Mass transfer enhancement and hydrodynamic performance with wire mesh coupling solid particles in bubble column reactor

It is of vital significance to investigate mass transfer enhancements for chemical engineering processes.This work focuses on investigating the coupling influence of embedding wire mesh and adding solid particles on bubble motion and gas-liquid mass transfer process in a bubble column.Particle image velocimetry(PIV)technology was employed to analyze the flow field and bubble motion behavior,and dynamic oxygen absorption technology was used to measure the gas-liquid volumetric mass transfer coefficient(kLa).The effect of embedding wire mesh,adding solid particles,and wire mesh coupling solid particles on the flow characteristic and kLa were analyzed and compared.The results show that the gas-liquid interface area increases by 33%-72%when using the wire mesh coupling solid particles strategy compared to the gas-liquid two-phase flow,which is superior to the other two strengthening methods.Compared with the system without reinforcement,kLa in the bubble column increased by 0.5-1.8 times with wire mesh coupling solid particles method,which is higher than the sum of kLa increases with inserting wire mesh and adding particles,and the coupling reinforcement mechanism for affecting gas-liquid mass transfer process was discussed to provide a new idea for enhancing gas-liquid mass transfer.

One-step preparation of efficient cuprous chloride catalyst for direct synthesis of trimethoxysilane

CuCl-based catalysts are the most commonly used catalysts for the“direct synthesis”of trimethoxysilane(M3).CuCl species are sensitive to air and water,and are prone to oxidation deactivation.When CuCl is directly used as a catalyst,it needs to be purified before the utilization,and the operating conditions for the catalyst preparation are relatively harsh,requiring the inert gas environment.Considering a high-temperature activation step required for CuCl-based catalysts used for catalyzing synthesis of M3 to form active phase Cu–Si alloys(Cu_(x)Si)with Si powder,in this work,a series of catalysts for the“direct synthesis”of M3 were obtained by a one-step high-temperature activation of the mixture of stable CuCl_(2) precursors,activated carbon-reducing agent,and Si powder,simultaneously achieving the reduction of CuCl_(2) to CuCl and the formation of active phase Cu_(x)Si alloys of CuCl with Si powder.The prepared samples were characterized through various characterization techniques,and investigated for the catalytic performance for the“direct synthesis”of M3.Moreover,the operation conditions were optimized,including the activation temperature,catalyst dosage,Si powder particle size,and reaction temperature.The characterization results indicate that during the one-step activation process,the CuCl_(2) precursor is reduced to CuCl,and the resulting CuCl simultaneously reacts with Si powder to form active phases Cu3Si and Cu15Si4 alloys.The optimal catalyst Sacm(250,0.8:10)exhibits a good catalytic activity with selectivity of 95%and yield of 77%for M3,and shows a good universality for various alcohol substrates.Furthermore,the catalytic mechanism of the prepared catalyst for the“direct synthesis”of M3 was discussed.

Desertification dynamic and the relative roles of climate change and human activities in desertification in the Heihe River Basin based on NPP

Relative roles of climate change and human activities in desertification are the hotspot of research on desertification dynamic and its driving mechanism.To overcome the shortcomings of existing studies,this paper selected net primary productivity （NPP） as an indicator to analyze desertification dynamic and its impact factors.In addition,the change trends of actual NPP,potential NPP and HNPP （human appropriation of NPP,the difference between potential NPP and actual NPP） were used to analyze the desertification dynamic and calculate the relative roles of climate change,human activities and a combination of the two factors in desertification.In this study,the Moderate Resolution Imaging Spectroradiometer （MODIS）-Normalised Difference Vegetation Index （NDVI） and meteorological data were utilized to drive the Carnegie-Ames-Stanford Approach （CASA） model to calculate the actual NPP from 2001 to 2010 in the Heihe River Basin.Potential NPP was estimated using the Thornthwaite Memorial model.Results showed that 61％ of the whole basin area underwent land degradation,of which 90.5％ was caused by human activities,8.6％ by climate change,and 0.9％ by a combination of the two factors.On the contrary,1.5％ of desertification reversion area was caused by human activities and 90.7％ by climate change,the rest 7.8％ by a combination of the two factors.Moreover,it was demonstrated that 95.9％ of the total actual NPP decrease was induced by human activities,while 69.3％ of the total actual NPP increase was caused by climate change.The results revealed that climate change dominated desertification reversion,while human activities dominated desertification expansion.Moreover,the relative roles of both climate change and human activities in desertification possessed great spatial heterogeneity.Additionally,ecological protection policies should be enhanced in the Heihe River Basin to prevent desertification expansion under the condition of climate change.

