THERMAL CHARACTERIZATION OF A GASOLINE TURBOCHARGED DIRECT INJECTION (GTDI) ENGINE UTILIZING LEAN OPERATION AND EXHAUST GAS RECIRCULATION (EGR)

The push for improved fuel economy and reduced emissions has led to great achievements in engine performance and control. These achievements have increased the efficiency and power density of gasoline engines dramatically in the last two decades. With the added power density, thermal management of the engine has become increasingly important. Therefore it is critical to have accurate temperature and heat transfer models as well as data to validate them. With the recent adoption of the 2025 Corporate Average Fuel Economy(CAFE) standard, there has been a push to improve the thermal efficiency of internal combustion engines even further. Lean and dilute combustion regimes along with waste heat recovery systems are being explored as options for improving efficiency. In order to understand how these technologies will impact engine performance and each other, this research sought to analyze the engine from both a 1st law energy balance perspective, as well as from a 2nd law exergy analysis. This research also provided insights into the effects of various parameters on in-cylinder temperatures and heat transfer as well as provides data for validation of other models. It was found that the engine load was the dominant factor for the energy distribution, with higher loads resulting in lower coolant heat transfer and higher brake work and exhaust energy. From an exergy perspective, the exhaust system provided the best waste heat recovery potential due to its significantly higher temperatures compared to the cooling circuit. EGR and lean combustion both resulted in lower combustion chamber and exhaust temperatures; however, in most cases the increased flow rates resulted in a net increase in the energy in the exhaust. The exhaust exergy, on the other hand, was either increased or decreased depending on the location in the exhaust system and the other operating conditions. The effects of dilution from lean operation and EGR were compared using a dilution ratio, and the results showed that lean operation resulted in a larger increase in efficiency than the same amount of dilution with EGR. Finally, a method for identifying fuel spray impingement from piston surface temperature measurements was found. Note: The material contained in this section is planned for submission as part of a journal article and/or conference paper in the future.

Reading Our Land Use Legacy in Groundwater: Nitrate Dynamics in the Judith River Watershed

Elevated nitrate in groundwater is common is agricultural areas where fertilizer has been added at high rates for decades. Within the Judith River Wastershed, high native soil fertility allowed for dryland wheat production without N fertilization until the 1980s, yet elevated nitrate levels were frequently observed in shallow aquifers. Dr. Stephanie Ewing presents results for soil, groundwater and surface water analyses from a hydrologically isolated strath terrace near Moccasin, MT. In context of this uniquely well constrained field setting, these observed data, along with land use history and a simple mass balance model, revel the long term development and perturbation of native soil fertility with cultivation.

A unified nomenclature of NITRATE TRANSPORTER 1/PEPTIDE TRANSPORTER family members in plants

Members of the plant NITRATE TRANSPORTER 1/PEPTIDE TRANSPORTER (NRT1/PTR) family display protein sequence homology with the SLC15/PepT/PTR/POT family of peptide transporters in animals. In comparison to their animal and bacterial counterparts, these plant proteins transport a wide variety of substrates: nitrate, peptides, amino acids, dicarboxylates, glucosinolates, IAA, and ABA. The phylogenetic relationship of the members of the NRT1/PTR family in 31 fully sequenced plant genomes allowed the identification of unambiguous clades, defining eight subfamilies. The phylogenetic tree was used to determine a unified nomenclature of this family named NPF, for NRT1/PTR FAMILY. We propose that the members should be named accordingly: NPFX.Y, where X denotes the subfamily and Y the individual member within the species.

