Facile preparation of glycine-based mesoporous graphitic carbons with embedded cobalt nanoparticles

Journal of Materials Science - A simple route has been developed for the preparation of mesoporous graphitic carbons with embedded cobalt nanoparticles just using glycine as a nitrogen source,...     

Vacuum impregnation of apple slices with Yacon (Smallanthus sonchifolius Poepp. & Endl) fructooligosaccharides to enhance the functional properties of the fruit snack

This work aimed to incorporate prebiotic FOS from yacon in apple slices using vacuum impregnation (VI). Three FOS concentrations (10.3, 14.1 and 18.9 g per 100 g of dry matter (DM)), two temperatures (25 and 35 °C), reuse of extracts and stability of the impregnated slices were evaluated. The highest impregnation level (30.5 g per 100 g DM) was obtained at 35 °C with 14.1% FOS extract while levels of common sugars were reduced. Total phenolics and ABTS antioxidant capacity (AC) slightly decreased while ORAC AC was reduced by 55%. Reuse of the impregnation solution in successive cycles after restoring the FOS level maintained the FOS concentration and profile (GF2–GF7), sugars and phenolic antioxidants. FOS in apple slices remained stable during 4 week storage, while a_w, colour and fracture point changed during storage. This work demonstrated the feasibility of yacon FOS to improve the functional properties of dehydrated apple slices.     

Photon Upconversion Hydrogels for 3D Optogenetics

The ability to optically induce biological responses in 3D has been dwarfed by the physical limitations of visible light penetration to trigger photochemical processes. However, many biological systems are relatively transparent to low-energy light, which does not provide sufficient energy to induce photochemistry in 3D. To overcome this challenge, hydrogels that are capable of converting red or near-IR (NIR) light into blue light within the cell-laden 3D scaffolds are developed. The upconverted light can then excite optically active proteins in cells to trigger a photochemical response. The hydrogels operate by triplet–triplet annihilation upconversion. As proof-of-principle, it is found that the hydrogels trigger an optogenetic response by red/NIR irradiation of HeLa cells that have been engineered to express the blue-light sensitive protein Cry2olig. While it is remarkable to photoinduce the clustering of Cry2olig with blanket NIR irradiation in 3D, it is also demonstrated how the hydrogels trigger clustering within a single cell with great specificity and spatiotemporal control. In principle, these hydrogels may allow for photochemical control of cell function within 3D scaffolds, which can lead to a wealth of fundamental studies and biochemical applications.     

Physicochemical and bioactive compounds at edible ripeness of eleven varieties of avocado (Persea americana) cultivated in the Andean Region of Peru

This work aimed evaluating some physicochemical compounds, hydrophilic (H-AC) and lipophilic (L-AC) antioxidant capacity of eleven avocado genotypes grown in the Andes. The results show great variability in physical and chemical properties, dry matter (DM) and lipid contents with ranges of 18.4–39.3% and 10.1–23.2%, respectively. All genotypes had high oleic acid content (50.4–69.9%) and a high unsaturated fatty acid/saturated fatty acid ratio (UFA/SFA, from 3.05 to 6.05), while the unsaponifiable fraction contained mainly β-sitosterol (140.83–235.51 mg/100 g DM) and α-tocopherol (17.44–71.29 µg/g DM). Total phenolic compounds (TPC), H-AC and L-AC ranged from 0.48 to 0.88 mg EAG/g DM, 5.37 to 14.00 and 1.87 to 6.71 μmol ET/g DM, respectively. Although the genotype influences avocado characteristics, climatic conditions in the Andean region seem to be important for the biosynthesis of metabolites of interest and should be considered in future studies.     

Nano and Microtechnologies for the Study of Magnetotactic Bacteria

Magnetotactic bacteria (MTB) naturally synthesize magnetic nanoparticles that are wrapped in lipid membranes. These membrane‐bound particles, which are known as magnetosomes, are characterized by their narrow size distribution, high colloidal stability, and homogenous magnetic properties. These characteristics of magnetosomes confer them with significant value as materials for biomedical and industrial applications. MTB are also a model system to study key biological questions relating to formation of bacterial organelles, metal homeostasis, biomineralization, and magnetoaerotaxis. The similar size scale of nano and microfluidic systems to MTB and ease of coupling to local magnetic fields make them especially useful to study and analyze MTB. In this Review, a summary of nano‐ and microtechnologies that are developed for purposes such as MTB sorting, genetic engineering, and motility assays is provided. The use of existing platforms that can be adapted for large‐scale MTB processing including microfluidic bioreactors is also described. As this is a relatively new field, future synergistic research directions coupling MTB, and nano‐ and microfluidics are also suggested. It is hoped that this Review could start to bridge scientific communities and jump‐start new ideas in MTB research that can be made possible with nano‐ and microfluidic technologies.     

