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1.
Environ Res ; 147: 218-32, 2016 May.
Artigo em Inglês | MEDLINE | ID: mdl-26897060

RESUMO

Black crust in buildings can be formed as a result of different kind of chemical and physical reactions between the stone surface and environmental factors (e.g. acid aerosols emitted to the atmosphere, airborne particulate matter, etc.). Moreover, biological colonizations can also be present on them. This kind of pathology is widely present in limestones, but fewer are the case study dealing with the characterization of black crusts on sandstones. In this work we present an innovative methodology based on the use of cauliflower-like black crusts formed on sandstone material as natural passive sampler to evaluate the environmental pollution related with the emission of natural (crustal particles and marine aerosol particles) and metallic elements in the airborne particulate matter from the surrounding atmosphere. To illustrate its usefulness, different cauliflower-like black crusts growing in areas protected from the rain growing in an historical construction, La Galea Fortress, made up of sandstone and placed in the Abra Bay (Getxo, Basque Country, Spain) were characterized. This area suffers the anthropogenic emissions coming from the surrounding industry, traffic, sea port, and the natural ones coming from the surrounding marine atmosphere. The applied analytical methodology began with a previous elemental in situ screening in order to evaluate and compare the presence of the metals trapped in black crusts from different orientations using a hand-held energy dispersive X-Ray Fluorescence spectrometer. After this preliminary study, samples of black crusts were taken in order to characterize them in the laboratory using molecular techniques (Raman spectroscopy and XRD) and elemental techniques (ICP-MS, SEM-EDS and micro energy dispersive X-Ray Fluorescence). With the last two elemental techniques, imaging analyses were performed at different lateral resolutions in order to observe the distribution of the metals and other kind of particles trapped in the black crust samples. Additionally, a biological colonization found beneath the black crusts was also characterized using Phase Contrast microscopy.


Assuntos
Materiais de Construção/análise , Materiais de Construção/microbiologia , Monitoramento Ambiental/métodos , Poluentes Ambientais/análise , Poluentes Ambientais/química , Monitoramento Ambiental/instrumentação , Microscopia Eletrônica de Varredura , Microscopia de Contraste de Fase , Espanha , Espectrometria de Fluorescência , Espectrofotometria Atômica , Análise Espectral Raman , Propriedades de Superfície
2.
Eur J Clin Pharmacol ; 71(6): 715-722, 2015 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-25953736

RESUMO

AIM: The aim of this pharmacokinetic (PK) study was to evaluate tacrolimus (TAC) exposure in stable cystic fibrosis (CF) lung transplant (LT) recipients, converted from TAC twice daily to TAC once daily in an open-label, prospective, single-centre study. METHODS: Eligible patients were post-transplant CF patients (18-65 years) with stable lung function, on stable doses of TAC twice daily and who were candidates to switch to TAC once daily. Twelve consecutive patients were included in the study. Patients had their first PK analysis on day 1, still under the stable TAC twice-daily regimen, and were converted to TAC once daily from day 2 onwards. The doses were adjusted according to clinical judgement to achieve target levels, and a second 24-h PK period profile was obtained once the patient was on a stable dosage on the therapeutic range. RESULTS: The mean total (SD) daily dose of TAC twice daily at baseline upon enrolment was 0.17 (0.10) mg/kg/day. The mean (SD) daily dose of TAC once daily after adjustments was 0.22 (0.12) mg/kg/day. In order to achieve target C min levels with a similar AUC0-24, 82% of subjects who were converted to TAC once daily required an increase of dose, in a range of 0-66.7%, with a mean dose increase of 28%. CONCLUSIONS: Our study results indicate that the switch for conversion from TAC twice daily to TAC once daily in patients with CF may need dose adjustment in order to reach levels within the therapeutic target.


