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Los lagartos del género Stenocercus comprenden 64 especies que pertenecen a la tribu Tropidurini. Se distribuyen en Sudamérica desde el norte de Venezuela y Colombia hasta el centro de Argentina desde los 0 a los 4000 m s.n.m en los Andes y tierras adyacentes. Algunas especies se encuentran en la zona atlántica en el sur de Argentina, Brasil y Uruguay., Facultad de Ciencias Naturales y Museo

This paper describes the development of a new flow system by substituting the injection valve of a FIA system with an automatic microburette controlled by a PC via an RS-232 interface to introduce flexibility into the system. Initially, the response of the system was characterized without a chemical reaction by using a reference system (6-port valve) and a modified system (automatic microburette). The response vs. flow rate and injected volume were studied. The statistic analysis and comparison of the dispersion coefficients obtained for both systems showed no significant difference between them. Comparative studies with chemical reactions were also performed using a reverse Flow Injection Analysis (r-FIA) technique and the Griess-Ilosvay model reaction for nitrite ions. Finally, the system based on the automatic microburette was validated for the analysis of nitrite in two complementary concentration ranges (0.0–0.1 and 0.0–3.0 mg · L−1) using 25 and 350 µL of reactant, respectively. The detection limits obtained were 0.009 and 0.024 mg · L−1, respectively. High repeatability was obtained for both concentration ranges (RSD: 0.52 and 1.35%, respectively).

Some new symmetrical and unsymmetrical near-infrared absorbing acidochromic dyes are synthesised by a simple one-step reaction. Such indicators belong to the ketocyanine dyes type and as well as their full characterisation as the relationship between their structure and optical properties are discussed. They are mainly tested for their future application as pH or solvent polarity sensors. The absorption maxima of the long-wavelength absorbing acidic form span the region from 715 to 750 nm, nearly matching the emission wavelength of the 780 nm laser diode. p K a values in ethanol cover the range between 1.7 and 4.3, and reversible absorption spectra are observed while pH is changed forth and back. As merocyanine dyes, the synthesised ketocyanine dyes show a positive solvatochromism. Since one of the requirements for a solvatochromic molecule to be useful to establish a solvent polarity scale is its stability, the photostability of the dyes is tested in ethanolic solution as well.

Twenty ketocyanine dyes are evaluated as potential pH fluoroionophores to be used in the development of new integrated waveguide fluorescence optodes (IWFOs). Its fluorescence characterization, as well as the pH response is first undertaken in ethanolic solution and then in plasticized PVC membranes with a conventional spectrofluorimeter. Analytical parameters such as basicity, reversibility, leaching and calibration curves are determined in both media and finally, photostability is also measured. Besides, some photophysical fluorescent parameters, such as the emission wavelength, are evaluated for both species, the acidic and the basic form, and quantum yields are calculated in ethanolic solution. Ketocyanine dyes have demonstrated their suitability for being used as acidochromic fluoroionophores in bulk optodes for the development of new IWFOs. They exhibit high fluorescence intensities in the far-visible region, an adequate photostability and an optimum pH response.

In this paper, the low-temperature co-fired ceramics (LTCC) technology, which has been commonly used for electronic applications, is presented as a useful alternative to construct continuous flow analytical microsystems. This technology enables not only the fabrication of complex three-dimensional structures rapidly and at a realistic cost but also the integration of the elements needed to carry out a whole analytical process, such as pretreatment steps, mixers, and detection systems. In this work, a simple and general procedure for the integration of ion-selective electrodes based on liquid ion exchanger is proposed and illustrated by using ammonium- and nitrate-selective membranes. Additionally, a screen-printed reference electrode was easily incorporated into the microfluidic LTCC structure allowing a complete on-chip integration of the potentiometric detection. Analytical features of the proposed systems are presented.

A set of near-infrared absorbing tricarbocyanine dyes has been synthesised and characterised for their future application as chromoionophores in optochemical sensors. Their absorption maxima are localised in the NIR region, where matrix interferences are minimal and the use of suitable and inexpensive optical communication components gives great advantages. The acid form of the synthesised dyes in pure ethanol spans the region from 675 to 815 nm and the molar absorptivities are up to 3.3 × 10 5 l/mol cm. The calculated p K a values in ethanol lie between 11.4 and more than 13. The effect of the introduction of substituents on the p K a values and on the spectroscopic characteristics of the dyes is also discussed. Moreover, pH-sensitive aggregation processes have been observed in aqueous solution.

Los moluscos, debido a su capacidad filtrante, pueden acumular metales llegando a contaminar los alimentos y como consecuencia pueden tener una repercusion negativa sobre la salud de los consumidores. En este estudio se han determinado los contenidos de algunos metales (Cu, Zn, Cd y Pb) en muestras de almejas comercializadas en Galicia (Espana) tanto en conserva como en fresco. Para su analisis se ha empleado la voltamperometria de redisolucion anodica, obteniendose los niveles de dichos metales en musculo y en hepatopancreas. Los resultados han sido tratados estadisticamente para evaluar las posibles correlacciones en el contenido de metales en las distintas porciones anatomicas establecidas. Destacan las concentraciones mucho mas elevadas en hepatopancreas que en musculo para zinc, plomo y cobre en muestras en fresco. Asi, los maximos en hepatopancreas de almejas en fresco fueron para Zn: 1250 mg/kg; para Pb: 15,60 mg/kg y para Cu: 75,04 mg/kg, frente a los maximos de Zn (60,36 mg/kg), Pb (0,67 mg/kg) y Cu (9,48 mg/kg), en musculo. En cuanto al cadmio, en general las muestras en conserva presentaron concentraciones mas elevadas que las muestras en fresco, llegando a alcanzar el hepatopancreas de una de ellas hasta 8,11 mg/kg. Teniendo en cuenta la importancia de estos moluscos en la alimentacion y de acuerdo con la legislacion vigente, se ha podido establecer, desde el punto de vista toxicologico, que los niveles de estos metales no suponen riesgo para el consumidor. © 2005 Altaga. Todos los derechos reservados. Articulo en Espanol

Acyclic Pd–diaminocarbene complex showed high catalytic activity in Suzuki arylation of meso-chlorine-substituted tricarboindocyanine dyes. Arylated dyes were obtained in 57–83% yields in the presence of 5 × 10−4 equiv of catalyst.

