Chemical Engineering

Many researchers have written about the importance and complexities of developing problem solving skills and encouraging creative thinking in engineering students. Research continues to suggest deficiencies in developing or assessing process skills; with the attention of engineering educators being on outcomes or products of problem solving scenarios.
This paper considers highlights of this previous work, and how this might inform action research to develop a module to improve and encourage process skills in engineering undergraduates. Findings from the first cycle of action research are presented. Lego Mindstorm robots have been used to provide suitable practical activities, and to stimulate student motivation.

Among all agro industrial material hydrolyzing enzymes, xylanases gained importance due to their role in production of xylose based products of industrial importance. An isolated fungal strain, Aspergillus sp. RSP-6, having potential in xylanase production specific to palm fiber was characterized for enzyme production properties under solid suspend fermentation environments. Effective enzyme production was achieved with palm fiber as carbon source compared to all other tested agro materials and carbohydrates. Among different nitrogen sources, beef extract supported maximum enzyme production. Various fermentation parameters (pH of the medium, particle size and its concentration, incubation time and medium volume in addition to carbon and nitrogen sources) influenced the xylanase production. Maximum enzyme production of 62,480 U/l was observed in the medium of pH 3.0 containing 2% palm material having particle size of 2.8–1.4 mm and 1% (w/v) beef extract in presence of other mineral salts in 144 hours of incubation. Over all, the enzyme production has increased significantly from 20,000 to 62,480 U/ l under optimized environment and observed to be constitutive in nature in this fungal strain.

Mucor rouxii biomass (MRB) was found to be most potent sorbent for the removal of copper from its aqueous solution. Maximum adsorption was noted within pH range 5.0–6.0, and the process follows Langmuir adsorption isotherm (r2 = 0.998). Adsorption process is very fast initially and reaches equilibrium very quickly following pseudo second order rate kinetics. Amino, carboxyl and phosphate groups present on the cell surface of the biomass are involved in chemical interaction with copper ion as revealed from FTIR and SEM-EDX study and also by blocking experiments. Both SEM and AFM micrographs revealed the formation of metal nanostructure on the biomass surface due to copper adsorption. Biomass surface modification indicates the major involvement of amino functional group for the binding probably through the chelation. Copper ion can be eluted from the adsorbed biomass with 0.1 M hydrochloric acid.

Jute stick powder (JSP) has been found to be a promising material for adsorptive removal of congo red (C.I. 22120) and rhodamine B (C.I. 45170) from aqueous solutions. Physico-chemical parameters like dye concentration, solution pH, temperature and contact time have been varied to study the adsorption phenomenon. Favorable adsorption occurs at around pH 7.0 whereas temperature has no significant effect on adsorption of both the dyes. The maximum adsorption capacity has been calculated to be 35.7 and 87.7 mg/g of the biomass for congo red and rhodamine B, respectively. The adsorption process is in conformity with Freundlich and Langmuir isotherms for rhodamine B whereas congo red adsorption fits well to Langmuir isotherm only. In both the cases, adsorption occurs very fast initially and attains equilibrium within 60 min. Kinetic results suggest the intra-particle diffusion of dyes as rate limiting step.

Statistical design of experiments was used to investigate the effect the process parameters on electrophoretic deposition (EPD) of alumina onto steel substrates from its suspension in iso-propanol. The process parameters considered were (i) concentration of particles in the suspension (solid loading), (ii) electrode separation, (iii) applied potential, and (iv) deposition time on the quantity of ceramic particles electrophoretically deposited. A 2^4 full factorial matrix, with four repetitions of the center point, was used to develop the predictive regression equation for deposition of alumina per unit area of the electrode in the design space. The results show that particle concentration has the most dominant effect with more than 50% contribution to the deposited amount. A good correlation was obtained between predicted and experimental values suggesting that the model can predict data accurately in the experimental matrix.

