Search

1. Normal dogs were trained to stand quietly upon a movable platform. The animals' postural adjustments in response to sinusoidal motion of the platform were assessed in both the normal and the blindfolded condition. The induced postural adjustments were described by the Fourier coefficients for the fundamental of the input together with the coefficients which were integral multiples of the fundamental. 2. All of the output variables, including motion at the hind limb joints and of the body, showed modifications when the dogs were blindfolded. The body motion increased in amplitude, as measured by the fundamental Fourier coefficient, and further lagged the input motion. Motion at the knee and phalangeal joints also increased in amplitude and the timing of these movements shifted from the normal in characteristic patterns for different frequencies of input motion. 3. The modifications of the postural response due to blindfolding were most pronounced at the lower input frequencies: 0·2–1·0 Hz. At 1·4 Hz or above the fundamental coefficients of most of the output measures resembled those of the normal condition. Even at the higher input frequencies, however, the postural response of the blindfolded dog was more distorted than that of the normal dog. 4. It is hypothesized that relatively slow movement of the visual surround provides the dog with information which is essential to normal operations of the postural control system.

Design aids to permit the rapid calculation of complete magnet and coil systems are presented.

Measurements of iodine dissolution rates in supercritical carbon dioxide and other supercritical fluids show when the iodine flux in these systems can be made fast. For these systems, the dominant factor in achieving this fast flux is the solubility; increases in diffusion coefficient have less effect. An approximate guide for estimating these fluxes is developed and compared with the experimental results.

The article deals with a hypersonic stream of viscous nonequilibrium-ionized gas around blunt bodies.

The properties of phantom modeling materials used in the fabrication of a trilayered spherical phantom and the characteristics of heating patterns induced in the phantom by 2450 MHz microwave radiation are discussed. The techniques used in the preparation of the simulated fat, muscle and brain materials resulted in material mixtures with homogeneous, reproducible and stable dielectric properties. The dielectric properties of these simulated materials exhibited no temperature dependence from 20° to 50°C. The heating patterns in the trilayered spherical phantom were obtained using an inexpensive liquid crystal photographic technique. The characteristics of these heating patterns are shown to be in good qualitative agreement with heating patterns obtained by thermographic techniques and theoretical calculations in homogeneous spherical phantoms. Heating patterns recorded in a bilayered spherical phantom by liquid crystal techniques have a shape and location similar to heating patterns observed in the...

An experimental characterization of the effects of thermal treatments and of fast-neutron irradiation on the elevated-temperature tensile and creep-rupture properties of a gas tungsten-arc-deposite...

Extension of PETP films at constant rate of deformation may, under certain conditions, result in stress oscillation and a periodic necking. The periodic necking results in formation of transverse bands, alternately opaque and transparent, in the sample. In this study, the temperature rise of such an oscillating neck was measured using an AGA Thermovision camera. The measured maximum surface temperature rise is very high, up to about 95° C and the temperature in the interior is probably higher. The formation of the opaque zone starts in the centre line of the foil and spreads out to a maximum width during the advance of the neck. It then suddenly ceases without reaching the surface of the sample. The opacity is probably a secondary effect dependent only on the high temperature formed by dissipated energy from the necking process and not affecting the mechanism of self-oscillating necking.

1 or 1.5 MeV He+ channeling techniques were used to study the lattice location and its annealing behavior of ion-implanted Te in GaAs single crystals as a function of implantation temperature. Channeling angular dips for He+ backscattering from both GaAs and Te atoms were measured. The relative amount of lattice disorder introduced by the implantation was also measured. It was concluded that most of room temperature implanted Te located on sites displaced by 0.34–0.49 A from the lattice rows after annealing at 550°C, while 72–100% of Te implanted above 200°C located exactly on the substitutional sites. It was observed that the lattice disorder remaining in the crystal after implantation decreased sharply at around 200°C implantation. An anneal stage for the lattice location and lattice disorder was found to exist in the temperature range between 100°C and 200°C.

