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  • 2000-2004  (256)
  • 1965-1969  (629)
  • 1870-1879  (6)
  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 4503-4511 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Charged closed-cell polypropylene polymer foams are highly sensitive and broadband piezoelectric materials with a quasistatic piezoelectric d33 coefficient about 250 pC/N and a dynamic d33 coefficient of 140 pC/N at 600 kHz. The piezoelectric coefficient is much larger than that of ferroelectric polymers, like polyvinylidene fluoride, and compares favorably with ferroelectric ceramics, such as lead zirconate titanate. The pyroelectric coefficient p3=0.25 μC/m2 K is small in comparison to ferroelectric polymers and ferroelectric ceramics. The low density, small pyroelectric coefficient and high piezoelectric sensitivity make charged polymer foams attractive for a wide range of sensor and transducer applications in acoustics, air-borne ultrasound, medical diagnostics, and nondestructive testing. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5283-5287 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Charged closed-cell polymer foams have been found to be highly sensitive piezoelectric materials. Charging is shown to arise from dielectric barrier microdischarges within the voids of the cellular polymer. Above the threshold voltage for breakdown in the voids, the microdischarges are evidenced by light emission from the polymer, as well as by displacement-voltage hysteresis loops. Monitoring light emission during breakdown is shown to provide a quick check for the suitability of foams for piezoelectric applications. Additionally it allows for the visualization of micropores in foams in a nondestructive way. The piezoelectric response of the foam can be switched by applying dc-voltage pulses of alternating polarity above the breakdown threshold, thereby showing the feasibility of patterning the piezoelectric properties within the film plane. Although piezoelectric foams are nonferroelectric, the experiments prove similarities to ferroelectric materials with respect to hysteresis behavior, as well as a threshold (coercive) field for switching of the polarization and piezoelectricity. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 3827-3829 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Charged closed-cell microporous polypropylene foams are shown to exhibit piezoelectric resonance modes in the dielectric function, coupled with a large anisotropy in the electromechanical and elastic material properties. Strong direct and converse dynamic piezoelectricity with a piezoelectric d33 coefficient of 140 pC/N at 600 kHz is identified. The piezoelectric d33 coefficient exceeds that of the ferroelectric polymer polyvinylidene fluoride by a factor of 5 and compares favorably with ferroelectric ceramics. Applications of similar concepts should provide a broad class of easily fabricated "soft" piezoelectric materials. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 2612-2614 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nanoemulsion polytetrafluoroethylene (nano-PTFE) is a promising low-dielectric-constant polymer, which can be prepared in thin-film form by spin-on techniques. Similarities and differences of the nano-PTFE material to the well-known class of PTFE polymers with respect to morphology and dielectric and electret characteristics are discussed. Nano-PTFE shows excellent dielectric properties up to 300 °C, and a charge stability that compares favorably with other members of the PTFE class. Nano-PTFE enlarges the family of PTFE materials and may become interesting for applications in microelectronics and miniaturized electret devices. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Anaesthesia 59 (2004), S. 0 
    ISSN: 1365-2044
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1365-2044
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Although several clinical studies have shown that increased serum concentrations of protein S100B predict ischaemic brain damage after cardiac surgery, S100B may also be released from the heart or other injured tissue. We therefore investigated the correlation between serum S100B levels and those of the specific cardiac marker troponin I in order to assess the cerebral vs. extracerebral origin of S100B. In 64 cardiac surgical patients, serial blood samples were drawn for the measurement of S100B and troponin I before surgery and for seven days after surgery. Neurological function was assessed before with the National Institutes of Health Stroke Scale and the Folstein Mini Mental Test. The data show that a sustained increase in serum S100B levels is associated with neurological dysfunction, as witnessed by a positive correlation between S100B values and the results of the neuropsychological tests. In contrast, the early postoperative increased levels of protein S100B derive from cardiac tissue, as shown by the positive correlation between S100B and cardiac troponin I levels.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-0630
    Keywords: PACS: 77.65.-j; 77.84.Jd; 85.50.+k
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. Large piezoelectric d33 coefficients around 600 pC/N are found in corona-charged non-uniform electrets consisting of elastically “soft” (microporous polytetrafluoroethylene PTFE) and “stiff” (perfluorinated cyclobutene PFCB) polymer layers. The piezoelectric activity of the two-layer fluoropolymer stack exceeds the d33 coefficient of the ferroelectric ceramic lead zirconate titanate (PZT) by more than a factor of two and that of the ferroelectric polymer polyvinylidene fluoride (PVDF) by a factor of 20. Soft piezoelectric materials may become interesting for a large number of sensor and transducer applications, in areas such as security systems, medical diagnostics, and nondestructive testing.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Annals of hematology 18 (1968), S. 114-122 
    ISSN: 1432-0584
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Zeitschrift für Herz-, Thorax- und Gefässchirurgie 14 (2000), S. 204-211 
    ISSN: 0930-9225
    Keywords: Schlüsselwörter Venenentnahme – Wundheilungsstörungen –¶kosmetische Inzision ; Key words Harvesting of the saphenous vein –¶wound healing disturbances – cosmetic incision
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary In Germany about 75000 patients received the CABG operation last year, these are about 75% of all open heart operation procedures. The most frequently used conduit is the greater saphenous vein. In the last years a lot of new minimally invasive techniques for vein harvesting revolutionized the field of CABG operation procedures, nevertheless the most common technique today is the traditional, open technique with long, continuous incision for the open preparation of the saphenous vein. Using traditional open saphenectomy, wound healing disturbances are common and have been reported to occur in 5–25% of patients. The prevalence of wound healing disturbances varies widely, depending to some degree of definition, as well of the intensity of follow up. Minimal and less invasive vein harvesting studies have been shown to be effective in decreasing leg wound disturbances, resulting much superior cosmetic results. Advantages and disadvantages of minimally invasive vein harvesting techniques are today the topic of controversy discussions in heart surgery.¶   We reported our experience of modified minimally invasive harvesting of the saphenous vein using the Aesculap retractor system with performing 3–4 small cutaneous incisions. According to our experience these results show that the use of modified minimally invasive harvesting of the great saphenous vein is an attractive alternative to the traditional open harvest technique with fewer wound complication, more patient satisfaction and excellent cosmetic aspects. Therefore, we hope that less or minimally invasive systems for harvesting of the saphenous vein will be established in the future in CABG operation procedures.
