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Synthesis of 3-stannyl and 3-silyl propargyl phosphanes and the formation of a phosphinoallene
The group 14 chloropropargyls R3ECCCH2Cl (R3E = Bu3Sn, Ph3Sn, Me2PhSi, iPr3Si, nPr3Si, nBu3Si), obtained by a modified literature procedure, react with LiPPh2 to afford the novel propargyl phosphanes Ph2PCH2CCER3 in high yield, as viscous oils; (Me3Si)2PCH2CCSiPhMe2 is similarly obtained from LiP(SiMe3)2. In contrast, the reaction of PhCCCH2MgCl with ClP(NEt2)2 fails to produce a comparable propargyl phosphane, but generates preferentially (>70%) the novel phosphinoallene (Et2N)2PC(Ph)=C=CH2, which is characterised spectroscopically, and through its reaction with HCl. The coordination chemistry of representative phosphanes is explored with respect to platinum and palladium for the first time
The complexities of failing (Social Work) students - a workshop for practice educators of Social Work students held at the University of Lincoln on Thursday 27th November 2014
This workshop for practice educators teaching social work students whilst on placement explored issues relating to failing students. Reasons why students might experience difficulties whilst on placement, early identification of problems, barriers to making a fail decision and resolution of concerns were discussed. The session considered how to evidence and articulate concerns in relation to HCPC Guidance on Conduct and Ethics for Students and the appropriate PCF levels and how to develop appropriate intervention plans, using the University's concerns process or Fitness to Practise procedures where necessary
Porous weirs for flood mitigation
[Abstract]: Porous weirs offer an alternative design that could be adopted for flood mitigation.
The aim of this project is to construct and simulate a 1:25 scale model of a porous weir in the wide flume of the USQ hydraulics laboratory. The goal is to determine a
relationship between upstream storage (depth) and the discharge of the weir to be use in being able to determine the flood mitigation potential of the porous weir.
The flow through the porous weir is to be analysed by analogy to the Darcy type equations and open channel flow equations. When the depth of flow exceeds the height of the weir an attempt will be made to fit a general weir type equation to the measured data.
Results have shown that turbulent flow exists in the model and that the traditional Darcy equation does not fit the flow through the weir. However a good relationship was found by analogy to the general equation of gradually varied flow when the flow was through the porous media. Once the flow exceeded the height of the weir it was found that the flow closely resembled the flow of a traditional hard weir
Phytoremediation of Heavy-Metals-Contaminated Soils:A Short-Term Trial Involving Two Willow Species from Gloucester WillowBank in the UK
Phytoremediation, as a bioremediation process in which plants are used to remove contaminants from an environment, has proved to be a practical and low-cost strategy for recovering mining-affected areas. This study aims to assess the potential for use in phytoremediation of two willow species, Salix viminalis and Salix dasyclados, by testing their potential for cleaning-up a range of soils with differing heavy metal concentrations: Pb (111, 141, 192 and 249 mg /kg), Zn (778.6, 1482, 2734 and 4411 mg/kg) and Cd (3.00, 5.03, 9.14 and 16.07 mg/kg). The extracted metals were preferentially translocated to the leaves with considerably higher concentrations and relative BAFs in the case of S. viminalis. The highest recorded Zn concentration of over 0.5% was found in the leaves of S. viminalis growing in soil 4. However, under the conditions of the experiments, S. dasyclados showed greater potential for use in phytoremediation, especially if coupled with use of biomass for energy production. An assessment of the suitability of willow species in this role, with regard to wider aspects involved, such as use of resultant biomass and/or waste management, revealed good potential. Willows are fast growing, grow vigorously from coppiced stumps and have extensive root systems. Therefore, their use in bioenergy production through pyrolysis or combustion, coupled with flue gas screening, is strongly advised
The role of feed-forward and feedback processes for closed-loop prosthesis control
