A CMOS 0.8- µm transistor-only 1.63-MHz switched-current bandpass ΣΔ modulator for AM signal A/D conversion

This paper presents a CMOS 0.8-/spl mu/m switched-current (SI) fourth-order bandpass /spl Sigma//spl Delta/ modulator (BP-/spl Sigma//spl Delta/M) IC capable of handling signals up to 1.63 MHz with 105-bit resolution and 60-mW power consumption from a 5-V supply voltage. This modulator Is intended for direct A/D conversion of narrow-band signals within the commercial AM band, from 530 kHz to 1.6 MHz. Its architecture is obtained by applying a low-pass-to-bandpass transformation (z/sup -1//spl rarr/-z/sup -2/) to a 1-bit second-order low-pass /spl Sigma//spl Delta/ modulator (LP-/spl Sigma//spl Delta/M). The design of basic building blocks is based upon a detailed analysis of the influence of SI errors on the modulator performance, followed by design optimization. Memory-cell errors have been identified as the dominant ones. In order to attenuate these errors, fully differential regulated-folded cascode memory cells are employed. Measurements show a best SNR peak of 65 dB for signals of 10-kHz bandwidth and an intermediate frequency (IF) of 1.63 MHz. A correct noise-shaping filtering is achieved with a sampling frequency of up to 16 MHz.This work has been supported by the Spanish CICYT Project TIC 97-0580

Reducción de selenito a Selenio elemental por Pantoea agglomerans

Selenium is required and essential for the growth and metabolism of several biological systems. Its transformation in the environment occurs mainly by the activity of microorganisms, able to reduce selenite into elemental Selenium. Pantoea agglomerans UC-32 reduces selenite to nanoparticles of elemental Selenium. The aims of this work were to determine the kinetics of selenite reduction and to determine the cellular localization of this activity in P. agglomerans UC-32. The selenite reducing activity of P. agglomerans UC-32 was assayed in the presence of different selenite concentrations and the decrease of selenite and appearance of elemental Selenium were evaluated. The location of this activity was studied by cellular fractioning and zymography. Results indicated that the selenite reducing enzyme saturates at low concentrations of this compound and the zymogram localized this activity in the cytoplasmic fraction and showed that NADPH is required as coenzyme. In conclusion, P. agglomerans reduces, under aerobic conditions, selenite into insoluble elemental Selenium, immobilized in the biomass and that the enzyme catalyzing this reduction is cytoplasmatic. These characteristics would allow the "green synthesis" of selenium nanoparticles which have application in the bioremediation of different contaminated matrices, such as soil or water.El selenio es esencial y requerido por distintos sistemas biológicos para su crecimiento y metabolismo. Su transformación en el ambiente ocurre principalmente por microorganismos que reducen el selenito a selenio elemental. Pantoea agglomerans UC-32 reduce el selenito a nanopartículas de selenio elemental. El objetivo de este trabajo fue determinar la cinética de reducción de selenito a selenio elemental y la ubicación celular de la actividad reductora en Pantoea agglomerans UC-32. Se ensayó la actividad reductora de P. agglomerans frente a diferentes concentraciones de selenito, evaluándose la disminución de selenito y aparición de selenio elemental. La ubicación de la actividad reductora fue estudiada por fraccionamiento celular y zimograma. Al ensayar la actividad reductora de selenito se encontró que la enzima se satura a concentraciones bajas de este compuesto y el zimograma localizó esta actividad en la fracción citoplasmática y que requiere NADPH como coenzima. En conclusión, P. agglomerans es capaz de reducir selenito a selenio elemental insoluble inmovilizado en la biomasa en condiciones aeróbicas y que la enzima que cataliza esta reducción se localiza en la fracción de citoplasmática. Estas características permitirían la "síntesis verde" de nanopartículas de selenio las cuales tienen aplicación en la biorremediación de diferentes matrices, como suelo o agua contaminadas

Preparation of Poly(vinyl Alcohol) Microparticles for Freeze Protection of Sensitive Fruit Crops

