Analysis of interdiffusion of Dy, Nd, and Pr in Mg

The diffusion characteristics of Mg–rare-earth diffusion couples were studied. Cylinders of pure Mg and rare earth (Dy, Nd, and Pr) were abutted and annealed at 500 °C for 100 h or 300 h. Point-by-point composition profiles were collected starting in pure Mg, across the diffusion zone, and ending in the pure rare earth, using energy dispersive x-ray spectroscopy with a scanning electron microscope. The intermetallic phases that resulted due to diffusion were identified and compared to existing phase diagrams, for which the data is limited. For each diffusion couple, a plot of concentration versus distance perpendicular to the original plane of contact was obtained and analyzed using the Boltzman–Matano method. The interdiffusion coefficients for each set of phases were then calculated. The results show that diffusion through the intermetallic phases is much slower than is expected in a solid solution

Intravenous infusion practices across England and their impact on patient safety: a mixed-methods observational study

BACKGROUND: Intravenous (IV) medication administration has traditionally been regarded to be error-prone with high potential for harm. A recent US multisite study revealed surprisingly few potentially harmful errors despite a high overall error rate. However, there is limited evidence about infusion practices in England and how they relate to prevalence and types of error. OBJECTIVES: To determine the prevalence, types and severity of errors and discrepancies in infusion administration in English hospitals, and to explore sources of variation in errors, discrepancies and practices, including the contribution of smart pumps. DESIGN: Phase 1 comprised an observational point-prevalence study of IV infusions, with debrief interviews and focus groups. Observers compared each infusion against the medication order and local policy. Deviations were classified as either errors or discrepancies based on their potential for patient harm. Contextual issues and reasons for deviations were explored qualitatively during observer debriefs, and analytically in supplementary analyses. Phase 2 comprised in-depth observational studies at five of the participating sites to better understand causes of error and how safety is maintained. Workshops were held with key stakeholder groups, including health professionals and policy-makers, the public and industry. SETTING: Sixteen English NHS hospital trusts. RESULTS: Point-prevalence data were collected from 1326 patients and 2008 infusions. In total, 240 errors were observed in 231 infusions and 1489 discrepancies were observed in 1065 infusions. Twenty-three errors (1.1% of all infusions) were considered potentially harmful; one might have resulted in short-term patient harm had it not been intercepted, but none was judged likely to prolong hospital stay or result in long-term harm. Types and prevalence of deviations varied widely among trusts, as did local policies. Deviations from medication orders and local policies were sometimes made for efficiency or to respond to patient need. Smart pumps, as currently implemented, had little effect. Staff had developed practices to manage efficiency and safety pragmatically by working around systemic challenges. LIMITATIONS: Local observers may have assessed errors differently across sites, although steps were taken to minimise differences through observer training, debriefs, and review and cleaning of data. Each in-depth study involved a single researcher, and these were limited in scale and scope. CONCLUSIONS: Errors and discrepancies are common in everyday infusion administration but most have low potential for patient harm. Findings are best understood by viewing IV infusion administration as a complex adaptive system. Better understanding of performance variability to strategically manage risk may be more helpful for improving patient safety than striving to eliminate all deviations. FUTURE WORK: There is potential value in reviewing policy around IV infusion administration to reduce unnecessary variability, manage staff workload and engage patients, while retaining the principle that policy has to be fit for purpose, contextualised to the particular ward situation and treatment protocol, and sensitive to the risks of different medications. Further work on understanding infusion administration as a complex adaptive system might deliver new insights into managing patient safety. FUNDING: This project was funded by the NIHR Health Services and Delivery Research programme and will be published in full in Health Services and Delivery Research; Vol. 8, No. 7. See the NIHR Journals Library website for further project information

Procedural and documentation variations in intravenous infusion administration: a mixed methods study of policy and practice across 16 hospital trusts in England

Background: Procedural and documentation deviations relating to intravenous (IV) infusion administration can have important safety consequences. However, research on such deviations is limited. To address this we investigated the prevalence of procedural and documentation deviations in IV infusion administration and explored variability in policy and practice across different hospital trusts. / Methods: We conducted a mixed methods study. This involved observations of deviations from local policy including quantitative and qualitative data, and focus groups with clinical staff to explore the causes and contexts of deviations. The observations were conducted across five clinical areas (general medicine, general surgery, critical care, paediatrics and oncology day care) in 16 National Health Service (NHS) trusts in England. All infusions being administered at the time of data collection were included. Deviation rates for procedural and documentation requirements were compared between trusts. Local data collectors and other relevant stakeholders attended focus groups at each trust. Policy details and reasons for deviations were discussed. / Results: At least one procedural or documentation deviation was observed in 961 of 2008 IV infusions (deviation rate 47.9%; 95% confidence interval 45.5–49.8%). Deviation rates at individual trusts ranged from 9.9 to 100% of infusions, with considerable variation in the prevalence of different types of deviation. Focus groups revealed lack of policy awareness, ambiguous policies, safety and practicality concerns, different organisational priorities, and wide variation in policies and practice relating to prescribing and administration of IV flushes and double-checking. / Conclusions: Deviation rates and procedural and documentation requirements varied considerably between hospital trusts. Our findings reveal areas where local policy and practice do not align. Some policies may be impractical and lack utility. We suggest clearer evidence-based standardisation and local procedures that are contextually practical to address these issues

