Search

Tolerance to innocuous antigens from the diet and the commensal microbiota is a fundamental process essential to health. Why tolerance is efficiently induced to substances arising from the hostile environment of the gut lumen is incompletely understood but may be related to how these antigens are encountered by the immune system. We observed that goblet cell associated antigen passages (GAPs), but not other pathways of luminal antigen capture, correlated with the acquisition of luminal substances by lamina propria (LP) antigen presenting cells (APCs) and with the sites of tolerance induction to luminal antigens. Strikingly this role extended beyond antigen delivery. The GAP function of goblet cells facilitated maintenance of pre-existing LP T regulatory cells (Tregs), imprinting LP-dendritic cells with tolerogenic properties, and facilitating LP macrophages to produce the immunomodulatory cytokine IL-10. Moreover, tolerance to dietary antigen was impaired in the absence of GAPs. Thus, by delivering luminal antigens, maintaining pre-existing LP Tregs, and imprinting tolerogenic properties on LP-APCs GAPs support tolerance to substances encountered in the hostile environment of the gut lumen.

151 Eu and 57 Fe Mossbauer spectroscopy, differential scanning calorimetry, and high-intensity high-resolution synchrotron powder diffraction were used to determine the extent of long- and short-range charge ordering below the first-order Verwey-type transition in EuBaFe 2 O 5 , the oxygen content of which was homogenized by annealing in sealed ampoule. The diffraction gives 0.68(5) valence unit of charge separation at 100 K. Interpretation of this value as 68% of iron being long-range charge ordered correlates with the total transition entropy per formula of about 0.7 of the theoretical value 2 R ln 2 that would be valid for all iron atoms being fully charge ordered. For long- and short-range order combined, 57 Fe Mossbauer spectroscopy suggests that about 90% of iron atoms occur as charge-ordered integer Fe 2 + and Fe 3 + . The residual 10% are the Fe 2 + and Fe 3 + that did not find the way to order. Local oxygen non-stoichiometry defects that revert the direction of the charge order are suggested as one of the origins of the short-range charge order. Accordingly, the long-range charge order seen by diffraction is highest in the portion of the sample that converts last upon heating, having the most ideal valence ratio.

Mixed-valence EuBaFe 2 O 5 + w exhibits a robust Verwey-type transition. The trend in the volume change suggests a first-order transition up to the nonstoichiometry level of about w = 0.25 . 57Fe Mossbauer spectroscopy, differential scanning calorimetry and synchrotron X-ray powder diffraction are used to study the valence mixing and charge ordering in EuBaFe 2 O 5 + w as a function of the nonstoichiometry parameter w. 151Eu Mossbauer spectroscopy is used as a selective probe into the ferromagnetic valence-mixing coupling along c above the Verwey transition, and reveals that increasing w destroys this coupling in favor of a G-type magnetic order in parallel with the progressive removal of the valence-mixed iron states accounted for by 57Fe Mossbauer spectroscopy. This removal proceeds according to a probability scheme of mixing between ferromagnetically coupled divalent and trivalent neighbor iron atoms along c across the R layer. In contrast, the concentration decrease of the orbital- and charge-ordered states in EuBaFe 2 O 5 + w is found to be a linear function of w. Valence mixing and charge ordering are therefore two separate cooperative phenomena. The enthalpy of the Verwey-type transition between these two cooperative systems is a linear function of w, which suggests that it originates from the latent heat of freezing into the long-range ordered orbital- and charge-ordered state. The enthalpy becomes zero at the nonstoichiometry level of about w = 0.25 .

The dilution refrigerator used to cool the large COMPASS polarized target is monitored through a PC running LabVIEW(TM) 6.1 under Windows 2000(TM). About 60 parameters of the target (temperatures, pressures, flow rates) are continuously plotted and checked. They are periodically recorded in an Oracle(TM) database and in a data file. An alarm for every parameter can be individually activated and optionally connected to a GSM (Global System for Mobile Communication) delivery message system. A web server receives and publishes the online status of the target with online tables and graphics on a dedicated COMPASS polarized target information web site. A Siemens programmable logic controller (PLC) powered by an uninterruptable source keeps the cryogenic system safe and stable during the long beam periods by controlling valves and interlocks. This safety feature protects the dilution refrigerator against potential damages in case of power failure. (C) 2004 Elsevier B.V. All rights reserved.

