33 research outputs found
Nonlinear Sigma Model for Disordered Media: Replica Trick for Non-Perturbative Results and Interactions
In these lectures, given at the NATO ASI at Windsor (2001), applications of
the replicas nonlinear sigma model to disordered systems are reviewed. A
particular attention is given to two sets of issues. First, obtaining
non-perturbative results in the replica limit is discussed, using as examples
(i) an oscillatory behaviour of the two-level correlation function and (ii)
long-tail asymptotes of different mesoscopic distributions. Second, a new
variant of the sigma model for interacting electrons in disordered normal and
superconducting systems is presented, with demonstrating how to reduce it,
under certain controlled approximations, to known ``phase-only'' actions,
including that of the ``dirty bosons'' model.Comment: 25 pages, Proceedings of the NATO ASI "Field Theory of Strongly
Correlated Fermions and Bosons in Low - Dimensional Disordered Systems",
Windsor, August, 2001; to be published by Kluwe
The Hubbard model within the equations of motion approach
The Hubbard model has a special role in Condensed Matter Theory as it is
considered as the simplest Hamiltonian model one can write in order to describe
anomalous physical properties of some class of real materials. Unfortunately,
this model is not exactly solved except for some limits and therefore one
should resort to analytical methods, like the Equations of Motion Approach, or
to numerical techniques in order to attain a description of its relevant
features in the whole range of physical parameters (interaction, filling and
temperature). In this manuscript, the Composite Operator Method, which exploits
the above mentioned analytical technique, is presented and systematically
applied in order to get information about the behavior of all relevant
properties of the model (local, thermodynamic, single- and two- particle ones)
in comparison with many other analytical techniques, the above cited known
limits and numerical simulations. Within this approach, the Hubbard model is
shown to be also capable to describe some anomalous behaviors of the cuprate
superconductors.Comment: 232 pages, more than 300 figures, more than 500 reference
Research misconduct in the fields of ethics and philosophy: researchers’ perceptions in Spain
This is the Author’s Original Manuscript (AOM) (also called a “preprint”) sent to review to Science and Engineering Ethics on 11/10/2020. The final version of the article was published online at SEE on 21/01/2021. The online version is available at: https://doi.org/10.1007/s11948-021-00278-wEmpirical studies have revealed a disturbing prevalence of research misconduct in a wide variety of disciplines, although not, to date, in the areas of ethics and philosophy. This study aims to provide empirical evidence on perceptions of how serious a problem research misconduct is in these two disciplines in Spain, particularly regarding the effects that the model used to evaluate academics’ research performance may have on their ethical behaviour. The methodological triangulation applied in the study combines a questionnaire, a debate at the annual meeting of scientific association, and in-depth interviews. Of the 541 questionnaires sent out, 201 responses were obtained (37.1% of the total sample), with a significant difference in the participation of researchers in philosophy (30.5%) and in ethics (52.8%); 26 researchers took part in the debate and 14 interviews were conducted. The questionnaire results reveal that 91.5% of the respondents considered research misconduct to be on the rise; 63.2% considered at least three of the fraudulent practices referred to in the study to be commonplace, and 84.1% identified two or more such practices. The researchers perceived a high prevalence of duplicate publication (66.5%) and self-plagiarism (59.0%), use of personal influence (57.5%) and citation manipulation (44.0%), in contrast to a low perceived incidence of data falsification or fabrication (10.0%). The debate and the interviews corroborated these data. Researchers associated the spread of these misconducts with the research evaluation model applied in Spain
The Addition of Lipid-Based Contrast Medium does not Inactivate the Detergent Sclerosant Sodium Tetradecyl Sulfate in-vitro.
PURPOSE
To investigate if the detergent sclerosant sodium tetradecyl sulfate (STS) is deactivated by the lipid-based contrast agent ethiodised oil.
METHOD
3% STS was mixed with ethiodised oil and room air in a 2:1:4 ratio in two luer lock syringes and a three way connector and agitated to make foam (the Tessari technique) to replicate the clinical use of the products. The assay of STS in the mixture was assessed using the British Pharmacopoeia method. Briefly this is a manual titration method where the solution of STS is mixed with an indicator solution and titrated with hyamine solution of known concentration; the concentration of the STS can then be calculated with the titration results. To further mimic the clinical environment with the presence of blood, the effect of adding increasing amounts of albumin to the STS-ethiodised oil mixture was assessed.
RESULTS
The assay of STS in the solution after mixing with ethiodised oil was 3% indicating that the ethiodised oil did not deactivate the STS. The addition of albumin to the STS-contrast mixture resulted in near linear neutralisation of the STS with increasing concentrations in the same quantities as with STS alone.
CONCLUSIONS
The mixture of the lipid-based contrast agent ethiodised oil with the detergent sclerosant STS did not affect the availability of the sclerosant. The continued use of STS-ethiodised oil in the management of vascular malformations can be supported