Zur Ermittlung von Spannungen am Rand eines elastischen Kontinuums

Für den Entwurf von Ingenieurbauten ist eine zuverlässige Prognose über den Spannungsverlauf im Bauwerk und auf dessen Rand von großer Bedeutung. Eine geschlossene Lösung der elastischen Bestimmungsgleichungen des Bauwerks ist in der Regel nicht verfügbar. Es wird daher unter Verwendung der Methode der gewichteten Reste eine schwache Form der Gleichungen abgeleitet, die zu einem gemischten Arbeitsprinzip führt. Das zugehörige Finite-Elemente-Modell erlaubt es Spannungen am Rand des Bauwerks zu ermitteln, die im Gleichgewicht zu den angreifenden Lasten stehen

Clinical outcome in decompression alone versus decompression and instrumented fusion in patients with isthmic spondylolisthesis:A prospective cohort study

OBJECTIVE In the surgical treatment of isthmic spondylolisthesis, it is debatable whether instrumented fusion is mandatory in addition to decompression. The objective of this prospective cohort study was to assess the long-term effect of decompression alone compared with decompression and instrumented fusion in patients who underwent the intervention of their own preference. The results were compared with those in patients who underwent randomly assigned treatment. METHODS The authors performed a prospective observational multicenter cohort study, including 91 patients with isthmic spondylolisthesis assigned to undergo either decompression alone (n = 44) or decompression and fusion (n = 47). The main outcomes were the Roland-Morris Disability Questionnaire (RDQ) scores and the patient's perceived recovery at the 2-year follow-up. Secondary outcomes were visual analog scale (VAS) leg pain and back pain scores and the reoperation rate. A meta-analysis was performed for data from this cohort study (n = 91) and from a randomized controlled trial (RCT) previously reported by the authors (n = 84). Subgroup analyses were performed on these combined data for age, sex, weight, smoking, and Meyerding grade. RESULTS At the 12-week follow-up, improvements of RDQ scores were comparable for the two procedures (decompression alone [D group] 4.4, 95% CI 2.3-6.5; decompression and fusion [DF group] 5.8, 95% CI −4.3 to 1.4; p = 0.31). Likewise, VAS leg pain scores (D group 35.0, 95% CI 24.5-45.6; DF group 47.5, 95% CI 37.4-57.5; p = 0.09) and VAS back pain scores (D group 23.5, 95% CI 13.3-33.7; DF group 34.0, 95% CI 24.1-43.8; p = 0.15) were comparable. At the 2-year follow-up, there were no significant differences between the two groups in terms of scores for RDQ (difference −3.1, 95% CI −6.4 to 0.3, p = 0.07), VAS leg pain (difference −7.4, 95% CI −22.1 to 7.2, p = 0.31), and VAS back pain (difference −11.4, 95% CI −25.7 to 2.9, p = 0.12). In contrast, patient-perceived recovery from leg pain was significantly higher in the DF group (79% vs 51%, p = 0.02). Subgroup analyses did not demonstrate a superior outcome for decompression alone compared with decompression and fusion. Nine patients (20.5%) underwent reoperation in total, all in the D group. The meta-analysis including both the cohort and RCT populations yielded an estimated pooled mean difference in RDQ of −3.7 (95% CI −5.94 to −1.55, p = 0.0008) in favor of decompression and fusion at the 2-year follow-up. CONCLUSIONS In patients with isthmic spondylolisthesis, at the 2-year follow-up, patients who underwent decompression and fusion showed superior functional outcome and perceived recovery compared with those who underwent decompression alone. No subgroups benefited from decompression alone. Therefore, decompression and fusion is recommended over decompression alone as a primary surgical treatment option in isthmic spondylolisthesis.</p

De Kaapse kopers van de Reis naar Syrië en Palestina in 1851 en 1852 (1854) van CWM van de Velde

Charles William Meredith van de Velde (1818-1898), a former Dutch naval officer, cartographer and draughtsman, an adherent of the Dutch pietist Réveil with wide international connections, a friend of Henry Dunant and a co-founder of the Red Cross in the 1860s, travelled to the Near East in 1851-1852 (and again in 1861-1862), to make a better map and description of the Holy Land. In 1854 he published an updated Reis naar Syrië en Palestina in 1851 en 1852 (“Travels to Syria and Palestine in 1851 and 1852”). By then, after forty years of anglicising, Dutch-language books generally attracted small numbers of Cape buyers only. Still, more than a hundred people at the Cape ordered copies of Van de Velde's comprehensive and therefore, expensive, description of the Holy Land comprising two volumes. Were they familiar with the author, as a result of his two years of residence at the Cape in 1848-1850, where he had shown interest in evangelisation and had translated Messenger of Mercy by the British preacher James Smith, published by the Cape Town printer HN Marais as De vredeboode voor geloovige lijders (1850)? Were the pious at the Cape eagerly awaiting new information to understand their Bible reading, to follow the paths of Abraham, the walk of Jesus, or the trails through the wilderness and desert to the promised land?

