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1.
Database (Oxford) ; 20242024 Apr 03.
Artigo em Inglês | MEDLINE | ID: mdl-38581360

RESUMO

When the scientific dataset evolves or is reused in workflows creating derived datasets, the integrity of the dataset with its metadata information, including provenance, needs to be securely preserved while providing assurances that they are not accidentally or maliciously altered during the process. Providing a secure method to efficiently share and verify the data as well as metadata is essential for the reuse of the scientific data. The National Science Foundation (NSF) funded Open Science Chain (OSC) utilizes consortium blockchain to provide a cyberinfrastructure solution to maintain integrity of the provenance metadata for published datasets and provides a way to perform independent verification of the dataset while promoting reuse and reproducibility. The NSF- and National Institutes of Health (NIH)-funded Neuroscience Gateway (NSG) provides a freely available web portal that allows neuroscience researchers to execute computational data analysis pipeline on high performance computing resources. Combined, the OSC and NSG platforms form an efficient, integrated framework to automatically and securely preserve and verify the integrity of the artifacts used in research workflows while using the NSG platform. This paper presents the results of the first study that integrates OSC-NSG frameworks to track the provenance of neurophysiological signal data analysis to study brain network dynamics using the Neuro-Integrative Connectivity tool, which is deployed in the NSG platform. Database URL: https://www.opensciencechain.org.


Assuntos
Neurociências , Publicações , Reprodutibilidade dos Testes , Bases de Dados Factuais , Metadados
2.
J Contam Hydrol ; 251: 104100, 2022 12.
Artigo em Inglês | MEDLINE | ID: mdl-36347658

RESUMO

This study evaluates the potential toxicity of the soils of the Guadiamar Green Corridor (GGC) affected by the Aznalcóllar mine spill (Andalusia, Spain), one of the most important mining accidents in Europe in recent decades. Twenty years after the accident, although the area is considered to be recovered, residual contamination in soils persists, and the bioavailability of some contaminants, such as As, is showing trends of increasing. Therefore, the potential residual toxicity in 84 soil samples was evaluated by bioassays with lettuce (Latuca sativa L.), earthworms (Eisenia andrei) and determining the microbial activity by basal respiration and metabolic quotient. The selected soils sampled along the GGC were divided into 4 types according to their physicochemical properties. In the closest part of the mine two soil types appear (SS1 and SS2), originally decarbonated and loamy, with a reduction in lettuce root elongation of 57% and 34% compared to the control, as well as a the highest metabolic quotient (23.9 and 18.1 ng CcO2 µg Cmicrob-1 h-1, respectively) with the highest risk of Pb and As toxicity. While, located in the middle and final part of the affected area of the spill (SS3 and SS4), soils presented alkaline pH, finer textures and the lowest metabolic quotient (<9.5 ng CcO2 µg Cmicrob-1 h-1). In addition, due to Pb and As exceeded the Guideline values established in the studied area, the human toxicity risk was determined according to US-EPA methodology. Although the total contents were higher than the Guidelines established, the obtained hazard quotients for both contaminants were less than one, so the risk for human health was discarded. However, monitoring over time of the toxicity risks of the GGC soils would be advisable, especially due to the existence of areas where residual contamination persist, and soil hazard quotient obtained for As in children was higher and close to unity.


Assuntos
Metais Pesados , Poluentes do Solo , Criança , Humanos , Solo/química , Chumbo , Metais Pesados/análise , Poluentes do Solo/análise , Monitoramento Ambiental , Medição de Risco
3.
Rev. esp. cir. ortop. traumatol. (Ed. impr.) ; 64(5): 318-325, sept.-oct. 2020. tab, graf
Artigo em Espanhol | IBECS | ID: ibc-197610

