Retinal slip during active head motion and stimulus motion

Gaze control in various conditions is important, since retinal slip deteriorates the perception of 3-D shape of visual stimuli. Several studies have shown that visual perception of 3-D shape is better for actively moving observers than for passive observers watching a moving object. However, it is not clear to what extent the improved percept of 3-D shape for active observers has to be attributed to corollary discharges to higher visual centers or whether the improved percept might be due to improved gaze stabilization during active head movements. The aim of this study was to measure binocular eye movements and to make a quantitative comparison of retinal slip for subjects instructed to fixate a visual stimulus in an active condition (subject makes an active head movement, object is stationary) and in a passive condition (the stimulus moves, the subject is stationary) for various movement frequencies, viewing distances, and stimulus diameters. Retinal slip remains below the acuity threshold of about 4 deg/s in active conditions, except for the highest frequency tested in this study (1.5 Hz) for nearby targets (0.25 cm). Retinal slip exceeds this threshold for most passive conditions. These results suggest that the enhanced performance in the visual perception of 3-D shape during active head movements can, at least partly, be explained by better fixation by actively moving observers.     

Development of a non-linear finite element modelling of the below-knee prosthetic socket interface

A non-linear finite element model has been established to predict the pressure and shear stress distribution at the limb-socket interface in below-knee amputees with consideration of the skin-liner interface friction and slip. In this model, the limb tissue and socket liner were respectively meshed into 954 and 450 three-dimensional eight-node isoparametric brick elements, based on measurements of an individual's amputated limb surface; the bone was meshed into three-dimensional six-node triangular prism elements, based on radiographic measurements of the individual's residual limb. The socket shell was assumed to be a rigid boundary. An important feature of this model is the use of 450 interface elements (ABAQUS INTER4) which mimic the interface friction condition. The results indicate that a maximum pressure of 226 kPa, shear stress of 53 kPa and less than 4 mm slip exist at the skin-liner interface when the full body weight of 800 N is applied to the limb. The results also show that the coefficient of friction is a very sensitive parameter in determining the interface pressures, shear stresses and slip. With the growth of coefficient of friction, the shear stresses will increase, while the pressure and slip will decrease.     

Anatomic Repair of the Central Slip with Anchor Suture Augmentation for Treatment of Established Boutonniere Deformity

BackgroudThe rupture of the central slip of an extensor tendon of a finger causes a boutonniere (or buttonhole) deformity, characterized by pathologic flexion at the proximal interphalangeal (PIP) joint and hyperextension at the distal interphalangeal (DIP) joint. Currently, there are no standard treatment guidelines for this deformity. This study aimed to report clinical results of surgery to correct chronic boutonniere deformity.MethodsThis retrospective case series was conducted between January 2010 and December 2018 and only 13 patients with trauma-induced chronic deformity were included. After excision of elongated scar tissue, a direct anatomic end-to-end repair using a loop suture technique with supplemental suture anchor augmentation was conducted. Total active motion was assessed before and after surgery and self-satisfaction scores were collected from phone surveys.ResultsAll patients presented with Burton stage I deformities defined as supple and passively correctable joints. The initial mean extension lag of the PIP joint (43.5°) was improved by an average of 21.9° at the final follow-up (p < 0.001). The mean hyperextension of the DIP joint averaged 19.2° and improved by 0.8° flexion contracture (p < 0.001). The average total active motion was 220.4° (range, 160°–260°). Based on the Souter''s criteria, 69.2% (9/13) of the patients had good results. Only 1 patient reported fair outcome and 23.1% (3/13) reported poor outcome. The average Strickland formula score was 70 (range, 28.6–97.1). In total, 10 patients (77%) had excellent or good results. Of 10 patients contacted by phone, self-reported satisfaction score was very satisfied in 2, satisfied in 3, average in 3, poor in 1, and very poor in 1. Three patients reported a relapse of the deformity during range of motion exercises, 1 of whom underwent revision surgery. One patient complained of PIP joint flexion limitation, and 2 complained of DIP joint flexion limitation at final follow-up.ConclusionsIn chronic boutonniere deformity, central slip reconstruction with anchor suture augmentation can be an easily applicable surgical option, which offers fair to excellent outcome in 77% of the cases. The risk of residual extension lag and recurrence of deformity should be discussed prior to surgery.     