Assuntos
Fibrose Cística/metabolismo , Fibrose Cística/fisiopatologia , Imunossupressores/administração & dosagem , Imunossupressores/farmacocinética , Tacrolimo/administração & dosagem , Tacrolimo/farmacocinética , Administração Oral , Adulto , Área Sob a Curva , Esquema de Medicação , Feminino , Humanos , Transplante de Pulmão/métodos , Masculino , Adulto Jovem
3.
Mycologia ; 107(1): 104-22, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-25376798

RESUMO

This study explores species limits of a group of Clavaria species with taxonomic and nomenclatural problems and discusses the phylogeny and circumscription of the genus. The nuc 28S rDNA (28S) and internal transcribed spacer region phylogenies resolve species relationships, and the ITS is shown to be an adequate barcode marker for Clavaria. Yellow, clamped species of Clavaria are distributed in two clades, (i) C. flavostellifera, sister to C. incarnata and C. asterospora in ITS analyses, characterized by producing ornamented spores, and (ii) C. argillacea-C. citrinorubra-C. flavipes-C. sphagnicola, with smooth spores. Clavaria flavostellifera is described as new species based on morphological and molecular characters. Molecular evidence that supports C. sphagnicola as distinct from C. argillacea is provided. The usefulness of spore ornamentation as a taxonomic character is discussed; it is present only in some taxa and then only on spores trapped in the hymenium. Descriptions of C. argillacea, C. flavipes and C. sphagnicola are provided, along with color photographs and a key to yellow species of Clavaria with clamped basidia. Camarophyllopsis and Clavicorona are recovered within a paraphyletic Clavaria in our 28S phylogeny. Clampless contextual hyphae and narrow, slightly thick-walled mycelial hyphae are proposed as synapomorphies of Camarophyllopsis and Clavaria.


Assuntos
Agaricales/classificação , Filogenia , Agaricales/genética , Agaricales/crescimento & desenvolvimento , Agaricales/isolamento & purificação , DNA Fúngico/genética , DNA Espaçador Ribossômico/genética , Dados de Sequência Molecular , Esporos Fúngicos/classificação , Esporos Fúngicos/genética , Esporos Fúngicos/isolamento & purificação
4.
Bone Marrow Transplant ; 59(6): 777-784, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38409332

RESUMO

Mesenchymal stromal cells (MSC) have immunomodulatory and tissue-regenerative properties and have shown promising results in acute respiratory distress syndrome (ARDS) of multiple causes, including COVID-19. We conducted a randomised (1:1), placebo-controlled, double-blind clinical trial to assess the efficacy and safety of one bone marrow-derived MSC infusion in twenty patients with moderate to severe ARDS caused by COVID-19. The primary endpoint (increase in PaO2/FiO2 ratio from baseline to day 7, MSC 83.3 versus placebo 57.6) was not statistically significant, although a clinical improvement at day 7 in the WHO scale was observed in MSC patients (5, 50% vs 0, 0%, p = 0.033). Median time to discontinuation of supplemental oxygen was also shorter in the experimental arm (14 versus 23 days, p = 0.007), resulting in a shorter hospital stay (17.5 versus 28 days, p = 0.042). No significant differences were observed for other efficacy or safety secondary endpoints. No infusion or treatment-related serious adverse events occurred during the one-year follow-up. This study did not meet the primary endpoint of PaO2/FiO2 increase by day 7, although it suggests that MSC are safe in COVID-19 ARDS and may accelerate patients' clinical recovery and hospital discharge. Larger studies are warranted to elucidate their role in ARDS and other inflammatory lung disorders.Trial Registration: EudraCT Number: 2020-002193-27, registered on July 14th, 2020, https://www.clinicaltrialsregister.eu/ctr-search/trial/2020-002193-27/ES . NCT number: NCT04615429, registered on November 4th, 2020, https://clinicaltrials.gov/ct2/show/NCT04615429 .


Assuntos
COVID-19 , Transplante de Células-Tronco Mesenquimais , Síndrome do Desconforto Respiratório , Humanos , Método Duplo-Cego , COVID-19/terapia , COVID-19/complicações , Transplante de Células-Tronco Mesenquimais/métodos , Masculino , Feminino , Pessoa de Meia-Idade , Síndrome do Desconforto Respiratório/terapia , Idoso , Adulto , SARS-CoV-2 , Resultado do Tratamento , Células-Tronco Mesenquimais/citologia
5.
J Fungi (Basel) ; 9(12)2023 Nov 25.
Artigo em Inglês | MEDLINE | ID: mdl-38132742

RESUMO

The systematics of the genus Hydnum have undergone important advances, and many new species have been described with the aid of molecular data. A revision of old names that refer to Hydnum s. str., considering the knowledge now available, might reveal prioritary names of recently described species. This study focuses on the study of names that refer to white Hydnum in Europe, among which earlier synonyms of Hydnum reginae (=Hydnum albidum s. auct. pl. eur.) are potentially found, a species characterized by producing white basidiomata and smaller spores than any other European species. Our revision revealed the existence of three earlier names based on European material, namely H. pallidum Raddi, H. album Fr. and H. heimii Maas Geest. The earliest of those, Hydnum pallidum, is epitypified using material from Tuscany (Italy), from where it was originally described, and hence, it becomes the correct name for H. albidum s. auct. pl. eur. A full description and photographs of H. pallidum are provided, and further comments on other names that refer to white Hydnum based on European material are made.

