The attentional demands of preferred and non-preferred gait patterns

The purpose of this study was to determine the attentional demands of natural and imposed gait, as well as the attentional costs of transitions between the walking and running co-ordination patterns. Seven healthy young men and four healthy young women undertook an auditory probe reaction time task concurrently with self-selected gait (Experiment 1) and imposed walking and running (Experiment 2) at different speeds on a motor-driven treadmill. In Experiment 1, where participants were free to choose their own movement pattern to match the speed of travel of the treadmill, normal gait control was shown to have a significant attentional cost, and hence not be automatic in the classical sense. However, this attentional cost did not differ between the two gait modes or at the transition point. In Experiment 2, where participants were required to maintain specific gait modes regardless of the treadmill speed, the maintenance of walking at speeds normally associated with running was found to have an attentional cost whereas this was not the case for running at normal walking speeds. Collectively the findings support a model of gait control in which the normal switching between gait modes is determined with minimal attention demand and in which it is possible to sustain non-preferred gait modes although, in the case of walking, only at a significant attentional/cognitive cost. © 2002 Elsevier Science B.V. All rights reserved.

Children’s respiratory health and daily particulate levels in ten non-urban communities

We conducted a study to assess the association between the acute respiratory health of children and the levels of particulates in communities near and away from active opencast coal mines. The study enrolled children aged 1–11 years from the general population of five socioeconomically matched pairs of nonurban communities in northern England. Diaries of respiratory events were collected for 1405 children, and information was collected on the consultations of 2442 children with family/general practitioners over the 6-week study periods during 1996–1997, with concurrent monitoring of particulate levels. The associations found between daily PM10 levels and respiratory symptoms were frequently small and positive and sometimes varied between communities. The magnitude of these associations were in line with those from previous studies, even though daily particulate levels were low, and the children were drawn from the general population, rather than from the population with respiratory problems. The associations among asthma reliever use, consultations with general practitioners, and daily particulate levels were of a similar strength but estimated less precisely. The strength of association between all respiratory health measures and particulate levels was similar in communities near and away from opencast coal mining sites.

Exact solution of the A(n-1)((1)) trigonometric vertex model with non-diagonal open boundaries

The A(n-1)((1)) trigonometric vertex model with generic non-diagonal boundaries is studied. The double-row transfer matrix of the model is diagonalized by algebraic Bethe ansatz method in terms of the intertwiner and the corresponding face-vertex relation. The eigenvalues and the corresponding Bethe ansatz equations are obtained.

Non-Equilibrium Reaction Rates in the Macroscopic Chemistry Method for DSMC Calculations

The Direct Simulation Monte Carlo (DSMC) method is used to simulate the flow of rarefied gases. In the Macroscopic Chemistry Method (MCM) for DSMC, chemical reaction rates calculated from local macroscopic flow properties are enforced in each cell. Unlike the standard total collision energy (TCE) chemistry model for DSMC, the new method is not restricted to an Arrhenius form of the reaction rate coefficient, nor is it restricted to a collision cross-section which yields a simple power-law viscosity. For reaction rates of interest in aerospace applications, chemically reacting collisions are generally infrequent events and, as such, local equilibrium conditions are established before a significant number of chemical reactions occur. Hence, the reaction rates which have been used in MCM have been calculated from the reaction rate data which are expected to be correct only for conditions of thermal equilibrium. Here we consider artificially high reaction rates so that the fraction of reacting collisions is not small and propose a simple method of estimating the rates of chemical reactions which can be used in the Macroscopic Chemistry Method in both equilibrium and non-equilibrium conditions. Two tests are presented: (1) The dissociation rates under conditions of thermal non-equilibrium are determined from a zero-dimensional Monte-Carlo sampling procedure which simulates ‘intra-modal’ non-equilibrium; that is, equilibrium distributions in each of the translational, rotational and vibrational modes but with different temperatures for each mode; (2) The 2-D hypersonic flow of molecular oxygen over a vertical plate at Mach 30 is calculated. In both cases the new method produces results in close agreement with those given by the standard TCE model in the same highly nonequilibrium conditions. We conclude that the general method of estimating the non-equilibrium reaction rate is a simple means by which information contained within non-equilibrium distribution functions predicted by the DSMC method can be included in the Macroscopic Chemistry Method.

