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Laser-based compact MeV X-ray sources are useful for a variety of applications such as radiography and active interrogation of nuclear materials. MeV X rays are typically generated by impinging the intense laser onto ~mm-thick high-Z foil. Here, we have characterized such a MeV X-ray source from 120 TW (80 J, 650 fs) laser interaction with a 1 mm-thick tantalum foil. Our measurements show X-ray temperature of 2.5 MeV, flux of 3 × 1012 photons/sr/shot, beam divergence of ~0.1 sr, conversion efficiency of ~1%, that is, ~1 J of MeV X rays out of 80 J incident laser, and source size of 80 m. Our measurement also shows that MeV X-ray yield and temperature is largely insensitive to nanosecond laser contrasts up to 10−5. Also, preliminary measurements of similar MeV X-ray source using a double-foil scheme, where the laser-driven hot electrons from a thin foil undergoing relativistic transparency impinging onto a second high-Z converter foil separated by 50–400 m, show MeV X-ray yield more than an order of magnitude lower compared with the single-foil results.
Although sorghum [Sorghum bicolor (L.) Moench ssp. bicolor] is the fifth most important grain crop in terms of global production, no commercial hybrids carry genetically engineered (GE) traits for resistance to insect pests or herbicides due to regulatory concerns about gene flow to weedy relatives. However, non-GE herbicide resistance currently is being developed in grain sorghum and will likely transfer to related weeds. Monitoring the impact of this new nuclear technology on the evolution and invasiveness of related weeds requires a baseline understanding of the population biology of grain sorghum genes once they transfer to in situ weed populations. We previously characterized the rate of gene flow from grain sorghum to shattercane [Sorghum bicolor (L.) Moench nothosubsp. drummondii (Steud.) de Wet ex. Davidse], a conspecific weed relatively common in North America; as well as the ecological fitness of an F1 population when S. bicolor nothosubsp. drummondii was the maternal parent. Here we report the ecological fitness of a S. bicolor nothosubsp. drummondii × S. bicolor ssp. bicolor F2 population relative to its crop and weed parents. Parental and F2 populations were grown in two Nebraska environments in 2012 and 2013. Traits evaluated included overwinter survival, field emergence, biomass production and partitioning at anthesis, total seed production, and 100-seed weight. Results indicated that F2 traits were generally intermediate between the parents, but more similar to S. bicolor nothosubsp. drummondii than to grain sorghum. The one exception was overwinter survival, which was nearly 0% for both the F2 and the grain sorghum parent in these northern environments. Thus, the frequency of crop alleles stably introgressed into S. bicolor nothosubsp. drummondii populations appears to primarily depend on overwinter survival of the F2 and which selective pressures are imposed upon it by the cropping system. These data provide needed baseline information about the environmental fate of nuclear genetic technologies deployed in this important global crop.
The discovery of the first electromagnetic counterpart to a gravitational wave signal has generated follow-up observations by over 50 facilities world-wide, ushering in the new era of multi-messenger astronomy. In this paper, we present follow-up observations of the gravitational wave event GW170817 and its electromagnetic counterpart SSS17a/DLT17ck (IAU label AT2017gfo) by 14 Australian telescopes and partner observatories as part of Australian-based and Australian-led research programs. We report early- to late-time multi-wavelength observations, including optical imaging and spectroscopy, mid-infrared imaging, radio imaging, and searches for fast radio bursts. Our optical spectra reveal that the transient source emission cooled from approximately 6 400 K to 2 100 K over a 7-d period and produced no significant optical emission lines. The spectral profiles, cooling rate, and photometric light curves are consistent with the expected outburst and subsequent processes of a binary neutron star merger. Star formation in the host galaxy probably ceased at least a Gyr ago, although there is evidence for a galaxy merger. Binary pulsars with short (100 Myr) decay times are therefore unlikely progenitors, but pulsars like PSR B1534+12 with its 2.7 Gyr coalescence time could produce such a merger. The displacement (~2.2 kpc) of the binary star system from the centre of the main galaxy is not unusual for stars in the host galaxy or stars originating in the merging galaxy, and therefore any constraints on the kick velocity imparted to the progenitor are poor.
