Scattering and tangential momentum accommodation at a 2D adsorbate-solid interface

We calculate tangential momentum coefficients for the exchange of momentum between molecules in transport and the internal surface of a membrane pore, modelled as a simple atomic structure. We introduce a local specular reflection (LSR) hypothesis, which states that impinging molecules undergo mirror-like reflection in a plane tangent to a surface atom at the point of impact. As a consequence, the components of the velocity, parallel to the direction of flow will (in general) change on impact. The overall effect is a loss of tangential momentum, since more is lost in the upstream direction than is gained in the downstream direction. The loss of tangential momentum is greater when the size ratio of fluid to solid atom is small, allowing more steeply inclined impact planes to become accessible to the fluid phase molecules. (c) 2005 Elsevier B.V. All rights reserved.

The effect of different levels of dietary crude protein on urea metabolism of rusa deer (Cervus timorensis)

Two experiments were conducted to measure urea recycling and rumen flow dynamics in young rusa deer fed low (LP) or high (HP) protein diets. Pool size and flux rate of labelled urea. into and out of the blood pool were measured using single intravenous (i.v.) injection solutions containing [C-14] - and [N-15]-urea. A curve peeling technique was used to fit the enrichment of N-15 or specific radioactivity (SRA) of C-14 to exponential equations. Body urea-N pool size was significantly greater (P < 0.05) when a HP, compared to a LP diet, was fed. Urea space, expressed as a percent of live weight, total flux rate of urea through the blood pool and the irreversible loss of urea was similar for both diets. The mean (+/- S.E.M.) concentration of plasma urea-N was greater when animals were fed the HP diet compared to the LP diet (2 1.1 +/- 0.3 versus 14.4 +/- 1.4 mg/100 ml, respectively). Voluntary feed intake and digestibility of dietary components were also measured. Daily dry matter intakes were not affected by the crude protein (CP) content of the diet, although apparent DM digestibility was significantly greater for HP diet fed in both experiments. An intraruminal infusion of CrEDTA was used to determine rumen flow dynamics. Ruminal mean retention time, relative net outflow rate of water and passage rate constant (k(w)) were significantly greater (P < 0.05) when the HP diet was fed compared to the LP diet. The extent of urea metabolism and flux rates of urea between the blood and secondary pools appear similar to those previously reported for other ruminants fed diets contrasting in CP content. (c) 2005 Elsevier B.V. All rights reserved.

The effect of manipulations to target contrast on emmetropization in chick

Emmetropization is dependent on visual feedback and presumably some measure of the optical and image quality of the eye. We investigated the effect of simple alterations to image contrast on eye growth and refractive development. A 1.6 cyc/deg square-wave-grating target was located at the end of a 3.3 cm cone,, imaged by a +30 D lens and applied monocularly to the eyes of 8-day-old chicks. Eleven different contrast targets were tested: 95, 67, 47.5, 33.5, 24, 17, 12, 8.5, 4.2, 2.1, and 0%. Refractive error (RE), vitreous chamber depth (VC) and axial length (AL) varied with the contrast of the image (RE diff. F-10.86 = 12.420, p < 0.0005; VC diff. F-10.86 = 8.756, p < 0.0005; AL diff. F-10.86 = 9.240, p < 0.0005). Target contrasts 4.2% and lower produced relative myopia (4.2%: RE diff = -7.48 +/- 2.26 D, p = 0.987; 2.1%: RE diff = -7.22 +/- 2.77 D, p = 0.951) of similar amount to that observed in response to a featureless 0% contrast target (RE diff = -9.11 +/- 4.68 D). For target contrast levels 47.5% and greater isometropia was maintained (95%: RE diff = 1.83 +/- 2.78 D; 67%: RE diff = 0.14 +/- 1.84 D; 47.5% RE diff = 0.25 +/- 1.82 D). Contrasts in between produced an intermediate amount of myopia (33.5%: RE diff = -2.81 +/- 1.80 D; 24%: RE diff = -3.45 +/- 1.64 D; 17%: RE diff = -3.19 +/- 1.54 D; 12%: RE diff = -4.08 +/- 3.56 D; 8.5%: RE diff = -4.09 +/- 3.60 D). We conclude that image contrast provides important visual information for the eye growth control system or that contrast must reach a threshold value for some other emmetropization signal to function. (c) 2005 Elsevier Ltd. All rights reserved.

