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PubMed2004

Quantum-to-classical transition with single-photon-added coherent states of light.

Single-photon-added coherent states are the result of the most elementary amplification process of classical light fields by a single quantum of excitation. Being intermediate between a single-photon Fock state (fully quantum-mechanical) and a coherent (classical) one, these states offer the opportunity to closely follow the smooth transition between the particle-like and the wavelike behavior of light. We report the experimental generation of single-photon-added coherent states and their complete characterization by quantum tomography. Besides visualizing the evolution of the quantum-to-classical transition, these states allow one to witness the gradual change from the spontaneous to the stimulated regimes of light emission.

Journal Article↗

PubMed2001

Perceptions of indoor air quality associated with ventilation system types in elementary schools.

With the increased utilization of school buildings on a year-round basis, school indoor air quality has become a national concern. The purpose of this study was to evaluate possible associations between ventilation system type and occupant perception of indoor air quality. Staff (n = 403) from 12 schools completed a self-administered questionnaire. Carbon dioxide (CO2) levels, air exchange rates, and particle counts were also measured for each school. Schools with unit ventilator (UV) systems had the lowest mean CO2 level at 637 ppm, followed by the variable air volume (VAV) systems with 664 ppm, and constant volume (CV) systems with a mean of 703 ppm. Schools with UV systems had the lowest mean air exchange rate at 2.67 air changes per hour (ACH), followed by the VAV system type at 2.80 ACH and the CV system type at 4.61 ACH. Indoor versus outdoor particle ratios were calculated for each ventilation system type. Particles with aerodynamic diameters ranging from 0.1-1.0 microm had a geometric mean ratio ranging from 0.38 to 0.68; particles with aerodynamic diameters ranging from 1-3 microm had ratios ranging from 1.39 to 5.47, and particles with aerodynamic diameters greater than 3 microm had ratios ranging from 3.20 to 14.76. Schools using VAV systems had a significantly lower prevalence of red and watery eyes while schools with UV systems had an elevated prevalence of nasal congestion, sore throat, headache, and dustiness complaints. This increased prevalence of complaints in buildings with UV systems may be due to the increased particulate levels.

Adult↗

PubMed1994

The LPS localization might explain the lack of protection of LPS-specific antibodies in abortion-causing Chlamydia psittaci infections.

Four monoclonal antibodies against chlamydial lipopolysaccharide (LPS) were used to study their localization and distribution in the Chlamydia psittaci AB7 abortion-causing strain by immunoelectron microscopy. A non-embedding technique on whole chlamydiae, together with a post-embedding technique on McCoy cells infected with the strain, were performed. Immunogold labelling was observed on the surface of reticular bodies (RB), but not on elementary bodies (EB). Immunolabelling was observed in ultrathin sections on both sides of the external chlamydial membrane, mainly on the inner side of EB and on the outer side of RB. Immunogold density was higher in EB than in RB; however, the absolute number of gold particles was higher in RB than EB, suggesting a loss of immunolabelling during the transformation of RB into EB. Specific labelling of LPS was also found in electrodense and adielectronic vacuoles near the surface of the cytoplasmic membrane of infected McCoy cells. These results suggest that the lack of protection against some chlamydial strains, despite the presence of anti-LPS specific antibodies, is due to the localization of LPS on the inner side of the external membrane of EB.

Abortion, Veterinary↗

PubMed1995

Prevalence of goiter in school children in the Wan-Hwa district of Taipei.

Salt has been iodized in Taiwan since 1967. To understand goiter status after salt iodization, we studied the prevalence of goiter in school children in rural areas where tap water or underground water are used. To further elucidate the prevalence of goiter in urban areas where tap water is used, we studied school children from the Tong-Yuan and Lao-Song elementary schools located in the Wan-Hwa District of Taipei. Thyroid enlargement was examined by palpation as recommended by the World Health Organization. Thyroid antibodies and hormones were determined in school children with goiter and in age- and sex-matched normal control children using particle agglutination methods and radioimmunoassay. A total of 4,623 school children were examined. Of these, 129 children (2.8%) had goiters of grade I or above, or nodular goiters. The prevalence of goiter was similar to that of Putai and Peimen in southern Taiwan where tap water is used, but less than that of Tachia and Chingshuei in middle Taiwan where underground water is used. The prevalence of goiter was much lower than recent studies in Tung-Lo, an oil-bearing area in middle Taiwan, where there was a 12.9% prevalence in school children residing in hill districts who relied on underground water for drinking purposes, and 8.2% in school children residing on lower plains, who depended upon tap water for drinking purposes. The prevalence of goiter is highly related to the quality of drinking water.(ABSTRACT TRUNCATED AT 250 WORDS)

Child↗

PubMed2006

Ultrasonic standing wave manipulation technology integrated into a dielectrophoretic chip.

