On the isobaric thermal expansivity of liquids

Implications of Anion Structure on Physicochemical Properties of DBU-Based Protic Ionic Liquids

Protic ionic liquids (PILs) are potential candidates as electrolyte components in energy storage devices. When replacing flammable and volatile organic solvents, PILs are expected to improve the safety and performance of electrochemical devices. Considering their technical application, a challenging task is the understanding of the key factors governing their intermolecular interactions and physicochemical properties. The present work intends to investigate the effects of the structural features on the properties of a promising PIL based on the 1,8-diazabicyclo[5.4.0]undec-7-ene (DBUH⁺) cation and the (trifluoromethanesulfonyl)(nonafluorobutanesulfonyl)imide (IM14^–) anion, the latter being a remarkably large anion with an uneven distribution of the C–F pool between the two sides of the sulfonylimide moieties. For comparison purposes, the experimental investigations were extended to PILs composed of the same DBU-based cation and the trifluoromethanesulfonate (TFO^–) or bis(trifluoromethanesulfonyl)imide (TFSI^–) anion. The combined use of multiple NMR methods, thermal analyses, density, viscosity, and conductivity measurements provides a deep characterization of the PILs, unveiling peculiar behaviors in DBUH-IM14, which cannot be predicted solely on the basis of differences between aqueous pK_a values of the protonated base and the acid (ΔpK_a). Interestingly, the thermal and electrochemical properties of DBUH-IM14 turn out to be markedly governed by the size and asymmetric nature of the anion. This observation highlights that the structural features of the precursors are an important tool to tailor the PIL’s properties according to the specific application.

Determination of derived volumetric properties and heat capacities at high pressures using two density scaling based equations of state. Application to dipentaerythritol hexa(3,5,5-trimethylhexanoate)

Scaling based EoSs describe the complex behavior of derived properties for broad temperature and pressure ranges from diPEiC₉ experimental densities.

The complex, non-monotonic thermal response of the volumetric space of simple liquids

We show that a non-monotonic solution of the equation ∂α_p(p,T)/∂T = 0 divides the phase diagram of simple liquids into two parts.

Circadian rhythm connections to oxidative stress: implications for human health

SIGNIFICANCE

Oxygen and circadian rhythmicity are essential in a myriad of physiological processes to maintain homeostasis, from blood pressure and sleep/wake cycles, down to cellular signaling pathways that play critical roles in health and disease. If the human body or cells experience significant stress, their ability to regulate internal systems, including redox levels and circadian rhythms, may become impaired. At cellular as well as organismal levels, impairment in redox regulation and circadian rhythms may lead to a number of adverse effects, including the manifestation of a variety of diseases such as heart diseases, neurodegenerative conditions, and cancer.

RECENT ADVANCES

Researchers have come to an understanding as to the basics of the circadian rhythm mechanism, as well as the importance of the numerous species of oxidative stress components. The effects of oxidative stress and dysregulated circadian rhythms have been a subject of intense investigations since they were first discovered, and recent investigations into the molecular mechanisms linking the two have started to elucidate the bases of their connection.

CRITICAL ISSUES

While much is known about the mechanics and importance of oxidative stress systems and circadian rhythms, the front where they interact has had very little research focused on it. This review discusses the idea that these two systems are together intricately involved in the healthy body, as well as in disease.

FUTURE DIRECTIONS

We believe that for a more efficacious management of diseases that have both circadian rhythm and oxidative stress components in their pathogenesis, targeting both systems in tandem would be far more successful.

Association effects in pure methanol via Monte Carlo simulations. II. Thermodynamics

A simple methodology [P. Gómez-Álvarez, A. Dopazo-Paz, L. Romani, and D. González-Salgado, J. Chem. Phys. 134, 014512 (2011)] recently developed in the light of the Monte Carlo molecular simulation technique was used in this work to study the association effects on the response functions of methanol over the whole thermodynamic state space. It consists basically on evaluating the first order properties of the fluid (energy and volume) in terms of those for two hypothetical fluids living in the bulk composed by monomers and associated molecules, respectively. In this context, the second order thermodynamic derivatives can be expressed in a perturbative way as the sum of the monomer term (reference term) and the association contribution. Specifically, both contributions to the residual isobaric heat capacity, and to the pressure and temperature derivatives of the volume were determined for the optimized potential for liquid simulation (OPLS) of methanol through NPT Monte Carlo simulations from 250 K to 1000 K along the supercritical isobars 25, 100, 200, 500 MPa, and from 800 K to 350 K at 0.1 MPa. Results showed that both terms are relevant for the residual isobaric heat capacity and that their influence depends considerably on the thermodynamic conditions; however, the volumetric response functions were found mainly affected by the monomer contribution, especially the pressure derivative of the volume.