Reentry Point Research Articles

Reflux elimination without any ablation or disconnection of the saphenous vein. A haemodynamic model for venous surgery.

to investigate the possibility of the haemodynamic suppression of reflux in the greater saphenous vein (GSV) without any high ligation and/or stripping procedure. prospective study; single group of patients. forty patients affected by primary chronic venous insufficiency of all clinical classes, with demonstrated duplex incompetence both of the sapheno-femoral junction (SFJ) and the GSV trunk, with the re-entry perforator located on a GSV tributary. The re-entry point was defined as the perforator, whose finger compression of the superficial vein above its opening eliminates reflux in the GSV. air-plethysmographic parameters as well as duplex scanning were performed both preoperatively, and 1 and 6 months later, respectively. Operation consisted in flush ligation and division from the GSV of the tributary containing the re-entry perforating vein. duplex investigation demonstrated both a forward flow and reflux disappearance in the GSV in 100% and 85% of the cases after 1 and 6 months, respectively. All air-plethysmographic parameters, with the exception of Ejection Fraction, improved significantly: Venous Volume changed from 150+/-9 ml to 114+/-7 ml (p <0.0001), Venous Filling Index from 4.9+/-0.5 ml/s to 2.3+/-0.2 ml/s ( p <0.0001), and Residual Volume Fraction from 42+/-3 ml to 30+/-2 ml ( p <0.0001). this study demonstrates that reflux in the GSV system is supported by a gradient of pressure between the anatomical point of reflux and the point of re-entry in the deep veins. Disconnection of the flow to the re-entry perforator without high ligation of the sapheno-femoral junction suppresses GSV reflux.

複数の２ライン軌道要素を利用したスペースデブリの落下予測手法

The uncontrolled reentry of space object is one of the serious problems that the space agencies face. This paper presents a new reentry prediction method which estimates the reentry time and point using multiple sets of orbital elements and an error-propagation model. In the low-altitude orbit, the dominant perturbing force is air drag. Analyzing how the air drag affects the accuracy of the orbit propagation, we constructed an error-propagation model. Combining the multiple orbital elements with this model, this method estimates the optimal air drag and predicts a reentry time accurately. To demonstrate the performance of this method, a reentry prediction experiment was conducted. The experimental prediction took an example of the H-II Rocket 2nd Body that actually reentered on 27 January, 1999. Results show that the method can provide accurate predictions of reentry.

The Politics of the Interface: Power and Its Exercise in Electronic Contact Zones

O ver a casual lunch at a recent professional conference, Trent Batson, a professor at Gallaudet University, told us a story that made us think about borders and their effects. He had been visiting Mexico on a short day trip in the company of an academic colleague who taught at Mt. Holyoke but had been born in India. On the way back into the United States, these colleagues entered two separate lines at the stations marking the official re-entry point to this country. Border guards, observing the darker skin of the one colleague stopped him-as they did all people who, in Batson's words, looked vaguely Mexican. The Indian colleague, having lived and worked in this country for a number of years, had made the mistake of thinking that this border, this country, was an open one. He carried only a photocopy of the green card that identified him as a resident alien, rather than the card itself, as required by United States law. Given these relatively unexceptional circumstances, what followed seemed significant to us-the Indian-born colleague was detained by officials and eventually fined-even though he carried additional materials identifying him as a professor at Holyoke. Batson was not stopped or questioned. He was also not allowed to accompany his friend, who was taken to an office by the border guards where he was detained for half an hour. Batson was allowed to watch the proceedings through a window, to gaze on the administration and application of American law.

Development of Coronary Collateral Circulation

Collateral coronary arteries provide alternate routes for delivery of blood to myocar­ dium distal to major coronary-artery obstructions. These channels may be extracar­ diac, endomural, or arterioluminal in origin (I). One additional source of collateral myocardial blood flow is from deliberate attempts to surgically augment blood flow to ischemic regions of myocardium. Over the years these have included methods such as promotion of adhesion formation with inflammation and epicardial in­ growth, direct intramyocardial tunneling of bleeding arterial vessels, and, most recently, the construction of aortocoronary interposition saphenous-vein bypass grafts. This review deals primarily with intercoronary collateral vessels, since these constitute the major and best studied class of naturally occurring collateral arteries. These arteries have an anatomic point of origin termed the stem, a mid-zone, and a reentry point. The presence, number, and transmural distribution of coronary collaterals appear to be determined genetically for different species and perhaps differences in collateral density within a given species may also be a hereditary characteristic (2, 3). For example, dogs form extensive epicardial collaterals, while pigs have primarily a dense subendocardial network of collateral arteries. In con­ trast, collateral vessels in man have been demonstrated at every depth of myocar­ dium, but subendocardial connections appear most numerous. Goats, however, do not generally form collateral vessels (4, 5). Gradual closure of a coronary artery in the canine model rarely results in myocardial infarction, but similar preparations in pigs invariably result in some degree of tissue necrosis. The same technique applied to a goat usually results in the death of the animal from massive myocardial necrosis (6). Although man may form abundant collateral channels, it is unpredicta-