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Search Results: 1 - 10 of 324714 matches for " G. E. Hahne "
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Schroedinger equation for joint bidirectional evolution in time: astrophysical applications
G. E. Hahne
Physics , 2006, DOI: 10.1063/1.2388747
Abstract: The theoretical framework established in arXiv:quant-ph/0404103 is extended to deal with possible astrophysical manifestations of phenomena involving reverse, as well as forward, causation in time. The basic idea is that space-time comprises the direct sum of a number of quantized fields, including a distinct physical vacuum for each space in the sum. It is presumed that these fields all contribute to, and are influenced by, gravitation, but generally do not interact electromagnetically, i.e., are mutually invisible. At least one term in the sum is proposed to consist of matter+vacuum evolving backward in time; the expectation values of energies, both of matter and vacuum, of this subspace are by construction negative, with a corresponding change of sign in classical gravitational and inertial masses.
Comment on Frank Wilczek's essay "Total Relativity: Mach 2004"
G. E. Hahne
Physics , 2005,
Abstract: Frank Wilczek's essay "Total Relativity: Mach 2004" (PHYSICS TODAY April, 2004, p. 10) cogently updates the status of the intuitively compelling, but partly unrealized, theory of Mach's Principle. I think, however, that an important consequence of the Principle has been skipped: that is, the possibility of linear deformations of the internal structure of elementary particles from the Minkowski structure imposed by the local gravitational (metric) field. [Note: This Comment is similar to one submitted to, but not published by, PHYSICS TODAY as a Letter to the Editor.]
Schroedinger equation for joint bidirectional motion in time
G. E. Hahne
Physics , 2004, DOI: 10.1088/0305-4470/35/33/309
Abstract: The conventional, time-dependent Schroedinger equation describes only unidirectional time evolution of the state of a physical system, i.e., forward or, less commonly, backward. This paper proposes a generalized quantum dynamics for the description of joint, and interactive, forward and backward time evolution within a physical system. [...] Three applications are studied: (1) a formal theory of collisions in terms of perturbation theory; (2) a relativistically invariant quantum field theory for a system that kinematically comprises the direct sum of two quantized real scalar fields, such that one field evolves forward and the other backward in time, and such that there is dynamical coupling between the subfields; (3) an argument that in the latter field theory, the dynamics predicts that in a range of values of the coupling constants, the expectation value of the vacuum energy of the universe is forced to be zero to high accuracy. [...]
Feynman's Path Integral to Ostrogradsky's Hamiltonian for Lagrangians with second derivatives
G. E. Hahne
Physics , 2013,
Abstract: A calculation is presented that shows that Feynman's path integral implies Ostrogradsky's Hamiltonian for nonsingular Lagrangians with second derivatives. The procedure employs the stationary phase approximation to obtain the limiting change of the wave function per unit time. By way of introduction, the method is applied anew to the case of nonsingular Lagrangians with only first derivatives, but not necessarily quadratic in the velocities. A byproduct of the calculation is an alternate derivation of the Legendre transformation of taking general classical Lagrangians into Hamiltonians. In both the first and second derivative cases, the outcome contains precisely the classical Hamiltonian, which represents the so-called "symbol" of a (not necessarily Hermitean) pseudodifferential operator acting on the wave function at an instant of time. The derivation herein argues for a claim that Feynman's method starts with a classical Lagrangian and ends with a classical Hamiltonian---nonclassical operator-ordering prescriptions in the passage from classical to quantum Hamiltonians require external input, and are generally not inherent in Feynman's path integral formalism.
