Proline content and protein patterns in Eucalyptus grandis shoots submitted to high and low temperature shocks

As respostas às mudanças de temperatura de plantas aclimatadas e não aclimatadas de E. grandis cultivadas in vitro foram avaliadas considerando alterações dos níveis de prolina e proteínas solúveis totais. Análises de proteínas solúveis através de SDS-PAGE e prolina foram realizadas após 12h a 12ºC (aclimatação ao frio) ou a 33ºC (aclimatação ao calor), e imediatamente depois dos choques térmicos a 41ºC e 0ºC. Análises também foram realizadas após um período de 24h depois dos choques térmicos (período de recuperação). O tratamento de temperatura a 0ºC não alterou o padrão de proteínas nas plantas aclimatadas e não aclimatadas, entretanto a temperatura baixa induziu altos níveis de prolina, que se mantiveram relativamente altos após o período de recuperação. Três novas proteínas (90,5, 75 e 39 kDa), provavelmente HSPs, foram observadas nas plantas aclimatadas e não aclimatadas submetidas às temperaturas altas. As plantas expostas a 41ºC foram capazes de recuperar-se dos choques após o período de recuperação, entretanto não houve recuperação completa das plantas expostas às baixas temperaturas. O efeito da aclimatação sobre a recuperação (homeostasis) pode variar dependendo do parâmetro avaliado, tipo e duração do choque térmico.

Density, heat capacity and thermal conductivity of liquid egg products

Density, heat capacity and thermal conductivity of liquid egg products, such as egg white, egg yolk, whole egg and various white and yolk blends, were determined as affected by temperature and water content ranging from 273 to 311 K and 51.8 to 88.2% (mass), respectively. Polynomial models fitted the experimental data very well, showing a linear relationship both for temperature and water content. (c) 2005 Published by Elsevier Ltd.

Low temperature crystallization of SrBi2Ta2O9 thin films using microwave oven

SrBi2Ta2O9 thin films, produced by the polymeric precursor method, were crystallized at low temperature using a domestic microwave oven. A SiC susceptor were used to absorb the microwave energy and rapidly transfer the heat to the film. Low microwave power and short time have been used. The films thus obtained are crack-free, well-adhered, and fully crystallized, even when treated at 600 degreesC for 10 min. The microstructure displayed a polycrystalline nature with an elongate grain size comparable to the films obtained by the conventional treatment. The dielectric constant values are 240, 159 and 67, for the films treated at 600 degreesC, 650 degreesC and 700 degreesC, respectively, when the films are placed directly on the SiC susceptor. Electrical measurements revealed that the increase of the temperature treatment to 700 degreesC causes a complete loss of ferroelectricity due to degradation of the bottom interface. A 4 nun-ceramic wool put between the susceptor and the substrate minimizes the interface degradation leading to a dielectric constant, a dielectric loss, and a remnant polarization (2P(r)) of 181 muC/cm(2), 0.032 muC/cm(2), and 12.8 muC/cm(2), respectively, for a film treated at 750 degreesC for 20 min. (C) 2004 Elsevier B.V. All rights reserved.

Low-temperature synthesis of single-phase Co7Sb2O12

Polycrystalline Co7Sb2O12 compounds have been synthesized by a chemical route, which is based on a modified polymeric precursor method. In order to study the physical properties of the samples, X-ray diffraction (XRD), thermal analyses (TG and DSC), infrared spectroscopy (IR), specific surface area (BET), and magnetization measurements were performed on these materials. Characterization through XRD revealed that the samples are single-phase after a heat-treatment at 1100degreesC for 2h, while the X-ray patterns of the samples heat-treated at lower temperatures revealed the presence of additional Bragg reflections belonging to the Co6Sb2O6 phase. These data were analyzed by means of Rietveld refinement and further analyze showed that Co7Sb2O12 displays an inverse spinel crystalline structure. In this structure, the Co2+ ions occupy the eight tetrahedral positions, and the sixteen octahedral positions are randomly occupied by the Sb5+ and Co2+ ions. IR studies disclosed two strong absorption bands, v(1) and v(2), in the expected spectral range for a spinel-type binary oxide with space group Fd3m. Exploratory studies concerning the magnetic properties indicated that this sample presents a spin-glass transition at T-f similar to 64 K. (C) 2004 Elsevier B.V. All rights reserved.

