Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 95
Filtrar
Más filtros

País/Región como asunto
Tipo del documento
Intervalo de año de publicación
1.
Environ Sci Technol ; 57(41): 15511-15522, 2023 10 17.
Artículo en Inglés | MEDLINE | ID: mdl-37791816

RESUMEN

Standard environmental hazard exposure assessment methods have been primarily based on residential places, neglecting individuals' hazard exposures due to activities outside home neighborhood and underestimating peoples' overall hazard exposures. To address this limitation, this study proposes a novel mobility-based index for the hazard exposure evaluation. Using large-scale human mobility data, we quantify the extent of population dwell time in high environmental hazard places in 239 US counties for three environmental hazards. We explore how human mobility extends the reach of environmental hazards and leads to the emergence of latent exposure for populations living outside high-hazard areas. Notably, neglect of mobility can lead to over 10% underestimation of hazard exposures. The interplay of spatial clustering in high-hazard regions and human movement trends creates "environmental hazard traps." Poor and ethnic minority residents disproportionately face multiple types of environmental hazards. This data-driven evidence supports the severity of these injustices. We also studied latent exposure arising from visits outside residents' home areas, revealing millions of the population having 5 to 10% of daily activities occur in high-exposure zones. Despite living in perceived safe areas, human mobility could expose millions of residents to different hazards. These findings provide crucial insights for targeted policies to mitigate these severe environmental injustices.


Asunto(s)
Etnicidad , Grupos Minoritarios , Humanos , Vivienda , Exposición a Riesgos Ambientales , Características de la Residencia
2.
Mikrochim Acta ; 189(9): 326, 2022 08 10.
Artículo en Inglés | MEDLINE | ID: mdl-35948696

RESUMEN

In a new approach, we considered the special affinity between Ni and poly-histidine tags of recombinant urate oxidase to utilize Ni-MOF for immobilizing the enzyme. In this study, a carbon paste electrode (CPE) was modified by histidine-tailed urate oxidase (H-UOX) and nickel-metal-organic framework (Ni-MOF) to construct H-UOX/Ni-MOF/CPE, which is a rapid, sensitive, and simple electrochemical biosensor for UA detection. The use of carboxy-terminal histidine-tailed urate oxidase in the construction of the electrode allows the urate oxidase enzyme to be positioned correctly in the electrode. This, in turn, enhances the efficiency of the biosensor. Characterization was carried out by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), and field emission scanning electron microscopy (FE-SEM). At optimum conditions, the biosensor provided a short response time, linear response within 0.3-10 µM and 10-140 µM for UA with a detection limit of 0.084 µM, repeatability of 3.06%, and reproducibility of 4.9%. Furthermore, the biosensor revealed acceptable stability and selectivity of UA detection in the presence of the commonly coexisted ascorbic acid, dopamine, L-cysteine, urea, and glucose. The detection potential was at 0.4 V vs. Ag/AgCl.


Asunto(s)
Técnicas Biosensibles , Urato Oxidasa , Técnicas Biosensibles/métodos , Carbono/química , Electrodos , Enzimas Inmovilizadas/química , Histidina , Reproducibilidad de los Resultados , Urato Oxidasa/química , Ácido Úrico
3.
Cities ; 128: 103805, 2022 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-35694433

RESUMEN

While several non-pharmacological measures have been implemented for a few months in an effort to slow the coronavirus disease (COVID-19) pandemic in the United States, the disease remains a danger in a number of counties as restrictions are lifted to revive the economy. Making a trade-off between economic recovery and infection control is a major challenge confronting many hard-hit counties. Understanding the transmission process and quantifying the costs of local policies are essential to the task of tackling this challenge. Here, we investigate the dynamic contact patterns of the populations from anonymized, geo-localized mobility data and census and demographic data to create data-driven, agent-based contact networks. We then simulate the epidemic spread with a time-varying contagion model in ten large metropolitan counties in the United States and evaluate a combination of mobility reduction, mask use, and reopening policies. We find that our model captures the spatial-temporal and heterogeneous case trajectory within various counties based on dynamic population behaviors. Our results show that a decision-making tool that considers both economic cost and infection outcomes of policies can be informative in making decisions of local containment strategies for optimal balancing of economic slowdown and virus spread.

