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In recent years, the discovery of massive quasars at
has provided a striking challenge to our understanding of the origin and growth of supermassive black holes in the early Universe. Mounting observational and theoretical evidence indicates the viability of massive seeds, formed by the collapse of supermassive stars, as a progenitor model for such early, massive accreting black holes. Although considerable progress has been made in our theoretical understanding, many questions remain regarding how (and how often) such objects may form, how they live and die, and how next generation observatories may yield new insight into the origin of these primordial titans. This review focusses on our present understanding of this remarkable formation scenario, based on the discussions held at the Monash Prato Centre from November 20 to 24, 2017, during the workshop ‘Titans of the Early Universe: The Origin of the First Supermassive Black Holes’.
The search for life in the Universe is a fundamental problem of astrobiology and modern science. The current progress in the detection of terrestrial-type exoplanets has opened a new avenue in the characterization of exoplanetary atmospheres and in the search for biosignatures of life with the upcoming ground-based and space missions. To specify the conditions favourable for the origin, development and sustainment of life as we know it in other worlds, we need to understand the nature of global (astrospheric), and local (atmospheric and surface) environments of exoplanets in the habitable zones (HZs) around G-K-M dwarf stars including our young Sun. Global environment is formed by propagated disturbances from the planet-hosting stars in the form of stellar flares, coronal mass ejections, energetic particles and winds collectively known as astrospheric space weather. Its characterization will help in understanding how an exoplanetary ecosystem interacts with its host star, as well as in the specification of the physical, chemical and biochemical conditions that can create favourable and/or detrimental conditions for planetary climate and habitability along with evolution of planetary internal dynamics over geological timescales. A key linkage of (astro)physical, chemical and geological processes can only be understood in the framework of interdisciplinary studies with the incorporation of progress in heliophysics, astrophysics, planetary and Earth sciences. The assessment of the impacts of host stars on the climate and habitability of terrestrial (exo)planets will significantly expand the current definition of the HZ to the biogenic zone and provide new observational strategies for searching for signatures of life. The major goal of this paper is to describe and discuss the current status and recent progress in this interdisciplinary field in light of presentations and discussions during the NASA Nexus for Exoplanetary System Science funded workshop ‘Exoplanetary Space Weather, Climate and Habitability’ and to provide a new roadmap for the future development of the emerging field of exoplanetary science and astrobiology.
Acute pulmonary embolism is a life-threatening condition and rarely occurs in children. In adults, catheter-directed therapy emerges as a potentially safer and effective therapeutic option. However, there is a paucity of data on the safety and efficacy of catheter-directed therapy for pulmonary embolism in children. We report a single-centred experience of catheter-directed therapy for acute pulmonary embolism in children.
This is a retrospective study of children who had no CHD and underwent catheter-directed therapy at Detroit Medical Center during a 12-year period from 2005 to 2017. Demographic and clinical data associated with pulmonary embolism were collected along with the outcome.
A total of nine patients of median age 16 years with the range from 12 to 20 received catheter-directed therapy for sub-massive (n = 6) and massive pulmonary embolism (n = 3). Among nine patients, one patient received Angiojet thrombectomy and balloon angioplasty, whereas eight patients received catheter-directed thrombolysis using tissue plasminogen activator through infusion catheters (n = 3) or EkoSonic ultrasound-accelerated thrombolysis system (n = 5). In four out of five patients treated with EkoSonic, significant clinical improvement was noticed within 24 hours. Among seven patients who survived, two patients had minor gastrointestinal bleeding with median hospital stay of 8 days with the range from 5 to 24 days, and two patients with massive pulmonary embolism died possibly due to delayed institution of catheter-directed therapy.
Catheter-directed therapy with/without EkoSonic is an emerging alternative therapy for sub-massive and massive pulmonary embolism in children. A timely institution of catheter-directed therapy appeared important to improve the outcome.
