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No abstract is provided for this article.
No abstract is provided for this article.
An interactive buckling model for sandwich struts accounting for buckle pattern localization is extended to cover such struts with differing face plate thicknesses. Although this does not affect the critical buckling characteristics of the structure, there is a significant change in the postbuckling behavior; formerly symmetric secondary buckling and imperfection sensitivity characteristics lose this quality as both become asymmetric.
Coronary stents have revolutionised the management of patients with obstructive coronary artery disease. This chapter will review the problems associated with percutaneous coronary intervention when performed using balloon angioplasty and bare-metal stents, before discussing the first and second generation DES. Finally the new generation of drug-eluting stents, which are currently undergoing evaluation in clinical trials, will be reviewed.
Historically, the 15 randomized clinical trials comparing coronary artery bypass graft surgery and percutaneous coronary intervention for intervention in coronary artery disease have been criticized for profound selection bias (‘cherry-picking’ of patients). The stringent clinical and angiographic-based inclusion criteria led to only 2–12% of all screened patients actually being randomized in these trials, resulting in recruitment of mainly low-risk subjects with predominant one- or two-vessel disease (and a low incidence of three-vessel disease), preserved left ventricular ejection fraction, and a low incidence of diabetes. This highly selective selection practice echoes that of a review of 31 antidepressant efficacy trials in 2002, demonstrating that despite the large number of trials and participants, only a minority of patients treated for depression in routine clinical were eligible for inclusion because of a large number of exclusion criteria.
Intracoronary blood flow velocity measurements with a Doppler probe and the radiographic assessment of myocardial perfusion with contrast media previously have been used to investigate regional coronary flow reserve. In the present study we applied both techniques in the same patients to measure the immediate improvement in coronary flow reserve as a result of angioplasty. In addition we compared papaverine induced hyperemia with reactive hyperemia following transient transluminal occlusion of a major coronary artery. In 13 consecutive patients with a single proximal stenosis, coronary flow reserve was measured pre‐ and postangioplasty by digital subtraction cineangiography, while pre‐ and postangioplasty Doppler measurements before and after papaverine were obtained in the proximal part of the stenotic vessel. After the last transluminal occlusion, reactive hyperemia recorded with the Doppler probe was also compared to the coronary flow reserve measurement obtained during papaverine induced hyperemia. As a result of the angioplasty, coronary flow reserve measured with the radiographic technique (mean ± SD) increased from 1.1 ± 0.4 to 2.2 ± 0.4 (P < 0.001), while coronary flow reserve measured with the Doppler probe (mean ± SD) increased from 1.2 ± 0.3 to 2.4 ± 0.4 (P < 0.001). Pharmacologically induced hyperemia measured with the radiographic technique and the Doppler probe were linearly related (r = 0.91 with a SEE 0.3) and confirmed the reliability of the intracoronary measurements. Using these two independent techniques, coronary flow reserve immediately after angioplasty was found to be substantially improved but still abnormal. In addition, the magnitude of hyperemia induced by papaverine was comparable to the reactive hyperemia following transluminal occlusion, although the latter measurement was recorded with the angioplasty catheter still across the dilated lesion. (J Interven Cardiol, 1988:1:1)
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Abstract We present SOFIA/HAWC+ continuum polarization data on the magnetic fields ( B fields) threading 17 pc-scale massive molecular clumps at the western end of the η Carinae giant molecular cloud (Region 9 of the Galactic Census of High- and Medium-mass Protostars, or CHaMP, representing all stages of star formation from pre-stellar to dispersing via feedback), revealing important details about the field morphology and role in the gas structures of this clump sample. We performed Davis–Chandrasekhar–Fermi (DCF) and histogram of relative orientation (HRO) analyses tracing column densities 25.0 < log( N /m −2 ) < 27.2. With HRO, B fields change from mostly parallel to column density structures to mostly perpendicular at a threshold N crit = (3.7 ± 0.6) × 10 26 m −2 , indicating that gravitational forces exceed magnetic forces above this value. The same analysis in 10 individual clumps gives similar results, with the same clear trend in alignments and a threshold N crit = (1.9 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow/> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.8</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>1.5</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> ) × 10 26 m −2 . In the other seven clumps, the alignment trend with N is much flatter or even reversed, inconsistent with the usual HRO pattern. Instead, these clumps’ fields reflect external environmental forces from the nearby H ii region NGC 3324. DCF analysis reveals field strengths somewhat higher than typical of nearby clouds, with the B–n data lying mostly above the R. M. Crutcher relation. The mass-to-flux ratio λ across all clumps has a Gaussian distribution, log λ DCF = –0.75 ± 0.45; only small areas are dominated by gravity. However, a significant trend of rising log λ with falling T dust parallels R. L. Pitts et al.’s result: T dust falls as <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>N</mml:mi> <mml:msub> <mml:mrow/> <mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> </mml:math> rises toward clump centres. In this massive clump sample, B fields provide enough support against gravity to explain their overall low star formation rate.
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No abstract is provided for this article.