Public Access to U.S. Conservation Land Trust Properties: Results From a National Survey

This article describes the process that yielded the president's 1982 National Urban Policy Report, stressing the role that ideology played in the resulting policy. Issues discussed include the role of the U.S. Department of Housing and Urban Development in the policy formulation process, and the administration's response to a law that is antithetical to its governing philosophy. The article concludes that the national urban policy reports are useful for explaining an administration's general approach to urban policy, but the reports are not action documents. For them to become so, the responsibility for preparing the reports must be shifted from a single agency to the White House.     

网络搜索智能化

不管你选用哪款工具,很快你就能和上网搜索却无功而返的日子说再见了。     

Seasonal bacterial community dynamics in a full-scale enhanced biological phosphorus removal plant

Activated sludge is one of the most abundant and effective wastewater treatment process used to treat wastewater, and has been used in developed countries for nearly a century. In all that time, several hundreds of studies have explored the bacterial communities responsible for treatment, but most studies were based on a handful of samples and did not consider temporal dynamics. In this study, we used the DNA fingerprinting technique called automated ribosomal intergenic spacer region analysis (ARISA) to study bacterial community dynamics over a two-year period in two different treatment trains. We also used quantitative PCR to measure the variation of five phylogenetically-defined clades within the Accumulibacter lineage, which is a model polyphosphate accumulating organism. The total bacterial community exhibited seasonal patterns of change reminiscent of those observed in lakes and oceans. Surprisingly, all five Accumulibacter clades were present throughout the study, and the total Accumulibacter community was relatively stable. However, the abundance of each clade did fluctuate through time. Clade IIA dynamics correlated positively with temperature (ρ = 0.65, p < 0.05) while Clade IA dynamics correlated negatively with temperature (ρ = −0.35, p < 0.05). This relationship with temperature hints at the mechanisms that may be driving the seasonal patterns in overall bacterial community dynamics and provides further evidence for ecological differentiation among clades within the Accumulibacter lineage. This work provides a valuable baseline for activated sludge bacterial community variation.     

Thermal behaviour of poly(lactic acid) in contact with compressed carbon dioxide

BACKGROUND: The thermal behaviour of poly(lactic acid) (PLA) in contact with compressed CO₂ was studied using high‐pressure differential scanning calorimetry. In particular, the effect of annealing below and above the glass transition temperature (T_g) on the glass transition, cold crystallization and melting temperatures was studied systematically as a function of annealing time and pressure. RESULTS: The effect of compressed CO₂ on the thermal properties of PLA is time dependent. Annealing below T_g decreases the temperature and enthalpy of cold crystallization. Similar, but more evident, behaviours are observed when annealing above T_g. Crystallization temperature and enthalpy during cooling decrease with increasing pressure, and the peak is narrower. CONCLUSION: Annealing PLA in the presence of compressed CO₂ accelerates cold crystallization, but retards crystallization during cooling. Copyright © 2009 Society of Chemical Industry     

Dynamics and fragmentation of thick-shelled microbubbles

Localized delivery could decrease the systemic side effects of toxic chemotherapy drugs. The unique delivery agents we examine consist of microbubbles with an outer lipid coating, an oil layer, and a perfluorobutane gas core. These structures are 0.5-12 /spl mu/m in radius at rest. Oil layers of these acoustically active lipospheres (AALs) range from 0.3-1.5 /spl mu/m in thickness and thus the agents can carry a large payload compared to nano-scale drug delivery systems. We show that triacetin-based drug-delivery vehicles can be fragmented using ultrasound. Compared with a lipid-shelled contrast agent, the expansion of the drug-delivery vehicle within the first cycle is similar, and a subharmonic component is demonstrated at an equivalent radius, frequency, and driving pressure. For the experimental conditions explored here, the pulse length required for destruction of the drug-delivery vehicle is significantly greater, with at least five cycles required, compared with one cycle for the contrast agent. For the drug-delivery vehicle, the observed destruction mechanism varies with the initial radius, with microbubbles smaller than resonance size undergoing a symmetric collapse and producing a set of small, equal-sized fragments. Between resonance size and twice resonance size, surface waves become visible, and the oscillations become asymmetrical. For agents larger than twice the resonance radius, the destruction mechanism changes to a pinch-off, with one fragment containing a large fraction of the original volume.     

Nondestructive subharmonic imaging

Ultrasound contrast agent microbubbles are intravascular agents that can be used to estimate blood perfusion. Blood perfusion may be estimated by destroying the bubbles in a vascular bed and observing the refresh of contrast agents back into the vascular bed. Contrast agents can be readily destroyed by traditional imaging techniques. The design of a nondestructive imaging technique is necessary for the accurate quantification of contrast agent refresh. In this work, subharmonic imaging is investigated as a method for nondestructive imaging with the contrast agent microbubble MP1950 (Mallinckrodt, Inc., St. Louis, MO). Optical observation during insonation, in conjunction with a modified Rayleigh-Plesset (R-P) analysis, provides insight into the mechanisms of and parameters required for subharmonic frequency generation. Subharmonic imaging with a transmission frequency that is the same as the resonant frequency of the bubble is shown to require a minimum pressure of insonation that is greater than the experimentally-observed bubble destruction threshold. Subharmonic imaging with a transmission frequency that is twice the resonant frequency of the bubble produces a subharmonic frequency response while minimizing bubble instability. Optimization is performed using optical experimental analysis and R-P analysis     

Inferential structure of the NEO Five-Factor Inventory: Construct validity of the Big Four personality clusters.

Four studies investigated the dimensionality of the NEO Five-Factor Inventory (NEO-FFI; P. T. Costa & R. R. McCrae, 1992). In Study 1, four inferential dimensions and four clusters represented the NEO-FFI when 114 undergraduates freely sorted items into categories. Construct validity for four item-clusters derived from the inferential space was obtained in Study 2 based on self-report with 304 undergraduates. Study 3 validated these inferential clusters using self and peer reports for 420 undergraduates. Study 4 validated the cluster scales for predicting quality of life and significant social and cultural behaviours for 110 undergraduates. Implications for implicit personality theory, the number of dimensions issue in personality, and test construction are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)