Thermal and convection analyses of the dendrite remelting rocket experiment; Experiment 74-21 in the space processing rocket program

The Dendrite Remelting Rocket Experiment was performed aboard a Black Brant VC Sounding Rocket during a period which gravity levels of approximately 0.00001 g prevailed. The experiment consisted of cooling an aqueous ammonium chloride solution in a manner such that crystallization of ammonium chloride crystals proceeded throughout a three minute period of zero-g. The crystallization process during flight was recorded on 35 mm panatomic-x film. A number of ground crystallizations were similarly recorded for comparison purposes. The convective and thermal conditions in aqueous and metallic liquid systems were assessed under conditions of the flight experiment to help establish the relevance of the rocket experiment to metals casting phenomena. The results indicate that aqueous or metallic convective velocities in the Dendrite Remelting Rocket Experiment cell are of insignificant magnitudes at the 0.0001 to 0.00001 g levels of the experiment. The crystallization phenomena observed in the Rocket Experiment, therefore, may be indicative of how metals will solidify in low-g

Coriolis force in Geophysics: an elementary introduction and examples

We show how Geophysics may illustrate and thus improve classical Mechanics lectures concerning the study of Coriolis force effects. We are then interested in atmospheric as well as oceanic phenomena we are familiar with, and are for that reason of pedagogical and practical interest. Our aim is to model them in a very simple way to bring out the physical phenomena that are involved.Comment: Accepted for publication in European Journal of Physic

Generalized Rosenfeld scalings for tracer diffusivities in not-so-simple fluids: Mixtures and soft particles

Rosenfeld [Phys. Rev. A 15, 2545 (1977)] noticed that casting transport coefficients of simple monatomic, equilibrium fluids in specific dimensionless forms makes them approximately single-valued functions of excess entropy. This has predictive value because, while the transport coefficients of dense fluids are difficult to estimate from first principles, excess entropy can often be accurately predicted from liquid-state theory. Here, we use molecular simulations to investigate whether Rosenfeld's observation is a special case of a more general scaling law relating mobility of particles in mixtures to excess entropy. Specifically, we study tracer diffusivities, static structure, and thermodynamic properties of a variety of one- and two-component model fluid systems with either additive or non-additive interactions of the hard-sphere or Gaussian-core form. The results of the simulations demonstrate that the effects of mixture concentration and composition, particle-size asymmetry and additivity, and strength of the interparticle interactions in these fluids are consistent with an empirical scaling law relating the excess entropy to a new dimensionless (generalized Rosenfeld) form of tracer diffusivity, which we introduce here. The dimensionless form of the tracer diffusivity follows from knowledge of the intermolecular potential and the transport / thermodynamic behavior of fluids in the dilute limit. The generalized Rosenfeld scaling requires less information, and provides more accurate predictions, than either Enskog theory or scalings based on the pair-correlation contribution to the excess entropy. As we show, however, it also suffers from some limitations, especially for systems that exhibit significant decoupling of individual component tracer diffusivities.Comment: 15 pages, 10 figure

Analytical support for SPAR experiment 76-36

The apparatus, materials, and procedures used in an analysis of thermal, convective, and rotational fluid flow for a second series of rocket experiments of dendrite growth are described. A constitutive supercooling criterion was calculated from the thermal data. A convection analysis was made of the various cases to ensure that convective velocities will not exceed about .01 cm/sec in the low-g tests. Damping times for fluid flow generated by rocket spin-up and spin-down were also determined, so that the conditions for this experiment are generally the same as those for the SPAR experiment 74-21 study of ammonium chloride low-g crystallizations

Experimental measurement of stress at a four-domain junction in lead zirconate titanate

A junction between two lamellar bands of ferroelectric domains in a lead zirconate titanate (PZT) ceramic is analysed using Kikuchi diffraction patterns in the transmission electron microscope. Indexing of the diffraction patterns allowed the determination of the 3D relative orientation of the 4 different domains at the junction and thus the characterisation of the domain boundaries. The local c/a ratio could also be determined from the misorientations at the domain boundaries. Analysis of the data showed that large stresses were concentrated at the junction, and that this is inevitable at such band junctions. Such stress concentrations could act as nuclei for cracking of the ceramic under additional loading in service, perhaps particularly as a consequence of extended electromechanical cycling. Moreover, the stresses would increase with increasing c/a making the issues all the more serious for Ti-rich compositions having larger c/a ratios

Neutronic study on conversion of SAFARI-1 to LEU silicide fuel

This paper marks the initial study into the technical and economic feasibility of converting the SAFARI-1 reactor in South Africa to LEU silicide fuel. Several MTR assembly geometries and LEU uranium densities have been studied and compared with MEU and HEU fuels. Two factors of primary importance for conversion of SAFARI-1 to LEU fuel are the economy of the fuel cycle and the performance of the incore and excore irradiation positions

Australian long-term care personnel's knowledge and attitudes regarding palliative care for people with advanced dementia.

