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Semi-permeable membranes of binary polymer blends of cellulose triacetate (CTA) and chitosan (CS) were produced to harvest microalgal biomass for biofuels. Relatively thick membranes of polymer blends containing more than 70% CTA were prepared via solution blending in formic acid. Various characterization methods revealed that both polymers are immiscible at the molecular level at room temperature. However, they were macroscopically compatible and exhibited uniform physical properties due to the molecular interactions between CTA and CS with the same cellulosic backbone containing two linear polysaccharides through a [beta]-1,4 glycoside bond. Careful visual inspection revealed that these membranes are transparent and their light transmittance was greater than 90% at all blend compositions. All membranes showed excellent tensile strength at all compositions and the maximum tensile strength was 52.4 MP from the membrane with a CTA/CS weight ratio of 9:1. The NOJ permeability of these blend films increased with increasing CS content and the maximum value was 44.28 mg/[m.sup.2]/day. To improve the NO3 permeability or transfer rate of the CTA/CS membranes, the porous CTA/CS membranes were also prepared using various amounts of silica nanoparticles., INTRODUCTION Production of liquid fuels from a variety of biomasses has recently attracted a great deal of interest from the fuel industry. Microalgae comprise one of the most promising sources [...]

Capacitance type sensors have been widely used to monitor soil water content and salinity, but little is known about their response to specific ions in soil solution. The goal of this laboratory study was to investigate the sensitivity of two capacitance probes, EC[H.sub.2]O EC-5 and EC-10, to N[O.sub.3] concentration in soil solutions, as well as to understand the differences in sensor response to the presence of other ions in the solutions. Forty-five uniformly packed soil samples were prepared using a homogenized loam soil wetted to five volumetric water contents (VWC) with nine solutions containing different concentrations of N[O.sub.3.sup.-], [Cl.sup.-], or both. A two-stage analysis of the normalized data revealed that ion type and concentration had a significant effect (P ~ 0.01) only for the response of the EC-10 probes operating at a frequency of 5 MHz. The response of the EC-5 probes, operating at 70 MHz, was mainly explained by changes in VWC. Multiple linear regression models fitted to the EC-10 response to individual solutions showed that concentration had a statistically significant predictive value only for samples wetted with N[O.sub.3] solutions when temperature was incorporated in the model. The study confirmed that capacitance probes operating at a relatively low frequency of 5 MHz are more sensitive to changes in N[O.sub.3] concentration than in Cl. We attributed this effect to the difference in ion mass that manifests through an increase in conductivity at ion-specific frequency. Additional experimental work is needed, however, to accurately define optimal frequencies for measuring ion-induced effects on dielectric measurement and to quantify interrelations between them. doi: 10.2136/sssaj2010.0074

A particulate nitrate analyzer based on a scrubber difference/NO-[O.sub.3] chemiluminescence method (SD--CL method) has been developed for measuring nitrate concentrations in remote areas. Particulate nitrate concentrations (N[O.sub.3]-(p)) were analyzed by the difference between the concentrations of N[O.sub.y]--gaseous nitric acid (HN[O.sub.3]) and N[O.sub.y]--HN[O.sub.3]-N[O.sub.3]-(p). Annular denuders coated with NaCl and PTFE filter were used as the scrubbers for HN[O.sub.3] and N[O.sub.3]--(p), respectively. The transmission efficiency of coarse particles in the denuder was found to be 93.4 [+ or -] 5.8%, so the loss of N[O.sub.3]-(p) to the denuder was within the uncertainty of the particulate nitrate analyzer ([+ or -]20%). The measurements of N[O.sub.y], HN[O.sub.3], and N[O.sub.3]-(p) were conducted from March 15 to April 31,2008, at Cape Hedo, Okinawa, Japan. Over 99.5% of the observed concentrations of N[O.sub.3]-(p) for 10 min integration times were higher than the detection limit of the SD--CL method (0.18/[micro]g [m.sup.-3]). The least-squares fit of the R&P nitrate monitor against the SD--CL method yielded a slope of 0.67 [+ or -] 0.02 and a correlation coefficient of R = 0.73. This result indicates that this method could also measure N[O.sub.3]-(p) when the diameter of aerosols was larger than 10 [micro]m. The SD--CL method was found to be useful as a measurement system for N[O.sub.3]-(p) in remote areas where coarse N[O.sub.3]-(p) dominates. 10.1021/ac101704w

