannel density aerogel Cherenkov detectors.

The Aerogel Cherenkov Detector for Cygnus (ACD/C) is a time-dependent, x-ray spectral detector that uses SiO2 aerogels spanning an index of refraction (n = 1.02-1.07) corresponding to a 1.1-2.3 MeV x-ray energy threshold. The ACD/C was developed for pulsed power x-ray sources like Cygnus located at the Nevada National Site and Mercury located at the Naval Research Laboratory (NRL). Aerogels sit between the measurement capabilities of gas (>2 MeV) and solids such as fused silica (>0.3 MeV). The detector uses an aluminum converter to Compton scatter incoming x-rays and create relativistic electrons, which produce Cherenkov light in an aerogel or a fused silica medium. The ACD/C was fielded at the NRL when Mercury was tuned to produce up to 4.8 MeV endpoint bremsstrahlung. Despite a high radiation and electromagnetic interference background, the ACD/C was able to achieve high signal over noise across five aerogel densities and fused silica, including a signal to noise for a 1.1 MeV aerogel threshold. Previous experiments at Cygnus observed a signal that was comparable to the noise (1×) at the same threshold. The ACD/C observed time-resolved rise and fall times for different energy thresholds of the photon spectrum. Monte Carlo simulations of the ACD/C's aerogel response curves were folded with a simulation of Mercury's photon energy spectrum and agree within the error to the observed result.

Veterans' views on military tobacco use and tobacco control policy.

National military and veteran service organizations (MVSOs) have the potential to be advocates for stronger military tobacco control. This study consisted of qualitative analysis of interviews with 5 MVSO leaders (or their designees) and 6 focus groups conducted with veterans, to explore the opinions of MVSO leaders and veterans about military tobacco use and tobacco control policy, and to assess their current knowledge, attitudes, and likelihood of engaging with civilian tobacco control. Themes discussed include the impact of tobacco use on the military mission and on veterans; the possibility of stronger military tobacco control policies; and the idea that such policies would affect the rights of military personnel. Participants considered whether tobacco use impacts the military mission in the most literal sense (e.g., giving away patrol locations), ignoring larger scale effects on long term health and costs. While familiar with tobacco's impacts on veterans' health, MVSO leaders did not endorse stronger policies, although some veterans did. Participants were largely unaware of the impact of tobacco use on military readiness. Establishment of better alliances among MVSOs and civilian public health groups for mutual education about tobacco's many negative effects on the military's mission may be necessary to achieve a tobacco-free military.

N loss to drain flow and N2O emissions from a corn-soybean rotation with winter rye.

Anthropogenic perturbation of the global nitrogen cycle and its effects on the environment such as hypoxia in coastal regions and increased N2O emissions is of increasing, multi-disciplinary, worldwide concern, and agricultural production is a major contributor. Only limited studies, however, have simultaneously investigated NO3- losses to subsurface drain flow and N2O emissions under corn-soybean production. We used the Root Zone Water Quality Model (RZWQM) to evaluate NO3- losses to drain flow and N2O emissions in a corn-soybean system with a winter rye cover crop (CC) in central Iowa over a nine year period. The observed and simulated average drain flow N concentration reductions from CC were 60% and 54% compared to the no cover crop system (NCC). Average annual April through October cumulative observed and simulated N2O emissions (2004-2010) were 6.7 and 6.0kgN2O-Nha-1yr-1 for NCC, and 6.2 and 7.2kgNha-1 for CC. In contrast to previous research, monthly N2O emissions were generally greatest when N loss to leaching were greatest, mostly because relatively high rainfall occurred during the months fertilizer was applied. N2O emission factors of 0.032 and 0.041 were estimated for NCC and CC using the tested model, which are similar to field results in the region. A local sensitivity analysis suggests that lower soil field capacity affects RZWQM simulations, which includes increased drain flow nitrate concentrations, increased N mineralization, and reduced soil water content. The results suggest that 1) RZWQM is a promising tool to estimate N2O emissions from subsurface drained corn-soybean rotations and to estimate the relative effects of a winter rye cover crop over a nine year period on nitrate loss to drain flow and 2) soil field capacity is an important parameter to model N mineralization and N loss to drain flow.

Next generation gamma-ray Cherenkov detectors for the National Ignition Facility.

