2,712 research outputs found
The impact of sea-level rise on tidal characteristics around Australia
An established tidal model, validated for present-day conditions, is used to
investigate the effect of large levels of sea-level rise (SLR) on tidal
characteristics around Australasia. SLR is implemented through a uniform
depth increase across the model domain, with a comparison between the
implementation of coastal defences or allowing low-lying land to flood. The
complex spatial response of the semi-diurnal M2 constituent does not
appear to be linear with the imposed SLR. The most predominant features of
this response are the generation of new amphidromic systems within the Gulf
of Carpentaria and large-amplitude changes in the Arafura Sea, to the north
of Australia, and within embayments along Australia's north-west coast.
Dissipation from M2 notably decreases along north-west Australia but is
enhanced around New Zealand and the island chains to the north. The diurnal
constituent, K1, is found to decrease in amplitude in the Gulf of
Carpentaria when flooding is allowed. Coastal flooding has a profound impact
on the response of tidal amplitudes to SLR by creating local regions of
increased tidal dissipation and altering the coastal topography. Our results
also highlight the necessity for regional models to use correct open boundary
conditions reflecting the global tidal changes in response to SLR.</p
Radius Dependent Luminosity Evolution of Blue Galaxies in GOODS-N
We examine the radius-luminosity (R-L) relation for blue galaxies in the Team
Keck Redshift Survey (TKRS) of GOODS-N. We compare with a volume-limited, Sloan
Digital Sky Survey sample and find that the R-L relation has evolved to lower
surface brightness since z=1. Based on the detection limits of GOODS this can
not be explained by incompleteness in low surface-brightness galaxies. Number
density arguments rule out a pure radius evolution. It can be explained by a
radius dependent decline in B-band luminosity with time. Assuming a linear
shift in M_B with z, we use a maximum likelihood method to quantify the
evolution. Under these assumptions, large (R_{1/2} > 5 kpc), and intermediate
sized (3 < R_{1/2} < 5 kpc) galaxies, have experienced Delta M_B =1.53
(-0.10,+0.13) and 1.65 (-0.18, +0.08) magnitudes of dimming since z=1. A simple
exponential decline in star formation with an e-folding time of 3 Gyr can
result in this amount of dimming. Meanwhile, small galaxies, or some subset
thereof, have experienced more evolution, 2.55 (+/- 0.38) magnitudes. This
factor of ten decline in luminosity can be explained by sub-samples of
starbursting dwarf systems that fade rapidly, coupled with a decline in burst
strength or frequency. Samples of bursting, luminous, blue, compact galaxies at
intermediate redshifts have been identified by various previous studies. If
there has been some growth in galaxy size with time, these measurements are
upper limits on luminosity fading.Comment: 34 Total pages, 15 Written pages, 19 pages of Data Table, 13 Figures,
accepted for publication in Ap
Interaction between U/UO2 bilayers and hydrogen studied by in-situ X-ray diffraction
This paper reports experiments investigating the reaction of H with
uranium metal-oxide bilayers. The bilayers consist of 100 nm of
epitaxial -U (grown on a Nb buffer deposited on sapphire) with a
UO overlayer of thicknesses of between 20 and 80 nm. The oxides were made
either by depositing via reactive magnetron sputtering, or allowing the uranium
metal to oxidise in air at room temperature. The bilayers were exposed to
hydrogen, with sample temperatures between 80 and 200 C, and monitored via
in-situ x-ray diffraction and complimentary experiments conducted using
Scanning Transmission Electron Microscopy - Electron Energy Loss Spectroscopy
(STEM-EELS). Small partial pressures of H caused rapid consumption of the
U metal and lead to changes in the intensity and position of the diffraction
peaks from both the UO overlayers and the U metal. There is an
orientational dependence in the rate of U consumption. From changes in the
lattice parameter we deduce that hydrogen enters both the oxide and metal
layers, contracting the oxide and expanding the metal. The air-grown oxide
overlayers appear to hinder the H-reaction up to a threshold dose, but
then on heating from 80 to 140 C the consumption is more rapid than for the
as-deposited overlayers. STEM-EELS establishes that the U-hydride layer lies at
the oxide-metal interface, and that the initial formation is at defects or
grain boundaries, and involves the formation of amorphous and/or
nanocrystalline UH. This explains why no diffraction peaks from UH
are observed. {\textcopyright British Crown Owned Copyright 2017/AWE}Comment: Submitted for peer revie
COVID‐19: Facemasks, healthcare policies and risk factors in the crucial initial months of a global pandemic
Previous pandemics have shown that facemask use becomes highly popular in public settings due to fear of the disease spreading. There is, however, a lack of strong scientific evidence that facemasks can significantly reduce the spread of respiratory diseases and as such, most governing policies do not mandate these coverings. There is a stark contrast between the policies and acceptance of facemasks across different geographies. In this work, several data sources have been thoroughly analysed to elucidate how viral diseases are transmitted and spread with particular emphasis on the novel SARS‐CoV‐2 virus which is causing an outbreak of COVID‐19. The different types of facemasks and respirators are also explained, the nature of their design and their efficacy is also examined. Several key factors which have been hypothesised to contribute to the spread of viral infections are elaborated in detail including the effect of temperature and humidity, public transportation systems, population density, socio‐economics and sociology. In this work, data are analysed to explain how the disease is spread, how facemasks function and the differences in the number of initial cases based on several contributing factors to the spread of disease. There are also some dangers in automatically recommending community facemask wearing, such as a reduction in the immune system functionality from the reduced exposure to microbes and the disposal issues which result from the large‐scale use of such materials. The questions of whether facemasks are useful in a community setting or if they divert valuable material away from critical healthcare providers are discussed
