Australian Institute for Bioengineering and Nanotechnology Publications - UQ eSpace

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

2007-09-19T00:00:00Z

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 modeling of the formation and migration of monovacancies in Ti2AlC

2011-03-22T00:00:00Z

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

2007-08-15T00:00:00Z

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 bioinspired route to various siliceous vesicular structures

2011-10-18T00:00:00Z

A biomarker panel to discriminate between systemic inflammatory response syndrome and sepsis and sepsis severity

2011-03-24T00:00:00Z

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

2007-08-15T00:00:00Z

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.

Absence of rejection after human liver orthotopic liver transplantation (OLT) is associated with leukocyte apoptosis, increased lymphocyte activation and higher donor cell chimerism

2011-03-09T08:36:31Z

Absorption of low molecular weight penetrants by a thermoplastic polyimide

2008-06-10T00:00:00Z

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 case in variant in cow's milk is atherogenic

2007-08-15T00:00:00Z

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

2009-04-17T00:00:00Z

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

2009-02-13T00:00:00Z

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 cell migration device that maintains a defined surface with no cellular damage during wound edge generation

2009-09-04T00:00:00Z

Studying the rate of cell migration provides insight into fundamental cell biology as well as a tool to assess the functionality of synthetic surfaces and soluble environments used in tissue engineering. The traditional tools used to study cell migration include the fence and wound healing assays. In this paper we describe the development of a microchannel based device for the study of cell migration on defined surfaces. We demonstrate that this device provides a superior tool, relative to the previously mentioned assays, for assessing the propagation rate of cell wave fronts. The significant advantage provided by this technology is the ability to maintain a virgin surface prior to the commencement of the cell migration assay. Here, the device is used to assess rates of mouse fibroblasts (NIH 3T3) and human osteosarcoma (SaOS2) cell migration on surfaces functionalized with various extracellular matrix proteins as a demonstration that confining cell migration within a microchannel produces consistent and robust data. The device design enables rapid and simplistic assessment of multiple repeats on a single chip, where surfaces have not been previously exposed to cells or cellular secretions.

Achieving maximum photo-oxidation reactivity of Cs(0.68)Ti(1.83)O(4-x)N(x) photocatalysts through valence band fine-tuning

2011-09-25T00:00:00Z

A clinical overview of WT1 gene mutations

Little, M. og Wells, C. — 2011-03-09T00:00:00Z

Mutations in the WT1 gene were anticipated to explain the genetic basis of the childhood kidney cancer, Wilms' tumour (WT). Six years on, we review 100 reports of intragenic WT1 mutations and examine the accompanying clinical phenotypes. While only 5% of sporadic Wilms' tumours have intragenic WT1 mutations, >90% of patients with the Denys-Drash syndrome (renal nephropathy, gonadal anomaly, predisposition to WT) carry constitutional intragenic WT1 mutations. WT1 mutations have also been reported in juvenile granulosa cell tumour, non-asbestos related mesothelioma, desmoplastic small round cell tumour and, most recently, acute myeloid leukemia.

A cluster of oppositely imprinted transcripts at the Gnas locus in the distal imprinting region of mouse chromosome 2

2011-03-09T00:00:00Z

Imprinted genes tend to occur in clusters. We have identified a cluster in distal mouse chromosome (Chr) 2, known from early genetic studies to contain both maternally and paternally imprinted, but unspecified, genes. Subsequently, one was identified as Gnas, which encodes a G protein α subunit, and there is clinical and biochemical evidence that the human homologue GNAS1, mutated in patients with Albright hereditary osteodystrophy, is also imprinted. We have used representational difference analysis, based on parent-of-origin methylation differences, to isolate candidate imprinted genes in distal Chr 2 and found two oppositely imprinted genes, Gnasxl and Nesp. Gnasxl determines a variant G protein α subunit associated with the trans-Golgi network and Nesp encodes a secreted protein of neuroendocrine tissues. Gnasxl is maternally methylated in genomic DNA and encodes a paternal-specific transcript, whereas Nesp is paternally methylated with maternal-specific expression. Their reciprocal imprinting may offer insight into the distal Chr 2 imprinting phenotypes. Remarkably, Gnasxl, Nesp, and Gnas are all part of the same transcription unit; transcripts for Gnasxl and Nesp are alternatively spliced onto exon 2 of Gnas. This demonstrates an imprinting mechanism in which two oppositely imprinted genes share the same downstream exons.

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

2007-08-14T00:00:00Z

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

2007-08-13T00:00:00Z

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 single-walled carbon nanotube purification techniques using Raman spectroscopy

2011-09-10T00:00:00Z

Raman spectroscopy has been utilized to show the increase of single-walled carbon nanotubes (SWCNTs) content in commercial grade samples synthesized by the chemical vapour deposition (CVD) technique with a minimization of impurities using both hydrochloric acid treatment and surfactant purification. Surfactant purification methods proved to be the most effective, resulting in a three-fold increase in the percentage of SWCNTs present in the purified product as determined by Raman spectroscopy.

