bluuebunny/crossref_metadata_2025_split huggingface dataset:
Enhanced chondrocyte densities on carbon nanotube composites: The combined role of nanosurface roughness and electrical stimulation
Authors: Khang Dongwoo , Park Grace E. , Webster Thomas J. 
Published: January 2008

AbstractSimultaneous incorporation of intrinsic nanosurface roughness and external electrical stimulation may maximize the regeneration of articular cartilage tissue more than on nanosmooth, electrically nonstimulated biomaterials. Here, we report enhanced functions of chondrocytes (cartilage synthesizing cells) on electrically and nonelectrically stimulated highly dispersed carbon nanotubes (CNT) in polycarbonate urethane (PCU) compared to, respectively, stimulated pure PCU. Specifically, compared to conventional longitudinal (or vertical) electrical stimulation of chondrocytes on conducting surfaces which require high voltage, we developed a lateral electrical stimulation across CNT/PCU composite films of low voltage that enhanced chondrocyte functions. Chondrocyte adhesion and long‐term cell densities (up to 2 days) were enhanced (more than 50%) on CNT/PCU composites compared to PCU alone without electrical stimulation. This study further explained why by measuring greater amounts of initial fibronectin adsorption (a key protein that mediates chondrocyte adhesion) on CNT/PCU composites which were more hydrophilic (than pure PCU) due to greater nanometer roughness. Importantly, the same trend was observed and was even significantly enhanced when chondrocytes were subjected to electrical stimulation (more than 200%) compared to nonstimulated CNT/PCU. For this reason, this study provided direct evidence of the positive role that conductive CNT/PCU films can play in promoting functions of chondrocytes for cartilage regeneration. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2008
In vitro evaluation of nanosized carbonate‐substituted hydroxyapatite and its polyhydroxyethylmethacrylate nanocomposite
Authors: Huang J. , Best S. M. , Brooks R. A. , Rushton N. , Bonfield W. 
Published: January 2008

AbstractNanometer scale carbonate‐substituted hydroxyapatite (nanoCHA) particles were prepared and examined using transmission electron microscopy, which revealed their polycrystalline nature with a rod‐like morphology (20–30 nm in width and 50–80 nm in length). In vitro cytotoxicity study showed that there was some evidence of lactate dehydrogenase (LDH) release when macrophages were in contact with high concentrations of nanoCHA particles. The levels of LDH release decreased significantly with a reduction in nanoCHA concentration. A similar trend was observed for the inflammatory cytokine TNF‐α. nanoCHA particles with high carbonate content induced a high level of TNF‐α release. Biological testing using a human osteoblast (HOB) cell model found that HOB cells were able to grow and proliferate on a nanoCHA deposited surface. Well organized actin fibers were observed for HOB cells in contact with nanoCHA particles with low carbonate content and the cell proliferation rate was higher on these particles in comparison with those of high carbonate nanoCHA particles. Therefore, low carbonate nanoCHA particles were incorporated into poly‐(2‐hydroxyethylmethacrylate) matrix to make a nanocomposite. It was found that the nanoCHA composite was hydrophilic and became rubber‐like after hydration. Both 20 wt % and 40 wt % composites were able to induce the formation of bone‐like apatite after immersion in simulated body fluid. A high bioactivity of the composite was obtained with high loading of the nanoCHA filler. These results demonstrate the potential of formulating nanocomposites for biomedical applications. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2008
In vitro oxidation of high polydimethylsiloxane content biomedical polyurethanes: Correlation with the microstructure
Authors: Hernandez Rebeca , Weksler Jadwiga , Padsalgikar Ajay , Runt James 
Published: January 2008

AbstractThe resistance to in vitro metal ion oxidation of a polydimethylsiloxane (PDMS)‐containing thermoplastic polyurethane elastomer (Elast‐Eon™) is compared with that of a polyurethane consisting of the same hard segment chemistry and content, but with aliphatic polycarbonate soft segments (PCU). Scanning electron microscopy and attenuated total reflectance Fourier transform infrared spectroscopy were used to assess changes in surface morphology and chemistry. The extent of bulk degradation was assessed indirectly by dynamic mechanical analysis and small‐angle X‐ray scattering experiments. The findings indicate that Elast‐Eon™ is more resistant to oxidation than the PCU, because of the presence of the PDMS soft segments as well as its phase separated microstructure. The PCU exhibits a rather high degree of intermixing between hard and soft segments, rendering the hard segments dissolved or trapped in the soft phase more susceptible to oxidative conditions. By contrast, we propose that the existence of a completely phase separated PDMS soft phase in Elast‐Eon™ protects the remainder of the segments from oxidation. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2008
New method for routine production of L‐[methyl‐11C]methionine: in loop synthesis
Authors: Gómez Vanessa , Gispert Juan Domingo , Amador Víctor , Llop Jordi 
Published: January 2008

