Nutrient distributions for Georges Bank and adjacent waters in 1979

In this report we describe the temporal and spatial distributions of inorganic nutrients over Georges Bank and in adjacent waters and discuss major features with respect to tbe nutrient environments of pbytoplankton. Nitrate and orthophosphorus were rapidly depleted from the surface layer of much of the study area in spring, but major differences were found between the shallow areas on Georges Bank and the surrounding stratified waters. In the "well-mixed" area of Georges Bank, the depletion encompassed the entire water column and ammonium became the dominant form of inorganic nitrogen throughout. Dissolved silicon was depleted slowly over central Georges Bank, reaching a minimum concentration in September while orthophosphorus gradually increased during the summer. The nutrient environment of phytoplankton over central Georges Bank may be described as vertically uniform but temporally changing in the relative availability of the various nutrients. In areas that undergo stratification (e.g., the central Gulf of Maine), a quasi-steady state was established as the surface water layer formed, consisting of declining nutrient gradients from below the euphotic layer to the top of the water column. These intergrading nutrient environments are relatively stable through time. Destratification reintroduced nutrients to depleted areas beginning in October; however, dissolved silicon was again depleted over shallow Georges Bank in late autumn though nitrate remained abundant. Slope water has been found to enter the bottom layer of the Gulf of Maine via the Northeast Channel. High nutrient concentrations observed in the bottom water of the Northeast Channel are consistent with this mechanism being the nutrient source for the Gulf of Maine. (PDF file contains 40 pages.)

Recent Developments in In Situ Nutrient Sensors: applications and future directions, Savannah, Georgia, December 11-13, 2006: workshop proceedings

The Alliance for Coastal Technologies (ACT) convened a Workshop on "Recent Developments in In Situ Nutrient Sensors: Applications and Future Directions" from 11-13 December, 2006. The workshop was held at the Georgia Coastal Center in Savannah, Georgia, with local coordination provided by the ACT partner at the Skidaway Institute of Oceanography (University System of Georgia). Since its formation in 2000, ACT partners have been conducting workshops on various sensor technologies and supporting infrastructure for sensor systems. This was the first workshop to revisit a topic area addressed previously by ACT. An earlier workshop on the "State of Technology in the Development and Application of Nutrient Sensors" was held in Savannah, Georgia from 10-12 March, 2003. Participants in the first workshop included representatives from management, industry, and research sectors. Among the topics addressed at the first workshop were characteristics of "ideal" in situ nutrient sensors, particularly with regard to applications in coastal marine waters. In contrast, the present workshop focused on the existing commercial solutions. The in situ nutrient sensor technologies that appear likely to remain the dominant commercial options for the next decade are reagent-based in situ auto-analyzers (or fluidics systems) and an optical approach (spectrophotometric measurement of nitrate). The number of available commercial systems has expanded since 2003, and community support for expanded application and further development of these technologies appears warranted. Application in coastal observing systems, including freshwater as well as estuarine and marine environments, was a focus of the present workshop. This included discussion of possible refinements for sustained deployments as part of integrated instrument packages and means to better promote broader use of nutrient sensors in observing system and management applications. The present workshop also made a number of specific recommendations concerning plans for a demonstration of in situ nutrient sensor technologies that ACT will be conducting in coordination with sensor manufacturers.[PDF contains 40 pages]