Anomalous drainage of the right superior caval vein into the left atrium is a rare congenital anomaly that causes cyanosis and occult infection owing to right-to-left shunting. Transcatheter management of this anomaly is unique and rarely reported. We report a 32-year-old man with a history of brain abscess, who was diagnosed with an anomalous right superior caval vein draining to the left atrium; right upper pulmonary vein and right middle pulmonary vein draining into the inferior portion of the right superior caval vein; and a left superior caval vein draining into the right atrium through the coronary sinus without a bridging vein. Pre-procedural planning was guided by three-dimensional printed model. The right superior caval vein was occluded with a 16-mm Amplatzer muscular Ventricular Septal Defect occluder inferior to the azygous vein, but superior to the entries of right upper and middle pulmonary veins. This diverted the right superior caval vein flow to the inferior caval vein system through the azygos vein in a retrograde manner and allowed the right upper pulmonary vein and right middle pulmonary vein flow to drain into the left atrium normally, achieving exclusion of right-to-left shunting and allowing normal drainage of pulmonary veins into the left atrium. At the 6-month follow-up, his saturation improved from 93 to 97% with no symptoms of superior caval vein syndrome.
Between July of 2012 and December of 2014, 39 patients were enrolled prospectively to investigate the prevalence of glucose transporter 1 (GLUT1) deficiency in a ketogenic diet clinic. None of them had GLUT1 deficiency. All patients seen in the same clinic within the same period were reviewed retrospectively. A total of 18 of these 85 patients had a genetic diagnosis, including GLUT1 deficiency, pathogenic copy number variants, congenital disorder of glycosylation, neuronal ceroid lipofuscinosis type II, mitochondrial disorders, tuberous sclerosis, lissencephaly, and SCN1A-, SCN8A-, and STXBP1-associated epileptic encephalopathies. The prevalence of genetic diagnoses was 21% and prevalence of GLUT1 deficiency was 2.4% in our retrospective cohort study.
Parents may experience anxiety and stress when their children undergo cardiac catheterisation. The goal of this study was to assess the level of anxiety in parents of children undergoing cardiac catheterisation and to identify factors that were associated with level of anxiety.
This was a cross-sectional survey of parents of children who underwent cardiac catheterisation. Anxiety levels were measured using a validated self-report questionnaire – State-Trait Anxiety Inventory, which generates state anxiety scores on the current state of anxiety and trait anxiety scores on the stable aspects of anxiety proneness. One sample t-test was used to compare the data with normative data. Multiple linear regression was used to assess the factors associated with the state score.
A total of 113 parents completed the survey. The mean age of parents was 34.0±7.7 years and the mean age of children undergoing catheterisation was 6.7±5.7 years. Compared with normative data, mean state score was significantly higher in our cohort (p<0.05) despite no difference in the trait score. Final multivariate model showed that the state score was significantly associated with child age group (<1 year [coefficient β 7.2] and 10–18 years [6.3], compared to 1 to <10 years of age [reference]) and history of previous catheterisation (−5.2) (p<0.05).
Concurrent state anxiety level was high among parents of children undergoing cardiac catheterisation, whereas trait anxiety level was not. Higher anxiety was experienced by parents of infants and adolescents without a history of previous catheterisation.
An extensive survey of [CII] line emission has been made with a balloon-borne infrared telescope. It has been found that the emission is diffuse and ubiquitously distributed in general interstellar space.
Spectroscopic observations of CII line emission at 157.7 μm have been made of the Galactic Center region with a Fabry-Perot spectrometer onboard a balloon telescope. Strong emission has been detected ubiquitously in a wide area extending between ± 0.7° in galactic longitude. A ring-like structure is suggested from the double lobed distribution of the emission around the Galactic Center.
