Heat transfer at thin molten layer crystallization I. Molten layer cooling stage

Summary The paper presents a theoretical study of heat transfer at the cooling stage of the crystallization process of a horizontal molten layer. The obtained mathematical model, based on a physical model and on the differential equation for temperature, enabled to study the influence of some parameters (the global heat transfer coefficient between the molten layer and the cooling agent and the thickness of the layer) on the temperature distribution inside on urea¹ molten layer.     

Kinetics of formic acid oxidation in advanced porous electrodes

The electrochemical oxidation of formic acid HCOOH at porous PTFE-bonded platinum-carbon electrodes in acidic electrolyte has been studied using the AC-impedance method. A reaction sequence based on known details of this process was transferred into an equivalent circuit which was used to simulate successfully the measured impedance data. The results confirm earlier data obtained with smooth platinum electrodes and allow, for the first time, a correlation between the electrode overpotential and the contribution of the various reaction steps. Further improvements of the porous electrode based on these results are suggested.     

Research Regarding a Correlation Core–Shell Morphology–Thermal Stability of Silica–Silver Nanoparticles

Silica nanoparticles repeatedly inhaled lead to acute and chronic lung inflammation and finally to pulmonary fibrosis and lung cancer, people with chronic respiratory diseases like asthma or allergic rhinitis being even more susceptible to their toxic effects. In order to reduce these above-mentioned toxic effects, the aim of this study was to engineer the environmental silica nanoparticles with silver and subsequent thermal treatment. Nanometer-sized and spherical silica particles were synthesized in a homogeneous state, using a simple one-pot chemical method. An applicable approach resulted in silver particles forming over the surface of the silica. The outcome was materialized in extremely small silver particles attached to silica core particles. Playing their well-known decisive role, precursors and catalysts effectively controlled the size of silver and silica particles. The synchronized structure of the synthesized particles was revealed by the electrostatic repulsion among the silica spheres and the electrostatic attraction between silica spheres and silver particles. The morphological images are revealed by means of a scanning electron microscope. The formation of silver–silica composite particles was confirmed by using infrared spectroscopy and X-ray photoelectron spectroscopy analysis. Following thermal analysis, the results concerning the thermal stability of the prepared particles provided higher temperature applications.     

Synthesis and photochromic behavior of new polyimides containing azobenzene side groups

Aromatic polyimides containing side azobenzene groups have been synthesized by low-temperature solution polycondensation of certain aromatic dianhydrides with aromatic diamines containing preformed side azobenzene groups followed by chemical imidization at 100 °C in the presence of pyridine and acetic anhydride. The weight average molecular weight of these polymers is in the range of 16,000-129,000. The glass transition temperature of these polyimides is in the range of 185-230 °C. The polymer architecture presents a special characteristic, one of the azobenzene aromatic units being in the main chain of the polymer. This situation is intermediary between main-chain and side-chain azobenzene-containing polymers. The photochromic behavior, determined by the trans-cis isomerization process of azo-groups, in solution and in solid state, was evaluated. The synthesized polyimides were studied by spectral methods (UV, IR), thermal analysis and molecular modeling. A preliminary study concerning the surface structuration capacity of the polyimides was accomplished. Good results were obtained using Nd:YAG laser at 355 nm, at an incident fluence of 35 mJ/cm² (situated below the laser ablation limit).     

Parathyroid Hormone Induces Human Valvular Endothelial Cells Dysfunction That Impacts the Osteogenic Phenotype of Valvular Interstitial Cells

Parathyroid hormone (PTH) is a key regulator of calcium, phosphate and vitamin D metabolism. Although it has been reported that aortic valve calcification was positively associated with PTH, the pathophysiological mechanisms and the direct effects of PTH on human valvular cells remain unclear. Here we investigated if PTH induces human valvular endothelial cells (VEC) dysfunction that in turn could impact the switch of valvular interstitial cells (VIC) to an osteoblastic phenotype. Human VEC exposed to PTH were analyzed by qPCR, western blot, Seahorse, ELISA and immunofluorescence. Our results showed that exposure of VEC to PTH affects VEC metabolism and functions, modifications that were accompanied by the activation of p38MAPK and ERK1/2 signaling pathways and by an increased expression of osteogenic molecules (BMP-2, BSP, osteocalcin and Runx2). The impact of dysfunctional VEC on VIC was investigated by exposure of VIC to VEC secretome, and the results showed that VIC upregulate molecules associated with osteogenesis (BMP-2/4, osteocalcin and TGF-β1) and downregulate collagen I and III. In summary, our data show that PTH induces VEC dysfunction, which further stimulates VIC to differentiate into a pro-osteogenic pathological phenotype related to the calcification process. These findings shed light on the mechanisms by which PTH participates in valve calcification pathology and suggests that PTH and the treatment of hyperparathyroidism represent a therapeutic strategy to reduce valvular calcification.     

