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In this paper we develop a symmetry preserving method for the rigorous computation of stationary states of the Ohta-Kawasaki partial differential equation in three space dimensions. By preserving the relevant symmetries we achieve an enormous reduction in computational cost. This makes it feasible to construct computer-assisted proofs of complex three-dimensional structures. In particular, we provide the first existence proofs for both the double gyroid and body centered cubic packed sphere solutions to this problem. [ABSTRACT FROM AUTHOR]

This article considers a new method for generating a moving mesh which is suitable for the numerical solution of partial differential equations (PDEs) in several spatial dimensions. The mesh is obtained by taking the gradient of a (scalar) mesh potential function which satisfies an appropriate nonlinear parabolic partial differential equation. This method gives a new technique for performing r-adaptivity based on ideas from optimal transportation combined with the equidistribution principle applied to a (time-varying) scalar monitor function (used successfully in moving mesh methods in one-dimension). Detailed analysis of this new method is presented in which the convergence, regularity, and stability of the mesh is studied. Additionally, this new method is shown to be straightforward to program and implement, requiring the solution of only one simple scalar time-dependent equation in arbitrary dimension, with adaptivity along the boundaries handled automatically. We discuss three preexisting methods in the context of this work. Examples are presented in which either the monitor function is prescribed in advance, or it is given by the solution of a partial differential equation. [ABSTRACT FROM AUTHOR]

An instrument has been developed to avoid the rotation of large electron sources and detectors in quantum single particle scattering experiments. The rotation of an electron beam has been achieved by combining three small cylindrical electrostatic electron energy analyzers in series such that the first analyzer is fixed and the other two rotate together around the exit axis of the first; it is a development from an S-shaped deflector used by Hegemann et al. [J. Phys. B 26, 4607 (1993)]. Novel design and construction, using copper, aluminum, and stainless steel parts mounted on polyvinyl printed circuit board, enabled an efficient, small-sized high vacuum compatible instrument. The characteristics and versatility of the instrument have been shown by measurements of angular and spin asymmetries of electron scattering phenomena. [ABSTRACT FROM AUTHOR]

In this paper we develop and analyze a moving mesh code for the adaptive simulation of fourth-order PDEs based on collocation. The scheme is shown to enforce discrete conservation for problems written in a generalized conservation form. To demonstrate the breadth of applicability we present examples from both Cahn--Hilliard and thin-film--type equations exhibiting metastable behavior, finite-time solution blow-up, finite-time extinction, and moving interfaces. [ABSTRACT FROM AUTHOR]

We study the nature and stability of stationary solutions u(x) of the fourth order Swift–Hohenberg equation on a bounded domain (0, L) with boundary conditions u = 0 and u'' = 0 at x = 0 and x = L. It is well known that as L increases, the set of stationary solutions becomes increasingly complex. Numerical studies have exhibited two interesting types of structures in the bifurcation diagram for (L, u). In this paper we demonstrate through a center manifold analysis how these structures arise naturally near certain bifurcation points, and that there are no others. We also analyze their stability properties. [ABSTRACT FROM AUTHOR]

An electron-pair coincidence spectrometer, using only a single electrostatic toroidal analyzer, has been developed for the study of final-state electron pairs following ionization by electron impact. The system allows the angular and energy distribution of electron pairs emitted in a selected plane to be detected by a single planar microchannel plate stack followed by two position-sensitive semicircular wedge-and-strip anodes. The output signals are decoded into energy, angle and nanosecond coincidence timing information from which relative energy and angular triple differential ionization cross sections are determined. The performance of the instrument is indicated by He I photoionization of krypton and the first measurements of differential cross sections for electron-impact ionization of the 2P3/2 and 2P1/2 states of krypton. For perpendicular-plane scattering and an excess energy of 10 eV for the 2P3/2 state and 0.67 eV less for the 2P1/2 state, these cross sections are significantly different for the two states and indicate the importance of the final state of the ion in the scattering process. [ABSTRACT FROM AUTHOR]

