12,166 research outputs found

    Promoting the wider use of electrical vehicles in Hong Kong : a strategic proposal

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    Transport Design Lab, School of DesignInvited conference paper2008-2009 > Academic research: not refereed > Invited conference paperVersion of RecordPublishe

    A Global Database of Surface Urban Heat Island Intensity

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    The urban heat island (UHI) effect - the phenomenon of higher temperatures in urban environments - is one of the most well-known consequences of urbanization on local climate. We develop the simplified urban-extent (SUE) algorithm, a new algorithm to estimate the urban heat island (UHI) intensity at a global scale. This algorithm is implemented on the Google Earth Engine platform and uses satellite-derived images to calculate the surface UHI intensity for over 9500 urban clusters covering 15 years, making this the most comprehensive global UHI database. The data are validated against previous multi-city studies and then used to estimate the diurnal, monthly, and long-term variability in the surface UHI in different climate zones. The global mean surface UHI intensity is 0.85 °C during daytime and 0.55 °C at night. Cities in arid climate zone, in particular, show unique diurnal and seasonal patterns, with higher nighttime surface UHI intensity and two peaks throughout the year. The diurnal variability in surface UHI is highest for the equatorial climate zone (0.88 °C) and lowest for the arid climate zone (0.53 °C). The inter-seasonal range is highest in the snow climate zone and lowest in equatorial climate zone. We also investigate the long-term change in the UHI intensity over 15 years and find an increase in the daytime UHI intensity at the rate of 0.03 °C per decade. We make our new database easily accessible by designing an interactive web portal for the data. The application is built on the Google Earth Engine platform and allows users to query the UHI data of urban areas using a simple interface. Users can generate charts showing the seasonal and long-term trend for individual urban clusters and can then download the data from the web portal. The link to the application and further information about it can be found at: https://yceo.yale.edu/research/global-surface-uhi-explore

    Loop expansion in Yang-Mills thermodynamics

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    We argue that a selfconsistent spatial coarse-graining, which involves interacting (anti)calorons of unit topological charge modulus, implies that real-time loop expansions of thermodynamical quantities in the deconfining phase of SU(2) and SU(3) Yang-Mills thermodynamics are, modulo 1PI resummations, determined by a finite number of connected bubble diagrams.Comment: 15 pages, 2 figures, v5: discussion of much more severely constrained nonplanar situation included in Sec.

    Evolving management for critical pulmonary stenosis in neonates and young infants

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    Over the years, management of critical pulmonary stenosis in young infants has evolved from surgical reconstruction of the right ventricular outflow tract and closed pulmonary valvotomy to transcatheter balloon valvoplasty. Our study aimed at evaluating how the changing policy for management had affected the immediate and long term outcomes of babies with this cardiac lesion. Interventions were made in 34 infants at a median age of 8.5 days (2-90 days). Reconstruction of the right ventricular outflow tract reconstruction was performed in 10 patients, closed pulmonary valvotomy in 13, and balloon valvoplasty in 11. Initial procedure-related mortality was 50%, 15% and 0% respectively. Multivariate analysis revealed transannular patching of the right ventricular outflow tract, and male sex, to be significant factors for death. For the 27 survivors, the ratio of right ventricular to systemic systolic pressure decreased from 1.6 ± 0.3 to 0.3 ± 0.2 after reconstruction of the outflow tract, 1.8 ± 0.5 to 0.8 ± 0.4 after closed valvotomy, and 1.8 ± 0.6 to 0.9 ± 0.3 after balloon valvoplasty. The decrease was significantly greater after patch reconstruction (p=0.025) that required no further reinterventions. The overall rate of reintervention for the survivors was 37% (10/27). The freedom from reintervention after closed valvotomy was 82%, 64% and 51% at 1, 5 and 10 years respectively. The figure remained at 78% at both 1 and 5 years (p=0.66) after balloon valvoplasty. The higher reintervention rate for closed valvotomy corresponded to the significantly greater residual gradient across the pulmonary valve noted on follow-up (p=0.01). Reinterventions included balloon dilation (n=6), reconstruction of the outflow tract (n=4), and 1 each of ligation of an arterial duct and systemic-pulmonary arterial shunting. The risk factor for reintervention was a hypoplastic right ventricle. In conclusion, transcatheter balloon valvoplasty appears to be the optimum initial approach in view of its low mortality, efficacy at relieving the obstruction, and low rate of reintervention. © Greenwich Medical Media Ltd.published_or_final_versio

    Plasmonic Nano-Rotamers with Programmable Polarization-Resolved Coloration

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    3D-shaped artificial Mg nano-rotamers with a programmable dihedral angle between two plasmonic arms, designed to exhibit both programmable linear and circular polarization properties, are presented. The nanoscale physical shadow growth technique offers precise control over the angular alignment in these nanostructures with 1° angular precision, thus controlling their symmetry from achiral C2v and C2h to chiral C2. As a result, they give rise to a wide range of polarization-resolved coloration, spanning from invisible to visible colors with 46% transmission contrast for linear polarization while exhibiting 0.08 g-factor in visible for circular polarization. These nano-rotamers hold great potential for various applications in adaptive photonic filters, memory, and anticounterfeiting devices, benefiting from their tunable plasmonic properties