The effect of reduced contrast on drivers' speed perception

It has been demonstrated, using abstract psychophysical stimuli, that speeds appear slower when contrast is reduced under certain conditions. Does this effect have any real life consequences? One previous study has found, using a low fidelity driving simulator, that participants perceived vehicle speeds to be slower in foggy conditions. We replicated this finding with a more realistic video-based simulator using the Method of Constant Stimuli. We also found that lowering contrast reduced participants’ ability to discriminate speeds. We argue that these reduced contrast effects could partly explain the higher crash rate of drivers with cataracts (this is a substantial societal problem and the crash relationship variance can be accounted for by reduced contrast). Note that even if people with cataracts can calibrate for the shift in their perception of speed using their speedometers (given that cataracts are experienced over long periods), they may still have an increased chance of making errors in speed estimation due to poor speed discrimination. This could result in individuals misjudging vehicle trajectories and thereby inflating their crash risk. We propose interventions that may help address this problem.

An automated failure mode and effect analysis based on high-level design specificication with behavior trees

Formal methods have significant benefits for developing safety critical systems, in that they allow for correctness proofs, model checking safety and liveness properties, deadlock checking, etc. However, formal methods do not scale very well and demand specialist skills, when developing real-world systems. For these reasons, development and analysis of large-scale safety critical systems will require effective integration of formal and informal methods. In this paper, we use such an integrative approach to automate Failure Modes and Effects Analysis (FMEA), a widely used system safety analysis technique, using a high-level graphical modelling notation (Behavior Trees) and model checking. We inject component failure modes into the Behavior Trees and translate the resulting Behavior Trees to SAL code. This enables us to model check if the system in the presence of these faults satisfies its safety properties, specified by temporal logic formulas. The benefit of this process is tool support that automates the tedious and error-prone aspects of FMEA.

Ultrasonic measurement technique of burning metals in normal and reduced gravity

The in situ real time measurement of the regression rate of a melting interface (RRMI) is performed by the ultrasonic measurement system reported here. The RRMI is the rate at which a solid/liquid interface (SLI) moves along a metallic rod while burning in an oxygen-enriched atmosphere and is an important flatnmability indicator. The ultrasonic transducer and associated equipment used to drive the transducer and record the echo signal is described, along with the process that transforms the acquired signals into a RRMI value. Test rods of various metals and geometric shapes were burned at several test conditions in different test facilities. The RRMI results with quantified errors are presented and reviewed. The effect of reduced gravity on burning metals is important to space-applications and RRMI results obtained in a reduced gravity environment are also presented.

O EFEITO DO CONTROLE RESPIRATÓRIO EM VARIÁVEIS ELETROFISIOLÓGICAS DA ATENÇÃO

A prática do ioga tem se tornado cada vez mais popular, não apenas pelos benefícios físicos, mas principalmente pelo bem-estar psicológico trazido pela sua prática. Um dos componentes do ioga é o Prãnãyama, ou controle da respiração. A atenção e a respiração são dois mecanismos fisiológicos e involuntários requeridos para a execução do Prãnãyama. O principal objetivo desse estudo foi verificar se variáveis contínuas do EEG (potência de diferentes faixas que o compõem) seriam moduladas pelo controle respiratório, comparando-se separadamente as duas fases do ciclo respiratório (inspiração e expiração), na situação de respiração espontânea e controlada. Fizeram parte do estudo 19 sujeitos (7 homens/12 mulheres, idade média de 36,89 e DP = ± 14,46) que foram convidados a participar da pesquisa nas dependências da Faculdade de Saúde da Universidade Metodista de São Paulo. Para o registro do eletroencefalograma foi utilizado um sistema de posicionamento de cinco eletrodos Ag AgCl (FPz, Fz, Cz, Pz e Oz) fixados a uma touca de posicionamento rápido (Quick-Cap, Neuromedical Supplies®), em sistema 10-20. Foram obtidos valores de máxima amplitude de potência (espectro de potência no domínio da frequência) nas frequências teta, alfa e beta e delta e calculada a razão teta/beta nas diferentes fases do ciclo respiratório (inspiração e expiração), separadamente, nas condições de respiração espontânea e de controle respiratório. Para o registro do ciclo respiratório, foi utilizada uma cinta de esforço respiratório M01 (Pletismógrafo). Os resultados mostram diferenças significativas entre as condições de respiração espontânea e de controle com valores das médias da razão teta/beta menores na respiração controlada do que na respiração espontânea e valores de média da potência alfa sempre maiores no controle respiratório. Diferenças significativas foram encontradas na comparação entre inspiração e expiração da respiração controlada com diminuição dos valores das médias da razão teta/beta na inspiração e aumento nos valores das médias da potência alfa, sobretudo na expiração. Os achados deste estudo trazem evidências de que o controle respiratório modula variáveis eletrofisiológicas relativas à atenção refletindo um estado de alerta, porém mais relaxado do que na situação de respiração espontânea.