Rats immunized with in vitro products and saline-soluble antigens derived from Taenia taeniae-formis were found to be significantly protected against challenge infection. Oral and intraperitoneal administration of antigen solutions alone were effective in stimulating resistance. Adjuvants, however, were required for successful immunization when the antigens were injected intramuscularly. Bordetella pertussis and aluminium hydroxide were able to improve markedly the protective effects of antigens given parenterally by either route, but Freund's complete adjuvant (FCA) was not effective as an adjuvant in this system. Reaginic antibodies to parasite antigens were detected in the sera of rats immunized with parasite antigens and B. pertussis or Al(OH)3, but none were detected in those given antigens incorporated in FCA. The possible role of reaginic antibodies in immunity to T. taeniaeformis is discussed. A single dose of antigen given orally produced significant protection. Increasing the number of daily doses of antigen administered orally enhanced the degree of protection to a limited but significant extent. There did not appear, however, to be any advantage to giving large doses (>1 mg protein) of antigen, or extending the immunizing schedule over several weeks. Reaginic antibodies were not detected in the sera of rats immunized orally, but these animals were resistant to both oral and intravenous challenge infection with parasites. These observations are discussed in relation to the phenomena of immune exclusion of antigen by the gut, and gastrointestinally induced systemic tolerance with respect to IgE production. Sera from rats immunized by all routes were found to be ineffective in conferring resistance upon recipients when given at the dose of 1 ml/rat. Further- more, sera from donors vaccinated intramuscularly with saline soluble antigens and B. pertussis increased the susceptibility of recipient rats to infection with T. taeniaeformis. This is in sharp contrast to our previous experience in which we have shown that sera from rats with an active infection are highly effective in passive transfer. Possible reasons for these observations are discussed. The requirements for adequately controlled immunization procedures to assess the contributory effects of adjuvant type and the route of antigen inoculation in immunizing against taeniid infections are emphasized in the discussion. [ABSTRACT FROM AUTHOR]

Chemical inhibitors of immediate hypersensitivity were used to treat rats passively immunized against Taenia taeniaeformis with serum containing 7Sγ2a, and reaginic antibodies. There was no significant reduction in protection against oral challenge with eggs in these animals, indicating that reagin-mediated hypersensitivity reactions were not an essential component of the protective mechanism. However, systemic reagin sensitization was shown to result in an acceleration of the rate at which challenge organisms were destroyed in immune rats. By 12 h after infection most of the parasites had been killed in the livers of rats which had been both passively immunized and reagin-sensitized, whereas a large proportion survived in rats passively immunized, but not reagin-sensitized. This effect of reagin appeared to be limited to the early stages of resistance since parallel groups left for 21 days after challenge were shown to have been equally well protected. In an effort to determine if vasoactive amines liberated by reagin-mediated reactions could act directly on invading parasites, early larval stages of T. taeniaeformis were exposed to histamine or serotonin (5HT) in vitro or in vivo. Consistent results were not obtained, but significant inhibition (P<0.05) of viability of parasites exposed to histamine occurred on two occasions. Significant (P<0.01) inhibition of infectivity of T. taeniaeformis also resulted when peritoneal anaphylactic diffusate was introduced into isolated gut loops containing hatched embryos of the parasite. The results are discussed in terms of the possible means whereby reagins may participate in protective immunity to infectious organisms. [ABSTRACT FROM AUTHOR]

Chemical inhibitors of immediate hypersensitivity were used to treat rats passively immunized against Taenia taeniaeformis with serum containing 7Sγ2a, and reaginic antibodies. There was no significant reduction in protection against oral challenge with eggs in these animals, indicating that reagin-mediated hypersensitivity reactions were not an essential component of the protective mechanism. However, systemic reagin sensitization was shown to result in an acceleration of the rate at which challenge organisms were destroyed in immune rats. By 12 h after infection most of the parasites had been killed in the livers of rats which had been both passively immunized and reagin-sensitized, whereas a large proportion survived in rats passively immunized, but not reagin-sensitized. This effect of reagin appeared to be limited to the early stages of resistance since parallel groups left for 21 days after challenge were shown to have been equally well protected. In an effort to determine if vasoactive amines liberated by reagin-mediated reactions could act directly on invading parasites, early larval stages of T. taeniaeformis were exposed to histamine or serotonin (5HT) in vitro or in vivo. Consistent results were not obtained, but significant inhibition (P<0.05) of viability of parasites exposed to histamine occurred on two occasions. Significant (P<0.01) inhibition of infectivity of T. taeniaeformis also resulted when peritoneal anaphylactic diffusate was introduced into isolated gut loops containing hatched embryos of the parasite. The results are discussed in terms of the possible means whereby reagins may participate in protective immunity to infectious organisms. [ABSTRACT FROM AUTHOR]

