In-Situ Nuclear Magnetic Resonance Investigation of Strain, Temperature, and Strain-Rate Variations of Deformation-Induced Vacancy Concentration in Aluminum

Critical strain to serrated flow in solid solution alloys exhibiting dynamic strain aging (DSA) or Portevin–LeChatelier effect is due to the strain-induced vacancy production. Nuclear magnetic resonance (NMR) techniques can be used to monitor in situ the dynamical behavior of point and line defects in materials during deformation, and these techniques are nondestructive and noninvasive. The new CUT-sequence pulse method allowed an accurate evaluation of the strain-enhanced vacancy diffusion and, thus, the excess vacancy concentration during deformation as a function of strain, strain rate, and temperature. Due to skin effect problems in metals at high frequencies, thin foils of Al were used and experimental results correlated with models based on vacancy production through mechanical work (vs thermal jogs), while in situ annealing of excess vacancies is noted at high temperatures. These correlations made it feasible to obtain explicit dependencies of the strain-induced vacancy concentration on test variables such as the strain, strain rate, and temperature. These studies clearly reveal the power and utility of these NMR techniques in the determination of deformation-induced vacancies in situ in a noninvasive fashion.

The course of health-related quality of life of preschool children with cerebral palsy

The purpose of this paper is to describe the course of the health-related quality of life (HR-QoL) of children with cerebral palsy (CP) between the ages of 2.5 and 4.5 years, at both group and individual level. We also examined whether CP characteristics are helpful in understanding which children show a decrease in HR-QoL. HR-QoL of 72 children with CP was measured using the TNO-AZL Preschool children Quality of Life (TAPQOL) questionnaire at the ages of 2.5, 3.5 and 4.5 years. The course of HR-QoL was compared between groups with different CP characteristics. Median scores for 10 of the 12 domains of the TAPQOL were found to be stable between ages 2.5 and 4.5 years. However, individual children showed great changes in HR-QoL at these ages, for all domains. A larger proportion of children with less severe CP showed a decrease in HR-QoL for the behaviour problems domain (p = 0.02), and a larger proportion of unilaterally affected children showed a decrease in HR-QoL regarding the anxiety (p <0.001) and social functioning (p = 0.01) domains. Although the median HR-QoL of children with CP is generally stable at these ages, much variation in the course of HR-QoL exists between individual children. There is no clear association between motor functioning or limb distribution and a decrease in HR-Qo

ORDERING IN CuNiZn ALLOYS

Par microscopie électronique et en mesurant la variation de résistivité les auteurs ont étudié quatre alliages de structure c.f.c., de composition Cu2NiZn, Cu3Zn, Ni3Zn et CuNi2Zn. La cinétique de grossissement isotherme de domaines ordonnés dans Cu2NiZn suit une loi [MATH] = Ktn avec n voisin de 0,3. Il n'existe pas d'ordre à grande distance dans les alliages Cu3Zn et Ni3Zn même après de longs recuits de mise en ordre aux températures de 61 et 110°C respectivement. Les micrographies en champ sombre fondamental de l'alliage CuNi2Zn présentent un fort "clustering".Electron microscopy and electrical resistivity have been used in a comparative study of Cu2NiZn, Cu3Zn, Ni3Zn and CuNi2Zn. Quantitative measurements on the kinetics of domain growth in ordered Cu2NiZn have been made and a t1'3 law is observed for the growth process. Alloys near the composition Cu3Zn and Ni3Zn do not show long range order even after long anneals at 61 and 110°C respectively. Dark field micrographs of CuNi2Zn using a fundamental reflection indicate strong clustering

Family-centred service: differences in what parents of children with cerebral palsy rate important

BackgroundA family-centred approach to services of children with disabilities is widely accepted as the foundational approach to service delivery in paediatric health care. The 56 items of the Measure of Processes of Care questionnaire (MPOC-56) all reflect elements of family-centred service. In this study, we investigated which elements of family-centred service are rated important by parents of children with cerebral palsy by adding a question on importance to each item of the MPOC-56 (MPOC-56-I). MethodsIn total, 175 parents of children with cerebral palsy completed the MPOC-56-I. For each MPOC item, parents were asked to rate the importance on a 5-point scale ranging from 0 (not important at all) up to and including 4 (very important). We used Spearman's rank correlation coefficient to further explore the variation in parents' importance ratings. ResultsParents' importance ratings of the MPOC-56 items varied. The percentage of parents rating an item important (importance rating 3 or 4) varied between 43.8% and 96.8%. The percentage of parents rating an item unimportant (rating 0 or 1) varied between 0.0% and 20.3%, and the percentage of parents rating an item neutral (rating 2) varied between 3.0% and 36.0%. Most diverse importance ratings were found for five items concerning the provision of general information. Three correlations between these items and child and parent characteristics were found. Six items were rated important by almost all (95%) parents. These items concern elements of specific information about the child, co-ordinated and comprehensive care for child and family and enabling and partnership. ConclusionsParents rate the importance of family-centred services for their situation in various ways. These findings endorse that family-centred services should recognize the uniqueness of families and should be tailored to what parents find importan