Characterization of NARJ: A molecular chaperone involved in assembly of nitrate reductase

The major goal of this work was to define the role of accessory protein, NARJ, in assembly of nitrate reductase which is a membrane-bound multisubunit enzyme that can catalyze the reduction of nitrate to nitrite under anaerobic growth in E. coli. Nitrate reductase is encoded by the nar GHJI operon under control of the narG promoter. The purified nitrate reductase is composed of three subunits: $\alpha,\ \beta,$ and $\gamma.$ The NARJ protein which is encoded by the third gene (narJ) is not found to be associated with any of the purified preparations of the enzyme, but is required for active nitrate reductase. In this study the product of the narJ gene was identified. NARJ appeared to be produced at a reduced level, compared to the other proteins encoded by the nar operon. Since NARJ could not be overexpressed to a level for an efficient purification, NARJ was expressed and purified as a recombinant protein with polyhistidine tag. The recombinant protein NARJ-6His could functionally replace native NARJ. Purified NARJ-6His is a dimeric protein which contains no identifiable cofactors or unique secondary structure. NARJ was localized in the cytoplasm, and was not associated with nitrate reductase in the membrane. In vivo NARJ activated the $\alpha\beta$ complex and stabilized the $\alpha$ subunit against protease degradation. In the absence of the membrane-bound $\gamma$ subunit, NARJ formed an intermediate complex with $\alpha\beta$ in the cytosol. Based on these studies, NARJ fits the formal definition of a molecular chaperone. It appears to be required only for the biogenesis of nitrate reductase and, therefore, is defined as a private chaperone specifically involved in the assembly of nitrate reductase system. ^

The role of menaquinone in the nitrate reductase complex

Membrane bound, respiratory nitrate reductase in Escherichia coli is composed of three subunits, αβγ. The active complex is anchored to the membrane by membrane-integrated γ subunit and can reduce nitrate to nitrite with membrane quinones, (ubiquinone or menaquinone) as physiological electron donors. The transfer of electrons through the complex is thought to involve the sequence: membrane quinols → b-type hemes (γ subunit) → Fe-S centers (β subunit) → molybdopterin (α subunit) → nitrate. The enzyme can be assayed with the artificial electron donor reduced methyl viologen (MVH) which transfers electrons directly to the molybdopterin cofactor. These studies have focused on the possible role of protein-bound menaquinone in the structure and function of this multisubunit complex. ^ Nitrate reductase was purified as two distinct forms; after solubilization of membrane proteins with detergents, purification rendered an αβγ complex (holoenzyme) which catalyzes nitrate reduction with MVH or the quinols analogs, menadiol and duroquinol, as electron donors. Alternatively, heat-treatment of the membranes in the absence of detergents and subsequent purification of the active enzyme produced an αβ complex, which reduces nitrate only with MVH as electron donor. The active αβ dimer was also separated from γ subunit by heat treatment of the holoenzyme. ^ Menaquinone-9 was isolated directly from the purified αβ complex, and identified by mass spectrometry. Based on the composition of the membrane quinone pool, it was concluded that menaquinone-9 is sequestered from the membrane pool in a specifically protein-bound form. ^ The role of the bound menaquinone in the structure-function of nitrate reductase was also investigated, along with its participation in UV-light inactivation of the enzyme. Menaquinone-depleted nitrate reductase from a menaquinone deficient mutant retained activity with all electron donors and it remained sensitive to UV inactivation. However, the MVH-nitrate reductase activity and the rate of UV inactivation of the enzyme were significantly reduced and the optical properties of the enzyme were modified by the absence of the bound menaquinone-9. ^ Menaquinone-9 is not absolutely required for electron transfer in nitrate reductase but it appears to be specifically-bound during assembly of the complex and to enhance the transfer of electrons through the complex. The possible plasticity of the functional electron transfer pathway in nitrate reductase is discussed. ^