Weanling rats born of mothers infected with Taenia taeniaeformis were found to be passively protected against homologous challenge. Cross-fostering of normal suckling rats onto immune mothers established that passive transfer occurred via the colostrum and milk. Immunoglobulin fractions containing γA from immune colostrum were fed to 12-14-day-old rats for 4 days via stomach tube. Significant passive protection against challenge with T. taeniaeformis was achieved with γA from one of three colostrum pools. The effect of colostral γA preparations on the infectivity of freshly hatched oncospheres of T. taeniaeformis was measured by the intra-intestinal inoculation of immunoglobulin solutions into isolated gut loops containing hatched eggs of the parasite. γA from one of three pools of immune colostrum caused a significant reduction in the number of parasites which reached the liver. This appears to be the first time that protective activity against a hel- minth infection has been achieved with γA. A fraction of immune colostrum containing both 7Sγ1 and 7Sγ2 immunoglobulins was found to confer passive protection when inoculated parenterally. In view of the prolonged period of absorption (ca 18 days) of 7S immunoglobulins from the gut by the suckling rat, it seems likely that these antibodies are primarily responsible for the natural passive transfer of protection from mother to young. [ABSTRACT FROM AUTHOR]

Skin sensitizing antibody or reagin was detected in rats 19 days after infection with Taenia taeniaeformis eggs. Peak titres were reached on day 32 and thereafter declined. A second dose of eggs was capable of increasing the levels of circulating reagin, even though it was highly unlikely that the embryos had survived more than a transient period of time in the intestinal mucosa. The physicochemical and biological characteristics of this reagin are consistent with those of the rat immunoglobulin designated γE. In no instance was it possible to demonstrate short-term skin sensitization by the rat 7Sγ2a immunoglobulin class, even though previous work had shown that antibodies of this type are produced during infection All short-term reactivity at 2-6 hours appeared to be a result of reaginic antibody fixation Reagins were not observed to cross the placenta or be transferred by the colostrum from highly immune females to their offspring The role of reagin in passive and specific acquired resistance to T. taeniaeformis is discussed and the mechanisms whereby it might be contributing to immunological events in this infection are outlined. An allergen was isolated from cysticerci of T. taeniaeformis which was capable of provoking passive cutaneous anaphylaxis (PCA) reactions in sensitized rats in approximately 5 μg quantities. A single band was obtained in polyacrylamide gel electrophoresis which stained for protein and carbohydrate but not for lipid. Chromatographic and electrophoretic studies indicated that the allergen was very negatively charged at slightly alkaline pH. Activity was as completely removed from larval extracts by absorption with a monospecific antiserum prepared against the allergen. The possibility of more than one allergen being associated with cysticerci and adult worms of T. taeniaeformis is discussed Cross-reactions with other taeniid parasitic extracts were observed but no positive PCA reactions were elicited with extracts prepared from two dissimilar helminths, Schistosoma mansoni and Fasciola hepatica although these parasites are known to cause cross-reactions in field tests. The potential value of the purification procedure is pointed out in the context of the continuing effort to improve the specificity of clinical diagnostic tests based on intradermal reactions. [ABSTRACT FROM AUTHOR]

