Prepulse Level Research Articles

Not a Deficit, Just Different: Prepulse Inhibition Disruptions in Autism Depend on Startle Stimulus Intensities.

Sensory processing disruptions are a core symptom of autism spectrum disorder (ASD) and other neurological disorders. The acoustic startle response and prepulse inhibition (PPI) are common metrics used to assess disruptions in sensory processing and sensorimotor gating in clinical studies and animal models. However, often there are inconsistent findings on ASD-related PPI deficits across different studies. Here, we used a novel method for assessing changes in startle and PPI in rodents, using the Cntnap2 knock-out (KO) rat model for neurodevelopmental disorder/ASD that has consistently shown PPI disruptions in past studies. We discovered that not only sex and prepulse intensity but also the intensity of the startle stimulus profoundly impacts whether PPI deficits are evident in the Cntnap2 KO rat or not. We show that rats do not universally exhibit a PPI deficit; instead, impaired PPI is contingent on specific testing conditions. Notably, at lower startle stimulus intensities, Cntnap2 KO rats not only demonstrated intact PPI but also exhibited evidence of enhanced PPI compared with their wild-type counterparts. This finding emphasizes the importance of considering specific testing conditions when evaluating startle and PPI in the context of ASD and other neuropsychiatric conditions and might explain some of the inconsistencies between different studies.

Buffering capacity of submerged macrophytes against nutrient pulses increase with its coverage in shallow lakes

Submerged macrophytes can improve water quality and buffer the effects of external nutrient loading, which helps to maintain a clear-water state in shallow lakes. We constructed 12 large enclosures with contrasting coverages (treatments) of submerged macrophytes (SMC) to elucidate their buffering capacity and resilience to nutrient pulses. We found that aquatic ecosystems with high SMC had higher buffering capacity and resilience, vice versa, i. e, the enclosures with high SMC quickly buffered the nutrient pulse and rebounded to clear-water state after a short stay in turbid-water state dominated by algae, while the treatments with low SMC could not fully buffer the pulse and rebound to clear-water state, and they slowly entered the transitional state after staying in turbid-water state. This means that the enclosures with high SMC had a better water quality than those with low SMC, i.e., the levels of nutrients and Chl-a were lower in the treatments with high plant coverage. In addition, plant coverage had a significantly positive buffering effect against nitrogen and phosphorus pulses, i.e., the nutrient concentrations in the treatments with high SMC took shorter time to return to the pre-pulse level. Overall, our results evidenced that the higher that the SMCs is, the better is the water quality and buffering capacity against nutrient pulses, i.e. the more stable is the clear-water state. However, low SMC may not be able to resist the impact of such strong nutrient pulse. Our results provide reference and guidance for water pollution control and water ecological restoration.

Twenty years of drought\u2010mediated change in snag populations in mixed\u2010conifer and ponderosa pine forests in Northern Arizona

BackgroundSnags (standing dead trees) are important biological legacies in forest systems, providing numerous resources as well as a record of recent tree mortality. From 1997 to 2017, we monitored snag populations in drought-influenced mixed-conifer and ponderosa pine (Pinus ponderosa) forests in northern Arizona.ResultsSnag density increased significantly in both forest types. This increase was driven largely by a pulse in snag recruitment that occurred between 2002 and 2007, following an extreme drought year in 2002, with snag recruitment returning to pre-pulse levels in subsequent time periods. Some later years during the study also were warmer and/or drier than average, but these years were not as extreme as 2002 and did not trigger the same level of snag recruitment. Snag recruitment was not equal across tree species and size classes, resulting in significant changes in species composition and size-class distributions of snag populations in both forest types. Because trees were far more abundant than snags in these forests, the effect of this mortality pulse on tree populations was far smaller than its effect on snag populations. Snag loss rates increased over time during the study, even though many snags were newly recruited. This may reflect the increasing prevalence of white fir snags and/or snags in the smaller size classes, which generally decay faster than snags of other species or larger snags. Thus, although total numbers of snags increased, many of the newly recruited snags may not persist long enough to be valuable as nesting substrates for native wildlife.ConclusionsIncreases in snag abundance appeared to be due to a short-term tree mortality “event” rather than a longer-term pattern of elevated tree mortality. This mortality event followed a dry and extremely warm year (2002) embedded within a longer-term megadrought. Climate models suggest that years like 2002 may occur with increasing frequency in the southwestern U.S. Such years may result in additional mortality pulses, which in turn may strongly affect trajectories in abundance, structure, and composition of snag populations. Relative effects on tree populations likely will be smaller, but, over time, also could be significant.