Time as an operator/observable in nonrelativistic quantum mechanics
G. E. Hahne
Mathematics , 2004, DOI: 10.1088/0305-4470/36/25/316
Abstract: The nonrelativistic Schroedinger equation for motion of a structureless particle in four-dimensional space-time entails a well-known expression for the conserved four-vector field of local probability density and current that are associated with a quantum state solution to the equation. Under the physical assumption that each spatial, as well as the temporal, component of this current is observable, the position in time becomes an operator and an observable in that the weighted average value of the time of the particle's crossing of a complete hyperplane can be simply defined: ... When the space-time coordinates are (t,x,y,z), the paper analyzes in detail the case that the hyperplane is of the type z=constant. Particles can cross such a hyperplane in either direction, so it proves convenient to introduce an indefinite metric, and correspondingly a sesquilinear inner product with non-Hilbert space structure, for the space of quantum states on such a surface. >... A detailed formalism for computing average crossing times on a z=constant hyperplane, and average dwell times and delay times for a zone of interaction between a pair of z=constant hyperplanes, is presented.
Modulation of Vitamin D Status and Dietary Calcium Affects Bone Mineral Density and Mineral Metabolism in G?ttingen Minipigs
Katharina E. Scholz-Ahrens,Claus-Christian Glüer,Felix Bronner,Günter Delling,Yahya A?il,Hans-Jürgen Hahne,Joachim Hassenpflug,Wolfram Timm,Jürgen Schrezenmeir
ISRN Rheumatology , 2013, DOI: 10.1155/2013/460512
Abstract: Calcium and vitamin D deficiency impairs bone health and may cause rickets in children and osteomalacia in adults. Large animal models are useful to study experimental osteopathies and associated metabolic changes. We intended to modulate vitamin D status and induce nutritional osteomalacia in minipigs. The control group (n = 9) was fed a semisynthetic reference diet with 6?g calcium and 6,500?IU vitamin D3/kg and the experimental group (n = 10) the same diet but with only 2?g calcium/kg and without vitamin D. After 15 months, the deficient animals were in negative calcium balance, having lost bone mineral density significantly (means ± SEM) with ?51.2 ± 14.7?mg/cm3 in contrast to controls (?2.3 ± 11.8?mg/cm3), whose calcium balance remained positive. Their osteoid surface was significantly higher, typical of osteomalacia. Their plasma 25(OH)D dropped significantly from 60.1 ± 11.4?nmol/L to 15.3 ± 3.4?nmol/L within 10 months, whereas that of the control group on the reference diet rose. Urinary phosphorus excretion and plasma 1,25-dihydroxyvitamin D concentrations were significantly higher and final plasma calcium significantly lower than in controls. We conclude that the minipig is a promising large animal model to induce nutritional osteomalacia and to study the time course of hypovitaminosis D and associated functional effects. 1. Introduction Adequate calcium and vitamin D intakes are essential for skeletal health and to minimize the incidence of osteoporosis and of rickets in children and nutritional osteomalacia in adults. Calcium and vitamin D supplementation is also key to the treatment of these diseases [1–3]. Rickets and osteomalacia remain endemic problems in developing countries but show increasing prevalence also in North America and Europe [3, 4] because of changes in life style with an increase of indoor activities and a decrease in sunlight exposure. Incidence of osteomalacia is also increased by the demographic shift, because calcium and vitamin D intakes are often inadequate in the elderly, in whom vitamin D synthesis, calcium absorption, and renal reabsorption tend to diminish [3]. Subjects with darker skin or covering clothing habits are at higher risk because both factors contribute to insufficient dermal vitamin D synthesis, responsible in turn for diminished bone density. Vitamin D combined with calcium has been shown to enhance lower-extremity function when vitamin D intake was sufficient to assure a serum concentration of 25-hydroxyvitamin D [25(OH)D] that exceeds 75?nmol/L [5]. This value is much higher than the current
Where ends the TRAIL in arthritis?
