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Thermal Evolution (thermal + evolution)
Selected AbstractsFormation of diffusion-hindering interlayers in metals in contact by dedicated thermal treatmentCRYSTAL RESEARCH AND TECHNOLOGY, Issue 1-2 2005D. C. Meyer Abstract Thermal evolution of the structure of Fe/Al multilayers (MLs) with nominal composition 5*(5 nm Al / 5 nm Fe) prepared by crossed-beam pulsed laser deposition is studied by wide-angle X-ray scattering and X-ray reflectometry after different temperature-time procedures of thermal treatments under high-vacuum conditions. In comparison to direct thermal annealing at temperatures of 250 °C and 275 °C, respectively, which results in nearly complete mixing of the MLs and formation of the FeAl intermetallic compound, quite different behaviour was found after dedicated thermal pretreatment. Annealing at successive growing temperatures before final annealing at temperatures mentioned, resulted in conservation of pronounced multilayer structure. From the results it is generalised, that also in the case of ML systems, the tendency of mixing a dedicated tuning of interface characteristics by thermal treatment allows for formation of diffusion-hindering interlayers. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Thermal evolution of pre-adult life history traits, geometric size and shape, and developmental stability in Drosophila subobscuraJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 6 2006M. SANTOS Abstract Replicated lines of Drosophila subobscura originating from a large outbred stock collected at the estimated Chilean epicentre (Puerto Montt) of the original New World invasion were allowed to evolve under controlled conditions of larval crowding for 3.5 years at three temperature levels (13, 18 and 22 °C). Several pre-adult life history traits (development time, survival and competitive ability), adult life history related traits (wing size, wing shape and wing-aspect ratio), and wing size and shape asymmetries were measured at the three temperatures. Cold-adapted (13 °C) populations evolved longer development times and showed lower survival at the highest developmental temperature. No divergence for wing size was detected following adaptation to temperature extremes (13 and 22 °C), in agreement with earlier observations, but wing shape changes were obvious as a result of both thermal adaptation and development at different temperatures. However, the evolutionary trends observed for the wing-aspect ratio were inconsistent with an adaptive hypothesis. There was some indication that wing shape asymmetry has evolutionarily increased in warm-adapted populations, which suggests that there is additive genetic variation for fluctuating asymmetry and that it can evolve under rapid environmental changes caused by thermal stress. Overall, our results cast strong doubts on the hypothesis that body size itself is the target of selection, and suggest that pre-adult life history traits are more closely related to thermal adaptation. [source] Thermal evolution of the orogenic lower crust during exhumation within a thickened Moldanubian root of the Variscan belt of Central EuropeJOURNAL OF METAMORPHIC GEOLOGY, Issue 2 2006L. TAJ, MANOVá Abstract At the eastern margin of the Bohemian Massif (Variscan belt of Central Europe), large bodies of felsic granulite preserve mineral assemblages and structures developed during the early stages of exhumation of the orogenic lower continental crust within the Moldanubian orogenic root. The development of an early steep fabric is associated with east,west-oriented compression and vertical extrusion of the high-grade rocks into higher crustal levels. The high-pressure mineral assemblage Grt-Ky-Kfs-Pl-Qtz-Liq corresponds to metamorphic pressures of ,18 kbar at ,850 °C, which are minimum estimates, whereas crystallization of biotite occurred at 13 kbar and ,790 °C during decompression with slight cooling. The late stages of the granulite exhumation were associated with lateral spreading of associated high-grade rocks over a middle crustal unit at ,4 kbar and ,700 °C, as estimated from accompanying cordierite-bearing gneisses. The internal structure of a contemporaneously intruded syenite is coherent with late structures developed in felsic granulites and surrounding gneisses, and the magma only locally explored the early subvertical fabric of the felsic granulite during emplacement. Consequently, the emplacement age of the syenite provides an independent constraint on the timing of the final stages of exhumation and allows calculation of exhumation and cooling rates, which for this part of the Variscan orogenic root are 2.9,3.5 mm yr,1 and 7,9.4 °C Myr,1, respectively. The final part of the temperature evolution shows very rapid cooling, which is interpreted as the result of juxtaposition of hot high-grade rocks with a cold upper-crustal lid. [source] Thermal evolution of rotating hybrid starsMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2007Miao Kang ABSTRACT As a neutron star spins down, the nuclear matter is continuously converted into quark matter due to the core density increase, and then latent heat is released. We have investigated the thermal evolution