Nitrous Oxide Research Papers - Academia.edu (original) (raw)

Batch experiments were carried out to investigate the stoichiometry and kinetics of microbial degradation of toluene under denitrifying conditions. The inoculum originated from a mixture of sludges from sewage treatment plants with... more

Batch experiments were carried out to investigate the stoichiometry and kinetics of microbial degradation of toluene under denitrifying conditions. The inoculum originated from a mixture of sludges from sewage treatment plants with alternating nitrification and denitrification. The culture was able to degrade toluene under anaerobic conditions in the presence of nitrate, nitrite, nitric oxide, or nitrous oxide. No degradation occurred in the absence of Noxides. The culture was also able to use oxygen, but ferric iron could not be used as an electron acceptor. In experiments with 14C-labeled toluene, 34% 4-8% of the carbon was incorporated into the biomass, while 53% 4-10% was recovered as t4CO2, and 6% + 2% remained in the medium as nonvolatile water soluble products. The average consumption of nitrate in experiments, where all the reduced nitrate was recovered as nitrite, was 1.3 :t: 0.2 mg of nitrate-N per mg of toluene. This nitrate reduction accounted for 70% of the electrons donated during the oxidation of toluene. When nitrate was reduced to nitrogen gas, the consumption was 0.7 4-0.2 nag per mg of toluene, accounting for 97% of the donated electrons. Since the ammonia concentration decreased during degradation, dissimilatory reduction of nitrate to ammonia was not the reductive process. The degradation of toluene was modelled by classical Monod kinetics. The maximum specific rate of degradation, k, was estimated to be 0.71 mg toluene per mg of protein per hour, and the Monod saturation constant, Ks, to be 0.2 mg toluene/1. The maximum specific growth rate,/~,~ax, was estimated to be 0.1 per hour, and the yield coefficient, Y, was 0.14 mg protein per mg toluene.

We measured nitrous oxide (N 2 O), dinitrogen (N 2 ), methane (CH 4 ), and carbon dioxide (CO 2 ) fluxes in horizontal and vertical flow constructed wetlands (CW) and in a riparian alder stand in southern Estonia using the closed chamber... more

We measured nitrous oxide (N 2 O), dinitrogen (N 2 ), methane (CH 4 ), and carbon dioxide (CO 2 ) fluxes in horizontal and vertical flow constructed wetlands (CW) and in a riparian alder stand in southern Estonia using the closed chamber method in the period from October 2001 to November 2003. The replicates' average values of N 2 O, N 2 , CH 4 and CO 2 fluxes from the riparian gray alder stand varied from −0.4 to 58 g N 2 O-N m −2 h −1 , 0.02-17.4 mg N 2 -N m −2 h −1 , 0.1-265 g CH 4 -C m −2 h −1 and 55-61 mg CO 2 -C m −2 h −1 , respectively. In horizontal subsurface flow (HSSF) beds of CWs, the average N 2 emission varied from 0.17 to 130 and from 0.33 to 119 mg N 2 -N m −2 h −1 in the vertical subsurface flow (VSSF) beds. The average N 2 O-N emission from the microsites above the inflow pipes of the HSSF CWs was 6.4-31 g N 2 O-N m −2 h −1 , whereas the outflow microsites emitted 2.4-8 g N 2 O-N m −2 h −1 . In VSSF beds, the same value was 35.6-44.7 g N 2 O-N m −2 h −1 . The average CH 4 emission from the inflow and outflow microsites in the HSSF CWs differed significantly, ranging from 640 to 9715 and from 30 to 770 g CH 4 -C m −2 h −1 , respectively. The average CO 2 emission was somewhat higher in VSSF beds (140-291 mg CO 2 -C m −2 h −1 ) and at the inflow microsites of HSSF beds (61-140 mg CO 2 -C m −2 h −1 ). The global warming potential (GWP) from N 2 O and CH 4 was comparatively high in both types of CWs (4.8 ± 9.8 and 6.8 ± 16.2 t CO 2 eq ha −1 a −1 in the HSSF CW 6.5 ± 13.0 and 5.3 ± 24.7 t CO 2 eq ha −1 a −1 in the hybrid CW, respectively). The GWP of the riparian alder forest from both N 2 O and CH 4 was relatively low (0.4 ± 1.0 and 0.1 ± 0.30 t CO 2 eq ha −1 a −1 , respectively), whereas the CO 2 -C flux was remarkable (3.5 ± 3.7 t ha −1 a −1 ). The global influence of CWs is not significant. Even if all global domestic wastewater were treated by wetlands, their share of the trace gas emission budget would be less than 1%.

Improving rehabilitation after a severe tissue injury does not only require a reduction in pain, but also requires alleviation of negative affects, particularly anxiety. Although opioids remain unsurpassed analgesics to relieve moderate... more

Improving rehabilitation after a severe tissue injury does not only require a reduction in pain, but also requires alleviation of negative affects, particularly anxiety. Although opioids remain unsurpassed analgesics to relieve moderate to severe pain, it has been shown that they also induce latent pain sensitization leading to long-lasting hyperalgesia via N-methyl-D-aspartate-(NMDA)-dependent pronociceptive systems. The present study evaluated the ability of nitrous oxide (N2O), a gas with NMDA antagonist properties, to prevent latent pain sensitization and long-term anxiety-like behavior (ALB) in rats with pain and opioid experiences. On D0, the pro-inflammatory drug carrageenan was injected in one hind paw of rats treated with fentanyl (4x100 microg/kg subcutaneously). Nociceptive threshold was evaluated with the paw pressure vocalization test. Rats were re-exposed to carrageenan or exposed to repeated non-nociceptive environmental stress (NNES) 2-3 weeks later. Rats were also challenged in the elevated plus-maze 2 weeks after fentanyl administration for evaluating ALB. The preventive effects of a single 4 h 50/50% N2O-O2 exposure performed on D0 was evaluated. Fifty percent N2O strongly reduced hyperalgesia induced by a first inflammation and its enhancement by fentanyl, and prevented exaggerated hyperalgesia induced by second inflammatory pain or NNES. Moreover, we provide first evidence that a high fentanyl dose induces long-term ALB 2 weeks after its administration. When associated with fentanyl, 50% N2O prevented such long-term ALB. These results suggest that a single exposure to N2O could improve post-injury pain management and facilitate rehabilitation especially when potent analgesics as opioids have to be used.

