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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 859-862 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Since the early work of Huxley and collaborators [H. E. Huxley, A. R. Faruqui, J. Bordas, M. H. J. Koch, and J. R. Milch, Nature 284, 5752, 140 (1980)], time-resolved x-ray diffraction using synchrotron radiation has provided and continues to provide unique information on the structural dynamics of muscle, thus addressing the fundamental question of how chemical energy is transformed into motion. While considerable progress has been made in improving data collection procedures, relatively little progress has taken place in the development of computational methods with which to interpret the large amounts of structural and functional information contained in the experimental data. Given the characteristics of the structure of muscle this poses a considerable computational challenge since realistic models of the molecular components making up the muscle fibres require extensive algorithms and computational resources. We present here a progress report on our work on this topic and describe some of the algorithmic aspects of muscle modeling as a dynamic structure and we show how visualization techniques are used to check the effect of different factors. We also describe briefly some of the insights we have gained from the modeling procedures and "theoretical experiments,'' and the current model that fits qualitatively the main features in the experimental pattern.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 6021-6028 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In this paper we investigate the ability of the Brownian dynamics simulation technique of Ermak and McCammon to evaluate rotational correlation functions of rigid hydrodynamic models. Concretely, we obtain from simulated trajectories the functions 〈Pi[cos θ(t)]〉, i=1,2 where Pi is the ith Legendre polynomial and θ(t) is the angle between two orientations, separated by time t, of a given vector. This function is closely related to the decay of fluorescence anisotropy and other time-dependent electro-optical properties. The simulation results are compared with exact results for these functions. We first consider dimers in a variety of conditions regarding the rigid constraint, the hydrodynamic interaction and the relative size of the two spheres. We next study bent trimers, for which the decays are typically multiexponential. In all cases we find that the simulated results of the correlation functions and the exact ones are in rather good agreement up to a time which is determined by the finite length of the simulated trajectory.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Macromolecules 27 (1994), S. 5371-5376 
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 7698-7705 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The rotational dynamics of a segmentally flexible model, the elastic trumbbell, has been studied using a Brownian dynamics simulation technique. The model is composed of three beads jointed by two bonds. A potential that is quadratic in the bending angle describes the partial flexibility of the model. The correlation analysis of the simulated trajectories gives rotational correlation functions, of which we have preferentially studied those of the second Legendre polynomial of the reorientation angle of the bond and end-to-end vectors. The relaxation times derived from these correlation functions are compared with those predicted by other treatments of the rotational dynamics of segmentally flexible macromolecules.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Acta neurochirurgica 77 (1985), S. 62-67 
    ISSN: 0942-0940
    Keywords: Instrumentation ; microsurgery ; needle ; suture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Lesions generated by the passage of micro-needles through vessel walls are of concern because any lesion may significantly alter hemodynamics of an anastomosis. To study this problem, three different needles were tested on the exposed carotid arteries of 30 rats: the 100μ taper point, the 100μ cutting point, and the 75μ taper point. Trauma generated by the penetration of needles was tested first as the needle and its attached suture was passed through the vessel, then the suture was left in place. One hour after penetration, the arteries were prepared for scanning electron microscopy. Differences between the 100μ taper point and the 75μ taper point were significant in terms of size and extent of lesions. An arc of endothelial cells surrounding the wounds showed flattening, tissue destruction and clotting. To minimize endothelial trauma, taper point needles are superior to cutting needles. The 100μ cutting needle caused damage to the vessel wall in tissue cutting on needle penetration, causing a slit-like incision, and in aggregation of platelets at the puncture site.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Acta neurochirurgica 91 (1988), S. 87-94 
    ISSN: 0942-0940
    Keywords: Carotid endarterectomy ; perioperative complications ; surgical pitfalls ; prevention
