The economic value of spatial network accessibility for UK cities: A comparative analysis using the hedonic price approach

Spatial network accessibility was found to be significant when associating with house prices using the hedonic price approach. These results suggest some individuals are willing to pay more for spatial isolation while some individuals will pay more for spatial co-presence. An obvious limitation of earlier research is a lack of comparative analysis between cities. Focusing on a single case study reduces the generalisability of the results and the extent to which different spatial contexts might value accessibility differently. The aim of this research was therefore to study the extent to which spatial network accessibility effects differ across cities in the UK. A hedonic price approach was used to explore the extent to which these differences are related to social-economic-mobility factors. Results show, both visually and quantitatively, the economic value of accessibility, measured using space syntax analysis, differs across geographical regions. The accessibility effect on house price ranges from strongly significant in London to insignificant in Birmingham. In general, the economic effect is weaker in smaller, more car dependent cities, with a greater proportion of the population employed in the manufacturing sector, and is stronger in cities that are denser, more walkable with greater productivity and a greater proportion of residents in the education sector. This exploration therefore suggests that the economic value placed upon urban accessibility may be related to a combination of mobility factors, its urban form and its economic profile. Finally, it appears that city productivity as measured by GVA is correlated with increased value placed upon accessibility

Estimating house price with spatial and land use accessibility components using a data science approach at the national scale

Extensive research had been conducted studying the spatial configuration effects on house price using the hedonic price approach. Previous research has mostly focused on using econometric approaches in estimating house price. With the growing popularity of machine learning methods, there is an opportunity to study this problem from a data science perspective. Following Law et al (2017) which studied how economic value of closeness centrality (integration) differed across cities in England, we conduct here a similar experiment examining these differences using a data science approach. We leveraged on an integrated urban model, a large-scale geographic database to compute a series of land use accessibility and space syntax accessibility measures at the country scale (~120 measures). We then use a compressed set of spatial and land use accessibility components to estimate a set of hedonic price models in England; i. first for the entire country, then ii. for all 22 cities and then iii. for 22 cities individually. We found that spatial and land use accessibility features improve house price prediction accuracy jointly and the improvements are greater when using nonlinear methods. This research serves as a basis on the application of data science approaches in space syntax research for predicting real estate outcomes at the National-Scale

Local Modularity, a measure that characterises street neighbourhood connectivity

Recent research in space syntax has shown the use of community detection methods on the street network dual graph can identify isolated local areas. Leveraging on this characteristic, we propose a new measure called local modularity that tries to capture street neighbourhood connectedness. We examine the measure visually for a number of cities where we found the measure can identify more neighbourhood connectivity. We also then validated the measure by running a network stability experiment where we simulate a network under different forms of attacks; a random attack scenario versus a targeted attack scenario. We found more stable behaviour when removing streets that have higher neighbourhood connectivity than attacking the same network randomly. These results have implications on the spatial design and planning of neighbourhoods and in measuring community severances

Structural Invariance of Sunspot Umbrae Over the Solar Cycle: 1993-2004

Measurements of maximum magnetic flux, minimum intensity, and size are presented for 12 967 sunspot umbrae detected on the NASA/NSO spectromagnetograms between 1993 and 2004 to study umbral structure and strength during the solar cycle. The umbrae are selected using an automated thresholding technique. Measured umbral intensities are first corrected for a confirming observation of umbral limb-darkening. Log-normal fits to the observed size distribution confirm that the size spectrum shape does not vary with time. The intensity-magnetic flux relationship is found to be steady over the solar cycle. The dependence of umbral size on the magnetic flux and minimum intensity are also independent of cycle phase and give linear and quadratic relations, respectively. While the large sample size does show a low amplitude oscillation in the mean minimum intensity and maximum magnetic flux correlated with the solar cycle, this can be explained in terms of variations in the mean umbral size. These size variations, however, are small and do not substantiate a meaningful change in the size spectrum of the umbrae generated by the Sun. Thus, in contrast to previous reports, the observations suggest the equilibrium structure, as testified by the invariant size-magnetic field relationship, as well as the mean size (i.e. strength) of sunspot umbrae do not significantly depend on solar cycle phase.Comment: 17 pages, 6 figures. Published in Solar Physic

