Dynamic response mechanism and precursor characteristics of gneiss rockburst under different initial burial depths

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.

Valorization of Camellia oleifera oil processing byproducts to value-added chemicals and biobased materials: A critical review

The C.oleifera oil processing industry generates large amounts of solid wastes,including C.oleifera shell(COS)and C.oleifera cake(COC).Distinct from generally acknowledged lignocellulosic biomass(corn stover,bamboo,birch,etc.),Camellia wastes contain diverse bioactive substances in addition to the abundant lignocellulosic components,and thus,the biorefinery utilization of C.oleifera processing byproducts involves complicated processing technologies.This reviewfirst summarizes various technologies for extracting and converting the main components in C.oleifera oil processing byproducts into value-added chemicals and biobased materials,as well as their potential applications.Microwave,ultrasound,and Soxhlet extractions are compared for the extraction of functional bioactive components(tannin,flavonoid,saponin,etc.),while solvothermal conversion and pyrolysis are discussed for the conversion of lignocellulosic components into value-added chemicals.The application areas of these chemicals according to their properties are introduced in detail,including utilizing antioxidant and anti-in-flammatory properties of the bioactive substances for the specific application,as well as drop-in chemicals for the substitution of unrenewable fossil fuel-derived products.In addition to chemical production,biochar fabricated from COS and its applications in thefields of adsorption,supercapacitor,soil remediation and wood composites are comprehensively reviewed and discussed.Finally,based on the compositions and structural characteristics of C.oleifera byproducts,the development of full-component valorization strategies and the expansion of the appli-cationfields are proposed.

Investigation of granite failure precursor under axial load using modified LSTM framework

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.

Stabilizing perovskite precursors with the reductive natural amino acid for printable mesoscopic perovskite solar cells

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.

Precursor engineering enables high-performance all-inorganic CsPbIBr_(2) perovskite solar cells with a record efficiency approaching 13%

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.

Disinfection Byproducts and Their Precursors in Drinking Water Sources:Origins,Influencing Factors,and Environmental Insights

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.

Numerical Simulation of the Mechanical Stirring Process in a Tannin-Based Foaming Precursor Resin

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.

Highly Defective Dark TiO_(2) Modified with Pt: Effects of Precursor Nature and Preparation Method on Photocatalytic Properties

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.

Engineering the coordination structure of Cu for enhanced photocatalytic production of C_(1) chemicals from glucose

Photocatalytic decomposition of sugars is a promising way of providing H_(2),CO,and HCOOH as sus-tainable energy vectors.However,the production of C_(1) chemicals requires the cleavage of robust C−C bonds in sugars with concurrent production of H_(2),which remains challenging.Here,the photo-catalytic activity for glucose decomposition to HCOOH,CO(C_(1) chemicals),and H_(2) on Cu/TiO_(2)was enhanced by nitrogen doping.Owing to nitrogen doping,atomically dispersed and stable Cu sites resistant to light irradiation are formed on Cu/TiO_(2).The electronic interaction between Cu and nitrogen ions originates valence band structure and defect levels composed of N 2p orbit,distinct from undoped Cu/TiO_(2).Therefore,the lifetime of charge carriers is prolonged,resulting in the pro-duction of C_(1) chemicals and H_(2) with productivities 1.7 and 2.1 folds that of Cu/TiO_(2).This work pro-vides a strategy to design coordinatively stable Cu ions for photocatalytic biomass conversion.

