A Whole Process Prediction Method for Temperature Field of Fire Smoke in Large Spaces

AbstractBased on the fire development model for the whole process of localized fires in large-space buildings and assisted by the technology of FDS large eddy simulation, the temperature fields of fire smoke of localized fires in large spaces were investigated with different building heights, building areas and fire powers. It has been found that for large-space buildings with a height greater than 6 m and a building area more than 1500 m2, factors like building height and building area can slightly affect the curve trend of fire smoke, while such factor like fire power has more significant influence on the curve trend of fire smoke. Through the analysis of temperature rise curves of fire smoke in various fire scenarios, the paper proposed a whole-process prediction model for the temperature fields of fire smoke of localized fires in large-space buildings. As long as the model uses the appropriate shape coefficient, the prediction model can accurately predict the temperature fields of fire smoke of localized fires in large-space buildings

The electronic structure of intrinsic magnetic topological insulator MnBi2Te4 quantum wires

The ferromagnetic and antiferromagnetic nanostructure are crucial for fundamental spintronics devices, motivated by its potential application in spintronics, we theoretically investigate the electronic structure of the ferromagnetic and antiferromagnetic phases of the cylindrical intrinsically magnetic topological insulator $\mathrm{MnBi_{2}Te_{4}}$ quantum wires for both cases. We demonstrate that a few surface states exist between the bulk band gap in the ferromagnetic phase, with only one spin branch. In the antiferromagnetic phase, we show that three coexistent states exist between the energy gaps of the quantum wires

Missing Lead and High 3He/4He in Ancient Sulfides Associated with Continental Crust Formation

Major terrestrial reservoirs have Pb isotopes more radiogenic than the bulk silicate Earth. This requires a missing unradiogenic Pb reservoir, which has been argued to reside in the lower continental crust or dissolved in the core. Chalcophile element studies indicate that continent formation requires the formation of sulfide-bearing mafic cumulates in arcs. Because Pb, but not U, partitions into sulfides, we show that continent formation must have simultaneously generated time-integrated unradiogenic Pb reservoirs composed of sulfide-bearing cumulates, now recycled back into the mantle or stored deep in the continental lithosphere. The generation of such cumulates could also lead to coupled He-Pb isotopic systematics because 4He is also produced during U-Th-Pb decay. Here, we show that He may be soluble in sulfide melts, such that sulfide-bearing cumulates would be enriched in both Pb and He relative to U and Th, “freezing” in He and Pb isotopes of the ambient mantle at the time of sulfide formation. This implies that ancient sulfide-bearing cumulates would be characterized by unradiogenic Pb and He isotopes (high-3He/4He). These primitive signatures are usually attributed to primordial, undifferentiated mantle, but in this case, they are the very imprint of mantle differentiation via continent formation

Intra-Storm Temporal Patterns of Rainfall in China Using Huff Curves

Intra-storm temporal distributions of precipitation are important for infiltration, runoff, and erosion process understanding and models. A convenient and established method for characterizing precipitation hyetographs is the use of non-dimensional Huff curves. In this study, 11,801 erosive rainfall events with 1 min resolution data collected over 30 to 40 years from 18 weather stations located across the central and eastern parts of China were analyzed to produce Huff curves. Each event was classified according to the quartile period within the event that contained the greatest fraction of rainfall. The results showed that 38.3% of events had the maximum rainfall amounts in the first quartile, followed by the second (26.8%), third (22.4%), and fourth (12.5%) quartiles. Quartile I and II events were generally characteristic of shorter duration and heavier intensity events. Quartile I events averaged 23% shorter durations than quartile IV events, whereas the mean intensity (Iavg), mean maximum 30 min intensity (I30), and mean rainfall erosivity index (EI30) were 1.71, 1.22, and 1.23 times greater, respectively, than those for quartile IV and were significant at a 5% level based on two-sample t-tests. The proportion of quartile I events was less for events of longer duration, whereas the proportions of quartile III and IV events were greater. Two-sample Kolmogorov-Smirnov tests suggested that regional Huff curves can be derived for the central and eastern parts of China. Regional Huff curves developed in this study exhibited dissimilarities in terms of the percentages of storms for different quartiles and the shapes of the curves compared to those reported for Illinois, peninsular Malaysia, and Santa Catarina in Brazil

The Last Stages of Terrestrial Planet Formation: Dynamical Friction and the Late Veneer

The final stage of terrestrial planet formation consists of the cleanup of residual planetesimals after the giant impact phase. Dynamically, a residual planetesimal population is needed to damp the high eccentricities of the terrestrial planets after the giant impact stage. Geochemically, highly siderophile element (HSE) abundance patterns inferred for the terrestrial planets and the Moon suggest that a total of about 0.01 M_Earth of chondritic material was delivered as `late veneer' by planetesimals to the terrestrial planets after the end of giant impacts. Here we combine these two independent lines of evidence for a leftover population of planetesimals and show that: 1) A residual planetesimal population containing 0.01 M_Earth is able to damp the eccentricities of the terrestrial planets after giant impacts to their observed values. 2) At the same time, this planetesimal population can account for the observed relative amounts of late veneer added to the Earth, Moon and Mars provided that the majority of the late veneer was delivered by small planetesimals with radii <10m. These small planetesimal sizes are required to ensure efficient damping of the planetesimal's velocity dispersion by mutual collisions, which in turn ensures that the planets' accretion cross sections are significantly enhanced by gravitational focusing above their geometric values. Specifically we find, in the limit that the relative velocity between the terrestrial planets and the planetesimals is significantly less than the terrestrial planets' escape velocities, that gravitational focusing yields an accretion ratio Earth/Mars~17, which agrees well with the accretion ratio inferred from HSEs of 12-23. For the Earth-Moon system, we find an accretion ratio of ~200, which is consistent with estimates of 150-700 derived from HSE abundances that include the lunar crust as well as mantle component. (Abridged)Comment: accepted for publication in ApJ, 9 pages, 4 figures; minor corrections, additional references adde