Soil fumigation has recently been shown to affect the greenhouse gas balance by increasing emissions of nitrous oxide (N 2 O) following chloropicrin (CP) application. However, the exact mechanisms of this increase were not investigated.... more

Soil fumigation has recently been shown to affect the greenhouse gas balance by increasing emissions of nitrous oxide (N 2 O) following chloropicrin (CP) application. However, the exact mechanisms of this increase were not investigated. The purpose of this study was to elucidate potential mechanisms of CP-induced N 2 O production through laboratory incubations using chemical inhibitors (acetylene, antibacterial, antifungal, and oxygen), isotopically labeled 15 N-CP, and pH modifications of a forest nursery soil. Results showed that N 2 O production increased by 12.6 times following CP fumigation. Microbial activity contributed 82% to the CP-induced N 2 O production, with the remaining 18% from abiotic processes as determined by incubation with sterilized soil. Inhibitor studies suggested that 20% of the N 2 O production was from bacteria and 70% from fungi. There were no significant differences in N 2 O production following CP fumigation under various levels of acetylene (0, 10, and 10 kPa), suggesting that traditional nitrification and denitification reactions did not significantly contribute to N 2 O production following CP fumigation. 15 N labeled studies indicated that 12% of fumigant source N was incorporated into the produced N 2 O. No enrichment in N 2 was observed, indicating that N 2 O was one of the terminal biotic mineralization products of CP. Production of N 2 O is aerobic and production rates increased with increasing oxygen concentrations. Our data strongly suggested that fungal mediated denitrification reactions under aerobic conditions were the primary mechanism for CP-induced N 2 O production.

Switchgrass ( L.) has been promoted as a potential feedstock for cellulosic biofuel in the United States. Switchgrass is known to respond to N fertilizer, but optimal rates remain unclear. Given the potential nonlinear response of nitrous... more

Switchgrass ( L.) has been promoted as a potential feedstock for cellulosic biofuel in the United States. Switchgrass is known to respond to N fertilizer, but optimal rates remain unclear. Given the potential nonlinear response of nitrous oxide (NO) emissions to N inputs, N additions to switchgrass above optimal levels could have large impacts on the greenhouse gas balance of switchgrass-based biofuel. Additionally, N additions are likely to have large impacts on switchgrass production costs. Yield, N removal, and net returns were measured in switchgrass receiving 0 to 200 kg N ha in Manhattan, KS, from 2012 to 2014. Emissions of NO were measured in the 0- to 150-kg N ha treatments. Total emissions of NO increased from 0.2 to 3.0 kg NO-N ha as N inputs increased from 0 to 150 kg N ha. The 3-yr averages of fertilizer-induced emission factors were 0.7, 2.1, and 2.6% at 50, 100, and 150 kg N ha, respectively. Removal of N at harvest increased linearly with increasing N rate. Switchgras...

Intrinsic data of N 2 O catalytic decomposition over a K-promoted Co-Mn-Al mixed oxide prepared by the thermal treatment of a layered double hydroxide was used for the design of a pilot reactor for the abatement of N 2 O emissions from... more

Intrinsic data of N 2 O catalytic decomposition over a K-promoted Co-Mn-Al mixed oxide prepared by the thermal treatment of a layered double hydroxide was used for the design of a pilot reactor for the abatement of N 2 O emissions from the off-gases in HNO 3 production. A pseudo-homogeneous one-dimensional model of an ideal plug flow reactor under an isothermal regime (450 °C) was used for reactor design. A catalyst particle diameter of 3 mm is a compromise size because increasing the size of the catalyst particle leads to a decrease in the reaction rate because of an internal diffusion limitation, and particles with a smaller diameter cause a large pressure drop. A catalyst bed of 11.5 m 3 was estimated for the target N 2 O conversion of 90% upon the treatment of 30000 m 3 /h of exhaust gas (0.1 mol% N 2 O, 0.005 mol% NO, 0.9 mol% H 2 O, 5 mol% O 2) at 450 °C and 130 kPa.

Antithrombin III (AT III) deficiency is a rare inherited disorder which predisposes patients to thrombotic complications. Anticoagulation is necessary to prevent recurrent thrombosis and high doses of heparin are often required.... more

Antithrombin III (AT III) deficiency is a rare inherited disorder which predisposes patients to thrombotic complications. Anticoagulation is necessary to prevent recurrent thrombosis and high doses of heparin are often required. Anticoagulation complicates analgesia in parturients with the condition. We describe such a patient, in pre-term labour, who was successfully managed during labour with intravenous nalbuphine and inhaled nitrous oxide (N20) La d~ficience en antithrombine est une maladie h~r~ditaire rare qui predispose aux complications thrombogbnes. L'anticoagulation est n~cessaire pour la prevention des thromboses r~cidivantes et requiert des doses levlevleves d'hdparine. L'anticoagulation complique dvidemment l'anesth~sie de la parturiente.

The objective of this study was to assess the radiative forcing due to Finnish anthropogenic greenhouse gas emissions in three scenarios. All the Kyoto Protocol gases, i.e., CO 2 , CH 4 , N 2 O, and fluorinated gases, were included. The... more

The objective of this study was to assess the radiative forcing due to Finnish anthropogenic greenhouse gas emissions in three scenarios. All the Kyoto Protocol gases, i.e., CO 2 , CH 4 , N 2 O, and fluorinated gases, were included. The calculations showed that forcing due to Finnish emissions will increase in the case of all gases except methane by the year 2100. In 1990, radiative forcing due to Finland's emission history of all Kyoto Protocol gases was 3.2 mW/m 2 , of which 71% was due to carbon dioxide, 17% to methane, and the rest to nitrous oxide. In 1990 the share of fluorinated gases

OBJECTIVE: To compare the time course of endotracheal tube cuff pressures in presence of nitrous oxide (N2O), obtained in a tracheal model with those measured during clinical anaesthesia. STUDY DESIGN: Experimental and clinical... more

OBJECTIVE: To compare the time course of endotracheal tube cuff pressures in presence of nitrous oxide (N2O), obtained in a tracheal model with those measured during clinical anaesthesia. STUDY DESIGN: Experimental and clinical prospective study. MATERIAL: ...

Objectives. Our objective is to examine spatial relationships between modeled criteria air pollutants (i.e., nitrous oxides, carbon monoxide, and ozone) and sociodemographics in metropolitan Phoenix, Arizona. Modeled air pollution offers... more

Objectives. Our objective is to examine spatial relationships between modeled criteria air pollutants (i.e., nitrous oxides, carbon monoxide, and ozone) and sociodemographics in metropolitan Phoenix, Arizona. Modeled air pollution offers environmental justice researchers a new and robust data source for representing chronic environmental hazards. Methods. We used multiple regression equations to predict criteria pollution levels using sociodemographic variables at the Census block group level. Results. We find that Census block groups with lower neighborhood socioeconomic status, higher proportions of Latino immigrants, and higher proportions of renters are exposed to higher levels of criteria air pollutants. Proportion African American, however, is not a significant predictor of criteria air pollution in the Phoenix metro area. Conclusions. These findings demonstrate clear social-class and ethnic-based environmental injustices in the distribution of air pollution. We attribute these patterns to the role of white privilege in the historical and contemporary development of industrial and transportation corridors in Phoenix in relation to racially segregated neighborhoods. Although all people are implicated in the production of criteria pollutants, lower-income and ethnic-minority residents are disproportionately exposed in metropolitan Phoenix. This article examines the environmental justice implications of spatial relationships between modeled criteria air pollutants (nitrous oxides, carbon monoxide, and ozone) and sociodemographics in metropolitan Phoenix (Maricopa County). The use of modeled air pollution data offers environn Direct correspondence to Sara Grineski, Department of Sociology and Anthropology, University of Texas at El Paso, El Paso, TX 79968 hsegrineski@utep.edui. Sara Grineski will share all coding information and data with those wishing to replicate the study. We acknowledge the contributions of Dr. Yu-Jin Choi, an environmental engineer at Arizona State University. Dr. Choi shared her pollution models with us and patiently answered our questions about them. We also acknowledge the assistance of Carol Atkinson-Palombo and

