Material Dependence of the Wire-Particle Casimir Interaction

We study the Casimir interaction between a metallic cylindrical wire and a metallic spherical particle by employing the scattering formalism. At large separations, we derive the asymptotic form of the interaction. In addition, we find the interaction between a metallic wire and an isotropic atom, both in the non-retarded and retarded limits. We identify the conditions under which the asymptotic Casimir interaction does not depend on the material properties of the metallic wire and the particle. Moreover, we compute the exact Casimir interaction between the particle and the wire numerically. We show that there is a complete agreement between the numerics and the asymptotic energies at large separations. For short separations, our numerical results show good agreement with the proximity force approximation

Universality versus material dependence of fluctuation forces between metallic wires

We calculate the Casimir interaction between two parallel wires and between a wire and a metall plate. The dielectric properties of the objects are described by the plasma, Drude and perfect metal models. We find that at asymptotically large separation interactions involving plasma wires and/or plates are independent of the material properties, but depend on the dc conductivity $\sigma$ for Drude wires. Counterintuitively, at intermediate separations the interaction involving Drude wires can become independent of $\sigma$. At smaller separations, we compute the interaction numerically and observe an approach to the proximity approximation

Elastic Lattice Polymers

We study a model of "elastic" lattice polymer in which a fixed number of monomers $m$ is hosted by a self-avoiding walk with fluctuating length $l$. We show that the stored length density $\rho_m = 1 - /m$ scales asymptotically for large $m$ as $\rho_m=\rho_\infty(1-\theta/m + ...)$, where $\theta$ is the polymer entropic exponent, so that $\theta$ can be determined from the analysis of $\rho_m$. We perform simulations for elastic lattice polymer loops with various sizes and knots, in which we measure $\rho_m$. The resulting estimates support the hypothesis that the exponent $\theta$ is determined only by the number of prime knots and not by their type. However, if knots are present, we observe strong corrections to scaling, which help to understand how an entropic competition between knots is affected by the finite length of the chain.Comment: 10 page

Collective charge fluctuations and Casimir interactions for quasi one-dimensional metals

We investigate the Casimir interaction between two parallel metallic cylinders and between a metallic cylinder and plate. The material properties of the metallic objects are implemented by the plasma, Drude and perfect metal model dielectric functions. We calculate the Casimir interaction numerically at all separation distances and analytically at large separations. The large-distance asymptotic interaction between one plasma cylinder parallel to another plasma cylinder or plate does not depend on the material properties, but for a Drude cylinder it depends on the dc conductivity $\sigma$. At intermediate separations, for plasma cylinders the asymptotic interaction depends on the plasma wave length $\lambda_{\rm p}$ while for Drude cylinders the Casimir interaction can become independent of the material properties. We confirm the analytical results by the numerics and show that at short separations, the numerical results approach the proximity force approximation

Experimental and theoretical investigation of angular dependence of the Casimir force between sinusoidally corrugated surfaces

In the current work we present the complete results for the measurement of normal Casimir force between shallow and smooth sinusoidally corrugated gold coated sphere and a plate at various angles between the corrugations using an atomic force microscope. All measured data were compared with the theoretical approach using the proximity force approximation and theory based on derivative expansion. In both cases real material properties of the surfaces and non-zero temperature were taken into account. Special attention is paid to the description of electrostatic interactions between corrugated surfaces at different angels between corrugations and samples reparation and characterization. The measured forces are found to be in good agreement with the theory including correlation effects of geometry and material properties and deviate significantly from the predictions of the proximity force approximation approach. This provides the quantitative confirmation for the observation of diffraction-type effects that are disregarded within the PFA approach. The obtained results open new opportunities for control of the Casimir effect in micromechanical systems

Completeness and properness of refinement operators in inductive logic programming

AbstractWithin Inductive Logic Programming, refinement operators compute a set of specializations or generalizations of a clause. They are applied in model inference algorithms to search in a quasi-ordered set for clauses of a logical theory that consistently describes an unknown concept. Ideally, a refinement operator is locally finite, complete, and proper. In this article we show that if an element in a quasi-ordered set 〈S, ≥〉 has an infinite or incomplete cover set, then an ideal refinement operator for 〈S, ≥〉 does not exist. We translate the nonexistence conditions to a specific kind of infinite ascending and descending chains and show that these chains exist in unrestricted sets of clauses that are ordered by θ-subsumption. Next we discuss how the restriction to a finite ordered subset can enable the construction of ideal refinement operators. Finally, we define an ideal refinement operator for restricted θ-subsumption ordered sets of clauses

