High Angular Resolution Study of the Ion and Neutral Spectra as a Probe of the Magnetic Field Structure     

Shih-Ping Lai  T. Velusamy  W.D. Langer 《Astrophysics and Space Science》2004,292(1-4):247-254

We present the observations and analysis of the spectral linewidths of neutral and ion species across the DR21(OH) core to investigate the cyclotron interaction as a probe of magnetic fields. It has been suggested that under average interstellar field strengths the cyclotron interaction between ions and magnetic fields is strong enough to narrow the linewidth and suppress the line wings in the ion spectra. We have obtained high spatial resolution spectral line images of H¹³CN and H¹³CO⁺ at 3 mm in DR21(OH) with the Millimeter Array of the Owens Valley Radio Observatory. Our results show that in the eastern parts of the DR21(OH) core the spectral linewidth of the ions is narrower than that of the neutrals. We use our results, along with the existing Zeeman and dust/CO polarization data on small scales, to derive the 3D magnetic field structure. We obtain a field strength of 0.44 ± 0.12 mG with inclination of 36° to the line of sight, directed toward the observer, and a position angle of ?75° in the plane of the sky.  相似文献   

Computation of X-Ray Blazar Light Curves Using RHD Simulations     

Petar Mimica  Miguel-Ángel Aloy  Ewald Müller  Wolfgang Brinkmann 《Astrophysics and Space Science》2004,293(1-2):165-172

We present the results of a two-dimensional relativistic hydrodynamic simulation of collisions of dense shells of matter moving within a uniform jet. The non-thermal synchrotron radiation produced by the relativistic electrons injected at shocks is computed following their temporal and spatial evolution. We test different parameterizations of the shock acceleration process and compute the corresponding X-ray light curves. A time lag between hard and soft X-ray radiation is found. The collision has an efficiency of few times 10^?3 in converting kinetic energy into radiation.  相似文献   

Exploratory seismic site response surveys in a complex geologic area: a case study from Mt. Etna volcano (southern Italy)     

Panzera  F.  Lombardo  G.  Longo  E.  Langer  H.  Branca  S.  Azzaro  R.  Cicala  V.  Trimarchi  F. 《Natural Hazards》2016,86(2):385-399

A preliminary study targeting to evaluate the local seismic response was performed in the eastern flank of Mt. Etna (southern Italy) using ambient noise measurements. The obtained spectral ratios were subdivided through cluster analysis into different classes of fundamental frequency permitting to draw an iso-frequency contour map. The analysis set into evidence the extreme heterogeneity of lava sequences, which makes difficult to identify a single seismic bedrock formation. Another important outcome, concerning the local seismic effects in terms of frequency and azimuth, is the important role played by the fracture fields associated with the main structural systems of the area. The existence of two zones with strong directional effects striking WNW–ESE and NW–SE, nearly orthogonal to the orientation of the main fracture fields, corroborate such hypothesis.

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Effects of hyperons on the vibrations of neutron stars     

William D. Langer  A. G. W. Cameron 《Astrophysics and Space Science》1969,5(2):213-253

We calculate the effects of hyperons and resonance particles on the vibrations of neutron stars. Vibrating neutron stars can store large amounts of energy in their vibrations; the interaction of the vibrations with the atmosphere would produce electromagnetic radiation. If any process damps out the vibrations rapidly on an astronomical time scale ( 1000 years) then vibrating neutron stars are not likely to be found. Previous work indicates that radiation by a neutrino URCA process (N+NP+N+e ^–+ ) does not rapidly damp many of the neutron star models. Some neutron stars are predicted to contain massive baryons; here we study thermal damping by nonequilibrium reactions involving these baryons.During vibrations the thermodynamic equilibrium state is changed and particle reactions attempt to restore equilibrium. If the reaction rates per particle are very rapid or slow compared to the frequency of vibration the system follows almost the same pressure-volume curve through both parts of the gas cycle, and very little work is done. In the intermediate case, when reaction rates are comparable to the frequency, damping is rapid.We find that the reaction rates for weak interactions such asN+NP+^– (the ^– is the first hyperon to appear with increasing density in degenerate neutron star matter) are of the right magnitude to cause rapid damping. If there is a hyperon region in the star then it cannot sustain vibrations. We also consider the much faster (and hence less important) processN+NP+^–.  相似文献   

Gravity and height changes in the ocean-continent transition zone in western Colombia     

Ewald Lüschen 《Tectonophysics》1986,130(1-4):141-146

Crustal studies in western Colombia, by deep seismic, gravity and geomagnetic surveys, during the last two decades have revealed an extremely anomalous crustal structure as compared to the South American Andes further south. Strong gravity gradients and differences in seismic velocities showed a transition from oceanic to continental character between the Western and Central Andes.

