List of Records in Australian Institute for Bioengineering and Nanotechnology Publications - UQ eSpace

A ballistic study of micro-particle penetration to the oral mucosa

2007-09-19T15:04:11Z

This paper describes the results of an investigation into the impact of model micro-particles to ex vivo buccal mucosa (the cheek) of pigs and beagle dogs. The work is aimed at optimizing a unique form of pharmaceutical delivery. The pharmaceutical is formulated into particle form and accelerated toward the target of skin or mucosa by using a gas jet. In this study, research devices designed using analytical, computational (computational fluid dynamics) and experimental methodologies were used to deliver particles at uniform and predetermined velocities. These velocities were confirmed using light obscuration, pressure measurement and particle image velocimetry methods. Polystyrene, glass, stainless steel and gold micro-particles at a range of size distributions were used for the payloads for injection using these devices. Injection occurred with a wide range of impact conditions into fresh canine (dog) and porcine (pig) buccal mucosa. Final positions of the particles were determined from histological sections and the results analyzed in relation to the known particle impact parameters of size, density and velocity. The experimental results are collated using an empirical term, based on particle impact parameters. Comparison is then made to a semi-empirical penetration model. This is done by analysing the penetration results in terms of each particle impact parameter. Analysis shows that this model fits the experimental data well when reasonable estimates of the tissue mechanical properties are chosen. (C) 2002 Elsevier Science Ltd. All rights reserved.

Ab initio studies of hydrogen desorption from low index magnesium hydride surface

2007-08-15T08:01:23Z

The low index Magnesium hydride surfaces, MgH2(001) and MgH2(110), have been studied by ab intio Density Functional Theory (DFT) calculations. It was found that the MgH2(110) surface is more stable than MgH2(001) surface, which is in good agreement with the experimental observation. The H-2 desorption barriers vary depending on the crystalline surfaces that are exposed and also the specific H atom sites involved-they are found to be generally high, due to the thermodynamic stability of the MgH2, system, and are larger for the MgH2(001) surface. The pathway for recombinative desorption of one in-plane and one bridging H atom from the MgH2(110) surface was found to be the lowest energy barrier amongst those computed (172 KJ/mol) and is in good agreement with the experimental estimates. (c) 2006 Elsevier B.V. All rights reserved.

A blank slate? Layer-by-layer deposition of hyaluronic acid and chitosan onto various surfaces

2007-08-15T10:39:21Z

Although poly(alpha-hydroxy esters), especially the PLGA family of lactic acid/glycolic acid copolymers, have many properties which make them promising materials for tissue engineering, the inherent chemistry of surfaces made from these particular polymers is problematic. In vivo, they promote a strong foreign-body response as a result of nonspecific adsorption and denaturation of serum proteins, which generally results in the formation of a nonfunctional fibrous capsule. Surface modification post-production of the scaffolds is an often-utilized approach to solving this problem, conceptually allowing the formation of a scaffold with mechanical properties defined by the bulk material and molecular-level interactions defined by the modified surface properties. A promising concept is the so-called blank slate: essentially a surface that is rendered resistant to nonspecific protein adsorption but can be readily activated to covalently bind bio-functional molecules such as extracellular matrix proteins, growth factors or polysaccharides. This study focuses on the use of the quartz crystal microbalance (QCM) to follow the layer-by-layer (LbL) electrostatic deposition of high molecular weight hyaluronic acid and chitosan onto PLGA surfaces rendered positively charged by aminolysis, to form a robust, protein-resistant coating. We further show that this surface may be further functionalized via the covalent attachment of collagen IV, which may then be used as a template for the self-assembly of basement membrane components from dilute Matrigel. The response of NIH-3T3 fibroblasts to these surfaces was also followed and shown to closely parallel the results observed in the QCM.

Abrupt structural transformation in hydrotalcite-like compounds Mg1-xAlx(OH)(2)(NO3)(x)center dot nH(2)O as a continuous function of nitrate anions

Xu, Z. P. og Zeng, H. C. — 2007-10-17T11:06:05Z

We report here a systematic XRD/FTIR/CHN/ICP investigation for structural transformation of hydrotalcite-like compounds Mg1-xAlx(OH)(2)(NO3)(x). nH(2)O as a continuous function of nitrate anions (x = 0.18-0.34). With seven finely divided steps in x value, a clear relationship between basal spacing and nitrate anion content (and thus trivalent cation content) has been found. In particular, we have been able to "arrest" an intermediate hydrotalcite-like phase that situates at the midpoint of an abrupt structural. transformation. Unlike that of normal hydrotalcites, the relationship revealed in our nitrated Mg1-xAlx(OH)(2)(NO3)(x). nH(2)O samples is much more complicated. While the lattice parameter a decreases with increase of nitrate content, the parameter c decreases slightly over x = 0.18-0.22, rises abruptly with a further increase of nitrate anions at x = 0.26, and then reaches maximums at x = 0.31-0.34. The compound at x = 0.26 also shows a sharp decrease in mean crystallite dimension. The abrupt structural change is attributed to a drastic change in nitrate anion arrangement. On the basis of our FTIR observations and Coulombic energy estimation, a "stick-lying" model for nitrate arrangement has been proposed, which is apparently superior to a "tilt-lying" model reported previously. The saturated charge density of the brucite-like layers for the "stick-lying" nitrate anions is about 4 e/nm(2). The sharp decrease in crystallite dimension can be ascribed to the change of nitrate configuration from "flat-lying" to "stick-lying" due to increasing lateral repulsion among the anions and thus discontinuation in the planar growth.

Absorption of low molecular weight penetrants by a thermoplastic polyimide

2008-06-10T13:16:52Z

The response of a thermoplastic polyimide (TPI) to immersion in a range of solvents was investigated by a number of experimental techniques. The kinetics of solvent diffusion were determined by weight uptake and NMR imaging, the effect of absorbed solvent on thermal behaviour was investigated by dynamic mechanical analysis and differential scanning calorimetry and the morphology of TPI exposed to solvent was determined by wide-angle X-ray scattering. The tensile properties of amorphous and crystalline TPI were measured before and after exposure to solvent. Amorphous TPI absorbed significant quantities of some solvents that lowered the T-g, but none were sufficiently plasticising to induce crystallisation at room temperature. There was a direct correlation between the extent of solvent ingress and the environmental stress cracking behaviour of amorphous TPI. Crystalline TPI absorbed only small quantities of all the solvents used, but showed limited environmental stress cracking resistance. (C) 2000 Elsevier Science Ltd. All rights reserved.