6.
Bone Marrow Transplant ; 58(9): 965-972, 2023 09.
Artigo em Inglês | MEDLINE | ID: mdl-37407728

RESUMO

Malnutrition is the most common comorbidity during the continuum of hematopoietic stem cell transplant (HSCT) and negatively impacts clinical outcomes, response to therapy, quality of life, and costs. The intensive conditioning regimen administered before transplant causes inflammatory damages to the gastrointestinal system, which themselves contribute to trigger graft versus host disease (GvHD) in the allogeneic setting. GvHD and other post-transplant complications such as infections adversely affect food intake and gut absorption of nutrients. Consequently, patients exhibit signs of malnutrition such as weight loss and muscle wasting, thus triggering a "vicious circle" that favours additional complications. Among HSCT centres, there is marked variability in nutritional care, from screening for malnutrition to nutritional intervention. The present paper, elaborated by the Cellular Therapy and Immunobiology Working Party and the Nurses Group of the European Society for Blood and Marrow Transplantation, aims at defining a roadmap that identifies the main nutritional critical issues in the field of HSCT. This document will be propaedeutic to the development of clinical algorithms to counteract risk factors of malnutrition, based on scientific evidence and shared among HSCT centres, and thus maximize transplant outcomes.


Assuntos
Doença Enxerto-Hospedeiro , Transplante de Células-Tronco Hematopoéticas , Desnutrição , Enfermeiras e Enfermeiros , Humanos , Medula Óssea , Qualidade de Vida , Transplante de Células-Tronco Hematopoéticas/efeitos adversos , Condicionamento Pré-Transplante/efeitos adversos , Doença Enxerto-Hospedeiro/etiologia , Doença Enxerto-Hospedeiro/prevenção & controle , Desnutrição/terapia , Desnutrição/complicações
7.
Mycologia ; 104(6): 1443-55, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22684286

RESUMO

Two new species of Hydnum, characterized by slender Hydnum rufescens-like basidiomes and ovoid to broadly ellipsoid basidiospores, are described from the Iberian Peninsula based on morphological and ITS molecular data. Hydnum ovoideisporum is distinguished by pilei with deep orange tones and strong preference for calcareous soil. It is widespread in the Iberian-Mediterranean area. Hydnum vesterholtii is characterized by its ocher to light ocher pileus, and nearly all the collections were made in the Pyrenees. Both ovoid-spored species are monophyletic well supported groups in the maximum parsimony and Bayesian ITS phylogenies, while the remainder of the samples assigned to H. rufescens s.l. and having globose basidiospores split into six well supported clades. The need to typify the name Hydnum rufescens is discussed, and a provisional key is given for the European taxa of Hydnum.


Assuntos
Basidiomycota/classificação , Filogenia , Esporos Fúngicos/citologia , Sequência de Bases , Basidiomycota/citologia , Basidiomycota/genética , Basidiomycota/isolamento & purificação , DNA Fúngico/química , DNA Fúngico/genética , DNA Espaçador Ribossômico/química , DNA Espaçador Ribossômico/genética , Carpóforos/classificação , Carpóforos/citologia , Carpóforos/isolamento & purificação , Dados de Sequência Molecular , Análise de Sequência de DNA , Esporos Fúngicos/classificação , Esporos Fúngicos/isolamento & purificação
8.
Chemosphere ; 309(Pt 2): 136743, 2022 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-36209867