Passive transfer of immunity to Taenza taeniaeformis infection in the rat was achieved with serum taken 14, 21 and 28 days after infection, with maximal activity at 28 days4 The protective capacity resided in the globulin fraction, which was further fractionated by gel filtration and anion exchange chromatography. The immunoglobulins present in each passively transferred fraction were detected with specific antisera to 7Sγ2, 7Sγl, γM and γA. Protective activity was confined to those fractions containing 7S immunoglobulirn. Fractions enriched for γM were unable to confer protection and it was possible to protect recipient rats against challenge with fractions devoid of γA and reaginic antibody activity. 7Sγ2a antibodies were able to confer passive protection when given alone, and probably contributed to the protective capacity of mixtures containing 7Sγ2 and 7Sγl immunoglobulins. A mechanism for specific acquired resistance to T. taeniaeformis is proposed based upon the recently established biological properties of 7Sγ2a, Absorption of protective activity from immune rat serum was unsuccessful using a variety of techniques, and an explanation is offered for this finding. The results are discussed in relation to the current understanding of acquired resistance in cysticercosis and hydatid disease in domesticated food animals. [ABSTRACT FROM AUTHOR]

Serum samples from twenty dogs infected with Echinococcus granulosus were tested for the presence of homocytotropic skin-sensitizing antibodies. Five of the twenty sera were positive in this test, while none of the sera from twenty normal dogs was positive. The antibody was thermolabile and susceptible to 2 mercaptoethanol reduction. Reaginic antibodies to cestode antigens have not been described previously in dogs, though they are frequently associated with helminth infection in other animals and may play a role in acquired resistance. [ABSTRACT FROM AUTHOR]

The article discusses advances in instrumentation motivated by the need to optimize efficiency of observations in quantum particle scattering experiments. Improvements have been made in analyzer design, position-sensitive detection, recording, and timing. Technology for parallel detection of multiple energies and scattering angles has emerged.

We present a rigorous numerical method for proving the existence of a localized radially symmetric solution for a Ginzburg-Landau-type equation. This has a direct application to the problem of finding spots in the Swift-Hohenberg equation. The method is more generally applicable to finding radially symmetric solutions of stationary PDEs on the entire space. One can rewrite such a problem in the form of a singular ODE. We transform this ODE into a finite domain and use a Green's function approach to formulate an appropriate integral equation. We then construct a mapping whose fixed points coincide with solutions to the ODE, and we show via computer-aided analytic estimates that the mapping is contracting on a small neighborhood of a numerically determined approximate solution. [ABSTRACT FROM AUTHOR]

This paper presents a two-dimensional investigation of the phase diagram for global minimizers to a Cahn-Hilliard functional with long-range interactions. Based upon the H-1 gradient flow, we introduce a hybrid numerical method to navigate through the complex energy landscape and access an accurate depiction of the ground state of the functional. We use this method to numerically compute the phase diagram in a (finite) neighborhood of the order-disorder transition. We demonstrate a remarkably strong agreement with the standard asymptotic estimates for stability regions based upon a small parameter measuring perturbation from the order-disorder transition curve. [ABSTRACT FROM AUTHOR]

It is shown for the first time that electron-electron scattering of slow electrons with an energy of 10–50 eV at the surface of some metals is mainly an event of binary scattering of particles with conserved total momentum and energy, while analogous scattering at the surface of a semiconductor ( n-Si) and an insulator (MgO) is a multiparticle event. A model is proposed, in which the electron subsystem of a solid is characterized by short-range order. Each electron is at the center of a spherical cell and surrounded by nearest neighbors (electrons) with a coordination number of 12. The overlap of the fields of charges gives rise to a negative potential U c( r) ≈ U c, which is virtually constant along the coordinate and contains spherical cells with a central field U( r) of individual charges. The value of constant negative potential U c depends on the extent of electron screening, which is high for metals and low for semiconductors and insulators. In metals, scattering governed by the binary mechanism may take place (i.e., scattering of a primary electron in the central field of an electron of the metal); this is ensured by a relatively small value of constant potential U c. The electron subsystem of the metal behaves as a Fermi gas of weakly interacting quasiparticles. Electron screening in semiconductors and insulators is insignificant, and constant negative potential U c is an order of magnitude higher than the analogous potential in metals. Slow primary electrons are scattered in the total field of many charges before they reach the central field of an individual electron. The electron subsystem of a semiconductor and an insulator in the excitation range studied here behaves as an ensemble of strongly interacting particles. [ABSTRACT FROM AUTHOR]

