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Children with complex disabilities sometimes have difficulty communicating with their parents, caregivers, and teachers. For these children, eye gaze assistive technology can be used to facilitate communication. Eye gaze assistive technology outcomes for children and youth were analyzed in this systematic review. Database and hand-searches yielded 4412 unduplicated results, of which 11 articles were eligible for this review. Outcome measures, as well as environmental and personal factors, were mapped to the World Health Organization's International Classification of Functioning, Disability and Health framework. Communication outcomes were most prevalent and co-occurred with outcomes in all reported activities and participation domains. Environmental and personal factors were classified as either facilitators or as barriers in relation to device uptake and success. Although comprehensive professional and caregiver support was the primary facilitator for success, barriers could lead to rejection of the technology even when children were successful using the system.

This study sought to understand the perceptions of special education staff and caregivers (n = 6) who took part in a brain-computer interface (BCI) technology trial for individuals with severe cerebral palsy. Participants were interviewed post-trials regarding the different BCI components. The transcripts were coded and analyzed using thematic analysis. Results showed that BCIs are not suitable for independent use outside of clinical/laboratory settings. The hardware needs to be configurable, comfortable and accommodate physical support needs. The training approach needs to be less cognitively demanding, motivating and support personalized mental tasks. For BCIs to transition into the real world, there should be adequate technological support, improved reliability, and a systemic assessment of how the technology will fit into the lives of end users. Participants emphasized the on-going need to involve users and individuals who support them, to create a system that truly meets the needs of the users.

The purpose of this study is to systematically review published evidence regarding the development, use, and effectiveness of assistive devices and technol ogies that enable internet access for individuals who are deafblind. Eight electronic research databases (CINAHL, Embase, Engineering Village MEDLINE, PsycINFO, PubMed, Cochrane Library, and Web of Science) and three clinical trials registries (ISRCTN Registry, WHO ICTRP, and ClinicalTrials.gov) were searched.Seven articles met the inclusion criteria for this systematic review. The assistive technologies described were in the preliminary stages of development, with only three of the technologies having undergone any testing. The effectiveness of all seven assistive technologies was quantified in this review based on the proposed impacts of internet access on the domains of the World Health Organization's International Classification of Functioning, Disability and Health framework.Internet access technologies for individuals with deafblindness are in the early stages of development and are targeted toward specific functions of the internet. It is imperative that future device development and evaluation seek input from persons who are deafblind. There is also a need to address the gap between academic research, which seeks to develop assistive technology to access the internet and the translation into real-world use of this technology.

Using a commercial electroencephalography (EEG)-based brain-computer interface (BCI), the training and testing protocol for six individuals with spastic quadriplegic cerebral palsy (GMFCS and MACS IV and V) was evaluated.A customised, gamified training paradigm was employed. Over three weeks, the participants spent two sessions exploring the system, and up to six sessions playing the game which focussed on EEG feedback of left and right arm motor imagery.The participants showed variable inconclusive results in the ability to produce two distinct EEG patterns. Participant performance was influenced by physical illness, motivation, fatigue and concentration.The results from this case study highlight the infancy of BCIs as a form of assistive technology for people with cerebral palsy. Existing commercial BCIs are not designed according to the needs of end-users. Implications for Rehabilitation Mood, fatigue, physical illness and motivation influence the usability of a brain-computer interface. Commercial brain-computer interfaces are not designed for practical assistive technology use for people with cerebral palsy. Practical brain-computer interface assistive technologies may need to be flexible to suit individual needs.

An accurate assessment of ankle ligament kinematics is crucial in understanding the injury mechanisms and can help to improve the treatment of an injured ankle, especially when used in conjunction with robot-assisted therapy. A number of computational models have been developed and validated for assessing the kinematics of ankle ligaments. However, few of them can do real-time assessment to allow for an input into robotic rehabilitation programs.An ankle computational model was proposed and validated to quantify the kinematics of ankle ligaments as the foot moves in real-time. This model consists of three bone segments with three rotational degrees of freedom (DOFs) and 12 ankle ligaments. This model uses inputs for three position variables that can be measured from sensors in many ankle robotic devices that detect postures within the foot-ankle environment and outputs the kinematics of ankle ligaments. Validation of this model in terms of ligament length and strain was conducted by comparing it with published data on cadaver anatomy and magnetic resonance imaging.The model based on ligament lengths and strains is in concurrence with those from the published studies but is sensitive to ligament attachment positions.This ankle computational model has the potential to be used in robot-assisted therapy for real-time assessment of ligament kinematics. The results provide information regarding the quantification of kinematics associated with ankle ligaments related to the disability level and can be used for optimizing the robotic training trajectory.

