In-situ electrical, mechanical and electrochemical characterizations of one-dimensional nanostructures

One-dimensional nanostructures initiated new aspects to the materials applications due to their superior properties compared to the bulk materials. Properties of nanostructures have been characterized by many techniques and used for various device applications. However, simultaneous correlation between the physical and structural properties of these nanomaterials has not been widely investigated. Therefore, it is necessary to perform in-situ study on the physical and structural properties of nanomaterials to understand their relation. In this work, we will use a unique instrument to perform real time atomic force microscopy (AFM) and scanning tunneling microscopy (STM) of nanomaterials inside a transmission electron microscopy (TEM) system. This AFM/STM-TEM system is used to investigate the mechanical, electrical, and electrochemical properties of boron nitride nanotubes (BNNTs) and Silicon nanorods (SiNRs). BNNTs are one of the subjects of this PhD research due to their comparable, and in some cases superior, properties compared to carbon nanotubes. Therefore, to further develop their applications, it is required to investigate these characteristics in atomic level. In this research, the mechanical properties of multi-walled BNNTs were first studied. Several tests were designed to study and characterize their real-time deformation behavior to the applied force. Observations revealed that BNNTs possess highly flexible structures under applied force. Detailed studies were then conducted to understand the bending mechanism of the BNNTs. Formations of reversible ripples were observed and described in terms of thermodynamic energy of the system. Fracture failure of BNNTs were initiated at the outermost walls and characterized to be brittle. Second, the electrical properties of individual BNNTs were studied. Results showed that the bandgap and electronic properties of BNNTs can be engineered by means of applied strain. It was found that the conductivity, electron concentration and carrier mobility of BNNTs can be tuned as a function of applied stress. Although, BNNTs are considered to be candidate for field emission applications, observations revealed that their properties degrade upon cycles of emissions. Results showed that due to the high emission current density, the temperature of the sample was increased and reached to the decomposition temperature at which the B-N bonds start to break. In addition to BNNTs, we have also performed in-situ study on the electrochemical properties of silicon nanorods (SiNRs). Specifically, lithiation and delithiation of SiNRs were studied by our STM-TEM system. Our observations showed the direct formation of Li22Si5 phases as a result of lithium intercalation. Radial expansion of the anode materials were observed and characterized in terms of size-scale. Later, the formation and growth of the lithium fibers on the surface of the anode materials were observed and studied. Results revealed the formation of lithium islands inside the ionic liquid electrolyte which then grew as Li dendrite toward the cathode material.

THE USE OF LIFE-CYCLE ANALYSIS TO REDUCE THE ENVIRONMENTAL IMPACT OF MATERIALS IN MANUFACTURING

This thesis is composed of three life-cycle analysis (LCA) studies of manufacturing to determine cumulative energy demand (CED) and greenhouse gas emissions (GHG). The methods proposed could reduce the environmental impact by reducing the CED in three manufacturing processes. First, industrial symbiosis is proposed and a LCA is performed on both conventional 1 GW-scaled hydrogenated amorphous silicon (a-Si:H)-based single junction and a-Si:H/microcrystalline-Si:H tandem cell solar PV manufacturing plants and such plants coupled to silane recycling plants. Using a recycling process that results in a silane loss of only 17 versus 85 percent, this results in a CED savings of 81,700 GJ and 290,000 GJ per year for single and tandem junction plants, respectively. This recycling process reduces the cost of raw silane by 68 percent, or approximately $22.6 and $79 million per year for a single and tandem 1 GW PV production facility, respectively. The results show environmental benefits of silane recycling centered around a-Si:H-based PV manufacturing plants. Second, an open-source self-replicating rapid prototype or 3-D printer, the RepRap, has the potential to reduce the environmental impact of manufacturing of polymer-based products, using distributed manufacturing paradigm, which is further minimized by the use of PV and improvements in PV manufacturing. Using 3-D printers for manufacturing provides the ability to ultra-customize products and to change fill composition, which increases material efficiency. An LCA was performed on three polymer-based products to determine the CED and GHG from conventional large-scale production and are compared to experimental measurements on a RepRap producing identical products with ABS and PLA. The results of this LCA study indicate that the CED of manufacturing polymer products can possibly be reduced using distributed manufacturing with existing 3-D printers under 89% fill and reduced even further with a solar photovoltaic system. The results indicate that the ability of RepRaps to vary fill has the potential to diminish environmental impact on many products. Third, one additional way to improve the environmental performance of this distributed manufacturing system is to create the polymer filament feedstock for 3-D printers using post-consumer plastic bottles. An LCA was performed on the recycling of high density polyethylene (HDPE) using the RecycleBot. The results of the LCA showed that distributed recycling has a lower CED than the best-case scenario used for centralized recycling. If this process is applied to the HDPE currently recycled in the U.S., more than 100 million MJ of energy could be conserved per annum along with significant reductions in GHG. This presents a novel path to a future of distributed manufacturing suited for both the developed and developing world with reduced environmental impact. From improving manufacturing in the photovoltaic industry with the use of recycling to recycling and manufacturing plastic products within our own homes, each step reduces the impact on the environment. The three coupled projects presented here show a clear potential to reduce the environmental impact of manufacturing and other processes by implementing complimenting systems, which have environmental benefits of their own in order to achieve a compounding effect of reduced CED and GHG.