We consider analytical and numerical aspects of the phase diagram for microphase separation of diblock copolymers. Our approach is variational and is based upon a density functional theory which entails minimization of a nonlocal Cahn-Hilliard functional. Based upon two parameters which characterize the phase diagram, we give a preliminary analysis of the phase plane. That is, we divide the plane into regions wherein a combination of analysis and numerics is used to describe minimizers. In particular we identify a regime wherein the uniform (disordered state) is the unique global minimizer; a regime wherein the constant state is linearly unstable and where numerical simulations are currently the only tool for characterizing the phase geometry; and a regime of small volume fraction wherein we conjecture that small well-separated approximately spherical objects are the unique global minimizer. For this last regime, we present an asymptotic analysis from the point of view of the energetics which will be complemented by rigorous G-convergence results to appear in a subsequent article. For all regimes, we present numerical simulations to support and expand on our findings. [ABSTRACT FROM AUTHOR]

We study the asymptotic behavior of classes of global and blow-up solutions of a semilinear parabolic equation of the "limit" Cahn-Hilliard type ut = -Δ(Δu + |u|p-1 u) in RN x R+, p > 1, with bounded integrable initial data. We show that in some {p,N}-parameter ranges it admits a countable set of blow-up similarity patterns. The most interesting set of blow-up solutions is constructed at the first critical exponent p = p0 = 1 + 2/N, where the first simplest profile is shown to be stable. Unlike the blow-up case, we show that, for p = p0, the set of global decaying source-type similarity solutions is continuous and determine the stable mass-branch. We prove that there exists a countable spectrum of critical exponents {p = pl = 1 + 2/N+l, l = 0, 1, 2, ...} creating bifurcation branches, which play a key role in general description of solutions globally decaying as t → ∞. [ABSTRACT FROM AUTHOR]

In this article we construct, both asymptotically and numerically, multibump, blow-up, self-similar solutions to the complex Ginzburg--Landau equation (CGL) in the limit of small dissipation. Through a careful asymptotic analysis, involving a balance of both algebraic and exponential terms, we determine the parameter range over which these solutions may exist. Most intriguingly, we determine a branch of solutions that are not perturbations of solutions to the nonlinear Schrödinger equation (NLS); moreover, they are not monotone, but they are stable. Furthermore, these axisymmetric ring-like solutions exist over a broader parameter regime than the monotone profile. [ABSTRACT FROM AUTHOR]

The pore size and type of aluminum oxy-hydroxide (boehmite) obtained using an optimized sol–gel method was investigated as a mesoporous material with the calcination temperature varied from 150 to 550 °C. Structural features were characterized by XRD, SEM, TEM, BET. Molecular interactions were identified by using PALS (positron annihilation lifetime spectroscopy) and CDBS (coincidence Doppler broadening spectroscopy). The XRD pattern showed that the sample synthesized at 250 °C has an orthorhombic phase characterizing the boehmite structure. All the samples prepared from pure aluminum metal were mesoporous according to BET results with a strong relationship between microstructure properties and temperature. The highest values of specific surface area and pore volume assigned to the sample prepared at 250 °C with 268.3 m2·g−1 and 0.313 cm3·g−1, respectively. The results of PAL-spectroscopy show that, the lifetime of positrons annihilating at pores of the boehmite at 350 °C increased as the average pore size growths because the free-volume defects in the samples increased. [ABSTRACT FROM AUTHOR]

A relaxor electroceramic 0. 3 5 Pb ( Mg 1 / 3 Nb 2 / 3) O 3 – 0. 3 5 ( Pb 1 − 1. 5 x La x) TiO 3 –0.30- ( Ba 1 − 1. 5 x La x) TiO 3 (PMN–PLT–BLT) with x = 0.25, 0.50 and 0.75 was synthesized using the two combination methods of auto-combination and hot-pressing. Characterization of the crystal phase, microstructure, optical and dielectric properties of PMN–PLT–BLT was made primarily by X-ray diffraction and TEM and SEM methods. The pure perovskite crystals (rhombohedral and tetragonal) prepared at 8 5 0 ∘ C for 2 h calcination were revealed by using X-ray diffraction. The average optical transmittance of these electroceramics in the range between 450 nm and 900 nm is higher than 60% while in the IR region reached 100%. The PMN–PLT–BLT with x = 0.75 displays the highest transparency around 70% near 1100 nm. The microstructures and dielectric measurements show that these three electroceramics have densities of about 98.8% and exhibit a normal relaxation characteristic. [ABSTRACT FROM AUTHOR]

