Approximate controllability for the semilinear heat equation in RN involving gradient terms

We prove the approximate controllability of the semilinear heat equation in R^N, when the nonlinear term is globally Lipschitz and depends both on the state u and its spatial gradient Ñu. The approximate controllability is viewed as the limit of a sequence of optimal control problems. In order to avoid the difficulties related to the lack of compactness of the Sobolev embeddings, we work with the similarity variables and use weighted Sobolev spaces.

Modeling heat transfer in die milling

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Using phenology to assess urban heat islands in tropical and temperate regions

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Spin-dependent beating patterns in thermoelectric properties: Filtering the carriers of the heat flux in a Kondo adatom system

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Occurrence of heat waves in Triangulo Mineiro and Alto Paranaiba and their effect on milk yield and feed intake in cattle

The aim of this study was to estimate milk production and food consumption during the occurrence of heat waves in the Triangulo Mineiro and Alto Paranaiba, MG by means of bioclimatic zoning based on the Temperature and Humidity Index (THI). Therefore a history of heat wave occurrence between the years 2000-2010 was compiled. The decline in milk production (DMP) and reduced food consumption (RFC) were simulated in cities where periods of heat waves were identified. Frutal and Ituiutaba had the highest rate of heat wave occurrence per year. The DMP and RFC showed bioclimatic differences between the cities of Uberaba, Ituiutaba and Frutal. The cities with the best bioclimatic conditions were Sacramento and Patrocinio, as they presented a THI classified outside of the emergency range, with a night THI of below 76 and without heat waves. Therefore, the occurrence of heat waves can impair food intake and decrease milk production, thereby most effectively demonstrating the effects of thermal stress on dairy cows in the Triangulo Mineiro and Alto Paranaiba, MG region.

The strategic application of elecytolyte balance to minimize heat stress in broilers

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Strategic feed formulation for relation of electrolytes to promote performance and prevent heat stress in broilers

An experiment was conducted to evaluate the impact in relation of dietary electrolytes, based on changes in the balance Na+K-Cl (DEB) and the ratio (K+Cl)/Na (DER) on the performance and survival of broilers subjected to acute heat stress. A total of 1575 male broiler chicks from 1 to 46 d of age were allocated in a 5x3 factorial arrangement in a completely randomized design, totaling of 15 treatments with 3 replicates of 35 birds each. The treatments consisted of 5 diets with electrolyte balances, arising from combinations DEB/DER (150/3, 250/2, 250/3, 250/4 and 350/3), associated with different times of application or not of the acute heat stress on birds at 25 and 36 d old. All diets were cornsoybean meal based and formulated to meet or exceed NRC requirements. Chicks had ad libitum access to feed and water in floor pens with wood shavings as litter. It was possible to verify that a DEB of 250 mEq/kg and a DER very close to the 3:1 providing a more nutritionally adequate diet. There was, however, the impossibility of obtaining a more suitable electrolyte ratio for a very low DEB (150 mEq/kg) or very high (350 mEq/kg) and also, to a very narrow DER (2:1) or very wide (4:1), due to an unfavorable performance and survival rate of birds in these conditions electrolytes adjustments of K, Na and Cl. There was clear indication, with significant difference (P < 0.05), that the DER has the potential to improve the performance of broilers, since simultaneous adjustment made in DEB, even in conditions of acute stress. The results of performance and survival rate of this study also indicate clearly that DER could not replace the DEB, and vice versa, in practical diets for broilers. Therefore, it can be affirmed that the strategic formulation of the correct electrolyte balance for DEB and DER enhances the performance and is able to prevent the effect of heat stress in broiler chickens, leading to better performance and survival.

Dietary electrolytes and thermal conditioning: minimizing heat stress in broilers

In tropical climates the heat is one of the major constraints to production of broilers and is responsible for inducing a high mortality, especially in the finishing phase. Thus, the objective of this study was to compare the thermal conditioning early (TC) and feed formulation using dietary electrolytes (DE). Therefore, the electrolyte balance of K+Na-Cl was set at 350 mEq/kg and electrolyte ratio (K+Cl)/Na) in the 3:1 program PPFR (http://www.fmva.unesp.br/ppfr). A total of 300 Cobb 500 1-dold male broiler chicks was randomly allocated to 24 floor pens with six replicates per treatment in a 2x2 factorial arrangement (with and without TC and with and without DE). Dietary treatments consisted: (T1) a traditional diet without TC; (T2) traditional diet with TC; (T3) with the application of dietary electrolyte and without TC and (T4) application of dietary electrolyte with TC. The thermal conditioning was conducted at 5 d of age (36°C for 24 h), only half of the batch (150 birds). After this period, all birds were transferred to boxes of 1.5 x3m (12 birds / box), with wood shavings reused as litter. Chicks were exposed to acute stress (36°C) for 8 h at the age 36, in all treatments, being electronically monitored the temperature and humidity of the microclimate of the birds. Feed and water were provided ad libitum, even during periods of stress. Were measured performance data (weight gain, feed intake and feed conversion) and mortality rate. The early thermal conditioning (T2) and effect of dietary electrolytes (T3) were effective to minimize the mortality of broilers subjected to acute heat stress with a significant difference (P<0.05), without prejudice on broiler performance. The results also showed that there was a more favorable effect when applied dietary electrolytes and thermal conditioning simultaneously (treatment T4). However, for the treatment none of these strategies has been applied (T1), the mortality rate was 83% over that in which they were applied (T4). It was concluded from this study that both techniques: the thermal conditioning early as the dietary electrolytes are efficacious in minimize the damaging effects caused by heat broiler.