The continuous monitoring of processes in the food industry, and in particular in wine production, holds great interest as it can help to increase the quality of the goods produced and also the efficiency of the production process. One process that is feasible to control is the stabilisation of wine by means of ion-exchange resins. The use of this technique is of great promise since it allows continuous wine treatment and also on-line monitoring systems can be applied to determine the saturation of the resin in addition to the fraction of wine requiring stabilisation. The development of a pH, calcium and potassium analyser for on-line monitoring of wine in a continuous flow system is reported here. The potentiometric sensors used are ion-selective field-effect transistors (ISFETs). The stability of these sensors in hydro-alcoholic media was studied obtaining a sensitivity of 56 mV per decade for the pH ISFET and sensitivities of −26 mV per decade and −50 mV per decade for calcium and potassium sensors, respectively. The long-term stability of pH-ISFETs was 7 and 4 months for cation sensors. Results obtained in the continuous flow system with wine samples demonstrated that the proposed system is capable to detect the saturation point of the ion-exchange resin in wine stabilisation process and also to determine the ratio of wine required to stabilise it.

The present report describes the development of a thick-film sensor with intended applications for soil analysis. A probe incorporates three sensors, each at a different depth and featuring a copper plate as the reference electrode. In addition, the probe also contains all necessary instrumentation required for processing the sensor signal and to transmit it via radio. The developed sensors were calibrated in situ using two different soil compositions by adding standard solutions. Results show a quasi-Nernstian response in soil, in response to the addition of fertilisers. Extracts of soil samples analysed by the Kjeldahl method were compared with results from the probe. This comparison confirms that the sensors are capable or measuring chemical parameters in situ in an automated fashion.

The first prototype of a technologically improved integrated waveguide absorbance optode (IWAO) was developed and tested with a membrane based on a new H+-selective ketocyanine dye and a cadmium ionophore. It was designed with curved instead of rectilinear planar waveguides. Results demonstrated the suitability of the new IWAOs to be employed as sensing platforms, which confer versatility, robustness, and mass production capabilities besides high sensitivity on conventional bulk optodes, as well as the usefulness of such dyes in developing ion-selective membranes in combination with a selective ionophore. The sensor integration as a detector in a flow injection system (FIA) was proposed to obtain an automated, simple, and sufficiently reproducible (RSD5%) analytical methodology with a sample throughput of 55 h(-1). Very sensitive optodes were obtained, and detection limits on the order of 20 ppb were achieved. Because of the ionophore employed, the optode system showed excellent selectivity over alkali and alkaline-earth metals with the exception of samples containing lead and cadmium ions, where the membrane responded to both analytes. The proposed procedure combines all the advantages of the FIA systems, the simplicity of optical detection, ion recognition selectivity, and sensitivity of ketocyanine dyes, and the features achieved using the integrated device, which comprise an improved sensitivity and short response times as well as robustness, easy handling, and mass production.

In this paper, the universal determination of non-ionic surfactants (NIS) of the polyethoxylate type is attempted using flow-injection potentiometry. Two systems are proposed which use specifically developed tubular flow-through ion selective electrodes (ISEs). These are sensitive to NIS with an hydrophilic chain between 6 and 18 ethoxylate units, which are predominant species in the environment. An on-line pre-concentration system is designed with the aim of a possible application for the unattended monitoring of NIS in surface waters. This on-line pre-concentration is achieved by employing a column packed with a commercial solid phase extraction (SPE) sorbent for the enrichment and purification of the target analytes. The procedure outlined improves the detection limit of a direct system, decreasing it from 1×10 −4 to 3×10 −6 M by use of a pre-concentration volume of 40.0 ml and 200 μl of 75% acetonitrile in water as the eluent. Precision was estimated as 4% relative standard deviation (R.S.D.) ( n =25) for a 1×10 −6 M (0.7 ppm) nonylphenol polyethoxylate with 12 ethoxylate units when 10.0 ml of sample are pre-concentrated. Finally, the on-line pre-concentration system is applied for the total NIS determination in environmental samples from Llobregat river basin of Barcelona area (NE Spain).

The design, construction and evaluation of a versatile cyclic olefin copolymer (COC)-based continuous flow potentiometric microanalyzer to monitor the presence of ammonium ion in recycling water processes for future manned space missions is presented. The microsystem integrates microfluidics, a gas-diffusion module and a detection system in a single substrate. The gas-diffusion module was integrated by a hydrophobic polyvinylidene fluoride (PVDF) membrane. The potentiometric detection system is based on an all-solid state ammonium selective electrode and a screen-printed Ag/AgCl reference electrode. The analytical features provided by the analytical microsystem after the optimization process were a linear range from 0.15 to 500 mg L−1 and a detection limit of 0.07 ± 0.01 mg L−1. Nevertheless, the operational features can be easily adapted to other applications through the modification of the hydrodynamic variables of the microfluidic platform.