Nutrient-phytoplankton interrelationships in the Eastern Tropical Pacific Ocean

ENGLISH: Near surface nutrient distributions in the eastern tropical Pacific Ocean, using data from the EASTROPAC Expedition of 1967-68 and pre~EASTROPAC data, are described. Nutrient concentrations were maximal along the equator, in the Peru Current and its offshore extension, and in the Costa Rica Dome and westward tensions of this feature. Nutrient-poor water was found north of the equator well offshore. In this water nitrate was often undetectable (<0.1 µg-at/liter) at the surface, but phosphate and silicic acid concentrations were moderate. Enrichment experiments showed that nitrogen was the primary limiting nutrient in poor water even though large amounts of organic N were found. Half saturation constants (K s ) were determined for ammonium-supported phytoplankton growth. These data were used to calculate near-surface primary productivity values which compared favorably with 14C values. Assimilation ratio measurements indicated that algae were not extremely nitrogen-deficient. Laboratory-determined K, values for phosphate and silicic acid indicated that these nutrients were rarely limiting. In rich water, chlorophyll levels were less than expected from nutrient levels, and this anomaly may be related to limitation by nutrients other than nitrogen (N), phosphorus (P), or silicon (Si), or to grazing. SPANISH: Se describe la distribución subsuperficial de los nutrientes en el Océano Pacífico oriental tropical, empleando los datos de la Expedición EASTROPAC de 1967~68 y datos anteriores a éstos. La concentración de nutrientes fue máxima a lo largo del ecuador, en la Corriente del Perú, en su prolongación mar afuera, en el Domo de Costa Rica y en las prolongaciones occidentales de esta característica. Se encontraron aguas pobres en nutrientes al norte del ecuador y bastante mar adentro. En estas aguas el nitrato era casi imperceptible (<0.1 µg-at/litro) en la superficie, pero las concentraciones de fosfato y ácido silícico fueron moderadas. Los experimentos de enriquecimiento indicaron que el nitrógeno era el principal nutriente limitante en aguas pobres, aun cuando se encontraron grandes cantidades de nitrógeno orgánico. Se determinaron las constantes de saturación media (K s ) para el desarrollo del fitoplancton sostenido por el amonio. Estos datos se emplearon para calcular los valores de la productividad primaria cerca a la superficie que pueden compararse favorablemente con los valores del 14C. Las medidas de la proporción de asimilación indican que las algas no tenían una deficiencia extremada de nitrógeno. Los valores determinados en el laboratorio de K, para el fosfato y ácido silícico indicaron que estos nutrientes limitaron rara vez la producción. En aguas ricas, los niveles de clorofila fueron inferiores a lo esperado según los niveles nutritivos y esta anomalía puede relacionarse a la alimentación o a la escasez de otros nutrientes distintos al nitrógeno (N), fósforo (P) o silicio (Si).

Studies of ambient and chamber aerosol composition using the aerosol mass spectrometer

This thesis presents composition measurements for atmospherically relevant inorganic and organic aerosol from laboratory and ambient measurements using the Aerodyne aerosol mass spectrometer. Studies include the oxidation of dodecane in the Caltech environmental chambers, and several aircraft- and ground-based field studies, which include the quantification of wildfire emissions off the coast of California, and Los Angeles urban emissions.

The oxidation of dodecane by OH under low NO conditions and the formation of secondary organic aerosol (SOA) was explored using a gas-phase chemical model, gas-phase CIMS measurements, and high molecular weight ion traces from particle- phase HR-TOF-AMS mass spectra. The combination of these measurements support the hypothesis that particle-phase chemistry leading to peroxyhemiacetal formation is important. Positive matrix factorization (PMF) was applied to the AMS mass spectra which revealed three factors representing a combination of gas-particle partitioning, chemical conversion in the aerosol, and wall deposition.

Airborne measurements of biomass burning emissions from a chaparral fire on the central Californian coast were carried out in November 2009. Physical and chemical changes were reported for smoke ages 0 – 4 h old. CO₂ normalized ammonium, nitrate, and sulfate increased, whereas the normalized OA decreased sharply in the first 1.5 - 2 h, and then slowly increased for the remaining 2 h (net decrease in normalized OA). Comparison to wildfire samples from the Yucatan revealed that factors such as relative humidity, incident UV radiation, age of smoke, and concentration of emissions are important for wildfire evolution.

Ground-based aerosol composition is reported for Pasadena, CA during the summer of 2009. The OA component, which dominated the submicron aerosol mass, was deconvolved into hydrocarbon-like organic aerosol (HOA), semi-volatile oxidized organic aerosol (SVOOA), and low-volatility oxidized organic aerosol (LVOOA). The HOA/OA was only 0.08–0.23, indicating that most of Pasadena OA in the summer months is dominated by oxidized OA resulting from transported emissions that have undergone photochemistry and/or moisture-influenced processing, as apposed to only primary organic aerosol emissions. Airborne measurements and model predictions of aerosol composition are reported for the 2010 CalNex field campaign.