Strategies to minimize heat stress in broilers chickens

The objective of this study was to evaluate the application of early age thermal conditioning (TC) and dietary electrolyte balances (DEB) to minimize the effect of heat stress. A total of 240 Cobb 500 1-d-old male broiler chicks was randomly allocated to 24 floor pens with six replicates per treatment in a 2x2 factorial arrangement (with and without TC and with and without DEB). Dietary treatments consisted: (T1) a traditional diet without TC; (T2) traditional diet with TC; (T3) with the application of dietary electrolyte and without TC and (T4) application of dietary electrolyte with TC. The thermal conditioning was conducted at 5 d of age (36°C for 24 h), only half of the batch (120 birds). After this period, all birds were transferred to boxes of 1.5 x 3m (10 birds / box), with wood shavings reused as litter. Chicks were exposed to chronic heat stress (32°C) for 6 h from 35 to 39 d of age, in all treatments, being electronically monitored the temperature and humidity of the microclimate of the birds. Feed and water were provided ad libitum, even during periods of stress. Were measured performance data (weight gain, feed intake and feed conversion) and mortality rate. Data were subjected to ANOVA using the GLM procedures of SAS. The results of this study demonstrated no interaction effects of all evaluated parameters (performance and mortality). Therefore, no synergism occurred when both strategies (TC and DEB) were applied. Only the first week there was prejudice on broiler performance with the application of the TC and apparently the technique of early age thermal conditioning no improve the resistance of broilers to chronic heat stress. On the other hand, DEB had significantly favorable effects (P<0.05) on performance and minimized mortality immediately after application of the TC.

Experimental and numerical study of heat transfer in hot machined workpiece using infrared radiation

One of the greatest problems found in machining is related to the cutting tool wear. A way for increasing the tool life points out to the development of materials more resistant to wear, such as PCBN inserts. However, the unit cost of these tools is considerable high, around 10 to 20 times compared to coated carbide insert, besides its better performance occurs in high speeds requiring modern machine tools. Another way, less studied is the workpiece heating in order to diminish the shear stress material and thus reduce the machining forces allowing an increase of tool life. For understanding the heat transfer influences by conduction in this machining process, a mathematical model was developed to allow a simplified numerical simulation, using the finite element method, in order to determine the temperature profiles inside the workpiece.

Saturated flow boiling heat transfer and critical heat flux in small horizontal flattened tubes

This paper presents experimental results for flow boiling heat transfer coefficient and critical heat flux (CHF) in small flattened tubes. The tested flattened tubes have the same equivalent internal diameter of 2.2 mm, but different aspect height/width ratios (H/W) of 1/4, 1/2, 2 and 4. The experimental data were compared against results for circular tubes using R134a and R245fa as working fluids at a nominal saturation temperature of 31 degrees C. For mass velocities higher than 200 kg/m(2)s, the flattened and circular tubes presented similar heat transfer coefficients. Such a behavior is related to the fact that stratification effects are negligible under conditions of higher mass velocities. Heat transfer correlations from the literature, usually developed using only circular-channel experimental data, predicted the flattened tube results for mass velocities higher than 200 kg/m(2)s with mean absolute error lower than 20% using the equivalent diameter to account for the geometry effect. Similarly, the critical heat flux results were found to be independent of the tube aspect ratio when the same equivalent length was kept. Equivalent length is a new parameter which takes into account the channel heat transfer area. The CHF correlations for round tubes predicted the flattened tube data relatively well when using the equivalent diameter and length. Furthermore, a new proposed CHF correlation predicted the present flattened tube data with a mean absolute error of 5%. (C) 2012 Elsevier Ltd. All rights reserved.

An inverse method to estimate the moving heat source in machining process

The present work propounds an inverse method to estimate the heat sources in the transient two-dimensional heat conduction problem in a rectangular domain with convective bounders. The non homogeneous partial differential equation (PDE) is solved using the Integral Transform Method. The test function for the heat generation term is obtained by the chip geometry and thermomechanical cutting. Then the heat generation term is estimated by the conjugated gradient method (CGM) with adjoint problem for parameter estimation. The experimental trials were organized to perform six different conditions to provide heat sources of different intensities. This method was compared with others in the literature and advantages are discussed. (C) 2012 Elsevier Ltd. All rights reserved.

