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1.
J Environ Manage ; 266: 110604, 2020 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-32310125

RESUMO

The high exposure to the endocrine disrupting compounds (EDC) in water represents a relevant issue for the health of living beings. The xenoestrogen Bisphenol A (BPA), a suspected EDC, is an industrial additive broadly used for manufacturing polycarbonate and epoxy resins. Due to its harmful effect in humans and the aquatic environment, an efficient method to remove BPA from wastewater is urgently required. The present work aims to study the adsorption of BPA from aqueous solutions onto carbonaceous materials, e.g., a synthesized carbon xerogel (RFX), a chemical-activated carbon from Kraft lignin (KLP) and a commercial activated carbon (F400) for comparative purposes. Batch kinetic and adsorption tests of BPA in ultrapure water were accomplished, finding higher adsorption capacities of BPA onto both F400 activated carbon (qsat = 407 mg g-1) and the biochar KLP (qsat = 220 mg g-1), versus to that obtained for the xerogel (qsat = 78 mg g-1). Furthermore, kinetic experiments revealed faster kinetic adsorption for RFX and KLP materials, achieving the equilibrium time within 24 h, attributed to their more-opened porous structure. Pseudo-first order, pseudo-second order, Elovich, intra-particle diffusion and film diffusion models were used to fit the experimental data. Thus, the BPA adsorption isotherms were analysed by Langmuir, Freundlich, Sips, Redlich-Peterson and Dual-site Langmuir (DLS) isotherm models.In addition, the influence of different aqueous matrices, such as a hospital wastewater, a wastewater treatment plant (WWTP) effluent and a river water, on BPA removal efficiency has been explored. These adsorption tests revealed a clear competitive effect between the target compound (BPA) and the natural organic matter content (NOM) present in the matrices for the active sites, resulting in a high decreasing of BPA adsorption removal.


Assuntos
Disruptores Endócrinos , Poluentes Químicos da Água , Purificação da Água , Adsorção , Compostos Benzidrílicos , Cinética , Fenóis
2.
J Environ Qual ; 47(4): 766-773, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30025048

RESUMO

No-till and increased cropping intensity (CI) can increase yield and soil organic C (SOC) in the US Great Plains compared with traditional wheat ( L.)-fallow management. However, gains in SOC and other C pools may not be permanent. Increasing frequency of drought may reduce C inputs and potentially reverse gains accrued during wetter periods. This study examined the effect of drought on the persistence of SOC with two objectives: (i) to determine soil C pools (0-20 cm) after 24 yr in no-till as influenced by potential evapotranspiration (PET), landscape position (slope), and CI; and (ii) to compare the size of the C pools after the first 12 yr (wet) versus the subsequent 12 yr, notable for frequent droughts. Rotations were wheat-corn ( L.)-fallow (WCF), continuous cropping (CC), and a grass Conservation Reserve Program mixture planted across slopes at three sites in Colorado with similar precipitation but increasing PET. After 24 yr, water-soluble organic C increased with CI from WCF to CC to grass with 250, 340, and 440 kg C ha, respectively. Soil microbial biomass C also increased with CI-1500, 1660, and 2135 kg C ha for WCF, CC, and grass, respectively. The particulate organic matter C pool had a three-way interaction with PET, slope, and CI. Overall, between Years 12 and 24, SOC increased in grass by 16.9%, with a rate of 425 kg C ha yr sequestration compared with 10.5 and 1.4% for the WCF and CC systems, respectively.


