Wheelchair stability : effect of body position KIRBY, R. L; SAMPSON, M. T; THOREN, F. A. V ...
Journal of rehabilitation research and development,
11/1995, Letnik:
32, Številka:
4
Journal Article
Recenzirano
When a wheelchair user reaches and leans, the static stability decreases in the direction of the lean and increases in the opposite direction. The purpose of this study was to determine the extent of ...this effect. We studied 21 nondisabled subjects in a representative wheelchair, measuring the static forward, rear, and lateral stability on a tilting platform. Reaching and leaning away from the tip added stability, with mean increases ranging from 9.1% to 124.3% of the neutral-position values, whereas reaching and leaning toward the tip reduced stability, with mean decreases ranging from 25.2% to 52.3% (p < 0.0001). The stability range ("away" minus "toward") varied from 52.4% to 149.5%. Reaching forward had a greater effect on stability than did reaching back or to the side. Wheelchair users with the ability to control their body positions can profoundly affect the stability of their wheelchairs, a factor that should be considered in wheelchair selection and training.
Prosthaphaeresis revisited Thoren, Victor E
Historia mathematica,
02/1988, Letnik:
15, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The trigonometric identities for the product of two sines and the product of two cosines were first published in 1588. The discovery of the two equations, however, clearly predates that publication. ...Credit for priority was debated at the end of the last century and tentatively assigned to Paul Wittich of Breslau. But at least some of the conclusions reached at that time were not completely sound, even with respect to the evidence then available; and in the meantime, new evidence has come to light. Reevaluation of the issue now suggests a very questionable role for Wittich in the discovery of either equation. The first one was certainly discovered by Johannes Werner in about 1510, and probably resurrected from his papers by Wittich, while the second one appears to have been discovered from a knowledge of the first by Joost Bürgi in about 1585. But if Wittich loses one aspect of his priority in this reevaluation, he gains in another aspect. For it is now clear that Wittich had developed the method of prosthaphaeresis—the idea of using a product formula to simplify calculations—well before he arrived on Hven in 1580.
Die trigonometrischen Identitäten für das Produkt zweier Sinus und das Produkt zweier Cosinus wurden 1588 zum ersten Mal veröffentlicht. Ohne Zweifel jedoch ereignete sich die Entdeckung der zwei Gleichungen vor jener Veröffentlichung. Am Ende des letzten Jahrhunderts wurde das Verdienst der Priorität debattiert und vorerst Paul Wittich aus Breslau zugeschrieben. Auf jeden Fall waren einige der zu der Zeit gezogenen Schlüsse (selbst in Anbetracht der damals zugänglichen Beweisstücke) nicht sehr gründlich durch-dacht. In der Zwischenzeit sind neue Befunde zum Vorschein gekommen. Eine neue Untersuchung der Streitfrage ergibt eine fragwürdige Rolle Wittichs in bezug auf die Entdeckung der beiden Gleichungen. Die erste, bestimmt von Johannes Werner ca. 1510 entdeckt, hat Wittich wahrscheinlich in Werners Nachlaß gefunden. Es scheint, als ob die zweite anhand der Kenntnis der ersten von Joost Bürgi ca. 1585 entdeckt wurde. Wenn aber Wittich einen Teil seiner Priorität dank diesen neuen Überlegungen verliert, so gewinnt er einen anderen. Es ist nämlich jetzt klar, daß Wittich die Methode der “Prosthaphaeresis” entwickelt hat, eine Methode, die das Produkt einer Formel verwendet, um Berechnungen zu vereinfachen.
Les identités trigonométriques pour les produits de deux sinus et de deux cosinus ont été publiées pour la première fois en 1588. Il est pourtant clair que leur découverte est antérieure à cette publication. A la fin du XIX
e siècle, après avoir débattu la question, on a attribué avec hésitation cette découverte à Paul Wittich de Breslau. Toutefois, même en tenant compte uniquement des documents alors connus, certaines conclusions de cette époque reposent sur des assises chancelantes. Depuis, de nouveaux éléments sonts venus s'ajouter au dossier. Le rôle de Wittich dans la découverte de ces deux identités apparaît maintenant contestable. La première identité fut certainement découverte par Johannes Werner vers 1510, et aurait vraisemblablement été reprise des papiers de ce dernier par Wittich. Par ailleurs, la seconde identité semble avoir été déduite de la première par Joost Bürgi vers 1585. Même si Wittich perd ici la priorité de ces découvertes, il y gagne sur un autre plan. En effet, il devient maintenant évident que Wittich avait développé la méthode de prosthaphaeresis—l'idée d'employér une formule de produit pour simplifier les calculs—bien avant son arrivée à Hven en 1580.
Although properly adjusted rear-antitip devices on wheelchairs prevent rear-tipping accidents, many wheelchair users do not use them because they limit manueverability. This study evaluated the use ...and effectiveness of antitip devices, particularly the effect of the devices' position on rear stability and maneuverability. In an epidemiologic study of the use of antitip devices, using a database of noninstitutionalized users of manually propelled chairs, we found no significant difference in the incidence or nature of rear-tipping accidents between the 167 who used antitip devices and the 399 who did not. We also evaluated seven common manually propelled wheelchairs, occupied by an anthropomorphic test dummy, with and without antitip devices. The added stability provided by the antitip devices varied considerably (from -1.0 to 27.1 degrees) depending on the type of chair, the configuration of the chair and the position of the antitip device. A representative wheelchair was then equipped with an adjustable antitip device that allowed us to test 68 combinations of vertical and horizontal positions. The relationships between the position of the antitip device and both the measured rear-stability and maneuverability values could be expressed by significant regression equations, and correlated highly with the values predicted by a theoretical model that we developed. These relationships should assist clinicians, users and wheelchair designers in finding appropriate compromises between safety and maneuverability.