Effect of polymorph derived oxidants on IgG in relation to rheumatoid factor binding

Immunoglobulin G from rheumatoid patients is denatured around the hinge region. This has been proposed as an explanation for the presence of circulating autoantibodies to IgG in these patients. It has previously been suggested that oxygen radicals (OR) derived from activated polymorphs may play a role in denaturation in vivo. Using sera from rheumatoid patients and age-matched controls in a modified ELISA technique, we have investigated the potential for polyclonal rheumatoid factors (RF) to bind to OR denatured IgG. Three model systems were used to generate OR in vitro: (a) purified PMN s activated by the cell surface stimulant PMA, (b) radiolysis of IgG in solution to generate specifically the superoxide radical and, in a separate system, the hydroxyl radical, (OH.), (c) purified myeloperoxide in the presence of H2O2 and halide ions. Results: 1. The binding of both IgA and IgM RF s to PMN denatured IgG increased dose dependently for seropositive sera only. 2. The OH. radical but not the superoxide radical significantly increased the binding of IgA and M RF, again only for seropositive sera. 3. The myeloperoxidase enzyme system did not increase RF binding. 4. IgG incubated with elastase was not found to be a better antigen than native IgG. These results indicate that IgG is denatured by OR released from activated PMN, thereby producing an antigen for polyclonal RF s.

An exploration of the effect of super large n-tuples on single layer RAMnets

N-tuple recognition systems (RAMnets) are normally modeled using a small number of input lines to each RAM, because the address space grows exponentially with the number of inputs. It is impossible to implement an arbitrarily-large address space as physical memory. But given modest amounts of training data, correspondingly modest numbers of bits will be set in that memory. Hash arrays can therefore be used instead of a direct implementation of the required address space. This paper describes some exploratory experiments using the hash array technique to investigate the performance of RAMnets with very large numbers of input lines. An argument is presented which concludes that performance should peak at a relatively small n-tuple size, but the experiments carried out so far contradict this. Further experiments are needed to confirm this unexpected result.

A method for profiling biometric changes during disaccommodation

PURPOSE: To demonstrate the application of low-coherence reflectometry to the study of biometric changes during disaccommodation responses in human eyes after cessation of a near task and to evaluate the effect of contact lenses on low-coherence reflectometry biometric measurements. METHODS: Ocular biometric parameters of crystalline lens thickness (LT) and anterior chamber depth (ACD) were measured with the LenStar device during and immediately after a 5 D accommodative task in 10 participants. In a separate trial, accommodation responses were recorded with a Shin-Nippon WAM-5500 optometer in a subset of two participants. Biometric data were interleaved to form a profile of post-task anterior segment changes. In a further experiment, the effect of soft contact lenses on LenStar measurements was evaluated in 15 participants. RESULTS: In 10 adult participants, increased LT and reduced ACD was seen during the 5 D task. Post-task, during fixation of a 0 D target, a profile of the change in LT and ACD against time was observed. In the two participants with accommodation data (one a sufferer of nearwork-induced transient myopia and other a non-sufferer), the post-task changes in refraction compared favorably with the interleaved LenStar biometry data. The insertion of soft contact lenses did not have a significant effect on LenStar measures of ACD or LT (mean change: -0.007 mm, p = 0.265 and + 0.001 mm, p = 0.875, respectively). CONCLUSIONS: With the addition of a relatively simple stimulus modification, the LenStar instrument can be used to produce a profile of post-task changes in LT and ACD. The spatial and temporal resolution of the system is sufficient for the investigation of nearwork-induced transient myopia from a biometric viewpoint. LenStar measurements of ACD and LT remain valid after the fitting of soft contact lenses.

The effect of ageing on in vivo human ciliary muscle morphology and contractility

Purpose. To assess the effect of ageing on in vivo human ciliary muscle morphology and contractility during accommodation. Methods. Seventy-nine subjects, aged 19–70 years were recruited. High-resolution images were acquired of nasal and temporal ciliary muscle in the relaxed state, and at stimulus vergence levels of -4 and -8 D, using anterior segment optical coherence tomography (AS-OCT). Objective refractions and axial lengths were also recorded. Linear regression analysis was performed to determine the effect of age on nasal and temporal ciliary muscle morphologic characteristics. Results. Ciliary muscle anterior length decreased significantly with age both nasally (R = 0.461, P = 0.001) and temporally (R = 0.619, P < 0.001) in emmetropic eyes. In a subset of 37 participants, ciliary muscle maximum width increased significantly with age, by 2.8 µm/year nasally (R = 0.54, P < 0.001) and 3.0 µm/year temporally (R = 0.44, P = 0.007), while the distance from the inner apex of the ciliary muscle to the scleral spur decreased significantly with age on both the nasal and temporal aspects (R = 0.47; P = 0.004 and R = 0.43; P = 0.009, respectively). During accommodation, changes to ciliary muscle thickness and length remained constant throughout life. Conclusions. The human ciliary muscle undergoes age-dependent changes in morphology that suggest an antero-inwards displacement of muscle mass, particularly in emmetropic eyes. However, the morphologic changes observed appear not to affect the ability of the muscle to contract during accommodation, even in established presbyopes, thus supporting a lenticular model of presbyopia development.