Assuntos
Carbono , Secas , Solo/química , Agricultura , Colorado
3.
Plant Dis ; 96(7): 1073, 2012 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30727247

RESUMO

Ascochyta blight, caused by Ascochyta rabiei, is a serious disease of chickpea (Cicer arietinum) and fungicide applications are used to manage the disease in the North Central plains (4). During the 2010 growing season, a commercial field near Stanley, SD was treated with pyraclostrobin (Headline, BASF, NC) and called a management failure by the grower. Similarly, limited efficacy of pyraclostrobin was observed in an ascochyta research trial near Scott's Bluff, NE. In both locations, symptoms and signs consistent with A. rabiei infection existed on leaves, stems, and pods; namely, circular brown lesions with concentric rings of dark brown pycnidia. Symptomatic samples were collected, disinfected with 95% ethanol for 1 min, rinsed with sterile water, placed in 0.5% NaOCl for 1 min, and rinsed again with sterile water for 1 min (4). Samples were air dried, placed on potato dextrose agar (PDA) plates for 3 to 7 days, and colonies with morphological characteristics typical of A. rabiei were single-spored and transferred to new PDA plates and incubated for 7 to 14 days. Three and six putative A. rabiei isolates were obtained from South Dakota and Nebraska samples, respectively. Morphological characteristics were consistent with A. rabiei; cultures were brown with concentric rings of dark, pear-shaped pycnidia with an ostiole, and conidia were hyaline, single-celled, and oval-shaped (2). Comparison of the internal transcribed spacer (ITS) region amplified from the genomic DNA of 3-day-old liquid cultures using ITS4/ITS5 primers by BLASTN searches using the nr database in GenBank (Accession Number FJ032643) also confirmed isolates to be A. rabiei. Mismatch amplification mutation assay (MAMA) PCR was used for detection of sensitive and resistant isolates to QoI fungicides (1). Confirmation of the presence of the G143A mutation was carried out by cloning an mRNA fragment of the cytochrome b gene using cDNA synthesized from total RNA of A. rabiei and CBF1/CBR2 (1,3). Total RNA was extracted from 3-day-old liquid cultures and it was used instead of genomic DNA for this PCR to avoid large intronic regions commonly present in mitochondrial genes. The G143A mutation has previously been correlated with resistance to QoI fungicides in other fungal plant pathogens (3). Also, these isolates were determined to be QoI-resistant in vitro by PDA amended with a discriminatory dose of 1 µg/ml of azoxystrobin (4). To our knowledge, this is the first report of QoIresistant A. rabiei isolates causing infections on chickpeas in South Dakota and Nebraska. QoI-resistant isolates were reported in North Dakota and Montana in 2005 and 2007, respectively (4). Of nearly 300 isolates collected from these states from 2005 and 2007, approximately 65% were determined to be QoI resistant (4). The widespread occurrence of QoIresistant isolates and reduction of fungicide performance in fields led the North Dakota State University Cooperative Extension Service to actively discourage the use of QoI fungicides on chickpeas in North Dakota and Montana (4). It is likely that similar recommendations will need to be adopted in South Dakota and Nebraska for profitable chickpea production. References: (1) J. A. Delgado, 2012 Ph.D. Diss. Department of Plant Pathology, North Dakota State University. (2) R. M. Harveson et al. 2011. Online. Plant Health Progress doi:10.1094/PHP-2011-0103-01-DG. (3) Z. Ma et al. Pestic. Biochem. Physiol. 77:66, 2003. (4) K. A. Wise et al. Plant Dis. 93:528, 2009.