Analysis of deformation and internal flow patterns for rising single bubbles in different liquids

Gas–liquid multiphase flow is a significant phenomenon in chemical processes. The rising behaviors of single bubbles in the quiescent liquids have been investigated but the internal flow patterns and deformation rules of bubbles, which influence the mass transfer efficiency to a large extent, have received much less attention. In this paper, the volume of fluid method was used to calculate the bubble shapes, pressure, velocity distributions,and the flow patterns inside the bubbles. The rising behavior of the bubbles with four different initial diameters,i.e., 3 mm, 5 mm, 7 mm and 9 mm was investigated in four various liquids including water, 61.23% glycerol,86.73% glycerol and 100% glycerol. The results show that the liquid properties and bubble initial diameters have great impacts on bubble shapes. Moreover, flow patterns inside the bubbles with different initial diameters were analyzed and classified into three types under the condition of different bubble shapes. Three correlations for predicting the maximum internal circulation inside the bubbles in 86.73% glycerol were presented and the R-square values were all bigger than 0.98. Through analyzing the pressure and velocity distributions around the bubbles, four rules of bubble deformation were also obtained to explain and predict the shapes.

Screening of stable internal reference genes by quantitative real-time PCR in humpback grouper Cromileptes altivelis

Humpback grouper Cromileptes altivelis is one commercial fish with considerable economic value.To determine the expression stabilities of six commonly used internal reference genes in C.altivelis challenged by Vibrio harveyi and viral nervous necrosis virus(VNNV)through quantitative real-time PCR(qRT-PCR),the expression levels of selected genes in five immune organs stimulated with pathogenic infection were carefully evaluated using algorithms of geNorm,NormFinder,and BestKeeper.The results show that the expre ssion stabilities of the six candidate inte rnal reference genes were diffe re nt.Under no rmal physiological conditions,RPL13 were identified as the most stably expressed genes among five different immune organs(liver,spleen,kidney,intestine,and gill).After V.harveyi stimulation,RPL13,RPL13,EF1 A,RPL13,and EF1 A were identified by geNorm,NormFinder,and BestKeeper as the most stable genes in liver,spleen,kidney,intestine,and gill,respectively.Combining these three algorithms suggested that under stimulation of VNNV,RPL13,EF1 A,Actin,RPL13,and Actin were as the most stable genes in liver,spleen,kidney,intestine,and gill,respectively.These results suggest that specific experiment conditions and tissue types shall be considered when selecting the reference genes in qRT-PCR analysis.This study provided a solid foundation for future studies on gene expression of C.altivelis under different conditions.

Estimation of Remote Sensing and Analysis of Temporal and Spatial Distribution of Grassland LAI

To estimate the leaf area index(LAI)in large areas,this paper analyzes the relationships between normalized difference vegetation index(NDVI)and the grassland LAI based on MODIS data in the southern grassy mountains and slopes of China.By using nonlinear fitting equation we constructed the basic estimation model of grassland LAI with NDVI as the independent variable and introduced precipitation and temperature as regulatory factors.The model was validated with observed data in different years and the results showed that there was a good correlation between the simulated and observed LAI value with a statistically significant level of R2.RMSE was 0.302 and RRMSE was 0.154.It was also found that the spatial distribution of grassland LAI in south China showed a remarkable zonal characterization,and temporal distribution showed a single peak curve.These results provided a theoretical basis for the effective management of southern grassland resources and the carbon sink estimation of the nationwide grasslands.