REGULATION OF THE EXPRESSION OF NAR OPERON ENCODING NITRATE REDUCTASE IN ESCHERICHIA COLI

The nar operon, which encodes the nitrate reductase in Escherichia coli, can be induced under anaerobic conditions without nitrate to a low level and with nitrate to a maximum level. The anaerobic formation of nitrate reductase is dependent upon the fnr gene product while the narL gene product is required for further induction by nitrate. The sequence was determined across the entire promoter and regulatory region of the nar operon. The translational start site of the first structural gene of the nar operon, narG gene, was established by identifying the nucleotide sequence for the first 20 N-terminal amino acid residues of the alpha subunit of nitrate reductase. The transcriptional start site and the level of the transcript was determined by S1 mapping procedure. One major transcript was identified which was initiated 50 base pair (bp) upstream from the translational start site of the first structural gene. The synthesis of the transcript was repressed aerobically, fully induced by nitrate anaerobically, and greatly reduced in a ${\rm Fnr\sp-}$ mutant. Deletions were created in the 5$\sp\prime$ nar regulatory sequence with either an intact nar operon or a nar::lacZ fusion. The expression of the plasmids with deletions were determined in a strain with wild type fnr and narL loci, a Fnr- mutant strain and a NarL- mutant strain. These experiments demonstrated that the $5\sp\prime$ limit of the nar operon lies at about $-210$ bp from the transcription start site. The region required for anaerobic induction by the fnr gene product is located around $-60$ bp. Two putative narL recognition sites were identified, one of which is around $-200$ and another immediately adjacent to the fnr recognition region. The deletion of the sequences around $-200$ rendered the remaining narL complex repressive and thus decreased the expression of nar operon, suggesting that the two potential narL sites interact with each other over a significant length of DNA. ^

The Aeolian Flux of Calcium, Chloride and Nitrate to the McMurdo Dry Valleys Landscape: Evidence from Snow Pit Analysis

We have determined the flux of calcium, chloride and nitrate to the McMurdo Dry Valleys region by analysing snow pits for their chemical composition and their snow accumulation using multiple records spanning up to 48 years. The fluxes demonstrate patterns related to elevation and proximity to the ocean. In general, there is a strong relationship between the nitrate flux and snow accumulation, indicating that precipitation rates may have a great influence over the nitrogen concentrations in the soils of the valleys. Aeolian dust transport plays an important role in the deposition of some elements (e.g. C(2+)) into the McMurdo Dry Valleys' soils. Because of the antiquity of some of the soil surfaces in the McMurdo Dry Valleys regions, the accumulated atmospheric flux of salts to the soils has important ecological consequences. Although precipitation may be an important mechanism of salt deposition to the McMurdo Dry Valley surfaces, it is poorly understood because of difficulties in measurement and high losses from sublimation.

Biodiversity effects on nitrate concentrations in soil solution: a Bayesian model

Ecosystems are faced with high rates of species loss which has consequences for their functions and services. To assess the effects of plant species diversity on the nitrogen (N) cycle, we developed a model for monthly mean nitrate (NO3-N) concentrations in soil solution in 0-30 cm mineral soil depth using plant species and functional group richness and functional composition as drivers and assessing the effects of conversion of arable land to grassland, spatially heterogeneous soil properties, and climate. We used monthly mean NO3-N concentrations from 62 plots of a grassland plant diversity experiment from 2003 to 2006. Plant species richness (1-60) and functional group composition (1-4 functional groups: legumes, grasses, non-leguminous tall herbs, non-leguminous small herbs) were manipulated in a factorial design. Plant community composition, time since conversion from arable land to grassland, soil texture, and climate data (precipitation, soil moisture, air and soil temperature) were used to develop one general Bayesian multiple regression model for the 62 plots to allow an in-depth evaluation using the experimental design. The model simulated NO3-N concentrations with an overall Bayesian coefficient of determination of 0.48. The temporal course of NO3-N concentrations was simulated differently well for the individual plots with a maximum plot-specific Nash-Sutcliffe Efficiency of 0.57. The model shows that NO3-N concentrations decrease with species richness, but this relation reverses if more than approx. 25 % of legume species are included in the mixture. Presence of legumes increases and presence of grasses decreases NO3-N concentrations compared to mixtures containing only small and tall herbs. Altogether, our model shows that there is a strong influence of plant community composition on NO3-N concentrations.

