Niobium(V) Chloride as Catalyst in Diels-Alder Reaction of Furan Ring

According to the relevant literature, the Diels-Alder reaction of furan without a catalyst can last several weeks and shows a low yield due to the diene's low reactivity. The use of Lewis acid catalysts or high pressures is described as an effective method for improving the reaction yields. This paper describes our recent study on the use of niobium pentachloride as the catalyst in Diels-Alder reactions between furan and several reactive dienophiles, among which methyl acrylate showed good yields, especially at lower temperatures. Other dienophiles have shown lower yields because of problems such as byproduct formation and the high reversibility of the reaction

Efeitos do exercício físico durante a hemodiálise em indivíduos com insuficiência renal crônica: uma revisão Effects of physical exercise during hemodialysis in patients with chronic renal insufficiency: a literature review

As principais alterações observadas em indivíduos com insuficiência renal crônica são anemia, hipertensão arterial sistêmica e atrofia muscular, que levam à baixa capacidade aeróbica e perda de força muscular. Assim, parte do tratamento desses indivíduos consiste em programas de exercício físico. O objetivo desta revisão da literatura foi documentar os efeitos agudos e as adaptações crônicas, cardiovasculares e musculares em indivíduos no estágio final da doença renal, submetidos a programas de exercício físico durante a hemodiálise. Foram selecionados artigos científicos nas bases eletrônicas Medline, Lilacs e PEDro, assim como no acervo de periódicos da biblioteca da Faculdade de Medicina da UFMG. Foram analisados 13 artigos envolvendo exercício físico aeróbico associado ou não a fortalecimento muscular durante a hemodiálise, variando quanto à intensidade, freqüência e duração da intervenção. A maioria demonstrou que exercícios físicos realizados durante a hemodiálise promovem efeitos benéficos na melhora da capacidade aeróbica, força muscular e no controle dos fatores de risco cardiovasculares, auxiliando a remoção dos solutos durante a hemodiálise. Embora o tema seja ainda pouco explorado, a literatura disponível evidencia benefícios do exercício durante a hemodiálise sobre a capacidade aeróbica e força muscular dos pacientes.<br>Main alterations seen in patients with chronic renal insufficiency are anemia, systemic arterial hypertension, and muscular atrophy, which lead to low aerobic capacity and loss of muscle strength. Hence part of these patients treatment consists in programs of physical exercise. The purpose of this literature review was to assess muscle and cardiovascular acute effects and chronic adaptations in end-stage renal disease patients submitted to physical exercise during hemodialysis. After browsing through Medline, Lilacs and PEDro databases, as well as searching for periodic articles at the UFMG Medicine School library, 13 articles were selected, related to aerobic exercise associated or not to muscle strengthening during hemodialysis. Studies varied as to exercise intensity, frequency and duration. Most articles found that physical exercise performed during hemodialysis favoured better aerobic capacity, muscle strength, and control of cardiovascular risk factors, helping solute removal during hemodialysis. Though the subject is scarcely studied, available literature shows that exercises during hemodialysis are beneficial to patients' aerobic capacity and muscle strength