Peroxycarboxylic nitric anhydrides (PANs) have long been recognized as important trace gas constituents of the troposphere. Here, we describe a blue diode laser thermal dissociation cavity ring-down spectrometer for rapid and absolute measurements of total peroxyacyl nitrate ([sigma]PAN) abundances at ambient concentration levels. The PANs are thermally dissociated and detected as N[O.sub.2], whose mixing ratios are quantified by optical absorption at 405 nm relative to a reference channel kept at ambient temperature. The effective N[O.sub.2] absorption cross-section at the diode laser emission wavelength was measured to be 6.1 x [10.sup.-19] [cm.sup.2] [molecule.sup.-1], in excellent agreement with a prediction based on a projection of a high-resolution literature absorption spectrum onto the laser line width. The performance, i.e., accuracy and precision of measurement and matrix effects, of the new 405 nm thermal dissociation cavity ring-down spectrometer was evaluated and compared to that of a 532 nm thermal dissociation cavity ring-down spectrometer using laboratory-generated air samples. The new 405 nm spectrometer was considerably more sensitive and compact than the previously constructed version. The key advantage of laser thermal dissociation cavity ring-down spectroscopy is that the measurement can be considered absolute and does not need to rely on external calibration. 10.1021/ac101441z

Yields of [beta]-hydroxynitrates, dihydroxynitrates, and trihydroxynitrates, in particles formed from OH radical-initiated reactions of [C.sub.9]-[C.sub.15] 2-methyl-1-alkenes in the presence of N[O.sub.x] were measured by using a thermal desorption particle beam mass spectrometer coupled to a high-performance liquid chromatograph with a UV-visible (UV-vis) detector. Yields of [beta]-hydroxynitrates and dihydroxynitrates increased with carbon number primarily due to enhanced gas-to-particle partitioning before reaching plateaus at [approximately equal to][C.sub.14]-[C.sub.15], where the compounds were essentially entirely in the particle phase. Plateau yields of [beta]-hydroxynitrates, dihydroxynitrates, and trihydroxynitrates were 0.183 [+ or -] 0.005, 0.045 [+ or ] 0.005, and 0.034 [+ or -] 0.005, and, after normalization for OH radical addition to the C = C double bond, were 0.225 [+ or -] 0.007, 0.055 [+ or -] 0.006, and 0.042 [+ or -] 0.006. The fractions of 1-hydroxy and 2-hydroxy [beta]-hydroxynitrate isomers were 0.90/0.10. Yields measured here and in our previous study of reactions of linear internal alkenes and linear 1-alkenes indicate that, for these alkene classes, the relative branching ratios for forming tertiary, secondary, and primary [beta]-hydroxyalkyl radicals by OH radical addition to the C = C double bond are 4.3/1.9/1.0, and the branching ratios for forming [beta]-hydroxynitrates from reactions of tertiary, secondary, and primary [beta]-hydroxyperoxy radicals with NO are 0.25, 0.15, and 0.12. The effects of [H.sub.2]O vapor and N[H.sub.3] on yields were also explored. aerosol | atmospheric chemistry | organice nitrate | particles doi/ 10.1073/pnas.0910585107

