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PubMed1995

Cytochemical localization of glycogen in Chlamydia trachomatis inclusions.

The origin and distribution of glycogen in inclusions of Chlamydia trachomatis were demonstrated with silver proteinate stain for electron microscopy. Glycogen particles were detected in all developmental stages of C. trachomatis, as well as free in the inclusions. Intrachlamydial glycogen was most common in elementary bodies but was also detected in intermediate forms and reticulate bodies (RBs). Abnormal divisions and breakdown of cytoplasmic membranes were common in RBs. Cytoplasmic contents, including glycogen particles, were released into the inclusions after rupture of the outer membranes of abnormal RBs and intermediate forms. From these observations, we conclude that glycogen in inclusions of C. trachomatis originates in the organisms themselves.

Amylases↗
PubMed1987

Explanation of parity nonconservation.

Space inversion and other discrete symmetries are treated within the frame of a theory of fundamental forces based only on general considerations of causality, symmetry, and stability, without ad hoc differential equations. The basic space-time M is the Einstein universe R(1) x S(3) as a causal (or conformal) rather than a pseudo-Riemannian manifold. Its connected symmetry group is then a 15-parameter group G locally equivalent to SO(2, 4), while the isometry group K of the Einstein universe is a 7-parameter subgroup. Correlation with conventional relativistic theory is based on a canonical imbedding of Minkowski space M(0) into M, together with the unique extendability of all transformations of the scaling-extended Poincaré group P from M(0) to global transformations on M. The fundamental fermion field F and boson field B are here restricted to be real and are fully invariant under G(e), where the superscript e denotes the inclusion of space and time inversions. The role of C on F is taken over by a real matrix having the eigenvalues +/-i, that commutes with G but anticommutes with space inversion. The spin space for B consists of the real linear transformations on that for F. There is a corresponding natural total Lagrangian that is both G(e) and O(2)-gauge invariant, the latter leading to lepton and baryon number conservation, and which is nonparametric except for scale. The Weyl and Maxwell equations are deduced, and compelling identifications made for neutrinos and the photon. The e and mu neutrino pairs occur in strikingly inequivalent positions in F, appearing symmetric only in the conventional relativistic limit R --> infinity, where R is the ( G-invariant) fundamental length interpretable as the radius of the space S(3). The photon occurs as the lowest member of a coherent subfamily of B that includes natural candidates for bare versions of the W and Z particles. In the relativistic limit the interaction Lagrangian becomes a sum over all elementary processes, one of which appears as quantum electrodynamics with Majorana-type electrons.

Journal Article↗
PubMed2000

Scaling of avalanche queues in directed dissipative sandpiles

Using numerical simulations and analytical methods we study a two-dimensional directed sandpile automaton with nonconservative random defects (concentration c) and varying driving rate r. The automaton is driven only at the top row and driving rate is measured by the number of added particles per time step of avalanche evolution. The probability distribution of duration of elementary avalanches at zero driving rate is exactly given by P1(t,c)=t(-3/2) exp[t ln(1-c)]. For driving rates in the interval 0 server queue in the queue theory. We study scaling properties of the busy period and dissipated energy of sequences of noninterrupted activity. In the limit c-->0 and varying linear system size L<<1/c we find that at driving rates r</=L(-1/2) the distributions of duration and energy of the avalanche queues are characterized by a multifractal scaling and we determine the corresponding spectral functions. For L>>1/c increasing the driving rate somewhat compensates for the energy losses at defects above the line r approximately sqrt[c]. The scaling exponents of the distributions in this region of phase diagram vary approximately linearly with the driving rate. Using properties of recurrent states and the probability theory we determine analytically the exact upper bound of the probability distribution of busy periods. In the case of conservative dynamics c=0 the probability of a continuous flow increases as F(infinity) approximately r(2) for small driving rates.

Journal Article↗
PubMed2005

Plane rectangular tritium target response to excitation by uniform distributed normal accelerated deuteron beam.

