Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

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

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Sonicated X-ray contrast agents for quantitative myocardial contrast echocardiography — a critical approach (1995)
    Springer
    Heart and vessels 10 (1995), S. 96-105 
    Details
    ISSN: 1615-2573
    Keywords: Non-ionic radiographic contrast agent ; Sonication ; Microbubbles ; Backscatter intensity ; Quantitative myocardial blood flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Contrast echocardiography with sonicated radiographic contrast agents has been used for the qualitative and quantitative determination of myocardial blood flow. One major problem has been the size of the microbubbles since only bubbles smaller than 8 µm are expected to pass the capillary bed and larger bubbles may obstruct the capillaries and, thus, alter myocardial blood flow. These techniques have been used for several years, but their reliability has not yet been assessed accurately. Five different methods for the production of sonicated radiographic contrast agents (methods 1–3 from the literature, and 4 and 5 from our laboratory; M1–5) were evaluated for their use in quantitative contrast echocardiography. The sonication of non-ionic X-ray contrast media was performed with a standard titanium probe (20 kHz) for methods 1–4, with variation in the sonication time and the number of sonication jets used for each method. In M5, we used bubbles that were produced by the insufflation of oxygen in the X-ray contrast agent; large (〉8 µm) bubbles were destroyed by sonication at 380kHz (resonance method). Mean bubble size was determined by computerized videomicroscopy. The effect of bubble size on the backscatter of the ultrasonic signal was calculated for each method. Mean bubble size (±1 SD) ranged between 11.5 ± 4µm and 16.1 ± 14 µm for M1–M5. The best values, i.e., the smallest bubbles, were found with M4 (prepressurized contrast medium). Assuming capillary passage for bubbles smaller than 8 µm, only 14%–48% of the bubbles were smaller than 8 µm (M1–M5). The best results with regard to bubble size (≤8 µm) were observed with M5 (48% ≤8 µm). In regard to the influence of bubble size on the backscatter of the ultrasonic signal, 56%–98.5% of the signal was produced by bubbles larger than 15 µm (M1–5) but the best results were obtained with M4. It is concluded that capillary-passage of sonicated microbubbles (≤8 µm) can be expected in only 14%–48% of the bubbles for the five different sonication techniques. More than 50% of all microbubbles produced by these techniques are larger than the expected 8 µm. These large bubbles are responsible for the backscatter of the ultrasonic signal in the vast majority of cases. Thus, the sonication of radiographic contrast agents appears to be inappropriate for the production of uniformly small microbubbles and, thus, this method is not suitable for quantitative measurements of coronary blood flow.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01744500
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Effects of aromatase inhibitors on reproduction in male three-spined sticklebacks, Gasterosteus aculeatus, exposed to long and short photoperiods (1997)
    Springer
    Fish physiology and biochemistry 16 (1997), S. 419-423 
    Details
    ISSN: 1573-5168
    Keywords: stickleback ; testes ; kidney ; secondary sexual characters ; maturation ; aromatization ; aromatase inhibitors ; 1,4,6-androstatriene-3,17-dione ; CGS16949 A ; 4-(5,6,7,8-tetrahydrimidazo[1,5-a]-pyridin-5-yl) benzonitrilemonohydrochloride ; photoperiod
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Three-spined stickleback Gasterosteus aculeatus, males were implanted with Silastic capsules filled with different aromatase inhibitors; 1,4,6-androstatriene-3,17-dione or the non-steroidal CGS16949 A, 4-(5,6,7,8-tetrahydrimidazol [1,5-a]pyridin-5-yl) benzonitrile monohydrochloride or empty capsules. The fish were then exposed to long or short photoperiod. Under the long photoperiod most fish in all treatments displayed a hypertrophied kidney (a secondary sexual character in sticklebacks) and completed, quiescent spermatogenesis, similar as in the natural spawning period. Under the short photoperiod the controls had unstimulated kidneys and an active spermatogenesis, whereas the males implanted with both aromatase inhibitors had stimulated kidneys, though not to the extent as in the long photoperiod, and completed, quiescent spermatogenesis. These findings suggest that aromatization is of importance for the inhibitory effects of short photoperiod on reproduction in the stickleback.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007776517447
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Simple proof of the pairing theoremThis article is dedicated to the memory of Professor Jean-Louis Calais. (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 63 (1997), S. 31-33 
    Details
    ISSN: 0020-7608
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A very simple constructive proof of Löwdin's pairing theorem is presented. © 1997 John Wiley & Sons, Inc.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 4
    Electronic Resource
    Electronic Resource
    The chemical Hamiltonian approach for treating the BSSE problem of intermolecular interactions (1998)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 70 (1998), S. 41-63 
    Details
    ISSN: 0020-7608
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The two alternative treatments of the BSSE problem of intermolecular interactions - the a posteriori counterpoise (CP) correction scheme of Boys and Bernardi (BB) and the a priori exclusion of the basic-set superposition error (BSSE) by using the “chemical Hamiltonian approach” (CHA) - are discussed. Alternative interpretations of the BB scheme are compared and some problems and paradoxes are described which can consistently be resolved by introducing a hierarchical scheme of N-body CP corrections. In CHA, one identifies those terms of the Hamiltonian (or Fockian) which cause the BSSE - the same terms cause the energy lowering in the “ghost orbitals” calculations; by omitting these terms from the Hamiltonian (Fockian), one can calculate BSSE-free wave functions, by use of which the BSSE-free values of the energy and of other physical quantities can be obtained in a conventional manner. CHA was successfully applied at the SCF and DFT levels of theory, including systems containing three or more interacting subsystems or even infinite periodic chains. The pivot full CI calculations performed for small model systems showed the applicability of the approach for treating electron correlation as well. Most recently, a CHA version of the MP2 theory and a second-order BSSE-free intermolecular PT have also been tested; they are also applicable for complexes of larger size. It was observed, at any level of theory, that the results given by the a posteriori BB and a priori CHA schemes converge to each other much faster than BSSE disappears from the uncorrected results.   © 1998 John Wiley & Sons, Inc. Int J Quant Chem 70: 41-63, 1998
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...