6.
J Contam Hydrol ; 228: 103566, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31740007

RESUMO

The removal of Bisphenol A, 2,2-bis (4-hydroxyphenyl) propane (BPA) in fixed-bed columns was investigated by breakthrough adsorption tests at different operation conditions and further prediction by a mathematical model to describe the adsorption-diffusion process onto two synthesized carbon porous materials. In this study, a xerogel (RFX) prepared by an optimized conventional sol-gel method and a lignin-based activated carbon (KLP) obtained via chemical activation were used in batch and fixed-bed adsorption experiments. The materials were fully characterized and their adsorptive properties were compared to those obtained with a commercial activated carbon (F400). RFX and KLP materials reached the equilibrium adsorption in only 24 h, whereas F400 activated carbon required 48 h. In addition, F400 and KLP adsorbents showed higher equilibrium adsorption capacity values (qe = 0.40 and 0.22 kg/kg, for F400 and KLP, respectively) than that obtained for the xerogel (qe = 0.08 kg/kg). Both synthesized carbon-adsorbents were studied in fixed-bed adsorption tests, exploring the effect of the operation conditions, e.g., initial BPA concentration (0.005-0.04 kg/m3), weight of adsorbent (0.01-0.05 g) and volumetric flow rate (0.2 to 1.0 mL/min), on the adsorption performance of the column. All the tested adsorption columns reached the equilibrium in a very short time, due to the efficient dimensionless of the bed. Additionally, the regeneration of the exhausted adsorbent was studied, achieving the total reuse of the solids after three consecutive cycles using methanol as regeneration agent. Finally, a mathematical model based on mass conservation equations was proposed, allowing to efficiently fit the experimental BPA breakthrough curves and estimate the external and adsorbed-phase mass transfer coefficients with a high accuracy.


Assuntos
Poluentes Químicos da Água , Purificação da Água , Adsorção , Compostos Benzidrílicos , Fenóis
7.
Bull Entomol Res ; 99(6): 583-91, 2009 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-19889254

RESUMO

Culicoides imicola is the main vector for bluetongue (BT) and African horse sickness (AHS) viruses in the Mediterranean basin and in southern Europe. In this study, we analysed partial mitochondrial cytochrome c oxidase subunit I (COI) gene to characterize and confirm population expansion of Culicoides imicola across Spain. The data were analysed at two hierarchical levels to test the relationship between C. imicola haplotypes in Spain (n = 215 from 58 different locations) and worldwide (n = 277). We found nineteen different haplotypes within the Spanish population, including 11 new haplotypes. No matrilineal subdivision was found within the Spanish population, while western and eastern Mediterranean C. imicola populations were very structured. These findings were further supported by median networks and mismatch haplotype distributions. Median networks demonstrated that the haplotypes we observed in the western Mediterranean region were closely related with one another, creating a clear star-like phylogeny separated only by a single mutation from eastern haplotypes. The two, genetically distinct, sources of C. imicola in the Mediterranean basin, thus, were confirmed. This type of star-like population structure centred around the most frequent haplotype is best explained by rapid expansion. Furthermore, the proposed northern expansion was also supported by the statistically negative Tajima's D and Fu's Fs values, as well as predicted mismatch distributions of sudden and spatially expanding populations. Our results thus indicated that C. imicola population expansion was a rapid and recent phenomenon.


Assuntos
Ceratopogonidae/fisiologia , Complexo IV da Cadeia de Transporte de Elétrons/genética , Variação Genética , Migração Animal , Animais , Ceratopogonidae/classificação , Ceratopogonidae/genética , Complexo IV da Cadeia de Transporte de Elétrons/química , Haplótipos , Densidade Demográfica , Análise de Sequência de DNA , Espanha
8.
J Environ Biol ; 30(2): 183-6, 2009 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-20121015

RESUMO

We have specifically carried out a greenhouse experiment to assess relationship between samara weight and seed success. Relationship assessed as dispersal potential, germination level, germination rate and early seedling mass for the invasive species Ailanthus altissima. For this purpose, we considered two close stands as seeds source. We found no correlation between samara size and neither germination level, germination rate, nor seedling mass, but a positive correlation with samara projected area. These results suggest that samara weight is not directly related to germination, dispersal and invasion potential neither. Nevertheless, stands differed in the invasion potential of their samaras; one stand presented samaras with higher projected area per weight unit whereas the other one presented samaras that produced heavier seedlings. Whatever the origin, (genetic or environmental) of this differences it should be advantageous for a colonizing invader species such as A. altissima since it could imply a wider range of habitats susceptible to invasion.


