Reconciling transport models across scales: the role of volume exclusion

Diffusive transport is a universal phenomenon, throughout both biological and physical sciences, and models of diffusion are routinely used to interrogate diffusion-driven processes. However, most models neglect to take into account the role of volume exclusion, which can significantly alter diffusive transport, particularly within biological systems where the diffusing particles might occupy a significant fraction of the available space. In this work we use a random walk approach to provide a means to reconcile models that incorporate crowding effects on different spatial scales. Our work demonstrates that coarse-grained models incorporating simplified descriptions of excluded volume can be used in many circumstances, but that care must be taken in pushing the coarse-graining process too far

RESIDENTS’ PREFERENCE FOR A PROPOSED PARKING FACILITY IN DAVAO CITY: A CONJOINT ANALYSIS

The study explored the clients’ preferences for a proposed parking facility in the central business district of Davao City by using the conjoint analysis method to determine the relative performance and the best combination of the parking attributes as preferred by clients, namely: parking structure, accessibility, safety and security, amenities, and parking fees.  A quantitative market research design was applied.  The analysis of data utilized the IBM SPSS software to identify the order of relative importance of the chosen attributes and the additive model to measure the total utility of a parking facility by calculating the sum of the constant and the utility estimate of each attribute level with the highest value.  The results revealed that the respondents in Davao City prefer a parking facility that is automated multi-level parking, equipped with internet-connected intelligent parking and CCTV surveillance systems, a parking facility near to car washing areas and coffee shops, and a parking fee priced at P30.00 for the 1st 3 hours.  The findings of the study served as a reference to prospective investors and businessmen who would be interested to know how the market behaves in relation to the attributes necessary in a proposed parking facility to address the parking problems in Davao City, and to achieve a better transportation management system to improve the quality of life of people, the economy, and the environment.  Article visualizations

Temperature-dependent vacancy formation during the growth of Cu on Cu(001)

URL:http://link.aps.org/doi/10.1103/PhysRevB.66.195413 DOI:10.1103/PhysRevB.66.195413X-ray diffraction measurements show that a large number of vacancies are incorporated in thin Cu films grown on Cu(001) at low temperatures. At any given deposition temperature between 110 and 160 K, the vacancy concentration cv, obtained from reflectivity data, does not change with the coverage Θ, for 2.5ML<~Θ<~20ML. However, cv is temperature dependent: for 15-ML-thick films, grown at different temperatures, it monotonically decreases with increasing T from cv≈2% at 110 K to zero at T=160K. A different “cv vs T” dependence is observed for films grown at 110 K and then annealed at progressively higher temperatures. Here cv≈2% persists over a broad temperature interval (between 110 and 200 K) and cv exhibits a slower decrease upon heating, reaching zero at 300 K.Support is acknowledged from the National Science Foundation under Contract Nos. ~P.W.S.! DMR-9202528 and ~P.F.M., C.E.B.! DMR-9623827 and the Midwest Superconductivity Consortium ~MISCON! under DOE Grant No. DEFG02-90ER45427. The SUNY X3 beamline is supported by the DOE, under Contract No. DE-FG02-86ER45231 and the NSLS is supported by the DOE, Division of Material Sciences and Division of Chemical Sciences

Temperature dependence of surface roughening during homoepitaxial growth on Cu(001)

URL:http://link.aps.org/doi/10.1103/PhysRevB.64.125427 DOI:10.1103/PhysRevB.64.125427X-ray scattering has been used to study the roughening of the Cu(001) surface during homoepitaxial growth, as a function of temperature. Between 370 and 160 K, the mean-square roughness σ2, obtained from specular reflectivity data, was found to increase as a power law σ2=Θ2β for coverages Θ, ranging from 3 to 96 ML. The roughening exponent β was observed to depend on the temperature of the substrate: it monotonically increases with decreasing temperature from β≈1/3 at T=370K to β≈1/2, at T=200K. At 110 K a smoother growth re-enters in the presence of a large vacancy concentration in the deposited film.Support is acknowledged from the National Science Foundation under contracts ~P.W.S.! DMR-9202528 and~P.F.M. and C.E.B.! DMR-9623827 and the Midwest Superconductivity Consortium ~MISCON! under DOE Grant No. DH-FG02-90ER45427. The SUNY X3 beamline was supported by the DOE, under Contract No. DE-FG02-86ER45231, and the NSLS was supported by the DOE, Division of Material Sciences, and Division of Chemical Sciences. We thank Ian Robinson for the Cu crystal and for valuable discussions