CO_(2) conversion to solar fuels and chemicals:Opening the new paths

This future article discusses the new prospects and directions of CO_(2)conversion via the photo-electrocatalytic(PEC)route.The second(2nd)generation solar fuels and chemicals(SFs)are generated directly in PEC systems via electrons/protons reactions without forming molecular H_(2)as an intermediate,overcoming the thermodynamics limitations and practical issues encountered for electro-fuels produced by multistep thermocatalytic processes(i.e.CO_(2)conversion with H_(2)coming from water electrolysis).A distributed and decentralized production of SFs requires very compact,highly integrated,and intensified technologies.Among the existing reactors of advanced design(based on artificial leaves or photosynthesis),the integrated photovoltaic plus electrocatalytic(PV-EC)device is the only system(demonstrated at large scale)to produce SFs with high solar-to-fuel(STF)efficiency.However,while the literature indicates STF efficiency as the main(and only)measure of process performance,we remark here the need to refer to productivity(in terms of current density)and make tests with reliable flow PEC systems(with electrodes of at least 5–10 cm^(2))to accelerate the scaling-up process.Using approaches that minimize downstream separation costs is also mandatory.Many limitations exist in PEC systems,but most can be overcome by proper electrode and cell engineering,thus going beyond the properties of the electrocatalysts.As examples of current developments,we present the progress of(i)artificial leaf/tree devices for green H_(2)distributed production and(ii)a PEC device producing the same chemicals at both cathode and anode parts without downstream operations for green solvent distributed production.Based on these developments,future directions,such as producing fertilizers and food components from the air,are outlined.The aim is to provide new ideas and research directions from a personal perspective.

Mo_(2)B_(2)O_(2) MBene for Efficient Electrochemical CO Reduction to C_(2) Chemicals:Computational Exploration

Emerging as a new class of two-dimensional materials with atomically thin layers,MBenes have great potential for many important applications such as energy storage and electrocatalysis.Toward mitigating carbon footprint,there has been increasing interest in CO_(2)/CO conversion on MBenes,but mostly focused on C_(1) products.C^(2+) chemicals generally possess higher energy densities and wider applications than C_(1) counterparts.However,C–C coupling is technically challenging because of high energy requirement and currently few catalysts are suited for this process.Here,we explore electrochemical CO reduction reaction to C_(2) chemicals on Mo_(2)B_(2)O_(2) MBene via density-functional theory calculations.Remarkably,the most favorable CO–COH coupling is revealed to be a spontaneous and barrierless process,making Mo_(2)B_(2)O_(2) an efficient catalyst for C–C coupling.Among C_(1) and C_(2) chemicals,ethanol is predicted to be the primary product.Furthermore,by charge and bond analysis,it is unraveled that there exist significantly more unbonded electrons in the C atom of intermediate*COH than other C_(1) intermediates,which is responsible for the facile C–C coupling.From an atomic scale,this work provides microscopic insight into C–C coupling process and suggests Mo_(2)B_(2)O_(2) a promising catalyst for electrochemical CO reduction to C_(2) chemicals.

Uniform deposition of ultra-thin TiO_(2) film on mica substrate by atmospheric pressure chemical vapor deposition: Effect of precursor concentration

The performance of pearlescent pigment significantly affected by the grain size and the roughness of deposited film. The effect of TiCl_(4) concentration on the initial deposition of TiO_(2) on mica by atmospheric pressure chemical vapor deposition(APCVD) was investigated. The precursor concentration significantly affected the deposition and morphology of TiO_(2) grains assembling the film. The deposition time for fully covering the surface of mica decreased from 120 to 10 s as the TiCl_(4) concentration increased from 0.38%to 2.44%. The grain size increased with the TiCl_(4) concentration. The AFM and TEM analysis demonstrated that the aggregation of TiO_(2) clusters at the initial stage finally result to the agglomeration of fine TiO_(2) grains at high TiCl_(4) concentrations. Following the results, it was suggested that the nucleation density and size was easy to be adjusted when the TiCl_(4) concentration is below 0.90%.