The newest generation of Gas Cherenkov Detector (GCD-3) employed in Inertial Confinement Fusion experiments at the Omega Laser Facility has provided improved performance over previous generations. Comparison of reaction histories measured using two different deuterium-tritium fusion products, namely gamma rays using GCD and neutrons using Neutron Temporal Diagnostic (NTD), have provided added credibility to both techniques. GCD-3 is now being brought to the National Ignition Facility (NIF) to supplement the existing Gamma Reaction History (GRH-6m) located 6 m from target chamber center (TCC). Initially it will be located in a reentrant well located 3.9 m from TCC. Data from GCD-3 will inform the design of a heavily-shielded "Super" GCD to be located as close as 20 cm from TCC. It will also provide a test-bed for faster optical detectors, potentially lowering the temporal resolution from the current ∼100 ps state-of-the-art photomultiplier tubes (PMT) to ∼10 ps Pulse Dilation PMT technology currently under development.

Aerogel Cherenkov detector for characterizing the intense flash x-ray source, Cygnus, spectrum.

An aerogel Cherenkov detector is proposed to measure the X-ray energy spectrum from the Cygnus-intense flash X-ray source operated at the Nevada National Security Site. An array of aerogels set at a variety of thresholds between 1 and 3 MeV will be adequate to map out the bremsstrahlung X-ray production of the Cygnus, where the maximum energy of the spectrum is normally around 2.5 MeV. In addition to the Cherenkov radiation from aerogels, one possible competing light-production mechanism is optical transition radiation (OTR), which may be significant in aerogels due to the large number of transitions from SiO2 clusters to vacuum voids. To examine whether OTR is a problem, four aerogel samples were tested using a mono-energetic electron beam (varied in the range of 1-3 MeV) at NSTec Los Alamos Operations. It was demonstrated that aerogels can be used as a Cherenkov medium, where the rate of the light production is about two orders magnitude higher when the electron beam energy is above threshold.

Extended performance gas Cherenkov detector for gamma-ray detection in high-energy density experiments.

A new Gas Cherenkov Detector (GCD) with low-energy threshold and high sensitivity, currently known as Super GCD (or GCD-3 at OMEGA), is being developed for use at the OMEGA Laser Facility and the National Ignition Facility (NIF). Super GCD is designed to be pressurized to ≤400 psi (absolute) and uses all metal seals to allow the use of fluorinated gases inside the target chamber. This will allow the gamma energy threshold to be run as low at 1.8 MeV with 400 psi (absolute) of C2F6, opening up a new portion of the gamma ray spectrum. Super GCD operating at 20 cm from TCC will be ∼400 × more efficient at detecting DT fusion gammas at 16.7 MeV than the Gamma Reaction History diagnostic at NIF (GRH-6m) when operated at their minimum thresholds.

Seeding of self-modulation instability of a long electron bunch in a plasma.

We demonstrate experimentally that a relativistic electron bunch shaped with a sharp rising edge drives plasma wakefields with one to seven periods along the bunch as the plasma density is increased. The plasma density is varied in the 10(15)-10(17) cm(-3) range. The wakefields generation is observed after the plasma as a periodic modulation of the correlated energy spectrum of the incoming bunch. We choose a low bunch charge of 50 pC for optimum visibility of the modulation at all plasma densities. The longitudinal wakefields creating the modulation are in the MV/m range and are indirect evidence of the generation of transverse wakefields that can seed the self-modulation instability, although the instability does not grow significantly over the short plasma length (2 cm). We show that the seeding provides a phase reference for the wakefields, a necessary condition for the deterministic external injection of a witness bunch in an accelerator. This electron work supports the concept of similar experiments in the future, e.g., SMI experiments using long bunches of relativistic protons.

Quantifying climate and management effects on regional crop yield and nitrogen leaching in the north china plain.

Better water and nitrogen (N) management requires better understanding of soil water and N balances and their effects on crop yield under various climate and soil conditions. In this study, the calibrated Root Zone Water Quality Model (RZWQM2) was used to assess crop yield and N leaching under current and alternative management practices in a double-cropped wheat ( L.) and maize ( L.) system under long-term weather conditions (1970-2009) for dominant soil types at 15 locations in the North China Plain. The results provided quantitative long-term variation of deep seepage and N leaching at these locations, which strengthened the existing qualitative knowledge for site-specific management of water and N. In general, the current management practices showed high residual soil N and N leaching in the region, with the amounts varying between crops and from location to location and from year to year. Seasonal rainfall explained 39 to 84% of the variability in N leaching (1970-2009) in maize across locations, while for wheat, its relationship with N leaching was significant ( < 0.01) only at five locations. When N and/or irrigation inputs were reduced to 40 to 80% of their current levels, N leaching generally responded more to N rate than to irrigation, while the reverse was true for crop yield at most locations. Matching N input with crop requirements under limited water conditions helped achieve lower N leaching without considerable soil N accumulation. Based on the long-term simulation results and water resources availability in the region, it is recommended to irrigate at 60 to 80% of the current water levels and fertilize only at 40 to 60% of the current N rate to minimizing N leaching without compromising crop yield.

