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  • Polymer and Materials Science  (29)
  • Albumine  (2)
  • Conductivity  (2)
  • 1
    ISSN: 1432-2013
    Schlagwort(e): Key words Arteries ; Conductivity ; Conductance method ; Double indicator dilution method ; Shear rate ; Intravascular ultrasound
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract A double indicator dilution technique for determining the mean cross-sectional area (CSA) of a blood vessel in vivo is presented. Analogous to the thermodilution method, dilution of hypertonic saline was measured by an electrical conductance technique. Because the change in conductance rather than absolute conductance was used to calculate CSA, pulsatile changes in shear rate of blood and conductance of surrounding tissues had no effect on the data. To calculate CSA from an ion mass balance, cardiac output was needed and estimated from the thermodilution curve using the same “cold” (hypertonic) saline injection. The mean CSA, obtained from this double indicator dilution method (CSAGD), was compared with the CSA obtained from the intravascular ultrasound method (IVUS) in 44 paired observations in six piglets. The regression line is close to the line of identity (CSAGD = −1.83 + 1.06⋅CSAIVUS, r = 0.96). The difference between both CSAs was independent of the diameter of the vessel, on average −0.99 mm2± 2.64 mm2 (mean CSAGD = 46.84 ± 8.21 mm2, mean CSAIVUS = 47.82 ± 9.08 mm2) and not significant. The results show that the double indicator dilution method is a reliable technique for estimating the CSA of blood vessels in vivo.
    Materialart: Digitale Medien
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  • 2
    ISSN: 1432-1238
    Schlagwort(e): Key words Oleic acid ; Lung injury ; Respiratory distress ; Albumine ; Bolus injections
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract   Objective: Development of a stable model of respiratory distress in pigs with oleic acid, fulfilling clinical criteria of the adult respiratory distress syndrome (ARDS). Design: Eight pigs (9.1±0.7 kg) were anesthetized with pentobarbital, paralyzed with tubocurarine and mechanically ventilated with an FIO2 of 0.6, an I:E ratio of 2:3 and a PEEP of 0.2 kPa. Oleic acid (dissolved 1:1 in 96% alcohol) was administered in a series of multiple injections of 0.1 ml until P aO2 was lower than 8 kPa. Measurements and results: Careful titration of the oleic acid injections on guidance of the P aO2 established a reproducible respiratory distress (P aO2=7.3±0.8 kPa), in which gas exchange and hemodynamic variables were stable for at least 4 h. The number of oleic acid injections (22±11, mean and SD) varied between the animals. Conclusions: With the use of multiple injections of oleic acid, a stable model of early respiratory distress in pigs can be achieved, in spite of individual differences in sensitivity. Such a stable model allows for a diversity of studies on early respiratory distress.
    Materialart: Digitale Medien
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  • 3
    ISSN: 1432-1238
    Schlagwort(e): Oleic acid ; Lung injury ; Respiratory distress ; Albumine ; Bolus injections
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Objective Development of a stable model of respiratory distress in pigs with oleic acid, fulfilling clinical criteria of the adult respiratory distress syndrome (ARDS). Design Eight pigs (9.1±0.7 kg) were anesthetized with pentobarbital, paralyzed with tubocurarine and mechanically ventilated with an $$F_{IO_2 } $$ of 0.6, an I∶E ratio of 2∶3 and a PEEP of 0.2 kPa. Oleic acid (dissolved 1∶1 in 96% alcohol) was administered in a series of multiple injections of 0.1 ml until $$P_{aO_2 } $$ was lower than 8 kPa. Measurements and results Careful titration of the oleic acid injections on guidance of the $$P_{aO_2 } $$ established a reproducible respiratory distress ( $$P_{aO_2 } $$ =7.3±0.8 kPa), in which gas exchange and hemodynamic variables were stable for at least 4 h. The number of oleic acid injections (22±11, mean and SD) varied between the animals. Conclusions With the use of multiple injections of oleic acid, a stable model of early respiratory distress in pigs can be achieved, in spite of individual differences in sensitivity. Such a stable model allows for a diversity of studies on early respiratory distress.
