Artificial guidance channels containing Schwann cells can promote the regeneration of injured peripheral nerve over long distances. However, primary Schwann cells are not suitable for autotransplantation. Under specif...Artificial guidance channels containing Schwann cells can promote the regeneration of injured peripheral nerve over long distances. However, primary Schwann cells are not suitable for autotransplantation. Under specific conditions, skin-derived progenitors can be induced to dif- ferentiate into Schwann cells. Therefore, adult rat dorsal skin （dermis）-derived progenitors were isolated and induced to differentiate with DMEM/F12 containing B27, neuregulin 1, and for- skolin. Immunofluorescence staining and reverse transcription polymerase chain reaction （RT- PCR） confirmed that the resultant cells were indeed Schwann cells. Artificial guidance channels containing skin-derived progenitors, Schwann cells originating from skin-derived progenitors, or primary Schwann cells were used to bridge 5 mm sciatic nerve defects. Schwann cells originating from skin-derived progenitors significantly promoted sciatic nerve axonal regeneration. The sig- nificant recovery of injured rat sciatic nerve function after the transplantation of Schwann cells originating from skin-derived progenitors was confirmed by electromyogram. The therapeutic effect of Schwann cells originating from skin-derived progenitors was better than that of skin-de- rived progenitors. These findings indicate that Schwann cells originating from skin-derived precursors can promote peripheral nerve regeneration in rats.展开更多
Autophagy has been shown to play an important role in Parkinson’s disease.We hypothesized that skin-derived precursor cells exhibit neuroprotective effects in Parkinson’s disease through affecting autophagy.In this ...Autophagy has been shown to play an important role in Parkinson’s disease.We hypothesized that skin-derived precursor cells exhibit neuroprotective effects in Parkinson’s disease through affecting autophagy.In this study,6-hydroxydopamine-damaged SH-SY5Y cells were pretreated with a culture medium containing skin-derived precursors differentiated into Schwann cells(SKP-SCs).The results showed that the SKP-SC culture medium remarkably enhanced the activity of SH-SY5Y cells damaged by 6-hydroxydopamine,reduced excessive autophagy,increased tyrosine hydroxylase expression,reducedα-synuclein expression,reduced the autophagosome number,and activated the PI3K/AKT/mTOR pathway.Autophagy activator rapamycin inhibited the effects of SKP-SCs,and autophagy inhibitor 3-methyladenine had the opposite effect.These findings confirm that SKP-SCs modulate the PI3K/AKT/mTOR pathway to inhibit autophagy,thereby exhibiting a neuroprotective effect in a cellular model of Parkinson’s disease.This study was approved by the Animal Ethics Committee of Laboratory Animal Center of Nantong University(approval No.S20181009-205)on October 9,2018.展开更多
Solution processability significantly advances the development of highly-efficient perovskite solar cells.However,the precursor solution tends to undergo irreversible degradation reactions,impairing the device perform...Solution processability significantly advances the development of highly-efficient perovskite solar cells.However,the precursor solution tends to undergo irreversible degradation reactions,impairing the device performance and reproducibility.Here,we utilize a reductive natural amino acid,Nacetylcysteine(NALC),to stabilize the precursor solution for printable carbon-based hole-conductorfree mesoscopic perovskite solar cells.We find that I_(2) can be generated in the aged solution containing methylammonium iodide(MI) in an inert atmosphere and speed up the MA-FA^(+)(formamidinium) reaction which produces large-size cations and hinders the formation of perovskite phase.NALC effectively stabilizes the precursor via its sulfhydryl group which reduces I_(2) back to I^(-)and provides H^(+).The NALC-stabilized precursor which is aged for 1440 h leads to devices with a power conversion efficiency equivalent to 98% of that for devices prepared with the fresh precursor.Furthermore,NALC improves the device power conversion efficiency from 16.16% to 18.41% along with enhanced stability under atmospheric conditions by modifying grain boundaries in perovskite films and reducing associated defects.展开更多
Tracing the contamination origins in water sources and identifying the impacts of natural and human processes are essential for ecological safety and public health.However,current analysis approaches are not ideal,as ...Tracing the contamination origins in water sources and identifying the impacts of natural and human processes are essential for ecological safety and public health.However,current analysis approaches are not ideal,as they tend to be laborious,time-consuming,or technically difficult.Disinfection byproducts(DBPs)are a family of well-known secondary pollutants formed by the reactions of chemical disinfectants with DBP precursors during water disinfection treatment.Since DBP precursors have various origins(e.g.,natural,domestic,industrial,and agricultural sources),and since the formation of DBPs from different precursors in the presence of specific disinfectants is distinctive,we argue that DBPs and DBP precursors can serve as alternative indicators to assess the contamination in water sources and identify pollution origins.After providing a retrospective of the origins of DBPs and DBP precursors,as well as the specific formation patterns of DBPs from different precursors,this article presents an overview of the impacts of various natural and anthropogenic factors on DBPs and DBP precursors in drinking water sources.In practice,the DBPs(i.e.,their concentration and speciation)originally present in source water and the DBP precursors determined using DBP formation potential tests—in which water samples are dosed with a stoichiometric excess of specific disinfectants in order to maximize DBP formation under certain reaction conditions—can be considered as alternative metrics.When jointly used with other water quality parameters(e.g.,dissolved organic carbon,dissolved organic nitrogen,fluorescence,and molecular weight distribution)and specific contaminants of emerging concern(e.g.,certain pharmaceuticals and personal care products),DBPs and DBP precursors in drinking water sources can provide a more comprehensive picture of water pollution for better managing water resources and ensuring human health.展开更多
Chilled chicken has become the mainstream of chicken consumption.In order to explore the effect of post-mortem aging on water-soluble flavor precursors of chicken,pH,adenosine triphosphate(ATP)degradation,flavor nucle...Chilled chicken has become the mainstream of chicken consumption.In order to explore the effect of post-mortem aging on water-soluble flavor precursors of chicken,pH,adenosine triphosphate(ATP)degradation,flavor nucleosides,free amino acids and water-soluble low molecular weight peptides were determined using Qingyuan partridge yellow-feathered broilers as material during 0-4℃ post-mortem aging in 48 h.The results showed that the pH value fell to the limit pH 5.64(4 h)in chicken breast and 6.21(3 h)in thigh.Regardless of chicken breast or thigh,ATP dropped rapidly within 3 h.It was found that the K-value in chicken thigh was the lowest at 2 h indicating the freshness was the best.Considering the equivalent umami concentration(EUC),the value at 3 h and 4 h was relatively high,but the corresponding electronic tongue umami value was not high,which further showed that the water-soluble low molecular taste peptide played an important role on the post-mortem aging process.Combined with cluster analysis and partial least squares discriminant analysis(PLS-DA),it was preliminarily inferred that the optimal time for chilled chicken during 0-4℃ post-mortem aging was 2 h,which could provide a theoretical basis for the further processing of fresh chicken.展开更多