Assessing the spatio-temporal variability of vegetation productivity in Africa: quantifying the relative roles of climate variability and human activities

Quantitative attribution at the individual pixel level of the relative contributions of climate variability and human activities to vegetation productivity dynamics across Africa is generally lacking.This is because of the difficulty in establishing a baseline or potential vegetation against which the relative impacts of these factors can be assessed.This study addresses these gaps.First,annual potential net primary productivity(NPP_(P))for 2000–2014 was estimated for Africa using a model constructed from samples of NPP and environmental covariates from protected areas.Second,trends in NPP_(P),actual NPP(NPP_(A)),and human-appropriated NPP(NPP_(H)=NPP P−NPP_(A))were estimated and used in quantifying the relative contributions of climate and human activities to NPP dynamics.Over 2000–2014,NPP improvement was largely concentrated in equatorial and northern Africa,while subequatorial Africa exhibited the most NPP decline.Parts of Mali,Burkina Faso,and the central Africa region are associated with the greatest influence of climate-driven NPP improvement.Areas where humans dominated NPP decline include parts of Ethiopia and South Africa.Climate had a stronger role in driving NPP decline in subequatorial Africa.Nonetheless,further work is required to validate the results of this study with high-resolution imagery and field information.

CSF S100B in patients treated by endovascular coiling or surgical clipping after aneurysmal subarachnoid hemorrhage and its correlation to cerebral vasospasm

Background: Aneurysmal subarachnoid hemorrhage (aSAH) is an acute neurosurgical emergency with a significant fatality rate. In addition to acute brain injury, a considerable part of patients suffering from aSAH develops secondary brain damage such as cerebral vasospasm (CVS). CVS exacerbates the mortality. Therefore, it is urgently needed to find a biomarker, which could predict secondary brain and lead to operation by physicians more promptly. S100B, produced and released by astrocytes, has proven to be an important biomarker for brain injury.Methods: In this present study, 51 patients with aSAH were included. Five CSF samples from each patient were obtained via lumbar puncture and were detected using electrochemiluminescence immunoassay (ECLIA).Results: It indicated that S100B had a higher concentration in CSF of patients treated by surgical clipping after aSAH than that treated with endovascular coiling. In addition, the mean CSF S100B level in patients without CVS was much lower compared with patients with CVS. And, the expression of S100B increased along with the Fisher Grade at the same day after aSAH attacked and decreased as time went on. Moreover, the CSF S100B level of different time points and the mean CSF S100B level can predict the risk of CVS.Conclusions: These data suggest that CSF S100B can be served as a predictor of CVS, which triggers an immediate management by clinicians to prevent secondary exacerbation.

Exploring the formation potential and optical properties of secondary organic aerosol from the photooxidation of selected short aliphatic ethers

Secondary organic aerosol(SOA)formation potential for six kinds of short aliphatic ethers has been studied.The size distribution,mass concentration,and yield of SOA formed by ethers photooxidation were determined under different conditions.The results showed that all six ethers can generate SOA via reaction with OH radicals even under no seed and NOxfree condition.The mass concentration for six seedless experiments was less than 10μg/m3 and the SOA yields were all below 1%.The strong increase in the SOA formation was observed when the system contained ammonium sulfate seed particles,while SOA yield decreased under the high-NOx condition.SOA composition was analyzed using offline methods.Infrared spectra indicated that there are complex components in the particle-phase including carbonyls acid and aldehydes species.Moreover,the aqueous filter extracts were analyzed using ultraviolet-visible spectrometer and fluorescence spectrophotometer.For the fresh methyl n-butyl ether SOA,the largest absorption peak occurs at 280 nm and there exists slightly absorption in the 300-400 nm.Excitation-emission matrices display the distinct peak at excitation/emission=470 nm/480 nm according to the fluorescence spectrum.These findings are important considerations of formation for ether SOA that can eventually be included in atmospheric models.