The use of stable isotope labeled substrates and subsequent analysis of urinary nitrate, forms a noninvasive test for evaluation of the in vivo NO metabolism. The present paper describes a new method for simultaneous quantification of [sup.15]N-nitrate and total nitrate with gas chromatography combustion isotope ratio mass spectrometry (GC-C-IRMS). Nitrate, isolated from urine with a nitrate selective resin, was reduced to nitrite using copperized cadmium. Subsequently, Sudan I was formed by diazotation. Sudan II was added as internal standard, and both molecules were analyzed with GC-C-IRMS as tert-butyldimethylsilyl derivatives. The accuracy was determined during a recovery study of two different known nitrate concentrations and two [sup.15]N-enrichments. A recovery of 101.6% and 103.9% for total nitrate and 107.6% and 91.2% for [sup.15]N-nitrate was obtained, respectively. The validated method was applied on complete 72 h urine collections after intravenous administration of [sup.15]N-nitrate and [sup.15]N-arginine in humans. On average, 51.8% (47.0-71.0%) of administered [sup.15]N-nitrate was excreted, while 0.68% (0.44-1.17%) of [sup.15]N-arginine was metabolized to nitrate. In conclusion, this method can be used for accurate simultaneous determination of [sup.15]N-nitrate and total nitrate concentrations in urine and can be applied in clinical studies for noninvasive evaluation of NO metabolism in vivo. 10.1021/ac9019208

The X-ray structure of the blue complex, [Cu(L)(N[O.sub.3])][N[O.sub.3]] obtained from the reaction of Cu[(N[O.sub.3]).sub.2]*3[H.sub.2]O with the ligand 1-(ferrocenemethyl)-1,4,7,10-tetraazacyclododecane (L) in acetonitrile showed an unexpected binding of a nitrate anion in that C[u.sup.II] center. The nitrate anion in the C[u.sup.II] center is observed to be surrounded by four N atoms of the 1,4,7,10-tetraazacyclododecane (cyclen) macrocycle and two O atoms from chelating nitrate anion, both Cu-O distances being below the sums of the van de Waals radii.

The interaction of N[O.sub.3] free radical and [N.sub.2][O.sub.5] with decane flame soot is examined in a Knudsen flow reactor at ambient temperature. The inverse concentration dependence of [gamma] below the concentration threshold has revealed a complex reaction mechanism for both N[O.sub.3] and [N.sub.2][O.sub.5].

Oxidation of ferrocenes (Fc) and 1,1'-dimethylferrocene (DmFc) by copper(II) was studied in 95% and 80% acetonitrile/water solutions. It was concluded that complexation increases the rate of self-exchange between the [Cu.sup.II][(X).sub.n] and [Cu.sup.I][(X).sub.n] species and nitrate ions were found to mildly inhibit the reaction while chloride ions substantially increased the rate.

A study of the reaction of nitrate radical with dimethyl sulfide using cavity ring-down spectroscopy in 20-200 Torr of [N.sub.2] diluent in the temperature range of 283-318 K is presented. The rate constant for the reaction was found to be temperature dependent and pressure independent.

The synthesis and characterization of three pendant-armed hexaazamacrocyclic ligands and their nitrate and perchlorate silver(I) complexes in 1:1 and 2:1 (Ag:L(super n)) molar ratios are presented. The Ag-Ag reactions have enabled the complexes to be fluorescent in the solid state at room temperatursile.

The initial steps in the gas-phase decomposition of urea and urea nitrate are investigated using electronic structure calculations. The HNO3-catalyzed breakdown of urea HNCO and NH3 is predicted to be the most favorable decomposition pathway for gaseous urea nitrate.

The organic/electrolyte interactions of ammonium sulfate, nitrate and sodium chloride with substances containing carboxylic acids (COOH) and hydroxyl (OH) functional groups are examined. A liquid-liquid phase separation in the 1,2-hexanediol/water system is induced by all salts.

The sonochemical synthesis of stable palladium nanoparticles are achieved by ultrasonic irradiation of palladium(II) nitrate solution where the starting solutions are prepared by the addition of different concentrations of palladium(II) nitrate in ethylene glycol and poly(inylpyrrolidone) (PVP). The resulting mixtures were irradiated with ultrasonic waves in a glass vessel.

The ultrasonic velocities, densities, viscosities, and electrical conductivities of aqueous solutions of magnesium nitrate and magnesium acetate is measured from dilute to saturation concentrations. The experimental results are supported by molecular dynamics simulations, which reveal the much stronger tendency of OAc(super -) compared to NO(sub 3)(super -) to associate with Mg(super 2+) in aqueous solutions.

