Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 19 de 19
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Biol Trace Elem Res ; 2023 Sep 25.
Artigo em Inglês | MEDLINE | ID: mdl-37747654

RESUMO

Cardiomyopathies (CMP) represent a significant health problem as they have a poor long-term prognosis and often require transplantation. Heavy metals are known to have cardiotoxic effects and some of them, such as cadmium (Cd), are found to be elevated in the urine and blood of individuals with heart diseases; nevertheless, direct measurement of metals (e.g. zinc (Zn) which is necessary for normal heart function), in the myocardium of individuals with CMP has not been performed. Here, we aimed to analyze the levels of a group of metals in the myocardium of the left ventricle in individuals with CMP. At the Institute of Pathology, we collected 52 samples of left ventricle post-mortem, out of which 19 subjects had been diagnosed with CMP (mean age: 72 y ± 10), and 33 subjects had not suffered from any heart disease (mean age: 67 y ± 15). We found out that individuals with CMP had a significantly higher concentrations of lead, nickel, manganese and copper than non-CMP subjects (p = 0.002, p < 0.001, p = 0.011, and p = 0.002). Interestingly, zinc was significantly lower in CMP subjects than in n-CMP individuals (p = 0.017). Our results indicated the involvement of an increased lead, nickel, copper and manganese heart load in individuals with CMP coupled with lower concentrations of zinc.

2.
Nutrients ; 15(12)2023 Jun 16.
Artigo em Inglês | MEDLINE | ID: mdl-37375681

RESUMO

Diet during pregnancy is one of the most important nutritional challenges associated with some risks for the mother and the fetus. For the first time, the study aims to estimate long-term (2018-2022) exposure to nitrate and phosphates in Serbian pregnant women, based on individual consumption data and accurate values measured in frequently consumed meat products. For this purpose, seven types of meat products, consisting of 3047 and 1943 samples, were collected from retail markets across Serbia, to analyze nitrites and phosphorus content, respectively. These data were combined with meat product consumption data from the Serbian National Food Consumption Survey to assess dietary intake of nitrites and phosphate. The results were compared with the acceptable daily intake (ADI) proposed by the European Food Safety Authority. The average dietary exposure (EDI) to phosphorus ranged from 0.733 mg/kg bw/day (liver sausage and pate) to 2.441 mg/kg bw/day (finely minced cooked sausages). Considering nitrite intake, the major sources were bacon (0.030 mg/kg bw/day) and coarsely minced cooked sausages (0.0189 mg/kg bw/day). In our study, average nitrite and phosphorus exposure in the Serbian pregnant women population are far below the EFSA recommendations (ADI 0.07 mg/kg bw/day and 40 mg/kg bw/day, respectively).


Assuntos
Produtos da Carne , Nitritos , Gravidez , Feminino , Humanos , Produtos da Carne/análise , Gestantes , Fosfatos , Dieta , Fósforo , Carne/análise
3.
Acta Chim Slov ; 69(4): 803-810, 2022 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-36562160

RESUMO

The binary adsorption isotherms of volatile organic compounds (VOCs), and water vapor from the air have been the focus of much research in recent years. The content of adsorbed VOCs in the presence of water vapor can be determined by the volumetric or gravimetric method, in a static or dynamic mode. This study focuses on the adsorption technique in a static mode for isotherm measurement of the co-adsorption of VOCs and water vapor from the air using the gravimetric method. The content of VOCs is determined using a total organic carbon analyzer, while the amount of the adsorbed water was calculated from the difference between total adsorption (VOCs and water) and the adsorbed VOCs. This paper presents several adsorption isotherms with different VOCs (toluene, benzene, methanol, ethanol and isopropyl alcohol) and adsorbents (ZSM-5 zeolite, silica gel and Na-Form mordernite) in the presence of water vapor. The well-known adsorption isotherm models (Langmuir, extended Langmuir, Freundlich, extended Freundlich and Hill) were used to treat experimental results. The adjusted R-Squared (adj. R2)  values obtained for those non-linear models for isotherms (total adsorpton (qe,tot) as a function of equilibrium concentration of VOC (Ce) and the adsorbed VOC (qe) as a function of equilibrium concentration of VOC (Ce) are used to determine the best-fit isotherm model. The modeling results showed that the 3-parameter models could fit the data better than the 2-parameter model, with relatively higher adj. R2. Experimental results demonstrate that the presented adsorption technique can be used for isotherm measurement of the co-adsorption of VOCs and water vapor from the air.

