<strong>Importance:</strong> Corona virus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the pandemic claiming millions of lives since the first outbr...<strong>Importance:</strong> Corona virus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the pandemic claiming millions of lives since the first outbreak was reported in Wuhan, China during December 2019. It is thus important to make cross-country comparison of the relevant rates and understand the socio-demographic risk factors. <strong>Methods: </strong>This is a record based retrospective cohort study. <strong>Table 1</strong> was extracted from <a href="https://www.worldometers.info/coronavirus/" target="_blank">https://www.worldometers.info/coronavirus/</a> and from the Corona virus resource center (<strong>Table 2</strong>, <strong>Figures 1-3</strong>), Johns Hopkins University. Data for <strong>Table 1</strong> includes all countries which reported >1000 cases and <strong>Table 2</strong> includes 20 countries reporting the largest number of deaths. The estimation of CFR, RR and PR of the infection, and disease pattern across geographical clusters in the world is presented. <strong>Results:</strong> From <strong>Table 1</strong>, we could infer that as on 4<sup>th</sup> May 2020, COVID-19 has rapidly spread world-wide with total infections of 3,566,423 and mortality of 248,291. The maximum morbidity is in USA with 1,188,122 cases and 68,598 deaths (CFR 5.77%, RR 15% and PR 16.51%), while Spain is at the second position with 247,122 cases and 25,264 deaths (CFR 13.71%, RR 38.75%, PR 9.78%). <strong>Table 2</strong> depicts the scenario as on 8<sup>th</sup> October 2020, where-in the highest number of confirmed cases occurred in US followed by India and Brazil (cases per million population: 23,080, 5007 & 23,872 respectively). For deaths per million population: US recorded 647, while India and Brazil recorded 77 and 708 respectively. <strong>Conclusion:</strong> Studying the distribution of relevant rates across different geographical clusters plays a major role for measuring the disease burden, which in-turn enables implementation of appropriate public healthcare measures.展开更多
In this paper,a discrete-time SIR epidemic model with nonlinear incidence and recovery rates is obtained by using the forward Euler’s method.The existence and stability of fixed points in this model are well studied....In this paper,a discrete-time SIR epidemic model with nonlinear incidence and recovery rates is obtained by using the forward Euler’s method.The existence and stability of fixed points in this model are well studied.The center manifold theorem and bifurcation theory are applied to analyze the bifurcation properties by using the discrete time step and the intervention level as control parameters.We discuss in detail some codimension-one bifurcations such as transcritical,period-doubling and Neimark–Sacker bifurcations,and a codimension-two bifurcation with 1:2 resonance.In addition,the phase portraits,bifurcation diagrams and maximum Lyapunov exponent diagrams are drawn to verify the correctness of our theoretical analysis.It is found that the numerical results are consistent with the theoretical analysis.More interestingly,we also found other bifurcations in the model during the numerical simulation,such as codimension-two bifurcations with 1:1 resonance,1:3 resonance and 1:4 resonance,generalized period-doubling and fold-flip bifurcations.The results show that the dynamics of the discrete-time model are richer than that of the continuous-time SIR epidemic model.Such a discrete-time model may not only be widely used to detect the pathogenesis of infectious diseases,but also make a great contribution to the prevention and control of infectious diseases.展开更多
In this paper,an extended heterogeneous SIR model is proposed,which generalizes the heterogeneous mean-field theory.Different from the traditional heterogeneous mean-field model only taking into account the heterogene...In this paper,an extended heterogeneous SIR model is proposed,which generalizes the heterogeneous mean-field theory.Different from the traditional heterogeneous mean-field model only taking into account the heterogeneity of degree,our model considers not only the heterogeneity of degree but also the heterogeneity of susceptibility and recovery rates.Then,we analytically study the basic reproductive number and the final epidemic size.Combining with numerical simulations,it is found that the basic reproductive number depends on the mean of distributions of susceptibility and disease course when both of them are independent.If the mean of these two distributions is identical,increasing the variance of susceptibility may block the spread of epidemics,while the corresponding increase in the variance of disease course has little effect on the final epidemic size.It is also shown that positive correlations between individual susceptibility,course of disease and the square of degree make the population more vulnerable to epidemic and avail to the epidemic prevalence,whereas the negative correlations make the population less vulnerable and impede the epidemic prevalence.展开更多
Objective: To examine the reproducibility of HRR in healthy individuals with slow HRR response undergoing routine annual checkups. Method: HRR data (>18 b/min;Group 1 and 18 b/min;Group 2) were analyzed using ...Objective: To examine the reproducibility of HRR in healthy individuals with slow HRR response undergoing routine annual checkups. Method: HRR data (>18 b/min;Group 1 and 18 b/min;Group 2) were analyzed using a fixed-effects regression model adjusted for age and gender, including random effects group-specific slopes on age. Results: One hundred and thirteen individuals (56.5 ± 9.2 y), underwent 573 cumulative ESTs with an average of 5.1 ± 1.6 tests per individual during a 21-year retrospective follow-up. No differences were found in anthropometric measurements and blood variables. All individuals achieved 94% ± 7.7% of age-predicted HR max at peak EST. Group 2 demonstrated 38% of inconsistent HRR. Regression analysis demonstrated a decrease of 0.5 b/min, on average across individuals, in HRR per each extra year of age. The random effects showed an inter-subject SD level of 9.91 b/min and an SD on the age slope of 0.40 b/min/year. Conclusion: HRR showed low reproducibility in nearly 40% of tests, which was not reflected by the variation of HR nor in the slope of age during a 21-year retrospective follow-up.展开更多
Measuring the tanning skin can provide a scientific method to evaluate the efficacy of cosmetics exfoliator.Dihydroxyacetone(DHA,5.0%(w/w))was used to stain the inner forearms cuticle of subjects.The skin surface L*an...Measuring the tanning skin can provide a scientific method to evaluate the efficacy of cosmetics exfoliator.Dihydroxyacetone(DHA,5.0%(w/w))was used to stain the inner forearms cuticle of subjects.The skin surface L*and b*were determined,then ITA and its recovery rate were calculated to evaluate the exfoliating efficacy of cosmetics.The results showed that no significant(P≥0.05)differences were observed for L*,b*and ITA on different skin surface of unstained subjects.After staining with DHA,no adverse reaction was found in the stained areas,and the changes of L*,b*and ITA on different skin surface were consistent(P≥0.05).Two different cosmetics were used continuously to exfoliate the skin in different areas.After treatment for 7 days,the corresponding areas of skin L*,b*and ITA had significant(P<0.05)improvement in comparison with negative control area.But there were differences in the evaluation results of the exfoliation efficacy using these three parameters.The recovery rate of ITA of two samples improved significantly(P<0.05)than the negative control area.The work indicated that using 5.0%DHA for skin browning and measuring the skin surface color change by ITA recovery rate can accurately and sensitively assess the skin cuticle renewal rate difference.This method can be used as one of the effective way to evaluate the efficacy of cosmetics exfoliation.展开更多