4.
Ethics Inf Technol ; 24(3): 30, 2022.
Artículo en Inglés | MEDLINE | ID: mdl-35915595

RESUMEN

We conducted a systematic literature review on the ethical considerations of the use of contact tracing app technology, which was extensively implemented during the COVID-19 pandemic. The rapid and extensive use of this technology during the COVID-19 pandemic, while benefiting the public well-being by providing information about people's mobility and movements to control the spread of the virus, raised several ethical concerns for the post-COVID-19 era. To investigate these concerns for the post-pandemic situation and provide direction for future events, we analyzed the current ethical frameworks, research, and case studies about the ethical usage of tracing app technology. The results suggest there are seven essential ethical considerations-privacy, security, acceptability, government surveillance, transparency, justice, and voluntariness-in the ethical use of contact tracing technology. In this paper, we explain and discuss these considerations and how they are needed for the ethical usage of this technology. The findings also highlight the importance of developing integrated guidelines and frameworks for implementation of such technology in the post- COVID-19 world. Supplementary Information: The online version contains supplementary material available at 10.1007/s10676-022-09659-6.

5.
Biometals ; 34(6): 1237-1246, 2021 12.
Artículo en Inglés | MEDLINE | ID: mdl-34420194

RESUMEN

Trimethoprim and sulfamethoxazole are prescribed for a broad spectrum of bacteria. However, the use of these medicines is restricted due to the risk of microbial resistance in the body. Nanotechnology is a strategy for overcoming this problem by helping develop novel drug delivery systems. This study aims to assess the ability of Fe3O4/Ag and Fe3O4@SiO2/Ag nanoparticles to improve efficiency of the traditional formulation of trimethoprim and sulfamethoxazole. Fe3O4/Ag and Fe3O4@SiO2/Ag were found to have sphere-like morphologies with average sizes of 33.2 and 35.1 nm, respectively. The values of the zeta potential for the pure sulfamethoxazole and trimethoprim were -30.6 and -10.0 mV, respectively, which increased to zero or even larger positive values after being conjugated with the NPs. The study of the release kinetics showed that 64.7% of the medicines were released from the carriers within 40 days. The values of MIC for sulfamethoxazole, trimethoprim, Fe3O4/Ag/sulfamethoxazole, Fe3O4/Ag/trimethoprim, Fe3O4@SiO2/Ag/sulfamethoxazole, and Fe3O4@SiO2/Ag/trimethoprim against Escherichia coli were calculated to be 12, 9, 4, 4, 4, and 4 µg/mL, respectively. Besides, the relevant values against Staphylococcus aureus were measured to be 12, 9, 4, 4, 3, and 2 µg/mL, respectively. The use of synthesized nanomaterials for the delivery of these antibiotics leads to smaller doses compared to their traditional forms.


Asunto(s)
Nanopartículas de Magnetita , Staphylococcus aureus Resistente a Meticilina , Antibacterianos/química , Antibacterianos/farmacología , Escherichia coli , Cinética , Nanopartículas de Magnetita/química , Pruebas de Sensibilidad Microbiana , Dióxido de Silicio/química , Plata/química , Plata/farmacología , Staphylococcus aureus , Sulfametoxazol/farmacología , Trimetoprim/farmacología
6.
Risk Anal ; 41(7): 1136-1144, 2021 07.
Artículo en Inglés | MEDLINE | ID: mdl-30408208