Nanotechnology is expected to be one of the future key technologies. One approach to realize nano-objects is by self assembly and involves an understanding of interaction on a molecular level. Numerous examples are found in nature as self organization on a nanometer scale is a fundamental building principle of life. Here we discuss recent advances for characterization of natural nano channels using a microfluidic setup for high-throughput and parallelized processing, making biological channels accessible for true engineering applications. As an example we focus on the permeation of antibiotics through specific channels, a current problem in drug-screening technology. For that we miniaturize a classical artificial bilayer set-up, automating the formation of planar membranes to host channels and combining this with microfluidics.

Various options in biotechnology have been exercised to produce industrially important metabolites from filamentous
organisms. To select a suitable production strategy, the direct and indirect roles of morphological parameters in
controlling bioprocess variables are observed. Some progress has been made in quantitation of morphology.Useful correlations
have been reported in the literature in this avenue. Of course, some of the models, with proper modification, can be
used to explain the morphological phenomena. This review is concerned with the application of morphological variables
to correlate with bioprocess parameters for explaining optimal production strategy.

This paper deals with the control of a catalytic reverse flow reactor. The aim of this process is to reduce, by catalytic reaction, the amount of volatile organic compounds (VOCs) released in the atmosphere. The peculiarity of this process is that the gas flow inside the reactor is periodically reversed in order to trap the heat released during the reaction inside the process. This allows use of the reactor in heat saving mode. The goal of this work is to provide a model predictive control (MPC) framework to significantly enhance the poor overall performance currently obtained through the actual control strategy. It is directly addressed for the nonlinear parabolic partial differential equations (PDEs) that describe the catalytic reverse flow reactor. In the context of the application of MPC to this particular distributed parameter system, we propose a method that aims to reduce the on-line computation time needed by the control algorithm. The nonlinear model is linearized around a given operating trajectory to obtain the model to be solved on-line in the approach. MPC strategy combined with internal model control (IMC) structure allows to use less accurate and less time consuming control algorithm. The efficiency of the method is shown in simulation for this SISO system.

The effect of metallurgical parameters on the Brinell hardness of heat-treated 319 type alloys was investigated, to quantify the effects of alloying elements (Mg, Fe, Mn, Sr) and aging parameters on the hardness of heat-treated 319 alloys containing alpha-Fe or beta-Fe intermetallics. The corresponding alloy melts (at 750°C +/- 5°C) were cast into preheated graphite-coated metallic molds to prepare samples for hardness measurements. These samples were heat treated (solution treatment: 8h@495°C; quenching in warm water (65°C); aging at 155°, 180°, 200° and 220°C for 4h). Different aging times (2, 4, 6 and 8h) were also studied for the 180° and 220°C aging temperatures. Hardness measurements were made using a Brinell hardness tester (10 mm diameter ball and 500 kgf). Experimental correlations between the metallurgical and heat treatment parameters and the hardness values obtained were analyzed using factorial analysis (2k factorial design). For this, two levels of Mg (0.1 and 0.28 wt%), Fe-intermetallics (2% and 5%), Sr (0 and 200 ppm - non-modified and modified conditions), and two aging temperatures (180° and 220°C) and times (2h and 8h) were selected. The results obtained are in agreement with the experimental findings for these aging times and temperatures. It is found that the hardness increases with increasing Mg content and volume fraction of -Fe intermetallics, but decreases with Sr modification and with increasing aging temperature and time.

The crystal structures of co-crystals of two systems of chiral carboxylic acids, optically active and racemic 2-phenylpropionic acid and 2-phenylbutyric acid, with isonicotinamide are reported to investigate the effects of the chirality of the chiral carboxylic acids on the melting point of the co-crystal complexes. It was found that the racemic co-crystal has a higher melting point than the optically active co-crystal, which correlates with the denser packing arrangement inherent in centrosymmetric space groups.

