Although micrites (abiotic limestone) and thrombolites (typical biotic limestone), according to the sedimentation and biological action, can be primarily distinguished from intuitively field ...observation and rock slices analysis. However, further analysis of thermal decomposition unique characteristics to distinguish them has rarely been reported. Here, the comparative studies of thermal decomposition behavior between micrites and thrombolites were carefully investigated using thermogravimetric analyzer in nitrogen atmosphere at multi-heating rates of 5, 10, 20 and 30 K min
−1
from 323.15 to 1273.15 K. Moreover, the mineralogical compositions were both analyzed by powder X-ray diffraction followed by the results of calcite acting as the basic constituent for further verified. The kinetic model function and kinetic parameters were calculated by Flynn–Wall–Ozawa, Kissinger–Akahira–Sunose and Popescu methods, respectively. The results showed that the kinetic parameter activation energy (
E
) of thrombolites was obviously higher than that of micrites, which suggests the former have a higher crystallinity. In addition, the results of difference significance analysis showed extremely significant differences (
P
< 0.01) via statistical analysis using SPSS v19.0 for the
E
values between micrites and thrombolites calculated by different methods. These above results further confirmed that the thermal stability and crystallinity of thrombolites were obviously higher under the inducing effects by typical microorganisms. This provided very important useful information for understanding the mechanisms of abiotic and biotic limestones formed in nature; in particular, the thermal analysis of thrombolites maybe also provides an important guiding significance for both indoor and outdoor similar studies.
A key problem of how to distinguish between biotic and abiotic carbonate minerals in nature and/or in the laboratory has confused researchers for some time. Although numerous studies have been ...performed to explore the formation mechanism and the unique characteristics of biotic minerals, the issue needs to be studied further. Here, biotic calcite precipitation was induced by the microorganism Bacillus cereus MRR2 (GenBank KY810857), while organogenic and inorganogenic calcite was investigated in parallel. The results indicate that carbonic anhydrase (CA, a common enzyme of bacteria) promoted carbon dioxide hydration to release HCO3− and CO32− in the process of calcite precipitation; the pH increased from 7.2 to 8.9 as a result of the combination effect of the released ammonia by B. cereus MRR2 and the HCO3− and CO32− ions originating from the CA reaction. Glutamic acid is the most abundant amino acid in the extracellular polymeric substances of the bacteria, and its free carboxyl ions with a large number of negative charges in the alkaline environment facilitated the adsorption of calcium ions. The biotic calcite has a series of unique characteristics different from the organogenic and inorganogenic calcites, such as particular morphologies, P element composition and a variety of organic functional groups. Intracellular amorphous nanospheres without any crystal structure are also recorded. Stable carbon isotope analyses show that the biotic calcite (−20.9‰) has more negative δ13C values than the organogenic calcite (−15.6‰) and inorganogenic calcite (−11.7‰), indicating that microbial activity strongly affected the carbon isotope composition of biotic calcite. More importantly, the crystallinity and activation energy of the biotic calcite are clearly higher than those of organogenic calcite, suggesting that the thermal stability of biotic calcite is much higher. Thus, this study provides important insights into understanding the mechanisms of microbial biomineralization and the processes of biotic calcite formation, especially the roles microbes played in mineral nucleation and growth, as well as the unique characteristics of the resulting minerals. This study may provide useful evidence for further recognizing biotic and abiotic calcite in the geological record.
The model of biotic, organogenic and inorganogenic calcite. Display omitted
•The pH increase is caused by the combination effect of ammonia and CA.•Biotic calcite has higher thermal stability than abiotic calcite.•Biotic calcite has more negative δ13C values than abiotic calcite.•Glutamic acid is the most abundant amino acid in EPS.•The intracellular amorphous nanospheres are found.