This study reports the morphological characteristics of anomalous variations in Global Navigation Satellite System Total Electron Content(GNSS-TEC) prior to the strong local earthquakes(EQ) that occurred during the pe...This study reports the morphological characteristics of anomalous variations in Global Navigation Satellite System Total Electron Content(GNSS-TEC) prior to the strong local earthquakes(EQ) that occurred during the period of 2011-2015.We have analyzed 20 earthquakes of magnitude M> 5.6.A statistical technique is implemented on the data of six GNSS stations located in Tashkent,Kitab,and Maidanak in Uzbekistan,and Islamabad,Multan,Quetta in Pakistan.The results show continuous anomalous variations in TEC during 24 h befo re the occupancy of local earthquakes.It is shown that the precursors before the occurrence of strong earthquakes,in particular of magnitude 5.7,7.7,7.5,7.8 and 7.3 are detected near Eastern Uzbekistan(26 May 2013),Southwestern Pakistan(24 September 2013),Hindukush region of Afghanistan(26 October 2015),and Central Nepal(25 April 2015) and(12 May 2015),respectively.The ionospheric anomalies appearing before the strong earthquakes at six GNSS stations are registered in 14cases(70%) out of 20 selected EQs.It is depicted that anomalies referred to as ionospheric precursors appeared about 1-7 days prior to the occurrence of strong earthquakes.展开更多
The damage of human corneal cells encounter with the problem of availability of corneal cells for replacement. Limitation of the source of corneal cells has been realized. An attempt of development of corneal epitheli...The damage of human corneal cells encounter with the problem of availability of corneal cells for replacement. Limitation of the source of corneal cells has been realized. An attempt of development of corneal epithelial-like cells from the human skin-derived precursor (hSKPs) has been made in this study. Combination of three essential growth factors: epidermal growth factor (EGF), keratinocyte growth factor (KGF) and hepatocyte growth factor (HGF) could demonstrate successfully induction of hSKPs to differentiation into corneal cells.The induced cells expressed the appearance of markers of corneal epithelial cells as shown by the presence of keratin 3 (K3) by antibody label and Western blot assay. The K3 gene expression of induced hSKPs cells as shown by reverse transcription-polymerase chain reaction (RT-PCR) technology was also demonstrated. The presence of these markers at both gene and protein levels could lead to our conclusion that the directional transdifferentiation of hSKPs cells into corneal epithelial cells was successfully done under this cell induction protocol. The finding shows a newly available stem cell source can be obtained from easily available skin. Cells from autologous human skin might be used for corneal disorder treatment in future clinical application.展开更多
To investigate the influence mechanism of geostress on rockburst characteristics,three groups of gneiss rockburst experiments were conducted under different initial geostress conditions.A high-speed photography system...To investigate the influence mechanism of geostress on rockburst characteristics,three groups of gneiss rockburst experiments were conducted under different initial geostress conditions.A high-speed photography system and acoustic emission(AE)monitoring system were used to monitor the entire rockburst process in real time.The experimental results show that when the initial burial depth increases from 928 m to 1320 m,the proportion of large fracture scale in rockburst increases by 154.54%,and the AE energy increases by 565.63%,reflecting that the degree and severity of rockburst increase with the increase of burial depth.And then,two mechanisms are proposed to explain this effect,including(i)the increase of initial geostress improves the energy storage capacity of gneiss,and then,the excess energy which can be converted into kinetic energy of debris ejection increases,consequently,a more pronounced violent ejection phenomenon is observed at rockburst;(ii)the increase of initial geostress causes more sufficient plate cracks of gneiss after unloading ofσh,which provides a basis for more severe ejection of rockburst.What’s more,a precursor with clear physical meaning for rockburst is proposed under the framework of dynamic response process of crack evolution.Finally,potential value in long term rockburst warning of the precursor obtained in this study is shown via the comparison of conventional precursor.展开更多
Although perifollicular repigmentation in the vitiligo lesions is owing to activation of follicular melanocyte stem cells and/or precursor cells followed by supplying matured melanocytes, the underlying mechanism of d...Although perifollicular repigmentation in the vitiligo lesions is owing to activation of follicular melanocyte stem cells and/or precursor cells followed by supplying matured melanocytes, the underlying mechanism of diffuse repigmentation on the whole vitiligo surface remains still unknown. In addition to the presence of remaining melanocytes, it is conceivable that dermal melanocyte precursor cells contribute to induce diffuse repigmentation after treatment. Therefore, we investigated here whether dermal and follicular melanocyte precursor cells were reduced or not in vitiligo lesions. We performed an immunostaining for Nestin and p75NGFR as dermal melanocyte precursor cells and MITF/Fzd4 as follicular melanocyte precursor cells and compared the positive cells number between lesions and non-lesions (n = 11). Although MITF<sup>+</sup>/Fzd4<sup>+</sup> cells in the hair follicle were significantly decreased in number in the lesions, Nestin<sup>+</sup> and p75NGFR<sup>+</sup> cells were not. This result indicates that dermal precursor cells could be retained in the vitiligo lesions but be disturbed to differentiate into matured melanocytes.展开更多
We statistically validate the 2011-2022 earthquake prediction records of Ada, the sixth finalist of the 2nd China AETA in 2021, who made 147 earthquake predictions (including 60% of magnitude 5.5 earthquakes) with a p...We statistically validate the 2011-2022 earthquake prediction records of Ada, the sixth finalist of the 2nd China AETA in 2021, who made 147 earthquake predictions (including 60% of magnitude 5.5 earthquakes) with a prediction accuracy higher than 70% and a confidence level of 95% over a 12-year period. Since the reliable earthquake precursor signals described by Ada and the characteristics of Alfvén waves match quite well, this paper proposes a hypothesis on how earthquakes are triggered based on the Alfvén (Q G) torsional wave model of Gillette et al. When the plume of the upper mantle column intrudes into the magma and lithosphere of the soft flow layer during the exchange of hot and cold molten material masses deep inside the Earth’s interior during ascent and descent, it is possible to form body and surface plasma sheets under certain conditions to form Alfven nonlinear isolated waves, and Alfven waves often perturb the geomagnetic field, releasing huge heat and kinetic energy thus triggering earthquakes. To explain the complex phenomenon of how Ada senses Alvfen waves and how to locate epicenters, we venture to speculate that special magnetosensory cells in a few human bodies can sense earthquake precursors and attempt to hypothesize an algorithm that analyzes how the human biological nervous system encodes and decodes earthquake precursors and explains how human magnetosensory cells can solve complex problems such as predicting earthquake magnitude and locating epicenters.展开更多