RESUMO

Over the last decades, the concern about air pollution has increased significantly, especially in urban areas. Active sampling of air pollutants requires specific instrumentation not always available in all the laboratories. Passive sampling has a lower cost than active alternatives but still requires efforts to cover extensive areas. The use of biological systems as passive samplers might be a solution that provides information about air pollution to assist decision-makers in environmental health and urban planning. This study aims to employ subaerial biofilms (SABs) growing naturally on façades of historical and recent constructions as natural passive biomonitors of atmospheric heavy metals pollution. Concretely, SABs spontaneously growing on constructions located in a tropical climate, like the one of the city of Barranquilla (Colombia), have been used to develop the methodological approach here presented as an alternative to SABS grown under laboratory conditions. After a proper identification of the biocolonizers in the SAB through taxonomic and morphological observations, the study of the particulate matter accumulated on the SABs of five constructions was conducted under a multi-analytical approach based mainly on elemental imaging studies by micro Energy Dispersive X-ray fluorescence spectrometry (µ-EDXRF) and Scanning Electron Microscopy coupled with Energy Dispersive X-ray spectrometry (SEM-EDS) techniques, trying to reduce the time needed and associated costs. This methodology allowed to discriminate metals that are part of the original structure of the SABs, from those coming from the anthropogenic emissions. The whole methodology applied assisted the identification of the main metallic particles that could be associated with nearby anthropogenic sources of emission such as Zn, Fe, Mn, Ni and Ti by SEM-EDS and by µ-EDXRF Ba, Sb, Sn, Cl and Br apart others; revealing that it could be used as a good alternative for a rapid screening of the atmospheric heavy metals pollution.


Assuntos
Poluentes Atmosféricos , Metais Pesados , Monitoramento Ambiental/métodos , Clima Tropical , Metais Pesados/análise , Poluentes Atmosféricos/análise , Material Particulado/análise , Biofilmes
9.
Mycol Res ; 113(Pt 11): 1261-70, 2009 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-19695328

RESUMO

The identification of the conventionally accepted species of Clavulina (Cantharellales, Basidiomycota) in Europe (Clavulina amethystina, Clavulina cinerea, Clavulina cristata, and Clavulina rugosa) is often difficult and many specimens are not straightforwardly assignable to any of those four species, which is why some authors have questioned their identity. In order to assess the status of those species, a morphological examination was combined with the molecular analysis of the ITS region. The same six major clades were obtained in the Bayesian and parsimony phylogenetic analyses, and all six clades were well-supported at least by one of the analyses. Morphological characters, such as the overall branching pattern, the presence and intensity of grey colour, the cristation of the apices, and basidiospore size and shape were to various extents correlated with the phylogenetic signal obtained from the ITS region. The congruence between the molecular analyses and morphology, rather than geographical origin, suggests the existence of several species that can be delimited using a combined phylogenetic and morphological species recognition. The analyses revealed that C. cristata and C. rugosa are well-delimited species. In contrast, more than one taxa could be subsumed under the names C. amethystina and C. cinerea, the taxonomical complexity of which is discussed. The ITS region is proved to be adequate to separate phylogenetic species of Clavulina.


Assuntos
Basidiomycota/classificação , Basidiomycota/genética , DNA Fúngico/genética , DNA Espaçador Ribossômico/genética , Filogenia , Europa (Continente)
10.
Sci Total Environ ; 654: 1379-1388, 2019 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-30527887

RESUMO

Machu Picchu Inca sanctuary (Cusco Region, Peru) was constructed on a granitic plateau, better known as Vilcabamba batholith. One of the most important carved granitic rocks from this archaeological site is the Sacred Rock, used by Inca citizens for religious rituals. Due to the location and climatic conditions, different rocks from this archaeological site are affected by biocolonizations. Concretely, the Sacred Rock shows flaking and delamination problems. In this work, a non-destructive multi analytical methodology has been applied to determine the possible role of the biodeteriogens, forming the biological patina on the Sacred Rock, in the previously mentioned conservation problems. Before characterizing the biological patina, a mineralogical characterization of the granitic substrate was conducted using X-ray Diffraction, Raman microscopy (RM) and micro energy dispersive X-ray fluorescence spectrometry. For the identification of the main biodeteriogens in the biofilm, Phase Contrast Microscopy was used. RM also allowed to determine the distribution (imaging) and the penetration (depth profiling) of the biogenic pigments present in the biopatina. Thanks to this study, it was possible to asses that some colonizers are growing on inner areas of the rock, reinforcing their possible assistance in the delamination. Moreover, the in-depth distribution of a wide variety of carotenoids in the patinas allowed to approach the penetration ability of the main biodeteriogens and the diffusion of these biogenic pigments to the inner areas of the rocky substrate.