RESUMO

INTRODUCCIÓN: Las infecciones osteoarticulares representan una complicación mayor en cirugía ortopédica. Se pretende identificar el porcentaje de cánulas de succión colonizadas y determinar la relación entre el tiempo de uso en cirugía y la colonización de estas. MATERIALES Y MÉTODOS: Estudio descriptivo y prospectivo que analiza 546 cánulas de succión utilizadas en cirugía ortopédica limpia en un centro de trauma, entre noviembre del 2017 a marzo del 2018. El extremo distal de la cánula fue cultivado para determinar la proporción de colonización. RESULTADOS: El 7,3% de las cánulas cultivadas tuvieron cultivos positivos para gérmenes patógenos, de los cuales el más frecuente fue Staphylococcus epidermidis con 27,5%. Además, se encontró asociación entre la colonización y el tiempo de uso de la cánula. La posibilidad de colonización de cánulas usadas entre 60 minutos o más, es mayor que en las que se usaron menos de 60 minutos; entre 60 y 90 minutos la posibilidad es dos veces mayor OR= 2,2 (IC:95% 1,1 - 4,1) y en las cánulas usadas por más de 90 minutos es 8 veces mayor OR= 8,49 (IC:95% 1,77 - 40,86). CONCLUSIONES: La proporción de colonización de las cánulas es menor a lo reportado en la literatura. El mayor tiempo de uso de la cánula en la cirugía aumenta el riesgo de la colonización de estas. Se considera realizar estudios de seguimiento para determinar si la colonización de las cánulas de succión se asocia a un incremento de infección postoperatoria


INTRODUCTION: Osteoarticular infections represent a major complication in orthopaedic surgery. The aim is to identify the percentage of suction cannulas colonised and to determine the relationship between the time they are used in surgery and the colonisation of these cannulas. MATERIALS AND METHODS: Descriptive and prospective study that analysed 546 suction cannulas used in clean orthopaedic surgery in a trauma centre, between November 2017 and March 2018. The distal end of the cannula was cultured to determine the colonisation rate. RESULTS: 7.3% of the cultured cannulas were positive for pathogens, the most frequent being Staphylococcus epidermidis at 27.5%. In addition, an association was found between colonisation and the length of time the cannula was used. The possibility of colonisation of cannulas used for between 60minutes or more, is greater than those used for less than 60 minutes; between 60 and 90 minutes the possibility is twice as high OR= 2.2 (CI:95% 1.1 - 4.1) and in cannulas used for more than 90 minutes it is 8 times higher OR= 8.49 (CI:95% 1.77 - 40.86). CONCLUSIONS: The colonisation rate of cannulas is lower than reported in the literature. The longer the cannula is used in surgery increases the risk of their colonisation. Follow-up studies are being considered to determine whether suction cannula colonisation is associated with increased postoperative infection


Assuntos
Humanos , Cânula/microbiologia , Sucção/instrumentação , Procedimentos Ortopédicos/estatística & dados numéricos , Doenças Ósseas Infecciosas/cirurgia , Contagem de Colônia Microbiana/métodos , Infecções Relacionadas a Cateter/microbiologia , Staphylococcus epidermidis/isolamento & purificação , Infecção da Ferida Cirúrgica/microbiologia
4.
ACS Omega ; 5(30): 18849-18861, 2020 Aug 04.
Artigo em Inglês | MEDLINE | ID: mdl-32775887

RESUMO

Controlling graphene conductivity is crucial for its potential applications. With this focus, this paper shows the effect of the non-covalent bonding of a pyrimidine derivative (HIS) on the electronic properties of graphene (G). Several G-HIS hybrids are prepared through mild treatments keeping unaltered the structures of both G and HIS. The attachment of HIS to G occurs by π-π stacking of the HIS-aromatic residue with the G surface. This partially blocks the p z electrons of G, giving rise to the splitting of both the valence and conduction bands. Moreover, the width of the splitting is directly related to the HIS content. This fact allows the fine-tuning of the band gap of G-HIS hybrids. Furthermore, HIS keeps its metal-complexing ability in the G-HIS hybrids. Taking advantage of this, a G-HIS-Cu(0) composite was prepared by H2 plasma reduction of a precursor of the G-HIS-Cu(II) type. G-HIS-Cu(0) contains Cu(0) clusters stabilized on the G surface due to interactions with the COO- functions of HIS. In an analogous hybrid, G-HIS-Au(0), the Au(0) NPs are also stabilized by COO- functions. This material, consisting of the coupling of Au(0) NPs and G-HIS, photocatalyzed water reduction under visible light radiation producing 12.5 µmol·g-1·h-1of hydrogen.