Three inorganic–organic layered perovskite-type hybrids of the general formula [(CnH2n + 1NH3)2PbI4], n = 4, 5 and 6, display a number of reversible first-order phase transitions in the temperature range from 256 to 393 K. [(C4H9NH3)2PbI4] has a single phase transition, [(C5H11NH3)2PbI4] has two phase transitions and [(C6H13NH3)2PbI4] has three phase transitions. In all three cases, the lowest-temperature phase transition is thermochromic and the crystals change colour from yellow in their lowest-temperature phase to orange in their higher-temperature phase for [(C4H9NH3)2PbI4] and [(C6H13NH3)2PbI4], and from orange to red for [(C5H11NH3)2PbI4]. The structural details associated with this phase transition have been investigated via single-crystal X-Ray diffraction, SC-XRD, for all three compounds.

In the crystal structure of 2,4,6-trimethylanilinium iodide, C9H11NH3+·I-, both ions are situated on mirror planes. The trimethylanilinium ions stack head-to-tail with no [pi]-[pi] interactions. The ammonium cations and I- anions interact via hydrogen bonds, forming ladder-like columns parallel to the b axis. The structure is compared to the related anilinium iodide.

The title compound, (C8H16N)2[PbI4], crystallizes as an inorganic-organic hybrid perovskite, adopting the unusual 2ap × 2ap superstructure. As such, the structure consists of two-dimensional sheets of corner-sharing PbI6 octahedra in the ab plane, separated by bilayers of 2-(1-cyclohexenyl)ethylammonium cations. The ethylammonium groups are not in the plane of the cyclohexenyl rings.

The title compound, (C10H7NH3)[PbI3], crystallizes as an organic-inorganic hybrid. As such, the structure consists of extended chains of [PbI3] units running along the b-axis. Each lead atom is octahedrally coordinated to six iodides, arranged as chains of face-sharing octahedra. These inorganic chains are separated by the isolated organic cations.

The crystal stucture of p-nitroaniline hydrobromide,(O2NC6H4NH3)+.Br- exhibits ionic layers separated by hydrocarbon layers. The hydrocarbon layer stacks head-to-tail but no pi-pi interactions are observed. In the inorganic layer, the ammonium group, bromide anion and nitro group interact to form a three dimensional hydrogen-bonded network. The structure is compared to the related material (O2NC6H4NH3)+.Cl-.

The presence of fibrillar protein deposits (amyloid) of human islet amyloid polypeptide (hIAPP) in the pancreatic islets of Langerhans is thought to be related to death of the insulin-producing islet β-cells in type 2 diabetes mellitus (DM2). The mechanism of hIAPP-induced β-cell death is not understood. However, there is growing evidence that hIAPP-induced disruption of β-cell membranes is the cause of hIAPP cytotoxicity. Amyloid cytotoxicity by membrane damage has not only been suggested for hIAPP, but also for peptides and proteins related to other misfolding diseases, like Alzheimer s disease, Parkinson’s disease, and prion diseases. Here we review the interaction of hIAPP with membranes, and discuss recent progress in the field, with a focus on hIAPP structure and on the proposed mechanisms of hIAPP-induced membrane damage in relation to β-cell death in DM2.

There have been increased interests in the research on mechanical and control system of underwater vehicles in the recent past. These ongoing research efforts are motivated by more pervasive applications of such vehicles including seabed oil and gas explorations, scientific deep ocean surveys, military purposes, ecological and waters environmental studies, and also for entertainments. However, the performance of underwater vehicles with screw type propellers is not prospective in terms of its efficiency and maneuverability. The main weaknesses of this kind of propellers are the production of vortices and sudden generation of thrust forces which make the control of the position and motion difficult.
On the other hand, fishes and other aquatic animals are efficient swimmers, posses high maneuverability, are able to follow trajectories, can efficiently stabilize themselves in currents and surges, create less wakes than currently used underwater vehicle, and also have a noiseless propulsion. The fish’s locomotion mechanism is mainly controlled by its caudal fin and paired pectoral fins part. They are classified into BCF (Body and/or Caudal Fin) and MPF (Median and/or paired Pectoral Fins). The study of highly efficient swimming mechanisms of fish can inspire a better underwater vehicles thruster design and its mechanism.
There have not been many studies on underwater vehicles or fish robots using paired pectoral fins as thruster. The work presented in this paper represents a contribution in this area covering study, design and implementation of locomotion mechanisms of paired pectoral fins in a fish robot. The performance and viability of the biomimetic method for underwater vehicles are highlighted through in-water experiment of a robotic fish.

