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PubMed2002

Nuclear democracy. Political engagement, pedagogical reform, and particle physics in postwar America.

The influential Berkeley theoretical physicist Geoffrey Chew renounced the reigning approach to the study of subatomic particles in the early 1960s. The standard approach relied on a rigid division between elementary and composite particles. Partly on the basis of his new interpretation of Feynman diagrams, Chew called instead for a "nuclear democracy" that would erase this division, treating all nuclear particles on an equal footing. In developing his rival approach, which came to dominate studies of the strong nuclear force throughout the 1960s, Chew drew on intellectual resources culled from his own political activities and his attempts to reform how graduate students in physics would be trained.

History↗
PubMed2006

Results of an indoor size fractionated PM school sampling program in Libby, Montana.

Libby, Montana is the only PM(2.5) non-attainment area in the western United States with the exceptions of parts of southern California. During January through March 2005, a particulate matter (PM) sampling program was conducted within Libby's elementary and middle schools to establish baseline indoor PM concentrations before a wood stove change-out program is implemented over the next several years. As part of this program, indoor concentrations of PM mass, organic carbon (OC), and elemental carbon (EC) in five different size fractions (>2.5, 1.0-2.5, 0.5-1.0, 0.25-0.5, and <0.25 microm) were measured. Total measured PM mass concentrations were much higher inside the elementary school, with particle size fraction (>2.5, 0.5-1.0, 0.25-0.5, and <0.25 microm) concentrations between 2 and 5 times higher when compared to the middle school. The 1.0-2.5 microm fraction had the largest difference between the two sites, with elementary school concentrations nearly 10 times higher than the middle school values. The carbon component for the schools' indoor PM was found to be predominantly composed of OC. Measured total OC and EC concentrations, as well as concentrations within individual size fractions, were an average of two to five times higher at the elementary school when compared to the middle school. For the ultrafine fraction (<0.25), EC concentrations were similar between each of the schools. Despite the differences in concentrations between the schools at the various fraction levels, the OC/EC ratio was determined to be similar.

Air Pollution, Indoor↗
PubMed2004

Highly resolved fluid flows: "liquid plasmas" at the kinetic level.

Fluid flow around an obstacle was observed at the kinetic (individual particle) level using "complex (dusty) plasmas" in their liquid state. These "liquid plasmas" have bulk properties similar to water (e.g., viscosity), and a comparison in terms of similarity parameters suggests that they can provide a unique tool to model classical fluids. This allows us to study "nanofluidics" at the most elementary-the particle-level, including the transition from fluid behavior to purely kinetic transport. In this (first) experimental investigation we describe the kinetic flow topology, discuss our observations in terms of fluid theories, and follow this up with numerical simulations.

Journal Article↗
PubMed2005

Electrostatic charge characteristics of aerosols produced from metered dose inhalers.

The electrostatic charge properties of aerosols produced by commercial metered dose inhalers (MDIs), including Ventolin, QVAR, Flixotide, Intal Forte, and Tilade were studied using a modified 13-stage electrical low pressure impactor (ELPI) with aerodynamic diameter cutoff ranging from 0.028 to 10.07 microm. All the stages are electrically insulated from each other with the last 12 stages connected individually to electrometers with sensitivity at femtoampere levels. Aerosol particles deposited on the impactor stages according to their aerodynamic diameters and their charges were measured by the electrometers. The deposited drug mass was assayed chemically using HPLC. The results show that particles of bipolar charge distribution were produced reproducibly from Intal Forte, Tilade, and Flixotide. In contrast, those from Ventolin and QVAR displayed charge variation, depending on the time lapse between actuations. This suggests that charge relaxation may influence the charging of these two MDIs. Mass distributions were reproducible for all MDIs except for Ventolin, the first puff from which was always the highest in dose. The different charge characteristics of the MDIs could be attributed to differences in the drug and formulation as well as valve materials. In general, submicron particles showed a larger variation in the charge-to-mass ratio (q/m). This indicated charge contribution by propellant/excipients (which produce submicron particles) rather than the drug itself. The calculated number of elementary charges per drug particle of size <or= 6.06 microm ranged from zero to several ten thousands. The charge level is sufficiently high to have a potential effect on the deposition of the inhaled particles in the respiratory tract. In conclusion, the ELPI provided more detailed charge information about the MDI aerosol particles. Different aerosol charge profiles were shown by commercial MDIs, and the results can be explained by variation in the drug, formulation and the MDI materials. The results may have practical significance on lung deposition of MDI aerosols and regulatory aspects of generic aerosol products.

