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  • 2000-2004  (178)
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  • 1
    ISSN: 1432-1866
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract A model of the cooling history of tin-bearing granitic magma forming the Schellerhau granites (Eastern Erzgebirge, Germany) is shown on the basis of quartz textures. Similar grain size, similar grain habit and correlatable growth textures of phenocrysts in different granite varieties give proof of a common crystallization history before the melts of the Schellerhau granite varieties were intruded. Four nucleation events occurred during crystallization in different crustal levels between about 20 and 1 km depth. The parental melt of the Schellerhau granites is interpreted to have contained〈2.5 wt% H2O originally. The water content of the melt during the subvolcanic intrusion stage amounted to more than 5 wt% and characterizes highly evolved residual melts that enable the formation of tin deposits. This study contributes to a better understanding of the development and behaviour of fractionated tin-bearing granitic melts, and links quartz cathodoluminescence (CL) with microanalytical studies.
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 9289-9300 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: This paper presents ion yields resulting from multiphoton ionization and fragmentation of gaseous toluene (C7H8) in the focus of an 80 fs Ti:sapphire laser beam (λ=800 nm) with a sufficiently small B-integral [Siegman, Lasers (University Science Books, Mill Valley, CA, 1986)]. The peak intensity was varied between 1.9×1013 and 2.8×1014 W cm−2, and both linear and circular polarization were used. Over the whole range of intensities studied, only the singly charged parent ion and its fragment, C7H7+, are found. Although the Keldysh adiabaticity parameter equals 0.86 for the saturation intensity of ∼1×1014 W cm−2, there is no indication of tunneling. The parent ion yield is found to be effectively proportional to the sixth power of the peak intensity. This is shown to be in good agreement with a multiple lowest-order perturbation multiphoton ionization model which takes into account successive channel closing for increasing peak intensities and orders up to 11 inclusive. On the assumption that the excess energy acquired by the toluene cation as a result of the interaction with the electromagnetic field is of the order of the ponderomotive energy for the intensity prevailing at the moment of the ionization, the internal energy distribution of the toluene cations created that is brought about by this multiple-order multiphoton ionization model is calculated. This internal energy distribution is in perfect agreement with the measured C7H7+ yield, if the rate-energy curve for the fragmentation of excited toluene cations as given by Golovin et al. [Sov. J. Chem. Phys. 2, 632 (1985)] is moderately reduced by a factor of 4.5. © 2000 American Institute of Physics.
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 800-803 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new microwave based plasma source for high current ion beam neutralization is presented. It consists of a tapered WR340 waveguide with a directly coupled 2.45 GHz magnetron and a quartz tube of 40 mm diameter inside the waveguide confined by two graphite electrodes. The upper electrode houses the gas feed, whereas the lower electrode serves as the plasma outlet. Both electrodes can be biased independently. Tuning is done via a magnetically controlled stab inserted into the waveguide. The plasma was characterized by use of the Langmuir probe. The electron concentration of 5×1011 cm−3 at 250 W was measured. Typical electron temperature is below 2.5 eV even for pressure as low as 2×10−3 Pa. The extractable electron current is dependent on microwave power and gas flow. A limitation is caused by the ion saturation current to the negatively biased electrodes. The voltage on the electrodes allows an easy control of electron current. Maximum electron current achieved so far is 400 mA for an argon flow of 5 sccm and microwave power of 300 W. © 2000 American Institute of Physics.
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Journal of fish biology 63 (2003), S. 0 
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: During peak spawning of sprat Sprattus sprattus in the Baltic Sea in May–June egg specific gravity averaged ±s.d. 1·00858 ± 0·00116 g cm−3 but was significantly higher in the beginning and significantly lower towards the end of the spawning season. A close relationship was found between egg diameter and egg specific gravity (r2 = 0·71). This relationship, however, changed during the spawning season indicating that some other factor was involved causing the decrease in specific gravity during the spawning period. The vertical egg distribution changed during the spawning season: eggs were distributed mainly in the deep layers early in the season, occurred in and above the permanent halocline during peak spawning, and above the halocline towards the end of the spawning season. Consequently, poor oxygen conditions in the deep layers and low temperatures in layers between the halocline and the developing thermocline may affect egg development. Thus, opportunities for egg development vary over the spawning season and among spawning areas, and depending on frequency of saline water inflows into the Baltic Sea and severity of winters, between years.
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  • 5
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] All properties of molecules—from binding and excitation energies to their geometry—are determined by the highly correlated initial-state wavefunction of the electrons and nuclei. Details of these correlations can be revealed by studying the break-up of these systems into their ...