To change the undesirable present situation of recovering and using converter gas in steel plants in China, the basic approaches to improving the converter gas recovery rate were analyzed theoretically along with the ...To change the undesirable present situation of recovering and using converter gas in steel plants in China, the basic approaches to improving the converter gas recovery rate were analyzed theoretically along with the change curves of the converter gas component content, based on the converter gas recovery system of Baosteel No. 2 steel- making plant. The effects of converter device, raw material, air imbibed quantity, recovery restricted condition, and intensity of oxygen blowing on the converter gas recovery rate were studied. Among these, the effects of the air im bibed quantity, recovery restricted condition, and intensity of oxygen blowing are remarkable. Comprehensive measures were put forward for improving the converter gas recovery from the point of devices, etc. , and good results were achieved.展开更多
A high-temperature reduction and smelting process was used to recover iron and calcium aluminate slag from high-ferrous bauxite. The effects of w(CaO)/w(SiO_2) ratio, anthracite ratio, and reduction temperature an...A high-temperature reduction and smelting process was used to recover iron and calcium aluminate slag from high-ferrous bauxite. The effects of w(CaO)/w(SiO_2) ratio, anthracite ratio, and reduction temperature and time on the recovery and size of iron nuggets and on the Al_2O_3 grade of the calcium aluminate slag were investigated through thermodynamic calculations and experiments. The optimized process conditions were the bauxite/anthracite/slaked lime weight ratio of 100:16.17:59.37, reduction temperature of 1450°C and reduction time of 20 min. Under these conditions, high-quality iron nuggets and calcium aluminate slag were obtained. The largest size and the highest recovery rate of iron nuggets were 11.42 mm and 92.79wt%, respectively. The calcium aluminate slag mainly comprised Ca_2 SiO_4 and Ca_(12)Al_(14)O_(33), with small amounts of Fe Al_2O_4, CaAl_2O_4, and Ca_2Al_2SiO_7.展开更多
Objective: To examine the autonomic function using HRV measures in apparently healthy individuals undergoing exercise stress test (EST) and demonstrating slow HRR response. Methods: HRV was measured with 12 lead ECGs ...Objective: To examine the autonomic function using HRV measures in apparently healthy individuals undergoing exercise stress test (EST) and demonstrating slow HRR response. Methods: HRV was measured with 12 lead ECGs during graded EST and analyzed via a post-processing method. Autonomic function was determined by Power Spectral Analysis of the very low frequency (VLF), low frequency (LF), high frequency (HF), and the ratio of LF/HF. We correlated HRV indices with resting, exercise, and recovery data. Results: No differences were found in anthropometric measurements, peak EST HR, and METS between individuals with slow HRR (below 18 b/min) compared with controls (HRR > 18 b/min). Only the VLF component of the HRV indices was statistically different (p = 0.03) at one-minute post-exercise compared with controls. Additionally, a significant correlation between HRR and resting LF and HF indices was found in the individuals with slow HRR but not in the controls. Conclusion: In apparently healthy individuals with slow HRR post-EST, autonomic function did not demonstrate any differences at any phase of the EST, including at one minute of recovery. However, a significant correlation was found between resting LF and HF powers and HRR in individuals with slow vagal reactivation post-exercise. The clinical and prognostic implications of such observation deserve further investigation.展开更多
Cattle encephalon glycoside and ignotin(CEGI)injection is a compound preparation formed by a combination of muscle extract from hea lthy rabbits and brain gangliosides from cattle,and it is generally used as a neuropr...Cattle encephalon glycoside and ignotin(CEGI)injection is a compound preparation formed by a combination of muscle extract from hea lthy rabbits and brain gangliosides from cattle,and it is generally used as a neuroprotectant in the treatment of central and peripheral nerve injuries.However,there is still a need for high-level clinical evidence from large samples to support the use of CEGI.We therefore carried out a prospective,multicenter,randomized,double-blind,parallel-group,placebo-controlled study in which we recruited 319 patients with acute cerebral infarction from 16 centers in China from October 2013 to May 2016.The patients were randomized at a 3:1 ratio into CEGI(n=239;155 male,84 female;61.2±9.2 years old)and placebo(n=80;46 male,34 female;63.2±8.28 years old)groups.All patients were given standard care once daily for 14 days,including a 200 mg aspirin enteric-coated tablet and 20 mg atorvastatin calcium,both taken orally,and intravenous infusion of 250–500 mL 0.9%sodium chloride containing 40 mg sodium tanshinone IIA sulfonate.Based on conventional treatment,patients in the CEGI and placebo groups were given 12 mL CEGI or 12 mL sterile water,respectively,in an intravenous drip of 250 mL 0.9%sodium chloride(2 mL/min)once daily for 14 days.According to baseline National Institutes of Health Stroke Scale scores,patients in the two groups were divided into mild and moderate subgroups.Based on the modified Rankin Scale results,the rate of patients with good outcomes in the CEGI group was higher than that in the placebo group,and the rate of disability in the CEGI group was lower than that in the placebo group on day 90 after treatment.In the CEGI group,neurological deficits were decreased on days 14 and 90 after treatment,as measured by the National Institutes of Health Stroke Scale and the Barthel Index.Subgroup analysis revealed that CEGI led to more significant improvements in moderate stroke patients.No drug-related adverse events occurred in the CEGI or placebo groups.In conclusion,CEGI may be a safe and effective treatment for acute cerebral infarction patients,especially for moderate stroke patients.This study was approved by the Ethical Committee of Peking University Third Hospital,China(approval No.2013-068-2)on May 20,2013,and registered in the Chinese Clinical Trial Registry(registration No.ChiCTR1800017937).展开更多
