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The National Enforcement Investigations Center of the EPA provides support services for the enforcement activities of the Agency. Recently, we have analyzed hazardous wastes as part of efforts to enforce the Resource Conservation and Recovery Act and the Superfund Act. Sample preparation for inorganic elemental analysis is a difficult and time-consuming step. Thus, it would be desirable to be able to use x-ray fluorescence methods which require relatively little sample preparation for the analysis of solid hazardous wastes. A major problem to be overcome is the need to calibrate for a large variety of samples. However, a compensating factor is that the error will be largely determined by the sampling error and the measurement accuracy is not quite so critical.
Despite improvements in the medical and surgical management of infants with CHD, growth failure before surgery in many infants continues to be a significant concern. A nutritional pathway was developed, the aim of which was to provide a structured approach to nutritional care for infants with CHD awaiting surgery.
Materials and methods
The modified Delphi process was development of a nutritional pathway; initial stakeholder meeting to finalise draft guidelines and develop questions; round 1 anonymous online survey; round 2 online survey; regional cardiac conference and pathway revision; and final expert meeting and pathway finalisation.
Paediatric Dietitians from all 11 of the paediatric cardiology surgical centres in the United Kingdom contributed to the guideline development. In all, 33% of participants had 9 or more years of experience working with infants with CHD. By the end of rounds 1 and 2, 76 and 96% of participants, respectively, were in agreement with the statements. Three statements where consensus was not achieved by the end of round 2 were discussed and agreed at the final expert group meeting.
Nutrition guidelines were developed for infants with CHD awaiting surgery, using a modified Delphi process, incorporating the best available evidence and expert opinion with regard to nutritional support in this group.
Extinction is the complete loss of a species, but the accuracy of that status depends on the overall information about the species. Dracaena umbraculifera was described in 1797 from a cultivated plant attributed to Mauritius, but repeated surveys failed to relocate it and it was categorized as Extinct on the IUCN Red List. However, several individuals labelled as D. umbraculifera grow in botanical gardens, suggesting that the species’ IUCN status may be inaccurate. The goal of this study was to understand (1) where D. umbraculifera originated, (2) which species are its close relatives, (3) whether it is extinct, and (4) the identity of the botanical garden accessions and whether they have conservation value. We sequenced a cpDNA region of Dracaena from Mauritius, botanical garden accessions labelled as D. umbraculifera, and individuals confirmed to be D. umbraculifera based on morphology, one of which is a living plant in a private garden. We included GenBank accessions of Dracaena from Madagascar and other locations and reconstructed the phylogeny using Bayesian and parsimony approaches. Phylogenies indicated that D. umbraculifera is more closely related to Dracaena reflexa from Madagascar than to Mauritian Dracaena. As anecdotal information indicated that the living D. umbraculifera originated from Madagascar, we conducted field expeditions there and located five wild populations; the species’ IUCN status should therefore be Critically Endangered because < 50 wild individuals remain. Although the identity of many botanical garden samples remains unresolved, this study highlights the importance of living collections for facilitating new discoveries and the importance of documenting and conserving the flora of Madagascar.
Carbon nanotube arrays were grown in the presence of an applied mechanical stress (30 min, 60 mN/mm2 mechanical pressure) and dispersed in aqueous solution (0.08 - 2.3 mm2/mL). Optical (450-950 nm) transmission and right angle scattering measurements were performed on these dispersions and on an analogous set of conventional (non-stressed) carbon nanotubes. Results show similar transmission behavior and different right angle scattering dependence on concentration for stress-grown and conventional carbon nanotubes. This investigation provides the first evidence of differentiation between stress-grown and conventional carbon nanotubes in the optical regime, suggesting a point of departure for future applications.
An enormous effort is underway worldwide to attempt to detect gravitational waves. If successful, this will open a new frontier in astronomy. An essential portion of this effort is being carried out in Australia by the Australian Consortium for Interferometric Gravitational Astronomy (ACIGA), with research teams working at the Australia National University, University of Western Australia, and University of Adelaide involving scientists and students representing many more institutions and nations. ACIGA is developing ultrastable high-power continuous-wave lasers for the next generation interferometric gravity wave detectors; researching the problems associated with high optical power in resonant cavities; opening frontiers in advanced interferometry configurations, quantum optics, and signal extraction; and is the world's leader in high-performance vibration isolation and suspension design. ACIGA has also been active in theoretical research and modelling of potential astronomical gravitational wave sources, and in developing data analysis detection algorithms. ACIGA has opened a research facility north of Perth, Western Australia, which will be the culmination of these efforts. This paper briefly reviews ACIGA's research activities and the prospects for gravitational wave astronomy in the southern hemisphere.
Nanoparticles (NP) are introduced in a growing number of commercial products,
including food and beverage, daily use hygiene products such as toothpaste, or
orally-administered drugs. To study the possible toxicity of these nanoparticles, a
model system is the in vitro response of eukaryotic cells to the presence of NP.