AbstractA fast, clean and reproducible method for the manufacture of the radiotracer L‐[methyl‐11C]methionine is reported. The reaction at room temperature of the non‐radioactive precursor L‐homocysteine (1 mg solution in ethanol/water 50/50) with [11C]CH3I in an HPLC loop led to the formation of the desired radiotracer with a high radiochemical yield (38.4±4.1% end of synthesis) in a short production time (12 min). Radiochemical purity of the final radiotracer was 99.9±0.05%. Specific activities in the range 11–45 GBq/µmol were obtained. The presence of the undesired enantiomer (D‐[methyl‐11C]methionine) was not detected in any of the cases. Copyright © 2008 John Wiley & Sons, Ltd.
Histological analysis of achilles tendons in an overuse rat model
Authors: Glazebrook Mark A. , Wright James R. , Langman Maxine , Stanish William D. , Lee J. Michael 
Published: January 2008

AbstractThe purpose of this study was to design an animal model that induces histological changes in Achilles tendons consistent with those cited in the literature for human Achilles tendon disease. Sprague‐Dawley rats were subjected to 10° uphill treadmill running on a custom‐designed rodent treadmill and at a speed of 17 meters per minute for 1 h, five times per week, over a 12‐week treatment period. Subsequent histological analysis revealed alterations in the rat Achilles tendon that were generally consistent with those described in the literature for diseased human tendon tissues. These features include: decreased collagen fiber organization, more intense collagen staining, and increased cell nuclei numbers. Interestingly, though, immunohistochemical cell typing suggests that the observed increased cellularity does not include a significant inflammatory component but is secondary to increased numbers of endothelial cells (i.e., vascularization) and fibroblasts. These histological features likely represent a biological repair/remodeling response resulting from overuse running. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:840–846, 2008
Chemical characterization of polyol ester aviation lubricant residues
Authors: Bartl P. , Völkl C. , Kaiser M. 
Published: January 2008

AbstractThis study was conducted to evaluate the potential of pyrolysis gas chromatography/mass spectrometry in the electron impact and the chemical ionisation mode to characterize the chemical nature of solid deposits of polyol ester aviation lubricants generated in a laboratory test. Pyrolysis products can be unambiguously identified or plausibly derived using previous results on the structure of oligomeric aging products. Experience gained from model esters can easily transferred to fully formulated lubricants. The results are complemented by 13C‐NMR data and thermal analysis which elucidate the heterogeneity of the deposits. Copyright © 2008 John Wiley & Sons, Ltd.
Plant‐derived polyphenols attenuate lipopolysaccharide‐induced nitric oxide and tumour necrosis factor production in murine microglia and macrophages
Authors: Shanmugam Kirubakaran , Holmquist Lina , Steele Megan , Stuchbury Grant , Berbaum Katrin , Schulz Oliver , Benavente García Obdulio , Castillo Julián , Burnell Jim , Garcia Rivas Vernon , Dobson Geoff , Münch Gerald 
Published: January 2008

AbstractLipopolysaccharides released during bacterial infections induce the expression of pro‐inflammatory cytokines and lead to complications such as neuronal damage in the CNS and septic shock in the periphery. While the initial infection is treated by antibiotics, anti‐inflammatory agents would be advantageous add‐on medications. In order to identify such compounds, we have compared 29 commercially available polyphenol‐containing plant extracts and pure compounds for their ability to prevent LPS‐induced up‐regulation of NO production. Among the botanical extracts, bearberry and grape seed were the most active preparations, exhibiting IC50 values of around 20 μg/mL. Among the pure compounds, IC50 values for apigenin, diosmetin and silybin were 15, 19 and 12 μM, in N‐11 murine microglia, and 7, 16 and 25 μM, in RAW 264.7 murine macrophages, respectively. In addition, these flavonoids were also able to down‐regulate LPS‐induced tumour necrosis factor production. Structure‐activity relationships of the flavonoids demonstrated three distinct principles: (i) flavonoid‐aglycons are more potent than the corresponding glycosides, (ii) flavonoids with a 4′‐OH substitution in the B‐ring are more potent than those with a 3′‐OH‐4′‐methoxy substitution, (iii) flavonoids of the flavone type (with a C2=C3 double bond) are more potent than those of the flavanone type (with a at C2‐C3 single bond).
MRI in ocular drug delivery
Authors: Li S. Kevin , J. Lizak Martin , Jeong Eun‐Kee 
Published: January 2008