Measurements of dissolved 02, NzO, NH4+, NOz-, and NOs-are used to study the biogeochemistry of nitrogen in the Potomac River near Washington, D.C. The nutrient budget of the Potomac is dominated by sewage inputs from treatment plants at... more

Measurements of dissolved 02, NzO, NH4+, NOz-, and NOs-are used to study the biogeochemistry of nitrogen in the Potomac River near Washington, D.C. The nutrient budget of the Potomac is dominated by sewage inputs from treatment plants at Blue Plains and Alexandria. Measurements taken in July and September 1977 indicate large supersaturated concentrations of NzO and exhibit significant short-period variations over distances >40 km. Concentrations of N20 and O2 appear to be inversely correlated and there are indications that N,O may be produced primarily near the sediment-water interface. Nitrous oxide is released to the air on a time scale of about 1 day and gas exchange may occur mainly in shallow embaymcnts in response to turbulence associated with tidal currents. Release of N20 to the atmosphere takes place at a rate of about 10' kg* d-' and may be attributed to prompt conversion to N,O of between 1 and 5% of the total nitrogen input. We report here results from an experimental study designed to quantify some aspects of the nitrogen cycle in the Potomac River near Washington, D.C. The Potomac drains a land area of about 3.8 x lo4 km2, from its source on the eastern slope of the Appalachian Mountains to the point where it enters Chesapeake Bay at Point Lookout downstream some 640 km. The river is tidal over the last 183 km of its course, with significant concentrations of chloride evident in waters below Indian Head, about 115 km from Chesapeake Bay. The drainage basin of the river serves a population of about 3.3 million people, with 2.8 million resident in the Washington metropolitan area. The Potomac is the main source of water for Washington and acts also as the receptacle for the city's waste. Flow rates in the river are variable, with an average value before diversion for urban use of 306 ms. s-l, a median value of 184 m3. s-r (Jaworski et al. 1972). Flow rates for the 1 Colonel and Mrs. J. W. Elkins provided laboratory facilities and hospitality during the course of these observations.

The effects of exposure to nitrous oxide on reproductive indices, fetal development, and male fertility were examined in SwisslICR mice. In experiment I, female mice were exposed for 4 hours per day on days 6-15 of pregnancy, to 0.5%... more

The effects of exposure to nitrous oxide on reproductive indices, fetal development, and male fertility were examined in SwisslICR mice. In experiment I, female mice were exposed for 4 hours per day on days 6-15 of pregnancy, to 0.5% (5,000 ppm), 5.0% (50,000 ppm), or 50% (500,000 ppm) nitrous oxide. Control mice were untreated, exposed to compressed air, or treated with retinoic acid on day 8 of gestation. In experiment 11, male mice were treated, as above, for 9 weeks and then mated nightly for 7 nights to untreated, virgin females. In experiment I, 1,761 fetuses from 154 dams were examined and found to be without evidence of adverse nitrous oxide treatment effects. In experiment 11 there were no differences among the groups in the ability of males to impregnate females or in litter size, fetal wastage, or fetal size. When we compare nitrous oxide with other inhalation anesthetics we have studied employing a similar protocol, we find the order of reproductive toxicity to be: halothane > enflurane > methoxyflurane > nitrous oxide. None of the agents were toxic, however, at the trace concentrations usually found in operating rooms.

Iron complexes in the ZSM-5 zeolite matrix (c~-centers) are shown to perform single-turnover cycles of methane oxidation to methanol at room temperature when nitrous oxide is used as a source of oxygen. The origin of carbon and oxygen in... more

Iron complexes in the ZSM-5 zeolite matrix (c~-centers) are shown to perform single-turnover cycles of methane oxidation to methanol at room temperature when nitrous oxide is used as a source of oxygen. The origin of carbon and oxygen in the product methanol was traced using ~3C and ~SO isotopes. Probable structure of c4-sites as well as mechanistic features of the reaction allow to consider this system as a first successful model of methane monooxygenase.

Neurons in the rat solitary nucleus (NTS) respond to mechanical stimulation of the uterine horn, cervix and vagina . The present study examined how these responses were affected by bilateral vagotomy and/or T10-T12 spinal transection for... more

Neurons in the rat solitary nucleus (NTS) respond to mechanical stimulation of the uterine horn, cervix and vagina . The present study examined how these responses were affected by bilateral vagotomy and/or T10-T12 spinal transection for 12 single NTS neurons recorded in 12 rats anesthetized with halothane/nitroUs oxide. Spinal transections eliminated all responses. Vagotomies eliminated responses only to uterine horn stimulation and either reduced the excitatory or enhanced the inhibitory responses to cervix and vaginal stimuli. These results suggest that NTS neuronal responses to cervix and vaginal stimulation depend upon input from the spinal dorsal horn and are facilitated by vagal input, whereas responses to uterine horn stimulation may require both spinal and vagal input.

Zeolite matrix FAU is applied as an effective support that can be readily exchanged with ferric ions simply by wet ion exchange. The high exchange degree in this zeolite (USY) probably benefits from its larger channel dimension, which... more

Zeolite matrix FAU is applied as an effective support that can be readily exchanged with ferric ions simply by wet ion exchange. The high exchange degree in this zeolite (USY) probably benefits from its larger channel dimension, which makes the diffusion of hydrated ferric ions into the channels easier. The as-prepared and subsequently calcined Fe-USY samples contain various kinds of iron species, which enable Fe-USY to efficiently decompose N 2 O to N 2 and O 2 . The presence of O 2 (20%), H 2 O (2%), or both reduces the N 2 O conversion only to a small extent at the same temperature. To test the feasibility and the catalytic activity in a practical situation, we prepared a monolithic Fe-USY/cordierite sample and investigated the N 2 O conversion under similar conditions. Such a cordieritesupported Fe-USY catalyst (∼9 wt % USY and 0.5 wt % Fe) shows the catalytic performance in N 2 O decomposition similar to the pure Fe-USY catalyst. Remarkably, both the pure Fe-USY and Fe-USY/cordierite catalysts demonstrate a very good durability because there is no activity lost after 100 and 144 h tests. Thus, the Fe-USY zeolite shows its potential as a cost-effective catalyst for N 2 O elimination in future applications.

Amidst controversy about methodology and safety, intraoperative neurophysiology has entered a new era of increasingly routine transcranial and direct electrical brain stimulation for motor evoked potential (MEP) monitoring. Based on... more

Amidst controversy about methodology and safety, intraoperative neurophysiology has entered a new era of increasingly routine transcranial and direct electrical brain stimulation for motor evoked potential (MEP) monitoring. Based on literature review and illustrative clinical experience, this tutorial aims to present a balanced overview for experienced practitioners, surgeons and anesthesiologists as well as those new to the field. It details the physiologic basis, indications and methodology of current MEP monitoring techniques, evaluates their safety, explores interpretive controversies and outlines some applications and results, including aortic aneurysm, intramedullary spinal cord tumor, spinal deformity, posterior fossa tumor, intracranial aneurysm and peri-rolandic brain surgeries. The many advances in motor system assessment achieved in the last two decades undoubtedly improve monitoring efficacy without unduly compromising safety. Future studies and experience will likely clarify existing controversies and bring further advances.

