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Search Results: 1 - 10 of 6880 matches for " Philip Meyers "
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Revisiting normal perfusion pressure breakthrough in light of hemorrhage-induced vasospasm
Matthew D Alexander, E Sander Connolly , Philip M Meyers
World Journal of Radiology , 2010,
Abstract: Cerebral arteriovenous malformations (AVMs) have abnormally enlarged arteries and veins prone to spontaneous hemorrhage. Immediately following surgical excision of a cerebral AVM, even normal brain tissue surrounding the lesion is subject to hemorrhage, a phenomenon termed normal perfusion pressure breakthrough (NPPB) syndrome. According to this theory, arteries supplying cerebral AVMs become dilated and lose their capacity to dilate or constrict to autoregulate pressure. Acutely after removal of a cerebral AVM, excessive blood pressure in these arterial feeders can cause normal brain tissue to bleed. However, this theory remains controversial. We present a patient with a cerebral AVM that demonstrated cerebrovascular reactivity and argues against an assumption underlying the theory of NPPB syndrome.
Treatment of mechanically-induced vasospasm of the carotid artery in a primate using intra-arterial verapamil: a technical case report
Alexander L Coon, Geoffrey P Colby, William J Mack, Lei Feng, Philip Meyers, E Sander Connolly
BMC Cardiovascular Disorders , 2004, DOI: 10.1186/1471-2261-4-11
Abstract: As part of a study assessing the placement feasibility and safety of a catheter capable of delivering intra-arterial cerebroprotective therapy, a female 16 kg baboon prophylaxed with intravenous nitroglycerin underwent transfemoral CCA catheterization with a metallic 6-Fr catheter without signs of acute spasm. The protocol dictated that the catheter remain in the CCA for 12 hours. Upon completion of the protocol, arteriography revealed a marked decrease in CCA size (mean cross-sectional area reduction = 31.6 ± 1.9%) localized along the catheter length. Intra-arterial verapamil (2 mg/2cc) was injected and arteriography was performed 10 minutes later. Image analysis at 6 points along the CCA revealed a 21.0 ± 1.7% mean increase in vessel diameter along the length of the catheter corresponding to a 46.7 ± 4.0% mean increase in cross-sectional area. Mean systemic blood pressure did not deviate more than 10 mm Hg during the procedure.Intraluminal CCBs like verapamil may constitute an effective endovascular treatment for mechanically-induced vasospasm in medium to large-sized vessels such as the CCA.Rapid advancements in endovascular technology and techniques allow for treatment of an ever-increasing range of neurovascular diseases. Despite improvements in the safety and efficacy of these procedures, complications such as vasospasm, stroke, and perforation still occur [1]. Vasospasm, or contraction of smooth muscle fibers in the wall of a vessel, is a commonly recognized adverse event that may complicate an endovascular procedure by limiting distal blood flow.Vasospasm complicates many disease states, particularly those affecting small vessels. Recently, treatment of small-vessel vasospasm has proven amenable to pharmacological intervention. For example, in the treatment of cerebral artery spasm, intravenous nitrates [2], intravenous calcium channel blockers (CCBs) [3], and intra-arterial papaverine [4] and CCBs [5] have been shown to prevent or mitigate this small artery
A Refutation of the Clique-Based P=NP Proofs of LaPlante and Tamta-Pande-Dhami
Hector A. Cardenas,Chester Holtz,Maria Janczak,Philip Meyers,Nathaniel S. Potrepka
Computer Science , 2015,
Abstract: In this work, we critique two papers, "A Polynomial-Time Solution to the Clique Problem" by Tamta, Pande, and Dhami, and "A Polynomial-Time Algorithm For Solving Clique Problems" by LaPlante. We summarize and analyze both papers, noting that the algorithms presented in both papers are flawed. We conclude that neither author has successfully established that P = NP.
Contrast-enhanced sonography as a novel tool for assessment of vascular malformations
Yukiko Oe, Lauren Orr, Sherelle Laifer-Narin, Eiichi Hyodo, Agnes Koczo, Shunichi Homma, Jessica Kandel, Philip Meyers
Vascular Cell , 2010, DOI: 10.1186/2040-2384-2-25
Abstract: We describe the use of contrast-enhanced sonography as a novel tool to define vascular anatomy and localize arteriovenous shunting in a young patient with a symptomatic vascular malformation.This method may effectively reduce radiation exposure and cost, and additionally provide unique information about arteriovenous shunting, offering a novel imaging application for patients with these conditions.Vascular malformations (VM) are congenital lesions with diverse clinical manifestations. In contrast to hemangiomas, a separate category of vascular tumors which tend to involute spontaneously, VM often grow in proportion with the child but may expand at an accelerated pace [1]. VM can occur throughout the body, involve multiple vessel types, and may be localized or extensive [2]. Although criteria have been developed for classifying vascular malformations according to flow velocity and vessel type [3], diagnosis of these heterogeneous lesions remains challenging.While these abnormalities may be asymptomatic, VM become clinically important when associated with disfigurement, functional impairment, pain, infection, and serious bleeding [4,5]. These patients require treatment, which varies according to the specific lesion, its location, functional impairment, and goals of therapy. Assembly of a multi-disciplinary team is advantageous when planning therapy. Further, precise characterization of problematic lesions is critically important both in designing the approach and understanding, likely outcomes (such as the potential need for multiple treatments). For example, malformations with arteriovenous shunting may require embolization [1,6], whereas sclerotherapy is the treatment of choice for venous and macrocystic lymphatic malformations [7,8]. Among venous malformations treated with sclerotherapy, smaller well-defined lesions have been associated with better outcomes than larger ill-defined lesions [6].Although VM can be partly characterized on the basis of history and physi
Update on the natural history of intracranial atherosclerotic disease: A critical review
Ricardo J Komotar, Christopher P Kellner, Daniel M Raper, Dorothea Strozyk, Randall T Higashida, Philip M Meyers
World Journal of Radiology , 2010,
Abstract: Intracranial atherosclerotic disease (ICAD) contributes to a significant number of ischemic strokes. There is debate in the recent literature concerning the impact of the location of stenosis in ICAD on outcome. Some reports have suggested that disease processes and outcomes vary by vessel location, potentially altering the natural history and indications for intervention. Here we have performed a comprehensive, critical review of the natural history of ICAD by vessel in an attempt to assess the differences in disease specific to each of the vascular territories. Our assessment concludes that only minor differences exist between patients with different vessels affected in vessel-specific ICAD. We have found that middle cerebral artery disease confers a lower mortality than vessel-specific ICAD in other intracranial vessels, asymptomatic disease follows a more benign course than symptomatic disease, and that plaque progression or the detection of microemboli on transcranial Doppler may predict poor outcome. Given the expanding indications for treatment of ICAD and rapidly developing endovascular techniques to confront this disease, a thorough understanding of the natural history of ICAD aids the interventional neuroradiologist in determining when to treat and how to predict outcome in this patient population.
