Analysis and preliminary design of optical sensors for propulsion control

A fiber-optic sensor concept screening study was performed. Twenty sensor subsystems were identified and evaluated. Two concepts selected for further study were the Fabry-Perot fiber-optic temperature sensor and the pulse-width-modulated phosphorescent temperature sensor. Various designs suitable for a Fabry-Perot temperature sensor to be used as a remote fiber-optic transducer were investigated. As a result, a particular design was selected and constructed. Tests on this device show that spectral peaks are produced from visible white light, and the change in wavelength of the spectral peaks produced by a change in temperature is consistent with theory and is 36 nm/C for the first order peak. A literature search to determine a suitable phosphor for implementing the pulse-width-modulated fiber optic temperature sensor was conducted. This search indicated that such a device could be made to function for temperatures up to approximately 200 C. Materials like ZnCdS and ZnSe activated with copper will be particularly applicable to temperature sensing in the cryogenic to room temperature region. While this sensing concept is probably not applicable to jet engines, the simplicity and potential reliability make the concept highly desirable for other applications

Pseudogap phase formation in the crossover from Bose-Einstein condensation to BCS superconductivity in low dimensional systems

A phase diagram for a 2D metal with variable carrier density has been studied using the modulus-phase representation for the order parameter in a fully microscopic treatment. This amounts to splitting the degrees of freedom into neutral fermion and charged boson degrees of freedom. Although true long range order is forbidden in two dimensions, long range order for the neutral fermions is possible since this does not violate any continuous symmetry. The phase fluctuations associated with the charged degrees of freedom destroy long range order in the full system as expected. The presence of the neutral order parameter gives rise to new features in the superconducting condensate formation in low dimensional systems. The resulting phase diagram contains a new phase which lies above the superconducting (here Berezinskii-Kosterlitz-Thouless) phase and below the normal (Fermi-liquid) phase. We identify this phase with the pseudogap phase observed in underdoped high-$T_{c}$ superconducting compounds above their critical temperature. We also find that the phase diagram persists even in the presence of weak 3-dimensionalisation.Comment: 4 pages, LaTeX; invited paper presented at New^3SC-1, Baton Rouge, USA, 1998. To be published in Int.J.Mod.Phys.

Generating intrafusal skeletal muscle fibres in vitro: Current state of the art and future challenges

Intrafusal fibres are a specialised cell population in skeletal muscle, found within the muscle spindle. These fibres have a mechano-sensory capacity, forming part of the monosynaptic stretch-reflex arc, a key component responsible for proprioceptive function. Impairment of proprioception and associated dysfunction of the muscle spindle is linked with many neuromuscular diseases. Research to-date has largely been undertaken in vivo or using ex vivo preparations. These studies have provided a foundation for our understanding of muscle spindle physiology, however, the cellular and molecular mechanisms which underpin physiological changes are yet to be fully elucidated. Therefrom, the use of in vitro models has been proposed, whereby intrafusal fibres can be generated de novo. Although there has been progress, it is predominantly a developing and evolving area of research. This narrative review presents the current state of art in this area and proposes the direction of future work, with the aim of providing novel pre-clinical and clinical applications

Neuregulin 1 Drives Morphological and Phenotypical Changes in C2C12 Myotubes: Towards De Novo Formation of Intrafusal Fibres In Vitro

Muscle spindles are sensory organs that detect and mediate both static and dynamic muscle stretch and monitor muscle position, through a specialised cell population, termed intrafusal fibres. It is these fibres that provide a key contribution to proprioception and muscle spindle dysfunction is associated with multiple neuromuscular diseases, aging and nerve injuries. To date, there are few publications focussed on de novo generation and characterisation of intrafusal muscle fibres in vitro. To this end, current models of skeletal muscle focus on extrafusal fibres and lack an appreciation for the afferent functions of the muscle spindle. The goal of this study was to produce and define intrafusal bag and chain myotubes from differentiated C2C12 myoblasts, utilising the addition of the developmentally associated protein, Neuregulin 1 (Nrg-1). Intrafusal bag myotubes have a fusiform shape and were assigned using statistical morphological parameters. The model was further validated using immunofluorescent microscopy and western blot analysis, directed against an extensive list of putative intrafusal specific markers, as identified in vivo. The addition of Nrg-1 treatment resulted in a 5-fold increase in intrafusal bag myotubes (as assessed by morphology) and increased protein and gene expression of the intrafusal specific transcription factor, Egr3. Surprisingly, Nrg-1 treated myotubes had significantly reduced gene and protein expression of many intrafusal specific markers and showed no specificity towards intrafusal bag morphology. Another novel finding highlights a proliferative effect for Nrg-1 during the serum starvation-initiated differentiation phase, leading to increased nuclei counts, paired with less myotube area per myonuclei. Therefore, despite no clear collective evidence for specific intrafusal development, Nrg-1 treated myotubes share two inherent characteristics of intrafusal fibres, which contain increased satellite cell numbers and smaller myonuclear domains compared with their extrafusal neighbours. This research represents a minimalistic, monocellular C2C12 model for progression towards de novo intrafusal skeletal muscle generation, with the most extensive characterisation to date. Integration of intrafusal myotubes, characteristic of native, in vivo intrafusal skeletal muscle into future biomimetic tissue engineered models could provide platforms for developmental or disease state studies, pre-clinical screening, or clinical applications

Table 4. Marking codes Type number

1. Product profile 1.1 General description Bidirectional ElectroStatic Discharge (ESD) protection diodes in a very small SOD323 (SC-76) SMD plastic package designed to protect one signal line from the damage caused by ESD and other transients

Phase Fluctuations and Pseudogap Properties: Influence of Nonmagnetic Impurities

The presence of nonmagnetic impurities in a 2D ``bad metal'' depresses the superconducting Berezinskii-Kosterlitz-Thouless transition temperature, while leaving the pairing energy scale unchanged. Thus the region of the pseudogap non-superconducting phase, where the modulus of the order parameter is non-zero but its phase is random, and which opens at the pairing temperature is substantially bigger than for the clean system. This supports the premise that fluctuations in the phase of the order parameter can in principle describe the pseudogap phenomena in high-$T_c$ materials over a rather wide range of temperatures and carrier densities. The temperature dependence of the bare superfluid density is also discussed.Comment: 11 pages, LaTeX, 1 EPS figure; final version to appear in Low.Temp.Phy