4.
Cancers (Basel) ; 13(7)2021 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-33915703

RESUMO

Autologous dendritic cells (DCs)-based vaccines are considered quite promising for cancer immunotherapy due to their exquisite potential to induce tumor antigen-specific cytotoxic T cells. However, a lack of efficient protocols for inducing immunogenic tumor antigens limits the efficacy of DC-based cancer vaccines. Here, we found that a plasma-activated medium (PAM) induces immunogenic cell death (ICD) in tumor cells but not in an immortalized L929 cell line or human peripheral blood mononuclear cells. PAM induced an accumulation of reactive oxygen species (ROS), autophagy, apoptosis, and necrosis in a concentration-dependent manner. The tumor lysates prepared after PAM treatment displayed increased immunogenicity in a model of human monocyte-derived DCs, compared to the lysates prepared by a standard freezing/thawing method. Mature DCs loaded with PAM lysates showed an increased maturation potential, as estimated by their increased expression of CD83, CD86, CD40, IL-12/IL-10 production, and attenuated PDL1 and ILT-4 expression, compared to the DCs treated with control tumor lysates. Moreover, in co-culture with allogeneic T cells, DCs loaded with PAM-lysates increased the proportion of cytotoxic IFN-γ+ granzyme A+ CD8+ T cells and IL-17A-producing T cells and preserved the Th1 response. In contrast, control tumor lysates-treated DCs increased the frequency of Th2 (CD4+IL-4+), CD4, and CD8 regulatory T cell subtypes, none of which was observed with DCs loaded with PAM-lysates. Cumulatively, these results suggest that the novel method for preparing immunogenic tumor lysates with PAM could be suitable for improved DC-based immunotherapy of cancer patients.

5.
J Sci Food Agric ; 99(11): 5202-5210, 2019 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-31032967

RESUMO

BACKGROUND: The impact of climate change has been identified as an emerging issue worldwide owing to potential effects that can provoke changes in the nature and occurrence of food safety hazards. Mycotoxins are a group of naturally occurring toxic substances produced by several genera of filamentous fungi, among which, primarily aflatoxins, fumonisins, ochratoxins, trichothecenes and zearalenone are of the greatest concern owing to their negative impact on human health, animal productivity and international trade. RESULTS: Extreme weather conditions such as floods and droughts which have not occurred previously in Serbia may be supporting factors for contamination of crops by various species of toxigenic fungi and their related mycotoxins. In this study, principal component analysis (PCA) and multivariate analyses were used as powerful tools allowing better understanding of the range of climate factors impacting on crop contamination by mycotoxins. Among the selected environmental variables, temperature and moisture significantly influenced aflatoxin production. Recent drought and then flooding confirmed that Serbia is one of the few European countries with very high risk exposure to natural hazards, as well as that mycotoxins are one of the foodborne hazards most susceptible to climate change. Thus climate change effects on mycotoxigenic fungi and mycotoxin contamination are now receiving scientific attention, especially from a risk analysis perspective. CONCLUSION: This paper evaluates the available information on the influence of climate change on mycotoxin contamination, especially aflatoxin M1 (AFM1). In addition, this investigation should beneficially contribute to more accurate predictions of the regional risk from mycotoxins in future decades. © 2019 Society of Chemical Industry.


