On the families of orthogonal polynomials associated to the Razavy potential

We show that there are two different families of (weakly) orthogonal polynomials associated to the quasi-exactly solvable Razavy potential V(x)=(\z \cosh 2x-M)^2 (\z>0, $M\in\mathbf N$). One of these families encompasses the four sets of orthogonal polynomials recently found by Khare and Mandal, while the other one is new. These results are extended to the related periodic potential U(x)=-(\z \cos 2x -M)^2, for which we also construct two different families of weakly orthogonal polynomials. We prove that either of these two families yields the ground state (when $M$ is odd) and the lowest lying gaps in the energy spectrum of the latter periodic potential up to and including the $(M-1)^{\rm th}$ gap and having the same parity as $M-1$. Moreover, we show that the algebraic eigenfunctions obtained in this way are the well-known finite solutions of the Whittaker--Hill (or Hill's three-term) periodic differential equation. Thus, the foregoing results provide a Lie-algebraic justification of the fact that the Whittaker--Hill equation (unlike, for instance, Mathieu's equation) admits finite solutions.Comment: Typeset in LaTeX2e using amsmath, amssymb, epic, epsfig, float (24 pages, 1 figure

Step-edge-induced resistance anisotropy in quasi-free-standing bilayer chemical vapor deposition graphene on SiC

Cataloged from PDF version of article.The transport properties of quasi-free-standing (QFS) bilayer graphene on SiC depend on a range of scattering mechanisms. Most of them are isotropic in nature. However, the SiC substrate morphology marked by a distinctive pattern of the terraces gives rise to an anisotropy in graphene's sheet resistance, which may be considered an additional scattering mechanism. At a technological level, the growth-preceding in situ etching of the SiC surface promotes step bunching which results in macro steps similar to 10 nm in height. In this report, we study the qualitative and quantitative effects of SiC steps edges on the resistance of epitaxial graphene grown by chemical vapor deposition. We experimentally determine the value of step edge resistivity in hydrogen-intercalated QFS-bilayer graphene to be similar to 190 Omega mu m for step height h(S) = 10 nm and provide proof that it cannot originate from mechanical deformation of graphene but is likely to arise from lowered carrier concentration in the step area. Our results are confronted with the previously reported values of the step edge resistivity in monolayer graphene over SiC atomic steps. In our analysis, we focus on large-scale, statistical properties to foster the scalable technology of industrial graphene for electronics and sensor applications. (C) 2014 AIP Publishing LLC

Kinetics of the urea–urease clock reaction with urease immobilized in hydrogel beads

Feedback driven by enzyme catalyzed reactions occurs widely in biology and has been well characterized in single celled organisms such as yeast. There are still few examples of robust enzyme oscillators in vitro that might be used to study nonlinear dynamical behavior. One of the simplest is the urea–urease reaction that displays autocatalysis driven by the increase in pH accompanying the production of ammonia. A clock reaction was obtained from low to high pH in batch reactor and bistability and oscillations were reported in a continuous flow rector. However, the oscillations were found to be irreproducible and one contributing factor may be the lack of stability of the enzyme in solution at room temperature. Here, we investigated the effect of immobilizing urease in thiol-poly(ethylene glycol) acrylate (PEGDA) hydrogel beads, prepared using emulsion polymerization, on the urea–urease reaction. The resultant mm-sized beads were found to reproduce the pH clock and, under the conditions employed here, the stability of the enzyme was increased from hours to days