Pleurodema guayapae is a species that inhabits saline environments and semidesert zones from central Argentina. To date, the knowledge about the reproductive biology of this species is very poor, and our aim is to contribute to its knowledge with the description of some important reproductive aspects. For this, field work was undertaken in an area near to Patquía, La Rioja province. Sampling was undertaken during three summer periods (2006-2007; 2007-2008; 2008-2009) in Chamical-Patquía area, where we could find reproductively active populations. We observed and described breeding sites, type of clutch, process of foam nest construction, clutch and egg number and sizes, and hatching time and stage. Behaviour observations were performed from the time that males began to call until the pairs ended up the foam nests building, and layed the eggs. Additionally, one amplected pair was observed and filmed in the process of foam nest construction, and four amplectant pairs were collected and separatelly placed in plastic containers, for nests observations in the laboratory. Hatching time was based on three different foam nests of known age. We found that P. guayapae populations were acoustically active only after a rainfall. Its breeding sites were represented by ephemeral ponds of fresh water, product of rains. The males emitted their calls inside or outside these ponds. A detailed description of the foam nest construction process by both females and males was made. The clutches were in dome-shaped foam nest type of 6-9cm in diameter and 1-3cm in height, some of which were in communal nests. The nests had an average of 1 137 pigmented eggs. This species showed a short hatching time. Our results allow us to conclude that this species should be considered an extreme explosive breeder. Our results are discussed with others obtained for related species. Pleurodema guayapae es una especie que habita en zonas semidesérticas y salinas del área central de Argentina. Los conocimientos actuales sobre la biología reproductiva de esta especie son muy pobres, por lo que nuestro objetivo fue contribuir a su conocimiento con la descripción de algunos aspectos reproductivos importantes. Para ello se realizaron tres campañas de muestreo durante los veranos (2006-2007, 2007-2008 y 2008-2009) en el área de Chamical-Patquía, provincia de La Rioja, donde se encontraron poblaciones reproductivamente activas. Se observaron y describieron los sitios reproductivos, tipo de puesta, proceso de construcción del nido de espuma, tamaño de la puesta y de los huevos, número de huevos por puesta y tiempo y estado de eclosión de la larva. Las observaciones de comportamiento se realizaron desde el momento en que los machos comenzaron a emitir los cantos hasta que la pareja en amplexo terminó de construir el nido de espuma con los huevos en su interior. Además, se observó y filmó una pareja en amplexo, en el proceso de construcción del nido de espuma y se recolectaron cuatro parejas en amplexo y se colocaron separadamente en recipientes plásticos para que sus puestas pudieran ser observadas en el laboratorio. El tiempo de eclosión se determinó en tres nidos de espuma de edad conocida. Se encontró que las poblaciones de P. guayapae solo estuvieron acústicamente activas luego de una lluvia torrencial. Los sitios de reproducción fueron charcas efímeras de agua de lluvia. Los machos emitieron sus cantos de advertencia desde adentro o fuera de esas charcas. Se realizó una descripción detallada del proceso de construcción del nido de espuma por parte de la hembra y el macho de P. guayapae. El tipo de la puesta en esta especie es un nido de espuma flotante con forma de domo de 6 a 9cm de diámetro y de 1 a 3cm de alto, algunos de los cuales estaban unidos entre sí formando puestas comunales. Los nidos de espuma poseen en promedio 1 137 huevos pigmentados. Esta especie mostró un tiempo de eclosión corto. Nuestros resultados nos permiten concluir que P. guayapae debe ser considerada como reproductor explosivo extremo. Nuestros resultados son discutidos con los obtenidos en otras especies afines.

A centrifugal microfluidic platform prototype with an integrated membrane for gas diffusion is presented for the first time. The centrifugal platform allows multiple and parallel analysis on a single disk and integrates at least ten independent microfluidic subunits, which allow both calibration and sample determination. It is constructed with a polymeric substrate material and it is designed to perform colorimetric determinations by the use of a simple miniaturized optical detection system. The determination of three different analytes, sulfur dioxide, nitrite and carbon dioxide, is carried out as a proof of concept of a versatile microfluidic system for the determination of analytes which involve a gas diffusion separation step during the analytical procedure.

Trabajo de Investigación En la actualidad el laboratorio de Ingeniería Civil no cuenta con manuales de consulta que ilustren los ensayos que se ejecutan a los componentes del concreto hidráulico siguiendo los parámetros de las normar técnicas colombianas. Para una adecuada formación académica de los estudiantes es fundamental contar con herramientas que ayuden a minimizar y aclarar ciertos conceptos y procedimientos en los ensayos de laboratorio que manejan el concreto hidráulico. En consideración a esto, surge la proposición del presente trabajo. Este documento corresponde a la investigación y elaboración de un Manual de Guías de Laboratorio Enfocadas al Control de Calidad de Materiales y Tecnología de Concreto. Es un manual de guías de laboratorio es de gran importancia ya que constituye un material de apoyo para las asignaturas que tengan relación con el manejo de materiales para concreto hidráulico, también sirve de herramienta de consulta para todos los estudiantes de Ingeniería Civil y carreras afines. Estas guías de laboratorio especifican los procedimientos para cada ensayo y también los materiales que son objeto de estudio de acuerdo con las normas técnicas colombianas. Pregrado Ingeniero Civil

