University of Maine

About: University of Maine is a education organization based out in Orono, Maine, United States. It is known for research contribution in the topics: Population & Ice sheet. The organization has 8637 authors who have published 16932 publications receiving 590124 citations. The organization is also known as: University of Maine at Orono.

Water in Nonpolar Confinement: From Nanotubes to Proteins and Beyond *

Abstract: Water molecules confined to nonpolar pores and cavities of nanoscopic dimensions exhibit highly unusual properties. Water filling is strongly cooperative, with the possible coexistence of filled and empty states and sensitivity to small perturbations of the pore polarity and solvent conditions. Confined water molecules form tightly hydrogen-bonded wires or clusters. The weak attractions to the confining wall, combined with strong interactions between water molecules, permit exceptionally rapid water flow, exceeding expectations from macroscopic hydrodynamics by several orders of magnitude. The proton mobility along 1D water wires also substantially exceeds that in the bulk. Proteins appear to exploit these unusual properties of confined water in their biological function (e.g., to ensure rapid water flow in aquaporins or to gate proton flow in proton pumps and enzymes). The unusual properties of water in nonpolar confinement are also relevant to the design of novel nanofluidic and molecular separation devices or fuel cells.

Reasoning about Binary Topological Relations

Abstract: A new formalism is presented to reason about topological relations. It is applicable as a foundation for an algebra over topological relations. The formalism is based upon the nine intersections of boundaries, interiors, and complements between two objects. Properties of topological relations are determined by analyzing the nine intersections to detect, for instance, symmetric topological relations and pairs of converse topological relations. Based upon the standard rules for the transitivity of set inclusion, the intersections of the composition of two binary topological relations are determined. These intersections are then matched with the intersections of the eight fundamental topological relations, giving an interpretation to the composition of topological relations.

Untreated Blood Pressure Level Is Inversely Related to Cognitive Functioning: The Framingham Study

Abstract: It was hypothesized that blood pressure would be inversely related to cognitive functioning, if unconfounded with antihypertensive medication and measured over many occasions prior to neuropsychological testing. For stroke-free Framingham Study participants aged 55-88 years (n = 1,702), blood pressure levels were averaged over five biennial examinations (1956-1964) when few hypertensives were being treated, and examined in relation to neuropsychological tests administered between 1976 and 1978. With age, education, occupation, cigarette smoking, alcohol consumption, and gender controlled, blood pressure levels and chronicity of hypertension were inversely related to the composite score and measures of attention and memory. This was true for the full sample, for a subsample untreated during blood pressure measurement (n = 1,485), and for a subsample untreated throughout the entire study period (n = 1,038). For example, decline per 10 mmHg increment in blood pressure ranged from -0.04 to -0.07 standard score units (z) for the composite score. A negative finding previously was most likely due to blood pressure measurement concurrently with neuropsychological testing, or too few measurements. Hypertension-associated pathogenic processes may cause mild cognitive impairment, but other mechanisms need to be considered.

Globalization, Roving Bandits, and Marine Resources

Abstract: Marine resource exploitation can deplete stocks faster than regulatory agencies can respond. Institutions with broad authority and a global perspective are needed to create a system with incentives for conservation.