2,051 research outputs found
Large grains in the disk of CQ Tau
No full textWe present 7 mm observations of the dusty disk surrounding the 10 Myr old 1.5 Msun pre-main-sequence star CQ Tauri obtained at the Very Large Array with 0.8 arcsec resolution and 0.1 mJy rms sensitivity. These observations resolve the 7 mm emission in approximately the north-south direction, confirming previous results obtained with lower resolution. We use a two-layer flared disk model to interpret the observed fluxes from 7 mm to 1.3 mm together with the resolved 7 mm structure. We find that the disk radius is constrained to the range 100 to 300 AU, depending on the steepness of the disk surface density distribution. The power law index of the dust opacity coefficient, beta , is constrained to be 0.5 to 0.7. Since the models indicate that the disk is optically thin at millimeter wavelengths for radii greater than 8 AU, the contribution of an optically thick region to the emission is less than 10%. This implies that high optical depth or complex disk geometry cannot be the cause of the observed shallow millimeter spectral index. Instead, the new analysis supports the earlier suggestion that dust particles in the disk have grown to sizes as large as a few centimeters. The dust in the CQ Tauri system appears to be evolved much like that in the TW Hydra system, a well-studied pre-main-sequence star of similar age and lower mass. The survival of gas-rich disks with incomplete grain evolution at such old ages deserves further investigations
Constraints on Properties of the Protoplanetary Disks around UX Orionis and CQ Tauri
No full textWe present Very Large Array observations of the intermediate-mass pre-main-sequence stars UX Ori and CQ Tau at 7 mm, 3.6 cm, and 6 cm. These stars are members of the UX Ori variability class, where the origin of optical variability is thought to derive from inhomogeneities in circumstellar disks. Both stars are detected at 7 mm but not at longer wavelengths, which confirms that the millimeter emission is dominated by dust. The UX Ori system exhibits a remarkably flat spectral index in the millimeter range, with αmm~2 (Fν~ναmm). Two different disk models can reproduce this property: (1) a physically small disk with optically thick emission, truncated at a radius of about 30 AU, or (2) a massive (~0.3-1 Msolar) disk mainly composed of dust particles grown to radii of 10 cm (``pebbles''). The observations do not spatially resolve the 7 mm emission. We discuss implications of these two models and suggest observational tests that will discriminate between them. The CQ Tau system exhibits a spectral index in the millimeter range of αmm~2.6, consistent with values commonly found for disks around pre-main-sequence stars. The observations marginally resolve the 7 mm emission as an elongated structure with full width at half-maximum of 2.4"×1.1" (240×110 AU at 100 pc distance). The size and inclination of ~63° (implied by circular symmetry) are consistent with flared disk models that have previously been suggested to explain the optical colors and polarization properties
Using Drosophila models to unravel pathogenic mechanisms that underlie neurodegeneration in Tauopathies
No full textLaser operation of an Nd:Gd<sub>3</sub>Ga<sub>5</sub>O<sub>12</sub> thin-film optical waveguide fabricated by pulsed laser deposition
No full textWe report the laser operation of a thin-film waveguide structure grown by the pulsed laser deposition technique. A 2.7-µm-thick crystalline film of neodymium doped Gd3Ga5O12 (Nd:GGG) lases at a wavelength centered at 1.06µm when pumped by a Ti:sapphire laser at 808 nm
Low-loss Ti:sapphire waveguides fabricated by pulsed laser deposition
No full textWe report the fabrication and characterisation of Ti:sapphire films epitaxially grown on c-cut sapphire substrates by pulsed laser deposition (PLD). Deposition conditions have been studied extensively and optimised in order to produce high-performance optical waveguides. In particular we have studied the effects of different values of oxygen pressure, background gases and substrate temperature on the resultant surface roughness, composition, crystallinity, fluorescence and waveguide losses. For instance we found that Ti:sapphire films deposited in Ar feature higher fluorescence than those grown in O2 and N2 (see Figure 1) under the same deposition conditions: laser fluence F ~ 3.3 J/cm2, laser repetition rate f = 20 Hz, substrate temperature T ~ 1050°C, gas pressure P ~ 2.10-3 mbar, target-substrate distance d = 4 cm
Performance of a low loss pulsed laser deposited Nd:Gd<sub>3</sub>Ga<sub>5</sub>O<sub>12</sub> waveguide laser at 1.06µm and 0.94µm