Standard methods to measure nutrient levels in soil are complex and time consuming due to the extraction and pre-treatment processes involved. The instrumentation used for these measurements is also expensive. Therefore, the use of chemical sensors would be interesting since they can be applied directly to the soil. Thus, it would provide results in real or quasi real time at a moderate cost. The control of these nutrients will permit an optimisation of the overall production process of the crop. Besides, this approach will be useful for reducing the environmental impact caused by excess of nutrients in crop soils. In this work, the use of chemical sensors based on Ion Sensitive Field Effect Transistors (ISFETs) for soil analysis is proposed. These devices are fabricated with microelectronic technology -providing this fact some important advantages- but their mechanism of response are similar to that of Ion selective electrodes (ISEs). Fabrication of pH, Ca 2+ , K + and NO 3 - ISFETs and their evaluation in aqueous solutions is reported. From the preliminary results of their application in soils it is possible to confirm their feasibility as sensors for in-soil monitoring and the promising future applications they have.

A method is described for the conductimetric determination of CO 2 . The proposed system was constructed with a pervaporator chamber coupled to a flow system comprised of a six-way solenoid valve, a conductivity cell, a conductivimeter and a PC microcomputer for data acquisition and external controls. An amount of 2 g of dry soil samples were directly weighted in the donor compartment of the pervaporation chamber. The CO 2 was determined from an analytical curve within 5.0 x 10 -3 -5.0 x 10 -2 mol kg -1 CaCO 3 . This curve was constructed with the matrix matching approach and presented a linear regression of y = 13.58 + 584.77r (r = 0.9962). Soils with different lime amounts were analyzed by the proposed methodology and with the official method, that uses the calcium difference between the total, extracted with HCl 1 mol l -1 and exchangeable, extracted with the KCl 1 mol l -1 After paired t-test application, no significant difference between the methods was found at the 95% probability level. The proposed method presented sampling rate of 17 h -1 , detection limit of 8.0 x 10 -4 mol kg -1 CaCO 3 , and R.S.D. < 3%. The use of the pervaporator allowed the in situ soil pretreatment for the residual lime determination.

A flow injection system for the determination of polyethoxylated nonionic surfactants is described. Potentiometric detection based on tubular flow-through ion-selective electrodes (ISEs) sensitive to this type of surfactants was used. As ion-exchanger, the plasticised PVC membrane incorporates the ion pair between the adduct of a nonionic surfactant with barium and tetraphenylborate. Two different membrane compositions were studied. They differed in the nonionic surfactant used in the ion-exchanger preparation: either nonylphenoxypolyethoxylate with 5 (Ig5) or 12 (Ig12) ethylene oxide units were used. Experimental results showed that the use of Ig5 membrane with a barium salt adjusting solution allowed lower detection limits, while Ig12 ISE with potassium salt solution presented enhanced sensitivity. Both FI systems were evaluated employing three different polyethoxylate standards, which could be determined down to ca. 10 −5 M. Precision was 3% R.S.D. for n = 50 using repetitive injections of a 3 × 10 −4 M Ig12 standard. Preliminary tests of an on-line preconcentration flow system employing the developed sensing devices are also shown. © 2001 Elsevier Science B.V. All rights reserved.

Standard methods to measure nutrient levels in soil are complex and time consuming due to the extraction and pre-treatment processes involved. Besides, the instrumentation used for these measurements is also expensive. Therefore, the use of chemical sensors warrants investigation since they can be placed directly in the soil and results can be provided in real or quasi-real time at a moderate cost. The control of nutrients with sensors will permit an optimisation of irrigation and fertilisation management systems and thus will be useful for reducing the environmental impact caused by the runoff of nutrients into surface and ground waters. In this work, the use of chemical sensors based on ion sensitive field effect transistors (ISFETs) for soil analysis is proposed. These devices are fabricated with microelectronic technology – providing some important advantages such as robustness, small size, low output impedance and mass production. Fabrication of pH, Ca2+, K+ and NO3− ISFETs with photocurable polymeric membranes and their evaluation in aqueous solutions is reported. Studies of their response in horticulture soils and comparison with standard methods have been performed. The results confirm the feasibility of ISFET based sensors for in-soil monitoring and the promising future applications they have.

The fabrication of ion-sensitive electrochemical sensors for calcium is described in the present work. The membrane uses a photocurable polymer based on aliphatic diacrylated polyurethane. The use of photocurable polymers as the support matrix instead of PVC simplifies the preparation and the casting of the developed ion-sensitive membranes. Additionally, these polymers are compatible with the photolithographic fabrication techniques used in the microelectronics industry. This aspect permits the patterning of membranes on wafer level for semiconductor based sensors thus the automatization of the whole sensor fabrication. These polymer matrices show also better adhesion to silanised semiconductor surfaces, such as the gate surfaces of ion selective field effect transistors (ISFETs). Membranes sensitive to calcium ions were optimised according the type of plasticizer and the polymer/plasticizer ratio. Ion selective electrodes (ISEs) with a solid internal reference and ISFETs were used to evaluate the membrane. The resulting sensors were functional for periods of more than 8 months and the resulting sensitivities were quasi-Nernstian (26–27 mV/dec) in a range of 5×10 −6 –8×10 −2 M. These sensors were used to measure calcium activity in water samples extracted from agricultural soils. The results were compared with those yielded by standard methods, finding a good correlation between the two analytical procedures.