Granite is usually composed of quartz,biotite,feldspar,and cracks,and the variation characteristics of these components could reflect the deformation and failure process of rock well.Taking granite as an example,the v...Granite is usually composed of quartz,biotite,feldspar,and cracks,and the variation characteristics of these components could reflect the deformation and failure process of rock well.Taking granite as an example,the video camera was used to record the deformation and failure process of rock.The distribution of meso-components in video images was then identified.The meso-components of rock failure precursors were also discussed.Moreover,a modified LSTM(long short-term memory method)based on SSA(sparrow search algorithm)was proposed to estimate the change of meso-components of rock failure precursor.It shows that the initiation and expansion of cracks are mainly caused by feldspar and quartz fracture,and when the quartz and feldspar exit the stress framework,rock failure occurs;the second large increase of crack area and the second large decrease of quartz or feldspar area may be used as a precursor of rock failure;the precursor time of rock failure based on meso-scopic components is about 4 s earlier than that observed by the naked eye;the modified LSTM network has the strongest estimation ability for quartz area change,followed by feldspar and biotite,and has the worst estimation ability for cracks;when using the modified LSTM network to predict the precursors of rock instability and failure,quartz and feldspar could be given priority.The results presented herein may provide reference in the investigation of rock failure mechanism.展开更多
All-inorganic CsPbIBr_(2) perovskite has attracted widespread attention in photovoltaic and other optoelectronic devices because of its superior thermal stability.However,the deposition of high-quality solutionprocess...All-inorganic CsPbIBr_(2) perovskite has attracted widespread attention in photovoltaic and other optoelectronic devices because of its superior thermal stability.However,the deposition of high-quality solutionprocessed CsPbIBr_(2) perovskite films with large thicknesses remains challenging.Here,we develop a triple-component precursor(TCP) by employing lead bromide,lead iodide,and cesium bromide,to replace the most commonly used double-component precursor(DCP) consisting of lead bromide and cesium iodide.Remarkably,the TCP system significantly increases the solution concentration to 1.3 M,leading to a larger film thickness(~390 nm) and enhanced light absorption.The resultant CsPbIBr_(2) films were evaluated in planar n-i-p structured solar cells,which exhibit a considerably higher optimal photocurrent density of 11.50 mA cm^(-2) in comparison to that of DCP-based devices(10.69 mA cm^(-2)).By adopting an organic surface passivator,the maximum device efficiency using TCP is further boosted to a record efficiency of 12.8% for CsPbIBr_(2) perovskite solar cells.展开更多
The study focused on the modification with platinum of dark defective titania obtained via pulsed laser ablation. Both the method of Pt introduction and the nature of the Pt precursor were varied. All samples exhibite...The study focused on the modification with platinum of dark defective titania obtained via pulsed laser ablation. Both the method of Pt introduction and the nature of the Pt precursor were varied. All samples exhibited similar phase compositions, specific surface areas, and Pt contents. High-resolution transmission electron microscopy coupled with pulsed CO adsorption revealed increased dispersity when photoreduction and the hydroxonitrate complex (Me _(4) N) _(2) [Pt _(2) (OH) _(2) (NO _(3) ) _(8) ] were used. The sample featured a high content of single-atom species and subnano-sized Pt clusters. The X-ray photoelectron spectroscopy results showed that the photoreduction method facilitated the appearance of a larger number of Pt ^(2+) states, which appeared owing to the strong metal-support interaction (SMSI) eff ect of the transfer of electron density from the electron-saturated defects on the TiO _(2) surface to Pt ^(4+) . In the hydrogen evolution reaction, samples with a significant fraction of the Pt ^(2+) ionic component, capable of generating short-lived Pt^(0) single-atom sites under irradiation due to the SMSI eff ect, exhibited the highest photocatalytic activity. The 0.5Pt(C)/TiO_(2) -Ph sample exhibited the highest hydrogen yield with a quantum efficiency of 0.53, retaining its activity even after 8 h of operation.展开更多
Tannin foam is a new functional material.It can be widely applied to the automobile industry,construction industry,and packaging industry due to its wide range of raw materials,renewable,easily degraded,low cost and a...Tannin foam is a new functional material.It can be widely applied to the automobile industry,construction industry,and packaging industry due to its wide range of raw materials,renewable,easily degraded,low cost and almost no pollution.Preparing tannin foam is a very complex process that includes high temperature,two phases,mechanical agitation,and phase change.To investigate the influence of the stirring velocity and paddle shape,simulation was calculated by making use of the volume of fluid(VOF)method and multiple reference frame(MRF)method in a three-dimensional flow field of tannin-based foaming precursor resin.The gas holdup and velocity magnitude were analysed with various conditions of mechanical velocities and paddle shape in the stirring flow field.The result shows the higher the velocity,the greater the disturbance and paddle shape between the eggbeater and the Rushton turbine,obviously the paddle shape of the eggbeater with a wider range of agitation,which can entrap more air into the tannin-based foaming precursor resin in a short time.Especially when the speed is 1500 rpm,the flow field of the Rushton turbine comes out of a ditch,which decreases the efficiency of mass transfer;there is less air to mix into the tannin-based foaming precursor resin,which causes unevenness.At the same time,the eggbeater shows the marvelous capability of hybrid as it has two vortexes and multiple cycles that make a difference from the Rushton turbine,which has only one vortex and two upper and lower loops;the structure makes the flow field more stable allowed evenness of flow field tannin-based foaming precursor resin.The results reveal that it is beneficial for tannin-based foaming precursor resin to use an eggbeater with a speed of 1500 rpm to reduce the consumption of resources while obtaining a uniform flow field.展开更多
Neuronal and glial differentiation potential of skin-derived precursors is of great interest for clinical application in the treatment of neurodegenerative disease. In this sense, the pig model is a great candidate fo...Neuronal and glial differentiation potential of skin-derived precursors is of great interest for clinical application in the treatment of neurodegenerative disease. In this sense, the pig model is a great candidate for the development of preclinical models. To the date, skin-derived precursor spheres have not been isolated from adult porcine skin. In order to optimize the protocol for isolating dermal precursor spheres from adult porcine skin, 15 porcine skin biopsies were subjected to three different processing protocols. Liberase-based digestion of ventral porcine skin gave rise to more cells with spherogenic capacity than other protocols and these spheres presented phenotypic and differentiation potential consistent with bona fide skin-derived precursor cells.展开更多
[Objective] This study aimed to investigate the changes of the transcriptional levels of molecules associated with endogenous antigen processing and presenta- tion in porcine skin-derived dendritic cells infected with...[Objective] This study aimed to investigate the changes of the transcriptional levels of molecules associated with endogenous antigen processing and presenta- tion in porcine skin-derived dendritic cells infected with PCV2 in vivo. [Method] Healthy 40-day-old Landrace piglets were infected with porcine circovirus type 2 （PCV2） and euthanized on the 34, 7rd, 14th, 21st and 35th d post inoculation （DPI）. The porcine skin-derived dendritic cells （DCs） were collected to analyze the transcrip- tional levels of molecules （LMP7, UBP, MHC-I, calreticulin） associated with endogenous antigen processing and presentation by using real-time fluorescent quantitative PCR （real-time FQ-PCR）. [Result] The results showed that the level of LMP7 mR- NAs was reduced significantly on the 3DPI （P〈0.05）; the level of UBP mRNAs was consistently up-regulated, which increased significantly on the 21DPI and 35DPI （P〈 0.05）; the level of MHC-I mRNAs was significantly down-regulated on the 7DPI （P〈 0.05）; the level of calreticulin mRNAs was up-regulated slightly without significant dif- ference. [Conclusion] PCV2 can inhibit the endogenous antigen processing and presentation ability of porcine skin-derived DCs at early stages of infection.展开更多
