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A photoresponsive micellar solution is developed as a promising working fluid for district heating/cooling systems (DHCs). It can be reversibly switched between a drag reduction (DR) mode and an efficient heat transfer (EHT) mode by light irradiation. The DR mode is advantageous during fluid transport, and the EHT mode is favored when the fluid passes through heat exchangers. This smart fluid is an aqueous solution of cationic surfactant oleyl bis(2-hydroxyethyl)methyl ammonium chloride (OHAC, 3.4 mM) and the sodium salt of 4-phenylazo benzoic acid (ACA, 2 mM). Initially, ACA is in a trans configuration and the OHAC/ACA solution is viscoelastic and exhibits DR (of up to 80% relative to pure water). At the same time, this solution is not effective for heat transfer. Upon UV irradiation, trans-ACA is converted to cis-ACA, and in turn, the solution is converted to its EHT mode (i.e., it loses its viscoelasticity and DR) but it now has a heat-transfer capability comparable to that of water. Subsequent irradiation with visible light reverts the fluid to its viscoelastic DR mode. The above property changes are connected to photoinduced changes in the nanostructure of the fluid. In the DR mode, the OHAC/trans-ACA molecules assemble into long threadlike micelles that impart viscoelasticity and DR capability to the fluid. Conversely, in the EHT mode the mixture of OHAC and cis-ACA forms much shorter cylindrical micelles that contribute to negligible viscoelasticity and effective heat transfer. These nanostructural changes are confirmed by cryo-transmission electron microscopy (cryo-TEM), and the photoisomerization of trans-ACA and cis-ACA is verified by (1)H NMR.

In practice, it is basically difficult even with controlled measurement environment to acquire a steady, uniform and fully developed flow. The flow entering diffuser was severely distorted despite a sufficient hydrodynamic entrance length already introduced. This was mainly due to the imperfect joining of duct and the abrupt change of the inlet cross-section applied. In this study, several basic features of a low subsonic wind tunnel, i.e. a centrifugal blower with 3-phase inverter, a settling chamber, screens and a contraction cone, are designed and developed for a turning diffuser application in order to improve the flow quality. The flow profiles are examined using Pitot static probe at five measurement points within the range of inflow Reynolds number, Rein= 5.786E+04-1.775E+05. The steady, uniform and fully developed turbulent flow profiles with an average deviation with theory of about 3.5% are obtained. This proves that a good flow quality could be produced by means of incorporating some basic features of a low subsonic wind tunnel to the system.

An attempt has been made to predict phase formation using a CALPHAD-based approach for a large number of compositions that are known to form FCC, BCC and a mixture of FCC and BCC phases. The stable phase is assumed to be the first phase that is formed upon cooling from liquid state with the highest driving force. The driving force for other phases at the transition for various compositions is also presented. A comparison between the parametric approach of phase prediction by study of thermodynamic and topological parameters on one hand and the CALPHAD approach on the other is also presented. CALPHAD approach appears to predict BCC phase formation much more accurately than the FCC phase formation. The results indicate that solid solution formation in multicomponent alloys is favored when the ratio of ?S config/?S fusion is greater than 1 and 1.2 for equiatomic and non-equiatomic alloys, respectively. The results also point out that BCC phase is favored when the atomic size difference is larger, which is reflected by a higher value of ?S ?/k. Formation of FCC phase appears to be governed mainly by ?H mix, while BCC phase governed by ?S ?/k, which is representative of strain in the structure. � 2012 Elsevier B.V. All rights reserved.

This paper presents a numerical investigation of pressure recovery and flow uniformity in turning diffusers with 90o angle of turn by varying geometric and operating parameters. The geometric and operating parameters considered in this study are area ratio (AR= 1.6, 2.0 and 3.0) and inflow Reynolds number (Rein=23, 2.653E+04, 7.959E+04, 1.592E+05 and 2.123E+05). Three turbulence models, i.e. the standard k-e turbulence model (std k-e), the shear stress transport model (SST-k-W) and the Reynolds stress model (RSM) were assessed in terms of their applicability to simulate the actual cases. The standard k-e turbulence model appeared as the best validated model, with the percentage of deviation to the experimental being the least recorded. Results show that the outlet pressure recovery of a turning diffuser at specified Rein improves approximately 32% by varying the AR from 1.6 to 3.0. Whereas, by varying the Rein from 2.653E+04 to 2.123E+05, the outlet pressure recovery at specified AR turning diffuser improves of approximately 24%. The flow uniformity is considerably distorted with the increase of AR and Rein. Therefore, there should be a compromise between achieving the maximum pressure recovery and the maximum possible flow uniformity. The present work proposes the turning diffuser with AR=1.6 operated at Rein=2.653E+04 as the optimum set of parameters, producing pressure recovery of Cp=0.320 and flow uniformity of su=1.62, with minimal flow separation occurring in the system.