RESUMEN

Although there is an emerging literature on interdisciplinary disaster research (IDR), one of the overlooked aspects relates to our thinking itself: how to actively think about our thinking-metacognition-while embarking on our interdisciplinary journeys. This article argues that metacognition has an instrumental value both for IDR projects and for individual researchers involved in IDR. For IDR projects, metacognition can help: (1)overcome disciplinary barriers in IDR by revealing cognitive abilities and inabilities for each team member through identifying what is hindering or enabling individuals and the group to transcend disciplinary boundaries toward true integration across the disciplines; (2)deal with "wicked" problems that characterize disaster contexts in a more effective and creative manner; (3)oversee team functioning; and (4)monitor and evaluate progress toward meeting project goals and objectives. For individual researchers, metacognition can help them grow intellectually, and understand the fallacies and limitations in their thinking. It can also encourage them to live an authentic and unified life as an individual. The article concludes with guidance on how individual researchers, principal investigators of IDR projects, and institutions such as universities and funding agencies can cultivate metacognition. To our knowledge, this is the first article that introduces metacognition as a tool for enhancing our thinking on IDR.


Asunto(s)
Planificación en Desastres/métodos , Investigación Interdisciplinaria , Metacognición , Humanos
7.
Risk Anal ; 41(7): 1078-1086, 2021 07.
Artículo en Inglés | MEDLINE | ID: mdl-30884546

RESUMEN

Scholars across disciplines use simulation methods as tools to build theories; however, the full potential of simulation methods has not been fully used for building theories in convergence disaster research. Simulation methods could provide four unique opportunities for building theories for convergence disaster research. First, simulation methods could help researchers model the underlying mechanisms of disaster phenomena by enabling integration of qualitative and quantitative data. Second, they could help researchers specify and characterize the mechanisms affecting specific disaster phenomena by facilitating integration of empirical information with existing theoretical elements from different disciplines. Third, simulation methods could enable multilevel understanding of relationships between factors influencing disaster phenomena and emergent behaviors across different levels of analysis (e.g., individual, household, neighborhood, and community levels). Fourth, simulation methods could help researchers integrate theoretical elements on disasters across different disciplines (e.g., engineering, social science, sociology, and epidemiology) for a more convergent understanding of complex relationships affecting resilience at different levels.

8.
Risk Anal ; 41(12): 2336-2355, 2021 12.
Artículo en Inglés | MEDLINE | ID: mdl-33914344

RESUMEN

The objective of this article is to systematically assess and identify factors affecting risk disparity due to infrastructure service disruptions in extreme weather events. We propose a household service gap model that characterizes societal risks at the household level by examining service disruptions as threats, level of tolerance of households to disruptions as susceptibility, and experienced hardship as an indicator for the realized impacts of risk. The concept of "zone of tolerance" for the service disruptions was encapsulated to account for different capabilities of the households to endure the adverse impacts. The model was tested and validated in the context of power outages through survey data from the residents of Harris County in the aftermath of Hurricane Harvey in 2017. The results show that households' need for utility service, preparedness level, the existence of substitutes, possession of social capital, previous experience with disasters, and risk communication affect the zone of tolerance within which households cope with service outages. In addition, sociodemographic characteristics, such as race and residence type, are shown to influence the zone of tolerance, and hence the level of hardship experienced by the affected households. The results reveal that population subgroups show variations in the tolerance level of service disruptions. The findings highlight the importance of integrating social dimensions into the resilience planning of infrastructure systems. The proposed model and results enable human-centric hazards mitigation and resilience planning to effectively reduce the risk disparity of vulnerable populations to service disruptions in disasters.