Assuntos
Ailanthus/crescimento & desenvolvimento , Ecossistema , Germinação
9.
Food Res Int ; 119: 135-142, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-30884641

RESUMO

The aim of this study is the chemical and sensory description of the aroma of wines white Chelva through five successive vintages. Solid Phase Extraction (SPE) was used for the isolation of volatile compounds and Gas Chromatography Mass Spectrometry (GC-MS) was employed by their analysis. Aroma Sensory Profile of wines was defined using the Quantitative Descriptive Sensory Analysis (QDA). A total of 77 volatile compounds were identified in Chelva wines. Chelva wines present a great quantity of aromatic compounds of very different chemical nature and with different aromatic descriptors, which will increase its aromatic complexity of these wines. Aroma sensory profile of Chelva wines was defined by higher intensity of fresh and peach aromas with notes citric, green apple, tropical fruit and sweet. This study showed that the Chelva grapes variety cultivated in La Mancha region present a great aroma potential and a complex sensory profile and can be considered a viable alternative to traditional grape varieties cultivated in this region for increasing the offer to the consumer.


Assuntos
Frutas/química , Odorantes/análise , Paladar , Compostos Orgânicos Voláteis/análise , Vinho/análise , Acetaldeído/análise , Ácidos/análise , Álcoois/análise , Benzeno/análise , Ésteres/análise , Cromatografia Gasosa-Espectrometria de Massas/métodos , Humanos , Malus , Prunus persica , Extração em Fase Sólida , Vitis/química
10.
Rev Gastroenterol Mex (Engl Ed) ; 84(4): 461-466, 2019.
Artigo em Inglês, Espanhol | MEDLINE | ID: mdl-31585687

RESUMO

INTRODUCTION: Subtotal cholecystectomy has been employed in cases of tecnically difficult cholecystectomy to prevent common bile duct injury. Given that there are few reports in Mexico on the theme, we consider it important to present the 18-year experience of a surgical group in the South-Southeast of Mexico. AIM: To determine the safety of laparoscopic subtotal cholecystectomy in patients with acute cholecystitis. MATERIALS AND METHODS: A retrospective, observational, and comparative study was conducted on patients with gallstones that underwent laparoscopic cholecystectomy. The variables analyzed were: anthropometric characteristics, comorbidities, conversion rate, surgery duration, hospital stay, and morbidity and mortality. STATISTICAL ANALYSIS: Descriptive statistics were applied through measures of central tendency and dispersion and standard deviation, utilizing the SPSS v22 program. RESULTS: A total of 1,101 medical records of patients with gallstones were reviewed. Of those patients, 223 presented with acute cholecystitis (20.25%) and they were divided into 2 groups: A) total cholecystectomy (82.95%) and B) subtotal cholecystectomy (17.05%). The anthropometric characteristics, risk factors, conversion rate, and hospital stay were similar in both groups. Only surgery duration was longer in the subtotal cholecystectomy group. Complications were more frequent, there was 1 death, and there was no bile duct injury in the subtotal cholecystectomy group. Those results were not statistically significant between the two groups. CONCLUSIONS: Subtotal cholecystectomy is a valuable resource in patients with acute cholecystitis. In our case series, it was a safe and reliable procedure for preventing bile duct injury. A larger number of cases are needed to corroborate those results.


Assuntos
Colecistectomia Laparoscópica/métodos , Colecistite Aguda/cirurgia , Adulto , Idoso , Idoso de 80 Anos ou mais , Colecistectomia Laparoscópica/efeitos adversos , Feminino , Humanos , Masculino , México , Pessoa de Meia-Idade , Estudos Retrospectivos
12.
Environ Pollut ; 220(Pt A): 732-736, 2017 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-27667676

