16,681 research outputs found

    Ultrasonic NDE of Green-State Ceramics by Focused Through-Transmission

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    Reliable NDE techniques for green-state (unfired) ceramics are needed (1) to evaluate ceramic powder processing and compaction methods and (2) to screen out defective ceramic components prior to the costly densification process. Past work in the application of ultrasonic NDE to green-state ceramics has been hampered by the lack of an efficient yet safe means to obtain ultrasonic coupling, since conventional coupling fluids (water, gels, oils, etc.) have a detrimental effect on fragile green-state materials. In early work, direct contact pressure was used to obtain dry coupling between transducer and specimen [1]. This approach was later improved upon by placing an elastomer membrane between the transducer and specimen; this method provided efficient coupling at significantly lower contact pressures [2]. In the study presented here, an acoustically transparent plastic membrane was held against the ceramic specimen by atmospheric pressure [3]. The advantage of this technique is that it allows the use of ultrasonic immersion techniques as well as contact transducers

    CD28- cells are increased in early rheumatoid arthritis and are linked with cytomegalovirus status

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    Objective: CD3+CD8+CD28− cells are higher in Rheumatoid Arthritis (RA). The aim of this study was to assess CD3+CD8+CD28− cells in patients with early RA and assess the effects of cytomegalovirus (CMV) seropositivity. Method: In this prospective observation study, 50 RA patients were recruited from Cardiff University Hospital of Wales (UHW) rheumatology outpatient, 25 patients with early disease (disease duration 0–6 months) and 25 patients with established disease (>2 years). These were compared with 25 healthy controls. Clinical and serological markers of inflammation were noted, and peripheral blood mononuclear cells were analyzed using flow cytometry. Results: The percentage of the CD8+CD28− T cells was increased in RA patients and was associated with disease duration. The percentage of CD8+CD28− T cells was increased in CMV positive early and established RA grouped and early RA patients in comparison to CMV negative patients (p < 0.05). There is a weak but statistically significant correlation between the percentage of CD3+CD8+CD28− cells and CRP in CMV positive RA patients (r = 0.227, p < 0.05). Conclusion: The percentage of CD8+CD28− T cells is higher in RA patients and correlates with disease duration, highlighting a potential role early in the disease process. These cells were also higher in CMV positive early RA patients which may suggest a role of CMV in disease development

    Dynamics of Quantum Vorticity in a Random Potential

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    I study the dynamics of a superfluid vortex in a random potential, as in the inner crust of a neutron star. Below a critical flow velocity of the ambient superfluid, a vortex is effectively immobilized by lattice forces even in the limit of zero dissipation. Low-velocity, translatory motion is not dynamically possible, a result with important implications for understanding neutron star precession and the dynamical properties of superfluid nuclear matter.Comment: Physical Review Letters, final versio

    Inclusive Scattering of Polarized Electrons on Polarized 3He Effects of Final State Interaction and the Magnetic Form Factor of the Neutron

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    Effects of final state interaction on asymmetries in inclusive scattering of polarized electrons on polarized 3He are investigated using consistent 3He bound state wave function and 3N continuum scattering states. Significant effects are found, which influence the extraction of the magnetic neutron form factor from A_T'. The enhancement found experimentally for A_TL' near the 3N breakup threshold, which could not be explained in calculations carried through in plane wave impulse approximation up to now, occurs now also in theory if the full final state interaction is included.Comment: 29 pages, 5 figure

    Highly unusual triangular crystals of theophylline: The influence of solvent on the growth rates of polar crystal faces

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    A noteworthy feature of the compound theophylline is that it forms crystals with a triangular habit, an extremely rare phenomenon for an organic molecule. Here, we investigate the formation of these crystals, comprised of the polymorph Form II (Pna21), and demonstrate that the triangles are obtained from solvents which are highly hydrophobic, or which have a hydrogen bond acceptor group and no hydrogen bond donor group. The formation of the triangular crystal habit is rationalized on the basis of the way such solvents interact with the inequivalent (001) and (00-1) polar crystal faces of Form II. Interactions are significantly stronger at one face than the other, inhibiting growth in one direction and limiting crystal growth to a single, triangle shaped, growth sector. This rationalization also enabled interesting surface features observed by atomic force microscopy to be interpreted. Furthermore, we report a second, previously unreported, type of triangular crystal of theophylline for which the angle at the tip of the triangle is obtuse rather than acute. These crystals are proposed, with the aid of transmission electron microscopy and crystal structure prediction, to be a new polymorphic form of theophyllin
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