A recent modification of the Kety-Schmidt wash-out technique for ' 33xenon was used to measure whole-brain blood flow (CBF) and oxygen consumption (CMR,,) 1 to 4 hours after termination of halothane anesthesia in 15 Wistar rats. I n this... more

A recent modification of the Kety-Schmidt wash-out technique for ' 33xenon was used to measure whole-brain blood flow (CBF) and oxygen consumption (CMR,,) 1 to 4 hours after termination of halothane anesthesia in 15 Wistar rats. I n this 3-hour experimental period, mean CBF and CMRo, were reduced to 29 and 43% of control values, respectively. CBF and CMR,, determincd at the beginning and end of the experimental period were not significantly different from each other. Cerebral venous O2 tension was significantly higher than in the control group, supporting recent suggestions of a primary, intrinsic effect of halothane on the homeostatic control of this variable. It is concluded that halothane is not useful for cerebral metabolic studies in the rat.

In natural and man-made ecosystems nitrifying bacteria experience frequent exposure to oxygen-limited conditions and thus have to compete for oxygen. In several reactor systems (retentostat, chemostat and sequencing batch reactors) it was... more

In natural and man-made ecosystems nitrifying bacteria experience frequent exposure to oxygen-limited conditions and thus have to compete for oxygen. In several reactor systems (retentostat, chemostat and sequencing batch reactors) it was possible to establish co-cultures of aerobic ammonium-and nitrite-oxidizing bacteria at very low oxygen concentrations (2-8 μM) provided that ammonium was the limiting N compound. When ammonia was in excess of oxygen, the nitrite-oxidizing bacteria were washed out of the reactors, and ammonium was converted to mainly nitrite, nitric oxide and nitrous oxide by Nitrosomonas-related bacteria. The situation could be rapidly reversed by adjusting the oxygen to ammonium ratio in the reactor. In batch and continuous tests, no inhibitory effect of ammonium, nitric oxide or nitrous oxide on nitrite-oxidizing bacteria could be detected in our studies. The recently developed oxygen microsensors may be helpful to determine the kinetic parameters of the nitrifying bacteria, which are needed to make predictive kinetic models of their competition.

Direct oxidation of benzene to phenol over Fe-ZSM-5 catalyst was chosen as a model reaction to characterize the influence of microwave irradiation on ad-/desorption processes during heterogeneously catalyzed reactions. The direct... more

Direct oxidation of benzene to phenol over Fe-ZSM-5 catalyst was chosen as a model reaction to characterize the influence of microwave irradiation on ad-/desorption processes during heterogeneously catalyzed reactions. The direct oxidation of benzene was investigated under different reaction conditions (temperature, residence time, reactant-concentrations) and microwave power in a specially designed reactor. The results obtained by additional microwave radiation were compared to those obtained by conventional heating under similar reaction conditions. In addition, ex situ TG-MS analyses were also conducted to study the sorption behaviour. Extensive investigations were carried out to determine adsorption-desorption effects (benzene, phenol and a mixture of both) and the coking behaviour under microwave conditions. Microwave induces a trend towards increased phenol selectivity and relative deactivation during the reaction. However, there was no conclusive improvement in the performance was obtained by means of microwave heating.

The Intergovernmental Panel on Climate Change (IPCC) standard methodology to conduct national inventories of soil N 2 O emissions is based on default (or Tier I) emission factors for various sources. The objective of our study was to... more

The Intergovernmental Panel on Climate Change (IPCC) standard methodology to conduct national inventories of soil N 2 O emissions is based on default (or Tier I) emission factors for various sources. The objective of our study was to summarize recent N 2 O flux data from agricultural legume crops to assess the emission factor associated with rhizobial nitrogen fixation. Average N 2 O emissions from legumes are 1.0 kg N ha À1 for annual crops, 1.8 kg N ha À1 for pure forage crops and 0.4 kg N ha À1 for grass legume mixes. These values are only slightly greater than background emissions from agricultural crops and are much lower that those predicted using 1996 IPCC methodology. These field flux measurements and other processlevel studies offer little support for the use of an emission factor for biological N fixation (BNF) by legume crops equal to that for fertiliser N. We conclude that much of the increase in soil N 2 O emissions in legume crops may be attributable to the N release from root exudates during the growing season and from decomposition of crop residues after harvest, rather than from BNF per se. Consequently, we propose that the biological fixation process itself be removed from the IPCC N 2 O inventory methodology, and that N 2 O emissions induced by the growth of legume crops be estimated solely as a function of crop residue decomposition using an estimate of above-and below-ground residue inputs, modified as necessary to reflect recent findings on N allocation.

Transfers of some important biogenic atmospheric constituents, carbon dioxide (CO 2), methane (CH 4), molecular nitrogen (N 2), nitrous oxide (N 2 O), nitrate ðNO À 3 Þ, ammonia (NH 3), methylamines (MAs) and dimethylsulphide (DMS),... more

Transfers of some important biogenic atmospheric constituents, carbon dioxide (CO 2), methane (CH 4), molecular nitrogen (N 2), nitrous oxide (N 2 O), nitrate ðNO À 3 Þ, ammonia (NH 3), methylamines (MAs) and dimethylsulphide (DMS), across the air-sea interface are investigated using published data generated mostly during the Arabian Sea Process Study (1992-1997) of the Joint Global Ocean Flux Study (JGOFS). The most important contribution of the region to biogeochemical fluxes is through the production of N 2 and N 2 O facilitated by an acute, mid-water deficiency of dissolved oxygen (O 2); emissions of these gases to the atmosphere from the Arabian Sea are globally significant. For the other constituents, especially CO 2 , even though the surface concentrations and atmospheric fluxes exhibit extremely large variations both in space and time, arising from the unique physical forcing and associated biogeochemical environment, the overall significance in terms of their global fluxes is not much because of the relatively small area of the Arabian Sea. Distribution and air-sea exchanges of some of these constituents are likely to be greatly influenced by alterations of the subsurface O 2 field forced by human-induced eutrophication and/or modifications to the regional hydrography.

