Preparation of porous α-Fe2O3-supported Pt and its sensing performance to volatile organic compounds

Porous α-Fe2O3 was synthesized by a simple hydrothermal treatment of FeCl3 aqueous solution followed by a calcination process. In the synthesis of porous α-Fe2O3, no templates or pore-directing agents were used. The as-prepared porous α-Fe2O3 was further employed as a support for loading Pt nanoparticles. The gas sensing performance of the obtained porous α-Fe2O3-supported Pt to VOCs was investigated. The sensor presented a high response and fast response-recovery characteristic to several VOCs including acetone, ether, methanol, ethanol, butanol and hexanol. Meanwhile, it exhibited a much higher response than the pure α-Fe2O3 at the operating temperature of 260°C. The enhanced sensing properties may be related to the unique porous structure of the α-Fe2O3 support and the promoting effect of active Pt nanoparticles for the sensing reactions.     

Determination of Trace Amounts of Vanadium by Kinetic-Catalytic Spectrophotometric Methods

Kinetic-catalytic spectrophotometric methods were proposed for the determination of trace amounts of vanadium element as vanadium（Ⅳ） and/or V（Ⅴ） ions. The vanadium（Ⅳ） as VO^2＋ ion and/or vanadium（Ⅴ） as VO3^- ion showed a catalytic effect on the kinetic reactions between a color reagent such as methylthymol blue （MTB） or SPADNS and bromate in acidic media. The rate of decrease in the absorbance of the reagent MTB at 440 nm or SPADNS at 510 nm was proportional to concentration of V（Ⅳ） and/or V（Ⅴ） ions in the solution. The linear ranges for determination of vanadium were obtained in the range of 1.0-150 and 5.0-100.0 μg/L by the fixed-time and slope methods, respectively, with using MTB as reagent. In the presence of SPADNS as reagent, the calibration curves were made in the amplitude 1.0-200.0 and 5.0-150 μg/L of vanadium ion by the fixed-time and slope methods, respectively. Using fixed-time method, the limits of detection were obtained to be 0.5 and 0.7 μg/L of vanadium in the presence of MTB and SPADNS as reagents, respectively. Detection limits of vanadium by slope method and reagents of SPADNS and MTB were obtained to be 3.5 and 3.8 μg/L of vanadium, respectively. The proposed methods were applied successfully to determination of vanadium in synthetic and real samples.     

Cuprous Iodide Catalyzed Synthesis of Diaryl Selenide and Telluride from Organoboronic Acids with Diphenyl Diselenide and Ditelluride

Organoselenium and tellurium compounds have received much attention not only as synthetic reagents or intermediates in organic synthesis but also as promising donor molecules for conductive materials.[1] A number of synthetic methods have been reported to prepare organoselenium and tellurium derivatives. A convenient and general method to introduce a selenium or tellurium moiety into organic molecules is the reaction of a metal selenolate or tellurolate with appropriate electrophiles such as organic halides, acyl chlorides, epoxides, and α, β-enones.[2] However, it is difficult to synthesize the unsymmetrical diarylselenides and tellurides through the reaction of selenide anion with organic halides because of the less reactivity of aryl halides. To accomplish this purpose, the reaction (iodobenzene with phenylselenol)was generally carried out in the presence of catalysts, ligands and strong bases. But, the reaction needs longer time to accomplish and form the products in moderate yields.     

TEMPO and its derivatives mediated reactions under transition-metal-free conditions

2,2,6,6-Tetramethyl-l-piperidinyl-N-oxyl(TEMPO)and its derivatives as stable radicals can participate in many reactions.During the process,TEMPO and its derivatives could act not only as the substrates to capture or initiate new radical intermediates to provide new compounds but also as organic catalysts or oxidants for transformations of alkenes,alcohols,aldehydes and so on to synthesize various high valueadded compounds.In this review,we would introduce recent advances of the transformations of different substrates mediated by TEMPO and its derivatives under transition-metal-free conditions.     

SPONTANEOUS DISPERSION OF SOME ACTIVE COMPONENTS ONTO THE SURFACES OF CARRIERS

If an ionic or molecular crystalline solid is mixed with a carrier of high specific surface and then heated at a suitable temperature below its melting point for several hours, the crystalline solid will disperse spontaneously onto the surface of the carrier. It has been proved by the fact that the X-ray diffraction peaks of the crystalline phase either diminish sharply or disappear completely according as whether the amount of the solid mixed with each unit weight of carrier exceeds the critical amount or not and this critical amount of solid is closely related to and usually varies directly as the specific surface of the carrier.If the active component of a catalyst is a compound instead of a metal, and its quantity is not enough to cover the surface of the carrier, it often disperses somewhat as a monolayer, because the ions or molecules of the active component combine strongly with the surface ions or groups of the carrier. This paper presents some fundamental points and methods of investigation in     

