Habitat characteristics and energy budget of the ocean quahog (Arctica islandica)

We compared lifetime and population energy budgets of the extraordinary long-lived ocean quahog Arctica islandica from 6 different sites - the Norwegian coast, Kattegat, Kiel Bay, White Sea, German Bight, and off northeast Iceland - covering a temperature and salinity gradient of 4-10°C (annual mean) and 25-34, respectively. Based on von Bertalanffy growth models and size-mass relationships, we computed organic matter production of body (PSB) and of shell (PSS), whereas gonad production (PG) was estimated from the seasonal cycle in mass. Respiration (R) was computed by a model driven by body mass, temperature, and site. A. islandica populations differed distinctly in maximum life span (40 y in Kiel Bay to 197 y in Iceland), but less in growth performance (phi' ranged from 2.41 in the White Sea to 2.65 in Kattegat). Individual lifetime energy throughput, as approximated by assimilation, was highest in Iceland (43,730 kJ) and lowest in the White Sea (313 kJ). Net growth efficiency ranged between 0.251 and 0.348, whereas lifetime energy investment distinctly shifted from somatic to gonad production with increasing life span; PS/PG decreased from 0.362 (Kiel Bay, 40 y) to 0.031 (Iceland, 197 y). Population annual energy budgets were derived from individual budgets and estimates of population mortality rate (0.035/y in Iceland to 0.173/y in Kiel Bay). Relationships between budget ratios were similar on the population level, albeit with more emphasis on somatic production; PS/ PG ranged from 0.196 (Iceland) to 2.728 (White Sea), and P/B ranged from 0.203-0.285/y. Life span is the principal determinant of the relationship between budget parameters, whereas temperature affects net growth efficiency only. In the White Sea population, both growth performance and net growth efficiency of A. islandica were lowest. We presume that low temperature combined with low salinity represent a particularly stressful environment for this species.

Radiosonde profiles and meteorological observations during Atlantic Expedition M2 in 1965 (IQSY) of RV "Meteor"

A radiosonde is described for measuring the upward and downward fluxes of visible light in the atmosphere. Photoresistors are used as sensors, the optical center of the spectral range beeing at 0.55 µ. The results of these flux-measurements obtained during the Atlantic Expedition 1965 with the research vessel "Meteor" are presented. The datas have been divided into three groups according to the amount of cloudiness. In group a) (small cloudiness) the extinction coefficient of the prevailing linear radiation is derived as a function of the height. Characteristics of airmasses of maritime or continental origin are shown. In group b) (cloud covered sky) microphysical quantities are determined from the radiative lapse rate in the clouds. The average radius of droplets is found to lie between 5.5 µm and 14.4 µm. The albedo of cloud surfaces varies between 25% and 54%, the transmission values are between 58% and 73%. One ascent through a Cirrus cloud of considerable vertical thickness is treated seperately. The observed distribution of extinction is compared with theoretical values in water clouds leading to the same order of magnitude. The relation between the albedo of the surface of the sea and the amount of cloudiness is discussed.

Analysis of the geometric altimetry to support aircraft optimal trajectories within the future 4d trajectory management

