Mechanical and wear behaviours of nano and microfilled polymeric composite: effect of filler fraction and size

The addition of ceramic reinforced material, SiC particles, to resin matrices, results in the improvement of the overall performance of the composite, allowing the application of these materials as tribo-materials in industries such as: automotive, aeronautical and medical. Particle-reinforced polymeric composites are widely used as biomaterials, for example as dental filler materials and bone cements. These reinforced composites have improved mechanical and tribological performance and have higher values of elastic modulus and hardness, and also reduce the shrinkage during the polymerisation compared with resin matrices. However, the effect of the filler level in mechanical and tribological behaviour is not quite understood. The aim of this work is to determine the influence of the particle volume fraction and particle size in the wear loss of the composites and their antagonists. Reciprocating wear tests were conducted using a glass sphere against resin polyester silica reinforced composite in a controlled medium, with an abrasive slurry or distilled water. For 6 μm average particle dimension, seven particles contents were studied ranging from 0% to 46% of filler volume fraction (FVF). Afterwards, filler volume fractions of 10% and 30% were selected; and, for these percentages, 7 and 4 average particle dimensions were tested and were evaluated regarding their wear behaviour, respectively. The reinforcement particle dimensions used ranged from 0.1 μm to 22 μm with the 10% filler fraction, and for 30% of filler content the range extended from 3 μm to 22 μm. The results allow us to conclude that in an abrasive slurry medium the composite abrasion resistance decreases with the increase of the particle volume fraction, in spite of the accompanying rise in hardness and elastic modulus. With constant FVF, and abrasive slurry, the composite wear resistance increases with increasing average particle dimension. In a distilled water medium and with several FVF values, the minimum wear was registered for a median particle content of 24%. In this medium and with constant FVF the highest wear resistance occurred for average reinforcement particles of 6 μm. The removal mechanisms involved in the wear process are discussed, taking into account the systematic SEM observations to evaluate the wear mechanisms

PHENYTOIN – BOUNDARIES OF THE TREATMENT

Introdução: As crises convulsivas são manifestações clínicas frequentes no período neonatal. Continua pouco claro qual a melhor abordagem terapêutica, nao existindo ainda consenso entre os diversos protocolos. A terapêutica antiepiletica usada tradicionalmente e, muitas vezes, pouco eficaz e pode originar efeitos secundários importantes. Caso Clínico: Apresenta-se o caso clínico de um recém-nascido que iniciou convulsões no primeiro dia de vida. Por persistência das crises após terapêutica com fenobarbital, foi iniciada fenitoina, tendo desenvolvido um quadro de encefalopatia devida a intoxicação por este fármaco, apesar do seu uso em doses habituais. Dado que a investigacao complementar foi normal, concluiu-se que esta se deveu provavelmente a susceptibilidade individual. Conclusão: Atendendo aos potenciais efeitos secundários da fenitoina, mais frequentes e graves em recém-nascidos, este fármaco tende a ser menos usado como segunda linha no tratamento das convulsões neste grupo etário, considerando-se atualmente as benzodiazepinas e a lidocaina alternativas mais eficazes e seguras.Introduction: Seizures are rather common in the neonatal period. It still remains unclear what is the best therapeutic approach, and there is no consensus protocol. Currently used antiepileptic drugs are sometimes ineffective and may cause significant adverse effects. Case report: We present the case of a newborn with seizures during the first day of life. After unsuccessful treatment with phenobarbital, phenytoin was added. He developed a picture of encephalopathy due to intoxication with this drug, despite the use of standard dosages. Given unchanged further investigations, individual’s susceptibility was considered to be the cause. Conclusion: Because of potential side effects, more frequent and severe in newborns, phenytoin tends to be less used in the treatment of neonatal seizures. Benzodiazepines and lidocaine seems to be safer and more effective options

The identification of multiple thrombophilic risk factors in an infant with cerebrovascular accident

