The use of process selection exercises for the training of welding technologists

Formal lectures and laboratory experiments do not give students sufficient experience of welding processes applied to specific fabrications. A series of designs has been evolved which ib.capable of being fabricated by several different methods and students are required to produce fabrication procedures for each design. Suggested procedures are then discussed in an open forum in which both staff and students participate. The use of these exercises has been found to be a useful method whereby course members can pass on their own experience to other students and in which students learn to make decisions based on available, but often incomplete, facts

Final report of grit blasting and metal spraying trials carried out at H. M. Dockyard, Devonport

Mild steel surfaces that are to be protected by aluminium or zinc spray coatings are generally prepared by blasting with chilled iron angular grit. Previous work1had shown that a relationship exists between the grit blasting conditions (at least in terms of blasting angle and grit condition), the reflectivity of the blasted surface and the bond strength of a spray coating of aluminium on the blasted surface. An instrument has been developed that assesses the suitability of a blasted surface for subsequent spraying by measuring the reflectivity and has proved reasonably successful under laboratory conditions. The present need is to ascertain the performance of this reflectivity meter under shop and site conditions. The opportunity to carry out such tests at H.M. Dockyard, Devonport, was offered by the Ministry of Defence and a series of tests was made on 16th June, 1965

Transmission of Predictable Sensory Signals to the Cerebellum via Climbing Fiber Pathways Is Gated during Exploratory Behavior

International audiencePathways arising from the periphery that target the inferior olive [spino-olivocerebellar pathways (SOCPs)] are a vital source of information to the cerebellum and are modulated (gated) during active movements. This limits their ability to forward signals to climbing fibers in the cerebellar cortex. We tested the hypothesis that the temporal pattern of gating is related to the predictability of a sensory signal. Low-intensity electrical stimulation of the ipsilateral hindlimb in awake rats evoked field potentials in the C1 zone in the copula pyramidis of the cerebellar cortex. Responses had an onset latency of 12.5 +/- 0.3 ms and were either short or long duration (8.7 +/- 0.1 vs 31.2 +/- 0.3 ms, respectively). Both types of response were shown to be mainly climbing fiber in origin and therefore evoked by transmission in hindlimb SOCPs. Changes in response size (area of field, millivolts per millisecond) were used to monitor differences in transmission during rest and three phases of rearing: phase 1, rearing up; phase 2, upright; and phase 3, rearing down. Responses evoked during phase 2 were similar in size to rest but were smaller during phases 1 and 3, i.e., transmission was reduced during active movement when self-generated (predictable) sensory signals from the hindlimbs are likely to occur. To test whether the pattern of gating was related to the predictability of the sensory signal, some animals received the hindlimb stimulation only during phase 2. Over similar to 10 d, the responses became progressively smaller in size, consistent with gating-out transmission of predictable sensory signals relayed via SOCPs

Divergent stereoisomers of molybdenum carbonyl complexes of NHC-based pincer ligands

The first molybdenum complexes of widely used NHC-based CNC and C^N^C pincer ligands are described, viz. [Mo(L)(CO)3] (L = 2,6-bis(mesityl-imidazolylidene)pyridine ≡ CNC-Mes, 1; α,α’-(diimidazolylidene-dodecamethylene)lutidine ≡ C^N^C-12, 2). These complexes have been thoroughly characterised in solution and the solid-state, revealing different stereochemical preferences of the tridentate ligands depending on the nature of the scaffold. In the case of flexible C^N^C-12 an uncommon fac-coordination geometry is observed, whilst the complex of rigid CNC-Mes adopts the expected mer-configuration. For the combination of donors associated with the ligands, DFT calculations establish preferential fac-coordination, however, within the CNC (ΔΔG = +63.1 kJ·mol-1) and C^N^C (ΔΔG = +20.0 kJ·mol-1) scaffolds this conformation is significantly destabilised relative to the mer-alternative

Neural Correlates of Fear in the Periaqueductal Gray

International audienceThe dorsal and ventral periaqueductal gray (dPAG and vPAG, respectively) are embedded in distinct survival networks that coordinate, respectively, innate and conditioned fear-evoked freezing. However, the information encoded by the PAG during these survival behaviors is poorly understood. Recordings in the dPAG and vPAG in rats revealed differences in neuronal activity associated with the two behaviors. During innate fear, neuronal responses were significantly greater in the dPAG compared with the vPAG. After associative fear conditioning and during early extinction (EE), when freezing was maximal, a field potential was evoked in the PAG by the auditory fear conditioned stimulus (CS). With repeated presentations of the unreinforced CS, animals displayed progressively less freezing accompanied by a reduction in event-related field potential amplitude. During EE, the majority of dPAG and vPAG units increased their firing frequency, but spike-triggered averaging showed that only ventral activity during the presentation of the CS was significantly coupled to EMG-related freezing behavior. This PAG–EMG coupling was only present for the onset of freezing activity during the CS in EE. During late extinction, a subpopulation of units in the dPAG and vPAG continued to show CS-evoked responses; that is, they were extinction resistant. Overall, these findings support roles for the dPAG in innate and conditioned fear and for the vPAG in initiating but not maintaining the drive to muscles to generate conditioned freezing. The existence of extinction-susceptible and extinction-resistant cells also suggests that the PAG plays a role in encoding fear memories