Forced Convective Diffusion and Interphase Heat and Mass Transfer: Computations of Radial Functions, Temperature and Concentration Fields, and Presentation of Local and Average Nusselt and Sherwood Numbers

Theoretical calculations have been carried out for forced convective transport for uniform streaming and uniaxial and biaxial extensional axisymmetric flows past single spheres. Homogeneous and heterogeneous chemical reactions, both of first and of second order have also been or are presently being treated. Orthogonality and other properties of Legendre functions have been used, together with introduction of an eigenfunction expansion, to reduce the mathematical description from a partial differential equation with variable coefficients, which is nonlinear for homogeneous second order chemical reactions, to a system of coupled ordinary differential equations for the radial modes. The numerical solutions of the latter have been obtained using the robust, adaptive grid algorithm of Pereyra and Lentini. Plots of the radial functions for given Peclet and Damkohler numbers give insight into the role and interaction of L and of r∞ (the number of terms necessary for convergence of the expansion and the finite radius at which the boundary conditions at infinity are imposed). From the radial modes, local and average Nusselt and Sherwood numbers, as well as the temperature and concentration fields, can be obtained. Plots of radial function families provide new insights that complement physicochemical understanding gained from isocontour plots of the temperature and concentration fields. Plots of local interphase transfer coefficients reflect the behavior of the flux field over the sphere surface and show how the average coefficients arise

Carbon Black Exposure Induces Alterations in Mitochondrial Morphology in Human Lung Cells: A Software-Based Quantitative Analysis

Nanoparticulates of pure carbon, carbon black (CB), are a common atmospheric pollutant in industrialized and heavily populated areas. They are produced primarily via combustion of fossil fuels, and represent a significant health hazard. They are known to worsen asthma and bronchitis when inhaled and to cause inflammation, heart dysfunction, and oxidative stress when incorporated into other organs. The key focal point of this work was to examine markers of stress signaling and cellular dysfunction when human bronchial epithelial cells (16HBE14o-) were exposed to CB particles ranging in size from 70 nm and averaging 130 nm in diameter. BrdU incorporation and DAPI staining studies revealed a 24-hour CB exposure (25 ug/ml and higher) to reduce rates of cell division and to significantly elevate percentages of cells exhibiting apoptotic nuclear morphology. Chronic exposure (24 days) of cells to low doses of CB (5 ug/ml) revealed a significant impact upon both cell division and survival. A central marker for stress signaling in these lung cells was elevation of reactive oxygen species, which rose within 12 hours of CB exposure, consistent with stress signals that induce mitochondrial apoptosis. Sirtuin 1, a stress regulated protein deacetylase in the cytosol, whose levels are known to be destabilized by ROS elevation in stressed cells, displayed no significant change following CB exposure at varied doses. Analysis of mitochondrial dynamics via fluorescence microscopy revealed clear changes in organization and morphology. HBE cells were treated with varying doses of CB, fixed, and analyzed via immunocytochemistry. Mitochondria were labelled using a Tom20 antibody conjugate (Alexa488), while microtubules were assessed with phalloidin (Alexa594). Using software developed in MatLab, mitochondria were analyzed for changes in mitochondrial size and localization. Significant changes were identified with regard to an increase in mitochondrial size, and strong trends were observed in an increased localization preference for the perinuclear region. A discussion of the link between elevated ROS levels and mitochondrial behavior will be discussed

Buoyancy-Driven Heat Transfer During Application of a Thermal Gradient for the Study of Vapor Deposition at Low Pressure Using and Ideal Gas