TYCHO AND KEPLER ON THE LUNAR THEORY THOREN, VICTOR E.
Publications of the Astronomical Society of the Pacific,
10/1967, Letnik:
79, Številka:
470
Journal Article
ABSTRACT
A single bout of low‐frequency electroacupuncture (EA) causing muscle contractions increases whole‐body glucose uptake in insulin‐resistant rats. We explored the underlying mechanism of this ...finding and whether it can be translated into clinical settings. Changes in glucose infusion rate (GIR) were measured by euglycemic–hyperinsulinemic clamp during and after 45 min of low‐frequency EA in 21 overweight/obese women with polycystic ovary syndrome (PCOS) and 21 controls matched for age, weight, and body mass index (experiment 1) and in rats receiving autonomic receptor blockers (experiment 2). GIR was higher after EA in controls and women with PCOS. Plasma serotonin levels and homovanillic acid, markers of vagal activity, decreased in both controls and patients with PCOS. Adipose tissue expression of pro‐nerve growth factor (proNGF) decreased, and the mature NGF/proNGF ratio increased after EA in PCOS, but not in controls, suggesting increased sympathetic‐driven adipose tissue metabolism. Administration of a‐/β‐adrenergic receptor blockers in rats blocked the increase in GIR in response to EA. Muscarinic and dopamine receptor antagonist also blocked the response but with slower onset. In conclusion, a single bout of EA increases whole‐body glucose uptake by activation of the sympathetic and partly the parasympathetic nervous systems, which could have important clinical implications for the treatment of insulin resistance.—Benrick, A., Kokosar, M., Hu, M., Larsson, M., Maliqueo, M., Marcondes, R. R., Soligo, M., Protto, V., Jerlhag, E., Sazonova, A., Behre, C. J., Højlund, K., Thorén, P., Stener‐Victorin, E. Autonomic nervous system activation mediates the increase in whole‐body glucose uptake in response to electroacupuncture. FASEB J. 31, 3288–3297 (2017). www.fasebj.org
Kepler's Second Law in England Thoren, Victor E.
The British journal for the history of science,
11/1974, Letnik:
7, Številka:
3
Journal Article
Recenzirano
In two recent articles by Russell and Whiteside, the reception of those particular conclusions of Kepler that have come to be called his laws of planetary motion has been subjected to the first ...research beyond the pioneering efforts of Delambre at the beginning of the nineteenth century. Independently conceived, and directed towards quite different ends, these two investigations overlapped in only one substantial area—their survey of citations of Kepler's second law by English astronomers between 1650 and 1670. Not surprisingly, they reached essentially identical conclusions about the situation in 1670. Finding ‘equant’ theories instead of the law of areas, wherever he looked, Russell qualified his general claim ‘that the importance of Kepler's ideas during the period up to 1666 has been greatly underestimated’, to the extent of describing the history of the second law as ‘chequered’ and ‘complicated’. And Whiteside simply reported that Kepler's scheme for reckoning motion in the elliptical orbit ‘was seemingly firmly accepted by no one, and even its formal enunciation but rarely stated in the period’.
Background and Purpose- A large infarct and expanding cerebral edema (CED) due to a middle cerebral artery occlusion confers a 70% mortality unless treated surgically. Reperfusion may cause ...blood-brain barrier disruption and a risk for cerebral edema and secondary parenchymal hemorrhage (PH). We aimed to investigate the effect of recanalization on development of early CED and PH after recanalization therapy. Methods- From the SITS-International Stroke Treatment Registry, we selected patients with signs of artery occlusion at baseline (either Hyperdense Artery Sign or computed tomography/magnetic resonance imaging angiographic occlusion). We defined recanalization as the disappearance of radiological signs of occlusion at 22 to 36 hours. Primary outcome was moderate to severe CED and secondary outcome was PH on 22- to 36-hour imaging scans. We used logistic regression with adjustment for baseline variables and PH. Results- Twenty two thousand one hundred eighty-four patients fulfilled the inclusion criteria (n=18 318 received intravenous thrombolysis, n=3071 received intravenous thrombolysis+thrombectomy, n=795 received thrombectomy). Recanalization occurred in 64.1%. Median age was 71 versus 71 years and National Institutes of Health Stroke Scale score 15 versus 16 in the recanalized versus nonrecanalized patients respectively. Recanalized patients had a lower risk for CED (13.0% versus 23.6%), adjusted odds ratio (aOR), 0.52 (95% CI, 0.46-0.59), and a higher risk for PH (8.9% versus 6.5%), adjusted odds ratio, 1.37 (95% CI, 1.22-1.55), than nonrecanalized patients. Conclusions- In patients with acute ischemic stroke, recanalization was associated with a lower risk for early CED even after adjustment for higher rate for PH in recanalized patients.
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