Over the past few years, the common practice within air traffic management has been that commercial aircraft fly by following a set of predefined routes to reach their destination. Currently, aircraft operators are requesting more flexibility to fly according to their prefer- ences, in order to achieve their business objectives. Due to this reason, much research effort is being invested in developing different techniques which evaluate aircraft optimal trajectory and traffic synchronisation. Also, the inefficient use of the airspace using barometric altitude overall in the landing and takeoff phases or in Continuous Descent Approach (CDA) trajectories where currently it is necessary introduce the necessary reference setting (QNH or QFE). To solve this problem and to permit a better airspace management born the interest of this research. Where the main goals will be to evaluate the impact, weakness and strength of the use of geometrical altitude instead of the use of barometric altitude. Moreover, this dissertation propose the design a simplified trajectory simulator which is able to predict aircraft trajectories. The model is based on a three degrees of freedom aircraft point mass model that can adapt aircraft performance data from Base of Aircraft Data, and meteorological information. A feature of this trajectory simulator is to support the improvement of the strategic and pre-tactical trajectory planning in the future Air Traffic Management. To this end, the error of the tool (aircraft Trajectory Simulator) is measured by comparing its performance variables with actual flown trajectories obtained from Flight Data Recorder information. The trajectory simulator is validated by analysing the performance of different type of aircraft and considering different routes. A fuel consumption estimation error was identified and a correction is proposed for each type of aircraft model. In the future Air Traffic Management (ATM) system, the trajectory becomes the fundamental element of a new set of operating procedures collectively referred to as Trajectory-Based Operations (TBO). Thus, governmental institutions, academia, and industry have shown a renewed interest for the application of trajectory optimisation techniques in com- mercial aviation. The trajectory optimisation problem can be solved using optimal control methods. In this research we present and discuss the existing methods for solving optimal control problems focusing on direct collocation, which has received recent attention by the scientific community. In particular, two families of collocation methods are analysed, i.e., Hermite-Legendre-Gauss-Lobatto collocation and the pseudospectral collocation. They are first compared based on a benchmark case study: the minimum fuel trajectory problem with fixed arrival time. For the sake of scalability to more realistic problems, the different meth- ods are also tested based on a real Airbus 319 El Cairo-Madrid flight. Results show that pseudospectral collocation, which has shown to be numerically more accurate and computa- tionally much faster, is suitable for the type of problems arising in trajectory optimisation with application to ATM. Fast and accurate optimal trajectory can contribute properly to achieve the new challenges of the future ATM. As atmosphere uncertainties are one of the most important issues in the trajectory plan- ning, the final objective of this dissertation is to have a magnitude order of how different is the fuel consumption under different atmosphere condition. Is important to note that in the strategic phase planning the optimal trajectories are determined by meteorological predictions which differ from the moment of the flight. The optimal trajectories have shown savings of at least 500 [kg] in the majority of the atmosphere condition (different pressure, and temperature at Mean Sea Level, and different lapse rate temperature) with respect to the conventional procedure simulated at the same atmosphere condition.This results show that the implementation of optimal profiles are beneficial under the current Air traffic Management (ATM).