A new approach for developing absorbance optochemical sensors is presented in this paper. It is based on a planar microoptic circuit where an optochemically active membrane, which responds selectively to a compound, is deposited in the device, yielding a part of the guiding planar structure. Light is propagated through the membrane, which changes its spectral absorption properties and controls the selectivity of the measurements by means of several immobilised compounds. This way, high sensitivity of the device can be easily obtained due to relatively long light paths through the membrane, and low response times can be achieved as the analyte diffusion occurs perpendicularly to the light path and through a thin membrane. Experimental results on measurements of the concentration of a specific ion in solution using the fabricated sensors are also presented.

A new type of absorbance-based optical sensor is presented. It is based on a chemical transduction membrane that acts simultaneously as the sensing element and as the light guiding medium. This membrane is inserted between two micromachined waveguides in a silica on silicon structure. Light propagates longitudinally through the membrane, which changes its spectral properties accordingly while interacting with the analyte. As the path length corresponds to the membrane length, not its thickness, high sensitivity can be achieved without an increase of the response time. This paper summarizes the design, the construction, and the validation results obtained with integrated waveguide absorbance optode (IWAO) prototypes. The main advantages of the reported optode are its simple configuration, high sensitivity, and versatility. Experimental results obtained with this IWAO, using a potassium-selective bulk optode, are shown and compared to those obtained with a conventional absorbance device incorporating the sa...

A colorimetric flow injection-system for the determination of Cu(II) in waters based on complexation reaction with 4-(2-pyridylazo)-resorcinol, usually termed PAR, is described. Performing measurements in 0.25 mol l −1 HNO 3 medium allowed improved selectivity of the analytical method. The lack of sensitivity deriving from the low complex absorption under acidic conditions was balanced by the insertion of an immobilised poly(ethylenimine) (PEI) column where Cu(II) pre-concentration in neutral media occurs. Using sample volumes ranging from 2 to 4 ml, sampling rates of 24 and 12 samples h −1 within a detection limit of 25 and 13 μg l −1 , respectively, were accomplished. Accuracy of the developed methodology was assessed by comparison with atomic absorption spectrometry being the relationship [FIA] mg l −1 =1.00 (±0.03)×[AAS] mg l −1 +0.00 (±0.02) obtained after analysing 15 samples. Precision was also evaluated using two samples of 0.05 and 0.5 mg l −1 copper, and a relative standard deviation (R.S.D.) better than 3% was attained for both.

The authors present an automated flow injection analysis (FIA) system for the determination of low levels of anionic surfactants in river water and wastewater. The system uses especially constructed tubular flow-through ion-selective electrodes (ISEs) as potentiometric sensors and on-line preconcentration techniques. The anionic surfactant ISEs employed are of the all-solid-state type with a plasticized PVC membrane. They show a general response to anionic surfactants with a lower limit of linear response of ∼10(-)(5) M, when used in direct determinations. However, their specificity is limited, which hampers their direct use with environmental samples. Therefore, the FIA system presented here includes a solid-phase extraction procedure for purification and preconcentration of analytes. Breakthrough curves were constructed to characterize different sorbents and different eluents were tested to optimize the preconcentration process. The FIA system was first applied to the determination of different types of anionic surfactant standards. Potentially interfering substances such as chloride, nitrate, and nonionic surfactants were checked to verify that they did not interfere on the response of the system. Concentrations of ∼10(-)(7) M (0.03 ppm) of sodium dodecyl sulfate could be detected in the nonlinear response region when 3 mL of sample was preconcentrated and eluted with 50 μL of a 75% acetonitrile/water (v/v) solution. Precision was 2% RSD (n = 31) for a 1 × 10(-)(6) M sodium dodecyl sulfate standard solution and the sample throughput was 10 h(-)(1). The FIA system was then used for the determination of total anionic surfactants in river water and wastewater.

The development of a new electrochemical microsensor based on silicon technology with a photocurable enzyme membrane based on polyurethane acrylate is described. The use of photocurable polymers as the entrapping matrix for enzymes fulfils all the requirements expected for these materials without damaging the biological material. Additionally, the preparation of biosensor devices following this methodology is fast and simple, and this entails the main improvement shown by the new immobilisation method proposed here. The polymer used for enzyme immobilisation enhances the adhesion of the membrane to the previously silanised ion-sensitive field effect transistor (ISFET) gate and assures a long-term stability of more than one month. Additionally, this material provides a membrane deposition methodology compatible with photolithographic techniques allowing mass-production of low cost biosensors. The membrane has been optimised taking into account a good entrapment of the biological material and the effective transport of the substrate and the products through the membrane. After mixing the components of the prepolymer solution, a short exposure (30 s) to 365 nm UV-radiation produced a polymeric membrane without damaging the enzyme. The calibration parameters for the sensors prepared compared well with other methods yielding a slope of 58 mV/dec and a linear range of 0.04–36.0 mM urea in a NH4Cl pH 5.6 solution. The response time (t 95%) was approximately 2 min.

The application of optimised poly(vinyl chloride) matrix, anionic surfactant-sensitive membranes to ion-selective field-effect transistors (ISFETs) is described. The developed devices showed a lifetime longer than four months, improving reported values of PVC membrane-ISFETs. Other characteristics are Nernstian slopes from 59 to 62 mV/dec, detection limits of about 10 ˇ6 M and good linearity. They also showed response to several anionic surfactant species and to the reagent used for the potentiometric titration. This allowed the measurement of the overall anionic surfactant content in different samples. Apart from the basic characteristics of the membranes, this report also shows the results of potentiometric titrations using the developed ISFETs with known samples. The devices were useful in a range from 0.02 to 10 mM for dodecylbenzenesulphonate solutions. End-point potential jumps up to 250 mV were obtained in the titrations. The reproducibility, expressed as relative standard deviation, was estimated, using a standard 4 mM sodium dodecylsulphate solution, as 1.45% (na14). Finally, in a comparative study, there were no significant differences between the results produced with the standard, two-phase titration method and the proposed potentiometric titration method using surfactant ISFETs as end-point indicators. # 1999 Elsevier Science B.V. All rights reserved.

