Adsorption and reaction of nitric oxide and oxygen on Rh(111)

Adsorption of NO and O₂ on Rh(111) has been studied by TPD and XPS. Both gases adsorb molecularly at 120 K. At low coverages (θ_NO < 0.3) NO dissociates completely upon heating to form N₂ and O₂ which have peak desorption temperatures at 710 and 1310 K., respectively. At higher NO coverages NO desorbs at 455 K and a new N₂ state obeying first order kinetics appears at 470 K. At saturation, 55% of the adsorbed NO decomposes. Preadsorbed oxygen inhibits NO decomposition and produces new N₂ and NO desorption states, both at 400 K. The saturation coverage of NO on Rh(111) is approximately 0.67 of the surface atom density. Oxygen on Rh(111) has two strongly bound states with peak temperatures of 840 and 1125 K with a saturation coverage ratio of 1:2. Desorption parameters for the 1125 peak vary strongly with coverage and, assuming second-order kinetics, yield an activation energy of $\text{85 ± 5}\text{kcal}\text{mol}$ and a pre-exponential factor of 2.0 cm² s^?1 in the limit of zero coverage. A molecular state desorbing at 150 K and the 840 K state fill concurrently. The saturation coverage of atomic oxygen on Rh(111) is approximately 0.83 times the surface atom density. The behavior of NO on Rh and Pt low index planes is compared.     

Ultrastructural localization of NADPH diaphorase and nitric oxide synthase in the neuropils of the snail CNS

Comparative studies on the nervous system revealed that nitric oxide (NO) retains its function through the evolution. In vertebrates NO can act in different ways: it is released solely or as a co-transmitter, released from presynaptic or postsynaptic site, spreads as a volumetric signal or targets synaptic proteins. In invertebrates, however, the possible sites of NO release have not yet been identified. Therefore, in the present study, the subcellular distribution of the NO synthase (NOS) was examined in the central nervous system (CNS) of two gastropod species, the terrestrial snail, Helix pomatia and the pond snail, Lymnaea stagnalis, which are model species in comparative neurobiology. For the visualization of NOS NADPH-diaphorase histochemistry and an immunohistochemical procedure using a universal anti-NOS antibody were applied. At light microscopic level both techniques labeled identical structures in sensory tracts ramifying in the neuropils of central ganglia and cell bodies of the Lymnaea and Helix CNS. At ultrastructural level NADPH-d reactive/NOS-immunoreactive materials were localized on the nuclear envelope and membrane segments of the rough and smooth endoplasmic reticulum, as well as the cell membrane and axolemma of positive perikarya. NADPH-d reactive and NOS-immunoreactive varicosities connected to neighboring neurons with both unspecialized and specialized synaptic contacts. In the varicosities, the majority of the NADPH-d reactive/NOS-immunoreactive membrane segments were detected in round and pleomorph agranular vesicles of small size (50–200 nm). However, only a small portion (16%) of the vesicles displayed the NADPH-d reactivity/NOS-immunoreactivity. No evidence for the postsynaptic location of NOS was found. Our results suggest that the localization of NADPH-diaphorase and NOS is identical in the snail nervous system. In contrast to vertebrates, however, NO seems to act exclusively in an anterograde way possibly released from membrane segments of the presynaptic transmitter vesicle surface. Based on the subcellular distribution of NOS, NO could be both a volume and a synaptic mediator, in addition NO may function as a co-transmitter.     

NO气体的空间交叉CARS

采用具有高空间分辨率的空间交叉BOX CARS相位匹配方法,完成了对NO气休室温下、Q支(v=0→v=1)振转CARS谱的测量,研究了它与NO气体压强及激光线宽的关系.从CARS基本理论出发,考虑到激光线宽及不同线型,计算出理论曲线,与实验谱线进行了比较,洛伦兹线型的理论模拟和实验结果符合较好.     