Leakage neutron spectra for monoenergetic sources and for slab shields of different compositions and thicknesses are calculated. Source energies ranging from 0.34 keV to 10.5 MeV are considered, for the following shield materials: water, concrete, boron-loaded polythene and iron, at thicknesses ranging from 5 to 60 cm. Corrections to readings of several dose-meters are determined, making use of the spectra. The measured percentages of the dose- equivalent are evaluated for the following devicesi thermal neutron detectors, the Harvey albedo dosemeter, Yoshida -Dennis proportional counter, Dennis - Loosemore counter, nuclear emulsion and proton-recoil scintillation coumter. Dose-meter reading calculations are extended up to 15 MeV energy, which is of great practical importance at neutron generator monitoring. Finally recommendations are given concerning the selection of dose-meters for different monoenergetic neutron sources wlth different shieldings. (auth)

A study has been made of domain nucleation and propagation phenomena by pricking with a non magnetic needle a single‐crystal MnBi film under zero external field perpendicular to the surface. The demagnetized pattern formed by needle pricking is very different from that of ``as‐grown'' film. When a thicker part of the film (ratio of thickness to characteristic length h/lc∼100) is touched, the reversed domain encloses the pricking center and a hollow bubble is formed. The reversed domains emanate from the hollow bubble forming many bubble lattices with the initial magnetization, as if the Huygens wave spread from the source to the surrounding, and finally the crystal is demagnetized.

11B+ ions of 1011−1012/cm2 were implanted through gate oxides of 800–2000 A into the channel regions of p‐channel MOS transistors. For 50‐keV implantation, the dose dependence of threshold voltage could be explained by Swanson and Meindl's theory. In the case of implantation above 100 keV, slight deviation of the threshold voltage from the theoretical values was observed. Corresponding to this, the gate‐oxide‐thickness dependence of the threshold voltage was slightly deviated from the theoretical values in the range of less than 1300 A. For more than 1500 A, the measured threshold voltages coincided with calculated values. The energy dependence of the dose limit for ``ability to turn on‐off'' showed good agreement with the curve calculated on the basis of Swanson and Meindl's theory within this experimental error. Source‐drain current in the saturation region was slightly increased with increasing dose at least up to 5 × 1011/cm2, presumably due to the carrier compensation (band bending) and increase of t...

An intranuclear-cascade-evaporation model has been applied to predict the energy spectra of the products (neutrons, protons, deuterons, tritons, /sup 3/ He's, alpha particles, and residual nuclei) from pi /sup -/ capture in several materials (tissue, tissue-equivalent plastic, silicon, and germaniuml of interest in pion dosimetry. Also, the energy spectra of the products from 90-MeV pi /sup -/ interactions in tissue are computed. (auth)

A theory of ultrasonic spin echoes valid for arbitrary spin is presented. Semiclassical vector-model equations are constructed for components of the dipole and quadrupole moment tensors which are excited by ultrasonic pulses in analogy with the well-known Bloch equations. The echo amplitudes are found to depend on the wave number of the pulse, the crystal length, spin density, sound velocity, the density of the medium as well as the magnitude of the appropriate macroscopic dipole or quadrupole moment. Our numerical estimates for a number of physical systems indicate that ultrasonic-spin-echo experiments are feasible for a variety of nuclear and electronic spin systems.

Previous calculations of the steady-state oxygen distribution in the in vivo cornea were made using assumed values for the needed parameters. Recent work has yielded experimental results on these quantities and we have used these to compute the oxygen tension distributions in the cornea for several conditions. The main result, which differs from the earlier calculations, is that there is an oxygen flux from the aqueous into the cornea in the open-eye steady-state condition. Oxygen tension profiles are also presented for the closed eye and for a corneal-contact lens system. Implications of the various profiles are discussed.

