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Search Results: 1 - 10 of 84447 matches for " W. Kutschera "
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Tracing Noble Gas Radionuclides in the Environment
P. Collon,W. Kutschera,Z. -T. Lu
Physics , 2004, DOI: 10.1146/annurev.nucl.53.041002.110622
Abstract: Trace analysis of radionuclides is an essential and versatile tool in modern science and technology. Due to their ideal geophysical and geochemical properties, long-lived noble gas radionuclides, in particular, 39Ar (t1/2 = 269 yr), 81Kr (t1/2 = 2.3x10^5 yr) and 85Kr (t1/2 = 10.8 yr), have long been recognized to have a wide range of important applications in Earth sciences. In recent years, significant progress has been made in the development of practical analytical methods, and has led to applications of these isotopes in the hydrosphere (tracing the flow of groundwater and ocean water). In this article, we introduce the applications of these isotopes and review three leading analytical methods: Low-Level Counting (LLC), Accelerator Mass Spectrometry (AMS) and Atom Trap Trace Analysis (ATTA).
Osteoporose und Orthop die
Lack W,Bretschneider W,Kutschera HP,Resch H
Journal für Mineralstoffwechsel , 1998,
Abstract:
Structure of Proton Component of Neutron Star Matter for Realistic Nuclear Models
M. Kutschera,S. Stachniewicz,A. Szmaglinski,W. Wojcik
Physics , 2001,
Abstract: We study properties of the proton component of neutron star matter for a number of realistic nuclear models. Protons which form a few percent admixture tend to be localized in potential wells corresponding to neutron matter inhomogeneities created by the protons in the neutron medium. We calculate the energy of the Wigner-Seitz cell enclosing a single localized proton. The neutron background is treated in the Thomas-Fermi approximation and the localized proton is described by the Gaussian wave function. The neutron density profile is obtained by solving the appropriate variational equation. This approach gives lower energies of localized protons than obtained previously with less sophisticated methods.
Light Meter for Measuring Photosynthetically Active Radiation  [PDF]
Alexander Kutschera, Jacob J. Lamb
American Journal of Plant Sciences (AJPS) , 2018, DOI: 10.4236/ajps.2018.912175
Abstract: Measurement of photosynthetically active radiation (PAR) incident on photosynthetic organisms is a crucial measurement for understanding how organisms respond to various light conditions, and for calculating electron flow through the photosynthetic machinery. Measurements of PAR are typically performed in the region of the electromagnetic spectrum between 400 - 700 nm, which is the region of radiation that is responsible for promoting photosynthesis. Typically, to ensure that the sensor measures in this range, the implementation of long- and short-pass filters is required. Although this allows the exclusion of radiation outside of the PAR region, such filters can be expensive. Additionally, the implementation of autonomous PAR measurements requires costly commercial instruments. Here, a straight-forward, inexpensive apparatus has been designed and constructed using a sensor that can distinguish between red, green, blue and white light. The constructed apparatus was able to perform comparably to a commercial PAR sensor. Furthermore, the implementation of the device to measure PAR intensity over a three-day period shows how the apparatus can be implemented for use as a constant light monitor.
