Exceeding of Henry's law by hydrogen peroxide associated with urban aerosols

Simultaneous measurements of gas- and aerosol-phase hydrogen peroxide (H2O2) have been made at two sites in Los Angeles, one near the Pacific coast at the University of California at Los Angeles (UCLA), and the other in downtown Los Angeles with close proximity to a heavily traveled freeway (freeway site). At both the freeway and UCLA sites, gas-phase H2O2 levels were similar, averaging 1.17 +/- 1.0 and 1.05 +/- 0.6 ppb, respectively. The particle-associated H2O2 in both fine (PM2.5) and coarse (>PM2.5) modes was higher at the freeway site, as compared to UCLA, by a factor of 2. However, when aerosol-phase H2O2 is normalized to particle mass loadings, the fine-mode H2O2 levels are very similar at the two sites: 0.42 +/- 0.3 and 0.58 +/- 0.3 ng H2O2/microg particle mass at the freeway and UCLA sites, respectively. The normalized coarse-mode H2O2 levels were significantly higher at the freeway site than at UCLA, 1.05 +/- 0.3 and 0.51 +/- 0.3 ng/microg, respectively. Estimating aerosol liquid water content on the basis of relative humidity and aerosol mass, a calculated equivalent H2O2 in aerosol liquid water averages 70 mM, more than 2 orders of magnitude higher than concentrations predicted by gas-particle partitioning (Henry's law), which averages 0.1 mM. This indicates that the sampled particles are capable of generating H2O2 in aqueous solution. These corresponding aqueous-phase H2O2 concentrations in aerosol liquid water exceed levels that have been observed to produce cellular damage to lung epithelial cells in laboratory experiments by at least 3 orders of magnitude. Although most measurements of H2O2 in particles were made using an extraction solution adjusted to pH 3.5, a set of measurements indicates that H2O2 from fine-mode particles extracted in the physiologically relevant pH range 5-7.5 also generate H2O2 with only slightly lowered efficiency; coarse-mode H2O2 production dropped by 75% at the upper end of this range. Finally, a small set of measurements was performed to investigate the degree to which the recently developed Versatile Aerosol Concentrator Enrichment System (VACES) affects H2O2 levels in concentrated ambient aerosols. The VACES appeared to a have minimal impact on particulate H2O2.     

Review on Manufacture of Military Composite Helmet

Applied Composite Materials - Despite of the fact that more and more accessory devices are integrated to functionalize a ballistic helmet system, its core ballistic protective function needs to be...     

Flexural Behaviour of Unreinforced and Z-Fibre Reinforced 3D Carbon/Epoxy Composites

Applied Composite Materials - This study compares the flexural properties of unreinforced and Z-fibre reinforced 3D carbon/epoxy composites. Z-fibre reinforcement is introduced by a novel stitching...     

Electrochemical promotion of heterogeneous catalysis

The catalytic activity and selectivity of metals interfaced with solid electrolytes can be altered dramatically and reversibly via potential application. The increase in catalytic rate can be several orders of magnitude higher than that anticipated from Faraday's Law. This new phenomenon of electrochemical promotion is of considerable theoretical and potentially practical importance in heterogeneous catalysis. In this paper the main phenomenological features of electrochemical promotion (or NEMCA effect) are surveyed and the origin of the effect is discussed in view of recent surface spectroscopic and quantum mechanical studies.     

A SIMPLIFIED MODEL FOR MERCURY POROSIMETRY HYSTERESIS

A modified Random Corrugated Pore Structure Model (CPSM) simulating Mercury Porosimetry (MP) hysteresis and entrapment phenomena is proposed. The model have been applied in parametric sensitivity studies and data regression tests by using a single parameter Bell Shape Distribution (BSD) function as the intrinsic pore size distribution (psd). The new CPSM version proved to be superior compared to its original counterpart since it achieves a sensible evaluation of the trapped mercury distribution, enables the construction of a “closed” (zero entrapment) hysteresis loop and makes realistic predictions of the intrinsic pore volume and surface area distributions. CPSM predicted intrinsic psd's for reservoir sand stones compare satisfactorily with those measured independently by a photomicrography method. The model also provides the basis for the development of a least square computer code suitable for further improved psd calculations.     

