4,938 research outputs found
Three-dimensional Binary Superlattices of Oppositely-charged Colloids
We report the equilibrium self-assembly of binary crystals of
oppositely-charged colloidal microspheres at high density. By varying the
magnitude of the charge on near equal-sized spheres we show that the structure
of the binary crystal may be switched between face-centered cubic, cesium
chloride and sodium chloride. We interpret these transformations in terms of a
competition between entropic and Coulombic forces
MIG gas shielding : Economic savings without detriment to quality
Over the years a number of claims have been made related to potential savings of the shielding gas used in the MIG process. A number of work streams have been set up to consider such areas from a technical and economic standpoint. The use of small helium additions has particular benefits and despite an increase in unit cost, the overriding benefits are achieved in reduced manhour cost. A similar situation has been established when using a high frequency process to switch shielding gases during welding. The outcome from this was very similar to that already described. Overlaid on these has been the increasing use of a technique that visualises actual gas flow during welding by the use of laser backlighting. Some preliminary work in this area is described particularly related to the effect of drafts on the gas distribution. A recent development on the market place is a piece of equipment, which regulates the gas flow automatically and synchronously with the welding current. Gas savings in the region of 50-60% have been obtained. Data has been produced to illustrate these benefits. The potential benefit of developing a computational fluid dynamic model of the gas flow is also described, and early development stages of the model shown. However, there will always exist the very basic management need to minimise leaks from the gas delivery systems
Electronic structure of boron and aluminum -doped layers in silicon
Recent work on atomic-precision dopant incorporation technologies has led to
the creation of both boron and aluminum -doped layers in silicon with
densities above the solid solubility limit. We use density functional theory to
predict the band structure and effective mass values of such layers,
first modeling them as ordered supercells. Structural relaxation is found to
have a significant impact on the impurity band energies and effective masses of
the boron layers, but not the aluminum layers. However, disorder in the
layers is found to lead to significant flattening of the bands in both
cases. We calculate the local density of states and doping potential for these
-doped layers, demonstrating that their influence is highly localized
with spatial extents at most 4 nm. We conclude that acceptor -doped
layers exhibit different electronic structure features dependent on both the
dopant atom and spatial ordering. This suggests prospects for controlling the
electronic properties of these layers if the local details of the incorporation
chemistry can be fine tuned.Comment: Main text 8 pages, 6 figures + Appendices 3 pages, 2 figure
A model for predicting dissolved organic carbon distribution in a reservoir water using fluorescence spectroscopy
A number of water treatment works (WTW) in the north of England (UK) have
experienced problems in reducing the dissolved organic carbon (DOC) present in
the water to a sufficiently low level. The problems are experienced in autumn/
winter when the colour increases and the coagulant dose at the WTW needs to be
increased in order to achieve sufficient colour removal. However, the DOC
content of the water varies little throughout the year. To investigate this
further, the water was fractionated using resin adsorption techniques into its
hydrophobic (fulvic and humic acid fractions) and hydrophilic (acid and non-acid
fractions) components. The fractionation process yields useful information on
the changing concentration of each fraction but is time consuming and labour
intensive. Here, a method of rapidly determining fraction concentration was
developed using fluorescence spectroscopy. The model created used synchronous
spectra of fractionated material compared against bulk water spectra and
predicted the fraction concentrations to within 10% for a specific water. The
model was unable to predict fraction concentrations for waters from a different
watershed
Using Mobile Data and Deep Models to Assess Auditory Verbal Hallucinations
Hallucination is an apparent perception in the absence of real external
sensory stimuli. An auditory hallucination is a perception of hearing sounds
that are not real. A common form of auditory hallucination is hearing voices in
the absence of any speakers which is known as Auditory Verbal Hallucination
(AVH). AVH is fragments of the mind's creation that mostly occur in people
diagnosed with mental illnesses such as bipolar disorder and schizophrenia.
Assessing the valence of hallucinated voices (i.e., how negative or positive
voices are) can help measure the severity of a mental illness. We study N=435
individuals, who experience hearing voices, to assess auditory verbal
hallucination. Participants report the valence of voices they hear four times a
day for a month through ecological momentary assessments with questions that
have four answering scales from ``not at all'' to ``extremely''. We collect
these self-reports as the valence supervision of AVH events via a mobile
application. Using the application, participants also record audio diaries to
describe the content of hallucinated voices verbally. In addition, we passively
collect mobile sensing data as contextual signals. We then experiment with how
predictive these linguistic and contextual cues from the audio diary and mobile
sensing data are of an auditory verbal hallucination event. Finally, using
transfer learning and data fusion techniques, we train a neural net model that
predicts the valance of AVH with a performance of 54\% top-1 and 72\% top-2 F1
score
Atoms-to-Circuits Simulation Investigation of CNT Interconnects for Next Generation CMOS Technology
In this study, we suggest a hierarchical model to
investigate the electrical performance of carbon nanotube (CNT)-
based interconnects. From the density functional theory, we have
obtained important physical parameters, which are used in TCAD
simulators to obtain the RC netlists. We then use these RC netlists
for the circuit-level simulations to optimize interconnect design in
VLSI. Also, we have compared various CNT-based interconnects
such as single-walled CNTs, multi-walled CNTs, doped CNTs, and
Cu-CNT composites in terms of conductivity, ring oscillator delay,
and propagation time delay
Improving Underrepresented Minority Student Persistence in STEM.
