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71.
M. Pierre L. Chiappetti F. Pacaud A. Gueguen C. Libbrecht B. Altieri H. Aussel P. Gandhi † O. Garcet E. Gosset L. Paioro T. J. Ponman A. M. Read A. Refregier J.-L. Starck J. Surdej I. Valtchanov C. Adami D. Alloin A. Alshino S. Andreon M. Birkinshaw M. Bremer A. Detal P.-A. Duc G. Galaz L. Jones J.-P. Le Fèvre O. Le Fèvre D. Maccagni A. Mazure H. Quintana H. J. A. Röttgering P.-G. Sprimont C. Tasse G. Trinchieri J. P. Willis 《Monthly notices of the Royal Astronomical Society》2007,382(1):279-290
72.
73.
The jets observed to emanate from many compact accreting objects may arise from the twisting of a magnetic field threading
a differentially rotating accretion disk which acts to magnetically extract angular momentum and energy from the disk. Two
main regimes have been discussed, hydromagnetic jets, which have a significant mass flux and have energy and angular momentum
carried by both matter and electromagnetic field and, Poynting jets, where the mass flux is small and energy and angular momentum
are carried predominantly by the electromagnetic field. Here, we describe recent theoretical work on the formation of relativistic
Poynting jets from magnetized accretion disks. Further, we describe new relativistic, fully electromagnetic, particle-in-cell
(PIC) simulations of the formation of jets from accretion disks. Analog Z-pinch experiments may help to understand the origin
of astrophysical jets. 相似文献
74.
Simple models of nonlinear stellar pulsation, whose temporal behavior may reproduce some of the observed features of different classes of variable stars, have been studied. The temporal behavior of dynamical variables of these models exhibits a cascade of period doubling chaos, depending on the specific values of the various control parameters. A multifractal detrended fluctuation analysis (MFDFA) method is further used to identify the scaling behavior of such synthetic time series. The MFDFA of the considered time series, for various models of nonlinear stellar pulsation, shows that the observed multifractal nature is due to long-range correlations. The pulsating star with increased nonadiabaticity and the star with increased convective luminosity, as represented by the simulated data, is shown to possess a strange attractor with noninteger correlation dimension that lies between 2–3. Also the problem of synchronization in coupled nonlinear pulsation models has been investigated using permutation entropy—a complexity measure of the system. The computed order parameter, Γ, representing the correlation of computed permutation entropy for different segments of the simulated time series of displacement of two nonidentical oscillators, has been further used to find the critical coupling parameter for general synchronization of the oscillators. 相似文献
75.
Parampreet Kaur Naveen Chaudhri Albrecht W. Hofmann Ingrid Raczek Martin Okrusch Susanne Skora Jürgen Koepke 《International Journal of Earth Sciences》2014,103(4):1083-1112
The late Palaeoproterozoic (1.72–1.70 Ga) ferroan granites of the Khetri complex, northern Aravalli orogen, NW India, were extensively metasomatised ~900 Ma after their emplacement, at around 850–830 Ma by low-temperature (ca. 400 °C) meteoric fluids that attained metamorphic character after exchanging oxygen with the surrounding metamorphic rocks. Albitisation is the dominant metasomatic process that was accompanied by Mg and Ca metasomatism. A two-stage metasomatic model is applicable to all the altered ferroan intrusives. The stage I is represented by a metasomatic reaction interface that developed as a result of transformation of the original microcline–oligoclase (An12–14) granite to microcline–albite (An1–3) granite, and this stage is rarely preserved. In contrast, the stage II metasomatic reaction front, where the microcline-bearing albite granite has been transformed to microcline-free albite granite, is readily recognisable in the field and present in most of the intrusives. Some of them lack an obvious reaction interface due to the presence of stage II albite granites only. When studied in isolation, these intrusives were incorrectly classified and their tectonic setting was misinterpreted. Furthermore, our results show that the mafic mineralogy of metasomatised granites has a significant impact on the characterisation of such rocks in the magmatic classification and discrimination diagrams. Nevertheless, the stage I metasomatised granites can be appropriately characterised in these diagrams, whereas the characterisation of the stage II granites will lead to erroneous interpretations. The close spatial association of these high heat producing ferroan granites with iron oxide–copper–gold (IOCG), U and REE mineralisation in the region indicates a genetic link between the metasomatism and the mineralisation. World-class IOCG, U and REE deposits are associated with metasomatised ferroan granites, suggesting that such a relationship may act as a critical first-order exploration target for undiscovered mineral deposits. 相似文献
76.
The present study provides improved chronology for the desert margin fluvial sediments of semi-arid region located in the Mahi river basin, western India. The sequence has preserved a near-continuous record of climate change since the Last Interglacial. An earlier attempt of dating based on feldspar IRSL chronology shows a combined effect of anomalous fading and unbleached components resulting in age inversions. The present work tries to explore the possibility of using blue light stimulated luminescence (BLSL) of quartz, infra-red stimulated luminescence (IRSL) of feldspar and the newly developed methodologies, like natural correction factor based single aliquot regeneration (NCF-SAR) protocol and decision making schemes based on distribution of doses and beta heterogeneity concept for luminescence dating of sediments. Observations suggest that quartz suffered from significant sensitivity changes during natural signal measurement and partial bleaching. A combination of NCF-SAR protocol and sample specific equivalent dose computation helped in arriving at better age estimate for present samples. The study also compares the criteria for the selection of different age models that are used at present. The age of the alluvial sequence is now bracketed between 10 ka (upper aeolian unit) and 75 ka (lowermost fluvial unit). 相似文献