Entropy and the Experience of Heat Fuchs, Hans U; D'Anna, Michele; Corni, Federico
Entropy (Basel, Switzerland),
05/2022, Volume:
24, Issue:
5
Journal Article
Peer reviewed
Open access
We discuss how to construct a direct and experientially natural path to entropy as a extensive quantity of a macroscopic theory of thermal systems and processes. The scientific aspects of this ...approach are based upon continuum thermodynamics. We ask what the roots of an experientially natural approach might be-to this end we investigate and describe in some detail (a) how humans experience and conceptualize an extensive thermal quantity (i.e., an amount of heat), and (b) how this concept evolved during the early development of the science of thermal phenomena (beginning with the Experimenters of the Accademia del Cimento and ending with Sadi Carnot). We show that a direct approach to entropy, as the extensive quantity of models of thermal systems and processes, is possible and how it can be applied to the teaching of thermodynamics for various audiences.
When working with, and learning about, the thermal balance of a chemical reaction, we need to consider two overlapping but conceptually distinct aspects: one relates to the process of reallocating ...entropy between reactants and products (because of different specific entropies of the new substances compared to those of the old), and the other to dissipative processes. Together, they determine how much entropy is exchanged between the chemicals and their environment (i.e., in heating and cooling). By making explicit use of (a) the two conjugate pairs chemical amount (i.e., amount of substance) and chemical potential, and entropy and temperature, respectively, (b) the laws of balance of amount of substance on the one hand and entropy on the other, and (c) a generalized approach to the energy principle, it is possible to create both imaginative and formal conceptual tools for modeling thermal balances associated with chemical transformations in general and exothermic and endothermic reactions in particular. In this paper, we outline the concepts and relations needed for a direct approach to chemical and thermal dynamics, create a model of exothermic and endothermic reactions, including numerical examples, and discuss how to relate the direct entropic approach to traditional models of these phenomena.
Abstract Background In solid organ transplantation, sensitive real-time biomarkers to assess the graft health are desirable to enable early intervention, for example, to avoid full-blown rejections. ...During rejection, high amounts of graft-derived cell-free DNA (GcfDNA) are shed into the blood stream. The quantification of this GcfDNA in allotransplantation is considered to fulfill this need, because it can be measured with great precision and at reasonable cost. Patients and Methods Patients from 2 ongoing studies in kidney (KTx) and heart (HTx) transplantation were monitored blinded on a scheduled basis, by means of a published universal droplet digital polymerase chain reaction to quantify the GcfDNA. Results Immediately after engraftment, GcfDNA reaches high values (>5% of total cfDNA), with a rapid decrease to values of <0.5% within 1 week. Living-related KTx recipients show lower initial values, reflecting the absence of preservation injury. Episodes of rejection in KTx and HTx are accompanied by a significant increase of GcfDNA (>5-fold) above values in patients without complications, occurring earlier than clinical or biochemical hints to rejection. One case of rejection, which became clinically suspect after 1 year and was proven with biopsy, showed a significant 10-fold increase 3 months earlier. Conclusions The quantification of GcfDNA has the potential to detect rejection episodes at early stages, when other means of diagnosis are not effective. The method's noninvasiveness enables the monitoring recipients at intervals that are desired to catch rejections at early actionable stages to prevent full-blown rejection. This biomarker will be particularly valuable in regimens to minimize immunosuppression.
Data regarding the effects of vitamin D on cardiac function are inconclusive.
In a post-hoc analysis of the EVITA (Effect of vitamin D on mortality in heart failure) trial, we investigated whether a ...daily vitamin D3 supplement of 4000 IU for three years affects echocardiography parameters like left ventricular end-diastolic diameter (LVEDD), LV end-systolic diameter (LVESD), and LV ejection fraction (LVEF) in patients with advanced heart failure (HF) and 25‑hydroxyvitamin D levels <75 nmol/L. Of 400 patients enrolled, 199 were assigned to vitamin D and 201 to placebo. We assessed time × treatment interaction effects using linear mixed models and analyzed in subgroups vitamin D effects at 12 and 36 months post-randomization using analysis of covariance with adjustments for baseline values.
At baseline, values of LVEDD, LVESD, and LVEF were 67.5 ± 10.5 mm, 58.9 ± 12.0 mm, and 30.47 ± 10.2%, respectively. There were no time × treatment interaction effects on LV echocardiographic parameters in the entire study cohort, neither at 12 months nor at 36 months post-randomization (P-values > 0.05). However, in the subgroup of patients aged ≥50 years, vitamin D treatment was associated with an increase in LVEF of 2.73% (95%CI: 0.14 to 5.31%) at 12 months post-randomization (n = 311). The increase was slightly attenuated to 2.60% (95%CI: −2.47 to 7.67%) at 36 months post-randomization (n = 242).