[Objective] This study was to explore the effect of three precursors on the accumulation of principal volatile oil constituents in tissue culture plantlets of Atractylodes lancea （Thunb.） DC. with the aim to provide...[Objective] This study was to explore the effect of three precursors on the accumulation of principal volatile oil constituents in tissue culture plantlets of Atractylodes lancea （Thunb.） DC. with the aim to provide references for the improvement of artificial cultivated A. lancea quality. [Method] Three precursors were added into the MS rooting medium for A. lancea tissue culture plantlets and the volatile oil was extracted by ultrasonication after cultured for several days. The content of atractylon, atractylol, β-eucalyptol and atractydin in the volatile oil were determined by using gas chromatography method. [Result] The addition of xylose, isoprene and tetrahydrofuran impacted the growth indicators, yield of volatile oil and relative percentage content of the four constituents of A. lancea tissue culture plantlets. In the 6 g/L xylose optimized medium, the atractylon and β-eucalyptol content reached up to 4.23% and 56.34%, respectively, 1.41% and 1.66% higher than the control; although the addition of isoprene into medium raised the atractylon content, the accumulation of total volatile oil was inhibited that it decreased by 23.67%, 31.06% and 7.10% to the control; for the tetrahydrofuran optimized medium, the content of atractylon, atractylol and atractydin all increased, and the total volatile oil content increased by 49.97% to the control when the concentration of tetrahydrofuran was 0.07 g/L. [Conclusion] The addition of xylose and tetrahydrofuran promoted the accumulation of principal constituents of the volatile oil, whereas the addition of isoprene inhibited the accumulation.展开更多
The effects of atmospheres and precursors on MnOx/TiO2 catalysts were studied, which were prepared by the impregnation method and tested for their NOx conversion activity in ammonia selective catalytic reduction （NH3...The effects of atmospheres and precursors on MnOx/TiO2 catalysts were studied, which were prepared by the impregnation method and tested for their NOx conversion activity in ammonia selective catalytic reduction （NH3-SCR） reactions. Results showed that the manganese carbonate （MC） precursor caused mainly Mn2O3, while the manganese nitrate （MN） precursor resulted primarily in MnO2 and the manganese sulfate （MS） precursor was unchanged. The manganese acetate （MA） precursor leaded obtaining a mixture of Mn2O3 and Mn304. NOn conversion decreased in the following order： MA/TiO2 〉 MC/TiO2 〉 MN/TiO2 〉 MS/TiO2 〉 P25, with a calcination temperature of 773 K in air. Catalysts that were prepared by MA and calcined in oxygen performed strong interaction between Ti and Mn, while MnTiO3 was observed. Compared to the catalysts calcined in nitrogen, those calcined in oxygen had larger diameter and smaller surface area and pore. Catalysts that were prepared by MA and calcined in nitrogen tended to gain higher denitration rates than those in air, since they could be prepared with significant specific surface areas. NO., conversion decreased with calcination atmospheres： Nitrogen〉 Air〉 Oxygen. Meanwhile, amorphous Mn2O3 turned into crystalline Mn2O3, when the temperatures increased from 673 to 873 K.展开更多
Structural changes in carbon fibers at each stage of, especially, preoxidation process are well known to play a great role in achieving the ultimate product quality. Differential scanning calorimetry (DSC), scanning e...Structural changes in carbon fibers at each stage of, especially, preoxidation process are well known to play a great role in achieving the ultimate product quality. Differential scanning calorimetry (DSC), scanning electron microscope (SEM), density method and optical microscope were used to characterize the preoxidation extent. A conventional approach, e.g., density aim, to evaluate the extent of preoxidation is not very exact. A DSC curve of a PAN precursor only can provide general information, major in the temperature regime of preoxidation reaction. However, the evaluation of a preoxidation extent, especially from conventional preoxidation temperature with a great span regime of 200~400癈, is put forward in this paper, in which the evolution of core/shell morphological structure is a kind of straightforward evidence.展开更多
Sol-gel technology was employed to synthesize nanosized precursors of La-Mg hydrogen storage alloy at different pH values (0.5, 1.5, 8.0 and 9.0) of reaction solution. The effect of pH value on microstructure of the n...Sol-gel technology was employed to synthesize nanosized precursors of La-Mg hydrogen storage alloy at different pH values (0.5, 1.5, 8.0 and 9.0) of reaction solution. The effect of pH value on microstructure of the nano precursors of La-Mg hydrogen storage alloy was studied by infrared radiation (IR), thermo-gravimetric and differential thermal analysis (TG/DTA), X-ray diffraction analyzer (XRD) and transmission electron microscopy (TEM). IR results indicate that the chelating agent, citric acid, is not fully ionized, and carboxyl groups are not entirely used to complex metal ions in acidic solutions. The efficiency of complexing metal ions is enhanced in basic solutions. TG/DTA results show that the combustion may take place with low rate of the flame propagation that causes the longer combustion time when pH<1.5. On the contrary, the dry gel synthesized in basic solution combusts at low ignition temperature and combustion reaction is violent; it is easy to form fine particles. XRD and TEM results reveal that the precursor powders are mainly two-phase mixture of La 2 O 3 and MgO. The morphology of the particles is almost flake with the size of ~30 nm when pH is 8.0.展开更多
基金supported by the National Natural Science Foundation of China,No.81171194
文摘Artificial guidance channels containing Schwann cells can promote the regeneration of injured peripheral nerve over long distances. However, primary Schwann cells are not suitable for autotransplantation. Under specific conditions, skin-derived progenitors can be induced to dif- ferentiate into Schwann cells. Therefore, adult rat dorsal skin （dermis）-derived progenitors were isolated and induced to differentiate with DMEM/F12 containing B27, neuregulin 1, and for- skolin. Immunofluorescence staining and reverse transcription polymerase chain reaction （RT- PCR） confirmed that the resultant cells were indeed Schwann cells. Artificial guidance channels containing skin-derived progenitors, Schwann cells originating from skin-derived progenitors, or primary Schwann cells were used to bridge 5 mm sciatic nerve defects. Schwann cells originating from skin-derived progenitors significantly promoted sciatic nerve axonal regeneration. The sig- nificant recovery of injured rat sciatic nerve function after the transplantation of Schwann cells originating from skin-derived progenitors was confirmed by electromyogram. The therapeutic effect of Schwann cells originating from skin-derived progenitors was better than that of skin-de- rived progenitors. These findings indicate that Schwann cells originating from skin-derived precursors can promote peripheral nerve regeneration in rats.