Surface InGaAs nanostructures for sensing applications

El desarrollo de sensores está ganando cada vez mayor importancia debido a la concienciación ciudadana sobre el medio ambiente haciendo que su desarrollo sea muy elevado en todas las disciplinas, entre las que cabe destacar, la medicina, la biología y la química. A pesar de la existencia de estos dispositivos, este área está aún por mejorar, ya que muchos de los materiales propuestos hasta el momento e incluso los ya comercializados muestran importantes carencias de funcionamiento, eficiencia e integrabilidad entre otros. Para la mejora de estos dispositivos, se han propuesto diversas aproximaciones basadas en nanosistemas. Quizá, uno de las más prometedoras son las nanoestructuras de punto cuántico, y en particular los semiconductores III-V basados en la consolidada tecnología de los arseniuros, las cuáles ofrecen excelentes propiedades para su uso como sensores. Además, estudios recientes demuestran su gran carácter sensitivo al medio ambiente, la posibilidad de funcionalizar la superficie para la fabricación de sensores interdisciplinares y posibilididad de mejorar notablemente su eficiencia. A lo largo de esta tesis, nos centramos en la investigación de SQD de In0.5Ga0.5As sobre substratos de GaAs(001) para el desarrollo de sensores de humedad. La tesis abarca desde el diseño, crecimiento y caracterización de las muestras hasta la el posterior procesado y caracterización de los dispositivos finales. La optimización de los parámetros de crecimiento es fundamental para conseguir una nanoestructura con las propiedades operacionales idóneas para un fin determinado. Como es bien sabido en la literatura, los parámetros de crecimiento (temperatura de crecimiento, relación de flujos del elemento del grupo V y del grupo I II (V/III), velocidad de crecimiento y tratamiento térmico después de la formación de la capa activa) afectan directamente a las propiedades estructurales, y por tanto, operacionales de los puntos cuánticos (QD). En esta tesis, se realiza un estudio de las condiciones de crecimiento para el uso de In0.5Ga0.5As SQDs como sensores. Para los parámetros relacionados con la temperatura de crecimiento de los QDs y la relación de flujos V / I I I se utilizan los estudios previamente realizados por el grupo. Mientras que este estudio se centrará en la importancia de la velocidad de crecimiento y en el tratamiento térmico justo después de la nucleación de los QDs. Para ello, se establece la temperatura de creciemiento de los QDs en 430°C y la relación de flujos V/III en 20. Como resultado, los valores más adecuados que se obtienen para la velocidad de crecimiento y el tratamiento térmico posterior a la formación de los puntos son, respectivamente, 0.07ML/s y la realización de una bajada y subida brusca de la temperatura del substrato de 100°C con respecto a la temperatura de crecimiento de los QDs. El crecimiento a una velocidad lo suficientemente alta que permita la migración de los átomos por la superficie, pero a su vez lo suficientemente baja para que se lleve a cabo la nucleación de los QDs; en combinación con el tratamiento brusco de temperatura que hace que se conserve la forma y composición de los QDs, da lugar a unos SQDs con un alto grado de homogeneidad y alta densidad superficial. Además, la caracterización posterior indica que estas nanoestructuras de gran calidad cristalina presentan unas propiedades ópticas excelentes incluso a temperatura ambiente. Una de las características por la cual los SQD de Ino.5Gao.5As se consideran candidatos prometedores para el desarrollo de sensores es el papel decisivo que juega la superficie por el mero hecho de estar en contacto directo con las partículas del ambiente y, por tanto, por ser capaces de interactuar con sus moléculas. Así pues, con el fin de demostrar la idoneidad de este sistema para dicha finalidad, se evalúa el impacto ambiental en las propiedades ópticas y eléctricas de las muestras. En un primer lugar, se analiza el efecto que tiene el medio en las propiedades ópticas. Para dicha evaluación se compara la variación de las propiedades de emisión de una capa de puntos enterrada y una superficial en distintas condiciones externas. El resultado que se obtiene es muy claro, los puntos enterrados no experimentan un cambio óptico apreciable cuando se varían las condiciones del entorno; mientras que, la emisión de los SQDs se modifica significativamente con las condiciones del medio. Por una parte, la intensidad de emisión de los puntos superficiales desaparece en condiciones de vacío y decrece notablemente en atmósferas secas de gases puros (N2, O2). Por otra parte, la fotoluminiscencia se conserva en ambientes húmedos. Adicionalmente, se observa que la anchura a media altura y la longitud de onda de emisión no se ven afectadas por los cambios en el medio, lo que indica, que las propiedades estructurales de los puntos se conservan al variar la atmósfera. Estos resultados apuntan directamente a los procesos que tienen lugar en la superficie entre estados confinados y superficiales como responsables principales de este comportamiento. Así mismo, se ha llevado a cabo un análisis más detallado de la influencia de la calidad y composición de la atmósfera en las propiedades ópticas de los puntos cuánticos superficiales. Para ello, se utilizan distintas sustancias con diferente polaridad, composición atómica y masa molecular. Como resultado se observa que las moléculas de menor polaridad y más pesadas causan una mayor variación en la intensidad de emisión. Además, se demuestra que el oxígeno juega un papel decisivo en las propiedades ópticas. En presencia de moléculas que contienen oxígeno, la intensidad de fotoluminiscencia disminuye menos que en atmósferas constituidas por especies que no contienen oxígeno. Las emisión que se observa respecto a la señal en aire es del 90% y del 77%, respectivamente, en atmósferas con presencia o ausencia de moléculas de oxígeno. El deterioro de la señal de emisión se atribuye a la presencia de defectos, enlaces insaturados y, en general, estados localizados en la superficie. Estos estados actúan como centros de recombinación no radiativa y, consecuentemente, se produce un empeoramiento de las propiedades ópticas de los SQDs. Por tanto, la eliminación o reducción de la densidad de estos estados superficiales haría posible una mejora de la intensidad de emisión. De estos experimentos de fotoluminiscencia, se deduce que las interacciones entre las moléculas presentes en la atmósfera y la superficie de la muestra modifican la superficie. Esta alteración superficial se traduce en un cambio significativo en las propiedades de emisión. Este comportamiento se atribuye a la posible adsorción de moléculas sobre la superficie pasivando los centros no radiativos, y como consecuencia, mejorando las