This case study describes how an individual with spastic quadriplegic cerebral palsy was trained over a period of four weeks to use a commercial electroencephalography (EEG)-based brain-computer interface (BCI).The participant spent three sessions exploring the system, and seven sessions playing a game focused on EEG feedback training of left and right arm motor imagery and a customised, training game paradigm was employed.The participant showed improvement in the production of two distinct EEG patterns. The participant's performance was influenced by motivation, fatigue and concentration. Six weeks post-training the participant could still control the BCI and used this to type a sentence using an augmentative and alternative communication application on a wirelessly linked device.The results from this case study highlight the importance of creating a dynamic, relevant and engaging training environment for BCIs. Implications for Rehabilitation Customising a training paradigm to suit the users' interests can influence adherence to assistive technology training. Mood, fatigue, physical illness and motivation influence the usability of a brain-computer interface. Commercial brain-computer interfaces, which require little set up time, may be used as access technology for individuals with severe disabilities.

The Gouldian Finch (Erythrura gouldiae) has experienced significant decline in population and the extent of its range over the past 40 years, which has generally been attributed to the availability of suitable foraging habitat. Less research, however, has investigated the suitability or availability of breeding habitat of the species. Gouldian Finches are obligate cavity nesters, and a recent study has shown that they select nest-sites non-randomly based on structural characteristics of the cavity. Here we investigated the relative effects of different environmental factors on the spatial distribution of Gouldian Finch nests at two different scales. At the broader, landscape scale (over ~60 km2), the strongest predictor of nesting density at a site was the abundance of suitable nest-sites. At the finer scale (~1 km2), no single factor explained the variation in location of nest-sites. Gouldian Finches require areas of habitat characterised by high densities of suitable nest-sites (tree-cavities). Within these patches, individuals are potentially selecting nest-sites based on the morphometry of cavities rather than landscape features such as topography, vegetation or proximity to water. Our findings should be integrated with studies of feeding and habitat requirements in the non-breeding season, with the aim of constructing holistic and predictive habitat-suitability models for this endangered species.

A prototype device was developed to allow individuals to hear ultrasound reflections off environmental obstacles. Previous studies have shown that this device allows for better distance judgement than audition and allows for effective passage through the centreline of apertures. The purpose of this research was to evaluate audification as a method to localise direct sound sources as compared to audition.In an anechoic environment, participants localised point-sound sources for three conditions: auditory, audified ultrasound with receivers facing laterally, and audified ultrasound with receivers facing forward.Azimuth localisation was similar within a range of -35° to 35° in front of the participant among all conditions. At the periphery, -70° and 70°, audified ultrasound was more accurate than audition for novice participants. No difference was evident in user elevation accuracy for these signals among the different conditions.Audification of ultrasound can be effective for localising point-source sounds in the azimuth direction, but more evidence is required to evaluate accuracy in the vertical direction. [Box: see text].

We have investigated the potential utility of monoclonal antibodies against mini-chromosome maintenance-2 protein (Mcm2) in predicting meningioma recurrence. MCM proteins are members of the DNA-binding prereplicative complex and are essential for eukaryotic DNA replication. They are present throughout the cell cycle, but are down-regulated in quiescence and cell differentiation, making them specific markers of proliferating cells. We analysed 10 benign meningiomas that subsequently recurred within a 5-year period, together with 20 matched non-recurrent benign meningiomas. There was no significant correlation between histological subtype, mitotic count or Ki-67 labelling index and tumour recurrence. We observed that whilst the average Mcm2 labelling index (LI) of the tumour section as a whole (LI(Ave)) is not significantly different between recurrent and nonrecurrent meningiomas, the Mcm2 labelling index in the area of highest proliferative activity within the tumour section (LI(Max)) is significantly higher in recurrent meningiomas (p0.0001). Seven out of the 10 recurrent meningiomas displayed a Mcm2 LI((Max) greater than 30%, compared to 0 out of 20 for non-recurrent tumours. In conclusion, these results suggest that analysis of Mcm2 expression may facilitate identification of patients with a high risk of meningioma recurrence, for whom adjuvant radiotherapy may be of benefit.

