A standard video-rate confocal laser-scanning reflection and fluorescence microscope

A confocal laser-scanning microscope (CLSM) differs from a conventional microscope by affording an extreme depth discrimination, as well as a slightly improved resolution. These features afford improved imaging, and make possible new imaging techniques. The CLSM developed at TNO has standard video-rate imaging, and is capable of working in reflection and in fluorescence mode simultaneously. Nonconfocally the laser-scanning microscope can also be used in transmission mode. In addition to the evident advantages of a fast system when searching objects or studying living objects, the time needed to produce an image of extended depth of focus and high resolution is very short. Furthermore, the high-speed averaging of many images at low laser-power levels, and the short dwelling time of the focused laser beam (60 ns) obviate quenching effects in fluorescence microscopy and prevent damage to the object. In this article the TNO-CLSM system is outlined. The most important specifications are summarized, and some representative micrographs obtained with the system are shown. Furthermore, the performance of the system is illustrated by some experimental results.     

The digital implementation of control compensators: The coefficient wordlength issue

There exist a number of mathematical procedures for designing discrete-time compensators. However, the digital implementation of these designs, with a microprocessor, for example, has not received nearly as thorough an investigation. The finite-precision nature of the digital hardware makes it necessary to choose a computational structure that will perform adequately with regard to the initial objectives of the design. This paper describes a procedure for estimating the required fixed-point coefficient wordlength for any given computational structure for the implementation of a single-input single-output LQG design. The results are compared to the actual number of bits necessary to achieve a specified performance index.     

Quantitative pH imaging in cells using confocal fluorescence lifetime imaging microscopy

In guinea pigs, activity of glutathione peroxidase in most organs is markedly lower than in organs of other rodents despite comparable dietary intakes and tissue levels of selenium. To determine if metabolism of selenium with respect to other selenoproteins also differs in guinea pigs, we measured the effects of selenium intake on thyroid hormone metabolism. Weanling male Hartley Albino guinea pigs were fed a selenium-deficient Torula yeast-based diet, or the same diet supplemented with 0.5 mg selenium/kg diet as sodium selenate for 72 d. Growth was impaired in guinea pigs fed the unsupplemented diet. Activity of glutathione peroxidase was higher in tissues and plasma of supplemented guinea pigs than in selenium-deficient animals. However, it was still far lower than reported values for other rodent species. In selenium deficiency, activity of type 1 5'-iodothyronine deiodinase was 60% less in liver and 45% less in kidney. Concentration of thyroxine was 68% lower in kidney of selenium-deficient animals, and levels of 3,3',5-triiodothyronine in kidney and plasma were 44 and 31% lower, respectively. Thus, with the exception of thyroxine concentrations, thyroid hormone metabolism responds to selenium deficiency in guinea pigs as it does in rats, although the magnitude of that response is not as great.     

Accelerated nodulosis in a patient with psoriasis and arthritis during treatment with methotrexate

A 66-year-old woman with longstanding psoriasis involving the skin presented with asymmetrical polyarthritis. Methotrexate (MTX) was given initially intramuscularly and orally. Intramuscular MTX was discontinued, and a few months after she had been taking only oral MTX she developed nodules, first in surgical incisions, and subsequently in her buttocks, thighs, legs, and arms. Reduction of the dose of oral MTX was followed by gradual diminution in size of the nodules and then total disappearance.     

Articular cartilage transplantation

This report describes the biopsy findings in four of 30 patients treated with cadaver osteochondral shell allografts for osteoarthritis in the knee. This study demonstrates that graft cartilage cells can survive in excess of 25 months, and that host bone can completely replace graft bone by creeping substitution. An inflammatory reaction in synovium and bone marrow was found in only one of four cases. Graft failure was related to prolonged down time of donor cartilage in one case and mechanical factors related to osteoarthritis in the apposing femoral surface in other cases. The clinical success of these grafts is attributed to the prolonged viability of cartilage cells, the capacity of host bone to join graft cartilage without histologic reaction, and the host's immunologic tolerance, which obviates the need for immunosuppressive therapy.     

IRON FISCHER-TROPSCH CATALYSIS — PROPERTIES OF AN ULTRAFINE IRON OXIDE CATALYST

Slurry phase Fischer-Tropsch synthesis has been conducted starting with an ultrafine iron oxide catalyst with an average particle size of 30A. Catalyst activity gradually increased during the first 400 hour of synthesis and then remained stable for 250 days. Potassium promotion greatly increased the initial activity of the catalyst; however, the stability decreased. The CO conversion of the unpromoted catalyst was found to vary linearly with the reciprocal of the space velocity up to 60% conversion. Alkene selectivity increased with increasing space velocity but remained constant above GHSV = 2,0. Secondary reactions are believed to account for the higher alkane content at low space velocity. Methane, ethane and alkane formation increased with increasing hydrogen partial pressure up to a H2/CO ratio of 1. CO conversion is highest at lowest CO partial pressure and likewise for hydrogen. In general it is observed that this ultrafine catalyst is not as active as precipitated catalysts and has poor selectivity for alkene synthesis.