No full textWe report the laser performance of a low propagation loss neodymium doped Gd3Ga5O12 (Nd:GGG) waveguide fabricated by pulsed laser deposition. An 8µm thick crystalline Nd:GGG film grown on an undoped Y3Al5O12 (YAG) substrate lases at 1.060µm and 1.062µm, when pumped by a Ti:sapphire laser operating at 740nm or 808nm. Using a 2.2% output coupler a 1060nm laser threshold of 4mW and a slope efficiency of 20% were observed. Laser action has also been achieved, we believe for the first time in Nd:GGG, on the quasi-three level 937nm transition. With a 2% output coupler at this wavelength a laser threshold of 17mW and a 20% slope efficiency were obtained. This demonstration of low propagation loss combined with the fact that these waveguides have a very high numerical aperture, make pulsed laser deposited thin films attractive for high power diode pumped devices
A low-loss waveguide laser grown by pulsed laser deposition
No full textWe report the fabrication of a low propagation loss (<1dB/cm) Nd:GGG waveguide by pulsed laser deposition. Using a 2% output coupler a 1.06µm laser threshold of 4mW and slope efficiency of 20% was observed
Zechariah 9-14 as the substructure of 1 Peter’s eschatological program
No full textThe principal aim of this study is to discern what has shaped the author of 1 Peter to regard Christian suffering as a necessary (1.6) and to-be-expected (4.12) component of faithful allegiance to Jesus Christ. Most research regarding suffering in 1 Peter has limited the scope of inquiry to two particular aspects—its cause and nature, and the strategies that the author of 1 Peter employs in order to enable his addressees to respond in faithfulness. There remains, however, the need for a comprehensive explanation for the source that has generated 1 Peter’s theology of Christian suffering. If Jesus truly is the Christ, God’s chosen redemptive agent who has come to restore God’s people, then how can it be that Christian suffering is a necessary part of discipleship after his coming, death and resurrection? What led the author of 1 Peter to such a startling conclusion, which seems to runs against the grain of the eschatological hopes and expectations of Jewish restoration ideology?
This thesis analyzes the appropriation of shepherd and fiery trials imagery,
and argues that the author of 1 Peter is dependent upon Zechariah 9-14 for his
theology of Christian suffering. Said in another way, the eschatological program of
Zechariah 9-14, read through the lens of the Gospel, functions as the substructure
for 1 Peter’s eschatology and thus its theology of Christian suffering.
In support of this hypothesis, this study highlights the fact that Zechariah 9-
14 was available and appropriated in early Christianity, in particular in the Passion
Narrative tradition; that the shepherd imagery of 1 Pet 2.25 is best understood
within the milieu of the Passion Narrative tradition, and that it alludes to the
eschatological program of Zechariah 9-14; that the fiery trials imagery found in 1
Peter 1.6-7 and 1 Pet 4.12 is distinct from that which we find in Greco-Roman and OT
wisdom sources, and that it shares exclusive parallels with some unique features of
the eschatological program of Zechariah 9-14; that Zechariah 9-14 offers a more
satisfying explanation for the modification of Isa 11.2 in 1 Pet 4.14, the transition
from 4.12-19 to 5.1-4, why Peter has oriented his letter with the term διασπορά,
and why he has described his addresses as οἶκος τοῦ θεοῦ; and finally that 1 Peter
contains an implicit foundational narrative that shares distinct parallels with the
eschatological program of Zechariah 9-14.
We can conclude that 1 Peter offers a unique vista into the way in which at
least one early Christian witness came to understand and to communicate the fact
that Christian suffering was a necessary feature of faithful allegiance to Jesus Christ
New (Probabilistic) Derivation of Diaz-Metcalf and Pólya-Szegő Inequalities and Consequences
No full textClassical inequalities of Diaz - Metcalf and Pólya - Szegő are generalized to
probabilistic setting which covers the initial deterministic (both discrete and integral) variants.
From these two inequalities, by the probabilistic derivation method further well -
known inequalities are obtained (that ones by Kantorovich, Rennie and Schweitzer)
Mouvance and the medieval author: re-editing Ancrene Wisse
No full textThe paper discusses the theoretical and practical problems of editing the early thirteenth-century guide for anchoresses, Ancrene Wisse, which (in Paul Zumthor's phrase) is an 'oeuvre mouvante', modified repeatedly from an early stage by its author and others
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