Background: The ketogenic diet (KD) is used to treat severe childhood-onset epileptic encephalopathies, such as Infantile Spasms (IS). Unfortunately, limited resources for KD initiation result in treatment delays. We ask if earlier KD treatment of early-onset drug-resistant epilepsy results in better seizure outcomes. Methods: Children who started KD before age 4 years between 2000-present at SickKids Hospital were identified. Six-month seizure outcome was calculated as percent of pre-diet baseline seizure frequency (BSF). Results: 67 children were identified. 30 (44.8%) started KD <2 years old, 37 (55.2%) started KD 2-4 years old. Among <2 years old group, 83.3% achieved 50% reduction in BSF and 36.7% achieved 90% reduction. Among 2-4 year old group, 62.2% achieved 50% reduction in BSF and 24.3% achieved 90% reduction. 38 children had a history of IS; 17 with IS at diet initiation and 21 with past history of IS. 41.2% of the spasms cohort achieved 90% reduction in BSF, compared to 23.8% of the post-spasms cohort. Conclusions: KD was more effective when started before age 2 years than 2-4 years, and more effective in children with IS than in children with past history of IS. A rapid protocol for KD initiation in young infants and children may improve long-term outcomes
We are using the VSOP space VLBI mission to observe a complete sample of Pearson-Readhead survey sources at 4.8 GHz to determine core brightness temperatures and pc-scale jet properties. To date we have imaged 27 of the 31 objects in our sample. Our preliminary results show that the majority of objects contain strong core components that remain unresolved on baselines of 30,000 km. The brightness temperatures of several cores significantly exceed 1012 K, which is indicative of highly relativistically beamed emission. We also find that core brightness temperature is correlated with intraday variability in compact AGNs.
The smoothed profile method is extended to study the rheological behaviour of colloidal dispersions under shear flow by using the Lees–Edwards boundary conditions. We start with a reformulation of the smoothed profile method, a direct numerical simulation method for colloidal dispersions, so that it can be used with the Lees–Edwards boundary condition, under steady or oscillatory-shear flow. By this reformulation, all the resultant physical quantities, including local and total shear stresses, become available through direct calculation. Three simple rheological simulations are then performed for (1) a spherical particle, (2) a rigid bead chain and (3) a collision of two spherical particles under shear flow. Quantitative validity of these simulations is examined by comparing the viscosity with that obtained from theory and Stokesian dynamics calculations. Finally, we consider the shear-thinning behaviour of concentrated colloidal dispersions.
The effect of Hybrid stage 1 palliation for hypoplastic left heart syndrome on right ventricular function is unknown. We sought to compare right ventricular function in normal neonates and those with hypoplastic left heart syndrome before Hybrid palliation and to assess the effect of Hybrid palliation on right ventricular function, using the right ventricular myocardial performance index and the ratio of systolic and diastolic durations.
We carried out a retrospective review of echocardiographic data on 23 infants with hypoplastic left heart syndrome who underwent Hybrid palliation and 35 normal controls. Data were acquired before Hybrid and after Hybrid palliation – post 1, 0–4 days; post 2, 1 week; post 3, 2–3 weeks; post 4, 1–1.5 months following Hybrid palliation.
Myocardial performance index and ratio of systolic and diastolic durations were higher in the pre-Hybrid hypoplastic left heart syndrome group (n=23) – 0.47±0.16 versus 0.25±0.07, p<0.001; 1.59±0.44 versus 1.09±0.14, p<0.0001 – compared with controls (n=35). There was no significant change in the myocardial performance index at any of the post-Hybrid time points. Ratio of systolic and diastolic durations increased significantly 2 weeks after Hybrid – post 3: 2.08±0.62 and post 4: 2.21±0.45 versus pre: 1.59±0.44, p=0.043 and 0.003. There were no significant differences in parameters between sub-groups of infants who died (n=10) and survivors (n=13).
Right ventricular myocardial performance index and ratio of systolic and diastolic durations were significantly higher in infants with hypoplastic left heart syndrome before intervention compared with controls. The ratio of systolic and diastolic durations increased significantly 2 weeks after Hybrid palliation. Our data suggest that infants with hypoplastic left heart syndrome have right ventricular dysfunction before intervention, which worsens over 2 weeks after Hybrid palliation.