Vibrational predissociation spectroscopy of mass-selected ionic clusters

This thesis presents structural investigations of molecular ions and ionic clusters using vibrational predissociation spectroscopy. Experimentally, a pulsed beam of the mass-selected ion is crossed by a tunable infrared laser beam generated by a Nd:YAG pumped LiNbO_3 optical parametric oscillator. The resulting fragment ion is mass-analyzed and detected, with its intensity as a function of the laser wavelength being the "action" spectrum of the parent ion. In the case of SiH_7^+, we observed a vibrational band centered at 3866 cm^(-1) with clear P, Q, R branches, which is assigned as a perturbed H_2 stretch. The absence of a second H_2 band suggests that the ion forms a symmetric complex with a structure H_2•SiH_3^+•H_2 , in contrast to the species CH_7^+, which has the structure CH_5^+•H_2. The infrared spectra of NO_2^+(H_2O)_n clusters exhibit a marked change with cluster size, indicating that an intracluster reaction occurs with sufficient solvation. Specifically, in NO_2^+(H_2O)_n clusters where n≤3, H_2O binds to a nitronium ion core; but at n=4 the NO_2^+ reacts, transforming the cluster to a new structure of H_3O^+•(H_2O)_(n_2)•HNO_3. For protonated chlorine nitrate, we have observed two distinct isomers previously predicted by ab initio calculations: NO_2^+•(HOC1), the lowest energy isomer, and (ClO)(HO)NO^+, a covalently bonded isomer about 20 kcal/mol higher in energy. Both isomers decompose to NO_2^+ and HOCl upon photo-excitation. These results for HClONO_2^+ lend strong support to the involvement of an ionic mechanism in the reaction of ClONO_2 on polar stratospheric cloud surfaces, a critical step in the dramatic springtime depletion of ozone over Antarctica. Current research activities on halide-solvent clusters and metal-ligand complexes as well as technological improvements of the apparatus are also discussed.

Photodissociation and reaction dynamics of chlorine-containing species important in stratospheric ozone chemistry

Chlorine oxide species have received considerable attention in recent years due to their central role in the balance of stratospheric ozone. Many questions pertaining to the behavior of such species still remain unanswered and plague the ability of researchers to develop accurate chemical models of the stratosphere. Presented in this thesis are three experiments that study various properties of some specific chlorine oxide species.

In the first chapter, the reaction between ClONO_2 and protonated water clusters is investigated to elucidate a possible reaction mechanism for the heterogeneous reaction of chlorine nitrate on ice. The ionic products were various forms of protonated nitric acid, NO_2 +(H_20)_m, m = 0, 1, 2. These products are analogous to products previously reported in the literature for the neutral reaction occurring on ice surfaces. Our results support the hypothesis that the heterogeneous reaction is acid-catalyzed.

In the second chapter, the photochemistry of ClONO_2 was investigated at two wavelengths, 193 and 248 nm, using the technique of photofragmentation translational spectroscopy. At both wavelengths, the predominant dissociation pathways were Cl + NO_3 and ClO + NO_2. Channel assignments were confirmed by momentum matching the counterfragments from each channel. A one-dimensional stratospheric model using the new 248 nm branching ratio determined how our results would affect the predicted Cl_x and NO_x partitioning in the stratosphere.

Chapter three explores the photodissociation dynamics of Cl_2O at 193, 248 and 308 nm. At 193 nm, we found evidence for the concerted reaction channel, Cl_2 + O. The ClO + Cl channel was also accessed, however, the majority of the ClO fragments were formed with sufficient internal energies for spontaneous secondary dissociation to occur. At 248 and 308 nm, we only observed only the ClO + Cl channel. . Some of the ClO formed at 248 nm was formed internally hot and spontaneously dissociated. Bimodal translational energy distributions of the ClO and Cl products indicate two pathways leading to the same product exist.

Appendix A, B and C discuss the details of data analysis techniques used in Chapters 1 and 2. The development of a molecular beam source of ClO dimer is presented in Appendix D.