The SkyMapper Transient survey (SMT) is exploring variability in the southern sky by performing (a) a rolling search to discover and study supernovæ, and (b) a Target of Opportunity programme that uses the robotic SkyMapper Telescope at Siding Spring Observatory. The supernova survey is obtaining a non-targeted sample of Type Ia supernovæ (SNe Ia) at low redshifts, z < 0.1, and studying other interesting transients found with the search strategy. We have a Target of Opportunity programme with an automatic response mechanism to search for optical counterparts to gravitational-wave and fast radio-burst events; it benefits from SkyMapper’s large field of view of 5.7 sq. deg. and a rapid data reduction pipeline.
We present first results of the SMT survey. The SMT pipeline can process and obtain potential candidates within 12 hours of observation. It disentangles real transients from processing artefacts using a machine-learning algorithm. To date, SMT has discovered over 60 spectroscopically confirmed supernovæ, several peculiar objects, and over 40 SNe Ia including one (SNIa 2016hhd) which was found within the first few days of explosion. We have also participated in searches for optical counterparts of gravitational waves, fast radio bursts and other transients, and have published observations of the optical counterpart of the gravitational-wave event GW170817. We also participate in coordinated observations with the Deeper Wider Faster programme, and the Kepler K2 cosmology project.
Recent evidence shows that the serotonin 2A receptor (5-hydroxytryptamine2A receptor, 5-HT2AR) is critically involved in the formation of visual hallucinations and cognitive impairments in lysergic acid diethylamide (LSD)-induced states and neuropsychiatric diseases. However, the interaction between 5-HT2AR activation, cognitive impairments and visual hallucinations is still poorly understood. This study explored the effect of 5-HT2AR activation on response inhibition neural networks in healthy subjects by using LSD and further tested whether brain activation during response inhibition under LSD exposure was related to LSD-induced visual hallucinations.
In a double-blind, randomized, placebo-controlled, cross-over study, LSD (100 µg) and placebo were administered to 18 healthy subjects. Response inhibition was assessed using a functional magnetic resonance imaging Go/No-Go task. LSD-induced visual hallucinations were measured using the 5 Dimensions of Altered States of Consciousness (5D-ASC) questionnaire.
Relative to placebo, LSD administration impaired inhibitory performance and reduced brain activation in the right middle temporal gyrus, superior/middle/inferior frontal gyrus and anterior cingulate cortex and in the left superior frontal and postcentral gyrus and cerebellum. Parahippocampal activation during response inhibition was differently related to inhibitory performance after placebo and LSD administration. Finally, activation in the left superior frontal gyrus under LSD exposure was negatively related to LSD-induced cognitive impairments and visual imagery.
Our findings show that 5-HT2AR activation by LSD leads to a hippocampal–prefrontal cortex-mediated breakdown of inhibitory processing, which might subsequently promote the formation of LSD-induced visual imageries. These findings help to better understand the neuropsychopharmacological mechanisms of visual hallucinations in LSD-induced states and neuropsychiatric disorders.
One of the greatest challenges in crop science worldwide is to generate a balance between crop production and environmental preservation. Agroforestry systems present promising strategies for balancing environmental health and crop production. The aim of this study was to evaluate yield components and the juice quality of five sugarcane crop years cultivated in the understory of Aleurites fordii, in two intercropping systems and a monocropping system. A field experiment was conducted from November 2011 to June 2016 in the city of Frederico Westphalen—Rio Grande do Sul, Brazil. Information generated in this study confirms the viability of the cultivation of sugarcane in agroforestry systems, and provides information for farmers which can be used to assist in the planning of more ideal agroforestry arrangements. Agroforestry systems should consider the benefits of both forest and cultivated plant species. In this study, A. fordii trees had greater growth in the intercrop II system; however, this system promoted reductions in sugarcane yield components due to the lowest relative amount of solar radiation intercepted by sugarcane plants. For sugarcane production, the use of an intercropping system with 12 × 12 m2 arrangements should be prioritized, because it promotes greater sugarcane yields when compared with 6 × 6 m2 intercropping systems; however, significant differences were not observed when the system (12 × 12 m2) was compared with the monocropping system for most of the analyzed variables. This study sought to provide new sustainable alternatives for farmers in order to increase the diversification of rural properties and maintain the preservation of existing agroecosystems.
