Dissertations / Theses on the topic 'Scavenging'

Scavenging is the consumption of carrion by living organisms. Often overlooked, it is common in all ecosystems. The assemblage of scavengers that act on carrion are important in maintaining this ecosystem service and are part of the necrobiome. Scavengers can be classified into distinct guilds comprised of vertebrates, invertebrates, and microorganisms whose collaborative roles operate efficiently when their community structure is diverse and intact. The goal of this thesis is to quantify how scavenger guilds can influence decay rates and how insect scavengers respond to the absence of competition from vertebrate scavengers. Individually, the functional roles vertebrate and insect scavengers are known, but there is limited understanding about how their interactions influence decay rates. Changes in the composition of vertebrate and insect scavenger communities around carrion may prolong carcass persistence possibly altering the localised effects of nutrient flow and increase the chance of carcass borne disease spread. This is important in Kosciuszko National Park where land managers cull both large herbivores and facultative vertebrate scavengers possibly creating and influx of carrion and altering the functionality of the vertebrate scavenger guild. Using exclusion cages, this study was able to limit access from vertebrate and insect scavengers to compare decay rates of carrion in the presence and absence of each guild. In contrast to similar systems, utilisation of carcasses by vertebrates did little to influence decay rates. This was pronounced in autumn and winter when carcasses persisted the longest despite elevated vertebrate activity and reduced competition from insects and microbes. This shifts the function of carrion removal towards insects as vertebrates contribute little to decomposition leading to a reduction of resiliency of this process. How each guild interacted and operated in the other’s absence had profound effects on carcass persistence.

Mestrado em Ciência e Engenharia de Materiais
Gadolinium-doped ceria based powders were co-fired with additions of silica, and silica and lanthanum oxide, to test the silicascavenging role of lanthanum. The formation of one ionic conducting secondary phase, instead of an insulating phase, was attempted. The structural, microstructural and electrical characterization of these samples confirmed the formation of one apatite-type lanthanum silicate-based phase and a significant enhancement of the grain boundary conductivity of these materials. ABSTRACT: Pós de céria dopada com gadolínio foram sinterizados com adições de sílica, e de sílica e óxido de lantânio, para testar o efeito de remoção de sílica do óxido de lantânio. Com esta abordagem explorou-se a formação de uma fase secundária condutora iónica em vez de uma fase isoladora. A caracterização estrutural, microestrutural e eléctrica das amostras confirmou a formação de uma fase tipo apatite derivada do silicato de lantânio e uma melhoria significativa da condutividade da fronteira de grão destes materiais.

The aerosol removal has a fundamental role because aerosol has impact on human health, on visibility and act as a condensation center for cloud droplets and ice crystals, changing cloud properties (indirect e�ects on cli- mate). In this work, di�erent removal processes of aerosol have been studies experimentally (thermophoresis, ice nuclei, cloud condensation nuclei and below-cloud scavenging), with the aim to obtain a global study of these processes. Concerning the study of thermophoresis, experiments were per- formed in microgravity conditions, in order to minimize the impact of grav- ity. Particle trajectories and consequently particle velocities were recon- structed by analyzing the sequence of particle positions. Studies on forma- tion of IN and CCN, realized through two experimental campaigns, permit- ted to improve knowledge about these phenomena. Measurements related to CCN reveal diurnal trend with lower values at about midday and higher ones during the night. Measurements of IN reveal a positive correlation between higher supersaturation with respect to ice and water values and ice nuclei number concentration. Finally, indoor and outdoor measurements of aerosol concentrations were carried out; it was found that the aerosol removal is in uenced by rainfall duration.

In recent years, there has been recent increase in the deployment of wireless sensor networks. These sensors are typically powered by a battery which has limited life span. This problem can be overcomed by using energy scavenging or power harvesting which is the process of converting ambient energy from the environment into usable electrical energy. It can be used in applications such as remote patient monitoring, implantable sensors, machinery/equipment monitoring and so on. The thesis presents the RF scavenging system and mainly focuses on the study of the rectifier architectures which is one of the key components in the RF scavenging system. The thesis also provides the design challenges while implementing the different rectifier structures, which are PMOS bridge rectifier, CMOS differential rectifier and charge pump. The functionality of the rectifier structures are studied by simulation using RF signal of 900 MHz and implemented in 0.35μm and 65 nm technologies to compare the results. The simulation results shows that there is a tradeoff between high output DC voltage and high power efficiency. Maximum DC output voltage of 1 V is obtained from input amplitude level of 0.16 V using 7-stage charge pump rectifier. In the other hand maximum power efficiency of 23 % is obtained using CMOS differential rectifier.

This item is only available in print in the UCF Libraries. If this is your Honors Thesis, you can help us make it available online for use by researchers around the world by following the instructions on the distribution consent form at http://library.ucf.edu/Systems/DigitalInitiatives/DigitalCollections/InternetDistributionConsentAgreementForm.pdf You may also contact the project coordinator, Kerri Bottorff, at kerri.bottorff@ucf.edu for more information.
Bachelors
Burnett College of Biomedical Sciences
Molecular Biology and Microbiology

Dissertação para a obtenção de grau de doutor em Bioquímica pelo Instituto de Tecnologia Química e Biológica. Universidade Nova de Lisboa.
The purpose of this thesis is to contribute to a better understanding of systems involved in the scavenging of reactive oxygen species. The work focuses on an enzyme from the Rubrerythrin family that reduces hydrogen peroxide and one from the Superoxide Reductase family that reduces the superoxide anion. Both of these families are distributed widely across the three domains of life, Archaea, Bacteria and Eukarya, but are mainly found in anaerobic and microaerophilic prokaryotes.(...)

Pyroelectric energy scavenging is the process of converting wasted energy from a system to power another one, based on the pyroelectric effect of piezoelectric materials. Pyroelectrically generated power is a function of the surface of material, the pyroelectric coefficient, and the temporal temperature gradient. In the current project, a simple model is developed to predict the power generation based on the temporal change in temperature of material. In addition, a model is validated with experimental measurements from several piezoelectric materials. It is shown that energy generation can be enhanced by using piezoelectric materials with significantly higher pyroelectric coefficients such as pre-stressed piezoelectric materials or thin films. Meanwhile, a method of continuously harvesting energy from pyroelectric materials is demonstrated using an innovative cyclic heating scheme. Besides, simple analytic expressions are developed for ideal voltage, power and power densities as a function of pyroelectric constant, permittivity, surface area, thickness, temperature variation.

Thermoelectric (TE) module integration into a notebook computer is experimentally investigated in this thesis for its energy harvesting opportunities. A detailed Finite Element (FE) model was constructed first for thermal simulations. The model outputs were then correlated with the thermal validation results of the selected system. In parallel, a commercial TE micro-module was experimentally characterized to quantify maximum power generation opportunity from the combined system and component data set. Next, suitable &ldquo
warm spots&rdquo
were identified within the mobile computer to extract TE power with minimum or no notable impact to system performance, as measured by thermal changes in the system, in order to avoid unacceptable performance degradation. The prediction was validated by integrating a TE micro-module to the mobile system under test. Measured TE power generation power density in the carefully selected vicinity of the heat pipe was around 1.26 mW/cm3 with high CPU load. The generated power scales down with lower CPU activity and scales up in proportion to the utilized opportunistic space within the system. The technical feasibility of TE energy harvesting in mobile computers was hence experimentally shown for the first time in this thesis.

