Apparent chemical composition of nine commercial or semi-commercial whey protein concentrates, isolates and fractions

Summary Analytical results are given for whey powders prepared on a commercial or semi-commercial scale by three companies. Altogether, five preparations enriched in β-lactoglobulin, four whey protein isolates and a fraction enriched in α-lactalbumin were analyzed for protein composition, including %β-lactoglobulin, α-lactalbumin, bovine serum albumin, casein (glyco) macropeptide and the main triglycerides. Protein composition was determined by high pressure gel permeation and reversed phase liquid chromatography and by capillary zone electrophoresis. The extent of modification of the native β-lactoglobulin structure was also measured through the degree of lactosylation and the fraction of accessible free sulphydryl groups. One significant finding was that the calculated recovery of protein following quantitation of the chromatogram or electropherogram was seldom above 90% and occasionally below 60% of that loaded onto the column or capillary, raising doubts as to the reliability of the analytical results. Extrapolation by linear regression to 100% recovery allowed estimates to be made of the true β-lactoglobulin composition of the samples. The nine samples could be placed into three distinct groups with estimated true β-lactoglobulin weight % of 70.9 ± 1.1, 62.0 ± 3.4 and 39.5 ± 4.9. Physico-chemical properties of the group of samples are reported elsewhere (Holt et al ., 1999).     

Melanin films on Au(1 1 1): Adsorption and molecular conductance

We have studied the adsorption and electronic properties of thin melanin films on Au(1 1 1) by scanning tunneling microscopy (STM), scanning tunneling spectroscopy (STS), and density functional (DF) calculations. We have found that the minimum melanin unit detected under different adsorption conditions is consistent with the structural model for eumelanin protomolecules based on tetramer macrocycles formed by four monomer units (hydroquinone, indolequinone and its tautomers) with an inner porphyrin ring. DF calculations reveal that the entire π structure of the tetramers is implied in the chemisorption process through its frontier orbitals (HOMO and LUMO), a fact that is reflected in the change of intramolecular bonds. Also van der Waals interactions give an important contribution to the adsorption energy (≈0.02 eV/Ų). Dried thin melanin films (1 monolayer in thickness) exhibit good electronic conductance due to the presence of localized states near the Fermi level while dried thicker films exhibit a semiconductor-like behavior. Illumination of the thicker films with white light results in significant photo-induced tunneling currents when the melanin-covered Au is made negative with respect to the tip.     

Texturization of silicon wafers with Na2CO3 and Na2CO3/NaHCO3 solutions for heterojunction solar-cell applications

The formation of pyramidal structures by anisotropic etching of 〈1 0 0〉-oriented monocrystalline silicon wafer surfaces is an effective method to reduce reflection losses originating on the front side of conventional silicon solar cells and silicon-heterojunction (SHJ) solar cells. One of the most common methods of texturization used in the solar-cell industry is based on aqueous solutions of NaOH or KOH and isopropyl alcohol (IPA). However, IPA is toxic and relatively expensive, so efforts are being made to replace it. Among the potential alternatives, solutions based on Na₂CO₃ and Na₂CO₃/NaHCO₃ mixtures have been proposed. In the present study, solutions of Na₂CO₃ and Na₂CO₃/NaHCO₃ mixtures were prepared in order to form pyramidal structures on silicon wafer surfaces. It was not possible to obtain uniform and completely textured surfaces by using aqueous solutions consisting only of Na₂CO₃. NaHCO₃ must be added in order to achieve uniform textured surfaces with low hemispherical reflectance suitable for SHJ solar-cell applications. Textured surfaces with good uniformity and low average hemispherical reflectance (15.4%) were prepared from 〈1 0 0〉 silicon substrates with relatively low etching times (25 min). Good surface passivation (lifetime >600 μs and implicit open-circuit voltage of 690±10 mV) on these p-type textured wafers were achieved.     