Estrous cycle influences the expression of neuronal nitric oxide synthase in the hypothalamus and limbic system of female mice

Background  

Nitric oxide plays an important role in the regulation of male and female sexual behavior in rodents, and the expression of the nitric oxide synthase (NOS) is influenced by testosterone in the male rat, and by estrogens in the female. We have here quantitatively investigated the distribution of nNOS immunoreactive (ir) neurons in the limbic hypothalamic region of intact female mice sacrificed during different phases of estrous cycle.     

YSZ-cells for potentiometric nitric oxide sensors

Potentiometric sensors based on zirconia can be used for determining gaseous NO at temperatures between 400 and 480 °C. For such mixed potential sensors, NO sensitive electrode materials such as CdMn₂O₄ and V₂O₅ have been described. In order to improve the cell voltage response, composite electrode materials based on V₂O₅-γ-Al₂O₃ were investigated. Sensors employing these materials show a better voltage response and an improved adhesion to the solid electrolyte compared with pure V₂O₅. The optimal temperature was found to be 440 °C. The NO sensitivity is nearly independent on the oxygen partial pressure in the gas. Paper presented at the 8th EuroConference on Ionics, Carvoeiro, Algarve, Portugal, Sept. 16–22, 2001.     

Chemisorption of nitric oxide by nickel

The adsorption of nitric oxide on clean and pre-oxidized nickel has been investigated by X-ray photoelectron spectroscopy. Three distinct states of chemisorption have been recognised at room temperature; one is dissociative while two involve molecularly adsorbed NO. Pre-exposing the nickel surface to oxygen enabled the activity of the surface to be controlled such that adsorption was confined to only one of the molecular states. The two molecular states are suggested to arise from “bent” and “linear” forms of NO.     

Infrared diode laser spectroscopy of nitric oxide

The lineshapes of the rotational-vibrational lines $\text{R(}\text{17}\text{2}\text{)}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{, R(}\text{19}\text{2}\text{)}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$, and $\text{R(}\text{19}\text{2}\text{)}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ of nitric oxide were measured using a PbS_0.61Se_0.39 diode laser. These lineshapes were measured for a NO/N₂ mixture and an NO/H₂O/N₂ mixture at atmospheric pressure. This is the first high resolution spectroscopic mearuement of the rotational-vibrational lineshape of NO broadened by H₂O. The effect of the H₂O is to broaden the lines, increasing the halfwidth by up to 30% for a 10% volume concentration of H₂O. For the case of NO broadened by N₂, the measured linestrengths for the $\text{R(}\text{19}\text{2}\text{)}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ and $\text{R(}\text{17}\text{2}\text{)}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ lines are within 2% of previously published values.     

Diode-laser-based ultraviolet absorption sensor for nitric oxide

An all-solid-state continuous-wave laser system for ultraviolet absorption measurements of the nitric oxide (NO) molecule has been developed and demonstrated. The single-mode, tunable output of a 10-mW, 395-nm external-cavity diode laser (ECDL) is sum-frequency-mixed with the output of a 115-mW, frequency-doubled, diode-pumped Nd:YAG laser in a beta-barium-borate crystal to produce 40 nW of tunable radiation at 226.8 nm. The wavelength of the 395-nm ECDL is then scanned over NO absorption lines to produce fully resolved absorption spectra. Initial results from mixtures of NO in nitrogen in a room-temperature gas cell are discussed. The estimated NO detection limit of the system for a demonstrated absorption sensitivity of 2×10^-3 is 0.2 ppm per meter of path length for 300 K gas. The estimated accuracy of the measurements is ±10%. Received: 25 February 2002 / Revised version: 31 May 2002 / Published online: 8 August 2002     

Ultrahigh-frame-rate nitric oxide planar laser-induced fluorescence imaging

We demonstrate the ability to generate ultrahigh frequency burst sequences of deep UV at 226 nm by mixing the optical parametric oscillator signal output at 622 nm with third harmonic at 355 nm from a pulse burst laser system. We obtained 226 nm burst sequences with uniform burst envelopes, and the average pulse energy is approximately 0.5 mJ. Nitric oxide planar laser-induced fluorescence image sequences at ultrahigh (100 kHz) frame rates have been obtained.     

