An analytical approach to sorting in periodic potentials

There has been a recent revolution in the ability to manipulate micrometer-sized objects on surfaces patterned by traps or obstacles of controllable configurations and shapes. One application of this technology is to separate particles driven across such a surface by an external force according to some particle characteristic such as size or index of refraction. The surface features cause the trajectories of particles driven across the surface to deviate from the direction of the force by an amount that depends on the particular characteristic, thus leading to sorting. While models of this behavior have provided a good understanding of these observations, the solutions have so far been primarily numerical. In this paper we provide analytic predictions for the dependence of the angle between the direction of motion and the external force on a number of model parameters for periodic as well as random surfaces. We test these predictions against exact numerical simulations

Knee joint neuromuscular activation performance during muscle damage and superimposed fatigue

This study examined the concurrent effects of exercise-induced muscle damage and superimposed acute fatigue on the neuromuscular activation performance of the knee flexors of nine males (age: 26.7 ± 6.1yrs; height 1.81 ± 0.05m; body mass 81.2 ± 11.7kg [mean ± SD]). Measures were obtained during three experimental conditions: (i) FAT-EEVID, involving acute fatiguing exercise performed on each assessment occasion plus a single episode of eccentric exercise performed on the first occasion and after the fatigue trial; (ii) FAT, involving the fatiguing exercise only and; (iii) CON consisting of no exercise. Assessments were performed prior to (pre) and at lh, 24h, 48h, 72h, and 168h relative to the eccentric exercise. Repeated-measures ANOVAs showed that muscle damage within the FAT-EEVID condition elicited reductions of up to 38%, 24%) and 65%> in volitional peak force, electromechanical delay and rate of force development compared to baseline and controls, respectively (F[io, 80] = 2.3 to 4.6; p to 30.7%>) following acute fatigue (Fp; i6] = 4.3 to 9.1; p ; Fp, iq = 3.9; p <0.05). The safeguarding of evoked muscle activation capability despite compromised volitional performance might reveal aspects of capabilities for emergency and protective responses during episodes of fatigue and antecedent muscle damaging exercise

Addition of hyaluronic acid improves cellular infiltration and promotes early-stage chondrogenesis in a collagen-based scaffold for cartilage tissue engineering.

The response of mesenchymal stem cells (MSCs) to a matrix largely depends on the composition as well as the extrinsic mechanical and morphological properties of the substrate to which they adhere to. Collagen-glycosaminoglycan (CG) scaffolds have been extensively used in a range of tissue engineering applications with great success. This is due in part to the presence of the glycosaminoglycans (GAGs) in complementing the biofunctionality of collagen. In this context, the overall goal of this study was to investigate the effect of two GAG types: chondroitin sulphate (CS) and hyaluronic acid (HyA) on the mechanical and morphological characteristics of collagen-based scaffolds and subsequently on the differentiation of rat MSCs in vitro. Morphological characterisation revealed that the incorporation of HyA resulted in a significant reduction in scaffold mean pore size (93.9 μm) relative to collagen-CS (CCS) scaffolds (136.2 μm). In addition, the collagen-HyA (CHyA) scaffolds exhibited greater levels of MSC infiltration in comparison to the CCS scaffolds. Moreover, these CHyA scaffolds showed significant acceleration of early stage gene expression of SOX-9 (approximately 60-fold higher,

Development of a collagen calcium-phosphate scaffold as a novel bone graft substitute.

Previous investigations have shown that collagen shows excellent biological performance as a scaffold for tissue engineering. As a primary constituent of bone and cartilage, it demonstrates excellent cell adhesion and proliferation. However, in bone tissue engineering, it has insufficient mechanical properties for implantation in a load-bearing defect. The objective of this preliminary study was to investigate the possibility of developing a collagen/calcium-phosphate composite scaffold which would combine the biological performance and the high porosity of a collagen scaffold with the high mechanical stiffness of a calcium-phosphate scaffold. Collagen scaffolds were produced by a lyophilisation process from a collagen slurry. The scaffolds were soaked for different exposure times in solutions of 0.1 M, 0.5 M or 1.0 M NaNH4HPO4 followed by 0.1 M, 0.5 M or 1.0 M CaCl2. Mechanical tests of each scaffold were performed on a uniaxial testing system. Young\u27s moduli were determined from stress-strain curves. The pore structure and porosity of the scaffolds were investigated using micro-computed tomography. A pure collagen scaffold served as a control. All scaffolds showed a significantly increased compressive stiffness relative to the pure collagen scaffolds. The exposure to the 0.5 M solutions showed significantly superior results compared to the other groups. Analysis of the pore structure indicated a decrease in the overall porosity of the composite scaffolds relative to the controls. Regarding mechanical stiffness and porosity, scaffolds after 1 hour exposure to the 0.5 M solutions showed the best properties for bone tissue engineering. Further work will involve producing a scaffold with a more homogeneous calcium phosphate distribution