Michael Hahne
Rheumatology Reports , 2009, DOI: 10.4081/rr.2009.e10
Abstract: A hallmark of rheumatoid arthritis (RA) is the pseudo-tumoral expansion of fibroblast-like synoviocytes (FLS), as these cells invade and finally destroy the joint structure. RA FLS have been proposed therefore as a therapeutic target. The TNF-related apoptosis-inducing ligand (TRAIL) has gained much attention as a possible therapeutic reagent for the treatment of tumors, as TRAIL was described originally to induce apoptosis specifically in cancer cells but not in normal cells. The fact that FLS in RA patients exhibit tumor-like features led to investigations on the effect of TRAIL on ex-vivo RA FLS. In this review we aim to summarize what is presently known on the role of TRAIL in RA.
Analyzing position effects within reasoning items using the LLTM for structurally incomplete data
JULIA HAHNE
Psychology Science Quarterly , 2008,
Abstract: Position or transfer effects on an individual’s ability while processing a series of test items are often ignored when tests are created. It is often implicitly assumed that such effects, if they occur, are a) the same for all persons and b) for all items and thus do not contribute to information about person ability or item difficulty. Rasch model analyses cannot quantify position effects because they are invariably confounded with the item difficulty parameters. In case of adaptive testing, where the examinees are administered the same items at different positions, effects of the position of item presentation lead to unfair estimations of item (and, consequently, person) parameters, and are therefore absolutely unwarranted. This study applies the Linear Logistic Test Model (LLTM, Fischer, 1973) for structurally incomplete data to illustrate how a series of test items can be evaluated for position effects. The test material consists of the Viennese Matrices (WMT, Formann & Piswanger, 1979) presented in varying item order to six groups of examinees. The study sample group consisted of 405 high school students. The concept of virtual items is introduced and applied to different models. Several hypotheses are tested by means of hierarchically applied Andersen’s Likelihood Ratio tests. As a result of these analyses, no significant position effect can be found.
Diffusion coefficients from signal fluctuations: Influence of molecular shape and rotational diffusion
Susanne Hahne,Philipp Maass
Physics , 2013, DOI: 10.1021/jp500479a
Abstract: Analysis of signal fluctuations of a locally fixed probe, caused by molecules diffusing under the probe, can be used to determine diffusion coefficients. Theoretical treatments so far have been limited to point-like particles or to molecules with circle-like shapes. Here we extend these treatments to molecules with rectangle-like shapes, for which also rotational diffusion needs to be taken into account. Focusing on the distribution of peak widths in the signal, we show how translational as well as rotational diffusion coefficients can be determined. We address also the question, how the distribution of interpeak time intervals and autocorrelation function can be employed for determining diffusion coefficients. Our approach is validated against kinetic Monte Carlo simulations.
High-Brightness Beams from a Light Source Injector: The Advanced Photon Source Low-Energy Undulator Test Line Linac
G. Travish,S. Biedron,M. Borland,M. Hahne,K. Harkay,J. W. Lewellen,A. Lumpkin,S. Milton,N. Sereno
Physics , 2000,
Abstract: The use of existing linacs, and in particular light source injectors, for free-electron laser (FEL) experiments is becoming more common due to the desire to test FELs at ever shorter wavelengths. The high-brightness, high-current beams required by high-gain FELs impose technical specifications that most existing linacs were not designed to meet. Moreover, the need for specialized diagnostics, especially shot-to-shot data acquisition, demands substantial modification and upgrade of conventional linacs. Improvements have been made to the Advanced Photon Source (APS) injector linac in order to produce and characterize high-brightness beams. Specifically, effort has been directed at generating beams suitable for use in the low-energy undulator test line (LEUTL) FEL in support of fourth-generation light source research. The enhancements to the linac technical and diagnostic capabilities that allowed for self-amplified spontaneous emission (SASE) operation of the FEL at 530 nm are described. Recent results, including details on technical systems improvements and electron beam measurement techniques, will be discussed. The linac is capable of accelerating beams to over 650 MeV. The nominal FEL beam parameters used are as follows: 217 MeV energy; 0.1-0.2% rms energy spread; 4-8 um normalized rms emittance; 80-120 A peak current from a 0.2-0.7 nC charge at a 2-7 ps FWHM bunch.
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