Showing papers by "Yi Chen published in 2002"

Measurements of the cross section for e(+)e(-) --> hadrons at center-of-mass energies from 2 to 5 GeV.

Abstract: We report values of $R\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\ensuremath{\sigma}({e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\mathrm{hadrons})/\ensuremath{\sigma}({e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}})$ for 85 center-of-mass energies between 2 and $5\mathrm{GeV}$ measured with the upgraded Beijing Spectrometer at the Beijing Electron-Positron Collider.

The new emerging model for the structure of cooling cores in clusters of galaxies

Abstract: New X-ray observations with XMM-Newton show a lack of spectral evidence for large amounts of cooling and condensing gas in the centers of galaxy clusters believed to harbour strong cooling flows. This paper re-explores the cooling flow scenario in the light of the new observations. We explore the diagnostics of the temperature structure of cooling cores with XMM-spectroscopy, tests for intracluster X-ray absorption towards central AGN, the effect of metal abundance inhomogeneities, and the implications of high resolution images in the centers of clusters. We find no evidence of intrinsic absorption in the center of the cooling flows of M 87 and the Perseus cluster. We further consider the effect of cluster rotation in cooling flow regions in the frame of cosmic structure evolution models. Also, the heating of the core regions of clusters by jets from a central AGN is reconsidered. We find that the power of the AGN jets as estimated by their interaction effects with the intracluster medium in several examples is more then sufficient to heat the cooling flows and to reduce the mass deposition rates. We explore in more detail which requirements such a heating model has to fulfill to be consistent with all observations, point out the way such a model could be constructed, and argue that such model building seems to be successful. In summary, it is argued that most observational evidence points towards much lower mass deposition rates than previously inferred in the central region of clusters thought to contain strong cooling flows.

Expression profiling of synovial sarcoma by cDNA microarrays: association of ERBB2, IGFBP2, and ELF3 with epithelial differentiation.

Abstract: Synovial sarcoma is an aggressive spindle cell sarcoma with two major histological subtypes, biphasic and monophasic, defined respectively by the presence or absence of areas of glandular epithelial differentiation It is characterized by a specific chromosomal translocation, t(X;18)(p112;q112), which juxtaposes the SYT gene on chromosome 18 to either the SSX1 or the SSX2 gene on chromosome X The chimeric SYT-SSX products are thought to function as transcriptional proteins that deregulate gene expression, thereby providing a putative oncogenic stimulus We investigated the pattern of gene expression in synovial sarcoma using cDNA microarrays containing 6548 sequence-verified human cDNAs A tissue microarray containing 37 synovial sarcoma samples verified to bear the SYT-SSX fusion was constructed for complementary analyses Gene expression analyses were performed on individual tumor samples; 14 synovial sarcomas, 4 malignant fibrous histiocytomas, and 1 fibrosarcoma Statistical analysis showed a distinct expression profile for the group of synovial sarcomas as compared to the other soft tissue sarcomas, which included variably high expression of ERBB2, IGFBP2, and IGF2 in the synovial sarcomas Immunohistochemical analysis of protein expression in tissue microarrays of 37 synovial sarcomas demonstrated strong expression of ERBB2 and IGFBP2 in the glandular epithelial component of biphasic tumors and in solid epithelioid areas of some monophasic tumors Fluorescence in situ hybridization analysis indicated that the ERBB2 overexpression was not because of gene amplification Differentially expressed genes were also found in a comparison of the expression profiles of the biphasic and monophasic histological subgroups of synovial sarcoma, notably several keratin genes, and ELF3, an epithelial-specific transcription factor gene Finally, we also noted differential overexpression of several neural- or neuroectodermal-associated genes in synovial sarcomas relative to the comparison sarcoma group, including OLFM1, TLE2, CNTNAP1, and DRPLA Our high-throughput studies of gene expression patterns, complemented by tissue microarray studies, confirm the distinctive expression profile of synovial sarcoma, provide leads for the study of glandular morphogenesis in this tumor, and identify a new potential therapeutic target, ERBB2, in a subset of cases

Ratio statistics of gene expression levels and applications to microarray data analysis.