AbstractConventional pharmacokinetic methods for studying ocular drug delivery are invasive and cannot be conveniently applied to humans. The advancement of MRI technology has provided new opportunities in ocular drug‐delivery research. MRI provides a means to non‐invasively and continuously monitor ocular drug‐delivery systems with a contrast agent or compound labeled with a contrast agent. It is a useful technique in pharmacokinetic studies, evaluation of drug‐delivery methods, and drug‐delivery device testing. Although the current status of the technology presents some major challenges to pharmaceutical research using MRI, it has a lot of potential. In the past decade, MRI has been used to examine ocular drug delivery via the subconjunctival route, intravitreal injection, intrascleral injection to the suprachoroidal space, episcleral and intravitreal implants, periocular injections, and ocular iontophoresis. In this review, the advantages and limitations of MRI in the study of ocular drug delivery are discussed. Different MR contrast agents and MRI techniques for ocular drug‐delivery research are compared. Ocular drug‐delivery studies using MRI are reviewed. Copyright © 2008 John Wiley & Sons, Ltd.
An investigation of human brain tumour lipids by high‐resolution magic angle spinning 1H MRS and histological analysis
Authors: Opstad Kirstie S. , Bell B. Anthony , Griffiths John R. , Howe Franklyn A. 
Published: January 2008

AbstractNMR‐visible lipid signals detected in vivo by 1H MRS are associated with tumour aggression and believed to arise from cytoplasmic lipid droplets. High‐resolution magic angle spinning (HRMAS) 1H MRS and Nile Red staining were performed on human brain tumour biopsy specimens to investigate how NMR‐visible lipid signals relate to viable cells and levels of necrosis across different grades of glioma. Presaturation spectra were acquired from 24 adult human astrocytoma biopsy samples of grades II (8), III (2) and IV (14) using HRMAS 1H MRS and quantified using LCModel to determine lipid concentrations. Each biopsy sample was then refrozen, cryostat sectioned, and stained with Nile Red, to determine the number of lipid droplets and droplet size distribution, and with Haematoxylin and Eosin, to determine cell density and percentage necrosis. A strong correlation (R = 0.92, P < 0.0001) was found between the number of Nile Red‐stained droplets and the ∼1.3 ppm lipid proton concentration by 1H MRS. Droplet sizes ranged from 1 to 10 µm in diameter, and the size distribution was constant independent of tumour grade. In the non‐necrotic biopsy samples, the number of lipid droplets correlated with cell density, whereas in the necrotic samples, there were greater numbers of droplets that showed a positive correlation with percentage necrosis. The correlation between 1H MRS lipid signals and number of Nile Red‐stained droplets, and the presence of lipid droplets in the non‐necrotic biopsy specimens provide good evidence that the in vivo NMR‐visible lipid signals are cytoplasmic in origin and that formation of lipid droplets precedes necrosis. Copyright © 2008 John Wiley & Sons, Ltd.
Preparation and characterization of thermally stable poly(amide‐urea)s functionalized with anthraquinone chromophore
Authors: Mehdipour‐Ataei Shahram , Bahri‐Laleh Naeemeh 
Published: January 2008

AbstractTwo new diamines containing bulky anthraquinone pendant units were prepared via reactions of 1‐ and 2‐aminoanthraquinone with 3,5‐dinitrobenzoylchloride and a subsequent reduction of their nitro groups. A novel series of highly organosoluble poly(amide‐urea)s were synthesized from the reactions of the prepared diamines with various commercially available diisocyanates via a step‐growth addition reaction process in N‐methyl‐2‐pyrrolidone (NMP). The effects of two factors (time and temperature) on the reaction were studied to optimize the conditions for the preparation of high molecular weight polymers. All poly(amide‐urea)s were characterized by Fourier Transform Infrared (FTIR) and 1H‐nuclear magnetic resonance (NMR) spectroscopies and elemental analysis. The resulting poly(amide‐urea)s had inherent viscosities in the range of 0.54–0.73 dl/g. They exhibited excellent solubility in polar solvents. The temperature for 10% weight loss of the polymers in air was all above 285°C, their residues were more than 36% at 700°C in air, and their Tg values were in the range of 148–190°C. According to the wide‐angle X‐ray diffraction (WAXD), the polymers were almost amorphous. The optical properties of poly(amide‐urea)s measured by ultraviolet–visible (UV–Vis) spectroscopy showed absorption maxima at 303–429 nm. Copyright © 2008 John Wiley & Sons, Ltd.
Subunit–subunit interactions in the human 26S proteasome
Authors: Chen Chuan , Huang Caoxin , Chen Shouhui , Liang Jie , Lin Wenbo , Ke Guifen , Zhang Hongxin , Wang Bing , Huang Jian , Han Zeguang , Ma Lixin , Huo Keke , Yang Xiaoming , Yang Pengyuan , He Fuchu , Tao Tao 
Published: January 2008

