231 research outputs found
The three regimes of atmospheric evaporation for super-Earths and sub-Neptunes
A significant fraction of super-Earths and sub-Neptunes are thought to
experience an extreme loss of volatiles because of atmospheric evaporation in
the early stages of their life. Though the mechanisms behind the extreme mass
loss are not fully understood, two contenders have been widely discussed:
photoevaporation from X-ray and ultraviolet irradiation and core powered mass
loss. Here, it is shown that both mechanisms occur but with different
timescales, and that atmospheric loss can take place over three regimes. In the
first regime, a planet has very high internal temperatures arising from its
high-energy formation processes. These high temperatures give rise to a fully
convecting atmosphere that efficiently loses mass without much internal
cooling. The second regime applies to planets with lower internal temperatures,
so a radiative region forms but the photosphere still remains outside the Bondi
radius. Hence, mass loss continues to depend only on the internal temperatures.
Planets with the lowest internal temperatures are in the third regime, when the
photosphere forms below the Bondi radius and mass is lost primarily because of
X-ray and ultraviolet irradiation. This paper provides the first unifying
framework for modeling atmospheric evaporation through the lifespan of a
planet.Comment: 37 pages, 13 figures, 2023 ApJ 943 1
RAPOC : the Rosseland and Planck opacity converter. A user-friendly and fast opacity program for Python
RAPOC (Rosseland and Planck Opacity Converter) is a Python 3 code that
calculates Rosseland and Planck mean opacities (RPMs) from wavelength-dependent
opacities for a given temperature, pressure, and wavelength range. In addition
to being user-friendly and rapid, RAPOC can interpolate between discrete data
points, making it flexible and widely applicable to the astrophysical and
Earth-sciences fields, as well as in engineering. For the input data, RAPOC can
use ExoMol and DACE data, or any user-defined data, provided that it is in a
readable format. In this paper, we present the RAPOC code and compare its
calculated Rosseland and Planck mean opacities with other values found in the
literature. The RAPOC code is open-source and available on Pypi and GitHub.Comment: 15 pages, 6 figures, 3 tables; Accepted for Publication in Exp.
Astro
Necessity and Methods of Designing Green Buildings in Cities and its Effect on Energy Efficiency
Population growth, increasing development of cities and subsequent destruction of green spaces and finally an increase in air pollution and global warming, have increased the need to find ways to coexist with the natural conditions, conserving energy, preventing land pollution, protecting the environment and reducing energy consumption. In order to increase green space in urban areas and greater energy efficiency in buildings, especially in cities, attitudes and new approaches of modern architecture are one of the strategies toward green architecture which has attracted the attention of many contemporary designers and architects in the world in recent years. This architecture is derived from the concept of sustainable development in harmony with environmental compatibility in order to meet the needs of people, step for the survival of human interaction and environment. To create green buildings, after examining the need to use them, first, we must be familiar with the principles of green architecture and then proceed to the design and construction. This paper attempts to investigate different parts of a building (green views, indoor and outdoor living walls, green walls and green roofs area), due to the possibility of planting and principles of construction. Then by examining samples of green buildings in the world today and expressing characteristics and their impact on the environment, some steps should be taken towards creating healthy cities and reducing energy consumption
Hot Super-Earths with Hydrogen Atmospheres: A Model Explaining Their Paradoxical Existence
In this paper we propose a new mechanism that could explain the survival of
hydrogen atmospheres on some hot super-Earths. We argue that on close-orbiting
tidally-locked super-Earths the tidal forces with the orbital and rotational
centrifugal forces can partially confine the atmosphere on the nightside.