Our data indicate that vitamin D supplementation does not significantly improve cardiac function in all patients with advanced HF. However, vitamin D probably improves LV function in HF patients aged ≥50 years.
•The effect of vitamin D on cardiac function is hotly debated but available data are inconclusive.•We investigated the effect of a daily vitamin D3 supplement of 4,000 IU for three years on cardiac function.•Vitamin D supplementation may not improve cardiac function in all patients with heart failure, but probably in patients aged ≥ 50 years.
•Foreign macroeconomic determinants affect the foreign exchange rate exposure of US companies.•Foreign GDP, current account balances, CPI, term spreads, unit labor costs and government expenditures ...influence after-hedging exposures of potential exporters.•Effect of foreign macroeconomic forecasts on expected exchange rates used to predict the hedging behavior of exporters and importers.
This paper examines the foreign exchange rate exposures of US companies and how they are linked to foreign macroeconomic determinants. I use US trade-weighted macroeconomic indices of foreign countries to explain the variation in foreign exchange rate exposures, measured as the sensitivities of stock returns to exchange rate returns of US non-financial companies over the period 1995 to 2017. I find strong evidence that the after-hedging exposures of potential exporters are affected by their expectations of foreign market gross domestic products, current account balances, consumer price indices, term spreads, unit labor costs as well as government expenditures.
Summary
Low vitamin D status is common in patients with heart failure and may influence bone health. A daily vitamin D dose of 4000 IU (moderately high dose) for 3 years had however no effect on ...parameters of bone metabolism, even in patients with very low vitamin D status.
Introduction
Low vitamin D status is common in patients with heart failure (HF) and has been related to disturbed bone turnover. The present study investigated the effect of a daily vitamin D
3
dose of 4000 IU on bone turnover markers (BTMs) in patients with advanced HF and 25-hydroxyvitamin D (25OHD) concentrations < 75 nmol/L.
Methods
In this pre-specified secondary analysis of a randomized controlled trial, we assessed in 158 male HF patients (vitamin D group:
n
= 80; placebo group:
n
= 78) between-group differences in calciotropic hormones (25OHD, 1,25-dihydroxyvitamin D 1,25(OH)
2
D, intact parathyroid hormone iPTH), and BTMs (cross-linked C-telopeptide of type I collagen, bone-specific alkaline phosphatase, undercarboxylated osteocalcin). Comparisons were performed at the end of a 3-year vitamin D supplementation period with adjustments for baseline values.
Results
Compared with placebo, vitamin D increased 25OHD on average by 54.3 nmol/L. At study termination, 25OHD and 1,25(OH)
2
D were significantly higher (
P
< 0.001 and
P
= 0.007, respectively), whereas iPTH tended to be lower in the vitamin D group than in the placebo group (
P
= 0.083). BTMs were initially within their reference ranges and did not differ significantly between groups at study termination, neither in the entire study cohort nor when data analysis was restricted to the subgroup of patients with initial 25OHD concentrations < 30 nmol/L (
n
= 54) or to patients with initial hyperparathyroidism (
n
= 65) (all
P
values > 0.05).
Conclusions
A daily vitamin D
3
dose of 4000 IU did not influence BTMs. Data indicate that vitamin D supplementation will not lower bone turnover in male patients with heart failure.
Narrative in science learning has become an important field of inquiry. Most applications of narrative are extrinsic to science-such as when they are used for creating affect and context. Where they ...are intrinsic, they are often limited to special cases and uses. To extend the reach of narrative in science, a hypothesis of narrative framing of natural and technical scenes is formulated. The term narrative framing is used in a double sense, to represent (1) the enlisting of narrative intelligence in the perception of phenomena and (2) the telling of stories that contain conceptual elements used in the creation of scientific models of these phenomena. The concrete case for narrative framing is made by conceptual analyses of simple stories of natural phenomena and of products related to modern continuum thermodynamics that reveal particular figurative structures. Importantly, there is evidence for a medium-scale perceptual gestalt called force of nature that is structured metaphorically and narratively. The resulting figurative conceptual structure gives rise to the notion of natural agents acting and suffering in storyworlds. In order to show that formal scientific models are deeply related to these storyworlds, a link between using (i.e. simulating) models and storytelling is employed. This link has recently been postulated in studies of narrative in computational science and economics.
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