Several cell-based biological applications in microfluidic systems require simultaneous high-throughput and individual handling of cells or other bioparticles. Available chip-based tools for contactless manipulation are designed for either high-precision handling of individual particles, or high-throughput handling of ensembles of particles. In order to simultaneously perform both, we have combined two manipulation technologies based on ultrasonic standing waves (USWs) and dielectrophoresis (DEP) in a microfluidic chip. The principle is based on the competition between long-range ultrasonic forces, short-range dielectrophoretic forces and viscous drag forces from the fluid flow. The ultrasound is coupled into the microchannel resonator by an external transducer with a refractive element placed on top of the chip, thereby allowing transmission light microscopy to continuously monitor the biological process. The DEP manipulation is generated by an electric field between co-planar microelectrodes placed on the bottom surface of the fluid channel. We demonstrate flexible and gentle elementary manipulation functions by the use of USWs and linear or curved DEP deflector elements that can be used in high-throughput biotechnology applications of individual cells.

Electrophoresis, Microchip↗

PubMed1993

Chlamydia trachomatis infection of cultured motile cells after uptake of chlamydiae from the substratum.

The ability of motile cells to remove small inanimate particles from solid substrata is well documented. We show here that motile cells will pick up and internalize infectious particles of the obligate intracellular parasite Chlamydia trachomatis when they are adherent to the substratum over which the host cells move. Two cell types were used to assess chlamydial uptake; a feeder independent human squamous cell carcinoma variant (AC3A cells) and the McCoy cell line. Purified chlamydia elementary bodies were attached to glass or collagen-coated glass by centrifugation. Suspensions of cells were then allowed to sediment on to the substrata to which chlamydiae had attached. Both types of cell picked up chlamydiae and transported them over their surface during the course of attachment and spreading. Stereoscopic images obtained by confocal microscopy demonstrated that chlamydiae were found mainly on the surface of non-spread cells. After the cells had spread on the substratum they began to move around forming tracks where the chlamydiae had been removed. Some cell-surface-attached chlamydiae were endocytosed and a proportion of these proliferated during the 48 h after plating. However, chlamydiae attached to the substratum lost infectivity by a simple exponential decay process within a few hours of incubation in the extracellular environment. Therefore, increasing numbers of non-viable organisms were probably endocytosed as the time of extracellular incubation increased. This mode of infection may be relevant to in vivo situations where cell migration occurs after damage to mucosal surfaces.

Bacterial Adhesion↗

PubMed2002

Maximal force exerted by a molecular motor.

We consider a particle diffusing in a one-dimensional periodic lattice with arbitrary transition rates between nearest-neighbor sites. We show rigorously that the ratio of the drift velocity V to the diffusion coefficient D has the upper bound 2N/d, where N is the number of nodes in an elementary cell and d denotes its length. Applying this result to a model of a molecular motor introduced by Fisher and Kolomeisky [Proc. Natl. Acad. Sci. USA 96, 6597 (1999)] we show that the so called Einstein force, which sets the lower bound for the force exerted by a molecular motor, is bounded from above by 2k(B)TN/d irrespective of the actual values of the jump rates between internal states of the motor.

Biophysical Phenomena↗

PubMed1985

The histopathology and electron microscopy of a human monkeypox lesion.

The histological and electron microscopic findings from a solitary cutaneous monkeypox lesion taken post mortem from a child who died after a five-day illness are reported. This child is 44th in the WHO register of monkeypox cases. The lesion was at the papulonecrotic stage, with early evidence of vesiculation and minimal evidence of pustulation. Necrosis affected the stratum basale, the related basement membrane and adjacent areas of the dermal papillae at the centre of the lesion. Cell necrosis affected the next two or three layers of stratum spinosum above the destroyed stratum basale. Lateral to this zone, marked hyperplasia and intracellular oedema of the stratum spinosum constituted the papule and produced spindle-cell features. In the middle layer of the stratum spinosum, above the necrotic focus, there were minute vesicles and between these were occasional multinuclear giant cells. Bodies similar to Guarnieri bodies (GB) were present in the cytoplasm of sweat duct-lining cells in the epidermis and upper corium. Very scanty similar bodies were evident elsewhere in the papular epidermis but were difficult to distinguish from debris. Granules in the lesion with the same size as mature virions (elementary bodies) have been assessed not to be these because similar granules are present in the normal epidermis. Changes in the dermis apart from those mentioned above were minimal oedema, very mild perivascular infiltration by round cells and an occasional eosinophil. Electron microscopy showed abundant immature and mature orthopoxvirus particles in the cytoplasms of infected epidermal cells. A limited range of histochemical tests is detailed. In general, the features are indistinguishable from the papulonecrotic stage of smallpox (variola) and from tanapox as recorded in man.