    EL2 deep donor state in semi-insulating GaAs revealed by frequency dependent positron mobility measurements

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    Positron mobility measurements carried out on semi-insulating GaAs, using the Doppler shift in annihilation radiation technique, show a sharp transition from a high mobility value ∼120 cm2 V-1 s-1 to a lower value ∼45 V-1 s-1 just below room temperature. The temperature of the transition is found to be dependent on the frequency of the applied AC bias. We show that this effect is an artifact due to the thermal ionization of the EL2 deep donor state, which in its ionized state forms a positive space charge that causes the positron to experience large electric fields. This observation suggests a new positron annihilation-based deep-level transient technique applicable to semi-insulating materials. © 1994 The American Physical Society.published_or_final_versio

    Supramolecular gating of guest release from cucurbit[7]uril using de novo design

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    Herein we computationally explore the modulation of the release kinetics of an encapsulated guest molecule from the cucurbit[7]uril (CB7) cavity by ligands binding to the host portal. We uncovered a correlation between the ligand-binding affinity with CB7 and the guest residence time, allowing us to rapidly predict the release kinetics through straightforward energy minimization calculations. These high-throughput predictions in turn enable a Monte-Carlo Tree Search (MCTS) to de novo design a series of cap-shaped ligand molecules with large binding affinities and boosting guest residence times by up to 7 orders of magnitude. Notably, halogenated aromatic compounds emerge as top-ranking ligands. Detailed modeling suggests the presence of halogen-bonding between the ligands and the CB7 portal. Meanwhile, the binding of top-ranked ligands is supported by 1H NMR and 2D DOSY-NMR. Our findings open up possibilities in gating of molecular transport through a nanoscale cavity with potential applications in nanopore technology and controlled drug release

    The role of transesophageal echocardiography in the diagnosis and management of children and young adults with valvar diseases of the left heart

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    Summary The role of transesophageal echocardiography in the diagnosis and management of left-sided cardiac valvar disease in children and young adults was assessed in terms of whether additional information (over transthoracic echocardiography) could be obtained, and whether the added information contributed to the better management of the patients. Between January 1991 to August 1992, 27 consecutive patients were studied. Their age ranged from 2.5 to 20 years (mean 12.7), with body weights ranging between 12 and 60 kg (mean 35.6). Twelve of the children suffered from atrioventricular valvar disease, 13 had predominant aortic valvar lesions and two had mixed valvar pathologies. Additional information was obtained by transesophageal over that of transthoracic echocardiography in 18 children (67%). Transesophageal echocardiography clarified the etiologies or mechanism of valvar regurgitation in eight and seven children with atrioventricular and aortic pathologies, respectively. The technique correctly diagnosed severe mitral regurgitation underestimated by conventional technique, detected a missed eccentric aortic regurgitant jet and convincingly excluded bacterial vegetations in one case each. The investigation contributed to the better management of three children (11%) by providing information that allowed the appropriate choice of therapy. Transesophageal echocardiography, therefore, is a useful technique for the diagnosis and management of valvar disease of the left heart in children and young adults.published_or_final_versio

    Expected Shannon entropy and Shannon differentiation between subpopulations for neutral genes under the finite island model

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    <div><p>Shannon entropy <i>H</i> and related measures are increasingly used in molecular ecology and population genetics because (1) unlike measures based on heterozygosity or allele number, these measures weigh alleles in proportion to their population fraction, thus capturing a previously-ignored aspect of allele frequency distributions that may be important in many applications; (2) these measures connect directly to the rich predictive mathematics of information theory; (3) Shannon entropy is completely additive and has an explicitly hierarchical nature; and (4) Shannon entropy-based differentiation measures obey strong monotonicity properties that heterozygosity-based measures lack. We derive simple new expressions for the expected values of the Shannon entropy of the equilibrium allele distribution at a neutral locus in a single isolated population under two models of mutation: the infinite allele model and the stepwise mutation model. Surprisingly, this complex stochastic system for each model has an entropy expressable as a simple combination of well-known mathematical functions. Moreover, entropy- and heterozygosity-based measures for each model are linked by simple relationships that are shown by simulations to be approximately valid even far from equilibrium. We also identify a bridge between the two models of mutation. We apply our approach to subdivided populations which follow the finite island model, obtaining the Shannon entropy of the equilibrium allele distributions of the subpopulations and of the total population. We also derive the expected mutual information and normalized mutual information (“Shannon differentiation”) between subpopulations at equilibrium, and identify the model parameters that determine them. We apply our measures to data from the common starling (<i>Sturnus vulgaris</i>) in Australia. Our measures provide a test for neutrality that is robust to violations of equilibrium assumptions, as verified on real world data from starlings.</p></div
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