RESUMO

Plastic intake by marine vertebrates has been widely reported, but information about its presence in continental waterfowl is scarce. Here we analyzed faeces of waterbirds species (European coot, Fulica atra, mallard, Anas platyrhynchos and shelduck, Tadorna tadorna) for plastic debris in five wetlands in Central Spain. We collected 89 faeces of shelduck distributed in four lakes, 43.8% of them presented plastic remnants. Sixty percent of 10 faeces of European coot and 45% of 40 faeces of mallard contained plastic debris. Plastic debris found was of two types, threads and fragments, and were identified as remnants of plastic objects used in agricultural fields surrounding the lakes. Differences in prevalence of plastic in faeces, number of plastic pieces per excrement and size of the plastic pieces were not statistically significant between waterfowl species. Thus, our results suggest that plastic may also be frequently ingested by waterfowl in continental waters, at least in our study area. Future studies should address this potential problem for waterbird conservation in other wetlands to evaluate the real impact of this pollutant on waterbirds living in inland water.


Assuntos
Patos/metabolismo , Fezes/química , Plásticos/análise , Poluentes Químicos da Água/análise , Poluição da Água/análise , Animais , Aves , Lagos , Plásticos/toxicidade , Espanha , Poluentes Químicos da Água/toxicidade , Áreas Alagadas
13.
Leukemia ; 31(2): 382-392, 2017 02.
Artigo em Inglês | MEDLINE | ID: mdl-27479184

RESUMO

The notion that plasma cells (PCs) are terminally differentiated has prevented intensive research in multiple myeloma (MM) about their phenotypic plasticity and differentiation. Here, we demonstrated in healthy individuals (n=20) that the CD19-CD81 expression axis identifies three bone marrow (BM)PC subsets with distinct age-prevalence, proliferation, replication-history, immunoglobulin-production, and phenotype, consistent with progressively increased differentiation from CD19+CD81+ into CD19-CD81+ and CD19-CD81- BMPCs. Afterwards, we demonstrated in 225 newly diagnosed MM patients that, comparing to normal BMPC counterparts, 59% had fully differentiated (CD19-CD81-) clones, 38% intermediate-differentiated (CD19-CD81+) and 3% less-differentiated (CD19+CD81+) clones. The latter patients had dismal outcome, and PC differentiation emerged as an independent prognostic marker for progression-free (HR: 1.7; P=0.005) and overall survival (HR: 2.1; P=0.006). Longitudinal comparison of diagnostic vs minimal-residual-disease samples (n=40) unraveled that in 20% of patients, less-differentiated PCs subclones become enriched after therapy-induced pressure. We also revealed that CD81 expression is epigenetically regulated, that less-differentiated clonal PCs retain high expression of genes related to preceding B-cell stages (for example: PAX5), and show distinct mutation profile vs fully differentiated PC clones within individual patients. Together, we shed new light into PC plasticity and demonstrated that MM patients harbouring less-differentiated PCs have dismal survival, which might be related to higher chemoresistant potential plus different molecular and genomic profiles.


Assuntos
Mieloma Múltiplo/diagnóstico , Mieloma Múltiplo/metabolismo , Plasmócitos/metabolismo , Plasmócitos/patologia , Adulto , Antígenos CD/metabolismo , Biomarcadores , Medula Óssea/metabolismo , Medula Óssea/patologia , Células da Medula Óssea/metabolismo , Células da Medula Óssea/patologia , Estudos de Casos e Controles , Ciclo Celular , Metilação de DNA , Feminino , Perfilação da Expressão Gênica , Heterogeneidade Genética , Sequenciamento de Nucleotídeos em Larga Escala , Humanos , Imunofenotipagem , Hibridização in Situ Fluorescente , Masculino , Pessoa de Meia-Idade , Mieloma Múltiplo/genética , Mieloma Múltiplo/mortalidade , Mutação , Gradação de Tumores , Fenótipo , Prognóstico , Análise de Célula Única , Adulto Jovem
14.
Rev Esp Enferm Dig ; 97(3): 155-60, 2005 Mar.
Artigo em Inglês, Espanhol | MEDLINE | ID: mdl-15839810