A casein variant in cow's milk is atherogenic

2007-08-15T02:34:00Z

Casein is a major protein in cow's milk that occurs in several variant forms, two of which are beta-casein A(1) and beta-casein A(2). The levels of these two proteins vary considerably in milk dependent on the breed of cow, and epidemiology studies suggest that there is a relationship between their consumption and the degree of atherosclerosis. In the present study, the direct effect of consumption of beta-casein A(1) vs beta-casein A(2) on atherosclerosis development was examined in a rabbit model. Sixty rabbits had their right carotid artery balloon de-endothelialised at t = 0, divided randomly into 10 groups (n = 6 per group), then for 6 weeks fed a diet containing 0, 5, 10 or 20% casein isolate, either beta-casein variant A(1) or A(2) made up to 20% milk protein with whey. Some groups had their diets supplemented with 0.5% cholesterol. Blood samples were collected at t = 0, 3 and 6 weeks and rabbits were sacrificed at t = 6 weeks. In the absence of dietary cholesterol, beta-casein A(1) produced significantly higher (P < 0.05) serum cholesterol, LDL, HDL and triglyceride levels than whey diet alone, which in turn produced higher levels than beta-casein A(2). Rabbits fed beta-casein A(1) had a higher percent surface area of aorta covered by fatty streaks than those fed beta-casein A(2) (5.2+/-0.81 vs 1.1+/-0.39, P < 0.05) and the thickness of the fatty streak lesions in the aortic arch was significantly higher (0.04+/-0.010 vs 0.00, P < 0.05). Similarly, the intima to media ratio (I:M) of the balloon injured carotid arteries in A(1) fed animals (0.77+/-0.07) was higher than in those that consumed A(2) (0.57+/-0.04) or whey (0.58+/-0.04), but this did not reach significance. In the presence of 0.5% dietary cholesterol, the thickness of the aortic arch lesions was higher (P < 0.05) in 5, 10 and 20% casein A(1) fed animals compared with their A(2) counterparts, while other parameters were not significantly different. It is concluded that beta-casein A(1) is atherogenic compared with beta-casein A(2). (C) 2003 Elsevier Science Ireland Ltd. All rights reserved.

Accelerated cell line development using two-color fluorescence activated cell sorting to select highly expressing antibody-producing clones.

2009-04-17T16:24:50Z

The success of engineered monoclonal antibodies as biopharmaceuticals has generated considerable interest in strategies designed to accelerate development of antibody expressing cell lines. Stable mammalian cell lines that express therapeutic antibodies at high levels typically take 6-12 months to develop. Here we describe a novel method to accelerate selection of cells expressing recombinant proteins (e.g., antibodies) using multiparameter fluorescence activated cell sorting (FACS) in association with dual intracellular autofluorescent reporter proteins. The method is co-factor-independent and does not require complex sample preparation. Chinese hamster ovary (CHO) clones expressing high levels of recombinant antibody were selected on the basis of a two-color FACS sorting strategy using heavy and light chain-specific fluorescent reporter proteins. We were able to establish within 12 weeks of transfection cell lines with greater than a 38-fold increase in antibody production when compared to the pool from which they were isolated, following a single round of FACS. The method provides a robust strategy to accelerate selection and characterization of clones and builds a foundation for a predictive model of specific productivity based upon on two-color fluorescence.

Accumulation of homolanthionine and activation of a novel pathway for isoleucine biosynthesis in corynebacterium glutamicum McbR deletion strains

2009-02-13T09:56:33Z

n the present work, the metabolic consequences of the deletion of the methionine and cysteine biosynthesis repressor protein (McbR) in Corynebacterium glutamicum, which releases almost all enzymes of methionine biosynthesis and sulfate assimilation from transcriptional regulation (D. A. Rey, A. Pühler, and J. Kalinowski, J. Biotechnol. 103:51-65, 2003), were studied. C. glutamicum ATCC 13032 {Delta}mcbR showed no overproduction of methionine. Metabolome analysis revealed drastic accumulation of a single metabolite, which was not present in the wild type. It was identified by isotopic labeling studies and gas chromatography/mass spectrometry as L-homolanthionine {S-[(3S)-3-amino-3-carboxypropyl]-L-homocysteine}. The accumulation of homolanthionine to an intracellular concentration of 130 mM in the {Delta}mcbR strain was accompanied by an elevated intracellular homocysteine level. It was shown that cystathionine-{gamma}-synthase (MetB) produced homolanthionine as a side reaction. MetB showed higher substrate affinity for cysteine (Km = 260 µM) than for homocysteine (Km = 540 µM). The cell is able to cleave homolanthionine at low rates via cystathionine-ß-lyase (MetC). This cleavage opens a novel threonine-independent pathway for isoleucine biosynthesis via 2-oxobutanoate formed by MetC. In fact, the deletion mutant exhibited an increased intracellular isoleucine level. Metabolic flux analysis of C. glutamicum {Delta}mcbR revealed that only 24% of the O-acetylhomoserine at the entry of the methionine pathway is utilized for methionine biosynthesis; the dominating fraction is either stored as homolanthionine or redirected towards the formation of isoleucine. Deletion of metB completely prevents homolanthionine accumulation, which is regarded as an important step in the development of C. glutamicum strains for biotechnological methionine production.