Freeze injury is an usual disaster for winter wheat in Shanxi Province, China, and monitoring freeze injury is of important economic significance. The aim of this article is to monitor and analyze the winter wheat fre...Freeze injury is an usual disaster for winter wheat in Shanxi Province, China, and monitoring freeze injury is of important economic significance. The aim of this article is to monitor and analyze the winter wheat freeze injury using remote sensing data, to monitor the occurrence and spatial distribution of winter wheat freeze in time, as well as the severity of the damage. The winter wheat freeze injury was monitored using multi-temporal moderate-resolution imaging spectroradiometer (MODIS) data, combined with ground meteorological data and field survey data, the change of normalized difference vegetation index (NDVI) before and after freeze injury was analyzed, as well as the effect of winter wheat growth recovery rate on yield. The results showed that the NDVI of winter wheat decreased dramatically after the suffering from freeze injury, which was the prominent feature for the winter wheat freeze injury monitoring. The degrees of winter wheat freeze injury were different in the three regions, of which, Yuncheng was the worst severity and the largest freeze injury area, the severity of freeze injury correlates with the breeding stage of the winter wheat. The yield of winter wheat showed positive correlation with its growth recovery rate (r=0.659^** which can be utilized to monitor the severity of winter wheat freeze injury as well as its impact on yield. It can effectively monitor the occurrence and severity of winter wheat freeze injury using horizontal and vertical profile distribution and growth wheat freeze injury in Shanxi Province. recovery rate, and provide a basis for monitoring the winter展开更多
The dynamics of accumulations of plant dry matter, nutrient uptake and N fertilizer recovery were studied with different water and N supply, using summer maize (Zea mays L. var. Shandan9) as an indicator crop. The tot...The dynamics of accumulations of plant dry matter, nutrient uptake and N fertilizer recovery were studied with different water and N supply, using summer maize (Zea mays L. var. Shandan9) as an indicator crop. The total dry matter (including roots) and N, P, K uptake amounts were continuously increased with plant growth, and their accumulations with time during plant-growing period were shaped in S curves that could be described by exponential regression equations. Differentiating the regression equations fitting the curves over time for first derivatives, the momentary rate was obtained of the dry matter and nutrient uptake. Results show that the dry matter and the nutrient uptake were not in the same rate at all time, but changed from one time to another. Usually, the rate increased rapidly at early stages, and gradually decreased after reaching their peak. Of N, P and K, the uptake rate of N and K was higher, and their increase and decrease were both fast while P was reversed. The time of the maximum absorptive rate appeared earlier for K, followed by N, and then by P. In any case, the maximum nutrient uptake rate appeared earlier than did the dry matter. The momentary N recovery rate was similar in trend to those of dry matter and N uptake, and its maximum recovery rate occurred almost at the same time as its maximum uptake rate. Supplemental irrigation raised the cumulative and momentary rates of N. Although water and N supplies increased dry matter and nutrient uptake rates, they did not alter their changing trends during the plant-growing period.展开更多
China has been the leading country worldwide in direct geothermal utilization for a rather long time, which has contributed significantly to reducing carbon emissions. But the installed capacity of geothermal power ge...China has been the leading country worldwide in direct geothermal utilization for a rather long time, which has contributed significantly to reducing carbon emissions. But the installed capacity of geothermal power generation in China is very small, and there are only a few geothermal power plants in China, specifically in Tibet, including the well-known Yangbajing geothermal power plant. Therefore, it is anticipated that more high-temperature geothermal resources will be discovered in order to promote China’s power generation. There is potential for high-enthalpy geothermal in the Eastern Linqing Depression in Shandong Province, where geothermal energy is stored in Ordovician and Cambrian carbonate strata. Based on the geothermal gradient in Cenozoic strata and the depth of the target geothermal reservoir, the temperature distribution pattern of the reservoir was analyzed, and two "sweet points" were identified in the Yucheng geothermal field and the Guanxian geothermal field, where the reservoir temperature is predicted to be higher than 200°C at a depth of less than 8000 m. Due to the low karst fissure ratio and the insufficient geothermal fluid in the geothermal reservoir, it is recommended that an enhanced geothermal system be set up, to increase the permeability of the natural fracture system in the carbonate formations and provide sufficient fluid for power generation through reinjection of used geothermal fluid. The power generation capacity of the two geothermal fields was estimated using a volumetric method, revealing a power generation capacity of 1621.02 MWe for the Yucheng geothermal field, and 1287.19 MWe for the Guanxian geothermal field.展开更多
BACKGROUND High humidity and temperature in Taiwan have significant effects on the reproductivity of Holstein cattle,resulting in the occurrence of bovine ovarian follicular cyst(OFC).Because of economic loss from OFC...BACKGROUND High humidity and temperature in Taiwan have significant effects on the reproductivity of Holstein cattle,resulting in the occurrence of bovine ovarian follicular cyst(OFC).Because of economic loss from OFC,manual rupture and hormone injection have been advocated for the management of OFC.However,these incomplete treatments increase hormone resistance in cattle.Mesenchymal stem cells(MSCs)derived from placental stem cells(PSCs)demonstrate potential properties for the treatment of several diseases via promoting angiogenesis and immune modulation.AIM To establish the possibility of cattle placental stem cells(CPSCs)as a treatment modality for OFC of cows in Taiwan.METHODS The cows with OFC were divided into three groups:control(BC1 and BC2),hormone(H1 and H2),and CPSC(PS1 and PS2)treatment groups.In the hormone treatment group,the cows were given gonadotrophin-releasing hormone(GnRH)-prostaglandin-GnRH intramuscular injection with or without drainage of follicular fluid.In the CPSC treatment group,CPSCs were isolated from the placenta after labor.With the identification of surface antigen on stem cells,the cows were administered ovarian injection of 1×106 or 6×106 CPSCs with drainage.In all groups,OFC was scanned by ultrasound once a week for a total of seven times.The concentrations of estradiol and progesterone in serum were tested in the same period.The estrus cycle was analyzed by food intake and activity.If estrus was detected,artificial insemination was conducted.Then the cow was monitored by ultrasound for confirmation of pregnancy.RESULTS After 7 d of culture,CPSCs were successfully isolated from placental pieces.CPSCs significantly proliferated every 24 h and had high expression of MSC markers such as cluster of differentiation 44,as determined by flow cytometry.Ultrasound showed lower numbers of OFCs with drainage of follicular fluid.We achieved recovery rates of 0%,50%,50%,75%,75%and 75%in BC1,BC2,H1,H2,PS1,and PS2,respectively.Higher concentrations of progesterone were detected in the CPSC treatment groups.However,both hormone and CPSC treatment groups had no significant difference in the concentration of estradiol.The estrus rate was 0%,100%,25%,75%,75%and 75%in BC1,BC2,H1,H2,PS1,and PS2,respectively.The two fetuses were born in H2 and PS1.In brief,cows with CPSC injection achieved higher recovery,estrus,and inseminated conception rates.CONCLUSION CPSCs have efficacy in treating cows with OFC,and thus,may serve as an alternative treatment for reproductive disorders.展开更多