5.
Artigo em Inglês, Espanhol | MEDLINE | ID: mdl-32563632

RESUMO

INTRODUCTION: Osteoarticular infections represent a major complication in orthopaedic surgery. The aim is to identify the percentage of suction cannulas colonised and to determine the relationship between the time they are used in surgery and the colonisation of these cannulas. MATERIALS AND METHODS: Descriptive and prospective study that analysed 546 suction cannulas used in clean orthopaedic surgery in a trauma centre, between November 2017 and March 2018. The distal end of the cannula was cultured to determine the colonisation rate. RESULTS: 7.3% of the cultured cannulas were positive for pathogens, the most frequent being Staphylococcus epidermidis at 27.5%. In addition, an association was found between colonisation and the length of time the cannula was used. The possibility of colonisation of cannulas used for between 60minutes or more, is greater than those used for less than 60minutes; between 60 and 90minutes the possibility is twice as high OR= 2.2 (CI:95% 1.1 - 4.1) and in cannulas used for more than 90minutes it is 8 times higher OR= 8.49 (CI:95% 1.77 - 40.86). CONCLUSIONS: The colonisation rate of cannulas is lower than reported in the literature. The longer the cannula is used in surgery increases the risk of their colonisation. Follow-up studies are being considered to determine whether suction cannula colonisation is associated with increased postoperative infection.


Assuntos
Bactérias/isolamento & purificação , Cânula/microbiologia , Contaminação de Equipamentos , Procedimentos Ortopédicos/instrumentação , Sucção/instrumentação , Adulto , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Adulto Jovem
6.
Chem Sci ; 10(4): 1126-1137, 2019 Jan 28.
Artigo em Inglês | MEDLINE | ID: mdl-30774910

RESUMO

DNA molecules containing a 1D silver array may be applied for nanotechnology applications, but first their conducting and photoluminescence behavior must be enhanced. Here we have synthesized and characterized three new helical compounds based on stacked silver-mediated cytosine base pairs [Ag(mC)2]X (mC = N1-methylcytosine; X = NO3 (1), BF4 (2) and ClO4 (3)), that contain uninterrupted polymeric AgI chains that run through the center of the helixes, comparable to related silver-DNA structures. The exposure of nanostructures of [Ag(mC)2]BF4 (2) to cold hydrogen plasma stimulates the reduction of the prearranged AgI polymeric chains to metallic silver along the material. This solvent-free reduction strategy leads to the compound [AgI(mC)2]X@Ag0 (2H) that contains uniformly well-distributed silver metallic nanostructures that are responsible for the new conducting and photoluminescence properties of the material. The presence of silver nanostructures alongside compound 2H has been evaluated by means of X-ray photoelectron spectroscopy (XPS), UV-vis spectroscopy, and X-ray powder diffraction (XRPD). The conducting and photoactive properties of 2H were studied by electrostatic force microscopy (EFM) and conducting-AFM (c-AFM), and photoluminescence microscopy (PL), respectively. The results demonstrate that the presence of well-organized metallic silver nanoentities on the material is responsible for the novel conductivity and photoactive properties of the material. This methodology can be employed for the generation of multifunctional silver-DNA related materials with tailored properties.