Experiment: Organic matter exudation by Emiliania huxleyi under simulated future ocean conditions

Emiliania huxleyi (strain B 92/11) was exposed to different nutrient supply, CO2 and temperature conditions in phosphorus controlled chemostats to investigate effects on organic carbon exudation and partitioning between the pools of particulate organic carbon (POC) and dissolved organic carbon (DOC). 14C incubation measurements for primary production (PP) and extracellular release (ER) were performed. Chemical analysis included the amount and composition of high molecular weight (>1 kDa) dissolved combined carbohydrates (HMW-dCCHO), particulate combined carbohydrates (pCCHO) and the carbon content of transparent exopolymer particles (TEP-C). Applied CO2 and temperature conditions were 300, 550 and 900 µatm pCO2 at 14 °C, and additionally 900 µatm pCO2 at 18 °C simulating a greenhouse ocean scenario. Enhanced nutrient stress by reducing the dilution rate (D) from D = 0.3 /d to D = 0.1 /d (D = µ) induced the strongest response in E. huxleyi. At µ = 0.3 /d, PP was significantly higher at elevated CO2 and temperature and DO14C production correlated to PO14C production in all treatments, resulting in similar percentages of extracellular release (PER; (DO14C production/PP) × 100) averaging 3.74 ± 0.94%. At µ = 0.1 /d, PO14C production decreased significantly, while exudation of DO14C increased. Thus, indicating a stronger partitioning from the particulate to the dissolved pool. Maximum PER of 16.3 ± 2.3% were observed at µ = 0.1 /d at elevated CO2 and temperature. While cell densities remained constant within each treatment and throughout the experiment, concentrations of HMW-dCCHO, pCCHO and TEP were generally higher under enhanced nutrient stress. At µ= 0.3 /d, pCCHO concentration increased significantly with elevated CO2 and temperature. At µ = 0.1 /d, the contribution (mol % C) of HMW-dCCHO to DOC was lower at elevated CO2 and temperature while pCCHO and TEP concentrations were higher. This was most pronounced under greenhouse conditions. Our findings suggest a stronger transformation of primary produced DOC into POC by coagulation of exudates under nutrient limitation. Our results further imply that elevated CO2 and temperature will increase exudation by E. huxleyi and may affect organic carbon partitioning in the ocean due to an enhanced transfer of HMW-dCCHO to TEP by aggregation processes.

Spatio-temporal distribution of pyrethroids in soil in Mediterranean paddy fields