Seasonality of presentation and birth in catatonia

BACKGROUND: Catatonia is a neuropsychiatric syndrome associated with both psychiatric disorders and medical conditions. Understanding of the pathophysiology of catatonia remains limited, and the role of the environment is unclear. Although seasonal variations have been shown for many of the disorders underlying catatonia, the seasonality of this syndrome has not yet been adequately explored. METHODS: Clinical records were screened to identify a cohort of patients suffering from catatonia and a control group of psychiatric inpatients, from 2007 to 2016 in South London. In a cohort study, the seasonality of presentation was explored fitting regression models with harmonic terms, while the effect of season of birth on subsequent development of catatonia was analyzed using regression models for count data. In a case-control study, the association between month of birth and catatonia was studied fitting logistic regression models. RESULTS: In total, 955 patients suffering from catatonia and 23,409 controls were included. The number of catatonic episodes increased during winter, with a peak in February. Similarly, an increasing number of cases was observed during summer, with a second peak in August. However, no evidence for an association between month of birth and catatonia was found. CONCLUSIONS: The presentation of catatonia showed seasonal variation in accordance with patterns described for many of the disorders underlying catatonia, such as mood disorders and infections. We found no evidence for an association between season of birth and risk of developing catatonia. This may imply that recent triggers may underpin catatonia, rather than distal events

Reliability, validity and factor structure of the GHQ-28 used among elderly Iranians

Background: The object of this study was to develop an Iranian version of the General Health Questionnaire-28 (GHQ-28) for use with elderly subjects. Methods: The GHQ-28 Farsi version was evaluated for face validity among 204 elderly subjects aged 59 years or older, chosen randomly from residents of Tehran. The Composite International Diagnostic Interview (CIDI) was used to establish a gold standard diagnosis of mental disorders. Results: The GHQ-28 was an internally consistent measure. Cronbach's α, split-half coefficients and test-retest reliability were 0.9, 0.89 and 0.58 respectively. Four factors were extracted using factor analysis: "depression," "psychosocial activity," "anxiety," and "somatic." Using receiver operating curve (ROC) analysis, the optimum cutoff score for the GHQ-28 in this group was 19/20 (sensitivity 0.83, specificity 0.76). Using a loading of 0.6 or greater, a short form of the instrument (GHQ-15) (α = 0.9) was derived and correlated well with the longer form of the scale (r = 0.97). Using ROC analysis, the optimum cutoff score was 10/11 (sensitivity 0.83, specificity 0.69). Conclusions: The short and long forms of the GHQ-28 are suitable screening instruments for elderly Iranian residents, particularly those living in urban areas. © 2006 International Psychogeriatric Association

Reliability, validity and factor structure of the GHQ-28 used among elderly Iranians

Background: The object of this study was to develop an Iranian version of the General Health Questionnaire-28 (GHQ-28) for use with elderly subjects. Methods: The GHQ-28 Farsi version was evaluated for face validity among 204 elderly subjects aged 59 years or older, chosen randomly from residents of Tehran. The Composite International Diagnostic Interview (CIDI) was used to establish a gold standard diagnosis of mental disorders. Results: The GHQ-28 was an internally consistent measure. Cronbach's α, split-half coefficients and test-retest reliability were 0.9, 0.89 and 0.58 respectively. Four factors were extracted using factor analysis: "depression," "psychosocial activity," "anxiety," and "somatic." Using receiver operating curve (ROC) analysis, the optimum cutoff score for the GHQ-28 in this group was 19/20 (sensitivity 0.83, specificity 0.76). Using a loading of 0.6 or greater, a short form of the instrument (GHQ-15) (α = 0.9) was derived and correlated well with the longer form of the scale (r = 0.97). Using ROC analysis, the optimum cutoff score was 10/11 (sensitivity 0.83, specificity 0.69). Conclusions: The short and long forms of the GHQ-28 are suitable screening instruments for elderly Iranian residents, particularly those living in urban areas. © 2006 International Psychogeriatric Association

The Queen Square Encephalitis Multidisciplinary Team Meeting - experience over three years, pre and post the COVID-19 pandemic

Background: Patients with suspected encephalitis continue to represent a diagnostic and therapeutic challenge, even in highly resourced centres. In February 2018, we set up a monthly in-person multidisciplinary team meeting (MDT). We describe the experience and outcomes of the MDT over three years. Methods: A retrospective analysis was performed to summarise patient demographics, MDT outcomes and final diagnoses. Results: Over the three-year period, 324 discussions of 238 patients took place. Cases were diverse; approximately 40% related to COVID-19 or brain infection, 40% autoimmune or other inflammatory disorders and 20% encephalitis mimics or uncertain aetiologies. Feedback from an online survey sent to referring teams and attendees highlighted the value of the MDT; 94% reported the discussion was useful and 69% reported resulting change in patient management. Conclusions: Multidisciplinary input is crucial in this challenging area, ensuring that all diagnostic avenues are explored and opening doors to novel diagnostics and therapeutics. It also supports clinicians dealing with unwell patients, including in centres where less specialist input is available, and when decisions have to be made where there is little or no evidence base