The ultrasonic echo back-scattered by blood fluctuates as a function of time delay and lateral displacement of the source-receiver. This granular echo is not due to any special structure in the blood on the scale observed, but probably arises from fluctuation scattering by the random distribution of red cells; the dimensions of the ultrasonic pulse determine the scale of fluctuation detected. A statistical diffraction theory is developed, and formulae derived for the mean relative echo envelope Pi , and the mean rates of fluctuation Ni and NR of the envelope about its mean as the time delay and lateral displacement are varied. Ni and NR agree reasonably with experiment, but Pi is in error by a factor of thirteen; this discrepancy is discussed, and possible explanations suggested.

The isochronal annealing behavior of the effective surface carrier concentration and effective Hall mobility of Zn-implanted layers in GaAs has been investigated. Ion implantation has been performed with 60 keV Zn ion at various doses up to 1016/cm2 at room temperature and 400°C. An annealing stage for effective Hall mobility exsists between 600 and 700°C. After annealing at 700°C and above, ionized-impurity scattering is a dominant mechanism affecting the mobility. The highest mobility obtained is 170 cm2/V sec. The maximum effective surface carrier concentration is achieved after annealing at temperatures around 700°C. Samples implanted with doses up to 1015/cm2 show a 100% doping efficiency and those implanted with heavier doses show a saturation tendency in the effective surface carrier concentration.

Pulsed NMR is used to study the kinetics of dehydration of frog gastrocnemius muscle. In addition, measurements are reported of the variation of the spin-lattice ( T 1 ) and transverse ( T 2 ) nuclear magnetic relaxation times of the water protons as a function of water content. The proton transverse relaxation and freezing properties of the water in muscles which had been dehydrated and then rehydrated are also investigated. Correlation of the double-exponential dehydration kinetics with the transverse relaxation at various water contents provides strong evidence for the evidence of a fraction of muscle water (10–20%) which is sufficiently strongly held to the solid substance of the muscle to make it relatively slowly removed under conditions of zero relative humidity but which is still dynamically very mobile on average. This is supported by the dependence of T 1 on water content. The relaxation times are interpreted qualitatively in terms of a number of possible effects which are at present not distinguishable. The properties of the dehydrated-rehydrated muscles indicated changes in the muscle proteins which affect the transverse relaxation of the water protons and the freezing properties of the muscle water.

Silicon specimens have been implanted either with phosphorous ions (30 keV, 1016 at/cm2) or with arsenic ions (energies between 30 and 140 keV, doses in the order of 1015 at/cm2). In the case of phosphorous implantation, an amorphous layer has been observed using electron microscopy. The epitaxial recrystallization of this layer occurs at 650 "C. During annealing at higher temperatures, the formation and evolution of defects such as dislocation loops and dipoles have been observed. In the case of arsenic implantations, the formation of defects such as microtwins, loops, linear defects ... takes place during the recrystallization of the amorphous layer.

A balanced superconducting second-derivative gradiometer has been constructed in order to measure magnetic phenomena in an unshielded environment. The essential design features of the gradiometer, including its insensitivity to rotation and its capability of discriminating effectively against magnetic fields from distant sources, are described. Several details of the measured response of the gradiometer are presented to establish a correspondence between the design and the actual performance. Two magnetocardio-grams and a measurement of remanent magnetization in the area of the chest resulting from a 100 Oe magnetizing field are shown as typical results obtained in an unshielded environment. The observation of a magnetic signal synchronized with the heartbeat but which depends upon orientation of the subject and apparatus in the earth's field is also reported.

This paper describes and presents results of an experiment measuring the fluence and absorbed dose delivered by electron accelerator-produced muons penetrating thick iron shields. The experiment was designed to check the theoretical calculations described in the preceding paper. Nuclear track emulsions and scintillation counters were used to measure fluence and 7 LiF was used for the dose measurements. It is shown that the absorbed dose can be calculated from the fluence data by using a restricted stopping power. The results of the measurements indicate that the theoretical calculation accurately predicts the muon fluence and absorbed dose at small angles (

