MRI-accreting inner regions of protoplanetary discs

<p>Short-period super-Earths and mini-Neptunes have been shown to be common, yet it is still not understood how and where inside protoplanetary discs they could have formed. To form these planets at the short periods at which they are detected, the inner regions of protoplanetary discs must be enriched in dust. Dust could accumulate in the inner disc if the innermost regions accrete via the magneto-rotational instability (MRI). We developed a model of the inner disc which includes MRI-driven accretion, disc heating by both accretion and stellar irradiation, vertical energy transport, dust opacities, dust effects on disc ionization, thermal and non-thermal sources of ionization. The inner disc is assumed to be in steady state, and the dust is assumed to be well-mixed with the gas. Using this model, we explore how various disc and stellar parameters affect the structure of the inner disc and the possibility of dust accumulation. We show that properties of dust strongly affect the size of the MRI-accreting region and whether this region exists at all. Increasing the dust-to-gas ratio increases the size of this region, suggesting that dust may accumulate in the inner disc without suppressing the MRI. Overall, conditions in the inner disc may be more favourable to planet formation earlier in the disc lifetime, while the disc accretion rate is higher.</p>

Dust Phenomenon: Threat Appraisal of Cardiovascular Patients

Introduction: Dust phenomenon is a major environmental problem in world that threatens the middle-east countries specifically. In order to develop a need-based policy and regulate the supporting health program to reduce dust effects requires a proper understanding of the public beliefs about threats posed by this issue. The purpose of this study was to explain the threat appraisal patients with cardiovascular diseases regarding exposure to dust phenomena. Method: This qualitative content-analysis study was conducted from January to June 2018. The participants included 28 cardiovascular patients who referred to the healthcare centers in Ahvaz City. Semi-structured interviews were conducted with open-ended questions and inspiration from threat appraisal process constructs were used to collect data. All data were gathered, transcribed, and analyzed using MAXQDA-10 software and in-depth analysis. Findings: Perceived threat constructs were used and 4 categories and 9 sub-categories were extracted: perceived likelihood of exposure to dust (perceived likelihood of increased non-respiratory problems, perceived likelihood of increased respiratory problems), belief in seriousness and danger of exposure to dust (understanding the severity of physical complications, understanding the severity of mental and psychological complications, understanding the severity of economic complications), external reward of exposure to dust (improving personal and social relationships, improving financial problems), internal reward of exposure to dust (pleasant feeling). Conclusion: This study provided a clearer and deeper understanding of the threat posed by exposure to dust among cardiovascular patients. Based on the results, the authorities can design more targeted and more effective protective plans to raise awareness among community members, especially cardiovascular patients about the negative effects of exposure to dust and the ways to reduce its exposure.

The potential of a synergestic lidar and sunphotometer retrieval for the characterization of a dust event over Finokalia and for aerosol model evaluation

<p>The ability of three-dimensional dust models to accurately represent the dust life cycle is crucial for describing dust effects on radiation and clouds and for reducing the uncertainties on these processes. To improve the reliabilty of dust models, it is therefore imperative to carry out thorough evaluations of the dust properties. Dust optical and microphysical properties are accurately accessed through groundbased observations: multiwavelength lidars and sunphotometers. In this study we use the Generalized Retrieval of Atmospheric and Surface Properties (GRASP) data algorithm that combines the lidar and sunphotometer data to retrieve dust properties. GRASP is applied on a Saharan dust episode over Finokalia, Crete in Greece, on 14 May 2017. More precisely the measurements from PollyXT lidar participating in the European Aerosol Research Network (EARLINET) and the CIMEL sunphotometer participating in Aerosol Robotic Network (AERONET) are synergetically combined using the GRASP algorithm. The dust event is fully characterised through the retrieval of dust optical and microphysical properties. The retrieved properties are found to be in good agreement with the initial measurements from the AERONET sunphotometer and the lidar. Then the aforementioned tools are used to evaluate the performance of the regional dust model NMME-DREAM that has been developed to simulate and predict the atmospheric cycle of mineral dust aerosols. It is shown that the model has problems in simulating the high dust concentration values at low levels, probably due to the low spatial resolution of the model that causes difficulties in capturing the orography and the downdrafts winds.</p>

Analysis of airborne dust effects on terrestrialmicrowave propagation in arid area

Sand and dust storms are environmental phenomena ,during these storms optical visibility might be decreased, consequently, atmospheric attenuation is clearly noticed.Micro-wave (MW) and Milimeter-wave (mm) propagation is severely affected by dust and sand storms in considerable areas around the world. Suspended dust particles may directly cause attenuation and cross polarization to the Electromagnetic waves propagating through the storm. In this paper, a thorough investigation of dust storm characteristics based onmeasured optical visibility and relative humidity is presented. In addition,the dust storms effects of on Micro-wave and Millimeter-wave propagation have been studied based on data measured Received Signal levels (RSL)and dust storm characteristics synchronously. Analyticaldustattenuationmodels predictions are matched to the measured attenuationdata at 14 GHz and 21 GHz. It has been found that the measured attenuation is approximately ten times higher than the predicted attenuation for both frequencies.