bluuebunny/crossref_metadata_2025_split huggingface dataset:
Age‐dependent changes in the nervous and endocrine control of the thymus
Authors: Hannestad Jonas , Monjil Diego F. , Díaz‐Esnal Belén , Cobo Juan , Vega José A. 
Published: January 2004

AbstractThe immune system, especially the thymus, undergoes age‐related modifications leading to structural and functional changes in the lymphoid organs and immunocompetent cells. Nevertheless, the consequences of thymic involution in the peripheral pool of T‐cells are still a matter of controversy. The control of the thymic function is very complex and involves intrathymic signals, the autonomic nervous system, and the endocrine system. Both thymocytes and thymic stromal cells express receptors for a wide range of hormones, as well as for neurotransmitters and neuropeptides, thus affecting thymocytes maturation. This review summarizes the age‐dependent variations in the extrathymic components of the thymic microenvironment, i.e., vegetative nerves and hormones, and the possible effects of those changes in the immune function. Microsc. Res. Tech. 63:94–101, 2004. © 2004 Wiley‐Liss, Inc.
Simultaneous fixation using glutaraldehyde and osmium tetroxide or potassium ferricyanide‐reduced osmium for the preservation of monogenean flatworms: An assessment for Merizocotyle icopae
Authors: Cribb Bronwen , Armstrong Wendy , Whittington Ian 
Published: January 2004

AbstractSimultaneous fixation was investigated for a marine organism: the monogenean flatworm ectoparasite Merizocotyle icopae. Four protocols for primary fixation were compared: 3% glutaraldehyde alone in 0.1M cacodylate buffer for a minimum of 2 hours; 1% glutaraldehyde in combination with 1% osmium tetroxide, both in 0.1M cacodylate buffer, until tissues darkened (5–20 minutes); 1% glutaraldehyde in 0.1M cacodylate buffer in combination with 0.5% potassium ferricyanide‐reduced osmium until tissues darkened (5–20 minutes); 1% glutaraldehyde in combination with 1% osmium tetroxide, both in 0.1M cacodylate buffer, for 30 minutes. The study confirms that the standard method for transmission electron microscopic fixation (first listed protocol) routinely applied to platyhelminths is optimal for ultrastructural preservation, but some simultaneous fixation methods (second and third listed protocols) are acceptable when rapid immobilization is needed. Scanning electron microscopic preparations may be improved using simultaneous primary fixation. Microsc. Res. Tech. 63:102–110, 2004. © 2004 Wiley‐Liss, Inc.
Cryo‐sectioning and chemical‐fixing ultramicrotomy techniques for imaging rubber latex particle morphology
Authors: Subramaniam Nadaraja , Simpson Anne , Monteiro Michael J. , Shaffer Olga , Fellows Christopher M. , Gilbert Robert G. 
Published: January 2004

AbstractTwo methods adapted from biological microscopy are described for a new application in imaging the morphology of rubbery latex particles. In the first method, a drop of latex is frozen in liquid nitrogen, sectioned with a diamond knife and vapour‐stained with osmium tetroxide, then viewed by transmission electron microscopy. When applied to latexes made by emulsion polymerization of methyl methacrylate in a natural rubber latex seed, inclusions are clearly visible. A chemical fixation method is then described for imaging the morphology of such rubbery latex particles. Glutaraldehyde is added to the latex, followed by osmium tetroxide. The sample is then dehydrated in ethanol, epoxy resin added, and the sample cured, ultramicrotomed, and imaged with transmission electron microscopy. An inclusion morphology is again clearly seen. Microsc. Res. Tech. 63:111–114, 2004. © 2004 Wiley‐Liss, Inc.
Imaging the cell surface: Argon sputtering to expose inner cell structures
Authors: De Stasio Gelsomina , Frazer Bradley H. , Girasole Marco , Wiese Lisa M. , Krasnowska Ewa K. , Greco Giulia , Serafino Annalucia , Parasassi Tiziana 
Published: January 2004

