Valorization of Pinus taeda bark: source of phenolic compounds,tannins and fuel

Pine bark is a byproduct of wood processing which is usually burnt for energy. This article analyzes the liquid–solid extraction of Pinus taeda bark to obtain phenolic compounds by using response surface methodology to determine extraction conditions. The independent variables studied were temperature, ethanol concentration and solid–liquid ratio, and the variables to be optimized were total extractives yield, phenolic content, antioxidant capacity and condensed tannins yield. In addition, the extract was characterized by Fourier transform infrared spectroscopy and UV–Vis spectroscopy. Furthermore, extraction kinetics were modeled, and mass transfer mechanisms were studied. The extraction condition that maximizes extraction yields was defined at 50 °C, with a solid–liquid ratio of 1/10 and with an ethanol concentration of 50%. The condensed tannins yield was 4.01 g catechin equivalent (CE)/100 g pine bark dry base (d.b.), the total extractive yield was 9.83 g extract/100 g pine bark d.b. and the Stiasny number was 77. The extract showed a FRAP antioxidant concentration of 20.89 mmol ascorbic acid equivalent (AAE)/100 g pine bark d.b and 0.35 mmol trolox (TRE)/g pine bark d.b. for ABTS assay. The results showed that extended Fick’s law was adequate to describe the extraction kinetics. The extraction did not significantly affect the calorific value of bark (21 kJ/g d.b.). After extraction, the ashes were reduced by 13% and potassium (K) by 48%. The extraction of Pinus taeda to obtain phenolic content is technically feasible, and this paper provides the scientific ground for further scaling the process.

     

Phosphorus‐Carbon Bond Formation: Palladium‐Catalyzed Cross‐Coupling of H‐Phosphinates and Other P(O)H‐Containing Compounds

Two generally applicable systems have been developed for the cross‐coupling of P(O)H compounds with C_sp2 X and related partners. Palladium catalysis using a ligand/additive combination, typically either xantphos/ethylene glycol or 1,1′‐bis(diphenylphosphino)ferrocene/1,2‐dimethoxyethane, with diisopropylethylamine as the base, proved to be generally useful for the synthesis of numerous P C containing compounds. Routinely, 2 mol% of catalyst are employed (less than half the amount typically employed in most other literature reports). In most cases, excellent results are obtained with a variety of electrophiles (RX, where R=alkenyl, allyl, alkynyl, etc.). The full account of our studies is disclosed, including tandem hydrophosphinylation/coupling and coupling/coupling for doubly catalytic phosphorus‐carbon bond formation. The methodology compares favorably with any existing literature report. The use of an additive appears to be a generally useful strategy to control the reactivity of phosphinylidene compounds.     

Simple Indoor Path Loss Prediction Algorithm and Validation in Living Lab Setting

A simple heuristic algorithm has been developed for an accurate prediction of indoor wireless coverage, aiming to improve existing models upon multiple aspects. Extensive measurements on several floors in four buildings are used as validation cases and show an excellent agreement with the predictions. As the prediction is based on the free-space loss model for every environment, it is generally applicable, while other propagation models are often too dependent on the environment upon which it is based. The applicability of the algorithm to a wireless testbed network in a living lab setting with WLAN 802.11b/g nodes is investigated by a site survey. The results can be extremely useful for the rollout of indoor wireless networks.     

Enhanced elasticity in parylene thin films by copolymerization approach

The application of poly(p-xylylene)s as barrier and passivation layer is limited by the high tensile modulus of this class of materials. In this view, we propose a modified chemical vapor deposition approach to realize a series of copolymers based on parylene C, where linear alkyl chains partially replace the chlorides substituents. Thanks to the efficacious inclusion of bulky alkyl chains into the parylene layer, these modified materials show clear differences in both thermal and mechanical properties with respect to pristine parylene C. In particular, by following this approach, a decrease of the Young’s modulus up to 0.3 GPa (13 times reduction of parylene C modulus) is observed, indicating a neat enhancement of the elastic behavior. Besides the improved mechanical performance, the modified materials retain both barrier and biocompatibility properties typical of neat parylene C. The results presented support copolymerization as a valuable approach for tuning parylene properties, which enlarges further the field of application of this excellent multipurpose material.     

From artifact to instrument: mathematics teaching mediated by symbolic calculators

The evolution of calculation tools available for the learning of mathematics has been quick and profound. After the first illusions on a naturally positive integration of these tools, new theoretical approaches have emerged. They take into account individual and social processes of the mathematical instrument construction from a given artifact. In this article we show how analyzing constraints of the tool allows the understanding of its influence on the knowledge construction. We propose the concept of instrumental orchestration to design different devices which may be built in class and thus strengthen the socialized part of the instrumental genesis: instrumental orchestration is defined by objectives, configuration and exploitation modes. It acts at the same time on the artifact, on the subject, on the relationship the subject has with the artifact and on the way the subject considers this relation.     

Tumors of the central nervous system

Neoplasia of the central nervous system (CNS) can be divided into two main categories: nonpituitary CNS neoplasia and pituitary adenomas. Nonpituitary CNS neoplasias are generally compressive in nature, although some are also invasive. The majority of reported CNS tumors are secondary with only a few originating from nervous tissue. Pituitary adenomas predominantly occur in the pars intermedia of the older horse. Clinical signs, diagnostic testing, and possible treatments are discussed.     

Characterization of the swelling during sintering of uniaxially pressed copper powders by in situ X-ray microtomography

Evolution of the inner microstructure of uniaxially pressed copper powders was investigated by in situ X-ray microtomography. Experiments were carried out at the European Synchrotron in Grenoble, France. Sintering was performed under reducing atmosphere at 1050 °C. Qualitative and quantitative information from the 3D images acquired along the whole sintering cycle were analyzed. From that, macro- and microstructural features of the evolving microstructure were obtained. We found that large pores can be created during sintering and then they can grow during the whole thermal cycle by reducing the initial relative density of the sample by 10 %. The effect of the pore shape and the heterogeneous distribution of the pore volume fraction inside the sample are responsible for the behavior observed during sintering. The heterogeneous deformation measured is controlled by the evolution of the porosity.