From the scala naturae to the symbiogenetic and dynamic tree of life
Ulrich Kutschera
Biology Direct , 2011, DOI: 10.1186/1745-6150-6-33
Abstract: This article was reviewed by Mark Ragan, W. Ford Doolittle, and Staffan Müller-Wille.In his Autobiography [1], Charles Darwin (1809 - 1882) presented a self-critical review of his achievements as a naturalist that revealed much about the character of this key figure of the evolutionary sciences and other branches of biology and geology [2-4]. With respect to the most influential of Darwin's 16 scientific books, On the Origin of Species, the author remarked that "Sixteen thousand copies have now (1876) been sold in England and considering how stiff a book it is, this is a large sale" [1]. This judgement is in part due to the fact that the Origin of Species was not designed by Darwin as a separate book; rather, it was published as an Abstract, taken from a much larger manuscript entitled Natural Selection [5]. Ironically, Darwin's major, scheduled "Magnum opus" with the tentative title Natural Selection never appeared in print, but the Extract published by the author in November 1859 in order to establish priority with respect to his theory of the "preservation of favourable variations and the rejection of injurious variations" became a best- and longseller [6].The second and more important reason for the "stiffness" of Darwin's Origin of Species is attributable to the almost complete lack of illustrations. In contrast to Darwin's books on botanical and zoological issues, which contain numerous pictures [2-4], his Abstract published in 1859 (6th and final edition, 1872) [6,7] contained only one rather "sterile" diagram, a phylogenetic scheme. This "tree-like" figure is part of Chapter IV entitled "Natural Selection" in the first edition [6], and re-named "Natural Selection; or the Survival of the Fittest" in the 6th and final version of the "Species book" [7]. It should be noted that the phrase "survival of the fittest" was borrowed by Darwin from the philosopher Herbert Spencer (1820-1903), who was also the first to introduce the word "evolution" sensu phylogenetic d
Hadron Physics and the Structure of Neutron Stars
Marek Kutschera
Physics , 1996,
Abstract: The equation of state of hadronic matter in neutron stars is briefly reviewed. Uncertainties regarding the stiffness and composition of hadronic matter are discussed. Importance of poorly known short range interactions of nucleons and hyperons is emphasized. Condensation of meson fields and the role of subhadronic degrees of freedom is considered. Empirical constraints on the equation of state emerging from observations of neutron stars are discussed. Implications of possible black hole remnant of SN1987A for the equation of state are also discussed.
Monopole gravitational waves from relativistic fireballs driving gamma-ray bursts
M. Kutschera
Physics , 2003, DOI: 10.1046/j.1365-8711.2003.07045.x
Abstract: Einstein's general relativity predicts that pressure, in general stresses, play a similar role to energy density in generating gravity. The source of gravitational field, the active gravitational mass density, sometimes referred to as Whittaker's mass density, is not conserved, hence its changes can propagate as monopole gravitational waves. Such waves can be generated only by astrophysical sources with varying gravitational mass. Here we show that relativistic fireballs, considered in modelling gamma-ray burst phenomena, are likely to radiate monopole gravitational waves from high-pressure plasma with varying Whittaker's mass. Also, ejection of a significant amount of initial mass-energy of the progenitor contributes to the monopole gravitational radiation. We identify monopole waves with h^11+h^22 waves of Eddington's classification which propagate (in the z-direction) together with the energy carried by massless fields. We show that the monopole waves satisfy Einstein's equations, with a common stress-energy tensor for massless fields. The polarization mode of monopole waves is Phi_22, i.e. these are perpendicular waves which induce changes of the radius of a circle of test particles only (breathing mode). The astrophysical importance of monopole gravitational waves is discussed.
Emergence of magnetic field due to spin-polarized baryon matter in neutron stars
M. Kutschera
Physics , 1999, DOI: 10.1046/j.1365-8711.1999.02655.x
Abstract: A model of the ferromagnetic origin of magnetic fields of neutron stars is considered. In this model, the magnetic phase transition occurs inside the core of neutron stars soon after formation. However, owing to the high electrical conductivity the core magnetic field is initially fully screened. We study how this magnetic field emerges for an outside observer. After some time, the induced field that screens the ferromagnetic field decays enough to uncover a detectable fraction of the ferromagnetic field. We conjecture that weak fields of millisecond pulsars of 10^8-10^9 G could be identified with ferromagnetic fields of unshielded fraction f=10^-4 resulting from the decay of screening fields by a factor 1-f in 10^8 yr since their birth.
Neutron Stars: Formation and Structure
Marek Kutschera
Physics , 1998,
Abstract: A short introduction is given to astrophysics of neutron stars and to physics of dense matter in neutron stars. Observed properties of astrophysical objects containing neutron stars are discussed. Current scenarios regarding formation and evolution of neutron stars in those objects are presented. Physical principles governing the internal structure of neutron stars are considered with special emphasis on the possible spin ordering in the neutron star matter.
Comment on "Brown Dwarfs, Quark Stars, and Quark-Hadron Phase Transition"
S. Kubis,M. Kutschera
Physics , 1996, DOI: 10.1103/PhysRevLett.76.3876
Abstract: Recently, Cottingham, Kalafatis and Vinh Mau proposed, in the framework of the Lee-Wick model, a scenario of formation of quark stars in the cosmological quark-hadron phase transition with high degree of supercooling. We show here that the cosmological quark-hadron phase transition in the Lee-Wick model with such a high degree of supercooling cannot be completed. No quark stars could be formed in this scenario.
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