8.
J Environ Manage ; 191: 228-236, 2017 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-28110163

RESUMO

Residual soil pollution from the Aznalcóllar mine spill is still a problem in some parts of the affected area, today converted in the Guadiamar Green Corridor. Dispersed spots of polluted soils, identified by the absence of vegetation, are characterized by soil acid pH and high concentrations of As, Pb, Cu and Zn. Ex situ remediation techniques were performed with unrecovered soil samples. Landfarming, Composting and Biopiles techniques were tested in order to immobilize pollutants, to improve soil properties and to promote vegetation recovery. The effectiveness of these techniques was assessed by toxicity bioassays: Lactuca sativa L. root elongation test, Vibrio fischeri bioluminescence reduction test, soil induced respiration test, and Eisenia andrei survival and metal bioaccumulation tests. Landfarming and Composting were not effective techniques, mainly due to the poor improvement of soil properties which maintained high soluble concentrations of Zn and Cu after treatments. Biopile technique, using adjacent recovered soils in the area, was the most effective action in the reduction of soil toxicity; the improvement of soil properties and the reduction in pollutants solubility were key to improve the response of the tested organisms. Therefore, the mixture of recovered soils with polluted soils in the areas affected by residual contamination is considered a more suitable technique to reduce the residual pollution and to promote the complete soil recovery in the Guadiamar Green Corridor.


Assuntos
Arsênio , Solo/química , Animais , Monitoramento Ambiental , Metais Pesados , Mineração , Poluentes do Solo
9.
Sci Technol Adv Mater ; 17(1): 541-553, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27877902

RESUMO

Controlling the chemistry on the surface of new carbon materials is a key factor to widen the range of their applicability. In this paper we show a grafting methodology of polyalkylamines to the surface of carbon nanomaterials, in particular, carbon nanotubes and a carbon black. The aim of this work is to reach large degrees of covalent functionalization with hyperbranched polyethyleneimines (HBPEIs) and to efficiently preserve the strong chelating properties of the HBPEIs when they are fixed to the surface of these carbon materials. This functionalization opens new possibilities of using these carbon nanotubes-based hybrids. The results show that the HBPEIs are covalently attached to the carbon materials, forming hybrids. These hybrids emerge from the reaction of amine functions of the HBPEIs with carbonyls and carboxylic anhydrides of the carbon surface which become imine and imide bonds. Thus, due to the nature of these bonds, the pre-oxidized samples with relevant number of C=O groups showed an increase in the degree of functionalization with the HBPEIs. Furthermore, both the acid-base properties and the coordination capacity for metal ions of the hybrids are equivalent to that of the free HBPEIs in solution. This means that the chemical characteristics of the HBPEIs have been efficiently transferred to the hybrids. To reach this conclusion we have developed a novel procedure to assess the acid-base and the coordination properties of the hybrids (solids) by means of potentiometric titration. The good agreement of the values obtained for the hybrids and for the free HBPEIs in aqueous solution supports the reliability of the procedure. Moreover, the high capacity of the hybrids to capture Ni2+ by complexation opens new possibilities of using these hybrids to capture high-value metal ions such as Pd2+ and Pt2+.

10.
Environ Pollut ; 208(Pt B): 553-61, 2016 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-26608875

RESUMO

Residual pollution in the Guadiamar Green Corridor still remains after Aználcollar mine spill in 1998. The polluted areas are identified by the absence of vegetation, soil acidic pH and high concentrations of As, Pb, Zn and Cu. Soil toxicity was assessed by lettuce root elongation and induced soil respiration bioassays. In bare soils, total As and Pb concentrations and water-extractable levels for As, Zn and Cu exceeded the toxicity guidelines. Pollutants responsible for toxicity were different depending on the tested organism, with arsenic being most toxic for lettuce and the metal mixture to soil respiration. Soil properties, such as pH or organic carbon content, are key factors to control metal availability and toxicity in the area. According to our results, there is a risk of pollution to living organisms and the soil quality criteria established in the area should be revised to reduce the risk of toxicity.


