Titanate Anodes for Sodium Ion Batteries

For reasons of cost and supply security issues, there is growing interest in the development of rechargeable sodium ion batteries, particularly for large-scale grid storage applications. Like the much better known and technologically important lithium ion analogs, the devices operate by shuttling alkali metal cations between two host materials, which undergo insertion processes at different electrochemical potentials. A particular challenge for the sodium systems is identification of a suitable anode material due to the fact that sodium does not intercalate into graphite. Although several alternatives, including disordered carbons and alloys are being investigated, the most promising options at present lie with titanates, not in the least because of attractive characteristics such as low toxicity, ease of synthesis, wide availability, and low cost. A large variety of sodium titanate compounds can be prepared, many of which have tunnel or layered structures that can readily undergo reversible reductive intercalation reactions. A brief overview of the physical, structural, and electrochemical characteristics of several of the most promising materials for sodium-ion battery applications is given in this paper, and a comparison is made between the sodium and the lithium insertion behaviors. For some of these compounds, insertion of sodium occurs at unusually low potentials, a feature that has important implications for the design of high-energy sodium-ion systems.     

Macroporous silicon for high-capacitance devices using metal electrodes

In this paper, high-capacity energy storage devices based on macroporous silicon are demonstrated. Small footprint devices with large specific capacitances up to 100 nF/mm², and an absolute capacitance above 15 μF, have been successfully fabricated using standard microelectronics and MEMS techniques. The fabricated devices are suitable for high-density system integration. The use of 3-D silicon structures allows achieving a large surface to volume ratio. The macroporous silicon structures are fabricated by electrochemical etching of silicon. This technique allows creating large structures of tubes with either straight or modulated radial profiles in depth. Furthermore, a very large aspect ratio is possible with this fabrication method. Macroporous silicon grown this way permits well-controlled structure definition with excellent repeatability and surface quality. Additionally, structure geometry can be accurately controlled to meet designer specifications. Macroporous silicon is used as one of the electrodes over which a silicon dioxide insulating layer is grown. Several insulator thicknesses have been tested. The second capacitor electrode is a solid nickel filling of the pores prepared by electroplating in a low-temperature industry standard process. The use of high-conductivity materials allows reaching small equivalent series resistance near 1 Ω. Thanks to these improvements, the presented devices are capable of operating up to 10 kHz.

PACS

84.32.Tt; 81.15.Pq; 81.05.Rm     

The interpretation of X-ray photoelectron spectra of pyrolized S-containing carbonaceous materials

Theoretical models and ab initio Hartree-Fock wavefunctions have been used to investigate the S(2p) core level binding energies (BE), of pyrolized S-containing, carbonaceous materials. Comparison between experimental and calculated data for thiophene permits the accuracy of the present approach to be established. A systematic study of different situations demonstrates that, in these materials, non-oxidized S atoms can show peaks at very high BE relative to the C(1s) peak at 285.0 eV. This study confirms that the peak at 164.1 eV corresponds to ‘thiophenic’ S atoms. On the other hand, it shows that the peaks at higher BE could correspond to S atoms replacing C atoms in three-coordinated structures of graphene layers, in agreement with the arguments suggested in the experimental works. The energetic similarity between the two peaks at very high BE makes it difficult to differentiate between them, although the results of the present study seem to suggest that the peak at experimental BE ≈ 166 eV could correspond to S atoms coordinated to two C and one H atoms at the edge of graphene layers, while the peak at ≈ 169 eV would correspond to S atoms replacing C atoms in inner positions of the graphene layers, and it is bonded to three C atoms.     

Adenosine Signaling in Mast Cells and Allergic Diseases

Adenosine is a nucleoside involved in the pathogenesis of allergic diseases. Its effects are mediated through its binding to G protein-coupled receptors: A1, A2a, A2b and A3. The receptors differ in the type of G protein they recruit, in the effect on adenylyl cyclase (AC) activity and the downstream signaling pathway triggered. Adenosine can produce both an enhancement and an inhibition of mast cell degranulation, indicating that adenosine effects on these receptors is controversial and remains to be clarified. Depending on the study model, A1, A2b, and A3 receptors have shown anti- or pro-inflammatory activity. However, most studies reported an anti-inflammatory activity of A2a receptor. The precise knowledge of the adenosine mechanism of action may allow to develop more efficient therapies for allergic diseases by using selective agonist and antagonist against specific receptor subtypes.     

Angiotensin Receptor-Neprilysin Inhibitor (ARNI) and Cardiac Arrhythmias

The renin-angiotensin-aldosterone system (RAAS) plays a major role in cardiovascular health and disease. Short-term RAAS activation controls water and salt retention and causes vasoconstriction, which are beneficial for maintaining cardiac output in low blood pressure and early stage heart failure. However, prolonged RAAS activation is detrimental, leading to structural remodeling and cardiac dysfunction. Natriuretic peptides (NPs) are activated to counterbalance the effect of RAAS and sympathetic nervous system by facilitating water and salt excretion and causing vasodilation. Neprilysin is a major NP-degrading enzyme that degrades multiple vaso-modulatory substances. Although the inhibition of neprilysin alone is not sufficient to counterbalance RAAS activation in cardiovascular diseases (e.g., hypertension and heart failure), a combination of angiotensin receptor blocker and neprilysin inhibitor (ARNI) was highly effective in several clinical trials and may modulate the risk of atrial and ventricular arrhythmias. This review summarizes the possible link between ARNI and cardiac arrhythmias and discusses potential underlying mechanisms, providing novel insights about the therapeutic role and safety profile of ARNI in the cardiovascular system.     

Effect of the annealing procedure and the molecular weight on the crystalline phase morphology and thermal properties of polylactide

The thermomechanical properties of poly(lactide) (PLA) are strongly related to its semicrystalline microstructure and morphology. Thermal annealing is a strategy to improve the crystallinity of PLA. However, the different techniques and specimen types needed for each kind of characterization could lead to misleading conclusions. In this work, annealed samples of three PLA grades with different molecular weights were studied by DSC, wide angle X‐ray scattering and polarized optical microscopy (POM) and the results are related to their thermomechanical and impact properties. Special focus is put on the POM results obtained by different approaches and the suitability of each of them to be related to the thermomechanical properties. By annealing medium molecular weight PLA specimens at 140 °C an important increase of the heat distortion temperature was obtained, which was not related to the spherulite size but to the combination of high crystallinity degree together with high α/α′ crystal type ratio. However, the impact properties of annealed PLA decreased with increase in the annealing temperature according to an increment in crystallinity and in the α/α′ crystal ratio. © 2019 Society of Chemical Industry     

Self-adaptive utility-based web session management

In the Internet, where millions of users are a click away from your site, being able to dynamically classify the workload in real time, and predict its short term behavior, is crucial for proper self-management and business efficiency. As workloads vary significantly according to current time of day, season, promotions and linking, it becomes impractical for some ecommerce sites to keep over-dimensioned infrastructures to accommodate the whole load. When server resources are exceeded, session-based admission control systems allow maintaining a high throughput in terms of properly finished sessions and QoS for a limited number of sessions; however, by denying access to excess users, the website looses potential customers.In the present study we describe the architecture of AUGURES, a system that learns to predict Web user’s intentions for visiting the site as well its resource usage. Predictions are made from information known at the time of their first request and later from navigational clicks. For this purpose we use machine learning techniques and Markov-chain models. The system uses these predictions to automatically shape QoS for the most profitable sessions, predict short-term resource needs, and dynamically provision servers according to the expected revenue and the cost to serve it. We test the AUGURES prototype on access logs from a high-traffic, online travel agency, obtaining promising results.