Conservation laws of semidiscrete canonical Hamiltonian equations

There are many evolution partial differential equations which can be cast into Hamiltonian form. Conservation laws of these equations are related to one-parameter Hamiltonian symmetries admitted by the PDEs. The same result holds for semidiscrete Hamiltonian equations. In this paper we consider semidiscrete canonical Hamiltonian equations. Using symmetries, we find conservation laws for the semidiscretized nonlinear wave equation and Schrodinger equation.Comment: 19 pages, 2 table

Approximation of excitonic absorption in disordered systems using a compositional component weighted CPA

Employing a recently developed technique of component weighted two particle Green's functions in the CPA of a binary substitutional alloy $A_cB_{1-c}$ we extend the existing theory of excitons in such media using a contact potential model for the interaction between electrons and holes to an approximation which interpolates correctly between the limits of weak and strong disorder. With our approach we are also able to treat the case where the contact interaction between carriers varies between sites of different types, thus introducing further disorder into the system. Based on this approach we study numerically how the formation of exciton bound states changes as the strengths of the contact potentials associated with either of the two site types are varied through a large range of parameter values.Comment: 27 pages RevTeX (preprint format), 13 Postscript figure file

Impact of COVID-19 Pandemic on Patients\u27 Perceptions of Safety and Need for Elective Foot and Ankle Surgery in the United States

Background: With the development of the COVID-19 pandemic, elective foot and ankle surgeries were delayed throughout the United States to divert health care resources and limit exposure. Little is known about the impact of COVID-19 on patient\u27s willingness to proceed with elective procedures once restrictions are lifted and factors contributing to such decision. Methods: Patients across 6 US orthopedic institutions who had their elective foot and ankle surgeries cancelled secondary to the pandemic were given a questionnaire. Specifically, patients were asked about their willingness to move forward with surgery once restrictions were lifted and if not why. Pain-level and pain medication use were also assessed. Univariate analysis was used to identify factors that contribute to patient\u27s decisions. Results: A total of 150 patients participated in this study. Twenty-one (14%) opted not to proceed with surgery once restrictions were lifted. Forty-three percent (n = 9) listed concern for COVID infection as the reason; however, 14% of them would proceed if procedures were performed in surgery center. Twenty-nine (19% of the total cohort) patients had increased pain and 11% of patients were taking more pain meds because of the delay to their procedure. Patients who decided not to proceed with surgery reported pain reduction (3% vs 14%) and lower increase in pain medication used (5% vs 12%). Conclusion: COVID-19 has made a significant impact on the health care system. Delay of elective foot and ankle procedures impact patient quality of life and outcomes. Access to surgery centers may provide a partial solution during the pandemic. Level of Evidence: Level III

How are "teaching the teachers" courses in evidence based medicine evaluated? A systematic review

Background Teaching of evidence-based medicine (EBM) has become widespread in medical education. Teaching the teachers (TTT) courses address the increased teaching demand and the need to improve effectiveness of EBM teaching. We conducted a systematic review of assessment tools for EBM TTT courses. To summarise and appraise existing assessment methods for teaching the teachers courses in EBM by a systematic review. Methods We searched PubMed, BioMed, EmBase, Cochrane and Eric databases without language restrictions and included articles that assessed its participants. Study selection and data extraction were conducted independently by two reviewers. Results Of 1230 potentially relevant studies, five papers met the selection criteria. There were no specific assessment tools for evaluating effectiveness of EBM TTT courses. Some of the material available might be useful in initiating the development of such an assessment tool. Conclusion There is a need for the development of educationally sound assessment tools for teaching the teachers courses in EBM, without which it would be impossible to ascertain if such courses have the desired effect

Gene Expression Signature of DMBA-Induced Hamster Buccal Pouch Carcinomas: Modulation by Chlorophyllin and Ellagic Acid

Chlorophyllin (CHL), a water-soluble, semi-synthetic derivative of chlorophyll and ellagic acid (EA), a naturally occurring polyphenolic compound in berries, grapes, and nuts have been reported to exert anticancer effects in various human cancer cell lines and in animal tumour models. The present study was undertaken to examine the mechanism underlying chemoprevention and changes in gene expression pattern induced by dietary supplementation of chlorophyllin and ellagic acid in the 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis model by whole genome profiling using pangenomic microarrays. In hamsters painted with DMBA, the expression of 1,700 genes was found to be altered significantly relative to control. Dietary supplementation of chlorophyllin and ellagic acid modulated the expression profiles of 104 and 37 genes respectively. Microarray analysis also revealed changes in the expression of TGFβ receptors, NF-κB, cyclin D1, and matrix metalloproteinases (MMPs) that may play a crucial role in the transformation of the normal buccal pouch to a malignant phenotype. This gene expression signature was altered on treatment with chlorophyllin and ellagic acid. Our study has also revealed patterns of gene expression signature specific for chlorophyllin and ellagic acid exposure. Thus dietary chlorophyllin and ellagic acid that can reverse gene expression signature associated with carcinogenesis are novel candidates for cancer prevention and therapy

Nuclear fission as a Markov process

Starting from the assumption of a random transfer of nucleons between the two sides of a fissioning nucleus, during the time from saddle point to scission, a new theory of fission is developed to show that the mass distribution in low, intermediate and high energy fission can be explained on arguments based on the ground state properties of nuclei. The theory is extended to show that the shape of the deformation energy-mass curves follows as a direct consequence of the equilibrium conditions which determine the mass distributions and the gap in the "zig-zag" curves is essentially due to the proton transfers. The time of fission is shown to be of the order of 500 nucleonic times in spontaneous and low energy fission and results from the properties of the transition matrix. The theory is also able to explain the small range of the threshold energies of fission of heavy nuclei and the formation of a symmetry axis early in the process

Oriented films of LaNiO<SUB>3</SUB> and other members of the La<SUB>n+1</SUB>Ni<SUB>n</SUB>O<SUB>3n+1</SUB> series, LaCuO<SUB>3−δ</SUB> and Pb(Zr<SUB>0.52</SUB>Ti<SUB>0.48</SUB>)O<SUB>3</SUB>, obtained by nebulized spray pyrolysis

This article does not have an abstract

Epitaxial nature of the films of LaNiO<SUB>3</SUB>, Pb(Zr<SUB>0.5</SUB>Ti<SUB>0.5</SUB>)O<SUB>3</SUB>, and La<SUB>0.95</SUB>Mn<SUB>0.95</SUB>O<SUB>3</SUB> obtained by nebulized spray pyrolysis

Films of complex oxide materials deposited on single-crystal substrates by means of nebulized spray pyrolysis have been investigated for their epitaxial nature by employing X-ray rocking curve studies and high-resolution electron microscopy, the latter enabling a direct study of the interface between the film and the substrate. It has been demonstrated that films of metallic LaNiO3, ferroelectric Pb(Zr0.5Ti0.5)O3, and La0.95Mn0.95O3 exhibiting giant magnetoresistance, deposited by nebulized spray pyrolysis on SrTiO3(100) or LaAlO3(100) are all epitaxial. Nebulized spray pyrolysis is a valuable inexpensive tool to deposit epitaxial films of complex oxide materials