During storage of solid animal manure, biological transformation of nitrogen and carbon may increase the temperature to 60 to 70 o C, i.e. composting. The rise in temperature may cause a substantial loss of ammonia, as the ammonium is... more

During storage of solid animal manure, biological transformation of nitrogen and carbon may increase the temperature to 60 to 70 o C, i.e. composting. The rise in temperature may cause a substantial loss of ammonia, as the ammonium is transformed to ammonia at high temperatures and because the heat is generating a flow of air through the dung heap. In

Over a 3-years period, the CO 2 , N 2 O and CH 4 fluxes exchanged with the atmosphere were studied in an upland semi-natural grassland site which was divided at the start of the experiment in two large paddocks continuously grazed by... more

Over a 3-years period, the CO 2 , N 2 O and CH 4 fluxes exchanged with the atmosphere were studied in an upland semi-natural grassland site which was divided at the start of the experiment in two large paddocks continuously grazed by cattle. The soil at the site is an Andosol with high organic matter content. The intensively managed paddock was supplied with mineral N fertilizer and was grazed at a target sward height of 6 cm. The extensively managed paddock received no N fertilization and was stocked at half the stocking density of the intensive paddock. The net ecosystem exchange of CO 2 was continuously measured in each paddock using the eddy covariance technique. Nitrous oxide emissions were measured fortnightly in both paddocks using static chambers. Methane emissions by the grazing cattle were measured four times per year in each paddock using the SF 6 tracer method. Averaged across the 3 years, the two paddocks were net sinks of atmospheric CO 2 (97 and 75 g CO 2 -C m À2 year À1 in the intensive and extensive treatments, respectively). Taking into account the LW gain of the cattle and the C loss through methane emissions, the net C storage was estimated at 87 and 69 g C m À2 year À1 in the intensive and extensive treatments, respectively. Emissions of nitrous oxide and methane reduced by 89 and 55% the atmospheric sink activity of the intensive and extensive treatments, respectively. The average greenhouse gas (GHG) balance across the 3 years was À10 and À31 g CO 2 -C equivalents in the intensive and extensive treatments, respectively. However, the net biome productivity (NBP) and GHG sink activities increased over time in the intensive grazing treatment, whereas they declined after 1 year in the extensive treatment, possibly as a result of a reduced nitrogen status of the vegetation. It is concluded that the suppression of fertilizer N supply combined with a strong reduction in grazing pressure may not be able to increase in the short term the GHG sink per unit land area of managed grasslands. #

There is concern about environmental impacts of cropping in catchments of Australia's Great Barrier Reef, especially losses of nitrogen (N) from cropping systems. Sugarcane production in the Burdekin region in the dry tropics stands out... more

There is concern about environmental impacts of cropping in catchments of Australia's Great Barrier Reef, especially losses of nitrogen (N) from cropping systems. Sugarcane production in the Burdekin region in the dry tropics stands out from other crops/regions because it is grown with the highest applications of irrigation water and N fertiliser rates of any sugarcane producing region in Australia, attributes which may enhance losses of N. Little is known about N losses from sugarcane production systems, especially irrigated systems. We measured parts of the water and N balance over three sugarcane crops at three contrasting sites in different parts of the Burdekin region, covering a range of soil types/textures and irrigation managements. The experimental data were used to parameterise the APSIM-Sugarcane cropping systems model, and the model then used to 'infill' missing data and develop more complete water and N balances for each of the crops at the three sites. The model was also used to simulate long-term yields and N losses through runoff and leaching below the root zone at the sites under a range of N fertiliser and irrigation management practices. Unlike the experience in other cropping systems, N losses through runoff and leaching below the root zone were not higher at our sites than measured in rainfed sugarcane production systems. The long-term simulations showed there were clear opportunities for reducing N losses while maintaining yields through reducing N fertiliser application rates. Simulations results suggested that long-term N surpluses of 50 kg ha −1 yr −1 , considerably less than those during the experiment or common in the study region, were sufficient to maintain yields but reduce N losses by 50-57%. So, N fertiliser management should aim to keep surpluses to that level. Improved irrigation management could also help reduce N losses but generally to a much lesser extent than reduced N fertiliser applications. Research is required to confirm these predicted benefits, and investigate potential interaction between N fertiliser and irrigation management practices, and impacts of other management practices.

Amidst controversy about methodology and safety, intraoperative neurophysiology has entered a new era of increasingly routine transcranial and direct electrical brain stimulation for motor evoked potential (MEP) monitoring. Based on... more

Amidst controversy about methodology and safety, intraoperative neurophysiology has entered a new era of increasingly routine transcranial and direct electrical brain stimulation for motor evoked potential (MEP) monitoring. Based on literature review and illustrative clinical experience, this tutorial aims to present a balanced overview for experienced practitioners, surgeons and anesthesiologists as well as those new to the field. It details the physiologic basis, indications and methodology of current MEP monitoring techniques, evaluates their safety, explores interpretive controversies and outlines some applications and results, including aortic aneurysm, intramedullary spinal cord tumor, spinal deformity, posterior fossa tumor, intracranial aneurysm and peri-rolandic brain surgeries. The many advances in motor system assessment achieved in the last two decades undoubtedly improve monitoring efficacy without unduly compromising safety. Future studies and experience will likely clarify existing controversies and bring further advances.

Silane-nitrous oxide mixtures are widely used in some industries such as semiconductor manufacturing. Since the decomposition of silane is faster than the one of N 2 O and involves the formation of H 2 , the H 2 -N 2 O system might be an... more

Silane-nitrous oxide mixtures are widely used in some industries such as semiconductor manufacturing. Since the decomposition of silane is faster than the one of N 2 O and involves the formation of H 2 , the H 2 -N 2 O system might be an important sub-system of the silane oxidation mechanism. The induction delay times of this system have been widely studied but limited to low pressures. Consequently, the aim of the present study is to investigate the highpressure behaviour of H 2 -N 2 O-Ar. Induction delays behind reflected shock waves have been measured between 1300-1860 K, at pressure of 910±50 kPa for mixtures with equivalence ratios of 0.5, 1, 2. It has been shown that equivalence ratio variations have no effect on these delays. The modelling of delays has been improved by including an excited OH* kinetic submechanism. Finally, various techniques of detonation cell size predictions have been evaluated in comparison with available experimental data.

Burning of rice straw is a common practice in northwest India, where rice–wheat cropping system is extensively followed. The practice results in loss of nutrients, atmospheric pollution and emission of greenhouse gases. A field experiment... more

Burning of rice straw is a common practice in northwest India, where rice–wheat cropping system is extensively followed. The practice results in loss of nutrients, atmospheric pollution and emission of greenhouse gases. A field experiment was conducted at Indian Agricultural Research Institute, New Delhi, India during the rabi season (November to April) of 2002–2003 to evaluate the efficacy of the various modes of rice straw recycling in soil in improving yield and soil fertility and reducing not only carbon dioxide emission but also nitrous oxide (N2O) emission. The treatment with no rice straw incorporation and application of recommended doses of fertilizer (120, 26 and 50 kg N, P and K ha−1, respectively), gave the highest yield of wheat. Treatments with the incorporation of rice straw at 5 Mg ha−1 with additional amount of inorganic N (60 kg N ha−1) or inoculation of microbial culture had similar grain yields to that of the treatment with no straw incorporation. The lowest yield was recorded in the plots where rice straw was incorporated in soil without additional inorganic N and with manure application. All the treatments with rice straw incorporation had larger soil organic C despite the effect on the mineralisation of soil organic matter. Emission of N2O was more when additional N was added with rice straw and secondary when straw was added to the soil because of higher microbial activity. The study showed that burning of rice straw could be avoided without affecting yield of wheat crop by incorporating rice straw in soil with an additional dose of inorganic N or microbial inoculation. However, the reduction of N2O emission due to avoiding burning is in part counterbalanced by an increase in emission during the subsequent wheat cultivation.