Effects of Permethrin or Deltamethrin Exposure in Adult Sprague Dawley Rats on Acoustic and Light Prepulse Inhibition of Acoustic or Tactile Startle.

The effects of permethrin (PRM) and deltamethrin (DLM) on acoustic or light prepulse inhibition of the acoustic startle response (ASR) and tactile startle response (TSR) were studied in adult male Sprague Dawley rats. Preliminary studies were conducted to optimize the parameters of light and acoustic prepulse inhibition of ASR and TSR. Once these parameters were set, a new group of rats was administered PRM (0 or 90mg/kg) or DLM (0 or 25mg/kg) by gavage in 5mL/kg corn oil. ASR and TSR were assessed using acoustic or light prepulses 6, 8, and 12h after PRM and 2, 4, and 6h after DLM exposure. PRM increased ASR 6h post-treatment with no interaction with acoustic prepulse levels and with no effect on TSR. When light was used as the prepulse, PRM increased ASR and TSR at 6h with no interaction with prepulse levels. DLM decreased ASR and TSR on trials without prepulses but not on trials with acoustic prepulses. DLM also decreased ASR when light prepulses were present 4h post-treatment. A final experiment assessed whether the house light in the test cabinet affected ASR and TSR after PRM or DLM exposure. Rats had increased ASR and TSR when house lights were on compared with when they were off, but lighting did not differentially interact with PRM or DLM. Light and acoustic prepulses of ASR and TSR have different effects depending on the test agent and the test parameters.

Optimization of high energy x ray production through laser plasma interaction

A standard technique for generating a burst of hard x rays (above 30 keV) is to use ultra high intensity lasers incident on a target. The strong laser field causes rapid electron oscillations which then generate hard x rays via bremsstrahlung. We have demonstrated a new technique for optimizing the conversion efficiency of laser light to hard x rays at moderate Iλ2 (mid 1013 W/cm2.µm2) assuming that the two plasmon decay plasma instability is the predominant acceleration mechanism. In this scheme, electrons are not directly accelerated by the laser field but by electron plasma waves. Experiments at the National Ignition Facility show the effect of a pre-pulse on the hard x ray spectrum and conversion efficiency. Different experimental configurations are investigated to optimize the conversion efficiency using various pre-pulse levels as well as different target designs (gold vs. silver, varying target thickness, presence of an ablator layer of CH). The conversion efficiency of laser energy into photon above 30 keV for a 100 ps short pulse scales as ∼ I1.23 for laser intensity ranging from 1 × 1016 to 1 × 1017 W/cm2 at 3ω for high Z target. A 1-ns-long pre-pulse pre-seeding an 88-ps Gaussian laser pulse coupled with a CH-coated thin Au target led the highest conversion efficiency above 30 keV of ∼ 3×10−4.

Remote sensing vegetation index methods to evaluate changes in greenness and evapotranspiration in riparian vegetation in response to the Minute 319 environmental pulse flow to Mexico

Abstract. During the spring of 2014, 130 million m3 of water were released from the United States' Morelos Dam on the lower Colorado River to Mexico, allowing water to reach the Gulf of California for the first time in 13 years. Our study assessed the effects of water transfer or ecological environmental flows from one nation to another, using remote sensing. Spatial applications for water resource evaluation are important for binational, integrated water resources management and planning for the Colorado River, which includes seven basin states in the US plus two states in Mexico. Our study examined the effects of the historic binational experiment (the Minute 319 agreement) on vegetative response along the riparian corridor. We used 250 m Moderate Resolution Imaging Spectroradiometer (MODIS), Enhanced Vegetation Index (EVI) and 30 m Landsat 8 satellite imagery to track evapotranspiration (ET) and the normalized difference vegetation index (NDVI). Our analysis showed an overall increase in NDVI and evapotranspiration (ET) in the year following the 2014 pulse, which reversed a decline in those metrics since the last major flood in 2000. NDVI and ET levels decreased in 2015, but were still significantly higher (P < 0.001) than pre-pulse (2013) levels. Preliminary findings show that the decline in 2015 persisted into 2016 and 2017. We continue to analyse results for 2018 in comparison to short-term (2013–2018) and long-term (2000–2018) trends. Our results support the conclusion that these environmental flows from the US to Mexico via the Minute 319 “pulse” had a positive, but short-lived (1 year), impact on vegetation growth in the delta.

