Bending behaviour of step-wise graded carbon nanofiber/polymer nanocomposites

In this study, a finite element-based model was developed to investigate the mechanical behavior of step-wise graded carbon nanofibre/phenolic nanocomposites. Four step-wise graded nanocomposites (FGNs), a non-graded nanocomposite (NGN), and a pure phenolic with the same geometry and total carbon nanofiber content were designed, fabricated and analyzed. Flexural tests were conducted to validate the finite element model. Close agreement was obtained between experimental results and numerical predictions. The results showed that flexural modulus was highly influenced by the compositional gradients.

Online motor control in children with developmental coordination disorder: chronometric analysis of double-step reaching performance

Background
Although there are a number of plausible accounts to explain movement clumsiness in children [or developmental coordination disorder (DCD)], the cause(s) of the disorder remain(s) an issue of debate. One aspect of motor control that is particularly important to the fluid expression of skill is rapid online control (ROC). Data on DCD have been conflicting. While some recent work using double-step reaching suggests no difficulty in online control, others suggest deficits (e.g. based on sequential pointing). To help resolve this debate, we suggest two things: use of recent neuro-computational models as a framework for investigating motor control in DCD, and more rigorous investigation of double-step reaching. Our working assumption here is that ROC is only viable through the seamless integration of predictive (or forward) models of movement and feedback-based mechanisms.

Aim
The aim of this chronometric study was to explore ROC in children with DCD using a double-step reaching paradigm. We predicted slower online adjustments in DCD based on the argument that these children manifest a core difficulty in predictive control.

Methods
Participants were a group of 17 children with DCD and 27 typically developing children aged between 7 and 12 years. Visual targets were presented on a 17-inch LCD touch screen, inclined to an angle of 15° from horizontal. The children were instructed to press each target as it appeared as quickly and accurately as possible. For 80% of the trials, the central target location remained unchanged for the duration of the movement (non-jump trials), while for the remaining 20% of trials, the target jumped at movement onset to one of the two peripheral locations (jump trials). Reaction time (RT), movement time (MT) and reaching errors were recorded.

Results
For both groups, RT did not vary according to trial condition, while children with DCD were slower to initiate movement. Further, the MT of children with DCD was prolonged to a far greater extent on jump trials relative to controls, with a large effect size. As well, children with DCD committed significantly more errors, notably a reduced ability to inhibit central responses on jump trials.

Conclusion
Our findings help reconcile some disparate findings in the literature using similar tasks. The pattern of performance in children with DCD suggests impairment in the ability to make rapid online adjustments that are based on a predictive (or internal) model of the action. These results pave the way for future kinematic investigation.

Driving down daily step counts: the impact of being driven to school on physical activity and sedentary behavior

This study investigated whether being driven to school was associated with lower weekday and weekend step counts, less active out-of-school leisure pursuits, and more sedentary behavior. Boys aged 10–13 years (n = 384) and girls aged 9–13 years (n = 500) attending 25 Australian primary schools wore a pedometer and completed a travel diary for one week. Parents and children completed surveys capturing leisure activity, screen time, and sociodemographics. Commute distance was objectively measured. Car travel was the most frequent mode of school transportation (boys: 51%, girls: 58%). After adjustment (sociodemographics, commute distance, and school clustering) children who were driven recorded fewer weekday steps than those who walked (girls: –1,393 steps p < .001, boys: –1,569 steps, p = .009) and participated in fewer active leisure activities (girls only: p = .043). There were no differences in weekend steps or screen time. Being driven to and from school is associated with less weekday pedometer-determined physical activity in 9- to 13-year-old elementary-school children. Encouraging children, especially girls, to walk to and from school (even for part of the way for those living further distances) could protect the health and well-being of those children who are insufficiently active.

Reducing the pilling propensity of wool knits with a three-step plasma treatment

A three-step plasma treatment, including surface activation with argon, surface functionalization with oxygen and then thin film deposition using a pulsed plasma polymerization of hexamethyldisiloxane (HMDSO), was used in low-pressure plasma to improve the pilling resistance of knitted wool fabric. The pilling propensity of the treated samples was investigated and compared with the pilling propensity of untreated, argon activated and oxygen functionized samples and argon and oxygen plasma-treated samples that were afterwards subject to continuous wave plasma polymerization of HMDSO. With the three-step treatment, a pilling grade of four was achieved for the treated wool fabric, while that of untreated and other plasma-treated was two and three, respectively. For the three-step plasma-treated sample, a uniform HMDSO polymer coating of 300 nm thickness was obtained; X-ray photoelectron spectroscopy (XPS) showed the presence of the silicone element, and Fourier transform infrared (FTIR) spectroscopy confirmed the chemical structure of the coating. No apparent differences were found in the whiteness index between the treated and untreated wool knits, but there was deterioration in the bursting strength and handle of the plasma-treated wool samples.

