Multi-camera imaging to characterize jet and liner uniformity on the Plasma Liner Experiment (PLX).

At Plasma Liner Experiment, a set of 36 coaxial plasma guns are deployed quasi-uniformly over a 9 ft diameter spherical chamber and are used to form a high-Z spherically compressive plasma liner. Simulations indicate that for the concept to ultimately achieve optimal target density and temperature, a high degree of timing uniformity is required between all guns. To aid in quantifying and correcting gun-to-gun nonuniformities, a key diagnostic will consist of up to six fisheye-view CCD cameras positioned inside the main chamber such that each has all plasma guns within its view. The individual cameras can be triggered at different times to determine each plasma jet's muzzle velocity and structure for different operating conditions. This camera array is currently under development, and the implementation needs and challenges for this camera array are discussed here. Additionally, we detail the analysis methodology for determining jet-to-jet uniformity deviations and how we can correct them, thereby improving overall liner uniformity.

Experimental Measurements of Ion Diffusion Coefficients and Heating in a Multi-Ion-Species Plasma Shock.

Collisional plasma shocks generated from supersonic flows are an important feature in many astrophysical and laboratory high-energy-density plasmas. Compared to single-ion-species plasma shocks, plasma shock fronts with multiple ion species contain additional structure, including interspecies ion separation driven by gradients in species concentration, temperature, pressure, and electric potential. We present time-resolved density and temperature measurements of two ion species in collisional plasma shocks produced by head-on merging of supersonic plasma jets, allowing determination of the ion diffusion coefficients. Our results provide the first experimental validation of the fundamental inter-ion-species transport theory. The temperature separation, a higher-order effect reported here, is valuable for advancements in modeling HED and ICF experiments.

High-resolution fiber imaging for pulsed power experiments.

This work presents a novel approach for imaging the visible emissions from plasmas in pulsed power experiments using high-resolution plastic optical fibers. The diagnostic consists of a 2 mm diameter core commercial cable constructed of 13 000 individual acrylic fibers. The fibers are fused together to create a single high-resolution bundle. Different designs were investigated to cover a wide range of resolutions and fields of view (3-700 µm and 0.05-45 mm, respectively). The system was tested on the 1-MA Mykonos accelerator at Sandia National Laboratories and successfully imaged visible emission from a hybrid x-pinch target. Diagnostic development and preliminary results are presented.

Distinct Mineralogy and Age of Individual Lava Flows in Atla Regio, Venus Derived From Magellan Radar Emissivity.

NASA's Magellan mission revealed that many Venus highlands exhibit low radar emissivity values at higher altitudes. This phenomenon is ascribed to the presence of minerals having high dielectric constants, produced or stabilized by temperature-dependent chemical weathering between the rocks and the atmosphere. Some large volcanoes on Venus have multiple reductions of radar emissivity at varying altitudes. The authors present morphological maps of major lava flow units at Maat, Ozza, and Sapas montes and compare them to radar emissivity. Sapas has a single reduction in emissivity values at 6,054.6 km, while Maat and Ozza have several reductions at altitudes of 6,052.5-6,056.7 km. Emissivity values are highly spatially correlated to individual lava flows indicating that minerals in the rocks control the emissivity signature. The emissivity patterns at these volcanoes require at least four individual ferroelectric mineral compositions in the rocks that are highly conductive at Curie temperatures of 693-731 K. These temperatures are compatible with chlorapatite and some perovskite oxides. Modeling the minimum volumes of ferroelectrics (10-100s ppm) shows the volume and type of ferroelectric may vary over the lifetime of a single volcano. The modeled volumes of ferroelectrics in Ozza and Sapas are greater than in Maat, consistent with the production of ferroelectrics via weathering over a longer period of time, and supporting the idea that Maat has younger volcanic activity. The stratigraphic relationship of Maat's youngest flows with impact craters may indicate the timeframe of the production of specific ferroelectrics via chemical weathering is over 9-60 Ma.

Low radar emissivity signatures on Venus volcanoes and coronae: New insights on relative composition and age.