This work is a contribution to analytical study of the spatial dependency of the d-T mean neutron energy in the vicinity of a homogeneous tritium-occluded rectangular plane target. An accelerated deuteron beam excites the tritium target with normal incidence to the target plane. The transverse density of accelerated deuteron beam is assumed to be constant close to the target. Due consideration being paid to d-T collision kinetics, depending upon mass and kinetic energy of particles involved in the nuclear collision, nuclear reaction energy, etc, in particular circumstances, the elementary neutron energy emission in non-dispersive media can be considered to be omni-directional or very low anisotropical. Consequently, analytical expressions can be considerably simplified, taking into account the exothermic character of d-T fusion reaction. A number of expressions for energetic prediction of the fast neutron generated, in this case, by d-T reaction are proposed. Animated three-dimensional-graphics is suggested. Computationally tractable tools are of importance in the study of some situations such as induced reactions and activation analysis using 14MeV neutrons, investigations in health-physics, radiation dose characterization, nuclear medicine, damage effects, and simulation studies.

Journal Article↗
PubMed2006

Automatic filters for the detection of coherent structure in spatiotemporal systems.

Most current methods for identifying coherent structures in spatially extended systems rely on prior information about the form which those structures take. Here we present two approaches to automatically filter the changing configurations of spatial dynamical systems and extract coherent structures. One, local sensitivity filtering, is a modification of the local Lyapunov exponent approach suitable to cellular automata and other discrete spatial systems. The other, local statistical complexity filtering, calculates the amount of information needed for optimal prediction of the system's behavior in the vicinity of a given point. By examining the changing spatiotemporal distributions of these quantities, we can find the coherent structures in a variety of pattern-forming cellular automata, without needing to guess or postulate the form of that structure. We apply both filters to elementary and cyclical cellular automata (ECA and CCA) and find that they readily identify particles, domains, and other more complicated structures. We compare the results from ECA with earlier ones based upon the theory of formal languages and the results from CCA with a more traditional approach based on an order parameter and free energy. While sensitivity and statistical complexity are equally adept at uncovering structure, they are based on different system properties (dynamical and probabilistic, respectively) and provide complementary information.

Automation↗
PubMed1965

ULTRASTRUCTURE OF A MYCOPLASMA (NEGRONI) ISOLATED FROM HUMAN LEUKEMIA.

Hummeler, Klaus (The Children's Hospital of Philadelphia, Philadelphia, Pa.), Natale Tomassini, and Leonard Hayflick. Ultrastructure of a mycoplasma (Negroni) isolated from human leukemia. J. Bacteriol. 90:517-523. 1965.-A strain of mycoplasma isolated in tissue cultures from human leukemic bone marrow was cultivated in cell-free media for 23 passages. Concentrates of broth cultures were investigated under the electron microscope in thin sections and negative contrast. The ultrastructure of the mature mycoplasma cells and their elementary bodies is described. It was found that the elementary bodies, particularly in the negative contrast preparations, bear a close resemblance to viruslike particles seen in tissues and plasmas of leukemic patients.

Bone Marrow Cells↗
PubMed1991

Coxiella and Rickettsiella: comparison of ultrastructure with special reference to their envelope.

Ultrastructure of Rickettsiella phytoseiuli (R.p.) multiplying in female ticks Dermacentor reticulatus was compared with that of Coxiella burnetii (C.b.) in the same ticks and in mice. C.b. in ticks and mice were always represented by 2 main cell types: small dense round or rod-like cells (DC) and larger bacteria-like cells (BC). DC were surrounded with a characteristic five-layered 20 nm thick envelope. Under the envelope DC had a stack of parallel intracytoplasmic membranes with a periodicity 5-6 nm. R.p. in tick fat body and synganglion were also inside phagosomes and formed 6 sequentially developing cell forms: dense (elementary), intermediate, bacterial, giant, and crystal-forming in which small dark bodies (initial particles) condensed. Two of them--dense and bacterial--corresponded to DC and BC of C.b. The DC envelope structure of R.p. was strikingly similar to that of some C.b. DC in mouse. We confirmed the general morphologic similarities in the structure of C.b. and R.p. DC and that of C.b. BC and intermediate cells of R.p. The envelope structure of DC type was found in other gracilicute bacteria and is supposed to have no taxonomic value but to be a reflection of population heterogeneity.

