Fluorometric method for the determination of gas-phase hydrogen peroxide

The fluorometric gas-phase hydrogen peroxide procedure is based on the technique used by Lazrus et. al. for the determination of H2O2 in the liquid phase. The analytical method utilizes the reaction of H2O2 with horseradish peroxidase and p-hydroxphenylacetic acid (POPHA) to form the fluorescent dimer of POPHA. The analytical reaction responds stoichiometrically to both H2O2 and some organic hydroperoxides. To discriminate H2O2 from organic hydroperoxides, catalase is used to preferentially destroy H2O2. Using a dual-channel flow system the H2O2 concentration is determined by difference

A reinvestigation of the vibrational spectroscopy of pentaphenylarsenic and pentaphenylantimony

The laser-Raman and infrared spectra of pentaphenylarsenic and pentaphenylantimony have been recorded both in the solid state and in solution. Structural conclusions for these molecules are based on an analysis of the phenyl-metal vibrations. These show that both pentaphenylarsenic and pentaphenylantimony retain their solid state geometries, trigonal bipyramidal and square pyramidal respectively, in solution.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22390/1/0000839.pd

Relationships of Biomass-Burning Aerosols to Ice in Orographic Wave Clouds

Ice concentrations in orographic wave clouds at temperatures between −24° and −29°C were shown to be related to aerosol characteristics in nearby clear air during five research flights over the Rocky Mountains. When clouds with influence from colder temperatures were excluded from the dataset, mean ice nuclei and cloud ice number concentrations were very low, on the order of 1–5 L^(−1). In this environment, ice number concentrations were found to be significantly correlated with the number concentration of larger particles, those larger than both 0.1- and 0.5-μm diameter. A variety of complementary techniques was used to measure aerosol size distributions and chemical composition. Strong correlations were also observed between ice concentrations and the number concentrations of soot and biomass-burning aerosols. Ice nuclei concentrations directly measured in biomass-burning plumes were the highest detected during the project. Taken together, this evidence indicates a potential role for biomass-burning aerosols in ice formation, particularly in regions with relatively low concentrations of other ice nucleating aerosols

Scavenging of black carbon by ice crystals over the northern Pacific

Airborne measurements over the northern Pacific are evaluated to characterize properties of black carbon (BC) in cirrus crystal residuals and background aerosols in the upper troposphere. Although the mass and number concentrations of BC were 7–25 times lower in crystal residuals than in particles outside of cloud, twice as many of the residuals (31%) contained BC compared to 17% of the particles in cloud-free air. In addition the average mass equivalent diameter (MED) of BC was 10% larger in crystal residuals than in particles outside of cloud. These differences in crystal residuals compared to the background aerosols suggest that inertial scavenging is a significant mechanism for removing BC compared to removal by nucleation. The scavenging efficiency, calculated as the BC mass in condensed cloud water, ranged from 7–44 ng of carbon per gram of water, consistent with previous studies in marine stratus clouds

Immunization coverage and risk factors for failure to immunize within the Expanded Programme on Immunization in Kenya after introduction of new Haemophilus influenzae type b and hepatitis b virus antigens

Background: Kenya introduced a pentavalent vaccine including the DTP, Haemophilus influenzae type b and hepatitis b virus antigens in Nov 2001 and strengthened immunization services. We estimated immunization coverage before and after introduction, timeliness of vaccination and risk factors for failure to immunize in Kilifi district, Kenya. Methods: In Nov 2002 we performed WHO cluster-sample surveys of > 200 children scheduled for vaccination before or after introduction of pentavalent vaccine. In Mar 2004 we conducted a simple random sample (SRS) survey of 204 children aged 9 - 23 months. Coverage was estimated by inverse Kaplan-Meier survival analysis of vaccine- card and mothers' recall data and corroborated by reviewing administrative records from national and provincial vaccine stores. The contribution to timely immunization of distance from clinic, seasonal rainfall, mother's age, and family size was estimated by a proportional hazards model. Results: Immunization coverage for three DTP and pentavalent doses was 100% before and 91% after pentavalent vaccine introduction, respectively. By SRS survey, coverage was 88% for three pentavalent doses. The median age at first, second and third vaccine dose was 8, 13 and 18 weeks. Vials dispatched to Kilifi District during 2001 - 2003 would provide three immunizations for 92% of the birth cohort. Immunization rate ratios were reduced with every kilometre of distance from home to vaccine clinic (HR 0.95, CI 0.91 - 1.00), rainy seasons ( HR 0.73, 95% CI 0.61 - 0.89) and family size, increasing progressively up to 4 children ( HR 0.55, 95% CI 0.41 - 0.73). Conclusion: Vaccine coverage was high before and after introduction of pentavalent vaccine, but most doses were given late. Coverage is limited by seasonal factors and family siz