Assuntos
Monitoramento Ambiental , Metais Pesados/análise , Mineração , Poluentes do Solo/análise , Arsênio/análise , Poluição Ambiental/estatística & dados numéricos , Solo/química
11.
Ann Oncol ; 25(8): 1578-84, 2014 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-24827127

RESUMO

BACKGROUND: This phase II, open-label study investigated intercalated combinations of eribulin and erlotinib in unselected patients with advanced non-small-cell lung cancer previously treated with platinum-based chemotherapies. PATIENTS AND METHODS: Eligible patients were randomized to eribulin mesylate 2.0 mg/m(2) on day 1 with erlotinib 150 mg on days 2-16 (21-day regimen) or eribulin mesylate 1.4 mg/m(2) on days 1 and 8 with erlotinib 150 mg on days 15-28 (28-day regimen). The primary end point was objective response rate (ORR). RESULTS: One hundred and twenty-three patients received ≥ 1 cycle of therapy (63, 21-day regimen; 60, 28-day regimen). ORRs were 13% [95% confidence interval (CI) 6%-24%] and 17% (95% CI 8%-29%), and disease control rates were 48% (95% CI 35%-61%) and 63% (95% CI 50%-75%) for the 21- and 28-day regimens, respectively. The median progression-free survival and overall survival were similar with both regimens. Both regimens were well tolerated with common grade ≥ 3 toxicities being neutropenia, asthenia/fatigue, and dyspnoea. Sequential administration of erlotinib did not interfere with the pharmacokinetic profile of eribulin. CONCLUSION: Intercalated combination of eribulin and erlotinib demonstrated modest activity and the addition of erlotinib did not appear to improve treatment outcome in an unselected population. The 28-day regimen is suitable for further investigation. Clinicaltrials.gov identifier: NCT01104155.


Assuntos
Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Carcinoma Pulmonar de Células não Pequenas/tratamento farmacológico , Furanos/administração & dosagem , Cetonas/administração & dosagem , Neoplasias Pulmonares/tratamento farmacológico , Quinazolinas/administração & dosagem , Adulto , Idoso , Idoso de 80 Anos ou mais , Protocolos de Quimioterapia Combinada Antineoplásica/farmacocinética , Carcinoma Pulmonar de Células não Pequenas/patologia , Quimioterapia Adjuvante , Progressão da Doença , Intervalo Livre de Doença , Esquema de Medicação , Cloridrato de Erlotinib , Feminino , Furanos/farmacocinética , Humanos , Cetonas/farmacocinética , Neoplasias Pulmonares/patologia , Masculino , Pessoa de Meia-Idade , Quinazolinas/farmacocinética
12.
Rev Sci Instrum ; 82(3): 034903, 2011 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-21456780

RESUMO

We demonstrate the fabrication of acoustically engineered diamond nanoparticles-based metamaterials and their internal microstructure characterization using x-ray microcomputed tomography (XµCT). The state-of-the-art technique based on the radiation force of ultrasound standing (or stationary) waves in a rectangular chamber is utilized to pattern clusters of 5-nm-diameter diamond nanoparticles in parallel planes within a three-dimensional (3D) matrix of epoxy before solidification. Gradually, the periodic pattern becomes permanent with full cure of the epoxy matrix so as to form a 3D metamaterial structure. We also show that the periodicity of the pattern can be changed by selecting a different ultrasound frequency. Furthermore, XµCT is used as a quality control tool to map the internal structure and characterize each metamaterial. The ultimate application is to use the results as a base for the development of finite-element models which take into account all the structural features to study the various metamaterial (optical, acoustical, thermal, etc.) functional properties.

13.
Rev. méd. Urug ; 25(1): 59-68, mar. 2009.
Artigo em Espanhol | LILACS | ID: lil-512496

RESUMO

En este artículo se describe la última enfermedad y muerte del importante gran estadista uruguayo José Batlle y Ordóñez, 18 de setiembre al 20 de octubre de 1929. El relato está basado en tres importantes documentos, dos de ellos muy poco difundidos y conocidos y otro inédito.


The present article describes the last disease and death of important statesman José Batlle y Ordoñez, from 18 September through 20 October 1929.The account is based on three important documents, two of which scarcely made public and the third unpublished.


Neste artigo faz-se a descrição da última doença e da morte do importante estadista uruguaio José Batlle y Ordóñez, no período de 18 de setembro a 20 de outubro de 1929. Está baseado em três documentos importantes, dois deles pouco conhecidos e um terceiro documento inédito.


