Simultaneous determination of carbohydrates, carboxylic acids, alcohols, and metals in foods by high-performance liquid chromatography inductively coupled plasma atomic emission spectrometry

The applicability of the HPLC-ICP-AES coupling for the simultaneous determination of carbohydrates, carboxylic acids, alcohols, and metals in a single chromatographic run has been demonstrated in the present work. Five saccharides, glucose, fructose, sucrose, sorbitol, and lactose; five carboxylic acids, citric, tartaric, malic, lactic, and acetic; and three alcohols, glycerol, ethanol, and methanol, have been determined. A H+ cation exchange column has been used to separate these compounds. The chromatograms have been obtained by monitoring the carbon emission signal at 193.09 nm. The results obtained by HPLC-ICP-AES have been compared against those found with conventional detection systems (i.e., refractive index, UV, and photodyode array detectors). The HPLC-ICP-AES method has shown the following features: (i) organic compounds and metals can be simultaneously determined; (ii) the detection method is universal; (iii) for nonvolatile organic compounds, a complete calibration line can be obtained from a single injection; and (iv) it provides absolute limits of detection similar to or lower than those found with conventional detection systems (i.e., on the order of several tens of nanograms of organic compound). The methodology has been validated through the analysis of food samples such as juices, isotonic beverages, wines, and a certified nonfat milk powder sample.     

Development of a flashlamp-pumped Cr:LiSAF laser operating at 30 Hz

Cr3+:LiSrAlF6 crystals are an interesting laser medium because of their spectroscopic characteristics: They present a broad emission band in the near infrared and can be pumped either by a flashlamp or by diodes. Up to now, their limitation has been mostly due to their poor thermal properties that limit the laser performance either in the repetition rate in a pulsed system or output power in cw systems. We have designed and constructed a flashlamp-pumped laser using a standard rod pumping cavity that avoids most of the heat generated in the pumping process and allows operation at a fairly high repetition rate of 30 Hz with a high average power of 20 W in a conservative operation mode.     

Ionisation density dependence of the optically and thermally stimulated luminescence from Al2O3:C

This paper presents an overview of recent results on ionisation density dependence of the thermally stimulated luminescence (TL) and optically stimulated luminescence (OSL) signals from Al2O3:C, with emphasis on the sensitivity, efficiency, shape of the TL/OSL curves and the emission spectrum. High-ionisation densities are created uniformly by accumulated high doses of low-linear energy transfer radiation (gamma, beta, X rays) or non-uniformly in heavy charged particle tracks, even at low fluences, as in the case of space radiation fields. Significant deep trap filling, which occurs at these high-ionisation densities, ultimately results in changes in the concentration of recombination centres (F+-centres) and, consequently, in sensitivity changes and other effects. An OSL emission band at 335 nm has been observed in addition to the main F-centre luminescence band, and the relative intensities of these bands have been observed to be dependent on the ionisation density. The implications of these results and open issues are discussed.     

Gelation under dynamic conditions: A strategy for in vitro cell ordering

Ordered gelation under spin-coating conditions, as reported here, is a suitable method to order cells in biogels. Cell ordering is of great importance for functional repair of central nervous system (CNS) injuries, because therapies must include strategies to bridge chystic gaps and facilitate axon growth towards its target. Organized biocompatible and biodegradable substrates may be used for this purpose, to supply trophic support and provide directional cues for neuronal process outgrowth. Atomic force microscopy (AFM) and low temperature scanning electron microscopy (LTSEM), confirmed that fibrils in κ–carrageenan/chitosan and fibrin hydrogels prepared under spin-coating conditions, were longitudinally arranged. The cell model was conveniently tested using rat C6 glioma cells. C6 cells were distributed regularly in fibrin gels formed under centrifugal force. The ability of ordered fibrin scaffolds to promote uniform distribution of transplanted cells, was confirmed by fluorescence microscopy.     