of neutron stars undergoing such deconfinement phase transition. We have taken into account the conversion in the frame of the general theory of relativity. The released energy has been estimated as a function of changed rate of deconfinement baryon number. The numerical solutions to the cooling equation are seen to be very different from those without the heating effect. The results show that neutron stars may be heated to higher temperatures which is well matched with pulsar's data despite the onset of fast cooling in neutron stars with quark matter cores. It is also found that the heating effect has a magnetic field strength dependence. This feature could be particularly interesting for high temperatures of low-field millisecond pulsars at a later stage. The high temperature could fit the observed temperature for PSR J0437,4715. [source] Thermal evolution of a rotating strange star in the colour superconductivity phaseMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2006Xiaoping Zheng ABSTRACT Under the combination effect of recommencement heating due to the spin-down of strange stars (SSs) and heat preservation due to the weak conduction heat of the crust, Cooper pair breaking and formation (PBF) in colour superconducting quark matter arises. We investigate the cooling of SSs with a crust in the colour superconductivity phase including both deconfinement heating (DH) and the PBF process. We find that DH can delay the thermal evolution of SSs and the PBF process suppresses the early temperature rise of the stars. The cooling SSs behave within the brightness constraint of young compact objects when the colour superconductivity gap is small enough. [source] Temperature dependent larval resource allocation shaping adult body size in Drosophila melanogasterJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 6 2003Z. Bochdanovits Abstract Geographical variation in Drosophila melanogaster body size is a long-standing problem of life-history evolution. Adaptation to a cold climate invariably produces large individuals, whereas evolution in tropical regions result in small individuals. The proximate mechanism was suggested to involve thermal evolution of resource processing by the developing larvae. In this study an attempt is made to merge proximate explanations, featuring temperature sensitivity of larval resource processing, and ultimate approaches focusing on adult and pre-adult life-history traits. To address the issue of temperature dependent resource allocation to adult size vs. larval survival, feeding was stopped at several stages during the larval development. Under these conditions of food deprivation, two temperate and two tropical populations reared at high and low temperatures produced different adult body sizes coinciding with different probabilities to reach the adult stage. In all cases a phenotypic trade-off between larval survival and adult size was observed. However, the underlying pattern of larval resource allocation differed between the geographical populations. In the temperate populations larval age but not weight predicted survival. Temperate larvae did not invest accumulated resources in survival, instead they preserved larval biomass to benefit adult weight. In other words, larvae from temperate populations failed to re-allocate accumulated resources to facilitate their survival. A low percentage of the larvae survived to adulthood but produced relatively large flies. Conversely, in tropical populations larval weight but not age determined the probability to reach adulthood. Tropical larvae did not invest in adult size, but facilitated their own survival. Most larvae succeeded in pupating but then produced small adults. The underlying physiological mechanism seemed to be an evolved difference in the accessibility of glycogen reserves as a result of thermal adaptation. At low rearing temperatures and in the temperate populations, glycogen levels tended to correlate positively with adult size but negatively with pupation probability. The data presented here offer an explanation of geographical variation in body size by showing that thermal evolution of resource allocation, specifically the ability to access glycogen storage, is the proximate mechanism responsible for the life-history trade-off between larval survival and adult size. [source] INFLUENCE OF FLOW REGIMES ON TEMPERATURE HETEROGENEITIES WITHIN A SCRAPED SURFACE HEAT EXCHANGERJOURNAL OF FOOD PROCESS ENGINEERING, Issue 3 2000ERIC DUMONT ABSTRACT In industrial applications, fluids processed in scraped surface heat exchangers often show large temperature heterogeneities at the exchanger outlet. Our study deals with the thermal evolution of model fluids, Newtonian and non-Newtonian in heating or cooling conditions and allows us to link the phenomena of appearance and disappearance of temperature heterogeneities with the changes in the flow pattern within the exchanger. Based on literature data dedicated to scraped surface heat exchangers as well as to annular spaces without blades, we have shown that thermally homogeneous products can be obtained when Taylor vortices appear in the exchanger. Studies done on the exchanger with and without blades show that the thermal