Polarization dependence of coherent phonon generation and detection in the 3D topological insulator Bi2Te3

We have studied the polarization dependence of coherent phonons in the topological insulator Bi2Te3. Using polarization-dependent femtosecond pump-probe spectroscopy, we measured coherent phonons as a function of angle when the pump and probe polarizations were fixed, and the crystal orientation was rotated. For isotropic detection, depending on the spot position, oscillations either from only low- and high-frequency phonons of A1g symmetry, or in addition from the mode at 3.6 THz were observed. All the modes were found to be independent of the orientation of electric field vector with respect to the crystal axes testifying to their full symmetry while no modes of lower symmetry appeared in any polarization geometry. For anisotropic detection both modes of Eg symmetry could be detected, but their amplitudes were considerably smaller than those of A1g symmetry. To clarify the coherent phonon assignment and the process of coherent phonon generation in Bi2Te3, the time-domain measurements were complemented by spontaneous Raman scattering. The comparison of frequency- and time-domain results and the polarization dependence suggest that the 3.6 THz mode belongs to crystalline Te arising due to tellurium segregation. A discrepancy between the time- and frequency domain data is discussed.Comment: Accepted to Pysical Review RB, 27 pages, 11 figure

Perioperative morbidity of different operative approaches in early cervical carcinoma: a systematic review and meta-analysis comparing minimally invasive versus open radical hysterectomy

Purpose: Radical hysterectomy and pelvic lymphadenectomy is the standard treatment for early cervical cancer. Studies have shown superior oncological outcome for open versus minimal invasive surgery, but peri- and postoperative complication rates were shown vice versa. This meta-analysis evaluates the peri- and postoperative morbidities and complications of robotic and laparoscopic radical hysterectomy compared to open surgery. Methods: Embase and Ovid-Medline databases were systematically searched in June 2020 for studies comparing robotic, laparoscopic and open radical hysterectomy. There was no limitation in publication year. Inclusion criteria were set analogue to the LACC trial. Subgroup analyses were performed regarding the operative technique, the study design and the date of publication for the endpoints intra- and postoperative morbidity, estimated blood loss, hospital stay and operation time. Results: 27 studies fulfilled the inclusion criteria. Five prospective, randomized-control trials were included. Meta-analysis showed no significant difference between robotic radical hysterectomy (RH) and laparoscopic hysterectomy (LH) concerning intra- and perioperative complications. Operation time was longer in both RH (mean difference 44.79 min [95% CI 38.16; 51.42]), and LH (mean difference 20.96 min; [95% CI − 1.30; 43.22]) than in open hysterectomy (AH) but did not lead to a rise of intra- and postoperative complications. Intraoperative morbidity was lower in LH than in AH (RR 0.90 [0.80; 1.02]) as well as in RH compared to AH (0.54 [0.33; 0.88]). Intraoperative morbidity showed no difference between LH and RH (RR 1.29 [0.23; 7.29]). Postoperative morbidity was not different in any approach. Estimated blood loss was lower in both LH (mean difference − 114.34 [− 122.97; − 105.71]) and RH (mean difference − 287.14 [− 392.99; − 181.28]) compared to AH, respectively. Duration of hospital stay was shorter for LH (mean difference − 3.06 [− 3.28; − 2.83]) and RH (mean difference − 3.77 [− 5.10; − 2.44]) compared to AH. Conclusion: Minimally invasive radical hysterectomy appears to be associated with reduced intraoperative morbidity and blood loss and improved reconvalescence after surgery. Besides oncological and surgical factors these results should be considered when counseling patients for radical hysterectomy and underscore the need for new randomized trials. © 2021, The Author(s)

A simple model for the evolution of the dust population in protoplanetary disks

Context: The global size and spatial distribution of dust is an important ingredient in the structure and evolution of protoplanetary disks and in the formation of larger bodies, such as planetesimals. Aims: We aim to derive simple equations that explain the global evolution of the dust surface density profile and the upper limit of the grain size distribution and which can readily be used for further modeling or for interpreting of observational data. Methods: We have developed a simple model that follows the upper end of the dust size distribution and the evolution of the dust surface density profile. This model is calibrated with state-of-the-art simulations of dust evolution, which treat dust growth, fragmentation, and transport in viscously evolving gas disks. Results: We find very good agreement between the full dust-evolution code and the toy model presented in this paper. We derive analytical profiles that describe the dust-to-gas ratios and the dust surface density profiles well in protoplanetary disks, as well as the radial flux by solid material "rain out", which is crucial for triggering any gravity assisted formation of planetesimals. We show that fragmentation is the dominating effect in the inner regions of the disk leading to a dust surface density exponent of -1.5, while the outer regions at later times can become drift-dominated, yielding a dust surface density exponent of -0.75. Our results show that radial drift is not efficient in fragmenting dust grains. This supports the theory that small dust grains are resupplied by fragmentation due to the turbulent state of the disk.Comment: 12 pages, 10 figures, accepted to A&

IUCN Conservation Status Does Not Predict Glucocortoid Concentrations in Reptiles and Birds