Acoustic prepulse inhibition in male and female prairie voles: Implications for models of neuropsychiatric illness

Sensory gating, the ability to suppress sensory information of irrelevant stimuli, is affected in several neuropsychiatric diseases, notably schizophrenia and autism. It is currently unclear how these deficits interact with other hallmark symptoms of these disorders, such as social withdrawal and difficulty with interpersonal relationships. The highly affiliative prairie vole (Microtus ochrogaster) may be an ideal model organism to study the neurobiology underlying social behavior. In this study, we assessed unimodal acoustic sensory gating in male and female prairie voles using the prepulse inhibition (PPI) paradigm, whereby a lower amplitude sound (prepulse) decreases the startle response to a high amplitude sound (pulse) compared to the high amplitude sound alone. Prairie voles showed evidence of PPI at all prepulse levels compared to pulse alone, with both males and females showing similar levels of inhibition. However, unlike what has been reported in other rodent species, prairie voles did not show a within-session decrease in startle response to the pulse alone, nor did they show a decrease in startle response to the pulse over multiple days, highlighting their inability to habituate to startling stimuli (short- and long-term). When contrasted with a cohort of male wildtype C57Bl/6J mice that underwent a comparable PPI protocol, individual voles showed significantly higher trial-by-trial variability as well as longer latency to startle than mice. The benefits and caveats to using prairie voles in future sensory gating experiments are discussed.

BS19. Reorganization of sensory input in brainstem after peripheral facial paralysis

Peripheral facial nerve palsy (PFP) is characterized by reduced motor performance on one side of face. The electrophysiological findings show smaller or delayed motor and facial reflex responses. It leads to a cortical reorganization and an imbalance in sensorimotor gating is also likely since sensory pathways innervating facial structures are intact and sensory inputs to face are transmitted smoothly. Herein, we aimed to analyze the alterations in sensorimotor gating at the level of brainstem after PFP. To examine sensorimotor gating, we used prepulse modulation (PPM) of blink reflex (BR). We also recorded recovery (RC) of BR to identify excitability changes in the facial nucleus. We included 33 patients with PFP and 39 recordings in those patients. Six patients had serial recordings. Control group was composed of 16 healthy subjects with similar age and gender to the patient group (Table). Baseline BR, BR recovery at ISI of 300 ms and BR-PPM at ISI of 100 ms were performed on the right sides of healthy subjects and on both sides of patients. Severity of PFP was assessed according to clinical findings by House-Brackman scale and using electrophysiological methods. Patients with BR, facial motor response or electromyography findings indicating axon loss more than 85% were considered to have severe axon loss. Time lapse from the onset was categorized as early (<15 days), middle (12–45 days) and late (>45 days). R1, R2 and R2c components of BR on symptomatic side were absent in 17, 9 and 13 recordings, respectively. When they were recorded, latencies were longer and magnitude was lower over symptomatic sides of patients compared to healthy subjects or asymptomatic sides of patients. Multivariate ANOVA showed significance at group level, at prepulse level and group x prepulse level. Mean magnitude of R1 was increased whereas mean R2 and R2c magnitude were reduced in all groups after prepulse stimulation (prepulse inhibition, PPI). Interestingly, suppression of R2 or R2c was lower on both sides of patient group compared to healthy subjects. There was no association between PPM% and categories according to time lapse or HBs. PPM% did not correlate with time lapse, either. Although R2-RC and R2C-RC were lower in healthy subjects compared to both sides of patients, the difference was not significant. When we conducted a multivariate analysis between BR-RC with fixed factor time lapse and HB, recovery rates were significantly lower in patients with lower HB scores. Prepulse inhibition of R2 BR is reduced in patients with PFP. Filtering of facial sensory input at brainstem level is decreased leading to an increased transfer of trigeminal sensory inputs through brainstem. Although increased BR-RC correlated with disease severity, there was no correlation between reduced PPI-BR. Thus, reduced PPI is presumably related to monitor and to choose correct sequence of facial movements.

