Production,partial purification and properties of β‐mannanases obtained by solid substrate fermentation of spent soluble coffee wastes and copra paste using Aspergillus oryzae and Aspergillus niger

In order to achieve a higher added value of two galactomannan‐containing wastes, copra paste and spent coffee from the soluble coffee industry (SCW), solid substrate fermentation (SSF) was used. Filamentous fungi Aspergillus oryzae and A niger were used to evaluate the feasibility of producing β‐mannanase by SSF. A 2³ factorial design was used to select the best interaction among the two fungi, the two substrates and two fermentation times. The treatment ‘A niger–copra–2.5 days’ produced a significantly higher (p < 0.05) β‐mannanase activity, having five different isoforms of the enzyme, one of which was partially purified to a specific activity of 764 U mg⁻¹ (U = nmol of mannose released per second from a galactomannan substrate). Copra paste had a higher mannose/galactose ratio (14:1) than SCW (6:1), and low oil content, which led to higher β‐mannanase production from SSF. A β‐mannanase from SSF of copra produced by A oryzae was highly purified using acetone precipitation and cation exchange and size exclusion chromatographies. This enzyme had an MW of 110 kDa, a pI between 3.5 and 4.5 and a specific activity of 1760 U mg⁻¹; purification achieved was 90.7 times. The temperature and pH for optimal activity were 40 °C and 6.0 respectively. The optimal temperature was lower and the optimal pH higher than others previously reported (produced by submerged fermentation), which could be important for viscosity reduction of concentrated coffee extract in instant coffee manufacture. Copra is an interesting alternative for β‐mannanase production, since it is readily available in Mexico; moreover, the residue after SSF has a reduced galactomannan content and may be used for monogastric animal feed. © 2000 Society of Chemical Industry     

Ellipsometric spectroscopy study of cobalt oxide thin films deposited by sol–gel

Due to their unique optical properties, solar selective coatings enhance the thermal efficiency of solar photothermal converters. Hence it seems to be interesting to study the optical properties of promising materials as solar selective coatings. In an earlier work, it was demonstrated that sol–gel deposited cobalt oxide thin films possess suitable optical properties as selective coatings. In this work, cobalt oxide thin films were prepared by same technique and their optical properties were analyzed as a function of the dipping time of the substrate in the sol, using the spectroscopy ellipsometry, atomic force microscopy and X-ray photoelectron spectroscopy techniques. The optical constants (n and k) for these films, in the 200–800 nm range, are reported as a function of the dipping time. The fitting of ellipsometric data, I_s and I_c, for the glass substrate and the cobalt oxide thin film, as modeled with the Lorentz and Tauc–Lorentz dispersion relations, indicated that the film microstructure resembles a multilayer stack with voids. From these results, the Co₃O₄ and void percentages in the film were estimated. Both, thin film thickness and void/Co₃O₄ percentage ratio, were determined to be strongly dependent on the immersion time. Furthermore, the total thickness of a multilayered film was found to be the sum of thickness of each individual layer.     

An Organic Electrochemical Transistor Integrated Photodetector for High Quality Photoplethysmogram Signal Acquisition

The organic photodiode (OPD) is a promising building block for solution-processable, flexible, lightweight, and miniaturized photodetectors, ideal for wearable applications. Despite the advances in materials used in OPDs, their photocurrent and light responsivity are limited, and alternative methods are required to boost the signal response. Herein, a miniaturized organic electrochemical transistor (OECT) is integrated with an OPD module to unlock the potential of OPDs to acquire physiological signals. In this integrated photodetector (IPD) system, the light intensity regulates the OPD voltage output that modulates the OECT channel current. The high transconductance of the OECT provides efficient voltage-to-current conversion, enhancing the signal-to-noise ratio on the sensing site. A microscale, p-type enhancement-mode OECT with high g_m and fast switching speed performs better in this application than depletion-mode OECT of the same geometry. The IPD achieves a photocurrent and responsivity 318 and 140 times higher than the standalone OPD, respectively. It is shown that with the IPD, the amplitude of the photoplethysmogram signals detected by the OPD is enhanced by a factor of 2.9 × 10³, highlighting its potential as a wearable biosensor and to detect weak, often uncaptured, light-based signals from living systems.     