Proceeding of: 2013 Asia-Pacific Microwave Conference Proceedings (APMC), Seoul, Korea (South), 5-8 Nov. 2013 A novel design combining standard microstrip technology with single ring resonator and high dielectric constant resonator for design of low and band pass filtering electromagnetic band gap(EBG) structures, operating in the range from 1 to 20 GHz is presented in this paper. The design is based on a high dielectric constant resonator embedded in a microstrip structure substrate. The dielectric resonator is fabricated by using commercial high dielectric constant EPOXY paste in a process compatible with serigraphy and screen printing technology. This work has been supported by Ministerio de Ciencia y Educación of the Spanish government under the project TEC2010-16060.

The advertisement call plays an important role in the life history of anuran amphibians, mainly during the breeding season. Call features represent an important character to discriminate species, and sound emissions are very effective to assure or reinforce genetic incompatibility, especially in the case of sibling species. Since frogs are ectotherms, acoustic properties of their calls will vary with temperature. In this study, we described the advertisement call of C. cranwelli, quantifying the temperature effect on its components. The acoustic emissions were recorded during 2007 using a DAT record Sony TCD-100 with stereo microphone ECM-MS907 Sony and tape TDK DAT-RGX 60. As males emit their calls floating in temporary ponds, water temperatures were registered after recording the advertisement calls with a digital thermometer TES 1300+/-0.1 degreeC. Altogether, 54 calls from 18 males were analyzed. The temporal variables of each advertisement call were measured using oscillograms and sonograms and the analyses of dominant frequency were performed using a spectrogram. Multiple correlation analysis was used to identify the temperature-dependent acoustic variables and the temperature effect on these variables was quantified using linear regression models. The advertisement call of C. cranwelli consists of a single pulse group. Call duration, Pulse duration and Pulse interval decreased with the temperature, whereas the Pulse rate increased with temperature. The temperature-dependent variables were standardized at 25 degreeC according to the linear regression model obtained. The acoustic variables that were correlated with the temperature are the variables which emissions depend on laryngeal muscles and the temperature constraints the contractile properties of muscles. Our results indicated that temperature explains an important fraction of the variability in some acoustic variables (79% in the Pulse rate), and demonstrated the importance of considering the effect of temperature in acoustic components. The results suggest that acoustic variables show geographic variation to compare data with previous works.

In this work, an analytical microsystem based on LTCC (low-temperature co-fired ceramic) technology with monolithic incorporation of an optical flow cell for determination of dipyrone in pharmaceuticals is described. The detection system is based on the formation of a blue chromophore between dipyrone and Fe(III) photometrically monitored at 630 nm using a lab-made LED mini-photometer constructed with a light emitting diode as a radiation source and a Si photodiode as a detector. The lab-made mini-photometer elaborated presented a good performance in regard to high signal/noise ratio, low drift and good sensitivity. The analytical curve was linear in the dipyrone concentration range from 1.0 × 10-4 to 3.5 × 10-3 mol L-1, limit of detection of 4.5 × 10-5 mol L-1 and total time of analyses of 20 s yielding an analytical frequency of 195 h-1 with a low waste generation per analysis (480 µL). Neste trabalho, a aplicação de um microssistema analítico construído com tecnologia LTCC (cerâmica cossinterizada a baixa temperatura) com incorporação monolítica de uma cela óptica de fluxo para determinação de dipirona em formulações farmacêuticas é descrita. O sistema de detecção baseou-se na formação de um cromóforo azul entre a dipirona e Fe(III) monitorado fotometricamente em 630 nm usando um minifotômetro de LED lab-made construído com um diodo emissor de luz como fonte de radiação e um fotodiodo de Si como detector. O minifotômetro elaborado apresentou um bom desempenho com respeito à elevada relação sinal ruído, baixo ruído e sensibilidade satisfatória. A curva analítica foi linear na região de concentração de dipirona de 1,0 × 10-4 a 3,5 × 10-3 mol L-1 tendo sido obtido um limite de detecção de 4,5 × 10-5 mol L-1 e um tempo total de análise de 20 s equivalente à uma frequência analítica de 195 h-1 com pouca geração de resíduos por análise (480 µL).

En el sector de la distribución TaT actualmente se presenta un ambiente altamente competitivo. Por esta razón la eficiencia y eficacia en la operación logística es un requerimiento para mantenerse en el mercado. En este es­tudio se presentan estrategias logísticas derivadas de la caracterización y consolidación del perfil logístico de un grupo de empresas distribuidoras TaT de la ciudad de Ibagué. Como resultado de este diagnóstico se encontraron debilidades principalmente en las variables relacionadas con la planeación de la cadena. Las estrategias se con­figuran en una oportunidad para fortalecer los procesos logísticos y están enmarcadas inicialmente en áreas de formación y formalización de los procesos antes que en la inversión de nuevas tecnologías.

A flow-injection system based on potentiometric detection and designed for the monitoring of anionic surfactant content of printing plates washing solutions is described. Two new PVC membrane ion-selective electrodes, constructed with an all-solid-state tubular flow-through design, are used. The sample, with high ionic strength and extremely alkaline pH, is conditioned in a two-channel flow-injection system, allowing for surfactant determination in the 1 × 10 −4 to 1 × 10 −3 M range, with NaOH contents up to 0.3 M.