Proton acceleration measurements using fs laser irradiation of foils in the target normal sheath acceleration regime

We present experimental results obtained at the CELIA laboratory using the laser ECLIPSE to study proton acceleration from ultra-intense laser pulses. Several types of targets were irradiated with different laser conditions (focusing and prepulse level). Proton emission was characterized using time-of-flight detectors (SiC and diamond) and a Thomson parabola spectrometer. In all cases, the maximum energy of observed protons was of the order of 260 keV with a large energy spectrum. Such characteristics are typical of protons emitted following the target normal sheath acceleration mechanism for low-energy short-pulse lasers like ECLIPSE.

Reorganization of sensorimotor gating after peripheral facial palsy starts at brainstem

ABSTRACTBackground and objective We aimed to analyze the alterations in sensorimotor gating at brainstem after peripheral facial palsy (PFP). To examine sensorimotor gating, we used prepulse modulation (PPM) of blink reflex (BR). We also recorded BR recovery to identify excitability changes in the facial nucleus.Patients and method We included 33 patients and 39 recordings. Control group was composed of 16 healthy subjects. Simultaneous bilateral baseline BR, BR recovery at ISI of 300-ms and BR-PPM at ISI of 100-ms recordings were performed after stimulation of trigeminal nerve on right sides of healthy subjects and on both sides of patients. Severity of PFP and time lapse from the onset was noted.Results Mean R1 amplitude was increased, whereas mean R2 and R2c magnitude were reduced in all groups after prepulse stimulation. However, multivariate ANOVA showed significance at group level (patients and healthy subjects), at prepulse level (no prepulse and 100-ms prepulse) and group and prepulse level. Suppression of R2 or R2c was lower on both sides of patients compared to healthy subjects and the deficit first started on the symptomatic side.Conclusion Suppression of R2 and R2c after prepulse stimulation is reduced in PFP suggesting decreased filtering of facial sensory input at brainstem level. Trigeminal sensitization at brainstem develops early after PFP.

Effects of short-duration hydraulic pulses on the treatment performance of a periphyton-based treatment wetland

The effect of high flows on total phosphorus (TP) removal in a 40-ha periphyton-based stormwater treatment area wetland (PSTA Cell) located in Stormwater Treatment Area (STA)-3/4 was evaluated by subjecting the PSTA Cell to three short-duration (3-day) hydraulic (high-inflow) pulses. The intent was to mimic hydraulic conditions that would be experienced during large storm events should the PSTA concept be implemented throughout the complex of treatment wetlands (STAs) operated by the South Florida Water Management District for Everglades restoration. The average inflow rate to the PSTA Cell during the pulses (1.3–2.0m3s−1) was approximately three to four times higher than under normal operation. The hydraulic loading rates (HLRs) during the pulses (28–43cmd−1) matched the peak 3-day HLRs observed in STA-3/4 during high inflows associated with storm runoff. Correspondingly, the phosphorus loading rates (PLRs) and hydraulic retention times (HRTs) during the pulses (2.3–6.3mgm−2d−1 and 1.4–1.8 days, respectively) were substantially higher and lower, respectively, compared to PLRs and HRTs in the PSTA Cell under normal operation. No reduction in TP removal performance was observed in the PSTA Cell during the pulses, and there was no indication that post-pulse outflow TP concentrations increased compared to pre-pulse levels in response to the pulse events. The short-term increase in hydraulic and TP loads during this study did not compromise the treatment efficacy of the PSTA Cell. If implementable in a cost-effective manner in the STAs, the PSTA concept could be part of a treatment strategy that achieves TP effluent limits mandated for these wetlands.

