994 research outputs found
The relative importance of competing pathways for the formation of high-molecular-weight peroxides in the ozonolysis of organic aerosol particles
High-molecular-weight (HMW) organic compounds are an important component of atmospheric particles, although their origins, possibly including in situ formation pathways, remain incompletely understood. This study investigates the formation of HMW organic peroxides through reactions involving stabilized Criegee intermediates (SCI's). The model system is methyl oleate (MO) mixed with dioctyl adipate (DOA) and myristic acid (MA) in submicron aerosol particles, and Criegee intermediates are formed by the ozonolysis of the double bond in methyl oleate. An aerosol flow tube coupled to a quadrupole aerosol mass spectrometer (AMS) is employed to determine the relative importance of different HMW organic peroxides following the ozonolysis of different mixing mole fractions of MO in DOA and MA. Possible peroxide products include secondary ozonides (SOZ's), α-acyloxyalkyl hydroperoxides and α-acyloxyalkyl alkyl peroxides (αAAHP-type compounds), diperoxides, and monoperoxide oligomers. Of these, the AMS data identify two SOZ's as major HMW products in the ozonolysis of pure methyl oleate as well as in an inert matrix of DOA to as low as 0.04 mole fraction MO. In comparison, in mixed particles of MO and MA, αAAHP-type compounds form in high yields for MO mole fractions of 0.5 or less, suggesting that SCI's efficiently attack the carboxylic acid group of myristic acid. The reactions of SCI's with carboxylic acid groups to form αAAHP-type compounds therefore compete with those of SCI's with aldehydes to form SOZ's, provided that both types of functionalities are present at significant concentrations. The results therefore suggest that SCI's in atmospheric particles contribute to the transformation of carboxylic acids and other protic groups into HMW organic peroxides
Microarray analysis of salt-responsive genes in common wheat
DissertaĆ§Ć£o apresentada Ć Faculdade de Direito da
Universidade de Coimbra no Ć¢mbito do 2Āŗ Ciclo de Estudos em
Direito, Ć”rea de especializaĆ§Ć£o
em CiĆŖncias JurĆdico-PolĆticas, Direito Internacional
PĆŗblico e Europeu
Diurnal variation and size dependence of the hygroscopicity of organic aerosol at a forest site in Wakayama, Japan: their relationship to CCN concentrations
Formation of biogenic secondary organic aerosol (BSOA)
and its subsequent evolution can modify the hygroscopicity of the organic
aerosol component (OA) in the forest atmosphere, and affect the
concentrations of cloud condensation nuclei (CCN) there. In this study,
size-resolved aerosol hygroscopic growth at 85 % relative humidity and
size-resolved aerosol composition were measured using a hygroscopic tandem
differential mobility analyzer and an aerosol mass spectrometer,
respectively, at a forest site in Wakayama, Japan, in August and September
2015. The hygroscopicity parameter of OA (Īŗorg) presented daily
minima in the afternoon hours, and it also showed an increase with the increase in particle dry diameter. The magnitudes of the diurnal variations in
Īŗorg for particles with dry diameters of 100 and 300 nm were on
average 0.091 and 0.096, respectively, and the difference in Īŗorg between particles with dry diameters of 100 and 300 nm was on
average 0.056. The relative contributions of the estimated fresh BSOA and
regional OA to total OA could explain 40 % of the observed diurnal
variations and size dependence of Īŗorg. The hygroscopicity
parameter of fresh BSOA was estimated to range from 0.089 to 0.12 for
particles with dry diameters from 100 to 300 nm. Compared with the use of
time- and size-resolved Īŗorg, the use of time- and
size-averaged Īŗorg leads to under- and over-estimation of the
fractional contribution of OA to CCN number concentrations in the range from
ā5.0 % to 26 %. This indicates that the diurnal variations and
size dependence of Īŗorg strongly affect the overall
contribution of OA to CCN concentrations. The fractional contribution of
fresh BSOA to CCN number concentrations could reach 0.28 during the period
of intensive BSOA formation. The aging of the fresh BSOA, if it occurs,
increases the estimated contribution of BSOA to CCN number concentrations by
52 %ā84 %.</p
Role of glycosaminoglycans of biglycan in BMP-2 signaling
Recently we have reported that biglycan (BGN) promotes osteoblast differentiation and that this function is due in part to its ability to positively modulate bone morphogenetic protein (BMP) functions. In this study we investigated the role of glycosaminoglycans (GAGs) of BGN in this function using in vitro and in vivo models. C2C12 myogenic cells were treated or untreated with BMP-2 alone or in combination with glycanated, partially glycanated or de-glycanated BGN, and the effects on BMP signaling and function were assessed by Smad1/5/8 phosphorylation and alkaline phosphatase (ALP) activity. Furthermore, the effect of de-glycanation of BGN on BMP-2 induced osteogenesis was investigated employing a rat mandible defect model. The defects were filled with collagen scaffolds loaded with glycanated, partially glycanated or de-glycanated BGN alone or in combination with a sub-optimal dose of BMP-2 (subBMP). In in vitro experiments, BMP signaling and function were the greatest when BMP-2 was combined with de-glycanated BGN among the groups tested. In the rat mandible experiments, Ī¼CT analyses revealed that the newly formed bone was significantly increased only when subBMP was combined with de-glycanated BGN. The data indicate that the GAG component of BGN functions as a suppressor for the BGN-assisted BMP function
Comprehensive Functional Analyses of Expressed Sequence Tags in Common Wheat (Triticum aestivum)
About 1 million expressed sequence tag (EST) sequences comprising 125.3 Mb nucleotides were accreted from 51 cDNA libraries constructed from a variety of tissues and organs under a range of conditions, including abiotic stresses and pathogen challenges in common wheat (Triticum aestivum). Expressed sequence tags were assembled with stringent parameters after processing with inbuild scripts, resulting in 37 138 contigs and 215 199 singlets. In the assembled sequences, 10.6% presented no matches with existing sequences in public databases. Functional characterization of wheat unigenes by gene ontology annotation, mining transcription factors, full-length cDNA, and miRNA targeting sites were carried out. A bioinformatics strategy was developed to discover single-nucleotide polymorphisms (SNPs) within our large EST resource and reported the SNPs between and within (homoeologous) cultivars. Digital gene expression was performed to find the tissue-specific gene expression, and correspondence analysis was executed to identify common and specific gene expression by selecting four biotic stress-related libraries. The assembly and associated information cater a framework for future investigation in functional genomics
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