The development and management of fresh groundwater resources in coastal aquifers are seriously constrained by the presence of seawater intrusion. Underutilisation of the available groundwater resource means that valuable fresh water discharges naturally to the sea and is wasted; overdevelopment, on the other hand, mines the resource and will cause a gradual degradation of water quality due to the encroachment of seawater. Over the years, many models have been developed to represent and study the problem of seawater intrusion. They range from relatively simple analytical solutions to complex numerical models. Ernakulam is one of the important ports in west coast of India. Due to increase in population, fast urbanisation and land reforms, the district is facing a number of environment problems such as flooding, groundwater pollution due to discharge of industrial effluents, seawater intrusion etc. There exists an urgent need to study systematically the causes and remedial measures for seawater intrusion. This paper presents the simulation of seawater intrusion in a section of Ernakulam coast through Saturated-Unsaturated TRAnsport (SUTRA) model and examines the impact of increased pumping scenarios on extent of seawater intrusion.

The Yankee-Hood dryer is the crucial section of the paper machine due to the consumption of energy. As a consequence of continuously increasing energy costs, determination of the proper operating conditions is essential to operate the tissue machine in the most efficient and economic means while ensuring paper quality. The objective of this study is to evaluate the Yankee-Hood dryer in Ipekkağit' tissue paper factory, set the mass and energy balances and make optimization studies in order to achieve the desired production rate whilst keeping the drying parameters within limits at the minimum energy costs. The approach to solve the problem is to develop a steady state analytical model. The complicated drying system is simplified as the overall and sub systems. Material and energy balances are set up for each system. Data of machine parameters at several paper grades are collected at the factory during production. Material and energy balance equations are solved with the available data for the unknown parameters and for the determination of the drying parameters most effective on energy consumption. The critical drying parameters are air supply velocity, wet- and dry-hood temperatures, steam pressure in cylinder and exhaust humidity. Efficiency, defined as the ratio of energy required to evaporate the water to energy input through the system boundaries, is calculated as 28-30% for different grades of tissue paper production., Steady state rate of heat transfer to the wet sheet is analyzed considering the two-way mechanism, from steam through the cast iron shell and from heated air. The transfer of heat is eased in both mechanisms by the lightweight tissue paper that has a comparatively lower internal thermal resistance with respect to other types of paper products. Steam side is modeled considering different thermal resistances in series: Condensate layer, shell, shell-sheet contact, and paper sheet. These resistances are to the same order of magnitude, cast iron shell being the largest and paper sheet the smallest in value. Sheet-shell contact heat transfer coefficient is strongly dependent on sheet moisture content that is assumed to vary almost linearly due to the angular position on the Yankee. Air side heat transfer is mostly affected by the temperature, humidity and velocity of the air that is blown on to the sheet. Calculations resulted out that rate ofheat transfer from air side is 55-65% while that from steam side is 35-45% of their total indicating the dominance of air side on drying.

For highly entangled linear chains, the mean-square displacement of the primitive chain segments [d(n,t)] 2 (n ) segment index) not including a contribution from a nondiffusive part of the contour length fluctuation (CLF) was analyzed on the basis of the tube concept. The analysis was made by just considering the Gaussian nature of the chains (without detailed assumptions about the chain motion). A simple analytic relationship between this [d(n,t)] 2 and the normalized viscoelastic relaxation function µ(t) was derived in a range of µ(t) > 0.5 and at t longer than the Rouse time τRouse for CLF. This relationship was significantly affected by the dynamic tube dilation (DTD) mechanism. For example, the end segment exhibited d 2 ) 〈R 2 〉(1µ) in the absence of DTD and d 2 = 〈R 2 〉(1µ 1/2 ) in the presence of DTD, with 〈R 2 〉 being the mean-square end-to-end distance of the chain. This difference should enable a test of the DTD picture at short t (but still longer than τ Rouse) through comparison of the viscoelastic and segmental displacement data.