The research reported in this thesis investigated the ability of P. melanarius to control slug populations, and the impacts that alternative prey, particularly carrion, has on the efficacy of this predator as an agent of slug pest control. A suite of laboratory- and field-based experiments were conducted to achieve those ends. The main findings were: (1) Prey vital status was significant in determining the feeding preference hierarchy of P. melanarius. The mucus defence of live slugs (Deroceras reticulatum) deterred attacks by beetles, but feeding on dead D. reticulatum emphasized a preference for this prey type by P. melanarius. (2) The survival rate of D. reticulatum bitten by P. melanarius was not different to that of non-attacked control slugs. Attacking bites by P. melanarius, visited upon live slugs, did not yield slug DNA-positive results during molecular analysis of beetle foregut contents. (3) Pterostichus melanarius was not able to detect by olfaction the presence of live or 12 h-decayed dead D. reticulatum. (4) The feeding history of P. melanarius had a significant influence on subsequent prey selection. However, the effect interacted with an innate, overarching prey preference hierarchy. (5) A large-scale semi-field experiment identified that P. melanarius fed upon slugs, but the effect of predation pressure was not sufficient to induce negative growth in slug population density. The presence of alternative prey, and the increasing mass of individual slugs exerted rate-limiting effects on slug-predation by P. melanarius.

Thesis (M.S.) -- University of Maryland, College Park, 2004.
Thesis research directed by: Dept. of Civil Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

In this study, the autoxidation of squalane inhibited by phenolic and aminic antioxidants was analysed between 160 and 220 °C representing piston assembly temperatures of automotive engines. The mechanism of the phenolic antioxidant octadecyl 3-(3,5-di-tert-butyl-4- hydroxyphenyl) (OHPP) in the presence of oxygen at these temperatures was analysed. It was concluded that OHPP autoxidation formed four products; a hydroxyl-substituted phenolic, octadecyl 3-(3,5-ditert-butyl-4-hydroxy-phenyl)-3-hydroxy-propanoate, a hydroxyl-substituted quinone methide (octadecyl 3-(3,5-ditert-butyl-4-oxo-cyclohexa- 2,5-dien-1-ylidene)-2-hydroxy-propanoate), and the previously observed hydroxycinnamate and di-tert-butyl benzoquinone. Quantification of the time development of these products indicates that benzoquinone is formed from hydroxycinnamate and not from the phenoxyl radical as previously thought. Mechanisms are suggested to account for this. In the presence of alkyl hydroperoxide, the aminic antioxidant octylated diphenylamine (ODPA) was found to be less effective at high temperatures with large amounts of ODPA remaining at the end of the induction period where the substrate started to oxidise significantly. This is contrary to most previous studies where all the ODPA was consumed by the end of the induction period. The suggested reason for this is that autoxidation occurs preferentially by abstraction of tertiary hydrogen atoms, forming tertiary alkyl peroxy radicals and hydroperoxides. The difference of the O-H bond strength of tertiary alkyl hydroperoxides and the N-H bond strength of ODPA was relatively small resulting in the abstraction of hydrogen atoms from ODPA by tertiary alkyl peroxy radicals being noticeably reversible at higher temperatures. Aminic antioxidants containing naphthalene rings and heteroatom bridges were found to increase the induction period relative to substituted diphenylamines. The alkylated naphthenic antioxidant N-[4-(1,1,3,3-tetramethylbutyl)phenyl]naphthalen-1-amine could achieve this despite 53% of the reacted antioxidant in the initial stages forming dehydrodimer structures. N-(1-naphthyl)naphthalene-1-amine was investigated and was found to form the product (4E)-4-(1-naphthylimino)-1H-naphthalen-1-ol. Based on the aminic antioxidants used, (1,1,3,3-tetramethylbutyl)-12H-benzo-α-phenothiazine was synthesised and used as an antioxidant in squalane autoxidation.

Thermal scavenging is a unique behavior restricted to a few desert ant genera. Workers are among the most thermotolerant land animals known to this day, being able to survive body temperatures of sometimes more than 50°C for several minutes. Making use of their remarkable heat-hardiness, they search for food in plain day, a feat that other desert creatures cannot accomplish. They mostly feed on the corpses of heat-stricken, less tolerant arthropods that were unable to survive the blazing sun of the midday desert. Thermal scavenging has evolved independently at least three times in distantly related genera, geographical well segregated inside the different deserts of the world. First, the Cataglyphis genus ranges from the Sahara Desert and extends its distribution to reach minor Asia through the Mediterranean Basin. Second the Ocymyrmex genus can be found in the Namib and Karoo deserts of southern Africa, extending its range to eastern Africa savanna plains. Finally, the Melophorus genus can be found in Australia, with thermal scavenging species distributed in the central desert of the outback region.While this impressive behavior was already well-described by the start of this PhD project, little was known about the mechanisms supporting the remarkable heat-tolerance of workers. Using biophysical and physiological approaches in Cataglyphis and Ocymyrmex, we’ve been able to pinpoint key aspects underlying stress tolerance in those genera. First, from a biophysical standpoint, the Sahara silver ant Cataglyphis bombycina is covered with a unique and dense array of prismatic hairs reflecting visible wavelengths by total internal reflection. This allows reflection of up to 50% of the incident sunlight energy, thus shifting down the ant’s thermal equilibrium and sparing its body a few critical degrees. Second, in a comparative framework, we found numerous genes involved with critical cellular processes to be constitutively expressed or strongly up-regulated to heat in thermal scavenging ants, while their orthologs were not in mesophilic species. Those processes, such as molecular chaperoning, cell-cycle regulation, energy metabolism and muscular functions are keys that allow those ants to meet the higher requirement needed to scavenge for food at both stunning speed and under extreme heat-pressure. Overall, this work investigates the physiological and biophysical basis enabling thermal scavenging ants to survive extreme heat conditions. It provides a deeper understanding of cellular heat-tolerance pathways in non-model animals and contribute to our knowledge of life’s adaptation to extreme conditions.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished

Like many large raptors, vultures are intolerant of humans, making them difficult to study; consequently their ecology is not well understood. New technologies such as satellite tracking, and more powerful statistical analysis have the potential to reveal more about these birds. White-backed vultures display an aversion to nesting in proximity to humans, and, in areas with high human population densities, are restricted to nesting in nature reserves and private game farms; lappet-faced vultures display even less tolerance to human presence. Cape vultures, fitted with satellite tracking devices, showed a preference for foraging close to their nest or roost, but avoided areas of human settlement when foraging. White-backed vultures appear adaptable in their choice of nest site and can nest at high densities; they appear able to survive in small protected areas, but this is not true of other species. Habitat associations of vultures were not general across regions. Breeding success of vultures and marabou storks is apparently related to food availability. In the case of white-backed vultures nest success was also negatively affected by nesting density, but density did not affect the colonially nesting marabou or territorial lappet-faced vulture. Immature birds are capable of moving large distances after fledging: movements of over 1000km from the nest site were recorded by cape vultures and marabous. These results have implications for the continued survival of these species; their differing abilities to adapt to human presence will most likely affect those chances of survival.