A MODEL FOR THE RELEASE BEHAVIOR OF DRUGS FROM HYDROGEL NANOPARTICLE

1. INTRODUCTION In recent years, significant efforts has been devoted to develop nanoparticle for drug delivery since it offers a suitable means of delivering small molecular weight drugs, as well as macromolecules such as proteins, peptides, vaccine, genes or antineoplastic drugs by either localized or targeted delivery to the special site or the tissue of interest. However, most studies only focused on the preparation and characterization of nanoparticles as well as the therapeutic appli…     

碳纳米管为基质对氨基酸的MALDI-FT MS分析

Twenty common amino acids have been analyzed successfully by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) using carbon nanotubes as matrix. From the spectra, little or no background interference or fragmentation of the analytes has been observed. This method was also applied to the analysis of amino acid mixture successfully. Carbon nanotubes have some features such as large surface area to disperse the analyte molecules sufficiently and prevent the sample aggregation and strong ultraviolet absorption to transfer energy easily to the analyte molecules. The present method has potential application for the rapid and sensitive analysis of amino acids and their mixture.     

ON INFLUENCE OF CHARACTERISTICS OF FLOW FIELDS AND THERMAL FACTORS ON MOTION OF TYPHOONS

This paper mainly aims at studying the influence of the characteristics of flow fields and thermal factors on the motion of typhoons, Results show that the northward (or southward) component of typhoon motion shows up when the southerly maximum wind on the east periphery of a typhoon is stronger (or weaker) than the northerly one to the west. A westward (or eastward) component appears when the westerly maximum wind to the south is weaker (or stronger and exceeds a certain value) than the easterly one to the north. The speeds of motion differ from each other depending on the different flow patterns. Counterclockwise rotation occurs when two typhoons are close to such an extent that they interact on each other. A typhoon also has the tendency of moving towards the stronger heating and more unstable areas, as well as in the direction of the gradient of temperature variation. In addition, the impact of the variation of subtropical high on typhoon motion is also discussed.     

PREPARATION AND CRYSTAL STRUCTURE OF TETRAKIS(TETRAHYDROFURAN) MAGNESIUM DICHLORIDE[MgCl_2·4THF]

<正> INTRODUCTION. The magnesim, dichloride is widely used as a supporter of the highly efficient Ziegler-Natta catalyst with ether or ester as a donor. To study the interaction between the supporter and the donor would lead to a better understanding of the mechenisms of stereoregular polymerization. Here we wish to report the preparation and X-ray crystal structure of MgCl_2 4THF, which is the first example of the MgCl_2 complex uncontaining coordinated water or solvent water.     

STUDIES ON ORGANOMETALLIC COMPOUNDS OF TITANIUM,ZIRCONIUM AND HAFNIUM TITANIUM, ZIRCONIUM AND HAFNIUM——SYNTHESES AND PROPERTIES OF BIS (CYCLOPENTADIENYL) DI-(ARYLOXY) DERIVATIVES

The dichlorides of bis(cyclopentadienyl) or bis(methylcyclopentadienyl) titanium, zircon-ium and hafnium reacting with phenol or substituted phenols in the presence of base give aseries of new aryloxymetal derivatives. The activities of chlorine atoms in the dichlorides ofbis(cyclopentadienyl)titanium, zirconium and hafnium molecules towards phenols are compared.The influence upon HNMR of the cyclopentadienyl ring due to the electronegativities of themetals and the substituents on the phenyl rings, as well as the number and position of thesubstituents are discussed.     

Multi-walled carbon nanotubes as a ligand in nickel α-diimine based ethylene polymerization

Two novel heterogeneous nickel ?-diimine based polymerization catalysts, containing MWCNT as the main ligand, were synthesized by novel in situ catalyst preparation technique. The in situ synthesis was performed by covalent attachment of the acenaphthenic ligand core to amine functionalized MWCNT ligand arms through diimine bonding and further nickel dibromide chelation. The prepared catalysts were fully characterized and their structures and supporting efficiencies were determined. Single or double introduction of the MWCNTs through their ends or sidewall(s) in the catalytic system, as a ligand, influenced the catalytic performance, microstructure and morphology of obtained polyethylenes. MWCNT sidewall bonding to para-aryl position of the tetramethylphenyl moiety performed as more electron-donating ligand than MWCNT ends linked to the imine bond and protected the catalytic system to retain its activity. This character resulted in the maintenance of the resulting polymer topology at elevated temperatures so that the catalytic activity and the obtained polymer melting points remained around 110 g PE?mmol?1 Ni?h?1 and 123 ℃ in all polymerization temperatures respectively. In polymerization trials, molecular weight fall against temperature was not as sharp as what had been observed in sequentially prepared catalysts insofar as the molecular weight of resultant polymer at 60 ℃ reached to 310000 g?mol?1 which was close to the highest value had been reported at 30 ℃ for sequentially prepared catalysts. TEM observations showed the presence of the stopped-growth polymer chains due to geometrical constrains or ligand debonding for both catalytic systems.     