Assuntos
Aflatoxina M1/análise , Produtos Agrícolas/microbiologia , Leite/química , Aflatoxina M1/metabolismo , Ração Animal/análise , Animais , Aspergillus/metabolismo , Bovinos , Mudança Climática , Produtos Agrícolas/química , Ecossistema , Feminino , Contaminação de Alimentos/análise , Inocuidade dos Alimentos , Modelos Biológicos , Análise de Componente Principal , Sérvia , Temperatura
6.
Clin Oral Investig ; 23(3): 1383-1396, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30022272

RESUMO

OBJECTIVES: The study aims to evaluate the effects of non-thermal atmospheric plasma (NTAP) treatments on dentin wetting and surface free energy (SFE) and compare the effects of NTAP treatment, etch-and-rinse, and self-etch protocols for application of universal adhesives. MATERIALS AND METHODS: Mid-coronal dentin of intact third molars was used to measure contact angles of distilled water, ethylene-glycol, and diiodomethane and calculate SFE following different NTAP preset treatments (feeding gas consisting of pure He, He + 1% O2, He + 1.5% O2), power input (1 or 3 W), and tip-to-surface distance (2, 4, or 8 mm). Contact angles of reference liquids and SFE of dentin following He + 1.5% O2 at 3-W and 4-mm treatment was compared to phosphoric acid etching. Contact angles of Single Bond Universal (SBU; 3M ESPE) and Clearfil Universal Bond (CUB; Kuraray Noritake) were measured following NTAP, etch-and-rinse, and self-etch protocols. RESULTS: NTAP significantly reduced contact angles of reference liquids and increased dentin SFE compared to untreated dentin (p < 0.05). O2 intensified the effect of He NTAP (p < 0.05). NTAP and phosphoric acid increased dentin polarity and Lewis base surface characteristics. Phosphoric acid increased contact angles of adhesives compared to the self-etch protocol (p < 0.05). NTAP resulted in lower adhesive contact angles than phosphoric acid, the difference being statistically significant for CUB (p < 0.05). Compared to the self-etch protocol, NTAP slightly reduced CUB contact angle but not that of SBU (p > 0.05). CONCLUSIONS: He NTAP with and without O2 increased dentin wetting and SFE, surpassing the effect of phosphoric acid and lowering adhesive contact angles. NTAP produced no apparent micro-morphological changes on dentin surface comparable to acid etching. CLINICAL SIGNIFICANCE: NTAP treatment of dentin prior to adhesive application increases dentin wetting and surface free energy facilitating better adhesive distribution on dentin surface compared to phosphoric acid etching and similar to the "self-etch" application protocol.


Assuntos
Colagem Dentária , Dentina , Gases em Plasma , Cimentos Dentários , Adesivos Dentinários , Teste de Materiais , Cimentos de Resina , Propriedades de Superfície , Resistência à Tração
7.
Polymer (Guildf) ; 121: 26-37, 2017 Jul 14.
Artigo em Inglês | MEDLINE | ID: mdl-28970639

RESUMO

Novel fast response shape-memory polyurethanes were prepared from bio-based polyols, diphenyl methane diisocyanate and butane diol for the first time. The bio-based polyester polyols were synthesized from 9-hydroxynonanoic acid, a product obtained by ozonolysis of fatty acids extracted from soy oil and castor oil. The morphology of polyurethanes was investigated by synchrotron ultra-small angle X-ray scattering, which revealed the inter-domain spacing between the hard and soft phases, the degree of phase separation, and the level of intermixing between the hard and soft phases. We also conducted thorough investigations of the thermal, mechanical, and dielectric properties of the polyurethanes, and found that high crystallization rate of the soft segment gives these polyurethanes unique properties suitable for shape-memory applications, such as adjustable transition temperatures, high degree of elastic elongations, and good mechanical strength. These materials are also potentially biodegradable and biocompatible, therefore suitable for biomedical and environmental applications.

