The applicability of a two-parameter Fickian diffusion model for predicting the skin steady-state permeability based on measurements of the transient transport of permeants across the skin was tested. Using five model permeants possessing different physicochemical properties and pig skin as the model membrane, the skin permeabilities predicted by the two-parameter Fickian diffusion model were compared with the measured skin permeabilities. Results show that the transient skin permeation profiles of the hydrophobic permeants, estradiol, testosterone, and dolichol, across splitthickness pig skin can be modeled adequately by the two-parameter Fickian diffusion model (with constant parameter values), and therefore, that this model can be utilized to shorten the experimental time required to determine the skin permeabilities of these compounds. However, the skin permeabilities of the highly hydrophilic permeants, mannitol and sucrose, predicted by the two-parameter Fickian diffusion model (with constant parameter values) were significantly lower than the experimentally determined values, indicating that the dominant skin pathway of polar permeants within the excised pig skin undergoes significant structural changes during the in vitro diffusion cell studies. Although the skin permeability values determined experimentally using the traditional steady-state method normally correspond to a highly hydrated skin sample, the two-parameter Fickian diffusion model enables an estimation of the skin permeability of the skin membrane at its less-hydrated state (a condition more representative of in vivo and clinical situations). Using the two-parameter Fickian diffusion model and a recently developed skin porous-pathway theory, the effects of skin hydration on the skin porous pathway within the excised pig skin were characterized. Specifically, we found that hydration leads to induction of new pores/reduction of the tortuosity of existing pores within the excised pig skin during the 48 h diffusion cell studies conducted, while the skin average pore radii remain relatively constant ($26 Å ) for up to 48 h. ß

The St. Lawrence Lowlands platform, Quebec, Canada, is a densely-populated area, heavily dependent on groundwater resources. In 1999, the Geological Survey of Canada initiated a large-scale hydrogeological assessment study over a 1,500 km2 region northwest of Montreal. The objectives were to define the regional groundwater flow, and to give quantitative estimates of the groundwater dynamic parameters and of the available groundwater resources. The applied approach consisted of defining the hydrogeologic framework, hydraulic properties of the aquifer units, and groundwater dynamic components. Lower Paleozoic sedimentary rocks represent regional aquifer units. Coarse Quaternary fluvio-glacial sediments locally overlay the rock sequence and constitute an interface aquifer unit. Fine marine sediments confine most of the regional aquifers. Collected GIS based information was synthesized in a finite element numerical model. The regional saturated steady-state flow was calibrated under current stress conditions assuming an equivalent porous medium approach. Water budget calculations show that the total groundwater flow in regional aquifers amounts to 97.7 Mm3/y. Infiltration from precipitation provides 86.6% of the groundwater supply, while 9.6% comes from subsurface inflow and the remaining 3.8% is induced recharge from surface waters. Discharge from regional aquifers occurs through flow to streams (76.9%), groundwater withdrawal (18.4%), and underground outflow (4.7%). La plateforme Lowllands du Saint-Laurent, Québec, Canada, est une aire densément peuplée, dépendant grandement des ressources en eau souterraine. En 1999, le Service Géologique du Canada a initié une étude hydrogéologique à grande-échelle sur 1500 km2 au Nord-Ouest de Montréal. Le sobjectifs ont été de définir la dynamique de l’écoulement régional, et de donner des estimations quantitatives des paramètres dynamiques des ressources disponibles en eau souterraine. L’approche utilisée consista à définir le cadre hydrogéologique de travail, les propriétés hydrauliques des unités aquifères, et les composantes dynamiques des eaux souterraines. Les roches sédimentaires du Paléozoïque Inférieur représentent les unités aquifères régionales. Les sédiments marins fins confinent la plus grande partie des aquifères régionaux. Les informations de base, collectées dans un SIG, ont été synthétisées dans un modèle numérique aux éléments finis. L’écoulement permanent régional, en zone saturée, a été calibré en conditions de stress en assumant une approche de milieu poreu équivalent. Les calculs du bilan hydrologique montrent que l’écoulement total des eaux souterraines dans les aquifères régionaux atteind 97,7 Mm3/an. L’infiltration à partir des précipitations apporte 86.6% de l’eau souterraine exploitée; sachant que 9,6% proviennent d’écoulement de subsurfaces, et que les 3,8% restants proviennent de la recharge via les eaux de surface. Le débit pompé des aquifères régionaux apparaît à travers l’écoulement des cours d’eau, le rabattement des eaux souterraines (18.4%), et l’écoulement ascendant (4.7%). La plataforma de Tierras Bajas San Lorenzo, Quebec, Canadá, es un área densamente poblada que depende fuertemente de recursos de agua subterránea. En 1999 el Servicio Geológico de Canadá inició un estudio de evaluación hidrogeológica a gran escala sobre un área de 1,500 km2 en la región noroeste de Montreal. Los objetivos fueron definir el flujo regional de agua subterránea y aportar estimados cuantitativos de los parámetros dinámicos de agua subterráne y de los recursos disponibles de agua subterránea. El enfoque aplicado consistió en definir el marco hidrogeológico, propiedades hidráulicas de las unidades acuíferas, y los componentes dinámicos de agua subterránea. Rocas sedimentarias del Paleozoico Inferior representan unidades regionales de acuíferos. Sedimentos fluvio-glaciares Cuaternarios gruesos sobreyacen localmente la secuencia rocosa y constituyen una unidad acuífera interfacial. Sedimentos marinos finos confinan la mayoría de acuíferos regionales. Información colectada basada en SIG se sintetizó en un modelo numérico de elemento finito. El flujo regional saturado en régimen permanente se calibró bajo condiciones de stress asumiendo un enfoque de medio poroso equivalente. Los cálculos de balance hídrico muestran que el flujo total de agua subterránea en acuíferos regional alcanza 97.7 Mm3/año. Infiltración a partir de lluvia aporta el 86.6% del abastecimiento al agua subterránea, mientras que el 9.6% proviene de entradas subsuperficiales y el restante 3.8% consiste de recarga inducida a partir de aguas superficiales. La descarga proveniente de acuíferos regionales ocurre a través de flujo a ríos (76.9%), utilización de agua subterránea (18.4%), y salida subterránea (4.7%).