AbstractUbiquitin‐dependent proteolysis is mediated by the proteasome. To understand the structure and function of the human 26S proteasome, we cloned complete ORFs of 32 human proteasome subunits and conducted a yeast two‐hybrid analysis of their interactions with each other. We observed that there are 114 interacting‐pairs in the human 26S proteasome. About 10% (11/114) of these interacting‐pairs was confirmed by the GST‐pull down analysis. Among these observed interacting subunits, 58% (66/114) are novel and the rest 42% (48/114) has been reported previously in human or in other species. We observed new interactions between the 19S regulatory particle and the β‐rings of the 20S catalytic particle and therefore proposed a modified model of the 26S proteasome.
Natural orbital functional description of van der Waals interactions: A case study of the effect of the basis set for the helium dimer
Authors: Piris Mario , Lopez Xabier , Ugalde Jesus M. 
Published: January 2008

AbstractWe report on natural orbital functional calculations of the potential energy curve of the helium dimer. The performance of the recently proposed natural orbital functional (Piris et al. J Chem Phys 2007, 126, 214103) for the treatment of van der Waals interactions is assessed with respect to the increase of the number functions of the augmented correlation consistent polarized valence basis set series. Satisfactory converged towards the experimental equilibrium distance and binding energy is observed with the increase of the number of functions of the basis set. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Water flow through nanopore
Authors: Di Leo Julio Marañón , Marañón Julio 
Published: January 2008

AbstractA molecular dynamics simulation of water flow through a prismatic surface of van der Waals particles at 300 K is reported. The application of different pressure gradients to a water produces a large spectrum of average velocities from Poiseuille to turbulent flow. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Laser ablation synthesis of phosphorus sulphides, selenides and ternary PpSqSer clusters from various precursors
Authors: Houška Jan , Alberti Milan , Havel Josef 
Published: January 2008

AbstractLaser ablation (LA) synthesis with simultaneous time‐of‐flight mass spectrometric (TOF MS) analysis was used to examine the formation and composition of ternary PpSqSer clusters. Clusters formed by LA of various precursors are singular, binary and ternary. Formation of negative or positive singly charged Pp, Sq and Ser clusters, where P (p = 1–249), P (p = 1–191), S (q = 1–15), S (q = 1–12), Se (r = 1–8) and Se (r = 1–9), was identified. High numbers of binary PpSq, SqSer (35) or ternary PpSqSer (138) clusters were formed by LA synthesis from the various mixtures. Most of the ternary PpSqSer clusters were formed either from a mixture of P4S3 with selenium (grey) or from a mixture of SeS2 with red phosphorus. In total, 138 new ternary PpSqSer clusters were identified. The conditions for the formation of such possible prospective nano‐materials are given. Copyright © 2008 John Wiley & Sons, Ltd.
Vacuum: a void full of questions
Authors: Paparazzo Ernesto 
Published: January 2008

AbstractThis paper discusses views of vacuum proposed by Greek philosophers in the time span ranging from the 5th century B.C. to the 6th century A.D. The Eleatic Melissus (5th century B.C.) denied the existence of vacuum. The Early Atomist Leucippus, his followers and Epicurus asserted that the full (matter) and the empty (vacuum) are the irreducible elements of the universe. While the Early Atomists emphasized the metaphysical status of vacuum, which they defined as that which is ‘the nothing’ or ‘the non‐existent’, Epicurus was mostly concerned with stating that it was a sort of fluid medium with an ‘intangible nature’, which allowed material objects to move within it by yielding to them. Plato held that a vacuum does not exist, apart from small interstices in matter. Aristotle rejected the existence of both vacuum and the motion of a body in it. Also, the Stoics denied its existence, except outside the cosmos. These philosophical views are compared with the notion of a vacuum relevant to a typical surface science experiment. Copyright © 2008 John Wiley & Sons, Ltd.
Spectroscopic investigations of the role of Ge in modifying the Si to SiC conversion process
Authors: Pezoldt Jörg , Nader Richard , Zgheib Charbel , Ecke Gernot , Pieterwas Ralph , Stauden Thomas , Wöhner Thomas , Masri Pierre 
Published: January 2008

