Cataract surgery and YAG-laser capsulotomy following vitrectomy for diabetic retinopathy

The present study was initiated to assess time-course and risk factors for the development of cataract and posterior-capsule opacification as well as complications of cataract surgery and YAG-laser capsulotomy following vitrectomy for diabetic retinopathy. The charts of all patients undergoing vitrectomy for diabetic retinopathy during a 5-year period in a university eye hospital were retrospectively reviewed. The course of 306 consecutive eyes in which the lens was retained during vitrectomy was analyzed for subsequent cataract surgery and YAG-laser capsulotomy. The first 6 months after cataract or YAG-laser surgery were examined for the occurrence of complications. Data were analyzed with regard to the time course using Kaplan-Meier life-table analysis. The proportion of eyes that underwent cataract surgery after vitrectomy increased nearly linearly with time, approaching 75% after 5 years. Silicone tamponade (relative risk 1.9; P = 0.0005) and transscleral retinal cryotherapy (relative risk 1.4; P = 0.003) were risk factors for subsequent cataract surgery. No significant cataractogenous effect of intravitreal gas as compared with balanced salt solution was found. YAG-laser capsulotomy was performed in 60% of vitrectomized diabetic eyes within 2 years but in only 10% of nondiabetic controls (P < 0.0001). Within 6 months of extracapsular cataract surgery with implantation of an intraocular lens (IOL) in 54 eyes, no serious complication was observed. After YAG-laser capsulotomy, vitreous hemorrhage occurred within 6 months in 6 of 21 eyes. In conclusion, cataract surgery was performed in 75% of the phakic eyes within 5 years of vitrectomy for diabetic retinopathy. Posterior capsular opacification is particularly common in this subset of eyes. No serious complication was observed after extracapsular cataract surgery with IOL implantation, but YAG-laser capsulotomy was associated with an increased risk for vitreous hemorrhage.     

Hereditary macular dystrophies

BACKGROUND: Orthostatic hypotension is a common phenomenon in the elderly. Hormonal changes during orthostatic stress have been described in elderly normotensive people and in those with essential hypertension. However, the hormonal response in elderly people who have systolic hypertension during orthostasis has not yet been quantified. METHODS: In this study we investigated 14 non-diabetic men, aged 60 to 75 years, with untreated systolic hypertension who were subjected to 45 degrees passive head-up incline on a tilt table for 15 min. Their hormonal profile and hemodynamic changes were analyzed before and after the stress. RESULTS: In the supine position, plasma levels of norepinephrine, atrial natriuretic peptide and aldosterone were in the normal range, while the plasma renin activity was low. Immediately upon tilt the systolic blood pressure fell but it reverted to baseline values after 15 min of orthostasis. At that time the cardiac output decreased while the systemic vascular resistance and the plasma norepinephrine concentration rose. The atrial natriuretic peptide appeared to fall, and the renin-aldosterone level did not change. CONCLUSION: The physiologic response to orthostatic stress in elderly people with systolic hypertension is comparable to that of elderly normotensive people and those with essential hypertension, i.e. a decrease in cardiac output and an increase in plasma norepinephrine levels. The atrial natriuretic peptide appeared to fall appropriately. The response of the renin-aldosterone system mimicked that in elderly patients with low renin essential isolated hypertension. These observations may have a bearing on the management of elderly people with systolic hypertension who also have orthostatic symptoms; they may not require a different approach from that needed for others of the same age group.     

Ultraschall-induzierte Synthese von Trlmethylsilylessigsäuresilylestern

Ultrasound-induced Synthesis of Trimethylsilylacetic Acid Trimethylsilylester . The reaction of bromoacetic acid trimethylsilylester with zinc in presence of chlorotrimethylsilane is promoted by sono-waves. The trimethylsilylacetic acid trimethylsilylester could be obtained in high yield. Different products are observed in presence of dichloro dimethylsilane. Mechanical aspects are discussed.     