Multiple studies reveal that most of Venus highlands exhibit anomalously high radar reflectivity and low radar emissivity relative to the lowlands. This phenomenon is thought to be the result of atmosphere-surface interactions in the highlands, due to lower temperatures. These reactions are a function of rock composition, atmospheric composition, and degree of weathering. We examine the Magellan radar emissivity, altimetry and SAR data for all major volcanoes and coronae on Venus. We characterize and classify edifices according to the pattern of the variation of radar emissivity with altitude. The volcanic highlands can be classified into 7 distinct patterns of emissivity that correspond to at least 3 discrete types of mineralogy based on the altitude (temperature) of the emissivity anomalies. The majority of emissivity anomalies support the hypothesis of a weathering phenomenon at high altitude (>6053 km), but we also find strong emissivity anomalies at lower altitudes that correspond spatially to individual lava flows, indicating variations in mineralogy within an evolving volcanic system. The emissivity signature of tallest volcanoes on Venus are consistent with the presence of ferroelectric minerals in their rocks, while volcanic edifices in western Ishtar Terra and eastern Aphrodite Terra are consistent with the presence of semiconductor minerals. Sapas Mons and Pavlova Corona are also consistent with ferroelectrics, but at a different Curie temperature than the other volcanoes in Atla Regio. The spatial distribution of radar emissivity classes correlates to different geologic settings indicating that different mantle source regions (deep/shallow plumes, and possible convergence zones) may contribute to differences in mineralogy for the studied edifices. Finally, we show that the emissivity signatures of Idunn, Maat and other volcanic edifices are consistent with relatively fresh and unweathered rocks, indicating recent or possibly current volcanism on Venus.

Relationships between cerebral autoregulation and markers of kidney and liver injury in neonatal encephalopathy and therapeutic hypothermia.

OBJECTIVE: We studied whether cerebral blood pressure autoregulation and kidney and liver injuries are associated in neonatal encephalopathy (NE). STUDY DESIGN: We monitored autoregulation of 75 newborns who received hypothermia for NE in the neonatal intensive care unit to identify the mean arterial blood pressure with optimized autoregulation (MAPOPT). Autoregulation parameters and creatinine, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were analyzed using adjusted regression models. RESULTS: Greater time with blood pressure within MAPOPT during hypothermia was associated with lower creatinine in girls. Blood pressure below MAPOPT related to higher ALT and AST during normothermia in all neonates and boys. The opposite occurred in rewarming when more time with blood pressure above MAPOPT related to higher AST. CONCLUSIONS: Blood pressures that optimize cerebral autoregulation may support the kidneys. Blood pressures below MAPOPT and liver injury during normothermia are associated. The relationship between MAPOPT and AST during rewarming requires further study.

Threats to intact tropical peatlands and opportunities for their conservation.

Large, intact areas of tropical peatland are highly threatened at a global scale by the expansion of commercial agriculture and other forms of economic development. Conserving peatlands on a landscape scale, with their hydrology intact, is of international conservation importance to preserve their distinctive biodiversity and ecosystem services and maintain their resilience to future environmental change. We explored threats to and opportunities for conserving remaining intact tropical peatlands; thus, we excluded peatlands of Indonesia and Malaysia, where extensive deforestation, drainage, and conversion to plantations means conservation in this region can protect only small fragments of the original ecosystem. We focused on a case study, the Pastaza-Marañón Foreland Basin (PMFB) in Peru, which is among the largest known intact tropical peatland landscapes in the world and is representative of peatland vulnerability. Maintenance of the hydrological conditions critical for carbon storage and ecosystem function of peatlands is, in the PMFB, primarily threatened by expansion of commercial agriculture linked to new transport infrastructure that is facilitating access to remote areas. There remain opportunities in the PMFB and elsewhere to develop alternative, more sustainable land-use practices. Although some of the peatlands in the PMFB fall within existing legally protected areas, this protection does not include the most carbon-dense (domed pole forest) areas. New carbon-based conservation instruments (e.g., REDD+, Green Climate Fund), developing markets for sustainable peatland products, transferring land title to local communities, and expanding protected areas offer pathways to increased protection for intact tropical peatlands in Amazonia and elsewhere, such as those in New Guinea and Central Africa which remain, for the moment, broadly beyond the frontier of commercial development.

ArI/ArII laser induced fluorescence system for measurement of neutral and ion dynamics in a large scale helicon plasma.