Removing atmospheric carbon (C) and storing it in the terrestrial biosphere is one of the options, which have been proposed to compensate greenhouse gas (GHG) emissions. Agricultural lands are believed to be a major potential sink and... more

Removing atmospheric carbon (C) and storing it in the terrestrial biosphere is one of the options, which have been proposed to compensate greenhouse gas (GHG) emissions. Agricultural lands are believed to be a major potential sink and could absorb large quantities of C if trees are reintroduced to these systems and judiciously managed together with crops and/or animals. Thus, the importance of agroforestry as a land-use system is receiving wider recognition not only in terms of agricultural sustainability but also in issues related to climate change. The objective of this paper was to analyse C storage data in some tropical agroforestry systems and to discuss the role they can play in reducing the concentration of CO 2 in the atmosphere. The C sequestration potential of agroforestry systems is estimated between 12 and 228 Mg ha −1 with a median value of 95 Mg ha −1 . Therefore, based on the earth's area that is suitable for the practice (585-1215 × 10 6 ha), 1.1-2.2 Pg C could be stored in the terrestrial ecosystems over the next 50 years. Long rotation systems such as agroforests, homegardens and boundary plantings can sequester sizeable quantities of C in plant biomass and in long-lasting wood products. Soil C sequestration constitutes another realistic option achievable in many agroforestry systems. In conclusion, the potential of agroforestry for CO 2 mitigation is well recognised. However, there are a number of shortcomings that need to be emphasised. These include the uncertainties related to future shifts in global climate, land-use and land cover, the poor performance of trees and crops on substandard soils and dry environments, pests and diseases such as nematodes. In addition, more efforts are needed to improve methods for estimating C stocks and trace gas balances such as nitrous oxide (N 2 O) and methane (CH 4 ) to determine net benefits of agroforestry on the atmosphere.

A Detroit 6I/-92 TA coach diesel engine and a Cummins NTA-855-C diesel engine were operated on fuels produced by blending methyl soyate with No. 2 diesel fuel. Seven fuels, namely, neat diesel fuel; 90:10, 80:20, 70:30, 50:50 and 25:75%... more

A Detroit 6I/-92 TA coach diesel engine and a Cummins NTA-855-C diesel engine were operated on fuels produced by blending methyl soyate with No. 2 diesel fuel. Seven fuels, namely, neat diesel fuel; 90:10, 80:20, 70:30, 50:50 and 25:75% (v/v) blends of diesel fuel:methyl soyate; and neat methyl soyate were prepared and tested for the performance of the Detroit engine using standard test code SAE J1349. Specific gravity, viscosity, and heating values of all seven fuels were determined. Power developed by the engine, brake specific fuel consumption, and emissions analyses including brake specific hydrocarbon, brake specific oxides of nitrogen, brake specific carbon monoxide and smoke were measured. The performance of the engine was found to be satisfactory without a significant reduction in power output on methyl soyate blends up to 30%. Based on these results, the Cummins engine was run on four fuel blends, namely, neat diesel fuel; and 90:10, 80:20 and 70:30% (v/v) blends of diesel:methyl soyate. The performance of the Cummins engine was found to be satisfactory without any significant reduction in power. Engine exhaust emissions, except NO×, were reduced for both engines as the concentration of the methyl soyate in the fuel increased. , for statistical analyses and computer programming.

Labor pain and methods to relieve it are major concerns of childbearing women and their families, with considerable implications for the course, quality, outcome, and cost of intrapartum care. Although these issues affect approximately 4... more

Labor pain and methods to relieve it are major concerns of childbearing women and their families, with considerable implications for the course, quality, outcome, and cost of intrapartum care. Although these issues affect approximately 4 million women and families annually in the United States alone and have major consequences for health care systems, both professional and public discourse revealed considerable uncertainty, with major areas of disagreement and controversy about the safety and effectiveness of some methods to relieve labor pain, and inattention to others. In addition, little attention ap-peared to have been given to women's access to a choice of methods in US hospitals, to organizational factors and decision-making processes that determine methods used, and to actual patterns of use of pain relief methods.

Loss of nitrate in subsurface drainage water from agricultural fields is an important problem in the Midwestern United States and elsewhere. One possible strategy for reducing nitrate export is the use of denitrification bioreactors. A... more

Loss of nitrate in subsurface drainage water from agricultural fields is an important problem in the Midwestern United States and elsewhere. One possible strategy for reducing nitrate export is the use of denitrification bioreactors. A variety of experimental bioreactor designs have been shown to reduce nitrate losses in drainage water for periods up to several years. This research reports on the denitrification activity of a wood chip-based bioreactor operating in the field for over 9 years. Potential denitrification activity was sustained over the 9-year period, which was consistent with nitrate removal from drainage water in the field. Denitrification potentials ranged from 8.2 to 34 mg N kg −1 wood during the last 5 years of bioreactor operation. Populations of denitrifying bacteria were greater in the wood chips than in adjacent subsoil. Loss of wood through decomposition reached 75% at the 90-100 cm depth with a wood half-life of 4.6 years. However, wood loss was less than 20% at 155-170 cm depth and the half-life of this wood was 36.6 years. The differential wood loss at these two depths appears to result from sustained anaerobic conditions below the tile drainage line at 120 cm depth. Pore space concentrations of oxygen and methane support this conjecture. Nitrous oxide exported in tile water from the wood chip bioreactor plots was not significantly higher than N 2 O exports in tile water from the untreated control plots, and loss of N 2 O from tile water exiting the bioreactor accounted for 0.0062 kg N 2 O-N kg −1 NO 3 -N.

Labor pain and methods to relieve it are major concerns of childbearing women and their families, with considerable implications for the course, quality, outcome, and cost of intrapartum care. Although these issues affect approximately 4... more

Labor pain and methods to relieve it are major concerns of childbearing women and their families, with considerable implications for the course, quality, outcome, and cost of intrapartum care. Although these issues affect approximately 4 million women and families annually in the United States alone and have major consequences for health care systems, both professional and public discourse revealed considerable uncertainty, with major areas of disagreement and controversy about the safety and effectiveness of some methods to relieve labor pain, and inattention to others. In addition, little attention ap-peared to have been given to women's access to a choice of methods in US hospitals, to organizational factors and decision-making processes that determine methods used, and to actual patterns of use of pain relief methods.

As the population ages, with increased retention of the natural dentition, there will be a greater responsibility for dental professionals to maintain the oral health of medically, behaviorally, cognitively, and physically impaired... more

As the population ages, with increased retention of the natural dentition, there will be a greater responsibility for dental professionals to maintain the oral health of medically, behaviorally, cognitively, and physically impaired adults. Oral sedatives and nitrous oxide analgesia are frequently and successfully used for dental treatments in these patients. However, many compromised older adults cannot safely tolerate dental treatment with these sedative techniques in an outpatient setting. This paper describes the use of general anesthesia in a hospital environment, coordinated with medical and anesthesia specialists, that is a viable, safe, and effective treatment tool for providing comprehensive dental and oral sugical treatment for the older patient.