Using the clay slip game in art therapy: a sensory intervention

ABSTRACT

The goal of the present study was to achieve a better understanding of the experience of playing with slip and the ways in which participants experience the Clay Slip Game and how they perceive the therapeutic qualities of the material, thus including the potential for art therapists to add the Slip Game to their toolbox. Ten experienced qualified art therapists and 48 art therapy students took part. All participants engaged in the Slip Game during the study and reported their experiences in an interview (therapists) or in written personal reflections (students). Data analysis adhered to the principles of Grounded Theory [Charmaz (2006). Constructing grounded theory: A practical guide through qualitative analysis. London: Sage Publications]. The findings indicate that the experience of the Slip Game is mainly a sensory (tactile), playful, pleasant and calming experience of making without the need to produce an end product. The experience is more internal (meditative) and stimulates feelings of regression. The therapeutic qualities of the material, as discussed by the participants, are related to the regressive and sublimative processes afforded by the material, and as a material that enables sensory, behavioural, emotional, and motor regulation.

Plain-language summary

Art therapy is a type of psychotherapy that uses artistic materials and creative processes in the therapeutic process. Since art materials are the primary tools through which the art therapy processes occur, therapists need to have an in-depth understanding of the art materials they offer to their clients [Moon (2010). Materials & media in art therapy: Critical understandings of diverse artistic vocabularies. New York, NY: Routledge].

Slip is a mixture of water with an additional substance that produces a thick and saline-type paste [De Montmollin (2010). The barbotine game-challenge of creativity. Antwerpen.]. It can be made by diluting and filtering any kind of clay to make it semi-fluid. Playing with slip as a distinct and separate technique was defined as a ‘game’ by Daniel De Montmollin, a ceramicist. De Montmollin created the Slip Game as a way to help people free themselves from internal and external censorship or criticism.

The goal of this study was to understand the participants’ experience of the Slip Game and whether they found the process therapeutic. Forty-eight art therapy students and 10 art therapists took part in the study. After engaging in the Slip Game, the art therapists reported their experiences in an interview and the students wrote personal reflections. These were then analysed using Grounded Theory.

The findings show that the participants experienced the Slip Game as mainly sensory and reported it was pleasant, calming, playful and tactile, a way of ‘making’ without the need to produce an end product. They also found the experience to be meditative, that it stimulated feelings of regression and felt that engaging with slip also improved behaviour, emotional control and fine hand-movement skills.     

Al2O3/ZrO2 Materials as an Environmentally Friendly Solution for Linear Infrastructure Applications

The present work deals with the evaluation of the effect of ZrO₂ on the structure and selected properties of shapes obtained using the centrifugal slip casting method. The samples were made of alumina and zirconia. The applied technology made it possible to produce tubes with a high density reaching 99–100% after sintering. Very good bonding was obtained at the Al₂O₃/ZrO₂ interphase boundaries with no discernible delamination or cracks, which was confirmed by STEM observations. In the case of Al₂O₃/ZrO₂ composites containing 5 vol.% and 10 vol.% ZrO₂, the presence of equiaxial ZrO₂ grains with an average size of 0.25 µm was observed, which are distributed along the grain boundaries of Al₂O₃. At the same time, the composites exhibited a very high hardness of 22–23 GPa. Moreover, the environmental influences accompanying the sintering process were quantified. The impacts were determined using the life cycle analysis method, in the phase related to the extraction and processing of raw materials and the process of producing Al₂O₃/ZrO₂ composites. The results obtained show that the production of 1 kg of sintered composite results in greenhouse gas emissions of 2.24–2.9 kg CO₂ eq. which is comparable to the amount of emissions accompanying the production of 1 kg of Polyvinyl Chloride (PVC), Polypropylene (PP), or hot-rolled steel products.     