Keywords Biomineralization; Bacillus cereus; Biotic calcite; Crystallinity; TG-DTG-DSC; Amino acid Highlights * The pH increase is caused by the combination effect of ammonia and CA. * Biotic calcite ...has higher thermal stability than abiotic calcite. * Biotic calcite has more negative delta.sup.13C values than abiotic calcite. * Glutamic acid is the most abundant amino acid in EPS. * The intracellular amorphous nanospheres are found. A key problem of how to distinguish between biotic and abiotic carbonate minerals in nature and/or in the laboratory has confused researchers for some time. Although numerous studies have been performed to explore the formation mechanism and the unique characteristics of biotic minerals, the issue needs to be studied further. Here, biotic calcite precipitation was induced by the microorganism Bacillus cereus MRR2 (GenBank KY810857), while organogenic and inorganogenic calcite was investigated in parallel. The results indicate that carbonic anhydrase (CA, a common enzyme of bacteria) promoted carbon dioxide hydration to release HCO.sub.3.sup.- and CO.sub.3.sup.2- in the process of calcite precipitation; the pH increased from 7.2 to 8.9 as a result of the combination effect of the released ammonia by B. cereus MRR2 and the HCO.sub.3.sup.- and CO.sub.3.sup.2- ions originating from the CA reaction. Glutamic acid is the most abundant amino acid in the extracellular polymeric substances of the bacteria, and its free carboxyl ions with a large number of negative charges in the alkaline environment facilitated the adsorption of calcium ions. The biotic calcite has a series of unique characteristics different from the organogenic and inorganogenic calcites, such as particular morphologies, P element composition and a variety of organic functional groups. Intracellular amorphous nanospheres without any crystal structure are also recorded. Stable carbon isotope analyses show that the biotic calcite (-20.90/00) has more negative delta.sup.13C values than the organogenic calcite (-15.60/00) and inorganogenic calcite (-11.70/00), indicating that microbial activity strongly affected the carbon isotope composition of biotic calcite. More importantly, the crystallinity and activation energy of the biotic calcite are clearly higher than those of organogenic calcite, suggesting that the thermal stability of biotic calcite is much higher. Thus, this study provides important insights into understanding the mechanisms of microbial biomineralization and the processes of biotic calcite formation, especially the roles microbes played in mineral nucleation and growth, as well as the unique characteristics of the resulting minerals. This study may provide useful evidence for further recognizing biotic and abiotic calcite in the geological record. Author Affiliation: (a) Shandong Provincial Key Laboratory of Depositional Mineralization and Sedimentary Minerals, College of Earth Science and Engineering, University Hospital, Shandong University of Science and Technology, Qingdao 266590, China (b) Laboratory for Marine Mineral Resources, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266237, China (c) Department of Bioengineering, College of Chemical and Environmental Engineering, Shandong University of Science and Technology, Qingdao 266590, China. (d) School of Earth Sciences, University of Bristol, Bristol BS8 1RJ, UK (e) Cabot Institute, University of Bristol, Cantock's Close, Bristol BS8 1UJ, UK * Corresponding authors at: Shandong Provincial Key Laboratory of Depositional Mineralization and Sedimentary Minerals, College of Earth Science and Engineering (Zuozhen Han); College of Chemical and Environmental Engineering (Hui Zhao), Shandong University of Science and Technology, Qingdao 266590, China. Article History: Received 28 April 2018; Revised 7 September 2018; Accepted 11 September 2018 (miscellaneous) Editor: Dong Hailiang (footnote)1 Dingxiang Zhuang and Huaxiao Yan contributed equally to this work and are considered as co-first authors. Byline: Dingxiang Zhuang (a,b,1), Huaxiao Yan (a,c,1), Maurice E. Tucker (d,e), Hui Zhao zhsdust@126.com (a,c,*), Zuozhen Han hanzuozhen65@126.com (a,b,*), Yanhong Zhao (a), Bin Sun (a,b), Dan Li (a,b), Juntong Pan (b,c), Yanyang Zhao (a,b), Ruirui Meng (a,b), Guanghe Shan (b,c), Xinkang Zhang (a,b), Rongzhen Tang (a,b)