Unresolved excess accumulation of myelin-derived cholesterol contributes to scar formation after spinal cord injury

Background: Spinal cord injury triggers complex pathological cascades, resulting in destructive tissue damage and incomplete tissue repair. Scar formation is generally considered as a barrier for regeneration in central nervous system (CNS), while the intrinsic mechanism of scar-forming after spinal cord injury has not been completed deciphered. Methods: We assessed cholesterol hemostasis in spinal cord lesions and injured peripheral nerves using confocal reflection microscopy and real-time PCR analyses. The involvement of the proteins, which were predicted to promote cholesterol efflux in spinal cord lesions, were assessed with Liver X receptor (LXR) agonist and Apolipoprotein E (APOE) deficiency. The role of reverse cholesterol transport (RCT) in cholesterol clearance was examined in APOE KO mice injured sciatic nerves and myelin-overloaded macrophages in vitro. Finally, we determined the consequence of excess cholesterol accumulation in CNS by transplantation of myelin into neonatal spinal cord lesions. Results: We found that excess cholesterol accumulates in phagocytes and is inefficiently removed in spinal cord lesions in young-adult mice. Interestingly, we observed that excessive cholesterol also accumulates in injured peripheral nerves, but is subsequently removed by RCT. Meanwhile, preventing RCT led to macrophage accumulation and fibrosis in injured peripheral nerves. Furthermore, the neonatal mouse spinal cord lesions are devoid of myelin-derived lipids, and able to heal without excess cholesterol accumulation. We found that transplantation of myelin into neonatal lesions disrupts healing with excessive cholesterol accumulation, persistent macrophage activation and fibrosis, indicating myelin-derived cholesterol plays a critical role in impaired wound healing

Mg isotopic heterogeneity, Al-Mg isochrons, and canonical ^(26)Al/^(27)Al in the early solar system

There is variability in the Mg isotopic composition that is a reflection of the widespread heterogeneity in the isotopic composition of the elements in the solar system at approximately 100 ppm. Measurements on a single calcium-aluminum-rich inclusion (CAI) gave a good correlation of ^(26)Mg/^(24)Mg with ^(27)Al/^(24)Mg, yielding an isochron corresponding to an initial (^(26)Al/^(27)Al)_o = (5.27 ± 0.18) × 10^(−5) and an initial (^(26)Mg/^(24)Mg)_o = −0.127 ± 0.032‰ relative to the standard. This isochron is parallel to that obtained by Jacobsen et al. (2008), but is distinctively offset. This demonstrates that there are different initial Mg isotopic compositions in different samples with the same ^(26)Al/^(27)Al. No inference about uniformity/heterogeneity of ^(26)Al/^(27)Al on a macro scale can be based on the initial (^(26)Mg/^(24)Mg)_o values. Different values of ^(26)Al/^(27)Al for samples representing the same point in time would prove heterogeneity of ^(26)Al/^(27)Al. The important issue is whether the bulk solar inventory of ^(26)Al/^(27)Al was approximately 5 × 10^(−5) at some point in the early solar system. We discuss ultra refractory phases of solar type oxygen isotope composition with ^(26)Al/^(27)Al from approximately 5 × 10^(−5) to below 0.2 × 10^(−5). We argue that the real issues are: intrinsic heterogeneity in the parent cloud; mechanism and timing for the later production of ^(16)O-poor material; and the relationship to earlier formed ^(16)O-rich material in the disk. ^(26)Al-free refractories can be produced at a later time by late infall, if there is an adequate heat source, or from original heterogeneities in the placental molecular cloud from which the solar system formed

High prevalence of thalassemia in migrant populations in Guangdong Province, China

BACKGROUND: The objectives of this study were to estimate the prevalence of thalassemia and to analyze the need for public health services for migrant populations in different cities in Guangdong Province, China. METHODS: A cross-sectional survey was conducted in 21 cities of Guangdong Province. Twenty-three types of a- and β-globin gene mutations were detected in a total of 14,230 pregnant women and 14,249 husbands. RESULTS: There was a 16.45% prevalence of thalassemia among the 28,479 individuals, and the prevalences of α-, β-, and combined α-/β- thalassemia were 12.03%, 3.80%, and 0.63%, respectively. Compared with the native city residents in the province, the migrants from within the province and the immigrants from outside the province had lower prevalences of thalassemia, but the prevalence values were >11%. CONCLUSIONS: The prevalence values for thalassemia gene mutations were high in all three population groups studied in Guangdong Province. The results indicate that all segments of the Guangdong population should be screened for thalassemia