This study aimed to describe Australian long-term care (LTC) personnel's knowledge and attitudes concerning palliative care for residents with advanced dementia, and explore relationships with LTC facility/personnel characteristics. An analysis was undertaken of baseline data from a cluster randomised controlled trial of facilitated family case conferencing for improving palliative care of LTC residents with advanced dementia (the 'IDEAL Study'). Participants included any LTC personnel directly involved in residents' care. Knowledge and attitudes concerning palliative care for people with advanced dementia were measured using the questionnaire on Palliative Care for Advanced Dementia. Univariate and multivariate analyses explored relationships between personnel knowledge/attitudes and facility/personnel characteristics. Of 307 personnel in the IDEAL Study, 290 (94.5%) from 19/20 LTCFs provided sufficient data for inclusion. Participants included 9 (2.8%) nurse managers, 59 (20.5%) registered nurses, 25 (8.7%) enrolled nurses, 187 (64.9%) assistants in nursing/personal care assistants and 9 (3.1%) care service employees. In multivariate analyses, a facility policy not to rotate personnel through dementia units was the only variable associated with more favourable overall personnel knowledge and attitudes. Other variables associated with favourable knowledge were a designation of nursing manager or registered or enrolled nurse, and having a preferred language of English. Other variables associated with favourable attitudes were tertiary level of education and greater experience in dementia care. Like previous international research, this study found Australian LTC personnel knowledge and attitudes regarding palliative care for people with advanced dementia to be associated with both facility and personnel characteristics. Future longitudinal research is needed to better understand the relationships between knowledge and attitudes, as well as between these attributes and quality of care

Effects of facilitated family case conferencing for advanced dementia: A cluster randomised clinical trial

© 2017 Agar et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Background: Palliative care planning for nursing home residents with advanced dementia is often suboptimal. This study compared effects of facilitated case conferencing (FCC) with usual care (UC) on end-of-life care. Methods: A two arm parallel cluster randomised controlled trial was conducted. The sample included people with advanced dementia from 20 Australian nursing homes and their families and professional caregivers. In each intervention nursing home (n = 10), Palliative Care Planning Coordinators (PCPCs) facilitated family case conferences and trained staff in person-centred palliative care for 16 hours per week over 18 months. The primary outcome was family-rated quality of end-of-life care (End-of-Life Dementia [EOLD] Scales). Secondary outcomes included nurse-rated EOLD scales, resident quality of life (Quality of Life in Late-stage Dementia [QUALID]) and quality of care over the last month of life (pharmacological/ non-pharmacological palliative strategies, hospitalization or inappropriate interventions). Results: Two-hundred-eighty-six people with advanced dementia took part but only 131 died (64 in UC and 67 in FCC which was fewer than anticipated), rendering the primary analysis underpowered with no group effect seen in EOLD scales. Significant differences in pharmacological (P < 0.01) and non-pharmacological (P < 0.05) palliative management in last month of life were seen. Intercurrent illness was associated with lower family-rated EOLD Satisfaction with Care (coefficient 2.97, P < 0.05) and lower staff-rated EOLD Comfort Assessment with Dying (coefficient 4.37, P < 0.01). Per protocol analyses showed positive relationships between EOLD and staff hours to bed ratios, proportion of residents with dementia and staff attitudes. Conclusion: FCC facilitates a palliative approach to care. Future trials of case conferencing should consider outcomes and processes regarding decision making and planning for anticipated events and acute illness. Trial registration: Australian New Zealand Clinical Trial Registry ACTRN12612001164886

Plasticity in dormancy behaviour of Calanoides acutus in Antarctic coastal waters

Copepods that enter dormancy, such as Calanoides acutus, are key primary consumers in Southern Ocean food webs where they convert a portion of the seasonal phytoplankton biomass into a longer-term energetic and physiological resource as wax ester (WE) reserves. We studied the seasonal abundance and lipid profiles of pre-adult and adult C. acutus in relation to phytoplankton dynamics on the Western Antarctic Peninsula. Initiation of dormancy occurred when WE unsaturation was relatively high, and chlorophyll a (Chl a) concentrations, predominantly attributable to diatoms, were reducing. Declines in WE unsaturation during the winter may act as a dormancy timing mechanism with increased Chl a concentrations likely to promote sedimentation that results in a teleconnection between the surface and deep water inducing ascent. A late summer diatom bloom was linked to early dormancy termination of females and a second spawning event. The frequency and duration of high biomass phytoplankton blooms may have consequences for the lifespan of the iteroparous C. acutus females (either 1 or 2 years) if limited by a total of two main spawning events. Late summer recruits, generated by a second spawning event, likely benefitted from lower predation and high phytoplankton food availability. The flexibility of copepods to modulate their life-cycle strategy in response to bottom-up and top-down conditions enables individuals to optimize their probability of reproductive success in the very variable environment prevalent in the Southern Ocean