Effect of channel block on the collective spiking activity of coupled stochastic Hodgkin-Huxley neurons

Toxins, such as tetraethylammonium (TEA) and tetrodotoxin (TTX), can make potassium or sodium ion channels poisoned, respectively, and hence reduce the number of working ion channels and lead to the diminishment of conductance. In this paper, we have studied by numerical simulations the effects of sodium and potassium ion channel poisoning on the collective spiking activity of an array of coupled stochastic Hodgkin-Huxley (HH) neurons. It is found for a given number of neurons sodium or potas- sium ion channel block can either enhance or reduce the collective spiking regularity, depending on the membrane patch size. For a given smaller or larger patch size, potassium and sodium ion channel block can reduce or enhance the collective spiking regularity, but they have different patch size ranges for the transformation. This result shows that sodium or potassium ion channel block might have dif- ferent effects on the collective spiking activity in coupled HH neurons from the effects for a single neuron, which represents the interplay among the diminishment of maximal conductance and the in- crease of channel noise strength due to the channel blocks, as well as the bi-directional coupling be- tween the neurons.     

The hierarchical structure of chemical engineering

Around the turn of the present century,scholars began to recognize chemical engineering as a com-plex system,and have been searching for a convenient point of entry for refreshing its knowledge base.From our study of the dynamic structures of dispersed particles in fluidization and the resultingmulti-scale method,we have been attempting to extend our findings to structures prevailing in othermultiphase systems as well as in the burgeoning industries producing functional materials.Chemicalengineering itself is hierarchically structured.Besides structures based on space and time,such hier-archy could be built from ChE history scaled according to science content,or from ChE operation ac-cording to the expenditure of manpower and capital investment.     

EFFECTS OF K_2O AND MnO PROMOTERS ON THE PRODUCTION OF LIGHT ALKENES VIA SYNGAS OVER Fe/SILICALITE-2 CATALYST IL REDUCIBILITY OF K-Fe-MnO/SILICALITE-2 CATALYST

K_2O and MnO are two kinds of necessary promoters to theselective production of light alkenes from CO hydrogenation over silicalite-2(Si-2) zeolite supported Fe catalyst. The addition of both K_2O and MnOpromoters into Fe/Si-2 catalyst leads to a remarkable increase in the COconversion and the selectivity to light oletins. Silicalite-2 zeolite as Fe-MnOcatalyst support can suppress the formation of α-Fe_2MnO_3 or/andα-Fe_(2-y)Mn_yO_3 as Well as α-Fe_2O_3 and/or α-Mn_2O_3, being favorable for(?)ncreasing the dispersion of active metal component. So MnO can promotethe reduction of Fe~(3-) and enhance the capacity of CO adsorption, which canimprove the activity of the activity of the catalyst for CO hydrogenation. While K_2Opromoter is unfavorable for reduction of Fe~(3-) to some degree with formation of Fe~(2-) as a new species after reduction. However, K_2O promoter can enhance the capacity and strength of CO adsorption greatly.So K_2O can alsoimprove the activity of catalyst for CO hydrogenation.     

过氧化氢溶液中单和双金属金-银纳米粒子氧化L-亮氨酸的动力学(英文)

The catalytic activity of surfactant stabilized mono-and bimetallic Au and Ag nanoparticles for the oxidation of an amino acid,L-leucine,was studied using hydrogen peroxide as the oxidant.The Au and Ag nanoparticle catalysts exhibited very good catalytic activity and the kinetics of the reaction were found to be pseudo-first order with respect to the amino acid.The effects of several factors,such as oxidant concentration,ionic strength,pH,and catalyst concentration on the reaction,were also investigated.In particular,optimal oxidant and catalyst concentrations were determined.Very high concentrations of the metal nano-catalysts or the oxidant led to a dramatic increase in reaction rate.Moreover,bimetallic Au-Ag catalysts provided higher selectivity than pure Au or Ag.     

Effects of Temperature and Energy on Stability of Oligomeric Enzyme Probed on Electrospray Ionization Mass Spectrometry

Escherichia coli 3-Deoxy-D-manno-octulosonate 8-phosphate（KDO8P） synthase catalyzed the condensation reaction between D-arabinose 5-phosphate（A5P） and phosphoenolpyruvate（PEP） to form KDO8P and inorganic phosphate（Pi）. The noncovalent tetrameric association ofKDO8P synthase was observed and dissociated in gas phase by means of electrospray ionization mass spectrometry under the very ＂soft＂ conditions. The results indicate that PEP-bound enzyme generated abundant tetrameric species as well as monomeric species at the ＂soft＂ conditions, whereas, the unbound enzyme favored the formation of a dimeric species. The mass spectra of the mixture of the enzyme with one of substrates, PEP, and A5P or one of products, KDO8P and Pi show that the complex of the unbound enzyme with PEP or Pi was prone to the formation of a monomeric species, whereas, that of the unbound enzyme with A5P or KDO8P was similar to the unbound enzyme. The intensity of the dimeric species increased with the increase of temperature at a collision voltage of 10 V. Taken together, the results presented here suggest that mass spectrometry will be a powerful tool to explore subtile conformational changes and/or subunit-subunit interactions of multiprotein assembly induced by ligand-binding and/or the changes of environmental conditions.     