In order to investigate the role of both neutral and ion dynamics in large-scale helicon discharges, a laser induced fluorescence (LIF) system capable of measuring both ArI and ArII fluorescence using a single tunable laser is being developed. The system is based on a >250 mW solid state laser. For ArI measurements, the laser pumps the metastable (2P03/2)4s level to the (2P01/2)4p level using 696.7352 nm light, and fluorescence radiation from decay to the (2P01/2)4s level at 772.6333 nm is observed. For ArII, currently in development, the metastable (3P)3d 4F7/2 level will be pumped to the (3P)4p 4D07/2 level using 688.8511 nm, and decay fluorescence to the (3P)4s 4P5/2 level at 434.9285 nm measured. Here all wavelengths are in a vacuum.

Withholding feeding during transfusion: Standardization of practice and nutritional outcomes in premature infants.

OBJECTIVE: To evaluate the nutritional impact of a feed-holding guideline during transfusion for infants <32 weeks gestation. STUDY DESIGN: A pre-/post-interventional study was conducted after introduction of a guideline to hold feeds during transfusion. Demographic variables in addition to nutritional outcomes were collected on all infants admitted within 48 hours of birth with gestational age <32 weeks. Data was collected during a 6 month period pre-intervention and the 6 month period post-intervention. RESULTS: There were 145 eligible infants. Mean birth weight and gestational age were similar in both periods. In total, 98 infants received transfusions, and 82 of those had an active feeding order prior to at least one transfusion. Total transfusions per infant and transfusions ordered while an infant had active feeding orders were similar in both periods. Time to full feedings was decreased post-intervention (p <  0.001). Weight at 34 weeks, incidence of second IV placement, additional IV fluid use, and hypoglycemia were similar between groups.Of 593 total transfusions, 207 were ordered while an infant had an active order for enteral nutrition. Pre-intervention, 64% of transfusions had feeds held during transfusion. Post-intervention, 87% of transfusions had feeds held during transfusion. Feeds were held more often (p <  0.001) and for a shorter duration (p = 0.005) in the post-intervention group. CONCLUSION: Implementing a guideline standardizing feeding practices during transfusions in premature infants increases standardization of care and results in decreased variability in practice. Adverse nutritional consequences were not found after the introduction of the routine practice of holding feedings during transfusion in preterm infants.

Apparent diffusion coefficient scalars correlate with near-infrared spectroscopy markers of cerebrovascular autoregulation in neonates cooled for perinatal hypoxic-ischemic injury.

BACKGROUND AND PURPOSE: Neurologic morbidity remains high in neonates with perinatal hypoxic-ischemic injury despite therapeutic hypothermia. DTI provides qualitative and quantitative information about the microstructure of the brain, and a near-infrared spectroscopy index can assess cerebrovascular autoregulation. We hypothesized that lower ADC values would correlate with worse autoregulatory function. MATERIALS AND METHODS: Thirty-one neonates with hypoxic-ischemic injury were enrolled. ADC scalars were measured in 27 neonates (age range, 4-15 days) in the anterior and posterior centrum semiovale, basal ganglia, thalamus, posterior limb of the internal capsule, pons, and middle cerebellar peduncle on MRI obtained after completion of therapeutic hypothermia. The blood pressure range of each neonate with the most robust autoregulation was identified by using a near-infrared spectroscopy index. Autoregulatory function was measured by blood pressure deviation below the range with optimal autoregulation. RESULTS: In neonates who had MRI on day of life ≥10, lower ADC scalars in the posterior centrum semiovale (r = -0.87, P = .003, n = 9) and the posterior limb of the internal capsule (r = -0.68, P = .04, n = 9) correlated with blood pressure deviation below the range with optimal autoregulation during hypothermia. Lower ADC scalars in the basal ganglia correlated with worse autoregulation during rewarming (r = -0.71, P = .05, n = 8). CONCLUSIONS: Blood pressure deviation from the optimal autoregulatory range may be an early biomarker of injury in the posterior centrum semiovale, posterior limb of the internal capsule, and basal ganglia. Optimizing blood pressure to support autoregulation may decrease the risk of brain injury in cooled neonates with hypoxic-ischemic injury.