Effect of Low-Temperature Storage on Diaeretiella rapae (McIntosh) (Hymenoptera: Braconidae)

We evaluated the effects of constant low-temperature storage on Diaeretiella rapae (McIntosh) (Braconidae, Aphidiinae). Diaeretiella rapae mummies were stored at 5 ± 1°C for 0-36 days. The percentage of D. rapae emergence varied (100-83%) after 0-32 days of storage. After 32 days, emergence reduced to 55%. According to our Probit analysis, 50% mortality (LT50) of the population of D. rapae was reached after 40 days of storage at 5°C. Storage for up to 32 days did not negatively affect emergence and survival. Cold exposure of D. rapae for 36 days did not influence morphological malformations, sex ratio, and emergence of the F1 generation. After 4-36 days of storage, D. rapae showed a gradual decrease in emergence, longevity, reproductive capacity, and F1 sex ratio. Diaeretiella rapae can be stored for up to 24 days at 5°C, at which time the percentage of parasitism and the F1 sex ratio remain above 38% and at 0.50, respectively. © 2013 Sociedade Entomológica do Brasil.

Low-temperature thermodynamic properties near the field-induced quantum critical point in NiCl2-4SC(NH2)(2)

We present a comprehensive experimental and theoretical investigation of the thermodynamic properties: specific heat, magnetization, and thermal expansion in the vicinity of the field-induced quantum critical point (QCP) around the lower critical field H-c1 approximate to 2 T in NiCl2-4SC(NH2)(2). A T-3/2 behavior in the specific heat and magnetization is observed at very low temperatures at H = H-c1, which is consistent with the universality class of Bose-Einstein condensation of magnons. The temperature dependence of the thermal expansion coefficient at H-c1 shows minor deviations from the expected T-1/2 behavior. Our experimental study is complemented by analytical calculations and quantum Monte Carlo simulations, which reproduce nicely the measured quantities. We analyze the thermal and the magnetic Gruneisen parameters, which are ideal quantities to identify QCPs. Both parameters diverge at H-c1 with the expected T-1 power law. By using the Ehrenfest relations at the second-order phase transition, we are able to estimate the pressure dependencies of the characteristic temperature and field scales.

Regioregular improvement on the oxidative polymerization of poly-3-octylthiophenes by slow addition of oxidant at low temperature

Many pathways can be used to synthesize polythiophenes derivatives. The polycondensation reactions performed with organometallics are preferred since they lead to regioregular polymers (with high content of heat-to-tail coupling) which have enhanced conductivity and luminescence. However, these pathways have several steps; the reactants are highly moisture sensitive and expensive. On the other hand, the oxidative polymerization using FeCl3 is a one-pot reaction that requires less moisture sensitive reactants with lower cost, although the most common reaction conditions lead to polymers with low regioregularity. Here, we report that by changing the reaction conditions, such as FeCl3 addition rate and reaction temperature, poly-3-octylthiophenes with different the regioregularities can be obtained, reaching about 80% of heat-to-tail coupling. Different molar mass distributions and polydispersivities were obtained. The preliminary results suggest that the oxidative polymerization process could be improved to yield polythiophenes with higher regioregularity degree and narrower molar mass distributions by just setting some reaction conditions. We also verified that it is possible to solvent extract part of the lower regioregular fraction of the polymer further improving the regioregularity degree. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Unmyelinated afferents in human skin and their responsiveness to low temperature

In humans, there are different types of cutaneous cold-sensitive afferents responsible for cold sensation and cold pain. Innocuous cold is primarily mediated by a population of slow A delta afferents, based on psychophysical and neurophysiological studies. Noxious cold (usually below 15 degrees C) is mediated, at least in part, by polymodal nociceptors. There is also a population of unmyelinated afferents responsive to innocuous low temperature, some of which also respond to heat, whose sensory function has not been completely defined. A paradoxical hot/burning evoked by cooling is unmasked by A-fibre block, and similar sensations are evoked by applying simultaneous cool and warm stimuli to adjacent skin areas. These unmyelinated fibres activated by innocuous cooling (and heating) may contribute to this hot/burning sensation, along with other thermoregulatory functions.

