An experimental approach to quantify strain transfer efficiency of fibre bragg grating sensors to host structures

This paper developed a method to evaluate the strain transfer efficiency of fibre Bragg grating sensors to host structures. Various coatings were applied to fibre Bragg grating sensors after being fabricated. They were epoxy, silane agent and polypropylene, representing different surface properties. A neat epoxy resin plate was used as the host in which the coated fibre sensors were embedded in the central layer. The tensile strain output from the FBGs was compared with that obtained from electrical strain gauges which were attached on the surface of the specimen. A calculating method based on the measured strains was developed to quantify the strain transfer function of different surface coatings. The strain transfer coefficient obtained from the proposed method provided a direct indicator to evaluate the strain transfer efficiency of different coatings used on the FBG sensors, under either short or long-term loading. The results demonstrated that the fibre sensor without any coating possessed the best strain transfer, whereas, the worst strain transfer was created by polypropylene coating. Coatings play a most influential role in strain measurements using FBG sensors

Advanced Manned Launch System (AMLS) study

To assure national leadership in space operations and exploration in the future, NASA must be able to provide cost effective and operationally efficient space transportation. Several NASA studies and the joint NASA/DoD Space Transportation Architecture Studies (STAS) have shown the need for a multi-vehicle space transportation system with designs driven by enhanced operations and low costs. NASA is currently studying an advanced manned launch system (AMLS) approach to transport crew and cargo to the Space Station Freedom. Several single and multiple stage systems from air-breathing to all-rocket concepts are being examined in a series of studies potential replacements for the Space Shuttle launch system in the 2000-2010 time frame. Rockwell International Corporation, under contract to the NASA Langley Research Center, has analyzed a two-stage all-rocket concept to determine whether this class of vehicles is appropriate for the AMLS function. The results of the pre-phase A study are discussed

Functional evaluation of ES cell-derived endodermal populations reveals differences between Nodal and Activin A-guided differentiation

Embryonic stem (ES) cells hold great promise with respect to their potential to be differentiated into desired cell types. Of interest are organs derived from the definitive endoderm, such as the pancreas and liver, and animal studies have revealed an essential role for Nodal in development of the definitive endoderm. Activin A is a related TGFβ member that acts through many of the same downstream signaling effectors as Nodal and is thought to mimic Nodal activity. Detailed characterization of ES cell-derived endodermal cell types by gene expression analysis in vitro and functional analysis in vivo reveal that, despite their similarity in gene expression, Nodal and Activin-derived endodermal cells exhibit a distinct difference in functional competence following transplantation into the developing mouse embryo. Pdx1-expressing cells arising from the respective endoderm populations exhibit extended differences in their competence to mature into insulin/c-peptide-expressing cells in vivo. Our findings underscore the importance of functional cell-type evaluation during stepwise differentiation of stem cells.Stem Cell and Regenerative Biolog

The Coupled Cluster Method in Hamiltonian Lattice Field Theory: SU(2) Glueballs

The glueball spectrum within the Hamiltonian formulation of lattice gauge theory (without fermions) is calculated for the gauge group SU(2) and for two spatial dimensions. The Hilbert space of gauge-invariant functions of the gauge field is generated by its parallel-transporters on closed paths along the links of the spatial lattice. The coupled cluster method is used to determine the spectrum of the Kogut-Susskind Hamiltonian in a truncated basis. The quality of the description is studied by computing results from various truncations, lattice regularisations and with an improved Hamiltonian. We find consistency for the mass ratio predictions within a scaling region where we obtain good agreement with standard lattice Monte Carlo results.Comment: 13 pages, 7 figure

Surface tension of the isotropic-nematic interface

We present the first calculations of the pressure tensor profile in the vicinity of the planar interface between isotropic liquid and nematic liquid crystal, using Onsager's density functional theory and computer simulation. When the liquid crystal director is aligned parallel to the interface, the situation of lowest free energy, there is a large tension on the nematic side of the interface and a small compressive region on the isotropic side. By contrast, for perpendicular alignment, the tension is on the isotropic side. There is excellent agreement between theory and simulation both in the forms of the pressure tensor profiles, and the values of the surface tension.Comment: Minor changes; to appear in Phys. Rev.

Instabilities in the transient response of muscle

We investigate the isometric transient response of muscle using a quantitative stochastic model of the actomyosin cycle based on the swinging lever-arm hypothesis. We first consider a single pair of filaments, and show that when values of parameters such as the lever-arm displacement and the crossbridge elasticity are chosen to provide effective energy transduction, the T2 curve (the tension recovered immediately after a step displacement) displays a region of negative slope. If filament compliance and the discrete nature of the binding sites are taken into account, the negative slope is diminished, but not eliminated. This implies that there is an instability in the dynamics of individual half-sarcomeres. However, when the symmetric nature of whole sarcomeres is taken into account, filament rearrangement becomes important during the transient: as tension is recovered, some half-sarcomeres lengthen while others shorten. This leads to a flat T2 curve, as observed experimentally. In addition, we investigate the isotonic transient response and show that for a range of parameter values the model displays damped oscillations, as recently observed in experiments on single muscle fibers. We conclude that it is essential to consider the collective dynamics of many sarcomeres, rather than the dynamics of a single pair of filaments, when interpreting the transient response of muscle.Comment: 11 pages, 11 figures, Submitted to Biophysical Journa

A review of contemporary work on the ethics of ambient assisted living technologies for people with dementia

Ambient assisted living (AAL) technologies can provide assistance and support to persons with dementia. They might allow them the possibility of living at home for longer whilst maintaining their comfort and security as well as offering a way towards reducing the huge economic and personal costs forecast as the incidence of dementia increases worldwide over coming decades. However, the development, introduction and use of AAL technologies also trigger serious ethical issues. This paper is a systematic literature review of the on-going scholarly debate about these issues. More specifically, we look at the ethical issues involved in research and development (R&D), clinical experimentation, and clinical application of AAL technologies for people with dementia and related stakeholders. In the discussion we focus on: 1) the value of the goals of AAL technologies, 2) the special vulnerability of persons with dementia in their private homes, 3) the complex question of informed consent for the usage of AAL technologies