Sorption and diffusion of water,salt water,and concrete pore solution in composite matrices

In recent years, the use of fiber‐reinforced polymer composites in civil infrastructure has been promoted as a solution to the deterioration of bridges, buildings, and other structures composed of traditional materials, such as steel, concrete, and wood. Any application of a polymer composite in an outdoor environment invariably involves exposure to moisture. There is also potential for exposure to saline conditions in waterfront or offshore structures, and alkaline environments, as would be encountered by a reinforcing bar in a cementitious material. This study characterizes the sorption and transport of distilled water, salt solution, and a simulated concrete pore solution in free films of vinyl ester, isophthalic polyester (isopolyester) and epoxy resins, all commercially important materials for use in structural composites. Diffusion of all three liquids in each of the three materials was observed to follow a Fickian process. Mass loss was observed for the isopolyester in salt water and concrete pore solution at 60°C, suggesting hydrolysis that was accelerated by the high temperature exposure. Both the rate of uptake, as well as the equilibrium uptake, were greater at 60°C, compared with ambient conditions. Diffusion coefficients calculated from the mass uptake data revealed that, although the epoxy resin had the highest equilibrium uptake, it had the lowest diffusion coefficient. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 483–492, 1999     

Optimization of Blood Handling and Peripheral Blood Mononuclear Cell Cryopreservation of Low Cell Number Samples

Background: Rural/remote blood collection can cause delays in processing, reducing PBMC number, viability, cell composition and function. To mitigate these impacts, blood was stored at 4 °C prior to processing. Viable cell number, viability, immune phenotype, and Interferon-γ (IFN-γ) release were measured. Furthermore, the lowest protective volume of cryopreservation media and cell concentration was investigated. Methods: Blood from 10 individuals was stored for up to 10 days. Flow cytometry and IFN-γ ELISPOT were used to measure immune phenotype and function on thawed PBMC. Additionally, PBMC were cryopreserved in volumes ranging from 500 µL to 25 µL and concentration from 10 × 10⁶ cells/mL to 1.67 × 10⁶ cells/mL. Results: PBMC viability and viable cell number significantly reduced over time compared with samples processed immediately, except when stored for 24 h at RT. Monocytes and NK cells significantly reduced over time regardless of storage temperature. Samples with >24 h of RT storage had an increased proportion in Low-Density Neutrophils and T cells compared with samples stored at 4 °C. IFN-γ release was reduced after 24 h of storage, however not in samples stored at 4 °C for >24 h. The lowest protective volume identified was 150 µL with the lowest density of 6.67 × 10⁶ cells/mL. Conclusion: A sample delay of 24 h at RT does not impact the viability and total viable cell numbers. When long-term delays exist (>4 d) total viable cell number and cell viability losses are reduced in samples stored at 4 °C. Immune phenotype and function are slightly altered after 24 h of storage, further impacts of storage are reduced in samples stored at 4 °C.     

Fluoroalcohol-mediated reductive iodonio-Claisen rearrangement: Synthesis of complex ortho-substituted-allyl iodoarenes? ?

Reductive iodonio-Claisen rearrangement (RICR) involving λ³-iodanes and allyl or substituted-allyl silanes in fluoroalcohols, such as 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) and 2,2,2-trifluoroethanol (TFE), was studied for the synthesis of complex ortho-allyl or substituted-allyl iodoarenes. In comparison to the previously reported condition involving boron trifluoride diethyl etherate, the RICR mediated by fluoroalcohols was found to proceed more effectively. The resulting complex ortho-allyl iodoarenes are useful synthetic intermediates and can be readily converted to various heterocyclic compounds.     

Study of particle size effects on an optical fiber sensor response examined with Monte Carlo simulation

Optical fiber sensors based on the total light transmittance are widely used to measure the volume fraction of particles in suspensions. However, the sensor response depends not only on the volume fraction but also on the particle size. The particle size effect is studied for a sensor configuration consisting of two linear arrays of fibers on each of two blocks: the emitting and receiving blocks. These two linear arrays are arranged with three adjacent fibers (one fiber on the first array, two fibers on the second array) forming a perfect triangle. The almost superimposition of the calculated sensor response versus the extinction factor for different particle sizes allows for the application of single- curve models. Two single-curve models that describe the sensor response for all particle sizes ranging from 36 to 200 microm are proposed. The models are validated by Monte Carlo simulation for different particle sizes and are valid within a detectable volume fraction. The single-curve models proposed provide an easier approach to creating a database for sensor calibration for suspended sediment concentration measurements.     

Non-smokers seeking help for smokers: a preliminary study

Objectives

To examine the phenomenon of non‐smokers spontaneously taking action to seek help for smokers; to provide profiles of non‐smoking helpers by language and ethnic groups.