Cerium is the most abundant of the rare earth metals, found on average at a level of 66 parts per million in the earth's crust. The unique redox properties of cerium and cerium oxide nanoparticles have led to its use in a wide variety of industrial and commercial uses such as oxygen sensors, fertilizers and as a catalyst to remove toxic gases in automobile exhaust. The use of cerium has also garnered interest in the nanotechnology field. Nanoceria has been generated in its oxide form as nanoparticles and nanorods. Recently, nanoceria has been shown to protect against oxidative stress in both animal and cell culture models. Although not fully understood, this observed protective effect of nanoceria is believed to be the result of recently identified SOD mimetic activity. Currently there is little understanding as to how nanoceria is capable of scavenging radicals or what properties makes nanoceria an effective SOD mimetic. Our data shows strong evidence that the oxidation state of nanoceria is directly related to its reported SOD mimetic activity. As such, future studies of nanoceria should be mindful of the oxidation state of nanoceria preparations as only nanoceria with a high concentration of cerium (III) have shown effective SOD mimetic activity. In addition to the characterization of nanoceria and its SOD mimetic activity, we have evidence that free cerium is capable of generating radicals and damaging DNA in vitro in the presence of hydrogen peroxide. These data strongly suggests that the rare earth inner-transition metal cerium is capable of generating hydroxyl radicals via a Fenton-like reaction. Based on these results the use of free cerium salts should be monitored to limit environmental exposure to cerium. Altogether our data would suggest that cerium by virtue of its unique redox chemistry is quite capable of accepting and donating electrons from its surroundings. In its free form cerium is able to redox cycle easily and can generate radicals. However, paradoxically nanoceria may not easily redox cycle due to the bound lattice structure of the particle. The unique nature of nanoceria and cerium leads to a unique circumstance where nanoceria is a radical scavenger while free cerium generates radicals. As such, further investigation is needed to insure that leeching or cerium from nanoceria does not abrogate any potential benefit nanoceria may provide.
M.S.
Department of Molecular Biology and Microbiology
Burnett College of Biomedical Sciences
Molecular and Microbiology MS

Arsenic contamination of drinking water is problematic across the globe, with a serious effect on human health. The WHO guideline of 10 μg L-1 maximum concentration for arsenic in drinking water is regularly exceeded in developing countries in South East Asia, and many other countries across the world including the USA and Japan. Aqueous arsenic is commonly found in two oxidation states, AsV (arsenate) or AsIII (arsenite). Arsenate exists in water as a tetrahedral oxyanion, analogous to phosphate. Recently there has been great interest in developing new materials than can remove arsenate from drinking water. Specifically, chelating resins loaded with transition metal cations have shown potential for use in arsenate remediation. This Thesis describes the synthesis of two series of metal complexes that were evaluated as arsenate receptors and subsequent development of one of these receptors into a novel arsenate adsorbent. Firstly, a range of bridging di-metallic complexes was synthesised. The aqueous phase oxyanion binding properties of these receptors were investigated by indicator displacement assays, isothermal titration calorimetry and in the solid phase by X-ray crystallography. Metallo-receptors containing boronic acid binding sites were also synthesised and arsenate binding was studied by isothermal titration calorimetry, UV-vis spectroscopy and NMR spectroscopy. An arsenate sorbent was prepared by immobilising a phenolate di-zinc(II) complex onto a polystyrene resin. The novel material thus obtained was studied as an arsenate adsorbent in a range of batch adsorption experiments. The effects of solution pH and presence of competing ions on arsenate uptake were investigated and the Langmuir adsorption capacity was obtained. These results were compared with those of a commercially used arsenic adsorbent, Bayoxide E33. Finally the novel adsorbent was packed into a glass column and its ability to adsorb arsenate in flow through experiments was studied.

Clear Lake represents an economically significant mesotrophic lake located in southwest Manitoba. In an attempt to describe the biogeochemical factors and mechanisms controlling the cycling of phosphorus in this waterbody various physio-chemical and chemical attributes of the lake water, seston and sediments were measured. Within the water column clear seasonal summer stratification was evident. Hypolimnetic water remained oxic throughout the ice-free period and pH remained neutral to alkaline throughout the entire period of observation. Chemical analysis of the lake indicated the water is enriched in Ca²⁺ and Mg²⁺, likely as a result of the calcareous Cretaceous shale in the surrounding watershed. During summer stratification in 2008, large concurrent increases in dissolved oxygen, pH and CaCO₃ saturation index were observed to occur simultaneously with large reductions in total and dissolved P. This was interpreted as an incidence of biologically-mediated pH shift during an algal bloom leading to a precipitation of CaCO₃ in association with occluded organic and inorganic P. Fractional P analysis, conducted on particulate seston and sediment, separated the total P (TP) into Organic P (OP), Non-Apatite Inorganic P (NAIP), and Apatite P (AP). Significant amounts of AP in the seston and sediment provide support for the interpretation that authigenic CaCO₃ scavenged P from the water column. Within the sediment cores, large and increasing amounts of AP indicate that all co-precipitated P is retained long term within the sediment as refractory AP. The combination of efficient scavenging during co-precipitation events and long-term storage of P as AP in the sediments suggests that the calcareous nature of the lake is playing an important role in the biogeochemical cycles.

Peroxiredoxins are a family of multifunctional enzymes that are able to protect the cell against oxidative stress. Peroxiredoxins form part of a recently discovered peroxide scavenging system along with thioredoxin, thioredoxin reductase and sulfiredoxin. This study describes the purification of a recombinant human peroxiredoxin II from human erythrocytes. The original recombinant clone contained a point mutation at the fourth residue from glycine to valine and a number of problems were encountered with aggregation during purification. Reverting back to the original amino acid sequence allowed the protein to be purified and concentrated without aggregation, as well as leading to over-expression in the same oligomeric state as the native sample from blood. This study also describes the over-expression and purification of the human peroxiredoxin II protein in the intermolecular disulfide form as well as the subsequent crystallisation and X-ray diffraction studies. The crystal structure for this form of the protein was obtained to 3.3 Å resolution revealing the peroxiredoxin to be in the decameric form. In addition conformational changes in the protein that are necessary for formation of the intermolecular disulfide between the peroxidatic (Cys52) and resolving cysteine (Cys172) have been observed. The structure also revealed that these movements did not interfere with the dimer:dimer interface as had been previously suggested. This then allows the disulfide to be seen within the decameric form of peroxiredoxin. The production of covalent complexes formed between peroxiredoxin and sulfiredoxin, and peroxiredoxin and thioredoxin was also investigated. Complexes were stabilised by using DTNB to form a covalent bond between specific cysteine residues. The complex binding results from size exclusion chromatography showed that decameric peroxiredoxin bound to sulfiredoxin in a 1:5 ratio and decameric peroxiredoxin bound to thioredoxin in a 1:10 ratio. Cloning, over-expression and purification of the selenocysteine containing enzyme thioredoxin reductase was achieved. A minimal selenocysteine insertion sequence was added to the 3’ end of the DNA sequence to drive selenocysteine insertion in place of the typical stop UGA codon. The activity of this protein was found to be low but was greatly increased when co-expressed with a plasmid containing the selA, selB and selC genes. Although the activity of this co-expressed thioredoxin reductase was ~20% of the native enzyme activity, it was comparable to the activity of other recombinant forms of the enzyme. These studies report the purification of all of the proteins necessary to reform the peroxiredoxin system and allow the production of a working assay for peroxiredoxin activity. Together with the first report for a structure of a decameric disulfide form of human peroxiredoxin II a greater insight into the peroxiredoxin system has been obtained.