A comparative study of carbon gasification with O-2 and CO2 by density functional theory calculations

2007-08-14T18:41:45Z

A comparative study of carbon gasification with O-2 and CO2 was conducted by using density functional theory calculations. It was found that the activation energy and the number of active sites in carbon gasification reactions are significantly affected by both the capacity and manner of gas chemisorption. O-2 has a strong adsorption capacity and the dissociative chemisorption of O-2 is thermodynamically favorable on either bare carbon surface or even isolated edge sites. As a result, a large number of semiquinone and o-quinone oxygen can be formed indicating a significant increase in the number of active sites. Moreover, the weaker o-quinone C-C bonds can also drive the reaction forward at (ca. 30%) lower activation energy. Epoxy oxygen forms under relatively high O-2 pressure, and it can only increase the number of active sites, not further reduce the activation energy. CO2 has a lower adsorption capacity. Dissociative chemisorption of CO2 can only occur on two consecutive edge sites and o-quinone oxygen formed from CO2 chemisorption is negligible, let alone epoxy oxygen. Therefore, CO2-carbon reaction needs (ca 30%) higher activation energy. Furthermore, the effective active sites are also reduced by the manner Of CO2 chemisorption. A combination of the higher activation energy and the fewer active sites leads to the much lower reaction rate Of CO2-carbon.

A comparative study of N2O conversion to N-2 over Co/AC and Cu/AC catalysts

2007-08-13T11:16:19Z

Catalytic conversion of N2O to N-2 over Cu- and Co-impregnated activated carbon catalysts (Cu/AC and Co/AC) was investigated. Catalytic activity measurements were carried out in a fixed-bed flow reactor at atmospheric pressure. The catalysts were characterized by N-2 adsorption, X-ray diffraction (XRD) and thermogravimetric analysis (TGA). This study aimed to provide insights into the following aspects: the metal dispersion, changes in pore structure, influence of catalyst loading on reaction, and reaction mechanism. Increasing loading of Co or Cu led to decreasing dispersion, but 20 wt % loading was an upper limit for optimal activities in both cases, with too high loading causing sintering of metal. Co exhibited a relatively better dispersion than Cu. Impregnation of metal led to a large decrease in surface area and pore volume, especially for 30 wt % of loading. 20 wt % of loading has proved to be the optimum for both Cu and Co, which shows the highest activity. Both N2O-Co/AC and -Cu/AC reactions are based upon a redox mechanism, but the former is limited by the oxygen transfer from catalysts to carbon, while N2O chemisorption on the surface of Cu catalyst controls the latter. The removal of oxygen from cobalt promotes the activity of Co/AC, but it is beneficial for Cu/AC to keep plenty of oxygen to maintain the intermediate oxidation of copper-Cu1+. The different nature of the two catalysts and their catalytic reaction mechanisms are closely related to their different electronegativities.

A comparative study of the fluidized-bed coating of cylindrical metal surfaces with various thermoplastic polymer powders

Leong, K. C. og Lu, G. Q. og Rudolph, V. — 2007-08-13T11:12:00Z

This paper reports the results of an experimental investigation into the fluidized-bed coating of cylindrical metal specimens using two types of thermoplastic powders, Rilsan(R) PA11, a nylon-11 powder produced by Elf Atochem, France and Cotene(TM) 4612, a linear low density polyethylene powder produced by J.R Courtenay (New Zealand). The effects of dipping time, preheat temperature and particle size distribution on coating thickness and surface finish were investigated. Consistent trends in coating thickness growth with dipping time were obtained for both nylon-11 and polyethylene powders with increases in coating thickness with preheat temperature. For the same preheat temperature, the lower melting point of polyethylene results in thicker coatings compared to those of nylon-11. There is a negligible change in the coating thickness for sieved powders compared to that for unsieved powders. A pre-heat temperatures of between 240 degrees C and 300 degrees C is necessary to achieve an acceptable surface finish with both nylon-11 and polyethylene powders. To minimize errors in achieving the desired coating thickness, dipping times shorter than 2 s are not recommended. The use of graphs of coating thickness versus dipping time in combination with the coating surface roughness plots presented in this paper enable the optimal choice of pre-heat temperature and dipping time to achieve acceptable surface finish. (C) 1999 Elsevier Science S.A. All rights reserved.

A comparison of sesquiterpene scaffolds across different populations of the tropical marine sponge Acanthella cavernosa

2008-03-18T14:05:36Z

Specimens of the Indo-Pacific sponge Acanthella cavernosa Dendy collected from locations along the Eastern coastline of Australia have been shown to contain a range of sesquiterpenes including isothiocyanate 1, isocyanide 10, and the isocyanates 15 and 22. These metabolite studies have provided a basis for chemical comparisons between sponge populations from different geographic locations and between individual specimens collected from a single location.

A comprehensive study on carbon dioxide reforming of methane over Ni/gamma-Al2O3 catalysts

Wang, S. B. og Lu, G. Q. — 2007-08-13T11:14:49Z

Carbon dioxide reforming of methane into syngas over Ni/gamma-Al2O3 catalysts was systematically studied. Effects of reaction parameters on catalytic activity and carbon deposition over Ni/gamma-Al2O3 catalysts were investigated. It is found that reduced NiA1204, metal nickel, and active species of carbon deposited were the active sites for this reaction. Carbon deposition on Ni/gamma Al2O3 varied depending on the nickel loading and reaction temperature and is the major cause of catalyst deactivation. Higher nickel loading produced more coke on the catalysts, resulting in rapid deactivation and plugging of the reactor. At 5 wt % Ni/gamma-Al2O3 catalyst exhibited high activity and much lesser magnitude of deactivation in 140 h. Characterization of carbon deposits on the catalyst surface revealed that there are two kinds of carbon species (oxidized and -C-C-) formed during the reaction and they showed different reactivities toward hydrogenation and oxidation. Kinetic studies showed that the activation energy for CO production in this reaction amounted to 80 kJ/mol and the rate of CO production could be described by a Langmuir-Hinshelwood model.