behavior is basically the same for both geometries but with a difference in critical Taylor numbers value for change in heat transfer regime. The presence of blades promotes the appearance of instabilities at lower values of generalized Taylor number (Tag= 10 with blades; Tag= 39 without blades). It shows as well, that the value of critical Taylor number in scraped surface heat exchanger closely depends upon the flow-rate even for very low values for Reaxg (Reaxg < <1). [source] Variations in the transient prograde geothermal gradient from chloritoid-staurolite equilibria: a case study from the Barrovian and Buchan-type domains in the Bohemian MassifJOURNAL OF METAMORPHIC GEOLOGY, Issue 1 2007M. KO Abstract Thermodynamic modelling of metamorphic rocks increases the possibilities of deciphering prograde paths that provide important insights into early orogenic evolution. It is shown that the chloritoid,staurolite transition is not only an indicator of temperature on prograde P,T paths, but also a useful indicator of pressure. The approach is applied to the Moravo-Silesian eastern external belt of the Bohemian Massif, where metamorphic zones range from biotite to staurolite-sillimanite. In the staurolite zone, inclusions of chloritoid occur in garnet cores, while staurolite is included at garnet rims and is widespread in the matrix. Chloritoid XFe = 0.91 indicates transition to staurolite at 5 kbar and 550 °C and consequently, an early transient prograde geothermal gradient of 29 °C km,1. The overall elevated thermal evolution is then reflected in the prograde transition of staurolite to sillimanite and in the achievement of peak temperature of 660 °C at a relatively low pressure of 6.5 kbar. To the south and to the west of the studied area, high-grade metamorphic zones record a prograde path evolution from staurolite to kyanite and development of sillimanite on decompression. Transition of chloritoid to staurolite was reported in two places, with chloritoid XFe = 0.75,0.80, occurring at 8,10 kbar and 560,580 °C, and indicating a transient prograde geothermal gradient of 16,18 °C km,1. These data show variable barric evolutions along strike and across the Moravo-Silesian domain. Elevated prograde geothermal gradient coincides with areas of Devonian sedimentation and volcanism, and syn- to late Carboniferous intrusions. Therefore, we interpret it as a result of heat inherited from Devonian rifting, further fuelled by syntectonic Carboniferous intrusions. [source] The Tertiary collision-related thermal history of the NW HimalayaJOURNAL OF METAMORPHIC GEOLOGY, Issue 9 2002G. Foster Abstract Garnet-whole rock Sm-Nd data are presented for several samples from the Indian plate in the NW Himalaya. These dates, when combined with the P-T evolution of the Indian plate rocks, allow a thorough reconstruction of the prograde thermal evolution of this region (including the Nanga Parbat Haramosh Massif) during the early Cenozoic. Combining these data with Rb-Sr mineral separate ages, enables us to constrain the post-peak cooling history of this region of the Himalaya. The data presented here indicate that the upper structural levels of the cover rocks of the Nanga Parbat Haramosh Massif, and similar rocks in the Kaghan Valley to the south-west, were buried to pressures of c. 10 kbar and heated to temperatures of c. 650 °C at 46,41 Ma. The burial of the lower structural levels of the cover rocks of the Nanga Parbat Haramosh Massif, to similar depths but at higher temperatures of c. 700 °C, occurred slightly later at 40,36 Ma, synchronous with the imbrication and exhumation of the amphibolite- and eclogite-grade rocks of the Kaghan Valley. In contrast, the cover rocks of the Nanga Parbat Haramosh Massif were not imbricated or exhumed at this time, remaining buried beneath the Kohistan-Ladakh Island Arc until the syntaxis-forming event that occurred in the last 10 Myr. The timing of tectonic events in the north-western Himalaya differs from that experienced by the rocks of the Central Himalaya in that the earliest stage of burial in the NW Himalaya predates that of the Central Himalaya by c. 6 Myr. This difference may result from the diachronous nature of the Indo-Asian collision or may simply be a reflection of differing timing at different structural levels. [source] Mineralogy, petrology, and thermal evolution of the Benton LL6 chondriteMETEORITICS & PLANETARY SCIENCE, Issue S7 2003Erin L. WALTON Internally, the meteorite comprises light-colored, subangular to subrounded clasts embedded in a dark grey-colored matrix. Clasts comprise the same mineral phases as the matrix, as well as chondrules and larger (50,100 ,m) single mineral grains (mainly olivine and orthopyroxene). Composite (polyphase) clasts can be several millimeters in length. Numerous examples of post-brecciation and post-annealing shearing and displacement at the micron to millimeter scale occur in the form of shock veins. Benton is a shock stage S3 chondrite, which experienced shock pressures on the order of 15,20 GPa, with an estimated post-shock temperature increase of 100,150°C. Benton's history comprises a sequence of events as follows: 1) chondrule formation and initial assembly; 2) brecciation; 3) thermal