Experimental characterization of the stagnation layer between two obliquely merging supersonic plasma jets.

We present spatially resolved measurements characterizing the stagnation layer between two obliquely merging supersonic plasma jets. Intrajet collisionality is very high, but the interjet ion-ion mean free path is of the order of the stagnation layer thickness of a few centimeters. Fast-framing camera images show a double-peaked emission profile transverse to the stagnation layer, with the central emission dip consistent with a density dip in the interferometer data. We demonstrate that our observations are consistent with collisional oblique shocks.

Absorption and tolerability of aqueous chlorhexidine gluconate used for skin antisepsis prior to catheter insertion in preterm neonates.

OBJECTIVE: To assess chlorhexidine absorption and skin tolerability in premature infants, following skin antisepsis with 2% aqueous chlorhexidine gluconate (CHG) prior to peripherally inserted central catheter (PICC) placement. STUDY DESIGN: Neonates less than 32 weeks gestation had skin cleansed with CHG prior to PICC placement. CHG concentrations were measured on serial blood samples. Skin integrity was evaluated for 2 weeks after CHG exposure. RESULT: Twenty infants were enrolled; median gestational age was 28 2/7 weeks (range 24 3/7 to 31 4/7). Ten infants had detectable serum chlorhexidine concentrations (range 1.6 to 206 ng ml(-1)). Seven of these infants had their highest serum concentration 2 to 3 days following exposure. No CHG-related skin irritation occurred in any infant. CONCLUSION: CHG was detected in the blood of preterm infants receiving CHG skin antisepsis for PICC insertion. Highest serum concentrations occurred 2 to 3 days after exposure. Further investigation is needed to determine the clinical relevance of CHG absorption in preterm infants.

Relationship between cerebrovascular dysautoregulation and arterial blood pressure in the premature infant.

OBJECTIVE: To evaluate cerebrovascular autoregulation as a function of arterial blood pressure (ABP) in the critically ill, premature infant. STUDY DESIGN: A prospective observational pilot study was conducted in two tertiary care Neonatal Intensive-Care Units. Premature infants (n=23, ≤30 weeks estimated gestational age with invasive ABP monitoring) were enrolled and received routine care while undergoing continuous autoregulation monitoring, using the cerebral oximetry index (COx). The COx is a moving, linear correlation coefficient between cortical reflectance oximetry and ABP. COx values were stratified as a function of ABP for individual subject recordings and for the cohort. RESULT: The mean duration of autoregulation monitoring was 3.2 days (median: 2.97, range: 0.61-3.99). A total of 10 of 23 (43%) developed intraventricular hemorrhage and 1 of 23 (4%) developed periventricular leukomalacia by head ultrasound. No association was found between neurologic injury and percentage of the monitoring periods with autoregulation impairment (defined as COx>0.5). Lower ABP was associated with dysautoregulation (higher COx values, P<0.01). The percentage of time with impaired autoregulation was greater with lower ABP (P=0.013, Spearman r=0.51). CONCLUSION: All infants studied had periods with intact and periods with impaired cerebrovascular autoregulation, measured with the COx. Low ABP was associated with impaired autoregulation.

Diagnostics for the plasma liner experiment.

The goal of the Plasma Liner Experiment (PLX) is to explore and demonstrate the feasibility of forming imploding spherical "plasma liners" via merging high Mach number plasma jets to reach peak liner pressures of ∼0.1 Mbar using ∼1.5 MJ of initial stored energy. Such a system would provide HED plasmas for a variety of fundamental HEDLP, laboratory astrophysics, and materials science studies, as well as a platform for experimental validation of rad-hydro and rad-MHD simulations. It could also prove attractive as a potential standoff driver for magnetoinertial fusion. Predicted parameters from jet formation to liner stagnation cover a large range of plasma density and temperature, varying from n(i)∼10(16) cm(-3), T(e)≈T(i)∼1 eV at the plasma gun mouth to n(i)>10(19) cm(-3), T(e)≈T(i)∼0.5 keV at stagnation. This presents a challenging problem for the plasma diagnostics suite which will be discussed.

Design and implementation of a 120 GHz tracking interferometer with near diffraction limited focal spot.