Purpose The demand of rice by the increase in population in many countries has intensified the application of pesticides and the use of poor quality water to irrigate fields. The terrestrial environment is one compartment affected by these situations, where soil is working as a reservoir, retaining organic pollutants. Therefore, it is necessary to develop methods to determine insecticides in soil and monitor susceptible areas to be contaminated, applying adequate techniques to remediate them. Materials and methods This study investigates the occurrence of ten pyrethroid insecticides (PYs) and its spatio-temporal variance in soil at two different depths collected in two periods (before plow and during rice production), in a paddy field area located in the Mediterranean coast. Pyrethroids were quantified using gas chromatography?mass spectrometry (GC?MS) after ultrasound-assisted extraction with ethyl acetate. The results obtained were assessed statistically using non-parametric methods, and significant statistical differences (p < 0.05) in pyrethroids content with soil depth and proximity to wastewater treatment plants were evaluated. Moreover, a geographic information system (GIS) was used to monitor the occurrence of PYs in paddy fields and detect risk areas. Results and discussion Pyrethroids were detected at concentrations ?57.0 ng g?1 before plow and ?62.3 ng g?1 during rice production, being resmethrin and cyfluthrin the compounds found at higher concentrations in soil. Pyrethroids were detected mainly at the top soil, and a GIS program was used to depict the obtained results, showing that effluents from wastewater treatment plants (WWTPs) were the main sources of soil contamination. No toxic effects were expected to soil organisms, but it is of concern that PYs may affect aquatic organisms, which represents the worst case scenario. Conclusions A methodology to determine pyrethroids in soil was developed to monitor a paddy field area. The use of water fromWWTPs to irrigate rice fields is one of the main pollution sources of pyrethroids. It is a matter of concern that PYs may present toxic effects on aquatic organisms, as they can be desorbed from soil. Phytoremediation may play an important role in this area, reducing the possible risk associated to PYs levels in soil.

Characterization of a Leishmania tropica antigen that detects immune responses in Desert Storm viscerotropic leishmaniasis patients.

A chronic debilitating parasitic infection, viscerotropic leishmaniasis (VTL), has been described in Operation Desert Storm veterans. Diagnosis of this disease, caused by Leishmania tropica, has been difficult due to low or absent specific immune responses in traditional assays. We report the cloning and characterization of two genomic fragments encoding portions of a single 210-kDa L. tropica protein useful for the diagnosis of VTL in U.S. military personnel. The recombinant proteins encoded by these fragments, recombinant (r) Lt-1 and rLt-2, contain a 33-amino acid repeat that reacts with sera from Desert Storm VTL patients and with sera from L. tropica-infected patients with cutaneous leishmaniasis. Antibody reactivities to rLt-1 indicated a bias toward IgG2 in VTL patient sera. Peripheral blood mononuclear cells from VTL patients produced interferon gamma, but not interleukin 4 or 10, in response to rLt-1. No cytokine production was observed in response to parasite lysate. The results indicate that specific leishmanial antigens may be used to detect immune responses in VTL patients with chronic infections.

Produção de hidrogênio por fermentação por um novo isolado de Clostridium beijerinckii

O hidrogênio (H2) tem sido considerado uma fonte de energia limpa bastante promissora, pois sua combustão origina apenas moléculas de água, sendo uma alternativa ao uso de combustíveis fósseis. Entretanto, os métodos atuais de produção de H2 demandam matérias-primas finitas e uma grande quantidade de energia, tornando a sua obtenção não sustentável. Mais recentemente, a via fermentativa tem sido considerada para a produção de H2, utilizando como matérias-primas efluentes industriais, materiais lignocelulósicos e biomassa de algas, denominado de bio-hidrogênio de primeira, segunda e terceira geração, respectivamente. Neste trabalho foi isolada uma bactéria anaeróbia a partir de uma cultura mista (lodo) de um sistema de tratamento de vinhaça, após pré-tratamento do lodo a pH 3 por 12 horas. Este microrganismo foi identificado com 99% de similaridade como Clostridium beijerinckii com base na sequência do gene RNAr 16S denominado de C. beijerinckii Br21. A temperatura e o pH mais adequados para o crescimento e produção de H2 por esta cultura foi 35 °C e pH inicial 7,0. A bactéria possui a capacidade de utilizar ampla variedade de fontes de carbono para a produção de H2 por fermentação, especialmente, monossacarídeos resultantes da hidrólise de biomassa de algas, tais como glicose, galactose e manose. Foram realizados ensaios em batelada para a produção de H2 com a bactéria isolada empregando diferentes concentrações de glicose e galactose, visando a sua futura utilização em hidrolisados de alga. Os parâmetros cinéticos dos ensaios de fermentação estimados pelo modelo de Gompertz modificado, como a velocidade máxima de produção (Rm), a quantidade máxima de hidrogênio produzido (Hmáx) e o tempo necessário para o início da produção de hidrogênio (fase lag) para a glicose (15 g/L) foram de: 58,27 mL de H2/h, 57,68 mmol de H2 e 8,29 h, respectivamente. Para a galactose (15 g/L), a Rm, Hmáx e foram de 67,64 mL de H2/h, 47,61 mmol de H2 e 17,22 horas, respectivamente. O principal metabólito detectado ao final dos ensaios de fermentação, foi o ácido butírico, seguido pelo ácido acético e o etanol, tanto para os ensaios com glicose, como com galactose. C. beijerinckii é um candidato bastante promissor para a produção de H2 por fermentação a partir de glicose e galactose e, consequentemente, a partir de biomassa de algas como substratos.

