Influence of engine operating conditions on diesel particulate matter emissions in relation to transient and steady-state conditions

Airborne particulate matter is an important pollutant affecting air quality. Currently, diesel PM regulations are based on emitted particle mass; however, the particle size distributions are also important factors in air quality. While the distributions of particulate emissions under steady-state conditions are well-known and have been generalized, varying distributions undertransient conditions are not well-understood. This study investigates the size distributions of PM, focusing on the nuclei- and accumulation-modes, emitted from diesel engines under transient operations. Some engine conditions during transient testing produced particle size distributions that were notably different from those produced under steady-state conditions. During transient operation, the size distributions were either mono- or bimodal with peaks that were able to switch quickly between the nuclei- and accumulation-modes. These distributions have not been observed during steady-state testing but are significant because environmental and health effects and emission control solutions are highly dependent on particle size.     

Kinetics of emulsion polymerization of styrene using the reactive surfactant HITENOL BC20

The effect of the reactive surfactant HITENOL BC20 (polyoxyethylene alkylphenyl ether ammonium sulfate; 20 U of ethylene oxide (EO)) on the emulsion polymerization of styrene was studied via reaction calorimetry (Mettler RC1; 70°C). For polymerizations carried out above the cmc of BC20, the reaction kinetics and evolution of the number of particles (N_p) resembled those reported using the conventional surfactant sodium lauryl sulfate, indicating that nucleation proceeded by a combination of micellar and homogenous nucleation (Interval I and Stage 2). The reaction rate (R_p) not only increased with increasing initiator (K₂S₂O₈) and surfactant concentrations, as expected, but the increase in rate in Stage 2 was dependent on the initiator concentration and independent of the surfactant concentration. This is consistent with the proposed nucleation mechanisms. The molecular weight increased with increasing surfactant concentration and decreasing initiator concentration as would also be expected for a conventional surfactant. The dependencies of R_p and N_p on the BC20 and initiator concentrations, however, were lower than the classical Smith‐Ewart values (R_p ∝ [E]^0.47–0.52; R_p ∝ [I]^0.21–0.25) although R_p was found to be directly proportional to N_p. Chain transfer to the reactive surfactant is considered a likely source of divergence. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Dispersion polymerization of methyl methacrylate: Effect of stabilizer concentration

In dispersion polymerizations of methyl methacrylate (MMA), little difference was found in the polymerization kinetics with varying stabilizer (PVP K‐30) concentration, indicating that in contrast to emulsion polymerization, the kinetics of these dispersion polymerizations are independent of the number of particles. Comparing MMA precipitation and dispersion polymerizations revealed that nuclei formation in the latter results from precipitation polymerization occurring in the continuous phase, which can contribute significantly to the kinetics, and especially to the molecular weight distributions. No change was found in the molecular weight distribution of the PVP during a dispersion polymerization, nor was there any measurable difference between using fresh and recycled stabilizer. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis, surface-active properties, and antimicrobial activities of new double-chain gemini surfactants

A novel series of neutral and cationic dimeric surfactants were prepared involving ketalization reaction, Williamson etherification, and regioselective oxirane ring opening with primary and tertiary alkyl amines. The critical micelle concentration (CMC), effectiveness of surface tension reduction (gamma(CMC)), surface excess concentration (Gamma), and area per molecule at the interface (A) were determined and values indicate that the cationic series is characterized by good surface-active and self-aggregation properties. For the first time, we reported the antimicrobial activities against representative bacteria and fungi for dimeric compounds. The antimicrobial activity was found to be dependent on the target microorganism (Gram-positive bacteria > fungi > Gram-negative bacteria), as well as both the neutral or ionic nature (cationic > neutral) and alkyl chain length (di-C(12) > di-C(18) > di-C(8)) of the compounds. The cationic di-C(12) derivative was found to have equipotent activity to that of benzalkonium chloride (BAC) used as standard.     