Assuntos
História da Medicina , Uruguai
14.
Eur. j. anat ; 12(3): 139-143, dic. 2008. tab
Artigo em Inglês | IBECS | ID: ibc-61833

RESUMO

Gamma-hydroxybutyrate (GHB), a precursorto gamma aminobutyric acid (GABA), wasinitially employed as an anesthetic. As a relativelynovel drug, few people are aware of itsharmful effects and few studies have beenundertaken to investigate its long-term effectsor its action on developing tissues.We performed an experimental study onthe action of GHB on the developing eye, anorgan very closely related to the developmentof the CNS. Chick embryos were treated with20% or 30% dilutions of 100 ìl GHB at 7(30-31 HH) and 11 (37 HH) days of incubation(i.e., two doses per group), and the effectswere observed at 21 days of incubation (45HH). An ophthalmologic ultrasonographydevice (Hondex A/B SCAN IS-500) was usedto measure different eye parameters (cornealthickness; posterior surface of cornea – anteriorsurface of lens; anteroposterior diameter oflens; anteroposterior diameter of eye).We observed significant differencesbetween the treated and control groups asregards the thickness of the cornea and lens,and in the anteroposterior diameter of the eye.The present results demonstrate a possibleeffect of GHB on development (AU)


No disponible


Assuntos
Animais , Hidroxibutiratos/uso terapêutico , Ácido gama-Aminobutírico/uso terapêutico , Embrião de Galinha/anatomia & histologia , Embrião de Galinha/inervação , Córnea/anatomia & histologia , Córnea/inervação , Embrião de Galinha/fisiopatologia , Olho/anatomia & histologia , Olho , Olho/inervação
15.
J Chromatogr A ; 1214(1-2): 121-7, 2008 Dec 19.
Artigo em Inglês | MEDLINE | ID: mdl-18995860

RESUMO

The methods to obtain the dispersive component of the surface energy (gamma(s)(d)) of active carbons (AC) from inverse gas chromatography (IGC) measurements usually render values much higher than those obtained by other techniques. In this paper this is ascribed to two factors: (i) the high temperatures at that IGC measurements are carried out and (ii) the microporosity of the AC. It is shown that the temperature dependence of the area of the methylene group is an important factor in the high gamma(s)(d) values. Thus, corrections for this dependence should be considered in the calculations. In relation to microporosity, the cooperative effect of the pore walls is also an important factor to be considered in the evaluation of gamma(s)(d). The values gamma(s)(d) obtained after these corrections have their own physical meaning related to ideal flat carbon surfaces. Critical comments are made about some reported relationships between gamma(s)(d), obtained from IGC, and the BET surface area or pore volume of AC as determined from nitrogen adsorption at 77K. These are based on the very different experimental conditions at which nitrogen and IGC measurements are carried out.


Assuntos
Carbono/química , Cromatografia Gasosa/métodos , Adsorção , Algoritmos , Nitrogênio , Porosidade , Propriedades de Superfície , Temperatura , Termodinâmica
16.
J Chromatogr A ; 1190(1-2): 271-7, 2008 May 09.
Artigo em Inglês | MEDLINE | ID: mdl-18394638

RESUMO

Inverse gas chromatography (IGC) is frequently used to study adsorption processes at zero surface coverage on microporous activated carbons. This allows to determine the thermodynamic adsorption parameters as equilibrium constants, V(S), standard enthalpies of adsorption, Delta HA degrees, standard free energy of adsorption, Delta GA degrees, and so on. Nevertheless, the surface areas of the adsorbents (microporous carbons in this case) are needed for this purpose. The experimental determination of the surface areas of microporous solids is not univocal and the results depend on the adsorbate employed in the measurements, usually N2 or CO2. This means that the thermodynamic parameters obtained by IGC are subjected to a degree of uncertainty depending on whether N2 or CO2 is used to determine the surface area values. The aim of this paper is to discuss which of the two surface area values is more appropriate to be used in IGC measurements at zero surface coverage. Experimental and theoretical considerations are supplied in a thorough discussion which supports that CO2 surface area value is more appropriate. Thus, it is proposed that this should be used instead of the more generally extended nitrogen specific surface area obtained by the BET equation.


