Ophthalmologic findings in Usher syndrome type 2A

Thirty-seven patients, comprising 24 familial cases and 13 isolated patients with Usher syndrome type II (USH2), underwent ophthalmologic examination. Based on the degree of hearing loss, normal vestibular function, and gene-linkage analysis, familial cases were assumed to have USH2A. An analysis of genetic heterogeneity failed to reveal the presence of a second locus in the Dutch population. Although the patients appear to belong to a genetically homogeneous group, remarkable ophthalmologic variability was found. Corrected visual acuity decreased with age and remarkable differences in visual acuity were found within one family. Fundoscopic findings were classified as type A if attenuated vessels and bone corpuscles in all quadrants were found or as type B if findings other than these were found. The prevalence of type A significantly increased with age.     

Clinical applications of fundus reflection densitometry

Fundus reflection densitometry or retinal densitometry is a non-invasive technique to examine the visual photopigment kinetics in living eyes. The technique is based on the comparison of the reflected light from the fundus in a fully light adapted eye (when all visual photopigment has been bleached) with the reflected light following complete dark adaptation (when the retina contains its maximum amount of visual photopigment). The technique provides a measure of the density of visual photopigment, its time constant of regeneration, its distribution and spectral characteristics if measured at a series of wavelengths. Fundus reflection densitometry in the human eye was introduced 40 years ago. Presently, it is the only available technique from which direct and objective insight can be obtained into visual photopigment. This knowledge is particularly relevant in eyes where abnormalities of photoreceptor function are suspected. This paper summarizes the current knowledge of fundus reflection densitometry in the diseased and in the aging human retina, gathered over the last 30 years. Considerable improvements of the instrument for clinical purposes have been obtained, and are also discussed.     

Treatment of perianal fistulas with ND:YAG laser--results in twenty cases

Excision of perianal fistulas using a 1.064 micron wavelength neodymium:yttrium aluminum garnet (ND:YAG) contact tipped laser with primary wound closure was used to treat 20 dogs with perianal fistulas. Overall, 19 of 20 (95%) dogs had resolution of fistulas after one or more ND:YAG treatments. The period of resolution ranged from 10 to 42 months with a mean of 22.9 months. Sixteen of 20 (80%) dogs had resolved fistulas after one laser excision. Three of the four recurrences underwent additional laser treatments with successful results. The total number of laser procedures ranged from one to three with a mean of 1.2 procedures. Postoperatively, anal tone as judged by digital rectal examination was reduced in about 60% of the cases, but clinical evidence of fecal incontinence only occurred in four of 20 cases. This was managed effectively with diet modification. The tendency toward loss of anal tone or fecal incontinence depended on the severity of preexisting anal stenosis. On a client survey, 19 of 20 owners believed that their animals experienced less pain during defecation after surgery and rated the results as excellent or good. The overall success rate using ND:YAG laser excision compared very favorably with previously reported studies of other methods of treatment for perianal fistulas in dogs.     

A histological and histomorphometrical evaluation of screw-type calciumphosphate (Ca-P) coated implants; an in vivo experiment in maxillary cancellous bone of goats

The bone response to different calcium phosphate (Ca-P) coated implants was evaluated in a goat animal model. Two types of plasma spray coatings were applied to a commercially pure titanium (cpTi) tapered, conical screw-design implant (BioComp^®); hydroxyapatite (HA-PS) and a dual coating, consisting of FA and HA (FA/HA-PS). In addition an amorphous RF magnetron sputter coating (Ca-P-a) and uncoated implants were investigated. Forty-eight implants were inserted in the maxilla of 12 adult female goats. After implantation periods of 3 and 6 months, the bone implant interface was evaluated histologically and histomorphometrically. After both implantation periods all plasma spray coated implants were maintained. On the other hand three Ca-P-a and two cpTi implants were lost. Histological examination revealed a better bone response to both plasma spray coated implants. Histomorphometrical evaluation confirmed this finding. At 3 and 6 months significantly higher percentages of bone contact (p<0.001, ANOVA) were measured for both plasma spray coated implants than for the cpTi and Ca-P-a implants, while no significant difference (p<0.05) existed between both implantation periods. Degradation of both plasma spray coatings was observed. Supported by the results, it is concluded that, although Ca-P coatings can improve the performance of dental implants, the presence of a Ca-P coating is not the only important factor for bone healing around implants placed in low density trabecular bone.     

MEASUREMENT OF THE SPECIFIC SURFACE AREA OF POWDERS BY THIN LAYER WICKING

The specific surface areas (A) of different clay mineral powders were measured by both the BET method and by thin layer wicking. The values of A for the BET and the wicking experiments coincided within a few percent. Thus, the simple and inexpensive thin layer wicking approach may well suffice to obtain reliable specific surface area values for most powders. From the wicking data it is also possible to obtain a rough estimate of the average particle size.     

Direct finite element design optimisation of the cagelessreluctance synchronous machine

The finite element analysis method is used directly in optimisation algorithms to optimise in multidimensions the design of the cageless reluctance synchronous machine. Two optimisation methods are evaluated to minimise or maximise the function value. These are the direction set method of Powell and the quasi-Newton algorithm. Both methods proved to be successful, with some advantages and disadvantages. Using these methods at a power level below 10 kW, results are given of structures of the reluctance synchronous machine which have been optimised according to specific criteria. Calculated and measured results show that the maximum torque optimum designed reluctance synchronous machine has the advantages of high power density and high efficiency     

Comparison between normal and reverse thin crystalline silicon solar cells

The newly developed ingot growing techniques, as the three-grain and the columnar multigrain ingot processes, are now offering the possibility of slicing thinner wafers (≤ 100 μm). In this paper we present the results obtained on p type large area (≥ 100 cm²) and 100 μm thick wafers by using both conventional and reverse cell manufacturing technologies.The conventional cells are provided with aluminium or boron BSF plus screen-printed silver mirror or a silver-aluminium net; the reverse cells have a FSF and the deep back junction completely covered by a screen-printed or CVD silver layer.The constructing parameters have been chosen on the base of one and two dimensions modeling and both raw material and devices have been completely characterized.This work shows that very thin wafers do not introduce serious problems for the conventional manufacturing of solar cells. The efficiencies of the normal and of the reverse cells are found to be comparable and are of the same order than those of thicker cells, however at a significant lower cost. The main obtained result has to be related to the demonstration of a cell manufacturing feasibility starting from very thin wafers.     

Incomplete inversion and double-valued fundamental linewidth ofinfrared HeNe and HeXe lasers

We have measured the quantum-limited linewidths of small HeNe 3.39 μm and HeXe 3.51 μm lasers. In contrast to the expected Schawlow-Townes behaviour strong deviations from the inverse power dependence are observed, leading to a double-valued relation between the linewidth and the output power. This phenomenon is analyzed in terms of the increase of spontaneous emission, by a factor N_sp, due to incompleteness of the inversion. Our analysis shows that typically N_sp has a value ranging from 1-10. Combining existing models for the pump power dependence of the level populations with measurements of the small signal gain, we are able to explain the observed double-valued linewidth behaviour in a quantitative way