Animals↗
PubMed1997

Electric Potential and Concentration of Ion Species in the Proximity of a Cell Membrane: ab initio Calculations

The mathematical model of ion transport in the field of electric forces and diffusion gradients is based on particle conservation equations and the Poisson equation which governs the distribution of the electric potential. Designed for evaluating the currents through passive ion channels in cellular membranes, the model is formulated in a two-dimensional approximation assuming rotational symmetry. Three ionic species are considered in the present study: sodium, calcium and chlorine. The program developed for the numerical solution is based on a semi-analytical approximation suggested by Gummel & Scharfetter. The present contribution reports calculations of the steady-state distributions of ionic species induced by an electric field due to a negative potential drop across the cellular membrane, which represent initial conditions for future calculations of the time development of the ion flux through the calcium channel. The numerical calculations were performed from the moment of potential application up to the time 6.2 μs, when a new steady state is established. At this stage, the maximum values of the sodium and calcium concentrations at the membrane surface are about 22% and 47% above the initial values of 145 mM and 1 mM, respectively, while the chlorine concentration is approximately 18% below. The electric field at the membrane surface is about 6.7x10(4) and decreases exponentially with distance. The length of the boundary layer is about 40 A. Since the model is based on fundamental principles, it can be used for the quantitative solution of any problem possessing rotational symmetry where a continuum approach is applicable and some elementary conditions are fulfilled, such as equilibrium (or at least quasi-equilibrium) of the particle energy distributions with respect to time and electric field, and the assumption that the transport coefficients are defined as functions of the field and their numerical values are known. Copyright 1997 Academic Press Limited

Journal Article↗
PubMed2002

Effect of spatial bias on the nonequilibrium phase transition in a system of coagulating and fragmenting particles.

We examine the effect of spatial bias on a nonequilibrium system in which masses on a lattice evolve through the elementary moves of diffusion, coagulation, and fragmentation. When there is no preferred directionality in the motion of the masses, the model is known to exhibit a nonequilibrium phase transition between two different types of steady state, in all dimensions. We show analytically that introducing a preferred direction in the motion of the masses inhibits the occurrence of the phase transition in one dimension, in the thermodynamic limit. A finite-size system, however, continues to show a signature of the original transition, and we characterize the finite-size scaling implications of this. Our analysis is supported by numerical simulations. In two dimensions, bias is shown to be irrelevant.

Journal Article↗
PubMed2004

Chaotic mixing in cross-channel micromixers.

In this article we concentrate on a particular micromixer that exploits chaotic trajectories to achieve mixing. The micromixer we consider here is a cross-channel intersection, in which a main stream is perturbed by an oscillatory flow, driven by an external source. Depending on the amplitude and frequency of the oscillatory flow, one obtains wavy and chaotic regimes, reminiscent of a tendril-whorl mapping. The chaotic states, in which material lines are stretched and folded, favour mixing. A spatiotemporal resonance phenomenon, in which the material-line deformation is transient, is shown. An experiment using soft lithography and integrated valves, in which the resonant states are revealed, is described. From a practical viewpoint, the cross-channel micromixer offers a variety of regimes, which can be exploited to mix fluids or separate particles of different sizes. In the context of microsystems, it can be viewed as a 'smart' elementary system.

Complex Mixtures↗
PubMed1977

[Chromatin fibril. Structure and relationship to the nuclear membrane].

