Fewer bone histomorphometric abnormalities with intermittent than with continuous slow-release sodium fluoride therapy

To help resolve the uncertainty whether sodium fluoride (NaF) therapy should be given intermittently or continuously, we examined iliac crest bone biopsies (before and after treatment) and fragility fracture rates in 35 intermittently treated (group I) and 69 continuously treated (group C) patients; all received calcium. The following statistically significant results were obtained. Reduction in vertebral fracture rate was similar in the two groups. Trabecular thickness and the structurally more important mineralized thickness increased only in group I. Group I also accumulated less excess osteoid (surface, volume). Mean osteoid thickness did not change in either group because of a bimodal distribution of wide seams with osteoblasts and double tetracycline labels, and thin seams without osteoblasts or labels. Osteoid was lamellar. Osteoid in abnormal sites (within bone marrow or bone, or around osteocytes) was found less frequently in group I. Adjusted apposition rate declined and mineralization lag time increased in both groups because of extended unlabelled osteoid seams. Erosion surface increased only in group C. Hook and/or tunnel erosion was seen less frequently in group I; it was closely associated with osteoid in abnormal sites and correlated with osteoid surface. Extended osteoid surface may have forced osteoclasts to hollow out trabeculae, leaving the empty osteoid shell in marrow. Excess osteoid volume and eroded surface and osteoid and erosion in abnormal sites correlated with bone fragility in group C. We conclude that intermittent therapy is to be preferred because it (1) increased mineralized trabecular thickness, (2) did not cause excessive osteoid accumulation and erosion, (3) showed less osteoid and erosion in abnormal sites and (4) led to a similar reduction in the vertebral fracture rate as did continuous treatment. The question of whether intermittency of therapy has some other effect independent of the cumulative dose of fluoride administered cannot be answered by this study.     

Drift mobility measurements in thin epitaxial semiconductor layers using time-of-flight techniques

The conventional time-of-flight technique for measuring drift velocity in high mobility semiconductors is limited to relatively thick (> 200 μm) and high resistivity material. The microwave time-of-flight technique described here allows thin (～ 10 μm) low resistivity epitaxial layers to be measured with greater accuracy than is afforded by the conventional technique. The new experimental method is applied to the measurement of electron drift velocity in n-type GaAs at room temperature. The method, and its theory, is described in detail and its advantages and limitations are discussed.     

Hydroelectric power in emissions-constrained electricity generation

The positioning of generating plant in rank (merit) order has been based traditionally on minimised system economic cost. If regulations were introduced to place a financial penalty on gaseous emissions from fossil-fuelled power stations, the result would be an increased economic burden on such generating plant. This paper examines the effect on merit order of the imposition of a tax on carbon dioxide emissions, and looks in particular at the potential role to be played by hydroelectric power     

An airborne far-infrared spectrometer for astronomical observations

A Fabry-Perot spectrometer for airborne observations of astronomical spectral lines has been designed for use in the 50 to 200 μm region of the far-infrared. The spectrometer uses a fixed wavelength Fabry-Perot filter cooled to 4.2 K in conjunction with a high order scanning Fabry-Perot at room temperature. This arrangement provides high spectral resolution and also minimizes the thermal background radiation on the detector. The instrument has been successfully used to study all the presently detected fine structure lines between 50 and 120 μm.     

The effect of changes in initial reactant composition on solid-gas equilibria resulting from constant-volume,adiabatic processes

A method is given for the computation of the chemical equilibria attained by adiabatic chemical reactions in similar systems, all with the same volume and mass, as a result of changes in the initial reactant compositions. Changes in equilibrium composition and temperature are directly related to changes in the initial elemental abundances, in the form of a set of simultaneous equations. Since it is not necessary to perform complete calculations for each solution required, the solution of these equations constitutes a saving in computation. The method can be applied to solid-gas systems. The systems must be ideal or they have to obey an empirical equation of state, wherein covolume is a function of volume only.     

New polyisobutylene-based model ionomers

Mechanical properties of tri-arm polyisobutylene based ionomers have been investigated. Number average molecular weights (¯M_n's) of the polymers were varied from 8,300 to 34,000. The ionomer of lowest ¯M_n (8,300) exhibits very low extension at break (～ 150%) while the others with ¯M_n's of 11,000, 14,000 and 34,000 show very high extensions, often exceeding 1,000%, and display relatively low permanent set and low hysteresis behavior. Since the ionic bonding is located exclusively at the chain ends, end-linked pseudo networks are formed due to coulombic attractions.At higher temperatures the coulombic interactions are weakened and the networks can be compression molded (～150°C).     

Etiology of growth failure in a clinic population

To identify the basis of growth failure, the background of preschool children whose growth fell below 97 per cent of their peers was compared with that of those who demonstrated a higher level of growth achievement. A questionnaire administered at the home of each child documented living conditions, health history, and other family characteristics. Families of the growth-retarded children had higher income, higher credit payments, and used higher dollar values of Food Stamps. A greater percentage of the growth-retarded children were low-birth-weight infants. However, neither low birth weight nor any other one factor consistently predicted poor growth achievement. The need for adequate growth standards to correctly diagnose achievement remains a primary need in the field of nutritional assessment.