263 research outputs found
Orbital orientation evolution of massive binary black holes at the centres of non-spherical galaxies
At the centre of a spherical and kinematically isotropic galaxy, the
orientation of a massive binary black hole (BBH) orbit (i.e., the direction of
the BBH orbital angular momentum) undergoes a random walk. If the stars in a
spherical system have a non-zero total angular momentum, the BBH orbital
orientation evolves towards aligning with the total stellar angular momentum
direction. In this paper, we show that a triaxial galaxy has an
alignment-erasing effect, that is, the alignment of the BBH orientations
towards the galaxy rotation axis can be decreased significantly or erased. We
also show that in a non-rotating axisymmetric galaxy, the BBH orbital
orientation evolves towards the axisymmetric axis and precesses about it in a
retrograde direction. Our results provide a step towards understanding the spin
orientations of the final merged BH (and hence probable orientation of any jet
produced) within its host galaxy, and may help to constrain the recoiling
velocity of the merged BH arose from gravitational wave radiation as well.Comment: 16 pages, 9 figures, MNRAS accepte
Parallel Numerical Simulation of Complex Unsteady Multi-Component Three-Dimensional Flow Field of Nonequilibrium Chemical Reaction
In this paper, the gridless method, which is known for its complete independence of grids, is combined with parallel method to obtain a dynamic parallel multi-component three-dimensional (3D) gridless method to compute the complex unsteady multi-component 3D flow field of nonequilibrium chemical reaction (NCR). Specifically, the flow field was described with a multi-component arbitrary Lagrangian-Eulerian (ALE) control equation, which contains the source term of the chemical reaction. The flow term was decoupled from the chemical reaction term, and the stiff problem of the latter term was solved by time splitting. To control the convective flux in the control equation, the multi-component artificially upstream flux vector splitting (AUFS) scheme was derived for the 3D space. In addition, 3D local point cloud reconstruction was carried out to reconstruct the abnormal point cloud near the large moving boundary in real time. Besides, geometrical zoning was adopted for the parallel part to dynamically balance the computing load across different zones. The message passing interface (MPI) was selected to realize the communication between the zones. After that, the proposed multi-component gridless algorithm was proven accurate through two examples: hydrogen combustion reaction in a vessel, and shock-induced combustion with blunt projectile. Finally, the proposed dynamic parallel multi-component 3D gridless method was applied to compute the 3D muzzle flow field of prefilled serial-connected projectiles. The evolution of the complex flow field was obtained for projectile 2. The parallel efficiency of our method surpassed 79%
Work stress, life stress, and smoking among ruralâurban migrant workers in China
Background
Stimulated by rapid modernization and industrialization, there is massive ruralâurban migration in China. The migrants are highly susceptible to smoking and mental health problems. This study examined the association between both perceived work stress and perceived life stress with smoking behavior among this group during the period of migration. Methods
Participants (nâ=â1,595) were identified through stratified, multi-stage, systematic sampling. Smoking status separated non-smokers from daily and occasional smokers, and migration history, work stress, and life stress were also measured. Analyses were conducted using the Chi-square test and multiple logistic regression. Two models were utilized. The first was the full model that comprised sociodemographic and migration-related characteristics, as well as the two stress variables. In addressing potential overlap between life and work stress, the second model eliminated one of the two stress variables as appropriate. Results
Overall smoking prevalence was 64.9% (95% CI: 62.4-67.2%). In the regression analysis, under the full model, migrants with high perceived life stress showed a 45% excess likelihood to be current smokers relative to low-stress counterparts (OR: 1.45; 95% CI: 1.05 â 2.06). Applying the second model, which excluded the life stress variable, migrants with high perceived work stress had a 75% excess likelihood to be current smokers relative to opposites (OR: 1.75; 95% CI: 1.26â2.45). Conclusions
Ruralâurban migrant workers manifested a high prevalence of both life stress and work stress. While both forms of stress showed associations with current smoking, life stress appeared to outweigh the impact of work stress. Our findings could inform the design of tobacco control programs that would target Chinese ruralâurban migrant workers as a special population
