A microfluidic approach for development of hybrid collagen-chitosan extracellular matrix-like membranes for on-chip cell cultures

To advance organ-on-a-chip development and other areas befitting from physiologically-relevant biomembranes,a microfluidic platform is presented for synthesis of biomembranes during gelation and investigation into their role as extracellular matrix supports.In this work,high-throughput studies of collagen,chitosan,and collagen-chitosan hybrid biomembranes were carried out to characterize and compare key properties as a function of the applied hydrodynamic conditions during gelation.Specifically,depending on the biopolymer material used,varying flow conditions during biomembrane gelation caused width,uniformity,and swelling ratio to be differently affected and controllable.Finally,cell viability studies of seeded fibroblasts were conducted,thus showing the potential for biological applications.     

Speaking rate from proximal and distal contexts is used during word segmentation.

A series of eye-tracking and categorization experiments investigated the use of speaking-rate information in the segmentation of Dutch ambiguous-word sequences. Juncture phonemes with ambiguous durations (e.g., [s] in 'eens (s)peer,' “once (s)pear,” [t] in 'nooit (t)rap,' “never staircase/quick”) were perceived as longer and hence more often as word-initial when following a fast than a slow context sentence. Listeners used speaking-rate information as soon as it became available. Rate information from a context proximal to the juncture phoneme and from a more distal context was used during on-line word recognition, as reflected in listeners' eye movements. Stronger effects of distal context, however, were observed in the categorization task, which measures the off-line results of the word-recognition process. In categorization, the amount of rate context had the greatest influence on the use of rate information, but in eye tracking, the rate information's proximal location was the most important. These findings constrain accounts of how speaking rate modulates the interpretation of durational cues during word recognition by suggesting that rate estimates are used to evaluate upcoming phonetic information continuously during prelexical speech processing. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Relations between in-treatment and follow-up abstinence among cocaine-dependent homeless persons in three clinical trials.

Clinical trials with cocaine-dependent outpatients have found a strong relation between in-treatment and follow-up abstinence, and the strength of this relation is constant across treatment conditions with variable efficacy in generating abstinence. The authors conducted secondary analyses of data from 3 clinical trials to determine whether this relation generalizes to cocaine-dependent homeless persons. The 3 trials (total N = 543) were conducted in a community health care facility for homeless people. The 7 treatment arms across the 3 trials were combinations of day treatment, abstinence-contingent housing, and vocational training. Drug use was measured with urine toxicology testing. Consecutive weeks of abstinence during treatment were strongly related to abstinence at the 12-month follow-up, whether or not missing 12-month data were included in the analysis. The treatment arms differed in their efficacy in generating abstinence, but the relation between in-treatment and follow-up abstinence did not differ across treatment arms. These results replicate earlier reports of these relations and extend them to a population of homeless people. The lack of differences between treatment arms in the in-treatment–follow-up abstinence relation implies that that relation is independent of the treatment-specific intervention components that generate group differences in abstinence. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ion irradiation induced nanocrystal formation in amorphous Zr55Cu30Al10Ni5 alloy

Ion irradiation can be used to induce partial crystallization in metallic glasses to improve their surface properties. We investigated the microstructural changes in ribbon Zr₅₅Cu₃₀Al₁₀Ni₅ metallic glass after 1 MeV Cu-ion irradiation at room temperature, to a fluence of 1.0 × 10¹⁶ cm⁻². In contrast to a recent report by others that there was no irradiation induced crystallization in the same alloy [S. Nagata, S. Higashi, B. Tsuchiya, K. Toh, T. Shikama, K. Takahiro, K. Ozaki, K. Kawatusra, S. Yamamoto, A. Inouye, Nucl. Instr. and Meth. B 257 (2007) 420], we have observed nanocrystals in the as-irradiated samples. Two groups of nanocrystals, one with diameters of 5–10 nm and another with diameters of 50–100 nm are observed by using high resolution transmission electron microscopy. Experimentally measured planar spacings (d-values) agree with the expectations for Cu₁₀Zr₇, NiZr₂ and CuZr₂ phases. We further discussed the possibility to form a substitutional intermetallic (Ni_xCu_1−x)Zr₂ phase.     

The Effect of Simultaneously Developing Flow on Heat Transfer in Rectangular Tubes

A study of heat transfer in simultaneously developing flow through rectangular tubes is presented in this article. Heat transfer coefficients were measured for three different tube sizes and shapes (D h = 2.21 mm, f = 0.050; D h = 3.02 mm, f = 0.108; and D h = 1.74 mm, f = 0.029), which correspond to typical dimensions used in automotive heat exchangers. For each of these tubes, several different tube lengths were tested to measure the effect of developing flow on the Nusselt number. The results demonstrate that developing flow enhances Nusselt numbers, especially for short tubes. For the geometry range studied, the effect of aspect ratio was not very significant. Heat transfer correlations that accounted for the effects of Reynolds number (118 < Re < 10,671) Prandtl number (6.48 < Pr < 16.20), and bulk-to-wall property variations (0.243 < w b / w w < 0.630), and geometric features such as tube length, hydraulic diameter, and aspect ratio, were developed from the data.     