Groundwater response to the 2014 pulse flow in the Colorado River Delta

During the March-May 2014 Colorado River Delta pulse flow, approximately 102×106m3 (82,000 acre-feet) of water was released into the channel at Morelos Dam, with additional releases further downstream. The majority of pulse flow water infiltrated and recharged the regional aquifer. Using groundwater-level and microgravity data we mapped the spatial and temporal distribution of changes in aquifer storage associated with pulse flow. Surface-water losses to infiltration were greatest around the Southerly International Boundary, where a lowered groundwater level owing to nearby pumping created increased storage potential as compared to other areas with shallower groundwater. Groundwater levels were elevated for several months after the pulse flow but had largely returned to pre-pulse levels by fall 2014. Elevated groundwater levels in the limitrophe (border) reach extended about 2km to the east around the midway point between the Northerly and Southerly International Boundaries, and about 4km to the east at the southern end. In the southern part of the delta, although total streamflow in the channel was less due to upstream infiltration, augmented deliveries through irrigation canals and possible irrigation return flows created sustained increases in groundwater levels during summer 2014. Results show that elevated groundwater levels and increases in groundwater storage were relatively short lived (confined to calendar year 2014), and that depressed water levels associated with groundwater pumping around San Luis, Arizona and San Luis Rio Colorado, Sonora cause large, unavoidable infiltration losses of in-channel water to groundwater in the vicinity.

Assessment of sensorimotor gating following selective lesions of cholinergic pedunculopontine neurons.

Sensorimotor gating is the state-dependent transfer of sensory information into a motor system. When this occurs at an early stage of the processing stream it enables stimuli to be filtered out or partially ignored, thereby reducing the demands placed on advanced systems. Prepulse inhibition (PPI) of the acoustic startle reflex (ASR) is the standard measure of sensorimotor gating. A brainstem-midbrain circuitry is widely viewed as mediating both PPI and ASR. In this circuitry, the pedunculopontine tegmental nucleus (PPTg) integrates sensory input and cortico-basal ganglia output and, via presumed cholinergic signaling, inhibits ASR-generating neurons within the reticular formation. Non-selective damage to all neuronal types within PPTg reduces PPI. We assessed whether this effect originates in the loss of cholinergic signaling by examining ASR and PPI in rats bearing non-selective (excitotoxic) or selective cholinergic (Dtx-UII) lesions of PPTg. Excitotoxic lesions had no effect on ASR but reduced PPI at all prepulse levels tested. In contrast, selective depletion of cholinergic neurons reduced ASR to the extent that PPI was not measurable with standard (10-20 s) inter-trial intervals. Subsequent testing revealed appreciable ASRs could be generated when the inter-trial interval was increased (180 s). Under these conditions, PPI was assessed and no deficits were found after lesions of cholinergic PPTg neurons. These results show that cholinergic output from PPTg is essential for rapidly regenerating the ASR, but has no influence on PPI. Results are discussed in terms of sensorimotor integration circuitry and psychiatric disorders that feature disrupted ASR and PPI.

Review of the current status of fast ignition research at the IAPCM

AbstractWe review the present status and future prospects of fast ignition (FI) research of the theoretical group at the IAPCM (Institute of Applied Physics and Computational Mathematics, Beijing) as a part of the inertial confinement fusion project. Since the approval of the FI project at the IAPCM, we have devoted our efforts to improving the integrated codes for FI and designing advanced targets together with the experimental group. Recent FI experiments [K. U. Akli et al., Phys. Rev. E 86, 065402 (2012)] showed that the petawatt laser beam energy was not efficiently converted into the compressed core because of the beam divergence of relativistic electron beams. The coupling efficiency can be improved in three ways: (1) using a cone–wire-in-shell advanced target to enhance the transport efficiency, (2) using external magnetic fields to collimate fast electrons, and (3) reducing the prepulse level of the petawatt laser beam. The integrated codes for FI, named ICFI, including a radiation hydrodynamic code, a particle-in-cell (PIC) simulation code, and a hybrid fluid–PIC code, have been developed to design this advanced target at the IAPCM. The Shenguang-II upgraded laser facility has been constructed for FI research; it consists of eight beams (in total $24~ {\rm kJ}/3\omega $, 3 ns) for implosion compression, and a heating laser beam (0.5–1 kJ, 3–5 ps) for generating the relativistic electron beam. A fully integrated FI experiment is scheduled for the 2014 project.