Accounting for signal loss due to dephasing in the correction of distortions in gradient-echo EPI via nonrigid registration

Gradient-echo (GE) echo planar imaging (EPI) is susceptible to both geometric distortions and signal loss. This paper presents a retrospective correction approach based on nonrigid image registration. A new physics-based intensity correction factor derived to compensate for intravoxel dephasing in GE EPI images is incorporated into a previously reported nonrigid registration algorithm. Intravoxel dephasing causes signal loss and thus intensity attenuation in the images. The new rephasing factor we introduce, which changes the intensity of a voxel in images during the registration, is used to improve the accuracy of the intensity-based nonrigid registration method and mitigate the intensity attenuation effect. Simulation-based experiments are first used to evaluate the method. A magnetic resonance (MR) simulator and a real field map are used to generate a realistic GE EPI image. The geometric distortion computed from the field map is used as the ground truth to which the estimated nonrigid deformation is compared. We then apply the algorithm to a set of real human brain images. The results show that, after registration, alignment between EPI and multi-shot, spin-echo images, which have relatively long acquisition times but negligible distortion, is improved and that signal loss caused by dephasing can be recovered.     

Economic development's effect on road transport-related mortality among different types of road users: a cross-sectional international study

The relationship between a country's stage of economic development and its motor vehicle crash (MVC) mortality rate is not defined for different road users. This paper presents a cross-sectional regression analysis of recent national mortality in 44 countries using death certificate data provided by the World Health Organization. For five types of road users, MVC mortality is expressed as deaths per 100,000 people and per 1000 motor vehicles. Economic development is measured as gross national income (GNI) per capita in U.S. dollars and as motor vehicles per 1000 people. Results showed overall MVC mortality peaked among low-income countries at about US$ 2000 GNI per capita and at about 100 motor vehicles per 1000 people. Overall mortality declined at higher national incomes up to about US$ 24,000. Most changes in MVC mortality associated with economic development were explained by changes in rates among nonmotorized travelers, especially pedestrians. Overall MVC rates were lowest when pedestrian exposure was low because there were few motor vehicles or few pedestrians, and were highest during a critical transition to motorized travel, when many pedestrians and other vulnerable road users vied for use of the roadways with many motor vehicles.     

The engineering options for mitigating the climate impacts of aviation

Aviation is a growing contributor to climate change, with unique impacts due to the altitude of emissions. If existing traffic growth rates continue, radical engineering solutions will be required to prevent aviation becoming one of the dominant contributors to climate change. This paper reviews the engineering options for mitigating the climate impacts of aviation using aircraft and airspace technologies. These options include not only improvements in fuel efficiency, which would reduce carbon dioxide (CO2) emissions, but also measures to reduce non-CO2 impacts including the formation of persistent contrails. Integrated solutions to optimize environmental performance will require changes to airframes, engines, avionics, air traffic control systems and airspace design.While market-based measures, such as offset schemes and emissions trading, receive growing attention, this paper sets out the crucial role of engineering in the challenge to develop a 'green air traffic system'.     

An adenoviral platform for selective self-assembly and targeted delivery of nanoparticles

Metallic nanoparticles (NPs) can be used for the diagnosis, imaging, and therapy of tumors and cardiovascular disease. However, targeted delivery of NPs to specific cells remains a major limitation for clinical realization of these potential treatment options. Herein, a novel strategy for the specific coupling of NPs to a targeted adenoviral (Ad) platform to deliver NPs to specific cells is defined. Genetic manipulation of the gene-therapy vector is combined with a specific chemical coupling strategy. In particular, a high-affinity interaction between a sequence of six-histidine amino acid residues genetically incorporated into Ad capsid proteins and nickel(II) nitrilotriacetic acid on the surface of gold NPs is employed. The selective self-assembly of gold NPs and Ad vectors into multifunctional platforms does not negatively affect the targeting of Ad to specific cells. This opens the possibility of using Ad vectors for targeted NP delivery, thereby providing a new type of combinatorial approach for the treatment of diseases that involves both nanotechnology and gene therapy.     

The cultural grounding of personal relationship: The importance of attractiveness in everyday life.

Previous research has suggested that physically attractive people experience more positive life outcomes than do unattractive people. However, the importance of physical attractiveness in everyday life may vary depending on the extent to which different cultural worlds afford or require individual choice in the construction and maintenance of personal relationships. The authors hypothesized that attractiveness matters more for life outcomes in settings that promote voluntaristic-independent constructions of relationship as the product of personal choice than it does in settings that promote embedded-interdependent constructions of relationship as an environmental affordance. Study 1 examined self-reported outcomes of attractive and unattractive persons. Study 2 examined expectations about attractive and unattractive targets. Results provide support for the hypothesis along four dimensions: national context, relationship context, rural-urban context, and experimental manipulation of relationship constructions. These patterns suggest that the importance of physical attractiveness documented by psychological research is the product of particular constructions of reality. (PsycINFO Database Record (c) 2010 APA, all rights reserved)