Thermal expansion of the Ag(111) surface measured by x-ray scattering

URL:http://link.aps.org/doi/10.1103/PhysRevB.63.113404 DOI:10.1103/PhysRevB.63.113404We have investigated the structure of the Ag(111) surface, for temperatures between 300 and 1100 K (90% of the bulk melting point), using synchrotron x-ray diffraction. Our data show no evidence of the anomalously large surface thermal expansion previously reported by medium-energy ion-scattering [Phys. Rev. Lett. 72, 3574 (1994)]. At all temperatures we find that the interlayer separations at the surface differ from their bulk counterparts by less than 1%, indicating that the surface expands similarly to the underlying bulk crystal. This behavior is in good agreement with results from molecular dynamics simulations.Support is acknowledged from the National Science Foundation under Contract Nos. ~PWS! DMR-9202528 and ~PFM, CEB, WCE! DMR-9623827 and the Midwest Superconductivity Consortium ~MISCON! under DOE Grant No. DE-FG02-90ER45427. The SUNY X3 beam line is supported by the DOE, under Contract No. DE-FG02-86ER45231, and the NSLS was supported by the DOE, Division of Material Sciences and Division of Chemical Sciences

Vacancy formation in homoepitaxially grown Ag films and its effect on surface morphology

URL:http://link.aps.org/doi/10.1103/PhysRevB.66.075418 DOI:10.1103/PhysRevB.66.075418Synchrotron x-ray diffraction was used to investigate the low-temperature homoepitaxial growth on Ag(001) and Ag(111) surfaces. For both orientations, the Ag films deposited at T=100K were observed to exhibit a 1% surface-normal compressive strain, indicating that an appreciable vacancy concentration (∼2%) is incorporated in the growing film. Concomitantly with the incorporation of vacancies, the growth on Ag(111) leads to the formation of pyramidlike structures with a non-Gaussian distribution of heights, whereas a similar effect was not observed for Ag(001).Support is acknowledged from the National Science Foundation under Contract ~P.W.S.! No. DMR-9202528 and ~P.F.M., C.E.B., W.C.E.! No. DMR-9623827 and the Midwest Superconductivity Consortium ~MISCON! under DOE Grant No. DE-FG02-90ER45427. The SUNY X3 beam line is supported by the DOE, under Contract No. DE-FG02-86ER45231, and the NSLS is supported by the DOE, Division of Material Sciences and Division of Chemical Sciences

Biomechanical, ultrastructural, and electrophysiological characterization of the non-human primate experimental glaucoma model.

Laser-induced experimental glaucoma (ExGl) in non-human primates (NHPs) is a common animal model for ocular drug development. While many features of human hypertensive glaucoma are replicated in this model, structural and functional changes in the unlasered portions of trabecular meshwork (TM) of laser-treated primate eyes are understudied. We studied NHPs with ExGl of several years duration. As expected, ExGl eyes exhibited selective reductions of the retinal nerve fiber layer that correlate with electrophysiologic measures documenting a link between morphologic and elctrophysiologic endpoints. Softening of unlasered TM in ExGl eyes compared to untreated controls was observed. The degree of TM softening was consistent, regardless of pre-mortem clinical findings including severity of IOP elevation, retinal nerve fiber layer thinning, or electrodiagnostic findings. Importantly, this softening is contrary to TM stiffening reported in glaucomatous human eyes. Furthermore, microscopic analysis of unlasered TM from eyes with ExGl demonstrated TM thinning with collapse of Schlemm's canal; and proteomic analysis confirmed downregulation of metabolic and structural proteins. These data demonstrate unexpected and compensatory changes involving the TM in the NHP model of ExGl. The data suggest that compensatory mechanisms exist in normal animals and respond to elevated IOP through softening of the meshwork to increase outflow