Can peer-to-peer lending platforms mitigate fraudulent behaviors?Or have lending players been acting similar to free-riders?This paper constructs a new proxy to investigate lending platform misconduct and compares the...Can peer-to-peer lending platforms mitigate fraudulent behaviors?Or have lending players been acting similar to free-riders?This paper constructs a new proxy to investigate lending platform misconduct and compares the FICO score and the LendingClub credit grade.To examine whether the lack of verification by the Fintech platform affects lenders’collection performance,I explore the recovery rate(RR)of non-performing loans through a mixed-continuous model.The regression results show that the degree of prudence taken by the lending platform in the pre-screening activity negatively affects the detection of some misreporting borrowers.I also find that the Fintech platform’s missing verification information(e.g.,annual income and employment length)affects the RR of non-performing loans,thereby hampering lenders’collection performance.展开更多
Copper recovery is the core of waste printed circuit boards (WPCBs) treatment. In this study, we proposed a feasible and efficient way to recover copper from WPCBs concentrated metal scraps by direct electrolysis an...Copper recovery is the core of waste printed circuit boards (WPCBs) treatment. In this study, we proposed a feasible and efficient way to recover copper from WPCBs concentrated metal scraps by direct electrolysis and thctors that affect copper recovery rate and purity, mainly CuSO4.5H2O concentration, NaCI concentration, H2SO4 concentration and current density, were discussed in detail. The results indicated that copper recovery rate increased first with the increase ofCuSO4- 5H2O, NaCI, H2SO4 and current density and then decreased with further increasing these conditions. NaCI, H2SO4 and current density also showed a similar impact on copper purity, which also increased first and then decreased. Copper purity increased with the increase of CuSO4.5H2O. When the concentration of CuSO4-5H2O NaCI and H2oSO4 was respectively 90, 40 and 118 g/L and current density was 80 mA/cm-, copper recovery rate and purity was up to 97.32% and 99.86%, respectively. Thus, electrolysis proposes a feasible and prospective approach for waste printed circuit boards recycle, even for e-waste, though more researches are needed for industrial application.展开更多
To evaluate the values of abnormal heart rate recovery (HRR) after treadmill exercise test in patients with coronary artery disease (CAD). Methods One hundred and seventy-eight consecutive cases of suspected CAD w...To evaluate the values of abnormal heart rate recovery (HRR) after treadmill exercise test in patients with coronary artery disease (CAD). Methods One hundred and seventy-eight consecutive cases of suspected CAD who underwent symptom-limited treadmill exercise test (TET) and coronary angiography (CAG) were enrolled and divided into normal and abnormal HRR group based on the status of the values of HRR one or two minutes after TET. The clinical characteristics, TET parameters and CAG results of the two groups were compared attempted to assess the value of HRR on patients with CAD. Results ( 1 ) The cases of smoking, diabetes mellitus (DM) and ST segment deviation at rest in abnormal HRR group were more significantly than those in normal HRR group ( all P 〈 0. 05 ). (2) The subjects of abnormal HRR usually had higher basal heart rate, more cases exhibited ST segment abnormality and or exercise-limited angina during or after TET(P 〈 0. 01 and P 〈 0. 05, respectively), but lower level of peak heart rate attained ( P 〈 0. 05 ) than those in normal group. The values of metabolism equivalents and duration of TET between the two groups displayed phenomenal difference ( P 〈 0. 05 ). There were more samples acquired moderate to high level of Duke test score and chronotropic incompetence in the group of abnormal HRR, compared to the normal HRR group (P 〈 0. 01 ). (3) The cases of negative CAG results in the group of normal and abnormal HRR group were 73 (66. 97 % ) and 24 (34. 78 % ). Cases of significant coronary lesions ( at least one major coronary vessel ≥ 50 % stenosis) amongst the subgroup of positive CAG were 36 ( 33.03 % ) and 45 (65.22 % ), severe coronary lesions ( three-vessel, left main or the equivalents of left main) were 10 (9. 17 % ) and 17 (24. 64 % ) for normal and abnormal HRR respectively (P 〈 0. 01 ). Accordingly, the Gensini scores in the subunit of abnormal HRR increased. (4)Linear correlation analysis indicate there was a negative correlation between the values of HRR in the first and second minutes and indices of severity of CAD ( all P 〈 0. 01 ). The analysis of auxiliary diagnostic value of abnormal HRR indicated the annexed HRR standard had higher negative predictive value. Conclusions The status of HRR after TET are not only influenced by the clinical factors related to the cardiac autonomic function, but also associated with the extent of CAD. ( S Chin J Cardiol 2009 ; 10(1):1-8)展开更多
In order to recycle the phosphorus from P-bearing steelmaking slag, the influences of magnetic field inten- sities, slag particle sizes and slag compositions were investigated by magnetic separation experiments. SiO2,...In order to recycle the phosphorus from P-bearing steelmaking slag, the influences of magnetic field inten- sities, slag particle sizes and slag compositions were investigated by magnetic separation experiments. SiO2, A1203 and TiO2 melting modification of converter slag was made respectively and phosphorus-rich phase was extracted by magnetic separation. The results show that MgO, MnO, Na2 0 and CaF2 have little effect on the phosphorus recovery, whereas the addition of SiO2, Al2 03, and TiO2 has great effect on phosphorus enrichment in slag and magnetic separation. With adding the reagent of SiO2 Al2 03 and TiO2, recycled non-magnetic substances are increased obviously and P2 05 content in nowmagnetic substances and phosphorus recovery rate are also increased. The phosphorus recovery rates of modified slag No. 8 (SiO2 modification), slag No. 10 (AI2 03 modification) and slag No. 11 (TiO2 modification) are 84.75 %, 82.16 % and 74.46 %, respectively. Then, most of phosphorus was recycled.展开更多
The pre-reduced Bayan Obo ferroniobium(FeNb)ore concentrate block was taken as raw materials for studying the physical properties of niobium-enriched slag and changes in niobium recovery rate.In addition,the dephosp...The pre-reduced Bayan Obo ferroniobium(FeNb)ore concentrate block was taken as raw materials for studying the physical properties of niobium-enriched slag and changes in niobium recovery rate.In addition,the dephosphorization rate of the slag under different melting-separation conditions was investigated using the melting-separation test.The research results demonstrate that(i)the niobium recovery rate and dephosphorization rate of the slag decrease with the increase in melting-separation temperature;(ii)the niobium recovery rate of the slag initially increases and then decreases with increase in basicity and time;and(iii)the dephosphorization rate of the slag increases with the increase in basicity and time.When the test was performed under the conditions of basicity of 0.6-0.7,time of 7-10min,and temperature of 1400-1450°C,the niobium recovery rate and dephosphorization rate are over 96%and 95%,respectively.By scanning electron microscopy,it is observed that niobium mainly exists in the form of calcium and titanium silicate within the slag phase,with uneven distribution.展开更多