Members of the Joint Working Group on Improving Underrepresented Minorities (URMs) Persistence in Science, Technology, Engineering, and Mathematics (STEM)-convened by the National Institute of General Medical Sciences and the Howard Hughes Medical Institute-review current data and propose deliberation about why the academic "pathways" leak more for URM than white or Asian STEM students. They suggest expanding to include a stronger focus on the institutional barriers that need to be removed and the types of interventions that "lift" students' interests, commitment, and ability to persist in STEM fields. Using Kurt Lewin's planned approach to change, the committee describes five recommendations to increase URM persistence in STEM at the undergraduate level. These recommendations capitalize on known successes, recognize the need for accountability, and are framed to facilitate greater progress in the future. The impact of these recommendations rests upon enacting the first recommendation: to track successes and failures at the institutional level and collect data that help explain the existing trends
Closing the Nuclear Fuel Cycle with a Simplified Minor Actinide Lanthanide Separation Process (ALSEP) and Additive Manufacturing
Expanded low-carbon baseload power production through the use of nuclear fission can be enabled by recycling long-lived actinide isotopes within the nuclear fuel cycle. This approach provides the benefits of (a) more completely utilizing the energy potential of mined uranium, (b) reducing the footprint of nuclear geological repositories, and (c) reducing the time required for the radiotoxicity of the disposed waste to decrease to the level of uranium ore from one hundred thousand years to a few hundred years. A key step in achieving this goal is the separation of long-lived isotopes of americium (Am) and curium (Cm) for recycle into fast reactors. To achieve this goal, a novel process was successfully demonstrated on a laboratory scale using a bank of 1.25-cm centrifugal contactors, fabricated by additive manufacturing, and a simulant containing the major fission product elements. Americium and Cm were separated from the lanthanides with over 99.9% completion. The sum of the impurities of the Am/Cm product stream using the simulated raffinate was found to be 3.2âĂâ10â3âg/L. The process performance was validated using a genuine high burnup used nuclear fuel raffinate in a batch regime. Separation factors of nearly 100 for 154Eu over 241Am were achieved. All these results indicate the process scalability to an engineering scale
Assessment of genetic structure among Australian east coast populations of snapper Chrysophrys auratus (Sparidae)
Snapper Chrysophrys auratus is a high-value food fish in Australia targeted by both commercial and recreational fisheries. Along the east coast of Australia, fisheries are managed under four state jurisdictions (Queensland, Qld; New South Wales, NSW; Victoria, Vic.; and Tasmania, Tas.), each applying different regulations, although it is thought that the fisheries target the same biological stock. An allozyme-based study in the mid-1990s identified a weak genetic disjunction north of Sydney (NSW) questioning the single-stock hypothesis. This study, focused on east-coast C. auratus, used nine microsatellite markers to assess the validity of the allozyme break and investigated whether genetic structure exists further south. Nine locations were sampled spanning four states and over 2000Â km, including sites north and south of the proposed allozyme disjunction. Analyses confirmed the presence of two distinct biological stocks along the east coast, with a region of genetic overlap around Eden in southern NSW, ~400Â km south of the allozyme disjunction. The findings indicate that C. auratus off Vic. and Tas. are distinct from those in Qld and NSW. For the purpose of stock assessment and management, the results indicate that Qld and NSW fisheries are targeting a single biological stock.
Health-Related Factors Associated with Mode of Travel to Work
Active commuting (AC) to the workplace is a potential strategy for incorporating physical activity into daily life and is associated with health benefits. This study examined the association between health-related factors and mode of travel to the workplace. Methods. A volunteer convenience sample of employed adults completed an online survey regarding demographics, health-related factors, and the number of times/week walking, biking, driving, and using public transit to work (dichotomized as no walk/bike/drive/PT and walk/bike/drive/PT 1 + x/week). Logistic regression was used to predict the likelihood of each mode of transport and meeting PA recommendations from AC according to demographics and health-related factors. Results. The sample was aged 43.5 11.4 years and was primarily White (92.7%) and female (67.9%). Respondents reported walking (7.3%), biking (14.4%), taking public transit (20.3%), and driving (78.3%) to work at least one time/week. Among those reporting AC, 9.6% met PA recommendations from AC alone. Mode of travel to work was associated with several demographic and health-related factors, including age, number of chronic diseases, weight status, and AC beliefs. Discussion. Mode of transportation to the workplace and health-related factors such as disease or weight status should be considered in future interventions targeting AC
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