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. — 2007-08-13T00:00:00Z

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 comparative study of the SET-LRP of oligo(ethylene oxide) methyl ether acrylate in DMSO and in H2O

2013-01-06T00:31:01Z

A comparative study on liquid phase alkylation of 2-methylnaphthalene with long chain olefins using different solid acid catalysts

2012-10-16T00:00:00Z

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

2008-03-18T00:00:00Z

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 investigation of influences of NO and O2 on N2O-SCR by CH4 over Fe-USY zeolite

2010-04-06T00:00:00Z

A comprehensive study of deep catalytic oxidation of benzene, toluene, ethyl acetate, and their mixtures over Pd/ZSM-5 catalyst: Mutual effects and kinetics

2010-05-23T00:00:00Z

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

Wang, S. B. og Lu, G. Q. — 2007-08-13T00:00:00Z

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.

A convenient approach to synthesize silver nanoshell covered functionalized polystyrene beads: A substrate for surface enhanced Raman scattering

2010-01-15T00:00:00Z

The synthesis of ultra-thin silver nanoshell on anionic polystyrene bead has been reported from specific silver precursor [Ag(NH3)2]+ primarily through ion exchange mechanism. The particles were characterized by SEM, EDX, XPS and XRD analysis. Finally, the particles were exploited as a solid substrate for surface enhanced Raman scattering study using crystal violet as a Raman probe.

A convenient synthesis of 1-[6-fluoro-(2S)-3H,4H-dihydro-2H-2-chromenyl](1R)-1,2-ethanediol and 1-[6-fluoro-(2R)-3H,4H-dihydro-2H-2-chromenyl](1R)-1,2-ethanediol

2011-09-11T00:00:00Z

Activity of three sorghum pathogenesis related class 10 protein gene promoters

2010-02-25T00:00:00Z

Adatom CCV Auger rates via the local density of states

2008-01-25T00:00:00Z

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

2008-04-30T00:00:00Z

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 defined medium and substrate for expansion of human mesenchymal stromal cell progenitors that enriches for osteo- and chondrogenic precursors

2011-02-06T00:00:00Z

A degradable biopolymer with tunable modulus for control of human bone marrow mesenchymal stem cells

2010-10-12T00:00:00Z

A density functional theory study of CO2 and N-2 adsorption on aluminium nitride single walled nanotubes

2010-12-05T00:00:00Z

A density functional theory study on CO2 capture and activation by graphene-like boron nitride with boron vacancy

2011-05-23T00:00:00Z

A designed biosurfactant for reversible emulsification of crude oil

2010-07-05T00:00:00Z

A designed biosurfactant protein for switchable foam control

Middelberg, Anton P. J. og Dimitrijev-Dwyer, Mirjana — 2012-03-08T00:00:00Z

A designed nanoporous material for phosphate removal with high efficiency

2011-03-13T00:11:57Z

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

2007-08-23T00:00:00Z

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

Hannan, Nicholas R.F. og Wolvetang, Ernst J. — 2009-04-07T00:00:00Z

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

2007-08-15T00:00:00Z

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

2007-09-19T00:00:00Z

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 — 2007-08-13T00:00:00Z

Adsorption and dissociation of ammonia borane outside and inside single-walled carbon nanotubes: A density functional theory study

2012-03-20T00:00:00Z

Adsorption and release of biocides with mesoporous silica nanoparticles

2012-02-26T05:51:25Z

Adsorption and structural properties of ordered mesoporous alumina synthesized in the presence of F127 block copolymer

2012-10-16T00:00:00Z

Adsorption characteristics of carbonized bark for phenol and pentachlorophenol

Edgehill, RU og Lu, GQ — 2007-08-13T00:00:00Z

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 — 2007-08-13T00:00:00Z

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

2007-08-14T00:00:00Z

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 myoglobin over mesoporous silica molecular sieves: Pore size effect and pore-filling model

2012-10-16T00:00:00Z

The present work describes the adsorption of myoglobin over mesoporous materials with different pore diameters (SBA-15 and MCM-41) from buffered solutions. The Langmuir-type adsorption of myoglobin occurs with monolayer coverage on the inner surface of the mesoporous channels. These adsorbents were thoroughly characterized by X-ray diffraction, nitrogen adsorption/desorption and FT-IR spectroscopy before and after the myoglobin adsorption. The amount of myoglobin adsorbed significantly depends on the specific pore volume and/or the pore diameter of the mesoporous silica adsorbents. These experimental results were analyzed using pore-filling models, suggesting that myoglobin molecules are well-packed in the SBA-15 pores. FT-IR spectra before and after the adsorption confirm the structural stability of the adsorbed myoglobin.