Investigation into the phenomenon of resistive switching, a reversible change in electrical resistance by the application of a voltage bias, has given rise to the device fabrication, DC electrical testing, and cross sectional TEM/EELS characterization of nanoscale resistive switching devices. Typically, resistive switching devices are composed of a thin oxide layer between two conductive electrodes where applied bias can alter the resistance states. In a cross-bar array, nonlinearity of device I-V relation is a highly desirable characteristic that helps to mitigate the sneak path current leakage issue. Negative differential resistance (NDR) switching behavior offers such nonlinearity and has been observed in TaOx nanoscale devices utilizing certain electrode materials. To investigate this phenomenon, nanodevices were fabricated by sputtering TaOx onto TiN nanovias capped Nb electrodes. Cross sectional TEM/EELS were performed to reveal the physical and chemical changes in these devices to explore possible origins of nonlinear behavior when these top electrode materials are utilized with TaOx films.
Resistive switching, a reversible change in electrical resistance of a dielectric layer through the application of a voltage bias, has propelled a field of research to form improved non-volatile memory device. Tantalum oxide has been investigated as the dielectric component of resistive switching devices as a leading candidate for a few years. Presented here is a structural and chemical investigation of TaOx devices with 55nm in diameter in the virgin, forming on, and switched off (reset) states for comparison using cross sectional TEM techniques including HRTEM, and EELS to gain further understanding of this material system. The nanodevices imaged in this study were switched below 100µA. Unique features found in this study are in agreement with previous hypotheses made by various researchers based on X-ray fluorescence microscopy of micron-scale devices, indicating a variation in oxygen concentration around the switching area.
Astronomical telescopes continue to demand high-endurance high-reflectivity silver mirrors that can withstand years of exposure in earth-based observatory environments. The University of California Observatories Astronomical Coatings Lab has undertaken development of protected silver coatings suitable for telescope mirrors that maintain high reflectivity at wavelengths from 340 nm through the mid-infrared spectrum. We present promising results of enhanced corrosion barriers using plasma-enhanced atomic layer deposition (PEALD) of aluminum oxide (AlOx) as a top barrier layer. Novel coating recipes developed with ion-assisted electron beam deposition (IAEBD) of materials including yttrium fluoride and oxides of yttrium, tantalum, and silicon are used to compare the endurance of physical vapor deposition-grown barriers with PEALD-grown barriers of similar thickness. Samples of these mirror coatings were covered with conformal layers of AlOx deposited by PEALD using trimethylaluminum as a metal precursor and plasma-activated oxygen as an oxidant gas. Samples of coating recipes with and without PEALD oxide undergo aggressive high temperature/high humidity (HTHH) environmental testing in which samples are exposed to an environment of 80% humidity at 80°C for ten days in a simple test set-up. HTHH testing show visible results suggesting that the PEALD oxide offers enhanced robust protection against chemical corrosion and moisture from an accelerated aging environment. Mirror samples are further characterized by reflectivity/absorption before and after deposition of oxide coatings. AlOx is suitable for many applications and has been the initial material choice for this study.
We present a concept to increase efficiencies utilizing nonlinear elements integrated with our semiconductor nanowire networks. Demonstrated here is power generation with thermoelectric devices made of two nanowire networks, one silicon and one indium phosphide, grown on a mechanically flexible copper substrate. Electron microscopy was utilized to characterize structural integrity of the nanowire networks. Non-linear current-voltage characteristics were observed, which suggests a new platform to increase maximum electrical power generation for a given temperature gradient.
A range of optical and optoelectronic applications would benefit from high refractive index (n), dense and transparent films that guide, concentrate and couple light. However, materials with high n usually have a high optical extinction coefficient (κ) which keeps these materials from being suitable for optical components that require long optical paths. We studied titanium hafnium oxide alloy films to obtain high refractive index (n>2) with minimum optical extinction coefficients (κ < 10−5) over the visible and near IR spectrum (380-930 nm). Titanium hafnium oxide alloys were deposited using pulsed DC reactive magnetron sputtering with and without RF substrate bias on silicon dioxide. For a given deposition condition intended for a specific titanium/hafnium molar fraction ratio, the ion energy of deposition species was explicitly controlled by varying the RF substrate bias. Spectroscopic ellipsometry, transmission electron microscopy (TEM), energy dispersive x-ray spectroscopy (EDS) and atomic force microscopy (AFM) were used to characterize the films. It appears that applying RF substrate bias reduces the nanocrystalline size, changes the surface morphology and increases the refractive index while maintaining comparable titanium/hafnium cation molar fraction. Precise control of the nanostructure of ternary metal oxides can alter their macroscopic properties, resulting in improved optical films.