A set of amino-group possessing cyanine dyes is obtained from their N-acetyl derivatives via deprotection with boron trifluoride–methanol complex in good yields.

In this paper, a computer controlled microreactor to synthesize water soluble CdS and CdS/ZnS nanocrystals with in situ monitoring of the reaction progress is developed. It is based on ceramic tapes and the Low-Temperature Co-fired Ceramics technology (LTCC). As well the microsystem set-up, the microreactor fluidic design has also been thoroughly optimized. The final device is based on a hydrodynamic focusing of the reagents followed by a three-dimensional micromixer. This generates monodispersed and stable CdS and core–shell CdS/ZnS nanocrystals of 4.5 and 4.2 nm, respectively, with reproducible optical properties in terms of fluorescence emission wavelengths, bandwidth, and quantum yields, which is a key requirement for their future analytical applications. The synthetic process is also controlled in real time with the integration of an optical detection system for absorbance and fluorescence measurements based on commercial miniaturized optical components. This makes possible the efficient managing of the hydrodynamic variables to obtain the desired colloidal suspension. As a result, a simple, economic, robust and portable microsystem for the well controlled synthesis of CdS and CdS/ZnS nanocrystals is presented. Moreover, the reaction takes place in aqueous medium, thus allowing the direct modular integration of this microreactor in specific analytical microsystems, which require the use of such quantum dots as labels.

Microfluidic reactors offer many potential advantages in several research and industrial fields such as processes intensification, which includes a better reaction control (kinetics and thermodynamics), a high throughput and a safer operational environment (reduced manipulation of dangerous reagents and low sub-products generation). Nevertheless, scaling-down limitations appear concerning the materials used in the fabrication of microreactors for most of the liquid-phase reactions, since they usually require high temperatures (up to 300 °C), solvents and organic reagents. In this work, the development of a set of modular and monolithic microreactors based on the integration of microfluidics and a thermal platform (sensor/high-temperature heater) is proposed to perform high temperature reactions. The reliability and performance of both configurations were evaluated through an exhaustive characterization process regarding their thermal and microfluidic performance. Obtained results make the devices viable for their application in controlled and reproducible synthetic processes occurring at high temperatures such as the synthesis of quantum dots. The proposed microfluidic approach emerge as an engaging tool for processes intensification, since it provides better mass and temperature transfer than conventional methods with a reduction not only of the size and energy consumption, but also of by-products and reagents consumption. This work has been supported by the Spanish Ministry of Science and Innovation (MICINN) through projects CTQ2009-12128 and the Consolider Ingenio 2010 project CSD2006 -12 and Catalonia Government through SGR 2009 -0323.

The spatial distribution of tiny holes in sheet materials generated by means of electrical discharges is investigated using spatial statistics techniques. It is shown that whereas the holes appear to be randomly distributed according to a Poisson point pattern, there is in fact a small region around each hole in which the generation of a new one is statistically inhibited as a consequence of the lower impedance path offered by the already made hole. The resulting pattern is known in spatial statistics as a point process with a soft-core inhibition potential, which can be characterized using the pair correlation function. This work was supported by the Ministerio de Ciencia e Innovación of the Spanish Government under the project TRACE TRA2009-0119. Publicado

Nowadays, the attainment of microsystems that integrate most of the stages involved in an analytical process has raised an enormous interest in several research fields. This approach provides experimental set-ups of increased robustness and reliability, which simplify their application to in-line and continuous biomedical and environmental monitoring. In this work, a novel, compact and autonomous 10 microanalyzer aimed at multiwavelength colorimetric determinations is presented. It integrates the microfluidics (a three-dimensional mixer and a 25 mm length "Z-shape" optical flow-cell), a highly versatile multiwavelength optical detection system and the associated electronics for signal processing and drive, all in the same device. The flexibility provided by its design allows the microanalyzer to be operated 15 either in single fixed mode to provide a dedicated photometer or in multiple wavelength mode to obtain discrete pseudospectra. To increase its reliability, automate its operation and allow it to work under unattended conditions, a multicommutation sub-system was developed and integrated to the experimentalset-up. The device was initially evaluated in the absence of chemical reactions using four acidochromic dyes and later applied to determine some key environmental parameters such as phenol index, chromium 20 (VI) and nitrite ions. Results were comparable with those obtained with commercial instrumentation and allowed to demonstrate the versatility of the proposed microanalyzer as an autonomous and portable device able to be applied to other analytical methodologies based on colorimetric determinations. The authors would like to acknowledge the Spanish, Brazilian and Mexican authorities and agencies for its financial support through projects CTQ2009-12128, CONSOLIDER INGENIO2010-CSD2006-12, PHB2010-0064-PC (MEC-50 CAPES) and P509AC0376 (CYTED). Z.M da Rocha would like to acknowledge FAPESP (Project 2009/08486-4) for their financial support.

The synthesis and characterization of new nor-indocrococyanine dyes are described. The acid form of the obtained dyes has an absorbance maxima in the 759–800 nm range. They present spectral changes at pH 6.5–9.7.

This work proposes a new dielectric resonator type characterized by an extreme topology that confines the electromagnetic fields in such a way that only superficial modes are allowed. The technique can be potentially utilized to combine dielectric resonators with multilayer planar technologies.

