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  • 1
    ISSN: 0003-2670
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1439-6327
    Keywords: Syncope ; Blood pressure ; Bed-rest ; Fluid shifts ; Capillary filtration ; Tissue thickness
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract To evaluate mechanisms of late orthostatic intolerance, slow fluid shifts along the body axis were studied during deconditioning by 24-h bed-rest and during 13-min upright tilts before and after this manoeuvre. In 11 healthy male subjects the fluid volumes of a thorax and a calf segment (impedance plethysmography) as well as tissue thickness at the forehead and the tibia (miniature ultrasonic plethysmograph) were recorded. Cardiovascular performance was monitored by recording heart rate (electrocardiogram), brachial and finger arterial pressure (by the Riva Rocci method and by the Finapres technique) as well as stroke volume (by impedance cardiography). Bed-rest led to a cephalad fluid shift with a mean interstitial leg dehydration of 2.2 ml·-100 ml−1 with no changes in body mass and plasma volume. No syncope during the tilt occurred before bed-rest, while after bed-rest 8 subjects fainted between min 2.1 and 9.0 of the tilt. Bed-rest resulted in an augmented initial heart rate response to tilting which was similar in all subjects. In later orthostasis, bed-rest caused two- to threefold faster caudad fluid shifts with higher calf filtration rates in fainters (prior to hypotension) than in nonfainters. Through bed-rest the estimated extravasation within 10 min into general lower body tissue spaces increased by 192 ml in (late) fainters as opposed to only 23 ml in nonfainters. It was concluded that contributing factors to orthostatic intolerance may be slow transcapillary fluid shifts which are easily underestimated and whose quantity and time course call for further investigation after various deconditioning manoeuvres. In particular, the postflight fluid shifts in astronauts who will have markedly dehydrated legs, may impose a circulatory stress which needs to be evaluated. In general, the filtration rate in relevant areas appears to be an integrative and easily determined parameter, reflecting hormonal and neurogenic vascular as well as local interstitial control of the Starling forces.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1439-6327
    Keywords: Finapres ; Pulse pressure ; Vasomotor state ; Warming up ; Exercise
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary To compare the readings of blood pressure by the Riva-Rocci (RR) method with those of peripheral arterial pressure (PAP) as recorded by the Finapres (FP) device, exercise was performed by six male subjects on a cycle ergometer at a constant exercise intensity of 140 W. In addition, forearm volume was determined by impedance plethysmography. At rest, systolic FP values exceeded RR values by ≥ 10 mmHg. During 60-min exercise both values at first increased almost in parallel with each other. While RR reached a plateau after 3 min, FP then started to decrease continuously up to the 10th min and finally stabilized at 20–30 mmHg below RR. The impedance values showed a similar declining slope, indicating vasodilatation. To separate the effects of sympathetic drive from heat elicited vasodilatation, a second experimental series was performed with ischaemic static calf exercise (5 min, 90 N), since this increases the sympathetic tone but prevents systemic heat distribution. In contrast to findings reported from intra-arterial measurements, no exercise effect on the pulse pressure amplification was obtained. However, the heating of one fingertip distal to the FP-cuff led to a significant decrease in PAP compared to the control recording made simultaneously from the other hand. It was concluded that heat induced vasodilatation may make FP unrepresentative of systemic blood pressure, in particular during exercise. Moreover, the FP-cuff seemed to induce substantial vasoconstriction due to venous occlusion. The FP method would therefore be useful for monitoring continuously systemic blood pressure if no (dilative) vasomotor changes occurred or their ranges and time courses were known sufficiently well.