Optical waveguides are formed by implantation of various ions (H+, H2+, He+, Li+, and B+) in fused quartz and the properties of mode propagation are investigated at 6328 A. The origin of the refractive index change is discussed from the ESR measurement. The depth distribution of defects is measured by ESR measurements and the effective thickness of the high-refractive index region is estimated from the measured depth distribution of defects. In as-implanted samples, the propagation loss decreases with decreasing fluence, but a minimum fluence is required for a given implantation energy for the lowest mode to be propagated. The propagation loss is explained to be internal absorption due to color centers introduced by ion implantation. It is shown that the propagation losses are different for various implanted ions. Annealing behavior of the propagation loss and the refractive index change is also presented.

Small-angle multiple scattering of high energy protons has recently been shown to give rise to an edge pattern which can be used for radiography. The authors derive the intensity pattern involved and discuss its implications for radiography. They also derive the degradation of the intensity pattern by obscuring matter and various instrumental effects and use it in design of arrangements for taking scattering radiographs with protons of 160 MeV and 7 100 MeV. Sample radiographs illustrate the main differences from, and advantages of the technique over, x-radiography recorded on film. The resemblance to xero-radiography is pointed out.

Dose buildup factors for normally incident 662-keV gamma rays penetrating multilayered aluminum-lead slabs were measured for various combinations using thermoluminescence dosimeters. The results were compared with calculated values obtained from a gamma-ray transport code and with values inferred from a semiempirical formula using single-layer slab buildup factors. This formula, a slightly modified version of the Kalos formula, predicts buildup factors in excellent agreement with both experiments and calculations, even for multilayered combinations. The formula also provides buildup factors which are in good agreement with transport calculations for other source energies and slab materials, indicating a probable wide range of validity. (auth)

An adiabatic scanning calorimeter has been made with a controlled heating rate. The sample used was relatively small (3-10g), but the accuracy of the calorimeter was found to be within 2% in temperatures ranging from room temperature to 1000K. It is shown that the temperature distribution in the sample vessel produced in the continuous heating type calorimeter is proportional to the heating rate and inversely proportional to the thermal diffusivity in the sample vessel. An estimate of, and the correction for, the error due to the temperature distribution in the sample vessel has been made. The dehydration reaction of CuSO45H2O was studied, and very sharp, separate, endothermic peaks of the dehydration reaction were obtained.

We have used low‐energy electron irradiations in conjunction with a bending‐cantilever‐plate technique to investigate the volume dilatations produced by ionization effects in fused silica. Our irradiations generally cause compaction in agreement with previous data from high‐energy electron irradiations, but we consistently observe a slowly saturating compaction‐dose relationship rather than the sublinear power‐law relationship seen in the high‐energy data. Our results show agreement with the apparent ionization compaction effect extracted from low‐dose‐rate 1H+‐ion‐implantation experiments. We find no dose‐rate dependence in the electron ionization compaction effect, in marked contrast with the apparent ionization compaction effect in the implantation experiments. We therefore conclude that the enhancement of the apparent ionization compaction effect at high dose rates in the implantation experiments results from an interaction between the ionization and the atomic displacements accompanying the implanati...

Helium andargon ions in the energy range 100 to 1400 eV and at doses varying from 1012 to 1015 ions/cm2 were implanted in a 304L stainless steel sample. Following implantation a linear temperature increase of the sample caused the gases to be released. The thermal release rates were studied as a function of ion dose and energy. The maxima observed in the thermal release rates are used to determine activation energies for thermally activated processes occurring in the metal. A rapid increase in the CO release rate coincident with the highest temperature He re-emission maximum indicates that the same mechanism is responsible for the release of both CO and He. It is suggested that the transport mechanisms revealed here are important in controlling void formations in neutron irradiated metals.

The spatial distribution and the charge-accumulation kinetics during electron irradiation have been studied. The value of the injected charge which produces the destruction of the glass has been evaluated. Experiments have been made on the transmission of polarized light through a charged specimen. An optical method is proposed for measuring the distribution of the aecumulated-charge density throughout the specimen.