Liposomes based on dimethyldioctadecylammonium promote a depot effect and enhance immunogenicity of soluble antigen

The mechanism behind the immunostimulatory effect obtained with the cationic liposomal vaccine adjuvant DDA:TDB remains unclear. One of the proposed hypotheses is the 'depot effect' in which the liposomal carrier helps to retain the antigen at the injection site thereby increasing the time of vaccine exposure to the immune cells. In the present study we devise a method to quantify the in vivo movement of liposomes and vaccine antigen using the radioisotopes H(3) and I(125) respectively. H(3)-labeled liposomes composed of dimethyldioctadecylammonium bromide (DDA) or an 8:1 molar ratio of DDA and trehalose 6,6-dibehenate (TDB) were administered in combination with I(125)-labeled Ag85B-ESAT-6 antigen, both via intramuscular and subcutaneous injection to mice. Furthermore characterisation of the liposomal system in simulated in vivo conditions was undertaken. Our results show that this dual-labeling technique is functional and reproducible. The administration of Ag85B-ESAT-6 without a liposomal carrier leads to rapid dissemination of the antigen from the site of injection. The administration of Ag85B-ESAT-6 together with either DDA or DDA:TDB liposomes however leads to deposition of the antigen at the injection site with detectable levels still being present 14 days post injection. Neither the incorporation of TDB nor the route of injection had any significant influence on the depot effect of DDA-based liposomes. The presence of TDB in DDA liposomes improves draining of liposomes to the lymph node in addition to increasing monocyte influx to the site of injection as highlighted by the intensive blue colouring of the injection site after pontamine blue staining of phagocytic cells in vivo. Our findings provide conclusive evidence for a cationic liposome-mediated deposition of antigen at the injection site with improved monocyte infiltration.

Feasibility studies of an on-line identification technique

This thesis is concerned with the study of a non-sequential identification technique, so that it may be applied to the identification of process plant mathematical models from process measurements with the greatest degree of accuracy and reliability. In order to study the accuracy of the technique under differing conditions, simple mathematical models were set up on a parallel hybrid. computer and these models identified from input/output measurements by a small on-line digital computer. Initially, the simulated models were identified on-line. However, this method of operation was found not suitable for a thorough study of the technique due to equipment limitations. Further analysis was carried out in a large off-line computer using data generated by the small on-line computer. Hence identification was not strictly on-line. Results of the work have shovm that the identification technique may be successfully applied in practice. An optimum sampling period is suggested, together with noise level limitations for maximum accuracy. A description of a double-effect evaporator is included in this thesis. It is proposed that the next stage in the work will be the identification of a mathematical model of this evaporator using the teclmique described.

Seeing light vs dark lines: psychophysical performance is based on separate channels, limited by noise and uncertainty

Visual detection performance (d') is usually an accelerating function of stimulus contrast, which could imply a smooth, threshold-like nonlinearity in the sensory response. Alternatively, Pelli (1985 Journal of the Optical Society of America A 2 1508 - 1532) developed the 'uncertainty model' in which responses were linear with contrast, but the observer was uncertain about which of many noisy channels contained the signal. Such internal uncertainty effectively adds noise to weak signals, and predicts the nonlinear psychometric function. We re-examined these ideas by plotting psychometric functions (as z-scores) for two observers (SAW, PRM) with high precision. The task was to detect a single, vertical, blurred line at the fixation point, or identify its polarity (light vs dark). Detection of a known polarity was nearly linear for SAW but very nonlinear for PRM. Randomly interleaving light and dark trials reduced performance and rendered it non-linear for SAW, but had little effect for PRM. This occurred for both single-interval and 2AFC procedures. The whole pattern of results was well predicted by our Monte Carlo simulation of Pelli's model, with only two free parameters. SAW (highly practised) had very low uncertainty. PRM (with little prior practice) had much greater uncertainty, resulting in lower contrast sensitivity, nonlinear performance, and no effect of external (polarity) uncertainty. For SAW, identification was about v2 better than detection, implying statistically independent channels for stimuli of opposite polarity, rather than an opponent (light - dark) channel. These findings strongly suggest that noise and uncertainty, rather than sensory nonlinearity, limit visual detection.