AbstractEstablished microscopies such as Scanning Electron Microscopy (SEM) and more recent developments such as Atomic Force Microscopy (AFM) and X‐ray Photo‐Electron Emission spectroMicroscopy (X‐PEEM) can only image the sample surface. We present an argon sputtering method able to progressively expose inner cell structures without apparent damage. By varying the sputtering time, the structure of cell cytoskeleton, vesicles, mitochondria, nuclear membrane, and nucleoli can be imaged. We compared images obtained with confocal fluorescence microscopy, transmission electron microscopy (TEM), SEM, and X‐PEEM on similar samples after argon sputtering, then confirmed the similarity of reference intracellular structures, including cytoskeleton fibers, cell‐cell and cell‐substrate adhesion structures, and secretory vesicles. We conclude that the sputtering method is a new valuable tool for surface sensitive microscopies. Microsc. Res. Tech. 63:115–121, 2004. © 2004 Wiley‐Liss, Inc.
Methods for determining the composition of nasal fluid by X‐ray microanalysis
Authors: Vanthanouvong Viengphet , Roomans Godfried M. 
Published: January 2004

AbstractThe nasal fluid is an easily accessible form of airway surface liquid. The objective of this study was to find a technically easy and reproducible method for sampling and analysis of this fluid. In a pilot study, several methods to carry out X‐ray microanalysis of sub‐microliter droplets were compared. Acceptable results were obtained with several of these methods (pipeting on filter paper or analysis of frozen‐hydrated droplets at low temperature). Nasal fluid was collected from the inferior turbinate with a micropipette after occlusion of a nostril for 5–10 minutes. Ion concentrations in nasal fluid from six control subjects were (in mM, mean ± standard error): sodium (Na) 127 ± 6, chloride (Cl) 140 ± 7, potassium (K) 27 ± 3, and calcium (Ca) 5 ± 1. This sampling method proved difficult to apply to cystic fibrosis (CF) patients because of the viscous quality of their nasal secretion. Therefore, an alternative method was devised. Sephadex G‐25, ion exchange beads were mounted on double‐sided tape, which was stuck on a filter paper as support. The filter paper was applied for 10 minutes to the nostril of a subject, and kept loosely in place. During the exposure period, the nasal fluid equilibrates with the beads. After removal of the filter paper with the beads from the nostril, the beads were rinsed with a hydrophobic volatile silicone oil to remove excess nasal fluid, dried, and analyzed. This method of collection is not cumbersome for the subject and gives results similar to those obtained by the direct collection method: Na 142 ± 28 mM, Cl 150 ± 36 mM, K 43 ± 10 mM (mean and standard error of four determinations). Small differences between the filter method and the bead method can be explained by the fact that the filter method measured total nasal fluid, whereas the bead method measures predominantly the fluid component. Subjects suffering from mild respiratory illness or rhinitis had higher values for Na, K, and Cl in their nasal fluid. Microsc. Res. Tech. 63:122–128, 2004. © 2004 Wiley‐Liss, Inc.
Zeros of eigenfunctions of a class of generalized second order differential operators on the Cantor set
Authors: Freiberg Uta , Löbus Jörg‐Uwe 
Published: January 2004

AbstractGeneralized second order differential operators of the form $ {d \over {d \mu}} {d \over {dx}} $ when μ is a selfsimilar measure whose support is the classical Cantor set are considered. The asymptotic distribution of the zeros of the eigenfunctions is determined. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The canonical solution operator of $ {\bar \partial } $ on weighted spaces with holomorphic coefficients
Authors: Knirsch Wolfgang 
Published: January 2004

AbstractOn weighted spaces with strictly plurisubharmonic weightfunctions the canonical solution operator of $ {\bar \partial } $ and the $ {\bar \partial } $‐Neumann operator are bounded. In this paper we find a class of strictly plurisubharmonic weightfunctions with certain growth conditions, so that they are Hilbert‐Schmidt operators between weighted spaces with different weightfunctions, if they are restricted to forms with holomorphic coefficients. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nonlinear artificial boundary conditions for the Navier‐Stokes equations in an aperture domain
Authors: Nazarov Sergueï A. , Specovius‐Neugebauer Maria , Videman Juha H. 
Published: January 2004