Literature for the recent years on chromatin fibrilla structure is reviewed in the work. Ultrastructural and molecular organization of the elementary chromatin subunits--nucleosomes, discovered in 1974 is discussed and their relation to other discrete chromatin particles is analyzed. The author represents his own data on electron microscopic studies of the cell nucleus after certain experimental effect demonstrating a complex structure of chromatin particles. The scheme of chromatin fibrilla structure is given; morphologic and functional aspects of its connection with the nuclear membrane are considered.

Animals↗
PubMed2007

Composite particles of polyethylene @ silica.

Polyethylene (PE) and silica are perhaps the simplest and most common organic and inorganic polymers, respectively. We describe, for the first time, a physically interpenetrating nanocomposite between these two elementary polymers. While polymer-silica composites are well known, the nanometric physical blending of PE and silica has remained a challenge. A method for the preparation of such materials, which is based on the entrapment of dissolved PE in a polymerizing tetraethoxysilane (TEOS) system, has been developed. Specifically, the preparation of submicron particles of low-density PE@silica and high-density PE@silica is detailed, which is based on carrying out a silica sol-gel polycondensation process within emulsion droplets of TEOS dissolved PE, at elevated temperatures. The key to the successful preparation of this new composite has been the identification of a surfactant, PE-b-PEG, that is capable of stabilizing the emulsion and promoting the dissolution of the PE. A mechanism for the formation of the particles as well as their inner structure are proposed, based on a large battery of analyses, including transmission electron microscopy (TEM) and scanning electron microscopies (SEM), surface area and porosity analyses, various thermal analyses including thermal gravimetric analysis (TGA/DTA) and differential scanning calorimetry (DSC) measurements, small-angle X-ray scattering (SAXS) measurements and solid-state NMR spectroscopy.

Journal Article↗
PubMed1991

Transport of Balbiani ring granules through nuclear pores in Chironomus tentans.

Balbiani ring granules are premessenger RNP particles synthesized in the larval salivary glands of the dipteran Chironomus tentans and containing the genetic information for large-sized secretory proteins. The granules in the nucleoplasm consist of a thin elementary RNP fiber tightly packed into an RNP ribbon, which is bent into a ring-like shape. When the 50-nm granule is translocated through the nuclear pore, it attains an elongated conformation. We have now demonstrated that the particle in transition can be described as an RNP ribbon with the same thickness and the same minimal width as the ribbon of the nucleoplasmic granules. The ribbon in the pore is, however, somewhat longer and it lacks the broad regions of the ribbon in the nucleoplasmic granule. We conclude that when entering the pore the bent ribbon of the Balbiani ring granule is being straightened and also somewhat drawn out, while its width is accommodated to the maximal size of the pore, i.e., about 25 nm. On the cytoplasmic side the ribbon is unpacked, and the elementary fiber can be seen extending into cytoplasm, probably being available for polysome assembly.

Animals↗
PubMed2001

A four-dimensional generalization of the quantum Hall effect.

We construct a generalization of the quantum Hall effect, where particles move in four dimensional space under a SU(2) gauge field. This system has a macroscopic number of degenerate single particle states. At appropriate integer or fractional filling fractions the system forms an incompressible quantum liquid. Gapped elementary excitation in the bulk interior and gapless elementary excitations at the boundary are investigated.

Journal Article↗
PubMed1975

The effect of purification on the ultrastructure and infectivity of egg-attenuated Chlamydia psittaci (6BC).

A procedure is described for the purification of mixed populations of the three different morphological forms of Chlamydia psittaci (6BC) from infected yolk sac membranes. Elementary bodies and small intermediate bodies are not perceptibly damaged during purification which involves homogenization of the host cells, differential centrifugation, sedimentation through 20% sucrose, and treatment with trypsin. The observation that elementary bodies undergo plasmolysis in 20% sucrose is interpreted as indicating that the cytoplasmic membrane of these particles is intact at that stage in the purification. Reticulate bodies and large intermediate bodies are damaged, to a degree, by the homogenization step. This damage takes the form of discontinuities of the outer envelope membrane, and results in the loss of the regular coccobacillary shape of these particles and in an increase in their size. Treatment with a combination of RNase and DNase was found to cause profound damage to all three morphological forms of the chlamydiae.