However, to understand the observed effects, it is clear that good physical and
chemical characterization of NP, and in particular of their dispersion are needed.
Indeed, the expected effects should be different if the study is dealing with
agglomerates or isolated nanoparticles. For fundamental understanding, it appears
important to work with nanoparticles as well dispersed as possible while being in
relevant biological condition, i.e. cellular culture cell.
In this context, we have studied the dispersion of a very common industrial titania
NP (Degussa P25 produced in ton quantities). When dispersed in water, the suspensions
of NP appear stable for weeks.. When transferred in the cell culture medium (DMEM) or
if directly dispersed in DMEM, strong evolution of size is seen as well as
sedimentation. To address this problem, we have compared different ways, coming from
materials science, of dispersing NP in water with the idea to break in a preliminary
step some of the necks between nanoparticles. The effect of dry ball milling, liquid
ball milling, size of the balls and Ultrasonic dispersion will be compared. The best
results were obtained from high power ultrasonic dispersion. To avoid direct
aggregation, when going to DMEM, a “surfactant” relevant with biological studies
(Foetal Bovine Serum (FBS)) was added in the suspension in order to coat the
nanoparticles prior to transfer in DMEM (or other cell media). The result obtained
with various surfactants and cell media will be presented. It must be noted that our
best results were obtained in the FBS + DMEM medium.
Carbon nanotubes (CNTs) are appealing materials for biomedical applications due to their unique chemical, electrical and mechanical properties. The emphasis of the present work is on controlling the structure and symmetry of carbon nanotubes by imposing an applied stress at the CNT growth site. CNTs were grown under these conditions using standard chemical vapor deposition (CVD) techniques and were subsequently characterized with a scanning electron microscope; the methodology and implications of this approach are discussed herein.
Titanium dioxide has been extensively tested in environmental applications, especially in
separation technologies. In the present study, anatase nanoparticles were synthesized by
using a sol-gel method, and batch adsorption experiments were carried out to analyze
arsenic removal capacity of the anatase nanoparticles from water. The maximum arsenic
removal percentages were found ~ 84 % for As(III) at pH 8 and ~98% for As(V) at pH 3,
respectively, when 5 g/l anatase nanoparticles were used at an initial arsenic
concentration of 1 mg/l. The results of the sorption experiments, which take into
consideration the effects of equilibrium concentration on adsorption capacity, were
analyzed with two popular adsorption models, Langmuir and Freundlich models. From the
comparison of R2 values, the adsorption isotherm for As(III) was fitted
satisfactorily well to the Langmuir equation (R2 > 0.996) while the
adsorption behavior of As(V) on anatase nanoparticles was described better with Freundlich
equation (R2 > 0.991). This study proposes the potential adsorbent material
for water which is contaminated with arsenic species.
Earlier experimental findings concluded that electromigration voids in these meandering stripe test structures were not randomly distributed and that void nucleation frequently occurred sub-surface at the metal/thermal oxide interface. The data showed a strong correlation between void area, void growth rate and stripe segment length . The influence of mechanical stress on electromigration damage in these test structures has been examined by applying tensile stresses to both passivated and unpassivated samples. The stress distributions are calculated using finite element analysis for each of the test conditions. The resulting impact on electrornigration voiding, as well as mechanical stress voiding, and lateral hillock formation is discussed.
We have previously shown greatly enhanced resistance to stressinduced hillock formation through fluorine incorporation in aluminum films. Utilizing relatively low F incorporation (<0.1 atomic %), hillock formation density is reduced ∼10x over pure or similarly Cu-doped aluminum films. Electromigration tests were performed on a matrix of structures with varying topology (step heights and slopes) and fluorine incorporation dose. We find that although F improves the stress-induced hillock formation by an order of magnitude, the electromigration performance of flat structures is only slightly improved with F incorporation. Analyzing various step heights and step slopes, the nonfluorinated Al experienced a decreasing electromigration lifetime with increasing step height. However, the optimally implanted F samples showed almost no lifetime reduction with step coverages over a similar regime. In addition, scanning electron micrographs of the failed samples revealed that the failures of the fluorinated samples differ markedly from the non-fluorinated samples. Finally, SIMS profiles taken on F and Cu (for comparison) implanted samples reveal the fundamentally different nature of the two beneficial components: Cu redistributes relatively easily throughout the Al film to segregate to grain boundaries. In contrast, the F profile is extremely stable with simnilar anneals and provides its beneficial effect by forming a distributed refractory metal-like structure within the interconnect.
