Hydroxyapatite Modified with Carbon‐Nanotube‐Reinforced Poly(methyl methacrylate): A Nanocomposite Material for Biomedical Applications

The paper reports on a freeze‐granulation technique to prepare a novel nanocomposite of poly(methyl methacrylate) (PMMA)‐modified hydroxyapatite (HA) with multiwalled carbon nanotubes (MWCNTs) as reinforcement for a new generation biomedical bone cement and implant coatings. By using this technique it is possible to increase material homogeneity and also enhance the dispersion of MWCNTs in the composite matrix. The phase composition and the surface morphology of the nanocomposite material were studied using X‐ray diffraction, field‐emission scanning electron microscopy, and micro‐Raman spectroscopy. Additionally, nanomechanical properties of different concentrations of MWCNT‐reinforced nanocomposite were performed by a nanoindentation technique, which indicates that a concentration of 0.1 wt % MWCNTs in the PMMA/HA nanocomposite material gives the best mechanical properties.     

Uplink Channel Estimation for Multi-user OFDM-based Systems

In this paper we propose a simple, yet flexible and efficient, channel estimator for the uplink in broadband orthogonal frequency division multiplexing (OFDM) systems. The processing is performed in the time-domain, by extracting the Channel’s Impulse Response (CIR) for each user from a joint training signal. In this OFDM system, the pilot sequence we advocate, where all users share the same pilot sub-carriers, consists of one OFDM-symbol endowed with time-shifted properties per user, which isolates each user’s CIR and is robust against multi-user interference. The feasibility of our approach is substantiated by system simulation results obtained using BRAN-A broadband mobile wireless channel model.

用压电蜂音器收集能量

能量收集系统是从环境中获得能量的系统。不幸的是,这类发电装置提供的能量要比标准的电池少得多。然而,随着当今可佩戴设备尺寸和功耗的降低,在一些低功耗系统中,用能够从用户所处环境收集能量（如用户行走和跑动中产生的振动能）的发电装置替代电池已具有可行性。此设计实例利用标准和易于获得的压电蜂音器的压电效应将机械振动转化为电能。尽管压电蜂音器通常是在施加交流电后发出声波,但也可以反过来利用它,也就是说,在振动频率与压电蜂音器共振频率匹配时,压电蜂音器可以产生最大的交流峰值电压供人使用。     

Changes in the volatile composition of red wines during aging in oak barrels due to microoxygenation treatment applied before malolactic fermentation

Microoxygenation is a wine-making technique consisting in the addition of small and controlled amounts of oxygen. This study has examined the effect of this technique on the volatile composition of two red single variety wines during two successive vintages. The microoxygenation treatment was applied at the end of alcoholic fermentation and before beginning malolactic fermentation. Once the microoxygenation treatment had finished, wines were aged in new American oak barrels for 12 months. The results obtained showed that the microoxygenation treatment did not cause significant changes in the varietal and fermentation volatile compounds, however microoxygenation slowed down the extraction of some of the volatile compounds extracted from wood. A varietal and vintage effect was also observed for some of the compounds studied.     

Determination of daily dietary intake of chromium by duplicate diet sampling: in vitro availability study

Intake of chromium was estimated using a duplicate diet sampling method of 108 meals (36 breakfasts, 36 lunches and 36 dinners) from the restaurant of the Hospital of Motril (S.E. Spain), corresponding to 36 consecutive days. Total and dialyzable Cr levels were measured by a validated electro-thermal atomic absorption spectrometry (ETAAS) method. A mean Cr fraction of 26 +/- 12 microg meal (-1) was found. The Cr uptake from meals was directly and significantly (p < 0.001) correlated with their macronutrient (carbohydrates, fibre and protein) content. Cereals and cereal by-products, legumes, dry fruits, meat, potatoes, dairy products and seafood are the primary sources of Cr. The mean Cr fraction dialyzed through dialysis tubing was 1.2 +/- 1.1 microg meal(-1) (4.6 +/- 3.8% as mean Cr dialysability). Cr intake for breakfasts was significantly lower (p < 0.001). A correlation between the logarithmic data of total and dialyzable fraction of Cr in meals (p = 0.020) was found and dialysis ratio enhancement and, therefore, bioavailability increased with total Cr. The dialysed element content present in meals was significantly correlated with fibre, protein, Fe, Na, I, F, sodium, ascorbic acid and vitamin A levels (p < 0.05). At Fe contents in meals higher than congruent with7.5 mg meal(-1) the net absorption of Cr decreased significantly. The mean Cr daily dietary intake (DDI) was 77 +/- 17 microg day (-1) which indicates that no adverse effects in relation to Cr nutrition (deficiency or toxicity) should occur in individuals from the area.     