8.
Environ Sci Pollut Res Int ; 21(24): 14058-68, 2014 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-25047014

RESUMO

A total of 63 European hares have been collected from five Serbian agricultural regions. The hares assayed were divided into four age groups (3-6 months, 12 months, 12-24 months, and 24-36 months) and investigated upon presence at cadmium (Cd) and mercury (Hg) in the kidney and liver. The positive significant correlation (Ps-Pearson's coefficient) between Cd concentrations in the kidney and liver within age group the 3-6 months was found (Ps = 0.81, p < 0.001). Differences between Cd content in the kidney in comparison to liver were significant within all presented age groups (p < 0.001). Differences between recorded Hg levels in the kidney were not significant between presented age groups (p > 0.05). Statistically significant differences were registered between Hg content in the liver of the hares aged 24-36 and 12 months (p < 0.05). There were no statistically significant correlations registered between Hg concentrations in the kidney and liver within any particular age group (p > 0.05). The strong statistically significant associations were registered between Cd and Hg content in the liver (Cd L/Hg L) in the age group 3-6 and 12-24 months (Cd L/Hg L, Ps = 0.94; p < 0.001 and Ps = 0.91; p < 0.001, respectively). The polynomial regression model used for graphing the observed data seems to be a method for modeling the relationship between measured Cd and Hg concentrations in the liver and kidney as first approximation for bioaccumulation in hares.


Assuntos
Envelhecimento , Cádmio/química , Lebres , Rim/química , Fígado/química , Mercúrio/química , Animais , Monitoramento Ambiental , Poluentes Ambientais/química , Feminino , Masculino , Sérvia
9.
Lipids Health Dis ; 13: 42, 2014 Mar 03.
Artigo em Inglês | MEDLINE | ID: mdl-24588940

RESUMO

BACKGROUND: The objective of the study was to present information about the chemical composition, the fatty acids profile, and cholesterol content of chicken meat in order to investigate the impact of chicken meat consumption on cardiovascular risk in the general population. METHODS: A total of 48 6-wk-old broiler chickens broilers from two farms in June to November of 2012, and February of 2013, were used in this trial. Total lipid content was determined by extraction of fat by petrol ether (Soxhlet) after acid hydrolysis of samples. Fatty acids were determined by capillary gas chromatography. Cholesterol determination was performed by using HPLC/PDA system. RESULTS: The results indicate that the total free cholesterol content in raw breast and drumstick of chickens was in the range of 37,41-79,9 mg/100 g and 48,35-99,5 mg/100 g, respectively. The main fatty acids identified in all cuts were C18:1c9, C18:2n6, C16:0, C18:0, and C16:1. Decreasing the dietary n-6/n-3 clearly decreased the content in breast and drumstick muscle of C18:2n6, C18:3n3, and C20: 3n6, but increased that of C16:0, C18:0, and C20:2. Also, the major saturated fatty acid (SFA) (C16:0 and C18:0) was significantly differ among the four treatments. CONCLUSION: Our study shows that dietary fat and fatty acid composition influence the concentrations of total cholesterol content, total fat content, and fatty acid composition in broiler muscle. This information will aid in determining the burden of chicken meat as a cardiovascular risk factors disease and act as a planning tool for public-health Programmes.


Assuntos
Doenças Cardiovasculares/etiologia , Colesterol/metabolismo , Ácidos Graxos Insaturados/metabolismo , Ácidos Graxos/metabolismo , Carne/efeitos adversos , Ração Animal , Animais , Galinhas/metabolismo , Culinária , Dieta/efeitos adversos , Feminino , Humanos , Masculino , Músculo Esquelético/metabolismo , Fatores de Risco
10.
Appl Radiat Isot ; 83 Pt B: 148-54, 2014 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-23466009

RESUMO

In this paper we make a parallel between the swarm method in physics of ionized gases and modeling of positrons in radiation therapy and diagnostics. The basic idea is to take advantage of the experience gained in the past with electron swarms and to use it in establishing procedures of modeling positron diagnostics and therapy based on the well-established experimental binary collision data. In doing so we discuss the application of Monte Carlo technique for positrons in the same manner as used previously for electron swarms, we discuss the role of complete cross section sets (complete in terms of number, momentum and energy balance and tested against measured swarm parameters), we discuss the role of benchmarks and how to choose benchmarks for electrons that may perhaps be a subject to experimental verification. Finally we show some samples of positron trajectories together with secondary electrons that were established solely on the basis of accurate binary cross sections and also how those may be used in modeling of both gas filled traps and living organisms.