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary It is estimated that between 1971 and 1987 the number of carotid endarterectomies has increased from 15,000 to over 85,000 per year. Unless the procedure can be performed safely with a combined morbidity and mortality which is below the yearly risk of stroke (5%) for patients with symptomatic carotid artery disease, one should reconsider this operation as a therapeutic option. We review our experience with 891 carotid endarterectomies performed between January 1979 and June 1987. There were 579 (65%) men and 312 (35%) women of ages from 34 to 82 (median 65); risk factors included diabetes mellitus 213 (14%), hypertension 603 (68%), and smoking 630 (70%). Clinical presentation consisted of transient ischemic attacks 506 (57%), cerebral infarction with minimal neurological residual 252 (28%), stroke in evolution 3 (0.3%) and, asymptomatic stenosis 130 (15%). All patients were operated on under endotracheal anesthesia with transoperative monitoring of intra-arterial pressure, central venous pressure and arterial blood gases. Thiopental (3–5 mg/kg) and lidocaine (1 mg/kg) were given for induction and at 15 minute intervals during carotid cross-clamping. Intraluminal shunts were used in 13 (2%). A conventional (open) endarterectomy was performed in 561 (63%) and a limited endarterectomy (closed) in 330 (37%). Complications included 11 (1%) deaths, 26 (3%) developed a major neurological deficit that persisted, 30 (3%) had perioperative TIA's which resolved completely. Of the patients with preoperative neurological deficits, 33 (4%) recovered. Therefore, at one month after surgery, 854 (96%) were either as well or better than preoperatively. Of 514 (58%) postoperative angiograms, 23 (5%) showed an internal carotid artery occlusion; six of them developed an immediate postoperative cerebral infarction and one of them died, Non-neurologic complications were: cardiac 43 (5%), peripheral nerve 33 (3%), and local wound problems 20 (2%). We believe a carotid endarterectomy can be performed safely when it is done with meticulous attention to detail and consistent surgical technique founded on frequent exposure to the procedure.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Acta neurochirurgica 94 (1988), S. 117-128 
    ISSN: 0942-0940
    Keywords: Carotid artery ; EC-IC bypass ; moya-moya ; TIA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Eight cases of stroke in children treated with surgery are reported. Four of the patients had Moya-moya disease and presented with TIA. They were treated by surgically creating collaterals through the STA-MCA bypass, encephalomyosyangiosis and encephalomyoarteriosynangiosis operations. Three patients with traumatic or idiopathic carotid artery stenosis or occlusion presented with TIA and were treated with STA-MCA bypass. One patient with idiopathic carotid artery stenosis presented with a complaint of a continuous swishing noise in the ear and had a STA-MCA bypass followed by carotid artery ligation. Although stroke in children is usually secondary to systemic disease, there is a group of children with surgically treatable disease who need to be identified and treated. The potential benefit of surgery may depend on the promptness with which a definitive diagnosis is reached.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-0568
    Keywords: Cat caudate nucleus ; Ischemia ; Plasmalemmal glial assemblies ; Cytotoxic edema
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Selective cerebral ischemia was induced in the caudate nucleus of seven normothermic anesthetized cats through transorbital clamping of the anterolateral penetrating lenticulostriated arteries. The plasmalemma of astrocytic foot processes has been studied with the freeze-fracture technique and conventional electron microscopy 10, 15 and 30 min after ischemia. After 15 min of circulatory arrest, assemblies of intramembrane particles (IMPs) disappear in some areas of astroglial perivascular plasmalemma in the ischemic caudate nucleus. Interastrocytic gap junctions do not change significantly. 30 min after ischemia, the pericapillary astroglial end foot is expanded and organelles are greatly perturbed (cytotoxic edema). Although the function of astrocytic intramembrane particle assemblies is unclear, it is postulated that the disappearance of this membrane specialization may play a role in the pathophysiology of cytotoxic astroglial edema.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Interastrocytic gap junctions in the blood-brain barrier of the experimental penumbra area were studied in the cat caudate nucleus 1 h after ischemia. Transmission electron microscopy and freeze-fracture studies revealed only slight changes in gap junctions between astrocytes, indicating that these junctions are very resistant to hypoxia.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Acta neurochirurgica 106 (1990), S. 132-135 
    ISSN: 0942-0940
    Keywords: Ethnic ; epidemiology ; cerebral aneurysm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The reported higher incidences of intracranial arterial aneurysms (IAA) in Africa and Asia raised the question of possible racial differences in aneurysm incidence. This prompted a retrospective study of the 244 cases of IAA seen at the Henry Ford Hospital (HFH) from 1979 to 1985. There were 171 whites and 73 blacks in the study group. The results showed a higher white to black case ratio (2.3∶1) than the white to black hospital population ratio (1.14∶1). If only bleeding aneurysms were considered, there were 81 whites and 52 blacks, with a white to black case ratio of 1.6∶1, thus giving only a borderline racial difference. The peak age of aneurysm incidence was the fifth decade for blacks and the sixth decade for whites. The most common aneurysm sites were: White Black Middle cerebral artery 26% 12% Posterior communicating artery 20% 27% Anterior communicating artery 16% 22%
    Type of Medium: Electronic Resource
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