The discussions about stellar populations and their spatial distribution can be best advanced by studies of special and well defined star types. The study of subdwarf B stars provides great promise: it is relatively easy both to find sdB stars and to determine their physical parameters.
Sublimation (vaporization) of the icy component of a cometary nucleus determines the initial composition of the coma gas as it streams outward and escapes. Photolytic reactions in the inner coma, escape of fast, light species such as atomic and molecular hydrogen, and solar wind interaction in the outer coma alter the chemical composition and the physical nature of the coma gas. Models that describe these interactions must include (1) chemical kinetics, (2) coma energy balance, (3) multifluid flow for the rapidly escaping light components, the heavier bulk fluid, and the plasma with separate temperatures for electrons and the remainder of the gas, (4) transition from a collision dominated inner region to free molecular flow of neutrals in the outer region, (5) pickup of cometary ions by the solar wind, (6) counter and cross streaming of neutrals with respect to the plasma which outside of the contact surface also contains solar wind ions, and (7) magnetic fields carried by the solar wind. Progress on such models is described and results including velocity, temperature, and number density profiles for important chemical species are presented and compared with observations.
In continuation of a series of studies devoted to the dynamics of the solar photosphere and chromosphere we have attempted to further extend the range of heights in the atmosphere towards the transition region by including observations of the He I 10830 line. We have recorded simultaneous time series of He I 10830 and Mg I 8807 spectra in the quiet solar atmosphere using the echelle spectrograph at the German Vacuum Tower Telescope in Izaña, Tenerife. The velocity signal derived from the Doppler shifts of He 10830 clearly reveals oscillatory motions. The intensity of He 10830, on the other hand, is hardly affected by the oscillations. In the cell interior the 3-min oscillations prevail. Longer periods are found ain the cell boundaries of the chromospheric network where He absorption is enhanced. The V–V phase difference spectrum between the oscillations of He 10830 and those of Mg 8807 confirms previous observations of a non-propagating component that dominates the acoustic wave spectrum in the chromosphere.
We sought to comprehensively assess the prevalence and outcomes of complications associated with Staphylococcus aureus bacteremia (SAB) in children. Secondarily, prevalence of methicillin resistance and outcomes of complications from methicillin-resistant S. aureus (MRSA) vs. methicillin-susceptible S. aureus SAB were assessed. This is a single-center cross-sectional study of 376 patients ⩽18 years old with SAB in 1990–2014. Overall, 197 (52%) patients experienced complications, the most common being osteomyelitis (33%), skin and soft tissue infection (31%), and pneumonia (25%). Patients with complications were older (median 3 vs. 0·7 years, P = 0·05) and more had community-associated SAB (66% vs. 34%, P = 0·001). Fewer patients with complications had a SAB-related emergency department or hospital readmission (10% vs. 19%, P = 0·014). Prevalence of methicillin resistance increased from 1990–1999 to 2000–2009, but decreased in 2010–2014. Complicated MRSA bacteremia resulted in more intensive care unit admissions (66% vs. 47%, P = 0·03) and led to increased likelihood of having ⩾2 foci (58% vs. 26%, P < 0·001). From multivariate analysis, community-associated SAB increased risk and concurrent infections decreased risk of complications (odds ratio (OR) 1·82 (1·1–3·02), P = 0·021) and (OR 0·58 (0·34–0·97), P = 0·038), respectively. In conclusion, children with SAB should be carefully evaluated for complications. Methicillin resistance remains associated with poor outcomes but have decreased in overall prevalence.
