43,268 research outputs found
Dust-to-gas ratio, factor and CO-dark gas in the Galactic anticentre: an observational study
We investigate the correlation between extinction and H~{\sc i} and CO
emission at intermediate and high Galactic latitudes (|b|>10\degr) within the
footprint of the Xuyi Schmidt Telescope Photometric Survey of the Galactic
anticentre (XSTPS-GAC) on small and large scales. In Paper I (Chen et al.
2014), we present a three-dimensional dust extinction map within the footprint
of XSTPS-GAC, covering a sky area of over 6,000\,deg at a spatial angular
resolution of 6\,arcmin. In the current work, the map is combined with data
from gas tracers, including H~{\sc i} data from the Galactic Arecibo L-band
Feed Array H~{\sc i} survey and CO data from the Planck mission, to constrain
the values of dust-to-gas ratio and CO-to-
conversion factor for the entire GAC
footprint excluding the Galactic plane, as well as for selected star-forming
regions (such as the Orion, Taurus and Perseus clouds) and a region of diffuse
gas in the northern Galactic hemisphere. For the whole GAC footprint, we find
\, and \,. We have also
investigated the distribution of "CO-dark" gas (DG) within the footprint of GAC
and found a linear correlation between the DG column density and the -band
extinction: . The mass fraction of DG is found to be toward
the Galactic anticentre, which is respectively about 23 and 124 per cent of the
atomic and CO-traced molecular gas in the same region. This result is
consistent with the theoretical work of Papadopoulos et al. but much larger
than that expected in the cloud models by Wolfire et al.Comment: 11 pages, 7 figures, accepted for publication in MNRA
Hertz-level Measurement of the 40Ca+ 4s 2S1/2-3d 2D5/2 Clock Transition Frequency With Respect to the SI Second through GPS
We report a frequency measurement of the clock transition of a single ^40Ca^+
ion trapped and laser cooled in a miniature ring Paul trap with 10^-15 level
uncertainty. In the measurement, we used an optical frequency comb referenced
to a Hydrogen maser, which was calibrated to the SI second through the Global
Positioning System (GPS). Two rounds of measurements were taken in May and June
2011, respectively. The frequency was measured to be 411 042 129 776 393.0(1.6)
Hz with a fractional uncertainty of 3.9{\times}10^-15 in a total averaging time
of > 2{\times}10^6 s within 32 days
Enhancing solar chimney performance in urban tunnels: Investigating the impact factors through experimental and theoretical model analysis
Efficient and sustainable ventilation in urban tunnels is crucial for combating air pollution and safeguarding human health. This study investigates the design factors impacting solar chimney performance in urban tunnels to optimize ventilation efficiency. Experimental trials analyzed the effects of blockage ratio, chimney height, and solar radiation on temperature distribution and ventilation rate. The results demonstrate that increased chimney height and solar radiation positively influence airflow velocity at the chimney outlet, enhancing ventilation. The temperature rise near absorber is higher than that closed to glazing wall. Temperature distribution within the chimney follows a distinctive horizontal two-piecewise semi-parabolic decay pattern, enabling accurate prediction of temperature profiles along the cavity depth. Novel analytical models predict temperature distribution, airflow velocity, and ventilation rate within the solar chimney system, aiding precise design and optimization. Remarkably, the blockage ratio has limited impact on ventilation rate, allowing for disregarding vehicle blockage effects in solar chimney design for urban tunnels. Matching chimney width to tunnel width and ensuring a relatively high chimney height are emphasized for optimal functionality. The study holds substantial implications for ventilation system design in urban environments, promoting healthier and more sustainable cities
Spatio-temporal modelling of dam deformation using independent component analysis
Modelling dam deformation based on monitoring data plays an important role in the assessment of a dam’s safety. Traditional dam deformation modelling methods generally utilise single monitoring point. It means it is necessary to model for each monitoring point and the spatial correlation between points will not be considered using traditional modelling methods. Spatio-temporal modelling methods provide a way to model the dam deformation with only one functional expression and analyse the stability of dam in its entirety. Independent component analysis (ICA) is a statistical method of blind source separation (BSS) and can separate original signals from mixed observables. In this paper, ICA is introduced as a spatio-temporal modelling method for dam deformation. In this method, the deformation data series of all points were processed using ICA as input signals, and a few output independent signals were used to model. The real data experiment with displacement measurements by wire alignment of Wuqiangxi Dam was conducted and the results show that the output independent signals are correlated with physical responses of causative factors such as temperature and water level respectively. This discovery is beneficial in analysing the dam deformation. In addition, ICA is also an effective dimension reduced method for spatio-temporal modelling in dam deformation analysis applications
The Degasperis-Procesi equation with self-consistent sources
The Degasperis-Procesi equation with self-consistent sources(DPESCS) is
derived. The Lax representation and the conservation laws for DPESCS are
constructed. The peakon solution of DPESCS is obtained.Comment: 15 page
Purification and Characterization of Thermostable Cellulase from Consortium XM70 in Terrestrial Hot Spring with Sugarcane Bagasse
Purpose: To better understand the sugarcane bagasse (SCB) degradation process and obtain thermostable cellulase from terrestrial hot spring.Methods: Molecular community structure of the newly selected thermophilic bacterial consortium XM70 was determined using the method of the full-length 16S rRNA library-based analysis. The thermostable CMCase was purified with ion-exchange and gel filtration chromatography.Results: Sequence-based identification of species belonging to the genera, Geobacillus, Desulfotomaculum, Bacillus, Exiguobacterium, Paenibacillus and Enterobacter were identified. The maximal activities of carboxymethyl cellulase (CMCase), filter paper cellulase and β-glucosidase of the consortium XM70 were obtained after incubation at 60 °C and pH 6.0 (4 days), 80 °C and pH 7.0 (2 days) and 70 °C and pH 8.0 (4 days), respectively. The yield of reducing sugars in the culture broth achieved 0.11 g.g-1 dry SCB. An extracellular CMCase from consortium XM70 (XM70-CMCase) was purified 7.9-fold to apparent homogeneity with a recovery of 65.41 % and its molecular mass was about 31.0 kDa. Maximum CMCase activity of the purified XM70-CMCase was 3.77 U/mg at 70 °C and pH 7.0. CMCase activity maintained about its maximal value of 70 % after incubation at 80 °C for 60 min.Conclusion: Due to its high temperature stability, the purified XM70-CMCase may be useful for industrial application such as biofuel, animal feed industry, paper industry and clarification of fruit juices.Keywords: Thermostable cellulase, Sugarcane bagasse, Purification, Characterization, Hot sprin
- …