Children with autism spectrum disorders show abnormal conditioned response timing on delay, but not trace, eyeblink conditioning.

Children with autism spectrum disorder (ASD) and age-matched typically-developing (TD) peers were tested on two forms of eyeblink conditioning (EBC), a Pavlovian associative learning paradigm where subjects learn to execute an appropriately-timed eyeblink in response to a previously neutral conditioning stimulus (CS). One version of the task, trace EBC, interposes a stimulus-free interval between the presentation of the CS and the unconditioned stimulus (US), a puff of air to the eye which causes the subjects to blink. In delay EBC, the CS overlaps in time with the delivery of the US, usually with both stimuli terminating simultaneously. ASD children performed normally during trace EBC, exhibiting no differences from TD subjects with regard to the learning rate or the timing of the conditioned response. However, when subsequently tested on delay EBC, subjects with ASD displayed abnormally-timed conditioned eye blinks that began earlier and peaked sooner than those of TD subjects, consistent with previous findings. The results suggest an impaired ability of children with ASD to properly time conditioned eye blinks which appears to be specific to delay EBC. We suggest that this deficit may reflect a dysfunction of the cerebellar cortex in which increases in the intensity or duration of sensory input can temporarily disrupt the accuracy of motor timing over short temporal intervals.

The neutron imaging diagnostic at NIF (invited).

A neutron imaging diagnostic has recently been commissioned at the National Ignition Facility (NIF). This new system is an important diagnostic tool for inertial fusion studies at the NIF for measuring the size and shape of the burning DT plasma during the ignition stage of Inertial Confinement Fusion (ICF) implosions. The imaging technique utilizes a pinhole neutron aperture, placed between the neutron source and a neutron detector. The detection system measures the two dimensional distribution of neutrons passing through the pinhole. This diagnostic has been designed to collect two images at two times. The long flight path for this diagnostic, 28 m, results in a chromatic separation of the neutrons, allowing the independently timed images to measure the source distribution for two neutron energies. Typically the first image measures the distribution of the 14 MeV neutrons and the second image of the 6-12 MeV neutrons. The combination of these two images has provided data on the size and shape of the burning plasma within the compressed capsule, as well as a measure of the quantity and spatial distribution of the cold fuel surrounding this core.

Soil-test N recommendations augmented with PEST-optimized RZWQM simulations.

Improved understanding of year-to-year late-spring soil nitrate test (LSNT) variability could help make it more attractive to producers. We test the ability of the Root Zone Water Quality Model (RZWQM) to simulate watershed-scale variability due to the LSNT, and we use the optimized model to simulate long-term field N dynamics under related conditions. Autoregressive techniques and the automatic parameter calibration program PEST were used to show that RZWQM simulates significantly lower nitrate concentration in discharge from LSNT treatments compared with areas receiving fall N fertilizer applications within the tile-drained Walnut Creek, Iowa, watershed (>5 mg NL(-1) difference for the third year of the treatment, 1999). This result is similar to field-measured data from a paired watershed experiment. A statistical model we developed using RZWQM simulations from 1970 to 2005 shows that early-season precipitation and early-season temperature account for 90% of the interannual variation in LSNT-based fertilizer N rates. Long-term simulations with similar average N application rates for corn (Zea mays L.) (151 kg N ha(-1)) show annual average N loss in tile flow of 20.4, 22.2, and 27.3 kg N ha(-1) for LSNT, single spring, and single fall N applications. These results suggest that (i) RZWQM is a promising tool to accurately estimate the water quality effects of LSNT; (ii) the majority of N loss difference between LSNT and fall applications is because more N remains in the root zone for crop uptake; and (iii) year-to-year LSNT-based N rate differences are mainly due to variation in early-season precipitation and temperature.

Turning negative into positive: public health mass media campaigns and negative advertising.

