Coordination shells and coordination numbers of the vertex graph of the Ammann-Beenker tiling

The vertex graph of the Ammann-Beenker tiling is a well-known quasiperiodic graph with an eightfold rotational symmetry. The coordination sequence and coordination shells of this graph are studied. It is proved that there exists a limit growth form for the vertex graph of the Ammann-Beenker tiling. This growth form is an explicitly calculated regular octagon. Moreover, an asymptotic formula for the coordination numbers of the vertex graph of the Ammann-Beenker tiling is also proved.

Coordination sequences and layer-by-layer growth of periodic structures

A new approach to the problem of coordination sequences of periodic structures is proposed. It is based on the concept of layer-by-layer growth and on the study of geodesics in periodic graphs. We represent coordination numbers as sums of so called sector coordination numbers arising from the growth polygon of the graph. In each sector we obtain a canonical form of the geodesic chains and reduce the calculation of the sector coordination numbers to solution of the linear Diophantine equations. The approach is illustrated by the example of the 2-homogeneous kra graph. We obtain three alternative descriptions of the coordination sequences: explicit formulas, generating functions and recurrent relations.

Coordination numbers of the vertex graph of a Penrose tiling

A new approach to study coordination shells and coordination sequences of quasiperiodic graphs is suggested. The structure of the coordination shells in the vertex graph of a Penrose tiling is described. An asymptotic formula for its coordination numbers is obtained. An essentially different behaviour of the coordination numbers for even and odd shells is revealed.

Cisapride and cimetidine in the treatment of erosive esophagitis

The efficacy of cisapride, as compared with cimetidine, in the treatment of erosive esophagitis was studied in a double-blind trial. One hundred and twenty-nine patients were assigned to one of four dosage schedules: cisapride 10 mg b.i.d. (20 mg group) or q.i.d. (40 mg group), or cimetidine 400 mg b.i.d. (800 mg group) or q.i.d. (1600 mg group). Treatment lasted 8 to 12 weeks. The degree of esophagitis and the severity of diurnal and nocturnal heartburn and regurgitation were significantly (p less than 0.01) reduced in the four treatment groups. Endoscopy did not show any significant differences among the four groups, although cisapride tended to be more effective in moderate to severe esophagitis, in which cases mucosal healing (i.e. absence of erosions and ulcers) was observed in 69%, 64%, 55% and 55% of the patients treated with cisapride 40 mg, cisapride 20 mg, cimetidine 1600 mg and cimetidine 800 mg. Improvement in reflux symptoms in the two cisapride groups was not significantly different from that in the cimetidine 1600 mg group, but was better (p less than 0.05) than that in the cimetidine 800 mg patients. The severity score for all reflux symptoms had decreased by 79%, 74% (cisapride 40 mg and 20 mg), 69% and 57% (cimetidine 1600 mg and 800 mg) by the end of treatment. These results show that cisapride is at least as effective as acid-suppressing therapy in patients with reflux esophagitis, and is therefore a valuable alternative to it.

Nabumetone (BRL 14777) presystemic elimination and disposition in patients with liver impairments

The effect of presystemic elimination of nabumetone disposition was evaluated in 6 cirrhotic patients after oral administration of a single dose of 1000 mg of the drug. The data revealed the major role of hepatic metabolism in the removal of the drug from the body. The relatively high values of hepatic plasma excretion ratio (= 0.60 +/- 0.04) and of the total intrinsic clearance (= 90.74 +/- 15.87 l/h) places nabumetone between drugs with intermediate properties; clearance being partly dependent on plasma (blood) flow rate and on the hepatic metabolism whose systemic availability was 32% of the dose. Very good coincidence was obtained when ranging patients according to morphological evaluation of liver impairments was compared to the values of nabumetone disposition parameters. There was a statistically significant positive correlation (r = 0.831, p less than 0.05) between the fraction of the dose reaching the systemic circulation, f, and the gamma-GT "normalization index" (i.e., ratio between the observed decrease of serum gamma-glutamyl transpeptidase activity and the pretreatment difference from the upper normal value). A definite interpretation of the data cannot be provided until more knowledge about the effect of 6-mO-2-naphthylacetic acid on nabumetone metabolism is available.

Liver insufficiency as a factor modifying the pharmacokinetic characteristic of the preparation nabumetone

The effectiveness of the nonsteroidal anti-inflammatory agent nabumetone is related to the formation of an active metabolite: 6-methoxy-2-naphthylacetic acid. The plasma concentrations of nabumetone and its active metabolite, after administration of 1,000 mg single dose p.o., are followed at 0, 0.5, 1, 2, 4, 6, 8, 12, 24, 30 and 48 h in 6 patients with laboratory evidence for functional liver insufficiency caused by liver cirrhosis, confirmed by biopsy. In the patients with liver insufficiency the mean values of Cmax and AUC0-24 h for 6-methoxy-2-naphthylacetic acid were 26.75 +/- 8.45 mg/l and 623.64 +/- 161.8 mg X h/l respectively. They did not differ significantly from the values observed in healthy volunteers [v. Schrader et al. 1983]. The Tmax-value was prolonged to 8 h, compared to 4 h Tmax-value of the volunteers. There is a tendency towards a reduced bioavailability of 6-methoxy-2-naphthylacetic acid after nabumetone administration in patients with a more severely expressed pathologic impairment, compared to patients with slight morphologic changes of the liver parenchyma.

Infection with hepatitis delta virus in patients with fulminant hepatitis B and chronic HBsAg carriers in Bulgaria

To evaluate the prevalence and clinical significance of delta infection in a Bulgarian population, 105 HBsAG positive patients with chronic liver diseases, and 42 patients who had died of fulminant hepatitis B were studied. Delta antigen was detected by direct immunofluorescence in the liver of 9 patients with chronic HBV infection (8.6%), and in 3 patients with fulminant hepatitis (7.14%). All chronic HBsAg carriers with delta superinfection had chronic active hepatitis or active liver cirrhosis. They were predominantly anti-HBe (+) in the serum. The mean age and the mean values of serum transaminase did not differ in delta antigen positive and negative patients with chronic liver diseases. A history of parenteral manipulations directly before the hepatitis was present in patients with delta antigen positive fulminant hepatitis. These results indicate a relatively low incidence of delta infection in our population, but it is invariably associated with severe liver disease.