    Materialart: Digitale Medien
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  • 4
    ISSN: 1573-9686
    Schlagwort(e): Conductivity ; Erythrocytes ; Ultrasound ; Shear stress
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin , Technik allgemein
    Notizen: Abstract A modified conductance method to determine the cross-sectional areas (CSAs) of arteries in piglets was evaluated in vivo. The method utilized a conductance catheter having four electrodes. Between the outer electrodes an alternating current was applied and between the inner electrodes the induced voltage difference was measured and converted into a conductance. CSA was determined from measured conductance minus parallel conductance, which is the conductance of the tissues surrounding the vessel times the length between the measuring electrodes of the conductance catheter divided by the conductivity of blood. The parallel conductance was determined by injecting hypertonic saline to change blood conductivity. The conductivity of blood was calculated from temperature and hematocrit and corrected for maximal deformation and changes in orientation of the erythrocytes under shear stress conditions. The equations to calculate the conductivity of blood were obtained from in vitro experiments. In vivo average aortic CSAs, determined with the conductance method CSA (G) in five piglets, were compared to those determined with the intravascular ultrasound method CSA(IVUS). The regression equation between both values was CSA (G) =−0.09+1.00·CSA(IVUS) r=0.97, n=53. The mean difference between the values was −0.29% · 5.57% (2 standard deviations). We conclude that the modified conductance method is a reliable technique to estimate the average cross-sectional areas of the aorta in piglets. © 1999 Biomedical Engineering Society. PAC99: 8780-y, 8437+q, 8719Nn
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 4 (1993), S. 213-219 
    ISSN: 1045-4861
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: The aim of this study was to investigate the bone response to three different types of titanium (Ti) alloys and hydroxyapatite (HA) coated titanium alloy by histological and histomorphometrical analysis. Therefore, implants made of these materials were inserted into the tibia of rabbits. Implantation times were 6 and 16 weeks. The histological evaluation included measurement of the amount of bone apposition and analysis of the bone reaction and interface characteristics around the implants. The results demonstrated no marked differences in bony reaction to the different implant materials. In addition, the HA coatings showed loss of thickness. © 1993 John Wiley & Sons, Inc.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 24 (1990), S. 295-307 
    ISSN: 0021-9304
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: This study reports on certain aspects of wound-healing around percutaneous implants. Plasma-sprayed and dense hydroxylapatite, titanium, and carbon test implants were inserted into the tibia and the cranium of 12 rabbits. Four and 8 months after insertion, the animals were sacrificed and the implants with their surrounding tissues were processed histologically. Light- and transmission electron microscopic investigations were performed. It is found that direct and indirect boneanchoring favors the longevity of percutaneous implants. No differences in tissue reaction between the various implant materials were observed.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 29 (1995), S. 511-518 
    ISSN: 0021-9304
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: To evaluate the effect of surface treatment and surface microtexture on cellular behavior, smooth and microtextured silicone substrata were produced. The microtextured substrata possessed parallel surface grooves with a width and spacing of 2.0 (SilD02), 5.0 (SilD05), and 10 μm (SilD10). The groove depth was approximately 0.5 μm. Subsequently, these substrata were either left untreated (NT) or treated by ultraviolet irradiation (UV), radiofrequency glow discharge treatment (RFGD), or both (UVRFGD). After characterization of the substrata, rat dermal fibroblasts (RDF) were cultured on the UV, RFGD, and UVRFGD treated surfaces for 1, 3, 5, and 7 days. Comparison between the NT and UV substrata revealed that UV treatment did not influence the contact angles and surface energies of surfaces with a similar surface topography. However, the contact angles of the RFGD and UVRFGD substrata were significantly smaller than those of the UV and NT substrata. The dimension of the surface microevents did not influence the wettability characteristics. Cell culture experiments revealed that RDF cell growth on UV-treated surfaces was lower than on the RFGD and UVRFGD substrata. SEM examination demonstrated that the parallel surface grooves on the SilD02 and SilD05 substrata were able to induce stronger cell orientation and alignment than the events on SilD10 surfaces. By combining all of our findings, the most important conclusion was that physicochemical parameters such as wettability and surface free energy influence cell growth but play no measurable role in the shape and orientation of cells on microtextured surfaces. © 1995 John Wiley & Sons, Inc.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 28 (1994), S. 1047-1054 
