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Search Results: 1 - 10 of 297543 matches for " J. Schuetzmann "
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In-plane optical response of Bi2Sr2CuO6
A. A. Tsvetkov,J. Schuetzmann,D. van der Marel
Physics , 1997, DOI: 10.1103/PhysRevB.55.14152
Abstract: We report on infrared reflectivity measurements of the $ab$-plane response of superconducting Bi$_2$Sr$_2$CuO$_6$ single crystals. The frequency dependent conductivity has a maximum near 700 cm$^{-1}$ at room temperature, which shifts to lower frequency and merges with a Drude-peak below 100 K. We attribute the unusual behaviour of the mid-infrared conductivity to low frequency transitions between electronic bands of mainly BiO character near the $\overline{M}$ point. The linear temperature dependence of the low-frequency resistivity can be followed down to approximately 40 K where it saturates.
Non-equilibrium Superconductivity and Quasiparticle Dynamics studied by Photo Induced Activation of Mm-Wave Absorption (PIAMA)
B. J. Feenstra,J. Schuetzmann,D. van der Marel R. Pérez Pinaya,M. Decroux
Physics , 1997, DOI: 10.1103/PhysRevLett.79.4890
Abstract: We present a study of non-equilibrium superconductivity in DyBa2Cu3O7-d using photo induced activation of mm-wave absorption (PIAMA). We monitor the time evolution of the thin film transmissivity at 5 cm-1 subject to pulsed infrared radiation. In addition to a positive bolometric signal we observe a second, faster, decay with a sign opposite to the bolometric signal for T>40 K. We attribute this to the unusual properties of quasi-particles residing near the nodes of an unconventional superconductor, resulting in a strong enhancement of the recombination time.
Global and Local Measures of the Intrinsic Josephson Coupling in Tl2Ba2CuO6
A. A. Tsvetkov,D. van der Marel,K. A. Moler,J. R. Kirtley,J. L. de Boer,A. Meetsma,Z. F. Ren,N. Koleshnikov,D. Dulic,A. Damascelli,M. Grueninger,J. Schuetzmann,J. W. van der Eb,H. S. Somal,J. H. Wang
Physics , 1998, DOI: 10.1038/26439
Abstract: The Intlerlayer Josephson coupling between the planes of Tl2Ba2CuO6 was determined using infrared spectroscopy and magnetic flux vortex imaging. These methods give a consistent value of $\omega_J$= 28 cm$^{-1}$ which, when combined with the condensation energy produces a discrepancy of at least an order of magnitude with deductions based on the interlayer tunneling model.
New components of the mercury’s perihelion precession  [PDF]
J. J. Smulsky
Natural Science (NS) , 2011, DOI: 10.4236/ns.2011.34034
Abstract: The velocity of perihelion rotation of Mercury's orbit relatively motionless space is computed. It is prove that it coincides with that calculated by the Newtonian interaction of the planets and of the compound model of the Sun’s rotation.
Simple General Purpose Ion Beam Deceleration System Using a Single Electrode Lens  [PDF]
J. Lopes, J. Rocha
World Journal of Engineering and Technology (WJET) , 2015, DOI: 10.4236/wjet.2015.33014
Abstract: Ion beam deceleration properties of a newly developed low-energy ion beam implantation system were studied. The objective of this system was to produce general purpose low-energy (5 to 15 keV) implantations with high current beam of hundreds of μA level, providing the most wide implantation area possible and allowing continuously magnetic scanning of the beam over the sample(s). This paper describes the developed system installed in the high-current ion implanter at the Laboratory of Accelerators and Radiation Technologies of the Nuclear and Technological Cam-pus, Sacavém, Portugal (CTN).
Constraints on velocity anisotropy of spherical systems with separable augmented densities
J. An
Physics , 2011, DOI: 10.1088/0004-637X/736/2/151
Abstract: If the augmented density of a spherical anisotropic system is assumed to be multiplicatively separable to functions of the potential and the radius, the radial function, which can be completely specified by the behavior of the anisotropy parameter alone, also fixes the anisotropic ratios of every higher-order velocity moment. It is inferred from this that the non-negativity of the distribution function necessarily limits the allowed behaviors of the radial function. This restriction is translated into the constraints on the behavior of the anisotropy parameter. We find that not all radial variations of the anisotropy parameter satisfy these constraints and thus that there exist anisotropy profiles that cannot be consistent with any separable augmented density.