The calorimeter developed in this laboratory for isothermal enthalpy-of-dilution measurements is adapted for use as an adiabatic calorimeter for freezing-point studies. Results are obtained for ethanol solutions in cyclohexane at mole fractions of ethanol from 0.001 up to 0.08. Activities calculated from the results are used to test association models.

Use of the threshold detector system is considered for the measurement of neutron doses below the fission threshold of/sup 237/Np. For the real neutron spectra of different critical assemblies the specific dose in the energy region 400 eV to 0.56 MeV varies widely. This leads to inaccuracy in the dose estimate using the simple assumption of a 1/E spectrum. A new interpretation is proposed using a different spectral model, which enables the accuracy of the dose estimate to be greatly improved. (auth)

The data presented here are intended for use in studying the effects of electron contamination in negatively charged pion beams which are used in cancer radiotherapy. Electron-photon cascade calculations have been carried out for zero-width beams of electrons with kinetic energies of 50, 100, 150, and 200 MeV normally incident on a water phantom. The energy deposition per unit volume as a function of depth and radius in the phantom is given. To make the results more accessible for treatment planning, a quasi-analytic representation of the energy-deposition data has been obtained and is presented.

The magnetic rotational strengths (MRS) associated with the non‐totally‐symmetric vibrations in formaldehyde are calculated with CNDO/2 wave functions. The effects of configuration interaction are examined. We have also identified a single term that dominates the MRS. This raises the possibility of an economy of thought in attempts at correlating MRS data with molecular structure in the case of magnetic dipole allowed transitions.

The physical properties of the concepts frequently used in radiationdosimetry to compute dose are studied for high‐energy x‐ray beams. The dose in tissue is divided into total incident and phantom‐scatter components. The incident beam includes the primary photons as well as the collimatorscattering contribution. The phantom scattering is composed of back‐ and front‐scatter functions. The former function is shown to have essentially zero effect on dose at 33‐ and 45‐MV energy x rays.Characteristics of tissue‐maximum‐ratio (TMR) at high energies are investigated and TMR tables are provided. Contrary to the definition of TMR, this function is observed to depend on SSD. TMR curves are fitted with a semi‐empirical function with a maximum deviation of 1%. Mathematical equations are derived for the computation of dose from TMR. The applicability of the equivalent square technique to high energy photons is examined and found to be adequate. Properties of percent depth dose are studied and a number of related phenomena are discussed.

The formulas for the Raman intensities of fundamental and n-th overtones were investigated theoretically, starting from the Kramers-Heisenberg dispersion formula and referring to a diatomic molecule in a harmonic potential approximation. The derived formulas were then applied to fifteen overtone bands of iodine, which have been observed in gas, and to the exciting frequency dependence of the fundamental and the first overtone intensities of iodine in a CHCl3 solution. It was shown that the formulas quantitatively explain the trend of the observed data well.

Using the time-of-flight technique, the drift mobilities, trapping levels, and trap concentrations were measured for both holes and electrons in Cl- and Br-doped CdTe grown by the Travelling Heater Method. Electron traps 25 and 50 MeV below the conduction band and hole traps 140 and 350 MeV above the valence band were found in Cl-doped material. The 25 MeV electron and 140 MeV hole traps were also found in the Br-doped CdTe, but with a concentration nearly 10 times that of the Cl-doped CdTe. A model based on the mass action approach of Kroeger which describes the association of cadmium vacancies and halogen atoms substitutionally located on tellurium sites has been used to interpret the different behavior of Br and Cl in CdTe. The stronger bonding of the Cl increases the tendency to form associates, thus decreasing the number of unassociated species (cadmium vacancies and isolated Cl) which act as trapping-centers in CdTe.

A study has been made of atrial transmembrane potentials of rabbit and guinea pig hearts. In addition to the voltage-time record the first time derivative of the action potential was displayed as a function of voltage, yielding a phase-plane trajectory. A number of parameters of the action potential were determined from the trajectory, assuming cable behaviour. The validity of this assumption is discussed, and the effects of temperature reduction determined.