Aerosols↗
PubMed1977

Apparent electric charge of protein molecules. Human thyroxine - binding proteins.

1. By comparison of electrophoretic mobilities of two different charged particles under the same conditions the net elementary electrostatic charge of one particle could be calculated when the charge of the other is known. 2. The electrophoretic mobility of human thyroxine - binding globulin does not depend upon the concentration of Tris - HCl buffer in the range 0.05 to 0.20 molar. The value of this mobility is 0.078 and 0.083 cm2 vol(-1) hour(-1) at pH 7.0 and 8.6, respectively. 3. The net elementary electrostatic charge of the human thyroxine - binding globulin appears to be approximately 22 negative elementary electrostatic units in mild alkaline solutions.

Electrochemistry↗
PubMed1993

Biological markers as indicators of exposure and pneumoconiotic risk: prospective study.

This research is designed to evaluate a number of biological markers to estimate harmful exposure on coal miners from different mining regions in France and to relate the outcome to differences in prevalence of coal worker pneumoconiosis (CWP) between these regions. Eight epidemiological groups of active and ex-miners (smokers and non-smokers) have been selected in the French collieries (North, Lorraine and Provence) according to their occupational and pneumoconiotic status. The following biomarkers have been evaluated: cellularity of sputum, elementary analysis of particles in TEM/EDAX, plasma neutral metalloendo-peptidase elastase type (NMEP), leucocyte elastase (HLE), fibronectin (FN) and elastin peptides. Pulmonary alveolitis, expressed by sputum cellularity, is different between active workers groups but not related to the general background of pneumoconiosis prevalence in the French collieries. In the plasma parameters, fibronectin, HLE and NMEP significantly increased in all groups of coal mine workers as compared to the control group, except for fibronectin parameter in Lorraine collierie. The degree of increase of these parameters allow us to discriminate the different groups and suggest that plasma FN, HLE and NMEP may be considered as biological markers of chronic inhalation of coal mine dust particles. The decrease of elastin peptides level in the Lorraine group alone suggests a specific alteration of elastin metabolism. These parameters were not related to the development of pneumoconiosis and its degree of severity.

Biomarkers↗
PubMed2004

Colloidal stability of aqueous dispersions of block ionomer complexes: effects of temperature and salt.

This work characterized colloidal stability of the dispersions, formed by the complexes of poly(ethylene oxide)-b-poly(sodium methacrylate) and hexadecyltrimethylammonium bromide. At room temperature, the dispersion was stabilized by the poly(ethylene oxide) (PEO) chains and did not aggregate for at least several months. Elevation of temperature caused aggregation of the dispersion because of dehydration of the PEO chains. At initial stages (minutes), the aggregation was reversible and the particles spontaneously redispersed once the temperature was decreased. However, it became irreversible at the later stages (hours), probably indicating fusion of the hydrophobic cores of the BIC particles. Addition of elementary salts led to a decrease of the aggregation temperature. The effects of various salts were dependent on the chemical nature of the ions and were consistent with the Hofmeister series. This behavior was discussed in terms of hydration and London (dispersion) interactions between the ions and the PEO.

Journal Article↗
PubMed1954

Intracellular forms of meningopneumonitis virus.

Electron micrographs of intracellular memngopneumonitis virus have shown several types of particles which are presumably representative of different stages of a life cycle. They are: (a) Elementary bodies-dense particles 250 to 300 mmicro in diameter with very dense central granules. (b) Intermediate forms-less dense than elementary bodies and larger. They are 300 to 400 mmicro in diameter, contain a very dense central granule, and often have two or three limiting zones, (c) Circles 400 to 500 mmicro in diameter-homogeneous structures with single membranes and no internal granules. They are often elongated and constricted at the center in the manner of budding yeast cells, (d) Circles 500 to 600 mmicro in diameter with single membranes.mdash;One, two, and three dense granules may be present in some of these structures, (e) "Larger" structures, circular to elliptical, often with discontinuities or ruptures in their membranes. They sometimes seem to have internal septa. It has been inferred from these observations that the virus can multiply by binary fission or by multiple endosporulation and that elementary bodies are a spore-like stage.