11.
Coll Antropol ; 38 Suppl 2: 191-4, 2014 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-25643548

RESUMO

Croatia started implementing the national programs for early breast cancer detection in 2006, early detection of colon cancer and early detection of cervical cancer. A possible way to improve the adherence of the women to the screening on breast cancer could be by transferring the responsibility for the program implementation from the public health institutes to family physicians. The Project: "Model of early cancer detection integrated in a practice of family physician", was carried out by the Department of Family Medicine of the Osijek University School of Medicine. The results have shown that responsiveness of women invited to do preventive mammography was significantly higher in the experimental than in the control group. The central role of FM in the implementation of preventive programmes has already been recognized in many countries as an advantage from the organizational aspects and by means of decreased expenditure, compared to the vertical programmes with strict formal control centered to the public institutions.


Assuntos
Neoplasias da Mama/diagnóstico por imagem , Medicina de Família e Comunidade/organização & administração , Mamografia , Programas de Rastreamento/organização & administração , Programas Nacionais de Saúde/organização & administração , Neoplasias da Mama/prevenção & controle , Neoplasias da Mama/terapia , Croácia , Feminino , Humanos
12.
Bull Environ Contam Toxicol ; 90(2): 203-7, 2013 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-23212889

RESUMO

A total of 84 European hares collected from eleven Serbian regions investigated upon cadmium (Cd) and zinc (Zn) presence. Strong statistically significant correlations between Cd concentrations in kidney and liver were registered in animals older than 12 months. Significant differences between Zn concentrations in liver in comparison to kidney were found within every single age group with exception of the oldest. Negative correlation (Ps-Pearson's correlation) between Zn and Cd concentrations were found in liver samples within the age group of 12 months (Ps = -0.67, p = 0.004).


Assuntos
Cádmio/metabolismo , Poluentes Ambientais/metabolismo , Rim/metabolismo , Fígado/metabolismo , Zinco/metabolismo , Fatores Etários , Animais , Cádmio/farmacocinética , Poluentes Ambientais/farmacocinética , Lebres , Sérvia , Distribuição Tecidual , Zinco/farmacocinética
13.
Biomacromolecules ; 13(1): 261-6, 2012 Jan 09.
Artigo em Inglês | MEDLINE | ID: mdl-22148512

RESUMO

New monomers were prepared by introducing the azide groups in castor, canola, corn, soybean, and linseed oils. Polymerization of the azidated oils with alkynated soybean oil under thermal "click" chemistry conditions (without using a solvent or a catalyst) yielded fully cross-linked elastomers (1-5) of almost the same density (1.05 × 10(-3) kg/m(3)). The degree of cross-linking gradually increased from the castor-derived polymer (220 mol/m(3)) to the linseed-derived polymer (683 mol/m(3)). A systematic correlation between the degree of cross-linking and the thermal and mechanical properties was observed in these biopolymers. Tensile strength (0.62-3.39 MPa) and glass transition temperature (-5 to 16 °C) increased and the linear thermal expansion coefficient decreased in the series from the canola-derived polymer (2) to the linseed-derived polymer (5). The castor-derived polymer (1) that possesses an additional hydroxyl group per fatty acid chain behaved differently.


Assuntos
Química Click/métodos , Óleos de Plantas/química , Polímeros/química , Polímeros/síntese química , Transição de Fase , Resistência à Tração
14.
Med Arh ; 63(2): 64-6, 2009.
Artigo em Inglês | MEDLINE | ID: mdl-19537657

RESUMO

We report genetic counseling and prenatal diagnostics in the Obstetrics and Gynecology Department of the Clinical Center Brcko District (BiH) which works for more than 4 years in prevention of giving birth to children with hereditary diseases and congenital malformations. Pregnant women from Brcko District, Tuzla Canton and wider area of BiH underwent genetic counseling. In the period from 2003 to 2007, 1234 pregnant woman underwent amniocentesis and genetic counseling. Among them 27 foetuses with chromosome disorders were discovered (2.19%). There were 9 (0.72%) cases of autosomal numerical aberrations, 9 (0.72%) of numerical anomalies of sex chromosomes and 12 (1.07%) of structural chromosome aberrations. Chordocentesis was performed in 86 pregnant women: 7 foetuses were found carrying chromosome aberrations (8.14%). Frequency of chromosomes in comparison to the Centre of Medicine Genetics in the Children Clinic in Novi Sad (Serbia) indicates that it is significantly higher (1.67% compared to 2.19%), and in both cases the populations are significantly large (12210:1234)--there is a large difference in structural chromosomal aberrations (0.39% -1.07%). This could point to harmful factors of the environment which contribute to induced genome damages. Frequency of chromosomopathies found by prenatal diagnostics is high. The causes for this have to be looked for, but the increase of structural anomalies points to environmental factors.