Asunto(s)
Planificación en Desastres , Desastres , Composición Familiar , Medición de Riesgo/métodos , Capital Social , Poblaciones Vulnerables , Estrés Financiero , Humanos , Riesgo , Texas
9.
Med J Islam Repub Iran ; 35: 161, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-35465168

RESUMEN

Background:There has been considerable interest in target immunotherapy in patients with diabetes. This study was designed to identify the effect of BCG vaccination in the treatment of Iranian patients with longstanding diabetes mellitus type 1. Methods: After approval of the cross-sectional study protocol by the ethics committee under number IRCT2017042919940N2, a total of 19 Iranian volunteers with diabetes mellitus type 1 completed this 48-month study. These patients received three 0.1 ml intradermal injections of BCG vaccination in weeks 0, 4 and 24. The serum level of glucose, HgbA1C and c-peptide was measured before and serially after the interventions. Insulin requirements were recorded for each patient in different weeks as the mean and standard deviation. Results: This study showed a decrease in the blood sugar level of 171.15±75.54 mg/dL in baseline to 133.77±76.97 mg/dL in 12 weeks after the first dose of BCG vaccination in these patients. There was no significant change in the mean± SD of serum blood sugar, HgbA1C and c-peptide after BCG vaccination in the baseline and week 48. Conclusion: Our results showed that small doses of BCG vaccination were not effective in long-term treatment of Iranian patients with diabetes mellitus type 1 up to 48 weeks.

10.
Ecotoxicol Environ Saf ; 189: 109886, 2020 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-31759746

RESUMEN

Chlorpyrifos (CP) is an organophosphorus pesticide used to control pests in agriculture. Brilliant green (BG) is a cationic dye widely used in textile and dyeing industry. However, the presence of pollutants in the aquatic environment has harmful effects on the environment and humans. Photocatalytic degradation can be appropriate method for water purification. Therefore, the Fe3O4/CdS-ZnS magnetic nanocomposite was synthesized and characterized by Brunauer-Emmett-Teller (BET) surface area analysis, Energy dispersive x-ray spectroscopy (EDX), X-ray diffraction (XRD), vibrating sample magnetometry (VSM), UV-Vis-diffuse reflectance spectroscopy (DRS), and field emission scanning electron microscopy (FESEM) analyses and was used to degrade pollutants such as chlorpyrifos pesticide and brilliant green dye under visible light with source 300 W. Parameters that may be effective on photocatalytic degradation include pH, photocatalyst amount, contaminant concentration, photocatalyst and contaminant contact temperature and duration, light intensity as well as distance of light source from the reaction vessel. In the present study, the parameters that have the most influence on the degradation process were experimentally optimized, including pH, photocatalyst amount, photocatalyst reuse, and initial concentration. The study of the photocatalytic degradation rate of chlorpyrifos and brilliant green in optimal conditions (pH = 7, the concentration of pollutants = 10 ppm, volume of pollutants = 5 mL, and photocatalyst amounts for CP and BG were 0.0100 and 0.0015 g respectively) was obtained by Langmuir-Hinshelwood model. According to this model, the kapp value for CP and BG were respectively 0.0315 and 0.0119 min-1 respectively. It has been concluded that the composition of CdS and ZnS caused inhibition of the recombination of photogenerated charge carriers, leading to high catalytic efficiency. Based on the results, the synthesized nanocatalyst showed that it has the ability to photocatalytic degradation of chlorpyrifos and brilliant green in aqueous solutions.


Asunto(s)
Cloropirifos/química , Plaguicidas/química , Compuestos de Amonio Cuaternario/química , Catálisis , Colorantes/química , Microscopía Electrónica de Rastreo , Modelos Químicos , Nanocompuestos/química , Sulfuros , Agua , Purificación del Agua , Difracción de Rayos X , Compuestos de Zinc
11.
Nitric Oxide ; 73: 9-14, 2018 02 28.
Artículo en Inglés | MEDLINE | ID: mdl-29248688