Adatom CCV Auger rates via the local density of states

2008-01-25T16:02:57Z

In this letter the core-core-valence Auger transitions of an atomic impurity, both in bulk or adsorbed on a jellium-like surface, are computed within a DFT framework. The Auger rates calculated by the Fermi golden rule are compared with those determined by an approximate and simpler expression. This is based on the local density of states (LDOS) with a core hole present, in a region around the impurity nucleus. Different atoms, Na and Mg, solids, Al and Ag, and several impurity locations are considered. We obtain an excellent agreement between KL1V and KL23V rates worked out with the two approaches. The radius of the sphere in which we calculate the LDOS is the relevant parameter of the simpler approach. Its value only depends on the atomic species regardless of the location of the impurity and the type of substrate. (C) 2003 Elsevier B.V. All rights reserved.

Addition of Diazomethane to Armchair Single-walled Carbon Nanotubes and Reaction Sequences: A Computational Study

2008-04-30T09:43:13Z

The sidewall additions of diazomethane to (n, n), n = 3-10 armchair single-walled carbon nanotubes (SWCNTs) on two different orientations of C-C bonds have been studied using the ONIOM(B3LYP/6-31G(d):PM3) approach. The binding energies of SWCNTs complexes with CH2N2, CH2 and their transition-,state structures were computed at the B3LY-P/6-31G(d) level. The effects of diameters of armchair SWCNTs on their binding energies were studied. Relative reactivities of all the SWCNTs and their complexes based on their frontier orbital energies gaps are reported. (c) 2007 Elsevier B.V. All rights reserved.

A detailed investigation of the influence of organo-layered silicate (oils) aspect ratio on polyurethane nanocomposite structure and properties

2007-08-23T21:25:59Z

Adipocyte differentiation in human embryonic stem cells transduced with Oct4 shRNA lentivirus

Hannan, Nicholas R.F. og Wolvetang, Ernst J. — 2009-04-07T11:51:51Z

Oct4 is one of the master pluripotency genes that controls differentiation of human embryonic stem cells (hESCs). We generated HES2 and HES3 hESC lines stably transduced with lentivirus carrying Oct4 short hairpin RNA (shRNA) that display 80–90% reduction of Oct4 expression. Analysis of pluripotency marker expression shows that these Oct4 shRNA-transduced hESCs display normal wild-type expression levels of the pluripotency marker CD9 but an absence of GCTM2 expression. These hESC-derived adipocyte precursor cells display a characteristic morphology and can be propagated and cryopreserved as a standard stem cell line. Interestingly, Oct4 shRNA-transduced hESCs display a remarkably high lineage-specific spontaneous differentiation toward adipocytes. After two weeks of spontaneous differentiation under feeder-free conditions, 60–70% of cells display a mature adipocyte morphology as well as the expression of multiple adipocyte-specific mRNAs as assessed by RT-PCR. The upregulation of trophoblast, mesoderm, and endoderm transcripts is, however, also detected in these spontaneously differentiating cultures. These Oct4 shRNA hESCs will be an interesting model system to study human fetal adipogenesis and constitutes a renewable resource for obesity drug screening purposes.

Adipose tissue engineering based on the controlled release of fibroblast growth factor-2 in a collagen matrix

2007-08-15T09:41:07Z

Adipose tissue forms when basement membrane extract ( Matrigel (TM)) and fibroblast growth factor-2 (FGF-2) are added to our mouse tissue engineering chamber model. A mouse tumor extract, Matrigel is unsuitable for human clinical application, and finding an alternative to Matrigel is essential. In this study we generated adipose tissue in the chamber model without using Matrigel by controlled release of FGF-2 in a type I collagen matrix. FGF-2 was impregnated into biodegradable gelatin microspheres for its slow release. The chambers were filled with these microspheres suspended in 60 mu L collagen gel. Injection of collagen containing free FGF-2 or collagen containing gelatin microspheres with buffer alone served as controls. When chambers were harvested 6 weeks after implantation, the volume and weight of the tissue obtained were higher in the group that received collagen and FGF-2 impregnated microspheres than in controls. Histologic analysis of tissue constructs showed the formation of de novo adipose tissue accompanied by angiogenesis. In contrast, control groups did not show extensive adipose tissue formation. In conclusion, this study has shown that de novo formation of adipose tissue can be achieved through controlled release of FGF-2 in collagen type I in the absence of Matrigel.

A drop impact study of worm-like viscoelastic surfactant solutions

2007-09-19T15:43:06Z

In this paper, we investigate the impact dynamics of drops of complexed surfactant solutions. Dilute to semi-dilute solutions of rod-like to worm-like micelles of equimolar cetyltrimethylammonium bromide (CTAB) and sodium salicylate (Nasal) in water (CTAB-NaSal (1:1)) have been dropped onto a smooth hydrophobic surface. The variations in impact behaviour of each solution are discussed in terms of the dynamic surface tension and viscoelastic properties. Increases in the concentration of CTAB-NaSal (1:1) in solution resulted in enhanced reduction in the maximum height achieved during recoil, even though the maximum diameter reached during spreading was equivalent for all solutions over the range of concentrations explored. The equivalence in the maximum diameter during spreading is due to the loss of fluid structure at high extension rates, whilst the resulting reduction in rebound tendency is due to a rapid restructuring of the fluid post impact. The drop impact of such complexed surfactant solutions provides significant insight into the contributions of a 'dynamic' fluid microstructure to the rebound behaviour of dilute 'living polymer' solutions. (C) 2002 Elsevier Science B.V. All rights reserved.

Adsorbents and catalysts for clean energy and emissions control

Lu, GQ og Rudolph, V — 2007-08-13T10:46:57Z

Adsorption characteristics of carbonized bark for phenol and pentachlorophenol

Edgehill, RU og Lu, GQ — 2007-08-13T10:20:17Z

The potential of using carbonized slash pine bark as a substitute for activated carbon was examined in this study. The bark was carbonized by slow heating in nitrogen for 6.5 h to 672 degrees C. The BET-N-2 surface area, average micropore and mesopore diameter, and micropore volume were 332 m(2) g(-1) 21.7 Angstrom, and 0.125 cm(3) g(-1), respectively. The adsorption capacities for phenol and pentachlorophenol (PCP) at pH 2 and pH 8 were evaluated. The Langmuir equation provided a slightly better fit than the Freundlich equation to two sets of phenol data. The calculated Freundlich constants, K = 0.41 - 0.58 mmol/g/(mmol dm(-3))(1/n) and 1/n = 0.30 - 0.41, were lower and higher, respectively, than literature values for activated carbons. The adsorption capacity of the carbonized bark was much lower for PCP than for phenol. The protonated and anionic PCP isotherms were Type II or III, respectively, in the Brunauer classification. The BET equation provided the best fit to protonated PCP isotherm data. The anionic PCP data were fitted to both the BET model and an equation used in the literature to represent phosphate adsorption on activated carbons. Nonlinear regression of the data for both phenol and PCP adsorption with the Freundlich, Langmuir and BET equations generally gave more accurate parameters, compared with the use of linearized equations to obtain the parameters. (C) 1998 SCI.