Double actuation architectures for rendering variable impedance in compliant robots: A review

Novel compliant actuation systems have been developed in recent years for a variety of possible advantages, such as establishing a safe human–robot interaction, increasing energy efficiency, reducing the effects of impacts and even for the development of neuro-inspired robotic platforms to be used in human motor control studies.In this rapidly growing and transversal research field, systems involving more than one active element (typically motors) for each actuated degree of freedom are being investigated to allow separate position and impedance regulations. Considering the wide range of applications and the large number of different arrangements deriving from the combination of two active elements and passive elastic components, several actuation architectures have been devised.This paper reviews state-of-the-art rotary variable impedance units incorporating two separate motors. Existing devices are grouped in three main categories. A critical and comparative analysis of the most relevant features is carried out, also based on most representative prototypes. Recently proposed methodologies and evaluation criteria for design optimization are illustrated and perspectives on potential applications of double actuation systems are presented.     

Operator precedence and the visibly pushdown property

Floyd?s operator precedence grammars and languages (FG, FL) are a classical subclass of deterministic context-free (DCF) grammars and languages. We prove that several recently introduced language families motivated by the needs of model checking and of specifying XML-like languages are proper subsets of FL. The main cases considered include visibly pushdown languages (VPL) and balanced languages (BALAN), which are characterized by restricted precedence relations. FL have all the closure properties available for regular languages and generally viewed as necessary for application to model checking: reversal, prefixing and suffixing, concatenation, Kleene star, and boolean operations. All but the last results are new, and some require complex proofs, due to the necessary changes of syntax structure. Thus FL are the largest known subfamily of DCF having the same closure properties as VPL. FG, unlike VPL grammars, which are intended for abstract syntax modelling, are structurally adequate to specify real programming languages.     

Sacha inchi (Plukenetia volubilis L.) shell: an alternative source of phenolic compounds and antioxidants

Sacha inchi seed (SI) is known as a rich source of oil with high content of polyunsaturared fatty acids of the ω‐3 and ω‐6 type (~85% of total fatty acids). However, few studies have focused on the use of by‐products from the seed. The aim of this study was to characterise the main phenolic families present in SI shell and to evaluate the best extraction solvent for the extraction of phenolic compounds (PC) and antioxidant capacity (AOXC). The PC content corresponded to 74.5 ± 5.1 mg g^?1 of which 93.1% were condensed tannins and the remaining compounds corresponded to free and bound phenolic acids, hydrolyzable tannins, flavonoids and flavanoids. Protocatechic and p‐coumaric acids but also hydroxycinammic acid derivatives of ferulic and o‐coumaric type and lignan derivatives were identified. Acetone containing solvents favoured the extraction of higher amounts of total PC and AOXC. This study highlights the potential use of SI shell as a novel and alternative source of PC antioxidants for the nutraceutical and/or functional food industries.     

Self and mutual ground impedances of cylindrical metal plates buried in homogeneous earth

This paper presents a numerical procedure for computation of self and mutual impedance of cylindrical metal plates buried in homogeneous earth. Procedure is based on an analytical expression for scalar potential distribution of an equipotential metal plate in homogeneous unbounded medium. The effect of the air–earth boundary condition is taken into account by the exact imaging method. The robustness and accuracy of the computation procedure is based on the combination of analytical integration and 1D and 2D Gaussian quadratures for solving integrals present in expressions for self and mutual ground impedances of metal plates. The attenuation and phase shift is taken into account approximately by introducing the attenuation‐phase shift factor. The numerical procedure developed for the computation of self and mutual ground impedances of cylindrical metal plates buried in homogeneous earth is efficient, numerically stable and generally applicable. Numerical model developed for the computation of self and mutual ground impedances of cylindrical metal plates buried in homogeneous earth represents a basis of a wider numerical model for computation of ground fault current distribution in which grounding grids are approximated by metal cylindrical plates. Copyright © 2014 John Wiley & Sons, Ltd.     

Electrocatalytic hydrogen gas generation by cobalt molybdenum disulfide (CoMoS2) synthesized using alkyl-containing thiomolybdate precursors

Cobalt molybdenum disulfide, (CoMoS₂) catalysts are evaluated as active electrocatalysts for the production of hydrogen gas in acidic aqueous media. These highly-active hydrogen evolution reaction (HER) catalysts are obtained from pretreatment of ammonium tetrathiomolybdate (ATM) with different amines precursors, and characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM) and their surface areas are determined by Brunauer–Emmett–Teller (BET) surface area analyses. Electrochemical studies indicate that these CoMoS₂ materials exhibit enhanced catalytic performance for hydrogen gas production with overpotentials ranging from 0.127 to 0.144 V, which are significant less than CoMoS₂ synthesized directly from ATM under the same synthetic techniques (0.173 V). These CoMoS₂ catalysts are also stable in the presence of strong acidic media after a considerably long period of time (10 h) for maintaining their efficiencies for hydrogen gas evolution.