RESUMEN

A novel, inexpensive and sensitive type of magnetic nanosorbent based on the functionalized silica-coated Fe3O4 nanoparticles was prepared and used for the adsorption of trace amounts of nitrite and nitrate ions. The work is based on selective ion-pairing complex formation of nitrate and nitrite with Cu(I)-neocuproine which are covalently bounded on nanoparticles. Nitrite was determined according to its reaction with barbituric acid to give violuric acid and determination of nitrate was based on its reduction to nitrite in the presence of Zn/NaCl. After formation of violuric acid, the absorbance was measured spectrophotometrically at 310 nm. The quantitative recoveries were obtained at pH 5.5 for the analytes. Under optimum conditions, the limits of detection in the original solutions were 0.49 µg L-1 and 0.40 µg L-1 for nitrate and nitrite, respectively. The linearity ranges were found to be 1.5 to 2.8 × 103 µg L-1(NO3-) and 1.2 to 1.9 × 103 µg L-1 (NO2-). The preconcentration factor was 120 for nitrate and 150 for nitrite. This method has been successfully applied to the determination of trace amounts of nitrite and nitrate in various water and food samples and also accuracy was confirmed by the analysis of the spiked recovery test.


Asunto(s)
Nanopartículas de Magnetita/química , Nitratos/aislamiento & purificación , Nitritos/aislamiento & purificación , Fenantrolinas/química , Cobre/química , Análisis de los Alimentos/instrumentación , Análisis de los Alimentos/métodos , Concentración de Iones de Hidrógeno , Nitratos/análisis , Nitritos/análisis , Dióxido de Silicio/química , Factores de Tiempo
12.
J Vector Borne Dis ; 55(3): 230-234, 2018.
Artículo en Inglés | MEDLINE | ID: mdl-30618450

RESUMEN

BACKGROUND AND OBJECTIVES: : The dogs are considered the main reservoir of visceral leishmaniasis (VL), but lately the disease incidence has been reported in cats also. In this study, the susceptibility of domestic cats to experimental Leishmania infantum infection was assessed by different diagnostic methods. METHODS: : A total of 12 healthy adult male cats were captured by double door live trap cages containing baits. Of them eight cats were intraperitoneally inoculated with 107 L. infantum promastigotes (stationary phase), and four cats were used as controls. Whole blood and serum samples were collected at weekly intervals for 16 wk after inoculation for testing by polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA) methods. Aspirates of prescapular lymph nodes and bone marrow were obtained at monthly intervals. Clinical examination was performed twice weekly and histopathological evaluation was done on necropsy samples at the termination of the study. Results: One week after inoculation, blood nested PCR was able to detect the L. infantum infection and it remained positive until 16 wk. ELISA test remained negative during the study. Amastigote phase of parasite was not observed in bone marrow aspiration and necropsy samples. INTERPRETATION AND CONCLUSION: : The feline model described in this work would be useful in further understanding of L. infantum immunopathogenensis in cats. The results of this preliminary study suggest that cats might be resistant to VL as the inoculation dose which induces pathognomonic clinical features in dogs, just creates asymptomatic parasitaemia in cats. Though, due to long-lasting parasitaemia, cats may act as appropriate reservoir for transmission of VL to human population. Further studies are needed to describe the possible role of cats in the epidemiology of VL in endemic areas.


Asunto(s)
Enfermedades de los Gatos/parasitología , Susceptibilidad a Enfermedades/veterinaria , Leishmaniasis Visceral/veterinaria , Parasitemia/veterinaria , Mascotas/parasitología , Animales , Anticuerpos Antiprotozoarios/sangre , Gatos , Reservorios de Enfermedades/parasitología , Reservorios de Enfermedades/veterinaria , Susceptibilidad a Enfermedades/parasitología , Ensayo de Inmunoadsorción Enzimática , Leishmania infantum , Leishmaniasis Visceral/diagnóstico , Masculino , Reacción en Cadena de la Polimerasa
13.
J Sep Sci ; 40(20): 4041-4049, 2017 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-28841257

RESUMEN

For the first time, we coupled a microextraction technique using a magnetic ionic liquid with voltammetric determination. A hydrophobic magnetic ionic liquid that contains the tetrachloromanganate(II) anion, namely, aliquat tetrachloromanganate(II), was synthesized and used for the extraction of ascorbic acid from aqueous solutions followed by voltammetric determination. The extraction procedure was carried out using a single drop microextraction technique in which the ascorbic acid containing magnetic ionic liquid was separated with a magnet and then cast onto the surface of a carbon paste electrode modified with TiO2 nanoparticles for the voltammetric quantification of the extracted ascorbic acid. Electrochemical quantification was carried out in a blank phosphate buffer solution. After optimizing different experimental conditions, a linear concentration range of 1.50-40.0 nM with a detection limit of 0.43 nM was obtained for the determination of ascorbic acid. The presented approach was successfully applied to the determination of ascorbic acid in samples of vitamin C effervescent tablets and orange juice.