[Abstract] Poly(vinyl alcohol) (PVA) displays ice recrystallization inhibition (IRI) properties as many antifreeze proteins found in cold tolerant organisms. The molecular architecture and composition (molecular weight and distribution of pendant OH and acetate groups) have been studied to improve the antifreezing properties of PVA, suggesting that the molecular architecture of PVA plays an important role in IRI activity. The present work deals with the preparation of PVA microparticles using an alkaline treatment. The effect of PVA molecular weight on the morphology and antifreezeing properties of PVA microparticles was investigated. The antifreezeing property of PVA microparticles on the susceptibility of flower bud tissues to freeze damage was also evaluated. The alkaline treatment of an aqueous PVA solution produced stable polymer chain aggregates with spherical shapes. The average size of the PVA microparticles increased significantly with the increasing molecular weight of the PVA macromolecule precursor. The PVA microparticles inhibited the growth of ice crystals and blocked ice growth at concentrations as low as 0.01 % w/v. The effect of impeding ice crystal growth by preventing the joining of adjacent ice crystals is attributed to the larger size of the PVA particles adsorbed on the ice surface compared to the aggregated PVA macromolecules in saline solution. The thermal hysteresis activity of PVA macromolecules and microparticles was not detected by differential scanning calorimetry analysis. The PVA microparticles reduced the incidence of freeze injuries in flower bud tissues by 55% and their application, considering the low toxicity of PVA, has a high potential for freeze protection in fruit crops.Chile. Comisión Nacional de Investigación Científica y Tecnológica; ID16I10425Chile. Comisión Nacional de Investigación Científica y Tecnológica; ID16I20425Chile. Gobierno Regional del Biobío; R17A10003Chile. Agencia Nacional de Investigación y Desarrollo; ACE210016Chile. Agencia Nacional de Investigación y Desarrollo; ACE210012Chile. Comisión Nacional de Investigación Científica y Tecnológica; AFB170007This research was funded by projects CONICYT + FONDEF/tercer concurso IDeA en Dos Etapas del Fondo al Desarrollo Científico Y Tecnológico, FONDEF/CONICYT 2016 [grant numbers ID16I10425 and ID16I20425], CIPA, ANID Regional, GORE BIO BIO [grant number: R17A10003], ANID [grant numbers: ACE210016 and ACE210012] and CONICYT PIA/APOYO CCTE [grant number: AFB170007

Improvement of Endothelial Function by Gunnera Tinctoria Extract With Antioxidant Properties

[Abstract] Background: Gunnera tinctoria has been collected by Mapuche-Pewenche people for food and medicinal purposes. The high polyphenol content of methanolic extract from G. tinctoria leaves with chemical constituents such as ellagic acid and quercetin derivatives suggests its application to prevent endothelial dysfunction and oxidative stress. The aim of this study was to provide evidence of the protective effect of this extract on endothelial function by reducing oxidative stress induced by high D-glucose and H2O2, as well as by stimulating nitric oxide (NO) levels in human umbilical vein endothelial cells (HUVECs). Results: A methanolic extract with a high content of polyphenols (520 ± 30 mg gallic acid equivalents/g dry extract) was obtained from G. tinctoria leaves. Its main constituent was ellagic acid. The results of Ferric reducing antioxidant power and 2,2-diphenyl-1-picrylhydrazyl radical scavenging assays of the extract confirmed its antioxidant activity by inhibition pathway of radical species. The incubation of HUVECs with the extract decreased the apoptosis and reactive oxygen species (ROS) synthesis induced by high extracellular concentration of D-glucose or hydrogen peroxide. The extract increased endothelial NO levels and reduced vasoconstriction in human placental vessels. Conclusions: This study provides evidence about the antioxidant and endothelial protective properties of methanolic G. tinctoria leaf extract. The extract improves the availability of NO in HUVECs, inhibiting the production of ROS and vasoconstriction.Comisión Nacional de Investigación Científica y Tecnológica (Chile); 1191651InnovaChile; 13IDL223120Gobierno Regional del Biobío (Chile); R17A10003Comisión Nacional de Investigación Científica y Tecnológica (Chile); AFB170007Comisión Nacional de Investigación Científica y Tecnológica (Chile); EQM150025Comisión Nacional de Investigación Científica y Tecnológica (Chile); AFB170007Universidad de Concepción (Chile); VRID-Asociativo 213.A84.014-1.0Universidad de Concepción (Chile); VRID-Asociativo 217.033.110-1.0Universidad de Concepción (Chile); VRID-Enlace 216.033.108-1.0This work has been financed by Fondecyt Regular [Grant Number 1191651], InnovaChile [Grant Number 13IDL223120], CIPA, CONICYT Regional, GORE BIO BIO [Grant Number R17A10003], CONICYT PIA/APOYO CCTE [Grant Number AFB170007], Fondequip [Grant Numbers EQM150025 and AFB170007] and Universidad de Concepción, Chile [Grant Numbers VRID-Asociativo 213.A84.014-1.0, VRID-Asociativo 217.033.110-1.0, VRID-Enlace 216.033.108-1.0

Injectable hybrid hydrogels physically crosslinked based on carrageenan and green graphene for tissue repair

Financiado para publicación en acceso aberto: Universidade da Coruña/CISUG[Abstract] Injectable and biocompatible novel hybrid hydrogels based on physically crosslinked natural biopolymers and green graphene for potential use in tissue engineering are reported. Kappa and iota carrageenan, locust bean gum and gelatin are used as biopolymeric matrix. The effect of green graphene content on the swelling behavior, mechanical properties and biocompatibility of the hybrid hydrogels is investigated. The hybrid hydrogels present a porous network with three-dimensionally interconnected microstructures, with lower pore size than that of the hydrogel without graphene. The addition of graphene into the biopolymeric network improves the stability and the mechanical properties of the hydrogels in phosphate buffer saline solution at 37 °C without noticeable change in the injectability. The mechanical properties of the hybrid hydrogels were enhanced by varying the dosage of graphene between 0.025 and 0.075 w/v%. In this range, the hybrid hydrogels preserve their integrity during mechanical test and recover the initial shape after removing the applied stress. Meanwhile, hybrid hydrogels with graphene content of up to 0.05 w/v% exhibit good biocompatibility for 3T3-L1 fibroblasts; the cells proliferate inside the gel structure and show higher spreading after 48 h. These injectable hybrid hydrogels with graphene have promising future as materials for tissue repair.Xunta de Galicia; ED431C 2019/17Instituto de Salud Carlos III; CD21/00042Chile. CORFO; 22CVID-20683