The synthesis, electrochemical and spectroscopic properties of a series of thiophene-substituted 1,3-dithiole-2-ones is described. The derivatives Th-3,3, Th-2,2, Th-2,3, Th-3,3(2,2′-Me), and Th3,3-(2,5,2′,5′-Me), have been successfully polymerized by cyclic voltammetry. From the UV−visible spectra of the neutral films, it was determined that PTh-3,3, PTh-2,2 and PTh-2,3 have a bandgap of 2.04, 2.30, and 2.18 eV, respectively. The voltammetric response of Th-3,3(2,2′-Me) was noticeably different from the other polymers. The SNIFTIRS data suggested that Th-3,3(2,2′-Me) was formed by bonding via the β-positions of the thiophene ring, resulting in a poorly conductive polymer. The in situ solid-state modification of PTh-3,3 to produce a new TTF-derivatized polythiophene was carried out. The cyclic voltammetry of the modified polymer confirmed the inclusion of TTF into the backbone of the film.

An experiment to assess the influence of commercially available infant formulas on characteristics of feces in a weanling piglet model was conducted. Seven commercial infant formulas [whey, whey + a-lactalbumin Ò , whey + a-lactalbumin + oligofructose, whey + GOS + polyfructose, whey protein concentrate 1 (with 27.3% acid hydrolyzed fat), whey protein concentrate 2 (with 29.4% acid hydrolyzed fat), and enzymatically hydrolyzed whey protein concentrate] were offered to weanling piglets ad libitum for 14 d. Fecal attributes that were assessed include: consistency, color, odor, dry matter, organic matter, pH, biogenic amines, short-and branched-chain fatty acids, phenols, indoles, and ammonia. Overall, there were very few differences among treatment groups in fecal attributes assessed. Minor differences in the concentrations of fecal acetate, valerate, putrescine, and cadaverine were observed in piglets fed GOS + polyfructose-containing formula. However, stool consistency, score, odor, pH, ammonia, phenols, and indoles were similar among treatment groups. Diet had an effect on fecal dry matter percentage, organic matter percentage, color, and 4 week body weights of the piglets. The results obtained in this experiment demonstrate that healthy gut function is prevalent in weanling piglets consuming the experimental treatments.

The project discussed in this paper has been conducted as part of the Autonomatic research cluster based at University College Falmouth. The cluster is focused on research projects that explore the use of digital production technologies within the context of designer maker and craft practice.

My project is concerned with developing more direct control of processes that are typically automated by CAD software and CAM tools. I believe the use of these standardised tools limit the ability of the maker to create unique visual vocabularies.

It is possible to view the aesthetic qualities emerging in the new genre of ‘digital craft’ - such as the use of triangulation and the quality of line produced by generic pre-set machine parameters - as a temporary phase in the digital craft timeline. As more makers adopt digital technologies, we may discover that these visual aesthetic qualities are more attributable to the technology than the maker rather than being understood as unique. The author believes it is therefore important for makers wishing to further their practice in this field to seek ways in which they can gain greater control over the processes and tools they are using.

This paper presents research that explores ways in which programmed mathematical elements in 3D CAD can be deconstructed and manipulated throughout the design and production phases. Employing an iterative designing and making process I have used this ‘hand’ manipulated CAD data to drive CNC machine tools in highly specified ways. This has lead to an in depth understanding of the inter-relationship between CAD and CAM as intrinsic to the development of unique aesthetic qualities. The development of a dialogue between CAD code and CNC tooling has resulted in a greater level of control enabling the realisation of complex and completely controlled patterning on 3D forms that go beyond the restrictions of standard toolsets.