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  • 4
    ISSN: 1439-6327
    Keywords: Dynamic exercise ; Interstitial muscle fluid ; Heart rate ; Cardiovascular afferents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The volume of interstitial fluid in the limbs varies considerably, due to hydrostatic effects. As signals from working muscle, responsible for much of the cardiovascular drive, are assumed to be transmitted in this compartment, blood pressure and heart rate could be affected by local or systemic variations in interstitial hydration. Using a special calf ergometer, eight male subjects performed rhythmic aerobic plantar flexions in a supine position with dependent calves for periods of 7 min. During exercise heart rate, blood pressure, oxygen uptake (VO2) and blood lactate concentrations were measured in two different tests, one before and after interstitial calf dehydration through limb elevation for 25 min, compared to the other, a control with unaltered fluid volume in a maintained working position. Impedance plethysmography showed calf volume to be stabilized in the control position. Leg elevation by passive hip flexion to 90° resulted in a fast (vascular) volume decrease lasting 〈2 min, followed by a slow linear fluid loss from the interstitial compartment. Then, when returned to the control position, adjustment of vascular volume was completed within 2 min and exercise could be performed with dehydration remaining in the interstitium only. Cadiovascular response was identical at the start of both tests. However, exercising with dehydrated calves elicited a significantly larger increase in heart rate compared to the control, whereasVO2 was identical. The blood pressure response was shown to be only slightly enhanced. Structural interstitial features varying with hydration, most likely chemical or mechanical ones, may have been responsible for this amplification of signals.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: By reactions of SiCl4, RSiCl3, RSiCl2(OCOCH3), R2SiCl2 and R3SiCl, [R—CH3 and C2H5], with C6H5CO—CH2—CO—OC2H5 the substances listed in ‘Inhaltsübersicht’ have been prepared and investigated by means of UV and IR spectroscopy concerning the problem of chelate complexes with hexacovalent Si atoms.
    Notes: Durch Umsetzungen von SiCl4, RSiCl3, RSiCl2(OCOCH3), R2SiCl2 und R3SiCl[R = CH3, C2H5] mit Benzoylessigsäureäthylester wurden Produkte folgender Zusammensetzung dargestellt: Die dargestellten Verbindungen wurden mittels UV- und IR-Absorptionsspektren daraufhin untersucht, ob Chelatkomplexe mit hexakovalentem Silicium vorliegen.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Alternative Ligands. XIX. Platinum(II) Complexes with Donor/Acceptor Ligands of the Type Me2PCH2CH2SiXneM3-n (X = F, C6H4F) and (2-Me2PC6H4)SiFMe2Reactions of Me2PCH2CH2SiXneM3-n (X = F, Cl, C6H4F) and L = (2-Me2PC6H4)SiFMe2 with Cl2M(NCPh)2 (M = Pd, Pt) and R2Pt(COD)2 (R = I, Me, Ph), respectively, yield 20 complexes of the types X2ML2 (X = Hal) or R2PtL2. In general, mixtures of cis and trans isomers are obtained, in which the cis complex is the main product. The R2PtL2 compounds show a much better solubility than the corresponding halogen complexes X2PtL2 and, therefore, can be clearly characterized by spectroscopic methods. The assignment of the data to the cis or trans compound is possible on the basis of the characteristic values of δP and 1J(PtP). Pt → Si donor/acceptor interactions are clearly indicated by low field shifts ΔδF of 13 to 28 ppm and J(PtF) couplings of about 40 Hz only for the complexes R2Pt[(2-Me2PC6H4)SiFMe2]2. For other derivatives with ΔδF values of 3 to 12 ppm PtF coupling is not detectable because of the broadness of the 19F signals.