Injectable hybrid hydrogels physically crosslinked based on carrageenan and green graphene for tissue repair

Injectable and biocompatible novel hybrid hydrogels based on physically crosslinked natural biopolymers and green graphene for potential use in tissue engineering are reported. Kappa and iota carrageenan, locust bean gum and gelatin are used as biopolymeric matrix. The effect of green graphene content on the swelling behavior, mechanical properties and biocompatibility of the hybrid hydrogels is investigated. The hybrid hydrogels present a porous network with three-dimensionally interconnected microstructures, with lower pore size than that of the hydrogel without graphene. The addition of graphene into the biopolymeric network improves the stability and the mechanical properties of the hydrogels in phosphate buffer saline solution at 37 °C without noticeable change in the injectability. The mechanical properties of the hybrid hydrogels were enhanced by varying the dosage of graphene between 0.025 and 0.075 w/v%. In this range, the hybrid hydrogels preserve their integrity during mechanical test and recover the initial shape after removing the applied stress. Meanwhile, hybrid hydrogels with graphene content of up to 0.05 w/v% exhibit good biocompatibility for 3T3-L1 fibroblasts; the cells proliferate inside the gel structure and show higher spreading after 48 h. These injectable hybrid hydrogels with graphene have promising future as materials for tissue repair.The research leading to these results received funding from the Xunta de Galicia Government: program of consolidation and structuring competitive research units [grant number: ED431C 2019/17]. Y.F. is a ‘Sara Borrell’ researcher funded by Instituto de Salud Carlos III (ISCIII) and co-funded by Fondo Europeo de Desarrollo Regional (FEDER) [CD21/00042]. Thanks to Corfo 22CVID-206836, CIPA, ANID Regional, GORE BIO BIO, R17A10003, ACE210016, ACE210012. Funding for open access charge was provided by Universidade da Coruna/CISU

The effect of molecular weight and hydrolysis degree of poly(vinyl alcohol)(PVA) on the thermal and mechanical properties of poly(lactic acid)/PVA blends

The effect of molecular weights and hydrolysis degrees (HD) of polyvinyl alcohol (PVA) on thermal and mechanical properties and crystallinity of polylactic acid (PLA)/PVA blends was investigated. Blends were prepared by the melt blending method using PLA/PVA ratios: 80/20, 90/10 and 97/3 wt. %. A single glass transition temperatures was observed for all PLA/PVA blends, suggesting the formation of binary compatible blends at concentration range studied. Thermogravimetric analysis results showed a better thermal stability for PLA/PVA blends containing PVA of higher Mw and HD. According to mechanical properties, low quantities of PVA (3 wt. %) do not affect the tensile strength of blends (irrespective of Mw and HD). However, as the PVA content increases, tensile strength tends to lower values, especially for blends with 20 wt.% of PVA, with 98% of HD.Comision Nacional de Investigacion Cientifica y Tecnologica CONICYT (Beca de Doctorado Nacional - Proyecto) PAI 781411004 CONICYT-REGIONAL R08C1002 Programa de Financiamiento Basal para Centros Cientificos y Tecnologicos de Excelencia PFB-2

Progress in Starch-Based Materials for Food Packaging Applications

The food packaging sector generates large volumes of plastic waste due to the high demand for packaged products with a short shelf-life. Biopolymers such as starch-based materials are a promising alternative to non-renewable resins, offering a sustainable and environmentally friendly food packaging alternative for single-use products. This article provides a chronology of the development of starch-based materials for food packaging. Particular emphasis is placed on the challenges faced in processing these materials using conventional processing techniques for thermoplastics and other emerging techniques such as electrospinning and 3D printing. The improvement of the performance of starch-based materials by blending with other biopolymers, use of micro- and nano-sized reinforcements, and chemical modification of starch is discussed. Finally, an overview of recent developments of these materials in smart food packaging is given

Progress in Starch-Based Materials for Food Packaging Applications

The food packaging sector generates large volumes of plastic waste due to the high demand for packaged products with a short shelf-life. Biopolymers such as starch-based materials are a promising alternative to non-renewable resins, offering a sustainable and environmentally friendly food packaging alternative for single-use products. This article provides a chronology of the development of starch-based materials for food packaging. Particular emphasis is placed on the challenges faced in processing these materials using conventional processing techniques for thermoplastics and other emerging techniques such as electrospinning and 3D printing. The improvement of the performance of starch-based materials by blending with other biopolymers, use of micro- and nano-sized reinforcements, and chemical modification of starch is discussed. Finally, an overview of recent developments of these materials in smart food packaging is given