Physical and Chemical Characteristics and Volatility of PM in the Proximity of a Light-Duty Vehicle Freeway

Abstract

Volatility properties of ultrafine particles were analyzed next to State Route 110 (Pasadena freeway CA), a light-duty vehicle freeway where heavy-duty traffic is prohibited. In addition, mass concentration and chemical composition of particulate matter (PM) were measured in coarse, accumulation, and ultrafine modes. On weekdays from 17 May to 4 June 2004, measurements were performed in two locations, one very close to the freeway (within 2.5 m from the curb) and one at a distance of about 50 m from the freeway. For measurement of mass and chemical composition, the study employed in each location a micro-orifice uniform deposit impactor (MOUDI) and a modified high-volume sampler. Both instruments sampled with the same size cutpoints: a coarse mode from 2.5 to 10 μm, an accumulation mode from 0.18 to 2.5 μm, and an ultrafine mode of particles less than 0.18 μm in aerodynamic diameter. Alternately, a tandem differential mobility analyzer (TDMA) was used at the two sites. A heater between the two DMAs evaporated volatile material from the monodisperse aerosol, size selected by the first DMA. The second DMA analyzed the losses of volatile components. The ultrafine number concentrations next to the freeway were 46,000 cm^?3 on average during the sampling period. The MOUDI ultrafine mass concentration, nitrate, and EC were higher next to the freeway than at the background site farther from the freeway. The other components analyzed in the ultrafine mode had similar concentrations next to the freeway and at the background site. Volatility ranged from about 65% volume losses of 120 nm particles heated to 110°C to 95% of 20 nm particles. The 20 nm aerosol was only internally mixed, whereas increasing nonvolatile fractions were found for 40 nm (6% next to the freeway), 80 nm (20%), and 120 nm (28%) aerosols.     

Optimal location of measurements for parameter estimation of distributed parameter systems

Systematic methodologies for the optimal location of spatial measurements, for efficient estimation of parameters of distributed systems, are investigated. A review of relevant methods in the literature is presented, and a comparison between the results obtained with three distinctive existing techniques is given. In addition, a new approach based on the Proper Orthogonal Decomposition (POD), to address this important problem is introduced and discussed with the aid of illustrative benchmark case studies from the literature. Based on the results obtained here, it was observed that the method based on the Gram determinant evolution (Vande Wouwer et al., 2000), does not always produce accurate results. It is strongly dependent on the behaviour of sensitivity coefficients and requires extensive calculations. The method based on max-min optimisation (Alonso, Kevrekidis, Banga, & Frouzakis, 2004) assigns optimal sensor locations to the positions where system outputs reach their extrema values; however, in some cases it produces more than one optimal solution. The D-optimal design method, Uciński (2003, June 18-20), produces as results the optimal number and spatial positions of measurements based on the behaviour (rather than the magnitude) of the sensitivity functions. Here we show that the extrema values of POD modes can be used directly to compute optimal sensor locations (as opposed e.g. to Alonso, Kevrekidis, et al., 2004, where PODs are merely used to reduce the system and further calculations are needed to compute sensor locations). Furthermore, we demonstrate the equivalence between the extrema of POD modes and of sensitivity functions. The added value of directly using PODs for the computation of optimal sensor locations is the computational efficiency of the method, side-stepping the tedious computation of sensitivity coefficient Jacobian matrices and using only system responses and/or experimental results directly. Furthermore, the inherent combination of model reduction and sensor location estimation in this method becomes more important as the complexity of the original distributed parameter system increases.     

Evaluation of the Role of p53 Tumour Suppressor Posttranslational Modifications and TTC5 Cofactor in Lung Cancer

Mutations in the p53 tumor suppressor are found in over 50% of cancers. p53 function is controlled through posttranslational modifications and cofactor interactions. In this study, we investigated the posttranslationally modified p53, including p53 acetylated at lysine 382 (K382), p53 phosphorylated at serine 46 (S46), and the p53 cofactor TTC5/STRAP (Tetratricopeptide repeat domain 5/ Stress-responsive activator of p300-TTC5) proteins in lung cancer. Immunohistochemical (IHC) analysis of lung cancer tissues from 250 patients was carried out and the results were correlated with clinicopathological features. Significant associations between total or modified p53 with a higher grade of the tumour and shorter overall survival (OS) probability were detected, suggesting that mutant and/or modified p53 acts as an oncoprotein in these patients. Acetylated at K382 p53 was predominantly nuclear in some samples and cytoplasmic in others. The localization of the K382 acetylated p53 was significantly associated with the gender and grade of the disease. The TTC5 protein levels were significantly associated with the grade, tumor size, and node involvement in a complex manner. SIRT1 expression was evaluated in 50 lung cancer patients and significant positive correlation was found with p53 S46 intensity, whereas negative TTC5 staining was associated with SIRT1 expression. Furthermore, p53 protein levels showed positive association with poor OS, whereas TTC5 protein levels showed positive association with better OS outcome. Overall, our results indicate that an analysis of p53 modified versions together with TTC5 expression, upon testing on a larger sample size of patients, could serve as useful prognostic factors or drug targets for lung cancer treatment.