Background To study the changes of children lead exposure in the city of Torreon during the last five years, after environmental and public health interventions, using the timeline of lead in blood concentration as the biomarker of exposure and its relation to lead in soil concentrations. Methods This follow-up study started in 2001 and consisted of 232 children living in nine neighborhoods in Torreon. Children were tested at 0, 6, 12 and 60 months. Lead in blood concentrations, Hemoglobin, Zinc-Protoporphyrin, anthropometric measures and socioeconomic status questionnaire was supplied to the parents. Results Median and range of lead in blood concentrations obtained at 0, 6, 12, 60 months were: 10.12 μg/dl (1.9 - 43.8), 8.75 μg/dl (1.85 - 41.45), 8.4 μg/dl (1.7 - 35.8) and 4.4 μg/dl (1.3 - 30.3), respectively. The decrease of lead in blood levels was significantly related to ages 0, 6, 12 and 60 months of the follow-up study. The timeline of B-Pb was associated with the timeline of lead in soil concentrations. Conclusions B-Pb levels have significantly decreased in the group of children studied. This could be explained by a) environmental interventions by authorities and the smelter companies, b) normal changes in hygienic habits as children age and c) lead redistribution from blood to hard tissues.

The Electrical Discharge Machining (EDM) is used to drill and mechanize a variety of rigid materials that cannot be cut or shaped by typical tools because of their high hardness or complex shape. The EDM operating principle is based on the interaction between solid matter and the electronic arc discharge. The severe physical conditions around the spark are be used to mill and drill all kind of materials [1]. The electro-perforation is a particular case of the EMD which allows to make holes in permeable materials such as paper or biological membranes to generate a drilling pattern with controlled porosity for different applications[2].

To study the effects of the management of hip fracture patients in an acute orthogeriatric unit shared between the departments of Orthopedic Surgery and Geriatrics compared with the usual hospital care, and to analyse financial differences in both systems of care.Prospective quasy-experimental randomized intervention study in 506 patients admitted to a terciary hospital with an osteoporotic hip fracture. The usual model of care was the admission to the orthopedic ward with a request to Geriatrics (RC) and the study model consisted of the admission to an orthogeriatric unit (OGU) for the shared co-management between orthopaedic surgeons and geriatricians. This model included the appointment of one spokesperson from each department, the specialist geriatric nurse management, early geriatric assessment, shared daily clinical care, weekly joint ward round and coordinated planning of the surgery schedule, the start of the ambulation and the time and setting of patient discharge.Two hundred fifty five consecutive patients admitted to the OGU and 251 patients managed simultaneously by the RC model were included. Except for a mean age slightly lower in the OGU group, there were no differences neither in the baseline patients characteristics nor in the surgical rates between the two groups. Among the OGU patients group it was more frequent to receive rehabilitation in the acute setting, to be able to walk at discharge and to be referred to a geriatric rehabilitation unit (all with P.05). The OGU patients received geriatric assessment and were operated on earlier than the RC patients (P.001). The length of stay in the acute ward was 34% shorter in the OGU patients (mean 12.48 ± 5 vs 18.9 ± 8.6 days, P.001) (median 12 [9-14] vs 17 [13-23] days, P.001). The whole hospital length of stay, including the days spent in the geriatric rehabilitation units, was 11% shorter in the OGU patients (mean 21.16 ± 14.7 vs 23.9 ± 13.8 days, P0.05) (median 14 [10-31] vs 20 [14-30] days, P.001). The OGU saved 1,207 € to 1,633 € per patient when estimated by the costs for process model, and 3,741 € when estimated by the costs for stay model.The OGU is a hospital setting that provides an improvement in the patients functional outcome and a reduction in the hospital length of stay. Therefore it saves health care resources. These findings show the OGU as an advisable setting for the acute care of hip fracture patients.

Proceeding of: 13th International Conference on Electrostatics (Electrostatics 2011), 10–14 April 2011, Bangor, Wales (UK). The aims of this work are to show the influence of adding a series resistance at the output of a discharge generator circuit and to point out that this component can be used to control the spark energy in electrostatic perforation systems. Analysis of the experimental results reveals that there exists a close connection between the resistor value and the obtained perforation pattern both in hole density and size. The use of a series resistor has a strong influence on the material porosity, which is an important industrial parameter for assessing the pattern perforation quality. Publicado

Several methods to enhance the efficiency of paper electroperforation processes are presented in this work. In all the cases, the discharge confinement effect is used for obtaining higher perforation densities than those found in the standard industrial processes. To quantify the efficiency of the proposed methods, statistical tools are used to characterize the 2-D perforation pattern. Publicado

Proceeding of: Electrostatics 2011 The electroperforation distribution in thin porous materials is investigated using the quadrat counts method (QCM), a classical statistical technique aimed to evaluate the deviation from complete spatial randomness (CSR). Perforations are created by means of electrical discharges generated by needle-like tungsten electrodes. The objective of perforating a thin porous material is to enhance its air permeability, a critical issue in many industrial applications involving paper, plastics, textiles, etc. Using image analysis techniques and specialized statistical software it is shown that the perforation locations follow, beyond a certain length scale, a homogeneous 2D Poisson distribution. The authors acknowledge the TRACE project from Ministerio de Ciencia e Innovación, Spain. Publicado

A simulation procedure for the optimization of enzymatic reactors used in sandwich flow injection systems is evaluated. The system is modeled as a plug-flow reactor with axial dispersion. To calibrate it, dispersion coefficients can be evaluated using residence time distribution techniques; meanwhile, enzymatic kinetics must be determined for the system considered, according to the values of the substrate conversion attained. The model has been linked to an optimization routine based on the Powell algorithm. The proposed approach has been evaluated in a system performing simultaneous determinations of glucose and glycerol, considered the common carbon sources in a fermentation process.