Many parts of the world have arsenic contamination problems in drinking and ground water. The high toxicity of arsenic threatens people’s health, since exposure to it can cause cancer and other dangerous diseases. Inorganic arsenic in natural water is found in two oxidation states, AsV(arsenate) or AsIII(arsenite). AsIII has the highest toxicity comparing with AsV and difficult to remove due to zero charge species of AsIII at pH below 9. Consequently, photocatalytic oxidation of arsenite is a key challenge to improve removal efficiencies of future sorbents. Recent work has suggested that a TiO2/Fe2O3 binary mixed oxides could play a key role in the design of future sorbents as it combines photocatalytic oxidation and adsorptive properties alike. The aim of this thesis presented was to characterise the interaction of arsenic with TiO2/Fe2O3 binary mixed oxides synthesised using different methods and to critically evaluate the potential of these bicomposites for future development work. To this end, three different synthetic methods with respect to cost, time and energy consumption during production were tested. The mechanisms of arsenic interaction were assessed using macroscopic (i.e. adsorption isotherms, adsorption kinetics) and microscopic (i.e. synchrotron techniques) studies and the photocatalytic oxidation was studied using synchrotron and UV irradiation. An electrochemical method for detection of arsenic has been implemented for the accurate analytical determination of AsIII and AsV down to levels of 0.4 ppb using stripping voltammetry. TiO2/Fe2O3 binary mixed oxides have been prepared using a co-precipitation method, a mesoporous method and sol-gel method. The adsorption capacities of AsIII on mesoporous TiO2/Fe2O3 binary mixed oxides were found at 29.44±2.99, 22.64±1.74 and 21.60±0.33 mg g-1 at pH 5, 7 and 9, respectively. The adsorption kinetics study found the rate constant (k2) 0.02 g mg-1 min-1. The photocatalytic oxidation rate constant (kox) of AsIII onto the surface of TiO2/Fe2O3 binary mixed oxides with synchrotron beam irradiation found in between 0.062 to 0.078 min-1. Additionally, the rate constant (kox) of AsIII phototalytic oxidation in bicomposite suspension with UV irradiation found at 4.37x10-3 min-1. The binding mode of AsIII and AsV onto the surface of TiO2/Fe2O3 binary mixed oxides was to be a bidentate mononuclear edge sharing (2E) complex and a bidentate binuclear corner sharing (2C) complex. Mesoporous TiO2/Fe2O3 binary mixed oxides have been highlighted to be the best bicomposites in this study due to the highest adsorption capacities and ability to photocatalytic oxidation of AsIII to AsV.

Thesis: Ph. D., Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2018.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 321-351).
Many chemical constituents are removed from the ocean by attachment to settling particles, a process referred to as "scavenging." Radioisotopes of thorium, a highly particle-reactive element, have been used extensively to study scavenging in the ocean. However, this process is complicated by the highly variable chemical composition and concentration of particles in oceanic waters. This thesis focuses on understanding the cycling of thorium as affected by particle concentration and particle composition in the North Atlantic. This objective is addressed using (i) the distributions 228,230,234 Th, their radioactive parents, particle composition, and bulk particle concentration, as measured or estimated along the GEOTRACES North Atlantic Transect (GA03) and (ii) a model for the reversible exchange of thorium with particles. Model parameters are either estimated by inversion (chapter 2-4), or prescribed in order to simulate 230Th in a circulation model (chapter 5). The major findings of this thesis follow. In chapters 2 and 3, I find that the rate parameters of the reversible exchange model show systematic variations along GA03. In particular, k1 , the apparent first-order rate "constant" of Th adsorption onto particles, generally presents maxima in the mesopelagic zone and minima below. A positive correlation between k, and bulk particle concentration is found, consistent with the notion that the specific rate at which a metal in solution attaches to particles increases with the number of surface sites available for adsorption. In chapter 4, I show that Mn (oxyhydr)oxides and biogenic particles most strongly influence k1 west of the Mauritanian upwelling, but that biogenic particles dominate ki in this region. In chapter 5, I find that dissolved 230Th data are best represented by a model that assumes enhanced values of k, near the seafloor. Collectively, my findings suggest that spatial variations in Th radioisotope activities observed in the North Atlantic reflect at least partly variations in the rate at which Th is removed from the water column.
by Paul Lerner.
Ph. D.

With ample radio transmitters scattered throughout urban landscape, RF energy scavenging emerges as a promising approach to extract energy from propagating radio waves in the ambient environment to continuously charge low power electronics. With the ability of generating power from RF energy, the need for batteries could be eliminated. The effective distance of a RF energy scavenging system is highly dependent on its conversion efficiency. This results in significant limitations on the mobility and space requirement of conventional RF energy scavenging systems as they operate only in presence of physically large antennas and conversion circuits to achieve acceptable efficiency. This thesis presents a number of novel design strategies in the antenna and rectifier designs for miniaturized RF energy scavenging system. In the first stage, different energy scavenging systems including solar energy scavenging system, thermoelectric energy scavenging system, wind energy scavenging system, kinetic energy scavenging system, radio frequency energy scavenging system and hybrid energy scavenging system are investigated with regard to their principle and performance. Compared with the other systems, RF energy scavenging system has its advantages on system size and power density with relatively stable energy source. For a typical RF energy scavenging system, antenna and rectifier (AC-DC convertor) are the two essential components to extract RF energy and convert to usable electricity. As the antenna occupies most of the area in the RF energy scavenging system, reduction in antenna size is necessary in order to design a miniaturized system. Several antennas with different characteristics are proposed in the second stage. Firstly, ultra-wideband microstrip antennas printed on a thin substrate with a thickness of 0.2 mm are designed for both half-wave and full-wave wideband RF energy scavenging. Ambient RF power is distributed over a wide range of frequency bands. A wideband RF energy scavenging system can extract power from different frequencies to maximize the input power, hence, generating sufficient output power for charging devices. Wideband operation with 4 GHz bandwidth is obtained by the proposed microstrip antenna. Secondly, multi-band planar inverted-F antennas with low profile are proposed for frequency bands of GSM 900, DCS 1800 and Wi-Fi 2.4 GHz, which are the three most promising frequency bands for RF energy scavenging. Compared with previous designs, the triple band antenna has smaller dimensions with higher antenna gain. Thirdly, a novel miniature inverted-F antenna without empty space covering Wi-Fi 2.4 GHz frequency band is presented dedicated for indoor RF energy scavenging. The antenna has dimensions of only 10 × 5 × 3.5 mm3 with appreciable efficiency across the operating frequency range. In the final stage, a passive CMOS charge pump rectifier in 0.35 μm CMOS technology is proposed for AC to DC conversion. Bootstrapping capacitors are employed to reduce the effective threshold voltage drop of the selected MOS transistors. Transistor sizes are optimized to be 200/0.5 μm. The proposed rectifier achieves improvements in both power conversion efficiency and voltage conversion efficiency compared with conventional designs. The design strategies proposed in this thesis contribute towards the realization of miniaturized RF energy scavenging systems.