This research has resulted in a range of 3D aluminium sample pieces that I have used to create a visual knowledge bank which documents the relationship between software input, machine parameters and their effects on the visual form. This knowledge has been applied to my working digital design practice enabling me to create aluminium platters and beakers that counter the affects of automation.

This paper aims to offer other makers methods which allow the potential for 'hacking' into code in order to expand the possibilities for control and creative engagement with digital tools and thereby offering more unique opportunities for developing visual vocabularies than using standard toolsets alone.

. Total reflection X-ray fluorescence analysis excited with synchrotron radiation SR-TXRF has been used for rainwater trace element analysis. The samples were collected from four different sites at Campinas City, SP, Brazil. Standard solutions with gallium as internal standard were prepared for the calibration system. Rainwater samples of 10 l were added to Perspex reflector disks, dried under vacuum and analyzed for 100 s measuring time. The detection limits obtained for K-shell lines varied from 29 ng ml y1 for sulfur to 1.3 ng ml y1 for zinc and copper, while for L-shell the values were 4.5 ng ml y1 for mercury and 7.0 ng ml y1 for lead. ᮊ

This study aims to apply the ultrasound technique in the
field of clean technology to protect environment. The principle
of ultrasound was conducted here to study the effect of applying
high frequency of ultrasound waves. Four kinds of water
namely; Seawater from Aqaba gulf, Red Sea, brackish from
Maan desert southern part of Jordan, hot spring from northern
part of Jordan and tap water (Amman City) were selected to
study the effect of ultrasound on its physical properties. High
ultrasound frequency device with 1.7 MHz was applied to
study the effect of ultrasound waves. All conducted experiments
were fixed at room temperature. The effect of liquid volume
while applying a constant ultrasound waves on the water properties
were investigated here. Exposing time of ultrasound
waves was fixed at 0.5, 1.0 and 1.5 h. The experimental
results showed that ultrasonic wave irradiation for different
samples of water at different period of time has its significant
impacts on physical and chemical properties of water such as
pH, total dissolved solids and consequently the conductivity.
Key Words: High frequency ultrasound, Total dissolved
solids, Water desalination, Water treatment, Environmental
protection, Physical properties.

In this paper the fly ash, which is the finest residue of the lignite combustion entrapped by electrostatic filters at the electrical power stations, is examined, in order to determine the possibility of its usage in the production of concrete. It is implemented by testing concrete models in actual scale. Mineralogical, petrographical and chemical analyses of the fly ash as well as of the produced concrete are presented. The concrete that was produced by cement, sand, water, aggregates and fly ash (in various percentages) showed micro-cracks in its structure, due to the reduced interconnection of the fly ash with the aggregates. Nevertheless, the fly ash may act as adhesive material, as well as the material that fills the cracks of the concrete. Tests of the strength on models made by this concrete have shown comparable results in strength with reference concrete produced without ash. It is concluded that the mixing of fly ash in concrete does not affect its strength and sometimes it fills the cracks of the concrete mass.

Μελέτη της δυνατότητας χρήσης ιπτάμενης τέφρας στο σκυρόδεμα.

Paper in the Ash Library (http://www.flyash.info/) in the web http://www.flyash.info/2005/15kou.pdf .

The aim of this work is to define the chemical and mineralogical composition of the fuel gas desulphurization (FGD) gypsum produced from the Meliti thermal power plant in the region of Florina in North West Greece, in order to investigate potential uses in the cement industry. Mineralogical and microprobe analyses were carried out on FGD gypsum samples collected from the Meliti 330 MW lignite-fired power plant.
Results show that the main component of the FGD gypsum is pure mineral gypsum (CaSO4·2H2O). The particle size of the gypsum ranges from 5 to 50 µm and the crystals are mainly of rhomboid shape. Microprobe analysis shows that the concentration of CaO and SO3, which are the main components, range from 31.9%-32.5% and from 45.90-46.40%, respectively. 
This FGD gypsum can easily substitute the natural gypsum used in the production of cement. Copyright © 2007 Society of Chemical Industry

Ορυκτολογική και ορυκτοχημική μελέτη της γύψου που προκύπτει ως παραπροϊόν κατά τη διαδικασία της αποθείωσης των καυσαερίων στο λιγνητικό σταθμό της Φλώρινα. Δυνατοότητες αξιοποίησής της στην τσιμεντοβιομηχανία.