The orientation dependence of dislocation slip in NaCl single crystals

Results are presented of investigations into the role of dislocation motion in deforming NaCl single crystals, using the technique of pulsed N.M.R. In particular, the spin-locking pulse sequence is used to measure T 1p, which is the spin-lattice relaxation time in the presence of a resonant r.f. magnetic field. T 1p, depends strongly on the mean free path L which is covered by the dislocations during successive jumps between obstacles in their glide plane. The mean free path is determined in crystals compressed in different directions, in which cases either the {110} or the {100} planes are primarily activated. It is shown that both the mean free path, measured as a function of strain rate and of the applied stress, and the work hardening differ remarkably for the two different primary slip planes. The magnitude of the mean free path is compared with the mean distance between dislocations in the crystal and the activation length of dislocations at obstacles, as obtained from mechanical stress relaxation experiments

Parents' perceptions of the services provided to children with cerebral palsy in the transition from preschool rehabilitation to school-based services

Aim: To describe the course of parents' perceptions of the family centredness of rehabilitation services provided to their children with cerebral palsy (CP) before and after the transition from preschool to school-based services. Background: Parents of 59 children with CP aged 2.5 to 4.5 years filled in the 56-item Measure of Processes of Care (MPOC-56) on three occasions pre (2) and post (1) transition to school-based services. Friedman tests were used to describe changes in parents' perceptions over time. Mann–Whitney U tests were used to describe differences in course of parents' perceptions between regular school and special school or day care. Results: Parents' perceptions of preschool services were stable between the ages of 2.5 and 3.5 years, with a decline after transition on four of the five domains of the MPOC (P <0.05). The domain providing general information was scored lowest (median at baseline 3.56, IQR 2.39) compared with the four other MPOC domains, but remained stable over time. No differences in course of parental perceptions were found for school type. Conclusion: The transition from preschool to school-based services for children with CP is associated with a decrease in parents' perception of family centredness independent of the type of school. The transition in services has a negative impact on perceived family-centred practices

Assessment of family needs in children with physical disabilities: Development of a family needs inventory

Background: Valid tools to assess family needs for children with physical disabilities are needed to help tune paediatric rehabilitation care processes to individual needs of these families. To create such a family needs inventory, needs of families of children with a physical disability (age 0-18 years) were identified. We examined differences in the number and type of needs listed by families when asked for by means of an interview compared with using an inventory. Methods: Forty-nine families of children with a wide variety of physical disabilities (mean age 7.7 years; SD 4.6) participated in semi-structured interviews, focusing on family needs. They also checked an inventory of 99 items (based on a previously conducted literature review), regarding their family needs. In addition, individual interviews with healthcare professionals, and panel meetings with healthcare professionals and parents were held to further identify relevant family needs for the inventory. Results: The individual parent and healthcare professional interviews raised 41 needs that were not included in the original inventory of 99 items. Moreover, the panel meetings raised a further 49 needs. After restructuring and reformulating several items, a 187-item Family Needs Inventory - Paediatric Rehabilitation (FNI-PR) was created. The parent interviews revealed significantly less family needs (mean number of needs = 10.8; SD = 6.0) compared with using the inventory (mean number of needs = 31.7; SD = 19.7) (P < 0.0001). Most expressed family needs were related to both general and specific information concerning the child's development and treatment, aids and information about legislation and to rules relating to compensation of costs. Conclusion: Based on responses of parents and healthcare professionals the FNI-PR has been developed, a comprehensive inventory for family needs that can be used in paediatric rehabilitation. An inventory checked by parents resulted in more family needs than a single open-ended question. The inventory may facilitate the implementation of family-centred care

Dislocation dynamics in alkali halide single crystals investigated by nuclear spin relaxation measurements

La résonance magnétique nucléaire est appliquée à l'étude de la variation de la vitesse des dislocations avec la contrainte de compression appliquée dans des cristaux d'halogénures alcalins. T1ρ a été mesurée en fonction du taux [MATH] de la déformation plastique. La route moyenne des dislocations mobiles a été déterminée. Nous indiquons les résultats des expériences sur de différents noyaux, sur de différentes orientations des cristaux et sur des températures différentes.Dislocations moving at various velocities in deforming alkali halide single crystals were studied using the technique of pulsed nuclear magnetic resonance. The spin lattice relaxation rate in the rotating frame is measured as a function of the plastic deformation rate [MATH]. From this the mean free path of mobile dislocations can be determined. The results for different resonant nuclei, different crystal orientations with respect to the crystal axis and different temperatures are presented

The mean free path of mobile dislocations in doped NaCl single crystals measured by N.M.R. between room temperature and 300°C

The mean free path of mobile dislocations has been measured by determining the spin–lattice relaxation rate of deforming NaCl single crystals as a function of temperature and of the concentration of Ca2+ impurities. The latter may influence the magnitude of the mean free path, but this depends to a large extent on the point-defect configuration. The degree of association and the mobility of the point defects has been studied by measuring the spin–lattice relaxation rate without deforming the samples. On the other hand, the distribution of dislocations also varies with temperature, and this affects the mobility of dislocations too. The work-hardening rate of the crystals is compared with the mean free path as a function of temperature, and it is shown that both quantities have extremes under the influence of competitive mechanisms such as an enhanced thermal activation of dislocations at obstacles, an increasing mobility of point defects and an increasing number of intersections of mobile dislocations with dislocation dipoles