How do informal self-care strategies evolve among patients with chronic obstructive pulmonary disease managed in primary care? A qualitative study

Background: There is much description in the literature of how patients with chronic obstructive pulmonary disease (COPD) manage their breathlessness and engage in self-care activities; however, little of this is from the perspective of those with less severe disease, who are primarily managed in primary care. This study aimed to understand the self-care experiences of patients with COPD who are primarily managed in primary care, and to examine the challenges of engaging in such behaviors. Methods: Semistructured interviews were carried out with 15 patients with COPD as part of a larger project evaluating a self-management intervention. Thematic analysis was supported by NVivo software (version 8, QSR International, Melbourne, Australia). Results: Three main themes are described, ie, experiencing and understanding symptoms of COPD, current self-care activities, and the importance of family perceptions in managing COPD. Conclusion: Self-care activities evolved spontaneously as participants experienced symptoms of COPD. However, there was a lack of awareness about whether these strategies would impact upon symptoms. Perceptions of COPD by family members posed a challenge to self-care for some participants. Health care professionals should elicit patients' prior disease experiences and utilize spontaneous attempts at disease management in future self-management. These findings have implications for promoting self-management and enhancing quality of life

Whightman function and scalar Casimir densities for a wedge with a cylindrical boundary

Whightman function, vacuum expectation values of the field square, and the energy-momentum tensor are investigated for a scalar field inside a wedge with and without a coaxial cylindrical boundary. Dirichlet boundary conditions are assumed on the bounding surfaces. The vacuum energy-momentum tensor is evaluated in the general case of the curvature coupling parameter. Making use of a variant of the generalized Abel-Plana formula, expectation values are presented as the sum of two terms. The first one corresponds to the geometry without a cylindrical boundary and the second one is induced by the presence of this boundary. The asymptotic behaviour of the field square, vacuum energy density and stresses near the boundaries are investigated. The additional vacuum forces acting on the wedge sides due the presence of the cylindrical boundary are evaluated and it is shown that these forces are attractive. As a limiting case, the geometry of two parallel plates perpendicularly intersected by a third one is analyzed.Comment: 19 pages, 6 figures, new section is added on the VEVs for the region outside the cylidrical shell, discussion and references added, accepted for publication in J. Phys.

Preclinical transgenic and patient-derived xenograft models recapitulate the radiological features of human adamantinomatous craniopharyngioma

To assess the clinical relevance of transgenic and patient-derived xenograft models of adamantinomatous craniopharyngioma (ACP) using serial magnetic resonance imaging (MRI) and high resolution post-mortem microcomputed tomography (μ-CT), with correlation with histology and human ACP imaging. The growth patterns and radiological features of tumors arising in Hesx1(Cre/+) ;Ctnnb1(lox(ex3)/+) transgenic mice, and of patient-derived ACP xenografts implanted in the cerebral cortex, were monitored longitudinally in vivo with anatomical and functional MRI, and by ex vivo μ-CT at study end. Pathological correlates with hematoxylin and eosin stained sections were investigated. Early enlargement and heterogeneity of Hesx1(Cre/+) ;Ctnnb1(lox(ex3)/+) mouse pituitaries was evident at initial imaging at 8 weeks, which was followed by enlargement of a solid tumor, and development of cysts and hemorrhage. Tumors demonstrated MRI features that recapitulated those of human ACP, specifically, T1 -weighted signal enhancement in the solid tumor component following Gd-DTPA administration, and in some animals, hyperintense cysts on FLAIR and T1 -weighted images. Ex vivo μ-CT correlated with MRI findings and identified smaller cysts, which were confirmed by histology. Characteristic histological features, including wet keratin and calcification, were visible on μ-CT and verified by histological sections of patient-derived ACP xenografts. The Hesx1(Cre/+) ;Ctnnb1(lox(ex3)/+) transgenic mouse model and cerebral patient-derived ACP xenografts recapitulate a number of the key radiological features of the human disease and provide promising foundations for in vivo trials of novel therapeutics for the treatment of these tumors