Library

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • 1970-1974  (12)
  • 1925-1929
  • 1900-1904
  • 1880-1889
  • Polymer and Materials Science  (11)
  • Electron Microscopy  (1)
Material
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Acta neuropathologica 18 (1971), S. 34-57 
    ISSN: 1432-0533
    Keywords: Hypertrophic Interstitial Polyneuropathy ; Guillain-Barré Syndrome ; Multiple Sclerosis ; Myelin ; Electron Microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Licht- und elektronenmikroskopische Befunde von zwei N. suralis-Biopsien eines 9 jährigen Knaben mit rezidivierender idiopathischer Polyneuropathie werden beschrieben. Die Biopsien wurden kurz nach einer klinischen Exazerbation und 6 Jahre nach Beginn der Neuropathie durchgeführt. Die Erkrankung hatte akut im Anschluß an Varizellen begonnen. Lichtoptisch fand sich eine aktive primäre Entmarkung bei Auftreten von Infiltraten aus Mononukleären, Lymphocyten und Makrophagen sowie Zwiebelschalenbildung, die in Araldit-Schnitten erkennbar waren. Folgende ultrastrukturelle Veränderungen wurden beobachtet: 1. Der Markzerfall schien durch Makrophagen hervorgerufen, die in intakte Fasern eindringen und in die Markscheiden entlang der minor dense line einbrechen. Myelin und Schwannzellen ohne direkten Kontakt mit den invadierenden Zellen erschienen normal. Extracelluläre bläschenförmige Markauflösung wie beim Landry-Guillain-Barré-Syndrom wurde nicht beobactet. Eine Art von mononukleären Zellen einschließlich solcher nach Art von transformierten Lymphocyten fanden sich im Endoneuralraum und wurden oft in Kontakt untereinander und mit Makrophagen beobachtet. 2. Die Schwannzellen, die Zwiebelschalen-Lamellen bildeten, zeigten wenig morphologische Hinweise auf aktive Proteinsynthese. Sie schienen jene Zellen darzustellen, die ursprünglich die Internoden gestützt hatten und während der Entmarkung und am Beginn der Remyelinisation abgerissen waren. 3. Der mittlere Durchmesser von Axonen in Nervenfasern mit aktiver oder frischer Demyelinisation war geringer als jener in Fasern mit fortgeschrittener Remyelinisierung. Das weist auf eine Querschnittszunahme der Axone während der Remyelinisation hin. Die ultrastrukturellen Befunde werden diskutiert und mit jenen bei anderen nicht-infektiösen entzündlichen primären Entmarkungskrankheiten der peripheren und zentralen weißen Substanz verglichen. Es wird vermutet, daß die rezidivierende idiopathische Polyneuropathie des beschriebenen Typs und die multiple Sklerose verwandte Erkrankungen darstellen.
    Notes: Summary The light and electron microscopical features of two sural nerve biopsies obtained from a nine year old boy with recurrent idiopathic polyneuropathy are described. The biopsies were obtained shortly after an exacerbation of symptoms and six years after the onset of the neuropathy which began acutely following an attack of varicella. Light microscopy revealed active primary demyelination occurring in the presence of an infiltrate of mononuclear cells, lymphocytes and macrophages, with onion-bulb formation discernible in araldite sections. The following fine-structural changes were observed: 1. Myelin breakdown appeared to be initiated by macrophages penetrating intact fibres and burrowing into the myelin sheath along minor dense lines. Myelin and Schwann cells not in direct contact with the invading cell appeared normal. Extracellular vesicular dissolution of myelin, as seen in the Landry-Guillain-Barré syndrome, was not observed. A variety of mononuclear cells including cells with the appearance of transformed lymphocytes were present in the endoneurial space and they were frequently observed to contact each other and macrophages. 2. The Schwann cells forming onion-bulb lamellae showed little morphological evidence of active protein synthesis, and appeared to be effete cells which had originally subserved the internode and which were cast off during demyelination and the commencement of remyelination. 3. The average diameter of axons in nerve fibres showing active or recent demyelination was less than that observed in fibres exhibiting advanced remyelination, suggesting that the diameter of axons increased during remyelination. The ultrastructural findings are discussed with respect to those observed in other noninfectious inflammatory primary demyelinating diseases of peripheral and central white matter, and it is suggested that recurrent idiopathic polyneuropathy of the type described in the present study and multiple sclerosis may be related disorders.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Mechanical properties were correlated with glass transition temperatures for a series of random copolymers of methyl methacrylate with comonomers selected from the higher n-alkyl acrylates and N-n-alkylacrylamides. The plasticizing comonomers were the n-butyl, 2-ethylhexyl, n-octadecyl, and oleyl acrylates, and the N-n-butyl-, N-n-octyl-, N-n-octadecyl-, and N-oleylacrylamides. The complete range of compositions was investigated. However, the bulk of the data was obtained on compositions in the glassy region below the onset of the vitreous transition. In this region it was found that the decrease in tensile and flexural moduli and strengths with increase in internal plasticizer for all of the systems was directly proportional to the decrease in Tg. It was concluded that the additive contribution to the free volume made by each side-chain methylene group was alone responsible for the magnitude of the rate of change of properties. However, polar contributions of the amide group to stiffening the main chain exceeded those of the ester, so that the amides were less efficient plasticizers. An empirical equation was derived which described, with fair accuracy, the decrease in the mechanical parameters with composition for the amorphous copolymers. It was reasonably successful in predicting properties even into the composition range where the ambient testing temperature corresponded to or exceeded the transition temperature. In this transition region an accelerated decrease in the magnitude of the physical properties was observed. All samples exhibited brittle fracture except those tested in the transition region. Here the strain was largely irrecoverable flow. Side-chain crystallinity did not interfere significantly with the mechanical properties because moduli and strengths had already decayed to small values near the compositions where crystallinity commenced. Non-random copolymers of vinyl stearate and methyl methacrylate showed no internal plasticization, apparently because of macrophase aggregation.