Cell Division↗
PubMed2005

Electrostatically stabilized metal oxide particle dispersions in carbon dioxide.

We report electrostatic stabilization of micrometer-sized TiO(2) particles at long range (several micrometers) in liquid and supercritical CO(2) despite the ultralow dielectric constant, as low as 1.5. The counterions were solubilized in dry reverse micelles, formed with a low-molecular weight cationic perfluoropolyether trimethylammonium acetate surfactant, to prevent ion pairing with the particle surface. Dynamic light scattering and settling velocities indicate a particle diameter of 620-740 nm. The electrophoretic mobility of -2.3 x 10(-8) m(2)/V s indicated a particle charge on the order of -1.7 x 10(-17) C, or 105 elementary negative charges per particle. The balance of particle compression by an electric field versus electrostatic repulsion generated an amorphous arrangement of particles with 5-9 mum spacing, indicating Debye lengths greater than 1 mum. Scattering patterns also indicate that chains of particles may be achieved in CO(2) by dielectrophoresis with alternating fields. The electrostatic stabilization has been achieved by solubilizing a small concentration of counterions in only a small fraction of the reverse micelles in the double layer. Whereas many low-molecular weight surfactants have been shown to form reverse micelles in CO(2), very few polymers are able to stabilize micrometer-sized colloids sterically. Thus, electrostatic stabilization has the potential to expand markedly the domain of colloid science in apolar supercritical fluids.

Journal Article↗
PubMed2006

Nanoparticle assembly on patterned "plus/minus" surfaces from electrospray of colloidal dispersion.

Selective deposition of metal (Au) and oxide (SiO2) nanoparticles with a size range of 10-30 nm on patterned silicon-silicon oxide substrate was performed using the electrospray method. Electrical charging characteristics of particles produced by the electrospray and patterned area created by contact charging of the electrical conductor with non- or semi-conductors were investigated. Colloidal droplets were electrosprayed and subsequently dried as individual nanoparticles which then were deposited on substrates, and observed using field emission-scanning electron microscopy. The number of elementary charge units on particles generated by the electrospray was 0.4-148, and patterned area created by contact charging contained sufficient negative charges to attract multiple charged particles. Locations where nanoparticles were (reversibly) deposited depended on voltage polarity applied to the spraying colloidal droplet and the substrate, and the existence of additional ions such as those from a stabilizer.

Journal Article↗
PubMedDate not supplied

Overview of Chlamydia trachomatis infection and the requirements for a vaccine.

Chlamydia trachomatis is an important human pathogen. The development of vaccines designed to prevent C. trachomatis-associated morbidity would be highly desirable. In the developing world the major goal is the prevention of blindness due to trachoma; in industrialized societies and in some developing countries, the major goal is the prevention of chlamydial salpingitis and its consequences. In early trials of trachoma vaccine composed of a suspension of elementary bodies (the infectious particles), short-lived protective immunity was induced, but deleterious effects, i.e., hyperreactivity to infection, were also noted. Thus it is likely that separation of the protective from the sensitizing antigens and the development of a subunit vaccine will be necessary. Chlamydial virulence factors include the surface structures (presumably antigenic) that are responsible for specific attachment of the organism to a susceptible host cell, induction of phagocytosis by the host cell, or inhibition of phagolysosomal fusion. Serotype-specific neutralizing antigens might also be candidate antigens. Purification of such subunit antigens from chlamydial particles is probably impractical. It is likely that genetic engineering will be required for the production of cloned antigens after such antigens have been identified.

Bacterial Vaccines↗
PubMedDate not supplied

Probing pores using elementary quantum mechanics.

The relaxation of polarized spins in a porous medium has been utilized as a probe of its structure. We note that the governing diffusion problem has a close parallel to that of a particle in a box, an elementary Quantum mechanics toy model. Following the spirits of "free electron" model, we use generic properties of the eigen spectrum to understand features common to a wide variety of pore geometry, consistent with large scale numerical simulations and experimental data.

Magnetic Resonance Spectroscopy↗
PubMed1980

Host influence on the density of chlamydiae in Renografin gradients.