In recent years, the Swirling Fluidized Bed has been regarded as one of the novel designs in fluidization technology. This new technique features an annular blade distributor which injects the fluidizing gas through a certain inclination, is capable of fluidizing the bed and at the same time causes swirling motion of particles in a circular trajectory. In the present work, the fluidization characteristics and hydrodynamics of a swirling bed are studied using an experimental approach. The behavior of gas-particle interaction in a swirling bed in terms of operation regimes, trend of pressure drop across the bed and the hysteresis effect, are explored with varying bed configurations. Seven sets of particles, three in spherical shape, two in cylindrical shape and two in irregular shape, are used as bed material by considering bed weights from 500 g to 2000 g and blade overlap angles 18° for air velocities up to approximately 3.5 m/s and blade inclination of 10°. The results evidently showed that particle configurations dramatically affect the beds’ behavior.

This article describes the synthesis and characterization of a new type of discrete microparticle immunosensor employing macroporous methacrylate polymer microspheres. The microspheres are produced using a simple microfluidic tubing co-flow droplet generator to produce large populations of microparticles with exceptional size uniformity and controllable macroporosity. Subsequent grafting treatments are demonstrated to anchor immunoactive ligands on the porous surfaces, converting the microspheres into discrete immunosensor elements, with direct immunoassay tests demonstrating good detection limits and capturing specificity. This work demonstrates the adaptation of a traditional polymer monolith stationary phase material into a discrete microparticle immunosensor format using a synthesis and functionalization path with significant flexibility toward a diverse range of biological and chemical sensing applications.

The S matrix ansatz is a rigorously model independent approach to describe the cross-sections and asymmetries in e+e- annihilation. Using the cross-sections and asymmetries measured with the L3 detector during the 1990 and 1991 running period, we determine the mass and the width of the Z boson, the contributions of the Z exchange and of the yZ interference. Including the polarization of the t lepton in the analysis, the leptonic helicity amplitudes of the scattering process are determined assuming lepton universality. The results are compared with other model independent ansatzes as realized in ZFITTER. A systematic bias of the Z mass due to the yZ interference term is detected, which leads to an underestimation of the error on mz for model independent determinations., Facultad de Ciencias Exactas

We describe the upgrade of the L3 detector for running at LHC. The principle goals are the precise measurement of electrons, photons and muons.

Charm data from 360 GeV/c π− p interactions are used to give results on D-meson branching ratios. The analysis is based on 114 charm events containing 183 observed charm particle decays. We present topological branching ratios and decay multiplicities, as well as the following inclusive branching ratios of D-mesons: B( D ± → K ∓ + anything ) = 0.16 −0.07 +0.08 , if B( D 0 → K ± + anything ) = 0.44 −0.10 +0.11 , ifB( D ± → e ± + 2,4 (rmcharged hadrons) = 0.07 −0.05 ++0.08 , B( D 0 → e ± + anything ) = 0.17 −0.06 +0.08 .

A search for rare charmless decays of B0d and B0s mesons has been performed in the exclusive channels B0d(s) →ηη0, B0d(s) →ηπ0 and B0d(s) →π0π0. The data sample consisted of three million hadronic Z decays collected by the L3 experiment at LEP from 1991 through 1994. No candidate event has been observed and the following upper limits at 90% confidence level on the branching ratios have been set: Br(B0d→ηη) −4, Br(B0s →ηη) < 1.5 x 10−3, Br(B0d→ηπ0) < 2.5 x 10−4, Br(B0s→ηπ0) < 1.0 x 10−3, Br(B0d→π0π0) < 6.0 x 10−5, Br(B0s→π0π0) < 2.1 x 10−4. These are the first experimental limits on Bd0→ηη and on the Bs0 neutral charmless modes., Facultad de Ciencias Exactas

Recently there has been much interest in using light to activate self-assembly of molecules in a fluid, leading to gelation. The advantage of light over other stimuli lies in its spatial selectivity, i.e., its ability to be directed at a precise location, which could be particularly useful in microfluidic applications. However, existing light-responsive fluids are not suitable for these purposes since they do not convert into sufficiently strong gels that can withstand shear. Here, we address this deficiency by developing a new light-responsive system based on the well-known polysaccharide, alginate. The fluid is composed entirely of commercially available components: alginate, a photoacid generator (PAG), and a chelated complex of divalent strontium (Sr(2+)) cations. Upon exposure to ultraviolet (UV) light, the PAG dissociates to release H(+) ions, which in turn induce the release of free Sr(2+) from the chelate. The Sr(2+) ions self-assemble with the alginate chains to give a stiff gel with an elastic modulus ∼2000 Pa and a yield stress ∼400 Pa (this gel is strong enough to be picked up and held by one's fingers). The above fluid is sent through a network of microchannels and a short segment of a specific channel is exposed to UV light. At that point, the fluid is locally transformed into a strong gel in a few minutes, and the resulting gel blocks the flow through that channel while other channels remain open. When the UV light is removed, the gel is gradually diluted by the flow and the channel reopens. We have thus demonstrated a remote-controlled fluidic valve that can be closed by shining light and reopened when the light is removed. In addition, we also show that light-induced gelation of our alginate fluid can be used to deposit biocompatible payloads at specific addresses within a microchannel.