propiedades ópticas. Además, los resultados demuestran que las moléculas que contienen oxígeno con mayor polaridad y más ligeras son adsorbidas con mayor facilidad, lo que hace que la intensidad óptica sufra variaciones despreciables con respecto a la emisión en aire. Con el fin de desarrollar sensores, las muestras se procesan y los dispositivos se caracterizan eléctricamente. El procesado consiste en dos contactos cuadrados de una aleación de Ti/Au. Durante el procesado, lo más importante a tener en cuenta es no realizar ningún ataque o limpieza que pueda dañar la superficie y deteriorar las propiedades de las nanostructuras. En este apartado, se realiza un análisis completo de una serie de tres muestras: GaAs (bulk), un pozo cuántico superficial (SQW) de Ino.5Gao.5As y SQDs de Ino.5Gao.5As. Para ello, a cada una de las muestras se le realizan medidas de I-V en distintas condiciones ambientales. En primer lugar, siguiendo los resultados obtenidos ópticamente, se lleva a cabo una comparación de la respuesta eléctrica en vacío y aire. A pesar de que todas las muestras presentan un carácter más resistivo en vacío que en aire, se observa una mayor influencia sobre la muestra de SQD. En vacío, la resistencia de los SQDs decrece un 99% respecto de su valor en aire, mientras que la variación de la muestras de GaAs e Ino.5Gao.5As SQW muestran una reducción, respectivamente, del 31% y del 20%. En segundo lugar, se realiza una evaluación aproximada del posible efecto de la humedad en la resistencia superficial de las muestras mediante la exhalación humana. Como resultado se obtiene, que tras la exhalación, la resistencia disminuye bruscamente y recupera su valor inicial cuando dicho proceso concluye. Este resultado preliminar indica que la humedad es un factor crítico en las propiedades eléctricas de los puntos cuánticos superficiales. Para la determinación del papel de la humedad en la respuesta eléctrica, se somete a las muestras de SQD y SQW a ambientes con humedad relativa (RH, de la siglas del inglés) controlada y se analiza el efecto sobre la conductividad superficial. Tras la variación de la RH desde 0% hasta el 70%, se observa que la muestra SQW no cambia su comportamiento eléctrico al variar la humedad del ambiente. Sin embargo, la respuesta de la muestra SQD define dos regiones bien diferenciadas, una de alta sensibilidad para valores por debajo del 50% de RH, en la que la resistencia disminuye hasta en un orden de magnitud y otra, de baja sensibilidad (>50%), donde el cambio de la resistencia es menor. Este resultado resalta la especial relevancia no sólo de la composición sino también de la morfología de la nanostructura superficial en el carácter sensitivo de la muestra. Por último, se analiza la influencia de la iluminación en la sensibilidad de la muestra. Nuevamente, se somete a las muestras SQD y SQW a una irradiación de luz de distinta energía y potencia a la vez que se varía controladamente la humedad ambiental. Una vez más, se observa que la muestra SQW no presenta ninguna variación apreciable con las alteraciones del entorno. Su resistencia superficial permanece prácticamente inalterable tanto al modificar la potencia de la luz incidente como al variar la energía de la irradiación. Por el contrario, en la muestra de SQD se obtiene una reducción la resistencia superficial de un orden de magnitud al pasar de condiciones de oscuridad a iluminación. Con respecto a la potencia y energía de la luz incidente, se observa que a pesar de que la muestra no experimenta variaciones notables con la potencia de la irradiación, esta sufre cambios significativos con la energía de la luz incidente. Cuando se ilumina con energías por encima de la energía de la banda prohibida (gap) del GaAs (Eg ~1.42 eV ) se produce una reducción de la resistencia de un orden de magnitud en atmósferas húmedas, mientras que en atmósferas secas la conductividad superficial permanece prácticamente constante. Sin embargo, al inicidir con luz de energía menor que Eg, el efecto que se produce en la respuesta eléctrica es despreciable. Esto se atribuye principalmente a la densidad de portadores fotoactivados durante la irradiación. El volumen de portadores excita dos depende de la energía de la luz incidente. De este modo, cuando la luz que incide tiene energía menor que el gap, el volumen de portadores generados es pequeño y no contribuye a la conductividad superficial. Por el contrario, cuando la energía de la luz incidente es alta (Eg), el volumen de portadores activados es elevado y éstos contribuyen significantemente a la conductividad superficial. La combinación de ambos agentes, luz y humedad, favorece el proceso de adsorción de moléculas y, por tanto, contribuye a la reducción de la densidad de estados superficiales, dando lugar a una modificación de la estructura electrónica y consecuentemente favoreciendo o dificultando el transporte de portadores. ABSTRACT Uncapped three-dimensional (3D) nanostructures have been generally grown to assess their structural quality. However, the tremendous growing importance of the impact of the environment on life has become such nanosystems in very promising candidates for the development of sensing devices. Their direct exposure to changes in the local surrounding may influence their physical properties being a perfect sign of the atmosphere quality. The goal of this thesis is the research of Ino.5Gao.5As surface quantum dots (SQDs) on GaAs(001), covering from their growth to device fabrication, for sensing applications. The achievement of this goal relies on the design, growth and sample characterization, along with device fabrication and characterization. The first issue of the thesis is devoted to analyze the main growth parameters affecting the physical properties of the Ino.5Gao.5As SQDs. It is well known that the growing conditions (growth temperature , deposition rate, V/III flux ratio and treatment after active layer growth) directly affect the physical properties of the epilayer. In this part, taking advantage of the previous results in the group regarding Ino.5Gao.5As QD growth temperature and V/III ratio, the effect of the growth rate and the temperature treatment after QDs growth nucleation is evaluated. Setting the QDs growth temperature at 430°C and the V/III flux ratio to ~20, it is found that the most appropriate conditions rely on growing the QDs at 0.07ML/s and just after QD nucleation, rapidly dropping and again raising 100°C the substrate temperature with respect to the temperature of QD growth. The combination of growing at a fast enough growth rate to promote molecule migration but sufficiently slow to allow QD nucleation, together with the sharp variation of the temperature preserving their shape and composition yield to high density, homogeneous Ino.5Gao.5As SQDs. Besides, it is also