Biomass briquette fuel,boiler types and pollutant emissions of industrial biomass boiler:A review

Biomass is considered a renewable and cleaner energy source alternative to fossil fuels.In recent years,industrial biomass boilers have been rapidly developed and widely used in the industrial field.This work makes a review on the fuel types used in industrial biomass boilers,the fuel characteristics and the characteristics of air pollutants emitted from the combustion of industrial biomass boilers and other contents in different studies.However,the existing research still has many deficiencies.In the future,further research on biomass fuel,industrial biomass boiler combustion process and the pollutants emitted by industrial biomass boiler combustion,especially the carbonaceous aerosol emitted by in-dustrial biomass boiler and carbonaceous aerosol optical properties still need to be made.At the same time,the potential harm of carbonaceous aerosols emitted from industrial biomass boiler sources to human health and climate change needs to be studied in depth.This review provides a scientific basis for the accurate evaluation of industrial biomass boilers and the effective prevention and control of various pollutants of industrial biomass boilers.

食源米曲霉菌株的分离及其降解高效氯氰菊酯和3-苯氧基苯甲酸的特性研究

【目的】通过研究不同食源米曲霉菌株对高效氯氰菊酯(beta-cypermethrin,β-CP)及其必经代谢产物3-苯氧基苯甲酸(3-phenoxybenzoic acid,3-PBA)的降解特性,了解不同菌株的降解共性及差异性,为农副产品和发酵食品的农残减除提供理论基础和食品用安全微生物资源。【方法】以发酵食品为菌源,通过形态学鉴定、ITS测序和菌株产黄曲霉毒素B1(AFB1)的测定筛选鉴定米曲霉菌株,采用高效液相色谱法(HPLC)、气相色谱-质谱法(GC-MS)、液相色谱-质谱法(LC-MS)对米曲霉模式菌株RIB40(保藏编号:ATCC 42149)、米曲霉M4(保藏编号:CGMCC 11645)和鉴定获得的米曲霉菌株的β-CP和3-PBA降解特性进行研究。【结果】鉴定获得15株不产AFB1的食源米曲霉,17株米曲霉在马铃薯液体培养基(PD)中振荡培养5 d,对50 mg/L的β-CP降解率为19.33%−50.29%不等,检测到降解产物3-PBA,对50 mg/L的3-PBA降解率为45.59%−99.67%不等;分别在添加50 mg/Lβ-CP和3-PBA的无机盐培养基(MM)中振荡培养5 d,米曲霉菌株均未生长,对β-CP和3-PBA无降解;在富集培养基(GM)中振荡培养2 d,对100 mg/L的3-PBA转化或降解率为69.28%−99.58%不等,检测到3-苯氧基苄醇(3-PBlc)和羟基-3-苯氧基苯甲酸(HO-3-PBA)。【结论】食源米曲霉具有共代谢降解β-CP和3-PBA的共性,3-PBA为β-CP降解中间产物,米曲霉对3-PBA普遍具有较高的降解率。在3-PBA降解初期,米曲霉可将其短暂还原生成毒性相对较低的3-PBlc,同时,3-PBA逐渐羟基化生成水溶性更强的HO-3-PBA参与下游降解。

Water-soluble matter in PM_(2.5)in a coastal city over China:Chemical components,optical properties,and source analysis

Although marine and terrestrial emissions simultaneously affect the formation of atmospheric fine particles in coastal areas,knowledge on the optical properties and sources of water-soluble matter in these areas is still scarce.In this work,taking Qingdao,China as a typical coastal location,the chemical composition of PM_(2.5)duringwinter 2019was analyzed.Excitation-emission matrix fluorescence spectroscopy was combined with parallel factor analysis model to explain the components of water-soluble atmospheric chromophores of PM_(2.5).Our analysis indicated that NO_(3)^(-),NH_(4)^(+)and SO_(4)^(2-)ions accounted for 86.80%of the total ion mass,dominated by NO_(3)^(-).The ratio of[NO_(3)^(-)]/[SO_(4)^(2-)]was up to 2.42±0.84,suggesting thatmobile sources play an important role in local pollutants emission.The result of positive correlation between Abs_(365)with K^(+)suggests that biomass burning is an important source of water-soluble organic compounds(WSOC).Six types of fluorophores(C1-C6),all humic-like substances,were identified in WSOC.Humification index,biological index and fluorescence index in winter were 1.66±0.34,0.51±0.44 and 1.09±0.78,respectively,indicating that WSOC in Qingdao were mainly terrestrial organic matters.Overall,although the study area is close to the ocean,the contribution of terrestrial sources to PM_(2.5),especially vehicle exhaust and coal combustion,is still much higher than that of marine sources.Our study provides a more comprehensive understanding of chemical and optical properties of WSOC based on PM_(2.5)in coastal areas,and may provide ground for improving local air quality.