Über heteroorganische Verbindungen. IL. Zur Umsetzung von N-Morpholinoschwefelchlorid mit O-Alkyl-äthanthiophosphoniger Säure und O-Äthyl-äthan-dithiophosphonsäure

Heteroorganic Substances. IL. Reactions between N-morpholinosulfenylchloride and Ethane-alcoxy-thiophosphonous Acids and Ethane-ethyl-dithiophosphonic Acid The syntheses of bis-(ethane-alkoxy-thiophosphonyl)-monosulfides 3a – c and bis-ethane-ethoxy-thiophosphonyl)-trisulfide 5 are described. It is established, that the reaction path depends on the acidity of the starting compounds. In the first case (pK ∼ 7 the reactions between ethane-alkoxy-thiophosphonous acids and morpholinosulfenylchloride are three-step reactions, the intermediates being the unknown S-morpholino-ethane-alkoxy-dithiophosphonates 1a – c as well as the sulfenylchlorides of ethane-alkoxy-thiophosphonic acid 2a – c . In the second case (pK ∼ 3) a fourth reaction has to been taken into account. The intermediate sulfenamide derivatives are isolated and characterised. The sulfenylchlorides derivatives could not been isolated; their presence was indirectly demonstrated by chemical reactions.     

Femtosecond laser multi-patterning of zirconia for screening of cell-surface interactions

Yttria-stabilised tetragonal zirconia polycrystals (3Y-TZP) bioinert ceramics combine excellent strength and toughness, good aesthetics, high resistance to corrosion and absence of allergic reaction. However, improved osseointegration is needed as higher marginal bone loss was sometimes reported. In the present work, 3Y-TZP multi-patterned samples for rapid screening of cell-surface interactions were fabricated by femtosecond laser micromachining. Pits with well-defined edges and micrometric precision in pit diameter, depth and spacing were produced, as determined by white light interferometry. Pits showed a nanometric granular texture on the sidewalls and ripples at pit bottom, as attested by scanning electron microscopy. Focused ion beam analyses indicated limited laser-induced damage. Micropatterns impacted human mesenchymal stem cell (hMSC) size and morphology. Cell area and aspect ratio were mainly influenced by pit diameter, while solidity and circularity were affected by both pit diameter and depth. The pattern 30 μm diameter/10 μm depth induced the strongest osteoblastic hMSC commitment.     

Tactics for a Transgressive Practice

In the last decade, Internet access and social media have reshaped the possibilities for experimental practice in terms of reach and immediacy. Doina Petrescu and Constantin Petcou of atelier d'architecture autogérée (aaa) describe a project that they initiated for a collective platform in Paris that acts as a catalyst for community engagement in the urban realm and particularly the reappropriation of vacant plots of land in the city.     

Investigation of hydrogen and power co-generation based on direct coal chemical looping systems

This paper evaluates hydrogen and power co-generation based on direct coal chemical looping systems with total decarbonization of the fossil fuel. As an illustrative example, an iron-based chemical looping system was assessed in various plant configurations. The designs generate 300–450 MW net electricity with flexible hydrogen output in the range of 0–200 MW_th (LHV). The capacity of evaluated plant concepts to have a flexible hydrogen output is an important aspect for integration in modern energy conversion systems. The carbon capture rate of evaluated concepts is almost total (>99%). The paper presents in details evaluated plant configurations, operational aspects as well as mass and energy integration issues. For comparison reason, a syngas-based chemical looping concept and Selexol^®-based pre-combustion capture configuration were also presented. Direct coal chemical looping configuration has significant advantages compared with syngas-based looping systems as well as solvent-based carbon capture configurations, the more important being higher energy efficiency, lower (or even zero) oxygen consumption and lower plant complexity. The results showed a clear increase of overall energy efficiency in comparison to the benchmark cases.