Communication with young people in paediatric and adult endocrine consultations: an intervention development and feasibility study

Background: Communication is complex in endocrine care, particularly during transition from paediatric to adult services. The aims of this study were to examine the feasibility of interventions to support young people to interact with clinicians. Methods: Development and evaluation of a complex intervention in 2 phases: Pre-intervention observational study; Intervention feasibility study. Purposive sample of recordings of 62 consultations with 58 young people aged 11-25 years with long-term endocrine conditions in two paediatric and two adult endocrine clinics. Proportion of time talked during consultations, number and direction of questions asked; Paediatric Consultation Assessment Tool (PCAT); OPTION shared decision making tool; Medical Information Satisfaction Scale (MISS- 21). Young people were invited to use one or more of: a prompt sheet to help them influence consultation agendas and raise questions; a summary sheet to record key information; and the www.explain.me.uk website. Results: Nearly two thirds of young people (63%) chose to use at least one communication intervention. Higher ratings for two PCAT items (95% CI 0.0 to 1.1 and 0.1 to 1.7) suggest interventions can support consultation skills. A higher proportion of accompanying persons (83%) than young people (64%) directed questions to clinicians. The proportion of young people asking questions was higher (84%) in the intervention phase than in the observation phase (71%). Conclusions: Interventions were acceptable and feasible. The Intervention phase was associated with YP asking more questions, which implies that the availability of interventions could promote interactivity

A biomimetic multi-layered collagen-based scaffold for osteochondral repair.

Cartilage and osteochondral defects pose a significant challenge in orthopedics. Tissue engineering has shown promise as a potential method for the treatment of such defects; however, a long-lasting repair strategy has yet to be realized. This study focuses on the development of a layered construct for osteochondral repair, fabricated through a novel \u22iterative layering\u22 freeze-drying technique. The process involved repeated steps of layer addition followed by freeze-drying, enabling control over material composition, pore size and substrate stiffness in each region of the construct, while also achieving a seamlessly integrated layer structure. The novel construct developed mimics the inherent gradient structure of healthy osteochondral tissue: a bone layer composed of type I collagen and hydroxyapatite (HA), an intermediate layer composed of type I collagen, type II collagen and HA and a cartilaginous region composed of type I collagen, type II collagen and hyaluronic acid. The material properties were designed to provide the biological cues required to encourage infiltration of host cells from the bone marrow while the biomechanical properties were designed to provide an environment optimized to promote differentiation of these cells towards the required lineage in each region. This novel osteochondral graft was shown to have a seamlessly integrated layer structure, high levels of porosity (\u3e97%), a homogeneous pore structure and a high degree of pore interconnectivity. Moreover, homogeneous cellular distribution throughout the entire construct was evident following in vitro culture, demonstrating the potential of this multi-layered scaffold as an advanced strategy for osteochondral defect repair

On the making and taking of professionalism in the further education workplace

This paper examines the changing nature of professional practice in English further education. At a time when neo-liberal reform has significantly impacted on this under-researched and over-market-tested sector, little is known about who its practitioners are and how they construct meaning in their work. Sociological interest in the field has tended to focus on further education practitioners as either the subjects of market and managerial reform or as creative agents operating within the contradictions of audit and inspection cultures. In challenging such dualism, which is reflective of wider sociological thinking, the paper examines the ways in which agency and structure combine to produce a more transformative conception of the further education professional. The approach contrasts with a prevailing policy discourse that seeks to re-professionalise and modernise further education practice without interrogating either the terms of its professionalism or the neo-liberal practices in which it resides

The Unreasonable Effectiveness of Contact Tracing on Networks with Cliques

Contact tracing, the practice of isolating individuals who have been in contact with infected individuals, is an effective and practical way of containing disease spread. Here, we show that this strategy is particularly effective in the presence of social groups: Once the disease enters a group, contact tracing not only cuts direct infection paths but can also pre-emptively quarantine group members such that it will cut indirect spreading routes. We show these results by using a deliberately stylized model that allows us to isolate the effect of contact tracing within the clique structure of the network where the contagion is spreading. This will enable us to derive mean-field approximations and epidemic thresholds to demonstrate the efficiency of contact tracing in social networks with small groups. This analysis shows that contact tracing in networks with groups is more efficient the larger the groups are. We show how these results can be understood by approximating the combination of disease spreading and contact tracing with a complex contagion process where every failed infection attempt will lead to a lower infection probability in the next attempts. Our results illustrate how contract tracing in real-world settings can be more efficient than predicted by models that treat the system as fully mixed or the network structure as locally tree-like.Comment: 15 pages, 13 figures, 4 table