ABSTRACT
Rational synthesis and simple methodology for the purification of large (35-45 nm in lateral size) and flat (1.0-1.5 nm of height) nitrogen-doped graphene oxide quantum dots (GOQDs) are presented. The methodology allows robust metal-free and acid-free preparation of N-GOQDs with a yield of about 100% and includes hydrothermal treatment of graphene oxide with hydrogen peroxide and ammonia. It was demonstrated that macroscopic impurities can be separated from N-GOQD suspension by their coagulation with 0.9% NaCl solution. Redispersible in water and saline solutions, particles of N-GOQDs were characterized using tip-enhanced Raman spectroscopy (TERS), photoluminescent, XPS, and UV-VIS spectroscopies. The size and morphology of N-GOQDs were studied by dynamic light scattering, AFM, SEM, and TEM. The procedure proposed allows nitrogen-doped GOQDs to be obtained, having 60-51% of carbon, 34-45% of oxygen, and up to 7.2% of nitrogen. The N-GOQD particles obtained in two hours of synthesis contain only pyrrolic defects of the graphene core. The fraction of pyridine moieties grows with the time of synthesis, while the fraction of quaternary nitrogen declines. Application of TERS allows demonstration that the N-GOQDs consist of a graphene core with an average crystallite size of 9 nm and an average distance between nearest defects smaller than 3 nm. The cytotoxicity tests reveal high viability of the monkey epithelial kidney cells Vero in the presence of N-GOQDs in a concentration below 60 mg L-1. The N-GOQDs demonstrate green luminescence with an emission maximum at 505 nm and sedimentation stability in the cell culture medium.
ABSTRACT
INTRODUCTION: For post-surgical rehabilitation of the anterior cruciate ligament, the medialis and the lateralis vastus need to be worked on for good recovery. There is the discussion about the isometric and isotonic exercises to be used in the rehabilitation phase, and their results diverge in the literature. OBJECTIVE: This study aims to compare the activation of the medialis and the lateralis vastus in isometric and isotonic exercises. METHODS: Eleven subjects (seven men and four women) physically active and experienced in resistance training participated in the study. Anamnesis, anthropometric assessment, 10 Repetition maximum (RM) load test, maximum voluntary isometric contraction test and squat test were performed. RESULTS: For the vastus lateralis of the right leg, the electromyographic activity was significantly higher in the maximal isometric voluntary contraction compared to the dynamic squatting (p<0.05). The same was observed for the left leg (p<0.05). CONCLUSION: Recruitment of the medial and the lateral vastus in isometric exercises is higher in relation to isotonic exercises.
INTRODUÇÃO: Para a reabilitação pós-cirúrgica do ligamento cruzado anterior, os vastos medial e lateral precisam ser trabalhados visando uma boa recuperação. Discute-se a respeito dos exercícios isométricos e isotônicos a serem utilizados na fase de reabilitação, tendo seus resultados divergentes na literatura. OBJETIVO: Assim, o objetivo do presente estudo é comparar a ativação dos vastos medial e lateral em exercícios isométricos e isotônicos. MÉTODOS: Participaram deste estudo 11 sujeitos (sete homens e quatro mulheres), fisicamente ativos e com experiência em musculação. Foi realizada a anamnese, a avaliação antropométrica, o teste de carga de 10 repetições máximas (RM), o teste de contração voluntária isométrica máxima e o teste de agachamento. RESULTADOS: No vasto lateral da coxa direita, a atividade eletromiográfica foi significativamente maior na contração voluntária isométrica máxima em relação ao agachamento dinâmico (p<0,05). O mesmo foi observado na coxa esquerda (p<0,05). CONCLUSÃO: O recrutamento dos vastos medial e lateral em exercícios isométricos é maior em relação a exercícios isotônicos.