Asunto(s)
Ácido Ascórbico/aislamiento & purificación , Electrodos , Jugos de Frutas y Vegetales/análisis , Líquidos Iónicos , Iones , Microextracción en Fase Líquida , Magnetismo , Comprimidos
14.
J Environ Manage ; 176: 128-38, 2016 Jul 01.
Artículo en Inglés | MEDLINE | ID: mdl-27045541

RESUMEN

Through a critical review and systematic analysis of pavement life cycle assessment (LCA) studies published over the past two decades, this study shows that the available information regarding the environmental impacts of pavement infrastructure is not sufficient to determine what pavement type is more environmentally sustainable. Limitations and uncertainties related to data, system boundary and functional unit definitions, consideration of use and maintenance phase impacts, are identified as the main reasons for inconsistency of reported results in pavement LCA studies. The study outcomes also highlight the need for advancement of knowledge pertaining to: (1) utilization of performance-adjusted functional units, (2) accurate estimation of use, maintenance, and end-of-life impacts, (3) incorporation of the dynamic and uncertain nature of pavement condition performance in impact assessment; (4) development of region-specific inventory data for impact estimation; and (5) consideration of a standard set of impact categories for comparison of environmental performance of different pavement types. Advancing the knowledge in these areas is critical in providing consistent and reliable results to inform decision-making toward more sustainable roadway infrastructure.


Asunto(s)
Conservación de los Recursos Naturales , Materiales de Construcción/análisis , Monitoreo del Ambiente/métodos , Transportes , Contaminantes Atmosféricos/análisis , Ambiente , Modelos Teóricos , Análisis de Sistemas , Emisiones de Vehículos
15.
J Sep Sci ; 38(24): 4286-91, 2015 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-26496188

RESUMEN

A green, facile, fast, and sensitive liquid-phase microextraction method is presented for the extraction and preconcentration of hemin in the presence of free iron ions prior to flame atomic absorption spectroscopic determination. In this technique, an anion-functionalized task-specific ionic liquid is used as the extracting solvent. The interface between the extracting solvent and the bulk aqueous phase containing hemin is enormously enlarged by dispersing the ionic liquid to the aqueous phase with the help of ultrasound radiation. Hemin is selectively extracted into the ionic liquid after interaction with the functional group of the ionic liquid. Then, the concentration of the extracted hemin is determined through the absorbance of the iron ions contained in the hemin structure using flame atomic absorption spectroscopy. Different experimental parameters affecting the extraction efficiency have been optimized. Under the optimized conditions, the proposed method has a hemin concentration linear range of 0.020-0.80 mg/L with a detection limit of 0.0080 mg/L. This method has been successfully applied to the extraction and determination of hemin in human serum and supernatant samples.


Asunto(s)
Neoplasias de la Mama/patología , Hemina/aislamiento & purificación , Microextracción en Fase Líquida/métodos , Suero/química , Línea Celular Tumoral , Femenino , Hemina/química , Humanos , Concentración de Iones de Hidrógeno , Límite de Detección , Estructura Molecular
16.
J Sep Sci ; 38(10): 1777-83, 2015 May.
Artículo en Inglés | MEDLINE | ID: mdl-25735972

