low pressures
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2021 ◽  
Vol 1 (2) ◽  
pp. 9-17
Timothy Chibueze ◽  
Fabian Ezema

The search for spin injectors and spin sources in spintronic devices is a significant facet of materials research today. Consequently, half-Heusler (HAH) KMnGe alloy has been recommended as one such admissible materials. Herein, a rigorous examination of the structural, magnetic and electronic properties of HAH KMnGe alloy is done using ab initio method within the bolstered up rendition of the functional by Perdew and his group. Our result shows that HAH KmnGe alloy expresses type-1 and type-2 HAH  structural ground state at high and low pressures respectively, which may pose a challenge in application. Impressively, HAH KMnGe alloy exhibits half metallic characteristic with an indirect energy gap in the Γ-X symmetry k-point and direct band gap at X-point in the minority electronic spin states for type-1 and type-2 phase respectively. Our findings agree fundamentally with some previous findings in the literature and suggests that the HAH KMnGe alloy is a credible excellent spin source in future spintronic devices.

2021 ◽  
Vol 12 ◽  
Jaume Puig ◽  
Nastassia Knödlseder ◽  
Jaume Quera ◽  
Manuel Algara ◽  
Marc Güell

Some organisms have shown the ability to naturally survive in extreme environments, even outer space. Some of these have natural mechanisms to resist severe DNA damage from conditions such as ionizing and non-ionizing radiation, extreme temperatures, and low pressures or vacuum. A good example can be found in Deinococcus radiodurans, which was exposed to severe conditions such as those listed in the Exposure Facility of the International Space Station (ISS) for up to three years. Another example are tardigrades (Ramazzottius varieornatus) which are some of the most resilient animals known. In this study, the survival under simulated Low earth Orbit (LEO) environmental conditions was tested in Escherichia coli. The radiation resistance of this bacteria was enhanced using the Dsup gene from R. varieornatus, and two more genes from D. radiodurans involved in DNA damage repair, RecA and uvrD. The enhanced survival to wide ranges of temperatures and low pressures was then tested in the new strains. This research constitutes a first step in the creation of new bacterial strains engineered to survive severe conditions and adapting existing species for their survival in remote environments, including extra-terrestrial habitats. These strains could be key for the development of environments hospitable to life and could be of use for ecological restoration and space exploration. In addition, studying the efficacy and the functioning of the DNA repair mechanisms used in this study could be beneficial for medical and life sciences engineering.

2021 ◽  
Shenlin Yang ◽  
Fang Pu ◽  
Zhen Wang ◽  
Zhaoqi Liu ◽  
Manhou Li

2021 ◽  
Vol 2119 (1) ◽  
pp. 012123
M Y Hrebtov ◽  
M S Bobrov

Abstract The paper presents a simplified numerical model of the hydrogen plasma generation process in a microwave resonant cavity. The model assumes electroneutrality and the prescribed electron temperature of the plasma, thus significantly reducing the computational cost. This allows for the parametric study in a wide range of operating pressures end electric field magnitudes (at a frequency of 2.45GHz). The prescribed model allows finding the effective range of operating pressures for the plasma generation. At low pressures, the collision rate is too low to effectively absorb all the emitted energy while at high pressures the electron conductivity drops which also reduces the absorption efficiency.

Takumi Tominaga ◽  
Shinji Takayanagi ◽  
Takahiko Yanagitani

Abstract Scandium aluminum nitride (ScAlN) films are being actively researched to explore their potential for use in bulk acoustic wave (BAW) and surface acoustic wave (SAW) resonators because of their good piezoelectric properties. Sputtering is commonly used in ScAlN film deposition. Unfortunately, it has been reported that film quality metrics such as the crystallinity and piezoelectric properties can deteriorate before the Sc concentration reaches 43% without an isostructural phase transition. One reason for this is bombardment with negative ions generated from carbon and oxygen impurities in the Sc ingots. Because the number of negative ions increases during low-pressure sputtering deposition, their effect on film quality may be considerable. In this study, we investigated negative-ion bombardment of the substrate during sputtering deposition and its effects on ScAlN crystallinity and piezoelectric properties. Negative-ion energy distribution measurements indicated that many more negative ions collide with the substrate during ScAlN film deposition than during AlN deposition. In addition, decreasing the sputtering pressure further increased the number of negative ions and their energies. It is well known that film quality improves at low pressures because increasing the mean free path reduces thermalization and scattering of sputtered particles. Although, AlN crystallinity and piezoelectric properties improved at low pressures, the properties of ScAlN films deteriorated dramatically. Therefore, the results indicated that ion bombardment increase at low pressure adversely effects ScAlN crystal growth, deteriorating crystallinity and piezoelectric properties. ScAlN films may be improved further by suppressing negative-ion bombardment of the substrate.

2021 ◽  
Thomas Mikal-Evans ◽  
David Sing ◽  
Joanna Barstow ◽  
Tiffany Kataria ◽  
Jayesh Goyal ◽  

Abstract The temperature profile of a planetary atmosphere is a key diagnostic of radiative and dynamical processes governing the absorption, redistribution, and emission of energy. Observations have revealed dayside stratospheres that either cool [1,2] or warm [3,4] with altitude for a small number of gas giant exoplanets, while others are consistent with constant temperatures [5,6,7,8]. Here we report spectroscopic phase curve measurements for the gas giant WASP-121b,[9] which constrain stratospheric temperatures throughout the diurnal cycle. Variations measured for a water vapor spectral feature reveal a temperature profile that transitions from warming with altitude on the dayside hemisphere to cooling with altitude on the nightside hemisphere. The data are well explained by models assuming chemical equilibrium, with water molecules thermally dissociating at low pressures on the dayside and recombining on the nightside [10,11]. Nightside temperatures are low enough for perovskite (CaTiO3) to condense, which could deplete titanium from the gas phase [12,13] and explain recent non-detections at the day-night terminator [14,15,16,17]. Nightside temperatures are also low enough for refractory species, such as magnesium, iron, and vanadium, to condense. Detections [16,17,18,19] of these metals at the day-night terminator suggest, however, that if they do form nightside clouds, cold trapping is not as effective at removing them from the upper atmosphere. Note: Numbered references have been entered into the "Manuscript Comment" box.

2021 ◽  
Ernest Henry Rutter ◽  
Julian Mecklenburgh ◽  
Yusuf Bashir

Abstract. The effective pressure sensitivity of gas flow through two shales (Bowland and Haynesville shales) and a tight gas sandstone (Pennant sandstone) was measured over the typical range of reservoir pressure conditions. These are low permeability rocks such as can be exploited as caprocks above reservoirs that might be developed to store compressed air, methane, hydrogen or to bury waste carbon dioxide, all of which may become important components of the forthcoming major changes in methods of energy generation and storage. Knowledge of the petrophysical properties of such tight rocks will be of great importance in such developments. All three rocks display only a small range in log10 permeability at low pressures, but these decrease at dramatically different rates with increasing effective pressure, and the rate of decrease itself decreases with pressure, as the rocks stiffen. The pressure sensitivity of the bulk moduli of each of these rocks was also measured, and used to formulate a description of the permeability decrease in terms of the progressive closure of narrow, crack-like pores with increasing pressure. In the case of the shales in particular, only a very small proportion of the total porosity takes part in the flow of gases, particularly along the bedding layering.

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