Random Walk with Shrinking Steps: First Passage Characteristics

We study the mean first passage time of a one-dimensional random walker with step sizes decaying exponentially in discrete time. That is step sizes go like $\lambda^{n}$ with $\lambda\leq1$ . We also present, for pedagogical purposes, a continuum system with a diffusion constant decaying exponentially in continuous time. Qualitatively both systems are alike in their global properties. However, the discrete case shows very rich mathematical structure, depending on the value of the shrinking parameter, such as self-repetitive and fractal-like structure for the first passage characteristics. The results we present show that the most important quantitative behavior of the discrete case is that the support of the distribution function evolves in time in a rather complicated way in contrast to the time independent lattice structure of the ordinary random walker. We also show that there are critical values of $\lambda$ defined by the equation $\lambda^{K}+2\lambda^{P}-2=0$ with $\{K,N\}\in{\mathcal N}$ where the mean first passage time undergo transitions.Comment: Major Re-Editing of the article. Conclusions unaltere

The efficiency of US elastography in the differential diagnosis of thyroid nodules

Aim: To evaluate the efficiency of ultrasound elastography (USE) in the differential diagnosis of thyroid nodules. Methods: One hundred thyroid nodules in 100 patients (79 females, 21 males, age range 18-78; mean age = 45.6 years) were evaluated with real-time freehand USE, using Hitachi EUB 7500 equipment and elasticity scores were obtained. The elasticity was scored as follows: Score 1, elasticity in the entire nodule; Score 2, mainly elastic nodule with the presence of inelastic areas not constant during real time examination; Score 3, constant inelastic areas prevalently arranged at the periphery of the nodule; Score 4, constant inelastic areas prevalently arranged at the center of the nodule; Score 5, no elasticity in the nodule. Also mean strain ratio values were calculated for all nodules. Results: Eighty-four (86%) of cases were benign and sixteen (16%) were malignant. Elasticity score 3 and higher and strain ratio higher than 2.485 had statistically significant relation with malignancy (p < 0.05). Conclusions: USE including strain ratio calculations besides subjective evaluation of elasticity scores is an efficient imaging method which may contribute to the differential diagnosis of thyroid nodules

The Relativistic Electrodynamics Least Action Principles Revisited: New Charged Point Particle and Hadronic String Models Analysis

The classical relativistic least action principle is revisited from the vacuum field theory approach. New physically motivated versions of relativistic Lorentz type forces are derived, a new relativistic hadronic string model is proposed and analyzed in detail.Comment: n/

Characteristics of patients operated for primary hyperparathyroidism at university hospitals in Türkiye: Differences among Türkiye's geographical regions

Purpose: The aim of this study was to define the clinical and laboratory characteristics of patients operated on for primary hyperpatathyroidism (PHPT) at university hospitals in Türkiye, and to investigate the differences in the clinical presentations of the disease between different geographical regions. Methods: Patients operated on for PHPT in the university hospitals of Türkiye were included in the study. The demographic, clinical, and laboratory findings and the operational data of the patients were investigated according to the whole country and to different geographical regions. Comparisons were performed according to whole country and regions. Results: A total of 1,162 cases were included in the study from different regions and 20 university hospitals. The mean age of patients was 52.4 ± 0.38 (mean ± standard error) in the general population of Türkiye. The rates of hypertension, urolithiasis, bone disease and 25-hydroxyvitamin D insufficiency were 35%, 18.6%, 67.6%, and 63%, respectively. The median parathormone (PTH), serum total calcium (Ca+2) and phosphorus value were 220 pg/mL (range, 70-2,500 pg/mL), 11.2 mg/dL (range, 9.5-11.2 mg/dL), and 2.4 mg/dL (range, 1-4.7 mg/dL), respectively. The median size of the adenomas resected was 16 mm (range, 4-70 mm). Significant differences were observed in the clinical and laboratory findings of the patients operated on due to PHPT between different geographical regions of Türkiye (P &lt; 0.05). Conclusion: The clinical and laboratory characteristics of the patients with PHPT in different geographical regions of Türkiye differ. Furthermore, the general findings of the cases in Türkiye give us a hint that the severity of the disease here is somewhere between Eastern and Western countries. Copyright © 2016, the Korean Surgical Society

A preliminary investigation on the estimation of the sustained-release of indomethacin from agar beads part I

In this study agar beads containing indomethacin were prepared at different polymer-drug ratios. It was found that the release rate of indomethacin from agar beads was inversely related to the drug content. Lactose was added to the formulations in order to investigate its effect on the release of indomethacin from agar beads. Lactose increased the release rate of indomethacin and in vitro release studies exhibited a ?t dependence indicating a diffusion controlled process from a matrix formulation. All of the prepared formulations gave prolonged release. The release profiles of the formulations were compared with Indocid-R available in the market. The release criteria of all the formulations and Indocid-R were examined according to USP criteria given for indomethacin and general release criteria. At the end of the study, the obtained data were evaluated mathematically. Two equations to be used in the preparation of agar-indomethacin beads with or without lactose for optimum formulation were estimated. It was found that the estimated equations were in good agreement with the observed release results. In addition, in this study the in vivo distribution of agar beads prepared with barium sulfate as a contrast substance in the gastro-intestinal tract was also examined

Sustained release bioadhesive effervescent ketoconazole microcapsules tabletted for vaginal delivery

PubMed ID: 12022501Microcapsules of ketoconazole with 1:1 and 1:2 core-wall ratios were prepared by means of the phase separation technique using sodium carboxymethylcellulose as a coating material. The microcapsules were mixed with effervescent granules and were tabletted. Dissolution studies of microcapsules, tabletted microcapsules and commercial ovules were carried out with a new basket method (horizontal rotating basket). A good sustained action was obtained with tablets. Micromeritic investigations were carried out on microcapsules in order to standardize the microcapsule product and to optimize the pilot production of the dosage forms prepared with these microcapsules. Bulk volume and weight, tapping volume and weight, fluidity, angle of repose, weight deviation, relative deviation, particle size distribution, density and porosity values of the microcapsules were determined. In addition, to evaluate whether some kind of glidant will be needed during tabletting of microcapsules, the Hausner ratio and consolidation index were also calculated and it may be concluded that microcapsules do not need any glidant