demonstrated that this high quality SQDs show excellent optical properties even at room temperature (RT). One of the characteristics by which In0.5Ga0.5As/GaAs SQDs are considered promising candidates for sensing applications is the crucial role that surface plays when interacting with the gases constituting the atmosphere. Therefore, in an attempt to develop sensing devices, the influence of the environment on the physical properties of the samples is evaluated. By comparing the resulting photoluminescence (PL) of SQDs with buried QDs (BQDs), it is found that BQDs do not exhibit any significant variation when changing the environmental conditions whereas, the external conditions greatly act on the SQDs optical properties. On one hand, it is evidenced that PL intensity of SQDs sharply quenches under vacuum and clearly decreases under dry-pure gases atmospheres (N2, O2). On the other hand, it is shown that, in water containing atmospheres, the SQDs PL intensity is maintained with respect to that in air. Moreover, it is found that neither the full width at half maximun nor the emission wavelength manifest any noticeable change indicating that the QDs are not structurally altered by the external atmosphere. These results decisively point to the processes taking place at the surface such as coupling between confined and surface states, to be responsible of this extraordinary behavior. A further analysis of the impact of the atmosphere composition on the optical characteristics is conducted. A sample containing one uncapped In0.5Ga0.5As QDs layer is exposed to different environments. Several solvents presenting different polarity, atomic composition and molecular mass, are used to change the atmosphere composition. It is revealed that low polarity and heavy molecules cause a greater variation on the PL intensity. Besides, oxygen is demonstrated to play a decisive role on the PL response. Results indicate that in presence of oxygen-containing molecules, the PL intensity experiments a less reduction than that suffered in presence of nonoxygen-containing molecules, 90% compared to 77% signal respect to the emission in air. In agreement with these results, it is demonstrated that high polarity and lighter molecules containing oxygen are more easily adsorbed, and consequently, PL intensity is less affected. The presence of defects, unsaturated bonds and in general localized states in the surface are proposed to act as nonradiative recombination centers deteriorating the PL emission of the sample. Therefore, suppression or reduction of the density of such states may lead to an increase or, at least, conservation of the PL signal. This research denotes that the interaction between sample surface and molecules in the atmosphere modifies the surface characteristics altering thus the optical properties. This is attributed to the likely adsoption of some molecules onto the surface passivating the nonradiative recombination centers, and consequently, not deteriorating the PL emission. Aiming for sensors development, samples are processed and electrically characterized under different external conditions. Samples are processed with two square (Ti/Au) contacts. During the processing, especial attention must be paid to the surface treatment. Any process that may damage the surface such as plasma etching or annealing must be avoided to preserve the features of the surface nanostructures. A set of three samples: a GaAs (bulk), In0.5Ga0.5As SQDs and In0.5Ga0.5As surface quantum well (SQW) are subjected to a throughout evaluation. I-V characteristics are measured following the results from the optical characterization. Firstly, the three samples are exposed to vacuum and air. Despite the three samples exhibit a more resistive character in vacuum than in air, it is revealed a much more clear influence of the pressure atmosphere in the SQDs sample. The sheet resistance (Rsh) of SQDs decreases a 99% from its response value under vacuum to its value in air, whereas Rsh of GaAs and In0.5Ga0.5As SQW reduces its value a 31% and a 20%, respectively. Secondly, a rough analysis of the effect of the human breath on the electrical response evidences the enormous influence of moisture (human breath is composed by several components but the one that overwhelms all the rest is the high concentration of water vapor) on the I-V characteristics. Following this result, In0.5Ga0.5As SQDs and In0.5Ga0.5As SQW are subjected to different controlled relative humidity (RH) environments (from 0% to 70%) and electrically characterized. It is found that SQW shows a nearly negligible Rsh variation when increasing the RH in the surroundings. However, the response of SQDs to changes in the RH defines two regions. Below 50%, high sensitive zone, Rsh of SQD decreases by more than one order of magnitude, while above 50% the dependence of Rsh on the RH becomes weaker. These results remark the role of the surface and denote the existence of a finite number of surface states. Nevertheless, most significantly, they highlight the importance not only of the material but also of the morphology. Finally, the impact of the illumination is determined by means of irradiating the In0.5Ga0.5As SQDs and In0.5Ga0.5As SQW samples with different energy and power sources. Once again, SQW does not exhibit any correlation between the surface conductivity and the external conditions. Rsh remains nearly unalterable independently of the energy and power of the incident light. Conversely, Rsh of SQD experiences a decay of one order of magnitude from dark-to-photo conditions. This is attributed to the less density of surface states of SQW compared to that of SQDs. Additionally, a different response of Rsh of SQD with the energy of the impinging light is found. Illuminating with high energy light results in a Rsh reduction of one order of mag nitude under humid atmospheres, whereas it remains nearly unchanged under dry environments. On the contrary, light with energy below the bulk energy bandgap (Eg), shows a negligible effect on the electrical properties regardless the local moisture. This is related to the density of photocarriers generated while lighting up. Illuminating with excitation energy below Eg affects a small absorption volume and thus, a low density of photocarriers may be activated leading to an insignificant contribution to the conductivity. Nonetheless, irradiating with energy above the Eg can excite a high density of photocarriers and greatly improve the surface conductivity. These results demonstrate that both illumination and humidity are therefore needed for sensing. The combination of these two agents improves the surface passivation by means of molecule adsorption reducing the density of surface states, thus modifying the electronic structures, and consequently, promoting the carrier motion.

