Ultrafast Atomic Diffusion Inducing a Reversible (2sqrt[3]×2sqrt[3])R30°â†”(sqrt[3]×sqrt[3])R30° Transition on Sn/Si(111)∶B.

Dynamical phase transitions are a challenge to identify experimentally and describe theoretically. Here, we study a new reconstruction of Sn on silicon and observe a reversible transition where the surface unit cell divides its area by a factor of 4 at 250 °C. This phase transition is explained by the 24-fold degeneracy of the ground state and a novel diffusive mechanism, where four Sn atoms arranged in a snakelike cluster wiggle at the surface exploring collectively the different quantum mechanical ground states.

Analysis of Turner syndrome patients within the Jordanian population, with a focus on four patients with Y chromosome abnormalities.

This study presents findings in Turner syndrome (TS) patients from the Jordanian population, with focus on 4 patients with Y chromosomal abnormalities. From 1989 to 2011, 504 patients with TS stigmata were referred to our institute for karyotyping, resulting in 142 positive TS cases. Of these, 62 (43.7%) had the typical 45,X karyotype and the remaining individuals (56.3%) were found to be mosaics. Fifteen TS patients (10.5%) carried a structural abnormality of the Y chromosome and presented with the mosaic 45,X/46,XY karyotype. From these, 4 TS cases were investigated further. Karyotyping revealed that 1 patient carried a small supernumerary marker chromosome, whereas cytogenetic and molecular analyses showed that 3 patients carried 2 copies of the SRY gene. Further analysis by SRY sequencing revealed no mutations within the gene. The analyzed patients were found to be phenotypically either females or males, depending on the predominance of the cell line carrying the Y chromosome. This study demonstrates the importance of detailed cytogenetic analysis (such as FISH) in TS patients, and it also emphasizes the need for molecular analysis (such as PCR and sequencing) when fragments of the Y chromosome are present.

Preclinical evaluation of pharmacokinetic-pharmacodynamic rationale for oral CR metformin formulation.

We examined the pharmacokinetic (PK) and pharmacodynamic (PD) rationales to develop controlled release (CR) formulations of metformin. Unrestrained diabetic rats received the drug as intravenous bolus (i.v.), oral solution (p.o.), intra-duodenal bolus, 4-h infusion, or intra-colonic bolus. In addition, we developed two CR-gastroretentive dosage forms (CR-GRDF) that released the drug over 3 or 6 h (in vitro), and retained in the rats' stomach for 8-10 h. Metformin exhibited flip-flop PK. The colonic absorption was low but sustained and was associated with highly variable glucose-lowering effects, thus providing a PK rationale to develop CR-GRDF. In addition, the glucose-lowering effect was greater following p.o. vs. i.v. administration, despite equivalent AUC, indicating a first pass PD effect, thus, adding a PD rationale to develop metformin CR-GRDF. When administered to the diabetic rats, CR-GRDFs produced bioavailability and extent of glucose-lowering effects that were similar to those of the duodenal infusion and p.o. metformin administration. These findings are attributed to the adsorption of metformin to the intestine that yields slow and prolonged absorption even following p.o. administration of drug solution. The data indicates that unless the CR formulation could significantly extend the absorption period, it is not likely to improve glucose-lowering efficacy.