RESUMO

AIMS: To report a new strategy for the detection of hepatotoxic adverse drug reactions (ADRs) in hospitalized patients improving the results obtained with other methods. DESIGN: The model is based on the identification of a single alert signal in various target clinical departments over a 12-month period. Each patient was later interviewed following a set protocol. The main results analyzed were the drugs suspected of ADR; causal relationship between suspected drugs and ADRs; ADR severity, and incidence of hepatotoxic ADR/100,000 inhabitants. SUBJECTS: Population served by a university-affiliated urban teaching hospital (519,381 inhabitants). RESULTS: The overall ratio of confirmed/suspected ADRs was high (35/80). The most commonly reported drug was amoxicillin-clavulanic acid (4 cases). With regard to causality, 2 suspected cases were classified as definite and 14 as probable. The distribution according to the severity of hepatotoxicity was 6 severe and 29 mild cases. The incidence of hepatotoxic ADRs/100,000 inhabitants as revealed by our method was much higher versus voluntary report (6.74 and 1.79, respectively). CONCLUSIONS: Our method has proven effective for improving the detection of hepatotoxic ADRs, and may be extended to other types of adverse reactions.


Assuntos
Sistemas de Notificação de Reações Adversas a Medicamentos , Doença Hepática Induzida por Substâncias e Drogas/diagnóstico , Sistemas de Medicação no Hospital/normas , Adulto , Idoso , Doença Hepática Induzida por Substâncias e Drogas/prevenção & controle , Feminino , Hospitais de Ensino , Hospitais Urbanos , Humanos , Masculino , Pessoa de Meia-Idade , Projetos Piloto , Garantia da Qualidade dos Cuidados de Saúde , Espanha
16.
Biomaterials ; 25(17): 3671-80, 2004 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-15020142

RESUMO

The development of the new technologies of bone tissue engineering requires the production of bioresorbable macroporous scaffolds. Calcium phosphate cements are good candidate materials for the development of these scaffolds, as an alternative to the traditional porous sintered ceramics. In this work a novel two-step method, based in the foaming of an alpha-tricalcium phosphate (alpha-TCP) cement paste and its subsequent hydrolysis to a calcium deficient hydroxyapatite (CDHA) is presented. The foaming agent was a hydrogen peroxide (H2O2) solution, which decomposes in water and oxygen gas. CDHA foams, which combined an interconnected macroporosity with a high microporosity were obtained. The apatitic phase obtained by the hydrolysis reaction was more similar to the biologic one, in terms of chemical composition, crystallinity and specific surface than the hydroxyapatites obtained by sintering. The percentage of porosity in the foams reached a 66%. It was shown that it was possible to control the porosity, and pore size and shape by different processing parameters such as the liquid-to-powder ratio, the concentration of the H2O2 solution and the particle size of the powder.


Assuntos
Materiais Biocompatíveis/química , Cimentos Ósseos/química , Substitutos Ósseos/química , Fosfatos de Cálcio/química , Durapatita/química , Engenharia Tecidual , Força Compressiva , Gases/química , Hidrólise , Manufaturas/análise , Teste de Materiais , Pomadas , Tamanho da Partícula , Transição de Fase , Porosidade , Pós , Propriedades de Superfície , Resistência à Tração
17.
J Photochem Photobiol B ; 57(2-3): 90-3, 2000 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-11154088

RESUMO

The increasing application of light in new medical treatments has led to the need for optical characterization of tissues in order to obtain correct dosimetry. This study presents the results of measurements of the optical penetration depth of different human tissues based on the diffusion approximation of the transport theory of light.