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 9 (1971), S. 853-865 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The rate of adsorption of fractionated polyethylenimine (PEI) from water onto regenerated cellulose fibers was studied as a function of the polymer diffusion coefficient. Differences in polymer molecular weight, salt concentration, and pH were employed to vary the diffusion coefficient which was measured independently by a free-diffusion technique. The sorption rate was measured at the same conditions and found to increase with decreasing molecular weight, increasing polymer concentration, decreasing salt concentration, and increasing pH. A simplified rate equation based on diffusion control with Langmuirian adsorption in stirred solution was developed by utilizing the concept of a Nernst diffusional film. The equation was successful in predicting the relationship between adsorption rate and diffusion coefficient for most cases studied. It was found, however, that a very large barrier to mass transfer retards the adsorption rate. For the system studied it was concluded that this barrier is a result of diffusion into and subsequent adsorption onto the internal porous structure of the cellulose.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 6 (1972), S. 185-192 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Abrasion and performance of artificial heart valves are related to geometrical configuration, blood flow dynamics, manufacturing techniques, and interaction of materials. Incidence of thromboembolism, valve insufficiency, and shortened longevity are critically dependent upon these factors. The effect of construction parameters on valve performance is discussed in general terms and illustrated from in vivo experience with a specific low-profile design.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 5
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 5 (1971), S. 411-412 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 6
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 6 (1972), S. 473-476 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 7
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 7 (1973), S. 267-269 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 8
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The purpose of this study was to determine the effect of air-borne gaseous impurities, introduced during trituration, on the strength of amalgams.Four experiments were conducted. Each experiment consisted of a control group (1) in which the amalgam was triturated in air and an experimental group (2) in which the amalgam was triturated in argon, an inert gas. Standard specimens yielded mean diametral tensile strengths of 5950 psi (1) and 6603 psi (2). Hand compacted specimens yielded mean diametral tensile strengths of 5829 psi (1) and 6412 psi (2). Standard specimens yielded mean compressive strengths of 46,636 psi (1) and 47,269 psi (2). Specimens compacted hydraulically yielded mean uniaxial tensile strengths of 10,928 psi (1) and 11,660 psi (2).Statistically, the differences between the means for each experiment are significant. Hence, trituration in an inert gas has been shown to be an effective method for increasing the strength of amalgam.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 9
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 5 (1971), S. 373-387 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Segmented polyurethane does not indiuce acute toxcity when subjected to intracutaneous and intravascular tests with mices and rabbits. Specimens, which have been implanted in dogs for 18 months, exhibit stability heretofore unattributed tothe general class of polyurethanes. Data on tensile properties, abraxion resistance when wet, tolerance to autoclaving, results of acute toxicity test, and stablity of long-term implants are described along with appropriate means of processing the polymer into useful biomedial devices.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 10
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 12 (1974), S. 29-43 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The polyethyleneimine (PEI)-water-silica gel absorption system was used as a model system to investigate the relationship between diffusion into the porous structure, adsorption rate, and molecular weight of the polymer. Three silica gels, Porasil A, B, and and C having a range of characteristic porosity were used as adsorbents. Adsorption of PEI on Porasil C, which has the majority of its pores much larger than the dimensions of the adsorbate molecule, increased initially with increased molecular weight but became nearly constant at higher molecular weight. Little increase in adsorption occurred for this silica gel with increased ionic strength or with increased pH between 9.5 and 10.8. In contrast, adsorption increased sharply with increased ionic strength and for the same pH range on Porasil A. Molecular weight dependence was reversed. Adsorption decreased with increased molecular weight on Porasil A. In this case, the molecular size of PEI investigated was the same as the majority of pore apertures in the adsorbent. Solution environments (i.e., pH and ionic strength) that decrease the size of the PEI molecule and its affinity for the anionic silica gel surface, thus enabling it to more readily diffuse into the smaller porous regions of the adsorbent, are the apparent causes of the very large adsorption increase. Electrostatic repulsion between PEI molecules do not appear greatly to affect adsorption. Similar adsorption behavior has been reported in the literature for the PEI-cellulosic fiber adsorption system. Maximum adsorption on Porasil A occurred at pH 10.8, the same maximum generally reported for adsorption of PEI on cellulosic fibers. In this case, the silica gel (Porasil A) was found to have a pore size distribution and specific surface area of the same magnitude as cellulosic fibers prepared in the expanded state.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...