Third law of thermodynamics as a key test of generalized entropies

The laws of thermodynamics constrain the formulation of statistical mechanics at the microscopic level. The third law of thermodynamics states that the entropy must vanish at absolute zero temperature for systems with nondegenerate ground states in equilibrium. Conversely, the entropy can vanish only at absolute zero temperature. Here we ask whether or not generalized entropies satisfy this fundamental property. We propose a direct analytical procedure to test if a generalized entropy satisfies the third law, assuming only very general assumptions for the entropy S and energy U of an arbitrary N-level classical system. Mathematically, the method relies on exact calculation of β=dS/dU in terms of the microstate probabilities p(i). To illustrate this approach, we present exact results for the two best known generalizations of statistical mechanics. Specifically, we study the Kaniadakis entropy S(κ), which is additive, and the Tsallis entropy S(q), which is nonadditive. We show that the Kaniadakis entropy correctly satisfies the third law only for -1<κ<+1, thereby shedding light on why κ is conventionally restricted to this interval. Surprisingly, however, the Tsallis entropy violates the third law for q<1. Finally, we give a concrete example of the power of our proposed method by applying it to a paradigmatic system: the one-dimensional ferromagnetic Ising model with nearest-neighbor interactions.

Co3O4 nanoparticles/cellulose nanowhiskers-derived amorphous carbon nanoneedles: sustainable materials for supercapacitors and oxygen reduction electrocatalysis

Amorphous carbon nanoneedles-supported Co₃O₄ nanoparticles, materials that have electrocatalytic activity for ORR and the ability to store charges, are synthesized with nanoreactors using Co(ii) ions and cellulose nanowhiskers as precursor.

Characterisation of systemic reactions to subcutaneous immunotherapy with airborne allergens and classification according to WAO 2010

BACKGROUND

Systemic reactions (SR) to subcutaneous immunotherapy (SCIT) are rare but potentially severe. The use of different definitions and classifications hampered comparability between studies.

AIMS

To determine the frequency of SR to SCIT with airborne allergens, and to characterise and classify them according to the WAO 2010 recommendations.

METHODS

Cross-sectional, retrospective study. Data on patients, immunotherapy and SR to SCIT were collected from the SCIT record forms. During the study period, 22,332 SCIT injections were administered (3732 patients).

RESULTS

A total of 26 SR (0.1% of administrations) were recorded in 16 (0.6%) patients (median age 22 years, nine males, all with rhinitis and nine with asthma). Twenty-one (81%) SR occurred during the induction phase; eight (31%) in the first hour after administration. According to the WAO 2010 classification, 12 (46%) were grade 1 and 14 (54%) were grade 2. Most grade 2 reactions occurred in asthmatics, presented as mild asthma symptoms and resolved without need for medical observation. Only two individuals without asthma presented grade 2 reactions, both with concurrent cutaneous and low respiratory symptoms; both required medical observation and treatment despite late onset; 82% (n=12) of grade 2 reactions were late. No grade 3-5 reactions were registered and only one patient needed adrenaline treatment. No risk factors for SR to SCIT were identified in this study.

CONCLUSIONS

SCIT is a safe treatment when administered by trained staff. The WAO 2010 classification might be useful for retrospectively classifying the severity of reactions, although its usefulness in treatment decision needs further research.

Hydroxyapatite nanowhiskers embedded in chondroitin sulfate microspheres as colon targeted drug delivery systems

An inorganic/organic hybrid material with a triggering mechanism for specific drug delivery at the colon is synthesized.

Dietary intake of calcium, vitamins A and E and bleeding on probing in Sri Lankan preschoolers

OBJECTIVE

To determine the prevalence of gingival bleeding on probing and the associations between dietary intake of calcium, vitamins A and E and gingival bleeding on probing in Sri Lankan preschool children.

BASIC RESEARCH DESIGN

A cross-sectional study.

PARTICIPANTS

784 children aged 48-72 months attending preschools in the Kegalle district and their mothers/carers.

RESULTS

The prevalence of gingival bleeding on probing was 52.9%. A Poisson logistic regression model revealed that children with a high daily dietary intake of calcium were less likely to have gingival bleeding on probing than those with low intake (PR=0.80; 95%CI 0.64,0.98). Also prevalence of gingival bleeding was higher in children: with plaque on their teeth; whose mothers were not employed; or, were from families with three or more children.

CONCLUSIONS

The prevalence of gingivitis was high in the children and the findings suggest that high levels of dietary calcium intake are associated with reduced gingival bleeding in preschool children.

