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Average Pore Diameter (average + pore_diameter)

Distribution by Scientific Domains
Polymers and Materials Science50%

Selected Abstracts

Solvent/non-solvent sintering: A novel route to create porous microsphere scaffolds for tissue regeneration

JOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2008
Justin L. Brown
Abstract Solvent/non-solvent sintering creates porous polymeric microsphere scaffolds suitable for tissue engineering purposes with control over the resulting porosity, average pore diameter, and mechanical properties. Five different biodegradable biocompatible polyphosphazenes exhibiting glass transition temperatures from ,8 to 41°C and poly (lactide- co -glycolide), (PLAGA) a degradable polymer used in a number of biomedical settings, were examined to study the versatility of the process and benchmark the process to heat sintering. Parameters such as: solvent/non-solvent sintering solution composition and submersion time effect the sintering process. PLAGA microsphere scaffolds fabricated with solvent/non-solvent sintering exhibited an interconnected porosity and pore size of 31.9% and 179.1 ,m, respectively which was analogous to that of conventional heat sintered PLAGA microsphere scaffolds. Biodegradable polyphosphazene microsphere scaffolds exhibited a maximum interconnected porosity of 37.6% and a maximum compressive modulus of 94.3 MPa. Solvent/non-solvent sintering is an effective strategy for sintering polymeric microspheres, with a broad spectrum of glass transition temperatures, under ambient conditions making it an excellent fabrication route for developing tissue engineering scaffolds and drug delivery vehicles. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2008 [source]

Towards ideal hexagonal self-ordering of TiO2 nanotubes

PHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 5 2007
Jan M. Macak
Abstract The present work reports on key factors that influence the degree of order in anodic TiO2 nanotube layers. We show that the anodization voltage and the Ti purity are of crucial importance for the ideality of self-organization within the nanotube layers and that repeated anodization can significantly improve hexagonal ordering. Optimizing each factor significantly reduces the variation in the average pore diameter and strongly reduces the areal density of polygon ordering/packing errors. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Analysis of native and chemically modified oligonucleotides by tandem ion-pair reversed-phase high-performance liquid chromatography/electrospray ionization mass spectrometry

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 7 2003
Kenneth J. Fountain
Ion-pair reversed-phase high-performance liquid chromatography (IP-RP-HPLC) was utilized in tandem with negative-ion electrospray ionization time-of-flight mass spectrometry (ESI-TOFMS) for the analysis of native and chemically modified oligonucleotides. Separation was performed on a 1.0,×,50,mm column packed with porous C18 sorbent with a particle size of 2.5,,m and an average pore diameter of 140 Å. A method was developed which maximizes both chromatographic separation and mass spectrometric sensitivity using an optimized buffer system containing triethylamine and 1,1,1,3,3,3-hexafluoro-2-propanol with a methanol gradient. The ESI-TOFMS tuning parameters were also optimized in order to minimize in-source fragmentation and achieve the best sensitivity. Analyses of native, phosphorothioate, and guanine-rich oligonucleotides were performed by LC/MS. Detection limits were at sub-picomole levels with an average mass accuracy of 125,ppm. The described method allowed for the LC/MS analysis of oligonucleotides up to 110mer in length with little alkali cation adduction. Since sensitive detection of oligonucleotides was achieved with ultraviolet (UV) detection, we utilized a combination of UV-MS for quantitation (UV) and characterization (MS) of oligonucleotides and their failure sequence fragments/metabolites. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Control of Phase and Pore Structure of Titania Powders Using HCl and NH4OH Catalysts

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2001
Ki Chang Song
Porous titania powders were prepared by hydrolysis of titanium tetraisopropoxide (TTIP) and were characterized at various calcination temperatures by nitrogen adsorption, X-ray diffraction, and microscopy. The effect of HCl or NH4OH catalysts added during hydrolysis on the crystallinity and porosity of the titania powders was investigated. The HCl enhanced the phase transformations of the titania powders from amorphous to anatase as well as anatase to rutile, while NH4OH retarded both phase transformations. Titania powders calcined at 500°C showed bimodal pore size distributions: one was intra-aggregated pores with average pore diameters of 3,6 nm and the other was interaggregated pores with average pore diameters of 35,50 nm. The average intra-aggregated pore diameter was decreased with increasing HCl concentration, while it was increased with increasing NH4OH concentration. [source]