Concepção de um receptor de cavidade para concentração de energia solar para aplicação em reatores químicos.

Este trabalho dimensionou um receptor de cavidade para uso como reator químico de um ciclo de conversão de energia solar para energia química. O vetor energético proposto é o hidrogênio. Isso implica que a energia solar é concentrada em um dispositivo que absorve a radiação térmica e a transforma em energia térmica para ativar uma reação química endotérmica. Essa reação transforma o calor útil em gás hidrogênio, que por sua vez pode ser utilizado posteriormente para geração de outras formas de energia. O primeiro passo foi levantar os pares metal/óxido estudados na literatura, cuja finalidade é ativar um ciclo termoquímico que possibilite produção de hidrogênio. Esses pares foram comparados com base em quatro parâmetros, cuja importância determina o dimensionamento de um receptor de cavidade. São eles: temperatura da reação; estado físico de reagentes e produtos; desgaste do material em ciclos; taxa de reação de hidrólise e outros aspectos. O par escolhido com a melhor avaliação no conjunto dos parâmetros foi o tungstênio e o trióxido de tungstênio (W/WO3). Com base na literatura, foi determinado um reator padrão, cujas características foram analisadas e suas consequências no funcionamento do receptor de cavidade. Com essa análise, determinaram-se os principais parâmetros de projeto, ou seja, a abertura da cavidade, a transmissividade da janela, e as dimensões da cavidade. Com base nos resultados anteriores, estabeleceu-se um modelo de dimensionamento do sistema de conversão de energia solar em energia útil para um processo químico. Ao se analisar um perfil de concentração de energia solar, calculou-se as eficiências de absorção e de perdas do receptor, em função da área de abertura de um campo de coleta de energia solar e da radiação solar disponível. Esse método pode ser empregado em conjunto com metodologias consagradas e dados de previsão de disponibilidade solar para estudos de concentradores de sistemas de produção de hidrogênio a partir de ciclos termoquímicos.

Materiales carbonosos nanoestructurados para la preparación de catalizadores híbridos mediante el sistema SILP

The main objective of this Doctoral thesis is the preparation of hybrid active catalysts using the SILP (Supported Ionic Liquid Catalysis) methodology and employing carbon materials as support. For that, in first place, SILP samples have been prepared and characterized. In second place, hybrid the SILP catalysts have been prepared, characterized and tested in some hydrogenation reactions, including an asymmetric hydrogenation. The investigated variables are mainly the amount and kind of ionic liquid and the physical, chemical and morphological properties of the support.

The distribution of macrobenthos in surface sediments at Fladen Ground stations, North Sea

A general study of structure, biomass estimates and dynamics on the macrofauna was carried out in August 1975 and March 1976 during PREFLEX (1975) and FLEX (1976), the Fladen Ground Experiment. On the basis of these data an attempt was made to estimate macrobenthic production expressed as minimum production (MP). The macrobenthic production is discussed together with meiobenthic annual production and with indirectly estimated microbenthic production in relation to an energy input from the water column of about 25 g C m**-2 year**-1. From the production estimates of the three benthic components a rough energy budget is proposed. Sampling was performed at five stations for endofauna twice during the time of investigation and for epifauna once. At each station two replicate box core samples (30 X 20 cm) were taken for endofauna. Epifauna was sampled with an Agassiz trawl once at each station. The total numbers of endofauna increased from station 1 to 5. This was valid as well for August 1975 (4,233-12,166 individuals per m**2 and 10 cm sediment depth) as for March 1976 (1,008-2,925 individuals). The polychaetes were the dominant organisms with a share of 33 to 62 %. The densities for the endofauna decreased from August 1975 to March 1976 by a mean factor of 2.8. Abundances of epifauna amounted to values between 11 and 102 individuals per 1000 m**2. The biomass dry weights (DWT) for macrobenthic endofauna varied between 0.97 g DWT m**-2 and 6.42 g DWT m**-2 in August 1975 and between 0.27 g DWT m**-2 and 2.64 g DWT m**-2 in March 1976. The mean amounted to 1.74 g DWT m**-2. Dry weights of epifauna biomass gave values between 4.9 and 83.1 g DWT * 1000 m**-2. The minimum production for the total macro-endofauna at Fladen Ground amounted to 1.43 g DWT m**-2 yr**-1 or 0.82 g C m**-2 yr**-1. This resulted in a minimum turnover rate (P/B) of 0.8. The share produced by the polychaetes amounted to 1.06g DWT m**-2 yr**-1 or 74 %.