We found 1 article: Rev Neurol. 2005 Apr 16-30;40(8):479-81. [The identification of multiple thrombophilic risk factors in an infant with cerebrovascular accident] [Article in Spanish] Neves J, Costa E, Branca R, Carrilho I, Barbot J, Barbot C. Servicio de Hematología, Hospital de Crianças Maria Pia, 4050-111 Porto, Portugal. Abstract INTRODUCTION: Neonatal stroke (NNS) incidence appears to be increasing over the last years. This is believed to be a consequence of diagnostic accuracy rather than a real amplification of this entity. Nowadays, NNS incidence is estimated to be 1:4000 full newborns. CASE REPORT: Child with left middle cerebral artery territory infarction in which several thromboembolic risk factors were documented both in the child (neonatal sepsis and factor V Leiden) and his mother (lupus anticoagulant, pre-eclampsy and factor V Leiden). CONCLUSIONS: This case supports the increasing evidence in recent reports that association of multiple prothrombotic risk factors (maternal and foetal) is present in NNS genesis. This way the authors agree that wide prothrombotic study may be of crucial interest in identifying subjacent thrombophilic disease, even when an exogenous risk factor is present. PMID: 15861329 [PubMed - indexed for MEDLINE

Genetic polymorphism of CYP2D6 influences susceptibility to papillary thyroid cancer

OBJECTIVE: Xenobiotic-metabolizing enzymes are widely polymorphic and confer interindividual variation in the ability to detoxify carcinogens or to activate pro-carcinogens. A common polymorphism of cytochrome P450 2D6 (CYP2D6) results in lack of enzyme activity and has been associated with an altered susceptibility to several cancers. The aim of this study was to investigate the association between the CYP2D6 poor metaboliser genotype and the risk of papillary thyroid cancer (PTC). DESIGN: Retrospective case-control study. PATIENTS: One hundred and eighty-seven patients with PTC and 256 controls. MEASUREMENTS: Genotyping was performed by PCR and restriction enzyme analysis to detect the presence of the common CYP2D6*4 poor metaboliser allele. RESULTS: The frequency of individuals with the homozygous poor metaboliser genotype was lower in the patient group [1.6 vs. 5.5%, P = 0.037, OR = 0.28 (95% CI 0.09-0.93)]. The CYP2D6*4 allele frequency was also lower in the patient group [13.4 vs. 21.7%, P = 0.002, OR = 0.56 (95% CI 0.39-0.80)]. CONCLUSIONS: The results suggest that the poor metaboliser genotype is associated with a protective effect against PTC. This could be explained by a possible role of CYP2D6 on the metabolic activation of putative environmental chemical thyroid carcinogens or by linkage to another cancer-causing gene. Further research may allow the identification of metabolic risk factors and contribute towards understanding the molecular mechanisms involved in thyroid carcinogenesis

Anaplastic thyroid tumor: retrospective analysis of 12 cases

Anaplastic thyroid tumor is a rare tumor and constitutes 5 to 10% of thyroid carcinomas. Is one of the most aggressive solid tumors and the prognosis is always fatal with a mean survival of 3 to 7 months. The current therapeutics are scarce and inefficacious. A retrospective analysis was performed in 12 clinical cases of anaplastic thyroid tumor observed at the Department of Endocrinology, Diabetes and Metabolism of the University Hospital of Coimbra. We analysed data relative to sex, previous thyroid pathology, clinical signs and symptoms, date of diagnosis, treatment and outcome. In this series, the anaplastic thyroid carcinoma showed to be a highly malignant tumor with a mortality rate of 100% with a survival after the diagnosis between 15 days and 9 months

Adrenalectomia parcial laparoscópica – será que vale a pena o esforço?

info:eu-repo/semantics/publishedVersio

Incidental adrenal mass: is 4 cm a good cut-off for surgical decision?

info:eu-repo/semantics/publishedVersio

Adrenalectomia parcial laparoscópica – será que vale a pena o esforço?

info:eu-repo/semantics/publishedVersio