Non-extensive entropy from incomplete knowledge of Shannon entropy?

In this paper we give an interpretation of Tsallis' nonextensive statistical mechanics based upon the information-theoretic point of view of Luzzi et al. [cond-mat/0306217; cond-mat/0306247; cond-mat/0307325], suggesting Tsallis' entropy to be not a fundamental concept but rather a derived one, stemming from an incomplete knowledge of the system, not taking properly into account its interaction with the environment. This interpretation seems to avoid some problems occurring with the original interpretation of Tsallis statistics.Comment: v.4. 11 pages. Title changed. Content substantially changed: added discussion of several points raised by various referees and readers; Also reference made to work by Luzzi, Vasconcellos, Galvao Ramos. Physica Scripta, to appea

An analysis of referrals to a level 3 intensive care unit in a resource-limited setting in South Africa

Background. With a shortage of intensive care unit (ICU) beds and rising healthcare costs in resource-limited settings, clinicians need to appropriately triage admissions into ICU to avoid wasteful expenditure and unnecessary bed utilisation. Objective. To assess the nature, appropriateness and outcome of referrals to a tertiary centre ICU. Methods. A retrospective review of ICU consults from September 2016 to February 2017 at King Edward VIII Hospital was performed. The study was approved by the University of KwaZulu-Natal Biomedical Research Ethics Committee (BE291/17). Data pertaining to patients’ demographics, referring doctor, diagnosis, comorbidities as well as biochemical and haemodynamic parameters were extracted. This information was then cross- referenced to the outcome of the ICU consultation. Data were descriptively analysed. Results. Five hundred consultations were reviewed over a 6-month period; 52.2% of patients were male and the mean age was 44 years. Junior medical officers referred 164 (32.8%) of the consultations. Although specialist supervision was available in 459 cases, it was only utilised in 339 (73.9%) of these cases. Most referrals were from tertiary (46.8%) or regional (30.4%) hospitals; however, direct referrals from district hospitals and clinics accounted for 20.4% and 1.4% of consultations, respectively. The appropriate referral pathway was not followed in 81 (16.2%) consultations. Forty-five percent of consults were accepted; however, 9.3% of these patients died before arrival in ICU. A total of 151 (30.2%) patients were refused ICU admission, with the majority (57%) of these owing to futility. Patients were unstable at the time of consult in 53.2% of referrals and 34.4% of consults had missing data. Conclusion. Critically ill patients are often referred by junior doctors without senior consultation, and directly from low-level healthcare facilities. A large proportion of ICU referrals are deemed futile and, of the patients accepted for admission, almost 1 in 10 dies prior to ICU admission. More emphasis needs to be placed on the training of doctors to appropriately triage and manage critically ill patients and ensure appropriate ICU referral and optimising of patient outcomes

Stability and Antioxidant Activity of Semi-synthetic Derivatives of 4-Nerolidylcatechol.

4-nerolidylcatechol (4-NC) is an unstable natural product that exhibits important antioxidant, anti-inflammatory and other properties. It is readily obtainable on a multi-gram scale through straightforward solvent extraction of the roots of cultivated Piper peltatum or P. umbellatum, followed by column chromatography on the resulting extract. Semi-synthetic derivatives of 4-NC with one or two substituent groups (methyl, acetyl, benzyl, benzoyl) on the O atoms have been introduced that have increased stability compared to 4-NC and significant in vitro inhibitory activity against the human malaria parasite Plasmodium falciparum. Antioxidant and anti-inflammatory properties may be important for the antiplasmodial mode of action of 4-NC derivatives. Thus, we decided to investigate the antioxidant properties, cytotoxicity and stability of 4-NC derivatives as a means to explore the potential utility of these compounds. 4-NC showed high antioxidant activity in the DPPH and ABTS assays and in 3T3-L1 cells (mouse embryonic fibroblast), however 4-NC was more cytotoxic (IC50 = 31.4 µM) and more unstable than its derivatives and lost more than 80% of its antioxidant activity upon storage in solution at −20 °C for 30 days. DMSO solutions of mono-O-substituted derivatives of 4-NC exhibited antioxidant activity and radical scavenging activity in the DPPH and ABTS assays that was comparable to that of BHA and BHT. In the cell-based antioxidant model, most DMSO solutions of derivatives of 4-NC were less active on day 1 than 4-NC, quercetin and BHA and more active antioxidants than BHT. After storage for 30 days at −20 °C, DMSO solutions of most of the derivatives of 4-NC were more stable and exhibited more antioxidant activity than 4-NC, quercetin and BHA and exhibited comparable antioxidant activity to BHT. These findings point to the potential of derivatives of 4-NC as antioxidant compounds

The Critical Care Society of Southern Africa guidelines on the allocation of scarce critical care resources during the COVID-19 public health emergency in South Africa

Letter by Gopalan et al. on article by Singh and Moodley (Singh JA, Moodley K. Critical care triaging in the shadow of COVID-19: Ethics considerations. S Afr Med J 2020;110(5):355-359. https://doi.org/10.7196/SAMJ.2020.v110i5.14778); and response by Singh and Moodle

Nycthemeral and Monthly Occupation of the Fish Assemblage on a Sheltered Beach of Baía Norte, Florianópolis, Santa Catarina State, Brazil

Interpreting fish community records is challenging for several reasons, including the lack of past ichthyofauna data, the cyclical temporal variations in the community, and the methodology employed, which usually underestimates fish assemblages. The objective of this study was to describe short-scale and meso-scale (nycthemeral period and months, respectively) temporal variations in the ichthyofauna composition and structure of a sheltered beach of Baía Norte (Florianópolis, Santa Catarina state, Brazil), using a capéchade net. Samples were collected monthly for a period of 48 hours. During the period from December 2010 to November 2011, a total of 19,302 individuals belonging to 89 species and 39 families were captured. The number of individuals that were sampled during the day and/or night was dependent on the sampling month. On average, the daytime assemblage was more abundant and different in structure and composition than the nighttime assemblage. Of the eight species that had the highest Index of Relative Importance (%IRI), five had higher variations (ANOVA F) between the day and night than between the months. This finding reinforced the need for sampling during both the day and night. The capéchade net effectively captured demersal and pelagic individuals in a broad range of sizes

Statistical Mechanics and the Physics of the Many-Particle Model Systems

The development of methods of quantum statistical mechanics is considered in light of their applications to quantum solid-state theory. We discuss fundamental problems of the physics of magnetic materials and the methods of the quantum theory of magnetism, including the method of two-time temperature Green's functions, which is widely used in various physical problems of many-particle systems with interaction. Quantum cooperative effects and quasiparticle dynamics in the basic microscopic models of quantum theory of magnetism: the Heisenberg model, the Hubbard model, the Anderson Model, and the spin-fermion model are considered in the framework of novel self-consistent-field approximation. We present a comparative analysis of these models; in particular, we compare their applicability for description of complex magnetic materials. The concepts of broken symmetry, quantum protectorate, and quasiaverages are analyzed in the context of quantum theory of magnetism and theory of superconductivity. The notion of broken symmetry is presented within the nonequilibrium statistical operator approach developed by D.N. Zubarev. In the framework of the latter approach we discuss the derivation of kinetic equations for a system in a thermal bath. Finally, the results of investigation of the dynamic behavior of a particle in an environment, taking into account dissipative effects, are presented.Comment: 77 pages, 1 figure, Refs.37