Tripling the capacity of wireless communications using electromagnetic polarization.

Wireless communications are a fundamental part of modern information infrastructure. But wireless bandwidth is costly, prompting a close examination of the data channels available using electromagnetic waves. Classically, radio communications have relied on one channel per frequency, although it is well understood that the two polarization states of planar waves allow two distinct information channels; techniques such as 'polarization diversity' already take advantage of this. Recent work has shown that environments with scattering, such as urban areas or indoors, also possess independent spatial channels that can be used to enhance capacity greatly. In either case, the relevant signal processing techniques come under the heading of 'multiple-input/multiple-output' communications, because multiple antennae are required to access the polarization or spatial channels. Here we show that, in a scattering environment, an extra factor of three in channel capacity can be obtained, relative to the conventional limit using dual-polarized radio signals. The extra capacity arises because there are six distinguishable electric and magnetic states of polarization at a given point, rather than two as is usually assumed.

Dehydration in the terminal patient: perception of hospice nurses.

Recent discussion about the care of the terminally ill patient has focused on the appropriateness of withholding and withdrawing food and fluid and on the discomfort of the dehydrated state. Evidence is mounting that suggests that dehydration in this group of people is not painful, but rather may be more comfortable than hydration by means of IV fluids or enteral and parenteral feedings. This study examines the relationship between the experience of hospice nurses in observing terminal dehydration and their perception of this state. The scores for the degree of positive perception of dehydration are compared for the experienced and nonexperienced groups of nurses. This study suggests that those hospice nurses who have observed terminal dehydration have a more positive perception of this state than those who have not.