Nanoparticle Growth via Concentration Gradients Generated by Enzyme Nanopatterns

Biomineralizing organisms can grow nanomaterials with unexpected morphologies in an organic matrix where temporal and vectorial gradients of crystal growth precursors are established. Here, concentration gradients for the crystallization of gold nanoparticles are generated and applied on silicon substrates. Gradients of crystal growth precursors are generated by enzymes patterned as lines that are separated by distances ranging from the micro‐ to the nanoscale. The concentration of crystallization precursors around the lines separated by nanometric distances is not only determined by mass transport and enzyme activity but also by the nanoscale organization of biocatalysts. This nanoscale organization favors non‐classical crystal growth conditions that lead to the formation of nanoparticle clusters containing nanocrystals that are highly crystallographically aligned. The combination of bottom‐up crystal growth with top‐down electron beam lithography enables the fabrication of micrometric patterns containing gold nanoparticles of different size, shape, and surface density. These are all critical parameters that determine the physical properties of these nanomaterials.     

Toward the Determination of Joint Volatility-Hygroscopicity Distributions: Development and Response Characterization for Single-Component Aerosol

This work presents the development and characterization of a thermodenuder for the study and interpretation of aerosol volatility. Thermodenuder measurements are further combined with a continuous-flow streamwise thermal gradient CCN counter to obtain the corresponding aerosol hygroscopicity. The thermodenuder response function is characterized with monodisperse aerosol of variable volatility and hygroscopicity. The measurements are then interpreted with a comprehensive instrument model embedded within an optimization framework to retrieve aerosol properties with constrained uncertainty. Special attention is given to the interpretation of the size distribution of the thermodenuded aerosol, deconvoluting the effects of impurities and multiple charging, and to simplifications on the treatment of thermodenuder geometry, temperature, the cooling section, and the effects of curvature and accommodation coefficient on inferred particle volatility. Retrieved vapor pressures are consistent with published literature and shown to be most sensitive to uncertainty in the accommodation coefficient.

Copyright 2014 American Association for Aerosol Research     

Precise dental ablation using ultra-short-pulsed 1552 nm laser

A desktop diode pulsed laser having pulse width of 1.3 ps and wavelength of 1552 nm is utilized for precise targeted ablation of dentin, enamel, and composite material while minimizing thermal damage to the surrounding healthy tissue and nerve endings. A thermal imaging camera is used to measure the dental surface temperature rise during ablation. Following ablation, scanning electron microscopy (SEM) and optical microscopy are used to determine the quality of ablation and the volumetric ablation rate as a function of laser parameters. Surface temperature measurements are compared with the numerical modeling results obtained using the transient heat conduction equation. A good agreement between experimental and modeling results for the surface temperature is obtained which ensures accurate prediction of the temperature distribution throughout the tooth using numerical models. The SEM generates images of precise ablation of each dental material when the optimal laser parameters are used and the sample is scanned at a velocity to limit the number of overlapping pulses. During the ablation process there is minimal collateral damage to the surrounding healthy tissue and minimal heat spread throughout the tooth thus preserving the integrity of the pulp.     

智利建筑的形式及其对材料的使用

设计中对材料的选择表明设计者重视物理与文化地理的联系，重视技术变化、环境问题和项目的预算。在智利，设计过程中何时以及如何选择材料说明了智利的设计哲学与其他国家的差异。随着新的经济发展和社会的开放，建筑设计中出现了新的实验。一些建筑师努力应用本国样式或地方性材料作为发现新形式的基础；一些建筑师使用标准化的尺寸和特定材料以降低建筑成本：     

Getting into the Living Memory Box: Family archives & holistic design

Digital archives of personal memories are becoming increasingly technically feasible, but there remain significant interaction design challenges. In this paper, we present a research and design study of the Living Memory Box, a device and service to assist families in preserving memories in a variety of media forms. Through a series of ethnographic interviews, design activities and focus groups, we have developed recommendations for the design and development of future personal memory systems and appliances. These improvements must be considered by future researchers in the coordination of multiple disciplines toward successful holistic systems.     

Child influences on adult controls: An experimental investigation.

A major assumption of Bell's (1977) model of parent–child bidirectionality is that the members of dyadic systems behave in ways that maintain an equilibrium. When a member's behavior falls below a lower threshold, the other member elicits increased behavior (lower-limit control). Similarly, when a member's behavior surpasses an upper threshold, the other acts to reduce this excessive behavior (upper-limit control). An observational method was used to assess the effects of lower-limit and upper-limit child behaviors on adult controls. Two 10-year-old child confederates, trained in conduct-problem and anxious-withdrawn roles, interacted with 32 mothers in a semistructured play situation. Multivariate and univariate statistical analyses revealed that mothers exhibited more stimulating controls (helping and rewards) in the anxious-withdrawn condition and more restrictive controls (ignoring, commands, and discipline) in the conduct-problem condition. Analyses of behavioral sequences indicated specific effects of the child's role that suggest that mothers responded more to cognitive sets they developed during the interaction than to the child's actual behavior. The results supported Bell's model of bidirectionality. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Transparency and trust as antecedents to perceptions of commitment to stated diversity goals.

Student perceptions of their university's commitment to its stated diversity goals impact important outcomes on campus. Perceptions that the university is committed to its stated diversity goals decreases perceptions of racial tensions on campus, while perceptions that the university is not committed to its stated diversity goals causes a host of negative outcomes for students, including higher perceptions of hostility and discrimination. Using a sample of 360 students at a small university, the current study addresses the relationships between trust, breach of obligations, transparency, and perceptions of the university's commitment to stated diversity goals. Results indicate that transparency and trust are important to building and maintaining the perception that the university is committed to its stated diversity goals. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Ammunition is the principal source of lead accumulated by California condors re-introduced to the wild

The endangered California Condor (Gymnogyps californianus) was reduced to a total population of 22 birds by the end of 1982. Their captive-bred descendants are now being released back into the wild in California, Arizona, and Baja California, where monitoring indicates they may accumulate lead to toxic levels. Fragments of ammunition in the carcasses of game animals such as deer, elk, and feral pigs not retrieved by hunters or in gut piles left in the field have been considered a plausible source of the lead, though little direct evidence is available to support this hypothesis. Here, we measured lead concentrations and isotope ratios in blood from 18 condors living in the wild in central California, in 8 pre-release birds, and in diet and ammunition samples to determine the importance of ammunition as a source of exposure. Blood lead levels in pre-release condors were low (average 27.7 ng/mL, SD 4.9 ng/ mL) and isotopically similar to dietary and background environmental lead in California. In contrast, blood lead levels in free-flying condors were substantially higher (average 246 ng/mL, SD 229 ng/mL) with lead isotopic compositions that approached or matched those of the lead ammunition. A two-endmember mixing model defined by the background 207Pb/206Pb ratio of representative condor diet samples (0.8346) and the upper 207Pb/206Pb ratio of the ammunition samples (0.8184) was able to account for the blood lead isotopic compositions in 20 out of the 26 live condors sampled in this study (i.e., 77%). Finally, lead in tissues and in a serially sampled growing feather recovered postmortem from a lead-poisoned condor in Arizona evidence acute exposure from an isotopically distinct lead source. Together, these data indicate that incidental ingestion of ammunition in carcasses of animals killed by hunters is the principal source of elevated lead exposure that threatens the recovery in the wild of this endangered species.