Setting

A large, statewide tobacco quitline (California Smokers'' Helpline) in operation since 1992 in California, providing free cessation services in English, Spanish, Mandarin, Cantonese, Korean, and Vietnamese.

Subjects

Callers between August 1992 and September 2005 who identified themselves as either white, black, Hispanic, American Indian, or Asian (n  =  349 110). A subset of these were “proxies”: callers seeking help for someone else. For more detailed analysis, n  =  2143 non‐smoking proxies calling from October 2004 through September 2005.

Main outcome measures

Proportions of proxies among all callers in each of seven language/ethnic groups; demographics of proxies; and proxies'' relationships to smokers on whose behalf they called.

Results

Over 22 000 non‐smoking proxies called. Proportions differed dramatically across language/ethnic groups, from mean (±95% confidence interval) 2.7 (0.3)% among English‐speaking American Indians through 9.3 (0.3)% among English‐speaking Hispanics to 35.3 (0.7)% among Asian‐speaking Asians. Beyond the differences in proportion, however, remarkable similarities emerged across all groups. Proxies were primarily women (79.2 (1.7)%), living in the same household as the smokers (65.0 (2.1)%), and having either explicit or implicit understandings with the smokers that calling on their behalf was acceptable (90.0 (1.3)%).

Conclusions

The willingness of non‐smokers to seek help for smokers holds promise for tobacco cessation and may help address ethnic and language disparities. Non‐smoking women in smokers'' households may be the first group to target.     

Design of pedestrian friendly vehicle bumper

Car-pedestrian accidents take thousands of lives worldwide annually. Therefore, pedestrian protection is an important issue in traffic safety. How to consider a pedestrian friendliness vehicle and then propose pedestrian protection methods are urgent works for minimizing pedestrian injury. For designing a pedestrian friendly vehicle bumper, this study adopts the European Enhanced Vehicle-safety Committee/ Working Group 17 (EEVC/WG17) regulations of legform impactor to bumper tests. Analyzing the pedestrian friendliness of a vehicle bumper by using LS-DYNA is described in detail. Simulation results were analyzed to identify the reasons for the unfriendliness. Furthermore, the analysis of the influence of bumper structure on pedestrian leg was performed and then some guideline was suggested. The analyzed models and results obtained could help evaluate pedestrian friendliness of a vehicle and guide the future development of pedestrian friendly vehicle technologies.     

Heat transfer enhancement by recirculating flow within liquid plugs in microchannels

Plug flow can significantly enhance heat transfer in microchannels as compared to single phase flow. Using an analytical model of flow field, heat transfer in plug flow is investigated. The constant-surface-temperature boundary condition is considered. Three stages of the heat transfer in plugs are identified: (i) development of thermal boundary layer; (ii) advection of heated/fresh fluid in the plug; and (iii) thermally fully developed flow. Due to the transport of heated fluid and fresh fluid within the plug by the recirculating flow, oscillations of the Nusselt number at high Peclet numbers are observed and explained. The effects of the Peclet number and the plug length on the heat transfer process are evaluated. The results show that short plugs are preferable to long plugs since short plugs result in high Nusselt numbers and high heat transfer indices.     

Electrochemical and mechanical properties of superhydrophobic aluminum substrates modified with nano-silica and fluorosilane

Nano-silica particles were deposited on acid-etched hydrophilic aluminum (Al) substrates by immersion in well-dispersed nano-silica aqueous suspension and tetramethylamonium hydroxide, followed by a heat treatment. The surface was then further treated by a reaction with fluorosilane. The hydrophobicity, surface morphology, and mechanical properties of the coated Al substrates were investigated, along with their electrochemical properties over time of exposure to two NaCl solutions (0.3% and 3% by weight). All the coated Al surfaces exhibited a water contact angle of 155–158°, i.e., superhydrophobicity. The use of nano-silica suspension significantly enhanced the hydrophobicity of the coated Al. Artificial neural networks were used to provide quantitative understanding in how the microstructure of the treated Al surface contributed to its superhydrophobicity and electrochemical properties. When R_{a, total} (nano-roughness + micro-roughness) exceeds 450 nm, WCA is greater than 154°, independent of the nano/micro-roughness ratio (RR_NM). FESEM and AFM images of these surfaces suggest that a rough two-length-scale hierarchical structure coupled with the low surface energy of fluorosilane topcoat led to the superhydrophobicity of the formed coatings. The coating prepared with the 0.2% nano-silica suspension (vs. other concentrations) featured the highest Young's modulus and the best corrosion protection to the Al substrate in both NaCl solutions.