Heterogeneous reaction of SO_(2) on CaCO_(3) particles:Different impacts of NO_(2) and acetic acid on the sulfite and sulfate formation

Despite the heterogeneous reaction of sulfur dioxide(SO_(2))on mineral dust particles significantly affects the atmospheric environment,the effect of acidic gases on the formation of sulfite and sulfate from this reaction is not particularly clear.In this work,using the in-situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS)technique,we employed a mineral dust particle model(CaCO_(3))combined with NO_(2)and acetic acid to investigate their effects on the heterogeneous reaction of SO_(2)on CaCO_(3)particles.Itwas found that water vapor can promote the formation of sulfite and simulated radiation can facilitate the oxidation of sulfite to sulfate.The addition of NO_(2)or acetic acid to the reaction system altered the production of sulfate and sulfite accordingly.There was a synergistic effect between NO_(2)and SO_(2)that promoted the oxidation of sulfite to sulfate,and a competitive effect between acetic acid and SO_(2)that inhibited the formation of sulfite.Moreover,light and water vapor can also affect the heterogeneous reaction of SO_(2)with the coexistence ofmultiple gases.These findings improve our understanding of the effects of organic and inorganic gases and environmental factors on the formation of sulfite and sulfate in heterogeneous reactions.

Earthworm biomass and population structure are negatively associated with changes in organic residue nitrogen concentration during vermicomposting

Vermicomposting is an efficient and environmentally friendly technology to dispose of agricultural organic residues.The efficiency of organic residue decomposition during vermicomposting is directly affected by the biomass and population structure of earthworms.In this study,we investigated how the earthworm biomass and population structure responded to changes in the physicochemical properties of six types of organic residue(cattle dung,herbal waste,rice straw,soybean straw,garden waste,and tea residues)during vermicomposting.Each type of organic residues was placed in a pot with earthworms Eisenia fetida,and the physicochemical properties of the organic residues and earthworm growth dynamics were recorded at 0,30,60,and 90 d of vermicomposting.The biomass and population structure of earthworms were stable or increased in rice straw,garden waste,and cattle dung within 60 d of vermicomposting,whereas in tea residues and herb waste,very little earthworm activity(3 adults and 2 cocoons)was recorded on day 30.Among the physicochemical parameters,the substrate C/N ratio was negatively correlated with earthworm growth dynamics.Decomposing organic residues showed higher NH_(4)^(+)-N and NH_(3)^(-)-N concentrations but a lower total organic carbon content,which negatively affected earthworm growth and reproduction.We recommend that chemical properties of vermicomposting systems should be monitored regularly.At the threshold levels of decomposing organic residue NH_(4)^(+)-N and NH_(3)^(-)-N concentrations,earthworms should be removed and the vermicompost can be harvested.Small-and large-scale farmers thus need to monitor the physicochemical properties of vermicompost to sustain active earthworm populations.

Predicting siRNA activity based on back-propagation neural network

RNA interference(RNAi)is a phenomenon of gene silence induced by a double-stranded RNA(dsRNA)homologous to a target gene.RNAi can be used to identify the function of genes or to knock down the targeted genes.In RNAi technology,19 bp double-stranded short interfering RNAs(siRNA)with characteristic 39 overhangs are usually used.The effects of siRNAs are quite varied due to the different choices in the sites of target mRNA.Moreover,there are many factors influencing siRNA activity and these factors are usually nonlinear.To find the motif features and the effect on siRNA activity,we carried out a feature extraction on some published experimental data and used these features to train a backpropagation neural network(BP NN).Then,we used the trained BP NN to predict siRNA activity.