Comparison of in situ measurements of cirrus cloud ice water content

Aircraft-based in situ measurements of cirrus cloud ice water content (IWC) are important for cloud microphysical/radiative modeling and satellite validation studies, yet the measurements have proven challenging due, in part, to the large dynamic range of IWC values present in cirrus clouds. To date, three instruments designed for the measurement of IWC have been flown aboard the NASA WB-57F research aircraft: the University of Colorado closed-path laser hygrometer, the Droplet Measurement Technologies Cloud Spectrometer and Impactor, and the Harvard University Lyman-a total water photofragment-fluorescence hygrometer. This paper compares IWC measurements from these three instruments taken during the Midlatitude Cirrus Experiment (MidCiX) in 2004. At larger values of IWC (IWC > 10 mg m¯³), the three instruments agree, on average, to within 20%, which is of the order of their estimated instrumental uncertainties. At smaller IWC values (<10 mg m¯³), the agreement is worse, in part due to increasing instrument uncertainties. These results have implications for measurements in thin and subvisual cirrus. Particle sampling and evaporation, instrument background levels, and hysteresis are not found to be significant contributors to discrepancies among the measurements. For remote sensing validation studies where IWC data are vertically integrated to obtain ice water path, the agreement between the instruments is better than 20% for thick cirrus (τ > 1), implying that IWC measurements in thicker clouds are of sufficient accuracy for validation studies

Relationships of Biomass-Burning Aerosols to Ice in Orographic Wave Clouds

Ice concentrations in orographic wave clouds at temperatures between −24° and −29°C were shown to be related to aerosol characteristics in nearby clear air during five research flights over the Rocky Mountains. When clouds with influence from colder temperatures were excluded from the dataset, mean ice nuclei and cloud ice number concentrations were very low, on the order of 1–5 L⁻¹. In this environment, ice number concentrations were found to be significantly correlated with the number concentration of larger particles, those larger than both 0.1- and 0.5-μm diameter. A variety of complementary techniques was used to measure aerosol size distributions and chemical composition. Strong correlations were also observed between ice concentrations and the number concentrations of soot and biomass-burning aerosols. Ice nuclei concentrations directly measured in biomass-burning plumes were the highest detected during the project. Taken together, this evidence indicates a potential role for biomass-burning aerosols in ice formation, particularly in regions with relatively low concentrations of other ice nucleating aerosols.Keywords: Aerosols, Orographic effects, Wave clouds, Biosphere-atmosphere interactio

Mineral dust increases the habitability of terrestrial planets but confounds biomarker detection

Identification of habitable planets beyond our solar system is a key goal of current and future space missions. Yet habitability depends not only on the stellar irradiance, but equally on constituent parts of the planetary atmosphere. Here we show, for the first time, that radiatively active mineral dust will have a significant impact on the habitability of Earth-like exoplanets. On tidally-locked planets, dust cools the day-side and warms the night-side, significantly widening the habitable zone. Independent of orbital configuration, we suggest that airborne dust can postpone planetary water loss at the inner edge of the habitable zone, through a feedback involving decreasing ocean coverage and increased dust loading. The inclusion of dust significantly obscures key biomarker gases (e.g. ozone, methane) in simulated transmission spectra, implying an important influence on the interpretation of observations.We demonstrate that future observational and theoretical studies of terrestrial exoplanets must consider the effect of dust

Whole Transcriptome Sequencing Reveals Gene Expression and Splicing Differences in Brain Regions Affected by Alzheimer's Disease

Recent studies strongly indicate that aberrations in the control of gene expression might contribute to the initiation and progression of Alzheimer's disease (AD). In particular, alternative splicing has been suggested to play a role in spontaneous cases of AD. Previous transcriptome profiling of AD models and patient samples using microarrays delivered conflicting results. This study provides, for the first time, transcriptomic analysis for distinct regions of the AD brain using RNA-Seq next-generation sequencing technology. Illumina RNA-Seq analysis was used to survey transcriptome profiles from total brain, frontal and temporal lobe of healthy and AD post-mortem tissue. We quantified gene expression levels, splicing isoforms and alternative transcript start sites. Gene Ontology term enrichment analysis revealed an overrepresentation of genes associated with a neuron's cytological structure and synapse function in AD brain samples. Analysis of the temporal lobe with the Cufflinks tool revealed that transcriptional isoforms of the apolipoprotein E gene, APOE-001, -002 and -005, are under the control of different promoters in normal and AD brain tissue. We also observed differing expression levels of APOE-001 and -002 splice variants in the AD temporal lobe. Our results indicate that alternative splicing and promoter usage of the APOE gene in AD brain tissue might reflect the progression of neurodegeneration