RESUMEN

First, the extraction and preconcentration of ultratrace amounts of lead(II) ions was performed using microliter volumes of a task-specific ionic liquid. The remarkable properties of ionic liquids were added to the advantages of microextraction procedure. The ionic liquid used was trioctylmethylammonium thiosalicylate, which formed a lead thiolate complex due to the chelating effect of the ortho-positioned carboxylate relative to thiol functionality. So, trioctylmethylammonium thiosalicylate played the roles of both chelating agent and extraction solvent simultaneously. Hence, there is no need to use a ligand. The main parameters affecting the efficiency of the method were investigated and optimized. Under optimized conditions, this approach showed a linear range of 2.0-24.0 ng/mL with a detection limit of 0.0010 ng/mL. The proposed method was applied to the extraction and preconcentration of lead from red lipstick and pine leaves samples prior to electrothermal atomic absorption spectroscopic determination.

17.
J AOAC Int ; 98(5): 1375-81, 2015.
Artículo en Inglés | MEDLINE | ID: mdl-26525257

RESUMEN

This paper presents an easy, fast, low cost, and sensitive approach for the electrochemical determination of quercetin based on its intercalation into DNA double helix. Electrochemical studies of the interaction between quercetin and DNA showed a decrease in peak currents with a reduction in redox reversibility of quercetin in the presence of the DNA. The electrochemical behavior of quercetin at a chitosan-entrapped carbon nanotube paste electrode coated with DNA was studied. A considerable increase was observed in the oxidation signal of quercetin at the DNA-coated electrode compared with a DNA-free electrode, indicating the preconcentration of quercetin due to its interaction with the surface-confined DNA layer. After optimizing the main experimental parameters influencing the biosensor response, its performance was evaluated from an analytical point of view. Two linear dependences of the anodic peak current of quercetin on its concentration were observed in the ranges of 0.40-7.50 and 7.50-30.0 µmol/L, with LOD and LOQ of 0.039 and 0.13 µmol/L, respectively. The proposed biosensor was successfully applied to the analysis of black and green tea extracts for their quercetin content.


Asunto(s)
Técnicas Biosensibles/instrumentación , ADN/química , Técnicas Electroquímicas/instrumentación , Nanotubos de Carbono/química , Quercetina/análisis , Té/química , Carbono/química , Quitosano/química , Electrodos , Concentración de Iones de Hidrógeno , Pomadas , Oxidación-Reducción
18.
Analyst ; 139(17): 4356-64, 2014 Sep 07.
Artículo en Inglés | MEDLINE | ID: mdl-25014312

RESUMEN

A novel carbon paste electrode modified with ZnO nanorods and 5-(4'-amino-3'-hydroxy-biphenyl-4-yl)-acrylic acid (3,4'-AAZCPE) was fabricated. The electrochemical study of the modified electrode, as well as its efficiency for the electrocatalytic oxidation of levodopa, is described. The electrode was employed to study the electrocatalytic oxidation of levodopa, using cyclic voltammetry (CV), chronoamperometry (CHA), and square-wave voltammetry (SWV) as diagnostic techniques. It has been found that the oxidation of levodopa at the surface of the modified electrode occurs at a potential of about 370 mV less positive than that of an unmodified carbon paste electrode. The SWV results exhibit a linear dynamic range from 1.0 × 10(-7) M to 7.0 × 10(-5) M and a detection limit of 3.5 × 10(-8) M for levodopa. In addition, this modified electrode was used for the simultaneous determination of levodopa and carbidopa. Finally, the modified electrode was used for the determination of levodopa and carbidopa in some real samples.


Asunto(s)
Carbidopa/análisis , Dopaminérgicos/análisis , Técnicas Electroquímicas/métodos , Levodopa/análisis , Nanotubos/química , Óxido de Zinc/química , Acrilatos/química , Carbono/química , Electrodos , Límite de Detección , Nanotubos/ultraestructura , Oxidación-Reducción , Comprimidos
19.
Nutr Neurosci ; 17(2): 65-71, 2014 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-23602205