Assuntos
Transtornos Cromossômicos/diagnóstico , Aconselhamento Genético , Diagnóstico Pré-Natal , Bósnia e Herzegóvina , Transtornos Cromossômicos/prevenção & controle , Anormalidades Congênitas/diagnóstico , Anormalidades Congênitas/genética , Anormalidades Congênitas/prevenção & controle , Feminino , Humanos , Masculino , Gravidez
15.
Int J Environ Res Public Health ; 6(12): 3127-42, 2009 12.
Artigo em Inglês | MEDLINE | ID: mdl-20049251

RESUMO

In order to ensure the safety of consumers in Serbia the prevalence of toxic elements (As, Cd, Hg, Pb) in swine kidney collected from three different areas in Serbia (n = 90) was determined by atomic absorption spectrometry. Also, in order to find information on the effects of accumulation of toxic elements on swine kidney, pathohistological examination of the kidneys was performed. The presence of mercury was found in 33.3% of kidney samples in the range of 0.005-0.055 mg/kg, while the presence of cadmium was detected less often (27.7%) but in larger amounts (0.05-1.23 mg/kg). The presence of arsenic was found only in one sample, while no lead was found. The results of the metal-to-metal correlation analysis supported there were the result of different sources of contamination. Pathohistological examination of kidneys confirms tubulopathies with oedema and cell vacuolization. In addition, haemorrhages and necrosis of proximal kidney tubule cells were found. This study demonstrates that toxic elements in Serbian slaughtered pigs are found at levels comparable to those reported in other countries, and consequently the levels reported in this study do not represent a concern from a consumer safety point of view. The lack of a strong correlation between histopathological changes and the incidence of toxic elements found in this study might be explained as the result of synergism among toxic elements and other nephrotoxic compounds which enhance the toxicity of the individual toxins even at the relatively low mean concentrations observed in this study.


Assuntos
Abastecimento de Alimentos , Rim , Metais Pesados/toxicidade , Saúde Pública , Medição de Risco/métodos , Segurança , Suínos , Animais , Arsênio/toxicidade , Cádmio/toxicidade , Qualidade de Produtos para o Consumidor , Poluição Ambiental , Humanos , Chumbo/toxicidade , Mercúrio/toxicidade , Sérvia , Espectrofotometria Atômica , Estatística como Assunto
16.
Acta Chir Iugosl ; 53(2): 143-50, 2006.
Artigo em Inglês | MEDLINE | ID: mdl-17139902

RESUMO

PURPOSE: We studied the prognostic value of thymidylate synthase (TS), Epidermal Growth Factor Receptors (EGFR) and Vascular Endothelial Growth Factor (VEGF) expression in primary colon cancer (CC). PATIENTS AND METHODS: Those three markers were immunohistochemically assessed on tumour sections from 100 patients with CC Dukes C. All patients received the same adjuvant chemotherapy with FU/Leukovocin according to Mayo protocol. Considering the clinical course they were classified in two groups: bad in which all patients progressed and good in which neither progressed during the five year follow up period. RESULTS: TS, EGFR and VEGF were an independent prognostic factor for time to progression (TTP) and overall survival (OS). Findings of at least two maximum expressed investigated markers, significantly increases the risk of progression which influences shorter five year survival, and the single maximum expression does not necessarily have to be a bad prognostic sign. CONCLUSION: Highest expression of TS, EGFR and VEGF carries prognostic significance with respect to TTP and OS for patients with Dukes C colon cancer.