A New Experimental Design to Study the Kinetics of Solid Dissolution into Liquids at Elevated Temperature

Metallurgical and Materials Transactions B - A new method was developed to study the dissolution of a solid cylinder in a liquid under forced convection at elevated temperature. In the new design,...     

Defining resilience for the US building industry

ABSTRACT

Initiatives to operationalize the concept of resilience in the building industry are rapidly emerging. The concept of resilience has introduced a way to explore solutions to some important problems in the building industry. However, much of the work that has taken place to date represents activities generally assigned to risk management, which is discussed as being inherently insufficient for sustaining the functions of the built environment under stresses. This commentary considers the opportunities and limitations for mainstreaming resilience into building industry processes and actors. Barriers include indeterminate analytical meaning, event and performance uncertainty, immature regulatory standards setting, and untested enterprise economics. Further, the multiple outcomes of recovery and the relationship between building recovery and adaptation are discussed and, along with economics of resilience investments, a research need highlighted. A simple heuristic is presented to illustrate the complement of resilience to risk management and advance the integration of resilience into existing industry workflows.     

Three-dimensional vortex wake structure of flapping wings in hovering flight

Flapping wings continuously create and send vortices into their wake, while imparting downward momentum into the surrounding fluid. However, experimental studies concerning the details of the three-dimensional vorticity distribution and evolution in the far wake are limited. In this study, the three-dimensional vortex wake structure in both the near and far field of a dynamically scaled flapping wing was investigated experimentally, using volumetric three-component velocimetry. A single wing, with shape and kinematics similar to those of a fruitfly, was examined. The overall result of the wing action is to create an integrated vortex structure consisting of a tip vortex (TV), trailing-edge shear layer (TESL) and leading-edge vortex. The TESL rolls up into a root vortex (RV) as it is shed from the wing, and together with the TV, contracts radially and stretches tangentially in the downstream wake. The downwash is distributed in an arc-shaped region enclosed by the stretched tangential vorticity of the TVs and the RVs. A closed vortex ring structure is not observed in the current study owing to the lack of well-established starting and stopping vortex structures that smoothly connect the TV and RV. An evaluation of the vorticity transport equation shows that both the TV and the RV undergo vortex stretching while convecting downwards: a three-dimensional phenomenon in rotating flows. It also confirms that convection and secondary tilting and stretching effects dominate the evolution of vorticity.     

Contribution of first- versus second-generation products to secondary organic aerosols formed in the oxidation of biogenic hydrocarbons

Biogenic hydrocarbons emitted by vegetation are important contributors to secondary organic aerosol (SOA), but the aerosol formation mechanisms are incompletely understood. In this study, the formation of aerosols and gas-phase products from the ozonolysis and photooxidation of a series of biogenic hydrocarbons (isoprene, 8 monoterpenes, 4 sesquiterpenes, and 3 oxygenated terpenes) are examined. By comparing aerosol growth (measured by Differential Mobility Analyzers, DMAs) and gas-phase concentrations (monitored by a Proton Transfer Reaction Mass Spectrometer, PTR-MS), we study the general mechanisms of SOA formation. Aerosol growth data are presented in terms of a "growth curve", a plot of aerosol mass formed versus the amount of hydrocarbon reacted. From the shapes of the growth curves, it is found that all the hydrocarbons studied can be classified into two groups based entirely on the number of double bonds of the hydrocarbon, regardless of the reaction systems (ozonolysis or photooxidation) and the types of hydrocarbons studied: compounds with only one double bond and compounds with more than one double bond. For compounds with only one double bond, the first oxidation step is rate-limiting, and aerosols are formed mainly from low volatility first-generation oxidation products; whereas for compounds with more than one double bond, the second oxidation step may also be rate-limiting and second-generation products contribute substantially to SOA growth. This behavior is characterized by a vertical section in the growth curve, in which continued aerosol growth is observed even after all the parent hydrocarbon is consumed.     

Carbonic anhydrase textile structured packing for efficient CO2 absorption in methyldiethanolamine solvent

Carbonic anhydrase (CA) is an attractive biodegradable catalyst for CO₂ absorption in solvent-based CO₂ capture. However, maintaining the stability of CA as a homogeneous component of the solvents is a challenge. Solvent regeneration temperature typically exceeds the enzyme thermal tolerance, which leads to CA deactivation. To reduce the need for frequent CA replenishment and to avoid inactive CA accumulation in the solvent, this work shows the benefits of an immobilization strategy where CA is fixed in a second-generation design of textile structured packing (CATSP-2) modules. The enzyme-immobilized packing showed 1.5 times better performance in CO₂ separation compared with traditional structured packing with a corresponding increased CO₂ loading in the rich solvent. The modules exhibited good CA activity retention of ~80% during the tests without any CA replenishment. Applying CATSP-2 could potentially decrease the packing height and absorber column size for a lower cost per amount of CO₂ captured.