Nitrous oxide (N2O) has become a routine intervention in contemporary American dental practice, especially in the management of children. However, routines translate to confidence which in turn may lead to overconfidence, such that... more

Nitrous oxide (N2O) has become a routine intervention in contemporary American dental practice, especially in the management of children. However, routines translate to confidence which in turn may lead to overconfidence, such that possible risks and misuses are insufficiently acknowledged. This article ethically evaluates the use of nitrous oxide as a practice routine in treating children. Nitrous oxide administration is analyzed in reference to three internationally acknowledged principles of dental ethics: nonmaleficence, beneficence, and patient autonomy. In reference to the principle of nonmaleficence, the potential for adverse effects of N2O is discussed, particularly when it is administered in conjunction with other sedatives and anesthetics. The importance of abiding by clinical protocols is emphasized. Next, in reference to the principle of beneficence, the authors address the problematic application of N2O for the benefit of individuals other than the patient (e.g., dentis...

Bubbles impart a very unique texture, chew, and mouth-feel to foods. However, little is known about the relationship between structure of such products and consumer response in terms of mouth-feel and eating experience. The objective of... more

Bubbles impart a very unique texture, chew, and mouth-feel to foods. However, little is known about the relationship between structure of such products and consumer response in terms of mouth-feel and eating experience. The objective of this article is to investigate the sensory properties of 4 types of bubble-containing chocolates, produced by using different gases: carbon dioxide, nitrogen, nitrous oxide, and argon. The structure of these chocolates were characterized in terms of (1) gas hold-up values determined by density measurements and (2) bubble size distribution which was measured by undertaking an image analysis of X-ray microtomograph sections. Bubble size distributions were obtained by measuring bubble volumes after reconstructing 3D images from the tomographic sections. A sensory study was undertaken by a nonexpert panel of 20 panelists and their responses were analyzed using qualitative descriptive analysis (QDA). The results show that chocolates made from the 4 gases could be divided into 2 groups on the basis of bubble volume and gas hold-up: the samples produced using carbon dioxide and nitrous oxide had a distinctly higher gas hold-up containing larger bubbles in comparison with those produced using argon and nitrogen. The sensory study also demonstrated that chocolates made with the latter were perceived to be harder, less aerated, slow to melt in the mouth, and having a higher overall flavor intensity. These products were further found to be creamier than the chocolates made by using carbon dioxide and nitrous oxide; the latter sample also showed a higher intensity of cocoa flavor.

Inhaled nitric oxide (NO) is a selective pulmonary vasodilator used to treat intraoperative pulmonary hypertension and hypoxemia. In contrast to NO delivered by critical care ventilators, NO delivered by anesthesia machines can be... more

Inhaled nitric oxide (NO) is a selective pulmonary vasodilator used to treat intraoperative pulmonary hypertension and hypoxemia. In contrast to NO delivered by critical care ventilators, NO delivered by anesthesia machines can be complicated by rebreathing. We evaluated two methods of administering NO intraoperatively: via the nitrous oxide (N 2 O) flowmeter and via the INOvent (Datex-Ohmeda, Madison, WI). We hypothesized that both systems would deliver NO accurately when the fresh gas flow (FGF) rate was higher than the minute ventilation (V e). Each system was set to deliver NO to a lung model. Rebreathing of NO was obtained by decreasing FGF and by simulating partial NO uptake by the lung. At FGF Ն V e (6 L/min), both systems delivered an inspired NO concentration [NO]) within approximately 10% of the [NO] set. At FGF Ͻ V e and complete NO uptake, the N 2 O flowmeter delivered a lower [NO] (70 and 40% of the [NO] set at 4 and 2 L/min, respectively) and the INOvent delivered a higher [NO] (10 and 23% higher than the [NO] set at 4 and 2 L/min, respectively). Decreasing the NO uptake increased the inspired [NO] similarly with both systems. At 4 L/min FGF, [NO] increased by 10%-20% with 60% uptake and by 18%-23% with 30% uptake. At 2 L/min, [NO] increased by 30%-33% with 60% uptake and by 60%-69% with 30% uptake. We conclude that intraoperative NO inhalation is accurate when administered either by the N 2 O flowmeter of an anesthesia machine or by the INOvent when FGF Ն V e. Implications: Inhaled nitric oxide (NO) is a selective pulmonary vasodilator. In a lung model, we demonstrated that NO can be delivered accurately by a N 2 O flowmeter or by a commercial device. We provide guidelines for intraoperative NO delivery. (Anesth Analg 2000;90:482-8) I nhaled nitric oxide (NO) is used as an investigational treatment for intraoperative pulmonary hypertension and hypoxemia (1-3). With adult critical care ventilators (4), NO delivery is simplified because fresh gas flow (FGF) is delivered during inspiration only; the circuit is open and gas rebreathing does not occur. In neonatal ventilators (4), FGF is continuous throughout the respiratory cycle; again, the circuit is open and rebreathing does not occur. With anesthesia machines, NO delivery is more complicated because FGF is continuous and the breathing circuit semi-open; thus, rebreathing can occur. During inspiration, the patient receives a variable combination of fresh and exhaled gas. During exhalation, the circuit may be filled by FGF without NO, FGF with a set NO concentration ([NO]), or exhaled gas with a variable [NO]. The breathing circuit is further complicated by the presence of a gas reservoir (bag or ventilator bellows) and a carbon dioxide (CO 2 ) absorber. Ultimately, inspired [NO] is the result of several variables, including the [NO] added to the system, FGF rate, ratio of inspiratory-to-expiratory (I:E) time, breathing circuit size, patient minute ventilation (V e), dead space (Vd), and NO uptake.

Nitrous oxide is an important greenhouse gas primarily produced by microbial nitrification and denitrification processes in soil. Emissions of N 2 O also occur indirectly when N is lost through NH 3 volatilization or nitrate leaching and... more

Nitrous oxide is an important greenhouse gas primarily produced by microbial nitrification and denitrification processes in soil. Emissions of N 2 O also occur indirectly when N is lost through NH 3 volatilization or nitrate leaching and subsequently converted to N 2 O in another location. Direct and indirect N 2 O emissions represent an unproductive N loss from agricultural systems and therefore reducing emissions has benefits for greenhouse gas mitigation and improving N use efficiency. This paper reviews strategies for mitigating direct and indirect emissions of N 2 O from land applied manure. The discussion focuses on cattle and pig manure and includes strategies such as dietary measures, manure treatment, manure application timing, method and rate, tillage, cover crops and nitrification inhibitors. Finally, to illustrate the extent of mitigation potential, two mitigation options (i.e., shifting autumn manure application to spring and incorporating all manure within one day of application) were applied to the swine sector in Ontario, Canada. Emissions calculated for the baseline scenario and mitigation scenarios were compared. Results suggest that if both mitigation strategies were adopted, N 2 O emissions from field applied manure could be reduced by 17%. It is clear that opportunity for mitigation exists, but further research is needed to reduce uncertainty about the efficacy of mitigation options and barriers to on farm adoption.