The effect of initial density and rapid prestraining on superplastic ductility of 1 wt-%CuO doped cubic zirconia (8Y - CSZ) was investigated, To obtain a range of initial densities, the tensile test specimens were slip cast to net shape and pressureless sintered over a range of temperatures in air. The specimens were then superplastically tested at a temperature of 1500 K and at a constant strain rate of 1 x 10(-4) s(-1). The results showed that specimens with low initial densities had lower flow stresses and higher superplastic elongations to failure than higher density specimens. The reasons for the ductility change were discussed with reference to the presence of porosity and grain growth, For the prestraining test, a specimen with an initial density of 95% was prestrained to 30%, at a temperature of 1550 K and at a prestrain rate epsilon (1) of 1 x 10(-3) s(-1), followed by elongation to failure at a slower test strain rate epsilon (2) of 1 x 10(-4) s(-1). It was seen that prestraining at the above test conditions considerably improved superplastic ductility, The reasons for this ductility enhancement were explained in terms of suppression of grain growth. MST/4602.

As part of a three year study of the use of reed beds for the treatment of wastewater, two pilot scale constructed wetlands (30m × 5m), one planted with Phragmites australis and the other serving as an unplanted control, were used to treat primary domestic sewage. This paper describes an experiment conducted to test the hypothesis that increasing available oxygen by aeration of the wastewater in the treatment beds could increase nitrification, and hopefully nitrogen removal rates. Prior to aeration, the influent nitrogen load in the wastewater passing through the beds was reduced by approximately 45% and 10% in the planted and control beds respectively. With aeration of the wastewater as it passed through each bed, nitrogen removal was approximately 51% and 20% for the planted and control beds respectively. High rates of nitrification were recorded for the planted bed with aeration, but removal of nitrogen by denitrification was limited, probably because of the absence of a suitable carbon source (indicat...

Changes that occur during compaction are described utilising three equations related to stages in the densification of monosize spherical metal powders, consisting of an equation to describe geometric changes, an equation relating to the effect of pressure which causes flattening of originally spherical particles, and a third equation relating green strength and compacting pressure. Two new concepts are proposed, involving a quantitative description of the change of shape of originally spherical particles by flattening and the increase in interparticle contact area, and a parameter s, a function of particle coordination, packing state, and flattening parameter, is introduced. The continuous development of relative density during compaction is described in terms of the parameter s. PM/0720

Background: Many U.S. medical schools struggle to identify how to teach students the content and skills needed to communicate effectively with patients. Some schools have developed predoctoral curricula emphasizing both biomedical and psychosocial dimensions of patient care. It is important to identify whether this approach has a measurable impact on doctor‐patient communication. Purpose: This study examined the impact of learning styles on 200 Ist‐year medical students’ academic performance and interviewing skills. Methods: Analysis of variance were conducted comparing academic performance and interviewing skills across 4 learning styles in Kolb ‘s Learning Style Inventory. Results: Findings revealed statistically significant differences in academic performance (p < .05) and interviewing skills (p < .05) by students’ learning styles. Conclusions: Students possess different learning styles that influence their success in medical school. Educators can vary their teaching methods to ensure that students, re...

An explanation of the stability of the α ferrite or γ austenite phase in steels containing transition metal alloying elements that lie either to the left or right hand side of iron in the periodic table (except manganese which has an anomalous behaviour) is usually based on the empirical electron state and thermokinetic considerations evolved by Hume-Rothery and Zener. An alternative interpretation of the phase stability is proposed, based on the moments theorem of Cyrot-Lackman, i.e. an electron theory approach. It is also proposed that if the moments theorem approach can be coupled to thermokinetic aspects of phase transformations, it may be possible to predict some structural properties of steels from first principles.MST/2066

