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51.
Fluoropolymer blends have been widely used as binders for exterior coatings because of their excellent resistance to ultra-violet (UV) radiation as well as to many corrosive chemical agents.It is known that the fluorinated component usually has a lower glass transition temperature and easily crystallizes in the final structure depending upon the blend composition and sample annealing condition.We investigated the effect of blend composition and annealing process (slow and fast cooling) on the surface mor... 相似文献
52.
Juan Jose Pavn Jean Paul Allain Devendra Verma Mnica Echeverry‐Rendn Christy L. Cooper Lisa M. Reece Akshath R. Shetty Vikas Tomar 《Macromolecular bioscience》2019,19(2)
Surgical clipping and endovascular coiling are well recognized as conventional treatments of Penetrating Brain Injury aneurysms. These clinical approaches show partial success, but often result in thrombus formation and the rupture of aneurysm near arterial walls. The authors address these challenging brain traumas with a unique combination of a highly biocompatible biopolymer hydrogel rendered magnetic in a flexible and resilient membrane coating integrated to a scaffold stent platform at the aneurysm neck orifice, which enhances the revascularization modality. This work focuses on the in situ diagnosis of nano‐mechanical behavior of bacterial nanocellulose (BNC) membranes in an aqueous environment used as tissue reconstruction substrates for cerebral aneurysmal neck defects. Nano‐mechanical evaluation, performed using instrumented nano‐indentation, shows with very low normal loads between 0.01 to 0.5 mN, in the presence of deionized water. Mechanical testing and characterization reveals that the nano‐scale response of BNC behaves similar to blood vessel walls with a very low Young´s modulus, E (0.0025 to 0.04 GPa), and an evident creep effect (26.01 ± 3.85 nm s?1). These results confirm a novel multi‐functional membrane using BNC and rendered magnetic with local adhesion of iron‐oxide magnetic nanoparticles. 相似文献
53.
Roth J. Reece 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1978,6(2):158-165
The toroidal ring of plasma contained in the NASA Lewis Bumpy Torus may be biased to positive or negative potentials approaching 50 kilovolts by applying DC voltage to twelve or fewer midplane electrode rings. The electric fields, which are responsible for raising the ions to high energies by ExB/B2 drift, then point radially outward or inward. The profiles of plasma number density are observed to be flat or triangular across the plasma diameter. The absence of a second derivative in the density profile, combined with the flat electron temperature profiles which are observed, implies that the radial transport processes are not diffusional in nature and are dominated by the strong radial electric fields which are applied to the plasma. Evidence from a paired comparison test shows that the plasma number density and confinement time can increase more than an order of magnitude if the electric field acting along the minor radius of the toroidal plasma points inward, relative to the values observed when the electric field points radially outward. Some characteristic data taken under nonoptimized conditions yielded the highest plasma number density (2.7 × 1011/cc on axis) and the longest particle containment times (1.9 milliseconds) observed so far in this experiment. 相似文献
54.
55.
We derive a master equation for a mirror interacting with the vacuum field via radiation pressure. The dynamical Casimir effect leads to decoherence of a superposition state in a time scale that depends on the degree of "macroscopicity" of the state components, and which may be much shorter than the relaxation time scale. Coherent states are selected by the interaction as pointer states. 相似文献
56.
Reece JS Miller MJ Arnold MA Waterhouse C Delaplaine T Cohn L Cannon T 《Applied biochemistry and biotechnology》2003,104(1):1-11
A compact, flow-through oxygen sensor device based on luminescence quenching was used to monitor dissolved oxygen levels during
mammalian cell growth on the STS-93 mission of the Columbia space shuttle. Excitation of an oxygen-sensitive ruthenium complex
was provided by a radiolumin escent light source (0.9 mm in diameter, 2.5 mm long), and the intensity of the resulting luminescence
was measured by a simple photodiode detector. The use of radiolum inescence for the excitation light source is a unique approach
that provides many features important for long-term and remote monitoring applications. For the spaceflight experiment, human
lung fibroblast cells (WI-38) were grown in hollow-fiber bioreactors. Oxygen concentration was measured in the flow path both
before and after the bioreactor cartridge in order to gain information about the metabolism of the cells. The sensor was found
to be nonperturbing to cell growth and withstood the challenging physical conditions of shuttle launch and landing while maintaining
a stable calibration function. In addition, the sensor provided physically meaningful oxygen predictions. 相似文献
57.