Very low temperatures, their attainment and uses : a survey of the physical principles underlying the attainment of extremely low temperatures and of their technical and scientific applications, as illustrated in a special exhibition held in the Science museum--March-May, 1936 /

"Chart of fixed points and temperature scales": p. [3] of cover.

Physiological thermoregulation in a crustacean? Heart rate hysteresis in the freshwater crayfish Cherax destructor

Differential heart rates during heating and cooling (heart rate hysteresis) are an important thermoregulatory mechanism in ectothermic reptiles. We speculate that heart rate hysteresis has evolved alongside vascularisation, and to determine whether this phenomenon occurs in a lineage with vascularised circulatory systems that is phylogenetically distant from reptiles, we measured the response of heart rate to convective heat transfer in the Australian freshwater crayfish, Cherax destructor. Heart rate during convective heating (from 20 to 30 degreesC) was significantly faster than during cooling for any given body temperature. Heart rate declined rapidly immediately following the removal of the heat source, despite only negligible losses in body temperature. This heart rate 'hysteresis' is similar to the pattern reported in many reptiles and, by varying peripheral blood flow, it is presumed to confer thermoregulatory benefits particularly given the thermal sensitivity of many physiological rate functions in crustaceans. (C) 2004 Published by Elsevier Inc.

Effect of metal chlorides on the sintering and densification of hydroxyapatite adsorbent

This work is part of a series of studies dealing with the evaluation of the effects of major elements of solid waste, especially metallic oxides, nitrates, sulfates, and chlorides, on the sintering and the densification of calcium hydroxyapatite (Ca-HAP) adsorbent. The effects of chloride salts of potassium (KCl) and zinc (ZnCl2) on sintering and densification of Ca-HAP were studied using surface area reduction and shrinkage measurements. The addition of KCl (2% w/w) activated the sintering process by bringing a swift reduction in surface area and lowering the densification temperature. However, a low final densification was achieved. Increasing the amount of this additive to 10% w/w further lowered the final densification and lowered the densification temperature of hydroxyapatite by 150 degrees C. On the other hand, the addition of 2 wt % of ZnCl2 deactivated the sintering process by slowing down the densification process and raising the densification temperature. However, the reduction of surface area was comparable to that of Ca-HAP. The densification rate contained two or more rate maxima indicating the additives (salts) bring multiple speeds in the densification process.

The effects of nitrogen application and assimilate availability on engorged pollen production and spikelet sterility in rice

Increased rates of nitrogen fertilizer application lead to increased spikelet sterility. A field experiment was conducted to investigate the effects on engorged pollen production and spikelet sterility, of nitrogen and assimilate availability during microspore development, in two rice cultivars (Doongara and Amaroo) grown under two different water depths. Despite the temperature not being low enough during microspore development to cause spikelet sterility, the number of engorged pollen grains was lower in cv. Doongara than in cv. Amaroo. Nitrogen application decreased the number of engorged pollen grains per anther through increased spikelet density. Nitrogen application increased spikelet sterility as a result of increased panicle density showing pronounced indirect effect of N on spikelet sterility. Engorged pollen number was also closely related (r = -0.636*) to the nitrogen content of the leaf blade, indicating a direct negative effect of plant N status on engorged pollen production. The results suggest that the intrinsic pollen producing ability is the key element in the difference in cold tolerance between the two cultivars, particularly under high N rates. Opening the canopy for increased solar radiation interception by the treated plants increased the level of engorged pollen, indicating the importance of immediate assimilate availability for engorged pollen production. Shading reduced crop growth rate, but did not effect engorged pollen production. There was no effect of variation in assimilates production on spikelet sterility.

