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  • 1
    Electronic Resource
    Electronic Resource
    The Influence of Vascular Pressure and Angiographic Characteristics on Haemorrhage from Arteriovenous Malformations (2000)
    Springer
    Acta neurochirurgica 142 (2000), S. 39-43 
    Details
    ISSN: 0942-0940
    Keywords: Keywords: Arteriovenous malformation; haemorrhage; vascular pressure.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary ¶ Background. The present study was designed to determine whether there is a physiological explanation for the predisposition of patients with certain angiographic characteristics to haemorrhage from cerebral arteriovenous malformations (AVMs).  Methods. Intra-operative measurement of feeding artery pressure (FAP) and intravascular pressures in the draining venous system [draining vein pressure (DVP) and cranial sinus pressure (SP)] were performed for 30 AVM cases using direct puncture of the vessels. The correlation between pressures and previously described angiographic characteristics predisposing to haemorrhage were evaluated.  Findings. Small nidus size and only one draining vein increased the risk of haemorrhage. FAP and DVP are both inversely related to the number of draining veins and the size of the AVMs. DVP was significantly higher in AVMs with haemorrhage (23.1±8.7 mmHg) than in those without (13.5±4.4), as was FAP (58.6±12.8 as opposed to 38.7±4.7) (p〈0.05). Moreover, the difference between systemic blood pressure and the FAP with haemorrhagic AVMs (17.0±9.5 mmHg) was significantly lower than that in nonhaemorrhagic cases (33.7±5.5) (p〈0.05). The pressure difference between the feeding artery and draining vein was not significant between the haemorrhagic and nonhaemorrhagic groups. There was no significant difference of SP between haemorrhagic and nonhaemorrhagic patients.  Interpretation. The present study suggests that a high DVP probably induced by high resistance in the venous drainage system, as well as a high FAP, may contribute to the development of haemorrhage from AVMs, and physiologically supports previous reports that small AVMs and AVMs with only one draining vein are susceptible to haemorrhage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007010050005
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  • 2
    Electronic Resource
    Electronic Resource
    The Factors Influencing Haematoma Volume due to Arteriovenous Malformations (1999)
    Springer
    Acta neurochirurgica 141 (1999), S. 385-388 
    Details
    ISSN: 0942-0940
    Keywords: Keywords: Arteriovenous malformation; cerebral haemorrhage; haematoma volume; angiography; computed tomography.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary  Haemorrhage due to cerebral arteriovenous malformations (AVMs) varies from massive, requiring urgent operations, to clinically silent. The present study was designated to identify factors influencing haematoma size, and the pathophysiological mechanisms of massive haemorrhage were studied. 55 patients with intracerebral haematomas due to supratentorial AVMs were included in this study. Angiographic and clinical findings were retrospectively evaluated in relation to haematoma size.  Statistical analysis demonstrated that small size and the presence of only one draining vein were high risk factors for massive haemorrhage. The haematoma volume in small AVMs (30±4 cm3) was significantly larger than in other AVMs (7±3 cm3) (p=0.0005). AVMs with only one draining vein were associated with massive haematoma volume as compared to AVMs with two or more draining veins (30±4 versus 11±3 cm3, p=0.0023).  Our previous study demonstrated that feeding artery pressure (FAP) was significantly higher in AVMs with haemorrhage than in those without, as was draining vein pressure (DVP), and FAP and DVP were inversely related to the number of draining veins and the size of the AVMs. Thus, in small AVMs and AVMs with only one draining vein, local increase in DVP may thus contribute to massive haemorrhage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007010050314
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  • 3
    Electronic Resource
    Electronic Resource
    A source of haemorrhage in adult patients with moyamoya disease: The significance of tributaries from the choroidal artery (1996)
    Springer
    Acta neurochirurgica 138 (1996), S. 1282-1286 
    Details
    ISSN: 0942-0940
    Keywords: Moyamoya disease ; intraventricular haemorrhage ; angiography ; choroidal artery ; medullary artery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary This study concerns 19 patients over 16 years of age with Moyamoya disease. Ten cases of intracranial haemorrhage, as the initial haemorrhagic event in patients aged from 21 to 55 (haemorrhagic group) and 9 cases of ischaemic events in 18- to 53-year-old patients (ischaemic group) were included. All haemorrhages were associated with intraventricular haemorrhages (IVH); and all but one case of thalamic haemorrhage were thought to be primary IVH (2 cases of small paraventricular haemorrhage; 2 of small haemorrhages in the splenium; 5 with no intracerebral haematoma). In the 9 patients of the ischaemic group, there were 2 cases of transient ischaemic attacks and 7 of cerebral infarction. Angiographic evaluations demonstrated that the abnormal basal vessel formation and the collateral supplies from the external carotid arteries were poorly developed in both groups. In contrast, the collateral circulation via the choroidal and posterior pericallosal arteries was well demonstrated. Furthermore, marked enlargement of the choroidal arteries and the medullary arteries derived from them was seen more frequently in the haemorrhagic group. These findings suggested that the haemodynamic load in the vessels supplying the walls of the posterior parts of the ventricles and the periventricular region was increased, especially in the haemorrhagic group. Those vessels were considered to be important sites of IVH in adult patients with Moyamoya disase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01411056