    Notes: Durch Umsetzung von L = Me2PCH2CH2SiXneM3-n (X = F, Cl, C6H4F) und L = (2-Me2PC6H4)SiFMe2 mit Cl2M(NCPh)2 (M = Pd, Pt) bzw. R2Pt(COD)2 (R = I, Me, Ph) werden 20 Komplexe des Typs X2ML2 (X = Hal) bzw. R2PtL2 dargestellt. Sie fallen in der Regel als cis/trans-Isomerengemische an, in denen der Anteil des cis-Komplexes überwiegt. Die R2PtL2-Verbindungen sind wesentlich besser löslich als die entsprechenden Halogenkomplexe X2PtL2 und daher spektroskopisch eindeutig charakterisierbar. Die Zuordnung der Daten zur cis- oder trans-Verbindung gelingt anhand der charakteristischen Parameter δP und 1J(PtP). Deutliche Hinweise auf Pt → Si Donor/Akzeptor-Wechselwirkungen ergeben sich nur im Fall der Komplexe R2Pt[(2-Me2PC6H4)SiFMe2]2 durch Tieffeldverschiebungen ΔδF zwischen 13 und 18 ppm und J(PtF)-Kopplungen um 40 Hz. Bei anderen Derivaten mit ΔδF-Werten zwischen 3 und 12 ppm sind PtF-Kopplungen aufgrund breiter und unstrukturierter 19F-Signale nicht sicher nachzuweisen.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Alternative Ligands. XXI. Novel Donor/Acceptor Ligands Me2PCH2CH2SiFnMe3-n, Me2PCH2CH2SiR(C6H4F)2, and (2-Me2PC6H4)SiXMe2Donor/acceptor ligands of the type Me2PCH2CH2SiX3 [X = Cl (1), F (2), Me (3), OMe (4)], (Me2PCH2CH2)2SiX2 [X = Cl (6), F (7)], Me2PCH2CH2SiX(C6H4F)2 [X = F (5), Me (8)], and Me2PCH2CH2SiXnMe3-n[n = 1; X = Cl (10), F (11); n = 2; X = F (9)] are prepared in yields between 42 and 95% by photochemical addition of Me2PH to the corresponding vinylsilane precursors. In case of the halogen containing representatives formation of solid polyadducts, due to Lewis acid/base interaction between P-donor and Si-acceptor function, reduces the yields. Ligands of the type (2-Me2PC6H4)SiXMe2 [X = NMe2 (12), Cl (13), F (14)] are obtained by two different routes (Abb. 3), using 2-chlorobromobenzene as the starting material. New compounds have been characterized by analytical (C, H) and spectroscopic (NMR, MS) investigations. In order to elucidate the associative properties compounds 2 and 9 were used for the following experiments: - Study of the influence of dissolution on the proton and fluorine resonances of 2 and 9,- investigation of the adduct equilibrium (-H2CF3Si←PMe2CH2-)n + nBF3 → n[F3B←PMe2CH2CH2SiF3],- cleavage of the polyadduct of 2 using [NH4]F and [Me4N]F, respectively, for the formation of hexacoordinate complex anions [Me2PCH2CH2SiF5]2-.The results obtained confirm the assumption that oligo- and polymerisation are due to P→Si interaction.
    Notes: Die Donor/Akzeptor-Liganden Me2PCH2CH2SiX3 [X = Cl (1), F (2), Me (3), OMe (4)], (Me2PCH2CH2)2SiX2 [X = Cl (6), F (7)], Me2PCH2CH2SiX(C6H4F)2 [X = F (5), Me (8)] und Me2PCH2CH2SiXnMe3-n [n = 1; X = Cl (10), F (11); n = 2; X = F (9)] entstehen in Ausbeuten von 42 bis 95% bei der photochemischen Addition von Me2PH an die entsprechenden Vinylsilane. Ausbeutemindernd wirkt sich bei der Darstellung halogenhaltiger Vertreter die Bildung fester Polyaddukte aus, die durch Lewis-Säure/Base-Wechselwirkung zwischen P-Donor- und Si-Akzeptorfunktion entstehen. Liganden des Typs (2-Me2PC6H4)SiXMe2 [X = NMe2 (12)], Cl (13), F (14) sind, ausgehend von 2-Chlorbrombenzol, auf zwei Wegen nach dem in Abb. 3. angegebenen Syntheseplan zugänglich. Die neuen Verbindungen werden durch analytische (C, H) und spektroskopische Untersuchungen (NMR, MS) charakterisiert. Zur Klärung des Assoziationsverhaltens werden ausgewählte Vertreter (2 und 9) folgenden Experimenten unterzogen: - Kontrolle des Einflusses der Verdünnung auf die Protonen- und Fluorresonanzen von 2 und 9,- Untersuchung des Adduktgleichgewichtes (-H2CF3Si←PMe2CH2-)n + nBF3 → n[F3B←PMe2CH2CH2SiF3],- Aufspaltung des Polyaddukts von 2 mit [NH4]F bzw. [Me4N]F unter Bildung hexakoordinierter komplexer Anionen [Me2PCH2CH2SiF5]2-.Die Ergebnisse dieser Untersuchungen bestätigen die P→Si-Adduktbildung als Ursache der Oligo- und Polymerisation.
    Additional Material: 5 Ill.
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