Vapor‐Phase Carbonylation of Dimethoxymethane over H‐Faujasite

Carbonylation gets a phase lift : The usual liquid‐phase, high‐pressure processes for carbonylating formaldehydes are avoided in a novel vapor‐phase reaction. Using an acid zeolite (Faujasite) at near‐atmospheric pressure dimethoxymethane (DMM; the dimethyl acetal of formaldehyde; see scheme) is carbonylated to produce methyl methoxyacetate (MMAc). This approach provides a new route to ethylene glycol under mild conditions.

     

The mechanism of the protonation of metal (hydr)oxides in aqueous solutions studied for various interfacial/surface ionization models and physicochemical parameters: a critical review and a novel approach

The mechanism of the protonation of solid metal (hydr)oxides in aqueous media was investigated using simulation and experimental work. It was found that the apparent acidity/basicity of each kind of surface sites of metal (hydr)oxides in aqueous suspensions is strongly influenced by the overall surface charge of the (hydr)oxide and thus by the electrical potential smeared out at the interfacial region. Depending on its sign this increases or decreases the hydrogen ion concentration on the surface, thus promoting or hindering protonation. This is manifested by the shifts of the protonation peaks of the various kinds of sites with respect to the -pK values of the corresponding intrinsic protonation constants and the appearance of an extra peak in the d[H+cons,surf]/dpH vs. pH curves. Potentiometric titrations experiments performed for four technologically important oxides showed that the proposed protonation mechanism describes indeed the protonation of polycrystalline (hydr)oxides in aqueous media.     

Entropy Corrections for a Charged Black Hole of String Theory

We study the entropy of the Gibbons-Maeda-Garfinkle-Horowitz-Strominger (GMGHS) charged black hole, originated from the effective action thatemerges in the low-energy of string theory, beyond semiclassical approximations. Applying the properties of exact differentials for three variables to the first law thermodynamics we derive the quantum correctionsto the entropy of the black hole. The leading (logarithmic) and non leading corrections to the area law are obtained.     

A Rigorous Derivation of the Coupling of a Kinetic Equation and Burgers’ Equation

In this article, we investigate the kinetic/fluid coupling on a toy model, which we obtain rigorously from a hydrodynamical limit. The idea is that at the level of the full kinetic model, the coupling is obvious. We then investigate the coupling obtained when passing into the limit. We show that, especially in presence of a shock stuck on the interface, the coupling involves a kinetic layer known as the Milne problem. Due to this layer, the limit process is quite delicate and some blow-up techniques are needed to ensure its strong convergence.     

Criteria on Contractions for Entropic Discontinuities of Systems of Conservation Laws

We study the contraction properties (up to shift) for admissible Rankine–Hugoniot discontinuities of \({n\times n}\) systems of conservation laws endowed with a convex entropy. We first generalize the criterion developed in (Serre and Vasseur, J l’Ecole Polytech 1, 2014), using the spatially inhomogeneous pseudo-distance introduced in (Vasseur, Contemp Math AMS, 2013). Our generalized criterion guarantees the contraction property for extremal shocks of a large class of systems, including the Euler system. Moreover, we introduce necessary conditions for contraction, specifically targeted for intermediate shocks. As an application, we show that intermediate shocks of the two-dimensional isentropic magnetohydrodynamics do not verify any of our contraction properties. We also investigate the contraction properties, for contact discontinuities of the Euler system, for a certain range of contraction weights. None of the results involve any smallness condition on the initial perturbation or on the size of the shock.     

Systemic Administration of Polymer‐Coated Nano‐Graphene to Deliver Drugs to Glioblastoma

Graphene—2D carbon—has received significant attention thanks to its electronic, thermal, and mechanical properties. Recently, nano‐graphene (nGr) has been investigated as a possible platform for biomedical applications. Here, a polymer‐coated nGr to deliver drugs to glioblastoma after systemic administration is reported. A biodegradable, biocompatible poly(lactide) (PLA) coating enables encapsulation and controlled release of the hydrophobic anticancer drug paclitaxel (PTX), and a hydrophilic poly(ethylene glycol) (PEG) shell increases the solubility of the nGr drug delivery system. Importantly, the polymer coating mediates the interaction of nGr with U‐138 glioblastoma cells and decreases cytotoxicity compared with pristine untreated nGr. PLA‐PEG‐coated nGr is also able to encapsulate PTX at 4.15 wt% and sustains prolonged PTX release for at least 19 d. PTX‐loaded nGr‐PLA‐PEGs are shown to kill up to 20% of U‐138 glioblastoma cells in vitro. Furthermore, nGr‐PLA‐PEG and CNT‐PLA‐PEG, two carbon nanomaterials with different shapes, are able to kill U‐138 in vitro as well as free PTX at significantly lower doses of drug. Finally, in vivo biodistribution of nGr‐PLA‐PEG shows accumulation of nGr in intracranial U‐138 glioblastoma xenografts and organs of the reticuloendothelial system.     

Entropic and electrostatic effects on the folding free energy of a surface-attached biomolecule: an experimental and theoretical study

Surface-tethered biomolecules play key roles in many biological processes and biotechnologies. However, while the physical consequences of such surface attachment have seen significant theoretical study, to date this issue has seen relatively little experimental investigation. In response we present here a quantitative experimental and theoretical study of the extent to which attachment to a charged-but otherwise apparently inert-surface alters the folding free energy of a simple biomolecule. Specifically, we have measured the folding free energy of a DNA stem loop both in solution and when site-specifically attached to a negatively charged, hydroxylalkane-coated gold surface. We find that whereas surface attachment is destabilizing at low ionic strength, it becomes stabilizing at ionic strengths above ~130 mM. This behavior presumably reflects two competing mechanisms: excluded volume effects, which stabilize the folded conformation by reducing the entropy of the unfolded state, and electrostatics, which, at lower ionic strengths, destabilizes the more compact folded state via repulsion from the negatively charged surface. To test this hypothesis, we have employed existing theories of the electrostatics of surface-bound polyelectrolytes and the entropy of surface-bound polymers to model both effects. Despite lacking any fitted parameters, these theoretical models quantitatively fit our experimental results, suggesting that, for this system, current knowledge of both surface electrostatics and excluded volume effects is reasonably complete and accurate.     

Capacity and Covering Numbers

We establish the inequality $1/C_K(E)\ge \int_0^\infty |dK(t)|/N_E(t)$ , where E is a compact metric space, K is a kernel function, C _K is the associated capacity, and N _E (t) denotes the minimal number of sets of diameter t needed to cover E. We give applications to the capacity of generalized Cantor sets, and to the capacity of δ-neighborhoods of a set. We also investigate possible converses to the inequality.     

Nitric oxide release: part II. Therapeutic applications

A wide range of nitric oxide (NO)-releasing materials has emerged as potential therapeutics that exploit NO's vast biological roles. Macromolecular NO-releasing scaffolds are particularly promising due to their ability to store and deliver larger NO payloads in a more controlled and effective manner compared to low molecular weight NO donors. While a variety of scaffolds (e.g., particles, dendrimers, and polymers/films) have been cleverly designed, the ultimate clinical utility of most NO-releasing macromolecules remains unrealized. Although not wholly predictive of clinical success, in vitro and in vivo investigations have enabled a preliminary evaluation of the therapeutic potential of such materials. In this tutorial review, we review the application of macromolecular NO therapies for cardiovascular disease, cancer, bacterial infections, and wound healing.