Implementation of a phenomenological evaporation model into a porous network simulation for water management in low temperature fuel cells

A phenomenological transition film evaporation model was introduced to a pore network model with the consideration of pore radius, contact angle, non-isothermal interface temperature, microscale fluid flows and heat and mass transfers. This was achieved by modeling the transition film region of the menisci in each pore throughout the porous transport layer of a half-cell polymer electrolyte membrane (PEM) fuel cell. The model presented in this research is compared with the standard diffusive fuel cell modeling approach to evaporation and shown to surpass the conventional modeling approach in terms of predicting the evaporation rates in porous media. The current diffusive evaporation models used in many fuel cell transport models assumes a constant evaporation rate across the entire liquid-air interface. The transition film model was implemented into the pore network model to address this issue and create a pore size dependency on the evaporation rates. This is accomplished by evaluating the transition film evaporation rates determined by the kinetic model for every pore containing liquid water in the porous transport layer (PTL). The comparison of a transition film and diffusive evaporation model shows an increase in predicted evaporation rates for smaller pore sizes with the transition film model. This is an important parameter when considering the micro-scaled pore sizes seen in the PTL and becomes even more substantial when considering transport in fuel cells containing an MPL, or a large variance in pore size. Experimentation was performed to validate the transition film model by monitoring evaporation rates from a non-zero contact angle water droplet on a heated substrate. The substrate was a glass plate with a hydrophobic coating to reduce wettability. The tests were performed at a constant substrate temperature and relative humidity. The transition film model was able to accurately predict the drop volume as time elapsed. By implementing the transition film model to a pore network model the evaporation rates present in the PTL can be more accurately modeled. This improves the ability of a pore network model to predict the distribution of liquid water and ultimately the level of flooding exhibited in a PTL for various operating conditions.

Implementation of the Heated Pulsed Theory using actively heated fiber optics: measurements of soil volumetric water content and soil volumetric heat capacity