Chemisorption and decomposition of nitric oxide on ruthenium

Nitric oxide, strongly chemisorbed on ruthenium, is desorbed almost completely as oxygen and nitrogen. Oxygen, nitrogen, and nitric oxide were observed singly on ruthenium with field emission microscopy. Thermal desorption spectroscopy from Ru(101&#x0304;0) showed that molecular nitrogen is only physisorbed but nitrogen from NO decomposition is strongly chemisorbed. Nitrogen from NO shows three binding states, the most strongly bound being present to only a small extent. NO shows three and two binding states when adsorbed at 120 K and 295 K respectively. Work function measurements gave Δφ = 1.3 eV for a monolayer of NO. NO is dissociatively adsorbed above 250 K but a lower temperature limit was not established. The decomposition of NO on $\text{Ru}\text{(10}\text{1}\text{0)}$ under high vacuum conditions is catalytic in that no oxides of ruthenium were observed to form in the process.     

Physical adsorption of nitric oxide on metal oxides

Adsorption isotherms have been measured at 77.5 K for nitric oxide and nitrogen on Al₂O₃, MgO, ZnO and NiO, and at 90.2 K. for nitric oxide on A1₂O₃ and NiO. Three isotherm measurements at 77.5 K were made on the Al₂O₃ sample for each adsorbate to examine the effect of different degrees of surface dehydroxylation. The latter was assessed by means of infrared absorption studies on an Al₂O₃ disc. Isosteric heats for NO adsorption on Al₂O₃ and NiO increase from ca. 8 kJ mol^?1 and 6 kJ mol^?1 (respectively) at half monolayer coverage to near the value of the enthalpy of sublimation (16.6 kJ mol^?1) at monolayer completion. These results are discussed in terms of adsorbate dimerisation. Anomalous adsorption-desorption behaviour for the NONiO system is discussed. Effective adsorbate molecular cross-sectional areas and results for N2 adsorption on preadsorbed NO do not support the existence of either localisation or micro-porosity.     

Quinone-enhanced sonochemical production of nitric oxide from s-nitrosoglutathione

Sonolysis at 75 kHz of argon- and air-saturated aqueous solutions at pH 7.4 containing s-nitrosogluthathione (GSNO) enhances the production rate of nitric oxide (NO). The quinones, anthraquinone-2-sulfonate (AQ2S) and anthraquinone-2,7-disulfonate (AQ27S) further enhance the NO production over that produced in quinone-depleted sonicated solutions. In contrast, the hydrophobic quinones juglone (JQ) and 1,4-naphthoquinone (NQ) inhibit ultrasound-induced NO detection as compared to quinone-depleted solutions. Larger sonolytical decomposition of the hydrophobic quinones NQ and JQ, as compared to AQ2S and AQ27S, is detected which correlates with a larger production of pyrolysis-derived carbon-centered radicals. Reaction of those radicals with NO could explain NQ and JQ inhibition. This work suggests that sulfonated quinones could be used to enhance NO release from GSNO in tissues undergoing ultrasound irradiation.     

Interstitial oxygen in zinc oxide single crystals

Irradiation of zinc oxide single crystals with 2.5 MeV electrons produces both interstitial ions and vacancies. By means of ESR measurements oxygen ions on interstitial sites with tetrahedral and octahedral symmetry have been identified. Furthermore the behaviour of the oxygen vacancyV _o ⁺ is discussed.     

Heterodyne frequency measurements on the nitric oxide fundamental band

Heterodyne frequency measurements have been made on the fundamental band of nitric oxide from 1750 to 1931 cm⁻¹. Based on the analysis of these new measurements, minor changes are made in the band constants and an improved list of calculated energy levels for the v = 0 and v = 1 states is given.     

Absorptivity of nitric oxide in the fundamental vibrational band

From observations of the spectral absorbance of mixtures of nitric oxide in nitrogen at room temperature, we derive an integrated absorptivity for the NO fundamental band of 137.3±4.6 cm^-2 atm^-1 at 0°C. The indicated uncertainty is the estimated maximum error.