The design and implementation of a 120 GHz monostatic tracking interferometer with near diffraction limited focal spot size, used to measure line-averaged plasma density in the source of a plasma opening switch (POS), is described. Physical dimensions of the switch source place an upper limit on the focal spot size. Focusing quasioptics utilize a standard pyramidal horn and a pair of cylindrical lenses that are easily fabricated. The combination of the two cylindrical lenses transforms the asymmetric and approximately Gaussian beam produced by the pyramidal horn into a small focal spot. The circuit utilizes a tracking receiver configuration to track oscillator frequency drifts, which allow for full heterodyne quadrature operation, while avoiding the added complexity of phase or frequency locking of the sources. In order to reduce system noise in the POS pulsed power environment, all sources and amplifiers are battery powered and other noise-reducing techniques are employed. Finally, an improved Gaussian optics design methodology, which tracks the phase center of the Gaussian beam, is proposed. While not critical to this application, this method may yield improvements in systems with short focal lengths.

Triple probe signal detection electronics for systems lacking a well defined ground.

Triple probes have been used to measure plasma parameters of low temperature and edge plasmas, yielding simultaneous measurements of electron temperature, ion density, and floating potential. Unlike standard Langmuir and double probe techniques, there is no requirement to sweep the probe potential relative to the plasma, thus allowing fast time resolution. However, in some plasma systems "ground" is not well defined with respect to a known ground, may vary strongly in time, or may be at an inconveniently high voltage. The resulting high plasma (or floating) potential requires common mode rejection before the signals can be digitized. A signal detection circuit constructed from inexpensive operational amplifiers and that makes use of a novel floating bias generation configuration is described.

Virulence factors in vancomycin-resistant and vancomycin - susceptible Enterococcus faecalis from Brazil / Fatores de virulência em Enterococcus faecalis resistentes e suscetível à vancomicina isolados no Brasil

Enterococci are members of commensal flora of animals and insects, but are also important opportunistic pathogens. Our objective was to observe if there was any difference of virulence in several groups of E. faecalis, mainly between vancomycin-resistant E. faecalis (VREFS) of colonization and infection. VREFS and vancomycin-sensitive E. faecalis from Brazil were screened for the presence of virulence factor genes. Phenotypic assays were used to assess in vitro expression, to understand the pathogenic potential of these isolates and to determine whether a correlation exists between virulence and antibiotic resistance. Different virulence profiles were found suggesting that the disseminating clone may have generated several variations. However, our study showed that one constellation of traits appeared most commonly: gelatinase, aggregation substance and esp (GEA). These factors are important because they have been implicated in cell aggregation and biofilm formation. Biofilm formation may promote the conjugation of plasmids harboring resistance and virulence genes, enhancing the probability of entry of new resistance genes into species. Curiously, the profile GEA was not exclusive to VREFS, it was the second most observed in VSEFS isolates from colonization and infection in hospitalized patients and also from rectal swabs of healthy volunteers. Such strains appear to represent the entry gateway to new resistance genes into E. faecalis and may contribute to the spreading of E. faecalis mainly in hospitals.

Enterococci são membros da microbiota comensal de animais e insetos, mas também são importantes patógenos oportunistas. Nosso objetivo foi observar se há qualquer diferença na virulência nos diversos grupos de Enterococcus faecalis, principalmente nos E. faecalis resistente à vancomicina (VREFS) isolados de colonização e infecção. VREFS e E. faecalis sensíveis à vancomicina (VSEFS) do Brasil foram pesquisadas quanto a presença de fatores de virulência. Ensaios fenotípicos foram usados para obter a expressão in vivo, entender o potencial patogênico destas amostras e determinar se existe correlação entre virulência e resistência a antibióticos. Diferentes perfis de virulência foram encontrados sugerindo que o clone que está se disseminado pode ter gerado diversas variações. No entanto, nosso estudo mostrou que um conjunto de fatores parece ser mais comum entre as amostras: gelatinase, substância de agregação e esp (GEA). Estes fatores tem sido correlacionados com a agregação de células e formação de biofilmes. A formação de biofilme pode promover a conjugação de plasmídeos contendo genes de resistência entre as espécies. Curiosamente, o perfil GAE não foi exclusivo para VREFS, foi o segundo mais observado em amostras VSEFS provenientes de colonização e infecção em pacientes hospitalizados e também de swabs retais de voluntários saudáveis. Tais linhagens pacerem representar a "porta de entrada" para novos genes de resistência em E. faecalis e podem contribuir para a disseminação de E. faecalis principalmente nos hospitais.