Microalgae harvesting remains a challenging step in microalgae industrialization,thereby provoking the necessity to explore sustainable and economically feasible approaches.This research investigated the use of magnet...Microalgae harvesting remains a challenging step in microalgae industrialization,thereby provoking the necessity to explore sustainable and economically feasible approaches.This research investigated the use of magnetic flocculated nanoparticles in the harvesting of the common microalgae Chlorella pyrenoidosa and Scenedesmus obliquus.The results showed that magnetic flocculated nanoparticles efficiently adsorbed negatively charged microalgae cells,and a magnetic field could adsorb the magnetic flocculated nanoparticles,thereby harvesting the microalgae cells.Harvesting efficiency was remarkably increased at the optimum magnetic field strength of 0.5 T with the magnetic flocculated nanoparticles at 0.738 g/L,and microalgae broth at pH 9.0,whereas the recovery rates of both C.pyrenoidosa and S.obliquus were around 97%and the sedimentation speed of both was above 2.63 cm/min.This study exemplified the magnetic flocculated nanoparticles-based approach to effectively harvest the microalgae cells.展开更多
文摘<strong>Importance:</strong> Corona virus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the pandemic claiming millions of lives since the first outbreak was reported in Wuhan, China during December 2019. It is thus important to make cross-country comparison of the relevant rates and understand the socio-demographic risk factors. <strong>Methods: </strong>This is a record based retrospective cohort study. <strong>Table 1</strong> was extracted from <a href="https://www.worldometers.info/coronavirus/" target="_blank">https://www.worldometers.info/coronavirus/</a> and from the Corona virus resource center (<strong>Table 2</strong>, <strong>Figures 1-3</strong>), Johns Hopkins University. Data for <strong>Table 1</strong> includes all countries which reported >1000 cases and <strong>Table 2</strong> includes 20 countries reporting the largest number of deaths. The estimation of CFR, RR and PR of the infection, and disease pattern across geographical clusters in the world is presented. <strong>Results:</strong> From <strong>Table 1</strong>, we could infer that as on 4<sup>th</sup> May 2020, COVID-19 has rapidly spread world-wide with total infections of 3,566,423 and mortality of 248,291. The maximum morbidity is in USA with 1,188,122 cases and 68,598 deaths (CFR 5.77%, RR 15% and PR 16.51%), while Spain is at the second position with 247,122 cases and 25,264 deaths (CFR 13.71%, RR 38.75%, PR 9.78%). <strong>Table 2</strong> depicts the scenario as on 8<sup>th</sup> October 2020, where-in the highest number of confirmed cases occurred in US followed by India and Brazil (cases per million population: 23,080, 5007 & 23,872 respectively). For deaths per million population: US recorded 647, while India and Brazil recorded 77 and 708 respectively. <strong>Conclusion:</strong> Studying the distribution of relevant rates across different geographical clusters plays a major role for measuring the disease burden, which in-turn enables implementation of appropriate public healthcare measures.
基金supported by the NSF of Shandong Province(ZR2021MA016,ZR2019MA034,ZR2018BF018)the China Postdoctoral Science Foundation(2019M652349)the Youth Creative Team Sci-Tech Program of Shandong Universities(2019KJI007).
文摘In this paper,a discrete-time SIR epidemic model with nonlinear incidence and recovery rates is obtained by using the forward Euler’s method.The existence and stability of fixed points in this model are well studied.The center manifold theorem and bifurcation theory are applied to analyze the bifurcation properties by using the discrete time step and the intervention level as control parameters.We discuss in detail some codimension-one bifurcations such as transcritical,period-doubling and Neimark–Sacker bifurcations,and a codimension-two bifurcation with 1:2 resonance.In addition,the phase portraits,bifurcation diagrams and maximum Lyapunov exponent diagrams are drawn to verify the correctness of our theoretical analysis.It is found that the numerical results are consistent with the theoretical analysis.More interestingly,we also found other bifurcations in the model during the numerical simulation,such as codimension-two bifurcations with 1:1 resonance,1:3 resonance and 1:4 resonance,generalized period-doubling and fold-flip bifurcations.The results show that the dynamics of the discrete-time model are richer than that of the continuous-time SIR epidemic model.Such a discrete-time model may not only be widely used to detect the pathogenesis of infectious diseases,but also make a great contribution to the prevention and control of infectious diseases.
基金This work is supported by the National Natural Science Foundation of China under Grant No.11331009The Science and Technology Innovation Team in Shanxi Province No.201605D131044-06。
文摘In this paper,an extended heterogeneous SIR model is proposed,which generalizes the heterogeneous mean-field theory.Different from the traditional heterogeneous mean-field model only taking into account the heterogeneity of degree,our model considers not only the heterogeneity of degree but also the heterogeneity of susceptibility and recovery rates.Then,we analytically study the basic reproductive number and the final epidemic size.Combining with numerical simulations,it is found that the basic reproductive number depends on the mean of distributions of susceptibility and disease course when both of them are independent.If the mean of these two distributions is identical,increasing the variance of susceptibility may block the spread of epidemics,while the corresponding increase in the variance of disease course has little effect on the final epidemic size.It is also shown that positive correlations between individual susceptibility,course of disease and the square of degree make the population more vulnerable to epidemic and avail to the epidemic prevalence,whereas the negative correlations make the population less vulnerable and impede the epidemic prevalence.
文摘Objective: To examine the reproducibility of HRR in healthy individuals with slow HRR response undergoing routine annual checkups. Method: HRR data (>18 b/min;Group 1 and 18 b/min;Group 2) were analyzed using a fixed-effects regression model adjusted for age and gender, including random effects group-specific slopes on age. Results: One hundred and thirteen individuals (56.5 ± 9.2 y), underwent 573 cumulative ESTs with an average of 5.1 ± 1.6 tests per individual during a 21-year retrospective follow-up. No differences were found in anthropometric measurements and blood variables. All individuals achieved 94% ± 7.7% of age-predicted HR max at peak EST. Group 2 demonstrated 38% of inconsistent HRR. Regression analysis demonstrated a decrease of 0.5 b/min, on average across individuals, in HRR per each extra year of age. The random effects showed an inter-subject SD level of 9.91 b/min and an SD on the age slope of 0.40 b/min/year. Conclusion: HRR showed low reproducibility in nearly 40% of tests, which was not reflected by the variation of HR nor in the slope of age during a 21-year retrospective follow-up.