Circulating glucocorticoids (GCs) are the most commonly used biomarkers of stress in wildlife. However, their utility as a tool for identifying and/or managing at-risk species has varied. Here, we took a very broad approach to conservation physiology, asking whether International Union for the Conservation of Nature (IUCN) listing status (concern versus no obvious concern) and/or location within a geographic range (edge versus non-edge) predicted baseline and post-restraint concentrations of corticosterone (CORT) among many species of birds and reptiles. Even though such an approach can be viewed as coarse, we asked in this analysis whether CORT concentrations might be useful to implicate species at risk. Indeed, our effort, relying on HormoneBase, a repository of data on wildlife steroids, complements several other large-scale efforts in this issue to describe and understand GC variation. Using a phylogenetically informed Bayesian approach, we found little evidence that either IUCN status or edge/non-edge location in a geographic distribution were related to GC levels. However, we did confirm patterns described in previous studies, namely that breeding condition and evolutionary relatedness among species predicted some GC variation. Given the broad scope of our work, we are reluctant to conclude that IUCN status and location within a range are unrelated to GC regulation. We encourage future more targeted efforts on GCs in at-risk populations to reveal how factors leading to IUCN listing or the environmental conditions at range edges impact individual performance and fitness, particularly in the mammals, amphibians, and fish species we could not study here because data are currently unavailable

Characterization of Ring Substructures in the Protoplanetary Disk of HD 169142 from Multiwavelength Atacama Large Millimeter/submillimeter Array Observations

We present a detailed multiwavelength characterization of the multi-ring disk of HD 169142. We report new Atacama Large Millimeter/submillimeter Array (ALMA) observations at 3 mm and analyze them together with archival 0.89 and 1.3 mm data. Our observations resolve three out of the four rings in the disk previously seen in high-resolution ALMA data. A simple parametric model is used to estimate the radial profile of the dust optical depth, temperature, density, and particle size distribution. We find that the multiple ring features of the disk are produced by annular accumulations of large particles, probably associated with gas pressure bumps. Our model indicates that the maximum dust grain size in the rings is ∼1 cm, with slightly flatter power-law size distributions than the interstellar medium-like size distribution (p ∼ 3.5) found in the gaps. In particular, the inner ring (∼26 au) is associated with a strong and narrow buildup of dust particles that could harbor the necessary conditions to trigger the streaming instability. According to our analysis, the snowlines of the most important volatiles do not coincide with the observed substructures. We explore different ring formation mechanisms and find that planet-disk interactions are the most likely scenario to explain the main features of HD 169142. Overall, our multiwavelength analysis provides some of the first unambiguous evidence of the presence of radial dust traps in the rings of HD 169142. A similar analysis in a larger sample of disks could provide key insights on the impact that disk substructures have on the dust evolution and planet formation processes.© 2019. The American Astronomical Society. All rights reserved..E.M., and C.C.E. acknowledge support from the National Science Foundation under CAREER grant No. AST-1455042 and the Sloan Foundation. M.O., G.A., J.M.T., and J.F.G. acknowledge financial support from the State Agency for Research of the Spanish MCIU through the AYA2017-84390-C2-1-R grant (co-funded by FEDER). M.O., G. A., and J.F.G. acknowledge support from the >Center of Excellence Severo Ochoa> award for the Instituto de Astrofisica de Andalucia (SEV-2017-0709). M. F. and G.H.M.B. acknowledge support from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement no 757957).Peer Reviewe

Underestimation of the dust mass in protoplanetary disks: effects of disk structure and dust properties

Stars and planetary system

Disk Evolution Study Through Imaging of Nearby Young Stars (DESTINYS):Late Infall Causing Disk Misalignment and Dynamic Structures in SU Aur

Gas-rich circumstellar disks are the cradles of planet formation. As such, their evolution will strongly influence the resulting planet population. In the ESO DESTINYS large program, we study these disks within the first 10 Myr of their development with near-infrared scattered light imaging. Here we present VLT/SPHERE polarimetric observations of the nearby class II system SU Aur in which we resolve the disk down to scales of ~7 au. In addition to the new SPHERE observations, we utilize VLT/NACO, HST/STIS and ALMA archival data. The new SPHERE data show the disk around SU Aur and extended dust structures in unprecedented detail. We resolve several dust tails connected to the Keplerian disk. By comparison with ALMA data, we show that these dust tails represent material falling onto the disk. The disk itself shows an intricate spiral structure and a shadow lane, cast by an inner, misaligned disk component. Our observations suggest that SU Aur is undergoing late infall of material, which can explain the observed disk structures. SU Aur is the clearest observational example of this mechanism at work and demonstrates that late accretion events can still occur in the class II phase, thereby significantly affecting the evolution of circumstellar disks. Constraining the frequency of such events with additional observations will help determine whether this process is responsible for the spin-orbit misalignment in evolved exoplanet systems.Comment: 18 pages, 12 figures, published in ApJL on 18-02-202

ALMA and VLA Observations of EX Lupi in its Quiescent State

Extreme outbursts in young stars may be a common stage of pre-main-sequence stellar evolution. These outbursts, caused by enhanced accretion and accompanied by increased luminosity, can also strongly impact the evolution of the circumstellar environment. We present ALMA and VLA observations of EX Lupi, a prototypical outburst system, at 100 GHz, 45 GHz, and 15 GHz. We use these data, along with archival ALMA 232 GHz data, to fit radiative transfer models to EX Lupi's circumstellar disk in its quiescent state following the extreme outburst in 2008. The best fit models show a compact disk with a characteristic dust radius of 45 au and a total mass of 0.01 M$_{\odot}$. Our modeling suggests grain growth to sizes of at least 3 mm in the disk, possibly spurred by the recent outburst, and an ice line that has migrated inward to $0.2-0.3$ au post-outburst. At 15 GHz, we detected significant emission over the expected thermal disk emission which we attribute primarily to stellar (gyro)synchrotron and free-free disk emission. Altogether, these results highlight what may be a common impact of outbursts on the circumstellar dust.Comment: Accepted to ApJ, 15 pages, 8 figure