Child, Preschool↗

PubMed2001

"Vector Chromatography": Modeling Micropatterned Separation Devices.

A repetitive sequence of quiescent fluid layers of differing viscosities through which small spherical Brownian particles move is analyzed in order to illustrate in a simple context how the theory of macrotransport processes, a generalization of Taylor dispersion theory, may be employed to rigorously analyze spatially periodic micropatterned chromatographic separation devices for circumstances in which the solute species to be separated are animated by the action of species-specific external forces oriented asymmetrically relative to the body-fixed pattern. In the generic "vector" separation scheme, illustrated by our elementary example, the different species undergoing separation move, on average, in different directions relative to pattern-fixed axes, whence their chromatographic sorting is effected according to their different mean angular trajectories through the device. This scheme differs fundamentally from traditional "scalar" chromatographic separation schemes, wherein all species move on average parallel to the animating force (including circumstances in which they are passively entrained in a unidirectional solvent flow) and hence for which the sorting is effected by the relative speeds of the several species through the chromatographic column. Vector chromatography is quantified by two global "macrotransport coefficients", namely the solute mobility dyadic M* (representing the tensor proportionality coefficient between the mean solute velocity vector U* and the external force vector F acting upon the solute molecules) and the dispersivity dyadic D* (resulting from the deviation of the instantaneous position of the particle from its mean position based upon its mean velocity vector). In the present example these coefficients are studied parametrically as functions of: (i) the orientation of the external force relative to the symmetry axis of the fluid layers; (ii) the local viscosity distribution within a layer; (iii) the vector particle Peclet number (constructed from the vector force, the length of the viscosity period, and the Boltzmann factor kT); and (iv) the thermodynamic interphase solute partition distribution coefficient between the two fluid layers comprising a unit cell. Copyright 2001 Academic Press.

Journal Article↗

PubMed2000

Single-particle tracking: Brownian dynamics of viscoelastic materials.

A unifying theoretical framework for analyzing stochastic data from single-particle tracking (SPT) in viscoelastic materials is presented. A generalization of the bead-spring model for linear polymers is developed from a molecular point of view and from the standpoint of phenomenological linear viscoelasticity. The hydrodynamic interaction in the former is identified as the dashpots in the latter. In elementary terms, the intimate correspondence between time-correlation of the fluctuation measurements and transient relaxation kinetics after perturbation is discussed, and the central role of the fluctuation-dissipation relation is emphasized. The work presented here provides a bridge between the microscopic and the macroscopic views of linear viscoelastic biological materials, and is applicable to membrane protein diffusion, linear DNA chain dynamics, and mechanics of intracellular cytoskeletal networks.

Biopolymers↗

PubMed1996

Quantum chaos in nano-sized billiards in layered two-dimensional semiconductor structures.

We consider two-dimensional, electron-rich cavities that can be created at a (AlGa)As-GaAs interface. In the modelling of such cavities we include features that are typical for small semiconductor structures or devices, i.e., soft walls representing electrostatic confinement and disorder due to ionized impurities. The introduction of soft walls is found to have a profound effect on the dynamic behaviour. There are situations in which there is a crossover from a Wigner distribution for the nearest level spacing to an effectively Poisson-like one as the confining walls are softened. The crossover occurs in a region which is accessible experimentally. A mechanism for the crossover is discussed in terms of groups of energy levels being separated from each other as walls become soft. The effects of disorder are found to be negligible for high-mobility samples, i.e., the motion of the particles is ballistic. These findings are of a general nature. Chaotic Robnik dots, circular dots with a special "dent," are also investigated. In this case there is no crossover from Wigner to Poisson distributions. An explanation for this difference is proposed. Finally, the effects of leads are investigated in an elementary way by simply attaching two stubs to a circular dot. For wide stubs, which in our simple model would correspond to open leads, we obtain Wigner statistics indicating a transition to irregular behaviour. A lead-induced transition of this kind appears consistent with recent measurements of the line-shape of the weak localization peak, observed in the low-temperature magnetoresistance of square semiconductor billiards. Finally, implications for conductance fluctuations are briefly commented on. (c) 1996 American Institute of Physics.