Molecular cocrystals of carboxylic acids. XXVII - An investigation into the use of triphenylphosphine oxide cocrystals for non-linear optics: the crystal structure of the adduct of triphenylphosphine oxide with N-methylpyrrole-2-carboxylic acid

Four adducts of triphenylphosphine oxide with aromatic carboxylic acids have been synthesized and tested for second-order non-linear optical properties. These were with N-methylpyrrole-2-carboxylic acid (I), indole-2-carboxylic acid (2), 3-dimethylaminobenzoic acid (3), and thiophen-2-carboxylic acid (4). Compound (1) produced clear, colourless crystals (space group P2(1)2(1)2(1) With a 9.892(1), b 14.033(1), c 15.305(1) Angstrom, Z 4) which allowed the structure to be determined by X-ray diffraction.

Characterization of serum antibodies to Porphyromonas gingivalis in individuals with and without periodontitis

Although Porphyromonas gingivalis is a defined pathogen in periodontal disease, many subjects control the infection without experiencing loss of attachment. Differences in host susceptibility to the disease may be reflected in the pattern of humoral antibodies against specific P. gingivalis antigens. The aim of this study was to determine the presence of antibodies against immunodominant P. gingivalis antigens as well as the isotype and subclass of anti-P. gingivalis antibodies against outer membrane antigens in four groups of patients: P. gingivalis-positive, 1) with and 2) without periodontitis, and P. gingivalis-negative, 3) with and 4) without periodontitis. Antigens of molecular weight 92, 63, and 32 kDa and lipopolysaccharide were found to be immunodominant. Group 1 subjects showed a significantly higher response to the 92 and 63 kDa antigens compared with other groups. The response to lipopolysaccharide was significantly higher in group 1, and lower in group 4 than in groups 2, 3. Immunoglobulin G(1) (IgG(1)), IgG(2) and IgM antibodies against P. gingivalis outer membrane were present in all subjects, while only some subjects were seropositive for IgG(3), IgG(4) and IgA. There were no differences in concentrations for IgG(1), IgG(3) and IgM. The IgG(2) concentration in group 4 was significantly higher than in groups 1 and 2, while the IgG(4) concentration in group 4 was significantly lower than in other groups. The frequency of seropositivity for IgG(4) and IgA was lowest in group 4, while IgG; seropositivity was almost exclusively seen in healthy patients iii groups 2, 4. These findings suggest that the presence of IgG(3) may reflect non-susceptibility to the disease, while lack of IgG(4) may be indicative of periodontal health and lack of infection.

Morphine has a dual concentration-dependent effect on K+-evoked substance P release from rat peripheral airways

Our previous investigations of possible lung mechanisms underlying the effectiveness of nebulized morphine for the relief of dyspnoea, have shown a high density of non-conventional opioid binding sites in rat airways with similar binding characteristics (opioid alkaloid-sensitive, opioid peptide-insensitive) to that of putative mu(3)-opioid receptors on immune cells. To investigate whether these lung opioid binding sites are functional receptors, this study was designed to determine (using superfusion) whether morphine modulates the K+-evoked release of the pro-inflammatory neuropeptide, substance P (SP), from rat peripheral airways. Importantly, K+-evoked SP release was Ca2+-dependent, consistent with vesicular release. Submicromolar concentrations of morphine (1 and 200 nM) inhibited K+-evoked SP release from rat peripheral airways in a naloxone (1 mu M) reversible manner. By contrast, 1 mu M morphine enhanced K+-evoked SP release and this effect was not reversed by 1 mu M naloxone. However, 100 mu M naloxone not only antagonized the facilitatory effect of 1 mu M morphine on K+-evoked SP release from rat peripheral airways but it inhibited release to a similar extent as 200 nM morphine. It is possible that these latter effects are mediated by non-conventional opioid receptors located on mast cells, activation of which causes naloxone-reversible histamine release that in turn augments the release of SP from sensory nerve terminals in the peripheral airways. Clearly, further studies are required to investigate this possibility. (C) 1997 Academic Press Limited.