Abstract: Motivation Expression-based analysis for large families of genes has recently become possible owing to the development of cDNA microarrays, which allow simultaneous measurement of transcript levels for thousands of genes. For each spot on a microarray, signals in two channels must be extracted from their backgrounds. This requires algorithms to extract signals arising from tagged mRNA hybridized to arrayed cDNA locations and algorithms to determine the significance of signal ratios. Results This paper focuses on estimation of signal ratios from the two channels, and the significance of those ratios. The key issue is the determination of whether a ratio is significantly high or low in order to conclude whether the gene is upregulated or downregulated. The paper builds on an earlier study that involved a hypothesis test based on a ratio statistic under the supposition that the measured fluorescent intensities subsequent to image processing can be assumed to reflect the signal intensities. Here, a refined hypothesis test is considered in which the measured intensities forming the ratio are assumed to be combinations of signal and background. The new method involves a signal-to-noise ratio, and for a high signal-to-noise ratio the new test reduces (with close approximation) to the original test. The effect of low signal-to-noise ratio on the ratio statistics constitutes the main theme of the paper. Finally, and in this vein, a quality metric is formulated for spots. This measure can be used to decide whether or not a spot ratio should be deleted, or to adjust various measurements to reflect confidence in the quality of the measurement. Contact e-dougherty@tamu.edu

Can markov chain models mimic biological regulation

Abstract: A fundamental question in biology is whether the network of interactions that regulate gene expression can be modeled by existing mathematical techniques. Studies of the ability to predict a gene's...

Inference from clustering with application to gene-expression microarrays.

Abstract: There are many algorithms to cluster sample data points based on nearness or a similarity measure. Often the implication is that points in different clusters come from different underlying classes, whereas those in the same cluster come from the same class. Stochastically, the underlying classes represent different random processes. The inference is that clusters represent a partition of the sample points according to which process they belong. This paper discusses a model-based clustering toolbox that evaluates cluster accuracy. Each random process is modeled as its mean plus independent noise, sample points are generated, the points are clustered, and the clustering error is the number of points clustered incorrectly according to the generating random processes. Various clustering algorithms are evaluated based on process variance and the key issue of the rate at which algorithmic performance improves with increasing numbers of experimental replications. The model means can be selected by hand to test t...

Signal recycled laser-interferometer gravitational-wave detectors as optical springs

Abstract: Using the force-susceptibility formalism of linear quantum measurements, we study the dynamics of signal recycled interferometers, such as LIGO-II. We show that, although the antisymmetric mode of motion of the four arm-cavity mirrors is originally described by a free mass, when the signal-recycling mirror is added to the interferometer, the radiation-pressure force not only disturbs the motion of that “free mass” randomly due to quantum fluctuations, but also, and more fundamentally, makes it respond to forces as though it were connected to a spring with a specific optical-mechanical rigidity. This oscillatory response gives rise to a much richer dynamics than previously known for SR interferometers, which enhances the possibilities for reshaping the noise curves and, if thermal noise can be pushed low enough, enables the standard quantum limit to be beaten. We also show the possibility of using servo systems to suppress the instability associated with the optical-mechanical interaction without compromising the sensitivity of the interferometer.

Mutation of melanosome protein RAB38 in chocolate mice

Abstract: Mutations of genes needed for melanocyte function can result in oculocutaneous albinism. Examination of similarities in human gene expression patterns by using microarray analysis reveals that RAB38, a small GTP binding protein, demonstrates a similar expression profile to melanocytic genes. Comparative genomic analysis localizes human RAB38 to the mouse chocolate (cht) locus. A G146T mutation occurs in the conserved GTP binding domain of RAB38 in cht mice. Rab38cht/Rab38cht mice exhibit a brown coat similar in color to mice with a mutation in tyrosinase-related protein 1 (Tyrp1), a mouse model for oculocutaneous albinism. The targeting of TYRP1 protein to the melanosome is impaired in Rab38cht/Rab38cht melanocytes. These observations, and the fact that green fluorescent protein-tagged RAB38 colocalizes with end-stage melanosomes in wild-type melanocytes, suggest that RAB38 plays a role in the sorting of TYRP1. This study demonstrates the utility of expression profile analysis to identify mammalian disease genes.

