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  • 1
    Publication Date: 2020-04-02
    Description: Daylight vision in most mammals is mediated predominantly by a middle/long wavelength-sensitive (M/LWS) pigment. Although spectral sensitivity and associated shifts in M/LWS are mainly determined by five critical sites, predicted phenotypic variation is rarely validated, and its ecological significance is unclear. We experimentally determine spectral tuning of M/LWS pigments and show that two highly divergent taxa, the gerbil and the elephant-shrew, have undergone independent dramatic blue-green shifts to 490 nm. By generating mutant proteins, we identify additional critical sites contributing to these shifts. Our results, which extend the known range of spectral tuning of vertebrate M/LWS, provide a compelling case of functional convergence, likely related to parallel adaptive shifts from nocturnal to brighter light conditions in similar habitats.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 2
    Publication Date: 2019-06-10
    Description: The ability of vertebrates to occupy diverse niches has been linked to the spectral properties of rhodopsin, conferring rod-based vision in low-light conditions. More recent insights have come from nonspectral kinetics, including the retinal release rate of the active state of rhodopsin, a key aspect of scotopic vision that shows strong associations with light environments in diverse taxa. We examined the retinal release rates in resurrected proteins across early vertebrates and show that the earliest forms were characterized by much faster rates of retinal release than more recent ancestors. We also show that scotopic vision at the origin of tetrapods is a derived state that arose via at least 4 major shifts in retinal release rate. Our results suggest that early rhodopsin had a function intermediate to that of modern rod and cone pigments and that its well-developed adaptation to low light is a relatively recent innovation since the origin of tetrapods.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 3
    Publication Date: 2019-10-25
    Description: The high-temperature environment is a major factor that affects deep mining. Cooling has become a major expense, accounting for up to 25% of the total energy consumption of such mines. To address methods of cooling and the cooling cost, this paper studies the influence of the ventilation duct layout on the cooling effect. Six models were created in ICEM-CFD (3D modeling software), and the influence of cold airflow diffusion on the temperature of the mine environment was numerically simulated using ANSYS Fluent. Under the condition of the same ventilation volume, two models utilizing single pipe and double pipe scenarios were established, and six points were selected as the pipeline suspension position, forming six ventilation duct models. The cooling effect of each model was evaluated by analyzing the average temperature of the roadway section, the three-dimensional distribution of the roadway temperature and the velocity streamline of the whole roadway. The results show that the double-tube model has greater advantages than the single-tube model does, due to its superior local temperature, average temperature of the cross-section, range below 303 K, temperature uniformity and local wind speed. Among the models, model 4 (diameter of 0.5 m, 1.9 m away from the bottom of the roadway and 2.4 m away from the center of the circle) is the best pipeline layout scheme for comprehensive temperature values, roadway temperature uniformity and other factors. The average temperature is 299.3 K within 8 m from the mining face, which is 1.66 K lower than that of the single tube model. This configuration will increase the comfort of the mining environment and reduce cooling costs. These results can provide a reference for ventilation duct layouts of roadways in high temperature mines.
    Electronic ISSN: 1996-1073
    Topics: Energy, Environment Protection, Nuclear Power Engineering
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  • 4
    Publication Date: 2021-08-31
    Description: Rhodopsin comprises an opsin attached to a retinal chromophore and is the only visual pigment conferring dim-light vision in vertebrates. On activation by photons, the retinal group becomes detached from the opsin, which is then inactive until it is recharged. Of all vertebrate species, those that dive face unique visual challenges, experiencing rapid decreases in light level and hunting in near darkness. Here, we combine sequence analyses with functional assays to show that the rhodopsin pigments of four divergent lineages of deep-diving vertebrates have undergone convergent increases in their retinal release rate. We compare gene sequences and detect parallel amino acids between penguins and diving mammals and perform mutagenesis to show that a single critical residue fully explains the observed increases in retinal release rate in both the emperor penguin and beaked whale. At the same time, we find that other shared sites have no significant effect on retinal release, implying that convergence does not always signify adaptive significance. We propose that accelerated retinal release confers rapid rhodopsin recharging, enabling the visual systems of diving species to adjust quickly to changing light levels as they descend through the water column. This contrasts with nocturnal species, where adaptation to darkness has been attributed to slower retinal release rates.
    Print ISSN: 0737-4038
    Electronic ISSN: 1537-1719
    Topics: Biology
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  • 5
    Publication Date: 2021-10-25
    Description: High temperature smoke caused by fire is a major cause of casualties. In order to ensure the safety of personnel, it is very important to control the spread of smoke and enable personnel to quickly withdraw from the fire scene. While traditional hard isolation, such as fire doors, may hinder the safe evacuation of people, the use of an air curtain as a flexible isolation has received more and more attention from researchers. In this paper, the influence of jet direction of compound air curtain on the smoke control effect was studied, and six working conditions were designed. The temperature and smoke isolation of the compound air curtain were numerically simulated by using ANSYS FLUENT software. The parameters such as temperature, velocity pressure and velocity streamline were analyzed, and the smoke control effects of six different jet directions were discussed. The simulation results were verified by Pyrosim fire simulation software simulation software. The results show that the direction of jet flow has a significant influence on the smoke control effect, and the fire smoke control effect under working conditions 4 and 5 is better. The working condition 5 (both air curtain A and air curtain B have outward jet direction) has the best smoke prevention effect, which is suitable for a situation that is close to the fire source. Working condition 4 (outward direction of air curtain A and inward direction of air curtain B) has the second-best effect of smoke prevention, which is suitable for situations far from the fire source.
    Electronic ISSN: 1996-1073
    Topics: Energy, Environment Protection, Nuclear Power Engineering
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