Comparative labor market performance of visaed and non-visaed migrants: Pacific islanders in Sydney

Using survey data for Tongan and Samoan migrants in Sydney the effects of visa restrictions on labor market performance of migrants are assessed. Univariate analysis suggests a positive association between unemployment and the unrestricted entry of Samoan step-migrants from New Zealand. A probit model of the determinants of unemployment is estimated with controls for human capital and demographic variables. While human capital endowments are important, visa restrictions do not have a significant effect on either group's employability. Implications for policy are discussed highlighting the complementarities between host country immigration policies and foreign aid programs.

Dendritic cells in rheumatoid arthritis - A model autoimmune inflammatory site

Rheumatoid arthritis (RA) is a chronic autoimmune inflammatory disease in which unknown arthrogenic autoantigen is presented to CD4+ T cells. The strong association of the disease with an epitope within the HLA-DR chain shared between various alleles of HLA-DR4 and DR1 emphasizes the importance of antigen presentation. This immune response predominantly occurs in the synovial tissue and fluid of the joints and autoreactive T cells are readily demonstrable in both the synovial compartment and blood. Circulating dendritic cells (DC) are phenotypically and functionally identical with normal peripheral blood (PB) DC. In the synovial tissue, fully differentiated perivascular DC are found in close association with T cells and with B cell follicles, sometimes containing follicular DC. These perivascular DC migrate across the activated endothelium from blood and receive differentiative signals within the joint from monocyte-derived cytokines and CD40-ligand+ T cells. In the SF, DC manifest an intermediate phenotype, similar to that of monocyte-derived DC in vitro. Like a delayed-type hypersensitivity response, the rheumatoid synovium represents an effector site. DC at many effector sites have a characteristic pattern of infiltration and differentiation. It is important to note that the effector response is not self-limiting in RA autoimmune inflammation. In this article, we argue that the presentation of self-antigen by DC and by autoantibody-producing B cells is critical for the perpetuation of the autoimmune response. Permanently arresting this ongoing immune response with either pharmaceutical agents or immunotherapy is a major challenge for immunology.

Phosphorylation of the C-terminal sites of human p53 reduces non-sequence-specific DNA binding as modeled with synthetic peptides

Phosphorylation of the tumor suppressor p53 is generally thought to modify the properties of the protein in four of its five independent domains. We used synthetic peptides to directly study the effects of phosphorylation on the non-sequence-specific DNA binding and conformation of the C-terminal, basic domain. The peptides corresponded to amino acids 361-393 and were either nonphosphorylated or phosphorylated at the protein kinase C (PKC) site, Ser378, or the casein kinase II (CKII) site, Ser392, or bis-phosphorylated on both the PKC and the CKII sites. A fluorescence polarization analysis revealed that either the recombinant p53 protein or the synthetic peptides bound to two unrelated target DNA fragments. Phosphorylation of the peptide at the PKC or the CKII sites clearly decreased DNA binding, and addition of a second phosphate group almost completely abolished binding. Circular dichroism spectroscopy showed that the peptides assumed identical unordered structures in aqueous solutions. The unmodified peptide, unlike the Ser378 phosphorylated peptide, changed conformation in the presence of DNA. The inherent ability of the peptides to form an alpha-helix could be detected when circular dichroism and nuclear magnetic resonance spectra were: taken in trifluoroethanol-water mixtures. A single or double phosphorylation destabilized the helix around the phosphorylated Ser378 residue but stabilized the helix downstream in the sequence.