metamorphism; and 4) shock veining. Events (2) and (4) can be equated with distinct impact events, the former representing bombardment of target material that remained in situ or collisionally fragmented during metamorphism, and then gravitationally reassembled, the latter probably with release from the source body to yield a meteorite. Thermal metamorphism post-dates brecciation. The mean equilibration temperature recorded in the Benton LL6 chondrite is 890°C, obtained using the two pyroxene geothermometer. [source] Importance of the accretion process in asteroid thermal evolution: 6 Hebe as an exampleMETEORITICS & PLANETARY SCIENCE, Issue 5 2003Amitabha Ghosh Previous simulations of asteroid heat transfer have assumed that accretion was instantaneous. For the first time, we present a thermal model that assumes a realistic (incremental) accretion scenario and takes into account the heat budget produced by decay of 26Al during the accretion process. By modeling 6 Hebe (assumed to be the H chondrite parent body), we show that, in contrast to results from instantaneous accretion models, an asteroid may reach its peak temperature during accretion, the time at which different depth zones within the asteroid attain peak metamorphic temperatures may increase from the center to the surface, and the volume of high-grade material in the interior may be significantly less than that of unmetamorphosed material surrounding the metamorphic core. We show that different times of initiation and duration of accretion produce a spectrum of evolutionary possibilities, and thereby, highlight the importance of the accretion process in shaping an asteroid's thermal history. Incremental accretion models provide a means of linking theoretical models of accretion to measurable quantities (peak temperatures, cooling rates, radioisotope closure times) in meteorites that were determined by their thermal histories. [source] Chondrule thermal history from unequilibrated H chondrites: A transmission and analytical electron microscopy studyMETEORITICS & PLANETARY SCIENCE, Issue 10 2002C. Ferraris Nanotextural and nanochemical data indicate similar thermal evolution for chondrules of the same textural groups; minor, yet meaningful differences occur among the different groups. Olivine is the earliest phase formed and crystallizes between 1500 and 1400 °C. Protoenstatite crystallizes at temperatures higher than 1350,1200 °C; it later inverts to clinoenstatite in the 1250,1200 °C range. Enstatite is surrounded by pigeonitic or (less frequently) augitic rims; the minimal crystallization temperature for the rims is 1000 °C; high pigeonite later inverts to low pigeonite, between 935 and 845 °C. The outer pigeonitic or augitic rims are constantly exsolved, producing sigmoidal augite or enstatite precipitates; sigmoidal precipitates record exsolution temperatures between 1000 and 640 °C. Cooling rate (determined using the speedometer based upon ortho-clinoenstatite intergrowth) was in the order of 50,3000 °C/h at the clinoenstatite-orthoenstatite transition temperature (close to 1250,1200 °C), but decreased to 5,10 °C/h or slower at the exsolution temperature (between 1000 and 650 °C), thus revealing nonlinear cooling paths. Nanoscale observations indicate that the individual chondrules formed and cooled separately from 1500 °C down to at least 650 °C. Accretion into chondritic parent body occurred at temperatures lower than 650 °C. [source] Thermal evolution of rotating hybrid starsMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2007Miao Kang ABSTRACT As a neutron star spins down, the nuclear matter is continuously converted into quark matter due to the core density increase, and then latent heat is released. We have investigated the thermal evolution of neutron stars undergoing such deconfinement phase transition. We have taken into account the conversion in the frame of the general theory of relativity. The released energy has been estimated as a function of changed rate of deconfinement baryon number. The numerical solutions to the cooling equation are seen to be very different from those without the heating effect. The results show that neutron stars may be heated to higher temperatures which is well matched with pulsar's data despite the onset of fast cooling in neutron stars with quark matter cores. It is also found that the heating effect has a magnetic field strength dependence. This feature could be particularly interesting for high temperatures of low-field millisecond pulsars at a later stage. The high temperature could fit the observed temperature for PSR J0437,4715. [source] Thermal evolution of a rotating strange star in the colour superconductivity phaseMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2006Xiaoping Zheng ABSTRACT Under the combination effect of recommencement heating due to the spin-down of strange stars (SSs) and heat preservation due to the weak conduction heat of the crust, Cooper pair breaking and formation (PBF) in colour superconducting quark matter arises. We investigate the cooling of SSs with a crust in the colour superconductivity phase including both deconfinement heating (DH) and the PBF process. We find that DH can delay the thermal evolution