Virulence factors in vancomycin-resistant and vancomycin- susceptible Enterococcus faecalis from Brazil.

Enterococci are members of commensal flora of animals and insects, but are also important opportunistic pathogens. Our objective was to observe if there was any difference of virulence in several groups of E. faecalis, mainly between vancomycin-resistant E. faecalis (VREFS) of colonization and infection. VREFS and vancomycin-sensitive E. faecalis from Brazil were screened for the presence of virulence factor genes. Phenotypic assays were used to assess in vitro expression, to understand the pathogenic potential of these isolates and to determine whether a correlation exists between virulence and antibiotic resistance. Different virulence profiles were found suggesting that the disseminating clone may have generated several variations. However, our study showed that one constellation of traits appeared most commonly: gelatinase, aggregation substance and esp (GEA). These factors are important because they have been implicated in cell aggregation and biofilm formation. Biofilm formation may promote the conjugation of plasmids harboring resistance and virulence genes, enhancing the probability of entry of new resistance genes into species. Curiously, the profile GEA was not exclusive to VREFS, it was the second most observed in VSEFS isolates from colonization and infection in hospitalized patients and also from rectal swabs of healthy volunteers. Such strains appear to represent the entry gateway to new resistance genes into E. faecalis and may contribute to the spreading of E. faecalis mainly in hospitals.

Diathermy versus scalpel incisions for hemiarthroplasty for hip fracture: a randomised prospective trial.

As the age profile of our population expands, we can expect subsequent increase in patients presenting with intracapsular fracture. The onus remains on the surgeon to make all reasonable efforts to find new and innovative means of reducing associated morbidity and mortality of the treatment of these injuries. This challenge is particularly relevant in the elderly and in patients with multiple co-morbidities. In this study, 100 patients were randomly allocated into two groups. One group had dissection to the level of the hip joint under direct diathermy control; the other group had dissection using a scalpel with supplementary electrocautery. Intraoperative total blood loss prior to dissection of the abductors was measured by collecting blood using wound swabs using a local protocol and results were statistically analysed using PROC GLM SAS. We demonstrate a clear advantage in the use of diathermy to create a hip incision showing a significant reduction in wound-related blood loss and a reduction, whilst not statistically significant, in total operative blood loss using diathermy incision. Larger randomised prospective trials are necessary to study the effects of this intervention in a larger patient population so that these end-points can be adequately assessed.

Multilocus sequence typing and analysis of putative virulence factors in vancomycin-resistant and vancomycin-sensitive Enterococcus faecium isolates from Brazil.

Enterococci are leading causes of hospital-acquired infections that are often difficult to treat because of high-level aminoglycoside and glycopeptide resistance. Vancomycin-resistant enterococci are a global problem, and have been isolated with increasing frequency in hospitals in Brazil. The objective of this study was to determine the genetic relatedness of vancomycin-resistant Enterococcus faecium (VREFM) and vancomycin-sensitive E. faecium (VSEFM) isolated from human infections and faecal sources in Brazil, and to compare these isolates with those from domesticated animals. Isolates (n = 56) were classified by multilocus sequence typing (MLST) and assessed for putative virulence traits. The acm gene was detected in 98% of all isolates. The 56 isolates studied comprised 26 different MLST types. VSEFM isolates from the faeces of pigs were found to be distinct from all human isolates characterised previously by MLST, and were assigned new sequence type (ST) numbers. VREFM isolates were represented by four different STs (ST-114, ST-17, ST-281, ST-50). Among the 26 STs identified in this study, eBURST detected three groups of STs with related allelic profiles, and 19 unrelated STs. Among E. faecium isolates from Brazil, the esp gene was restricted to vancomycin-resistant isolates. Furthermore, isolates classified as ST-17 by MLST, an epidemic strain type isolated internationally with the purK-1 gene, were found among VREFM isolates from Brazil that also harboured the esp and hyl genes.