Catalytic transformations of cellulose and its derived carbohydrates into 5-hydroxymethylfurfural,levulinic acid,and lactic acid

The catalytic transformation of cellulose into key building-block or platform chemicals such as 5-hydoxymethylfurfural(HMF),levulinic acid,and lactic acid under mild conditions,has attracted much attention in recent years,as these conversions can be operated without consumption of hydrogen or oxygen and thus are more economical compared to the hydrogenolysis or oxidation of cellulose.This review article highlights recent advances in the development of novel catalysts or catalytic processes for the conversion of cellulose and its derived carbohydrates into HMF,levulinic acid,and lactic acid or their esters under inert atmosphere.We also analyze efficient catalytic systems for HMF production,in particular Lewis acids combined with ionic liquid or biphasic systems.For the formations of levulinic and lactic acids or their esters,we focus on the reactions in aqueous and alcohol media catalyzed by multifunctional catalysts that combine the functions of hydrolysis,isomerization,and dehydration-rehydration or retro-aldol reactions.The reaction mechanism for each process will also be discussed to gain insights into the activation of C–O and C–C bonds in the absence of hydrogen or oxygen.     

Quantitative High-Performance Liquid Chromatographic Determination of Neurotoxin β-ODAP and α- isomer in Grass Pea(Lathyrus sativus)

Grass pea (Lathyrus sativus) is leguminous crop cultivated in India,Bangladesh and Ethiopia, where it is a major protein source for people in the lowest income groups[1] .However, excessive ingestion of this pulse can lead to irreversible paralysis of the legs-a disease known as neurolathyrism or lathyrism.the causative agent was reported to be the non-protein amino acids,β-N-L-oxalyl-α,β-diaminopropionic acid (β-ODAP, sometimes, referred to as BOAA)[2]. The α-isomer of ODAP, α-N-oxaly 1-α,β-diaminopropionic acid, has been shown to be nontoxic to chicks and mice[3]. Lathyrus sativus shows good adaptation to the low rainfall conditions of northwestern China. It grows also in poor soil and is resistant to salt and flood. Our group was exploring to breed low or zero toxin varieties of Lathyrus sativus as grain crops for human consumption and as protein-rich feed for animals. So it is necessary to develop a method to detemine the toxin suitablefor differenth pu rpose.     

Study on the second-order non-linear optical properties of 10-hydrocarbylacridones

Twenty 10-hydrocarbylacridones and 2-methylacridone, 1-hydroxyacridone were synthesized from acridone and characterized by mp, IR, UV, 1H NMR and MS. Using Nd:YAG as a laser source, the second-order harmonic generation (SHG) values of the acridone derivatives were measured in powder state as compared with urea powder. The results showed that the SHG values of some of 10-hydrocarbylacridones were higher than that of urea, while others were lower. Although the hydrocarbyl substituents (R) attached to nitrogen atom of acridone were different in size and electronegativity, they had a little effect on the SHG values of 10-hydrocarbylacridones. Substituents, such as methyl or hydroxy group connected to the phenyl ring, caused a little effect on the SHG values, too, compared with acridone. The ability of R to push electron toward the nitrogen atom or to pull electron from the nitrogen atom play an important role on the maximum wavelengthes of UV-visible absorption of acridone derivatives.     

Mechanism of 1,2-shift through π-complex transition state

A systematic calculation of the potential curves or surfaces for 1,2-shift has been realized by using MNDO or other models in MOPAC programs. By referring to the previous authors' viewpoints, the 1,2-shift can be divided into two categories. 1,2-electron-deficient shift is that the electronic configuration of the atom which accepts the migrating group is a cation or an electron-deficient atom, and 1,2-anion shift is the one that the accepted atom of the migration group is a negative ion. In terms of the experimental facts and the calculation of the potential surfaces, in electron-deficient shift such as Beckmann or Baeyer-Villiger rearrangement, the migration occurs through a transition complex formed between the 7i-bond and the cation or electron-deficient migrating group, but in anion shift such as Wittig or Stevens rearrangement, the electron pair in it-orbit excites at first to π* orbit, and then the migration occurs through the new formed complex between the anion migration group and the vacant rc