Assuntos
Luz , Humanos
18.
Water Res ; 36(3): 599-608, 2002 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-11827321

RESUMO

This study deals with the adsorption of four chlorinated pollutants onto GAC (F-400); two pesticides (lindane and alachlor) and two PCB congeners: 2-PCB (MPCB) and 2,2',5,5'-PCB (TPCB). Equilibrium and kinetic parameters have been obtained for the adsorption of alachlor and each PCB. whereas the kinetic results for lindane presented elsewhere (Proc. First World Water Congr. Int. Water Assoc., Texts of Posters, CD-ROM, AGHTM, Paris, 2000) are reanalyzed in this work. A model assuming a bidisperse structure (macro- and micropores). each region having a different adsorption isotherm, is used to study the adsorption kinetics in a batch system in the period dominated by macropore diffusion. Both the saturation capacity and the rate of internal transport of TPCB are much lower than those of the other solutes. This difference is attributed to a chemisorption mechanism for this compound, which is favored by its very low solubility.


Assuntos
Acetamidas/química , Carvão Vegetal/química , Poluentes Ambientais/análise , Hexaclorocicloexano/química , Inseticidas/química , Bifenilos Policlorados/química , Purificação da Água/métodos , Adsorção , Cinética , Modelos Teóricos , Tamanho da Partícula
19.
Environ Exp Bot ; 46(1): 11-20, 2001 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-11378168

RESUMO

The different weight-number strategies of seed production displayed by individuals of a Mediterranean fire-prone plant species (Cistus ladanifer) were investigated in relation to seed germination responses to pre-germination heating. A control (no heating), a high temperature during a short exposure time (100 degrees C during 5 min) and a high temperature during a long exposure time (100 degrees C during 15 min) were applied to seeds from different individual plants with different mean seed weight. These pre-germination treatments resemble natural germination scenarios for the studied species, absence of fire, typical Mediterranean shrub fire, and severe fire with high fuel load. Seed germination was related to heat treatments and seed mass. Seed heating increased the proportion of seeds germinating compared with the control treatment. Mean seed weight was positively correlated to the proportion of germinated seeds but only within heat treatments. These results suggest that in periods without fire, the relative contributions to the population dynamics are equal for all seeds, regardless of their mass, whereas heavier seeds would be the main contribution after wildfire events. Since lighter seeds can be produced in higher quantities than heavier ones within a given fruit, the number of seedlings produced per fruit depended strongly on the germination conditions. In the absence of wildfire, fruits producing lighter seeds gave rise to more seedlings; nevertheless, they were numerically exceeded by those producing heavy seeds after a wildfire. The implications of these results are discussed in relation to their consequences on the population dynamics of this species, considering also additional information on stand flammability and changes in seed mass with plant age.

20.
Proc Inst Mech Eng H ; 218(3): 167-72, 2004.
Artigo em Inglês | MEDLINE | ID: mdl-15239567

RESUMO

In this work three iodine-containing monomers were proposed as new radiopaque agents for acrylic bone cements. In previous studies the addition of iodine-containing methacrylate monomers provided a statistically significant increase in tensile stress, fracture toughness and ductility, with respect to the barium sulphate (BaSO4)-containing cement. However, since fatigue resistance is one of the main properties required to ensure a good long-term performance of permanent prostheses, it is important to compare the fatigue properties of these new bone cement formulations with the radiolucent and BaSO4-containing bone cements. Because the acrylic cements have initial cracks, fatigue crack propagation studies were performed. It can be observed that these acrylic cements followed the Paris-Erdogan model. The results showed that the addition of some organic radiopacifiers (DISMA, TIBMA) increased the fatigue crack propagation resistance as compared to the radiolucent cement, being similar to the BaSO4-containing cement. The radiolucent cement showed a low crack propagation resistance.


Assuntos
Meios de Contraste/análise , Meios de Contraste/química , Teste de Materiais/métodos , Polimetil Metacrilato/análise , Polimetil Metacrilato/química , Misturas Complexas/análise , Misturas Complexas/química , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Propriedades de Superfície , Resistência à Tração
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