AbstractWe consider the Dirichlet problem for the stationary Navier‐Stokes system in a plane domain Ω, with two angular outlets to infinity. It is known that, under appropriate decay and smallness assumptions, this problem admits solutions with main asymptotic terms in Jeffrey‐Hamel form. We will approach these solutions by constructing an approximating problem in the domain ΩR, which is the intersection of Ω with a sufficiently large circle. The main difficulty, in contrast to the corresponding linear problem, arises from the fact that the main asymptotic term is not known explicitly. Here, we create nonlinear, but local, artificial boundary conditions which involve second order differential operators on the truncation arcs. Unlike for the analogous three‐dimensional exterior problem, we are able to show the existence of weak solutions to the approximating problem without smoothness nor smallness assumptions. For small data, we prove that the solutions of the approximating problem are unique and regular. Finally, we reach the main goal of this work, i.e. we obtain error estimates in weighted Hölder spaces which are asymptotically precise as R tends to infinity. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spaces of Bessel‐potential type and embeddings: the super‐limiting case
Authors: Neves Júlio S. 
Published: January 2004

AbstractWe consider Bessel‐potential spaces modelled upon Lorentz‐Karamata spaces and establish embedding theorems in the super‐limiting case. In addition, we refine a result due to Triebel, in the context of Bessel‐potential spaces, itself an improvement of the Brézis‐Wainger result (super‐limiting case) about the “almost Lipschitz continuity” of elements of H1+n/pp (ℝn). These results improve and extend results due to Edmunds, Gurka and Opic in the context of logarithmic Bessel potential spaces. We also give examples of embeddings of Besselpotential type spaces which are not of logarithmic type. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stereologische Analyse und Modelierung von Objektverteilungen aus Schnittbildern
Authors: Gegner J. , Henninger C. , Öchsner A. 
Published: January 2004

AbstractDas Gefüge von Werkstoffen kann mittels geeigneter Deskriptoren quantitativ charakterisiert werden. Eine solche Beschreibung erlaubt auch die Erstellung repräsentativer Modelle für die Simulation von Festkörperreaktionen. In der vorliegenden Arbeit werden diskontinuierliche Dualphasengefüge analysiert. Es wird ein mathematisches Korrekturverfahren zur Berechnung der wahren Größenverteilung kugelförmiger Objekte aus Schnittbildern abgeleitet. Ein Rechnerexperiment bestätigt die Anwendbarkeit dieser Methode. Nach entsprechender Analyse der Objektabstände können auch dreidimensionale Ersatzverteilungen berechnet werden. Ein stochastisches Suchverfahren, das auf einer Verbesserungsheuristik beruht, ermöglicht die Berücksichtigung höherer Nachbarschaftsordnungen. Das neue hybride Modellierungswerkzeug wird anhand eines praktischen Beispiels vorgestellt.
The influence of manganese addition on mechanical properties of commercial Al‐4Mg casting alloys
Authors: Bayram A. 
Published: January 2004

AbstractThe aim of this study was to investigate the mechanical properties of Al‐Mg‐Si alloys aged to peak hardness with different dispersoid volume fraction. It was found that the tensile strength increases with dispersoid content, for alloys having similar ductility. The effect of an increasingly triaxial stress state on a fracture strain above mentioned alloys were measured using a series of notched tensile specimens whose notch root radius of curvature was changed. The alloy ductility was found to increase with dispersoid content and root radius and to decrease with increased stress triaxiality. The fracture toughness of these alloys was determined as a function of dispersoid content and notch root radius of curvature. It was observed that the fracture toughness increased as the dispersoid content and the notch root radius increased. scanning electron microscope analysis of the fracture surfaces revealed that fracture mechanism was transgranular fracture with dimples formation. It is argued that optimum mechanical properties in these alloys can be achieved at about 0.5 % Mn content.
Die Anrisslebensdauerabschätzung unter Berücksichtigung des statistischen Größeneinflusses am Beispiel der AlMgSi0,7‐Legierung
Authors: Bazios I. , Gudladt H.‐J. 
Published: January 2004