Journal Article↗

PubMed1999

Combined immunoprecipitation and agglutination for the detection of the heterodimeric molecule: human chorionic gonadotropin as a study model.

Double-particle reversed passive hemagglutination (RPHA) was performed for the detection of an intact heterodimeric form of human chorionic gonadotropin (intact hCG) composed in Profasi hCG (P-hCG). This technique relied on two mixed types of human O RBC, which were individually coated with two distinct monoclonal antibodies that recognized alpha or beta subunit of hCG, i.e. ALC-1 and BEL-5, respectively. The positive hemagglutination result was achieved by this technique. However, in the BEL-5 coated single-particle control system, positive results for both P-hCG and beta subunit hCG solution were realized. The occurrence of beta-multimer hCG was a causative molecule revealed by the hemagglutination inhibition technique. Thereby, the novel method called "combined immunoprecipitation and agglutination" was developed to overcome this problem. The free beta subunit together with the betamultimer hCG were eliminated from other forms presented in P-hCG after using the ALC-1 coated particles. The precipitated particles, which captured the heterodimer hCG molecule, reacted further with soluble BEL-5 to subsequently form a trellis. A positive result was obtained only with P-hCG, but not with beta subunit hCG or hLH. This study is inferable as a model for the detection of heterodimeric molecule by an elementary method.

Antibodies, Monoclonal↗

PubMed1987

Mass, volume and dimensional distributions in biology, with special reference to cells.

The positively skewed distribution of mass (weight) in biology was examined, and it was concluded all weight or masses can best be described by lognormal theory. Examples are given ranging in weight from viruses to humans. The accretion of mass proceeds as "more of the same" and primarily does not alter function. Immunologic properties must be carefully preserved. Small biologic entities can afford only small mass gains or losses while preserving their functionality; the larger the entity, the larger is the variability of mass functionally permitted. A well-established, convenient graphic method of analyzing a sample is described, with the advantages and pitfalls discussed. At the cellular level, volume and dimensions are lognormally distributed whenever the specific gravity (g/cu cm) is nearly homogenous among the particles or cells. In multicellular organisms, dimensions and forms (such as height and cranial circumference) are primarily the product of multifactorial genetic determinants and frequently appear as normal distributions. This paper discusses the meaning of the law of proportionate effects for small biologic objects, especially cells, and how an initial or "elementary" distribution may be conceived.

Animals↗

PubMed1991

Exciton microscopy and reaction kinetics in restricted spaces.

We describe the development of a new biologically non-invasive ultraresolution light microscopy, based on combining the energy transfer "spectral ruler" method with the micro-movement technology employed in scanning tunneling microscopy (STM). We use near-field scanning optical microscopy, with micropipettes containing crystals of energy packaging donor molecules in the tips that can have apertures below 5 nm. The excitation of these tips extends near field microscopy well beyond the 50 nm limit. The theoretical resolution limit for this spectrally sensitive light microscopy is well below 1 nm. Exciton microscopy is ideally suited for kinetic studies that are spatially resolved on the molecular scale, i.e., at a single molecule site. Moreover, the successful operation of the scanning exciton tip depends on an understanding of reaction kinetics in restricted spaces. In contrast to the many recent reviews on scanning tip microscopies, there is no adequate review of the recent revolutionary developments in the area of reaction kinetics in confined geometries. We thus attempt such a review in this paper. Reactions in restricted spaces rarely get stirred vigorously by convection and are thus often controlled by diffusion. Furthermore, the compactness of the Brownian motion leads to both anomalous diffusion and anomalous reaction kinetics. Elementary binary reactions of the type A + A----Products, A + B----Products and A + C----C + Products are discussed theoretically for both batch and steady-state conditions. The anomalous reaction orders and time exponents (for the rate coefficients) are discussed for various situations. Global and local rate laws are related to particle distribution functions. Only Poissonian distributions guarantee the classical rate laws. Reactant self-organization leads to interesting new phenomena. These are demonstrated by theory, simulations, and experiments. The correlation length of reactant production affects the self-ordering length-scale. These effects are demonstrated experimentally, including the stability of reactant segregation observed in chemical reactions in one-dimensional spaces, e.g., capillaries and microcapillaries. The gap between the reactant A (cation) and B (anion) actually increases in time, and extends over millimeters. Excellent agreement is found among theory, simulation, and experiment for the various scaling exponents.