Surface Albedo Variation and Its Influencing Factors over Dongkemadi Glacier, Central Tibetan Plateau
Glacier albedo plays a critical role in surface-atmosphere energy exchange, the variability of which influences glacier mass balance as well as water resources. Dongkemadi glacier in central Tibetan Plateau was selected as study area; this research used field measurements to verify Landsat TM-derived albedo and MOD10A1 albedo product and then analyzed the spatiotemporal variability of albedo over the glacier according to them, as well as its influence factors and the relationship with glacier mass balance. The spatial distribution of glacier albedo in winter did not vary with altitude and was determined by terrain shield, whereas, in summer, albedo increased with altitude and was only influenced by terrain shield at accumulation zone. During 2000â2009, albedo in summer decreased at a rate of 0.0052 per year and was influenced by air temperature and precipitation levels, whereas albedo in winter increased at a rate of 0.0045 per year, influenced by the level and frequency of precipitation. The annual variation of albedo in summer during 2000â2012 has the high relative to that of glacier mass balance measurement, which indicates that glacier albedo in the ablation period can be considered as a proxy for glacier mass balance
High stable and accurate vehicle selection scheme based on federated edge learning in vehicular networks
Federated edge learning (FEEL) technology for vehicular networks is
considered as a promising technology to reduce the computation workload while
keep the privacy of users. In the FEEL system, vehicles upload data to the edge
servers, which train the vehicles' data to update local models and then return
the result to vehicles to avoid sharing the original data. However, the cache
queue in the edge is limited and the channel between edge server and each
vehicle is a time varying wireless channel, which makes a challenge to select a
suitable number of vehicles to upload data to keep a stable cache queue in edge
server and maximize the learning accuracy. Moreover, selecting vehicles with
different resource statuses to update data will affect the total amount of data
involved in training, which further affects the model accuracy. In this paper,
we propose a vehicle selection scheme, which maximizes the learning accuracy
while ensuring the stability of the cache queue, where the statuses of all the
vehicles in the coverage of edge server are taken into account. The performance
of this scheme is evaluated through simulation experiments, which indicates
that our proposed scheme can perform better than the known benchmark scheme.Comment: This paper has been submitted to China Communication
Characterization of bortezomib-adapted I-45 mesothelioma cells
<p>Abstract</p> <p>Background</p> <p>Bortezomib, a proteasome-specific inhibitor, has emerged as a promising cancer therapeutic agent. However, development of resistance to bortezomib may pose a challenge to effective anticancer therapy. Therefore, characterization of cellular mechanisms involved in bortezomib resistance and development of effective strategies to overcome this resistance represent important steps in the advancement of bortezomib-mediated cancer therapy.</p> <p>Results</p> <p>The present study reports the development of I-45-BTZ-R, a bortezomib-resistant cell line, from the bortezomib-sensitive mesothelioma cell line I-45. I-45-BTZ-R cells showed no cross-resistance to the chemotherapeutic drugs cisplatin, 5-fluorouracil, and doxorubicin. Moreover, the bortezomib-adapted I-45-BTZ-R cells had decreased growth kinemics and did not over express proteasome subunit ÎČ5 (PSMB5) as compared to parental I-45 cells. I-45-BTZ-R cells and parental I-45 cells showed similar inhibition of proteasome activity, but I-45-BTZ-R cells exhibited much less accumulation of ubiquitinated proteins following exposure to 40 nm bortezomib. Further studies revealed that relatively low doses of bortezomib did not induce an unfolded protein response (UPR) in the bortezomib-adapted cells, while higher doses induced UPR with concomitant cell death, as evidenced by higher expression of the mitochondrial chaperone protein Bip and the endoplasmic reticulum (ER) stress-related pro-apoptotic protein CHOP. In addition, bortezomib exposure did not induce the accumulation of the pro-apoptotic proteins p53, Mcl-1S, and noxa in the bortezomib-adapted cells.</p> <p>Conclusion</p> <p>These results suggest that UPR evasion, together with reduced pro-apoptotic gene induction, accounts for bortezomib resistance in the bortezomib-adapted mesothelioma cell line I-45-BTZ-R.</p