从皇城到投资者的城市—北京城的扩展与建设

北京具有2000多年的城市历史，留下许多层面的城市结构和建筑类型，目前，北京城的心脏依然是故宫，而且老城的几何秩序似乎仍然主宰着整个大都市，作为13亿人民的政治和文化中心的北京，正寻找着能够充分体现现代化成就和中国特色的建筑风格，北京也同样必须作出巨大的努力，来解决实现了房屋，基本设施和环境问题，最后，北京需要一个区域性发展的新概念，来控制城市的动态扩张。     

Ruthenium-106 brachytherapy for peripheral retinal capillary hemangioma

OBJECTIVE: This study aimed to evaluate the efficacy and safety of ruthenium-106 brachytherapy of large peripheral retinal capillary hemangiomas. DESIGN: A retrospective case series. PARTICIPANTS: In 25 eyes of 24 patients, peripheral capillary retinal hemangiomas were treated. INTERVENTION: Brachytherapy using 106-ruthenium/106-rhodium plaques was performed. MAIN OUTCOME MEASURES: Eyes were reviewed for hemangioma regression after brachytherapy, occurrence of retinal detachment, requirement of additional vitreoretinal surgery, final visual outcome, and final retinal status. RESULTS: Preoperative mean visual acuity of all eyes treated was 20/60, mean hemangioma diameter was 3.8 mm, corresponding to approximately 2 disc diameters. In 14 eyes, the retina was attached before surgery, 8 eyes showed an exudative detachment, and 3 eyes showed a traction detachment. Fifteen patients had definite von Hippel-Lindau syndrome. Twenty-three of 25 hemangiomas could be destroyed by single brachytherapy. In 16 eyes, a favorable outcome could be achieved. In nine eyes, outcome was unfavorable, characterized by a severe drop in visual acuity, a persisting exudative retinal detachment, or a recurrent traction detachment. In one eye requiring repeated brachytherapy, irradiation retinopathy occurred. Hemangiomas up to a size of approximately 5.0 mm without preoperative exudative detachment could be treated safely by brachytherapy, whereas a larger hemangioma size or a pre-existing exudative retinal detachment predisposed to an unfavorable outcome. CONCLUSION: Solitary peripheral retinal hemangioma can be ablated effectively by ruthenium-106 brachytherapy. A favorable outcome can be expected if the hemangioma diameter is 5.0 mm or smaller and if there is no preoperative exudative retinal detachment.     

Drop coalescence on inclined plates in liquids

Inclined plates are often installed as mechanical separation aids in gravity settlers for the separation of liquid-liquid systems. The authors investigated the process of coalescence of single drops on trickling films flowing off inclined plates. The method of investigation was developed by Blass and Rautenberg. It ensures that, under certain conditions, only hydrodynamic parameters influence the coalescence process to any significant extent. The coalescence time of the drops characterizes the process of coalescence. Short time between 1 and 3 seconds provide favourable conditions for coalescence whereas long times, often ten times as long or even longer are unfavourable. This contribution introduces a criterion for clear demarcation between these two ranges and also a determination of separation parameters for favourable conditions for coalescence. Furthermore, the function of the plates is described, which is determined by hydrodynamic and wetting processes. The characteristic operating regions of a plate are shown in a working diagram.     

Teilkondensation und nichtadiabate Rektifikation binärer Gemische in Füllkörperrohren

Partial condensation and non-adiabatic rectification of binary mixtures in packed columns. Vertical tube assemblies are preferred for partial condensation of vapour mixtures. The mixture of vapours is fed through the tubes in countercurrent flow to the falling condensate, while coolant flows through the jacket. Only with very large ratios of length L to diameter d of the tubes, i.e. L/d 200, does the separatory effect of partial condensation, owing to rectification mass transfer between the phases, exceed the enrichment effect of partial condensation. Use of ring-shaped packings drastically reduces the characteristic diameter, so that the additional separatory effect occurs at relatively short tube lengths. In the present paper, experimental results concerning the separation efficiency of tubes packed with Raschig rings for non-adiabatic rectification and partial condensation of the “negative” binary mixture n-heptane/benzene are reported and evaluated with the aid of the extended two-film theory. It is found that the resistance to mass transfer averaged over the length of the tube lies entirely on the liquid side on non-adiabatic rectification. Correlation of the Sherwood number of the condensate taken over the length of the tube and the condensate loading clearly shows that the usual calculation of partial condensation with average total mass transfer coefficients does not give physically meaningful results in the case of liquid-side resistance to transport. Calculating procedures which account for the variation of the partial mass transfer coefficients along the tube should lead to improved evaluation or prediction of separation efficiency.