Development of a National Anthropogenic Heating Database with an Extrapolation for International Cities

Given increasing utility of numerical models to examine urban impacts on meteorology and climate, there exists an urgent need for accurate representation of seasonally and diurnally varying anthropogenic heating data, an important component of the urban energy budget for cities across the world. Incorporation of anthropogenic heating data as inputs to existing climate modeling systems has direct societal implications ranging from improved prediction of energy demand to health assessment, but such data are lacking for most cities. To address this deficiency we have applied a standardized procedure to develop a national database of seasonally and diurnally varying anthropogenic heating profiles for 61 of the largest cities in the United Stated (U.S.). Recognizing the importance of spatial scale, the anthropogenic heating database developed includes the city scale and the accompanying greater metropolitan area. Our analysis reveals that a single profile function can adequately represent anthropogenic heating during summer but two profile functions are required in winter, one for warm climate cities and another for cold climate cities. On average, although anthropogenic heating is 40% larger in winter than summer, the electricity sector contribution peaks during summer and is smallest in winter. Because such data are similarly required for international cities where urban climate assessments are also ongoing, we have made a simple adjustment accounting for different international energy consumption rates relative to the U.S. to generate seasonally and diurnally varying anthropogenic heating profiles for a range of global cities. The methodological approach presented here is flexible and straightforwardly applicable to cities not modeled because of presently unavailable data. Because of the anticipated increase in global urban populations for many decades to come, characterizing this fundamental aspect of the urban environment – anthropogenic heating – is an essential element toward continued progress in urban climate assessment

Tuning the Loading and Release Properties of MicroRNA-Silencing Porous Silicon Nanoparticles by Using Chemically Diverse Peptide Nucleic Acid Payloads

Peptide nucleic acids (PNAs) are a class of artificial oligonucleotide mimics that have garnered much attention as precision biotherapeutics for their efficient hybridization properties and their exceptional biological and chemical stability. However, the poor cellular uptake of PNA is a limiting factor to its more extensive use in biomedicine; encapsulation in nanoparticle carriers has therefore emerged as a strategy for internalization and delivery of PNA in cells. In this study, we demonstrate that PNA can be readily loaded into porous silicon nanoparticles (pSiNPs) following a simple salt-based trapping procedure thus far employed only for negatively charged synthetic oligonucleotides. We show that the ease and versatility of PNA chemistry also allows for producing PNAs with different net charge, from positive to negative, and that the use of differently charged PNAs enables optimization of loading into pSiNPs. Differently charged PNA payloads determine different release kinetics and allow modulation of the temporal profile of the delivery process. In vitro silencing of a set of specific microRNAs using a pSiNP-PNA delivery platform demonstrates the potential for biomedical applications

Monitoring of degradation of porous silicon photonic crystals using digital photography

We report the monitoring of porous silicon (pSi) degradation in aqueous solutions using a consumer-grade digital camera. To facilitate optical monitoring, the pSi samples were prepared as one-dimensional photonic crystals (rugate filters) by electrochemical etching of highly doped p-type Si wafers using a periodic etch waveform. Two pSi formulations, representing chemistries relevant for self-reporting drug delivery applications, were tested: freshly etched pSi (fpSi) and fpSi coated with the biodegradable polymer chitosan (pSi-ch). Accelerated degradation of the samples in an ethanol-containing pH 10 aqueous basic buffer was monitored in situ by digital imaging with a consumer-grade digital camera with simultaneous optical reflectance spectrophotometric point measurements. As the nanostructured porous silicon matrix dissolved, a hypsochromic shift in the wavelength of the rugate reflectance peak resulted in visible color changes from red to green. While the H coordinate in the hue, saturation, and value (HSV) color space calculated using the as-acquired photographs was a good monitor of degradation at short times (t  pSi-ch.We acknowledge the financial support from Ministerio de Educación y Ciencia (Spain), Dirección General de Enseñanza Superior (Spain) (CTQ2009-14428-C02-01), and Junta de Andalucía (Spain) (P10-FQM-5974). A.N. wants to acknowledge Fundación Alfonso Martín Escudero for a postdoctoral fellowship. This material is based upon the work supported by the U.S. National Science Foundation under Grant No. DMR-1210417