文摘Measuring the tanning skin can provide a scientific method to evaluate the efficacy of cosmetics exfoliator.Dihydroxyacetone(DHA,5.0%(w/w))was used to stain the inner forearms cuticle of subjects.The skin surface L*and b*were determined,then ITA and its recovery rate were calculated to evaluate the exfoliating efficacy of cosmetics.The results showed that no significant(P≥0.05)differences were observed for L*,b*and ITA on different skin surface of unstained subjects.After staining with DHA,no adverse reaction was found in the stained areas,and the changes of L*,b*and ITA on different skin surface were consistent(P≥0.05).Two different cosmetics were used continuously to exfoliate the skin in different areas.After treatment for 7 days,the corresponding areas of skin L*,b*and ITA had significant(P<0.05)improvement in comparison with negative control area.But there were differences in the evaluation results of the exfoliation efficacy using these three parameters.The recovery rate of ITA of two samples improved significantly(P<0.05)than the negative control area.The work indicated that using 5.0%DHA for skin browning and measuring the skin surface color change by ITA recovery rate can accurately and sensitively assess the skin cuticle renewal rate difference.This method can be used as one of the effective way to evaluate the efficacy of cosmetics exfoliation.
基金Item Sponsored by National Natural Science Foundation of China (50334020)
文摘To change the undesirable present situation of recovering and using converter gas in steel plants in China, the basic approaches to improving the converter gas recovery rate were analyzed theoretically along with the change curves of the converter gas component content, based on the converter gas recovery system of Baosteel No. 2 steel- making plant. The effects of converter device, raw material, air imbibed quantity, recovery restricted condition, and intensity of oxygen blowing on the converter gas recovery rate were studied. Among these, the effects of the air im bibed quantity, recovery restricted condition, and intensity of oxygen blowing are remarkable. Comprehensive measures were put forward for improving the converter gas recovery from the point of devices, etc. , and good results were achieved.
基金financially supported by the International Scientific and Technological Cooperation and Exchange Projects of China (No. 2013DFG50640)
文摘A high-temperature reduction and smelting process was used to recover iron and calcium aluminate slag from high-ferrous bauxite. The effects of w(CaO)/w(SiO_2) ratio, anthracite ratio, and reduction temperature and time on the recovery and size of iron nuggets and on the Al_2O_3 grade of the calcium aluminate slag were investigated through thermodynamic calculations and experiments. The optimized process conditions were the bauxite/anthracite/slaked lime weight ratio of 100:16.17:59.37, reduction temperature of 1450°C and reduction time of 20 min. Under these conditions, high-quality iron nuggets and calcium aluminate slag were obtained. The largest size and the highest recovery rate of iron nuggets were 11.42 mm and 92.79wt%, respectively. The calcium aluminate slag mainly comprised Ca_2 SiO_4 and Ca_(12)Al_(14)O_(33), with small amounts of Fe Al_2O_4, CaAl_2O_4, and Ca_2Al_2SiO_7.
文摘Objective: To examine the autonomic function using HRV measures in apparently healthy individuals undergoing exercise stress test (EST) and demonstrating slow HRR response. Methods: HRV was measured with 12 lead ECGs during graded EST and analyzed via a post-processing method. Autonomic function was determined by Power Spectral Analysis of the very low frequency (VLF), low frequency (LF), high frequency (HF), and the ratio of LF/HF. We correlated HRV indices with resting, exercise, and recovery data. Results: No differences were found in anthropometric measurements, peak EST HR, and METS between individuals with slow HRR (below 18 b/min) compared with controls (HRR > 18 b/min). Only the VLF component of the HRV indices was statistically different (p = 0.03) at one-minute post-exercise compared with controls. Additionally, a significant correlation between HRR and resting LF and HF indices was found in the individuals with slow HRR but not in the controls. Conclusion: In apparently healthy individuals with slow HRR post-EST, autonomic function did not demonstrate any differences at any phase of the EST, including at one minute of recovery. However, a significant correlation was found between resting LF and HF powers and HRR in individuals with slow vagal reactivation post-exercise. The clinical and prognostic implications of such observation deserve further investigation.
文摘Cattle encephalon glycoside and ignotin(CEGI)injection is a compound preparation formed by a combination of muscle extract from hea lthy rabbits and brain gangliosides from cattle,and it is generally used as a neuroprotectant in the treatment of central and peripheral nerve injuries.However,there is still a need for high-level clinical evidence from large samples to support the use of CEGI.We therefore carried out a prospective,multicenter,randomized,double-blind,parallel-group,placebo-controlled study in which we recruited 319 patients with acute cerebral infarction from 16 centers in China from October 2013 to May 2016.The patients were randomized at a 3:1 ratio into CEGI(n=239;155 male,84 female;61.2±9.2 years old)and placebo(n=80;46 male,34 female;63.2±8.28 years old)groups.All patients were given standard care once daily for 14 days,including a 200 mg aspirin enteric-coated tablet and 20 mg atorvastatin calcium,both taken orally,and intravenous infusion of 250–500 mL 0.9%sodium chloride containing 40 mg sodium tanshinone IIA sulfonate.Based on conventional treatment,patients in the CEGI and placebo groups were given 12 mL CEGI or 12 mL sterile water,respectively,in an intravenous drip of 250 mL 0.9%sodium chloride(2 mL/min)once daily for 14 days.According to baseline National Institutes of Health Stroke Scale scores,patients in the two groups were divided into mild and moderate subgroups.Based on the modified Rankin Scale results,the rate of patients with good outcomes in the CEGI group was higher than that in the placebo group,and the rate of disability in the CEGI group was lower than that in the placebo group on day 90 after treatment.In the CEGI group,neurological deficits were decreased on days 14 and 90 after treatment,as measured by the National Institutes of Health Stroke Scale and the Barthel Index.Subgroup analysis revealed that CEGI led to more significant improvements in moderate stroke patients.No drug-related adverse events occurred in the CEGI or placebo groups.In conclusion,CEGI may be a safe and effective treatment for acute cerebral infarction patients,especially for moderate stroke patients.This study was approved by the Ethical Committee of Peking University Third Hospital,China(approval No.2013-068-2)on May 20,2013,and registered in the Chinese Clinical Trial Registry(registration No.ChiCTR1800017937).