Extensive tensile ductility during superplastic deformation in ceramics has been demonstrated experimentally in yttria stabilized tetragonal zirconia polycrystals, with the achievement of about 800% tensile elongation reported. It has not been possible to achieve such extensive elongations in other ceramics such as Si3N4/SiC composites and alumina. The authors consider that the extensive superplastic deformations obtained in ceramics could be associated with the fact that some ceramics can be classified as having a ‘metallic’ character based on the nature of the orbitals responsible for their bonding. These metallic ceramics show extensive superplastic deformation compared with other ceramics that can be classified as insulators based on the nature of their bonding orbitals. This observation would help to demarcate ceramic materials that can exhibit superplasticity from the brittle ceramics.MST/1911

It is proposed that a correlation exists between the d state electronic configuration of transition metal based hardmetals and the thermokinetic reactions that take place between binder and hardmetal during sintering.MST/1749

Barium hexa-aluminate refractories, ceramic fibres, and ribbon can be obtained by sol–gel processing from precursor solutions containing a barium salt and an aluminium salt, the solutions having th...

In the search for possible causes for the enormous increase in testicular cancer incidence in Denmark, we tested the hypothesis that a high fat or calorie intake in adolescence and consequently relative obesity is a promotional factor for testicular cancer. A total of 438 cases and three controls for each case were included in the study. Data originated from health examination of men liable for military service. Data were analysed by logistic regression analysis. No systematic statistically significant differences in body measurements [height, weight and body-mass index (weight/height2)] could be shown. Rather than being obese a slight trend was observed towards the future victims of testicular cancer being lighter, smaller and thinner than unaffected controls.

Using a radial density distribution function (based on previous work by Scott) a coordination number–density equation has been derived for random packing of spherical powders. A new concept, highest random close packing (HRCP), is defined. PM/0719

During the period 1968–1975 GLOMAR CHALLENGER drilled holes at 392 locations covering all the major ocean basins except the Arctic. Besides demonstrating the validity of the concept of seafloor spreading, deep-sea drilling has produced important new information regarding the nature of seismic reflectors, the processes of oceanic sediment diagenesis and the stratigraphy of the seafloor. Of particular interest is the occurrence of major gaps in the sedimentary record, oceanwide in extent, which can be interpreted in terms of paleo-oceanographic conditions. The deep-sea drilling results will provide the most important single body of data which may be used to reconstruct the environmental history of the oceans.

Maximal power output during short term constant velocity cycling and vertical jumping from a force platform has been studied in five healthy young male subjects. From the measurements on the force platform the peak (instantaneous) power output (P), net impulse (IN ), force (F1 ). velocity of take-off(VT ) and height of jump(h) were calculated. The corresponding values for power (H), force (F) and velocity (V) on the bicycle were obtained from analysis of the force-velocity relationship. The results (mean ± S.D.) showed that on the force platform F1 P, IN, VT and h were 1073± 167N, 2205±310W, 154±17Ns, 2·48+0·15ms−1 and 31 +4cm. h was positively associated with both IN (r= +0·77) and P (r = 0·67). The mean maximal power output for cycling was 854W(39%) greater than jumping and was achieved at a 271N (25%) increase in F and a reduction in V. Nevertheless they were closely related. Platform P(W) = 717·6 + 0·483 bicycle H(W) r= +0·74 A comparison of linear and curvilinear (hyperbolic) analysis of the F/V bicy...

The physiological responses of 8 healthy male subjects were studied during one- and two-arm cranking exercise performed on a suitably modified bicycle ergometer under carefully standardised conditions utilising a shoulder restraining board and harness designed to restrict trunk movement. 'Apparent ’ mechanical efficiency (E—defined as the ratio of work performed to aerobic energy expended) was found to be similar at low levels of exercise to that previously found for leg work, namely 0.25; although there was a fall in E at levels in excess of ∼40% [Vdot]o 2, max- [Vdot]E was higher in arm work than in leg work for a given [Vdot]o 2 or [Vdot]co 2,: [Qdot], however remained the same for a given [Vdot]o 2,, although stroke volume was reduced and cardiac frequency increased in arm work when compared with leg work. The maximum aerobic power of the arms was found to be i that of the logs, but for a given limb volume (muscle plus bone—measured after the method of Jones and Pearson (1909)) was ∼ 13% higher in arm...