Assuntos
Biofilmes/crescimento & desenvolvimento , Cianobactérias/fisiologia , Líquens/fisiologia , Microalgas/fisiologia , Arqueologia , Cianobactérias/isolamento & purificação , Líquens/isolamento & purificação , Microalgas/isolamento & purificação , Microscopia Óptica não Linear , Peru , Pigmentos Biológicos/classificação , Dióxido de Silício , Espectrometria por Raios X , Análise Espectral Raman , Difração de Raios X
11.
Sci Total Environ ; 626: 441-450, 2018 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-29358137

RESUMO

In this work, a reddish biocolonization composed mainly by Trentepohlia algae affecting a synthetic building material from a modern building from the 90s located in the Bizkaia Science and Technology Park (Zamudio, North of Spain) was characterized and its ability to accumulate metals coming from the surrounding atmosphere was evaluated. To asses if these biofilms can act as bioindicators of the surrounding metal pollution, a fast non-invasive in situ methodology based on the use of hand-held energy dispersive X-ray fluorescence (HH-ED-XRF) was used. In order to corroborate the in situ obtained conclusions, some fragments from the affected material were taken to analyze the metal distribution by means of micro-energy dispersive X-ray fluorescence spectroscopy (µ-ED-XRF) and to confirm the presence of metal particles deposited on it using Scanning Electron Microscopy coupled to an Energy Dispersive Spectrometer (SEM-EDS). In order to confirm if Trentepohlia algae biofilms growing on the surface of building materials could be a fast way to in situ provide information about the surrounding metal pollution, a second Trentepohlia algae biofilm growing on a different kind of material (sandstone) was analyzed from an older historical building, La Galea Fortress (Getxo, North of Spain).


Assuntos
Poluentes Atmosféricos/análise , Biofilmes/efeitos dos fármacos , Biomarcadores Ambientais/fisiologia , Monitoramento Ambiental/métodos , Metais/análise , Poluição Ambiental , Espanha
12.
Obes Surg ; 17(2): 258-9, 2007 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-17476883

RESUMO

The obesity epidemic is prevalent in Latin America. Our surgical team has had a significant number of consultations from parents and doctors of the obese child population. A case in a morbidly obese 12-year-old is hereby reported.


Assuntos
Gastrectomia , Laparoscopia , Obesidade Mórbida/cirurgia , Criança , Equador , Feminino , Humanos , Obesidade Mórbida/complicações , Obesidade Mórbida/psicologia
13.
Chem Commun (Camb) ; (10): 1168-9, 2003 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-12778718

RESUMO

The pseudotetrahedral, formally 5-coordinate complex [Ni(eta 3-CH2C(CH3)CH2)(SbPh3)3][BAr'4] (Ar' = 3,5-C6H3(CF3)2) as well as the 4-coordinate derivative [Ni(eta 3-CH2C(CH3)CH2)(AsPh3)2][BAr'4] act as extremely efficient catalysts for the oligomerization of styrene.

14.
PLoS One ; 9(7): e103416, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-25058128

RESUMO

For efficient use of conservation resources it is important to determine how species diversity changes across spatial scales. In many poorly known species groups little is known about at which spatial scales the conservation efforts should be focused. Here we examined how the community turnover of wood-inhabiting fungi is realised at three hierarchical levels, and how much of community variation is explained by variation in resource composition and spatial proximity. The hierarchical study design consisted of management type (fixed factor), forest site (random factor, nested within management type) and study plots (randomly placed plots within each study site). To examine how species richness varied across the three hierarchical scales, randomized species accumulation curves and additive partitioning of species richness were applied. To analyse variation in wood-inhabiting species and dead wood composition at each scale, linear and Permanova modelling approaches were used. Wood-inhabiting fungal communities were dominated by rare and infrequent species. The similarity of fungal communities was higher within sites and within management categories than among sites or between the two management categories, and it decreased with increasing distance among the sampling plots and with decreasing similarity of dead wood resources. However, only a small part of community variation could be explained by these factors. The species present in managed forests were in a large extent a subset of those species present in natural forests. Our results suggest that in particular the protection of rare species requires a large total area. As managed forests have only little additional value complementing the diversity of natural forests, the conservation of natural forests is the key to ecologically effective conservation. As the dissimilarity of fungal communities increases with distance, the conserved natural forest sites should be broadly distributed in space, yet the individual conserved areas should be large enough to ensure local persistence.