基金Technology Project of Nantong of China,Nos.JC2020052(to XSG),JCZ19087(to XSG)the National Natural Science Foundation of China,Nos.81873742(to KFK),81901195(to JBS),81502867(to TX),82073627(to TX).
文摘Autophagy has been shown to play an important role in Parkinson’s disease.We hypothesized that skin-derived precursor cells exhibit neuroprotective effects in Parkinson’s disease through affecting autophagy.In this study,6-hydroxydopamine-damaged SH-SY5Y cells were pretreated with a culture medium containing skin-derived precursors differentiated into Schwann cells(SKP-SCs).The results showed that the SKP-SC culture medium remarkably enhanced the activity of SH-SY5Y cells damaged by 6-hydroxydopamine,reduced excessive autophagy,increased tyrosine hydroxylase expression,reducedα-synuclein expression,reduced the autophagosome number,and activated the PI3K/AKT/mTOR pathway.Autophagy activator rapamycin inhibited the effects of SKP-SCs,and autophagy inhibitor 3-methyladenine had the opposite effect.These findings confirm that SKP-SCs modulate the PI3K/AKT/mTOR pathway to inhibit autophagy,thereby exhibiting a neuroprotective effect in a cellular model of Parkinson’s disease.This study was approved by the Animal Ethics Committee of Laboratory Animal Center of Nantong University(approval No.S20181009-205)on October 9,2018.
基金financial support from the National Natural Science Foundation of China(grant nos.52172198,51902117,and 91733301)。
文摘Solution processability significantly advances the development of highly-efficient perovskite solar cells.However,the precursor solution tends to undergo irreversible degradation reactions,impairing the device performance and reproducibility.Here,we utilize a reductive natural amino acid,Nacetylcysteine(NALC),to stabilize the precursor solution for printable carbon-based hole-conductorfree mesoscopic perovskite solar cells.We find that I_(2) can be generated in the aged solution containing methylammonium iodide(MI) in an inert atmosphere and speed up the MA-FA^(+)(formamidinium) reaction which produces large-size cations and hinders the formation of perovskite phase.NALC effectively stabilizes the precursor via its sulfhydryl group which reduces I_(2) back to I^(-)and provides H^(+).The NALC-stabilized precursor which is aged for 1440 h leads to devices with a power conversion efficiency equivalent to 98% of that for devices prepared with the fresh precursor.Furthermore,NALC improves the device power conversion efficiency from 16.16% to 18.41% along with enhanced stability under atmospheric conditions by modifying grain boundaries in perovskite films and reducing associated defects.
基金supported by the National Natural Science Foundation of China(52325001,52170009,and 52091542)the National Key Research and Development Program of China(2021YFC3200700)+3 种基金the Program of Shanghai Academic Research Leader,China(21XD1424000)the International Cooperation Project of Shanghai Science and Technology Commission(20230714100)the Key-Area Research and Development Program of Guangdong Province(2020B1111350001)Tongji University Youth 100 Program.
文摘Tracing the contamination origins in water sources and identifying the impacts of natural and human processes are essential for ecological safety and public health.However,current analysis approaches are not ideal,as they tend to be laborious,time-consuming,or technically difficult.Disinfection byproducts(DBPs)are a family of well-known secondary pollutants formed by the reactions of chemical disinfectants with DBP precursors during water disinfection treatment.Since DBP precursors have various origins(e.g.,natural,domestic,industrial,and agricultural sources),and since the formation of DBPs from different precursors in the presence of specific disinfectants is distinctive,we argue that DBPs and DBP precursors can serve as alternative indicators to assess the contamination in water sources and identify pollution origins.After providing a retrospective of the origins of DBPs and DBP precursors,as well as the specific formation patterns of DBPs from different precursors,this article presents an overview of the impacts of various natural and anthropogenic factors on DBPs and DBP precursors in drinking water sources.In practice,the DBPs(i.e.,their concentration and speciation)originally present in source water and the DBP precursors determined using DBP formation potential tests—in which water samples are dosed with a stoichiometric excess of specific disinfectants in order to maximize DBP formation under certain reaction conditions—can be considered as alternative metrics.When jointly used with other water quality parameters(e.g.,dissolved organic carbon,dissolved organic nitrogen,fluorescence,and molecular weight distribution)and specific contaminants of emerging concern(e.g.,certain pharmaceuticals and personal care products),DBPs and DBP precursors in drinking water sources can provide a more comprehensive picture of water pollution for better managing water resources and ensuring human health.
基金supported by China Agriculture Research System of MOF and MARA (CARS-41)Wens Fifth Five R&D Major Project (WENS-2020-1-ZDZX-007)
文摘Chilled chicken has become the mainstream of chicken consumption.In order to explore the effect of post-mortem aging on water-soluble flavor precursors of chicken,pH,adenosine triphosphate(ATP)degradation,flavor nucleosides,free amino acids and water-soluble low molecular weight peptides were determined using Qingyuan partridge yellow-feathered broilers as material during 0-4℃ post-mortem aging in 48 h.The results showed that the pH value fell to the limit pH 5.64(4 h)in chicken breast and 6.21(3 h)in thigh.Regardless of chicken breast or thigh,ATP dropped rapidly within 3 h.It was found that the K-value in chicken thigh was the lowest at 2 h indicating the freshness was the best.Considering the equivalent umami concentration(EUC),the value at 3 h and 4 h was relatively high,but the corresponding electronic tongue umami value was not high,which further showed that the water-soluble low molecular taste peptide played an important role on the post-mortem aging process.Combined with cluster analysis and partial least squares discriminant analysis(PLS-DA),it was preliminarily inferred that the optimal time for chilled chicken during 0-4℃ post-mortem aging was 2 h,which could provide a theoretical basis for the further processing of fresh chicken.