Cardiac output was measured as pulmonary blood flow by a non-invasive N2O rebreathing technique during exercise at submaximal and maximal work levels in three subjects. The standard deviation of repeated measurements over a period of 6-20 weeks was ±1·51 min −1 at all levels of work and in all subjects. This level of variability is comparable to that found in using the dye dilution and direct (O2) Fick methods in individual subjects during a more limited time span, and suggests that the method can be used effectively in non-steady state and maximal conditions of dynamic exercise.

This paper describes an experimental technique which has been used to study the physical and chemical changes which may be induced in powders heated to a high temperature very rapidly and held at t...

This paper gives an indication of the influence of inclusion content on the mechanical properties of two powder-forged low-alloy steels. The powders used were Hoganas ATST–D (0·3–0·4Mn–0·1–0·25Cr–0·2–0·3Ni–0·25–0·35Mo) and Hoganas ATST–A (0·25–0·35Mn–0·1 max. Cr–1·8–2·2Ni–0·45–0·55Mo). The inclusion content and distribution were modified by subjecting the powder preforms to different preforging treatments. Different matrices were produced for the ATST–D material by tempering at different temperatures after quench-hardening in oil. A number of fatigue samples were nitrocarburized to examine the effect of surface treatment on fatigue behaviour. An improvement in the fatigue endurance limit of 14% was achieved in the ATST–D material following a 60% reduction in the percentage area of inclusions. In comparison, nitrocarburizing improved the endurance limit of the higher inclusion content material by 43%. A combination of reduced inclusion content and nitrocarburizing produced an increase of 50% in en...

A simple inexpensive adaptation of a stationary bicycle ergometer is described which enables continuous recordings to be made of the forces exerted during one and two leg cycling. The system showed no systematic change in calibration characteristics over a six week period of intensive use. The coefficient of variation of 20 calibrations made during that period was

Fatigue of plain-carbon steels and low alloy steels in the as-powder-forged condition and after different surface treatments, namely nitriding (950K), nitro-carburizing (1020K), and carbonitriding (1330K), was undertaken at room temperature using rotating cantilever specimens. Tensile properties in both the as-forged and surface treated condition were used to assess the fatigue stress/UTS ratios of the materials. Quantitative television microscopy (QTM) was used to examine the nature, size, and distribution of non-metallic inclusions and pores in both as-forged and surface-treated materials on polished (unetched) surfaces. Some run-out fatigue specimens were also studied to evaluate porosity changes after fatigue at 10 Hz; the results indicated an increase in porosity mainly due to opening of collapsed pores under fatigue conditions. Although carbonitriding produced the largest improvement in fatigue strength (200% increase compared to untreated material) the nitrocarburizing of low alloy steels a...

Two low alloy powder forged vanadium steels of varying forged blank densities were controlled rolled in the austenitic range. Grain refinement of ferrite was aimed at, by processing the steels below the recrystallization temperature where nucleation takes place extensively on the elongated prior austenite grain boundaries. Effects of initial forged density and deformation on transformation were studied. The cooling rate effect was also examined by using four different cooling media (vermiculite, air, air blast, water) following the deformation. Rolling introduced deformation bands where ferrite nucleation occurred, which aided refinement of the transformed micro-structure. Also, densification achieved with increasing deformation led to almost pore free structures and improved grain refinement. Gas bubble formation observed in pore free zones in these hydrogen annealed powder forged steels was ascribed to a hydrogen gas reaction. Varying initial forged densities had no effect on specimen cooling ra...

The thermal responses to exercise in eight athletic pre-pubertal boys (mean age 12·8 years) and five young athletic adolescent girls (mean age 1·38 years) were studied in a moderate environment {T db = 21°C, T db = 17°C) and the results compared with data collected on eight adult athletes (mean age 36 years). The maximal aerobic power output (VO 2max) for the three groups averaged 66·7, 63·6 and 68·6 ml kg−1 min−1 respectively. At the same relative work load (%VO 2max), the metabolic heat production (M) was approximately 44% less in the children than the adults, but rectal temperature at the sixtieth min of exercise was the same in the two groups. The major difference between the subjects was in the mean skin temperature (T¯sk) and evaporative sweat loss (mdot;sk). Evaporative sweat loss was lower in children and T¯ sk was approximately 3°C higher, for the same environmental conditions, than in adults. The children were able to lose equal amounts of their total heat production (W)by physical (convection a...