<p>Abstract</p> <p>Background</p> <p>It is widely believed that both feed-forward and feed-back mechanisms are required for successful object manipulation. Open-loop upper-limb prosthesis wearers receive no tactile feedback, which may be the cause of their limited dexterity and compromised grip force control. In this paper we ask whether observed prosthesis control impairments are due to lack of feedback or due to inadequate feed-forward control.</p> <p>Methods</p> <p>Healthy subjects were fitted with a closed-loop robotic hand and instructed to grasp and lift objects of different weights as we recorded trajectories and force profiles. We conducted three experiments under different feed-forward and feed-back configurations to elucidate the role of tactile feedback (i) in ideal conditions, (ii) under sensory deprivation, and (iii) under feed-forward uncertainty.</p> <p>Results</p> <p>(i) We found that subjects formed economical grasps in ideal conditions. (ii) To our surprise, this ability was preserved even when visual and tactile feedback were removed. (iii) When we introduced uncertainty into the hand controller performance degraded significantly in the absence of either visual or tactile feedback. Greatest performance was achieved when both sources of feedback were present.</p> <p>Conclusions</p> <p>We have introduced a novel method to understand the cognitive processes underlying grasping and lifting. We have shown quantitatively that tactile feedback can significantly improve performance in the presence of feed-forward uncertainty. However, our results indicate that feed-forward and feed-back mechanisms serve complementary roles, suggesting that to improve on the state-of-the-art in prosthetic hands we must develop prostheses that empower users to correct for the inevitable uncertainty in their feed-forward control.</p
Symmetry groupoids and patterns of synchrony in coupled cell networks
A coupled cell system is a network of dynamical systems, or âcells,â coupled together. Such systems
can be represented schematically by a directed graph whose nodes correspond to cells and whose
edges represent couplings. A symmetry of a coupled cell system is a permutation of the cells that
preserves all internal dynamics and all couplings. Symmetry can lead to patterns of synchronized
cells, rotating waves, multirhythms, and synchronized chaos. We ask whether symmetry is the only
mechanism that can create such states in a coupled cell system and show that it is not.
The key idea is to replace the symmetry group by the symmetry groupoid, which encodes information
about the input sets of cells. (The input set of a cell consists of that cell and all cells
connected to that cell.) The admissible vector fields for a given graphâthe dynamical systems with
the corresponding internal dynamics and couplingsâare precisely those that are equivariant under
the symmetry groupoid. A pattern of synchrony is ârobustâ if it arises for all admissible vector
fields. The first main result shows that robust patterns of synchrony (invariance of âpolydiagonalâ
subspaces under all admissible vector fields) are equivalent to the combinatorial condition that an
equivalence relation on cells is âbalanced.â The second main result shows that admissible vector
fields restricted to polydiagonal subspaces are themselves admissible vector fields for a new coupled
cell network, the âquotient network.â The existence of quotient networks has surprising implications
for synchronous dynamics in coupled cell systems
The long and short of it: a comprehensive assessment of axial length estimation in myopic eyes from ocular and demographic variables.
Background/ObjectivesAxial length, a key measurement in myopia management, is not accessible in many settings. We aimed to develop and assess machine learning models to estimate the axial length of young myopic eyes.Subjects/MethodsLinear regression, symbolic regression, gradient boosting and multilayer perceptron models were developed using age, sex, cycloplegic spherical equivalent refraction (SER) and corneal curvature. Training data were from 8135 (28% myopic) children and adolescents from Ireland, Northern Ireland and China. Model performance was tested on an additional 300 myopic individuals using traditional metrics alongside the estimated axial length vs age relationship. Linear regression and receiver operator characteristics (ROC) curves were used for statistical analysis. The contribution of the effective crystalline lens power to error in axial length estimation was calculated to define the latterâs physiological limits.ResultsAxial length estimation models were applicable across all testing regions (pâ„0.96 for training by testing region interaction). The linear regression model performed best based on agreement metrics (mean absolute error [MAE]=0.31mm, coefficient of repeatability=0.79mm) and a smooth, monotonic estimated axial length vs age relationship. This model was better at identifying high-risk eyes (axial length >98th centile) than SER alone (area under the curve 0.89 vs 0.79, respectively). Without knowing lens power, the calculated limits of axial length estimation were 0.30mm for MAE and 0.75mm for coefficient of repeatability.ConclusionsIn myopic eyes, we demonstrated superior axial length estimation with a linear regression model utilising age, sex and refractive metrics and showed its clinical utility as a risk stratification tool
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