The size distribution of primary biological aerosol particles in the multiphase atmosphere

Primary biological aerosol particles are a ubiquitouscomponent of the atmospheric aerosol and have greatimportance within the whole atmosphere. Besides theireffect on air hygiene (i.e. causing allergic diseases), theycontribute to cloud and rain development. They amountto almost 25% of the total number of aerosolparticles both in dry air and in cloudwater. They showno seasonal variation in concentration but incomposition.     

液相沉积法制备聚(苯乙烯-丙烯酸)／铁的氧化物纳微核壳粒子

描述了一种基于液相沉积法制备纳微核壳粒子的新方法,即以聚(苯乙烯-丙烯酸)乳胶粒子为模板,利用静电相互作用和液相沉积的方法,将氢氧化铁包覆在模板粒子表面,形成聚(苯乙烯-丙烯酸)/铁的氧化物核壳纳米复合粒子。通过TEM和SEM观察,Fe2O3晶粒在模板粒子表面生长并呈草莓状,壳层厚度均匀。该特殊结构有利于通过煅烧除核的方法获得硬质空心磁球。     

Bioaerosol concentrator performance: comparative tests with viable and with solid and liquid nonviable particles

Aims:  Generally it is more economical to first characterize a concentrator system with nonbiological particles followed by more rigorous bioaerosol testing. This study compares sampling system performance for varions particle types and sizes.
Methods and Results:  Performances of five concentrators were characterized with five nonviable and viable laboratory aerosols, although not every concentrator was tested with all aerosol types. For particle sizes less than c. 6  μ m aerodynamic diameter, similar efficiencies are obtained for all test particles; however, for larger sizes there is a significant difference between liquid and dry particles.
Conclusions:  Aluminium oxide particles provide results over a broad range of sizes with a single test, but the method is less reproducible than other methods. A combination of monodisperse polystyrene spheres and oleic acid droplets provides an accurate representation of the system performance, but ultimately biological particle tests are needed.
Significance and Impact of the Study:  Devices are being developed for concentrating bioaerosol particles in the size range of 1–10  μ m aerodynamic diameter and this study provides insight into data quality for different test methodologies. Also, the results show some current concentrators perform quite poorly.     

Validation of a high-performance liquid chromatographic assay for the quantification of adenovirus type 5 particles

An anion-exchange–high-performance liquid chromatography (AE–HPLC) method for the quantification of adenovirus type 5 (Ad5) total particles was validated according to performance criteria of precision, specificity, linearity of calibration and range, limit of detection, limit of quantification, accuracy and recovery. The viral particles were detected by absorbance at 260 nm using photodiode array detector (PDA). Cesium chloride (CsCl) purified Ad5 and lysate samples were used for the validation of the method. Relative standard deviations (RSDs) for the inter-day, intra-day precision and reproducibility for both the lysate and the Ad5 standard were less than 10 and 2% for the peak area and retention time, respectively. The method was specific for Ad5 which was eluted at 8.0 min. The presence of DNA does not affect the recovery of Ad5 particles for accurate quantification. Based on the error in prediction to be less than 10%, the working range was established between 2×10¹⁰ and 7×10¹¹ VP/ml with correlation coefficient of 0.99975, standard deviation of 6.14×10⁹ VP/ml and a slope of 3.04×10⁵ VP/ml. The recovery of the method varied between 88 and 106% in all of the lysate samples investigated which is statistically similar to 100% recovery at 95% confidence interval.     

Assembly of a chimeric respiratory chain from bovine heart submitochondrial particles and cytochrome bd terminal oxidase of Escherichia coli

Cytochrome bd is a terminal quinol oxidase in Escherichia coli. Mitochondrial respiration is inhibited at cytochrome bc₁ (complex III) by myxothiazol. Mixing purified cytochrome bd oxidase with myxothiazol-inhibited bovine heart submitochondrial particles (SMP) restores up to 50% of the original rotenone-sensitive NADH oxidase and succinate oxidase activities in the absence of exogenous ubiquinone analogs. Complex III bypassed respiration and is saturated at amounts of added cytochrome bd similar to that of other natural respiratory components in SMP. The cytochrome bd tightly binds to the mitochondrial membrane and operates as an intrinsic component of the chimeric respiratory chain.     

Modifiable chemically crosslinked poli(κ-carrageenan) particles

Micron size κ-carrageenan hydrogel particles, p(CRN) from linear κ-carrageenan, were prepared via microemulsion polymerization using divinyl sulfone (DVS) as chemical crosslinker in a sodium bis(2-ethylhexyl) sulfosuccinate (AOT) reverse miceller system. Magnetic field responsive (m-p(CRN)) composite particles were also synthesized by encapsulating magnetic ferrite (Fe₃O₄) nanoparticles together with linear κ-carrageenan within the AOT reverse micelle before the crosslinking reaction. The synthesized bare p(CRN) particles were further modified to produce positive charges on the particles (q-p(CRN)) by a quaternization reaction with an 3-chloro-2-hydroxypropyl trimethyl ammonium chloride aqueous solution. Scanning electron microscopy (SEM), dynamic light scattering (DLS), zeta potential measurements and FT-IR analysis confirmed that particle sizes and charges were altered by chemical modification. Furthermore, a model drug, phenylephrine HCl was used for in vitro drug delivery studies to compare the effectiveness of modification of p(CRN) microgels by comparing bare p(CRN), m-p(CRN) and q-p(CRN) particles drug release capabilities in phosphate buffer solution (PBS) at pH 7.4.     