Sulfur-Cycling in Methane-Rich Ecosystems: Uncovering Microbial Processes and Novel Niches

Microbial sulfur cycling communities were investigated in two methane-rich ecosystems, terrestrial mud volcanoes (TMVs) and marine methane seeps, in order to investigate niches and processes that would likely be central to the functioning of these crucial ecosystems. Terrestrial mud volcanoes represent geochemically diverse habitats with varying sulfur sources and yet sulfur-cycling in these environments remains largely unexplored. Here we characterized the sulfur-metabolizing microorganisms and activity in 4 TMVs in Azerbaijan, supporting the presence of active sulfur-oxidizing and sulfate-reducing guilds in all 4 TMVs across a range of physiochemical conditions, with diversity of these guilds being unique to each TMV. We also found evidence for the anaerobic oxidation of methane coupled to sulfate reduction, a process which we explored further in the more tractable marine methane seeps. Diverse associations between methanotrophic archaea (ANME) and sulfate-reducing bacterial groups (SRB) often co-occur in marine methane seeps, however the ecophysiology of these different symbiotic associations has not been examined. Using a combination of molecular, geochemical and fluorescence in situ hybridization coupled to nano-scale secondary ion mass spectrometry (FISH-NanoSIMS) analyses of in situ seep sediments and methane-amended sediment incubations from diverse locations, we show that the unexplained diversity in SRB associated with ANME cells can be at least partially explained by preferential nitrate utilization by one particular partner, the seepDBB. This discovery reveals that nitrate is likely an important factor in community structuring and diversity in marine methane seep ecosystems. The thesis concludes with a study of the dynamics between ANME and their associated SRB partners. We inhibited sulfate reduction and followed the metabolic processes of the community as well as the effect of ANME/SRB aggregate composition and growth on a cellular level by tracking 15N substrate incorporation into biomass using FISH-NanoSIMS. We revealed that while sulfate-reducing bacteria gradually disappeared over time in incubations with an SRB inhibitor, the ANME archaea persisted in the form of ANME-only aggregates, which are capable of little to no growth when sulfate reduction is inhibited. These data suggest ANME are not able to synthesize new proteins when sulfate reduction is inhibited.

Mechanism study of femtosecond laser induced selective metallization (FLISM) on glass surfaces

We investigate the mechanism of selective metallization on glass surfaces with the assistance of femtosecond laser irradiation followed by electroless plating. Irradiation of femtosecond laser makes it possible to selectively deposit copper microstructures in the irradiated area on glass surfaces coated with silver nitrate films. The energy-dispersive X-ray (EDX) analyses reveal that silver atoms are produced on the surface of grooves formed by laser ablation, which serve as catalysis seeds for subsequent electroless copper plating. (C) 2008 Elsevier B.V. All rights reserved.

Studies of ambient organic and inorganic aerosol in Southern California

The negative impacts of ambient aerosol particles, or particulate matter (PM), on human health and climate are well recognized. However, owing to the complexity of aerosol particle formation and chemical evolution, emissions control strategies remain difficult to develop in a cost effective manner. In this work, three studies are presented to address several key issues currently stymieing California's efforts to continue improving its air quality.

Gas-phase organic mass (GPOM) and CO emission factors are used in conjunction with measured enhancements in oxygenated organic aerosol (OOA) relative to CO to quantify the significant lack of closure between expected and observed organic aerosol concentrations attributable to fossil-fuel emissions. Two possible conclusions emerge from the analysis to yield consistency with the ambient organic data: (1) vehicular emissions are not a dominant source of anthropogenic fossil SOA in the Los Angeles Basin, or (2) the ambient SOA mass yields used to determine the SOA formation potential of vehicular emissions are substantially higher than those derived from laboratory chamber studies. Additional laboratory chamber studies confirm that, owing to vapor-phase wall loss, the SOA mass yields currently used in virtually all 3D chemical transport models are biased low by as much as a factor of 4. Furthermore, predictions from the Statistical Oxidation Model suggest that this bias could be as high as a factor of 8 if the influence of the chamber walls could be removed entirely.

Once vapor-phase wall loss has been accounted for in a new suite of laboratory chamber experiments, the SOA parameterizations within atmospheric chemical transport models should also be updated. To address the numerical challenges of implementing the next generation of SOA models in atmospheric chemical transport models, a novel mathematical framework, termed the Moment Method, is designed and presented. Assessment of the Moment Method strengths and weaknesses provide valuable insight that can guide future development of SOA modules for atmospheric CTMs.