Herbivore-Induced Volatiles in the Perennial Shrub, <Emphasis Type="Italic">Vaccinium corymbosum</Emphasis>, and Their Role in Inter-branch Signaling

Herbivore feeding activates plant defenses at the site of damage as well as systemically. Systemic defenses can be induced internally by signals transported via phloem or xylem, or externally transmitted by volatiles emitted from the damaged tissues. We investigated the role of herbivore-induced plant volatiles (HIPVs) in activating a defense response between branches in blueberry plants. Blueberries are perennial shrubs that grow by initiating adventitious shoots from a basal crown, which produce new lateral branches. This type of growth constrains vascular connections between shoots and branches within plants. While we found that leaves within a branch were highly connected, vascular connectivity was limited between branches within shoots and absent between branches from different shoots. Larval feeding by gypsy moth, exogenous methyl jasmonate, and mechanical damage differentially induced volatile emissions in blueberry plants, and there was a positive correlation between amount of insect damage and volatile emission rates. Herbivore damage did not affect systemic defense induction when we isolated systemic branches from external exposure to HIPVs. Thus, internal signals were not capable of triggering systemic defenses among branches. However, exposure of branches to HIPVs from an adjacent branch decreased larval consumption by 70% compared to those exposed to volatiles from undamaged branches. This reduction in leaf consumption did not result in decreased volatile emissions, indicating that leaves became more responsive to herbivory (or “primed”) after being exposed to HIPVs. Chemical profiles of leaves damaged by gypsy moth caterpillars, exposed to HIPVs, or non-damaged controls revealed that HIPV-exposed leaves had greater chemical similarities to damaged leaves than to control leaves. Insect-damaged leaves and young HIPV-exposed leaves had higher amounts of endogenous cis-jasmonic acid compared to undamaged and non-exposed leaves, respectively. Our results show that exposure to HIPVs triggered systemic induction of direct defenses against gypsy moth and primed volatile emissions, which can be an indirect defense. Blueberry plants appear to rely on HIPVs as external signals for inter-branch communication.     

Experimental and numerical analysis of a waterproofing adhesive layer used on concrete-bridge decks

This paper studies the adhesive behavior of a waterproof layer used between a concrete-bridge deck and an asphalt–concrete overlay. The laboratory direct-shear and pull-off tests were designed to measure the interface adhesive strengths. A three-dimensional, finite-element model was developed to analyze the interfacial shear stress and tensile stress in response to vehicle loading. Results indicate that an interface friction coefficient of 0.5 could achieve high interfacial shear strength with relatively low shear stress. The safety factor (strength/stress) decreases significantly with increasing environmental temperatures. The effects of compaction temperature, modulus, and thickness of overlay on the adhesive strengths and stresses were also examined.     

Heavy metal pollution downstream the abandoned Coval da Mó mine (Portugal) and associated effects on epilithic diatom communities

This study examined trace-element concentrations in 39 sediment samples collected in the vicinity of the abandoned Coval da Mó mine, and evaluated the anthropogenic contaminant effects and other environmental variables in the taxonomic composition, structure and morphological changes of benthic diatom communities.The results show the existence of extremely high contamination in Pb, Zn and Cd (the mean values exceed the background values 376, 96 and 19 times, respectively) on the first 2.5 km in the water flow direction. Also Co, Cu, Mn and Ni are present in high concentrations. Dilution by relatively uncontaminated sediment reduces metal concentrations downstream, but Zn concentrations increase downstream Fílvida stream, as a result of several factors such as sewage and agriculture.To evaluate the biological effects caused by Pb, Cd and Zn, three sites were selected. In the stressed environment, near the mining area (C232), diatoms were extremely rare, however there was a slight recovery at site C79 located 2 km downstream. Fragilaria capucina var. rumpens, Fragilaria cf. crotonensis and Achnanthidium minutissimum showed abnormal valves which may be related to high levels of metals.Six km downstream, in Fílvida stream (C85), an increase in species richness and diversity was registered while the relative percentage of valve teratologies was lower. In the absence of OM, nutrients and low pH the diatom community patterns must be attributed to the metal concentration at some sites. Considering that community diversity can be affected by abiotic and biotic variables and valve deformations are caused by a small number of variables, basically metals, and acid conditions, we consider the presence of teratologies as an indication of the presence of metals.     

Blind identification of multiuser nonlinear channels using tensor decomposition and precoding

This paper presents two blind identification methods for nonlinear memoryless channels in multiuser communication systems. These methods are based on the parallel factor (PARAFAC) decomposition of a tensor composed of channel output covariances. Such a decomposition is possible owing to a new precoding scheme developed for phase-shift keying (PSK) signals modeled as Markov chains. Some conditions on the transition probability matrices (TPM) of the Markov chains are established to introduce temporal correlation and satisfy statistical correlation constraints inducing the PARAFAC decomposition of the considered tensor. The proposed blind channel estimation algorithms are evaluated by means of computer simulations.