Kinetic studies of the metathesis of 1-hexene using Re2O7/γ-Al2O3 and the synthesis and metathesis of oxazolines

The kinetics of the metathesis of 1-hexene using Re2O7/-Al_2O_3 as the catalyst were investigated under a variety of conditions. The experiments were carried out under high vacuum conditions. The product solutions were characterised by gas liquid chromatography and mass spectroscopy. The initial kinetics of the metathesis of 1-hexene showed that the reaction was first order in the weight of the catalyst and second order in the concentration of 1-hexene. A kinetic scheme which correlated the experimental data with the metallocarbene chain mechanism postulated by Herisson and Chauvin and the kinetics of the reaction was explained using a model based on the Langmuir-Hinshelwood theory. The low conversion of 1-hexene to its products is due to termination reactions which most likely occur by the decomposition of the metallocyclobutane intermediate to produce a cyclopropane derivative and an inactive centre. The optimum temperature for the metathesis of 1-hexene over Re_2O_7/-Al2O3 is 45oC and above this temperature, the rate of metathesis decreases rapidly. Co-catalysts alter the active sites for metathesis so that the catalyst is more selective to the metathesis of 1-hexene. However, the regeneration of metathesis activity is much worse for promoted catalysts than for the unpromoted. The synthesis and metathesis of 4,4-dimethyl-2-allowbreak (9-decenyl)-1,3-oxazoline and 4,4-dimethyl-2-allowbreak (3-pentenyl)-1,3-oxazoline was attempted and the products were analysed by thin layer chromatography, infra-red, 13C and 1H nmr and mass spectroscopy. Obtaining the oxazolines in a good yield with high purity was difficult and consequently metathesis of the impure products did not occur.

Seawater carbonate chemistry, nutrient uptake and biological processes of coral Stylophora pistillata during experiments, 2011

The effects of ocean acidification and elevated seawater temperature on coral calcification and photosynthesis have been extensively investigated over the last two decades, whereas they are still unknown on nutrient uptake, despite their importance for coral energetics. We therefore studied the separate and combined impacts of increases in temperature and pCO2 on phosphate, ammonium, and nitrate uptake rates by the scleractinian coral S. pistillata. Three experiments were performed, during 10 days i) at three pHT conditions (8.1, 7.8, and 7.5) and normal temperature (26°C), ii) at three temperature conditions (26°, 29°C, and 33°C) and normal pHT(8.1), and iii) at three pHT conditions (8.1, 7.8, and 7.5) and elevated temperature (33°C). After 10 days of incubation, corals had not bleached, as protein, chlorophyll, and zooxanthellae contents were the same in all treatments. However, photosynthetic rates significantly decreased at 33°C, and were further reduced for the pHT 7.5. The photosynthetic efficiency of PSII was only decreased by elevated temperature. Nutrient uptake rates were not affected by a change in pH alone. Conversely, elevated temperature (33°C) alone induced an increase in phosphate uptake but a severe decrease in nitrate and ammonium uptake rates, even leading to a release of nitrogen into seawater. Combination of high temperature (33°C) and low pHT(7.5) resulted in a significant decrease in phosphate and nitrate uptake rates compared to control corals (26°C, pHT = 8.1). These results indicate that both inorganic nitrogen and phosphorus metabolism may be negatively affected by the cumulative effects of ocean warming and acidification.

Laser Phototherapy as Topical Prophylaxis Against Radiation-Induced Xerostomia

The common consequences of radiotherapy (RT) to the head and neck are oral mucositis, xerostomia, and severe pain. The aim of this study was to verify how laser phototherapy (LPT) used for oral mucositis could influence xerostomia symptoms and hyposalivation of patients undergiong RT. Patients were divided into two groups: 12 individuals receiving three laser irradiations per week (G1) and 10 patients receiving one laser irradiation per week (G2). A diode laser (660 nm, 6 J/cm(2), 0.24 J, 40mW) was used until completely healing of the lesions or the end of the RT. At the first and last laser sessions, whole resting and stimulated saliva were collected, and questionnaires were administered. According to Wilcoxon and Student statistical test, xerostomia for G1 was lower than for G2 (p<0.05), and salivary flow rate was no different before and after RT, except for stimulated collection of G2, which was lower (p<0.05). Our results suggest that LPT can be beneficial as an auxiliary therapy for hypofunction of salivary glands.