Adsorption characteristics of phenolic compounds onto coal-reject-derived adsorbents

Haghseresht, F og Lu, GQ — 2007-08-13T10:47:02Z

Carbonaceous adsorbents were prepared by heat treatment of coal reject at 600 degrees C, after chemical treatment in HNO3, H2SO4, and NaOH at 25 and 75 degrees C. Pore structure characterization and the phenol adsorption capacities of the adsorbents showed that nitric acid pretreatment significantly enhanced the surface properties, consequently the adsorption capacities of the adsorbents. A number of samples were subsequently prepared by carbonizing coal reject at 600 degrees C, after pretreatment in HNO3 under various conditions. The acid concentration, residence time, and reaction temperature were varied to obtain adsorbents with various pore structures. The adsorption capacities of the derived adsorbents for phenol, p-nitrophenol, and benzene were measured to gain further insights into the pore structure evolution. Adsorption isotherms of phenol, p-nitrophenol, and p-chlorophenol on the best adsorbent prepared were determined and correlated with theoretical isotherm equations, such as the Langmuir, Freundlich, and Redlich-Peterson equations.

Adsorption kinetics for the removal of chromium(VI) from aqueous solution by adsorbents derived from used tyres and sawdust

2007-08-14T16:08:14Z

The batch removal of hexavalent chromium (Cr(Vl)) from wastewater under different experimental conditions using economic adsorbents was investigated in this study. These adsorbents were produced from the pyrolysis and activation of the waste tyres (TAC) and from the pyrolysis of sawdust (SPC). The performance of these adsorbents against commercial activated carbon F400 (CAC) has also been carried out. The removal was favoured at low pH, with maximum removal at pH = 2 for all types of carbon. The effects of concentration, temperature and particle size have been reported. All sorbents were found to efficiently remove Cr(VI) from solution. The batch sorption kinetics have been tested for a first-order reversible reaction, a first-order and second-order reaction. The rate constants of adsorption for all these kinetic models have been calculated. The applicability of the Langmuir isotherm for the present system has been tested at different temperatures. The thermodynamic parameters (AGO, K,) obtained indicate the endothermic nature of Cr(Vl) adsorption on TAC, SPC and CAC. (C) 2001 Elsevier Science B.V. All rights reserved.

Adsorption of aromatic compounds by activated carbon: Effects of functional groups and molecular size

Nouri, S og Haghseresht, F og Lu, M — 2007-08-14T18:43:27Z

The adsorption of three aromatic compounds on to an untreated carbon was investigated. The solution pH was lowered in all experiments so that all the solutes were in their molecular forms. It was shown that the difference in the maximum adsorption of the solutes was mainly a result of the difference in the sizes of the molecules and their functional groups. Further-more, it was illustrated that the packing arrangement was most likely edge-to-face (sorbate-sorbent) with various tilt angles. On the other hand, the affinity and heterogeneity of the adsorption systems were apparently related to the pK(a) values of the solutes.

Adsorption of dyes onto LDH-Modified Bentonite

2007-08-23T22:27:14Z

Adsorption of p-nitrophenol in untreated and treated activated carbon

Nouri, S. og Haghseresht, F. — 2007-08-15T05:14:04Z

The adsorption of p-nitrophenol in one untreated activated carbon (F100) and three treated activated carbons (H-2, H2SO4 and Urea treated F100) was carried out at undissociated and dissociated conditions. To characterize the carbon, N-2 and CO2 adsorption were used. X-ray Photoelectron Spectroscopy (XPS) was used to analyze the surface of the activated carbon. The experimental isotherms are fitted via the Langmuir homogenous model and Langmuir binary model. Variation of the model parameters with the solution pH is studied. Both Q(max) and the adsorption affinity coefficient (K-1) were dependent on the PZC of the carbons and solution pH. The Effect of pH must be considered due to its combined effects on the carbon surface and on the solute molecules. Adsorption of p-nitrophenol at higher pH was found to be dependent on the concentration of the anionic form of the solute.

Adsorption study for removal of basic red dye using bentonite

2007-08-15T10:10:29Z

Colored wastewater poses a challenge to the conventional wastewater treatment techniques. Solid-liquid phase adsorption has been found to be effective for the removal of dyes from effluent. In this paper, the ability of bentonite as an adsorbent for the removal of a commercial dye, Basic Red 2 (BR2), from an aqueous solution has been investigated under various experimental conditions. The adsorption kinetics was shown to be pseudo-second-order. It was found that bentonite had high adsorption capacity for BR2 due to cation exchange. The adsorption equilibrium data can be fitted well by the Langmuir adsorption isotherm model. The effect of the experimental parameters, such as temperature, salt, and pH was investigated through a number of batch adsorption experiments. It was found that the removal of dye increased with the increase in solution pH. However, the change of temperature (15-45 degrees C) and the addition of sodium chloride were found to have little effect on the adsorption process. The results show that electrostatic interactions are not dominant in the interaction between BR2 and bentonite. It was found that the adsorption was a rapid process with 80-90% of the dye removed within the first 2-3 min. Bentonite as an adsorbent is promising for color removal from wastewater.