Based on the Vlasov–Maxwell equations describing self-consistent nonlinear beam dynamics and collective processes, the evolution of an intense sheet beam propagating through a periodic focusing field has been studied. It has been shown that in the case of a beam with uniform phase-space density, the Vlasov–Maxwell equations can be replaced exactly by the hydrodynamic equations with a triple adiabatic pressure law coupled with the Maxwell equations. We further demonstrate that starting from the system of hydrodynamic and Maxwell equations, a set of coupled nonlinear Schrödinger equations for the slowly varying amplitudes of density waves can be derived. In the case where a parametric resonance between a certain mode of density waves and the external focusing occurs, the slow evolution of the resonant amplitudes in the cold-beam limit is shown to be governed by a system of coupled Gross–Pitaevskii equations. Properties of the nonlinear Schrödinger equation as well as properties of the Gross–Pitaevskii equation are discussed, together with soliton and condensate formation in intense particle beams.

This note provides explicit algebraic stabilizing formulas for clf 's when controls are restricted to certain Minkowski balls in Euclidean space. Feedbacks of this kind are known to exist by a theorem of Artstein, but the proof of Artstein's theorem is nonconstructive. The formulas are obtained from a general feedback stabilization technique and are used to construct approximation solutions to some stabilization problems.

A new notion of input-to-state stability involving infinity norms of input derivatives up to a finite order k is introduced and characterized. An example shows that this notion of stability is indeed weaker than the usual iss. Applications to the study of global asymptotic stability of cascaded non-linear systems are discussed. A function F : S ! R is positive definite if F ðxÞ > 0; 8x 2 S; x=0 and F ð0Þ ¼ 0: A function g : R 50 ! R 50 is of class K if it is continuous, positive definite, and strictly increasing. It is of class K 1 if it is also unbounded. Finally, b : R 50  R 50 ! R 50 is of class KL if for each fixed t50; bðÁ; tÞ is of class K and for each fixed s > 0; bðs; tÞ decreases to 0 as t ! 1: An important fact concerning K 1 functions which will often be used in the following sections is the socalled 'weak triangular inequality' gða þ bÞ4gð2aÞ þ gð2bÞ for all a; b50:

We are often uncertain about the identity of objects. This phenomenon appears in theories of object persistence in early childhood; in the well-known Morning Star/Evening Star example; in tracking and data association systems for radar; in security systems based on personal identification; and in many aspects of our everyday lives. The paper presents a formal probabilistic approach to reasoning about identity under uncertainty in the framework of first-order logics of probability, with application to wide-area freeway traffic monitoring.

Motivated by the viscous sintering of amorphous materials in the presence of a distribution of rigid platelet inclusions added to increase the strength of the final sintered medium, a simple model for the shrinkage of compressible pores close to a wall in Stokes flow is proposed. The model assumes that the pore remains elliptical/ellipsoidal in shape at all times. The model is expected to be valid provided the pore is not too far from spherical and not too close to the wall. It relies on a separation of the flow into 'inner' and 'outer' problems. The inner problem is to assume that the ellipsoid evolves in a linear ambient flow given by the first two terms in a local expansion of an outer flow produced by the image singularity distribution of a point-sink near a planar no-slip boundary. The focus of the present paper is to test the viability of the model in the planar case. Using a spectral method based on analytic functions and conformal mappings, the results of a full numerical simulation are compared with the predictions of the planar model. The effects of the proximity of the pore to the wall, the anisotropy in the pore shape and its relative orientation to the wall are all examined. It is observed that, as they shrink, pores drift towards the wall becoming elongated in the direction perpendicular to the wall.