A behavioral-based multi-agent optimization algorithm for system level radio design

This paper introduces a multi-agent behavioral-based optimization algorithm for system level radio design. Making multi-standard wireless communication receivers that meet their specs while keeping the requirements of the individual blocks as relaxed as possible is the goal of this algorithm. In order to achieve this goal a “divide and conquer” approach is proposed. Different agents focus on different objectives that are pursued in parallel. Agents adopt different behaviors depending on the status of the environment and their interaction with other agents. Agents are cooperative by default as they try to meet their spec without making changes that affect other agents. However, more aggressive behaviors that lead to global changes can be adopted when needed. The interaction between these simple entities yields an emergent behavior able to deal smoothly with the complexity of the problem at hand.     

Chemically Resistant,Shapeable, and Conducting Metal‐Organic Gels and Aerogels Built from Dithiooxamidato Ligand

Metal‐organic gels (MOGs) appear as a blooming alternative to well‐known metal‐organic frameworks (MOFs). Porosity of MOGs has a microstructural origin and not strictly crystalline like in MOFs; therefore, gelation may provide porosity to any metal‐organic system, including those with interesting properties but without a porous crystalline structure. The easy and straightforward shaping of MOGs contrasts with the need of binders for MOFs. In this contribution, a series of MOGs based on the assembly of 1D‐coordination polymer nanofibers of formula [M(DTA)]_n (M^II: Ni, Cu, Pd; DTA: dithiooxamidato) are reported, in which properties such as porosity, chemical inertness, mechanical robustness, and stimuli‐responsive electrical conductivity are brought together. The strength of the M? S bond confers an unusual chemical resistance, withstanding exposure to acids, alkalis, and mild oxidizing/reducing chemicals. Supercritical drying of MOGs provides ultralight metal‐organic aerogels (MOAs) with densities as low as 0.03 g cm^?3 and plastic/brittle behavior depending on the nanofiber aspect ratio. Conductivity measurements reveal a semiconducting behavior (10^?12 to 10^?7 S cm^?1 at 298 K) that can be improved by doping (10^?5 S cm^?1). Moreover, it must be stressed that conductivity of MOAs reversibly increases (up to 10^?5 S cm^?1) under the presence of acetic acid.     

A metaheuristic-based downlink power allocation for LTE/LTE-A cellular deployments

The explosive growth of cellular networks makes their deployment and maintenance more and more complex, time consuming, and expensive. Self-Organizing Networks have been recognized as a promising way to alleviate this problem by minimizing human intervention in such processes. This paper introduces a novel multiobjective framework, based on evolutionary optimization, aiming at improving network performance and users Quality of Service. By tuning the transmitted power at each cell, average intercell interference levels are minimized. The design of the proposed scheme is feasible for distributed implementations in Long Term Evolution (LTE) and LTE-Advanced networks and its operation is compatible with current specifications. The framework is able to provide effective network-specific optimization and obtained results show that gains in terms of network capacity and cell edge performance are 5 and 10 %, respectively. Energy savings always accompanied such enhancements with reductions up to 35 %.     

Effects of freezing preservation on mango (Mangifera indica, L.) peroxidase

This work describes the effects of freezing preservation on mango (cvs Lippens and Smith) peroxidase (E.C. 1.11.1.7); POD). Frozen mango slices showed lower levels of POD activity than raw fruits (17% cv Lippens; 50% cv Smith after 2 months storage time). A regeneration of this activity was found after 6 months of frozen storage. Regeneration continued to the end of the study (12 months) in both cultivars. During the whole period of storage, inactivation rates in Smith POD were higher than in Lippens. The isoenzymic pattern of Lippens POD showed four strongly anionic species that did not appear in the Smith pattern. The activity of these four bands is the most stable to low temperatures, and is the possible cause of the major resistence of Lippens peroxidase to freezing and frozen storage. Thus the Smith cultivar may be more suitable for freezing preservation.

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Einfluß der Gefrierlagerung auf die Aktivität der Mangoperoxidase (Mangifera indica, L.)