Catalytic conversion of lignocellulosic biomass into chemicals and fuels

In the search of alternative resources to make commodity chemicals and transportation fuels for a low carbon future,lignocellulosic biomass with over 180-billion-ton annual production rate has been identified as a promising feedstock.This review focuses on the state-of-the-art catalytic transformation of lignocellulosic biomass into value-added chemicals and fuels.Following a brief introduction on the structure,major resources and pretreatment methods of lignocellulosic biomass,the catalytic conversion of three main components,i.e.,cellulose,hemicellulose and lignin,into various compounds are comprehensively discussed.Either in separate steps or in one-pot,cellulose and hemicellulose are hydrolyzed into sugars and upgraded into oxygen-containing chemicals such as 5-HMF,furfural,polyols,and organic acids,or even nitrogen-containing chemicals such as amino acids.On the other hand,lignin is first depolymerized into phenols,catechols,guaiacols,aldehydes and ketones,and then further transformed into hydrocarbon fuels,bioplastic precursors and bioactive compounds.The review then introduces the transformations of whole biomass via catalytic gasification,catalytic pyrolysis,as well as emerging strategies.Finally,opportunities,challenges and prospective of woody biomass valorization are highlighted.

Effects of post-mortem aging process on characteristic water-soluble taste-active precursors in yellow-feathered broilers

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.

Ionospheric precursors of strong earthquakes observed using six GNSS stations data during continuous five years(2011-2015)

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.

In situ formed ultrafine metallic Ni from nickel(Ⅱ) acetylacetonate precursor to realize an exceptional hydrogen storage performance of MgH_(2)-Ni-EG nanocomposite

It has been well known that doping nano-scale catalysts can significantly improve both the kinetics and reversible hydrogen storage capacity of MgH_(2) . However, so far it is still a challenge to directly synthesize ultrafine catalysts(e.g., < 5 nm), mainly because of the complicated chemical reaction processes. Here, a facile one-step high-energy ball milling process is developed to in situ form ultrafine Ni nanoparticles from the nickel acetylacetonate precursor in the MgH_(2) matrix. With the combined action of ultrafine metallic Ni and expanded graphite(EG), the formed MgH_(2)-Ni-EG nanocomposite with the optimized doping amounts of Ni and EG can still release 7.03 wt.% H_(2) within 8.5 min at 300 ℃ after 10 cycles. At a temperature close to room temperature(50 ℃), it can also absorb 2.42 wt.% H_(2) within 1 h. It can be confirmed from the microstructural characterization analysis that the in situ formed ultrafine metallic Ni is transformed into Mg_(2)Ni/Mg_(2)NiH_4 in the subsequent hydrogen absorption and desorption cycles. It is calculated that the dehydrogenation activation energy of the MgH_(2)-Ni-EG nanocomposite is also reduced obviously in comparison with the pure MgH_(2) . Our work provides a methodology to significantly improve the hydrogen storage performance of MgH_(2) by combining the in situ formed and uniformly dispersed ultrafine metallic catalyst from the precursor and EG.

Nano-single-crystal-constructed submicron MnCO_(3) hollow spindles enabled by solid precursor transition combined Ostwald ripening in situ on graphene toward exceptional interfacial and capacitive lithium storage

Hollow structuring has been identified as an effective strategy to enhance the cycling stability of electrodes for rechargeable batteries due to the outstanding volume expansion buffering efficiency,which motivates ardent pursuing on the synthetic approaches of hollow materials.Herein,an intriguing route,combining solid precursor transition and Ostwald ripening(SPTOR),is developed to craft nano single-crystal(SC)-constructed MnCO_(3) submicron hollow spindles homogeneously encapsulated in a reduced graphene oxide matrix(MnCO_(3) SMHSs/rGO).It is noteworthy that the H-bonding interaction between Mn_(3)O_(4) nanoparticles(NPs)and oxygen-containing groups on GO promotes uniform anchoring of Mn_(3)O_(4) NPs on GO,mild reductant ascorbic acid triggers the progressive solid-to-solid transition from Mn_(3)O_(4) NPs to MnCO_(3) submicron solid spindles(SMSSs)in situ on GO,and the Ostwald ripening process induces the gradual dissolution of interior polycrystals of MnCO_(3) SMSSs and subsequent recrystallization on surface SCs of MnCO_(3) SMHSs.Remarkably,MnCO_(3) SMHSs/rGO delivers a 500th lithium storage capacity of 2023 mAh g^(-1) at 1000 mAg^(-1),which is 10 times higher than that of MnCO_(3) microspheres/rGO fabricated from a conventional Mn^(2+)salt precursor(202 mAh g^(-1)).The ultrahigh capacity and ultralong lifespan of MnCO_(3) SMHSs/rGO can be primarily attributed to the superior reaction kinetics and reversibility combined with exceptional interfacial and capacitive lithium storage capability,enabled by the fast ion/electron transfer,large specific surface area,and robust electrode pulverization inhibition efficacy.Moreover,fascinating in-depth lithium storage reactions of MnCO_(3) are observed such as the oxidation of Mn^(2+)in MnCO_(3) to Mn^(3+)in charge process after long-term cycles and the further lithiation of Li_(2)CO_(3) in discharge process.As such,the Carbon Energy.SPTOR approach may represent a viable strategy for crafting various hollow functional materials with metastable nanomaterials as precursors.