Calmodulin Kinase 1 Regulates the Vacuolar Calcium Exporter Yvc1p in Saccharomyces cerevisiae

We are interested in analyzing the key proteins involved in calcium homeostasis in Saccharomyces cerevisiae and undertook deletion mutant analysis, assaying cytosolic calcium concentration after a single extracellular pulse of 100 mM. In wild type cells a spike in cytosolic calcium was observed, followed by a decrease to approximately pre-pulse baseline level, which was maintained for the remainder of the 13 minute assay. In yeast mutants cmd1- 6, Δcnb1, Δcrz1, Δcmk1, and Δcmk2, an initial spike was also seen, followed by the baseline return, and then a second rise in cytosolic calcium after six minutes was observed. We wanted to identify the origin of this second rise in cytosolic calcium in the deletion mutants, hypothesizing it was due to the vacuolar calcium exporter channel, Yvc1p, aberrantly responding to the hyperosmolarity of the cytosol. In Δcmk1Δyvc1 cells, the second rise was absent. In Δcnb1Δyvc1 cells, the second rise was still observed and was not due to Vcx1p activity. We propose that in the presence of high extracellular calcium, an initial feedback mechanism regulated by calcineurin, in response to an elevated level of intracellular calcium entry, inhibits the plasma membrane calcium channel, while calmodulin kinase 1 inhibits Yvc1p during an additional feedback response.

Controlling output pulse and prepulse in a resonant microwave pulse compressor

A resonant microwave pulse compressor with a waveguide H-plane-tee-based energy extraction unit was studied in terms of its capability to produce output pulses that comprise a low-power long-duration (prepulse) and a high-power short-duration part. The application of such combined pulses with widely variable prepulse and high-power pulse power and energy ratios is of interest in the research area of electronic hardware vulnerability. The characteristics of output radiation pulses are controlled by the variation of the H-plane tee transition attenuation at the stage of microwave energy storage in the compressor cavity. Results of theoretical estimations of the parameters tuning range and experimental investigations of the prototype S-band compressor (1.5 MW, 12 ns output pulse; ∼13.2 dB gain) are presented. The achievable maximum in the prepulse power is found to be about half the power of the primary microwave source. It has been shown that the energy of the prepulse becomes comparable with that of the short-duration (nanosecond) pulse, while the power of the latter decreases insignificantly. The possible range of variation of the prepulse power and energy can be as wide as 40 dB. In the experiments, the prepulse level control within the range of ∼10 dB was demonstrated.

Substance use in prenatally cocaine-exposed adolescents

throughout the gestational period. In order to discern which effects are influenced by MB, PDE, or both, natural litters and a cross-fostering paradigm with vehicle-treated mothers raising PDE pups and drugtreatedmothers raisingvehicle-exposedpups are used. Preliminarydata indicate that non-PDE offspring behave differently in the PPI task based on the treatment (PD or Vehicle) the mother received during her pregnancy. Bothmales and females raised byvehicle-treateddams show adampening in theeffectof thepre-pulse at all but thehighestpre-pulse level. Whereas males raised by PD-treated dams show increased inhibition at all pre-pulse levels, females show no effect of the prepulse at any level. Reduced inhibition following the pre-pulse indicates abnormal sensory and motor information integration and processing, and is seen in schizophrenic patients. This suggests that abnormal MB produced by polydrug exposure during pregnancy has long-term effects on sensorimotor gating, which differs according to the sex of the offspring. (Supported by NIH P50 DA 025484-0001)

Poster #10 MAGNETIC RESONANCE IMAGING CHARACTERIZATION OF EARLY POSTNATAL PHENCYCLIDINE TREATMENT AS A RAT MODEL OF SCHIZOPHRENIA