An analytical model for gas-solid suspension flow through an inclined section of pipe was developed. This model predicts the ratio of the total pressure drop in an inclined pipe to that of a horizontal pipe. The model has been used to predict the critical pipe angle, which is defined as the angle at which the maximum pressure drop for a given solids flow rate is achieved. This angle differs from 90 ° (found in a single-phase flow) and is directly proportional to the ratio between the gas superficial velocity and the particle terminal velocity. The three-dimensional conservation equations for steady-state two-phase flow in an inclined pipe were solved numerically for constant solids and gas flow rates at different pipe inclinations. This model was based on the continuum theory for describing the mass and momentum balance equations for the fluid and solid phases. A packing model, describing the shear stress of the solid phase as a function of its volume fraction, is suggested in order to limit the maximum value of the solid volume fraction. A new model for particle-wall interaction was developed taking into account the angle of inclination of the pipe. The prediction of the numerical model was compared with experimental data obtained in a specially designed test rig. In general, the agreement between the experimental data and the models was satisfactory. The results of the numerical simulation also confirmed that the critical pipe angle for gas-solid flow is lower than 90 ° . The assumptions made during the development of the models were assessed in order to explain the differences between the predicted and measured values of the flow parameters for different flow regimes. © 1997 Elsevier Science S.A.

Survey Modelling Simulation a b s t r a c t Computer simulation has become a required tool in the design phase of vapor compression systems; however with relatively few exceptions most simulations focus on the basic four component systems. With an increasing focus being placed on energy efficiency, the simulation of multi-component vapor compression systems (having multiple evaporators, condenser or compressors) will become essential to assist in the design of these more complicated systems. The implementation of a component-based framework will facilitate the simulation of multi-component systems. This paper describes three algorithms used to simulate a component-based vapor compression system. A test matrix of 6174 sample runs covering a wide range of operating conditions was constructed to determine the robustness and speed of each method when using three different types of nonlinear equation solvers. Each method was tested by simulating a basic four component cycle and a more advanced multiple evaporator system. The results are presented in such a format as to describe the reasons that contribute to any instability of the solvers and the computational efficiency of each method is discussed. ª 2007 Elsevier Ltd and IIR. All rights reserved.

In developing countries undergoing liberalising economic reforms, there are typically local incumbents facing the loss of protection. Strategic lobbying by such firms for a price-capping regulatory regime is, under certain conditions, one way in which they can deter entry by competitors who are likely to be foreign firms. We show that a regulatory price can be set such that the net profit of the entrant is lower than the entry cost thus deterring entry. We then show that it is possible for the profit of the incumbent to be greater under regulation which deters entry than under unregulated duopoly. Counter-intuitively, we further discover that lobbying for regulation is to be expected where the incumbent firm is relatively cost-efficient. Finally, we consider the case of multiple incumbents threatened by entry. We observe a co-ordination problem and consider the possibility of co-operation in lobbying. We then show that such co-operation, if possible, is always preferable to non-co-o...