Gene expression signature of benign prostatic hyperplasia revealed by cDNA microarray analysis

Abstract: BACKGROUND Despite the high prevalence of benign prostatic hyperplasia (BPH) in the aging male, little is known regarding the etiology of this disease. A better understanding of the molecular etiology of BPH would be facilitated by a comprehensive analysis of gene expression patterns that are characteristic of benign growth in the prostate gland. Since genes differentially expressed between BPH and normal prostate tissues are likely to reflect underlying pathogenic mechanisms involved in the development of BPH, we performed comparative gene expression analysis using cDNA microarray technology to identify candidate genes associated with BPH. METHODS Total RNA was extracted from a set of 9 BPH specimens from men with extensive hyperplasia and a set of 12 histologically normal prostate tissues excised from radical prostatectomy specimens. Each of these 21 RNA samples was labeled with Cy3 in a reverse transcription reaction and cohybridized with a Cy5 labeled common reference sample to a cDNA microarray containing 6,500 human genes. Normalized fluorescent intensity ratios from each hybridization experiment were extracted to represent the relative mRNA abundance for each gene in each sample. Weighted gene and random permutation analyses were performed to generate a subset of genes with statistically significant differences in expression between BPH and normal prostate tissues. Semi-quantitative PCR analysis was performed to validate differential expression. RESULTS A subset of 76 genes involved in a wide range of cellular functions was identified to be differentially expressed between BPH and normal prostate tissues. Semi-quantitative PCR was performed on 10 genes and 8 were validated. Genes consistently upregulated in BPH when compared to normal prostate tissues included: a restricted set of growth factors and their binding proteins (e.g. IGF-1 and -2, TGF-β3, BMP5, latent TGF-β binding protein 1 and -2); hydrolases, proteases, and protease inhibitors (e.g. neuropathy target esterase, MMP2, alpha-2-macroglobulin); stress response enzymes (e.g. COX2, GSTM5); and extracellular matrix molecules (e.g. laminin alpha 4 and beta 1, chondroitin sulfate proteoglycan 2, lumican). Genes consistently expressing less mRNA in BPH than in normal prostate tissues were less commonly observed and included the transcription factor KLF4, thrombospondin 4, nitric oxide synthase 2A, transglutaminase 3, and gastrin releasing peptide. CONCLUSIONS We identified a diverse set of genes that are potentially related to benign prostatic hyperplasia, including genes both previously implicated in BPH pathogenesis as well as others not previously linked to this disease. Further targeted validation and investigations of these genes at the DNA, mRNA, and protein levels are warranted to determine the clinical relevance and possible therapeutic utility of these genes. Prostate 51: 189–200, 2002. © 2002 Wiley-Liss, Inc.

A novel method for preparation of nanocrystalline rutile TiO2 powders by liquid hydrolysis of TiCl4

Abstract: Nanocrystalline rutile TiO2 with average crystal sizes of 6.9–10.5 nm and specific surface areas of 70.3–141.0 m2g−1 were prepared by hydrolysis of TiCl4 aqueous solution at lower temperatures. The presence of small amounts of nano rutile TiO2 as crystal seed could obviously accelerate the crystallization of TiO2, make nanocrystalline rutile TiO2 well dispersed and make the reaction of formation of rutile more kinetically favorable than that of formation of anatase in the liquid hydrolysis of TiCl4.

Practical speed meter designs for quantum nondemolition gravitational-wave interferometers

Abstract: In the quest to develop viable designs for third-generation optical interferometric gravitational-wave detectors (e.g., LIGO-III and EURO), one strategy is to monitor the relative momentum or speed of the test-mass mirrors, rather than monitoring their relative position. A previous paper analyzed a straightforward but impractical design for a speed-meter interferometer that accomplishes this. This paper describes some practical variants of speed-meter interferometers. Like the original interferometric speed meter, these designs in principle can beat the gravitational-wave standard quantum limit (SQL) by an arbitrarily large amount, over an arbitrarily wide range of frequencies. These variants essentially consist of a Michelson interferometer plus an extra ``sloshing'' cavity that sends the signal back into the interferometer with opposite phase shift, thereby cancelling the position information and leaving a net phase shift proportional to the relative velocity. In practice, the sensitivity of these variants will be limited by the maximum light power W-circ circulating in the arm cavities that the mirrors can support and by the leakage of vacuum into the optical train at dissipation points. In the absence of dissipation and with squeezed vacuum (power squeeze factor e(-2R)similar or equal to0.1) inserted into the output port so as to keep the circulating power down, the SQL can be beat by h/h(SQL)similar torootW(circ)(SQL)e(-2R)/W-circ at all frequencies below some chosen f(opt)similar or equal to100 Hz. Here W(circ)(SQL)similar or equal to800 kW(f(opt)/100 Hz)(3) is the power required to reach the SQL in the absence of squeezing. (However, as the power increases in this expression, the speed meter becomes more narrow band; additional power and reoptimization of some parameters are required to maintain the wide band. See Sec. III B.) Estimates are given of the amount by which vacuum leakage at dissipation points will debilitate this sensitivity (see Fig. 12); these losses are 10% or less over most of the frequency range of interest (fgreater than or similar to10 Hz). The sensitivity can be improved, particularly at high freqencies, by using frequency-dependent homodyne detection, which unfortunately requires two 4-km-long filter cavities (see Fig. 4).

Gene Expression After Treatment With Hydrogen Peroxide, Menadione, or T-Butyl Hydroperoxide in Breast Cancer Cells

Abstract: Global gene expression patterns in breast cancer cells after treatment with oxidants (hydrogen peroxide, menadione, and t-butyl hydroperoxide) were investigated in three replicate experiments. RNA collected after treatment (at 1, 3, 7, and 24 h) rather than after a single time point, enabled an analysis of gene expression patterns. Using a 17,000 microarray, template-based clustering and multidimensional scaling analysis of the gene expression over the entire time course identified 421 genes as being either up- or down-regulated by the three oxidants. In contrast, only 127 genes were identified for any single time point and a 2-fold change criteria. Surprisingly, the patterns of gene induction were highly similar among the three oxidants; however, differences were observed, particularly with respect to p53, IL-6, and heat-shock related genes. Replicate experiments increased the statistical confidence of the study, whereas changes in gene expression patterns over a time course demonstrated significant additional information versus a single time point. Analyzing the three oxidants simultaneously by template cluster analysis identified genes that heretofore have not been associated with oxidative stress.

Strong feature sets from small samples.

Abstract: For small samples, classifier design algorithms typically suffer from overfitting. Given a set of features, a classifier must be designed and its error estimated. For small samples, an error estimator may be unbiased but, owing to a large variance, often give very optimistic estimates. This paper proposes mitigating the small-sample problem by designing classifiers from a probability distribution resulting from spreading the mass of the sample points to make classification more difficult, while maintaining sample geometry. The algorithm is parameterized by the variance of the spreading distribution. By increasing the spread, the algorithm finds gene sets whose classification accuracy remains strong relative to greater spreading of the sample. The error gives a measure of the strength of the feature set as a function of the spread. The algorithm yields feature sets that can distinguish the two classes, not only for the sample data, but for distributions spread beyond the sample data. For linear classifiers...

Amine-modified random primers to label probes for DNA microarrays

Abstract: DNA microarrays have been used to study the expression of thousands of genes at the same time in a variety of cells and tissues1,2,3. The methods most commonly used to label probes for microarray studies require a minimum of 20 μg of total RNA or 2 μg of poly(A) RNA4,5. This has made it difficult to study small and rare tissue samples. RNA amplification techniques and improved labeling methods have recently been described6,7,8,9. These new procedures and reagents allow the use of less input RNA, but they are relatively time-consuming and expensive. Here we introduce a technique for preparing fluorescent probes that can be used to label as little as 1 μg of total RNA. The method is based on priming cDNA synthesis with random hexamer oligonucleotides, on the 5′ ends of which are bases with free amino groups. These amine-modified primers are incorporated into the cDNA along with aminoallyl nucleotides, and fluorescent dyes are then chemically added to the free amines. The method is simple to execute, and amine-reactive dyes are considerably less expensive than dye-labeled bases or dendrimers.

E-CAST: a data mining algorithm for gene expression data

Abstract: Data clustering methods have been proven to be a successful data mining technique in the analysis of gene expression data. The Cluster affinity search technique (CAST) developed by Ben-Dor, et. al., 1999, which has been shown to cluster gene expression data well, has two drawbacks. First, the algorithm uses a fixed initial threshold value to start the clustering. As stated in the original paper, this parameter directly affects the size and number of clusters produced. Second, the algorithm requires a final cleaning step, which takes O(n2), to relocate n data points among the existing clusters. In this paper, we have developed and enhanced CAST algorithm, called E-CAST, that uses a dynamic threshold. The threshold value is computed at the beginning of each new cluster. We have implemented both CAST and E-CAST algorithms and tested their performance using three different data sets. The datasets are real gene expression data from melanoma, pheochromocytoma and brain cell tissue samples generated using micro-arrays technology. The results of both implementations were compared to the output from the hierarchical clustering program, written by Michael Eisen, with very comparable results. Not only did the final results compare favorably with the hierarchical approach, but they also indicate that the cleaning step of the original CAST algorithm may be unnecessary.

Laser-induced alloying Au–Pd and Ag–Pd colloidal mixtures: the formation of dispersed Au/Pd and Ag/Pd nanoparticles

Abstract: Laser irradiation of colloidal mixtures consisting of Au–Pd and Ag–Pd were conducted to synthesize Au/Pd and Ag/Pd alloy nanoparticles. Compositional ratios of 1∶1 and 2∶1 were prepared in both the Au/Pd and Ag/Pd systems. The compositions, the particle sizes, and the morphology were measured as a function of the laser irradiation period in order to monitor the changes from the two-component mixtures into the alloy colloids. The average particle sizes of the 1∶1 and 2∶1 metal ratios were 3.9 ± 1.2 nm and 4.3 ± 1.1 nm, respectively, for Au/Pd and 7.3 ± 2.0 nm and 5.4 ± 2.0 nm, respectively, for Ag/Pd. However, Ag/Pd with a 2∶1 ratio had difficult in forming dispersed spherical particles and the expected compositions. In addition to EDX analysis, X-ray diffraction measurements were carried out to confirm the formation of the alloy nanoparticles.

Determination of andrographolide, deoxyandrographolide and neoandrographolide in the Chinese herb Andrographis paniculata by micellar electrokinetic capillary chromatography.

Abstract: In this paper a micellar electrokinetic capillary chromatographic (MEKC) method has been developed for determining the active components (andrographolide, deoxyandrographolide and neoandrographolide) in water:ethanol extracts of the Chinese crude herb Andrographis paniculata and its preparations (Chuanxinlian and Xiaoyan Lidan tablets). The optimum separation conditions were 15 mM sodium dodecyl sulphate in 30 mM borate buffer (pH 9.5) with UV detection wavelength at 214 nm and a constant voltage of 16 kV. An HPLC method was employed in order to validate the MEKC method with respect to separation efficiency, sensitivity, linearity and repeatability. The two methods are shown to be complementary because of their different selectivity and thus are very suitable for cross-validation studies. The MEKC method is demonstrated to be more appropriate for the analysis of the active compounds in A. paniculata in that it is easier and less expensive to use and does not suffer from contamination of the chromatographic column.

Simulation of cDNA microarrays via a parameterized random signal model.

Abstract: cDNA microarrays provide simultaneous expression mea- surements for thousands of genes that are the result of processing images to recover the average signal intensity from a spot composed of pixels covering the area upon which the cDNA detector has been put down. The accuracy of the signal measurement depends on using an appropriate algorithm to process the images. This includes deter- mining spot locations and processing the data in such a way as to take into account spot geometry, background noise, and various kinds of noise that degrade the signal. This paper presents a stochastic model for microarray images. There are over 20 model parameters, each governed by a probability distribution, that control the signal intensity, spot geometry, spot drift, background effects, and the many kinds of noise that affect microarray images owing to the manner in which they are formed. The model can be used to analyze the performance of image algorithms designed to measure the true signal intensity be- cause the ground truth (signal intensity) for each spot is known. The levels of foreground noise, background noise, and spot distortion can be set, and algorithms can be evaluated under varying conditions.

Comparative Study of ABO3 Perovskite Compounds. 1. ATiO3 (A = Ca, Sr, Ba, and Pb) Perovskites

Abstract: Comparative studies on the four ATiO3 compounds are carried out to investigate the different ferroelectric behaviors of ATiO3 on the basis of the experimental and theoretically optimized lattice structures The stability predicted from the calculated total energies is in agreement with experimental observation The obtained potential energy surfaces (PESs) show Ti displacements in CaTiO3 and SrTiO3 result in single-well potential whereas in BaTiO3 and PbTiO3 they produce double-well potential In contrast to alkaline earth metal atoms, the PES of Pb displacement is double well The calculated PES supports the experimental conclusion that Ti displaces from 〈111〉 in tetragonal structure In addition, the calculated hopping barriers are in agreement with the prediction of the vibronic theory Charge distribution and the Ti−O and A−O bonding situation are analyzed on the basis of electronic structure calculations It is shown that symmetry lowering enhances Ti−O covalent bonding in all the titled compounds an

Model Reduction in the Time-Domain Using Laguerre Polynomials and Krylov Methods

Abstract: Presents a new passive model reduction algorithm based on the Laguerre expansion of the time response of interconnect networks. We derive expressions for the Laguerre coefficient matrices that minimize a weighted square of the approximation error, and show how these matrices can be computed efficiently using Krylov subspace methods. We discuss the connections between our method and other methods such as PRIMA. Numerical simulations show that our method can better approximate the original model as compared to PRIMA.

Dispersion state and catalytic properties of vanadia species on the surface of V2O5/TiO2 catalysts

Abstract: The dispersion state and catalytic properties of anatase-supported vanadia species are studied by means of X-ray diffraction (XRD), laser Raman spectroscopy (LRS), H2 temperature-programmed reduction (TPR) and the selective oxidation of o-xylene to phthalic anhydride. The almost identical values of the experimental dispersion capacity of V2O5 on anatase and the surface vacant sites available on the preferentially exposed (001) plane of anatase suggest that the highly dispersed vanadium cations are bonded to the vacant sites on the surface of anatase as derived by the incorporation model. When the loading amount of V2O5 is far below its dispersion capacity, the dispersed vanadia species might mainly consist of isolated VOx species bridging to the surface through V-O-Ti bonds. With the increase of V2O5 loading the isolated vanadia species interact with their nearest neighbors (either isolated or polymerized vanadia) through bridging V-O-V at the expenses of V-O-Ti bonds, resulting in the increase of the ratio of polymerized to isolated vanadia species and the decrease of the reactivity of the associated surface oxygen anions and, consequently, although the activity increases with loading to reach a maximum value, the turn over number (TON) of the V2O5/TiO2 catalyst decreases linearly. When the loading amount of V2O5 is higher than its dispersion capacity, the turn over number decreases more rapidly with the increase of V2O5 loading due to the formation of V2O5 crystallites in which the oxygen anions associated with V-O-V bonds are less reactive and only partially exposed on the surface.

A carbonyl oxygen migration in electrospray ionization mass spectrometry and its application in differentiating α- and β-alanyl peptides

Abstract: A novel rearrangement reaction with a carbonyl oxygen migration was observed in the electrospray ionization tandem mass spectra of N-diisopropyloxyphosphoryl dipeptides and their analogues. A possible mechanism was proposed and supported by the MS/MS study, derivatization of different functional groups and deuterium labeling experiments. It was found that metal ions could catalyze the rearrangement through a five-membered ring intermediate. A strong affinity between the phosphoryl group and oxygen atom in the gas phase was proposed to result in this kind of rearrangement reaction, which might provide some basic information on the nature of phosphorylation in biochemistry. The replacement of N-terminal α-alanine by β-alanine stopped the migration, which provides a simple method for differentiating the α- and β-alanine residues at the N-terminus of peptides. Copyright © 2002 John Wiley & Sons, Ltd.

Laser-interferometer gravitational-wave optical-spring detectors

Abstract: Using a quantum mechanical approach, we show that in a gravitational-wave interferometer composed of arm cavities and a signal recycling cavity, e.g., the LIGO-II configuration, the radiation-pressure force acting on the mirrors not only disturbs the motion of the free masses randomly due to quantum fluctuations, but also and more fundamentally, makes them respond to forces as though they were connected to an (optical) spring with a specific rigidity. This oscillatory response gives rise to a much richer dynamics than previously known, which enhances the possibilities for reshaping the LIGO-II's noise curves. However, the optical-mechanical system is dynamically unstable and an appropriate control system must be introduced to quench the instability.

The Preparation of Molybdenum Oxynitride by Hydrazine Reduction of MoO3 at Moderate Temperature and Its Application in the Selective Hydrogenation of Long-Chain Linear Alkadienes

Abstract: Molybdenum oxynitride was prepared by hydrazine reduction of MoO3 at moderate temperatures. The anhydrous condition was favorable to production of amorphous molybdenum oxynitride, and the presence of hydrogen favored the reduction of Mo6+ and Mo4+ species to Moδ+ (0 < δ < 4) species. These molybdenum oxynitrides exhibited activity for hydrogenation which depended on the amount of Moδ+ (0 < δ < 4) species produced under reaction conditions. The amorphous molybdenum oxynitride MoO1.83N0.36 catalyst showed a good catalytic activity, selectivity, and resistance to poisoning of H2S for liquid-phase hydrogenation of longer-chain alkadienes.