Live bacterial vaccines have great promise both as vaccines against enteric pathogens and as heterologous antigen vectors against diverse diseases. Ideally, room temperature stable dry formulations of live bacterial vaccines will allow oral vaccination without cold-chain storage or injections. Attenuated Salmonella can cross the intestinal wall and deliver replicating antigen plus innate immune activation signals directly to the intestinal immune tissues; however, the ingested bacteria must survive firstly gastric acid and secondly the antimicrobial defences of the small intestine. We found that the way in which cells are grown prior to formulation markedly affects sensitivity to acid and bile. Using a previously published stable storage formulation that maintained over 10% viability after 56 days storage at room temperature, we found dried samples of an attenuated Salmonella serovar Typhimurium vaccine lost acid and bile resistance compared to the same bacteria taken from fresh culture. The stable formulation utilised osmotic pre-conditioning in defined medium plus elevated salt concentration to induce intracellular trehalose accumulation before drying. Dried bacteria grown in rich media without osmotic pre-conditioning showed more resistance to bile, but less stability during storage, suggesting a trade-off between bile resistance and stability. Further optimisation is needed to produce the ultimate room temperature stable oral live bacterial vaccine formulation.

Numerical simulations reveal the formation of singular structures in the polymer stress field of a viscoelastic fluid modeled by the Oldroyd-B equations driven by a simple body force. These singularities emerge exponentially in time at hyperbolic stagnation points in the flow and their algebraic structure depends critically on the Weissenberg number. Beyond a first critical Weissenberg number the stress field approaches a cusp singularity, and beyond a second critical Weissenberg number the stress becomes unbounded exponentially in time. A local approximation to the solution at the hyperbolic point is derived from a simple ansatz, and there is excellent agreement between the local solution and the simulations. Although the stress field becomes unbounded for a sufficiently large Weissenberg number, the resultant forces of stress grow subexponentially. Enforcing finite polymer chain lengths via a FENE-P penalization appears to keep the stress bounded, but a cusp singularity is still approached exponentially in time.

Using slender-body hydrodynamics, we study the flow-induced deformation of a high-aspect-ratio elastic filament. For a filament of zero rest curvature rotating in a viscous linear shear flow, our model predicts a bifurcation to shape instabilities due to compression by the flow, in agreement with experimental observations. Further, nonlinear simulations of this shape instability show that in dilute solutions, flexibility of the fibers causes both increased shear thinning as well as significant nonzero first-normalstress differences. These stress differences are positive for small-to-moderate deformations, but negative for large-amplitude flexing of the fibers.

A mechanism by which smooth initial conditions evolve towards a topological reconfiguration of fluid interfaces is studied in the context of Darcy's law. In the case of thin fluid layers, nonlinear PDEs for the local thickness are derived from an asymptotic limit of the vortex sheet representation. A particular example considered is the Rayleigh-Taylor instability of stratified fluid layers, where the instability of the system is controlled by a Bond number B. It is proved that, for a range of B and initial data ''subharmonic'' to it, interface pinching must occur in at least infinite time. Numerical simulations suggest that ''pinching'' singularities occur generically when the system is unstable, and in particular immediately above a bifurcation point to instability. Near this bifurcation point an approximate analytical method describing the approach to a finite-time singularity is developed. The method exploits the separation of time scales that exists close to the first instability in a system of finite extent, with a discrete spectrum of modes. In this limit, slowly growing long-wavelength modes entrain faster short-wavelength modes, and thereby, allow the derivation of a nonlinear evolution equation for the amplitudes of the slow modes. The initial-value problem is solved in this slaved dynamics, yielding the time and analytical structure of a singularity that is associated with the motion of zeros in the complex plane, suggesting a general mechanism of singularity formation in this system. The discussion emphasizes the significance of several variational principles, and comparisons are made between the numerical simulations and the approximate theory.