Kyoto University (京都大学)
0048
新制・課程博士
博士(農学)
甲第15426号
農博第1811号
新制||農||979(附属図書館)
学位論文||H22||N4525(農学部図書室)
27904
京都大学大学院農学研究科農学専攻
(主査)教授 谷坂 隆俊, 教授 冨永 達, 教授 白岩 立彦
学位規則第4条第1項該当

Predation accounts for the majority of ruffed grouse mortality beyond the brooding period throughout grouse range. Most studies of ruffed grouse ecology have taken place in the central portion of the species range including the Great Lakes states and southern Canada where aspen (Populus tremuloides) is dominant. Populations in the central range of grouse distribution exhibit 10-year cyclic patterns of decline that have been associated with the invasions of boreal predators such as great horned owls and northern goshawks during crashes in small mammal populations. I completed an accuracy assessment of field sign to determine the role of scavenging as it related to diagnosing causes of proximate mortality. Potentially large numbers of grouse are scavenged after death, which can alter or completely falsify the reported cause of death.. My results indicated that stand-level and micro-site habitat variables did not influence scavenger detection of ruffed grouse carcasses (P > 0.05). Scavenging was limited to 24 of 64 carcasses and was entirely attributed to mammalian species. Scavenging behavior was related to the condition of the carcass following death (P = 0.003) and the ambient temperature (P = 0.01). As the temperature increased and as a carcasses entrails and muscle became more exposed, the probability of being scavenged increased. Nineteen percent of whole carcasses placed in the field were scavenged and would have been attributed to mammal predation based on the field sign; 56% of 32 mock avian kills were scavenged would have been attributed to mammal predation. I related indices of predators and weather patterns to trends in ruffed grouse predation. Using data collected at 10 study sites between February, 1997 and December, 2000, I compared predation rates, and animal and weather indices to predation rates, across sites, years, regions, seasons and month combinations pooled across years. Avian predators were the primary predators of ruffed grouse in the Appalachian region (50% of all predation). Predation rates on ruffed grouse were highest in fall (8.3%), due to high predation on juveniles, and spring (7.4%) in association with raptor migration and pre-breeding activity of grouse. Predation patterns and predator abundance did not indicate the occurrence of predator invasions during the years of this study. Predation rates on ruffed grouse were positively related to the presence of rain and negatively related to the average low temperature and number of rabbits and squirrels observed per hour. Observations of owls and Cooper's hawks per hour were correlated with predation rates on grouse while those of red-tailed, red-shouldered and broad-winged hawks were not.
Master of Science