Dysplasia detection rate of confirmatory EGD in nondysplastic Barrett's esophagus

Current guidelines for endoscopic surveillance of Barrett's esophagus (BE) recommend that patients with newly diagnosed BE undergo confirmatory esophagogastroduodenoscopy (EGD) to exclude the presence of dysplasia. The extent to which confirmatory endoscopy alters management and detects missed dysplasia in newly diagnosed BE has not been reported. The frequency with which confirmatory endoscopy changed surveillance management in patients with newly diagnosed BE was assessed. A two center cohort analysis was conducted on patients newly diagnosed with BE. The rate of dysplasia on confirmatory endoscopy for patients who had nondysplastic BE was obtained. Demographic and endoscopic variables were assessed for association with dysplasia detection using Firth logistic regression model. Out of the 146 patients newly diagnosed with BE and initially determined to be without dysplasia, 12 had dysplasia on the confirmatory second EGD (8.2%). Eleven of 12 cases with dysplasia on confirmatory endoscopy had long-segment BE (LSBE). Among all the LSBE cases in our cohort, 11 had newly diagnosed dysplasia on confirmatory EGD, 29.7% (11/37). The average number of biopsies obtained from the 11 LSBE cases with dysplasia was comparable with the rest of the LSBE cases without dysplasia (6.73 and 5.42, respectively, P-value 0.205). The rate of dysplasia detection in short-segment BE (SSBE) was much lower, 0.95% (1 out of 105). There were no cases of high-grade dysplasia (HGD) or cancer detected in any SSBE case. HGD was detected on confirmatory EGD in two cases, both were LSBE. Segment length was the only statistically significant factor to predict the presence of dysplasia on confirmatory endoscopy (odds ratio 9.158, P. 0.008). Confirmatory EGD in newly diagnosed LSBE had significant rate of dysplasia detection (29.7%) in this cohort. Among patients with SSBE, there was a low rate of dysplasia detection with confirmatory EGD, less than 1% of cases. No additional cases of HGD or esophageal carcinoma in SSBE cases were detected. This suggests that the yield of confirmatory EGD is greater in patients with LSBE.

On the effects of intercalators in DNA condensation: a force spectroscopy and gel electrophoresis study

In this work we have characterized the effects of the intercalator ethidium bromide (EtBr) on the DNA condensation process by using force spectroscopy and gel electrophoresis. We have tested two condensing agents: spermine (spm(4+)), a tetravalent cationic amine which promotes cation-induced DNA condensation, and poly(ethylene glycol) (PEG), a neutral polymer which promotes DNA ψ-condensation. Two different types of experiments were performed. In the first type, bare DNA molecules disperse in solution are first treated with EtBr for intercalation, and then the condensing agent is added to the sample with the purpose of verifying the effects of the intercalator in hindering DNA condensation. In the second experiment type, the bare DNA molecules are first condensed, and then the intercalator is added to the sample in order to verify its influence on the previously condensed DNA. The results obtained with the two different experimental techniques used agree very well, indicating that previously intercalated EtBr can hinder both cation-induced and ψ-condensation, being more efficient in the first case. On the other hand, EtBr has little effect on the previously formed cation-induced condensates, but is efficient in unfolding the ψ-condensates.

In vitro Antioxidant Activity, Phenolic Compounds and Protective Effect against DNA Damage Provided by Leaves, Stems and Flowers of Portulaca oleracea (Purslane)

This study analyzed the antioxidant properties of Portulaca oleracea L., known as purslane. The samples (leaves, flowers and stems) were collected at two different locations in Portugal: Tavira (L1) and Vendas Novas (L2). Assays for total antioxidant activity, total phenolic content and ferric-reducing antioxidant power were conducted and, for both locations, significantly higher values ( P<0,05) were observed for stems (508.8 and 982.3 mg AAE/100 g DW, 1008.6 and 2285.5 mg GAE/100 g DW, 121.0 and 166.3 mg TE/100 g DW, respectively for each location), than in leaves or flowers. In the DPPH assay, the three-plant parts from L2 reached the 50% inhibition rate in lower concentrations than plants from L1. On the other hand, higher concentrations of total monomeric anthocyanins were found in samples from L1 (95.5, 88.8 and 86.0 mg/L) than in samples from L2 (81.7, 70.5 and 59.8 mg/L). The same was true for phenolic acids, estimated by liquid-chromatography, where methanol extracts were used. Phenolic extracts from all three-plant parts from both locations showed protective effects on DNA against hydroxyl radicals. This work suggests the possibility of benefit to human health from its consumption, related to the high antioxidant activity of purslane, even the stems, usually discarded in daily consumption.