Novel demodulator structures are derived using a theory for the quasi-optimal on-line demodulation of pulse-frequency modulated (PFM) signals in the presence of white Gaussian channel noise. The basic demodulator consists of a phase-locked loop with time-varying gain elements. Furthermore, its integrators are appropriately reset as each new pulse is received. This modulator may be augmented with additional integrators and gain elements to achieve quasi-optimal demodulation with delay. The quasi-optimal demodulation approaches optimal demodulation, in the minimum mean-square-error sense, as the signal-to-noise ratio increases. The various quasi-optimal receivers are derived by application of the extended Kalman filter theory to a state-space signal model.

A dynamic model of oxygen uptake in the human lung is constructed by using unsteady mass balance equations in the gas phase and the blood phase. The model takes into account ventilation, perfusion, and oxygen transport from the alveolar gas to the capillary blood. Because of the non-linearity of the governing equations, a finite difference scheme is used for the calculations. Various effects of parameters characterizing breathing pattern, pulmonary capillary blood flow, and diffusion capacity of the alveolar-capillary membrane on the oxygen uptake are studied.

The use of thermoluminescent dosimeters (TLDs) to determine gamma-ray heating in a zero-power fast-reactor environment is considered. Generalized cavity-ionization theory is used to determine the relationship between the gamma- ray heating in the medium and the energy deposited in a TLD placed within the medium. The relationship is a function of the composition of the TLD and the surrounding medium, the size of the TLD, and the gamma-ray spectrum in the medium. Calculations are presented for several combinations of these variables. Data on the response of TLD materials to fast neutrons are reviewed. The fast-neutron- induced contribution to the thermoluminescent output relative to the gamma-ray- induced contribution is investigated. The relationship between the thermoluminescent response and the energy deposited in the dosimeter is also discussed. (auth)

Optical absorption, electron paramagnetic resonance absorption, and thermoluminescence have been measured in germanium-doped quartz crystals which have been X-irradiated at room temperature and subsequently heated. Strong bleaching of the 280 nm optical absorption and the A and C center magnetic resonance absorptions coincided with maxima of the total thermoluminescent glow curve. The temperature at which these several phenomena occurred varied for different quartz samples.

A calorimeter has been used to measure the absorbed dose in tissue from a beam of fast neutrons. The calorimeter is of the twin type and is made of tissue-equivalent plastic. The calorimeter was calibrated electrically using the electrical resistivity of the plastic. The partial dose due to gamma -radiation was measured separately with photographic film in order to derive the neutron dose alone. The results were compared with those found using ionization chambers. Satisfactory results were only obtained after pre-irradiation of the plastic by at least 100 krad of electrons. The accuracy obtainable by the calorimetric method seems similar to or slightly better than that obtainable with ionization chambers.

The effect of 40 keV Kr ion bombardment of Al2O3 single crystals has been investigated using a Rutherford backscattering-channelling (RBC) technique. Curves of lattice disorder were found to be sigmoidal; the disorder increasing slowly up to a fluence of 1 × 1015 ions cm−2 and then accelerating to a saturation level at ∼ 1 × 1016 ions cm−2. These doses are about 100 times higher than comparable values found for elemental and III–V semiconductor compounds. The number of displaced atoms per incident ion estimated for an ion dose of 3 ×1014 ions cm−2 was found to be less than that calculated using Sigmund's equation. This difference is discussed in terms of defect recombination and re-ordering during bombardment. Measurements taken from the RBC random spectra before and after each bombardment have indicated that the stoichiometry of the alumina crystals did not alter even at the highest bombardment fluences used.