The design and performance of a thin bakable in-line valve are described. The valve is designed for use in electron scattering experiments for efficient and minimal spatial separation of ultrahigh vacuum from a region containing metal vapors, base pressure of 8×10-8 Torr, or atmosphere. The simple compact design permits experiments with metal vapors and spin polarized electrons to be conducted with high efficiency and over months, without loss of emission from GaAs crystal or need for frequent bakeout of ultrahigh vacuum chamber. [ABSTRACT FROM AUTHOR]

Using Spin-polarized Electron-Energy Loss Spectroscopy (SPEELS), the plasmon excitations were probed in a few atomic layers thick Ag film deposited on an Fe layer or on a single crystal of W(110). The measurements were performed at two specular geometries with either a 25 or 72 angle of incidence. On a clean Fe layer (10 atomic layers thick), Stoner excitation asymmetry was observed, as expected. Deposition of a silver film on top of the Fe layer dramatically changed the asymmetry of the SPEELS spectra. The spin-effect depends on the kinematics of the scattering: angles of incidence and detection. The spin-dependence of the plasmon excitations in the silver film on the W(110) surface and on the ferromagnetic Fe film is suggested to arise from the spinactive Ag/W or Ag/Fe interfaces. [ABSTRACT FROM AUTHOR]

A double cantilever detector mount, constructed from aluminum, was designed to support an angle-resolving particle detector mounted on a rotary table. The mount allows precise and accurate alignment of the detector's field of view in the Cartesian x, y, and z plane, and allows precise control of the azimuthal angle of the detector. The mount is simple to adjust, provides high precision and stability, and can be used in any situation where precise and accurate detector alignment is required. [ABSTRACT FROM AUTHOR]

The present work studied the role of the polar group unconjugated oxygen on the inhibition of positronium (Ps) formation in two binary blends made from a set of chosen constituent polymers with polar and weakly polar groups (nonpolar). The polymer blend samples of PVC-EVA and PVC-SAN were investigated by coincidence Doppler broadening and positron lifetime techniques. The strong polar acetate group in the EVA contributed to positron annihilation with electrons of unconjugated oxygen (-C+=O-) as revealed by the momentum distribution curves peaking around 17 PL (10-3 m0c). The ortho-Ps intensity indicated the unconjugated oxygen shows about a 28% Ps reduction even in the presence of a strong Ps inhibiting halogen (Cl-). In contrast, this effect was not seen in the PVC-SAN blends since SAN contains a weakly polar (nonpolar) acrylonitrile group (C=N). Our results indicate the chlorine of PVC in the blends is a major contributor to Ps inhibition through the formation of a (Cl~-e+) bound state but the unconjugated oxygen in EVA of the PVC-EVA blend also plays a similar, but lesser, role. [ABSTRACT FROM AUTHOR]

A commonly used algorithm for generating adaptive meshes for a given adaptation function in one dimension is due to de Boor. In its original form the algorithm produces a sequence of meshes upon using piecewise constant interpolation for the adaptation function on the current mesh and generating a new mesh that exactly equidistributes the interpolant. In this paper we present a proof for the existence of a limit mesh and for the convergence of de Boor's algorithm. Numerical results are given to illustrate the theoretical findings, and stopping criteria necessary for the implementation of the algorithm are examined. [ABSTRACT FROM PUBLISHER]

The scanning probe electron energy spectra for micron-sized Ag islands on highly ordered pyrolytic graphite substrate are measured. One- and two-dimensional relative intensity distributions for Ag or graphite plasmon peaks have been acquired and a lateral resolution of 4.8±2.4 μm has been achieved. It is the first time for the scanning probe electron energy spectroscopy technique to obtain the spatially resolved electron energy spectra with elemental contrast for a surface, which demonstrates the possibility of the element identification for the scanning tunneling microscope. [ABSTRACT FROM AUTHOR]