Adsorption study of benzene in ink-bottle-like MCM-41

2007-08-14T16:10:17Z

The pore-opening size of MCM-41 is tailored to be in the microporous region using a chemical vapor deposition technique for selective tailoring. Although the pore opening is narrowed, the internal pore body of MCM-41 remains unchanged so the pore volume retains a substantial portion (80%) of its original value. The adsorption equilibrium of nitrogen and benzene in the modified MCM-41 shows a type I isotherm, which significantly improves the adsorption performance of MCM-41 for low-concentration volatile organic compounds. The adsorption kinetics of benzene in the modified MCM-41 is also studied.

A dual catalyst bed system for the elimination of hydrogen from CO2 feed gas in urea synthesis

2007-08-13T12:16:13Z

A dual catalyst bed system (Au/Fe2O3 + Pt-Pd/Al2O3) for eliminating hydrogen from the CO2 feed gas in urea synthesis is found to be far superior to commercially available and patented catalysts in catalytic activity. At relatively low temperatures, hydrogen is eliminated and coexistent CO is also oxidized completely to useful CO2. This can avoid effectively the accidental explosion of hydrogen-oxygen-ammonia mixed gases, thus ensuring the safety of urea synthesis.

Advances in the production of polyhydroxyalkanoates. Track 4-Biobased products and chemicals and renewable chemical platforms

Brumbley, S. M. — 2009-02-17T15:46:10Z

Advances in vascular tissue engineering

2007-08-15T02:30:45Z

Coronary and peripheral artery bypass grafting is commonly used to relieve the symptoms of vascular deficiencies, but the Supply Of autologous artery or vein may not be sufficient or suitable for multiple bypass or repeat procedures, necessitating the use of other materials. Synthetic materials are suitable for large bore arteries but often thrombose when used in smaller arteries. Suitable replacement grafts must have appropriate characteristics, including resistance to infection, low immunogenicity and good biocompatability and thromboresistance, with appropriate mechanical and physiological properties and cheap and fast manufacture. Current avenues of graft development include coating synthetic grafts with either biological chemicals or cells with anticoagulatory properties. Matrix templates or acellular tubes of extracellular matrix (such as collagen) may be coated or infiltrated with cultured cells. Once placed into the artery, these grafts may become colonised by host cells and gain many of the properties of normal artery. Tissue-engineered blood vessels may also be formed from layers of human vascular cells grown in culture. These engineered vessels have many of the characteristics of arteries formed in vivo. Artificial arteries may be also be derived from peritoneal granulation tissue in body bioreactors by adapting the body's natural wound healing response to produce a hollow tube. (C) 2003 Elsevier Inc. All rights reserved.

Aerobic cultivation of Streptococcus zooepidemicus and the role of NADH oxidase

Fong Chong, B. og Nielsen, L. K. — 2007-08-15T02:18:08Z

A metabolic flux model was developed for Streptococcus zooepidemicus to compare the metabolism of glucose and maltose during aerobic batch cultivation. Lactic acid was the main product of glucose metabolism whereas acetic acid was the main product of maltose metabolism. This difference was chiefly attributed to the two-fold higher flux through NADH oxidase in maltose-grown cells that enabled the ATP generation rate to remain high despite a slower maltose consumption rate. The two-fold higher flux was matched by a two-fold increase in NADH oxidase activity, 2.53 +/- 0.1 mumol NADH min(-1) mg(-1) protein on maltose versus 1.07 +/- 0.04 Rmol NADH min(-1) mg(-1) protein on glucose, indicating that NADH oxidase activity is regulated by the energy status of the cell. Surprisingly, the energy status of the cell had little impact on hyaluronic acid (HA) yield and molecular weight. (C) 2003 Elsevier Science B.V. All rights reserved.

A facile aqueous route to synthesize highly ordered mesoporous polymers and carbon frameworks with Ia(3)over-bard bicontinuous cubic structure

2008-01-25T16:40:16Z

A high-throughput system for screening transgenic sugarcane plants producing polyhydroxybutyrate

Brumbley, S. M. — 2009-02-18T10:35:39Z

AIN nanowire for AI-based composites with high strength and low thermal expansion

2008-04-30T13:56:50Z

Based on the synthesis of a sufficient amount of AlN nanowires (AlN-NWs), AlN-NWs/Al composites with homogenously distributed AlN-NWs were fabricated. Microstructural observations reveal that the interface between AlN-NWs and Al matrix is clean and bonded well, and no interfacial reaction product was formed at the nanowire-matrix boundary. Mechanical properties including yield and tensile strength of the composites were improved with AlN-NWs volume fraction changing from 5 to 15 vol%, and the maximum yield and tensile strengths of the composite were about 6 and 5 times, respectively, as high as those of Al matrix. Meanwhile, AlN-NWs effectively decreased the coefficient of thermal expansion (CTE) of the composites, and the CTE of 15 vol% composite was about one half that of Al matrix. The results obtained suggest that AlN nanowire is a promising reinforcement for optimizing the mechanical and thermal properties of metal matrix composites.

A Kinetic Model for Bleaching Vegetable Oils

de Oliveria, Christina Gomes og Porto, Luismar Marques — 2009-02-12T18:02:19Z

Very little data and very few kinetic models are available describing and evaluating the performance of bleaching processes, earths, and equipment. This work presents a general kinetic model for the adsorption of pigments by adsorbent earths in several edible oils. It reports the kinetic parameters found for two bleaching earths (one developed in the laboratory and one commercial) for the clarification of soybean oil, as well as their activation energies. The proposed kinetic model is second order in the dimensionless pigment concentration and is in good agreement with our experimental data. A very simple mechanistic explanation based on adsorption/deactivation is offered to justify its application. We also present mathematical modeling based on balance equations to show how the kinetic parameters can be used for bleaching earths and for industrial equipment evaluation and design, such as for the transient fed-batch stirred bleaching vessel. The model seems appropriate to represent data under different operating conditions such as temperature and adsorbent load. The simulation shows that startup procedures are very important in the bleaching process-at least as important as the batch step, in which the oil color reaches its desired standard.