基金supported by grants from the Key Tech-nologies R&D Program of Shanxi Province, China(20060311140)the Open Project Program of Weather Bureau of Shanxi Province, China (SX053001)
文摘Freeze injury is an usual disaster for winter wheat in Shanxi Province, China, and monitoring freeze injury is of important economic significance. The aim of this article is to monitor and analyze the winter wheat freeze injury using remote sensing data, to monitor the occurrence and spatial distribution of winter wheat freeze in time, as well as the severity of the damage. The winter wheat freeze injury was monitored using multi-temporal moderate-resolution imaging spectroradiometer (MODIS) data, combined with ground meteorological data and field survey data, the change of normalized difference vegetation index (NDVI) before and after freeze injury was analyzed, as well as the effect of winter wheat growth recovery rate on yield. The results showed that the NDVI of winter wheat decreased dramatically after the suffering from freeze injury, which was the prominent feature for the winter wheat freeze injury monitoring. The degrees of winter wheat freeze injury were different in the three regions, of which, Yuncheng was the worst severity and the largest freeze injury area, the severity of freeze injury correlates with the breeding stage of the winter wheat. The yield of winter wheat showed positive correlation with its growth recovery rate (r=0.659^** which can be utilized to monitor the severity of winter wheat freeze injury as well as its impact on yield. It can effectively monitor the occurrence and severity of winter wheat freeze injury using horizontal and vertical profile distribution and growth wheat freeze injury in Shanxi Province. recovery rate, and provide a basis for monitoring the winter
基金the projects(49890330,30230230,30070429 , 40201028) the Nat ional Natural Science Foundation of China(NSFC)+2 种基金 the project(G1999011707)the National Key Basic Research Support Funds(NKBRSF)the opportunity of thanking the NSFC and the NKBRSF for their kindness of supporting such projects.
文摘The dynamics of accumulations of plant dry matter, nutrient uptake and N fertilizer recovery were studied with different water and N supply, using summer maize (Zea mays L. var. Shandan9) as an indicator crop. The total dry matter (including roots) and N, P, K uptake amounts were continuously increased with plant growth, and their accumulations with time during plant-growing period were shaped in S curves that could be described by exponential regression equations. Differentiating the regression equations fitting the curves over time for first derivatives, the momentary rate was obtained of the dry matter and nutrient uptake. Results show that the dry matter and the nutrient uptake were not in the same rate at all time, but changed from one time to another. Usually, the rate increased rapidly at early stages, and gradually decreased after reaching their peak. Of N, P and K, the uptake rate of N and K was higher, and their increase and decrease were both fast while P was reversed. The time of the maximum absorptive rate appeared earlier for K, followed by N, and then by P. In any case, the maximum nutrient uptake rate appeared earlier than did the dry matter. The momentary N recovery rate was similar in trend to those of dry matter and N uptake, and its maximum recovery rate occurred almost at the same time as its maximum uptake rate. Supplemental irrigation raised the cumulative and momentary rates of N. Although water and N supplies increased dry matter and nutrient uptake rates, they did not alter their changing trends during the plant-growing period.
基金supported by the National Natural Science Foundation of China(Grant Nos.U1906209,42072331)。
文摘China has been the leading country worldwide in direct geothermal utilization for a rather long time, which has contributed significantly to reducing carbon emissions. But the installed capacity of geothermal power generation in China is very small, and there are only a few geothermal power plants in China, specifically in Tibet, including the well-known Yangbajing geothermal power plant. Therefore, it is anticipated that more high-temperature geothermal resources will be discovered in order to promote China’s power generation. There is potential for high-enthalpy geothermal in the Eastern Linqing Depression in Shandong Province, where geothermal energy is stored in Ordovician and Cambrian carbonate strata. Based on the geothermal gradient in Cenozoic strata and the depth of the target geothermal reservoir, the temperature distribution pattern of the reservoir was analyzed, and two "sweet points" were identified in the Yucheng geothermal field and the Guanxian geothermal field, where the reservoir temperature is predicted to be higher than 200°C at a depth of less than 8000 m. Due to the low karst fissure ratio and the insufficient geothermal fluid in the geothermal reservoir, it is recommended that an enhanced geothermal system be set up, to increase the permeability of the natural fracture system in the carbonate formations and provide sufficient fluid for power generation through reinjection of used geothermal fluid. The power generation capacity of the two geothermal fields was estimated using a volumetric method, revealing a power generation capacity of 1621.02 MWe for the Yucheng geothermal field, and 1287.19 MWe for the Guanxian geothermal field.
文摘BACKGROUND High humidity and temperature in Taiwan have significant effects on the reproductivity of Holstein cattle,resulting in the occurrence of bovine ovarian follicular cyst(OFC).Because of economic loss from OFC,manual rupture and hormone injection have been advocated for the management of OFC.However,these incomplete treatments increase hormone resistance in cattle.Mesenchymal stem cells(MSCs)derived from placental stem cells(PSCs)demonstrate potential properties for the treatment of several diseases via promoting angiogenesis and immune modulation.AIM To establish the possibility of cattle placental stem cells(CPSCs)as a treatment modality for OFC of cows in Taiwan.METHODS The cows with OFC were divided into three groups:control(BC1 and BC2),hormone(H1 and H2),and CPSC(PS1 and PS2)treatment groups.In the hormone treatment group,the cows were given gonadotrophin-releasing hormone(GnRH)-prostaglandin-GnRH intramuscular injection with or without drainage of follicular fluid.In the CPSC treatment group,CPSCs were isolated from the placenta after labor.With the identification of surface antigen on stem cells,the cows were administered ovarian injection of 1×106 or 6×106 CPSCs with drainage.In all groups,OFC was scanned by ultrasound once a week for a total of seven times.The concentrations of estradiol and progesterone in serum were tested in the same period.The estrus cycle was analyzed by food intake and activity.If estrus was detected,artificial insemination was conducted.Then the cow was monitored by ultrasound for confirmation of pregnancy.RESULTS After 7 d of culture,CPSCs were successfully isolated from placental pieces.CPSCs significantly proliferated every 24 h and had high expression of MSC markers such as cluster of differentiation 44,as determined by flow cytometry.Ultrasound showed lower numbers of OFCs with drainage of follicular fluid.We achieved recovery rates of 0%,50%,50%,75%,75%and 75%in BC1,BC2,H1,H2,PS1,and PS2,respectively.Higher concentrations of progesterone were detected in the CPSC treatment groups.However,both hormone and CPSC treatment groups had no significant difference in the concentration of estradiol.The estrus rate was 0%,100%,25%,75%,75%and 75%in BC1,BC2,H1,H2,PS1,and PS2,respectively.The two fetuses were born in H2 and PS1.In brief,cows with CPSC injection achieved higher recovery,estrus,and inseminated conception rates.CONCLUSION CPSCs have efficacy in treating cows with OFC,and thus,may serve as an alternative treatment for reproductive disorders.
文摘Can peer-to-peer lending platforms mitigate fraudulent behaviors?Or have lending players been acting similar to free-riders?This paper constructs a new proxy to investigate lending platform misconduct and compares the FICO score and the LendingClub credit grade.To examine whether the lack of verification by the Fintech platform affects lenders’collection performance,I explore the recovery rate(RR)of non-performing loans through a mixed-continuous model.The regression results show that the degree of prudence taken by the lending platform in the pre-screening activity negatively affects the detection of some misreporting borrowers.I also find that the Fintech platform’s missing verification information(e.g.,annual income and employment length)affects the RR of non-performing loans,thereby hampering lenders’collection performance.