A highly efficient time-of-flight electron spectrometer is described. An incident electron current of the order of 10[sup -14] A makes it suitable for studying secondary emission from dielectric surfaces. A microchannel plate position-sensitive detector allows flight distance correction while keeping a large acceptance angle. Measured energy distribution curves of secondary electrons generated from a LiF film by 19-31 eV incident electrons demonstrate good energy resolution and reveal reproducible and stable emission features at 2.6±0.3 eV, 7.2±0.3 eV, and 10.3±0.3 eV. [ABSTRACT FROM AUTHOR]

A four-dimensional histogramming data acquisition system has been developed for use on an 80386 IBM-compatible computer. The method has a large data storage capacity providing good experimental resolution and system flexibility. A custom-built analog-to-digital board generates a memory address in hardware from the incoming data which permit the use of a simple and elegant histogramming algorithm. The system is used to collect and analyze data from (e,2e) experiments. Results from coplanar symmetric (e,2e) experiments on argon, at an incident energy of 3 keV, are presented to demonstrate the performance of the instrument. The method is applicable to experiments where data from several sources have to be combined and then histogrammed in real time. [ABSTRACT FROM AUTHOR]

The two outgoing electrons from (e,2e) scattering processes are selected by two 180° electrostatic analyzers whose energy dispersed output spectra are detected by microchannel plates followed by resistive anodes. These detectors permit the identification of all multiple coincident events occurring within the dispersal width of the analyzers. It was found that the time difference between the two detectors for correlated events is strongly dependent on the energy of the incident electrons, which consequently causes the time coincidence window to move systematically. This behavior has been accounted for by a model that determines the time taken by an electron to go around a hemispherical analyzer. A description is given of a data collection system that can compensate for the shift in the coincidence spectra and that records all multiple coincidence events with an increase in the overall coincidence count rate of about two orders of magnitude relative to conventional non position sensitive detectors without position sensing. The performance of the system is shown for an (e,2e) spectrum of argon. [ABSTRACT FROM AUTHOR]

In this study Onchocerca gutturosa was compared with O. volvulus in an ELISA test to detect Onchocerca-specific IgG and IgG subclasses. The test was developed and standardized to detect Onchocerca-specific IgG and IgG subclasses in sera of onchocerciasis patients and endemic controls, Onchocerca volvulus and O. gutturosa crude water-soluble antigens showed no significant difference in detecting onchoccrca-specific IgG antibody (T = 1.88, P > 0.05). The levels of IgG subclasses varied greatly- IgG4 showed the highest detected mean level (0.84 ± 0.59) and the other three subclasses showed considerably lower mean levels (IgG1 = 0.27 ± 0.16, IgG2 = 0.24 ± 0.17, IgG3 = 0.28 ± 0.12). The status and score of skin lesions were found to have significant effect on the IgG and IgG subclasses levels (all P < 0.001), IgG4 showed a positive correlation with the microfiltirial (Mf) load(r = 0.21, P < 0.03). IgG3 levels have a significant negative correlation with the Mf load (r = 0.23 , P < 0.02). The biological significance of these IgG and IgG subclasses in onchocerciasis is discussed. [ABSTRACT FROM AUTHOR]

Characterization of in vitro lymphocyte responsiveness was performed on selected groups of onchocerciasis patients from Sudan and Sierra Leone. These patients manifested a very broad range of clinical signs and showed widely divergent parasite infection intensities. Lymphocyte proliferative responses to soluble Onchocerca volvulus antigen (sAg) were poor in infected persons; mitogen and PPD responses were maintained in the normal range in one group of patients from southwestern Sudan, but were profoundly depressed in a group from N.E. Sudan. Proliferative responses and interferon-gamma (INF-γ) secretion were very significantly depressed in the presence of live microfilariae of O. volvulus or secretions/excretions (S/E) from microfilariae (mf) or from female, but not male, adult parasites. Lymphocyte responses were maintained near normal when exogenous IL-2 was added to these cultures. The results indicate that O. volvulus infection and its clinical consequences are not consistently associated with systemic deficits in immune responsiveness. However, suppression of lymphocyte reactivity by mf and S/E in vitro suggests that direct parasite intervention in host cell responses could be taking place in vivo, perhaps at the local microenvironment level, mediated by effects on cytokine production. [ABSTRACT FROM AUTHOR]