Measured gravity and height variations of opposite sign and lengths of 50 to 100 km on three east-west running profiles correlate surprisingly well with the typical positive Bouguer anomaly of the Western Andes which represents an isostatic instability. A gravity decrease of 0.5–1.0 mGal on two profiles and an increase on an intermediate one and corresponding ratios of gravity to apparent height variations of nearly −20 mGal/m are interpreted as consequences of deep-seated density variations. They may be related to collision tectonics and recent obduction processes between aseismic ridges riding on the Pacific Nazca plate and the continent.  相似文献   

Natural occurrence of 4-methyl-phenanthrene in petroleums and recent marine sediments: A new sensitive method to identify and quantify isomers in a series of alkyl—PAH: High resolution spectrofluorimetry at 15 K in n-alkane (Shpolskii effect)     

P. Garrigues  M. Ewald 《Organic Geochemistry》1983,5(2):53-56

HPLC extracts of crude petroleums and of marine recent sediments, containing the monomethyl-phenanthrene series, are examined by high resolution spectrofluorimetry in n-hexane at 15 K (Shpolskii effect). Identification and relative quantification of each of the five isomers is obtained on six natural samples. The distribution of the monomethyl-phenanthrenes and the relative absence of 4-methyl-phenanthrene in petroleums compared to marine sediments may reflect steric inhibitions.  相似文献   

Hydrothermal recrystallization and transformation of tridymite     

O. W. Flörke  K. Langer 《Contributions to Mineralogy and Petrology》1972,36(3):221-230

Well ordered tridymites containing atmost 0.016% Na (0.004% Na) were prepared at 1400° C from Na₂WO₄-(K₂WO₄-) fluxes using high purity amorphous silica as starting material. No further reduction of these Na-contents was attainable by soxhlet extraction. These tridymites were treated hydrothermally at temperatures between 815 and 950° C and 200 bars H₂O. The products obtained were investigated optically as well as by powder X-ray methods and were analyzed for Na-contents: the hydrothermal treatment resulted either in recrystallization of tridymite or transformation into quartz mostly depending on Na-contents. Na-contents below about 0.015% tend to favour recrystallization of tridymite within the quartz field (<870° C), Na-contents above about 0.03% tend to favour formation of quartz within the tridymite field (>870° C). This may be due to influences of Na-traces either on the kinetics or on the equilibrium temperature of tridymite-quartz transformation.  相似文献   

Eine Methode zur Volumbestimmung von Gletschern auf Grund der Plastizitätstheorie     

Dr. Ewald Brückl 《Meteorology and Atmospheric Physics》1970,19(1):317-328

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Stability relations of chromium kyanite at high pressures and temperatures     

F. Seifert  K. Langer 《Contributions to Mineralogy and Petrology》1970,28(1):9-18

The pseudobinary section Al₂SiO₅-Cr₂SiO₅ of the system Al₂O₃-Cr₂O₃-SiO₂ has been investigated at 20 and 30 kb pressure in the temperature range 1,000–1,600° C. The solubility of Cr₂SiO₅ in kyanite (Al₂SiO₅) extends up to 24 mole % Cr₂SiO₅ at 20 kb and 31 mole % at 30 kb. The extent of this solid solution is not notably dependent on temperature in the range studied. The stability of kyanite is increased by the substitution Cr Al by about 80° C at 20 kb as compared to Cr-free kyanite. Cr-poor sillimanite and Cr-rich kyanite can stably coexist in a temperature interval of up to 80° C at 20 kb and about 150° C at 25 kb.  相似文献   

Reassignment of the absorption spectra of purple yoderite     

K. Langer  G. Smith  U. Hålenius 《Physics and Chemistry of Minerals》1982,8(3):143-145

Polarized spectra E∥X, E∥Y, and E∥Z of purple yoderite, taken at 295 and 100 K, result in a revised interpretation for the mineral. Major bands at around 16,900 (X>Y?Z), 18,600 (X?Y), and 20,600 cm^?1 (X≈Z>Y) may be attributed to spin-allowed transitions of Mn³⁺ in trigonal bipyramids (A2 or A3). Minor features may be assigned to single ion Fe³⁺. However, charge transfer possibilities for bands at 18,600 and 25,500 cm^?1 in yoderite cannot be ruled out and are discussed. The extremely high intensity of Mn³⁺ spin-allowed bands (?, 216 to 1,900 [1·g-atom^?1·cm^?1]) is attributed to fivefold coordination of the A2 and A3 position and to the covalency of the Mn³⁺-O bonds.  相似文献