Mass spectrometric (MS) methods are used for the analysis of two novel nitramine explosives--hexanitrohexaazaisowurzitane (HNIW) and 4,10-dinitro-2,6,8,12-tetraoxa-4,10-diazaisowurzitane (DTIW). The methods include electrospray (ESI) and aanospheric pressure chemical ionization techniques for liquid chromatography/MS (LC/MS), chemical ionization for direct introduction (DCI), and gas chromatography/MS (CI-GC/MS). It is found that HNIW (438 Da) is detectable using both positive and negative modes of DCI and in the negative mode ESI-MS. Several anions were found to complex with HNIW, e.g., C[F.sub.3]C[O.sub.2.sup.-], [Cl.sup.-], [Br.sup.-], [I.sup.-], N[O.sub.3.sup.-] , and N[O.sub.2.sup.-] . On the other hand, DTIW could only be detected using positive DCI and CI-GC/MS, where an M[H.sup.+] ion (m/z 263) was formed. The fragmentation pathways of the two nitramines were further studied by M[S.sup.2] experiments. Apparently, the main fragmentation pathway of the M[H.sup.+] ion of DTIW involves the loss of nitrous acid. Several anion adducts of HNIW that were studied dissociate to afford neutral HNIW and the added anions. However, [Cl.sup.-] , [Br.sup.-], [I.sup.-], and N[O.sub.2.sup.-] afford a series of fragments that resulted from the dissociation of the isowurzitane structure. For these anions, limit of detection was also found. To understand some of the HNIW fragmentation pathways, DFT calculations were used.

A convenient one-pot route for the synthesis of transition metal polynulcear complexes based on the in situ generation of carboxylate ligands by oxidation of aromatic aldehydes by mental nitrates in air, followed by isolation of target compounds by specific solvent choices is accomplished. This method bypasses the direct use of transition metal carboxylate salts as starting materials.

The rare-earth binding properties of two hydrophobic carbamoylmethylphosphine oxide (CMPO) ligands, the normal bidentate variety, a tridentate extractant and tributyl phosphate are evaluated. The results show that as the ionic radius of the lanthanide ion decreases, a pair of the carbamoylmethylphosphine ligands is able to completely solvate a bound metal ion thereby weakening the nitrate-metal interaction.

Myxococcus xanthus fibril exopolysaccharide (EPS), essential for the social gliding motility and development of this bacterium, is regulated by the Dif chemotaxis-like pathway. DifA, an MCP homolog, is proposed to mediate signal input to the Dif pathway. However, DifA lacks a prominent periplasmic domain, which in classical chemoreceptors is responsible for signal perception and for initiating transmembrane signaling. To investigate the signaling properties of DifA, we constructed a NarX-DifA (NafA) chimera from the sensory module of Escherichia coli NarX and the signaling module of M. xanthus DifA. We report here the first functional chimeric signal transducer constructed using genes from organisms in two different phylogenetic subdivisions. When expressed in M. xanthus, NafA restored fruiting body formation, EPS production, and S-motility to difA mutants in the presence of nitrate. Studies with various double mutants indicate that NafA requires the downstream Dif proteins to function. We propose that signal inputs to the Dif pathway and transmembrane signaling by DifA are essential for the regulation of EPS production in M. xanthus. Despite the apparent structural differences, DifA appears to share similar transmembrane signaling mechanisms with enteric sensor kinases and chemoreceptors.