AbstractThe influence of Ge on the conversion process of Si to SiC was studied by depositing Ge and C on Si(111) followed by a stepwise annealing procedure. After the annealing step, the carbon deposited on the surface was completely converted into SiC. In the case of Ge predeposition, the SiC amount detected by XPS, AES and ellipsometry was lower compared to the reference sample in which no Ge was predeposited on the Si(111) surface. Therefore, Ge lowers the probability of SiC formation in the early stages. During the conversion process, Ge diffuses into the Si substrate and is mainly located near the SiCSi interface with a concentration of around 2.5–3%. As a result of a complex alloying process promoted by interdiffusion of C and Ge as well as SiC nucleation, a thin 3C‐SiC layer is formed on top of a Si1−xGex buffer layer. Copyright © 2008 John Wiley & Sons, Ltd.
Characterization of surface oxide layers formed on FeAl alloys by annealing under different atmospheres
Authors: Suzuki Shigeru , Yamamoto Takamichi , Shinoda Kozo , Sato Shigeo 
Published: January 2008

AbstractXPS and SIMS were used for characterizing the surface oxide layers formed on FeAl alloys during annealing under atmospheres with different partial pressures of oxygen, which were controlled by H2O/H2 ratios in the gas. The XPS results showed that an aluminum oxide (Al2O3) layer was formed on the surfaces of samples annealed at a high temperature under a low partial pressure of oxygen, while such a layer was not formed on the surfaces of samples annealed under a high partial pressure of oxygen. SIMS depth profiles showed that the surfaces of samples annealed at high temperatures under a low partial pressure of oxygen were covered with a thin Al2O3 layer of approximately 50 nm thickness. It was also shown that oxygen penetrated the samples annealed under a high partial pressure of oxygen, and the depth profile of oxygen was correlated with that of aluminum. This indicates that internal oxidation of aluminum occurs in the samples annealed under a high partial pressure of oxygen. Grazing‐incidence X‐ray diffraction (GIXD) was also employed for analyzing the structure of the Al2O3 layer formed on the surface of samples annealed under a low partial pressure of oxygen. Copyright © 2008 John Wiley & Sons, Ltd.
Monte Carlo computations of the electron backscattering coefficient for bulk targets and surface thin films
Authors: Dapor Maurizio 
Published: January 2008

AbstractMonte Carlo computations of the electron backscattering coefficient as a function of the primary energy in the range 500 eV–5 keV for several bulk targets (Al, Si, Cr, Ni, Cu, Ge, Au) are provided. Monte Carlo simulated backscattering coefficients from several surface thin layers are also provided as a function of the electron primary energy and film thicknesses. While the elastic scattering cross‐sections have been calculated by the relativistic partial wave expansion method, the stopping power data utilized by the Monte Carlo code are taken from the literature. Copyright © 2008 John Wiley & Sons, Ltd.
Aussteifung von Gebäudehüllen durch randverklebte Glasscheiben
Authors: Wellershoff Frank 
Published: January 2008

AbstractDas Streben nach immer transparenteren Gebäudehüllen mit immer filigraneren Tragstrukturen weckt den Wunsch, die Verglasung als aussteifendes Element zu nutzen und Kräfte in der Scheibenebene abzutragen. Besonders geeignet erscheinen hierfür Stabgitterschalen mit viereckigen Maschen. Bei diesem Tragwerkstyp werden ebene oder gekrümmte Flächen durch ein Netz aus Stäben gebildet. Zur Minimierung der Stabquerschnitte und der Montagekosten können die Stäbe in der Schalenebene gelenkig aneinander geschraubt werden. Nach dem heutigen Stand der Technik wird dieser Stabgitterschalentyp durch diagonale Zugstäbe oder vorgespannte Seile in der Schalenebene stabilisiert. Diese Diagonalelemente könnten entfallen, wenn die Aussteifung von der Verglasung übernommen würde.Bei dem hier betrachteten System werden die Verglasungselemente als Schubfelder aktiviert. Hierzu werden die Glasscheiben umlaufend mit den viereckigen Stabgittermaschen verklebt. Für dieses System wurden Details konzipiert und das Tragverhalten der Anschlüsse sowie der Glasscheiben zwischen den Gittermaschen und der Verglasung untersucht und Bemessungsmodelle entwickelt. Diese berücksichtigen die Verbundwirkung von Verbundglasscheiben und die Interaktion von Aussteifungskräften in der Scheibenebene mit den Plattenbelastungen senkrecht zur Scheibenebene.