Finally, regional inorganic aerosol formation and evolution is investigated via detailed comparison of predictions from the Community Multiscale Air Quality (CMAQ version 4.7.1) model against a suite of airborne and ground-based meteorological measurements, gas- and aerosol-phase inorganic measurements, and black carbon (BC) measurements over Southern California during the CalNex field campaign in May/June 2010. Results suggests that continuing to target sulfur emissions with the hopes of reducing ambient PM concentrations may not the most effective strategy for Southern California. Instead, targeting dairy emissions is likely to be an effective strategy for substantially reducing ammonium nitrate concentrations in the eastern part of the Los Angeles Basin.

Propagation of a few-cycle laser pulse in a V-type three-level system

Propagation of a few-cycle laser pulse in a V-type three-level system (fine structure levels of rubidium) is investigated numerically. The full three-level Maxwell-Bloch equations without the rotating wave approximation and the standing slowly varying envelope approximation are solved by using a finite-difference time-domain method. It is shown that, when the usual unequal oscillator strengths are considered, self-induced transparency cannot be recovered and higher spectral components can be produced even for small-area pulses. (c) 2005 Pleiades Publishing, Inc.

Selective metallization on insulator surfaces with femtosecond laser pulses

We report selective metallization on surfaces of insulators ( glass slides and lithium niobate crystal) based on femtosecond laser modification combined with electroless plating. The process is mainly composed of four steps: (1) formation of silver nitrate thin films on the surfaces of glass or crystal substrates; (2) generation of silver particles in the irradiated area by femtosecond laser direct writing; (3) removal of unirradiated silver nitrate films; and (4) selective electroless plating in the modified area. We discuss the mechanism of selective metallization on the insulators. Moreover, we investigate the electrical and adhesive properties of the copper microstructures patterned on the insulator surfaces, showing great potential of integrating electrical functions into lab-on-a-chip devices. (C) 2007 Optical Society of America.

Avaliação da função endotelial microvascular, da rigidez arterial e da resposta inflamatória sistêmica em pacientes submetidos a cirurgia cardíaca com circulação extracorpórea

A Cirurgia de Revascularização do Miocárdio, realizada com o auxílio da Circulação Extracorpórea, está associada a alterações importantes na microcirculação e na produção e circulação de citocinas e marcadores inflamatórios. No presente estudo, foram avaliados 23 pacientes com indicação de Revascularização do Miocárdio, no dia do procedimento e 7 e 28 dias após a cirurgia. A microcirculação cutânea, enquanto reflexo da microcirculação coronariana, foi estudada através da hiperemia térmica e/ ou reativa pós oclusiva e da iontoforese de substâncias vasoativas por mecanismos dependentes e independentes do endotélio. A rigidez arterial foi aferida através da análise da onda de pulso digital. Foi avaliado ainda o impacto da doença e do procedimento cirúrgico sobre a produção e circulação sérica de citocinas e marcadores inflamatórios, tais como: PCR-HS, nitrito/ nitrato, IL-6, Il-7, IL-8, IL-10, IFN-γ, TNF-α e G-CSF. Foi observada uma tendência à redução da vasodilatação da microcirculação cutânea após a administração de doses acumulativas de acetilcolina (endotélio dependente) através da iontoforese de 7 e 28 dias após o procedimento cirúrgico. A hiperemia térmica foi mais pronunciada na avaliação basal do que aos 7 e 28 dias. A hiperemia reativa pós oclusiva não demonstrou alterações 7 dias após o procedimento. Aos 28 dias, houve um aumento da condutância microvascular cutânea. Quando avaliada a vasodilatação endotélio-independente (nitroprussiato de sódio), observamos aumento do fluxo microvascular cutâneo diretamente proporcional à carga/ dose aplicada, sem diferenças nos valores obtidos no basal e 7 e 28 dias após o procedimento. A rigidez arterial não apresentou alterações. A análise dos fatores inflamatórios e das citocinas demonstrou aumento marcante da IL-6 e da IL-8 após 7 dias do procedimento cirúrgico, com retorno parcial aos níveis basais da IL-6 e total da IL-8 após 28 dias. O IFN-γ, TNF-α e G-CSF apenas apresentaram níveis detectáveis na avaliação basal e IL-7 e IL-10 não demonstraram alterações significativas nos tempos avaliados. A PCR-HS demonstrou níveis mais elevados após 7 dias e retorno parcial aos níveis basais após 28 dias. O nitrito/ nitrato, após 7 dias, apresentou leve queda em sua concentração plasmática. Concluímos que a pequena diferença entre o valores obtidos entre o basal e após 7 dias do procedimento cirúrgico com a iontoforese de acetilcolina resulta em minimização do impacto endotelial e um valor constante deste dado após 28 dias, sugere recomposição fisiológica completa. Este resultado foi semelhante com a análise da hiperemia térmica e reativa pós oclusiva. As interleucinas IL-6 e IL-8, bem como a PCR-HS apresentaram comportamento correlacionável, refletindo a cinética inflamatória. A rigidez arterial não demonstrou alterações.