Size-Fractionated Nitrogen Uptake Measurements in the Equatorial Pacific and Confirmation of the Low Si-High-Nitrate Low-Chlorophyll Condition

The equatorial Pacific Ocean is the largest natural source of CO(2) to the atmosphere, and it significantly impacts the global carbon cycle. Much of the large flux of upwelled CO(2) to the atmosphere is due to incomplete use of the available nitrate (NO(3)) and low net productivity. This high-nutrient low-chlorophyll (HNLC) condition of the equatorial upwelling zone (EUZ) has been interpreted from modeling efforts to be due to low levels of silicate ( Si( OH) 4) that limit the new production of diatoms. These ideas were incorporated into an ecosystem model, CoSINE. This model predicted production by the larger phytoplankton and the picoplankton and effects on air-sea CO(2) fluxes in the Pacific Ocean. However, there were no size-fractionated rates available for verification. Here we report the first size-fractionated new and regenerated production rates (obtained with (15)N - NO(3) and (15)N - NH(4) incubations) for the EUZ with the objective of validating the conceptual basis and functioning of the CoSINE model. Specifically, the larger phytoplankton ( with cell diameters > 5 mu m) had greater rates of new production and higher f-ratios (i.e., the proportion of NO(3) to the sum of NO(3) and NH(4) uptake) than the picoplankton that had high rates of NH(4) uptake and low f-ratios. The way that the larger primary producers are regulated in the EUZ is discussed using a continuous chemostat approach. This combines control of Si(OH)(4) production by supply rate (bottom-up) and control of growth rate ( or dilution) by grazing ( top-down control).

Sulfate and Nitrate Assimilation in Leaves of Quercus ilex and Quercus pubescens Grown Near Natural CO2 Springs in Central Italy

The effect of long-term exposure to elevated pCO2 concentrations on sulfate and nitrate assimilation was studied under field conditions using leaves from Quercus ilex and Quercus pubescens trees growing with ambient or elevated CO2 concentrations in the vicinity of three natural CO2 springs, Bossoleto, Laiatico and Sulfatara, in Tuscany, Italy. The activity of the key enzymes of sulfate assimilation, adenosine 5′-phosphosulfate reductase (APR) and nitrate assimilation, nitrate reductase (NR), were measured together with the levels of acid soluble thiols, and soluble non-proteinogenic nitrogen compounds. Whereas NR activity remained unaffected in Q. ilex or increased Q. pubescence, APR activity decreased in the area of CO2 springs. The latter changes were often accompanied by increased GSH concentrations, apparently synthesized from H2S and SO2 present in the gas mixture emitted from the CO2 springs. Thus, the diminished APR activity in leaves of Q. ilex and Q. pubescence from spring areas can best be explained by the exposure to gaseous sulfur compounds. Although the concentrations of H2S and SO2 in the gas mixture emitted from the vents at the CO2 springs were low at the Bossoleto and Laiatico spring, these sulfur gases pose physiological effects, which may override consequences of elevated pCO2.

Isotopic effects of nitrate photochemistry in snow: a field study at Dome C, Antarctica

Stable isotope ratios of nitrate preserved in deep ice cores are expected to provide unique and valuable information regarding paleoatmospheric processes. However, due to the post-depositional loss of nitrate in snow, this information may be erased or significantly modified by physical or photochemical processes before preservation in ice. We investigated the role of solar UV photolysis in the post-depositional modification of nitrate mass and stable isotoperatios at Dome C, Antarctica, during the austral summer of 2011/2012. Two 30 cm snow pits were filled with homogenized drifted snow from the vicinity of the base. One of these pits was covered with a plexiglass plate that transmits solar UV radiation, while the other was covered with a different plexiglass plate having a low UV transmittance. Samples were then collected from each pit at a 2–5 cm depth resolution and a 10-day frequency. At the end of the season, acomparable nitrate mass loss was observed in both pits for the top-level samples (0–7 cm) attributed to mixing with the surrounding snow. After excluding samples impacted by the mixing process, we derived an average apparent nitrogen isotopic fractionation (15" app/of role in driving the isotopic fractionation of nitrate in snow.We have estimated a purely photolytic nitrogen isotopic fractionation (15"photo) of -55.8 12.0 ‰ from the difference in the derived apparent isotopic ractionations of the two experimental fields, as both pits were exposed to similar physical processes except exposure to solar UV. This value is in close agreement with the 15" photo value of -47.9 6.8 ‰ derived in a laboratory experiment simulated for Dome C conditions (Berhanu et al., 2014). We have also observed an insensitivity of 15" with depth in the snowpack under the given experimental setup. This is due to the uniform attenuation of incoming solar UV by snow, as 15" is strongly dependent on the spectral distribution of the incoming light flux. Together with earlier work, the results presented here represent a strong body of evidence that solar UV photolysis is the most relevant post-depositional process modifying the stable isotope ratios of snow nitrate at low-accumulation sites, where many deep ice cores are drilled. Nevertheless, modeling the loss of nitrate in snow is still required before a robust interpretation of ice core records can be provided.