Egg-grown and L cell-grown C. psittaci 6BC strains formed two bands when centrifuged through preformed Renografin gradients. No additional bands were observed by extending the time of centrifugation. Particles present in the bands which were collected from the Renografin gradients were examined by electron microscopy. Purified elementary bodies from both egg- and L cell-grown sources were located in a lower, minor bind; egg-derived elementary bodies showed a higher density (p < 0.01) than elementary bodies derived from L cells. Particles present in the major, upper band of both egg- and L cell-derived strains had similar densities and contained mixed populations of elementary bodies and polymorphic reticulate bodies.

Animals↗
PubMed1988

Resonant ac-dc magnetic fields: calculated response.

An elementary model consisting of one charged particle in a viscous medium exposed to weak ac-dc low-frequency magnetic fields is analyzed to identify and explain the fundamental characteristics of the physical mechanisms that result in a resonance response, which is similar to the familiar cyclotron resonance. The model predicts both frequency and amplitude windows, which are explained in terms of synchronization of the particle with electric fields. Although extrapolation of model results to biological systems is limited by the elementary nature of the model, the model results indicate that observed resonant responses by others of biological systems to ac-dc magnetic fields are probably not due to resonant response of ions in solution, since the model predicts that no resonant response is possible unless the viscous damping is very low, many orders of magnitude lower than the viscous damping of ions in solution.

Magnetics↗
PubMed1973

Interactions of TRIC agents with macrophages and BHK-21 cells observed by electron microscopy.

TRIC agents do not multiply in mouse peritoneal macrophages in culture but have a toxic effect on them, whereas they multiply readily in BHK-21 cells. Sections of macrophages and of BHK-21 cells fixed during the first 90 min after inoculation were examined by electron microscopy. Macrophages ingested all forms of the organism, which were eventually degraded in lysosomes. However, elementary bodies were distinguished from other TRIC particles by the delay in their transfer to lysosomes. BHK-21 cells ingested elementary bodies selectively, and in these cells the organisms were neither found in lysosomes nor degraded. Instead they showed morphological changes that probably represented an early stage of development.

Acid Phosphatase↗
PubMed1973

Fine structures of cell envelopes of Chlamydia organisms as revealed by freeze-etching and negative staining techniques.

The cell walls of Chlamydia psittaci (meningopneumonitis strain) were examined by the freeze-etching and negative staining techniques. It was observed that the cleaved convex surface of the developmental, reticulate body was covered with numerous non-etchable particles 9 to 10 nm in diameter, these particles being rarely seen on the concave surface. Similarly, the convex surface of the mature, elementary body (EB) was covered with many particles but the concavity lacked these particles. After etching, the smooth concave surface of the EB appeared to have a hexagonally arrayed subunit structure, on which the button structure (B structure) was observed. Each B structure had a diameter of 27 nm and several B structures were grouped together in a hexagonal arrangement with a center-to-center spacing of 45 nm. In a limited area of the negatively stained EB cell wall, hexagonally arrayed rosette structures were present, with a center-to-center spacing similar to the B structures seen in the freeze-etched preparation. Each rosette, about 19 to 20 nm in diameter, appeared to be composed of a radial arrangement of nine subunits. The freeze-fractured cell wall-cytoplasmic membrane complexes indicated that the outer surface of the cytoplasmic membrane which appeared as the convex surface was covered with the fine particles, and thus it was likely that frozen EB was cleaved at the gap between the cell wall and ctyoplasmic membrane. On the cleaved inclusion, several groups of fine particles were observed. In each group, the particles were arranged hexagonally with the spacing ranging from 20 to 50 nm.

Cell Membrane↗
PubMed1952

Studies by electron microscopy of thin sections of infectious myxomatosis in rabbits.

Rabbits were inoculated with the C.P.M. strain of myxoma virus and the resulting subcutaneous tumors were fixed, embedded, and sectioned for observation with the electron microscope. Both round cells and the typical stellate myxomatous cells were observed in addition to changes in the collagen pattern at the intercellular spaces. The cytoplasm of the cells showed a great number of bodies of varying size and density, the largest of them having the size and other characteristics of the elementary bodies of the virus. Some of the bodies showed an internal structure, being formed by the tight clumping of small dense particles. Distribution curves of the diameter of the elementary bodies and of the smaller internal particles are presented. The morphological problems involved in the virus-host cell relationship are discussed in the case of the myxoma virus.

Animals↗