Navigating with fingers and feet: Analysis of human (Homo sapiens) and rat (Rattus norvegicus) movement organization during nonvisual spatial tasks.

The current set of studies examines the contribution of movement segmentation to self-movement cue processing for estimating direction and distance to a start location in humans and rats. Experiments 1 and 2 examined the extent that ambulatory dead reckoning tasks can be adapted to the manipulatory scale in humans. Experiments 3 and 4 investigated the performance of rats in similar tasks at their ambulatory scale. Movement segmentation had differential effects on absolute heading error for humans and rats when only comparing performance on specific tasks; however, movement segmentation had similar effects for both species when performance was examined across all tasks. In general, magnitude of movement segmentation was associated with absolute heading error in both humans and rats. In contrast, both species modified homeward segment kinematics based on the distance to the start location in all tasks, consistent with the use of self-movement cues to estimate distance. The current study provides evidence for a role of movement segmentation in processing self-movement cues selective to direction estimation and develops a foundation for future studies investigating the neurobiology of spatial orientation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cholesterol-Dependent Energy Transfer between Fluorescent Proteins—Insights into Protein Proximity of APP and BACE1 in Different Membranes in Niemann-Pick Type C Disease Cells

Förster resonance energy transfer (FRET) -based techniques have recently been applied to study the interactions between β-site APP-cleaving enzyme-GFP (BACE1-GFP) and amyloid precursor protein-mRFP (APP-mRFP) in U373 glioblastoma cells. In this context, the role of APP-BACE1 proximity in Alzheimer’s disease (AD) pathogenesis has been discussed. FRET was found to depend on intracellular cholesterol levels and associated alterations in membrane stiffness. Here, NPC1 null cells (CHO-NPC1^−/−), exhibiting increased cholesterol levels and disturbed cholesterol transport similar to that observed in Niemann-Pick type C disease (NPC), were used to analyze the influence of altered cholesterol levels on APP-BACE1 proximity. Fluorescence lifetime measurements of whole CHO-wild type (WT) and CHO-NPC1^−/− cells (EPI-illumination microscopy), as well as their plasma membranes (total internal reflection fluorescence microscopy, TIRFM), were performed. Additionally, generalized polarization (GP) measurements of CHO-WT and CHO-NPC1^−/− cells incubated with the fluorescence marker laurdan were performed to determine membrane stiffness of plasma- and intracellular-membranes. CHO-NPC1^−/− cells showed higher membrane stiffness at intracellular- but not plasma-membranes, equivalent to cholesterol accumulation in late endosomes/lysosomes. Along with higher membrane stiffness, the FRET efficiency between BACE1-GFP and APP-mRFP was reduced at intracellular membranes, but not within the plasma membrane of CHO-NPC1^−/−. Our data show that FRET combined with TIRF is a powerful technique to determine protein proximity and membrane fluidity in cellular models of neurodegenerative diseases.     

Musculoskeletal, visual and psychosocial stress in VDU operators before and after multidisciplinary ergonomic interventions. A 6 years prospective study—Part II

A prospective epidemiological field study covering a 2 years period has earlier been published (Appl. Ergon. (1998) 29(5) 335). The study has a parallel group design with two intervention groups (T and S) and one control group (C) of Visual Display Unit (VDU) operators. The present paper covers the period from 2 to 6 years of the study. After 3.5 years, the C group got the same intervention in terms of new lighting system, new workplaces and at last an optometric examination and corrections if needed. The C group reported a significant reduction in visual discomfort after interventions while the two groups (T and S) continued to report significant reduction of visual discomfort after 6 years. By supporting the forearm on the table top, the C group reported significant reduction of shoulder and neck pain while the T group reported significant reduction in shoulder and back pain after 6 years. Organizational and psychosocial factors at work and outside work did not show any significant changes during the study period.     

A numerical estimation of the effects of a cylindrical hole and imperfect bonding on stability of a fibre in an elastic matrix

A simple numerical model based on three‐dimensional analytical considerations is proposed for an estimation of the local effects of a cylindrical hole in the matrix as well as of fibre–matrix interface imperfections on compressive stability of fibres in fibre‐reinforced composites. The geometry of the model includes an inclusion (a fibre) in a matrix with the assumption of an imperfect bonding at the interface and a cylindrical hole in the closest neighbourhood. Then the problem formulation is idealized in two directions, providing a possibility of establishing lower and upper bounds for critical loads for the case of a matrix with a cylindrical hole of a non‐circular cross‐section as well as for the case of interface imperfections with the possibility of sliding without discontinuity of the displacements normal to the interface. The model takes into account the distinct difference in the properties of the fibre and the matrix and the spatial character of the problem at the microlevel. It is based on individual consideration of the fibre and the matrix with a hole with the necessity of satisfying certain idealized bonding conditions between them. Copyright © 2001 John Wiley & Sons, Ltd.     

Thermo-mechanische Simulation einer Pressstumpfschweißung von 26MnB5

The physical simulation of resistance butt welding was conducted on a Gleeble^® 3800. 26MnB5 steel was used as material. The mechanical properties of the thermo-mechanically affected zone were determined by Charpy-V-notch, tensile, and Vickers hardness tests. Charpy-V-notched specimens with reduced thickness showed a fracture path deviation. This behaviour was prevented by redefining the specimen geometry. To determine the influence of compression on the mechanical-technological properties, thermo-mechanically simulated Gleeble specimens were compared to purely thermally simulated HAZ specimens. The absorbed energy of thermo-mechanically simulated specimens was constantly higher as compared to thermally simulated specimens.     

Micromechanical formulation and 3D finite element modeling of microinstabilities in composites

A 3D micromechanical formulation and a FE-model of fiber micro-buckling in materials with isotropic and transversal isotropic fibers in compression is presented. Three variants of geometrical modeling of the characteristic cell are proposed and compared. An appropriate one is then selected. An eigenvalue analysis of a characteristic cell is performed. The results show that the fiber anisotropy reduces significantly the critical loads and must be taken into account.     

An emulsion preparation for novel micro-porous polymeric hemi-shells

A modified oil-in-water (O/W) emulsion process was developed to produce novel micro-porous hemi-spherical polycaprolactone (PCL) micro-particles called “hemi-shells”. By addition of a porogen such as sodium bicarbonate (NaHCO₃) into the PCL-dichloromethane (DCM) oil phase and emulsification in an acidic polyvinyl alcohol (PVA) aqueous phase, micro-porous hemi-shells formed as solvent evaporated. CO₂ gas evolution from the porogen created particles with an externally micro-porous shell and a large internal cavity. The hemi-shells were characterized by SEM and optical microscopy. The number-average particle yield in the 50-200 μm range was 84%. The number-average hemi-shell yield in the same size range was 41%. These novel micro-particles have potential applications in tissue engineering and drug delivery.