Assuming a super terran body with an atmosphere dominated by volcanic species
and a large hydrogen component, the heavier molecules can be shown to be
confined within latitudes of whilst the volatile hydrogen
is not. Because of this disparity the hydrogen has to slowly diffuse out into
the dayside where XUV irradiation destroys it. For this mechanism to take
effect it is necessary for the exoplanet to become tidally locked before losing
the totality of its hydrogen envelop. Consequently, for super-Earths with this
proposed configuration it is possible to solve the tidal-locking and mass-loss
timescales in order to constrain their formation `birth' masses. Our model
predicts that 55 Cancri e formed with a day-length between approximately
hours and an initial mass less than hence
allowing it to become tidally locked before the complete destruction of its
atmosphere. For comparison, CoRoT-7b, an exoplanet with very similar properties
to 55 Cancri e but lacking an atmosphere, formed with a day-length
significantly different from hours whilst also having an initial
mass smaller than Comment: 20 pages, 15 figure
Molecular Identification of Six Honeybee Viruses in Iranian Apiaries
The identification of honeybee viruses is of serious importance, particularly considering the lack of information on the natural incidence of viral infections in honeybee populations worldwide. Moreover, the global spread of Varroa destructor in honeybee colonies has a significant effect on the viral infection. In the present study, 160 samples of adult bee from apparently healthy colonies but with a background of parasitic diseases, tremor, and paralysis, were collected during 2011-2012. The samples belonged to 23 different provinces of Iran. They were sent to Razi Vaccine and Serum Research Institute, Karaj, Iran, for further analysis, and examined for the presence of viruses using reverse transcription polymerase chain reaction assay. According to the results, out of 160 samples, 9 (5.8 %), 40 (25.6 %), 12 (7.8 %), 34 (21.8 %), 7 (4.5 %), and 29 (18.5%) cases were positive for acute bee paralysis virus (ABPV), black queen cell virus (BQCV), chronic bee paralysis virus (CBPV), deformed wing virus (DWV), Kashmir bee virus (KBV), and sacbrood virus (SBV). The samples collected from 18 provinces (78 %) were positive for at least one virus. Among all samples, 83 (53.2 %) specimens were infected with at least one virus. The highest prevalent virus was BQCV, followed by DWV, SBV, CBPV, ABPV, and KBV, respectively
Network Intrusion Detection with Limited Labeled Data
With the increasing dependency of daily life over computer networks, the
importance of these networks security becomes prominent. Different intrusion
attacks to networks have been designed and the attackers are working on
improving them. Thus the ability to detect intrusion with limited number of
labeled data is desirable to provide networks with higher level of security. In
this paper we design an intrusion detection system based on a deep neural
network. The proposed system is based on self-supervised contrastive learning
where a huge amount of unlabeled data can be used to generate informative
representation suitable for various downstream tasks with limited number of
labeled data. Using different experiments, we have shown that the proposed
system presents an accuracy of 94.05% over the UNSW-NB15 dataset, an
improvement of 4.22% in comparison to previous method based on self-supervised
learning. Our simulations have also shown impressive results when the size of
labeled training data is limited. The performance of the resulting Encoder
Block trained on UNSW-NB15 dataset has also been tested on other datasets for
representation extraction which shows competitive results in downstream tasks
بررسی مقایسه ای استحکام باند برشی براکت های سرامیکی با سه طرح متفاوت قاعده براکت باند شده بر روی ترمیمهای آمالگام و ترمیم های کامپوزیتی با آماده سازی متفاوت سطح
Exploring Super-Earth Surfaces: Albedo of Near-Airless Magma Ocean Planets and Topography
In this paper we propose an analytic function for the spherical albedo values
of airless and near-airless magma ocean planets (AMOPs). We generated 2-D
fractal surfaces with varying compositions onto which we individually threw
10,000 light rays. Using an approximate form of the Fresnel equations we
measured how much of the incident light was reflected. Having repeated this
algorithm on varying surface roughnesses we find the spherical albedo as a
function of the Hurst exponent, the geochemical composition of the magma, and
the wavelength. As a proof of concept, we used our model on Kepler-10b to
demonstrate the applicability of our approach. We present the spherical albedo
values produced from different lava compositions and multiple tests that can be
applied to observational data in order to determine their characteristics.
Currently, there is a strong degeneracy in the surface composition of AMOPs due
to the large uncertainties in their measured spherical albedos. In spite of
this, when applied to Kepler-10b we show that its high albedo could be caused
by a moderately wavy ocean that is rich in oxidised metallic species such as
FeO, , . This would imply that Kepler-10b is
a coreless or near-coreless body
GJ 357 b: A Super-Earth Orbiting an Extremely Inactive Host Star
In this paper we present a deep X-ray observation of the nearby M dwarf GJ
357 and use it to put constraints on the atmospheric evolution of its planet,
GJ 357 b. We also analyse the systematic errors in the stellar parameters of GJ
357 in order to see how they affect the perceived planetary properties. We
estimate the age of GJ 357 b by comparing the observed X-ray luminosity of its
host star, derived from a recent {\em XMM-Newton} observation {(), with age relations for M dwarfs. We
find that GJ 357 presents one of the lowest X-ray activity levels ever measured
for an M dwarf, and we put a lower limit on its age of \,Gyr.} Using this
age limit, we perform a backwards reconstruction of the original primordial
atmospheric reservoir. Furthermore, by considering the systematic errors in the
stellar parameters, we find a range of possible planetary masses, radii, and
densities. From the backwards reconstruction of GJ 357 b's irradiation history
we find that the upper limit of its initial primordial atmospheric mass is
. An initial atmospheric reservoir significantly larger
than this may have survived through the X-ray and ultraviolet irradiation
history, hence being inconsistent with current observations that suggest a
telluric composition. In spite of the unlikelihood of a currently existing
primordial envelope, volcanism and outgassing may have contributed to a
secondary atmosphere. Under this assumption, we present three different
synthetic infrared spectra for GJ 357 b that one might expect, consisting of
, , and , and .Comment: Accepted for publication in A&
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