Dynamic, multicompartment in vitro gastrointestinal simulators are often used to monitor gut microbial dynamics and activity. These reactors need to harbor a microbial community that is stable upon inoculation, colon region specific, and relevant to in vivo conditions. Together with the reproducibility of the colonization process, these criteria are often overlooked when the modulatory properties from different treatments are compared. We therefore investigated the microbial colonization process in two identical simulators of the human intestinal microbial ecosystem (SHIME), simultaneously inoculated with the same human fecal microbiota with a high-resolution phylogenetic microarray: the human intestinal tract chip (HITChip). Following inoculation of the in vitro colon compartments, microbial community composition reached steady state after 2 weeks, whereas 3 weeks were required to reach functional stability. This dynamic colonization process was reproducible in both SHIME units and resulted in highly diverse microbial communities which were colon region specific, with the proximal regions harboring saccharolytic microbes (e.g., Bacteroides spp. and Eubacterium spp.) and the distal regions harboring mucindegrading microbes (e.g., Akkermansia spp.). Importantly, the shift from an in vivo to an in vitro environment resulted in an increased Bacteroidetes/Firmicutes ratio, whereas Clostridium cluster IX (propionate producers) was enriched compared to clusters IV and XIVa (butyrate producers). This was supported by proportionally higher in vitro propionate concentrations. In conclusion, high-resolution analysis of in vitro-cultured gut microbiota offers new insight on the microbial colonization process and indicates the importance of digestive parameters that may be crucial in the development of new in vitro models.

We investigate theoretically a mode of heating layers using a laser beam. In this mode thermal energy, the temperature of the layer, propagates in a steady-state self sustained fashion from the bottom of the layer towards the surface and may exhibit a very steep front. The propagation exhibits a constant speed, related to the intensity of the power flux. To achieve this heating mode the absorption coefficient has to remain low in low temperatures and increase rapidly as a function of temperature in higher temperatures. Additionally, a significant temperature increase must be generated to trigger this propagation mode, for example through the presence of a strongly absorbing layer beneath the transparent layer. The mode is well suited to semiconductors, especially silicon. A few examples of applications are proposed. PACS. 81.40.gh Other heat and thermomechanical treatments-81.40.tv Optical and dielectric properties-81.40.wx Radiation treatment

In this study, a stable, differentiated culture format (primary hepatocytes cultured between two layers of collagen gel) was used to study the effect of the inducer 3,3',4,4'-tetrachlorobiphenyl (TCB) on the activity of cytochrome P4501Al. P450IAI (ethoxyresorufin O-deethylase) enzymatic activity was measured using the rate of conversion of ethoxyresorufin (ER) to resorufin (R). After I4 days of induction with 10mh M TCB, hepatocytes in the double collagen gel configuration exhibited a maximum activity of 180.3 + 46.8 pmol R/fig DNA/hr (3.6 + 0.9 nmol R/IO6 cells/hr) compared with 34.9 + 3.8 pmol R/pg DNA/hr for cells cultured on a single layer of gel. At a TCB level of IOms M, the P450IAI activity in the double-gel configuration peaked at 220.8 + 37.0 pmol R/pg DNA/hr. Cessation of 10e6 M TCB induction produced a decrease in activity to 25.8 + 4.1 pmol R/pg DNA/hr within 4 hr. Subsequent re-application of the inducer caused an increase in activity to 76.5 k-1 I. I pmol R/pg DNA/hr within 6 hr. reaching a maximal value of 131.0 + 38.6 nmol R/u~ DNAihr within I2 hr. Since TCB is ranidlv metabolized bv hepatocytes, a continuous perfusion cul&re system was developed to examine the effect of exposure to a constant level of TCB. Continuous perfusion of the cells with 10-s or IO-'M TCB, resulted in activities significantly higher than those of cultures induced by daily application of induction medium. A mechanistic model of TCB-dependent induction of P4501Al was developed using kinetic parameters estimated from static culture data. The model accurately predicted cyclic variations in P450IAl activity in static culture, and the steady-state activity level of perfusion cultures. This work describes procedures for exposing stable hepatocyte cultures to either continuous or declining levels of consumable inducers and for measuring the activity of cytochrome P450IAl in cultured hepatocytes by a non-invasive method.