Assuntos
Biomarcadores Tumorais/análise , Neoplasias do Colo/diagnóstico , Receptores ErbB/análise , Timidilato Sintase/análise , Fator A de Crescimento do Endotélio Vascular/análise , Neoplasias do Colo/química , Progressão da Doença , Humanos , Prognóstico
17.
Biomacromolecules ; 6(2): 713-9, 2005.
Artigo em Inglês | MEDLINE | ID: mdl-15762634

RESUMO

Ozonolysis was used to obtain polyols with terminal primary hydroxyl groups and different functionalities from trilinolein (or triolein), low-saturation canola oil, and soybean oil. The functionality of the model polyol from triolein (trilinolein) was 3.0 and that of soy polyol was 2.5, due to the presence of unreactive saturated fatty acids, while canola gave a polyol with a functionality of 2.8. All polyols exhibited a high tendency to crystallize at room temperature. The resulting waxes had melting points comparable to that of paraffin and very low viscosities in the liquid state. The polyols were cross-linked using 4,4'-methylenebis(phenyl isocyanate) to give polyurethanes. Glass transitions (T(g)) for the model-, canola-, and soy-based polyurethanes were 53, 36, and 22 degrees C, respectively. The about 30 degrees C lower T(g) of the soy-based polyurethane than that of the model polyurethane was the result not only of lower functionality but also of the presence of saturated fatty acids in the former. Polyurethane from the canola polyol had intermediate cross-linking density and properties. These polyurethanes displayed excellent mechanical properties and higher glass transition temperatures compared to polyurethanes from epoxidized and hydroformylated polyols of the same functionality, presumably due to the absence or lower content of dangling chains in the former.


Assuntos
Ozônio/química , Poliuretanos/síntese química , Triglicerídeos/química , Transição de Fase , Óleos de Plantas/química , Polímeros/química , Poliuretanos/química , Temperatura
18.
Environ Sci Technol ; 37(5): 1008-12, 2003 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-12666933

RESUMO

The aim of this study was to highlight the possibility of using recycled wool-based nonwoven material as a sorbent in an oil spill cleanup. This material sorbed higher amounts of base oil SN 150 than diesel or crude oil from the surface of a demineralized or artificial seawater bath. Superficial modification of material with the biopolymer chitosan and low-temperature air plasma led to a slight decrease of sorption capacity. Loose fibers of the same origin as nonwoven material have significantly higher sorption capacities than investigated nonwoven material. White light scanning interferometry analysis of the fibers suggested that roughness of the wool fiber surface has an important role in oil sorption. The laboratory experiments demonstrated that this material is reusable. Recycled wool-based nonwoven material showed good sorption properties and adequate reusability, indicating that a material based on natural fibers could be a viable alternative to commercially available synthetic materials that have poor biodegradability.


Assuntos
Carcinógenos Ambientais , Conservação dos Recursos Naturais , Gasolina , Petróleo , Poluentes do Solo , Lã/química , Adsorção , Animais , Biodegradação Ambiental , Poluição Ambiental/prevenção & controle
19.
Biomacromolecules ; 3(5): 1048-56, 2002.
Artigo em Inglês | MEDLINE | ID: mdl-12217052

RESUMO

Polyurethane networks based on vegetable oils have very heterogeneous composition, and it is difficult to find a close correlation between their structure and properties. To establish benchmark structure-properties relationships, we have prepared model polyurethane networks based on triolein and 4,4'-diphenylmethane diisocyanate (MDI). Cross-linking in the middle of fatty acid chains leaves significant parts of the triglyceride as dangling chains. To examine their effect on properties, we have synthesized another polyurethane network using triolein without dangling chains (removed by metathesis). The structure of polyols was studied in detail since it affects the structure of polyurethane networks. The network structure was analyzed from swelling and mechanical measurements and by applying network and rubber elasticity theories. The cross-linking density in both networks was found to be close to theoretical. The triolein-based model network displayed modulus (around 6 MPa), tensile strength (8.7 MPa), and elongation at break (136%), characteristic of hard rubbers. Glass transition temperatures of the networks from triolein and its metathesis analogue were 25 and 31.5 degrees C, respectively.


Assuntos
Poliuretanos/síntese química , Trioleína/química , Estrutura Molecular , Oxirredução , Óleos de Plantas/química , Polímeros , Poliuretanos/química , Estresse Mecânico , Temperatura , Resistência à Tração
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...