Resistojets operating at low power (less than lOO W) and using liquid propellants have re-emerged as attractive propulsion options for orbit-raising small satellites deployed at Space Shuttle altitudes (approx. 2OO km). Compared to low... more

Resistojets operating at low power (less than lOO W) and using liquid propellants have re-emerged as attractive propulsion options for orbit-raising small satellites deployed at Space Shuttle altitudes (approx. 2OO km). Compared to low power pulsed plasma thrusters (PPT), the resistojet produces two orders of magnitude more thrust (approximately 1.4 mN compared to 140 mN) which is required to overcome drag at solar maximum. The wet mass of both systems is approximately equal although the propellant volume for the PPT is significantly lower since it is stored in solid form. The major disadvantage of the resistojet propulsion system compared to the PPT, is in the complexity added from the propellant tanks. Shuttle integration concerns for the solid Teflon (trademark) propellant of the PPT are minimal or non-existent. Although non-toxic, the water or nitrous oxide propellant of the resistojet requires pressurized tanks and valves which increase safety requirements. To investigate the usefulness of the resistojet for small satellite applications, a series of performance tests have been completed at the AFRL Electric Propulsion Laboratory using the JPL inverted pendulum thrust stand. The tests were conducted for two types of resistojet thrusters developed at the University of Surrey which utilize a packed bed of SiC particles for the heat exchanger. Performance testing eas accomplished at power levels from 0-600 W for five propellants: water, nitrous oxide, water/ methanol, nitrogen, and helium. Two endurance tests were conducted to determine possible failure modes. Performance characterization and thermal models were developed for future design applications of these thrusters. Future USAF and Surrey Satellite Technology, Ltd. (SSTL) missions using these resistojets are also discussed.

A variety of substrates including linear, cyclic, heterocyclic alkenes and their derivatives were tested in the liquid phase non-catalytic oxidation with nitrous oxide (N 2 O). The structure and composition of the alkenes have a... more

A variety of substrates including linear, cyclic, heterocyclic alkenes and their derivatives were tested in the liquid phase non-catalytic oxidation with nitrous oxide (N 2 O). The structure and composition of the alkenes have a significant effect on the reaction selectivity. With many alkenes, N 2 O oxidation provides a selective way for the preparation of carbonyl compounds. The generation of carbene (or diazomethane) species is a remarkable feature of the oxidation of terminal alkenes.

Coastal salt marshes are sensitive to global climate change and may play an important role in mitigating global warming. To evaluate the impacts of Spartina alterniflora invasion on global warming potential (GWP) in Chinese coastal areas,... more

Coastal salt marshes are sensitive to global climate change and may play an important role in mitigating global warming. To evaluate the impacts of Spartina alterniflora invasion on global warming potential (GWP) in Chinese coastal areas, we measured CH4 and N2 O fluxes and soil organic carbon sequestration rates along a transect of coastal wetlands in Jiangsu province, China, including open water; bare tidal flat; and invasive S. alterniflora, native Suaeda salsa, and Phragmites australis marshes. Annual CH4 emissions were estimated as 2.81, 4.16, 4.88, 10.79, and 16.98 kg CH4 ha(-1) for open water, bare tidal flat, and P. australis, S. salsa, and S. alterniflora marshes, respectively, indicating that S. alterniflora invasion increased CH4 emissions by 57-505%. In contrast, negative N2 O fluxes were found to be significantly and negatively correlated (P < 0.001) with net ecosystem CO2 exchange during the growing season in S. alterniflora and P. australis marshes. Annual N2 O em...

This paper aims to provide an overview of the current knowledge regarding the management of adult dentally anxious patients. Furthermore, an attempt is made to formulate a number of preliminary clinical guidelines, based on the available... more

This paper aims to provide an overview of the current knowledge regarding the management of adult dentally anxious patients. Furthermore, an attempt is made to formulate a number of preliminary clinical guidelines, based on the available literature. The findings are discussed in the light of the following four problem areas or types of patients, those with: 1) a mild form of fear or anxiety, 2) a phobia of specific dental procedures or situations, 3) interfering psychiatric symptoms and/or 4) a high treatment need. The literature suggests that particularly the implementation of a high level of predictability during treatment, the training of patients in the use of coping skills, and the application of in vivo exposure to anxiety provoking stimuli are the most appropriate options for the management of anxious dental patients and the reduction of their anxiety level.

Low-cost and simple technologies are needed to reduce watershed export of excess nitrogen to sensitive aquatic ecosystems. Denitrifying bioreactors are an approach where solid carbon substrates are added into the flow path of contaminated... more

Low-cost and simple technologies are needed to reduce watershed export of excess nitrogen to sensitive aquatic ecosystems. Denitrifying bioreactors are an approach where solid carbon substrates are added into the flow path of contaminated water. These carbon (C) substrates (often fragmented wood-products) act as a C and energy source to support denitrification; the conversion of nitrate (NO 3 − ) to nitrogen gases. Here, we summarize the different designs of denitrifying bioreactors that use a solid C substrate, their hydrological connections, effectiveness, and factors that limit their performance. The main denitrifying bioreactors are: denitrification walls (intercepting shallow groundwater), denitrifying beds (intercepting concentrated discharges) and denitrifying layers (intercepting soil leachate). Both denitrifcation walls and beds have proven successful in appropriate field settings with NO 3 − removal rates generally ranging from 0.01 to 3.6 g N m −3 day −1 for walls and 2-22 g N m −3 day −1 for beds, with the lower rates often associated with nitrate-limitations. Nitrate removal is also limited by the rate of C supply from degrading substrate and removal is operationally zero-order with respect to NO 3 − concentration primarily because the inputs of NO 3 − into studied bioreactors have been generally high. In bioreactors where NO 3 − is not fully depleted, removal rates generally increase with increasing temperature. Nitrate removal has been supported for up to 15 years without further maintenance or C supplementation because wood chips degrade sufficiently slowly under anoxic conditions. There have been few field-based comparisons of alternative C substrates to increase NO 3 − removal rates but laboratory trials suggest that some alternatives could support greater rates of NO 3 − removal (e.g., corn cobs and wheat straw). Denitrifying bioreactors may have a number of adverse effects, such as production of nitrous oxide and leaching of dissolved organic matter (usually only for the first few months after construction and start-up). The relatively small amount of field data suggests that these problems can be adequately managed or minimized. An initial cost/benefit analysis demonstrates that denitrifying bioreactors are cost effective and complementary to other agricultural management practices aimed at decreasing nitrogen loads to surface waters. We conclude with recommendations for further research to enhance performance of denitrifying bioreactors. (L.A. Schipper). trated discharges in agricultural systems occur through under-field tile drainage and ditches while diffuse sources are typically through the discharge of shallow groundwater to surface waters. Nitrogen that is captured in biomass passes through the food chain and ends up in wastewater streams, which are ultimately discharged to surface waters.