On the augmented density of a spherical anisotropic dynamic system
J. An
Physics , 2010, DOI: 10.1111/j.1365-2966.2011.18324.x
Abstract: This paper presents a set of new conditions on the augmented density of a spherical anisotropic system that is necessary for the underlying two-integral phase-space distribution function to be non-negative. In particular, it is shown that the partial derivatives of the Abel transformations of the augmented density must be non-negative. Applied for the separable augmented densities, this recovers the result of van Hese et al. (2011).
Fractional calculus, completely monotonic functions, a generalized Mittag-Leffler function and phase-space consistency of separable augmented densities
J. An
Physics , 2012,
Abstract: Under the separability assumption on the augmented density, a distribution function can be always constructed for a spherical population with the specified density and anisotropy profile. Then, a question arises, under what conditions the distribution constructed as such is non-negative everywhere in the entire accessible subvolume of the phase-space. We rediscover necessary conditions on the augmented density expressed with fractional calculus. The condition on the radius part R(r^2) -- whose logarithmic derivative is the anisotropy parameter -- is equivalent to R(1/w)/w being a completely monotonic function whereas the condition on the potential part is stated as its derivative up to the order not greater than 3/2-b being non-negative (where b is the central limiting value for the anisotropy parameter). We also derive the set of sufficient conditions on the separable augmented density for the non-negativity of the distribution, which generalizes the condition derived for the generalized Cuddeford system by Ciotti & Morganti to arbitrary separable systems. This is applied for the case when the anisotropy is parameterized by a monotonic function of the radius of Baes & Van Hese. The resulting criteria are found based on the complete monotonicity of generalized Mittag-Leffler functions.
When is an axisymmetric potential separable?
J. An
Physics , 2013, DOI: 10.1093/mnras/stt1498
Abstract: An axially symmetric potential psi(R,z)=psi(r,theta) is completely separable if the ratio s:k is constant. Here r*s=d^2(r^2*psi)/dr/d(theta) and k=d^2(psi)/dR/dz. If beta=s/k, then the potential admits an integral of the form of I=(L^2+beta*v_z^2)/2+xi where xi is some function of positions determined by the potential psi. More generally, an axially symmetric potential respects the third axisymmetric integral of motion -- in addition to the classical integrals of the Hamiltonian and the axial component of the angular momentum -- if there exist three real constants a,b,c (not all simultaneously zero, a^2+b^2+c^2>0) such that a*s+b*h+c*k=0 where r*h=d^2(r*psi)/d(sigma)/d(tau) and (sigma,tau) is the parabolic coordinate in the meridional plane such that sigma^2=r+z and tau^2=r-z.
Flaws, Fallacies and Facts: Reviewing the Early History of the Lipid and Diet/Heart Hypotheses  [PDF]
J. Elliott
Food and Nutrition Sciences (FNS) , 2014, DOI: 10.4236/fns.2014.519201
Abstract: The lipid hypothesis of coronary heart disease proposes that a high total cholesterol level has a causative role in coronary heart disease (CHD), specifically in the development of atherosclerosis. It forms the basis for formulating target levels of serum cholesterol and hence the widespread use of statins for lowering cholesterol. An extension of the lipid hypothesis is the diet/heart hypothesis of coronary heart disease. This theory combines two ideas—that saturated fat raises cholesterol levels, and that a reduced saturated fat intake will lower cholesterol levels, thereby inhibiting the development of atherosclerosis and manifestations of CHD. Those who make diet recommendations or prescribe medication to reduce cholesterol may be unaware of the underpinning science. The original research behind these recommendations has given us “healthy heart” guidelines and preventive measures we assume to be true. While the lipid and diet/heart hypotheses are often presented as fact, they remain inadequately proven theories that have little agreement from experts. Historical perspectives can help us understand the basis of current-day beliefs. In the lipid hypothesis case, research from the 1950s and 60s was instrumental in its formation. This early work should not be considered irrelevant, outdated or obsolete because current recommendations from national heart associations in many countries continue to be shaped by these studies. This paper examines evidence used to formulate the lipid hypothesis and, subsequently, the diet/ heart hypothesis. By critically evaluating steps in the formation of the theory, inconsistencies, mistakes and alternate explanations become apparent and cast doubt on its validity.
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