of SSs and the PBF process suppresses the early temperature rise of the stars. The cooling SSs behave within the brightness constraint of young compact objects when the colour superconductivity gap is small enough. [source] Analysis of heat transfer in autoclave technologyPOLYMER COMPOSITES, Issue 5 2001Vincenza Antonucci In autoclave technology, polymer based composites are manufactured under the application of pressure and heat. The heat transferred between the energy carrying fluid and the bag-composite-tool element activates exothermic curing reactions, leading to composite consolidation. The convective heat transfer mechanism is the most relevant aspect controlling the rate of chemical and physical transformations associated with composite curing. Moreover, the fluidodynamic regime that results from the interactions between the autoclave and the tool geometry, even if totally predictable in theory, is unattainable in practice. In this study, the heat transfer phenomena occurring during the autoclave manufacturing cycle have been analyzed. The assumption of a negligible through-the-thickness thermal gradient led to simplified energy balance equations. In this case, the thermal evolution of the manufacturing elements has been completely determined by two parameters: the global convective heat exchange coefficient, setting the rate of the heat transfer between the autoclave environment and the bag-composite-tool element, and the adiabatic temperature rise, establishing the relevance of the polymerization exotherm. A scaling analysis has been performed in order to identify the dimensionless parameters controlling the autoclave process. The developed semitheoretical methodology has been extensively tested by comparison with experimental data from an industrial autoclave. [source] Secular changes of LOD associated with a growth of the inner coreASTRONOMISCHE NACHRICHTEN, Issue 4 2006C. Denis Abstract From recent estimates of the age of the inner core based on the theory of thermal evolution of the core, we estimate that nowadays the growth of the inner core may perhaps contribute to the observed overall secular increase of LOD caused mainly by tidal friction (i.e., 1.72 ms per century) by a relative decrease of 2 to 7 µs per century. Another, albeit much less plausible, hypothesis is that crystallization of the inner core does not produce any change of LOD, but makes the inner core rotate differentially with respect to the outer core and mantle. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Unravelling the multi-stage burial history of the Swiss Molasse Basin: integration of apatite fission track, vitrinite reflectance and biomarker isomerisation analysisBASIN RESEARCH, Issue 1 2006Martin Mazurek ABSTRACT A complex basin evolution was studied using various methods, including thermal constraints based on apatite fission-track (AFT) analysis, vitrinite reflectance (VR) and biomarker isomerisation, in addition to a detailed analysis of the regional stratigraphic record and of the lithological properties. The study indicates that (1) given the substantial amount of data, the distinction and characterisation of successive stages of heating and burial in the same area are feasible, and (2) the three thermal indicators (AFT, VR and biomarkers) yield internally consistent thermal histories, which supports the validity of the underlying kinetic algorithms and their applicability to natural basins. All data pertaining to burial and thermal evolution were integrated in a basin model, which provides constraints on the thickness of eroded sections and on heat flow over geologic time. Three stages of basin evolution occurred in northern Switzerland. The Permo-Carboniferous strike,slip basin was characterised by high geothermal gradients (80,100°C km,1) and maximum temperature up to 160°C. After the erosion of a few hundreds of metres in the Permian, the post-orogenic, epicontinental Mesozoic basin developed in Central Europe, with subsidence triggered by several stages of rifting. Geothermal gradients in northern Switzerland during Cretaceous burial were relatively high (35,40°C km,1), and maximum temperature typically reached 75°C (top middle Jurassic) to 100°C (base Mesozoic). At least in the early Cretaceous, a stage of increased heat flow is needed to explain the observed maturity level. After erosion of 600,700 m of Cretaceous and late Jurassic strata during the Paleocene, the wedge-shaped Molasse Foreland Basin developed. Geothermal gradients were low at this time (,20°C km,1). Maximum temperature of Miocene burial exceeded that of Cretaceous burial in proximal parts (<35 km from the Alpine front), but was lower in more distal parts (>45 km). Thus, maximum temperature as well as maximum burial depth ever reached in Mesozoic strata occurred at different times in different regions. Since the Miocene, 750,1050 m were eroded, a process that still continues in the proximal parts of the basin. Current average geothermal gradients in the uppermost 2500 m are elevated (32,47°C km,1). They are due to a Quaternary increase of heat flow, most probably triggered by limited advective heat transport along Paleozoic faults in the crystalline basement. [source] | |||||||||||||