Structure of aggregates of Tipula iridescent virus and polystyrene latex particles

Tipula iridescent virus aggregated with polystyrene latex particles 126 nm in diameter. There was a region of optimal proportion of the two particles. The aggregation proceeded faster and the amount of resultant aggregates was larger at the higher concentrations of the two particles, but the size of the individual aggregates was smaller. The aggregates consisted of clusters of the two particles with vacant spaces interspersed among them. A hypothetical model of the particle arrangements was presented. The aggregates were reversibly dissolved in 0.03% sodium dodecyl sulfate and 30% n-propanol and isopropanol. In the presence of lower concentrations of these solvents, the aggregation occurred at high temperatures but not at low temperatures. These results were interpreted as implicating hydrophobic interactions in the formation and stability of the aggregates.     

银纳米粉体制备研究的进展

介绍了在银纳米粉体制备中所采用的几种主要方法以及各种方法的优缺点。指出了目前研究中存在的问题,并对今后的研究进行了展望。     

Effects of Particle Size and Redox Potential on Arsenic Fractionation in Soils Irrigated with Arsenate-rich Water

Aging affects arsenic (As) bioaccessibility in soils. This study focuses on the influences of particle size and redox potential on As(V) aging in irrigated soils. The results showed that variation of As fractions in fine particles, except the loosely adsorbed fraction, was larger than that in coarse particles over time. Anoxic conditions decreased the change in As fractions, with the exception of the exchangeable fraction in soils over time, in comparison to the aerobic condition. The aging processes of As(V) in different particle sizes and soils at different redox potentials exhibited several stages. The only significant difference in the aging process of As(V) in different particle sizes was the longer transformation period of the water-soluble fraction into the Fe/Mn/Al oxides-bound fraction in fine particles than in coarse particles. The redox potential had a significant influence on the aging process of As(V) in soils after 10 days of incubation. In terms of As bioaccessibility, anoxic conditions shortened the aging process of As(V) in soils. During the aging process, fine particles and aerobic conditions intensified the decrease in As(V) bioaccessibility in soils in comparison to the coarse particles and anoxic condition.     

The interaction between the mitochondrial ATPase (F1) and the ATPase inhibitor

1. The naturally occurring mitochondrial ATPase inhibitor inhibits the mitochondrial ATPase (F₁) non-competitively.2. The interaction between inhibitor and inhibitor-depleted F₁ or submitochondrial particles is diminished when the ratio of ATP/ADP is low or when energy is generated by substrate oxidation.3. The dissociation of the inhibitor from coupled Mg-ATP particles is promoted when substrates are being oxidized. This results in the appearance of a large uncoupler-stimulated ATPase activity. Activation of the uncoupler-stimulated ATPase activity is also achieved by incubation of the particles with ADP.4. The ATPase activity of Mg-ATP particles is determined by the turnover capacity of F₁. When endogenous inhibitor is removed, energy dissipation becomes the rate-limiting step. This energy dissipation can be activated by an uncoupler.5. Evidence is presented for the existence of a non-inhibited intermediate F₁-inhibitor complex.     

Isometric virus-like particles from citrus red mites, Panonychus citri

Virus-like spherical particles found in laboratory-reared citrus red mites but not in field populations were independent of the pathogenic virus affecting this species. Three sizes of particles are present: 18-nm spheres occuring in crystalline array, and 30- and 37-nm spheres. The particles possess antigenic properties and contain RNA.     

Retrotransposon mdg3 Is Transferred between Somatic Cells of Unrelated Species in Mixed Culture

Since retrovirus-like particles of gypsy (mdg4) are capable of interspecific transfer, other Drosophila melanogaster gypsy-related retrotransposons were tested for this property. As a donor and a recipient, D. melanogaster and D. virilis cultured cells were used. Recipient cell DNA was analyzed with probes directed to mdg1, mdg3, 17.6, 297, 412, or B104/roo. Transfer was demonstrated for mdg3, which lacks env. The possible mechanism of transfer is discussed.     

A picornavirus-like pathogen of Cotylogaster occidentalis (Trematoda: Aspidogastrea), an intestinal parasite of freshwater mollusks

Nonoccluded, icosahedral picornavirus-like (PVL) particles, 23 nm in diameter, forming paracrystalline arrays were seen in the cytoplasm of various cells in Cotylogaster occidentalis. Viral inclusions were visible in live specimens and in sections prepared for light and electron microscopy. All worms examined over a 2-year period were found to be infected. Infections were naturally acquired and susceptibility was not associated with any particular developmental stages. Development of viral inclusions involved an increase in the inclusion volume, progressive accumulation and condensation of materials into the interior of the inclusions, and formation of multilamellar membrane networks. Virus particles were observed in the stroma of the inclusions in association with multilamellar spherical bodies. Mature PVL particles aggregated into polygonally shaped paracrystalline arrays. When such arrays occurred in the surface tegument, local disruption of the tegumentary membrane may liberate these particles into the environment. PVL particle production did not exhaust glycogen content of infected cells and did not appear to affect short-term survival of the parasite outside the molluscan host.     

Distinct genotype and antigenicity among genogroup II sapoviruses

SaV, a pathogen of acute gastroenteritis, is divided into five genogroups, GI to GV. However, the relation between SaV antigenicity and genetic clusters is not fully understood. We have recently identified two GII SaV strains, Mc10 and C12, which are grouped into the same cluster based on the polymerase but are grouped into distinct clusters based on the capsid. To evaluate the difference in antigenicity between these two strains, VLP were expressed in mammalian cells. An antigen ELISA demonstrated for the first time that strains in the same GII SaV genogroup, but within different clusters, have distinct antigenicities.