文摘Copper recovery is the core of waste printed circuit boards (WPCBs) treatment. In this study, we proposed a feasible and efficient way to recover copper from WPCBs concentrated metal scraps by direct electrolysis and thctors that affect copper recovery rate and purity, mainly CuSO4.5H2O concentration, NaCI concentration, H2SO4 concentration and current density, were discussed in detail. The results indicated that copper recovery rate increased first with the increase ofCuSO4- 5H2O, NaCI, H2SO4 and current density and then decreased with further increasing these conditions. NaCI, H2SO4 and current density also showed a similar impact on copper purity, which also increased first and then decreased. Copper purity increased with the increase of CuSO4.5H2O. When the concentration of CuSO4-5H2O NaCI and H2oSO4 was respectively 90, 40 and 118 g/L and current density was 80 mA/cm-, copper recovery rate and purity was up to 97.32% and 99.86%, respectively. Thus, electrolysis proposes a feasible and prospective approach for waste printed circuit boards recycle, even for e-waste, though more researches are needed for industrial application.
文摘To evaluate the values of abnormal heart rate recovery (HRR) after treadmill exercise test in patients with coronary artery disease (CAD). Methods One hundred and seventy-eight consecutive cases of suspected CAD who underwent symptom-limited treadmill exercise test (TET) and coronary angiography (CAG) were enrolled and divided into normal and abnormal HRR group based on the status of the values of HRR one or two minutes after TET. The clinical characteristics, TET parameters and CAG results of the two groups were compared attempted to assess the value of HRR on patients with CAD. Results ( 1 ) The cases of smoking, diabetes mellitus (DM) and ST segment deviation at rest in abnormal HRR group were more significantly than those in normal HRR group ( all P 〈 0. 05 ). (2) The subjects of abnormal HRR usually had higher basal heart rate, more cases exhibited ST segment abnormality and or exercise-limited angina during or after TET(P 〈 0. 01 and P 〈 0. 05, respectively), but lower level of peak heart rate attained ( P 〈 0. 05 ) than those in normal group. The values of metabolism equivalents and duration of TET between the two groups displayed phenomenal difference ( P 〈 0. 05 ). There were more samples acquired moderate to high level of Duke test score and chronotropic incompetence in the group of abnormal HRR, compared to the normal HRR group (P 〈 0. 01 ). (3) The cases of negative CAG results in the group of normal and abnormal HRR group were 73 (66. 97 % ) and 24 (34. 78 % ). Cases of significant coronary lesions ( at least one major coronary vessel ≥ 50 % stenosis) amongst the subgroup of positive CAG were 36 ( 33.03 % ) and 45 (65.22 % ), severe coronary lesions ( three-vessel, left main or the equivalents of left main) were 10 (9. 17 % ) and 17 (24. 64 % ) for normal and abnormal HRR respectively (P 〈 0. 01 ). Accordingly, the Gensini scores in the subunit of abnormal HRR increased. (4)Linear correlation analysis indicate there was a negative correlation between the values of HRR in the first and second minutes and indices of severity of CAD ( all P 〈 0. 01 ). The analysis of auxiliary diagnostic value of abnormal HRR indicated the annexed HRR standard had higher negative predictive value. Conclusions The status of HRR after TET are not only influenced by the clinical factors related to the cardiac autonomic function, but also associated with the extent of CAD. ( S Chin J Cardiol 2009 ; 10(1):1-8)
文摘In order to recycle the phosphorus from P-bearing steelmaking slag, the influences of magnetic field inten- sities, slag particle sizes and slag compositions were investigated by magnetic separation experiments. SiO2, A1203 and TiO2 melting modification of converter slag was made respectively and phosphorus-rich phase was extracted by magnetic separation. The results show that MgO, MnO, Na2 0 and CaF2 have little effect on the phosphorus recovery, whereas the addition of SiO2, Al2 03, and TiO2 has great effect on phosphorus enrichment in slag and magnetic separation. With adding the reagent of SiO2 Al2 03 and TiO2, recycled non-magnetic substances are increased obviously and P2 05 content in nowmagnetic substances and phosphorus recovery rate are also increased. The phosphorus recovery rates of modified slag No. 8 (SiO2 modification), slag No. 10 (AI2 03 modification) and slag No. 11 (TiO2 modification) are 84.75 %, 82.16 % and 74.46 %, respectively. Then, most of phosphorus was recycled.
基金financially supported by the National Science and Technology Support Program (2008BAB32087)
文摘The pre-reduced Bayan Obo ferroniobium(FeNb)ore concentrate block was taken as raw materials for studying the physical properties of niobium-enriched slag and changes in niobium recovery rate.In addition,the dephosphorization rate of the slag under different melting-separation conditions was investigated using the melting-separation test.The research results demonstrate that(i)the niobium recovery rate and dephosphorization rate of the slag decrease with the increase in melting-separation temperature;(ii)the niobium recovery rate of the slag initially increases and then decreases with increase in basicity and time;and(iii)the dephosphorization rate of the slag increases with the increase in basicity and time.When the test was performed under the conditions of basicity of 0.6-0.7,time of 7-10min,and temperature of 1400-1450°C,the niobium recovery rate and dephosphorization rate are over 96%and 95%,respectively.By scanning electron microscopy,it is observed that niobium mainly exists in the form of calcium and titanium silicate within the slag phase,with uneven distribution.
基金supported by the Guangdong Basic and Applied Basis Research Foundation(Grant No.2019B 1515120062).
文摘Microalgae harvesting remains a challenging step in microalgae industrialization,thereby provoking the necessity to explore sustainable and economically feasible approaches.This research investigated the use of magnetic flocculated nanoparticles in the harvesting of the common microalgae Chlorella pyrenoidosa and Scenedesmus obliquus.The results showed that magnetic flocculated nanoparticles efficiently adsorbed negatively charged microalgae cells,and a magnetic field could adsorb the magnetic flocculated nanoparticles,thereby harvesting the microalgae cells.Harvesting efficiency was remarkably increased at the optimum magnetic field strength of 0.5 T with the magnetic flocculated nanoparticles at 0.738 g/L,and microalgae broth at pH 9.0,whereas the recovery rates of both C.pyrenoidosa and S.obliquus were around 97%and the sedimentation speed of both was above 2.63 cm/min.This study exemplified the magnetic flocculated nanoparticles-based approach to effectively harvest the microalgae cells.