Lineament analysis as a seismic precursor:The El Mayor Cucapah earthquake of April 4,2010(MW7.2),Baja California,Mexico

An earthquake called the MW7.2“El Mayor Cucapah”earthquake on April 4,2010 has been analyzed for seismic precursor.The changes in the lineament system concerning its pattern and time intervals were analyzed during the earthquake preparation period and occurrence using the automated lineament detection method.The Landsat 5 TM images were processed using LESSA and ADALGEO software obtaining similar results.The statistical analysis revealed the stress accumulation due to plate interaction during earthquake formation.The study shows that the number of extracted lineaments changes rapidly about 23 months before the earthquake,and the systems return to the initial stage after 23 months.Most lineaments coincide with the extension of the San Andreas Fault as NW direction is the dominant trend.Thus,it can be concluded that the featural changes within the Rose diagram corresponding to the different strokes direction along with oriented elongation lines as disclosed in the present study using satellite images could be identified as a mid-term and/or short-term precursors of the earthquake.However,even though the dynamism of the El Mayor Cucapah earthquake is found in the extracted lineaments,it is possible to isolate more significant earthquakes even if new ones appear near the zone.Moreover,using two algorithms for lineament detection allows for the tectonics to corroborate the obtained lineaments and dynamism.

Not Follicular but Dermal Melanocyte Precursors Are Histopathologically Retained in Vitiligo

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+/Fzd4+ cells in the hair follicle were significantly decreased in number in the lesions, Nestin+ and p75NGFR+ 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.

Active precursor promoting nucleation/growth of MwW zeolite and controlling its morphology

MWW zeolites is an important catalyst in petrochemical industry.However,the efficient preparation of Mww zeolites still faces challenges,and the origin of influential factors for regulating its structure properties also remains obscure.Herein,we designed a nanoscale amorphous silica-alumina species denoted as active precursor(APS),and adopt the APS in the HMI mixture to synthesize MCM-22 zeolite(APS-MWW)successfully.To reveal the distinctive role of APS in promoting the crystallization of MWW zeolites,two crystal materials(ITQ-1 and MCM-22)and one mother liquor(ML)as seeds to synthesize three types of MWW zeolites.Typically,when adding APS in the synthetic mixture,the HMI amount was reduced to less than a quarter and crystallization time was reduced to 36 h.APS-MWW sample provides a smaller particle size(2-4μm)and thinner stacked layer thickness(5-20 nm).Synchrotron radiation Small Angle X-ray Scattering(SAXS)shows each seed has a different impact on the species'fractal structure and size distribution in the mixture,which is highly related to the nucleation and growth of MWW zeolites.APS shows a large number of 6 membered ring(MR)structure units which play a sig-nificant role in boosting the rapid nucleation and growth of APS-MwW zeolite.Among the synthesized MWW zeolites,the APS-MWW performs the highest ethylbenzene yield in the alkylation reaction of benzene-ethylene,which is attributed to its moderate flake thickness,appropriate texture properties and more external surface acidity.The results will provide a new perspective for producing MwW-types zeolites by using the available and effective active precursor.