With the advancement in the developmental project on the lower reaches of the Yarlung Tsangpo River, the influence of the plateau climate environment on the performance of a hydro-generator has ...received more and more attention from researchers. This study numerically simulated the thermal field of a hydro-generator with a 20 MW capacity under the effect of a plateau climate. Ambient pressure and temperature are two main factors that affect the temperature distribution of the generator. In addition, temperature distributions with different speeds are also studied under a plateau climate. The results show that the generator temperature decreases with increasing air pressure and speed. The generator temperature increases linearly with increasing ambient temperature. Among them, when the pressure lies in the range of 25–85 kPa, the temperature change gradient of the stator structure is very large. The temperature difference gradually decreases with the increase in air pressure. The temperature gradient gradually slows down when the air pressure is above 85 kPa. When the pressure is located at 55–85 kPa, the average temperature difference of the stator windings is 6.325 °C, and the average temperature difference of the stator core is 3.815 °C. Finally, the temperature distribution pattern can provide a basis for staff in different barometric pressure regions. It can also improve the safety and reliability of the hydro-generator under the effect of a plateau climate, which is important for improving its integrated hydraulic performance.
The motor temperature distribution characteristics help to understand the working condition of the unit, thus improving efficiency. Currently, the motors are gradually being used at high altitudes. ...However, the plateau region has low air pressure, thin air and large differences in humidity. There is a lack of research on the effect of its complex and special working environment on motor temperature. Therefore, in this study, the numerical analysis of the motor temperature field is carried out from the novel perspective of plateau characteristics. In this paper, the finite volume method is used to analyse the flow-heat-solid coupling of a 20 MW motor. By comparing and verifying the experimental data with the simulation data, it is found that the error between the two is within 5 %. In order to have a more comprehensive picture of the motor's operation in the plateau environment, the temperature effects of different air pressure, air intake and relative humidity on the motor were investigated. The results of the study show that air pressure changes have a large effect on the temperature of the stator structure. The temperature decreases when the air pressure increases and the temperature difference decreases gradually with the increase of air pressure. The largest temperature difference in the stator structure occurs when the air pressure increases from 10 kPa to 40 kPa. The change in air intake has a positive effect on the stator structure temperature, which decreases when the air intake increases. After simulation calculations, it was found that the best heat dissipation effect was achieved in the range of air intake between 3.5 m/s and 4.5 m/s. Relative humidity has a minimal effect on the stator structure temperature. The conclusions of this paper can provide certain theoretical reference for the temperature change law of the motor under plateau operation, which is of great significance to improve the comprehensive hydraulic performance.
A simple and convenient method was used to prepare a novel granular half wrapping-structured amendment (HWA) for stabilization of both cationic and anionic heavy metals. By coating Ca(OH)2 with ...silicate minerals to obtain the core-coating wrapping balls, followed by drying and mixing with FeSO4, the final HWA effectively prevented the reaction of FeSO4 with Ca(OH)2 and exihibited high stabilization of arsenic (As) and cadmium (Cd) in the contaminated soils simultaneously and continuously. XRD, FTIR and SEM characterization showed that Ca(OH)2 was successfully wrapped by zeolite without changing their chemical properties. The amendment illustrated relatively fast stabilization for As and Cd, and the stabilization rate by HMA prepared at FeSO4·7H2O: zeolite: Ca(OH)2 = 6.5:1:1 was 95.5% for As and 94.6% for Cd, much higher than the compound material (CM) which had side effect on Cd stabilization. In the effect of storage time experiment, when HWA was stored from 0 day to 365 days, the stabilization rate of As and Cd by HWA just decreased 3.4% and 4.3%, respectively. While the addition of CM to the soil reduced the As stabilization rate from 91.1% to 87.1% and the Cd stabilization rate was reduced from −139.8% to −223.1%. The long-term soil stabilization study demonstrated that HWA could decrease the concentration of extricable As and Cd simultaneously and continuously for 365 days without notable changes in soil pH. This research develops an easy method to synthesize granular HWA for the stabilization of cationic and anionic heavy metals from the actual contaminated soils.