A Kinetic Study on Photocatalytic Oxidation of Phenol in water by silica-dispersed titania nanoparticles

Ding, Z. og Lu, G. Q. og Greenfield, P. F. — 2008-06-10T12:27:27Z

Photocatalytic oxidation of phenol in water was carried out with nanoparticles of silica–titania mixtures, which were synthesized under different temperatures and silica-to-titania ratios. The crystal size of TiO2 (in anatase phase) was determined to be in the nanometer range and it increased with increasing autoclaving temperature. Furthermore, there was no obvious relationship between the ize and the SiO2/TiO2 ratio at the same preparation temperature. A specific reaction rate constant (ks) was used for comparison of photocatalytic activity of different samples. It was found that ks decreases with increasing anatase size and TiO2 concentration. A kinetic model was developed to describe the effect of the crystal size and titania concentration on the reactivity of the SiO2–TiO2 samples.

Alignment of TiO2 particles by electrophoretic deposition in a high magnetic field

2008-01-25T16:23:39Z

Textured titania thick films were fabricated by applying external electrical and magnetic fields. X-ray diffraction (XRD) results and scanning electron microscopy (SEM) images revealed that the titania grains in the c-axis direction were orientated along the high magnetic field (10 T) even though the anisotropic susceptibility of titania ceramic is quite weak. (C) 2004 Elsevier Ltd. All rights reserved.

Aluminophosphate-based mesoporous molecular sieves: synthesis and characterization of TAPOs

Zhao, XS og Lu, GQ — 2007-08-13T12:23:35Z

Mesoporous Ti-substituted aluminophosphates (AlPOs) with a hexagonal, cubic and lamellar pore structure, characteristic of MCM-41, MCM-48. and MCM-50, respectively, were synthesized. The stability of these mesophases upon template removal was studied. The pore structures, surface properties, and local atom environments of Al, P, and Ti of the hexagonal and cubic Ti-containing mesoporous products were extensively characterized using X-ray diffraction, magic angle spinning nuclear magnetic resonance, AAS, XPS, ultraviolet-visible, and adsorption of nitrogen and water vapor techniques while the lamellar mesophase was not further characterized due to its very poor thermal stability. Ti-containing mesoporous AlPO materials show a reasonable thermal stability upon template removal, a hydrophilic surface property, and high porosity showing application potentials in catalytic oxidation of hydrocarbons. (C) 2001 Elsevier Science B,V. All rights reserved.

Aluminophosphate-based mesoporous molecular sieves: Synthesis and characterization of TAPOs

Zhao, X. og Lu, M. G. — 2007-08-14T16:07:44Z

Mesoporous Ti-substituted aluminophosphates (AlPOs) with a hexagonal, cubic and lamellar pore structure, characteristic of MCM-41, MCM-48, and MCM-50, respectively, were synthesized. The stability of these mesophases upon template removal was studied. The pore structures, surface properties, and local atom environments of Al, P, and Ti of the hexagonal and cubic Ti-containing mesoporous products were extensively characterized using X-ray diffraction, magic angle spinning nuclear magnetic resonance, AAS, XPS, ultraviolet–visible, and adsorption of nitrogen and water vapor techniques while the lamellar mesophase was not further characterized due to its very poor thermal stability. Ti-containing mesoporous AlPO materials show a reasonable thermal stability upon template removal, a hydrophilic surface property, and high porosity showing application potentials in catalytic oxidation of hydrocarbons.

Ambipolar field-effect transistor on as-grown single-wall carbon nanotubes

Babic, B og Iqbal, M og Schonenberger, C — 2008-01-25T15:53:32Z

We use a simultaneous flow of ethylene and hydrogen gases to grow single-wall carbon nanotubes by chemical vapour deposition. Strong coupling to the gate is inferred from transport measurements for both metallic and semiconducting tubes. At low temperatures, our samples act as single-electron transistors where the transport mechanism is mainly governed by Coulomb blockade. The measurements reveal very rich quantized energy level spectra spanning from the valence to the conduction band. The Coulomb diamonds have similar addition energies on both sides of the semiconducting gap. Signatures of the subband population have been observed at intermediate temperature.

A mechanism for forming large fluorescent organo-silica particles: Potential supports for combinatorial synthesis

2007-10-17T15:28:14Z

The ability to track multiple compounds through a combinatorial synthesis on solid support particles can be a challenging exercise. A novel solution to this problem is to use the optical characteristics of each support particle to identify the biomolecule synthesized on its surface. To achieve this, we have synthesized a new class of porous, thiol-functionalized supports in a two-step process that used 3-mercaptopropyl trimethoxysilane as the monomer. The monomer was hydrolyzed and polymerized in an acidic solution, which formed an emulsion that was subsequently cross-linked with either ammonia (NH3) or methylamine (CH3NH2). The synthetic process and resulting organo-silica particles were characterized using silicon NMR, scanning electron microscopy techniques, and fluorescence microscopy. Furthermore, thin sections of the porous beads were successfully produced and analyzed via transmission electron microscopy. By controlling the reaction conditions during the synthesis, we achieved a variety of particle morphologies, including hollow particles, particles with macropores on the surface, and particles with a highly porous interior. The mechanism for forming and controlling the morphology of these particles is described here. Also described is the unique process of incorporating fluorescence dyes using combinatorial methods. This enabled the synthesis of a highly optically diverse population of particles, which could be produced over a small number of reactions. Flow cytometry was used to demonstrate the diversity of fluorescence signatures possessed by these encoded particles.