An extension of the principle of virtual work for the derivation of stresses

Mit der Methode der gewichteten Reste wird eine schwache Form der elastischen Bestimmungsgleichungen für lineare Kontinua hergeleitet, die einer Erweiterung des Prinzips virtueller Verschiebungen entspricht. Kennzeichnend für die Erweiterung ist, daß neben dem Ansatz für die Verschiebungen im Inneren des elastischen Kontinuums ein unabhängiger Ansatz für die Spannungen am Rand des Kontinuums aufgestellt wird. Die Verträglichkeit der Spannungen, die aus der Differentiation des Verschiebungsansatzes bestimmt werden, mit den Spannungen des zusätzlichen Ansatzes wird im erweiterten Prinzip im Sinne eines integralen Mittelwertes hergestellt. Die aus der Erweiterung resultierenden Randspannungen befriedigen das Gleichgewicht mit den angreifenden Lasten. Ihre Güte wird eingehend untersucht. Dafür werden sowohl analytische Betrachtungen herangezogen als auch vergleichende Untersuchungen an einer Reihe von Beispielen durchgeführt. Die Konvergenzrate des Fehlers für die Spannungen aus dem erweiterten Prinzip ist vergleichbar mit der Rate, die für die Spannungen aus der Differentiation der Verschiebungslösung erzielt werden kann. Der Absolutwert des Fehlers der Spannungen aus dem erweiterten Prinzip ist jedoch in vielen Fällen signifikant kleiner. Die softwaretechnische Umsetzung der Erweiterung des Prinzips erfordert die Erfassung der Topologie des Randes sowie die numerische Integration der Ansätze über den Rand. Für die Lösung dieser Aufgabe werden generalisierte Methoden entwickelt und in einem Prototyp implementiert. Der zusätzliche Zeit- und Speicherbedarf, der aus der Erweiterung resultiert, wird kritisch geprüft. Am Beispiel der instationären Wärmeströmung wird abschließend gezeigt, daß die Ergebnisse auch auf die Bestimmungsgleichungen anderer physikalischer Phänomene im Bauingenieurwesen übertragbar sind

Behind the scenes. Hendrik swellengrebel and the Cape Patriot movement

Hendrik Swellengrebel, Cape-born Utrecht gentleman, farmer and administrator and visitor at the Cape (1776–1777), functioned as informal informant, mediator and critic of both the Cape Patriot Movement (1778 onwards) and the VOC officials, at the Cape and in Amsterdam, using his extensive network of correspondents, both at the Cape and in the Dutch Republic. In essence, he agreed with the Patriots’ complaints about the lack of personal rights and freedom of trade, but he also tried to convince the Representatives of the Patriots Movement (1779) to give up the counter-productive personal invectives against high Company officials. Simultanously Swellengrebel tried to restrain the reactions of the Company administrators. The top officials of the Company were conservatives, afraid of any burgher rights, and too busy with politics in the Dutch Republic and international relations (War with England in 1780–1784). Therefore decisions on the Patriot Requests and even moderate changes were delayed (and therefore creating more burgher actions). Even Swellengrebel’s offer to be nominated as Governor and then to reorganise the Cape was opposed, and declined by the Opperbewindhebber Stadholder William V himself. This article describes decades of discussion and policies around the Cape and the Cape Patriots, behind the scenes of the VOC

papers of the dutch-Indonesian historical Conference

392 hal.;ill.;27 c

Het zendingsbusje en de toverlantaarn : twee eeuwen zendingsliefde en zendingsorganisatie in Protestants Nederland /

Met lit. opg., reg.Kuijk, Ja

Decompression alone versus decompression and instrumented fusion for the treatment of isthmic spondylolisthesis: a randomized controlled trial

OBJECTIVE The most advocated surgical technique to treat symptoms of isthmic spondylolisthesis is decompression with instrumented fusion. A less-invasive classical approach has also been reported, which consists of decompression only. In this study the authors compared the clinical outcomes of decompression only with those of decompression with instrumented fusion in patients with isthmic spondylolisthesis. METHODS Eighty-four patients with lumbar radiculopathy or neurogenic claudication secondary to low-grade isthmic spondylolisthesis were randomly assigned to decompression only (n = 43) or decompression with instrumented fusion (n = 41). Primary outcome parameters were scores on the Roland Disability Questionnaire (RDQ), separate visual analog scales (VASs) for back pain and leg pain, and patient report of perceived recovery at 12-week and 2-year follow-ups. The proportion of reoperations was scored as a secondary outcome measure. Repeated measures ANOVA according to the intention-to-treat principle was performed. RESULTS Decompression alone did not show superiority in terms of disability scores at 12-week follow-up (p = 0.32, 95% CI -4.02 to 1.34), nor in any other outcome measure. At 2-year follow-up, RDQ disability scores improved more in the fusion group (10.3, 95% CI 3.9–8.2, vs 6.0, 95% CI 8.2–12.4; p = 0.006, 95% CI -7.3 to -1.3). Likewise, back pain decreased more in the fusion group (difference: -18.3 mm, CI -32.1 to -4.4, p = 0.01) on a 100-mm VAS scale, and a higher proportion of patients perceived recovery as showing “good results” (44% vs 74%, p = 0.01). Cumulative probabilities for reoperation were 47% in the decompression and 13% in the fusion group (p < 0.001) at the 2-year follow-up. CONCLUSIONS In patients with isthmic spondylolisthesis, decompression with instrumented fusion resulted in comparable short-term results, significantly better long-term outcomes, and fewer reoperations than decompression alone. Decompression with instrumented fusion is a superior surgical technique that should in general be offered as a first treatment option for isthmic spondylolisthesis, but not for degenerative spondylolisthesis, which has a different etiology