Electrosprayed nanoparticle delivery system for controlled release
This study utilises an electrohydrodynamic technique to prepare core-shell lipid nanoparticles with a tunable size and high active ingredient loading capacity, encapsulation efficiency and controlled release. Using stearic acid and ethylvanillin as model shell and active ingredients respectively, we identify the processing conditions and ratios of lipid:ethylvanillin required to form nanoparticles. Nanoparticles with a mean size ranging from 60 to 70 nm at the rate of 1.37 × 109 nanoparticles per minute were prepared with different lipid:ethylvanillin ratios. The polydispersity index was ≈ 21% and the encapsulation efficiency ≈ 70%. It was found that the rate of ethylvanillin release was a function of the nanoparticle size, and lipid:ethylvanillin ratio. The internal structure of the lipid nanoparticles was studied by transmission electron microscopy which confirmed that the ethylvanillin was encapsulated within a stearic acid shell. Fourier transform infrared spectroscopy analysis indicated that the ethylvanillin had not been affected. Extensive analysis of the release of ethylvanillin was performed using several existing models and a new diffusive release model incorporating a tanh function. The results were consistent with a core-shell structure
Reaction-induced surface reconstruction of silver in contact with zirconium
When two solid metals are in contact at high temperature, interdi usion occurs leading in some cases to the growth of intermetallic compounds. The study of nucleation, growth and properties of these intermetallic compounds are of interest since it can be critical for many applications in industries. Yet, the e ect of these reactions on the initial surfaces of both metals is not well understood and particularly when surfaces are not perfectly flat and for short contact time. The purpose of the present study is to demonstrate that the growth of an intermetallic compound layer between to solid metals can lead to the surface reconstruction of one of them. The silver–zirconium system will be presented in order to illustrate this new phenomenon. The e ect of contact point on the di usion- reaction process has been modelled by patterning the Zr surface. The nucleation and growth of the intermetallic compounds occur along the contact points which leads to silver surface reconstruction with the growth of the preferential crystal planes f 111 g ad f 100 g . A model explaining this new phenomenon is developed based on the minimisation of Gibbs energy and the di usion rates af both Ag & Zr atoms in the binary system Ag / Zr
Continuation method for nonlinear complementarity problems via normal maps
Cataloged from PDF version of article.In a recent paper by Chen and Mangasarian (C. Chen, O.L. Mangasarian, A class of smoothing functions for
nonlinear and mixed complementarity problems, Computational Optimization and Applications 2 (1996), 97±138) a
class of parametric smoothing functions has been proposed to approximate the plus function present in many optimization
and complementarity related problems. This paper uses these smoothing functions to approximate the normal
map formulation of nonlinear complementarity problems (NCP). Properties of the smoothing function are investigated
based on the density functions that de®nes the smooth approximations. A continuation method is then proposed to
solve the NCPs arising from the approximations. Su cient conditions are provided to guarantee the boundedness of
the solution trajectory. Furthermore, the structure of the subproblems arising in the proposed continuation method
is analyzed for di erent choices of smoothing functions. Computational results of the continuation method are
reported. Ó 1999 Elsevier Science B.V. All rights reserved
Micro- and Nanomanufacturing for Biomedical Applications and Nanomedicine: A Perspective
Almost a century's dedicated research into micro- and nanomaterials has yielded fruitful development of preparation methods, achieving fine control over product properties among a broad spectrum of materials. One critical application of these materials lies within the healthcare sector for diagnostic, prophylactic, and therapeutic purposes. However, bench-to-bedside translations are still hindered by some unmet demands, especially the scaling-up from lab-scale preparation to industry-level production. The current review recapitulates the strategies of micro- and nanomaterial preparation from a holistic viewpoint. The similarities in synthesis and processing methods for various types of materials are highlighted. Furthermore, patents of commercialized nanomedicines are revisited to reveal a solid progress of micro- and nanomanufacturing in the last decade. In conclusion, further interdisciplinary research between fields in materials manufacturing is beneficial for the clinical translation and eventually unleashing the power of materials at small dimensions
GRAIN PROPERTIES OF COMET C/1995 O1 (HALE-BOPP)
We present the analysis of 7.6-13.2 μm infrared (IR) spectrophotometry (R 250) of comet C/1995 O1 (Hale-Bopp), in conjunction with concurrent observations that extend the wavelength coverage of the spectral energy distribution from near- to far-infrared wavelengths. The observations include temporal epochs preperihelion (1996 October and 1997 February UT), near perihelion (1997 April UT), and postperihelion (1997 June UT). Through the modeling of the thermal emission from small, amorphous carbon grains and crystalline and amorphous silicate grains in Hale-Bopp's coma, we find that as the comet approached perihelion, the grain size distribution (the Hanner modified power law) steepened (from N = 3.4 preperihelion to N = 3.7 near and postperihelion), along with an increase in the fractal porosity of larger (greater than 1 μm) grains. The peak of the grain size distribution remained constant (ap = 0.2 μm) at each epoch. We attribute the emergence of the 9.3 μm peak near perihelion to crystalline orthopyroxene grains released during epochs of high jet activity. Crystalline silicates (olivine and orthopyroxene) make up about 30% (by mass) of the submicron-sized (≤1 μm) dust grains in Hale-Bopp's coma during each epoch
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