Display omitted
•HWA is prepared by a novel half wrapping technique.•HWA exhibits enhanced high stabilization rate for both As and Cd.•HWA keeps high stabilization ability when stored up to 365 days.•HWA can stabilize As and Cd simultaneously and continuously for a year.
This study focuses on the splitter blade pump–turbine as the research object to analyze the problems of hump characteristics and the hysteresis effect. We simulated the operation of the pump ...condition with small opening of the guide vane, analyzed the hydraulic loss by using the entropy production theory and entropy wall function, and investigated the study of internal flow transfer characteristics. In this paper, it was first verified that the maximum error of the energy loss calculated by the pressure method and the entropy production method was less than 6% for the working zone. From the quantified energy loss results, a significant instability feature was observed in the 0.65 QBEP–0.9 QBEP operating interval, accompanied by the phenomenon of the non-overlapping of the characteristic curves. The results show that the hump characteristic with hysteresis effect also exists in the splitter blade pump–turbine. The percentage of energy loss in the hump zone is in descending order of runner, guide vanes, spiral casing, and draft tube, but this changes again at low flow rates. By analyzing the high-entropy production region, it was found that the high-hydraulic-loss region is mainly distributed at the trailing edge of the long blade in the vane-less space, which is different from the traditional runner.
Background:
Although many risk prediction models have been released internationally, the application of these models in the Chinese population still has some limitations.
Aims:
The purpose of the ...study was to establish a heart failure (HF) prognosis model suitable for the Chinese population.
Methods:
According to the inclusion criteria, we included patients with chronic heart failure (CHF) who were admitted to the Department of Cardiac Rehabilitation of Tongji Hospital from March 2007 to December 2018, recorded each patient's condition and followed up on the patient's re-admission and death. All data sets were randomly divided into derivation and validation cohorts in a ratio of 7/3. Least absolute shrinkage and selection operator regression and Cox regression were used to screen independent predictors; a nomogram chart scoring model was constructed and validated.
Results:
A total of 547 patients were recruited in this cohort, and the median follow-up time was 519 days. The independent predictors screened out by the derivation cohort included age, atrial fibrillation (AF), percutaneous coronary intervention (PCI), diabetes mellitus (DM), peak oxygen uptake (peak VO
2
), heart rate at the 8th minute after the cardiopulmonary exercise peaked (HR8min), C-reaction protein(CRP), and uric acid (UA). The C indexes values of the derivation and the validation cohorts were 0.69 and 0.62, respectively, and the calibration curves indicate that the model's predictions were in good agreement with the actual observations.
Conclusions:
We have developed and validated a multiple Cox regression model to predict long-term mortality and readmission risk of Chinese patients with CHF.
Registration Number:
ChicTR-TRC-00000235.
In offline reinforcement learning (RL), the performance of the learned policy highly depends on the quality of offline datasets. However, in many cases, the offline dataset contains very limited ...optimal trajectories, which poses a challenge for offline RL algorithms as agents must acquire the ability to transit to high-reward regions. To address this issue, we introduce Diffusion-based Trajectory Stitching (DiffStitch), a novel diffusion-based data augmentation pipeline that systematically generates stitching transitions between trajectories. DiffStitch effectively connects low-reward trajectories with high-reward trajectories, forming globally optimal trajectories to address the challenges faced by offline RL algorithms. Empirical experiments conducted on D4RL datasets demonstrate the effectiveness of DiffStitch across RL methodologies. Notably, DiffStitch demonstrates substantial enhancements in the performance of one-step methods (IQL), imitation learning methods (TD3+BC), and trajectory optimization methods (DT).
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