Holocene Vegetational Changes in Eastern Iowa

Pollen and plant macrofossil analysis from three sites along an east-west transect in southeastern Iowa provide evidence for Holocene vegetational development. Colo Marsh at the west end of the transect is relatively complete, with a late-glacial spruce zone ending about 11,500 yr B.P.; a deciduous forest zone from about 11,500 to 8300; a prairie zone from 8300 to 4500, and prairie with oak from 4500 to presettlement times. Sediments from the site at the Indian Creek Nature Center, midway in the transect, date only from about 6000 to 1600 yrs B. P. This site also was dominantly prairie from 6000 (and probably before) to 4500 yr B.P. Oak and hickory were present from 4500 to 3500, and were joined by more mesic trees from 3500 to 1600 yr B.P. Mud Creek occupies a very gently sloping drainage basin at the east end of the transect; the site there includes three dated levels ranging in age from about 9300 and 5500 yr B.P. The vegetation during that entire time was apparently mesic deciduous forest with abundant basswood. Apparently an important vegetational boundary existed in eastern Iowa during early and middle Holocene time. In western and central Iowa prairie was dominant and climate was driest between about 8300 and 4500 yr B.P. At this same time, mesic deciduous forest prevailed in eastern Iowa

The Residual Stress Relaxation Behavior of Weldments During Cyclic Loading

Accurate measurement of residual stress is necessary to obtain reliable predictions of fatigue lifetime and enable estimation of time-to-facture for any given stress level. In this article, relaxation of welding residual stresses as a function of cyclic loading was documented on three common steels: AISI 1008, ASTM A572, and AISI 4142. Welded specimens were subjected to cyclic bending (R = 0.1) at different applied stresses, and the residual stress relaxation existing near the welds was measured as a function of cycles. The steels exhibited very different stress relaxation behaviors during cyclic loadings, which can be related to the differences in the microstructures of the specimens. A phenomenological model, which treats dislocation motion during cyclic loading as being analogous to creep of dislocations, is proposed for estimation of the residual stress relaxation

Diffusion MRI of Structural Brain Plasticity Induced by a Learning and Memory Task

Background: Activity-induced structural remodeling of dendritic spines and glial cells was recently proposed as an important factor in neuroplasticity and suggested to accompany the induction of long-term potentiation (LTP). Although T1 and diffusion MRI have been used to study structural changes resulting from long-term training, the cellular basis of the findings obtained and their relationship to neuroplasticity are poorly understood. Methodology/Principal Finding: Here we used diffusion tensor imaging (DTI) to examine the microstructural manifestations of neuroplasticity in rats that performed a spatial navigation task. We found that DTI can be used to define the selective localization of neuroplasticity induced by different tasks and that this process is age-dependent in cingulate cortex and corpus callosum and age-independent in the dentate gyrus. Conclusion/Significance: We relate the observed DTI changes to the structural plasticity that occurs in astrocytes and discuss the potential of MRI for probing structural neuroplasticity and hence indirectly localizing LTP

Processing and mechanical properties of magnesium-lithium composites containing steel fibers

Deformation-processed metal-metal composites (DMMC) of Mg-Li alloys containing steel reinforcing fibers were prepared by infiltrating a preform of steel wool with the molten matrix. The Li content was varied to control the crystal structure of the matrix; Mg-4 wt pct Li is hexagonal close packed (hcp), while Mg-12 wt pct Li is body-centered cubic (bcc). The low carbon steel used as the reinforcing fiber is essentially bcc. The hcp/bcc and bcc/bcc composites were subsequently deformed by rolling and by extrusion/swaging and mechanically tested to relate the tensile strength of the composites to true deformation strain. The hcp/bcc composites had limited formability at temperatures up to 400 °C, while the bcc/bcc composites had excellent formability during sheet rolling at room temperature but limited formability during swaging at room temperature. The tensile strengths of the hcp/bcc composite rod and the bcc/bcc composite sheet and rod increased moderately with deformation, though less than predicted from rule-of-mixtures (ROM) calculations. This article presents the experimental data for these DMMC materials and comments on the possible effect of texture development in the matrix and fiber phases on the deformation characteristics of the composite material