A 150 cm long liquid hydrogen target has been built for the SLAC End Station A E158 experiment. The target loop volume is 55 liters, and the maximum target heat load deposited by the electron beam is {approx} 700 W. The liquid hydrogen density fluctuation with full beam current (120 Hz repetition rate, 6 x 10{sup 11} electrons/spill) on target is well below 10{sup -4} level, which fulfills the requirement for a precision measurement of the weak mixing angle in the polarized electron-electron scattering process.

The A(e,e{prime}K{sup +})YX reaction on H, D, {sup 3}He, and {sup 4}He was investigated in Hall C at CEBAF. Data were obtained for Q{sup 2} {approx} 0.35 and 0.5 GeV{sup 2} at 3.245 GeV. The missing mass spectra for both H and D are fitted with Monte-Carlo simulations incorporating peaks corresponding to {Lambda} production on the proton and {Sigma} production on both the proton and neutron. For D, the cross section ratio {Sigma}{sup 0}/{Sigma}{sup {minus}} {approx} 2, and excess yield close to the thresholds for {Lambda} and {Sigma} production can be attributed to final-state interactions that are compared to the data. The analysis of the data for the He targets is in a more preliminary state with broader quasi-free peaks resulting from the higher Fermi momenta. Evidence for bound {Lambda}-hypernuclear states is seen and other structure may be present.

A method for black-box identification of uncertain systems is presented. The method identifies a nominal model and an uncertainty model set, consisting of unfalsified uncertainty models. Minimisation of a Chebyshev criterion leads to computationally favourable linear programming problems and allows the possibility to include a priori information in the form of linear constraints without making the computations more complex. Using data compression via correlation computations solves the computation problem associated with identifying unfalsified uncertainty models. The application of set-valued uncertainty models to robust process control is illustrated in a simulation study of robust model predictive control of a distillation column.

A detailed investigation of the basic hyperon-nucleon interactions in nuclei is one of the aims of Experiment 91-016, approved with high priority at CEBAF, to study the electroproduction of kaons on targets of deuterium, {sup 3}He, and {sup 4}He. Inasmuch as both the electron and K{sup +} are particles that interact relatively weakly with nucleons, electroproduction of light hypernuclei provides a low-distortion method for investigating the fundamental interactions between nucleons, {Alpha}`s, and {Epsilon}`s in few-body systems. In particular, the (e,e`K{sup +}) reactions on cryogenic targets of D, {sup 3}He, and {sup 4}He will be studied at incident electron energies near 3 GeV with coincident detection of the emergent e and K{sup +} in the HMS and SOS magnetic spectrometers in Hall C. Construction of the He target, operating at {approximately}10 atm, {approximately}50 K and capable of dissipating {approximately}30 W, is expected to be complete prior to commencement of production runs in Hall C. The first data runs for E91-016, expected to begin late in FY 1995, will also be the basis for a doctoral thesis at Hampton University. In addition to providing new information on the phases of hyperon-nucleon interactions, measurements of cross sections for hypernuclear formation, and interference phenomena,more » the data may provide evidence for the presence of bound {Epsilon}`s and strange di-baryonic states that are the subject of considerable theoretical discussion.« less

In elastic electron-deuteron scattering, the tensor polarization moments t 20 , t 21 and t 22 , together with the unpolarized cross-sections, have been measured up to a momentum transfer of 1.8 (GeV/c) 2 , or 6.8 fm −1 . The experiment was performed at Jefferson Laboratory using the recoil deuteron polarimeter POLDER. Preliminary results are presented and discussed, especially in view of their significance concerning the applicability of perturbative QCD to this exclusive process.