The capacitors were irradiated with an electron beam at doses of 1011 to 1017 electrons/cm2 and energies of 5 kV and 15 kV. C-V measurements were made to characterise the effects of irradiation. The C-V curves revealed a positive fixed charge accumulation in the oxide at dose levels above 1013 electrons/cm2. In the thicker oxide samples at 5 kV there was evidence of negative charge trapping at the lower dose levels changing to positive at the highest dose. In all cases, there was a reversal in the sense of the hysteresis effects in the C-V curves above 1015 electrons/cm2, implying slow surface states which could follow the d.c. bias voltage but not the a.c. test signal. There was also a marked increase in the magnitude of the turn-on voltage for strong inversion implying an increase in fast surface states or lateral ionic charge nonuniformities.

Results are presented of an experimental investigation of light scattering by blood flow. The relationship between the observed dependence of the scattering on the time and strain rate and the aggregation of particles (erythrocytes) and hydrodynamic characteristics is discussed.

Problems of deformation in amorphous, glass-like polymers are considered. The deformation and strength properties of PMMA (polymethyl methacrylate) were studied, for different temperatures and conditions of deformation. It was established that the long-term resistance to deformation of glass-like polymers subjected to forced elastic deformation, as judged by the time lapse to "neck" formation, is described by a longevity equation, allowance being made for the displacement of the origin with respect to the coordinates.

Nitrous oxide, carbon dioxide and ethylene were utilized as gaseous chemical dosimeters, and measurements were made of the doses absorbed by these substances in a nuclear reactor. The neutron and photon fluxes as well as their contributions to the absorbed doses were determined by analyzing the data obtained from the chemical dosimetry, with particular consideration given to the fast neutron energy spectrum. The values of the photon, thermal neutron and fast neutron fluxes thus determined were 2. 6×1013 γ/cm2·sec, 3. 5 × 1013 n/cm2·sec and 7.0×1013 exp(- E)sinh√2E n/cm2·sec. These values were compared with the results from calorimetrie and activation methods, and were found to be in fair agreement with each other. From the above results, it was confirmed that the above combination of chemical dosimeters are serviceable for the measurement of both absorbed dose and fluxes in a nuclear reactor.

An ultrasonic critical-angle method and an ultrasonic resonance method have been successfully used to monitor the cross-linking reaction in amine-cured epoxide resins in both unfilled and filled states by measuring the ultrasonic velocity. Glass beads and glass fibre have been used as fillers to produce isotropic and unidirectional glass-fibre composites. The values of modulus measured on the isotropic composite were in agreement with an exact theory developed by Kerner. Theoretical results are also presented over a range of fibre loading showing how the modulus changes for the uncured and cured glass-fibre composites, with the fibre in a variety of geometrical arrays.

The elastic moduli for human and bovine bone specimens were determined by compression and tension tests and compared. No statistically significant difference was found between the moduli determined in the two loading modes.

A laser based optical densitometer system has been developed for scanning thin film dosimeters (T.F.D.'s). The system utilizes a laser beam whose wave length occurs in the maximum optical attenuation spectral range of the dosimeter film dye. A split beam comparitor technique allows accurate determination of radiation induced changes in the dosimeter film optical density.

An improved small-signal bipolar microwave transistor utilizing ion-implantation has been developed. The structure comprises oxide isolation, arsenic-doped emitters and an ion-implanted base region. A noise figure of 3·9 dB at 8 GHz has been achieved. The variation of the device parameters with the implanted dose has been investigated and the results are interpreted in terms of a simplified model. Implanted emitters and diffused emitters have been evaluated and found to give similar results.

The effects caused by bone present in phantoms irradiated by negatively charged pions on absorbed dose, cell survival, oxygen enhancement ratio, and relative biological effectiveness have been estimated using Monte Carlo methods. The influence of bone along the pion path and also the influence of a bone–tissue interface parallel to the direction of motion of the pions have been considered. Calculated results, as a function of spatial coordinates in a 30‐g/cm2‐thick tissue phantom with bone both included and excluded, are presented. All of the biological data reported here are for T‐1 human kidney cells. The extent to which the effects of bone in the path of the pion beam can be approximated by using results for tissue and measuring depth in the phantom in g/cm2 is considered and discussed.