RESUMEN

OBJECTIVE: Zinc is found in abundance in the human brain. Patients with depression may have decreased consumption of food sources rich in zinc, and zinc supplementation may have a potential influence on depressive symptoms. However, clinical trials on the effect of zinc supplementation in depression are limited. The objective of the present study was to determine the effect of zinc supplementation on efficacy of antidepressant therapy. Furthermore, the effect of zinc on plasma levels of interleukin-6 (IL-6), tumor necrosis factor (TNF-α), and brain-derived neurotrophic factor-a (BDNF-a) were assessed. DESIGN: A single-center, randomized, double-blind, placebo-controlled trial of zinc supplementation was conducted in patients with DSM-IV major depression. Forty-four patients of both sexes aged 18-55 years were recruited for this study from a university hospital. The zinc-supplemented group received zinc sulfate (25 mg elemental Zn/day) orally in addition to their selective serotonin reuptake inhibitor antidepressants for 12 weeks. Symptoms were evaluated using the Hamilton Depression Rating Scale (HDRS) on arrival, weeks 6 and 12. Plasma levels of IL-6, TNF-α and BDNF-a were measured at baseline and at the end of study. RESULTS: Twenty patients in zinc group and 17 patients in placebo groups completed the study. At baseline, there were no significant differences in any variable between the patients allocated to receive placebo and those taking zinc supplement. Zinc supplementation significantly reduced HDRS compared to placebo (P < 0.01 at 12th week). No significant differences were observed in plasma levels of IL-6, TNF-α, and BDNF-a between zinc-supplemented and placebo-supplemented group. CONCLUSION: Zinc supplementation in conjunction with antidepressant drugs might be beneficial for reducing depressive symptoms. However, its effect does not appear to be mediated through impact of zinc on inflammatory processes.


Asunto(s)
Antidepresivos/uso terapéutico , Factor Neurotrófico Derivado del Encéfalo/sangre , Citocinas/sangre , Trastorno Depresivo Mayor/tratamiento farmacológico , Zinc/administración & dosificación , Adolescente , Adulto , Citalopram/uso terapéutico , Trastorno Depresivo Mayor/sangre , Suplementos Dietéticos , Método Doble Ciego , Femenino , Fluoxetina/uso terapéutico , Humanos , Interleucina-6/sangre , Irán , Masculino , Persona de Mediana Edad , Placebos , Inhibidores Selectivos de la Recaptación de Serotonina/uso terapéutico , Factor de Necrosis Tumoral alfa/sangre
20.
J Sep Sci ; 37(14): 1856-61, 2014 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-24811255

RESUMEN

Here, task-specific ionic liquid solid-phase extraction is proposed for the first time. In this approach, a thiourea-functionalized ionic liquid is immobilized on the solid sorbent, multiwalled carbon nanotubes. These modified nanotubes packed into a solid-phase extraction column are used for the selective extraction and preconcentration of ultra-trace amounts of lead(II) from aqueous samples prior to electrothermal atomic absorption spectroscopy determination. The thiourea functional groups act as chelating agents for lead ions retaining them and so, give the selectivity to the sorbent. Elution of the retained ions can be performed using an acidic thiourea solution. The effects of experimental parameters including pH of the aqueous solution, type and amount of eluent, and the flow rates of sample and eluent solutions on the separation efficiency are investigated. The linear dependence of absorbance of lead on its concentration in the initial solution is in the range of 0.5-40.0 ng/mL with the detection limit of 0.13 ng/mL (3(Sb)/m, n = 10). The proposed method is applicable to the analysis of red lipstick, pine leaves, and water samples for their lead contents.


Asunto(s)
Cosméticos/química , Plomo/aislamiento & purificación , Pinus/química , Extracción en Fase Sólida/métodos , Tiourea/química , Contaminantes Químicos del Agua/aislamiento & purificación , Adsorción , Líquidos Iónicos/química , Plomo/análisis , Límite de Detección , Hojas de la Planta/química , Extracción en Fase Sólida/instrumentación , Análisis Espectral , Contaminantes Químicos del Agua/análisis
SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA