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Synergy study is of great importance to optimize the two-stage plasma-facilitated catalysis system and also necessary to gain a mechanistic understanding of the overall reaction process. In this paper, the effects of the long-lived chemical products of plasma pretreatment on the subsequent selective catalytic reduction (SCR) of N[O.sub.x] at fixed and changed energy density of dielectric-barrier-discharge plasma reactor were investigated, respectively, for the aim of the synergy study of plasma-facilitated [C.sub.2][H.sub.4]-SCR (PF-SCR) of N[O.sub.x] over Ag/[gamma]-[Al.sub.2][O.sub.3] catalyst at lower temperature. For comparison, [C.sub.2][H.sub.4]-SCR of N[O.sub.x] over Ag/[gamma]-[Al.sub.2][O.sub.3] catalyst alone was also considered. Results showed that PF-SCR for N[O.sub.x] removal exhibited obvious synergistic effect at 240 [degrees]C, and the N[O.sub.x] removal efficiency for plasma alone, [C.sub.2][H.sub.4]-SCR alone, and PF-SCR were 43.6%, 6.7%, and 90.1%, respectively. In the NO/N[O.sub.2]/[C.sub.2][H.sub.4]/[O.sub.2]/[N.sub.2] system, the long-lived chemical products of plasma pretreatment for the synergistic link between plasma and catalysis included N[O.sub.2], aldehyde (formaldehyde and acetaldehyde), and nitrogen-contained organic compounds (methyl nitrate, nitro methyl, and ethyl nitrate). Among the nitrogen-contained chemical products of plasma pretreatment, the major synergistic link between plasma and catalysis was N[O.sub.2] at lower input energy density, transferred to the mutual action of N[O.sub.2] and nitrogen-contained organic compounds over catalyst at higher input energy density. Index Terms--Long-lived chemical products, nitrogen-contained organic compounds, N[O.sub.x] removal, plasma-facilitated catalysis, synergy.

Localized proliferation of lateral roots in N[O.sub.3]-rich patches is a striking example of the nutrient-induced plasticity of root development. In Arabidopsis, N[O.sub.3] stimulation of lateral root elongation is apparently under the control of a N[O.sub.3]-signaling pathway involving the ANR1 transcription factor. ANR1 is thought to transduce the N[O.sub.3] signal internally, but the upstream N[O.sub.3] sensing system is unknown. Here, we show that mutants of the NRT1.1 nitrate transporter display a strongly decreased root colonization of N[O.sub.3]-rich patches, resulting from reduced lateral root elongation. This phenotype is not due to lower specific N[O.sub.3] uptake activity in the mutants and is not suppressed when the N[O.sub.3]-rich patch is supplemented with an alternative N source but is associated with dramatically decreased ANR1 expression. These results show that NRT1.1 promotes localized root proliferation independently of any nutritional effect and indicate a role in the ANR1dependent N[O.sub.3] signaling pathway, either as a N[O.sub.3] sensor or as a facilitator of N[O.sub.3] influx into N[O.sub.3]-sensing cells. Consistent with this model, the NRT1.1 and ANR1 promoters both directed reporter gene expression in root primordia and root tips. The inability of NRT1.1-deficient mutants to promote increased lateral root proliferation in the N[O.sub.3]-rich zone impairs the efficient acquisition of N[O.sub.3] and leads to slower plant growth. We conclude that NRT1.1, which is localized at the forefront of soil exploration by the roots, is a key component of the N[O.sub.3]-sensing system that enables the plant to detect and exploit N[O.sub.3]-rich soil patches. adaptive root development | ANR1 signaling pathway | plant growth | nitrate sensing | nitrogen nutrition

Rhizobium (Sinorhizobium) sp. strain NGR234 contains three replicons, the smallest of which (pNGR234a) carries most symbiotic genes, including those required for nodulation and lipo-chito-oligosaccharide (Nod factor) biosynthesis. Activation of nod gene expression depends on plant-derived flavonoids, NodD transcriptional activators, and nod box promoter elements. Nod boxes NB6 and NB7 delimit six different types of genes, one of which (fixF) is essential for the formation of effective nodules on Vigna unguiculata. In vegetative culture, wild-type NGR234 produces a distinct, flavonoid-inducible lipopolysaccharide (LPS) that is not produced by the mutant (NGR[OMEGA]fixF); this LPS is also found in nitrogen-fixing bacteroids isolated from V. unguiculata infected with NGR234. Electron microscopy showed that peribacteroid membrane formation is perturbed in nodule cells infected by the fixF mutant. LPSs were purified from free-living NGR234 cultured in the presence of apigenin. Structural analyses showed that the polysaccharide portions of these LPSs are specialized, rhamnose-containing O antigens attached to a modified core-lipid A carrier. The primary sequence of the O antigen is [[-3)-[alpha]-L-Rhap-(1,3)-[alpha]-L-Rhap-(l,2)-[alpha]-L-Rhap-(1-].sub.n], and the LPS core region lacks the acidic sugars commonly associated with the antigenic outer core of LPS from noninduced cells. This rhamnan O antigen, which is absent from noninduced cells, has the same primary sequence as the A-band O antigen of Pseudomonas aeruginosa, except that it is composed of L-rhamnose rather than the D-rhamnose characteristic of the latter. It is noteworthy that A-band LPS is selectively maintained on the P. aeruginosa cell surface during chronic cystic fibrosis lung infection, where it is associated with an increased duration of infection.

We have cloned and functionally characterized a N[a.sup.+]-coupled dicarboxylate transporter, SdcS, from Staphylococcus aureus. This carrier protein is a member of the divalent anion/N[a.sup.+] symporter (DASS) family and shares significant sequence homology with the mammalian N[a.sup.+]/dicarboxylate cotransporters NaDC-1 and NaDC-3. Analysis of SdcS function indicates transport properties consistent with those of its eukaryotic counterparts. Thus, SdcS facilitates the transport of the dicarboxylates fumarate, malate, and succinate across the cytoplasmic membrane in a N[a.sup.+]-dependent manner. Furthermore, kinetic work predicts an ordered reaction sequence with N[a.sup.+] ([K.sub.0.5] of 2.7 mM) binding before dicarboxylate ([K.sub.m] of 4.5 [micro]M). Because this transporter and its mammalian homologs are functionally similar, we suggest that SdcS may serve as a useful model for DASS family structural analysis.

Cyanobacteria are equipped with numerous mechanisms that allow them to survive under conditions of nutrient starvation, some of which are unique to these organisms. This review surveys the molecular mechanisms underlying acclimation responses to nitrogen and phosphorus deprivation, with an emphasis on non-diazotrophic freshwater cyanobacteria. As documented for other micro-organisms, nutrient limitation of cyanobacteria elicits both general and specific responses. The general responses occur under any starvation condition and are the result of the stresses imposed by arrested anabolism. In contrast, the specific responses are acclimation processes that occur as a result of limitation for a particular nutrient; they lead to modification of metabolic and physiological routes to compensate for the restriction. First, the general acclimation processes are discussed, with an emphasis on modifications of the photosynthetic apparatus. The molecular mechanisms underlying specific responses to phosphorus and nitrogen-limitation are then outlined, and finally the cross-talk between pathways modulating specific and general responses is described.

Generation of singlet and triplet 2-silylcyclopentane-1,3,-diyls and their reactivity is investigated in the thermal and photochemical denitrogenation of 2,3-diaza--7-silylbicyclo[2.2.1]-hept-2-ene. 5-Silylcyclopentene (silyl migration product) is quantitatively obtained, while 5-silylbicyclo[2.1.0]pentane (intramolecular ring-closure product) is not detected in the denitrogenation reactions.

The details of copper-catalyzed N-arylation of pi-excessive nitrogen heterocycles are specified. The coupling of either aryl iodides or aryl bromides with common nitrogen heterocycles (pyrroles, pyrazoles, indazoles, imidazoles, and triazoles) is successfully performed in good yield with catalysts derived from diamine ligands and CuI.

The O-O bond breaking reactions of methyl peroxynitrite and peroxynitrous acid was investigated using various methods. Analyses have confirmed that RO/NO2radical pairs are readily formed from cis-ROONO conformations than from trans-ROONO conformations.

New applications of dibenzyl carbonate are explored by studying its reactivity with other N-nucleophiles, especially with aliphatic amines in the presence of tetraalkylphosphonium salts. The phosphonium salt promotes high selectivity toward the benzylated amine and an increase in the reaction rate too.

A novel solid-phases intramolecular N-acyliminium Pictet-Spengler reaction is presented. A range of pharmacologically interesting tri- and tetracyclic scaffolds can be accessed when the intramolecular reaction is extended to other substituted indoles and reactive heterocycles.

The use of cascade cycloaddition to synthesize new polysulfur-nitrogen heterocycles with readily available polycyclic 1,2-dithiole-3-thiones is reported. Treatment of the [1,2]dithiolo[1,4]thiazine dithione with dibenzoylacetylene give the 1:2, 1:3 or 1:4 adducts and selectivity in fair to high yields.

The examination on cage isomers of N24, N30, and N36 by theoretical calculations to determine their relative thermodynamic stability is presented. It is concluded that the specific arrangement of pentagons relative to triangles plays a central role, leading to cylindrical structures in which nitrogen atoms keep their preferred pyramidal environments.

To validate the coexistence of the canonical form and the N3 and N7 tautomers in bulk water, a study of fourteen amino and imino tautomers of adenine was conducted in the gas phase, in a microhydrated environment and bulk water environment using the thermodynamic integration method, conductor-like polarizable continuum model and a hybrid model. It is reported that the results are consistent with the available experimental data from NMR measurement of the adenine tautometers in dimethyl sulfoxide (DMSO).

The individual H-bond energies were calculated at the B3LYP/D95 level for linear chains of H-bonding formamides containing from 2 to 15 monomeric units. The results are discussed with respect to their utility for improving the modeling of peptide structure and protein folding.

Ionic liquids based on various chelated orthoborate anions of different N-containing onium cations were synthesized using an economic synthesis strategy. The hydrophobic properties and their high fragilities of these liquids may provide model systems for fundamental liquid investigations.

The original and extended model-free (MF) formulas are perturbational expansions of slowly relaxing local structure (SRLS) models. A detailed analysis of eigenmodes and spectral densities is given.

The adsorption of nitromethane and 1,1-diamino-2,2-dinitroethylene molecules on the A1(111) surface is studied by using first-principles calculations that are based on spin-unrestricted density functional theory and the generalized gradient approximation. Determining the possible reaction mechanisms at the molecule--metallic-surface interface, is the main objective of the study.

Electron paramagnetic resonance (EPR) and photoluminescence (PL) spectroscopies have been used to study Brazilian and Central African carbonados. We report the first observation of the [N.sub.2][V.sup.+] and [N.sup.+.sub.2] nitrogen defect centers in carbonados. The fact that Brazilian carbonados contain the [N.sub.3]V (previously reported), [N.sub.2][V.sup.+], and [N.sup.+.sub.2] defects, the formation of which requires complicated aggregation of nitrogen, indicates histories at elevated temperature and pressure. The observation of both the radiation-induced A1 defect, which has an annealing temperature of 700 K, and radiation defects containing two and/or five vacancies, suggest a continuous process of the formation and transformation of radiation defects in the carbonado under variable pressure and temperature conditions while in the upper mantle. The temperature at which these defects are formed varies from 300 to 1500 K. In addition we report a hydrogen-containing defect labeled H1, previously only observed in synthetic diamonds prepared by chemical vapor deposition. Together with the previously reported light carbon isotope ratio, the results of this study confirm the hypothesis that carbonados are derived from hydrocarbon source material.

The study of the lowest 18 electronic surfaces of the NCl + NCl system is presented. It plays a significant role in search of low-energy self-annihilation pathways for two dNCl molecules in their first excited state.

Quenching and self-annihilation rate constants for NCI(a) are determined using pulsed 248 nm photolysis of CIN3 to generate the metastable. Previous quenching measurements that employed different sources for NCl(a) yielded dramatically different rate constants.

The first direct kinetic measurements on the NS radical are reported. The NS radical was produced from the photolysis of N4S4 at 248nm and detected via laser-induced fluorescence.

The kinetics of N2(X, epsilon) is studied with silane and N2(X, epsilon) diagnostics employing metastable energy transfer reactions are used for this purpose. Comparison of the relative excitation rate of SiH4(epsilon3) with that for N2O(epsilon3) excitation when N2O is added to the reactor, however, indicates that at most 15% of the N2(X, epsilon) quenching events result in epsilon3 excitation.

The rovibronic Renner-Teller (RT) effect in the N[(super 2)D] + H2 reaction is studied. A new approach to describe RT coupling within the framework of trajectory surface hopping is developed for this purpose and it is predicted that the RT effect is not important to the thermal rate constant but has measurable consequences for certain state-resolved experiments.

Research describes the stereospecific synthesis of beta-amino diacid 3-(N-carboxymethyl)-aminodecanoic acid enantiomers and the two diastereomers of minalemine A. Results reveal that nuclear magnetic resonance spectra of the natural and the diastereomers are similar but circular dichroism spectra of the former indicate a 3R,2S configuration.

The redox properties of the intermediate radicals derived from OH radical reactions of 5-substituted uracils 1c-h (R = F, Cl, Br, NO2, NH2, OH) was determined by using a redox titration method in the pulse radiolysis of N2O-saturated phosphate buffer solution. The product study showed that the yield of isobarbituric acid and isodialuric acid increased due to the one-electron reduction of 5-oxyl radical 5 by N,N,N',N'-tetramethyl-p-phenylenediamine and the one electron oxidation of 5-oxo radical by tetranitromethane respectively.

Depending upon the reagents used, the products of double silylation of aliphatic nitro compounds may behave either as beta-C-electrophiles or beta-C-nucleophiles, thereby allowing diverse functionalization of beta-carbon atom of starting nitro compounds. The realization of a general principle in electrophile or nucleophile combination in which incipient positive charge is stabilized by conjugation with silicon bearing functionality is presented.

The phenylsulfonyl group is known as a group leaving group and is also beneficial in the synthesis of optically active benzenesulfonyl lactams that, being solid compounds are easily purified by crystallization. The reactivity and stereoselectivity displayed by acyclic N-acyliminium ion intermediates prepared using optically active phenylsulfonylimidazolidin-2-ones is studied.

Gas-phase reactions of HONO with N2, O3, and HCI were investigated by means of ab initio transition-state theory (TST). The results indicate that the three gas-phase reactions were too slow to be significant under the stratospheric and tropospheric conditions.

The cyclization of acetylenic sulfones through the conjugate additions of acyclic or cyclic secondary beta- or gamma-chloroamines is described. The products obtained include variously substituted piperidines, pyrrolizidines, indolizidines and quinolizidines all containing the enamine sulfone moiety.

Sub Antarctic soft coral Alcyonium paessleri provided extracts for fifteen illudalane sesquiterpenoids, alcyopterosins A-O and their structures were determined using spectroscopic techniques. Eight of these compounds are the first natural nitrate esters.

Redox chemistry is discussed relative to laccase-catalyzed oxidation of N-hydroxy compounds. Three N-OH compounds that can mediate a range of laccase-catalyzed biotransformations have been studied. The mechanisms of the enzymatic oxidations were studied with seven fungal laccases. It is probable that an outer-sphere sort of single-electron transfer from the substrate to laccase and proton release is involved in the rate-limiting step of N-OH oxidation.

Research is presented demonstrating the use of a flow reactor to measure the temperature dependent quenching rate constants of NF(a1 delta) for Q = HCl, O2, CO, and Cl2 over the temperature range 300-480 K.

Research is presented demonstrating the measurements of infrared absorption cross sections for nitrous acid using spectra recorded by FTIR and UV/visable spectroscopy simultaneously.

This research uses the nonlinear least-squares procedure to study published electron capture detector data for nitromethane and alpha-nitrotoluene.

1-Naphthalenesulfonyl as a tosyl substitute is discussed relative to protection of amino functions. Cyclic voltammetry (CV) studies and been carried out on model sulfonamides with CV being is tested as a tool for study of cathodic stability of some sulfonyl moieties with nitrogen. Reduction cleavage was studed as a means of protection. The tosyl moiety, though a good protecting group for some nitrogen functions, often is unsatisfactory for that use because it requires such intense cleavage conditions.

The hydrogen bonding between hydrogen fluoride and a series of simple nitrile and carbonyl compounds was investigated using ab initio molecular calculations at the HF/6-31+G(d,p) level. The results can be explained in terms of the variation of the molecular electrostatic potential at the nitrile nitrogen for the series of nitrile compounds and at the carbonyl oxygen for the series of carbonyl compounds. A dependence between the calculated molecular electrostatic potential and interaction energy that unifies the two series was also observed.

Methanococcus voltae harbors genetic information for two pairs of homologous [NiFe]-hydrogenases. Two of the enzymes contain selenocysteine, while the other two gene groups encode apparent isoenzymes that carry cysteinyl residues in the homologous positions. The genes coding for the selenium-free enzymes, frc and vhc, are expressed only under selenium limitation. They are transcribed out of a common intergenic region. A series of deletions made in the intergenic region localized a common negative regulatory element for the vhc and frc promoters as well as two activator elements that are specific for each of the two transcription units. Repeated sequences, partially overlapping the frc promoter, were also detected. Mutations in these repeated heptanucleotide sequences led to a weak induction of a reporter gene under the control of the frc promoters in the presence of selenium. This result suggests that the heptamer repeats contribute to the negative regulation of the frc transcription unit.

The reaction dynamics of CN radicals with O2 are examined using infrared diode laser absorption spectroscopy. NCO products are shown to arise from the reaction, as do CO and CO2 products. The extent of secondary chemistry in the reaction is analyzed using experiments and kinetic modeling. Results reveal that the branching ratio into the CO + NO channel has a high negative temperature dependence over the temperature range 239-643 K.

Several possibilities were investigated to clarify the initial steps of the degradative pathway in bacterial strain LW1 of the family Comamonadaceae, which uses 1-chloro-4-nitrobenzene as a a sole source of carbon, nitrogen and energy. Results indicated that the initial attack on the nitro group was reductive, given the accumulation of ammonia but not of nitrite in conversion experiments performed with resting cells grown with 1C4NB and the observed 1C4NB reductase activity in LW1 cell extracts. Partial reduction of the nitro group was suggested by the complete conversion of 1C4NB to 2-amino-5-chlorophenol in the absence of oxygen.

A study was conducted to measure electron-spin-resonance spectra of hexadinitrogen and hexacarbonyl complexes of vanadium, niobium and tantalum at 4 K. Results showed that the axial ESR spectrum of Nb(CO)6 can be easily obtained but not the Ta(CO)6 spectrum. The dinitrogen complexes of V and Nb were found to have a unique spectra, involving overlap of parallel and perpendicular lines.

A novel and general approach for synthesizing thionoesters via thionoacyl nitrobenzotriazoles is described. The synthetic route proceeds under mild conditions and in short reaction times and proves to be more effective than previous approaches. The method is highly suitable because of the simplicity of reagent preparation and product isolation, high yields and enhanced reactivity of the thioacylating agents.

The kinetics of carbon-nitrogen bond rotations in alpha-amide radicals were measured using laser photolysis. Experimental results showed that the production of lactams by cyclizations of alpha-amide radicals consisting of allylic groups on nitrogen can be partially inhibited by slow carbon-nitrogen bond rotation that isolates a conformer. Carbon-nitrogen rotation rate constants are somewhat larger than those for carbon-carbon bond rotation.

The use of upper rim A,C, dinitro complexes for the upper rim substitution of calix(4)arenes was described. The nitro groups were also utilized as precursors to amino groups and various functionalities derived from the compounds. Experimental results showed that the p-tetranitrocalix(4)arene were not effectively reduced to the corresponding tetraamines with the 5,17-dinitro compounds, a result which may be attributed to their limited solubility.

The nitrogen heterocycle 3,3,7,7-tetrakis(difluoramino)-octahydro-1,5-dinitro-1,5-diazocine (HNFX) has been synthesized from N-nitrolysis of highly deactivated 3,3,7,7-tetrakis(difluoramino)octahydro-1,5-bis(4-nitrobenzenesulfonyl) 1,5-diazocine. Nitrolysis has been achieved by utilizing the protonitronium reagent produced in the nitric acid-trifluoromethanesulfonic acid system to form HNFX in 65% yield. The first morphology of HNFX contains a crystal structure with cavities that come in the form of channels through its unit cell.

The tricyclic compound (1alpha,2beta,5beta,6alpha)-3-butyl-9-methoxy-3,7-diazatricyclo(4.2.2.2 (super 2,5))dodeca-9,11-diene-4,8-dione was synthesized and its transformations from (4 + 4) photocycloaddition of N-butyl-2-pyridone with 4-methoxy-2-pyridone were examined. Experimental results showed for the first time a facile opening of the secondary lactam after activation of the amide nitrogen with a tert-butyl carboxylate group. Opening of the amide group was induced by methanolysis and lithium borohydride reduction under extremely mild conditions.

The thermal behavior of cycloadducts of nitrones to methyl 2-chloro-2-cyclopropylidene- and 2-chloro-2-spiropentylideneacetates was investigated. 5-spirocyclopropaneisoxazolidines were produced in good yields from the cycloaddition of methyl 2-chloro-2-cyclopropylideneacetate and its spiropentane derivative. The thermal behavior of the 5-spirocyclopropaneisoxazolidines was found to be differentiated and highly dependent on the constitution of nitrone and the solvent.

A three-dimensional quantum mechanical investigation within the nonreactive infinite order sudden approximation (IOSA) for the NH(D) + NO reactions was conducted. The numerical solution was performed within the nonreactive IOSA where in each computation the angles (gamma1gamma2) were held constant, and the out-of-plane angle phi, was eliminated by applying a phi-averaged potential. The Schrodinger equation was solved in the reagents' arrangement channels (ACs) only, and the exchange ACs were eliminated by applying negative imaginary potentials.