[ES] La presente tesis doctoral tuvo como objetivo desarrollar nuevos materiales biodegradables hechos a base de fibras obtenidas mediante la técnica de electroestirado, denominadas "biopapers" o biopapeles, con barrera a agua y a gases y propiedades de secuestro de oxígeno para su posible aplicación en recubrimientos de papel o como capas intermedias en envases alimentarios basados en papel y cartón. En un primer estudio, se desarrollaron biopapeles de PHB mediante electroestirado, usando dos tipos de colectores, colectores de placa plana y rotativo, para evaluar la influencia del alineamiento de las fibras. Con posterioridad se aplicó un tratamento de recocido por debajo del punto de fusión del polímero a diferentes temperaturas, tiempos y procesos de enfriamiento para obtener películas continuas por coalescencia de las fibras, lo que a su vez condujo a la adhesión entre capas, y a una mejora en las propriedades barrera y ópticas. En un segundo estudio, se depositaron biopapeles monocapa y multicapa hechos de PHB, PVOH y PLA sobre un sustrato de papel no estucado, utilizando los dos colectores citados; y el tiempo de procesamiento por electrospinning se varió para producir espesores diferentes. Para mejorar la adhesión al sustrato de papel, y las propiedades ópticas y de barrera de las multicapas, los biopapeles se sometieron a un proceso de recocido como se describe y optimiza en el primer estudio. Con respecto a la barrera al agua, el sistema de papel/ PVOH/PHB presentó las mejores propriedades. En un tercer estudio, se obtuvieron dos nanopapeles de alta barrera hechos a base de nanofibras de celulosa de dos tipos, nanofibras de celulosa (CNF) y nanofibras de lignocelulosa (LCNF) y se recubrieron con biopapeles de PHA electroestirados con barrera a agua. Como resultado, el carácter hidrófobo de los nanopapeles se mejoró significativamente. Por otra parte, estos también exhibieron un rendimiento mecánico más equilibrado. En un cuarto estudio, se desarrollaron biopapeles de PHA con capacidad activa de secuestro de oxígeno, para lo cual se usaron nanopartículas de paladio (PdNP) como catalizadores de la respuesta activa. La principal dificultad asociada con las nanopartículas es mantenerlas dispersas, por lo que en este trabajo evaluamos el uso de surfactantes CTAB y TEOS como sustancias permitidas en contacto con alimentos para ayudar a la dispersión y distribución de PdNP dentro de las fibras de PHA. Como resultado, se prepararon nanocompuestos electroestirados con capacidad de secuestro de oxígeno hechos de PHB y PdNP, seguidos de un tratamiento de recocido para obtener capas continuas y autoadhesivas. La capacidad de secuestro de oxígeno de los biopapeles, medida a un 100% de humedad relativa (HR), mostró un mejor rendimento para el material en forma de fibra que en forma de film. En cualquier caso, los resultados indicaron una cinética de absorcion relativamente baja. Con el fin de mejorar aún más la cinética de secuestro de oxígeno, incluso a una humedad intermedia y en forma de película, un quinto estudio, desarrolló biopapeles multicapa hechos de PCL y PHA aplicados sobre papel no estucado. Los nanocompuestos de PCL/PdNP mostraron uma cinética de secuestro de oxígeno mucho mayor que la del sistema PHA / PdNP anterior. Este resultado se atribuye a la mayor fración de volumen libre del PCL que permite que la humedad, el hidrógeno y la permeación de oxígeno desencadenen la reacción de eliminación catalítica de forma más eficiente. Finalmente, un sexto estudio, desarrolló un nuevo concepto de capa con capacidad de secuestro de oxígeno y con alta barrera passiva a gases y vapores orgánicos basado en PdNP, CNC y EVOH. Así, CNC y CNC oxidado com TEMPO (TEMPO oxidized CNC), se utilizaron para producir PdNP in situ sobre el nanorefuerzo, que se incorporaron en la matriz del polímero EVOH. El TEMPO oxidized CNC demostró poseer una mayor absorción de oxígeno debido a los grupos car
[CAT] La present tesi doctoral va tindre com a objectiu desenvolupar noves capes biodegradables actives obtingudes mitjançant electrospinning, denominades "biopapers" o biopapeles, amb barrera a aigua i a gasos i propietats de segrest d'oxigen per a la seua possible aplicació en recobriments de paper o com a capes intermèdies en envasos alimentaris basats en paper i cartó. En un primer estudi, es van desenvolupar bio-papers de PHB mitjançant electrospinning, utilitzant dos tipus de col·lectors, col·lectors de placa plana i rotatiu, per a avaluar la influència de l'alineament de les fibres. Amb posterioritat es va aplicar un tractament de recuita per davall del punt de fusió del polímer a diferents temperatures, temps i processos de refredament per a obtenir pel·lícules contínues per coalescència de les fibres, la qual cosa al seu torn va conduir a l'adhesió entre capes, i a una millora en les propietats barrera i òptiques. En un segon estudi, es van depositar bio-papers monocapa i multicapa fets de PHB, PVOH i PLA sobre un substrat de paper no estucat, utilitzant els dos col·lectors citats; i el temps de processament per electrospinning es va variar per a produir grossàries diferents. Per a millorar l'adhesió al substrat de paper, i les propietats òptiques i de barrera de les multicapes, els biopapers es van sotmetre a un procés de recuita com es descriu i optimitza en el primer estudi. Respecte a la barrera a l'aigua, el sistema de paper/PVOH/PHB va presentar les millors propietats. En un tercer estudi, es van obtenir dos nano-papers d'alta barrera fets a base de nanofibres de cel·lulosa de dos tipus, nanofibres de cel·lulosa (CNF) i nanofibres de lignocel·lulosa (LCNF) i es van recobrir amb bio-papers de PHA electro-estirats amb barrera a aigua. Com a resultat, el caràcter hidròfob dels nano-papers es va millorar significativament. D'altra banda, aquests també van exhibir un rendiment mecànic més equilibrat. En un quart estudi, es van desenvolupar bio-papers de PHA amb capacitat activa de segrest d'oxigen, per a això es van usar nanopartícules de pal·ladi (PdNP) com a catalitzadors de la resposta activa. La principal dificultat associada amb les nanopartícules és mantenir-les disperses, per la qual cosa en aquest treball avaluem l'ús de surfactants CTAB i TEOS com a substàncies permeses en contacte amb aliments per a ajudar la dispersió i distribució de PdNP dins de les fibres de PHA. Com a resultat, es van preparar nano-compostos electro-estirats amb capacitat de segrest d'oxigen fets de PHB i PdNP, seguits d'un tractament de recuita per a obtenir capes contínues i autoadhesives. La capacitat de segrest d'oxigen dels bio-papers, mesurada a un 100% d'humitat relativa (HR), va mostrar un millor rendiment per al material en forma de fibra que en forma de film. En qualsevol cas, els resultats van indicar una cinètica de absorció relativament baixa. Amb la finalitat de millorar encara més la cinètica de segrest d'oxigen, fins i tot a una humitat intermèdia i en forma de pel·lícula, un cinquè estudi, va desenvolupar bio-papers multicapa fets de PCL i PHA aplicats sobre paper no estucat. Els nano-compostos de PCL/PdNP van mostrar una cinètica de segrest d'oxigen molt major que la del sistema PHA/PdNP anterior. Aquest resultat s'atribueix a la major fracció de volum lliure del PCL que permet que la humitat, l'hidrogen i la permeància d'oxigen desencadenen la reacció d'eliminació catalítica de forma més eficient. Finalment, un sisè estudi, va desenvolupar un nou concepte de capa amb capacitat de segrest d'oxigen i amb alta barrera passiva a gasos i vapors orgànics basat en PdNP, CNC i EVOH. Així, CNC i CNC oxidat com TEMPO (TEMPO oxidat CNC), es van utilitzar per a produir PdNP in situ sobre el nano-reforç, que es van incorporar en la matriu del polímer EVOH. El TEMPO oxidat CNC va demostrar posseir una major absorció d'oxigen degut als grups carboxílics generats.
[EN] The present PhD thesis aimed to develop novel active fiber based biodegradable layers obtained by electrospinning, so-called biopapers, with water and gas barrier and oxygen scavenging properties for their potential use as paper coatings or packaging interlayers in fiber based packaging. In a first study, PHB biopapers were obtained by electrospinning, by means of two types of collectors namely, flat plate and rotation drum collectors, to evaluate the influence of the alignment of fibers. Annealing post-processing below the polymer melting point was carried at different temperatures, isothermal times and cooling processes to obtain transparent and pore free continuous films by fibers coalescence which in turn led to interlayer adhesion, enhanced barrier and optical properties. In a second study, mono and multilayer biopapers comprising PHB, PVOH and PLA were deposited onto a conventional uncoated paper substrate, using the cited two collectors; and the electrospinning processing time was varied to produce different thickneses. To enhance adhesion to the paper substrate, optical and barrier performance of the multilayer, the biopapers were subjected to an annealed process as described and optimized in the first study. Regarding water barrier, the system paper/PVOH/PHB presented the highest barrier performance. In a third study, environmentally friendly materials such as cellulose based nanopapers, i.e. gas barrier layers made of cellulose nanofibrils (CNFs) and lignocellulose nanofibrils (LCNFs), were obtained and coated with the water barrier electrospun PHA biopapers. As a result, the hydrophobic character of the nanopapers was significantly improved by the electrospun biopapers. Moreover, these also exhibited a more balanced mechanical performance. In a fourth study, active oxygen scavenging PHA biopapers were developed, in which palladium nanoparticles (PdNP) were used as catalysts to scavenge oxygen from the headspace. The main difficulty associated with nanoparticles is to keep them dispersed, so in this work we assessed the use of CTAB and TEOS surfactants as food contact permitted substances to help dispersion and distribution of the PdNP within the PHA fibers. As a result, oxygen scavenging nanocomposite biopapers made of electrospun PHB and PdNP were prepared, followed by annealing treatment to obtain homogeneous and continuous active layers. The oxygen scavenging capacity at 100% relative humidity (RH) of the biopapers in fiber form showed better performance than their annealed specimens as expected, but in general this was not considered optimal. In order to improve further the oxygen scavenging capacity, even at a low relative humidity and in film form, a fifth study, developed multilayered biopapers made of PCL and PHA coated on conventional cellulose paper. The PCL/PdNP nanocomposites showed much more enhanced oxygen scavenging performance in comparison with the above PHA/PdNP system. This result is attributed to the higher fractional free volume of the PCL polymer that allows moisture, hydrogen and oxygen permeation to trigger the catalytic scavenging reaction. Finally, a sixth study, developed a solvent casting high gas barrier and active oxygen scavenging layer concept based on PdNP, CNC and EVOH. Thus, CNC and TEMPO oxidized CNC, were used to produce in situ PdNP, which were incorporated into the EVOH polymer matrix. The TEMPO oxidized CNC exhibited higher oxygen absorption due to the generated carboxylic groups.
Spanish Ministry of Economy and Competitiveness (MINECO) project AGL2015-63855-C2-1-R for financial support. A. Cherpinski also would like to thank the Brazilian Council for Scientific and Technological Development (CNPq) of Brasilian Government for her predoctoral grant (205955/2014-2). A. Cherpinski also acknowledges the European Cooperation in Science and Technology (COST) Action FP1405 for funding through a Short Term Scientific Mission (STSM)
Cherpinski Correa, A. (2019). NOVEL ELECTROSPUN POLYHYDROXYALKANOATE BASED HIGH BARRIER AND ACTIVE BIOPAPERS OF INTEREST IN FOOD PACKAGING [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/123064
TESIS