Zirconia–Alumina Composites Obtained by Centrifugal Slip Casting as Attractive Sustainable Material for Application in Construction

This paper focuses on the possibility of adapting the centrifugal slip casting method to obtain zirconia–alumina composite materials in the form of finished tube-shaped products. These types of products, due to their unique properties, can be utilised, for example, in the transport of aggressive substances, even in extreme temperatures or corrosive conditions. The study reports on the two series of zirconia–alumina composites differing in the content of ZrO₂—2.5 and 25 vol%. The fabricated and sintered materials were characterised using scanning electron microscopy (SEM), X-ray diffraction (XRD) and stereological analysis. Moreover, a life cycle assessment (LCA) was provided in accordance with the requirements of the ISO 14044 and EN 15805 standards. The obtained data clearly show that the centrifugal slip casting method allows obtaining samples with high density and extremely uniform distribution of the ZrO₂ phase in the alumina matrix. The stereological analysis results proved also that the addition of ZrO₂ is effective in reducing the growth of Al₂O₃ grains during the sintering process. The phase analysis carried out by means of XRD showed that during the sintering process, in the case of composites with a lower ZrO₂ content (2.5 vol%), the monoclinic to tetragonal transformation of ZrO₂ was total, while for samples containing 25 vol% ZrO₂, the monoclinic phase remained in a small amount in the final product.     

Modeling Uniaxial Bond Stress–Slip Behavior of Reinforcing Bars Embedded in Concrete with Different Strengths

This paper aims to study the uniaxial bond stress–slip characteristics of reinforcing bars embedded in concrete with different strengths. Tests were conducted on tension–pull specimens that had a cross-sectional dimension with a reinforcing bar embedded in the center section. The experimental variable was the concrete compressive strength (20, 40, and 60 MPa). The test results show that in the specimen subjected to any fixed load, the maximum value of the concrete strain occurred around the central position, and its value increased as the compressive strength of the concrete increased. Depending on the embedded position of the steel bars, the bond stress–slip relationship was also different. In addition, the analytical results indicate that the proposed bond stress–slip constitutive relationship is very accurate in describing the true bond stress–slip relationship.     

Plasticity and Slip System of Plate-Shaped Crystals of L-Lysine Monohydrochloride Dihydrate

Purpose. To identify the slip system of L-lysine monohydrochloride dihydrate (LH) and to relate it to the deformation behavior under uniaxial compression. Methods. The indentation hardness of the {100} face and the indentation moduli of the {100} and {011} faces of plate-shaped single crystals of LH (LHP) were determined using Knoop and Berkovich indenters, respectively. The deformation behavior during uniaxial compression was studied by the punch-stress vs. punch-displacement profile and by electron microscopy of the deformed crystals within cracked compacts. Results. The different indentation (elastic) moduli of the {100} and {011} faces of the crystals are consistent with the molecular packing density along these planes and suggest anisotropy. The existence of the {001} <100> slip system is proposed based on the pattern of changing indentation hardness with varying orientation of the Knoop indenter. A jagged uniaxial compression profile suggests deformation by mechanical twinning and not simple slip. The hypothesis of deformation by mechanical twinning is supported by the appearance of twin bands along the crystal faces as observed by electron microscopy of the cracked compacts. Conclusions. During compression, most LHP crystals have their {100} faces oriented normal to, or inclined to, the compression axis, thereby facilitating plastic deformation along the {001} <100> slip system by mechanical twinning. Due to the low attachment energy between them, the {001} planes can also act as cleavage planes. This study demonstrates that knowledge of the crystal structure and slip systems can be used to model the tableting and compaction behavior of molecular crystals, such as LH.     

Control of dynamic stability during gait termination on a slippery surface in Parkinson's disease

This study investigated how Parkinson's disease (PD) affects the ability to switch from locomotion to gait termination (GT) during planned and cued GT and examined the effect of PD on the integration of a reactive, balance maintenance strategy into voluntary GT. After a series of stops on a stable surface, eight participants with and 10 without PD stopped on a surface, which slid quickly and unexpectedly forward mimicking a slippery surface. PD caused instability during the completely voluntary nonslippery stops (P = 0.012) but not during the slippery stops, which required a reactive movement. The PD group walked slower [0.9–1.0 m/s vs. 1.3 m/s, respectively (P < 0.001)] with shorter steps during the first step of nonslippery GT (P = 0.016) and with wider steps during all steps of nonslippery GT (P ≤ 0.05). Similar to controls, the PD group increased lateral stability during planned GT compared to cued GT (P = 0.007). The timing of gait termination was similar between groups in all conditions. During the unexpected perturbation, both groups used a generalized slip response to regain balance after the perturbation. PD did not affect the ability to stop walking or to integrate a balance‐correcting response into GT but did affect movement speed, size, and stability of the voluntary movement. © 2008 Movement Disorder Society