A disequilibrium model of endogenous innovation and growth is presented. The behaviour of the agents is supposed to be governed by routines, not by maximization. The entrepreneurs are assumed to invest a fraction of their operating profits in real capital accumulation, and another fraction in R&D. The latter leads to an increase in labour productivity via a R&D production function. In this 'Schumpeterian' model, not only the R&D processes of innovations are considered, but the diffusion processes as well. As in Schumpeter's theory of economic development the economic impact of technical change is considered a disequilibrium phenomenon. Thus, in a capitalist economy characterized by ongoing diffusion processes of innovations, time averages are more important than steady state values even in a long run perspective.

N O R M A S E M É T O D O S Introdução Durante o processo de extrusão o polímero experimenta uma complicada história térmica . No trajeto inicial da extrusora, as partículas sólidas do polímero são aquecidas até o ponto de fusão. Na região intermediária, a temperatura do polímero fundido é aumentada até um nível considerável acima do ponto de fusão, enquanto as partículas sólidas remanescentes continuam sendo aquecidas até a sua fusão. Na região final da extrusora, o polímero fundido tem que alcançar um estado termicamente homogêneo. Quando o material deixa a extrusora ele é, então, resfriado normalmente até a temperatura ambiente. Pode-se concluir, portanto, que o conhecimento das propriedades térmicas de polímeros é crucial na descrição e análise do processo de extrusão.

This study aims at comparing the predictions of skin temperature from different models of human thermoregulation and investigating the currently available methods for the prediction of the local and overall thermal sensations. In this paper, the Fiala model, the University of California, Berkeley (UCB) thermoregulation model and a multi-segmental (MS) Pierce model were tested against recently measured data from the literature. The local and overall thermal sensations were predicted for different room conditions, obtained from a recent experimental study, using the UCB comfort model coupled with the MS-Pierce model. The overall thermal sensation was further predicted using three other models. The predictions were then compared with the subjective votes obtained from that study. The equivalent temperature approach was also investigated based on the same experimental study. The results show comparisons of the predicted skin temperature by the thermoregulation models, under steady state and dynamic conditions, with the measured data as well as the predictions of the thermal sensations from the different models.

By using an approach based on the full nonlinear Barkhausen criterion, it is possible to describe oscillator behavior under the form of a nonlinear characteristic polynomial whose coefficients are functions of the circuit components and of the oscillation amplitude. Solving the polynomial in the frequency domain leads to the steady state oscillation amplitude and frequency. In the time domain, the characteristic polynomial represents a nonlinear differential equation whose solution gives the oscillator signal transient. It is shown how symbolic manipulation capabilities of commercially available softwares can be used to automatically generate the coding of the oscillator characteristic polynomial from the SPICE description netlist. The numerical processing of such an equation in the time domain leads to unacceptable computer time because of the high quality factor of the oscillator circuits involved. Nevertheless, by using the slowly varying amplitude and phase method, it is possible to transform the initial nonlinear differential equation into a nonlinear first order differential equation system in the amplitude and phase variables. The solution of this system directly gives the designer the most relevant features of the oscillation; that is, the amplitude, phase, or frequency transients which can be accurately obtained within a short computer time by using classical numerical algorithms.

The main reason for the flux decline during the initial period of all filtration processes is the usual phenomena of concentration polarization and fouling. After this stage follows the cake filtration process that allows to obtain the steady state flux. The solute accumulated on the membrane surface forms a high concentration gel layer, which increases the effective membrane thickness and so reduces its hydraulic permeability. Different techniques are used to reduce this formation and use of helical baffles inside the membrane element is one of such techniques. The selection of appropriate helical baffle is vital to get improved permeation flux with minimum pressure drop for cross-flow feed. The number of helices per unit length has a considerable influence on the selected helical baffle. All experiments have been conducted with an inorganic tubular ultrafiltration membrane for filtering a supernatant from activated sludge plant consisting of suspended and biological solids. The influence of the operational parameters is studied in this paper. Nevertheless, the feed temperature and the concentration were kept constant at the industrial values. We found 1 bar as an optimal pressure, above this pressure the permeation flux decreases, contrarily to several works, which observe a plateau after certain value of pressure. Progressive fouling can be limited by use of helical baffles in the filtration element operated at low pressures and the flocculation of particles is reduced. On the other hand, we have found that the influence of Reynolds number inside the membrane tube and the feed flow-rate are similar to other studies that used different helical baffles.