AbstractDie Abschätzung der Anrisslebensdauer wird unter Berücksichtigung des statistischen und technologischen Größeneinflusses im Rahmen eines analytischen Modells vorgestellt. Zur Verifikation dieses Modells werden Ergebnisse aus ein‐ und mehrstufigen Ermüdungsversuchen an ungekerbten und gekerbten Proben aus der mittelfesten AlMgSi‐Aluminiumlegierung AA6009 herangezogen.
Comparison of different methods for presenting variable amplitude loading fatigue results
Authors: Lagoda T. , Sonsino C. M. 
Published: January 2004

AbstractThis paper discusses eight methods for presenting fatigue test results for variable amplitude loading and their comparison with constant amplitude loading. While the maximum amplitude method compares constant and variable amplitude loading results by the Woehler and Gassner curves, all other seven methods try to transform the variable amplitude results into the Woehler curve by applying different equations. The advantage of the maximum amplitude method is the direct comparison of the maximum amplitude of the spectrum with the yield strength and with the high‐cycle fatigue strength, which is an important step in structural design. Among the other methods, the best results were obtained by following: most damaging, half damage and mean damage amplitudes. However, the presentation of constant and variable amplitude results by these methods in one scatter band is possible only when the real damage sum is close to D = 1.0.
Improvement of Mechanical Properties of Self Setting Calcium Phosphate Bone Cements Mixed With Different Metal Oxides
Authors: Gbureck U. , Spatz K. , Thull R. 
Published: January 2004

AbstractCalcium phosphate cements (CPC), based on multicomponent powder mixtures of calcium orthophosphates with medium particle sizes in the region of 1 ‐ 20 μm, set isothermally in an aqueous environment to form hydroxyapatite (HA). HA cement reactants include tetracalcium phosphate (TTCP), tricalcium phosphate (TCP), dicalcium phosphate anhydrate (DCPA), dicalcium phosphate dihydrate (DCPD), monocalcium phosphate (MCPA) or octacalcium phosphate (OCP). The aim of this study was to improve the mechanical performance of TTCP / DCPA cement by adding several metal oxides to tetracalcium phosphate during the fabrication process. Cements based on tetracalcium phosphate mixed with silica or titanium oxide showed significant increases in compressive strength, approximately 80 ‐ 100 MPa, whilst no change in the mechanical behavior of CPC was observed if zirconia was added. X‐ray diffraction measurement confirmed the setting reaction of doped cements was similar to that of pure CPC. Low crystalline HA was found to be the main constituant of set cement; additional phases, such as calcium titanate or calcium zirconate, were not involved in the reaction. A mechanical reinforcement effect was thought to result from changes in the thermodynamic or kinetic solubilities of doped tetracalcium phosphates, this would lead to slower HA crystal formation and a more cross‐linked cement structure.
Novel Polylactide‐Based Release Systems for Local Antibiotic Therapies
Authors: Vogt S. , Kühn K.‐D. , Ege W. , Pawlik K. , Schnabelrauch M. 
Published: January 2004

AbstractAntibiotic delivery systems based on biodegradable polymers have found considerable interest for the local therapy of bone infections. In this study polylactide based polymer and composite delivery systems for the release of gentamicin have been fabricated from poly‐L‐lactides and a poly(L‐lactide‐co‐D,L‐lactide) as well as biodegradable inorganic fillers (calcium hydrogen phosphate, calcium sulfate dihydrate). The in vitro release profiles of the polymer delivery systems were characterized by an initial burst release followed by a sustained release of small gentamicin amounts up to 3 weeks. In the composite delivery systems a loss of retardation was observed with an increasing content of inorganic filler material. It was found that the in situ complex formation of gentamicin by adding defined amounts of sodium dodecyl sulfate represents a valuable tool to overcome this problem and to modulate the release profile of the delivery systems in a wide range. Under in vitro conditions, calcium sulfate dihydrate containing delivery systems are rapidly degraded in aqueous medium within several months. Based on these results, the developed composite delivery systems are promising candidates for the efficient treatment of bone infections.
The Influence of Lipid Dipole Moment and Interfacial Water Structure on Protein Adsorption to Mixed Lipid Monolayers
Authors: Britt D. W. , Goodman Th. , Selle C. 
Published: January 2004