Existe una creciente necesidad de hacer el mejor uso del agua para regadío. Una alternativa eficiente consiste en la monitorización del contenido volumétrico de agua (θ), utilizando sensores de humedad. A pesar de existir una gran diversidad de sensores y tecnologías disponibles, actualmente ninguna de ellas permite obtener medidas distribuidas en perfiles verticales de un metro y en escalas laterales de 0.1-1,000 m. En este sentido, es necesario buscar tecnologías alternativas que sirvan de puente entre las medidas puntuales y las escalas intermedias. Esta tesis doctoral se basa en el uso de Fibra Óptica (FO) con sistema de medida de temperatura distribuida (DTS), una tecnología alternativa de reciente creación que ha levantado gran expectación en las últimas dos décadas. Específicamente utilizamos el método de fibra calentada, en inglés Actively Heated Fiber Optic (AHFO), en la cual los cables de Fibra Óptica se utilizan como sondas de calor mediante la aplicación de corriente eléctrica a través de la camisa de acero inoxidable, o de un conductor eléctrico simétricamente posicionado, envuelto, alrededor del haz de fibra óptica. El uso de fibra calentada se basa en la utilización de la teoría de los pulsos de calor, en inglés Heated Pulsed Theory (HPP), por la cual el conductor se aproxima a una fuente de calor lineal e infinitesimal que introduce calor en el suelo. Mediante el análisis del tiempo de ocurrencia y magnitud de la respuesta térmica ante un pulso de calor, es posible estimar algunas propiedades específicas del suelo, tales como el contenido de humedad, calor específico (C) y conductividad térmica. Estos parámetros pueden ser estimados utilizando un sensor de temperatura adyacente a la sonda de calor [método simple, en inglés single heated pulsed probes (SHPP)], ó a una distancia radial r [método doble, en inglés dual heated pulsed probes (DHPP)]. Esta tesis doctoral pretende probar la idoneidad de los sistemas de fibra óptica calentada para la aplicación de la teoría clásica de sondas calentadas. Para ello, se desarrollarán dos sistemas FO-DTS. El primero se sitúa en un campo agrícola de La Nava de Arévalo (Ávila, España), en el cual se aplica la teoría SHPP para estimar θ. El segundo sistema se desarrolla en laboratorio y emplea la teoría DHPP para medir tanto θ como C. La teoría SHPP puede ser implementada con fibra óptica calentada para obtener medidas distribuidas de θ, mediante la utilización de sistemas FO-DTS y el uso de curvas de calibración específicas para cada suelo. Sin embargo, la mayoría de aplicaciones AHFO se han desarrollado exclusivamente en laboratorio utilizando medios porosos homogéneos. En esta tesis se utiliza el programa Hydrus 2D/3D para definir tales curvas de calibración. El modelo propuesto es validado en un segmento de cable enterrado en una instalación de fibra óptica y es capaz de predecir la respuesta térmica del suelo en puntos concretos de la instalación una vez que las propiedades físicas y térmicas de éste son definidas. La exactitud de la metodología para predecir θ frente a medidas puntuales tomadas con sensores de humedad comerciales fue de 0.001 a 0.022 m3 m-3 La implementación de la teoría DHPP con AHFO para medir C y θ suponen una oportunidad sin precedentes para aplicaciones medioambientales. En esta tesis se emplean diferentes combinaciones de cables y fuentes emisoras de calor, que se colocan en paralelo y utilizan un rango variado de espaciamientos, todo ello en el laboratorio. La amplitud de la señal y el tiempo de llegada se han observado como funciones del calor específico del suelo. Medidas de C, utilizando esta metodología y ante un rango variado de contenidos de humedad, sugirieron la idoneidad del método, aunque también se observaron importantes errores en contenidos bajos de humedad de hasta un 22%. La mejora del método requerirá otros modelos más precisos que tengan en cuenta el diámetro del cable, así como la posible influencia térmica del mismo. ABSTRACT There is an increasing need to make the most efficient use of water for irrigation. A good approach to make irrigation as efficient as possible is to monitor soil water content (θ) using soil moisture sensors. Although, there is a broad range of different sensors and technologies, currently, none of them can practically and accurately provide vertical and lateral moisture profiles spanning 0-1 m depth and 0.1-1,000 m lateral scales. In this regard, further research to fulfill the intermediate scale and to bridge single-point measurement with the broaden scales is still needed. This dissertation is based on the use of Fiber Optics with Distributed Temperature Sensing (FO-DTS), a novel approach which has been receiving growing interest in the last two decades. Specifically, we employ the so called Actively Heated Fiber Optic (AHFO) method, in which FO cables are employed as heat probe conductors by applying electricity to the stainless steel armoring jacket or an added conductor symmetrically positioned (wrapped) about the FO cable. AHFO is based on the classic Heated Pulsed Theory (HPP) which usually employs a heat probe conductor that approximates to an infinite line heat source which injects heat into the soil. Observation of the timing and magnitude of the thermal response to the energy input provide enough information to derive certain specific soil thermal characteristics such as the soil heat capacity, soil thermal conductivity or soil water content. These parameters can be estimated by capturing the soil thermal response (using a thermal sensor) adjacent to the heat source (the heating and the thermal sources are mounted together in the so called single heated pulsed probe (SHPP)), or separated at a certain distance, r (dual heated pulsed method (DHPP) This dissertation aims to test the feasibility of heated fiber optics to implement the HPP theory. Specifically, we focus on measuring soil water content (θ) and soil heat capacity (C) by employing two types of FO-DTS systems. The first one is located in an agricultural field in La Nava de Arévalo (Ávila, Spain) and employ the SHPP theory to estimate θ. The second one is developed in the laboratory using the procedures described in the DHPP theory, and focuses on estimating both C and θ. The SHPP theory can be implemented with actively heated fiber optics (AHFO) to obtain distributed measurements of soil water content (θ) by using reported soil thermal responses in Distributed Temperature Sensing (DTS) and with a soil-specific calibration relationship. However, most reported AHFO applications have been calibrated under laboratory homogeneous soil conditions, while inexpensive efficient calibration procedures useful in heterogeneous soils are lacking. In this PhD thesis, we employ the Hydrus 2D/3D code to define these soil-specific calibration curves. The model is then validated at a selected FO transect of the DTS installation. The model was able to predict the soil thermal response at specific locations of the fiber optic cable once the surrounding soil hydraulic and thermal properties were known. Results using electromagnetic moisture sensors at the same specific locations demonstrate the feasibility of the model to detect θ within an accuracy of 0.001 to 0.022 m3 m-3. Implementation of the Dual Heated Pulsed Probe (DPHP) theory for measurement of volumetric heat capacity (C) and water content (θ) with Distributed Temperature Sensing (DTS) heated fiber optic (FO) systems presents an unprecedented opportunity for environmental monitoring. We test the method using different combinations of FO cables and heat sources at a range of spacings in a laboratory setting. The amplitude and phase-shift in the heat signal with distance was found to be a function of the soil volumetric heat capacity (referred, here, to as Cs). Estimations of Cs at a range of θ suggest feasibility via responsiveness to the changes in θ (we observed a linear relationship in all FO combinations), though observed bias with decreasing soil water contents (up to 22%) was also reported. Optimization will require further models to account for the finite radius and thermal influence of the FO cables, employed here as “needle probes”. Also, consideration of the range of soil conditions and cable spacing and jacket configurations, suggested here to be valuable subjects of further study and development.

