Aw investigation of the magnetocrystalline anisotropy in some of the heavy rare earth metals

The magnetocrystalline anisotroples of gadolinium, terbium, dysprosium and holmium have been investigated using a torque method. Measurements were made on single crystal oblate spheroids, the major planes of which contained either the hexagonal axis or the basal plane of the crystals. The torque magnetometer used automatically balanced the torque produced in the specimen by applying a current through a small coil suspended in a galvanometer magnet, the servoraechanism being provided by a light beam and photo cell amplifier system. Fourier analysis of the torque curves by computer provided values for the appropriate anisotropy constants. Torque measurements were made in the temperature range from 55 K to room temperature, and in applied magnetic field strengths up to 12.5 k0e. Because of the comparatively small field strengths available it was not possible to obtain any appreciable movement of the magnetisation from the basal plane in the cases of ferromagnetic Tb, Dy and Ho, and therefore no values could be assigned to the anisotropy constants. In the paramagnetic and antiferromagnetic temperature ranges the torque curves were described completely by one anisotropy constant K(_11), although the presence of strain In the specimen could greatly distort the curve. The anisotropy constant in the basal plane, K(_4), was measured for Gd, Tb and Dy. The easy directions in the basal plane were the a-axls for Gd, and the o-axls for Tb and Dy, although changes of easy direction were observed in Dy at temperatures where the anlsotropy was small. A torque measurement made in the basal plane of holmium just above the critical field showed twelvefold symmetry in the anisotropy energy, but the main energy minimum occurred at the b-axis. Comparison of the temperature variation of K(_4) with the prediction of Zener's theory was satisfactory only in the case of Gd. For torque measurements in the (lOIO) plane for antiferromagnetic Dy, the occurrence of ferromagnetism as a magnetic field larger than the critical value was rotated across the basal plane enabled the temperature variation of the critical field to be determined. The variation was found to be in agreement with other workers. Determinations of Ho showed a change of easy axis from the basal plane to the o-axis in the antiferromagnetic region, and back to the basal plane when the system became ferromagnetic. This behaviour contradicted neutron-diffraction measurements but is confirmed by magnetisation measurements. In the paramagnetic region a variation of K(_1) as H(^2)/(T-0)(^2) was established

Thermography Inspection for Early Detection of Composite Damage in Structures During Fatigue Loading

Advanced composite structures are commonly tested under controlled loading. Understanding the initiation and progression of composite damage under load is critical for validating design concepts and structural analysis tools. Thermal nondestructive evaluation (NDE) is used to detect and characterize damage in composite structures during fatigue loading. A difference image processing algorithm is demonstrated to enhance damage detection and characterization by removing thermal variations not associated with defects. In addition, a one-dimensional multilayered thermal model is used to characterize damage. Lastly, the thermography results are compared to other inspections such as non-immersion ultrasonic inspections and computed tomography X-ray

A clinical pathway for the postoperative management of hypocalcemia after pediatric thyroidectomy reduces blood draws

Objectives Postoperative calcium management is challenging following pediatric thyroidectomy given potential limitations in self-reporting symptoms and compliance with phlebotomy. A protocol was created at our tertiary children's institution utilizing intraoperative parathyroid hormone (PTH) levels to guide electrolyte management during hospitalization. The objective of this study was to determine the effect of a new thyroidectomy postoperative management protocol on two primary outcomes: (1) the number of postoperative calcium blood draws and (2) the length of hospital stay. Study design Institutional review board approved retrospective study (2010–2016). Methods Consecutive pediatric total thyroidectomy and completion thyroidectomy ± neck dissection cases from 1/1/2010 through 8/5/2016 at a single tertiary children's institution were retrospectively reviewed before and after initiation of a new management protocol. All cases after 2/1/2014 comprised the experimental group (post-protocol implementation). The pre-protocol control group consisted of cases prior to 2/1/2014. Multivariable linear and Poisson regression models were used to compare the control and experimental groups for outcome measure of number of calcium lab draws and hospital length of stay. Results 53 patients were included (n = 23, control group; n = 30 experimental group). The median age was 15 years. 41 patients (77.4%) were female. Postoperative calcium draws decreased from a mean of 5.2 to 3.6 per day post-protocol implementation (Rate Ratio = 0.70, p < .001), adjusting for covariates. The mean number of total inpatient calcium draws before protocol initiation was 13.3 (±13.20) compared to 7.2 (±4.25) in the post-protocol implementation group. Length of stay was 2.1 days in the control group and 1.8 days post-protocol implementation (p = .29). Patients who underwent concurrent neck dissection had a longer mean length of stay of 2.32 days compared to 1.66 days in those patients who did not undergo a neck dissection (p = .02). Hypocalcemia was also associated with a longer mean length of stay of 2.41 days compared to 1.60 days in patients who did not develop hypocalcemia (p < .01). Conclusions The number of calcium blood draws was significantly reduced after introduction of a standardized protocol based on intraoperative PTH levels. The hospital length of stay did not change. Adoption of a standardized postoperative protocol based on intraoperative PTH levels may reduce the number of blood draws in children undergoing thyroidectomy

The OSIRIS-REx Visible and InfraRed Spectrometer (OVIRS): Spectral Maps of the Asteroid Bennu

The OSIRIS-REx Visible and Infrared Spectrometer (OVIRS) is a point spectrometer covering the spectral range of 0.4 to 4.3 microns (25,000-2300 cm-1). Its primary purpose is to map the surface composition of the asteroid Bennu, the target asteroid of the OSIRIS-REx asteroid sample return mission. The information it returns will help guide the selection of the sample site. It will also provide global context for the sample and high spatial resolution spectra that can be related to spatially unresolved terrestrial observations of asteroids. It is a compact, low-mass (17.8 kg), power efficient (8.8 W average), and robust instrument with the sensitivity needed to detect a 5% spectral absorption feature on a very dark surface (3% reflectance) in the inner solar system (0.89-1.35 AU). It, in combination with the other instruments on the OSIRIS-REx Mission, will provide an unprecedented view of an asteroid's surface.Comment: 14 figures, 3 tables, Space Science Reviews, submitte

Externalising tacit overview knowledge: A model-based approach to supporting design teams

Successful realization of large-scale product development programs is challenging because of complex product and process dependencies and complicated team interactions. Proficient teamwork is underpinned by knowledge of the manner in which tasks performed by different design participants fit together to create an effective whole. Based on an extensive industrial case study with a diesel engine company, this paper first argues that the overview and experience of senior designers play an important part in supporting teamwork by coordinating activities and facilitating proactive communication across large project teams. As experts move on and novices or contractors are hired, problems are likely to occur as tacit overview knowledge is lost. If informal, overview-driven processes break down, the risk of costly oversights will increase, and greater management overhead will be required to realize successful product designs. Existing process models provide a means to express the connectivity between tasks and components thus to compensate partially for the loss of tacit overview. This paper proposes the use of design confidence, a metric that reflects the designer's belief in the maturity of a particular design parameter at a given point in the process, to address the limitations of existing models. The applicability of confidence-based design models in providing overview, as well as their shortcomings, will be demonstrated through the example of a diesel engine design process. Confidence can be used to make overview knowledge explicit and convey additional information about the design artifact, thereby informing communication and negotiation between team