Focused antithrombotic therapy: Novel anti-platelet salicylates with reduced ulcerogenic potential and higher first-pass detoxification than aspirin in rats

The use of aspirin as an anti-platelet drug is limited by its propensity to induce gastric injury and by its adverse effect on vascular prostacyclin formation. Two phenolic non-steroidal anti-inflammatory drugs (salicyclic acid and diflunisal) were modified by esterification with a series of O-acyl moieties. The short-term ulcerogenic in vitro and in vivo anti-platelet properties, pharmacodynamic profiles, and extent of hepatic extraction of these phenolic esters were compared with aspirin (acetylsalicylic acid). The more lipophilic esters (longer carbon chain length in O-acyl group) show significantly less gastrotoxicity in stressed rats than does aspirin after a single oral dose. The in vitro and in vivo anti-platelet studies show that these phenolic esters inhibited (1) arachidonate-triggered human platelet aggregation and (2) thrombin-stimulated rat serum thromboxane Ag production by platelets in the clotting process almost as effectively as aspirin. The hepatic extractions of these O-acyl derivatives are significantly higher than those of aspirin. The pharmacodynamic studies show that these O-acyl derivatives of salicylic acid and diflunisal probably bind to, or combine with, the same site on the platelet cyclooxygenase as aspirin. Replacing the O-acetyl group with longer chain O-acyl moiety in this series of phenolic esters markedly reduced the potential of these agents to induce short-term gastric injury but did not lessen their activity as inhibitors of platelet aggregation. These non-acetyl salicylates may therefore represent a novel class of anti-platelet drugs with less ulcerogenic potential.

Evolution of three-dimensional folds for a non-Newtonian plate in a viscous medium

We derive analytical solutions for the three-dimensional time-dependent buckling of a non-Newtonian viscous plate in a less viscous medium. For the plate we assume a power-law rheology. The principal, axes of the stretching D-ij in the homogeneously deformed ground state are parallel and orthogonal to the bounding surfaces of the plate in the flat state. In the model formulation the action of the less viscous medium is replaced by equivalent reaction forces. The reaction forces are assumed to be parallel to the normal vector of the deformed plate surfaces. As a consequence, the buckling process is driven by the differences between the in-plane stresses and out of plane stress, and not by the in-plane stresses alone as assumed in previous models. The governing differential equation is essentially an orthotropic plate equation for rate dependent material, under biaxial pre-stress, supported by a viscous medium. The differential problem is solved by means of Fourier transformation and largest growth coefficients and corresponding wavenumbers are evaluated. We discuss in detail fold evolutions for isotropic in-plane stretching (D-11 = D-22), uniaxial plane straining (D-22 = 0) and in-plane flattening (D-11 = -2D(22)). Three-dimensional plots illustrate the stages of fold evolution for random initial perturbations or initial embryonic folds with axes non-parallel to the maximum compression axis. For all situations, one dominant set of folds develops normal to D-11, although the dominant wavelength differs from the Biot dominant wavelength except when the plate has a purely Newtonian viscosity. However, in the direction parallel to D-22, there exist infinitely many modes in the vicinity of the dominant wavelength which grow only marginally slower than the one corresponding to the dominant wavelength. This means that, except for very special initial conditions, the appearance of a three-dimensional fold will always be governed by at least two wavelengths. The wavelength in the direction parallel to D-11 is the dominant wavelength, and the wavelength(s) in the direction parallel to D-22 is determined essentially by the statistics of the initial state. A comparable sensitivity to the initial geometry does not exist in the classic two-dimensional folding models. In conformity with tradition we have applied Kirchhoff's hypothesis to constrain the cross-sectional rotations of the plate. We investigate the validity of this hypothesis within the framework of Reissner's plate theory. We also include a discussion of the effects of adding elasticity into the constitutive relations and show that there exist critical ratios of the relaxation times of the plate and the embedding medium for which two dominant wavelengths develop, one at ca. 2.5 of the classical Biot dominant wavelength and the other at ca. 0.45 of this wavelength. We propose that herein lies the origin of parasitic folds well known in natural examples.