(1987). Compaction and Green Strength of Ferrite Powders. Powder Metallurgy: Vol. 30, No. 4, pp. 267-271.

SummaryLongitudinal data on the growth and development of African boys and girls attending an urban primary school in Dar es Salaam during the years 1966–1971 together with cross-sectional height and weight data of children aged 7–15 years attending urban and rural schools in Tanzania are presented. No significant differences were found between the two groups and standards of height and weight, skinfold thickness and arm circumference are given. The data suggest that though East African children are smaller and lighter than European children, their shape (i.e. weight for height) and the ages at which peak height and weight increase are attained, are approximately the same. The data may form a basis for assessing the present state of growth and physique in Tanzania, but for the future more general standards will be required and some attempt should be made to investigate the possibility of using indices of muscle mass which are more pertinent to the physiological development of the child.

The relationship between blood lactate, pyruvate and excess lactate removal and the excess oxygen consumed during the recovery from work on a stationary bicycle ergometer was studied intensively on two healthy male subjects. The results showed contrary to the recent work of Huckabee (1958) and the studies of Rowell et al. (1966) that a clear quantitative relationship exists between the area under the second portion of a double exponential Vo2, recovery curve and the O2 equivalents of LA: the association between the two variables being r = 0·93 which accounted for over 80% of the total variance of the two measurements. The findings fully support the earlier concept of Margaria et al. (1933) of separate ‘ alactic ’ and ‘ lactic ’ portions of the O2 debt and suggest that it is these components of the post exercise V˚o2, which must be used in the analysis and interpretation of the contribution of anaerobic processes during work.

1. The methods which are commonly used in work physiology for rapid sampling, laboratory storage and analysis of expired air have been examined 2. The rapid fractional sampling of expired air from both a mixing chamber and a side arm sampling device produces significant differences in [Vdot]oa values when compared to the standard Douglas method. However, provided the volume of the mixing chamber is above 4 litres, the differences are small for this technique, (293 ±18.1 mls) compared with the side arm technique (263.4± 62.9 mls), and introduce negligible error into the estimation of energy expenditure 3. The selective loss of CO2 from butyl rubber bladders, Douglas bags and syringes was found to be 0.11 per cent/hr., 0.2 per cent/hr. and 0.007 per cent/hr. respectively during the 8 hr. period. Loss of CO2 during the first 30 min was high in the case of the bladders and they were found to be very unsatisfactory storage containers. Douglas bags showed a negligible loss of CO2 during the first 2 hours, but t...

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The physiological responses to repeated negative (downhill) work have been studied on 3 healthy male subjects aged 26-41 years. The results show a remarkable decline in [Vdot]o2 for a given work load ([Wdot]) from 19-7 ml. Kg−1 min−1 on day 1 to 120 ml. kg−1 min−1on Day 5 at the 60th min of exercise, representing a change of ’ apparent ’ mechanical efficiency of —0-43. However [Vdot]E for given [Vdot]co2; or [Vdot]Tand [Qdot] jH and blood lactic acid for given [Vdot]o2; remained unchanged. This was also true of Tty and sweat rate for given metabolic heat production. Thus provided respiratory, circulatory, and temperature measurements are related to the appropriate physiological variable, valid comparison can be made between and within groups of subjects independently of the degree of habituation. This is marked contrast to the situation found for positive work (Davies et al. 1970). It was suggested that the decrease in the [Vdot]o2/[wdot] relationship was in part due to an increase in muscular strength an...

Admixture of lubricant with metal powder can assist or retard densification according to the applied pressure and the lubricant content. Lubricant exuded on to the die wall under pressure seems to be the main lubricating factor. The change-over or transition pressure from lubrication to inhibition varies in a Gaussian manner with lubricant content. Molecular films of lubricant are sufficient, but for reduction in ejection pressure a minimum content of 0.2% lubricant is necessary. Die-wall lubrication is far more useful and effective than admixed lubricant. Simultaneous die lubrication and admixture is of no value.

Inter-subject variability of oxygen intake ([Vdot]O2)n relation to the anaerobic component of work has been investigated intensely on two healthy subjects and extensively on two groups of young and older men during work on an upright, stationary bicycle ergometer. Significant differences (p

A list of 134 species of Mycetophilidae and Sciaridae (Diptera) is given with notes on abundance or scarcity in relation to trap catches only, and at 1 particular site.