Composition of sedimentary rocks from the Shapkina River valley, Bolshezemelskaya Tundra

A facies-genetic and stratigraphic subdivision of the Quaternary sequence in the Shapkina River valley has been accomplished. The riverbank shows outcrops of three glacial complexes with different mineralogical-petrographic compositions and structural characteristics, which can be correlated and stratificated. Datings of intermoraine horizons (alluvial, marine, lacustrine, and lacustrine-boggy sediments) have been based on palynological and paleomicrotheriological data. The Middle Neopleistocene section can be divided into two till horizons corresponding to two autonomous glaciations (Pechora and Vychegda). They are separated by a member of subaqueous Rodionov sediments. The Pechora till formed in the course of glacier motions from the northeast. Glacial horizons are mainly composed of the Vychegda till transported from the Northwest terrigenous provenance. Lithology of the Upper Neopleistocene Polyarnyi till testifies to its formation in the upper course of the river from material transported from the Northeast terrigenous-mineralogical provenance in the upper course of the river and from the Fennoscandian glaciation center in the lower course of the river. The paper presents the first lithological investigation and substantiation of genesis of various facies of Neopleistocene intermoraine marine sediments (sediments of the beach and fore-beach zones and shallow-water shelf).

The progress of the nation, in its various social and economical relations : from the beginning of the nineteenth century to the present time /

Includes tables.

Recherches astronomiques de l'Observatoire d'Utrecht.

Ceased with volume 18:2. Superseded by the Bullletin of the Astronomical Institutes of the Netherlands, Supplement series.

Quantum dynamics with stochastic gauge simulations

The general idea of a stochastic gauge representation is introduced and compared with more traditional phase-space expansions, like the Wigner expansion. Stochastic gauges can be used to obtain an infinite class of positive-definite stochastic time-evolution equations, equivalent to master equations, for many systems including quantum time evolution. The method is illustrated with a variety of simple examples ranging from astrophysical molecular hydrogen production, through to the topical problem of Bose-Einstein condensation in an optical trap and the resulting quantum dynamics.

New insights into the interactions of serum proteins with bis(maltolato)oxovanadium(IV): Transport and biotransformation of insulin-enhancing vanadium pharmaceuticals

Significant new insights into the interactions of the potent insulin-enhancing compound bis(maltolato)oxovanadium(IV) (BMOV) with the serum proteins, apo-transferrin and albumin, are presented. Identical reaction products are observed by electron paramagnetic resonance (EPR) with either BMOV or vanadyl sulfate (VOSO4) in solutions of human serum apo-transferrin. Further detailed study rules out the presence of a ternary ligand-vanadyl-transferrin complex proposed previously. By contrast, differences in reaction products are observed for the interactions of BMOV and VOSO4 with human serum albumin (HSA), wherein adduct formation between albumin and BMOV is detected. In BMOV-albumin solutions, vanadyl ions are bound in a unique manner not observed in comparable solutions Of VOSO4 and albumin. Presentation of chelated vanadyl ions precludes binding at the numerous nonspecific sites and produces a unique EPR spectrum which is assigned to a BMOV-HSA adduct. The adduct species cannot be produced, however, from a solution Of VOSO4 and HSA titrated with maltol. Addition of maltol to a VOSO4-HSA solution instead results in formation of a different end product which has been assigned as a ternary complex, VO(ma)(HSA). Furthermore, analysis of solution equilibria using a model system of BMOV with 1-methylimidazole (formation constant log K = 4.5(1), by difference electronic absorption spectroscopy) lends support to an adduct binding mode (VO(ma)(2)-HSA) proposed herein for BMOV and HSA. This detailed report of an in vitro reactivity difference between VOSO4 and BMOV may have bearing on the form of active vanadium metabolites delivered to target tissues. Albumin binding of vanadium chelates is seen to have a potentially dramatic effect on pharmacokinetics, transport, and efficacy of these antidiabetic chelates.