A mathematical model has been developed to determine heat transfer during vapor deposition of source materials under a variety of orientations relative to gravitational accelerations. The model demonstrates that convection can occur at total pressures as low as 10-2 mm Hg. Through numerical computation, using physical material parameters of air, a series of time steps demonstrates the development of flow and temperature profiles during the course of vapor deposition. These computations show that in unit gravity vapor deposition occurs by transport through a fairly complicated circulating flow pattern when applying heat to the bottom of the vessel with parallel orientation with respect to the gravity vector. The model material parameters for air predict the effect of kinematic viscosity to be of the same order as thermal diffusivity, which is the case for Prandtl number approx. 1 fluids. Qualitative agreement between experiment and the model indicates that 6-(2-methyl-4-nitroanilino)-2,4-hexadiyn-l-ol (DAMNA) at these pressures indeed approximates an ideal gas at the experiment temperatures, and may validate the use of air physical constants. It is apparent that complicated nonuniform temperature distribution in the vapor could dramatically affect the homogeneity, orientation, and quality of deposited films. The experimental test i's a qualitative comparison of film thickness using ultraviolet-visible spectroscopy on films generated in appropriately oriented vapor deposition cells. In the case where heating of the reaction vessel occurs from the top, deposition of vapor does not normally occur by convection due to a stable stratified medium. When vapor deposition occurs in vessels heated at the bottom, but oriented relative to the gravity vector between these two extremes, horizontal thermal gradients induce a complex flow pattern. In the plane parallel to the tilt axis, the flow pattern is symmetrical and opposite in direction from that where the vessel is positioned vertically. The ground-based experiments are sufficient preliminary tests of theory and should be of significant interest regarding vapor deposited films in microgravity

Microbial diversity and activity in the Nematostella vectensis holobiont: insights from 16S rRNA gene sequencing, isolate genomes, and a pilot-scale survey of gene expression

We have characterized the molecular and genomic diversity of the microbiota of the starlet sea anemone Nematostella vectensis, a cnidarian model for comparative developmental and functional biology and a year-round inhabitant of temperate salt marshes. Molecular phylogenetic analysis of 16S rRNA gene clone libraries revealed four ribotypes associated with N. vectensis at multiple locations and times. These associates include two novel ribotypes within the ε-Proteobacterial order Campylobacterales and the Spirochetes, respectively, each sharing 99% 16S rRNA identity with Endozoicomonas elysicola and Pseudomonas oleovorans, respectively. Species-specific PCR revealed that these populations persisted in N. vectensis asexually propagated under laboratory conditions. cDNA indicated expression of the Campylobacterales and Endozoicomonas 16S rRNA in anemones from Sippewissett Marsh, MA. A collection of bacteria from laboratory raised N. vectensis was dominated by isolates from P. oleovorans and Rhizobium radiobacter. Isolates from field-collected anemones revealed an association with Limnobacter and Stappia isolates. Genomic DNA sequencing was carried out on 10 cultured bacterial isolates representing field- and laboratory-associates, i.e., Limnobacter spp., Stappia spp., P. oleovorans and R. radiobacter. Genomes contained multiple genes identified as virulence (host-association) factors while S. stellulata and L. thiooxidans genomes revealed pathways for mixotrophic sulfur oxidation. A pilot metatranscriptome of laboratory-raised N. vectensis was compared to the isolate genomes and indicated expression of ORFs from L. thiooxidans with predicted functions of motility, nutrient scavenging (Fe and P), polyhydroxyalkanoate synthesis for carbon storage, and selective permeability (porins). We hypothesize that such activities may mediate acclimation and persistence of bacteria in a N. vectensis holobiont defined by both internal and external gradients of chemicals and nutrients in a dynamic coastal habitat.Massachusetts Institute of Technology. Department of Civil and Environmental EngineeringNational Science Foundation (U.S.). Graduate Research FellowshipNational Research Foundation of Korea (Fellowship

Coalescence Behavior of Gold Nanoparticles

The tetraoctylammonium bromide (TOAB)-stabilized gold nanoparticles have been successfully fabricated. After an annealing of the as-synthesized nanoparticles at 300 °C for 30 min, the coalescence behavior of gold nanoparticles has been investigated using high-resolution transmission electron microscopy in detail. Two types of coalescence, one being an ordered combination of two or more particles in appropriate orientations through twinning, and the other being an ordered combination of two small particles with facets through a common lattice plane, have been observed