Osmotic potential calculations of inorganic and organic aqueous solutions over wide solute concentration levels and temperatures.

PURPOSE: To demonstrate that the authors' new "aqueous solution vs pure water" equation to calculate osmotic potential may be used to calculate the osmotic potentials of inorganic and organic aqueous solutions over wide ranges of solute concentrations and temperatures. Currently, the osmotic potentials of solutions used for medical purposes are calculated from equations based on the thermodynamics of the gas laws which are only accurate at low temperature and solute concentration levels. Some solutions used in medicine may need their osmotic potentials calculated more accurately to take into account solute concentrations and temperatures. METHODS: The authors experimented with their new equation for calculating the osmotic potentials of inorganic and organic aqueous solutions up to and beyond body temperatures by adjusting three of its factors; (a) the volume property of pure water, (b) the number of "free" water molecules per unit volume of solution, "Nf," and (c) the "t" factor expressing the cooperative structural relaxation time of pure water at given temperatures. Adequate information on the volume property of pure water at different temperatures is available in the literature. However, as little information on the relative densities of inorganic and organic solutions, respectively, at varying temperatures needed to calculate Nf was available, provisional equations were formulated to approximate values. Those values together with tentative t values for different temperatures chosen from values calculated by different workers were substituted into the authors' equation to demonstrate how osmotic potentials could be estimated over temperatures up to and beyond bodily temperatures. RESULTS: The provisional equations formulated to calculate Nf, the number of free water molecules per unit volume of inorganic and organic solute solutions, respectively, over wide concentration ranges compared well with the calculations of Nf using recorded relative density data at 20 °C. They were subsequently used to estimate Nf values at temperatures up to and excess of body temperatures. Those values, together with t values at temperatures up to and in excess of body temperatures recorded in the literature, were substituted in the authors' equation for the provisional calculation of osmotic potentials. The calculations indicated that solution temperatures and solute concentrations have a marked effect on osmotic potentials. CONCLUSIONS: Following work to measure the relative densities of aqueous solutions for the calculation of Nf values and the determination of definitive t values up to and beyond bodily temperatures, the authors' equation would enable the accurate estimations of the osmotic potentials of wide concentrations of aqueous solutions of inorganic and organic solutes over the temperature range. The study illustrates that not only solute concentrations but also temperatures have a marked effect on osmotic potentials, an observation of medical and biological significance.

Diversity of the land resources in the Amazonian State of Rondônia, Brazil

Opiniões divergentes são encontradas na literatura com respeito ao uso de terras da Amazônia para agricultura sustentável apos desmatamento. Este artigo busca clarificar a questão com um resumo dos resultados de um estudo dos recursos naturais (clima, atributos de solos e terrenos, e vegetação) do estado de Rondônia. O trabalho seguiu a metodologia do World Soils and Terrain Digital Database (SOTER) e foi financiado pelo banco mundial. Durante a fase de investigação no campo, concentrou-se no estudo de solos onde 2914 perfis de solos foram analisados. O estudo mostra que Rondônia tem um mosaico complexo de unidades de terra com diferenças claras em clima, terrenos, solos e vegetação nativa. Observa-se a combinação de florestas, que originalmente predominaram na região, com savanas naturais mal drenadas e outras savanas bem drenadas mas pobres em nutrientes. As florestas mais altas e vigorosas podem ou podiam ser encontradas crescendo em solos bem drenados derivados de materiais paternos ricos em minerais. Muitos desses solos podem ser, ou estão sendo, utilizados para agricultura produtiva. Solos derivados de materiais paternos pobres em nutrientes suportam bosques baixos e requerem grandes quantidades de cal e fertilizante para agricultura. Por outro lado, bosques baixos com altas populações de palmeiras e pequenas áreas de savanas úmidas cobrem solos mal drenados. É evidente que o desmatamento da floresta no passado foi indiscriminado e isto não pode ser justificado. A variabilidade de solos encontrados em Rondônia indica que os estudos de terrenos e solos realizados na Amazônia ate o momento têm sido muito gerais para que se possa detectar variações significativas nos solos.

Improvements in the equation for calculating the contribution to osmotic potential of the separate solutes of water solutions.

A minor conceptual improvement, the elimination of an approximation and its revision in relativistic terms, has resulted in a twofold increase in the predictability of the equation for calculating the contribution to osmotic potential of the separate solutes of water solutions. The molecular model inherent to its formulation would provide unifying principles for visualizing water movements associated with solute concentration gradients in tissues.

Apreciacion inicial del potencial del uso de suelos de las regiones del pie de monte central y de Santa Cruz del tropico boliviano

Contenido:Notas sobre la apreciacion del uso potencial del suelo, clases de regimenes de humedad para cultivos y pastizales tropicales de tierras bajas, clases de regimenes de humedad de las tierras bajas centrales de Bolivia.