We have studied the effect of prepulses in enhancing the efficiency of generating ASE beams in soft X-ray laser plasma amplifiers based on pumping Ne-like ions. Slab targets were irradiated with a weak prepulse followed by a main plasma heating pulse of nanosecond duration. Time-integrated: time and spectrally resolved and time and angularly resolved lasing emissions on the 3p-3s (J = 0–1) XUV lasing lines of Ne-like Ni, Cu and Zn at wavelengths 232 Å, 221 Å and 212 Å respectively have been monitored. Measurements were made for pre-pulse/main-pulse intensity ratios from 10−5–10−1 and for pump delay times of 2 ns and 4.5 ns. Zinc is shown to exhibit a peak in output intensity at ∼ 2 × 10−3 pre-pulse fraction for a 4.5 ns pump delay, with a main pulse pump intensity of ∼ 1.3 × 1013W cm−2 on a 20 mm target. The Zn lasing emission had a duration of ∼ 240 ps and this was insensitive to prepulse fraction. The J = 0–1 XUV laser output for nickel and copper increased monotonically with prepulse fraction, with copper targets showing least sensitivity to either prepulse level or prepulse to main pulse delay. Under the conditions of the study, the pre-pulse level was observed to have no significant influence on the output intensity of the 3p-3s (J = 2−1) lines of any of the elements investigated.

Integrated experiments of fast ignition targets by Gekko-XII and LFEX lasers

Implosion and heating experiments at the Institute of Laser Engineering, Osaka University on Fast Ignition (FI) targets for the FIREX-1 project have been performed with Gekko-XII laser for implosions and LFEX laser for heating. We tried to reduce the prepulse level in the LFEX laser system and have improved the plasma diagnostics to observe the plasma in the harsh hard X-ray environment. A plastic (CD) shell target, 7-μm thick and 500 μm in diameter with a hollow gold cone was used in this experiment to guide the short-pulse laser at the time of the maximum compression. The shell target was imploded with 9 or 12 beams of Gekko-XII laser (527 nm) with energy of 300 J/beam in a 1.5 ns pulse. Two of the four LFEX laser (1053 nm) beams were injected into the inside bottom of the cone with an energy up to 0.7 kJ/beam in a 1.5 ps pulse at the time around the maximum implosion. We have observed neutron enhancement up to 3.5 × 107 with total heating energy of 300 J, which is higher than the yield obtained in the previous experiment in 2002 [R. Kodama et al. Nature 418, 933 (2002)]. We found the estimated heating efficiency is at a level of 10–20%. Fuel heating to 5 keV is expected when the full output of LFEX is used.

Impact of chronic and pulse dilution disturbances on metabolism and trophic structure in a saline Mediterranean stream

Predicting the consequences of global change involves investigating the mechanisms by which anthropogenic stress modifies ecosystem function. In this sense, naturally stressed ecosystems provide a new framework to test hypotheses in such a context. Here, we use a saline stream (Rambla Salada, SE Spain) as a study case to test the general hypothesis that chronic stress has stronger impacts on metabolism and trophic structure than pulse disturbances. We compared two reaches differing in the persistence of dilution stress over the course of 2 years: the chronically disturbed reach was subject to persistent dilution (chronic disturbance) by freshwater inputs from surrounding irrigated crops and presented a dense stand of the common reed Phragmites australis; and the reference reach, which presented pristine conditions. During the first study year, both reaches were affected by several freshwater inputs due to a diversion channel break (pulse disturbance) that significantly decreased conductivity. During the second year, conductivity recovered to mean pre-pulse disturbance levels. Pulse dilution disturbance had no significant effect on production:respiration ratios (P/R), although predator biomasses increased. However, chronic dilution significantly decreased P/R values as well as consumer and producer biomasses. Dilution disturbances had no significant effects on the relative importance of the different functional feeding groups. Isotopic signatures revealed that macroinvertebrates in both reaches relied upon aquatic autotrophs, despite the common reed inputs at the chronically disturbed reach. In summary, this study highlights the relevance of stress persistence and the usefulness of functional measures when aiming to predict disturbance effects. Thus, whilst pulse disturbances had minor effects on ecosystem function, chronic dilution produced biomass depletion and a change from an autotrophic to a heterotrophic ecosystem.