Zusammenfassung Diese Arbeit beschreibt die Auswirkungen der Gefrierlagerung auf die Peroxidase (E.C. 1.11.1.7) von Mangofrüchten, Sorte Lippens und Smith. Die gefrorenen Mangoscheiben wiesen niedrigere Peroxidasewerte auf als die rohen Früchte (um 17% geringer bei Lippens und um 50% bei Smith, nach zwei Monaten Lagerung). Eine Reaktivierung konnte nach sechs Monaten Tiefkühlung festgestellt werden. Diese Reaktivierung hielt bei beiden Mangosorten bis zum Ende der Untersuchung (also 12 Monate) an. Während der ganzen Lagerungszeit ließ die Inaktivierung der Peroxidase der Lippens vier stark anionische Formen erkennen, die bei der Sorte Smith nicht auftraten. Es stellte sich heraus, daß die Aktivität dieser vier Formen die größte Stabilität gegenüber tiefen Temperaturen aufweist. Wahrscheinlich ist das der Grund für die größere Widerstandsfähigkeit der Peroxidase der Sorte Lippens gegenüber Gefrieren und Tiefkühlung. Dieses Ergebnis weist auf eine bessere Eignung für die Gefrierkonservierung der Mangosorte Smith hin.

     

Pigment and colour stability of frozen kiwi-fruit slices during prolonged storage

Changes in major pigment constituents of frozen kiwi-fruit slices during prolonged storage at –18° C and correlation with colour measurements (Hunter Lab parameters) were studied. Kiwi-fruit cultivars (Hayward, Bruno, Monty and Abbot) were processed without previous treatment and vacuum packed after freezing. HPLC using a diode array detector was used to individually quantify and identify the three major pigment components (xanthophylls, chlorophylls and derivatives and-carotene). The colour of fresh and frozen slices by Hunter Color values were correlated with each class of pigment compounds. An apparent first order degradation rate was found for total chlorophylls and xanthophylls. Hayward and Bruno were more suitable for prolonged freezing preservation in terms of colour deterioration.

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Haltbarkeit von Pigment und Farbe gefrorener Kiwifrucht-Scheiben während langer Lagerung

Zusammenfassung Es wurden die Veränderungen der meisten Pigmentbestandteile gefrorener Kiwifrucht-Scheiben während langer Lagerzeit bei –18°C und die Korrelation mit Farbmessungen studiert. Kiwifrüchte der Sorten Hayward, Bruno, Monty und Abbot wurden ohne vorherige Behandlung unter Vakuum direkt nach dem Gefrierprozeß verpackt. Mit HPLC wurde quantitativ gemessen und die drei Pigmentbestandteile Xanthophyll, Chlorophyll und-Carotin identifiziert. Die Farbe der frischen, gefrorenen Scheiben (Hunter-Farb-Werte) korrelierte mit jedem der Pigmentbestandteile. Ein Verlust, scheinbar erster Ordnung, wurde für Chlorophyll und Xantophyll bei den Sorten Hayward und Bruno beobachtet, jedoch sind sie für das Gefrieren bei langer Lagerzeit trotz Farbverlust geeignet.

     

The influence of the Weibull assumption in monthly wind energy estimation

An estimation of the monthly wind energy output for the period 1999–2003 at five wind farms in northeastern Spain was evaluated. The methodology involved the calculation of wind speed histograms and the observed average wind power versus wind relation obtained from hourly data. The energy estimation was based on the cumulated contribution of the wind power from each wind speed interval. The impact of the Weibull distribution assumption as a substitute of the actual histogram in the wind energy estimation was evaluated. Results reveal that the use of a Weibull probability distribution has a moderate impact in the energy calculation as the largest estimation errors are, on average, no larger than 10% of the total monthly energy produced. However, the evaluation of the goodness of fit through the χ² statistics shows that the Weibull assumption is not strictly substantiated for most of the sites. This apparent discrepancy is based on the partial cancellation of the positive and negative departures of the Weibull fitted and the actual wind frequency distributions. Further investigation of the relation between the χ² and the error contribution exposes a tendency of the Weibull distribution to underestimate (overestimate) the observed histograms in the lower and upper (intermediate) wind speed intervals. This fact, together with the larger wind power weight over the highest winds, results in a systematic total wind energy underestimation. Copyright © 2008 John Wiley & Sons, Ltd.