It is known that hydrogen concentrations in excess of room temperature equilibrium solubility exist at room temperature in iron and steel, and it is thought that this excess resides in traps in the lattice.1 It has been postulated that traps are the cause of the anomalously low diffusivity and high apparent solubility of hydrogen in iron and steel at ambient and intermediate temperatures < 150°C.2 -4 Of the numerous sites proposed as trapping centres, the principal traps in commercial steels appear to be microvoids of all forms including ferrite/carbide interfaces and matrix/ inclusion interfaces.5-9 The purpose of this note is to present evidence, obtained from hydrogen evolution data, for the presence of traps of two different strengths in a hydrogenated cold-worked pearlitic steel. Hydrogen evolution curves were obtained as part of a study of the influence of microstructure on the fracture of hydrogen-charged plain carbon steels.10 evolution of hydrogen from a heated specimen. To obtain the pressure increase due only to hydrogen evolution, the gas collected was diffused through a palladium thimble so that the volume of hydrogen evolved could be determined by difference. The rates of hydrogen evolution for the cold-worked pearlite and tempered martensite structures were monitored at 100° and 400°C, respectively. Figure 2 shows a plot of the cumulative volume of evolved hydrogen as a fraction of the total hydrogen evolved against time at temperature for both structures. A final extraction was carried out at 650°C for all specimens. Values of diffusivity were calculatedll using data from Fig.2; these are shown in Table 1.

Manuscript received 21 November 1979. S. T. S. Al-Hassani, BSc, MSc, PhD, is in the Mechanical Engineering Department, and T. J. Davies, PhD, MIM, is in. the Metallurgy Department, Joint UMIST/University of Manchester Bu:ilding, Manchester. Metal powders can be compacted using a high-voltage electrical discharge. The experimental set-up consists of a relatively simple electricqJ circuit using a column of metal powder as a short circuit resistance across a capacitor bank. This isshown in Fig. 1. The capacitor bank used in the present work'consisted of fifteen 5 . 3 ,uF capacitors which could be charged to 20 kV and discharged through an ignition switch, allowing the instantaneous discharge as well as the instantaneous voltages at both ends of the powder column to be measured. More detailed descriptions and analyses of the electrical circuit and the discharge conditions have been given previously. 1-3 Some typical shapes which have been compacted are shown in Fig. 2. These range from simple cylindrical shapes to flats and tubes. The materials successfully compacted included powders of pure iron, plain -carbon steel, stainless steel, pure nickel and nickel alloys, cobalt and cobalt alloys, aluminium and aluminium alloys, tin, chromium, and molybdenum. The mesh sizes of the powders ranged from -150 to -400 mesh and component sizes ranged from 50 to 500mm length and 4 to.8 mm diameter. The effect of varying the discharge voltage on the' structure of the preforms is shown in Fig. 3. This illustrates the fact that at low discharge voltages the discharge jumps from one longitudinal 'fibre' to another, forming a loose network of fibres with some transverse bridging. With increasing voltage, there is an increase in number and shortening in length of the transverse bridging units; the similarity between this lateral contraction and the 'pinch effect' of magnetohydrodynam,.. ics has been noted previously. 2 Whereas the inductance of the powder column did not change appreciably 'with discharge voltage, the ohmic resistance underwent drastic reduction, as shown in Fig. 4. This drop in resistance is coincidental with good metaIl metal contact and the disruption of oxide films on particle surfaces; an example of these contacts forming liquid phase necks between. particles is shown in Fig. '5. Hardness measurements showed that the powders were fully annealed during the discharge compaction. Preform density and bending strength increased with increased energy input up to a limiting charged voltage. Densities 9f up to 96% theoretical density were obtained. by coldswaging the preforms. It was noted experimentally that particular powders had a range of discharge voltages within which sound handleable compacts could be produced. This is shown schematically in Fig. 6, where the minimum voltage indicates a voltage below which preforms were not sufficiently strong, and the maximum a' voltage above which the powder column

This editorial analysis and comment introduces the materials relevant to the Oak Ridge “Security Risk” cases presented on the following six pages of the BULLETIN. Dr. Davies is assistant professor of chemistry and member of the Institute for Nuclear Studies at the University of Chicago.