Assuntos
Agricultura Florestal/métodos , Fungos/classificação , Madeira/microbiologia , Biodiversidade , Conservação dos Recursos Naturais , Fungos/crescimento & desenvolvimento , Modelos Biológicos , Modelos Estatísticos
15.
Rev. ecuat. neurol ; 28(3): 101-104, sep.-dic. 2019. graf
Artigo em Espanhol | LILACS-Express | LILACS | ID: biblio-1058482

RESUMO

Resumen Los schwannomas son tumores usualmente benignos, de crecimiento lento y generalmente propios de adultos. Son muy raros en la población pediátrica y su diagnóstico requiere un alto índice de sospecha clínica. Se presenta el caso de un paciente de sexo masculino de 9 años con historia de una masa cervical asintomática, sin otros antecedentes clínicos relevantes. La escisión total de la masa fue posible e histopatología confirmó el diagnóstico de schwannoma. El paciente se recuperó completamente, con excelente pronóstico. Es necesario tener presente a los schwannomas en el diagnóstico diferencial en casos de masas cervicales en pacientes pediátricos.


Abstract Schwannomas are usually benign, slow-growing tumors, usually found in adults. They are very rare in the pediatric population and their diagnosis requires a high index of clinical suspicion. We present the case of a 9-year-old male patient with a history of an asymptomatic cervical mass, with no other relevant clinical history. Total excision of the mass was possible, and histopathology confirmed the diagnosis of schwannoma. The patient recovered completely, with excellent prognosis. It is necessary to keep in mind schwannomas in the differential diagnosis in cases of cervical masses in pediatric patients.

16.
Rev. ecuat. neurol ; 26(3): 296-300, sep.-dic. 2017. tab, graf
Artigo em Espanhol | LILACS-Express | LILACS | ID: biblio-1003997

RESUMO

Resumen Las enfermedades desmielinizantes inflamatorias comprenden una serie de desórdenes de origen autoinmune que afectan la mielina a nivel del sistema nervioso central (SNC) y periférico. Pueden ser monofásicas, multifásicas, progresivas, monofocales o multifocales, y su diagnóstico suele ser de exclusión. Se presenta el caso de una paciente de 15 años que debuta con cefalea, ataxia, hemiparesia, oftalmoparesia y alteración de la conciencia. En la resonancia magnética nuclear se observaron lesiones compatibles con enfermedad desmielinizante. Se realizó diagnóstico de encefalomielitis diseminada aguda. La paciente respondió favorablemente al tratamiento con corticoides.


Abstract Inflammatory demyelinating diseases comprise a series of autoimmune disorders affecting myelin at the level of the central nervous system (CNS) and peripheral nervous system. They can be monophasic, multiphasic, progressive, monofocal or multifocal, and their diagnosis is usually of exclusion. We report the case of a 15-year-old female patient with headache, ataxia, hemiparesis, ophthalmoplegia and altered consciousness. Magnetic resonance imaging showed lesions compatible with demyelinating disease. Acute disseminated encephalomyelitis was diagnosed. The patient responded to treatment with corticosteroids.

17.
Dalton Trans ; (10): 1842-52, 2009 Mar 14.
Artigo em Inglês | MEDLINE | ID: mdl-19240920

RESUMO

The cationic complexes [Ni(eta(3)-CH(2)C(R)CH(2))(SbPh(3))(3)][BAr'(4)] (R = CH(3), H ; Ar' = 3,5-C(6)H(3)(CF(3))(2)), [Ni(eta(3)-CH(2)C(R)CH(2))(AsPh(3))(2)][BAr'(4)] (R = CH(3), H ), [Ni(eta(3)-CH(2)CHCH(2))(PPh(3))(L)][BAr'(4)] (L = SbPh(3), AsPh(3)), and the neutral derivatives [Ni(eta(3)-CH(2)C(R)CH(2))Br(L)] (L = SbPh(3), R = CH(3), H ; L = AsPh(3), R = CH(3), H ) have been prepared and characterized. The X-ray crystal structures of , , , and have been determined. These complexes are very active catalyst precursors for the low-molecular weight oligomerization of RC(6)H(4)CH[double bond, length as m-dash]CH(2) to mainly dimers and trimers of styrene (R = H) or 4-methylstyrene (R = CH(3)). They also catalyse the oligomerization of alpha-methylstyrene to dimers and trimers, or to higher oligomers depending upon the reaction conditions (solvent and temperature). The oligomerization reactions were carried out at 25 degrees C in most cases, in dichloromethane, 1,2-dichloroethane or fluorobenzene, using a olefin/catalyst ratio equal to 2000. The oligomerization products were characterised by means of GPC/SEC.

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