Disruption of endogenous tidal rhythms of larval release linked to food supply and heat stress in an intertidal barnacle

The timing of larval release may greatly affect the survivorship and distribution of pelagic stages and reveal important aspects of life history tactics in marine invertebrates. Endogenous rhythms of breeding individuals and populations are valuable indicators of selected strategies because they are free of the neutral effect of stochastic environmental variation. The high-shore intertidal barnacle Chthamalus bisinuatus exhibits endogenous tidal and tidal amplitude rhythms in a way that larval release would more likely occur during fortnightly neap periods at high tide. Such timing would minimize larval loss due to stranding and promote larval retention close to shore. This fully explains temporal patterns in populations facing the open sea and inhabiting eutrophic areas. However, rhythmic activity breaks down to an irregular pattern in a population within the São Sebastião Channel subjected to large variation of food supply around a mesotrophic average. Peaks of chl a concentration precede release events by 6 d, suggesting resource limitation for egg production within the channel. Also, extreme daily temperatures imposing mortality risk correlate to release rate just 1 d ahead, suggesting a terminal reproductive strategy. Oceanographic conditions apparently dictate whether barnacles follow a rhythmic trend of larval release supported by endogenous timing or, alternatively, respond to the stochastic variation of key environmental factors, resulting in an erratic temporal pattern.

Heat conduction in a chain of harmonic and anharmonic oscillators under the presence of an energy conserving noise

Reproducing Fourier's law of heat conduction from a microscopic stochastic model is a long standing challenge in statistical physics. As was shown by Rieder, Lebowitz and Lieb many years ago, a chain of harmonically coupled oscillators connected to two heat baths at different temperatures does not reproduce the diffusive behaviour of Fourier's law, but instead a ballistic one with an infinite thermal conductivity. Since then, there has been a substantial effort from the scientific community in identifying the key mechanism necessary to reproduce such diffusivity, which usually revolved around anharmonicity and the effect of impurities. Recently, it was shown by Dhar, Venkateshan and Lebowitz that Fourier's law can be recovered by introducing an energy conserving noise, whose role is to simulate the elastic collisions between the atoms and other microscopic degrees of freedom, which one would expect to be present in a real solid. For a one-dimensional chain this is accomplished numerically by randomly flipping - under the framework of a Poisson process with a variable “rate of collisions" - the sign of the velocity of an oscillator. In this poster we present Langevin simulations of a one-dimensional chain of oscillators coupled to two heat baths at different temperatures. We consider both harmonic and anharmonic (quartic) interactions, which are studied with and without the energy conserving noise. With these results we are able to map in detail how the heat conductivity k is influenced by both anharmonicity and the energy conserving noise. We also present a detailed analysis of the behaviour of k as a function of the size of the system and the rate of collisions, which includes a finite-size scaling method that enables us to extract the relevant critical exponents. Finally, we show that for harmonic chains, k is independent of temperature, both with and without the noise. Conversely, for anharmonic chains we find that k increases roughly linearly with the temperature of a given reservoir, while keeping the temperature difference fixed.

Analisi del circuito di regolazione responsabile del controllo trascrizionale dei geni Heat-Shock in Helicobacter pylori

Helicobacter pylori, un patogeno umano in grado di colonizzare la nicchia gastrica, è associato a patologie del tratto gastrointestinale di varia gravità. Per sopravvivere nell’ambiente ostile dello stomaco dell’ospite, e mettere in atto un’infezione persistente, il batterio si serve di una serie di fattori di virulenza che includono anche le proteine Heat Shock (chaperone). I principali geni codificanti le proteine chaperone in H. pylori sono organizzati in tre operoni trascritti dall’RNA polimerasi contenente il fattore sigma vegetativo σ80. La trascrizione di due dei tre operoni è regolata negativamente da due regolatori trascrizionali, HspR e HrcA, mentre il terzo operone è represso solo da HspR. Fino ad ora, studi molecolari per la comprensione del ruolo di ciascuna proteina nel controllo trascrizionale dei geni heat shock sono stati ostacolati dalla citotossicità ed insolubilità di HrcA quando espressa in sistemi eterologhi. In questo lavoro, è stata analizzata la sequenza amminoacidica di HrcA ed è stata confermata sperimentalmente la predizione bioinformatica della sua associazione con la membrana interna. La citotossicità e l’insolubilità di HrcA in E. coli sono state alleviate inducendone l’espressione a 42°C. Saggi in vitro con le proteine ricombinanti purificate, HspR e HrcA, hanno consentito di definire i siti di legame dei due repressori sui promotori degli operoni heat shock. Ulteriori saggi in vitro hanno suggerito che l’affinità di HrcA per gli operatori è aumentata dalla chaperonina GroESL. Questi dati contribuiscono parzialmente alla comprensione del meccanismo di repressione della trascrizione espletato da HrcA e HspR e permettono di ipotizzare il coinvolgimento di altri regolatori trascrizionali. L’analisi di RNA estratti dal ceppo selvatico e dai mutanti hrcA, hspR e hrcA/hspR di H.pylori su DNAmacroarrays non ha evidenziato il coinvolgimento di altri regolatori trascrizionali, ma ha permesso l’identificazione di un gruppo di geni indotti da HrcA e/ HspR. Questi geni sono coinvolti nella biosintesi e regolazione dell’apparato flagellare, suggerendo un’interconnessione tra la risposta heat shock e la motilità e chemiotassi del batterio.