Novel electronic behavior driving NdNiO3 metal-insulator transition
M. H. Upton,Yongseong Choi,Jian Liu,D. Meyers,S. Middey,J. Chakhalian,Jong-Woo Kim,Philip J. Ryan
Physics , 2014,
Abstract: We present evidence that the metal-insulator transition (MIT) in a tensile strained NdNiO3 (NNO) film is facilitated by a redistribution of electronic density and neither requires Ni charge disproportionation nor symmetry change [1, 2]. Given epitaxial tensile strain in thin NNO films induces preferential occupancy of the $e_g$ $d_{x^2-y^2}$ orbital ($s_{3z^2-r^2}$) we propose the larger transfer integral of this orbital state with the O 2p mediates a redistribution of electronic density from the Ni atom. A decrease in Ni $d_{x^2-y^2}$ orbital occupation is directly observed by resonant inelastic x-ray scattering below the MIT temperature. Furthermore, an increase in Nd charge occupancy is measured by x-ray absorption at the Nd L3 edge. Both spin-orbit coupling and crystal field effects combine to break the degeneracy of the Nd 5d states shifting the energy of the Nd $e_g$ $d_{x^2-y^2}$ orbital towards the Fermi level allowing the A site to become an active acceptor during the MI transition. This work identifies the relocation of electrons from the Ni 3d to the Nd 5d orbitals across the MIT. We propose the insulating gap opens between the Ni 3d and O 2p resulting from Ni 3d electron localization mediated by charge loss. The transition seems neither purely Mott-Hubbard nor simple charge transfer.
Review of Helen Kraus, Gender Issues in Ancient and Reformation Translations of Genesis 1-4, Oxford: Oxford University Press 2011
Carol Meyers
Religion and Gender , 2012,
Abstract:
Surface superconducting states and paramagnetism in mesoscopic superconductors
C. Meyers
Physics , 2002, DOI: 10.1103/PhysRevB.68.104522
Abstract: In the framework of the Ginzburg-Landau equation, the temperature dependence of the upper critical field of small ring-like superconductors is studied. At equilibrium small parts of the phase diagram show paramagnetism for width / radius ratios below 0.85. Their number and extension increase with the size of the hole. In these regions, only the inner part of the ring shows a positive magnetic moment. The order parameter density profile appears to change, when crossing a first order transition line, which separates different angular momentum values, and we clarify the relationship between the localization of superconductivity nucleation and paramagnetism of those samples.
Non-Gaussian Correlations Outside the Horizon in Local Thermal Equilibrium
Joel Meyers
Physics , 2012,
Abstract: Making a connection between observations of cosmological correlation functions and those calculated from theories of the early universe requires that these quantities are conserved through the periods of the universe which we do not understand. In this paper, the results of [0810.2831] are extended to show that tree-approximation correlation functions of Heisenberg picture operators for the reduced spatial metric are constant outside the horizon during local thermal equilibrium with no non-zero conserved quantum numbers.
Evaluation of Energy-Efficiency Standards for Room Air Conditioners in the US  [PDF]
Alex Lekov, Victor Franco, Steve Meyers
Open Journal of Energy Efficiency (OJEE) , 2012, DOI: 10.4236/ojee.2012.12002
Abstract: This article describes an analysis of the energy and economic impacts of possible energy efficiency standards for room air conditioners on both U.S. consumers and the nation as a whole. We used two metrics to determine the effect of standards on a representative sample of U.S. consumers: life-cycle cost change and payback period. For the national impact analysis, we evaluated national energy savings attributable to each potential standard, the monetary value of the energy savings to consumers of room air conditioners, the increased total installed costs because of standards, and the net present value of the difference between the value of energy savings and increased total installed costs. Our analysis indicates that standards for room air conditioners at efficiency level 3, which is 17% more efficient than today’s typical unit in the case of room air conditioners less than 6000 Btu/h with louvers and 12% more efficient in the case of room air conditioners 8000 - 13,999 Btu/h with louvers, would save close to one quad of energy over 30 years and have a net present value of consumer benefit of between ?$0.14 billion and $1.82 billion, depending on the discount rate. In addition, such standards would reduce carbon dioxide emissions and NOx emissions.
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