Kinetics↗

PubMed1984

Ultrastructure of Chlamydia trachomatis infection of the mouse oviduct.

Chlamydial inclusions were found in the luminal epithelium of all segments of the oviducts (ostium, ampulla, and isthmus) of mice experimentally inoculated with the mouse pneumonitis (MoPn) biovar of Chlamydia trachomatis. Electron microscopy of infected oviducts revealed chlamydial inclusions in both ciliated and nonciliated cells of the oviduct epithelium. Inclusions contained typical elementary, intermediate and reticulate bodies as well as numerous "miniature reticulate bodies" and membrane ghosts. Small, vesicle-like structures were observed in infected cells near inclusions but were not seen in apparently uninfected cells nor in the oviducts of mice inoculated with the control (sterile tissue culture supernate) suspension. Chlamydia-like particles were seen in vacuoles of polymorphonuclear leukocytes. Intracellular Chlamydia-like particles were not seen in any other cell type in the mouse oviduct. Infection of the mouse oviduct with MoPn is a convenient model for the study of C. trachomatis morphology in vivo.

Animals↗

PubMed2006

An early event in the herpes simplex virus type-2 replication cycle is sufficient to induce Chlamydia trachomatis persistence.

Epidemiological studies have demonstrated that co-infections of herpes simplex virus type 2 (HSV-2) and Chlamydia trachomatis occur in vivo. Data from a tissue culture model of C. trachomatis/HSV-2 co-infection indicate that viral co-infection stimulates the formation of persistent chlamydiae. Transmission electron microscopic (TEM) analyses demonstrated that in both HeLa and HEC-1B cells, co-infection caused developing chlamydiae to exhibit swollen, aberrantly shaped reticulate bodies (RBs), characteristically observed in persistence. Additionally, HSV-2 co-infection suppressed production of infectious chlamydial elementary bodies (EBs) in both host cell types. Co-infection with HSV type 1 (HSV-1) produced similar morphologic alterations and abrogated infectious EB production. These data indicate that virus-induced chlamydial persistence was neither host cell- nor virus strain-specific. Purification of crude HSV-2 stocks demonstrated that viral particles were required for coinfection-induced chlamydial persistence to occur. Finally, co-infection with either UV-inactivated, replication-incompetent virus or replication-competent HSV-2 in the presence of cyclohexamide reduced chlamydial infectivity without altering chlamydial genomic DNA accumulation. These data demonstrate that productive viral replication is not required for the induction of chlamydial persistence and suggest that HSV attachment and entry can provide the necessary stimulus to alter C. trachomatis development.

Animals↗

PubMed1975

Ultrastructural studies of Chlamydia psittaci 6BC in situ in yolk sac explants and L cells: a comparison with gram-negative bacteria.

Chlamydia psittaci (6BC) was grown in yolk sac explants and in L cells and fixed by perfusion in situ to provide undamaged material for comparison with gram-negative bacteria. Reticulate, intermediate, and elementary bodies were all seen to lack a well-defined periplasmic space; intermediate and elementary bodies showed condensations of the nucleoid which differ from common bacterial configurations; and the cytoplasm of highly condensed elementary bodies was much more electron dense than that of the gram-negative bacteria, while retaining its basically particulate nature. These important morphological distinctions are interpreted as reflections of a significantly different cellular level of organization in these two groups of organisms. No important morphological differences were noted in comparisons of the chlamydial particles grown in the two different host systems.

Animals↗

PubMed1997

Dose-response relationship of fibrous dusts in intraperitoneal studies.

The relationship between the number of fibers injected intraperitoneally and the occurrence of peritoneal mesotheliomas in rats was investigated using data from a series of carcinogenicity studies with several fibrous dusts. Based on observed tumor incidences ranging between 10 and 90%, the hypothesis of a common slope of dose-response relationships (parallel probit lines in probit analysis) cannot be rejected. In general, parallelism of probit lines is considered an indication of a common mode of action. Analysis of the shape of the dose-response relationship, with one apparent exception, shows virtually linear or superlinear behavior, i.e., from these data, there is no indication of a decrease in carcinogenic potency of an elementary carcinogenic unit at lower doses.

Animals↗