基金supported by the National Natural Science Foundation of China (42030202)。
文摘This study reports the morphological characteristics of anomalous variations in Global Navigation Satellite System Total Electron Content(GNSS-TEC) prior to the strong local earthquakes(EQ) that occurred during the period of 2011-2015.We have analyzed 20 earthquakes of magnitude M> 5.6.A statistical technique is implemented on the data of six GNSS stations located in Tashkent,Kitab,and Maidanak in Uzbekistan,and Islamabad,Multan,Quetta in Pakistan.The results show continuous anomalous variations in TEC during 24 h befo re the occupancy of local earthquakes.It is shown that the precursors before the occurrence of strong earthquakes,in particular of magnitude 5.7,7.7,7.5,7.8 and 7.3 are detected near Eastern Uzbekistan(26 May 2013),Southwestern Pakistan(24 September 2013),Hindukush region of Afghanistan(26 October 2015),and Central Nepal(25 April 2015) and(12 May 2015),respectively.The ionospheric anomalies appearing before the strong earthquakes at six GNSS stations are registered in 14cases(70%) out of 20 selected EQs.It is depicted that anomalies referred to as ionospheric precursors appeared about 1-7 days prior to the occurrence of strong earthquakes.
基金Supported by Stem Cell Project,National Research Council of Thailand (NRCT),Cell Engineering and Tissue Growth, Institute of Molecular Biosciences and Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Thailand
文摘The damage of human corneal cells encounter with the problem of availability of corneal cells for replacement. Limitation of the source of corneal cells has been realized. An attempt of development of corneal epithelial-like cells from the human skin-derived precursor (hSKPs) has been made in this study. Combination of three essential growth factors: epidermal growth factor (EGF), keratinocyte growth factor (KGF) and hepatocyte growth factor (HGF) could demonstrate successfully induction of hSKPs to differentiation into corneal cells.The induced cells expressed the appearance of markers of corneal epithelial cells as shown by the presence of keratin 3 (K3) by antibody label and Western blot assay. The K3 gene expression of induced hSKPs cells as shown by reverse transcription-polymerase chain reaction (RT-PCR) technology was also demonstrated. The presence of these markers at both gene and protein levels could lead to our conclusion that the directional transdifferentiation of hSKPs cells into corneal epithelial cells was successfully done under this cell induction protocol. The finding shows a newly available stem cell source can be obtained from easily available skin. Cells from autologous human skin might be used for corneal disorder treatment in future clinical application.
基金support from the National Natural Science Foundation of China(No.41941018,No.52074299)the Fundamental Research Funds for the Central Universities(No.2023JCCXSB02)the China Geological Survey Project(DD20221816,DD20211376)are gratefully acknowledged.
文摘To investigate the influence mechanism of geostress on rockburst characteristics,three groups of gneiss rockburst experiments were conducted under different initial geostress conditions.A high-speed photography system and acoustic emission(AE)monitoring system were used to monitor the entire rockburst process in real time.The experimental results show that when the initial burial depth increases from 928 m to 1320 m,the proportion of large fracture scale in rockburst increases by 154.54%,and the AE energy increases by 565.63%,reflecting that the degree and severity of rockburst increase with the increase of burial depth.And then,two mechanisms are proposed to explain this effect,including(i)the increase of initial geostress improves the energy storage capacity of gneiss,and then,the excess energy which can be converted into kinetic energy of debris ejection increases,consequently,a more pronounced violent ejection phenomenon is observed at rockburst;(ii)the increase of initial geostress causes more sufficient plate cracks of gneiss after unloading ofσh,which provides a basis for more severe ejection of rockburst.What’s more,a precursor with clear physical meaning for rockburst is proposed under the framework of dynamic response process of crack evolution.Finally,potential value in long term rockburst warning of the precursor obtained in this study is shown via the comparison of conventional precursor.
文摘Although perifollicular repigmentation in the vitiligo lesions is owing to activation of follicular melanocyte stem cells and/or precursor cells followed by supplying matured melanocytes, the underlying mechanism of diffuse repigmentation on the whole vitiligo surface remains still unknown. In addition to the presence of remaining melanocytes, it is conceivable that dermal melanocyte precursor cells contribute to induce diffuse repigmentation after treatment. Therefore, we investigated here whether dermal and follicular melanocyte precursor cells were reduced or not in vitiligo lesions. We performed an immunostaining for Nestin and p75NGFR as dermal melanocyte precursor cells and MITF/Fzd4 as follicular melanocyte precursor cells and compared the positive cells number between lesions and non-lesions (n = 11). Although MITF<sup>+</sup>/Fzd4<sup>+</sup> cells in the hair follicle were significantly decreased in number in the lesions, Nestin<sup>+</sup> and p75NGFR<sup>+</sup> cells were not. This result indicates that dermal precursor cells could be retained in the vitiligo lesions but be disturbed to differentiate into matured melanocytes.
文摘We statistically validate the 2011-2022 earthquake prediction records of Ada, the sixth finalist of the 2nd China AETA in 2021, who made 147 earthquake predictions (including 60% of magnitude 5.5 earthquakes) with a prediction accuracy higher than 70% and a confidence level of 95% over a 12-year period. Since the reliable earthquake precursor signals described by Ada and the characteristics of Alfvén waves match quite well, this paper proposes a hypothesis on how earthquakes are triggered based on the Alfvén (Q G) torsional wave model of Gillette et al. When the plume of the upper mantle column intrudes into the magma and lithosphere of the soft flow layer during the exchange of hot and cold molten material masses deep inside the Earth’s interior during ascent and descent, it is possible to form body and surface plasma sheets under certain conditions to form Alfven nonlinear isolated waves, and Alfven waves often perturb the geomagnetic field, releasing huge heat and kinetic energy thus triggering earthquakes. To explain the complex phenomenon of how Ada senses Alvfen waves and how to locate epicenters, we venture to speculate that special magnetosensory cells in a few human bodies can sense earthquake precursors and attempt to hypothesize an algorithm that analyzes how the human biological nervous system encodes and decodes earthquake precursors and explains how human magnetosensory cells can solve complex problems such as predicting earthquake magnitude and locating epicenters.