Surgical treatment of abdominal paragangliomas

Introduction: Extraperitoneal, abdominal paragangliomas most commonly originate from the sympathetic nervous system. Typical features include catecholamine overproduction and the potential for malignancy. Lesions are usually located paravertebrally, but when growing in a more expansive manner they may also appear between the inferior vena cava and aorta. In the authors’ opinion this site excludes laparoscopic tumourectomy. Material and methods: Twenty-eight patients were selected for surgical management of abdominal paragangliomas in the past eight years at our endocrine surgical centre. This group consisted of 21 (75%) women and seven (25%) men, aged 14 to 84 years (mean 47.9). In 13 (46.4%) cases paroxysmal hypertension was observed. Type 2 diabetes was noted in another 10 (35.7%) patients, and Takotsubo acute coronary syndrome in two (7.1%). Patients were preoperatively qualified for either open surgery or laparoscopic tumourectomy based on visualisation and location of the tumours in imaging studies. Results: All patients were successfully operated. Eleven (39.3%) patients qualified for laparoscopy, while the remaining 17 (60.7%) were treated with an open surgical approach due to difficult access to the lesion. The mean operative time was 130 minutes for laparoscopy and 120 minutes for laparotomy (p = 0.2). There were no local or general complications after either type of procedure. Conclusions: The use of laparoscopic access is practically excluded in the treatment of paragangliomas located between the inferior vena cava and aorta, especially at the level of the renal vessels and extending superiorly to the diaphragm.

Analysis of fungal air pollution using different samplers

The aim of this study was the analysis of fungal air pollution in different rooms using different the air samplers. Air for mycological studies was collected from various hospital rooms. To monitor fungal air pollution were used samplers: SAS SUPER 100 (pbi-international), MAS 100 (Merck) and AIR IDEAL (BioMerieux). We found differences in CFU/L values in depending on hospital room and the air sampler type. The CFU/L values of air samples taken by the AIR IDEAL ranged from 350 to 850 and (724.2 ± 159.9), and the CFU/L values of air samples taken by the sampler SAS SUPER 100 ranged from 160 to 800 (455.3 ± 250.73). The CFU/L values of air samples taken by the MAS 100 sampler varied from 50 to 1340 (302.5±56.6) From the air samples of both samplers was incubated 6 genera/species of fungi. Candia albicans fungi species and genus Penicillium species were most frequently isolated from SAS Super 100 sampler, and Penicillium species from the AIR IDEAL sampler. From the air samples of MAS 100 was isolated 11 types/species of fungi and in air samples of SAS Super 100 was isolated 7 types/species. Significant differences of CFU/L values in the tested rooms were found in depending on the used sampler. Mycological analysis of the obtained cultures from air samples suggests that there is not same isolation of fungi using the different samplers

Supersymmetric Method for Constructing Quasi-Exactly and Conditionally-Exactly Solvable Potentials

Using supersymmetric quantum mechanics we develop a new method for constructing quasi-exactly solvable (QES) potentials with two known eigenstates. This method is extended for constructing conditionally-exactly solvable potentials (CES). The considered QES potentials at certain values of parameters become exactly solvable and can be treated as CES ones.Comment: 17 pages, latex, no figure

Upwelling events, coastal offshore exchange, links to biogeochemical processes - Highlights from the Baltic Sea Sciences Congress at Rostock University, Germany, 19-22 March 2007

The Baltic Sea Science Congress was held at Rostock University, Germany, from 19 to 22 March 2007. In the session entitled"Upwelling events, coastal offshore exchange, links to biogeochemical processes" 20 presentations were given,including 7 talks and 13 posters related to the theme of the session.This paper summarises new findings of the upwelling-related studies reported in the session. It deals with investigationsbased on the use of in situ and remote sensing measurements as well as numerical modelling tools. The biogeochemicalimplications of upwelling are also discussed.Our knowledge of the fine structure and dynamic considerations of upwelling has increased in recent decades with the advent ofhigh-resolution modern measurement techniques and modelling studies. The forcing and the overall structure, duration and intensity ofupwelling events are understood quite well. However, the quantification of related transports and the contribution to the overall mixingof upwelling requires further research. Furthermore, our knowledge of the links between upwelling and biogeochemical processes is stillincomplete. Numerical modelling has advanced to the extent that horizontal resolutions of c. 0.5 nautical miles can now be applied,which allows the complete spectrum of meso-scale features to be described. Even the development of filaments can be describedrealistically in comparison with high-resolution satellite data.But the effect of upwelling at a basin scale and possible changes under changing climatic conditions remain open questions