Assuntos
Cromatografia Gasosa/métodos , Propriedades de Superfície
17.
J Phys Chem B ; 110(23): 11327-33, 2006 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-16771403

RESUMO

Activated carbon materials have been prepared by pyrolysis of plasma pretreated recycled PET. The obtained carbon materials have been texturally characterized by N2 (77 K) and CO2 (273 K) adsorption. Atomic force microscopy (AFM) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) have been used to analyze the surface of the treated precursors. Carbon materials obtained by He, N2, and CO2 plasma pretreatments (4 min) of the precursor and subsequent pyrolysis have shown a higher adsorption capacity than the corresponding chars (untreated pyrolised PET). This effect seems to be related to the elimination by the plasma treatments of low-molecular-weight products in the precursor, which are responsible for the formation of amorphous carbon deposits during the carbonization that blocks the porosity. Longer periods of treatment (15 min) do not favor the opening of the microporosity because cross-linking reactions in the precursor producing high molecular weight deposits prevail. The development of porosity is less relevant if oxygen plasma is used, as a considerable amount of oxygen functionalities are also formed. These groups can decompose during pyrolysation producing the above-mentioned amorphous carbon deposits. The textural characteristics of the carbon materials obtained after 4 min of plasma treatment on the precursor are very similar to those obtained after 4 h of CO2 (1073 K) activation of the same char. Therefore, this method can be an alternative to avoid the burnoff and high energy cost of the activation step.

18.
J Colloid Interface Sci ; 293(2): 353-63, 2006 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-16081090

RESUMO

This paper reports the modifications produced by nitrogen and helium cold plasmas on the surface of PET. The changes have been studied by diffuse reflectance Fourier transform spectroscopy (DRIFTS), atomic force microscopy (AFM) and inverse gas-solid chromatography (IGSC). Nitrogen and oxygen atoms seem to appear on the surface of PET as a consequence of the exposure to the atmosphere after the treatments with plasmas. AFM shows that both plasmas altered in different extent the surface of PET as they break the polymer chains producing low molecular products which appear as bumps on the surface. The surface area and the porosity of PET does not change by plasma treatments even after 15 min. The dispersive component of the surface free energy, gamma(s)(d), decreases after long treatments with nitrogen plasma whereas it remains almost unchanged after long treatment with helium plasma.

19.
J Colloid Interface Sci ; 287(1): 57-66, 2005 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-15914148

RESUMO

Poly(ethylene terephthalate) was exposed to oxygen and carbon dioxide plasmas for different periods of time. The surface-modified samples were characterized by infrared spectroscopy, atomic force microscopy, and inverse gas-solid chromatography. The main difference between both types of plasma was connected to the time scale of degradation, which was much faster when using oxygen plasma. Aggregate globular features were produced by different treatments due to chain scission and further recombination of evolved products. Oxygenated functionalities were introduced in significant amounts after long exposure times to the oxygen plasma. As a consequence, the specific component of the surface free energy was clearly observed to increase after these long treatments.


Assuntos
Dióxido de Carbono/química , Oxigênio/química , Polietilenotereftalatos/química , Tensoativos/química , Temperatura Alta , Microscopia de Força Atômica , Espectroscopia de Infravermelho com Transformada de Fourier , Propriedades de Superfície , Termodinâmica , Fatores de Tempo
20.
J Colloid Interface Sci ; 248(1): 116-22, 2002 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-16290511

RESUMO

This paper deals with the use of several methods to characterize the chemical surface groups of carbon materials. Several samples embracing a wide range of acidic and basic characteristics have been used for this purpose. The quantitative determinations have been carried out by selective titrations in aqueous solutions, thermal programmed desorption connected to mass spectrometry (TPD-MS), and ammonia adsorption-desorption, measured by thermogravimetry (TG). The results show some inconsistencies between the different experimental methods. These mainly arise because chemical transformations can be produced during the experiments. Moreover, the textural characteristics of the carbon materials and the existence of pi electrons on the graphitic planes are important factors to be considered in the discussion of the results.

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