This paper reports a simple, rapid, and sugar-selective method to induce gelation from glucose-containing samples. This method employs glucose oxidase (GOx) to selectively "recognize" and oxidize glucose to generate gluconic acid, which acts to solubilize calcium carbonate and release calcium ions. The release of calcium ions triggers gelation of the calcium-responsive polysaccharide alginate to form a calcium-alginate hydrogel. Rheological measurements confirm that gel formation is triggered by glucose but not fructose or sucrose (consistent with GOx's selectivity). Vial inversion tests demonstrate that gel formation can be readily observed without the need for instrumentation. Proof-of-concept studies demonstrate that this gel-forming method can detect glucose in food/beverage products sweetened with glucose or high-fructose corn syrups. These results indicate that the enzyme-induced gelation of alginate may provide a simple means to test for sweeteners using components that are safe for use on-site or in the home.

We describe a new approach to creating hybrid polymer hydrogels that comprise two different gel types (gel 1 and gel 2) juxtaposed in predetermined zones or patterns and with the unique properties of each gel being retained. The key to our approach is to ensure that the viscosities of the pregel mixtures are high when they are brought into contact and subsequently polymerized; this limits the diffusion at gel/gel interfaces. The final gel appears as a single, homogeneous, transparent material with smooth, robust interfaces between the dissimilar zones. However, its hybrid nature is revealed by specific tests. In one example, we use the same monomer, N,N-dimethylacrylamide, for gels 1 and 2, but gel 1 is cross-linked by a chemical cross-linker while gel 2 is cross-linked by laponite nanoparticles. In this case, when the hybrid gel is immersed in a mixed solution of cationic and anionic dyes, gel 2 selectively absorbs the cationic dye due to the strong affinity of the nanoparticles in it for cationic specie...

An easy access to a library of simple organic salts derived from tert-butoxycarbonyl (Boc)-protected L-amino acids and two secondary amines (dicyclohexyl- and dibenzyl amine) are synthesized following a supramolecular synthon rationale to generate a new series of low molecular weight gelators (LMWGs). Out of the 12 salts that we prepared, the nitrobenzene gel of dicyclohexylammonium Boc-glycinate (GLY.1) displayed remarkable load-bearing, moldable and self-healing properties. These remarkable properties displayed by GLY.1 and the inability to display such properties by its dibenzylammonium counterpart (GLY.2) were explained using microscopic and rheological data. Single crystal structures of eight salts displayed the presence of a 1D hydrogen-bonded network (HBN) that is believed to be important in gelation. Powder X-ray diffraction in combination with the single crystal X-ray structure of GLY.1 clearly established the presence of a 1D hydrogen-bonded network in the xerogel of the nitrobenzene gel of GLY.1. The fact that such remarkable properties arising from an easily accessible (salt formation) small molecule are due to supramolecular (non-covalent) interactions is quite intriguing and such easily synthesizable materials may be useful in stress-bearing and other applications.

Methods that allow soft matter to be fabricated with controlled structure and function would be beneficial for applications ranging from flexible electronics to regenerative medicine. Here, the assembly of a multifunctional gelatin matrix is demonstrated by triggering its self-assembly and then enzymatically assembling biological functionality. Triggered self-assembly relies on electrodeposition of the pH-responsive hydrogelator, 9-fluorenylmethoxycarbonyl-phenylalanine (Fmoc-Phe), in response to electrical inputs that generate a localized pH-gradient. Warm solutions of Fmoc-Phe and gelatin are co-deposited and, after cooling to room temperature, a physical gelatin network forms. Enzymatic assembly employs the cofactor-independent enzyme microbial transglutaminase (mTG) to perform two functions: crosslink the gelatin matrix to generate a thermally stable chemical gel and conjugate proteins to the matrix. To conjugate globular proteins to gelatin these proteins are engineered to have short lysine-rich or glutamine-rich fusion tags to provide accessible residues for mTG-catalysis. Viable bacteria can be co-deposited and entrapped within the crosslinked gelatin matrix and can proliferate upon subsequent incubation. These results demonstrate the potential for enlisting biological materials and mechanisms to biofabricate multifunctional soft matter.

Swirling fluidized bed (SFB) is one of the recent technologies developed in fluidization to overcome various drawbacks in the conventional fluidized beds, particularly poor lateral mixing and relatively high distributor pressure drop. Though a number of beds operating with similar technique are commercially available, very little has been published on the subject, particularly on the distributor design. The distributor of the SFB is formed by an array of blades which are inclined to the horizontal, with a centre body in the middle of the bed. Air flow investigation was carried out on the empty bed via CFD approach. The study focused on the effects of number of blades and its inclination angle on the flow distribution and pressure drop, so as to arrive at an optimum choice of the distributor design. The findings indicate that higher number of has lower open area which resulted higher jet velocity of air from the distributor. Blade inclination has significant effect on the flow distribution where lower blade inclination produces higher magnitude of tangential velocity that creates intense swirling but at an expense of higher pressure drop. In conclusion, the distributor with 30 blades and 15º inclination was found to meet the design criterion outlined.

The study is conducted to evaluate the heat transfer characteristics of two new and versatile enhancement configurations in a double tube heat exchanger annulus. The novelty is that they are usable in single phase forced convection, evaporation and condensation. Heat transfer coefficients are determined by the Wilson Plot technique in laminar and turbulent flow and correlations are proposed for Nusselt numbers. Comparisons are then made between heat transfer and flow friction.

Two novel enhanced tubes, viz. Turbo-C with three dimensional surface corrugations and EXTEK with helical flutes, are evaluated in the present work. They are chosen for study because of their versatility for use in condensation as well as evaporation in a double tube heat exchanger assembly, typically as used in water source heat pumps. Average and local values of heat transfer coefficient and two-phase pressure drop are reported.

This paper presents computational fluid dynamics (CFD) studies to characterize air velocity distribution for various bed configurations in a swirling fluidized bed (SFB). Unlike conventional fluidized beds, a SFB provides radial mixing which is desirable is fluidization. Three velocities components were observed, the tangential velocity, radial velocity and axial velocity. These velocities were created as a result of using annular blade type distributor which mimics the turbine blades. In actual industrial applications, the axial velocity will create fluidization while the tangential velocity provides swirling effect. The presence of radial velocity can be explained as a consequence of centrifugal force generated by the swirling gas. Understanding these velocity distributions will enable optimization of the annular blade distributor design towards a high efficient fluidized bed system.

A relatively new variant in fluidized bed technology, designated as the swirling fluidized bed (SFB), was investigated for its heat transfer characteristics when operating with Geldart type D particles. Unlike conventional fluidized beds, the SFB imparts secondary swirling motion to the bed to enhance lateral mixing. Despite its excellent hydrodynamics, its heat transfer characteristics have not been reported in the published literature. Hence, two different sizes of spherical PVC particles (2.61 mm and 3.65 mm) with the presence of a center body in the bed have been studied at different velocities of the fluidizing gas. The wall-to-bed heat transfer coefficients were measured by affixing a thin constantan foil heater on the bed wall. Thermocouples located at different heights on the foil show a decrease in the wall heat transfer coefficient with bed height. It was seen that only a discrete particle model which accounts for the conduction between the particle and the heat transfer surface and the gas-convective augmentation can adequately represent the mechanism of heat transfer in the swirling fluidized bed.

Current gels used in blood separation tubes create an imperfect barrier between the blood components because of their physical and thixotropic nature. As a result, blood components tend to leak into the gel layer or vice versa during transport and storage. To overcome these problems, we demonstrate the use of a UV-curable thixotropic gel composed of a sorbitol-based gelator in a diacrylate oligomer. Initially, the sample is a physical gel composed of weak, non-covalent bonds, and its thixotropic nature allows it to flow under centrifugation and form a barrier between the density-stratified layers of blood. Immediately afterward, the gel is chemically crosslinked by short exposure to UV light for 10–30 s. This results in a rigid, impenetrable barrier that is freeze-thaw stable. The gel is compatible with blood, allowing blood samples to be stored in the tube and analyzed over long times. We believe the present method is a significant advance in the practice of blood analysis for medical purposes.

We describe the creation of monodisperse microbeads of polydimethylsiloxane (PDMS) via a microfluidic approach. Using a flow-focusing configuration, a PDMS precursor solution is dispersed into microdroplets within an aqueous continuous phase. These droplets are collected and thermally cured off-chip into solid microbeads. Our microfluidic technique allows for direct integration of payloads into the PDMS microbeads. Specifically, we integrate an oxygen-sensitive porphyrin dye into the beads and show that the resulting structures can function as non-invasive and real-time oxygen microsensors utilizing a simple optical readout at the single-particle level.

Alginate is a biocompatible polysaccharide that is commonly used in the pharmaceutical, biomedical, cosmetic, and food industries. Though solid dressings composed of alginate can absorb water and promote wound healing, they are not effective hemostatic materials, particularly against massive hemorrhage. The purpose of this study is to attempt to increase the hemostatic capabilities of alginate by means of hydrophobic modification. Previous studies have illustrated that modifying a different polysaccharide, chitosan, in this way enhances its hemostatic efficacy as well as its adhesion to tissue. Here, it was hypothesized that modifying alginate with hydrophobic groups would demonstrate analogous effects.Fifteen Yorkshire swine were randomized to receive hydrophobically-modified (hm) alginate lyophilized sponges (n=5), unmodified alginate lyophilized sponges (n=5), or standard Kerlix™ gauze dressing (n=5) for hemostatic control. Following a splenectomy, arterial puncture (6mm punch) of the femoral artery was made. Wounds were allowed to freely bleed for 30s, at which time dressings were applied and compressed for 3min in a randomized fashion. Fluid resuscitation was given to preserve the baseline mean arterial pressure. Wounds were monitored for 180min after arterial puncture, and surviving animals were euthanized.Blood loss for the hm-alginate group was significantly less than the two control groups of (1) alginate and (2) Kerlix™ gauze (p=0.0001). Furthermore, 80% of hm-alginate sponges were able to sustain hemostasis for the full 180min, whereas 0% of dressings from the control groups were able to achieve initial hemostasis.Hm-alginate demonstrates a greatly superior efficacy, relative to unmodified alginate and Kerlix™ gauze dressings, in achieving hemostasis from a lethal femoral artery puncture in swine. This is a similar result as has been previously described when performing hydrophobic modification to chitosan. The current study further suggests that hydrophobic modification of a hydrophilic biopolymer backbone can significantly increase the hemostatic capabilities relative to the native biopolymer.

Geldart Type-D particles are often associated with poor fluidization characteristics due to their large sizes and higher densities. This paper reports the hydrodynamics of various Geldart Type-D particles when fluidized in a swirling fluidized bed (SFB). Four different sizes of particles ranging from 3.85 mm to 9.84 mm with respective densities ranging from 840 kg/m3 to 1200 kg/m3 were used as bed material to study the effect of various bed weights (500 gram to 2000 gram) and centre bodies (cone and cylinder) for superficial velocities up to 6 m/s. The performance of the SFB was assessed in terms of pressure drop values, minimum fluidization velocity, Umf and fluidization quality by physical observation on regimes of operation. The swirling fluidized bed showed excellent capability in fluidizing Geldart Type-D particles in contrast to the conventional fluidized beds. The bed pressure drop of increased with superficial velocity after minimum fluidization as a result of increasing centrifugal bed weight. It was also found that the particle size and centre body strongly influence the bed hydrodynamics.

The study is conducted to evaluate the flow characteristics in a double tube heat exchanger using two new and versatile enhancement configurations. The novelty is that they are usable in single phase forced convection, evaporation and condensation. Correlations are proposed for flow development length and friction factor for use in predicting fluid pumping power in thermal equipment as well as in subsequent heat transfer characterization of the surface.

The work presented in this paper reports the quantitative study on the influence of the statistical moments of probability density function, i.e., mean, standard deviation, skew and kurtosis, for an air flow maldistribution profile on the thermal performance of a fin-tube heat exchanger. The effects of the geometrical parameters of the heat exchanger, i.e., tube diameter, fin pitch, row pitch, tube pitch, number of rows and fin surface pattern, are also investigated. The thermal performance is found to be noticeably affected by mean, standard deviation and skew but not the kurtosis. In addition, the interaction between the external and internal thermal resistances has a significant effect. All the geometrical parameters examined, except for the number of rows and fin pattern, have either a weak or an insignificant effect on the thermal performance degradation factor. Physical reasoning has been provided to explain the trends of the degradation with respect to the moments and geometrical parameters. From these trends, a new set of correlation equations is proposed to predict the degradation effect of the flow maldistribution on wavy fins. The correlation agrees well with experimental data within ±10%.

This paper presents the hydrodynamics of chopped oil palm fronds (OPF) from cold flow experiments carried out in a swirling fluidized bed dryer (SFBD). The chopped OPF was 10 – 15 mm in size and falls in between Geldart type B and D. The OPF which consisted of leaves and petiole (stem) were first separated before studied individually due to their different physical characteristics. 2 bed loadings of 120g and 140g were investigated for bed pressure drop, (ΔPb), minimum fluidization velocity (Umf) and minimum swirling velocity (Ums) while regimes of operation were closely observed. The experiments yield that the OPF leaves and petiole have distinct hydrodynamic behavior due to their different bulk densities and voidage, hence suggesting drying should also be conducted separately unlike the current industrial practice. The leaves have lower Umf and Ums compared to the petiole and thus swirling motion was initiated earlier in SFBD when operating with leaves. Both samples however, have limited operating velocities due to elutriation. In conclusion, the SFBD was found to fluidize the chopped OPF well while providing good solid-gas contact which is highly desired for drying.

The technique of direct infusions into brain tissue of therapeutic molecules that would otherwise not adequately cross the blood-brain barrier (BBB) continues to be used in clinical trials. As part of our research into understanding the transport of fluids and molecules in brain tissue, we performed infusions of a saline solution of the magnetic resonance (MR) marker Gadodiamide( Omniscan) into porcine brains. We use quantitative concentration measurements of contrast reagents from MR images to both measure the distribution profile of the infusate and to elucidate important determinants of fluid flow during infusions into brain parenchyma. Based on this, and from other MRI data collected during infusion, we give preliminary results for the quantification of the expansion of the volume fraction of the interstitium particularly in white matter regions of brain during infusion-induced edema. We claim this expansion, rather than an anisotropy of fluid conductivity, makes white matter tracts a preferred pathway for flow. We also comment briefly on other determinants that are currently being pursued such as the influence of the cerebrospinal fluid and perivascular spaces that may be elucidated with quantitative tracking of tracer, but which need further studies.

Biopolymers such as alginate and pectin are well known for their ability to undergo gelation upon addition of multivalent cations such as calcium (Ca(2+)). Here, we report a simple way to activate such ionic gelation by UV irradiation. Our approach involves combining an insoluble salt of the cation (e.g., calcium carbonate, CaCO(3)) with an aqueous solution of the polymer (e.g., alginate) along with a third component, a photoacid generator (PAG). Upon UV irradiation, the PAG dissociates to release H(+) ions, which react with the CaCO(3) to generate free Ca(2+). In turn, the Ca(2+) ions cross-link the alginate chains into a physical network, thereby resulting in a hydrogel. Dynamic rheological experiments confirm the elastic character of the alginate gel, and the gel modulus is shown to be tunable via the irradiation time as well as the PAG and alginate concentrations. The above approach is easily extended to other biopolymers such as pectin. Using this approach, a photoresponse can be imparted to conventional biopolymers without the need for any chemical modification of the molecules. Photoresponsive alginate gels may be useful in creating biomaterials or tissue mimics. As a step toward potential applications, we demonstrate the ability to photopattern a thin film of alginate gel onto a glass substrate under mild conditions.

Evolution of dislocation structure as a function of deformation, in case of a two phase zirconium alloy, was characterized by transmission electron microscopy as well as X-ray line profile analysis. Dislocation structures up to a deformation of 10% show that deformation is mitigated by a single active slip system. Dislocation cellular structures were observed at a deformation of 27%. Two different X-ray based techniques of evaluation of dislocation density were used in the present study. The methods though differed in the absolute values of dislocation densities (ρ), agreed with each other in terms of trend in variation of ρ with the amount of plastic strain.

In the context of intraparenchymal delivery of therapeutic agents into brain parenchyma for the purpose of treating serious brain diseases, we present the scientific and medical need for infusion from a single source to cover a large area of the cerebral cortex, which we refer to as 'surface-contoured distributions' (SCD). The designs of two devices suitable for obtaining such SCD's are described, and the results of preliminary experimental studies with prototypes of them are reported. The studies were done in ex vivo samples of mammalian brain tissues, and histological sections of the brains confirmed that we had covered the large surface area desired. Work to test that the infusate penetrates the thickness of the cortex remains for the future.

This paper reports the experimental findings on a swirling fluidized bed which operates with an annular-blade distributor. Spherical PVC particles (which fall under type D in Geldart’s classification) with two different sizes (5.75 mm and 9.84 mm) were used as bed material to study different bed configurations, taking into account the variation of fraction of open area (12.9% and 17.2%), blade overlapping angles (9° and 12°) and bed weight (500 gram to 2000 gram) for superficial velocities is from 1 m/s to 8 m/s. The performance of the swirling fluidized bed was assessed in terms of pressure drop values, minimum fluidization velocity and fluidization quality by physical observation on regimes of operation. The most significant finding is that the pressure drop of the bed increased with superficial velocity after minimum fluidization, in contrast with a conventional fluidized bed. It was also found that the blade geometry has less effect on bed performance, compared to fraction of open area and particle size. New regimes of operation were discovered, and designated as wave regime and two-layer bed regime. The best configuration obtained in the current work, which provides stable swirling at lower pressure drops, is the one with 60 distributor blades and 12° overlapping angle, operating with 9.84 mm particles.

Blood loss at the site of a wound in mammals is curtailed by the rapid formation of a hemostatic plug, i.e., a self-assembled network of the protein, fibrin that locally transforms liquid blood into a gelled clot. Here, we report an amphiphilic biopolymer that exhibits a similar ability to rapidly gel blood; moreover, the self-assembly underlying the gelation readily allows for reversibility back into the liquid state via introduction of a sugar-based supramolecule. The biopolymer is a hydrophobically modified (hm) derivative of the polysaccharide, chitosan. When hm-chitosan is contacted with heparinized human blood, it rapidly transforms the liquid into an elastic gel. In contrast, the native chitosan (without hydrophobes) does not gel blood. Gelation occurs because the hydrophobes on hm-chitosan insert into the membranes of blood cells and thereby connect the cells into a sample-spanning network. Gelation is reversed by the addition of α-cyclodextrin, a supramolecule having an inner hydrophobic pocket: polymer hydrophobes unbind from blood cells and embed within the cyclodextrins, thereby disrupting the cell network. We believe that hm-chitosan has the potential to serve as an effective, yet low-cost hemostatic dressing for use by trauma centers and the military. Preliminary tests with small and large animal injury models show its increased efficacy at achieving hemostasis - e.g., a 90% reduction in bleeding time over controls for femoral vein transections in a rat model.

The work presented in this paper investigates the degradation effect of flow maldistribution on the thermal and hydraulic performance of a heat exchanger. A new mathematical model is derived based on Taylor series expansion to describe the contribution of each of the four statistical moments of distribution on the degradation problem. It is found that the first two moments, i.e. mean and standard deviation, have the highest effect on the performance degradation. Subsequent higher moments will give declining degradation effects until the fourth moment, kurtosis, which has no significant effect. Maldistribution with low standard deviation and high positive skew will give low thermal deteriorations, though a distribution with negative skew is preferred for low hydraulic performance losses. The design of the heat exchanger could be modified to give these favourable moments which would minimize the degradation effects of the maldistribution. Consequently, any effort to modify the flow distribution profile should be focused on optimizing the first three moments.