A multimodel controller design procedure is proposed and evaluated on a strongly nonlinear chemical process. The objective is to design a controller which achieves good quadratic (LQ) performance and robustness for an uncertain nonlinear plant. In order to capture both parametric and unstructured plant uncertainties, a multimodel process description is introduced, in which the plant is represented by a discrete set of linear models and associated norm-bounded uncertainties. The controller design problem is then stated as a multimodel mixed H 2 / H ∞ problem for optimal quadratic ( H 2 ) performance subject to ( H ∞ -type) robustness bounds for the multimodel plant description. The problem of finding a linear controller with the specified optimality and robustness properties lacks a closed solution, and it is therefore solved with parametric controller optimization techniques. The proposed controller design procedure is demonstrated on a simulated pH neutralization process, and is shown to give a linear controller with good performance and robustness characteristics. The achievable global performance is further improved by combining the proposed design procedure with controller scheduling. Two implementations of controller scheduling which satisfy a set of linearization conditions are presented and successfully tested on the neutralization process.

The 1 H(e, e′K + )Λ and 1 H(e,e′K + )Σ 0 reactions were studied as a function of the squared four-momentum-transfer, Q 2 , and the virtual photon polarization, e, thus enabling the separation of the longitudinal and transverse parts of the cross section. The existence of a sizable longitudinal component for the 1 H(e,e′K + )Λ reaction seems to be indicated by these data.

A multimodel controller design procedure based on robust LQ design is evaluated for a highly nonlinear chemical process. The procedure is combined with two gain-scheduling methods: a fixed robust controller with scheduled output gain, and complete scheduling of locally optimal controllers. The performances obtained with the fixed controller, the gain scheduled controllers and conventional PID control are compared and tested on a simulated pH neutralization process.

Real plants are, in general, time-varying and uncertain. Yet most industrial control loops are designed using linear time-invariant (LTI) plant models. The present work formalizes the problem of best approximate LTI modelling of BIBO-stable linear time-varying (LTV) systems in a way that is compatible with the notion of induced l ∞ norm used in robust l 1 control. This setup is closely associated with certain identification methods and controlmotivated model validation/invalidation procedures that can be efficiently implemented with special-purpose linear programming (LP) techniques. Results are given for approximate modelling of BIBO-stable LTV and LTI systems using LTI models, especially BIBO-stable fixed-pole state-space model parametrizations. It is shown that such parametrizations are satisfactory from an approximate modelling point of view, and can be used in output-error-type LP identification techniques and in LP model validation procedures. Various useful constraints on model parameters etc. can be included, as long as they are linear in the unknown parameters, and both insensitive (statistically robust) and sensitive criteria can be used in identification and model validation. Simulation examples are included to illustrate that such techniques indeed give good results and can be used to solve problems of realistic size.

The choice of stepsize in a numerical integration method is an important issue that affects both accuracy and efficiency. We analyze the algorithms in use today from a feedback control point of view. The analysis points out deficiencies in the standard algorithm, and we derive a new improved controller. The new controller provides superior performance at little extra expense.

An error in the expression for the Fe 2+ , Fe 3+ valence-mixing probability in R BaFe 2 O 5+ w is acknowledged and correct formula is derived. The new formula slightly improves the least-squares fit to the experimental concentrations of the Mossbauer component Fe 2.5+ as a function of the oxygen-nonstoichiometry parameter w for R =Eu.

Backgrounds/Aims: Macroautophagy is a bulk degradation system that enables recycling of long-lived proteins and damaged organelles. It is at the crossroads of innate and adaptive immunity, inflammation and apoptosis. Previous studies have associated the NOD2 frameshift 1007fs mutation with a defect of autophagy induction and an increased intestinal permeability. The aim of this study was to investigate the role of autophagy in the intestinal permeability and to define the involvement of NOD2 and its variant 1007fs. Methods: Paracellular permeability was assessed by FITC 4kD Dextran flux and transepithelial resistance in Caco2 monolayers. Stably transfected cells with the wild-type or 1007fs NOD2 variant were also used. Activation of autophagy was induced by 24H of nutrient starvation and rapamycin treatment. Results: Nutrient starvation of Caco-2 monolayers increased significantly the paracellular permeability compared to basal conditions (respectively, 10.84% vs 0.84% of 4kD FITC dextran; P