Differentiated service strategies for ad-hoc wireless sensor networks in harsh communication environments

In some wireless sensor network applications, sensor nodes will be deployed in harsh communication environments. In such environments, the deployment may not be adequately controlled, and nodes may have to communicate with a single destination node. For nodes to alert the destination on critical data that has been sensed, in addition to the harsh communication environment, contention resulting from both the deployment and network density must be appropriately overcome. In this paper, we create theoretical models for the behavior of Timeout-MAC (T-MAC) protocol, and evaluate five possible solutions, each designed to be easy to implement on a device by simply tuning T-MAC parameters, so as to overcome these environment-specific issues and effectively alert the destination to critical data. Our results indicate that slight changes to the behavior of the network can improve the awareness of the destination to critical regions in the environment, and that these changes have different levels of effectiveness at different network densities.     

A Synchronous Reference Frame Robust Predictive Current Control for Three-Phase Grid-Connected Inverters

This paper presents a new predictive current control for three-phase grid-connected inverters in the synchronous reference frame. The control combines a deadbeat control law with a diagonal Luenberger observer to estimate the future value of the grid currents. It provides a decoupled control of the active and reactive power and offers robustness against the computational delay inherent in the digital implementation and against filter and grid-impedance uncertainties. This control exhibits a very fast current response while widely improving the gain and phase margins of the traditional predictive controllers.      

Galileo was Wrong: The Geometrical Design of Masonry Arches

Since antiquity master builders have always used simple geometrical rules for designing arches. Typically, for a certain form, the thickness is a fraction of the span. This is a proportional design independent of the scale: the same ratio thickness/span applies for spans of 10 m or 100 m. Rules of the same kind were also used for more complex problems, such as the design of a buttress for a cross-vault. Galileo attacked this kind of proportional design in his Dialogues. He stated the socalled square-cube law: internal stresses grow linearly with scale and therefore the elements of the structures must become thicker in proportion. This law has been accepted many times uncritically by historians of engineering, who have considered the traditional geometrical design as unscientific and incorrect. In fact, Galileo’s law applies only to strength problems. Stability problems, such as the masonry arch problem, are governed by geometry. Therefore, Galileo was wrong in applying his reasoning to masonry buildings     

From Remote Hosting to Self-Hosting of an Erp System: Lessons Learned from the City of El Paso

This article describes how the city of El Paso, Texas, initially used an application service provider (ASP) model, allowing the city to fast track its enterprise resource planning (ERP) system implementation. After a change in the ASP arrangements led to less responsiveness to its needs, the city government moved to a self-hosted ERP system. Lessons learned in the evolution from ASP hosting to self-hosting of the city's ERP system are compared to previously published literature.     

INFLUENCE OF A MISORIENTATION ANGLE ON AN ENERGR OF THE SYMMETRIC GRAIN BOUNDARY IN FCC METALS

In the present work the research of grain boundary (CB) energy versus angle of misorientation in fcc metals Al, Cu, An and Ni was carried out. An axis of CB misorientation is a direction [100], angle of misorientation makes from 2皍p in 23*. The interatomic interaction was opproximated by Morse' s pair semi-empirical potential. Two variants of relaxation technique were used: (1) rigid relax- ation with the change of atom quantity per a GB (vacancy relaxation ) and (2) full atomic relaxation by a molecular static method. The obtained orientation dependence has a good agreement with experi- ment. There are cusps on a curve in the range of special GB angles.The comparison of obtained curves with calculated ones in model Van der Merwe was carried out. Dependencies obtained in our investiga- tions are not smooth and have an oscillatory character. The oscillations reflect a discrete structure of a lattice.     

Experimental evaluation on the oil influence in capillary tubes

This work presents the results of an experimental study on pure refrigerant R-134a and refrigerant–oil mixtures flowing through capillary tubes in order to analyse the oil influence in component performance. Tests were carried out for capillary tubes internal diameters of 0.69 mm and 0.82 mm, condensing temperatures ranging from 40 °C to 50 °C, and subcooling degrees between 3 °C and 12 °C. Pure refrigerant flow measurements were compared to those for refrigerant–oil mixtures with oil concentrations of 1.0% and 3.0%.