 Ischemic stroke is the leading cause of death and disability in human diseases all around the world. As effective treatment for ischemic stroke is still absent, seeking for new therapy is of great interest. Currently, several key pathological cascades following cerebral ischemia have been explored to develop further therapies. Among them, reactive nitrogen species (RNS) has been indicated to play a critical role in cerebral ischemia reperfusion injury. As one of the RNS, peroxynitrite contributes to the neural cell death and subsequent brain dysfunction in the process. Thus, development of antioxidants targeting on peroxynitrite could be an important strategy for the treatment of cerebral ischemia-reperfusion injury. Baicalin is a polyphenolic compound isolated from roots of Scutellaria baicalensis. Baicalin exerted protective effects against cerebral ischemia-reperfusion injury but the mechanisms are not clear yet. In this study, we investigated the free radical scavenging ability and neuroprotective effects of baicalin. According to our results, baicalin neutralized DPPH radicals effectively. By using electron paramagnetic resonance (EPR) spin trapping technology and fluorescent probe DAF-2DA, we found that baicalin dose-dependently scavenged superoxide, but had very low effect on elimination of nitric oxide. The immunofluoresent results revealed that baicalin at the concentration of 50 M completely suppressed the nitrotyrosine formation induced by 3-morpholinylsydnoneimine chloride (SIN-1, a peroxynitrite donor) in neuroblastoma SH-SY5Y cells. Mass spetrum provided direct evidence of the peroxynitrite scavenging ability of baicalin. Using MTT assays, we found that baicalin totally reversed peroxynitrite-induced cytotoxicity in SH-SY5Y cells and protected SH-SY5Y cells in oxygen glucose deprivation (OGD) and following reoxygenation injury. Furthermore, in vivo experiments revealed that intravenous injection of baicalin exerted better neuroprotective effect than intraperitoneal administration in rats underwent middle cerebral artery occlusion (MCAO). After cerebral ischemia reperfusion, rats treated with 3 mg/kg of peroxynitrite decomposition catalyst (FeTMPyP) or 25 mg/kg of baicalin revealed a smaller size of infarction volume, suppressed neural cell death and reduced nitrotyrosine formation than MCAO rats. However, baicalin did not alter the expression of tight junction proteins, claudin-5 and ZO-1, in brain endothelial bEnd3 cell line treated with OGD following reoxygenation. In cerebral ischemia reperfusion rats, administration of FeTMPyP at the dosage of 3 mg/kg diminished the Evans blue leakage caused by blood brain barrier disruption, whereas treatment of baicalin did not show significant effect. In conclusion, this study suggests that baicalin can scavenge peroxynitrite and protect neural cells from peroxynitrite-induced injury. Furthermore, baicalin could prevent brains from cerebral ischemia-reperfusion injury and the neuroprotective mechanisms are associated with the scavenging effects on peroxynitrite. These findings provide new insights into the antioxidant and neuroprotective properties of baicalin and indicate the potential application of baicalin for the treatment of ischemic stroke.
published_or_final_version
Chinese Medicine
Master
Master of Philosophy

本文データは平成22年度国立国会図書館の学位論文(博士)のデジタル化実施により作成された画像ファイルを基にpdf変換したものである
Kyoto University (京都大学)
0048
新制・課程博士
博士(農学)
甲第5739号
農博第793号
新制||農||674(附属図書館)
学位論文||H6||N2672(農学部図書室)
UT51-94-J171
京都大学大学院農学研究科農芸化学専攻
(主査)教授 浅田 浩二, 教授 山田 康之, 教授 關谷 次郎
学位規則第4条第1項該当

Mn is a geochemically important element that contributes significantly to the cycling of heavy metals. During precipitation, Mn oxyhydroxides scavenge many heavy metals, including Pb, in a variety of natural environments. Because of this phenomenon, the precipitation of Mn oxyhydroxides may provide a remediation technique for removing Pb from contaminated aqueous solutions. Therefore, this study was undertaken to provide a quantitative understanding of the coprecipitation of Pb with Mn oxyhydroxides to demonstrate their capacity to remove Pb permanently from contaminated solutions. To accomplish this, a series of factorial experiments with varying initial Mn and Pb concentrations were run in the presence of a borate buffer or a bicarbonate buffer. All experiments were run in batch reactors, in the presence of a quartz substrate, at 25 degrees celcius, at pH 8.5, and were continuously stirred. Initial Mn and Pb concentrations were varied by half log units from 100 to 0 mg/L and from 3 to 0 mg/L, respectively. Solutions were analyzed for Mn using the formaldioxime colorimetric method and for Pb using AA. Precipitates on quartz surfaces were analyzed by SEM, XPS, and XRD for precipitate identification and morphology. The amount of Mn and Pb associated with the quartz sand was determined by dissolving the precipitates from selected quartz samples using concentrated nitric acid. Finally, a different set of precipitate-coated quartz grains were leached in pH 5 acetic acid solution to assess the metal retention capacity of the precipitated material. Mn oxyhydroxides precipitated onto the quartz sand in both the borate and bicarbonate buffered experiments. SEM and XPS data revealed tiny crystallites in etch pits on the quartz surfaces that contained predominantly Mn3+. XRD analysis did not produce an X-ray pattern for these Mn oxyhydroxides but did identify the suspended Pb precipitates as hydrocerrusite and Pb(HBO3)2 in the borate buffered experiments and hydrocerrusite in the bicarbonate buffered experiments. Much more Mn and Pb are associated with the quartz surfaces in the borate buffered experiments, but no Pb was associated with quartz surfaces initially (< 6 hrs. of reaction time). Leaching of precipitates resulted in extracted Mn in both experiments but Pb was extracted in only the bicarbonate buffered experiments. The Mn precipitation rate was greater in the borate buffered experiments and higher initial Mn and Pb concentrations appear to increase the precipitation rate in both sets of experiments. These results indicate that Mn oxyhydroxides nucleated onto suspended Pb precipitates. The growing Mn oxyhydroxide particles were attracted to the quartz sand, carrying along the Pb precipitates. Further precipitation of Mn oxyhydroxides on the quartz surfaces trapped the Pb. This process was much more significant in the borate buffered experiments where much more Mn precipitated. The greater amount of Mn oxyhydroxide growth acts as a barrier protecting the Pb from the pH 5 leaching solutions. As a result, Pb was retained by the sand grains from the borate buffered experiments during leaching while significant amounts of Pb (35-100%) was extracted from the sand produced by the bicarbonate experiments. These results strongly suggest that coprecipitation of Pb with Mn oxyhydroxides in the presence of a borate buffer and a quartz substrate may be a remediation tool for Pb contaminated aqueous solutions. Not only will this process remove aqueous Pb2+ from solution but it appears it will also substantially incorporate colloidal Pb particles as well.
Master of Science

The effects of aerosol in the atmosphere account for some of the largest uncertainties in estimates of the human impact on climate. These effects depend not only on the total mass of aerosol, but also its size distribution, mixing state and vertical profile. Previous studies have suggested that both the size distribution and mixing state of aerosol may be strongly influenced by repeated cycling through non-precipitating cloud. The extent of this process is assessed in the HadGEM3–UKCA model; although fewer cycles are seen for all aerosol than in previous studies, the figure varies considerably between aerosol types. The role of scavenging by precipitating cloud is also considered, and several approaches to increasing the physical realism of its representation are considered. In particular, coupling convective scavenging into the convective transport scheme is shown to provide significant benefits over an operator-split approach (which underestimates removal and allows excess aerosol to reach the upper troposphere and be transported to remote regions). To evaluate the alternative convective scavenging schemes, a method is developed for carrying out a pointwise evaluation against vertically-resolved in-situ observations from large-scale aircraft campaigns, based on nudging and flight-track sampling in the model. It is demonstrated that this approach can help to constrain the choice between different model configurations with a degree of statistical confidence. Finally, the processes controlling the vertical profile of aerosol are investigated using a series of model-based sensitivity tests, along with the extent to which these processes can account for the large diversity in vertical profiles seen amongst current models. For mass profiles and number profiles of large particles (greater than about 100nm dry diameter), removal and secondary production processes are shown to be most important; for number profiles of smaller particles, microphysical processes are shown to become increasingly dominant.