Experimental and Theoretical Electron Density Analysis of Copper Pyrazine Nitrate Quasi-Low-Dimensional Quantum Magnets

The accurate electron density distribution and magnetic properties of two metal-organic polymeric magnets, the quasi-one-dimensional (1D) Cu(pyz)(NO3)2 and the quasi-two-dimensional (2D) [Cu(pyz)2(NO3)]NO3·H2O, have been investigated by high-resolution single-crystal X-ray diffraction and density functional theory calculations on the whole periodic systems and on selected fragments. Topological analyses, based on quantum theory of atoms in molecules, enabled the characterization of possible magnetic exchange pathways and the establishment of relationships between the electron (charge and spin) densities and the exchange-coupling constants. In both compounds, the experimentally observed antiferromagnetic coupling can be quantitatively explained by the Cu-Cu superexchange pathway mediated by the pyrazine bridging ligands, via a σ-type interaction. From topological analyses of experimental charge-density data, we show for the first time that the pyrazine tilt angle does not play a role in determining the strength of the magnetic interaction. Taken in combination with molecular orbital analysis and spin density calculations, we find a synergistic relationship between spin delocalization and spin polarization mechanisms and that both determine the bulk magnetic behavior of these Cu(II)-pyz coordination polymers.

NO2-induced nitrate reductase activity in needles of Norway spruce (Picea abies) under laboratory and field conditions

The induction of activity of the enzyme nitrate reductase (NR, EC 1.6.6.1, 1.6.6.2) in needles of Norway spruce (Picea abies[L.] Karst.) by nitrogen dioxide (NO2) was studied under laboratory and field conditions. In fumigation chambers an increase in nitrate reductase activity (NRA) was detected 4 h after the start of the NO2 treatment. During the first 2 days with 100 µg NO2 m−3, NRA reached a constant level and did not change during the following 4 days. At the same level of NO2, NRA was lower in needles from trees grown on NPK-fertilized soil than on non-fertilized soil. After the transfer of spruce trees from fertilized soil to NPK-rich nutrient solution, NRA was transiently increased. This effect was assigned to root injuries causing nitrate transport to the shoot and subsequent induction of NRA. Neither trees on fertilized soil nor trees transferred to NPK-poor nutrient solution had increased NRA unless NO2 was provided. The NO2 gradient in the vicinity of a highway was used to test the long-term effect of elevated levels of NO2 on needle NRA of potted and field-grown spruce trees. Compared with less polluted sites, permanently increased NRAs were detected when NO2 concentrations were above 20 µg m−3. Controls of field measurements some 10 years after the introduction of catalytic converters in cars showed no significant change neither in NO2 levels nor in the decreasing NRA of spruce needles with the distance from the highway.

Nitrate Increases Membrane Stability of Potato Cells under Anoxia

Summary Potato cells (Solanum tuberosum L.), cultivated in original Murashige-Skoog (MS) medium for 5 days were subsequently transferred into {MS} media containing nitrate or ammonium as sole inorganic N source and incubated under anoxia for 24 h. With regard to lipid stability, these cells behaved differently. Although lipid hydrolysis occurred in both cases by the same mechanism, nitrate was able to postpone free fatty acid release for about 6 h compared with ammonium within the 24 h anoxia treatment. The increased membrane lipid stability of nitrate-treated cells under anoxia was correlated with a higher nitrate reduction capability and an improved energy status.