In this article, we analyze how to evaluate fishery resource management under "ecological uncertainty". In this context, an efficient policy consists of applying a different exploitation rule depending on the state of the resource and we could say that the stock is always in transition, jumping from one steady state to another. First, we propose a method for calibrating the growth path of the resource such that observed dynamics of resource and captures are matched. Second, we apply the calibration procedure proposed in two different fishing grounds: the European Anchovy (Division VIII) and the Southern Stock of Hake.

This paper presents a method for analysis and design of steady state recycling (SSR) chromatography under arbitrary purity or yield requirements. The approach applies to SSR processes in mixed-recycle operation and allows for the direct prediction of the steady state and the design parameters without performing dynamic simulations. Therefore, it simplifies optimal design of SSR processes and evaluation of process performance, while allowing minimizing the startup time of the process.

The objective of the study has been to investigate whether cold-adapted microorganisms (CAMs) are metabolising hydrocarbons in situ at sub-zero temperatures. Since the summer 2001, soil temperatures and soil gas concentrations of oxygen (O 2 ) and carbon dioxide (CO 2 ) at various depths at a petroleum hydrocarbon contaminated permafrost site at Longyearbyen, Spitsbergen, have continuously been measured and compared to data from a nearby non-contaminated site. We have previously reported on unchanged microbial O 2 consumption in the active layer for about 12 days after the soil temperatures decreased below 0 8C in late October 2001 and we are now reporting on the microbial activity in the soil profile from January to September 2002. The empirical data have been compared to theoretical simulations of O 2 concentration as a function of soil depth and time from when the CAMs became active in spring until steady-state conditions were achieved in the summer. At the 0.7 m depth in the oil-plume site, microbial O 2 consumption started in the middle of April, about 45 days before the soil thawed. There was no coincidence between the microbial activation time and the thawing time of the soil. The CAMs became active at temperatures of about À6 8C, but the main degradation activity occurred at temperatures between À1 and À3 8C. When the soil thawed, the hydrocarbon degradation was probably limited by the O 2 supply. In the summer months where we expected the greatest degradation activity to occur because of positive temperatures and access to water, the degradation was limited by O 2 depletion. The overall data from this arctic permafrost site indicate that without other limiting conditions such as O 2 and 0165-232X/$ -see front matter D substrate availability, the active biodegradation period can be extended to about 6 months despite periods with sub-zero soil temperatures. D

T cell populations are regulated both by signals specific to the T-cell receptor (TCR) and by signals and resources, such as cytokines and space, that act independently of TCR specificity. Although it has been demonstrated that disruption of either of these pathways has a profound effect on T-cell development, we do not yet have an understanding of the dynamical interactions of these pathways in their joint shaping of the T cell repertoire. Complete DiGeorge Anomaly is a developmental abnormality that results in the failure of the thymus to develop, absence of T cells, and profound immune deficiency. After receiving thymic tissue grafts, patients suffering from DiGeorge anomaly develop T cells derived from their own precursors but matured in the donor tissue. We followed three DiGeorge patients after thymus transplantation to utilize the remarkable opportunity these subjects provide to elucidate human T-cell developmental regulation. Our goal is the determination of the respective roles of TCR-specific vs. TCR-nonspecific regulatory signals in the growth of these emerging T-cell populations. During the course of the study, we measured peripheral blood T-cell concentrations, TCRb V gene-segment usage and CDR3length spectratypes over two years or more for each of the subjects. We find, through statistical analysis based on a novel stochastic population-dynamic T-cell model, that the carrying capacity corresponding to TCR-specific resources is approximately 1000-fold larger than that of TCR-nonspecific resources, implying that the size of the peripheral T-cell pool at steady state is determined almost entirely by TCR-nonspecific mechanisms. Nevertheless, the diversity of the TCR repertoire depends crucially on TCR-specific regulation. The estimated strength of this TCR-specific regulation is sufficient to ensure rapid establishment of TCR repertoire diversity in the early phase of T cell population growth, and to maintain TCR repertoire diversity in the face of substantial clonal expansion-induced perturbation from the steady state.