Specific heat capacity of Australian honeys from 35 to 165C as a function of composition using differential scanning calorimetry

Modulated temperature differential scanning calorimetry was used to investigate the specific heat capacity (C-p) of 10 Australian honeys within the processing and handling temperatures. The values obtained were found to be different from the literature values at certain temperatures, and are not predictable by the additive model. The C-p of each honey exhibited a cubic relationship (P < 0.001) with the temperature (T, C). In addition, the moisture (M, %), fructose (F, %) and glucose (G, %) contents of the honeys influenced their C-p. The following equation (r(2) = 0.92) was proposed for estimating C-p of honey, and is recommended for use in the honey industry and in research: C = 996.7 + 1.4 x 10(-3)T + 5.6 x 10(-5)T(2) - 2.4 x 10(-7)T(3) - 56.5M - 25.8F - 31.0G + 1.5(M * F) + 1.8(M * G) + 0.8(F * G) - 4.6 x 10(-2) (M * F * G).

Effect of preparation conditions on the formation of the active phase of carbon fiber catalytic systems for the low-temperature oxidation of carbon monoxide

We studied the effects of the composition of impregnating solution and heat treatment conditions on the activity of catalytic systems for the low-temperature oxidation of CO obtained by the impregnation of Busofit carbon-fiber cloth with aqueous solutions of palladium, copper, and iron salts. The formation of an active phase in the synthesized catalysts at different stages of their preparation was examined with the use of differential thermal and thermogravimetric analyses, X-ray diffraction analysis, X-ray photoelectron spectroscopy, and elemental spectral analysis. The catalytic system prepared by the impregnation of electrochemically treated Busofit with the solutions of PdCl, FeCl, CuBr, and Cu(NO ) and activated under optimum conditions ensured 100% CO conversion under a respiratory regime at both low (0.03%) and high (0.5%) carbon monoxide contents of air. It was found that the activation of a catalytic system at elevated temperatures (170-180°C) leads to the conversion of Pd(II) into Pd(I), which was predominantly localized in a near-surface layer. The promoting action of copper nitrate consists in the formation of a crystalline phase of the rhombic atacamite CuCl(OH). The catalyst surface is finally formed under the conditions of a catalytic reaction, when a joint Pd(I)-Cu(I) active site is formed. © 2014 Pleiades Publishing, Ltd.