Animals↗
PubMed1996

Resorption kinetics of osseous substitute: natural coral and synthetic hydroxyapatite.

Coral and hydroxyapatite may be used as substitution biomaterials for bone grafts. In this work, we extracted the implants from the femora to study the kinetics of elementary mineral transformation of the osseous substitutes. The use of physical analysis methods such as PIXE (particle-induced X-ray emission) shows that coral and hydroxyapatite, after their implantation in vivo, reach a mineral composition comparable with that of bone. For the first time we have measured the concentration of mineral elements, at different time intervals after implantation, along a cross-section. The distribution according to mineral elements (Ca, P, Sr, Zn, Fe) in the implant, in the receiver site and also at the interface, showed that the kinetics of coral resorption was faster than that of hydroxyapatite; in the same way, the osseous attack was not global but, rather, centripetal.

Animals↗
PubMed1996

Bremsstrahlung production at 50 MeV in different target materials and configurations.

A combination of Monte Carlo, convolution, and experimental techniques have been used to investigate bremsstrahlung production at 50 MeV in full-range targets to produce narrow elementary photon beams for scanning. Calculations using the ITS 3.0 Monte Carlo system for various target designs, including particle transport through the treatment head of an MM5O racetrack microtron and a water phantom, have been compared to experimental dose profiles from narrow photon beams at 10-cm depth in water. A reduction in the ITS 3.0 default substep size has been found necessary even for incomplete agreement, in consistency with the findings of Faddegon and Rogers [Nucl. Instrum. Meth. A 327, 556-565 (1993)] for a different experimental setup and energy using the previous version of ITS. Results show that the calculated shape of the tail of dose distributions from narrow photon beams agrees well with measurements, but CYLTRAN/ITS 3.0 fails to reproduce the central part of the distribution. The discrepancy at small angles, reported previously for EGS4 and ITS 2.1 simulations, possess a limitation to Monte Carlo simulations of narrow photon beams used in scanned systems of clinical accelerators. Radial dose profiles have been calculated by convolution of the energy fluence at the exit of the target with one polyenergetic Monte Carlo calculated dose kernel and also a database consisting of ten different dose kernels corresponding to different monoenergetic photon pencil beams for comparison. The agreement with the much slower fully detailed Monte Carlo calculations was better when using the database kernels than the polyenergetic kernel. Results for the mean energy, mean polar angle, and energy fluence at different depths within various targets have been obtained. These are discussed in the context of the design characteristics of bremsstrahlung targets with emphasis on their utilization for scanning photon beam techniques.

Biophysical Phenomena↗
PubMed1994

Discovery of extracellular multiple form of Chlamydia trachomatis in the tissue culture.

A strain of Chlamydia trachomatis was isolated from a patient with nongonococcal urethritis (NGU). Alternate passages between chick embryo and McCoy cell culture were examined. From the Giemsa stained coverslips taken from the cell culture 96 hours after inoculation, we found, to our surprise, that elementary bodies (EBs) distributed over a large area, and several intact cells embedded in them. These pure EB particles are round, fairly uniform in size and often appeared in pair. According to their morphology, distribution, arrangement and relationship with host cells, they are not the remains after cell lysis or directly released from host cells. We considered that they consisted of EBs which continued to divide by binary fission after their release. The name "Extracellular Multiply Form" was designated and their formation mechanism was proposed. This discovery gives a great challenge to primary theory, i.e. Chlamydias are obligate intracellular prokaryotic parasites. If we can further reveal the law of their formation, it will be of great significance both theoretically and practically.

Animals↗