The SkyMapper 1.3 m telescope at Siding Spring Observatory has now begun regular operations. Alongside the Southern Sky Survey, a comprehensive digital survey of the entire southern sky, SkyMapper will carry out a search for supernovae and other transients. The search strategy, covering a total footprint area of ~2 000 deg2 with a cadence of ⩽5 d, is optimised for discovery and follow-up of low-redshift type Ia supernovae to constrain cosmic expansion and peculiar velocities. We describe the search operations and infrastructure, including a parallelised software pipeline to discover variable objects in difference imaging; simulations of the performance of the survey over its lifetime; public access to discovered transients; and some first results from the Science Verification data.
Targets have been developed to measure supersonic radiation transport in aerogel foams using absorption spectroscopy. The target consists of an aerogel foam uniformly doped with either titanium or scandium inserted into an undoped aerogel foam package. This creates a localized doped foam region to provide spatial resolution for the measurement. Development and characterization of the foams is a key challenge in addition to machining and assembling the two foams so they mate without gaps. The foam package is inserted into a beryllium sleeve and mounted on a gold hohlraum. The target is mounted to a holder created using additive manufacturing and mounted on a stalk. The manufacturing of the components, along with assembly and metrology of the target are described here.
Oxtotitlán Cave paintings have been considered among the earliest in Mesoamerica on stylistic grounds, but confirmation of this hypothesis through absolute dating has not been attempted until now. We describe the application of advanced radiocarbon strategies developed for situations such as caves with high carbon backgrounds. Using a low-temperature plasma oxidation system, we dated both the ancient paint and the biogenic rock coatings that cover the paint layers at Oxtotitlán. Our research has significantly expanded the time frame for the production of polychrome rock paintings encompassing the Early Formative and Late Formative/Early Classic periods, statistically spanning a long era from before ca. 1500 cal B.C. to cal A.D. 600.
The dependency of the Hβ-index on two physical parameters is briefly discussed. The previous calibration of Mv(β) (Fernie, 1965 or Crawford, 1971) is confirmed for main sequence O and B stars; however, the β-values of the later B-supergiants tend to be too large for their absolute magnitudes. The problem of filtering out stars with marginal emission is emphasized.
The Antarctic ice sheet has almost no net annual ablation on its surface, so most mass losses are by iceberg calving along its perimeter, which may be either grounded in shallow water or floating in deep water. An ice cliff forms along the perimeter in both cases. Wave action undercuts ice margins in the tide-water zone along beaches, and causes coastal calving if the rate of undercutting compares with the forward ice velocity. If the ice velocity is sufficiently greater, the ice sheet advances into deeper water and becomes a float at depths of 200 to 300 m (Robin 1979). A floating ice shelf then forms and icebergs calve along the ice front. Iceberg calving along this ice front may be due to several causes (Holdsworth 1977,Robin 1979). Since iceberg calving, either from ice shelves or in the tidewater zone of beaches between ice shelves, is the principal ablation mechanism of the Antarctic ice sheet, it is important to understand calving dynamics quantitatively. This paper presents the results of a finite-element examination of calving along floating margins of the ice sheet.
Universal screening for postpartum depression is recommended in many countries. Knowledge of whether the disclosure of depressive symptoms in the postpartum period differs across cultures could improve detection and provide new insights into the pathogenesis. Moreover, it is a necessary step to evaluate the universal use of screening instruments in research and clinical practice. In the current study we sought to assess whether the Edinburgh Postnatal Depression Scale (EPDS), the most widely used screening tool for postpartum depression, measures the same underlying construct across cultural groups in a large international dataset.
Ordinal regression and measurement invariance were used to explore the association between culture, operationalized as education, ethnicity/race and continent, and endorsement of depressive symptoms using the EPDS on 8209 new mothers from Europe and the USA.
Education, but not ethnicity/race, influenced the reporting of postpartum depression [difference between robust comparative fit indexes (∆*CFI) < 0.01]. The structure of EPDS responses significantly differed between Europe and the USA (∆*CFI > 0.01), but not between European countries (∆*CFI < 0.01).
Investigators and clinicians should be aware of the potential differences in expression of phenotype of postpartum depression that women of different educational backgrounds may manifest. The increasing cultural heterogeneity of societies together with the tendency towards globalization requires a culturally sensitive approach to patients, research and policies, that takes into account, beyond rhetoric, the context of a person's experiences and the context in which the research is conducted.