We describe a simple way to create patterns of “soft” biomolecular nanostructures such as vesicles on “hard” surfaces such as gold. The key to our approach is the use of an amphiphilic biopolymer as an “interconnect” or tether. The polymer is hydrophobically modified chitosan (hm-chitosan), which is obtained by covalently attaching alkyl tails to the backbone of chitosan. We electrodeposit films of hm-chitosan onto microscale gold cathodes formed by lithography on a silicon wafer. Subsequently, the hm-chitosan films are used to spontaneously capture vesicles from solution; this is demonstrated both for surfactant as well as lipid vesicles (liposomes). Vesicles remain strongly bound to the hm-chitosan to a much greater extent than to native chitosan. This suggests that the mechanism for vesicle capture involves non-covalent binding of hydrophobes from hm-chitosan chains to the hydrophobic portions of vesicle bilayers. Importantly, the vesicles captured by hm-chitosan films are intact—this is shown both by direct visualization of captured vesicles (via optical and cryo-transmission electron microscopy) as well as through the capture and subsequent disruption of dye-filled vesicles. Various microscale patterns of immobilized vesicles are created and the vesicles are demonstrated to be capable of sensing a reporter molecule from the external solution.

Easy access to a class of chiral gelators has been achieved by exploiting primary ammonium mono- carboxylate (PAM), a supramolecular synthon. A combinatorial library com- prising of 16 salts, derived from 5 l- amino acid methyl esters and 4 cinnam- ic acid derivatives, has been prepared and scanned for gelation. Remarkably, 14 out of 16 salts prepared (87.5 % of the salts) show moderate to good gela- tion abilities with various solvents, in- cluding commercial fuels, such as petrol. Anti-solvent induced instant ge- lation at room temperature has been achieved in all the gelator salts, indicat- ing that the gelation process is indeed an aborted crystallization phenomenon. Rheology, optical and scanning elec- tron microscopy, small angle neutron scattering, and X-ray powder diffrac- tion have been used to characterize the gels. A structure-property correlation has been attempted, based on these data, in addition to the single-crystal structures of 5 gelator salts. Analysis of the FT-IR and 1 H NMR spectroscopy data reveals that some of these salts can be used as supramolecular contain- ers for the slow release of certain pest sex pheromones. The present study clearly demonstrates the merit of crys- tal engineering and the supramolecular synthon approach in designing new ma- terials with multiple properties.

We present a method for manipulating preselected quantum dots (QDs) with nanometer precision by flow control. The accuracy of this approach scales more favorably with particle size than optical trapping, enabling more precise positioning of nanoscopic particles. We demonstrate the ability to position a single QD in a 100 microm working region to 45 nm accuracy for holding times exceeding one hour and the ability to take active quantum measurements on the dynamically manipulated QD.

We present a microfluidic method to direct the self-assembly of temperature-sensitive liposome-hydrogel hybrid nanoparticles. Our approach yields nanoparticles with structural properties and highly monodisperse size distributions precisely controlled across a broad range relevant to the targeted delivery and controlled release of encapsulated therapeutic agents. We used microfluidic hydrodynamic focusing to control the convective-diffusive mixing of two miscible nanoparticle precursor solutions (a DPPC:cholesterol:DCP phospholipid formulation in isopropanol and a photopolymerizable N-isopropylacrylamide mixture in aqueous buffer) to form nanoscale lipid vesicles with encapsulated hydrogel precursors. These precursor nanoparticles were collected off-chip and were irradiated with ultraviolet (UV) light in bulk to polymerize the nanoparticle interiors into hydrogel cores. Multiangle laser light scattering in conjunction with asymmetric flow field-flow fractionation was used to characterize nanoparticle size distributions, which spanned the approximately 150 to approximately 300 nm diameter range as controlled by microfluidic mixing conditions, with a polydispersity of approximately 3% to approximately 5% (relative standard deviation). Transmission electron microscopy was then used to confirm the spherical shape and core-shell composition of the hybrid nanoparticles. This method may be extended to the directed self-assembly of other similar cross-linked hybrid nanoparticle systems with engineered size/structure-function relationships for practical use in healthcare and life science applications.

Fifteen non pregnant female dromedaries of different age were intra-tracheally and intra-nasally infected with a Brucella melitensis strain belonging to the genetic group East Mediterranean (former African group). The development of Brucella antibodies in the infected dromedaries was investigated over a period of 12 months by comparing 15 different serological tests. Three uninfected control dromedaries remained negative during the entire experiment. Our investigations revealed that only 2 serological tests were characterised by a high degree of sensitivity for the diagnosis of brucellosis in dromedaries. These two tests are a Rose Bengal Test (RBT) from Vircell, Spain and a competitive ELISA (cELISA) from Ingenasa, also from Spain. The blood culture revealed that all tested sodium citrate blood samples were negative. Results of the enriched citrate blood samples of the infected 15 dromedaries fluctuated and became positive for a short time, but at the end of the experiment only one remained positive. Direct examination by PCR did not show any evidence of the pathogen in the EDTA blood of the 15 infected dromedaries. Also, all nasal swabs taken up to a period of 3 months post infection remained negative in both PCR and microbial culture.

