The emission properties of poly(N-vinylcarbazole) (PVK), poly(N-ethyl-2-vinylcarbazole), and poly(N-ethyl-3-vinylcarbazole) have been investigated. Dilute fluid solutions of all three vinylcarbazole polymers are observed to exhibit a structureless emission band at energies approximately 5400 cm−1 to the red of the (0,0) band of the normal molecular fluorescence of isolated monomer compounds. On the basis of earlier work appropriate model compounds, this emission is assigned as that from an intrachain excimer state in which two interacting pendant groups, one of which is electronically excited, achieve an overlapping, eclipsed, sandwichlike configuration. The emission spectrum of PVK is characterized by the appearance of a second structureless emission band which appears at higher energy than the intrachain excimer fluorescence common to all three vinylcarbazole polymers. This emission band is unique to PVK and under certain conditions to its model compound, 1,3-bis(N-carbazolyl)propane. This emission is assigned as that from a second intrachain excimer. Contrary to the lower energy intrachain excimer, the polymer conformation appropriate for formation of this state exists prior to the initial excitation step.

Many hospitalists incorporate point‐of‐care ultrasound (POCUS) into their daily practice to answer specific diagnostic questions or to guide performance of invasive bedside procedures. However, standards for hospitalists in POCUS training and assessment are not yet established. Most internal medicine residency training programs, the major pipeline for incoming hospitalists, have only recently begun to incorporate POCUS in their curricula. The purpose of this document is to inform a broad audience on what POCUS is and how hospitalists are using it. This document is intended to provide guidance for the hospitalists who use POCUS and administrators who oversee its use. We discuss POCUS 1) applications, 2) training, 3) assessments, and 4) program management. Practicing hospitalists must continue to collaborate with their local credentialing bodies to outline requirements for POCUS use. Hospitalists should be integrally involved in decision‐making processes surrounding POCUS program management.

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This article uses information from a large administrative database (N = 3941) to outline five ideal typical pathways into adult homelessness. The pathways are called 'housing crisis', 'family breakdown', 'substance abuse', 'mental health' and 'youth to adult'. Then we explain why people on some pathways remain homeless for longer than others. People on a housing crisis or family breakdown pathway do not form strong friendships in the homeless subculture or accept homelessness as a way of life. Their homelessness is shorter. In contrast, people on the substance abuse and youth to adult pathways often become involved in the homeless subculture and engage in social practices that make it difficult to exit from homelessness. Their homelessness is longer. People on the mental health pathway also experience long-term homelessness, but they do not endorse homelessness as a way of life. They remain homeless because they have few exit options.

Solubility (S) and diffusion (D) of water in low-density polyethylene have been studied by means of desorption experiments. The dependence of S and D on the state of oxidation of the polymers has been measured. A model has been developed to describe the bound-oxygen dependence of S and D. Physically the oxygen groups act as traps that are strong enough to bind the water but not so deep as to remove the water from the diffusion process. Hydroxyl, hydroperoxide, and carboxylic acid groups form the strongest traps, ketone groups are weaker, and ester groups exhibit negligible trapping. Permeation is unaffected by bound oxygen. Trap volumes deduced from the analysis lie in the range of a few cubic angstroms. Some restriction of rotational motion of the trapped water is required by the analysis, and independent NMR evidence is presented to support this result.

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Ferroelectric copolymers of vinylidene fluoride with trifluoroethylene and tetrafluoroethylene have been investigated by means of broad band dielectric spectroscopy (10 mHz-1 GHz) at temperatures covering the ferroelectric, paraelectric and molten phases as well as the glassy and rubbery states. The low-temperature relaxation spectra near T, (--40°C) consist of two processes; a WLF-type segmental mode and an Arrhenius type local mode. These processes are unified near room temperature to be transferred continuously to the high-temperature process. After showing a peak at the Curie point T, (70-140"C), the relaxation strength decreases gradually in the paraelectric phase until the melting point T, (-150°C) is reached, where it decreases rapidly. It is found that the relaxation time in the molten phase lies on the Arrhenius line extended from the low-temperature local mode process. This implies that related molecular motions arise from a common elementary process. Departure from this Arrhenius line in the paraelectric phase is discussed by the use of a cooperative multi-site model.