The impact of intra-ensemble Förster resonant energy transfer (FRET) on the optical properties of monodispersed quantum dot (QD) monolayers and a donor/acceptor FRET bilayer structure are presented. The QD structures are characterized by steady-state absorption and photoluminescence (PL) spectroscopy as well as time-resolved PL measurements. The optical properties of the monodispersed monolayers, such as peak emission wavelength and PL decays, are strongly influenced by FRET from smaller to larger QDs within the ensemble. Comparing several QD samples, the spectral overlap of the QD ensemble and the QD concentration were identified as parameters that allow for tuning of FRET in monodispersed QD structures. For the donor/acceptor QD bilayer structure an unexpected decrease of the FRET efficiency between donor and acceptor layers is observed with increasing donor QD concentration. The concentration-dependent donor lifetime and a constant donor-acceptor FRET rate can explain this decrea...

... Suprasad V. Amari, Member, IEEE ... Notation label of component , [failure, repair] rate of component system-failure frequency “mean number of system-failures” per time-unit , Boolean variable indicating that component is [working, failed]; is the complement of , steady state ...

The Diffusion Poisson Coupled Model (DPCM) is presented to modelling the oxidation of a metal covered by an oxide layer. This model is similar to the Point Defect Model and the Mixed Conduction Model except for the potential profile which is not assumed but calculated in solving the Poisson equation. This modelling considers the motions of two moving interfaces linked through the ratio of Pilling-Bedworth. Their locations are unknowns of the model. Application to the case of iron in neutral or slightly basic solution is discussed. Then, DPCM has been first tested in a simplified situation where the locations of interfaces were fixed. In such a situation, DPCM is in agreement with Mott-Schottky model when iron concentration profile is homogeneous. When it is not homogeneous, deviation from Mott-Schottky model has been observed and is discussed. The influence of the outer and inner interfacial structures on the kinetics of electrochemical reactions is illustrated and discussed. Finally, simulations for the oxide layer growth are presented. The expected trends have been obtained. The steady-state thickness is a linear function of the applied potential and the steady-state current density is potential independent.

Abstract-We present a steady-state analysis of high-repetition-rate passively mode-locked semiconductor lasers. The analysis includes effects of amplitude-to-phase coupling in both gain and absorber sections. A many-mode eigenvalue approach is pre-sented to obtain supermode ...

An attempt was made to establish relationships between the physical properties of the seeds, expressed from the rheological behaviour, and their grinding behaviour, i.e., the particle size distribution and the specific energy requirement during grinding. The rheological Ž. behaviour of the seeds tested horse bean, pea, lupine, and vetch with different moisture content was measured with a traction-compression Instron apparatus on individual seeds. The motion of the piston was registered as well as the applied force and consequently different thresholds were defined and parameters were established. A small commercial hammermill Culatti was used for steady-state continuous grinding experiments. A significant relationship was found between the characteristics of the compression curve and the grinding energy requirement. Resumé Dans la recherche, nous avons essaye de trouver des relations entre des proprietes physiques des graines de legumineuses et lé´ć omportement au broyage, c'est a dire la dimension de particules et la consommation d'energie au cours du processus. Les proprietes des´ǵ rains dans une humiditie differentes, ont ete mesurees sur une machine de traction-compression Instron. Le test de compression a eté´´´´´ŕ ealise grain par grain en enregistrant en meme temps les valeurs de force appliquee et de deformation des graines. Le traitement deśˆć ourbes de compression a permis de degager, des seuils typiques du point de vue rheologique. L'analyse des resultats a permis de mettréé n evidence une relation entre les proprietes physiques et la consommation d'energie pendant le broyage des grains a l'aide d'un broyeuŕ´´à marteaux.

A high-power high-performance variable-speed drive system using a cycloconverter-fed synchronous motor is described. The control uses the field-orientation principle to give the drive system good steadystate and dynamic performance criteria. The accuracy of the field orientation is improved with the use of current regulators operating in the airgap flux reference frame. The system was manufactured to deliver 16 000 hp to the twin propeller shafts of a Canadian Coast Guard icebreaker. The electric components of the system were tested as a unit in the factory and the desired system performance was achieved.

The eects of the substrate conditions on the volumetric productivity of Lactobacillus helveticus at dierent cell densities up to 60 g l A1 in a continuous stirred-tank reactor with micro®ltration to retain the biomass were investigated. At low dilution rates, D, the steady-state volumetric productivity, r p , gradually increased to a maximum at D 1.2±1.5 h A1 , because of reduced product inhibition. At higher D values, r p unexpectedly decreased, although the substrate conditions further improved. The maxima of r p at dierent cell densities coincided with a critical speci®c substrate utilization rate beyond which the cell metabolism seems to be controlled through a catabolic modulator factor, and r p decreases.