Estimación de concentraciones de radicales nitrato (NO . 3) e hidroxilo ( . OH) en la atmósfera a partir de medidas de HCNM de alta resolución temporal

[ES]Los radicales nitrato e hidroxilo son especies químicas implicadas en la contaminación atmosférica. En el presente trabajo se ha tratado de estimar sus concentraciones empleando para ello medidas de las concentraciones de varios compuestos orgánicos volátiles registradas en el Parque Natural de Valderejo (Araba). La metodología de cálculo ya había sido empleada anteriormente para el ·OH y es la primera vez que se ha aplicado a concentraciones de NO·3 en una zona rural. Las concentraciones de radical hidroxilo calculadas (6,02·106 - 8,06·106 molec. cm-3) concuerdan con las obtenidas en medidas y estudios anteriores. En el caso del radical nitrato, las concentraciones estimadas (2,13·1011 – 2,02·1012 molec. cm-3) son bastante superiores a las encontradas en la bibliografía, por lo que se ha concluido que esta técnica de medida no es válida para el cálculo de NO·3 en una atmósfera de fondo rural como Valderejo. Esta desviación se debe probablemente a otros procesos no contemplados en la hipótesis de cálculo, por lo que se propone continuar con el estudio en este área.

Measurement of the neutron (^3He) spin structure function at low Q^2 : a connection between the Bjorken and Drell-Hearn-Gerasimov sum rules

The spin dependent cross sections, σT_1/2 and σT_3/2 , and asymmetries, A_∥ and A_⊥ for ³He have been measured at the Jefferson Lab's Hall A facility. The inclusive scattering process ³He(e,e)X was performed for initial beam energies ranging from 0.86 to 5.1 GeV, at a scattering angle of 15.5°. Data includes measurements from the quasielastic peak, resonance region, and the deep inelastic regime. An approximation for the extended Gerasimov-Drell-Hearn integral is presented at a 4-momentum transfer Q² of 0.2-1.0 GeV².

Also presented are results on the performance of the polarized ³He target. Polarization of ³He was achieved by the process of spin-exchange collisions with optically pumped rubidium vapor. The ³He polarization was monitored using the NMR technique of adiabatic fast passage (AFP). The average target polarization was approximately 35% and was determined to have a systematic uncertainty of roughly ±4% relative.

The contrasting invertebrate fauna of freshwater habitats in the Swavesey fens of East Anglia

During July and August 1988, 21 ponds and 33 ditch sites were sampled at Swavesey fens in East Anglia. Water from each site was collected and analysed at monthly intervals in the year preceding faunal sampling. Temperature and oxygen were measured on site. The "quality" of the faunal community was assessed by three approaches: a modification of the BMWP scoring system (Biological Monitoring Working Party); faunal richness was calculated as the number of faunal "groups" at each site; and by using Simpson's index of diversity. Statistical analysis was carried out to explore the relationships between sites, environmental variables and faunal diversity. The survey clearly showed the detrimental effects of elevated nitrate and phosphate from agricultural sources and the localised impacts of treated sewage effluent on invertebrates in ditches.