Review of low-temperature vapour power cycle engines with quasi-isothermal expansion

External combustion heat cycle engines convert thermal energy into useful work. Thermal energy resources include solar, geothermal, bioenergy, and waste heat. To harness these and maximize work output, there has been a renaissance of interest in the investigation of vapour power cycles for quasi-isothermal (near constant temperature) instead of adiabatic expansion. Quasi-isothermal expansion has the advantage of bringing the cycle efficiency closer to the ideal Carnot efficiency, but it requires heat to be transferred to the working fluid as it expands. This paper reviews various low-temperature vapour power cycle heat engines with quasi-isothermal expansion, including the methods employed to realize the heat transfer. The heat engines take the form of the Rankine cycle with continuous heat addition during the expansion process, or the Stirling cycle with a condensable vapour as working fluid. Compared to more standard Stirling engines using gas, the specific work output is higher. Cryogenic heat engines based on the Rankine cycle have also been enhanced with quasi-isothermal expansion. Liquid flooded expansion and expander surface heating are the two main heat transfer methods employed. Liquid flooded expansion has been applied mainly in rotary expanders, including scroll turbines; whereas surface heating has been applied mainly in reciprocating expanders. © 2014 Elsevier Ltd.

Low-temperature organic Rankine cycle engine with isothermal expansion for use in desalination

Groundwater salinity is a widespread problem that contributes to the freshwater deficit of humanity. Consequently, where conventional energy supply is also lacking, organic Rankine cycle (ORC) engines are being considered as a feasible option to harness readily available low-grade heat (<180°C) to drive the desalination of the saline water via reverse osmosis (RO). However, this application is still not very well developed, and has significantly high specific energy consumption (SEC). Hence, this study explores the isothermal expansion of the ORC working fluid to achieve improved efficiency for driving a batch-RO desalination process, "DesaLink". Here, the working fluid is directly vaporized in the expansion cylinder which is heated externally by heat transfer fluid, thus obviating the need for a separate external boiler and high-pressure piping. Experimental investigations with R245fa have shown cycle efficiency of 8.8%. And it is predicted that the engine could drive DesaLink to produce 256 L of freshwater per 8 h per day, from 4000 ppm saline water, with a thermal and mechanical SEC of 2.5 and 0.36 kWh/m3, respectively, representing a significant improvement on previously reported or predicted SEC values. © 2014 © 2014 Balaban Desalination Publications. All rights reserved.

Low-temperature isothermal Rankine cycle for desalination

In brackish groundwater desalination, high recovery ratio (of fresh water from saline feed) is desired to minimise concentrate reject. To this effect, previous studies have developed a batch reverse osmosis (RO) desalination system, DesaLink, which proposed to expand steam in a reciprocating piston cylinder and transmit the driving force through a linkage crank mechanism to pressurise batches of saline water (recirculating) in a water piston cylinder unto RO membranes. However, steam is largely disadvantaged at operation from low temperature (< 150oC) thermal sources; and organic working fluids are more viable, though, the obtainable thermal cycle efficiencies are generally low with low temperatures. Consequently, this thesis proposed to investigate the use of organic working fluid Rankine cycle (ORC) with isothermal expansion, to drive the DesaLink machine, at improved thermal efficiency from low temperature thermal sources. Following a review of the methods of achieving isothermal expansion, ‘liquid flooded expansion’ and ‘expansion chamber surface heating’ were identified as potential alternative methods. Preliminary experimental comparative analysis of variants of the heated expansion chamber technique of effecting isothermal expansion favoured a heated plain wall technique, and as such was adopted for further optimisation and development. Further, an optimised isothermal ORC engine was built and tested at < 95oC heat source temperature, with R245fa working fluid – which was selected from 16 working fluids that were analysed for isothermal operation. Upon satisfactory performance of the test engine, a larger (10 times) version was built and coupled to drive the DesaLink system. Operating the integrated ORC-RO DesaLink system, gave freshwater (approximately 500 ppm) production of about 12 litres per hour (from 4000 ppm feed water) at a recovery ratio of about 0.7 and specific energy consumption of 0.34 kWh/m3; and at a thermal efficiency of 7.7%. Theoretical models characterising the operation and performance of the integrated system was developed and utilised to access the potential field performance of the system, when powered by two different thermal energy sources – solar and industrial bakery waste heat – as case studies.