Influence of the Catalyst Particle Size on the Aqueous Phase Reforming of n-Butanol Over Rh/ZrO2

Butanol is a by-product obtained from biomass that can be valorized through aqueous phase reforming. Rh/ZrO₂ catalysts were prepared and characterized, varying the size of the support particles. The results showed a relatively mild effect of internal mass transport on butanol conversion. However, the influence of internal transport limitations on the product distribution was much stronger, promoting consecutive reactions, i.e., dehydrogenation, hydrogenolysis, and reforming of propane and ethane. Hydrogen consuming reactions, i.e., hydrogenolysis, were more strongly enhanced than hydrogen producing reactions due to internal concentration gradients. Large support particles deactivated faster, attributed to high concentrations of butyraldehyde inside the catalyst particles, enhancing deposit formation via aldol condensation reactions. Consequently, also the local butyric acid concentration was high, decreasing the local pH, enhancing Rh leaching. The influence of internal transfer limitation on product distribution and stability is discussed based on a reaction scheme with three main stages, i.e., (1) formation of liquid intermediates via dehydrogenation, (2) formation of gas via decarbonylation/decarboxylation reactions, and (3) hydrocarbon hydrogenolysis/reforming/dehydrogenation.

Netzhautablösung bei Kindern und Jugendlichen

During a 4-year period 22 eyes with rhegmatogenous retinal detachment in children and young adults up to 20 years of age were operated on. This group comprised 6.3 percent of all rhegmatogenous retinal detachments operated on during the same period. In 9 eyes (40.9%) the detachment was due to a direct ocular trauma. In the remaining cases the main etiological factors were: myopia with or without lattice degeneration (5 eyes), retinopathy of prematurity (2 eyes), hereditary vitreoretinal degeneration (1 eye), uveal coloboma (2 eyes), aphakia after congenital cataract (1 eye), sex-linked juvenile retinoschisis (1 eye), and central retinal vein occlusion (1 eye), Conventional surgical procedures using episcleral or intrascleral implants or an encircling band combined with cryotherapy were used. After a follow-up of 7 months to 3.3 years (mean 1.5 years) the retina was flat in 18 cases (82%) and still detached in those with uveal coloboma (2 eyes), hereditary vitreoretinal degeneration (1 eye), and central retinal vein occlusion (1 eye). All traumatic detachments were flat.

[Cesium 134 and 137 contamination of game killed in Hesse]

The amount of caesium 134 and 137 in Hessian game hunted for food (556 animals) after the reactor accident at Chernobyl was investigated. Comparisons have been made before and after the accident. Although there was only a very low level of contamination, the contamination rate of different species varied; on average, the Red Deer showed the highest activity (130 Bq/kg). The level of caesium contamination was mostly influenced by the permanent habitat of the animals. The main influence was due to regional, geographical and meteorological conditions. The influence of age or sex could not be determined. The contamination rate was shown to decrease with time.

Post-operative outcome in rhegmatogenous retinal detachment

Anatomic and visual results of retinal detachment surgery were analyzed in 352 consecutive eyes operated on for rhegmatogenous type of retinal detachment in 1978-1981 at the University Eye Hospital in Helsinki. From 1978-79 to 1980-81, both the re-attachment rate and the visual results improved significantly (P less than 0.05). In the latter period, the retina was re-attached in 87% and partially re-attached in 2%. In the same period, a good visual acuity (VA greater than or equal to 0.5) was achieved in 39%, reasonable (VA 0.4-0.15) in 28%, and an ambulatory vision (VA 0.1-CF2m) in 16%, whereas 18% of the eyes became blind (VA CF1m or worse). A favourable outcome was related to good pre-operative visual acuity, short duration and limited extent of detachment as well as sparing of the macula. Among factors which predicted an unfavourable outcome were aphakia, failure to detect retinal breaks, signs of proliferative vitreoretinopathy, multiple operations and old age. Poor outcome was more common after encircling as compared with localized procedures, but the success rate of the various types of operations was not comparable because encircling procedures were selected for more severe cases.

Bilateral rhegmatogenous retinal detachment

During a 4-year period, 1978-1981, 34 patients with bilateral rhegmatogenous retinal detachment were operated on at the University Eye Hospital in Helsinki. The incidence of bilaterality in the entire detachment population was 10%, in the aphakic group it was 16%. In 24 cases (71%) the interval from the first to the second eye detachment was less than 5 years, 6 patients (18%) had bilateral detachment simultaneously. The mean age of the patients when the first eye was affected (46 years, range 6-73) was significantly younger than the mean age of those with unilateral detachment (58 years, range 6-83) (P less than 0.001). Previous eye diseases were significantly (P less than 0.01) more common in patients with bilateral than in those with unilateral detachment, but the incidences of myopia, aphakia and lattice degeneration of the retina did not differ significantly between these groups. At least one of these predisposing factors was found in 85% and two or more of them in 53% of bilateral detachments. The retina was re-attached in 80% of the 44 eyes operated on during the study period. Of the 24 eyes operated on earlier, 71% were blind (visual acuity CF 1 m or worse). The latest visual acuities in both eyes or in the better eye for all patients were: greater than or equal to 0.5 in 38%, 0.4-0.2 in 35%, 0.1-CF2 m in 12%, and less than or equal to CF1 m in 15%.

Epidemiology of rhegmatogenous retinal detachment in a Finnish population

During a -4 year period, 1978-1981, 310 eyes of 301 patients living in the district of the Helsinki University Central Hospital were examined for rhegmatogenous detachment of the retina. This corresponds to an annual incidence of 6.9 per 100 000 mean population. The mean age of the patients was 54.2 years, and the sex distribution corresponded with that in the general population. The right eye was significantly (P less than 0.05) more often affected than the left eye. 78% of the eyes were phakic, and 22% were aphakic. The corresponding annual incidences were 5.4 for phakic and 1.5 for aphakic detachment per 100 000 mean population. Myopia was found in 51% of the phakic and in 24% of the aphakic eyes. The estimated annual incidence of rhegmatogenous detachment in the myopic population was more than 3 times that in the non-myopic population. The annual incidence of traumatic rhegmatogenous retinal detachment was 0.8 per 100 000 mean population. There were significant (P less than 0.005) seasonal variations in the occurrence of retinal detachment.

Macular hole and retinal detachment

Within a 4-year period 6 eyes with a macular hole and rhegmatogenous retinal detachment (1.7% of all rhegmatogenous detachments) were operated on. In 2 eyes no other retinal tears were found, 4 eyes showed additional peripheral tears. Three eyes were myopic (-3.75 to -9.0 D) and one was aphakic. All but one eye were encircled, 3 eyes had a peripheral radial plomb and another 3 had a macular sling procedure using a silastic sponge explant in addition. Cryotherapy was applied on the macular hole in one eye and photocoagulation in one eye. In 5 of the 6 cases the retina reattached. The silastic sponge sling resulted in shallow indentation and caused little distortion at the macula. Coagulation of the macular hole seemed to be unnecessary.