Chalcogenide materials have regained attention after the recent recognition of the compatibility of transition metal dichalcogenides with graphene. Additionally, there has been a recent appreciation for the rich variety of properties they support due to the anomalies in the materials’ intrinsic band structure. These materials generally have layered structures and weak interlayer connection through the chalcogen layer and its van der Waals type bonding. We have synthesized orthorhombic copper telluride and measured its electrical transport properties. The results of these measurements reveal that the conduction is metallic in both the in-plane and out-of-plane directions. The range of stability of this structure is examined along with the lattice constants. The independence of the resistivity in samples to changes in excess copper indicates that the transport is essentially within the conducting planes. This result shows that the material hosts two-dimensional character likely due to its covalent interlayer bonding.
More than 50% of total input energy is wasted as heat in various industrial processes. If we could harness a small fraction of the waste heat while satisfying the economic demands of cost versus performance, then thermoelectric (TE) power generation could bring substantial positive impacts. To meet these demands single-crystal semiconductor nanowire networks have been investigated as a method to achieve advanced TE devices because of their predicted large reduction in thermal conductivity and increase in power factor.
To further our goal of developing practical and economical TE devices, we designed and developed a material platform that combined a semiconductor nanowire network and a semiconductor thin film integrated directly on a mechanically flexible metallic substrate. We assessed the potential of this platform by using indium phosphide (InP) nanowire networks and a doped poly-silicon (poly-Si) thin film combined on copper sheets. InP nanowires were grown by metal organic chemical vapor deposition (MOCVD). In the nanowire network, InP nanowires were grown in three-dimensional networks in which electrical charges and heat travel under the influence of their characteristic scattering mechanisms over a distance much longer than the mean length of the constituent nanowires. Subsequently, plasma-assisted CVD was utilized to form a poly-Si thin film to prevent electrical shorting when an ohmic copper top contact was made. An additional facet to this design is the utilization of multiple materials to address the various temperature ranges at which each material is most efficient at heat-to-energy conversion. The utilization of multiple materials could enable the enhancement of total power generation for a given temperature gradient. We investigated the use of poly-Si thin films combined with InP nanowires to enhance TE properties. TE power production and challenges of a large area nanowire device on a flexible metallic substrate were presented.
The liver fluke, Opisthorchis viverrini, and the minute intestinal fluke, Haplorchis taichui, are prevalent in many Asian countries. This study analysed the patterns of infections of O. viverrini and H. taichui in Lahanam and Thakhamlien villages (Savannakhet Province, Lao PDR), in two cross-sectional investigations. Out of a total of 207 human participants, post-anthelmintic treatment positivity rates for expelled worms were 170 (82.1%) for H. taichui and 65 (31.4%) for O. viverrini. Both these species co-exist in the study villages. When each parasite was analysed separately, H. taichui infections reached a plateau among people aged >20 years. Opisthorchis viverrini infection rates were highest in the age group 21–30 years, with decreasing infection rates after the age of 30. Our findings indicated that fish-borne trematode infections were more prevalent among adults. Fish, common intermediate hosts, were acquired in the study area for analysis. The examination of 35 species of fish as intermediate hosts found O. viverrini metacercariae in only six species, and these were found mostly during the month of November. Many farmers who live on the rice fields obtain their food from their immediate environment, including these intermediate-host fish, potentially putting them at greater risk of O. viverrini infection. By contrast, H. taichui metacercariae were found in three species of fish obtained from the market, meaning that anyone could consume them and become infected. If people who work in rice fields limit the species of fish they consume, or avoid consuming raw fish during the month of November, they may reduce their risk of O. viverrini infection.