A membrane steady state simulator based on an open source concept is discussed. It is believe that this way of developing software will overcome weaknesses posed by available commercial membrane simulators. The application provides a cost effective state of the art tool for membrane modeling and object oriented design and its usage allows for easy incorporation of specific developments either open source or proprietary. This paper presents the components require to produce an open source membrane steady state simulator. This approach of development differs significantly from a close black-box approach. Several membrane models using the simulator will be elaborated and compared with literature results.

A consistent description of a shear flow, the accompanied viscous heating, and the associated entropy balance is given in the framework of a deterministic dynamical system, where a multibaker dynamics drives two fields: the velocity and the temperature distributions. In an appropriate macroscopic limit their transport equations go over into the Navier-Stokes and the heat conduction equation of viscous flows. The inclusion of an artificial heat sink can stabilize steady states with constant temperatures. It mimics a thermostating algorithm used in non-equilibrium molecular-dynamics simulations.

In this paper the authors present a predictive linear parameter varying (LPV) controller based on the GPC controller [1]-[3], for nonlinear systems. The resulting controller is denoted as GPC-LPV. This one has the same structure as a general LPV controller [4]-[7], which has a lineal fractional dependence on the process signal measurements. Therefore, this controller has the ability of modifying its dynamics depending on measurements leading to a possibly nonlinear controller. That controller is designed in two steps. First, for a given steady state point is obtained a linear GPC using a local model of the nonlinear system around that operating point. And second, using bilinear matrix inequalities (BMIs) the remaining matrices of GPC-LPV are selected in order to achieve some closed loop properties: stability in some operation zone, norm bounding of some input/output channels, maximum settling time, maximum overshoot, etc. This methodology of design can be applied to nonlinear systems which can be embedded in a LPV system using differential inclusion techniques. Finally, the GPC-LPV is applied to the nonlinear model of a liquid-gas separation process.

Changes in oceanic primary production, linked to changes in the network of global biogeochemical cycles, have profoundly influenced the geochemistry of Earth for over 3 billion years. In the contemporary ocean, photosynthetic carbon fixation by marine phytoplankton leads to formation of ϳ45 gigatons of organic carbon per annum, of which 16 gigatons are exported to the ocean interior. Changes in the magnitude of total and export production can strongly influence atmospheric CO 2 levels (and hence climate) on geological time scales, as well as set upper bounds for sustainable fisheries harvest. The two fluxes are critically dependent on geophysical processes that determine mixed-layer depth, nutrient fluxes to and within the ocean, and food-web structure. Because the average turnover time of phytoplankton carbon in the ocean is on the order of a week or less, total and export production are extremely sensitive to external forcing and consequently are seldom in steady state. Elucidating the biogeochemical controls and feedbacks on primary production is essential to understanding how oceanic biota responded to and affected natural climatic variability in the geological past, and will respond to anthropogenically influenced changes in coming decades. One of the most crucial feedbacks results from changes in radiative forcing on the hydrological cycle, which influences the aeolian iron flux and, in turn, affects nitrogen fixation and primary production in the oceans. P. G.

Hydrogen bonding substrates (S) trigger bright phosphorescence upon their addition to aqueous solutions containing 1bromonaphthalene (1-BrNp) and a glucosyl modified eyclodextrin (C~-CD). Steady-state and time-resolved luminescence measurements establish that the phosphorescence arises from 1-BrNp as part of a 1-BrNp.G/1-CD.S complex. In all cases, the substrate comprises a bulky t-butyl or cyclohexyl group spaced from the functional group of an alcohol, amine, carboxylie acid, ester, or aldehyde. Association constants, molecular models, and substrate binding studies are consistent with the substrate hydrogen bonding to the rim of the CD cup, with its aliphatic end flipped over the hydrophobic interior of the CD. The phosphorescence enhancement induced by substrate is related to its effectiveness in shielding photoexcited 1-BrNp from quenching by oxygen. The enhancements can be extremely large, approaching a 10 5 increase in intensity, depending on the fit of the substrate to the top of the CD. We have explored the topological features of the substrate that lead to the best shielding and hence greatest triggered luminescence response.