AbstractProtein interactions with a heterogeneous surface, such as a two‐component lipid film, often deviate from simple additivity of the adsorption to the respective single component, “homogenous” films. This behavior was highlighted in previous research where adsorption of the negatively charged protein ferritin to mixed cationic / non‐ionic lipid films was greater than adsorption to either of the single component lipid films [Britt et al., Phys. Chem. Chem. Phys., 2, 4594‐4599, 2000]. Here we investigate mixing induced changes in lipid dipole moments and local water structure as factors leading to amplification of monolayer charge and subsequent enhanced protein adsorption to the mixed lipid films. Surface potential and Fourier transform infrared spectroscopy (FTIR) revealed a reduction in both lipid tilt angle and gauche defects in the mixtures that would lead to a greater contribution of lipid alkyl‐tail dipoles to the measured (normal) surface potential; however, as the orientation of the alkyl‐tail dipole is from water (negative) to air (positive) the greater dipolar contribution for reduced tilt angles actually opposes adsorption of a negatively charged protein from the subphase. FTIR also revealed a mixing induced disordering of water solvating the cationic lipid head group, suggesting water dipoles were less effective in screening charge, which in turn would enhance the electrostatic interactions between anionic protein and the mixed cationic / nonionic lipid film.
Interactions of Osteoblastic and Other Cells with Bioactive Glasses and Silica In Vitro and In Vivo
Authors: Silver I. A. , Erecinska M. 
Published: January 2004

AbstractResponses of cells to the presence of 90‐150 μm particles of 3 bioactive glasses were compared with their reaction to non‐bioactive borosilicate glass and to a known tissue irritant, quartz/silica. Measurements were made in vitro and in vivo of changes of intra‐ and extracellular ion activities. Ion‐selective microelectrodes were used to determine intracellular pH, [Na+], [K+] and [Ca2+] in cultured rodent osteoblasts, fibroblasts and macrophages in contact with, or exposed to medium containing, Bioglass® 45S5, borosilicate glass and bioactive glasses 77S and 58S. The same materials were implanted in connective tissue in rabbit ear chambers and similar measurements were made in vivo. No significant differences were observed among the 3 cell‐types in their reactions, which were minimal, to the presence of the borosilicate and 58S and 77S glasses either in vivo or in vitro. However all cells were affected by interaction with Bioglass® 45S5 which caused significant alkalinisation at its extracellular contact sites and concomitant but smaller changes in internal pH. The latter were accompanied by significant increases in [K+], [Na+] and [Ca2+]. There was also hyperpolarisation of plasma membrane potential in fibroblasts and osteoblasts. In the presence of silica, macrophages showed marked and significant decreases in pH both at the contact zone and intracellularly. Among the cells used, osteoblasts showed higher and macrophages lower pH than fibroblasts when in contact with the test materials. Despite the known leaching of silicic acid from Bioglass® macrophages were not “activated” by its presence, but were by silica. It is concluded that materials developed as potential prostheses should also be examined for their ability to alter cellular metabolism.
Absence of genotoxic effects after exposure of mammalian cells to the recombinant human bone morphogenetic protein 2 (BMP‐2) prepared from E. coli
Authors: Rumpf H. M. , Dopp E. , Rettenmeier A. W. , Chatzinikolaidou M. , Jennissen H. P. 
Published: January 2004

AbstractRecombinant human bone morphogenetic protein 2 (rhBMP‐2) has been widely employed for the induction of bone growth in animal models and in clinical trials. Since rhBMP‐2 is commercially available only to a very limited extent, we have prepared our own recombinant material for the current testing and for future applications. As yet, no toxicological data on rhBMP‐2 has been reported to the knowledge of the authors. Therefore, it was considered necessary to apply the in vitro‐micronucleus assay to our preparation to monitor a possible genotoxic effect. A total of approximately 24500 nuclei from V79 Chinese hamster cells and more than 40000 nuclei from human amniotic fluid fibroblast‐like (AFFL) cells were screened for the frequency of micronuclei following incubation with 3‐300 nM rhBMP‐2, which covers the concentration range from initial biological activity to the begin of a maximal response in MC3T3‐E1 cells. It can be concluded from the results that our preparations of recombinant human BMP‐2 prepared in E. coli do not cause DNA damage in the concentration range tested.