Bai M Allgower C Ahrens L Alessi J Brown K Bunce G Cameron P Chu CM Courant ED Glenn JW Huang H Jeon D Kponou AE Krueger K Luccio A Makdisi YI Lee SY Ratner L Reece K Roser T Spinka H Syphers MJ Tsoupas N Underwood DG van Asselt W Williams N 《Physical review letters》2000,84(6):1184-1187
A new type of spin depolarization resonance has been observed at the Brookhaven Alternating Gradient Synchrotron (AGS). This spin resonance is identified as a strong closed-orbit sideband around the dominant intrinsic spin resonance. The strength of the resonance was proportional to the 9th harmonic component of the horizontal closed orbit and proportional to the vertical betatron oscillation amplitude. This "hybrid" spin resonance cannot be overcome by the partial snake at the AGS, but it can be corrected by the harmonic orbit correctors. 相似文献
58.
59.
Aoife Bharucha William Reece 《The European Physical Journal C - Particles and Fields》2010,69(3-4):623-640
We investigate the observables available in the angular distribution of B→K ? μ + μ ? to identify those suitable for measurements in the first few years of LHC data taking. There are three observables that may be extracted by counting signal events as a function of one or two decay angles and correspond to large features of the full angular distribution in the Standard Model: A FB, F L, and S 5. Two of these are well known in the experimental community; however, we show that measuring S 5 adds complementary sensitivity to physics beyond the Standard model. Like A FB, it features a zero-crossing point with reduced hadronic uncertainties at leading order and in the large recoil limit. Due to the high gradient of S 5 at this point, we find it would be possible for LHCb to measure it to high precision. Current experimental model independent constraints on parameter space are presented and predictions made for the values of the A FB and S 5 zero-crossing points. The relative impact of early LHCb measurements of A FB, F L, and S 5 is assessed. These issues are explored with a new model of the decay that can be used with standard simulation tools such as EvtGen. 相似文献
60.
Seyedsayamdost MR Yee CS Reece SY Nocera DG Stubbe J 《Journal of the American Chemical Society》2006,128(5):1562-1568
The Escherichia coli ribonucleotide reductase (RNR), composed of two subunits (R1 and R2), catalyzes the conversion of nucleotides to deoxynucleotides. Substrate reduction requires that a tyrosyl radical (Y(122)*) in R2 generate a transient cysteinyl radical (C(439)*) in R1 through a pathway thought to involve amino acid radical intermediates [Y(122)* --> W(48) --> Y(356) within R2 to Y(731) --> Y(730) --> C(439) within R1]. To study this radical propagation process, we have synthesized R2 semisynthetically using intein technology and replaced Y(356) with a variety of fluorinated tyrosine analogues (2,3-F(2)Y, 3,5-F(2)Y, 2,3,5-F(3)Y, 2,3,6-F(3)Y, and F(4)Y) that have been described and characterized in the accompanying paper. These fluorinated tyrosine derivatives have potentials that vary from -50 to +270 mV relative to tyrosine over the accessible pH range for RNR and pK(a)s that range from 5.6 to 7.8. The pH rate profiles of deoxynucleotide production by these F(n)()Y(356)-R2s are reported. The results suggest that the rate-determining step can be changed from a physical step to the radical propagation step by altering the reduction potential of Y(356)* using these analogues. As the difference in potential of the F(n)()Y* relative to Y* becomes >80 mV, the activity of RNR becomes inhibited, and by 200 mV, RNR activity is no longer detectable. These studies support the model that Y(356) is a redox-active amino acid on the radical-propagation pathway. On the basis of our previous studies with 3-NO(2)Y(356)-R2, we assume that 2,3,5-F(3)Y(356), 2,3,6-F(3)Y(356), and F(4)Y(356)-R2s are all deprotonated at pH > 7.5. We show that they all efficiently initiate nucleotide reduction. If this assumption is correct, then a hydrogen-bonding pathway between W(48) and Y(356) of R2 and Y(731) of R1 does not play a central role in triggering radical initiation nor is hydrogen-atom transfer between these residues obligatory for radical propagation. 相似文献