Literature suggests that 'negative advertising' is an effective way to encourage behavioral changes, but it has enjoyed limited use in public health media campaigns. However, as public health increasingly focuses on non-communicable disease prevention, negative advertising could be more widely applied. This analysis considers an illustrative case from tobacco control. Relying on internal tobacco industry documents, surveys and experimental data and drawing from political advocacy literature, we describe tobacco industry and public health research on the American Legacy Foundation's "truth" campaign, an example of effective negative advertising in the service of public health. The tobacco industry determined that the most effective advertisements run by Legacy's "truth" campaign were negative advertisements. Although the tobacco industry's own research suggested that these negative ads identified and effectively reframed the cigarette as a harmful consumer product rather than focusing solely on tobacco companies, Philip Morris accused Legacy of 'vilifying' it. Public health researchers have demonstrated the effectiveness of the "truth" campaign in reducing smoking initiation. Research on political advocacy demonstrating the value of negative advertising has rarely been used in the development of public health media campaigns, but negative advertising can effectively communicate certain public health messages and serve to counter corporate disease promotion.

Gamma bang time/reaction history diagnostics for the National Ignition Facility using 90 degrees off-axis parabolic mirrors.

Gas Cherenkov detectors (GCDs) have been used to convert fusion gamma into photons to achieve gamma bang time and reaction history measurements. The GCDs designed for OMEGA used Cassegrain reflector optics in order to fit inside a 10 in. manipulator. A novel design for the National Ignition Facility using 90 degrees off-axis parabolic mirrors will increase light collection efficiency from fusion gammas and achieve minimum time dispersion. The broadband Cherenkov light (from 200 to 800 nm) is relayed into a high-speed detector using three parabolic mirrors. Because light is collected from many source planes throughout the CO(2) gas volume, the detector is positioned at the stop position rather than at an image position. The stop diameter and its position are independent of the light-generation location along the gas cell. The current design collects light from a 100 mm diameter by 500 mm long gas volume. Optical ray tracings demonstrate how light can be collected from different angled trajectories of the Compton electrons as they fly through the CO(2) gas volume. A cluster of four channels will allow for increased dynamic range as well as for different gamma energy threshold sensitivities.

"Working to shape what society's expectations of us should be": Philip Morris' societal alignment strategy.

BACKGROUND: A key element of Philip Morris's (PM's) corporate social responsibility initiatives is "societal alignment", defined as "strategies and programs to meet society's expectations of a responsible tobacco company". This study explored the genesis and implementation of Philip Morris' (PM) societal alignment efforts. METHODS: The study retrieved and analysed approximately 375 previously undisclosed PM documents now available electronically. Using an iterative process, the study categorised themes and prepared a case analysis. RESULTS: Beginning in 1999, PM sought to become "societally aligned" by identifying expectations of a responsible tobacco company through public opinion research and developing and publicising programs to meet those expectations. Societal alignment was undertaken within the US and globally to ensure an environment favourable to PM's business objectives. Despite PM's claims to be "changing", however, societal alignment in practice was highly selective. PM responded to public "expectations" largely by retooling existing positions and programs, while entirely ignoring other expectations that might have interfered with its business goals. It also appears that convincing employees of the value and authenticity of societal alignment was difficult. CONCLUSIONS: As implementation of the Framework Convention on Tobacco Control proceeds, tobacco control advocates should closely monitor development of such "alignment" initiatives and expose the motivations and contradictions they reveal.

Modeling nitrogen and water management effects in a wheat-maize double-cropping system.

Excessive N and water use in agriculture causes environmental degradation and can potentially jeopardize the sustainability of the system. A field study was conducted from 2000 to 2002 to study the effects of four N treatments (0, 100, 200, and 300 kg N ha(-1) per crop) on a wheat (Triticum aestivum L.) and maize (Zea mays L.) double cropping system under 70 +/- 15% field capacity in the North China Plain (NCP). The root zone water quality model (RZWQM), with the crop estimation through resource and environment synthesis (CERES) plant growth modules incorporated, was evaluated for its simulation of crop production, soil water, and N leaching in the double cropping system. Soil water content, biomass, and grain yield were better simulated with normalized root mean square errors (NRMSE, RMSE divided by mean observed value) from 0.11 to 0.15 than soil NO(3)-N and plant N uptake that had NRMSE from 0.19 to 0.43 across these treatments. The long-term simulation with historical weather data showed that, at 200 kg N ha(-1) per crop application rate, auto-irrigation triggered at 50% of the field capacity and recharged to 60% field capacity in the 0- to 50-cm soil profile were adequate for obtaining acceptable yield levels in this intensified double cropping system. Results also showed potential savings of more than 30% of the current N application rates per crop from 300 to 200 kg N ha(-1), which could reduce about 60% of the N leaching without compromising crop yields.