Gas adsorption and capillary condensation in nanoporous alumina films

"Gas adsorption and capillary condensation of organic vapors are studied by optical interferometry, using anodized nanoporous alumina films with controlled geometry (cylindrical pores with diameters in the range of 10-60 nm). The optical response of the film is optimized with respect to the geometric parameters of the pores, for potential performance as a gas sensor device. The average thickness of the adsorbed film at low relative pressures is not affected by the pore size. Capillary evaporation of the liquid from the nanopores occurs at the liquid-vapor equilibrium described by the classical Kelvin equation with a hemispherical meniscus. Due to the almost complete wetting, we can quantitatively describe the condensation for isopropanol using the Cohan model with a cylindrical meniscus in the Kelvin equation. This model describes the observed hysteresis and allows us to use the adsorption branch of the isotherm to calculate the pore size distribution of the sample in good agreement with independent structural measurements. The condensation for toluene lacks reproducibility due to incomplete surface wetting. This exemplifies the relevant role of the fluid-solid (van der Waals) interactions in the hysteretic behavior of capillary condensation."http://deepblue.lib.umich.edu/bitstream/2027.42/64187/1/nano8_31_315709.pd

Porous Silicon Nanoparticles Embedded in Poly(lactic‐ co ‐glycolic acid) Nanofiber Scaffolds Deliver Neurotrophic Payloads to Enhance Neuronal Growth

Scaffolds made from biocompatible polymers provide physical cues to direct the extension of neurites and to encourage repair of damaged nerves. The inclusion of neurotrophic payloads in these scaffolds can substantially enhance regrowth and repair processes. However, many promising neurotrophic candidates are excluded from this approach due to incompatibilities with the polymer or with the polymer processing conditions. This work provides one solution to this problem by incorporating porous silicon nanoparticles (pSiNPs) that are pre-loaded with the therapeutic into a polymer scaffold during fabrication. The nanoparticle-drug-polymer hybrids are prepared in the form of oriented poly(lactic-co-glycolic acid) nanofiber scaffolds. We test three different therapeutic payloads: bpV(HOpic), a small molecule inhibitor of phosphatase and tensin homolog (PTEN); an RNA aptamer specific to tropomyosin-related kinase receptor type B (TrkB); and the protein nerve growth factor (NGF). Each therapeutic is loaded using a loading chemistry that is optimized to slow the rate of release of these water-soluble payloads. The drug-loaded pSiNP-nanofiber hybrids release approximately half of their TrkB aptamer, bpV(HOpic), or NGF payload in 2, 10, and >40 days, respectively. The nanofiber hybrids increase neurite extension relative to drug-free control nanofibers in a dorsal root ganglion explant assay

Beam Test Performance and Simulation of Prototypes for the ALICE Silicon Pixel Detector

The silicon pixel detector (SPD) of the ALICE experiment in preparation at the Large Hadron Collider (LHC) at CERN is designed to provide the precise vertex reconstruction needed for measuring heavy flavor production in heavy ion collisions at very high energies and high multiplicity. The SPD forms the innermost part of the Inner Tracking System (ITS) which also includes silicon drift and silicon strip detectors. Single assembly prototypes of the ALICE SPD have been tested at the CERN SPS using high energy proton/pion beams in 2002 and 2003. We report on the experimental determination of the spatial precision. We also report on the first combined beam test with prototypes of the other ITS silicon detector technologies at the CERN SPS in November 2004. The issue of SPD simulation is briefly discussed.Comment: 4 pages, 5 figures, prepared for proceedings of 7th International Position Sensitive Detectors Conference, Liverpool, Sept. 200

Improving Livability in Doha: The Role of Neighborhood Microclimates, Land Use, and Materials in Rapidly Urbanizing Regions

