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C Thum

Publications and source records attributed to C Thum.

13 recordsLinked to original sources
PubMed2006

The trans-neptunian object UB313 is larger than Pluto.

The most distant known object in the Solar System, 2003 UB313 (97 au from the Sun), was recently discovered near its aphelion. Its high eccentricity and inclination to the ecliptic plane, along with its perihelion near the orbit of Neptune, identify it as a member of the 'scattered disk'. This disk of bodies probably originates in the Kuiper belt objects, which orbit near the ecliptic plane in circular orbits between 30 and 50 au, and may include Pluto as a member. The optical brightness of 2003 UB313, if adjusted to Pluto's distance, is greater than that of Pluto, which suggested that it might be larger than Pluto. The actual size, however, could not be determined from the optical measurements because the surface reflectivity (albedo) was unknown. Here we report observations of the thermal emission of 2003 UB313 at a wavelength of 1.2 mm, which in combination with the measured optical brightness leads to a diameter of 3,000 +/- 300 +/- 100 km. Here the first error reflects measurement uncertainties, while the second derives from the unknown object orientation. This makes 2003 UB313 the largest known trans-neptunian object, even larger than Pluto (2,300 km). The albedo is 0.60 +/- 0.10 +/- 0.05, which is strikingly similar to that of Pluto, suggesting that the methane seen in the optical spectrum causes a highly reflective icy surface.

Journal Article↗
PubMed1976

Attempts at perfect normalization of glucose tolerance test of severe diabetics by artificial beta cell.

The artificial beta cell is a Glucose Controlled Insulin (and dextrose) Infusion System (GCIIS) for maintaining normoglycemia in diabetic conditions and other disturbances of metabolism. The insulin and dextrose infusion rates are calculated by a microcomputer according to the static glucose concentration (proportional control) and to its rate of change (dynamic control). The algorithms controlling the computer can be adapted to the subjects' requirements. It has already been shown, that the artificial beta cell is able to maintain blood sugar values in diabetics within physiological ranges during the course of the day. In our present study we examined the response of the artificial beta cell using a 100 gm oral glucose load in severe diabetics. The first type of control algorithms applied effected a rather small initial insulin infusion following OGTT in 8 juvenile diabetics connected with the artificial beta cell. The glucose responses thus obtained were similar to latent diabetes. In contrast, when the computer was controlled by the second type of algorithms with a more responsive dynamic control and a consequently higher initial insulin infusion, in one diabetic OGTT was fully normalized, whereas an improvement was achieved in another diabetic patient. Furthermore it was shown that control algorithms must be varied individually, depending on residual beta cell function and glucose regulatory mechanisms.

Blood Glucose↗
PubMed1976

Hypoglycemia in diabetics.

Hypoglycemia in diabetes can be divided into 1) spontaneous hypoglycemic reactions due to absolute or relative overproduction of endogenous insulin or some other blood glucose-lowering substance, as in islet cell adenoma or carcinoma, latent or protodiabetic conditions, (extrapancreatic) tumors and pituitary and/or adrenal disorders; and 2) hypoglycemia caused by exogenous, i.e. therapeutic, measures. The problem of hypoglycemia in insulin-treated diabetics is far from being solved. As revealed by continuous blood glucose monitoring, nocturnal hypoglycemic attacks frequently escape attention especially in juvenile diabetics. Circadian variations in peripheral glucose utilization, rather than changes in plasma insulin activity, are likely to be involved in this mechanism. At least, this was the conclusion drawn from studies carried out by means of a glucose-controlled insulin and glucose infusion system (GCIGIS) -or artificial pancreas-which delivers short-acting insulin and glucose on demand intravenously. Hypoglycemic reactions in patients being treated with oral anti-diabetic agents, on the other hand, should be regarded primarily as one of the side reactions intrinsic to the mechanism of action of some of these drugs, e.g. sulfonylureas, which act mainly via stimulation of secretion of endogenous insulin reserves not responding properly to postprandial blood glucose increments. In the case of glibenclamide, at least partial resensitization of the defective glucose receptor of the beta-cell also becomes operative. A higher incidence of a characteristic type of hypoglycemic reaction was observed soon after glibenclamide therapy was introduced. Better understanding of the drug and dissemination of the information about it to doctors and patients has reduced the number of hypoglycemic reactions caused by glibenclamide to the same proportions as for other sulfonylureas. Hypoglyoemia following therapeutic hypophysectomy retains its position as one of the main hazards of this heroic therapy.

Adenoma, Islet Cell↗
PubMed1975

[Continuous daily blood-sugar profile in relation to serum insulin in subjects with normal metabolism and ideal or normal weight (author's transl)].

Continuous blood-sugar measurement is at present the most suitable method for testing daily blood sugar profile. It allows to relate variations in blood sugar levels in metabolically normal subjects to body weight. Mean blood-sugar level and postprandial blood-sugar variations are greater in those of normal than of ideal weight. At the same time, metabolically normal subjects of normal weight have a high insulin secretion in the fasting and postprandial states. This makes it likely that those of normal weight, although it is only slightly different from those of ideal weight, have already reached a transitional stage to an increased diabetes risk from over-weight.

Blood Glucose↗
PubMed1975

Antidiabetic action of somatostatin--assessed by the artificial pancreas.

By means of a glucose-controlled insulin- and glucose-infusion system (GCIGIS) we examined the effect of somatostatin on insulin and glucose requirements following meals or oral glucose loads in juvenile diabetics. In six of seven patients the insulin requirement with somatostatin was remarkably reduced to between 38 per cent and 79 per cent of that of otherwise identical control experiments. No reduction could be found in the seventh case, fed only 575 kcal. In all cases we observed an increase in dextrose demanded from the GCIGIS ranging between 28 per cent and 192 per cent of the control amounts. In addition, a lowering and smoothing of postprandial blood glucose curves caused by somatostatin application was a general finding. It seems to us most likely that the well-known suppression of the secretion of growth hormone and glucagon, both insulin antagonists, is responsible for the antidiabetic action of somatostatin.

Adolescent↗