Effect of acid treatment on extraction yield and gel strength of gelatin from whiptail stingray (Dasyatis brevis) skin

Food Science and Biotechnology - Chemical properties of fish gelatins differ from those of conventional mammalian sources, representing an attractive technological alternative for the food...     

Pentalithium Ferrite (Li5FeO4) as Highly Active Material for Hydrogen Production in the Chemical Looping Partial Oxidation of Methane

In this work, the pentalithium ferrite was synthetized by solid-state method, and it was characterized by XRD and N₂ adsorption–desorption techniques. Then, H₂ production was obtained through a catalytic conversion process; chemical looping partial oxidation (CLPO) of methane using Li₅FeO₄ as multifunctional material. The catalytic decomposition of methane is an easy way to obtain clean energy, such as hydrogen, but in this process carbon deposition is also possible. The results showed that this material has the ability to convert methane to hydrogen, but it is also capable to donate oxygen atoms from its crystalline network, producing carbon monoxide and/or carbon dioxide, limiting the carbon deposition on the ceramic surface. In addition, it was demonstrated that this lithium-based ceramic produces hydrogen over a wide temperature range (550–900 °C), with a stable hydrogen production for 3 h at 825 °C. Furthermore, it was possible to achieve a cyclic test of methane decomposition with a pre-oxidation process between each cycle obtaining an outstanding increase in hydrogen production from 10% in cycle 1 to ~?100% in the cycle 10. This previous stage not only induces an increase in the decomposition of methane, but also avoids carbon deposition accompanied by the production of both CO_X compounds. Finally, it must be mentioned that Li₅FeO₄ is capable to chemisorb both carbon oxides produced, promoting high purity hydrogen production.

     

Enzyme activity during germination of different cereals: A review

The germination process increases enzymatic activity. However, this does not occur in the same way in all cereals. It depends on the type of enzyme, the cereal, and the conditions of germination. During germination, most enzymes are localized in the aleurone layer and the scutellum. Some of them, such as xylanases, proteases, and β-glucanases, are also localized in the endosperm while β-glucanases and lipases have been identified in the embryo. The maximum activity of the enzymes in most cereals start from day 4 of germination. Germination allows the hydrolysis of macromolecules and compounds like β-glucans and phytic acid. In cereals, starch is the component that presents the most morphological changes. Germination mobilizes and increases the activity of some enzymes. Temperature, steeping time, and variety are determining factors in the activation time. At higher temperatures, the enzymatic activation is generally faster; however, there are some exceptions. The use of germination could be a promising resource for modifying grain properties and increase enzymatic activity; also, this process is simple and economical.     

Bioleaching of metal from waste stream using a native strain of Acidithiobacillus isolated from a coal mine drainage

In this study, the feasibility of using a biohydrometallurgical technique for selective metals recovery from electronic waste (e‐waste) by bacterial bioleaching was investigated. Acidithiobacillus was identified in coal mining acid mine drainage (AMD). The microorganism was studied using specific sequencing of a 16s rDNA fragment. The potential for the dissolution of copper from waste printed wire boards (PWBs) using the isolated Acidithiobacillus ferrooxidans (A. ferroxidans) was evaluated. The bioleaching experiments were performed in an orbital shaker at 30 °C and 170 rpm, with 10 % (v/v) inoculum and a pulp density of 30 g/L. The copper concentration was determined by energy dispersive x‐ray fluorescence (XRF). The result shows that copper recovery from PWBs using our A. ferrooxidans strain was 95 % after 8 days, which showed the feasibility of this process.