Nitrate monitoring biosensors were prepared by immobilizing nitrate reductase derived from yeast on a glassy carbon electrode (GCE, d = 3 mm) or screen-printed carbon paste electrode (SPCE, d = 3 mm) using a polymer (poly(vinyl alcohol)) entrapment method. The sensor could directly determine the nitrate in an unpurged aqueous solution with the aid of an appropriate oxygen scavenger: the nitrate reduction reaction driven by the enzyme and an electron-transfer mediator, methyl viologen, at -0.85 V (GCE vs Ag/AgCl) or at -0.90 V (SPCE vs Ag/AgCl) exhibited no oxygen interference in a sulfite-added solution. The electroanalytical properties of optimized biosensors were measured: the sensitivity, linear response range, and detection limit of the sensors based on GCE were 7.3 nA/[micro]M, 15-300 [micro]M ([r.sup.2] = 0.995), and 4.1 [micro]M (S/N = 3), respectively, and those of SPCE were 5.5 nA/[micro]M, 15-250 [micro]M ([r.sup.2] = 0.996), and 5.5 [micro]M (S/N = 3), respectively. The disposable SPCE-based biosensor with a built-in well- or capillary-type sample cell provided high sensor-to-sensor reproducibility (RSD < 3.4% below 250 [micro]M) and could be used more than one month in normal room-temperature storage condition. The utility of the proposed sensor system was demonstrated by determining nitrate in real samples.

A new optical absorption-based disposable sensor for nitrate is described. The nitrate-sensitive element is a bicyclic cyclophane receptor next to a suitable pH-sensitive lipophilic dye immobilized in a plasticized polymeric membrane. The rigid amide-based receptor with [C.sub.3] symmetry controls the anion selectivity pattern of the optical element. The optical selectivity coefficients obtained for nitrate over a variety of naturally occurring anions in natural waters meet the requirements for the determination of nitrate in waters. The disposable sensor responds to nitrate rapidly--the typical response time is 5 min--and reversibly over a wide dynamic range (26 [micro]M--63 mM) with sensor-to-sensor reproducibility (relative standard deviation, RSD, 3.68%, as log [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII], at the medium level of the range and RSD 1.39% for repeated measurements with the same sensor). The performance of the optical disposable sensor was tested for the analysis of nitrate in different types of natural waters (river, well, spring), validating results against a reference procedure. The proposed method is quick, inexpensive, selective, and sensitive and uses only conventional instrumentation.

The synthesis of CIC(O)OONO2 is accomplished by photolysis of a mixture of Cl2, NO2 and CO in large excess of O2 at about -70 degree Celcius. The experimental geometry of CIC(O)OONO2 is reproduced reasonably well by B3LYP/6-311+G(2df) calculations, whereas the MP2 approximation predicts the N-O bond considerably too long and the dihedral angle too small.

One, five-Diamino-1 H-tetrazole could easily be protonated by reaction with strong mineral acids, yielding the poorly investigated 1, 5-diaminotetrazolium nitrate and perchlorate. The salts examined show good to reasonable physical properties that include high densities, good thermal stabilities, and distinctive melting points around 100 degree Celsius.

The last three decades have brought clear recognition that many populations of animals are experiencing severe declines or local and global extinctions. Many examples have become common knowledge to the general public, such as worldwide declines in amphibian populations and extensive loss of coral reefs. The mechanisms underlying these and other changes are poorly understood. However, a growing literature indicates that a wide array of chemical contaminants have the potential to disrupt normal cell-to-cell signaling mechanisms. A global pollutant of most aquatic systems, nitrate has the potential to be an endocrine disrupting contaminant. This paper reviews studies performed on vertebrates demonstrating that nitrate and/or nitrite have the potential to alter endocrine function. Further, a retrospective study of our work on alligators from various lakes in Florida suggests that nitrate could contribute to some of the altered endocrine parameters previously reported in juvenile animals. We propose hypotheses suggesting that nitrate could alter steroidogenesis by 1) conversion to nitrite and nitric oxide in the mitochondria, the site of initial steroid synthesis, 2) altering C[l.sup.-] ion concentrations in the cell by substituting for C[l.sup.-] in the membrane transport pump or 3) binding to the heine region of various P450 enzymes associated with steroidogenesis and altering enzymatic action. Future studies are needed to examine the endocrine disruptive action of this ubiquitous pollutant. A growing literature indicates that all biologists studying natural systems, whether they choose to or not, must now consider contaminant exposure as a direct influence on their studies. That is, ubiquitous global contamination has the potential to alter the endocrine, nervous and immune systems of all organisms with resulting changes in gene expression and phenotypes.