A model for the viscoelastic behaviour at gelation based on the relaxation behaviour of branched molecules

Altmann, N. og Halley, P. J. — 2007-08-24T00:41:09Z

A molecular mechanism for messenger RNA trafficking in neuronal dendrites

2007-08-24T01:07:16Z

A molecular mechanism for mRNA trafficking in neuronal dendrites

2007-08-15T01:22:00Z

Specific neuronal mRNAs are localized in dendrites, often concentrated in dendritic spines and spine synapses, where they are translated. The molecular mechanism of localization is mostly unknown. Here we have explored the roles of A2 response element (A2RE), a cis-acting signal for oligodendrocyte RNA trafficking, and its cognate trans-acting factor, heterogeneous nuclear ribonucleoprotein ( hnRNP) A2, in neurons. Fluorescently labeled chimeric RNAs containing A2RE were microinjected into hippocampal neurons, and RNA transport followed using confocal laser scanning microscopy. These RNA molecules, but not RNA lacking the A2RE sequence, were transported in granules to the distal neurites. hnRNP A2 protein was implicated as the cognate trans-acting factor: it was colocalized with RNA in cytoplasmic granules, and RNA trafficking in neurites was compromised by A2RE mutations that abrogate hnRNP A2 binding. Coinjection of antibodies to hnRNP A2 halved the number of trafficking cells, and treatment of neurons with antisense oligonucleotides also disrupted A2RE - RNA transport. Colchicine inhibited trafficking, whereas cells treated with cytochalasin were unaffected, implicating involvement of microtubules rather than microfilaments. A2RE-like sequences are found in a subset of dendritically localized mRNAs, which, together with these results, suggests that a molecular mechanism based on this cis-acting sequence may contribute to dendritic RNA localization.

A Monte Carlo simulation of the Chemorheology of epoxy-amine systems

Altmann, N. og Halley, P. J. — 2007-08-24T00:42:54Z

Amperometric nitric oxide biosensor based on the immobilization of hemoglobin on a nanometer-sized gold colloid modified Au electrode

2007-10-17T10:24:50Z

A novel reagentless NO biosensor based on hemoglobin (Hb) immobilized on nanometer-sized gold colloid particles associated with a cysteamine monolayer on gold electrode surface was presented. The experimental optimization was studied in detail. The immobilized Hb displayed an excellent electrocatalytic response to NO. The electrocatalytic currents were proportional to the NO concentration from 1.2 x 10(-8) to 5.0 x 10(-6) M and the detection limit was as low as 4.0 x 10(-9) M (S/N = 3) with good stability. Arginine, ascorbate, nitrite, uric acid, epinephrine and cystine didn't interfere with the determination of NO. The Michaelis-Menten constant (K-m) was determined to be 0.19 mM. This resulting biosensor has been applied to the direct determination of trace NO in raw blood.

Amplifying the cellular reduction potential of Streptococcus zooepidemicus

Chong, B. F. og Nielsen, L. K. — 2007-09-19T15:10:48Z

The valuable pharmaceutical polymer, hyaluronic acid, is produced industrially using the gram-positive bacterium Streptococcus zooepidemicus. Synthesis of this polymer is a significant energetic burden upon the microorganism hence the native NADH oxidase gene was cloned and overexpressed to increase the energy yield of catabolism during aerobic cultivation on glucose. Elevated NADH oxidase levels led to a decline in lactic acid generation and prevented ethanol formation, leaving acetate as the main fermentation product. Biomass yield increased due to the energy gained from the formation of acetate. Evaluation of the acetate flux control coefficient over a range of NADH oxidase expression levels revealed that acetate production was sensitive to the NADH oxidase level. However, at high NADH oxidase levels, the acetate flux was mainly influenced by another factor. The concomitant excretion of pyruvate at high NADH oxidase levels suggested that the flux through the pyruvate dehydrogenase enzyme complex was limiting the conversion of pyruvate to acetate. Published by Elsevier Science B.V.

Analysing diversity in sugarcane resistance gene analogues

2007-08-15T08:25:15Z

As resistance genes have been shown to contain conserved motifs and cluster in many plant genomes, the identification of resistance gene analogues can be used as a strategy for both the discovery of DNA markers linked to disease resistance loci and the map-based cloning of disease resistance genes. Sugarcane suffers from many important diseases and an analysis of resistance gene analogues offers a means to identify DNA markers linked to resistance loci. However, sugarcane has the most complex genome of any crop plant and initially it is important to understand the extent of resistance gene analogue diversity in the sugarcane genome before genetic analysis. We review herein how more than 100 expressed sequence tags with homology to different resistance genes have been identified in sugarcane with many mapped as single-dose restriction fragment length polymorphism markers. Importantly, some of these resistance gene analogues have been shown to be linked to disease resistance genes or disease quantitative trait loci. In an attempt to more efficiently analyse additional resistance gene analogues in sugarcane, we report on experiments aimed at investigating the molecular diversity of several resistance gene analogue families using a modified form of a technique termed Ecotilling. Using Ecotilling, we were able to rapidly detect single nucleotide polymorphisms in fragments amplified by PCR from four different resistance gene analogue families, SoRP1D, SoPTO, SoXa21 and SoHs1pro-1. An analysis of a diverse set of sugarcane varieties, including modern sugarcane cultivars and several S. officinarum and S. spontaneum clones, indicated that all amplicons, apart from SoHs1pro-1, contained significant polymorphism within the gene region studied. However, a comparison among these sugarcane clones, including between the parents of two sugarcane mapping populations, indicated that most polymorphisms were multi-dose, not single-dose, preventing their genetic map location or association with disease susceptibility or resistance from being determined.

Analysis of acute myelogenous leukemia: Preparation of samples for genomic and proteomic analyses

2007-09-19T15:23:14Z

During the last decade, several large clinical studies have demonstrated that analysis of chromosomal abnormalities is an essential basis for therapeutic decisions in patients with acute myelogenous leukemia (AML), and cytogenetic studies should now be regarded as mandatory both for routine treatment and as a part of clinical investigations in AML. However, new techniques for detailed genetic characterization and analysis of gene expression as well as protein modulation will become important in the further classification of AML subsets and the development of risk-adapted therapeutic strategies. In this context, we emphasize the importance of population-based clinical studies as a basis for future therapeutic guidelines. Such studies will then require the inclusion of patients at small clinical centers without specialized hematological research laboratories. To document a high and uniform quality of the laboratory investigations, it will be necessary to collect material for later analysis in selected laboratories. In this article, we describe current methods for collection of biological samples that can be used for later preparation of DNA, RNA, and proteins. With the use of gradient-separated AML cells, it should be possible to establish the necessary techniques for collection and handling of biological samples even at smaller centers, and complete collections from all included patients should then be possible even in population-based clinical studies.