基金Project(41472254)supported by the National Natural Science Foundation of China。
文摘Granite is usually composed of quartz,biotite,feldspar,and cracks,and the variation characteristics of these components could reflect the deformation and failure process of rock well.Taking granite as an example,the video camera was used to record the deformation and failure process of rock.The distribution of meso-components in video images was then identified.The meso-components of rock failure precursors were also discussed.Moreover,a modified LSTM(long short-term memory method)based on SSA(sparrow search algorithm)was proposed to estimate the change of meso-components of rock failure precursor.It shows that the initiation and expansion of cracks are mainly caused by feldspar and quartz fracture,and when the quartz and feldspar exit the stress framework,rock failure occurs;the second large increase of crack area and the second large decrease of quartz or feldspar area may be used as a precursor of rock failure;the precursor time of rock failure based on meso-scopic components is about 4 s earlier than that observed by the naked eye;the modified LSTM network has the strongest estimation ability for quartz area change,followed by feldspar and biotite,and has the worst estimation ability for cracks;when using the modified LSTM network to predict the precursors of rock instability and failure,quartz and feldspar could be given priority.The results presented herein may provide reference in the investigation of rock failure mechanism.
基金The authors acknowledge the financial support by the National Natural Science Foundation of China(52161145408 and 21975038)the Research and Innovation Team Project of Dalian University of Technology(DUT2022TB10)+2 种基金the Fundamental Research Funds for the Central Universities(DUT22QN213)the Innovation Technology Fund(MRP/040/21X)the Green Technology Fund(GTF202020164)for their financial support。
文摘All-inorganic CsPbIBr_(2) perovskite has attracted widespread attention in photovoltaic and other optoelectronic devices because of its superior thermal stability.However,the deposition of high-quality solutionprocessed CsPbIBr_(2) perovskite films with large thicknesses remains challenging.Here,we develop a triple-component precursor(TCP) by employing lead bromide,lead iodide,and cesium bromide,to replace the most commonly used double-component precursor(DCP) consisting of lead bromide and cesium iodide.Remarkably,the TCP system significantly increases the solution concentration to 1.3 M,leading to a larger film thickness(~390 nm) and enhanced light absorption.The resultant CsPbIBr_(2) films were evaluated in planar n-i-p structured solar cells,which exhibit a considerably higher optimal photocurrent density of 11.50 mA cm^(-2) in comparison to that of DCP-based devices(10.69 mA cm^(-2)).By adopting an organic surface passivator,the maximum device efficiency using TCP is further boosted to a record efficiency of 12.8% for CsPbIBr_(2) perovskite solar cells.
文摘The study focused on the modification with platinum of dark defective titania obtained via pulsed laser ablation. Both the method of Pt introduction and the nature of the Pt precursor were varied. All samples exhibited similar phase compositions, specific surface areas, and Pt contents. High-resolution transmission electron microscopy coupled with pulsed CO adsorption revealed increased dispersity when photoreduction and the hydroxonitrate complex (Me _(4) N) _(2) [Pt _(2) (OH) _(2) (NO _(3) ) _(8) ] were used. The sample featured a high content of single-atom species and subnano-sized Pt clusters. The X-ray photoelectron spectroscopy results showed that the photoreduction method facilitated the appearance of a larger number of Pt ^(2+) states, which appeared owing to the strong metal-support interaction (SMSI) eff ect of the transfer of electron density from the electron-saturated defects on the TiO _(2) surface to Pt ^(4+) . In the hydrogen evolution reaction, samples with a significant fraction of the Pt ^(2+) ionic component, capable of generating short-lived Pt^(0) single-atom sites under irradiation due to the SMSI eff ect, exhibited the highest photocatalytic activity. The 0.5Pt(C)/TiO_(2) -Ph sample exhibited the highest hydrogen yield with a quantum efficiency of 0.53, retaining its activity even after 8 h of operation.
基金supported by the Key Program of Applied and Basic Research in Yunnan Province(Grant No.202101AS070008)the National Natural Science Foundation of China(NSFC 31760187)+4 种基金supported by the 111 Project(D21027)the Yunnan Provincial Academician Workstation(YSZJGZZ-2020052)the Foreign Expert Workstation(202305AF150006)supported by the Scientific Research Foundation of Education Department of Yunnan Province(Grant Nos.2023J0696,2023Y0699)Foreign Talent Introduction Program of Science and Technology Department of Yunnan Province(Grant No.202305AO350002).
文摘Tannin foam is a new functional material.It can be widely applied to the automobile industry,construction industry,and packaging industry due to its wide range of raw materials,renewable,easily degraded,low cost and almost no pollution.Preparing tannin foam is a very complex process that includes high temperature,two phases,mechanical agitation,and phase change.To investigate the influence of the stirring velocity and paddle shape,simulation was calculated by making use of the volume of fluid(VOF)method and multiple reference frame(MRF)method in a three-dimensional flow field of tannin-based foaming precursor resin.The gas holdup and velocity magnitude were analysed with various conditions of mechanical velocities and paddle shape in the stirring flow field.The result shows the higher the velocity,the greater the disturbance and paddle shape between the eggbeater and the Rushton turbine,obviously the paddle shape of the eggbeater with a wider range of agitation,which can entrap more air into the tannin-based foaming precursor resin in a short time.Especially when the speed is 1500 rpm,the flow field of the Rushton turbine comes out of a ditch,which decreases the efficiency of mass transfer;there is less air to mix into the tannin-based foaming precursor resin,which causes unevenness.At the same time,the eggbeater shows the marvelous capability of hybrid as it has two vortexes and multiple cycles that make a difference from the Rushton turbine,which has only one vortex and two upper and lower loops;the structure makes the flow field more stable allowed evenness of flow field tannin-based foaming precursor resin.The results reveal that it is beneficial for tannin-based foaming precursor resin to use an eggbeater with a speed of 1500 rpm to reduce the consumption of resources while obtaining a uniform flow field.
基金financed by grants provided by the Department of Industry,Innovation,Commerce and Tourism of the Basque Government(Gaitek 10/002)Diputacion Foral de Gipuzkoa(OF 53/2011)+1 种基金Ministerio de Ciencia e Innovacion(PI10/02871 and INNPACTO pro-grams,IPT-300000-2010-17)A.I.was supported by the“Programa I3SNS”(CES09/015)from Instituto de Salud Carlos III and by Osaki-detza(Spain).
文摘Neuronal and glial differentiation potential of skin-derived precursors is of great interest for clinical application in the treatment of neurodegenerative disease. In this sense, the pig model is a great candidate for the development of preclinical models. To the date, skin-derived precursor spheres have not been isolated from adult porcine skin. In order to optimize the protocol for isolating dermal precursor spheres from adult porcine skin, 15 porcine skin biopsies were subjected to three different processing protocols. Liberase-based digestion of ventral porcine skin gave rise to more cells with spherogenic capacity than other protocols and these spheres presented phenotypic and differentiation potential consistent with bona fide skin-derived precursor cells.