Accurate computation of heat flux is a primary motivation for convection calculations, yet heat fluxes have generally been calculated to substantially less than optimal accuracy, given the accompanying temperature and velocity fields. We analyse this problem in the context of the finite element method, using bilinear shape functions to interpolate the nodal values of velocity and temperature throughout the medium. Our method, however, is general and also applies to finite difference and higher order finite elements. Consider (dimensionless) vertical heat flux qz = wT -dT/dz, with w vertical velocity and T temperature. The first term is quadratic within (bilinear) elements and continuous at nodes, while the second term is constant within elements and discontinuous at nodes. Usual practice is to evaluate qz at element centres. We instead assign to each element the volume average of qz over that element. Element values are then projected to nodes using a modification of a technique used for pressure smoothing (Hughes et al.) Our approach reduces the calculated depth variation in horizontallyaveraged flux by more than a factor of 10 and shows more rapid convergence of Nusselt number Nu as a function of grid size. It also eliminates the artificial diffusion of heat out of supposed insulating side walls.

A new technique for constructing dynamic equivalents of power systems is developed. The method identifies the important modes of the system utilising a performance index based on the notions of controllability and observability. The system state variables corresponding to the retained modes are identified by inspection of the elements of the sentivity matrix relating the eigenvalues to the state variables. The suitability of the method for obtaining reduced-order models of power systems for dynamic-control purposes is demonstrated on a single-machine infinite-bus system. Several reduced-order models are produced and their accuracy discussed.

Background: Alcohol, a substance that is most frequently abused, suppresses innate immune responses to microbial pathogens. The host senses pathogens via Toll-like receptors (TLRs). Recent studies indicate that alcohol affects TLR signaling.

The dynamic and steady state performance of a non-isothermal tubular reactor packed with spherical encapsulated enzyme particles has been modeled in terms of different dimensionless transport and kinetic parameters. The dynamic concentration profile for an initially substrate-free reactor reaches a maximum before achieving steady state. The steady state dimensionless bulk substrate concentration, unlike the temperature, progressively decreases along the reactor bed. On increase in the external mass transfer coefficient KL and Biot number Bi, for mass transfer, the concentration profile decreases more steeply. The simulation study shows that the biocatalyst particles may be considered isothermal.

Haploid leaf tissue of tobacco cultivars K326 and K149 was transformed with several transgenes containing cDNA of the potato virus Y (PVY) coat protein (CP) open reading frame (ORF). The various transgenes containing the PVY CP ORF sequence produced (1) the expected mRNA and CP product, (2) an mRNA rendered untranslatable by introduction of a stop codon immediately after the initiation codon, or (3) an antisense RNA that was untranslatable as a result of the incorrect orientation of the PVY CP ORF behind the transcriptional promoter. Homozygous doubled haploid (DH) (diploid) plants were generated, and selfed progeny from these plants were examined. Resistance was virus specific, functioning only against PVY. An inverse correlation between transgene-derived PVY transcript steady state levels and resistance was generally noted with lines expressing the untranslatable sense version of the PVY CP ORF. A collection of DH lines, derived from a single transformation event of a common haplo...

Repeated measurements of depth pro"les of Th (dissolved, 1}70 and '70 m particulate) at three stations (Orca, Minke, Sei) in the Ross Sea have been used to estimate the export of Th and particulate organic carbon (POC) from the euphotic zone. Sampling was carried out on three JGOFS cruises covering the period from October 1996 (austral early spring) to April 1997 (austral fall). De"ciencies of Th relative to its parent U in the upper 100 m are small during the early spring cruise, increase to maximum values during the summer, and decrease over the course of the fall. Application of a non-steady-state model to the Th data shows that the #ux of Th from the euphotic zone occurs principally during the summer cruise and in the interval between summer and fall. Station Minke in the southwestern Ross Sea appears to sustain signi"cant Th removal for a longer period than is evident at Orca or Sei. Particulate Th activities and POC are greater in the 1}70 m size fraction, except late in the summer cruise, when the '70 m POC fraction exceeds that of the 1}70 m fraction. The POC/Th ratio in the '70 m fraction exceeds that in the 1}70 m fraction, likely due in part to the greater availability of surface sites for Th adsorption in the latter. Particulate Th #uxes are converted to POC #uxes by multiplying by the POC/Th ratio of the '70 m fraction (assumed to be representative of sinking particles). POC #uxes calculated from a steady-state Th scavenging model range from 7 to 91 mmol C m\ d\ during late January}early February, with the greatest #ux observed at station Minke late in the cruise. Fluxes estimated with a non-steady-state Th model are 85 mmol C m\ d\ at Minke