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  • 4
    Electronic Resource
    Electronic Resource
    Microwave spectrum, large-amplitude motions, and ab initio calculations for N2O5 (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 7249-7262 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The rotational spectrum of dinitrogen pentoxide (N2O5) has been investigated between 8 to 25 GHz at a rotational temperature of ∼2.5 K using a pulsed-molecular-beam Fourier-transform microwave spectrometer. Two weak b-dipole spectra are observed for two internal-rotor states of the molecule, with each spectrum poorly characterized by an asymmetric-rotor Hamiltonian. The observation of only b-type transitions is consistent with the earlier electron-diffraction results of McClelland et al. [J. Am. Chem. Soc. 105, 3789 (1983)] which give a C2 symmetry molecule with the b inertial axis coincident with the C2 axis. Analysis of the 14N nuclear hyperfine structure demonstrates that the two nitrogen nuclei occupy either structurally equivalent positions or are interchanging inequivalent structural positions via tunneling or internal rotation at a rate larger than ∼1 MHz. For the two internal rotor states, rotational levels with Ka+Kc even have IN=0, 2, while levels with Ka+Kc odd have IN=1, where IN is the resultant nitrogen nuclear spin. This observation establishes that the equilibrium configuration of the molecule has a twofold axis of symmetry. Guided by ab initio and dynamical calculations which show a planar configuration is energetically unfavorable, we assign the spectrum to the symmetric and antisymmetric tunneling states of a C2 symmetry N2O5 with internal rotation tunneling of the two NO2 groups via a geared rotation about their respective C2 axes. Because of the Bose–Einstein statistics of the spin-zero oxygen nuclei, which require that the rotational–vibrational–tunneling wave functions be symmetric for interchange of the O nuclei, only four of the ten vibrational-rotational-tunneling states of the molecule have nonzero statistical weights. Model dynamical calculations suggest that the internal-rotation potential is significantly more isotropic than implied by the electron-diffraction analysis. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472586
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  • 5
    Electronic Resource
    Electronic Resource
    Straightforward methods to detect non-linear response of the soil. Application to the recordings of the Kobe earthquake (Japan, 1995) (2000)
    Springer
    Journal of seismology 4 (2000), S. 161-173 
    Details
    ISSN: 1573-157X
    Keywords: H/V ratio ; Kappa ; Kobe earthquake ; Non-Linearity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Simple straightforward methods are applied to testtheir ability to detect the non-linear response of thesoil. Recordings of the main shock and aftershocks ofthe 1995, Hyogo-ken Nanbu (Kobe) earthquake are used.Non-linear effects are investigated using twodifferent techniques, on a collection of data for 12sites situated on different geological structures inthe Kobe and Osaka areas. The first method used is theso-called receiver functions technique (Langston,1979), which consists of computing the spectral ratiobetween horizontal and vertical components of motion.This ratio has been shown to reveal the fundamentalfrequency of a site (Lachet and Bard, 1994; Lachet etal., 1996; Theodulidis et al., 1995, 1996). For eachsite, recordings of the main shock and a set ofaftershocks are considered. The variation of thisspectral ratio for different values of the maximumacceleration recorded at a site is investigated. Bothvariations of the amplitude of the H/V ratio (due tonon-linear behavior, on the horizontal components inparticular) and of the frequency position of theamplified band-width are observed. The secondtechnique used in this study is related to thevariation of the high frequency content of therecordings during the main-shock and its aftershocks.The high frequency spectral decay of the motion,characterized by κ parameter, is assumed to berelated mainly to the near-surface attenuation. Itshould then increase with increasing peak velocity, incase of non-linearity. The value of kappa iscalculated for the 12 sites in the Kobe area, fordifferent types of soil conditions, and againdifferent values of peak ground acceleration.Variations of kappa are then related to non-linearbehavior of the soil during the Kobe earthquake.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009886308449
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