Telechelic associating polymers (hydrophilic ethoxylated backbone, hydrophobic n-alkyl end-groups) form viscous solutions in water due to associations between the hydrophobes. The addition of alpha-, beta-, or gamma-cyclodextrin (CD) substantially reduces the solution viscosity because the CD molecules envelop and sequester the hydrophobes in their hydrophobic cavities. The present paper explores the variation in polymer-CD solution viscosity with temperature. We find that, in the case of alpha-CD alone, the solutions show "thermothickening", i.e., the viscosity increases from 25 to ca. 60 degrees C whereupon it reaches a peak value and then drops. In contrast, solutions with beta- and gamma-CD show monotonic drops in viscosity upon heating. At a fixed polymer content, the thermothickening is higher for higher alpha-CD concentrations. We have also studied how surfactants and lipids impact the thermothickening. Addition of single-tailed micelle-forming surfactants causes the viscosity to revert to the more typical decreasing trend with temperature. However, addition of double-tailed lipids to a polymer/alpha-CD solution accentuates the thermothickening behavior. The thermothickening is explained by the propensity of alpha-CDs to unbind from the hydrophobes and form inclusion complexes with the polymer backbone as the temperature is raised.

With sustainability as an important and driving theme, not merely of research, but that of our existence itself, the effort in developing sustainable systems takes many directions. One of these directions is in the transport sector, particularly personal transport using hydrogen as fuel, which logically leads on to the problem of hydrogen storage. This paper deals with the prediction of the effective conductivity of beds of metal hydride for hydrogen storage. To enable modeling of the effective thermal conductivity of these systems, it is necessary to arrive at the functional dependence of the thermal conductivity of the solid hydride on its hydrogen concentration or content. This is the inverse problem in thermal conductivity of multiphase materials. Inverse methods in general are those where we start from known consequences in order to find unknown causes. Using published and known data of the effective thermal conductivity of the hydride–hydrogen assemblage, we arrive at the unknown hydride conductivity by analysis. Among the models available in the literature for determination of the effective conductivity of the bed from the properties of the constituent phases, the model of Raghavan and Martin is chosen for the analysis as it combines simplicity and physical rigor. The result is expected to be useful for predicting the thermal conductivity of hydride particles and determining the optimum heat transfer rates governing the absorption and desorption rates of hydrogen in the storage system.

Photorheological (PR) fluids, i.e., fluids whose rheology can be tuned by light, have been a recent focus for our laboratory. We are interested in low-cost approaches to PR fluids using molecules or materials that are readily available. Toward this end, we report a new concept for such fluids based on light-activated assembly of nanoparticles into a physical network (gel). Our system consists of disk-like nanoparticles of laponite along with a surfactant stabilizer (Pluronic F127) and the photoacid generator (PAG), diphenyliodonium-2-carboxylate monohydrate. Initially, the nanoparticles are sterically stabilized by the surfactant, and the result is a stable, low-viscosity dispersion. Upon UV irradiation, the PAG gets photolyzed, lowering the pH by approximately 3 units. In turn, the stabilizing surfactant is displaced from the negatively charged faces of the nanoparticle disks while the edges of the disks become positively charged. The particles are thereby induced to assemble into a three-dimensional "house-of-cards" network that extends through the sample volume. The net result is a light-induced sol to gel transition, i.e., from a low, water-like viscosity to an infinite viscosity and yield stress. The yield stress of the photogel is sufficiently high to support the weight of small objects. The gel can be converted back to a sol by increasing either the pH or the surfactant content.

We describe a new way to impart pH-responsive properties to gels of biopolymers such as gelatin. This approach involves the embedding of pH-sensitive nanosized vesicles within the gel. The vesicles employed here are those of sodium oleate (NaOA), a fatty-acid-based amphiphile with a single C18 tail. In aqueous solution, NaOA undergoes a transition from vesicles at a pH approximately 8 to micelles at a pH higher than approximately 10. Here, we combine NaOA and gelatin at pH 8.3 to create a vesicle-loaded gel and then bring the gel in contact with a pH 10 buffer solution. As the buffer diffuses into the gel, the vesicles within the gel get transformed into micelles. Accordingly, a vesicle-micelle front moves through the gel, and this can be visually identified by the difference in turbidity between the two regions. Vesicle disruption can also be done in a spatially selective manner to create micelle-rich domains within a vesicle-loaded gel. A possible application of the above approach is in the area of pH-dependent controlled release. A vesicle-to-micelle transition releases hydrophilic solutes encapsulated within the vesicles into the bulk gel, and in turn these solutes can rapidly diffuse out of the gel into the external bath. Experiments with calcein dye confirm this concept and show that we can indeed use the pH in the bath to tune the release rate of solutes from vesicle-loaded gels.