The facile conversion of hydrated neodymium nitrate to anhydrous tetrahydrofuran and dimethoxyethane adducts and subsequent reactivity with cyclopentadienide reagents to form oligomeric organometallic species is reported. The reactions show that nitrates can be useful precursors in organolanthanide chemistry, and the structures of the organometallic lanthanide nitrate products are helpful for the assembly of extended systems.

Exploring further the fundamental issues by monitoring NO(sub x) emissions in real time from steadily illuminated nitrate-doped ice layers subjected to a linear temperature ramp is discussed. In contrast, the NO/NO2 ratio is largest at the lower temperatures, such as those prevalent in the South Pole, and drops steadily.

The photochemical reactions occurring after irradiation at 200 nm of the aqueous nitrate ion, No3(super -1)(aq) is examined. The formation and subsequent relaxation of the primary photoproducts of nitrate photolysis is characterized using the femtosecond transient absorption spectroscopy over the range 194-388 nm.

Rate coefficients for the reaction of OH radical with eleven C3-C6 hydroxyalkyl nitrates and with two C4 hydroxy nitrates containing a double bond were determined at atmospheric pressure and 296 (plus or minus) 2 K. The rate coefficients increase with increasing chain length and separation between the hydroxy and the nitroxy groups.

The reaction of ebselen and its derivatives with peroxynitrite anion (PN) is studied in the gas and aqueous phases. It is observed that ebselen reacts with PN to exhibit glutatione peroxidase activity.

The study was done on the decomposition of metal nitrates in air by thermogravimetry. The result shows that their reduction may be triggered by thermal decomposition.

It is observed that the thermal coefficient described by Defay seemed to be a useful tool for showing whether surface transitions occur in soluble surfactants. Classical thermodynamic relationships link this thermal coefficient to the isotherm adsorption of the surfactant at the liquid-vapor interface.

A theoretical study of the ROONO and RONO2 species derived from the OH-isoprene reactions to elucidate the chemistry of the RO2-NO reaction is described. The VRRKM/ME analysis reveals negligible stabilization of excited ROONO and provides an assessment of ROONO isomerization to RONO2.

Rate coefficients for the reactions of CL atoms with a series of C3-C6 hydroxyalkyl nitrates at 296 plus minus 2 K are studied. It is concluded that the reactivity of the hydroxyalkyl nitrates is enhanced towards the CL atom in the presence of the hydroxy group.

The reaction or isoprene with nitrate radicals (NO3) is studied through combined experimental and theoretical approaches. Detection of NO3-isoprene adducts radical via chemical ionization mass spectrometry (CIMS) method and geometrical optimization performed by density functional theory is discussed.

Research is done on the one-electron reduction product of nitrate, the NO3(super 2-) radical, which was reinvestigated because of the contemporary interest in its reactivity in high-level liquid radioactive systems. In conclusion, implications of the highly negative redox potential of the dianion and the existence of the protonated forms to practical systems are examined.

The products of the gas-phase reactions of OH radicals with the n-alkanes n-pentanes through n-octane at 298 plusmn 2 K and atmospheric pressure of air were investigated using gas chromatography with flame ionization detection (GC-FID). The formation yields of alkyl nitrate from n-hexane, n-heptane and n-octane were measured by GC-FID, with the sum of alkyl nitrate being 0.141 plusmn 0.020, 0.178 plusmn 0.024, and 0.226 plusmn 0.032 respectively.

The cluster chemistry employing a fast flow reactor was used to evaluate the enhanced reactivity of chlorine nitrate (ClONO2), with dissolved acid halide. The results provide direct evidence that an ionic reaction mechanism is involved in the heterogeneous reaction of hydrogen chloride and chlorine nitrate on clusters that mimic polar stratospheric cloud surfaces.

A general mechanism for the reactions of the NO3 radical with 1,2-dichloroethene, 1,2-dichloroethene and tetrachloroethene is proposed from ab inito Density functional theory DFT calculations, which shows three main parallel reaction pathways. The mechanism proposed in this study proves that at low temperatures, epoxides, NO2 and the radical adducts would be formed.