A Response to Critique of the Refreeze Step in Lewin’s Model of Organizational Change from the Viewpoint of Organizational Behavior

Problem Statement
This paper responds to criticism of Kurt Lewin’s three step model of organizational change in increasingly turbulent environments. It explores whether the refreeze step of Kurt Lewin’s notable three step model is still applicable to organizational change processes in the age of globalisation and digitalisation.

Method
Literature review and critical analysis of applied examples are used to provide an overview of Kurt Lewin’s three-step change model. Authors’ observations and reflections are integrated in the discussion. The changing contemporary environment and the implications for the refreeze step of Lewin’s model are accordingly discussed.

Conclusions
The paper concludes that a balance of stability and movement; of discrete and emergent change; is the reality for today’s organizations, and forms the touchstone for Lewin’s formulation of change theories. Alignment is observed between notions of desired equilibrium in Lewin’s model and the contemporary underpinnings of sustainability. Technology and the modern pace of organizational change are also factors to consider. There has hence been an adaptation of his theoretical heritage that is current and sufficiently robust to withstand the criticisms of the refreeze stage.

Scalable One-Step Wet-Spinning of Graphene Fibers and Yarns from Liquid Crystalline Dispersions of Graphene Oxide: Towards Multifunctional Textiles

Key points in the formation of liquid crystalline (LC) dispersions of graphene oxide (GO) and their processability via wet-spinning to produce long lengths of micrometer-dimensional fibers and yarns are addressed. Based on rheological and polarized optical microscopy investigations, a rational relation between GO sheet size and polydispersity, concentration, liquid crystallinity, and spinnability is proposed, leading to an understanding of lyotropic LC behavior and fiber spinnability. The knowledge gained from the straightforward formulation of LC GO “inks” in a range of processable concentrations enables the spinning of continuous conducting, strong, and robust fibers at concentrations as low as 0.075 wt%, eliminating the need for relatively concentrated spinning dope dispersions. The dilute LC GO dispersion is proven to be suitable for fiber spinning using a number of coagulation strategies, including non-solvent precipitation, dispersion destabilization, ionic cross-linking, and polyelectrolyte complexation. One-step continuous spinning of graphene fibers and yarns is introduced for the first time by in situ spinning of LC GO in basic coagulation baths (i.e., NaOH or KOH), eliminating the need for post-treatment processes. The thermal conductivity of these graphene fibers is found to be much higher than polycrystalline graphite and other types of 3D carbon based materials.

One-Step Wet-Spinning Process of Poly(3,4-ethylenedioxythiophene):Poly(styrenesulfonate) Fibers and the Origin of Higher Electrical Conductivity

A simplified wet-spinning process for the production of continuous poly (3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) fibers is reported. Conductivity enhancement of PEDOT:PSS fibers up to 223 S cm−1 has been demonstrated when these fibers are exposed to ethylene glycol as a post-synthesis processing step. In a new spinning approach it is shown that by employing a spinning formulation consisting of an aqueous blend of PEDOT:PSS and poly(ethlylene glycol), the need for post-spinning treatment with ethylene glycol is eliminated. With this approach, 30-fold conductivity enhancements from 9 to 264 S cm−1 are achieved with respect to an untreated fiber. This one-step approach also demonstrates a significant enhancement in the redox properties of the fibers. These improvements are attributed to an improved molecular ordering of the PEDOT chains in the direction of the fiber axis and the consequential enrichment of linear (or expanded-coil like) conformation to preference bipolaronic electronic structures as evidenced by Raman spectroscopy, solid-state electron spin resonance (ESR) and in situ electrochemical ESR studies.

Coating and functionalization of carbon fibres using a three-step plasma treatment

A three-step plasma treatment—activation, functionalization and polymerization—has been used to deposit a thin plasma polymer with amine groups on carbon fibres (CFs). This plasma polymer has strong adhesion to the CF surface and the amine groups enable strong bonding to a matrix. The CFs were first treated by Ar plasma to activate and clean the surface, followed by O2 plasma to incorporate oxygen-containing functional groups, and finally a heptylamine thin film was deposited using combined continuous wave and pulsed plasma polymerization. Strong adhesion between the plasma polymer and the CF was observed. The fibre strength was not affected by the treatment.