Recent evidence suggests that some densely populated areas of the world will be uninhabitable in the coming century due to extreme climate events (e.g. heat waves, atmospheric pollution, and drought) and due to shifts in microclimate and breathable air, which are directly related to livability. With estimates that over 75% of the global population will be living in cities by mid-century, scholars, practitioners, and government officials are asking what cities can do to address the pressing social and environmental challenges that emerge from climate change. They are also seeking to learn how this knowledge may inform policy decisions regarding physical, social, and economic planning to ensure an inviting quality of life and livability in these future places. We believe that we have an unprecedented opportunity to use our knowledge, technology, and social capacities to reduce the likelihood of producing a catastrophic future. This study compares the livability of two seemingly unlikely locations - Doha, Qatar, a capital city on the Arabian Gulf, and Portland, Oregon, an important American city in the Pacific Northwest. These cities are growing at different rates, have diverse cultural histories and varied development patterns, yet are attempting to improve urban livability for citizens in each place and its surrounding region. Through an in-depth examination of the physical changes that have occurred in both places and their corresponding urban climate conditions, especially thermal comfort, we describe the similarities and differences that help to define the challenges facing the management of each. We look specifically at two important empirically-derived measurements of livability: air quality and urban heat island effect. By focusing on these environmental stressors in each place, we are able to evaluate the extent to which different growth and policy drivers have impacted the ability for people to enjoy a desirable quality of life in both cities - different, but appropriate to each. We include as part of our approach a conceptual framework, which describes the coupling of environmental and human conditions for which changes in development patterns have direct implications on the livability of each location. As a result of our analysis, we offer insights about actions that show promise of managing future livability in each city and focus primarily on the ability to manipulate selected aspects of urban form - those characteristics of massing, surface materials, and tree cover that can change the air pollution and urban heat stress experience in each place. We focus specifically on landscape and site scale modifications that show promise of improving air quality and/or reducing urban heat as a stressor. Since cities around the world are looking to nature to provide benefits to city inhabitants, we emphasize the salutary role of green infrastructure. While much is still to be discovered regarding the capacity for cities and their managers to adapt to the emerging challenges of climate change, population growth, and conventional development patterns, yet without sustained and promising actions, the cities that are home to the majority of people today may likely become either obsolete in the coming centuries or present less than desirable living conditions for their future residents. We recognize that while all cities are unique reflections of their unique biophysical, microclimatic, social, cultural, and natural contexts, they also share many similar circumstances and conditions - the identification of which may help policy makers address climate change more effectively. Our conclusions also support the fact that seemingly diverse cities do, in fact, contain similarities in terms of the local, environmental, and urban design conditions that determine air quality and contribute to urban heat island effect.qscienc

Effect of surface interactions on the hysteresis of capillary condensation in nanopores

Gas adsorption and liquid desorption of a number of organic vapors in anodized nanoporous alumina, with controlled geometry (cylindrical pore diameters from 10 to 60 nm), are studied using optical interferometry. The narrow-diameter distribution of disconnected pores allows checking the validity of the (long-predicted but not experimentally verified) Kelvin equation without any adjustable parameters, modeling or other assumptions. Evaporation occurs at liquid-vapor equilibrium according to this equation, whereas condensation occurs from metastable states of the vapor phase by nucleation, enhanced by surface defects inside the nanopores. This produces hysteresis, in qualitative agreement with theoretical models and simulations that use Van der Waals interactions between the fluid and the pore surface. The reproducibility of the hysteresis depends on the strength of these interactions, which play an important role in the dynamics of capillary condensation

The International Urban Energy Balance Models Comparison Project: First Results from Phase 1

A large number of urban surface energy balance models now exist with different assumptions about the important features of the surface and exchange processes that need to be incorporated. To date, no com- parison of these models has been conducted; in contrast, models for natural surfaces have been compared extensively as part of the Project for Intercomparison of Land-surface Parameterization Schemes. Here, the methods and first results from an extensive international comparison of 33 models are presented. The aim of the comparison overall is to understand the complexity required to model energy and water exchanges in urban areas. The degree of complexity included in the models is outlined and impacts on model performance are discussed. During the comparison there have been significant developments in the models with resulting improvements in performance (root-mean-square error falling by up to two-thirds). Evaluation is based on a dataset containing net all-wave radiation, sensible heat, and latent heat flux observations for an industrial area in Vancouver, British Columbia, Canada. The aim of the comparison is twofold: to identify those modeling ap- proaches that minimize the errors in the simulated fluxes of the urban energy balance and to determine the degree of model complexity required for accurate simulations. There is evidence that some classes of models perform better for individual fluxes but no model performs best or worst for all fluxes. In general, the simpler models perform as well as the more complex models based on all statistical measures. Generally the schemes have best overall capability to model net all-wave radiation and least capability to model latent heat flux