    Notes: Zusammenfassung Jährlich werden in Deutschland ca. 75000 Patienten mit koronarer Herzerkrankung (ca. 75% aller Herzoperationen) operativ versorgt. Als Bypassmaterial stehen arterielle Grafts und autologe Venen, vorwiegend die Vena saphena magna, zur Verfügung. In den letzten Jahren revolutionieren minimal-invasive Venenentnahmetechniken die Bypasschirurgie, dennoch erfolgt heute die Saphenektomie zum Großteil mittels kontinuierlicher Inzision der Haut vom Knöchel bis in die Leiste zur offenen Präparation der Vena saphena magna. Wundheilungsstörungen nach offener Saphenektomie werden wiederholt diskutiert und sind Gegenstand jeder herzchirurgischen Nachbehandlung nach koronarchirurgischen Eingriffen und Grund für die Aufwertung neuer, minimal-invasiver Entnahmetechniken. Diese Wundheilungsstörungen, je nach Beobachtungszeitraum, werden in der Literatur zwischen 5–25% angegeben. Die Vor- und Nachteile minimal-invasiver Systeme sind derzeit Inhalt kontroverser Diskussion.¶   Die vorgestellte Technik (modifizierte „Bridge”-Technik) zeigt erwünschte Ergebnisse, insbesondere eine sehr hohe Patientenzufriedenheit hinsichtlich des kosmetischen Ergebnisses und der nur geringen Einschränkung durch die Saphenektomiewunde(n). Es ließ sich nur eine geringe Rate an postoperativen Komplikationen (hier 3%) feststellen. Minimal-invasive Venenentnahmesysteme halten wir für praktikabel, effizient und leicht erlernbar. Wir sehen es deshalb als wichtig an, diese Techniken weiter im klinischen Gebrauch zu etablieren.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1615-3146
    Keywords: Key Words Hemorrhagic shock ; Liver microcirculation ; Intravital microscopy ; Inflammation ; Leukocyte adhesion ; Tumor necrosis factor α ; Intercellular adhesion molecule-1
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Defined microcirculatory disturbances have been demonstrated during the first hours after hemorrhagic shock involving complex pathophysiological mechanisms. Since clinical complications associated with the inflammatory reaction that accompanies shock and resuscitation become apparent within days, our aim was to establish an experimental model of hemorrhagic shock which simulates this clinical situation. Therefore, a nonlethal rat model was developed allowing for the investigation of the hepatic microcirculation by intravital microscopy up to 4 days after hermorrhagic shock. Anesthetized Sprague-Dawley rats were subjected to hemorrhagic hyptension by blood withdrawal reducing MAP (mean arterial blood pressure) to 40 mm Hg. After 60 min of hypovolemic hypotension, the animals were resuscitated. After 1, 2, 3, or 4 days, sinusoidal perfusion pattern and leukocyte adhesion characteristics were investigated using intravital fluorescence microscopy. In separate, but parallel experiments, the time course of TNFα (tumor necrosis factor α) and ICAM-1 (intercellular adhesion molecule-1) mRNA expressio was examined in enriched parenchymal and non-parenchymal liver cell fractions by Northern blot hybridization. At day 1, sinusoidal narrowing as seen in previous experiments a few hours after shock was not observed but occurred at days 2 and 3 after shock. Permanent adhesion of leukocytes to the sinusoidal endothelium reached a maximum at day 2 after shock and remained significantly increased until day 4 compared with controls. An early TNFα mRNA accumulation was observed in shock animals but not in sham operated controls. In contrast, a sustained expression of ICAM-1 and prolonged accumulation of white blood cells were observed. The data reflect an early transient TNFα mRNA response and a sustained inflammatory reaction associated with shock and resuscitation. The inflammatory pathological alteration of the hepatic microcirculation after hemorrhagic shock are paralleled by a sustained disturbance of the sinusoidal flow patterns.
    Type of Medium: Electronic Resource
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