Les métaux lourds et les radionucléides sont présents dans différents écosystèmes du monde à cause de contaminations naturelles ou des activités anthropiques. L’utilisation de micro-organismes pour restaurer ces écosystèmes pollués, processus connu sous le nom de bioremédiation, suscite beaucoup d’intérêt, spécialement aux pH proches de la neutralité. Les minéraux de fer qui encroûtent les bactéries neutrophiles du fer, notamment les Oxydes de Fer Biogéniques (BIOS en anglais), ont une structure très faiblement cristalline, qui en plus de leur grande surface et réactivité font d’eux d’excellents supports pour le piégeage de polluants inorganiques. Dans cette thèse nous avons étudié les différents mécanismes de piégeage de l’uranium uranium par la bactérie neutrophile Sphaerotilus natans, choisie comme modèle bactérien de micro-organismes du fer capables de filamenter en formant des gaines. S. natans peut croître sous forme de cellules individuelles ou formant des filaments. Ces derniers ont été utilisés pour étudier la biosorption d’U(VI) et sa sorption sur les BIOS. De plus, la sorption d’U(VI) sur les analogues abiotiques de ces minéraux de fer a été testée. Afin d’utiliser les filaments de S. natans pour piéger l’U(VI), il était nécessaire d’identifier les facteurs induisant la filamentation de S. natans. L’influence de l’oxygène a été établie en utilisant des techniques de biologie moléculaire et nos résultats ont démontré que tandis qu’en condition d’oxygène saturé elle croît sous forme de cellules individuelles, une diminution modérée d’oxygène à ~ 3 mg O2.L-1 la fait croître sous la forme désirée, des filaments de S. natans.Les BIOS attachés aux filaments de S. natans ainsi que ses analogues abiotiques ont été analysés pas XAS au seuil K du Fe. Les deux matériaux identifiés sont des phosphates de fer(III) amorphes avec une faible proportion de fer(II), qui présentent une réactivité élevée pour le piégeage de polluants inorganiques. L’EXAFS au seuil LIII de l’U a montré la même structure pour les couches O, tandis que celles P, Fe et C étaient différentes en fonction des sorbants. Une étude intégrée qui combine des techniques expérimentales avec des calculs de spéciation a permis de décrire les isothermes d’adsorption de l’U(VI) en utilisant un modèle de complexation de surface. Ces résultats suggèrent que les groupes phosphoryles et carboxyles sont les groupes fonctionnels principaux pour la biosorption d’U(VI) par des filaments de S. natans. Les résultats de cette thèse vont aider à comprendre les processus contrôlant l’immobilisation de l’U(VI), soit par la biosorption sur S. natans, la sorption sur les BIOS ou la sorption sur les phosphates de fer, et en conséquence le devenir de l’U en conditions neutres
Heavy metals and radionuclides are present in some ecosystems worldwide due to natural contaminations or anthropogenic activities. The use of microorganisms to restore those polluted ecosystems, a process known as bioremediation, is of increasing interest, especially under near-neutral pH conditions. Iron minerals encrusting neutrophilic iron-related bacteria, especially Bacteriogenic Iron Oxides (BIOS), have a poorly crystalline structure, which in addition to their large surface area and reactivity make them excellent scavengers for inorganic pollutants. In this PhD work we studied the different mechanisms of uranium scavenging by the neutrophilic bacterium Sphaerotilus natans, chosen as a model bacterium for iron-related sheath-forming filamentous microorganisms. S. natans can grow as single cells and filaments. The latter were used to investigate U(VI) biosorption and U(VI) sorption onto BIOS. In addition, uranium sorption onto the abiotic analogues of such iron minerals was assessed. In order to use S. natans filaments for U(VI) scavenging, it was necessary to identify factors inducing S. natans filamentation. The influence of oxygen was ascertained by using molecular biology techniques and our results revealed that while saturated oxygen conditions resulted in single cell growth, a moderate oxygen depletion to ~ 3 mg O2.L-1 led to the desired filamentous growth of S. natans. BIOS attached to S. natans filaments as well as the abiotic analogues were analysed by XAS at Fe K-edge. Both materials were identified as amorphous iron(III) phosphates with a small component of Fe(II), with a high reactivity towards scavenging of inorganic pollutants. In addition, EXAFS at the U LIII-edge revealed a common structure for the O shells, while those for P, Fe and C were different for each sorbent. An integrated approach combining experimental techniques and speciation calculations made it possible to describe U(VI) adsorption isotherms by using a surface complexation model. These results suggested the role of phosphoryl and carboxyl groups as the main functional groups involved in the U(VI) biosorption by S. natans. The results of this PhD work will help to better understand the processes governing U(VI) immobilization, either by S. natans biosorption, sorption onto BIOS or sorption onto iron phosphates, an thus the fate of uranium in near-neutral pH environments

In biological systems, iron is extremely important due to its use in electron transport, redox centers, oxygen transport, dismutation of reactive oxygen species, and structural stabilization. Among bacteria, iron is essential for healthy growth and many mechanisms exist for its acquisition. A prominent example is the iron-regulated surface determinant (Isd) system, which is found in many pathogens including the causative agent of anthrax, Bacillus anthracis. In the Isd system of B. anthracis, the protein IsdX1 is responsible for scavenging heme from host hemoglobin so that iron can be acquired through heme degradation. This process is not novel among bacteria that express Isd proteins, but IsdX1 is unique as the only example of an extracellular hemophore in Gram-positive bacteria. In order to understand the functional mechanics of IsdX1, it is necessary to characterize the protein with and without heme bound. This is accomplished by assessing proteolytic and thermal stability with limited proteolysis and circular dichroism. Using these tools, it is clear that IsdX1 is a stable protein in both the apo and holo forms that is quite resistant to proteolytic degradation. The binding of heme increases thermal stability to a moderate extent. These results suggest that IsdX1 is important for the growth of B. anthracis, and that heme binding influences the secondary structure content, possibly through a stabilizing conformational change.

Most current space robotics vehicles use solar energy as their prime energy source. In spherical robotic vehicles the use of solar cells is very restricted. Focusing on the particular problem, an improved method to generate electrical power will be developed; the innovation is the use of an internal pendulum-generator mechanism to generate electrical power while the ball is rolling. This concept will enable spherical robots on future long-duration planetary exploration missions. Through a developed proof-of-concept prototype, inspired by the Russian thistle plant, or tumbleweed, this thesis will demonstrate power generation capabilities of such a mechanism. Furthermore, it will also present and validate a parametric analytical model that can be used in future developments as a design tool to quantify power and define design parameters. The same model was used to define the design parameters and power generation capabilities of such a system in Martian environment.