The asymptotic concentration approach combined with isogeometric analysis for topology optimization of two-dimensional linear elasticity structures
We propose an asymptotic concentration approach combined with isogeometric analysis (IGA) for the topology optimization of two-dimensional (2D) linear elasticity structures under the commonly-used framework of the solid isotropic materials and penalty (SIMP) model. Based on the SIMP framework, the B-splines are used as basis functions to describe geometric model in structural finite element analysis, which closely combines geometric modeling with structural analysis. Isogeometric analysis is utilized to define the geometric characteristics of the 2D linear elasticity structures, which can greatly improve the calculation accuracy. In addition, to eliminate the gray-scale intervals usually caused by the intermediate density in the SIMP approach, we utilize the asymptotic concentration method to concentrate the intermediate density values on either 0 or 1 gradually. Consequently, the intermediate densities representing gray-scale intervals in topology optimization results are sufficiently eliminated by virtue of the asymptotic concentration method. The effectiveness and applicability of the proposed method are illustrated by several typical examples
Charging-free electrochemical system for harvesting low-grade thermal energy
Efficient and low-cost systems are needed to harvest the tremendous amount of energy stored in low-grade heat sources (<100 °C). Thermally regenerative electrochemical cycle (TREC) is an attractive approach which uses the temperature dependence of electrochemical cell voltage to construct a thermodynamic cycle for direct heat-to-electricity conversion. By varying temperature, an electrochemical cell is charged at a lower voltage than discharge, converting thermal energy to electricity. Most TREC systems still require external electricity for charging, which complicates system designs and limits their applications. Here, we demonstrate a charging-free TREC consisting of an inexpensive soluble Fe(CN)[3â/4â over 6] redox pair and solid Prussian blue particles as active materials for the two electrodes. In this system, the spontaneous directions of the full-cell reaction are opposite at low and high temperatures. Therefore, the two electrochemical processes at both low and high temperatures in a cycle are discharge. Heat-to-electricity conversion efficiency of 2.0% can be reached for the TREC operating between 20 and 60 °C. This charging-free TREC system may have potential application for harvesting low-grade heat from the environment, especially in remote areas.United States. Dept. of Energy. Office of Science (Solid-State Solar-Thermal Energy Conversion Center Award DE-SC0001299/DE-FG02-09ER46577)United States. Air Force Office of Scientific ResearchUnited States. Dept. of Energy (EERE Award DE-EE0005806
Effect of liver histopathology on islet cell engraftment in the model mimicking autologous islet cell transplantation
Background: The inflammatory milieu in the liver as determined by histopathology is different in individual patients undergoing autologous islet cell transplantation. We hypothesized that inflammation related to fatty-liver adversely impacts islet survival. To test this hypothesis, we used a mouse model of fatty-liver to determine the outcome of syngeneic islet transplantation after chemical pancreatectomy. Methods: Mice (C57BL/6) were fed a high-fat-diet from 6 weeks of age until attaining a weight of â„28 grams (6â8 weeks) to produce a fatty liver (histologically > 30% fat);steatosis was confirmed with lipidomic profile of liver tissue. Islets were infused via the intra-portal route in fatty-liver and control mice after streptozotocin induction of diabetes. Outcomes were assessed by the rate of euglycemia, liver histopathology, evaluation of liver inflammation by measuring tissue cytokines IL-1ÎČ and TNF-α by RT-PCR and CD31 expression by immunohistochemistry. Results: The difference in the euglycemic fraction between the normal liver group (90%, 9/10) and the fatty-liver group (37.5%, 3/8) was statistically significant at the 18th day post- transplant and was maintained to the end of the study (day 28) (p = 0.019, X2 = 5.51). Levels of TNFâα and IL-1ÎČ were elevated in fatty-liver mice (p = 0.042, p = 0.037). Compared to controls cytokine levels were elevated after islet cell transplantation and in transplanted fatty-liver mice as compared to either fatty- or islet transplant group alone (p = NS). A difference in the histochemical pattern of CD31 could not be determined. Conclusion: Fatty-liver creates an inflammatory state which adversely affects the outcome of autologous islet cell transplantation
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