基金Supported by Natural Science Foundation of Beijing "Effect of porcine skin-derived dendritic cells on PCV infection" (6062006)Beijing Organization Department Project"Influence of PCV infection on bone marrow cell differentiation" (20061D0502100282)~~
文摘[Objective] This study aimed to investigate the changes of the transcriptional levels of molecules associated with endogenous antigen processing and presenta- tion in porcine skin-derived dendritic cells infected with PCV2 in vivo. [Method] Healthy 40-day-old Landrace piglets were infected with porcine circovirus type 2 （PCV2） and euthanized on the 34, 7rd, 14th, 21st and 35th d post inoculation （DPI）. The porcine skin-derived dendritic cells （DCs） were collected to analyze the transcrip- tional levels of molecules （LMP7, UBP, MHC-I, calreticulin） associated with endogenous antigen processing and presentation by using real-time fluorescent quantitative PCR （real-time FQ-PCR）. [Result] The results showed that the level of LMP7 mR- NAs was reduced significantly on the 3DPI （P〈0.05）; the level of UBP mRNAs was consistently up-regulated, which increased significantly on the 21DPI and 35DPI （P〈 0.05）; the level of MHC-I mRNAs was significantly down-regulated on the 7DPI （P〈 0.05）; the level of calreticulin mRNAs was up-regulated slightly without significant dif- ference. [Conclusion] PCV2 can inhibit the endogenous antigen processing and presentation ability of porcine skin-derived DCs at early stages of infection.
基金Supported by the National Natural Science Foundation of China(31070443)the National Science Foundation of China for Talent Training in Basic Research(J1103507)+1 种基金The Priority Academic Program Development of Jiangsu Higher Education Institutions,Innovation Promotion Project of Nanjing Municipal Science and Technology Commissions(201105058)the Practice and Innovation Training Program for the Students of Nanjing Normal University~~
文摘[Objective] This study was to explore the effect of three precursors on the accumulation of principal volatile oil constituents in tissue culture plantlets of Atractylodes lancea （Thunb.） DC. with the aim to provide references for the improvement of artificial cultivated A. lancea quality. [Method] Three precursors were added into the MS rooting medium for A. lancea tissue culture plantlets and the volatile oil was extracted by ultrasonication after cultured for several days. The content of atractylon, atractylol, β-eucalyptol and atractydin in the volatile oil were determined by using gas chromatography method. [Result] The addition of xylose, isoprene and tetrahydrofuran impacted the growth indicators, yield of volatile oil and relative percentage content of the four constituents of A. lancea tissue culture plantlets. In the 6 g/L xylose optimized medium, the atractylon and β-eucalyptol content reached up to 4.23% and 56.34%, respectively, 1.41% and 1.66% higher than the control; although the addition of isoprene into medium raised the atractylon content, the accumulation of total volatile oil was inhibited that it decreased by 23.67%, 31.06% and 7.10% to the control; for the tetrahydrofuran optimized medium, the content of atractylon, atractylol and atractydin all increased, and the total volatile oil content increased by 49.97% to the control when the concentration of tetrahydrofuran was 0.07 g/L. [Conclusion] The addition of xylose and tetrahydrofuran promoted the accumulation of principal constituents of the volatile oil, whereas the addition of isoprene inhibited the accumulation.
基金Funded by the National "Twelfth Five-Year" Plan for Science&Technology Support of China(No.2011BAE29B02))
文摘The effects of atmospheres and precursors on MnOx/TiO2 catalysts were studied, which were prepared by the impregnation method and tested for their NOx conversion activity in ammonia selective catalytic reduction （NH3-SCR） reactions. Results showed that the manganese carbonate （MC） precursor caused mainly Mn2O3, while the manganese nitrate （MN） precursor resulted primarily in MnO2 and the manganese sulfate （MS） precursor was unchanged. The manganese acetate （MA） precursor leaded obtaining a mixture of Mn2O3 and Mn304. NOn conversion decreased in the following order： MA/TiO2 〉 MC/TiO2 〉 MN/TiO2 〉 MS/TiO2 〉 P25, with a calcination temperature of 773 K in air. Catalysts that were prepared by MA and calcined in oxygen performed strong interaction between Ti and Mn, while MnTiO3 was observed. Compared to the catalysts calcined in nitrogen, those calcined in oxygen had larger diameter and smaller surface area and pore. Catalysts that were prepared by MA and calcined in nitrogen tended to gain higher denitration rates than those in air, since they could be prepared with significant specific surface areas. NO., conversion decreased with calcination atmospheres： Nitrogen〉 Air〉 Oxygen. Meanwhile, amorphous Mn2O3 turned into crystalline Mn2O3, when the temperatures increased from 673 to 873 K.
基金the National Natural Science Foundatlon of China under grant No.50172004,50273002 ,50333070.
文摘Structural changes in carbon fibers at each stage of, especially, preoxidation process are well known to play a great role in achieving the ultimate product quality. Differential scanning calorimetry (DSC), scanning electron microscope (SEM), density method and optical microscope were used to characterize the preoxidation extent. A conventional approach, e.g., density aim, to evaluate the extent of preoxidation is not very exact. A DSC curve of a PAN precursor only can provide general information, major in the temperature regime of preoxidation reaction. However, the evaluation of a preoxidation extent, especially from conventional preoxidation temperature with a great span regime of 200~400癈, is put forward in this paper, in which the evolution of core/shell morphological structure is a kind of straightforward evidence.
基金supported by the Open Foundation of Key Laboratory of the Ministry of Educationof Nonferrous Metal Alloys and Processes(No.EKL09002)The Ph.D.Fund Project of Lanzhou University of Science and Technology(No.BS01200904)
文摘Sol-gel technology was employed to synthesize nanosized precursors of La-Mg hydrogen storage alloy at different pH values (0.5, 1.5, 8.0 and 9.0) of reaction solution. The effect of pH value on microstructure of the nano precursors of La-Mg hydrogen storage alloy was studied by infrared radiation (IR), thermo-gravimetric and differential thermal analysis (TG/DTA), X-ray diffraction analyzer (XRD) and transmission electron microscopy (TEM). IR results indicate that the chelating agent, citric acid, is not fully ionized, and carboxyl groups are not entirely used to complex metal ions in acidic solutions. The efficiency of complexing metal ions is enhanced in basic solutions. TG/DTA results show that the combustion may take place with low rate of the flame propagation that causes the longer combustion time when pH<1.5. On the contrary, the dry gel synthesized in basic solution combusts at low ignition temperature and combustion reaction is violent; it is easy to form fine particles. XRD and TEM results reveal that the precursor powders are mainly two-phase mixture of La 2 O 3 and MgO. The morphology of the particles is almost flake with the size of ~30 nm when pH is 8.0.