There has been some uncertainty as to the impact of fluorine (F) on SiO2 quality and reliability. Several laboratories have shown greatly enhanced quality and reliability with fluorinated oxides, while others have been unable to repeat the results. In addition, the laboratories which have shown enhanced reliability with the fluorinated oxides have differed in their interpretation of the mechanism by which the enhancement occurs. X-ray diffraction stress measurements, partial time dependent dielectric breakdown (TDDB) measurements, SIMS depth profiling, transmission electron microscopy, standard high/low frequency C-V measurements, and hot-carrier aging of variously processed MOSFETs have been used to investigate a variety of fluorinated films. We believe that the apparent lack of consistency of the effects of fluorine on MOSFET reliability between laboratories may be explained by slight variations in the gate polysilicon processing which result in variations in polysilicon morphology. The polysilicon morphology determines both mechanical stress and F diffusion which ultimately impacts interface state density and thus hot carrier reliability.
Velocity and temperature measurements are taken of heat induced surface-tension driven flows in both silicone oil and Fluorinert FC-43. Each fluid is contained in an open rectangular box and heated from above by a single strand of electrically heated nichrome wire suspended slightly above the fluid's surface. Velocity measurements are obtained for both liquids with a laser anemometer system. For silicone oil the general flow pattern is recorded using time-lapse photography. The surface temperature measurements are taken by a radiation thermometer and the bulk temperature distributions are measured by thermocouples. The velocity and temperature measurements are compared with numerical solutions obtained for the present configuration.
A numerical tool is developed to simulate the optical and thermal interactions of selected lasers with precursors and substrates in support of the emerging technology for the direct write of Mesoscopic Integrated Conformal Electronics (MICE). The code couples the Discrete Ordinate Method (DOM) radiation model with the multi-physics computation fluid dynamics code CFD-ACE to predict the conductive and radiative heat transport in the process
This paper provides a brief overview of the numerical model. Selected simulations are presented including comparison with empirical data. The capabilities, limitations, and potential applications of the model with respect to MICE are discussed. Future model enhancements are proposed
A computational model for simulating laser-guided particle deposition process is described. This model solves for the transport of gas and particle phases in a fully coupled manner. The optical forces on the particles are evaluated from Mie theory based on local laser intensity. Simulations were performed for different operating conditions of laser power, ambient pressure, and substrate traverse speed. Simulations revealed potential problems such as particle deflected away from substrate due to ambient air current disturbances, substrate overheating, and optical fiber clogging. Possible solutions for these problems are discussed
A novel quasi-thermodynamic approach is suggested to simulate surface chemistry in III-V compound MOVPE. Blocking of free adsorption sites by methyl radicals is considered as the mechanism limiting the growth rate at low temperatures. This assumption has provided a good reproduction of experimental data on GaAs MOVPE in various types of reactor. The commercial computational fluid dynamics software CFD-ACE™ has been used to perform a detailed threedimensional modeling of AlGaAs and InGaP deposition in an AIX-200 horizontal reactor. The surface model has been incorporated into the code to obtain the growth rate and layer composition distributions over the substrate. Modeling results demonstrate a reasonable agreement with experimental data.
Costly and often highly-flammable chemicals, such as hydrogen and carbon-containing gases, are largely used for carbon supply in current carbon nanotube (CNT) synthesis technologies. To mitigate related economic and safety concerns, we have developed a versatile CNT synthesis sequence, where low-cost and safe-to-handle-and-store waste solid polymers (plastics) are used for in situ generation of hydrogen and carbon-containing gases. Introduction of different waste plastics, such as polyethylene, polypropylene and polystyrene, into a multi-stage pyrolysis/ combustion/synthesis reactor allows for efficient CNT formation. This process is largely exothermic and scalable. It uses low-cost stainless steel screens to serve both as substrates as well as catalysts for CNT synthesis. This technique enables a solution for both waste plastic utilization and sustainable CNT production.
The rapid rate of discovery and development in the nanotechnology field will undoubtedly
increase both human and environmental exposures to engineered nanomaterials. Whether these
exposures pose a significant risk remains uncertain. Despite recent collective progress
there remain gaps in our understanding of the nanomaterials physiochemical properties that
drive or dictate biological responses. The development and implementation of rapid
relevant and efficient testing strategies to assess these emerging materials prior to
large-scale exposures could help advance this exciting field. I present a powerful
approach that utilizes a dynamic in vivo zebrafish embryonic assay to rapidly define the
biological responses to nanomaterial exposures. Early developmental life stages are often
uniquely sensitive to environmental insults, due in part to the enormous changes in
cellular differentiation, proliferation and migration required to form the required cell
types, tissues and organs. Molecular signaling underlies all of these processes. Most
toxic responses result from disruption of proper molecular signaling, thus, early
developmental life stages are perhaps the ideal life stage to determine if nanomaterials
perturb normal biological pathways. Through automation and rapid throughput approaches, a
systematic and iterative strategy has been deployed to help elucidate the nanomaterials
properties that drive biological responses.