Substrate orientation effect on potential fluctuations in multiquantum wells of GaAs/AlGaAs

The photoluminescence (PL) technique as a function of temperature and excitation intensity was used to study the optical properties of multiquantum wells (MQWs) of GaAs/Al(x)Ga(1-x)As grown by molecular beam epitaxy on GaAs substrates oriented in the [100], [311]A, and [311]B directions. The asymmetry presented by the PL spectra of the MQWs with an apparent exponential tail in the lower-energy side and the unusual behavior of the PL peak energy versus temperature (blueshift) at low temperatures are explained by the exciton localization in the confinement potential fluctuations of the heterostructures. The PL peak energy dependence with temperature was fitted by the expression proposed by Passler [Phys. Status Solidi B 200, 155 (1997)] by subtracting the term sigma(2)(E)/k(B)T, which considers the presence of potential fluctuations. It can be verified from the PL line shape, the full width at half maximum of PL spectra, the sigma(E) values obtained from the adjustment of experimental points, and the blueshift maximum values that the samples grown in the [311]A/B directions have higher potential fluctuation amplitude than the sample grown in the [100] direction. This indicates a higher degree of the superficial corrugations for the MQWs grown in the [311] direction. (C) 2008 American Institute of Physics.

Development of composite adsorbents of carbon and intercalated clay for N2 and O2 adsorption: A preliminary study

Composite adsorbents of carbon and alumina intercalated montmorillonite were prepared and characterized by adsorption of N-2 and O-2 at various temperatures. The effects of pyrolysis, temperature, heating rate, subsequent degassing, and doping of cations and anions were investigated. The adsorption capacities of the composite adsorbents developed at higher temperatures (0 and -79 degrees C) are found to be larger than those of normal alumina pillared clays. The experimental results showed that the framework of these adsorbents is made of alumina particles and clay sheets while the pyrolyzed carbon distributes in the space of interlayers and interpillars. The pores between the carbon particles, clay sheets, and alumina pillars are very narrow with very strong adsorption forces, leading to enhanced adsorption capacities at 0 and -79 degrees C. The composite adsorbents exhibit features similar to those of carbonaceous adsorbents. Their pore structures, adsorption capacities, and selectivities to oxygen can be tailored by a controlled degassing procedure. Meanwhile, ions can be doped into the adsorbents to modify their adsorption properties, as usually observed for oxide adsorbents like zeolite and pillared clays. Such flexibility in pore structure tailoring is a potential advantage of the composite adsorbents developed for their adsorption and separation applications. (C) 1999 Academic Press.

Transport properties of strongly correlated metals: A dynamical mean-field approach

The temperature dependence of the transport properties of the metallic phase of a frustrated Hubbard model on the hypercubic lattice at half-filling is calculated. Dynamical mean-held theory, which maps the Hubbard model onto a single impurity,Anderson model that is solved self-consistently, and becomes exact in the limit of large dimensionality, is used. As the temperature increases there is a smooth crossover from coherent Fermi liquid excitations at low temperatures to incoherent excitations at high temperatures. This crossover leads to a nonmonotonic temperature dependence for the resistance, thermopower, and Hall coefficient, unlike in conventional metals. The resistance smoothly increases from a quadratic temperature dependence at low temperatures to large values which can exceed the Mott-Ioffe-Regel value ha/e(2) (where a is a lattice constant) associated with mean free paths less than a lattice constant. Further signatures of the thermal destruction of quasiparticle excitations are a peak in the thermopower and the absence of a Drude peak in the optical conductivity. The results presented here are relevant to a wide range of strongly correlated metals, including transition metal oxides, strontium ruthenates, and organic metals.

Effect of storage time and conditions on the hardness and cooking quality of adzuki (Vigna angularis)

A storage trial of two varieties of adzuki (Vigna angularis), Bloodwood and Erimo, produced in Australia, was conducted to determine the effect of various combinations of temperature, humidity and length of storage on bean quality. The beans were stored for up to 6 mo under the following conditions: temperature (10, 20 and 30degreesC), relative humidity (RH) (40 and 65%). Storage of adzuki at elevated temperature (30degreesC) and low relative humidity (40%) resulted in the greatest loss of bean moisture, increase in hydration times and decrease in bean cooking quality, i.e. increased hardness of cooked beans. The best storage conditions for the preservation of adzuki quality were 10degreesC and 65% RH.