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  • 6
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 2079-2081 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In scanning near-field optical microscopy, scanning ion conductance microscopy and for localized electrochemical deposition out of micropipettes, the detection of shear forces between the tip and sample is one of the most common methods of distance control. Here, pulled micropipettes were utilized to form an evaporating drop of water whose frictional force in air causes a specific resonance shift of the tip vibration. This resonance shift and the amplitude at the resonance were investigated with regard to their dependence on the drop diameter. In order to calculate the friction, the tip is approximated as a damped harmonic oscillator. The typical range of the shear forces in scanning probe microscopies is estimated to be between 1 pN and 0.1 nN. © 2001 American Institute of Physics.
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 56 (2000), S. 0 
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Potential and relative potential fecundity of 701 cod Gadus morhua caught in the Bornholm Basin (ICES Sub-division 25) during 1987–1996 and 106 from the Gdansk Deep (ICES Sub-division 26) in 1995 and 1996 varied significantly between years but neither between different spawning grounds nor between different sampling months within one spawning season. Growth and water temperature are factors identified to influence the mean relative fecundity explaining 66% of the variance between years.
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  • 8
    ISSN: 1434-601X
    Keywords: PACS. 07.81.+a Electron, ion spectrometers, and related techniques – 25.70.-z Low and intermediate energy heavy-ion reactions – 29.30.Aj Charged-particle spectrometers: electric and magnetic – 29.30.Ep Charged-particle spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The feasibility of the spectroscopy of dynamically ionized electrons (positrons) from heavy-ion collisions at intermediate energies, e.g. Pb+Pb at 60 A MeV has been studied. We propose a magnetic toroid spectrometer for lepton spectroscopy in an energy range between 5 and 50 MeV. Special emphasis was laid on large solid angles, on broad-band characteristics and on a good suppression of secondary events. The device is a versatile compact-size instrument for lepton detection in in-beam experiments at a moderate energy resolution of %.
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  • 9
    ISSN: 1432-2048
    Keywords: Key words: Arabidopsis (tryptophan mutant) – Auxin biosynthesis – Indole-3-glycerophosphate – Mutant (Arabidopsis) – Nitrilase – Tryptophan synthase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract.  The tryptophan auxotroph mutant trp3-1 of Arabidopsis thaliana (L.) Heynh., despite having reduced levels of l-tryptophan, accumulates the tryptophan-derived glucosinolate, glucobrassicin and, thus, does not appear to be tryptophan-limited. However, due to the block in tryptophan synthase, the mutant hyperaccumulates the precursor indole-3-glycerophosphate (up to 10 mg per g FW). Instability of indole-3-glycerophosphate leads to release of indole-3-acetic acid (IAA) from this metabolite during standard workup of samples for determination of conjugated IAA. The apparent increase in “conjugated IAA” in trp3-1 mutant plants can be traced back entirely to indole-3-glycerophosphate degradation. Thus, the levels of neither free IAA nor conjugated IAA increase detectably in the trp3-1 mutant compared to wild-type plants. Precursor-feeding experiments to shoots of sterile-grown wild-type plants using [2H]5-l-tryptophan have shown incorporation of label from this precursor into indole-3-acetonitrile and indole-3-acetic acid with very little isotope dilution. It is concluded that Arabidopsis thaliana shoots synthesize IAA from l-tryptophan and that the non-tryptophan pathway is probably an artifact.
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  • 10
    ISSN: 1572-9605
    Keywords: high-temperature superconductors ; angle-reserved photoemission ; x-ray absorption spectroscopy ; electronic structure ; cuprate superconductors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract On single crystals of the single-layer (n = 1) high-T c superconductor Bi2Sr2−x La x CuO6+δ at optimal doping (x = 0.4), the electron spectroscopies x-ray absorption (XAS) and high-resolution angle-resolved photoemission (ARPES) were performed. The XAS gives the intensity of the so-called prepeak of the O 1s line what is due to the unoccupied part of the Zhang–Rice (ZR) singlet band. For ARPES, the advantages of single-layer material are the absence of bilayer effects and the possibility to study the electronic properties of the normal state at a sample temperature where the thermal broadening is extremely small (〈10 meV). The controlled variation of the polarization vector of the synchrotron radiation made it possible to resolve a distinct fine-structure of the occupied part of the ZR singlet band at the Fermi level. These observations have enormous consequences for line shape analyses and the determination of pseudogaps, and thus the mechanism of high-T c superconductivity.
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