Of Cell Shapes and Motion: The Physical Basis of Animal Cell Migration.

Motile cells have developed a variety of migration modes relying on diverse traction-force-generation mechanisms. Before the behavior of intracellular components could be easily imaged, cell movements were mostly classified by different types of cellular shape dynamics. Indeed, even though some types of cells move without any significant change in shape, most cell propulsion mechanisms rely on global or local deformations of the cell surface. In this review, focusing mostly on metazoan cells, we discuss how different types of local and global shape changes underlie distinct migration modes. We then discuss mechanical differences between force-generation mechanisms and finish by speculating on how they may have evolved

Impact of alternative solid state forms and specific surface area of high-dose, hydrophilic active pharmaceutical ingredients on tabletability

YesIn order to investigate the effect of using different solid state forms and specific surface area (TBET) of active pharmaceutical ingredients on tabletability and dissolution performance, the mono- and dihydrated crystalline forms of chlorothiazide sodium and chlorothiazide potassium (CTZK) salts were compared to alternative anhydrous and amorphous forms, as well as to amorphous microparticles of chlorothiazide sodium and potassium which were produced by spray drying and had a large specific surface area. The tablet hardness and tensile strength, porosity, and specific surface area of single-component, convex tablets prepared at different compression pressures were characterized. Results confirmed the complexity of the compressibility mechanisms. In general it may be concluded that factors such as solid-state form (crystalline vs amorphous), type of hydration (presence of interstitial molecules of water, dehydrates), or specific surface area of the material have a direct impact on the tabletability of the powder. It was observed that, for powders of the same solid state form, those with a larger specific surface area compacted well, and better than powders of a lower surface area, even at relatively low compression pressures. Compacts prepared at lower compression pressures from high surface area porous microparticles presented the shortest times to dissolve, when compared with compacts made of equivalent materials, which had to be compressed at higher compression pressures in order to obtain satisfactory compacts. Therefore, materials composed of nanoparticulate microparticles (NPMPs) may be considered as suitable for direct compaction and possibly for inclusion in tablet formulations as bulking agents, APIs, carriers, or binders due to their good compactibility performanceSolid State Pharmaceutical Cluster (SSPC), supported by Science Foundation Ireland under Grant No. 07/SRC/B1158

Extent of myosin penetration within the actin cortex regulates cell surface mechanics.

In animal cells, shape is mostly determined by the actomyosin cortex, a thin cytoskeletal network underlying the plasma membrane. Myosin motors generate tension in the cortex, and tension gradients result in cellular deformations. As such, many cell morphogenesis studies have focused on the mechanisms controlling myosin activity and recruitment to the cortex. Here, we demonstrate using super-resolution microscopy that myosin does not always overlap with actin at the cortex, but remains restricted towards the cytoplasm in cells with low cortex tension. We propose that this restricted penetration results from steric hindrance, as myosin minifilaments are considerably larger than the cortical actin meshsize. We identify myosin activity and actin network architecture as key regulators of myosin penetration into the cortex, and show that increasing myosin penetration increases cortical tension. Our study reveals that the spatial coordination of myosin and actin at the cortex regulates cell surface mechanics, and unveils an important mechanism whereby myosin size controls its action by limiting minifilament penetration into the cortical actin network. More generally, our findings suggest that protein size could regulate function in dense cytoskeletal structures

Fast relaxation in a fragile liquid under pressure

The incoherent dynamic structure factor of ortho-terphenyl has been measured by neutron time-of-flight and backscattering technique in the pressure range from 0.1 MPa to 240 MPa for temperatures between 301 K and 335 K. Tagged-particle correlations in the compressed liquid decay in two steps. The alpha-relaxation lineshape is independent of pressure, and the relaxation time proportional to viscosity. A kink in the amplitude f_Q(P) reveals the onset of beta relaxation. The beta-relaxation regime can be described by the mode-coupling scaling function; amplitudes and time scales allow a consistent determination of the critical pressure P_c(T). alpha and beta relaxation depend in the same way on the thermodynamic state; close to the mode-coupling cross-over, this dependence can be parametrised by an effective coupling Gamma ~ n*T**{-1/4}.Comment: 4 Pages of RevTeX, 4 figures (submitted to Physical Review Letters

Brave new world: service robots in the frontline

Purpose – The service sector is at an inflection point with regard to productivity gains and service industrialization similar to the industrial revolution in manufacturing that started in the eighteenth century. Robotics in combination with rapidly improving technologies like artificial intelligence (AI), mobile, cloud, big data and biometrics will bring opportunities for a wide range of innovations that have the potential to dramatically change service industries. The purpose of this paper is to explore the potential role service robots will play in the future and to advance a research agenda for service researchers. Design/methodology/approach – This paper uses a conceptual approach that is rooted in the service, robotics and AI literature. Findings – The contribution of this paper is threefold. First, it provides a definition of service robots, describes their key attributes, contrasts their features and capabilities with those of frontline employees, and provides an understanding for which types of service tasks robots will dominate and where humans will dominate. Second, this paper examines consumer perceptions, beliefs and behaviors as related to service robots, and advances the service robot acceptance model. Third, it provides an overview of the ethical questions surrounding robot-delivered services at the individual, market and societal level. Practical implications – This paper helps service organizations and their management, service robot innovators, programmers and developers, and policymakers better understand the implications of a ubiquitous deployment of service robots. Originality/value – This is the first conceptual paper that systematically examines key dimensions of robot-delivered frontline service and explores how these will differ in the future