    ISSN: 0021-9304
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: This study reports on the soft-tissue response to titanium fiber mesh percutaneous implants. The implants were inserted in the backs of 15 rabbits. The surgical procedure was performed in two steps: implantation of the subcutaneous part of the implants and, after 3 months, fixation of the percutaneous part into the subcutaneous part. Two and 6 months after insertion the animals were sacrificed and the implants, with their surrounding tissues, were processed histologically. Light microscopic analysis demonstrated that only one implant showed considerable skin retraction in the percutaneous area. Around the rest of the implants no downgrowth or only a very limited epidermal downgrowth was observed. Furthermore, the fiber mesh material showed good biocompatible behavior. These results confirm the previous finding that sintered titanium fiberweb structures are effective for the stabilization of percutaneous devices located in soft tissues and can improve their performance. © 1994 John Wiley & Sons, Inc.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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  • 9
    ISSN: 0021-9304
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: The effects of discharge radiofrequency (RF) power and film thickness were studied on the characteristics of Ca5(PO4)3OH (hydroxyapatite) thin films fabricated by RF magnetron sputtering. The structure and chemical composition were investigated with α-step (thickness), scanning electron microscopy (SEM), X-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS), and infrared absorption spectrometry (FTIR). The films were analyzed assputtered and after annealing at 550°C under argon flow. SEM showed that the film surfaces had no cracks or other defects. X-ray diffraction showed that the deposited films were amorphous with low-discharge RF power, and crystalline with high-discharge RF power. After annealing, all the films had the same crystalline structure as apatite. However, the RBS measurements revealed that all films had a higher calcium-phosphate ratio than standard synthetic hydroxyapatite. Furthermore, statistical testing of the RBS data revealed the existence of only a weak correlation between the Ca/P ratio and the discharge power level. Although all sputtered films showed phosphate bonds in the infrared spectrum, only after annealing did the OH bonds of hydroxyapatite become visible. © 1995 John Wiley & Sons, Inc.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 10
    ISSN: 0021-9304
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin , Technik allgemein
    Notizen: The aim of this study was to investigate the bone response to calcium phosphate (Ca-P) plasma-spray and radiofrequency magnetron sputter-coated implants with comparable roughness. Therefore, tapered conical screw designed implants were installed in the trabecular bone of the femurs of nine goats. They were provided with two types of coatings, a plasma-spray dual coating of fluorapatite and hydroxyapatite (FA/HA-PS) and a titanium plasma-spray coating, covered with an amorphous Ca-P magnetron sputtercoating (TPS/Ca-P-a). These implants were evaluated histologically and mechanically after 3 months of implantation. A well-controlled method to apply and measure a torsional force to load the screw-type implants to the point of failure was introduced. All implants healed uneventful and were well fixed. No significant difference (Student t test, p 〉 0.05) for the torsional failure force was measured for both type of coatings. Nevertheless, SEM revealed differently situated fracture planes. Light microscopy showed intimate bone-implant contact for both types of coatings; original drill margins were still visible. A lamellar type of bone with some remodeling lacunae was shown. Histomorphometry revealed a higher percentage of bone contact for the FA/HA-PS-coated implants (student t test, p 〈 0.05). Measurement of the amount of bone revealed more bone mass around TPS/Ca-P-a-coated implants (analysis of variance and Tukey multiple comparison, p 〈 0.05). © 1997 John Wiley & Sons, Inc.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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