A number of experiments with diluents, cryoprotective agents, dilution rate, equihbration time, and freezing techniques have resulted in freezing methods for ram semen giving fairly good post-thaw sperm survival (9). Despite the acceptabIe post-thaw sperm survival in vitro, frozen-thawed semen usuaIIy yields an unsatisfactory conception rate when inseminated into the posterior cervix, In general, the conception rate appears to be at least 20% Iower than with fresh semen. There are, however, examples in which frozen semen, under ideal conditions, results in a normal conception rate (4). It should be pointed out that in Colas’ study, the insemination dose was high (400 x 10e) and that double inseminations 12 hr apart were used. Thus, only three to five ewes could be inseminated with one ejaculate-a very low efficiency. In this context, it is worthwhile to emphasize that sheep insemination also faces certain problems with fresh semen: Fertility is retained for a rather short storage time (9) and a fairly Iarge number of spermatozoa per insemination dose (100 x 10G) is required. This is about 10 times more than needed to achieve normal ferti,lity in cattle, Intrauterine versus cervical insemination. It has been known for at least 10 years that

A systematic treatment of the dynamics and control of acid-base reactions is presented. A state model consisting of mass balances for the species present is formed. Through a linear transformation of the concentration vector a new model is set up. The state vector of this model is partitioned into a reaction invariant and a reaction variant part. The model is thus split into two parts, one describing the physical properties of the reactor system independent of chemical reactions, the other describing the chemical reactions. For fast acid-base reactions the reaction invariant part of the model is sufficient to define the thermodynamic state of the system. The reaction rate vector is thus eliminated from the model. In this case the reaction variant part of the model consists of a static equation, relating pH to the reaction invariant state variables. The model obtained provides a sound basis for design of control loops for feedback and feedforward control of pH. As a direct application a new scheme for adaptive control of pH is proposed.

The vibrational behaviour of micromechanical elements has been studied theoretically and experimentally. It is found that classical formulae describing the dependence of mechanical resonance frequency on geometrical and material properties are valid for all practical designs using state-of-the-art technology. Only when the elements approach thickness close to atomic dimensions is it necessary to take surface energy effects into account. Experimentally, cantilever beams have been investigated made from a number of materials: silicon, gallium arsenide, glass, aluminum, Kapton¢ and polyvincylidene-fluoride. Simple formulae giving quality factors for mechanical resonances should be used with caution. Experimental values for quality factors measured in vacuum have a range of three orders of magnitude for different materials, reflecting properties of their inner structure.

Fibre-optic sensors are examined from a micro-mechanical viewpoint. Theoretical expressions for the signal modulation of three basic designs are given, showing the relationship of geometrical parameters and optical transmission properties of multimode fibres. Intensity modulation is considered, together with various compensation schemes. The possibility of designing sensors with frequency output is pointed out. Design examples are given, together with measured performance data on sensor prototypes. One pressure sensor having an outer diameter of less than 0.5 mm for biomedical applications has been fabricated using silicon micro-machining. Another fibre-optic pressure sensor for industrial applications is described. Finally, a fibre-optic voltmeter based on a micro-mechanical light scanning element is described.

Testicular interstitial fluid (ISF) was collected by in vivo perfusion of rat testes and analyzed for the presence of interleukin-1 (IL-1) activity by utilizing a murine thymocyte proliferation assay. IS obtained from nine rats were all positive with dose-response curves of IL-1 activity similar to those produced by rat testicular aqueous extracts, rat macrophage IL-1 and human recombinant IL-1 alpha. Chromato-focusing of pooled ISF revealed a single peak of IL-1 activity with an estimated isoelectric point of 6.1-6.3. HPLC size exclusion chromatography demonstrated two active peaks with apparent molecular ratios Mr of 15,000-18,000 and 5000-7000, respectively. The molecular properties of the 15,000-18,000 Mr component are very similar to those of an IL-1-like factor previously isolated from seminiferous tubules. Our results indicate that the testicular IL-1-like factor is secreted by the seminiferous tubules into the interstitial tissue. Its function in the testicular interstitium is unknown but it might be relevant for the tendency to testicular relapse of childhood lymphocytic leukemia.

We start from an earlier presented method of formulating models for fast acid-base reaction processes, where the reaction invariant and the reaction variant parts of the dynamic model are separated. Models suited for the design of controllers of pH in fast acid-base reaction processes with varying buffer concentrations are set up. The set of models includes a nonlinear model resulting in a controller with linearized feedback of a reaction invariant state vector and linearized models resulting in adaptive linear feedback of pH. Experimental results with some different implementations of these controllers are presented.