Littérature scientifique sur le sujet « Local Artificial Substrate »

Controlling nucleation and growth is crucial in biological and artificial mineralization and self-assembly processes. The nucleation barrier is determined by the chemistry of the interfaces at which crystallization occurs and local supersaturation. Although chemically tailored substrates and lattice mismatches are routinely used to modify energy landscape at the substrate/nucleus interface and thereby steer heterogeneous nucleation, strategies to combine this with control over local supersaturations have remained virtually unexplored. Here we demonstrate simultaneous control over both parameters to direct the positioning and growth direction of mineralizing compounds on preselected polymorphic substrates. We exploit the polymorphic nature of calcium carbonate (CaCO3) to locally manipulate the carbonate concentration and lattice mismatch between the nucleus and substrate, such that barium carbonate (BaCO3) and strontium carbonate (SrCO3) nucleate only on specific CaCO3 polymorphs. Based on this approach we position different materials and shapes on predetermined CaCO3 polymorphs in sequential steps, and guide the growth direction using locally created supersaturations. These results shed light on nature’s remarkable mineralization capabilities and outline fabrication strategies for advanced materials, such as ceramics, photonic structures, and semiconductors.

This paper presents the fabrication of Si3N4-based artificial basilar membrane (ABM) with ZnO nanopillar array. Structure of ABMs is composed of the logarithmically varying membrane fabricated by MEMS process and piezonanopillar array grown on the Si3N4-based membrane by hydrothermal method. We fabricate the bottom substrate containing Si3N4-based membrane for inducing the resonant motions from the sound wave and the top substrates of electrodes for acquiring electric signals. In addition, the bonding process of the top and bottom substrate is performed to build ABM device. Depending on sound wave input of the specific frequency, specific location of the ABM produces a resonant behavior. Then a local deformation of the piezonanopillar array produces an electric signal between top and bottom electrode. As experimental results of the fabricated ABM, the measured resonant frequencies are 2.34 kHz, 3.97 kHz, and 8.80 kHz and the produced electrical voltages on each resonant frequency are 794 nV, 398 nV, and 89 nV. Thus, this fabricated ABM device shows the possibility of being a biomimetic acoustic device.

The construction of an artificial channel to a small embayment in the Chetumal Bay coastal lagoon complex, located on the Caribbean coast of Mexico, provided an opportunity to evaluate how large environmental changes influenced the structure of a low diversity benthic system. The objective of this study was to demonstrate that despite the absence of previous baseline information, the artificial channel has induced measurable changes in the biodiversity patterns of a hard substrata benthic community. The experimental design took into account the environmental setting influencing local benthic community structure and the sources of variability as a result of different substrate types and water depth. Four localities with ten replicates each were surveyed, and the presence/absence of macrobenthic biota species recorded during the rainy season. Our analysis using permutational multivariate analysis of variance indicated a significant increase in species richness in locations adjacent to the artificial channel. The highest species richness (66 species) was observed in the immediate area adjacent to the artificial channel and where exclusive species density was three to six times (18 exclusive species) than those present in other localities (6, 5 and 3 species) away from the channel. The presence of six species of hard corals indicated that the artificial channel offers a more suitable habitat for marine organisms colonizing the area than the natural channel. This study indicates the relative significance of confinement in structuring coastal lagoon benthic assemblages in tropical systems. Our results are similar to other findings underscoring the rate of colonization of marine organisms as a relevant process to explain benthic assemblage gradients and the importance of spatial–temporal interactions. The changes in species diversity caused by the artificial channel were clearly identified based on a sampling design that incorporated the main sources of environmental variability (distance to channels, substrate type and depth). Our study further demonstrates that changes in benthic community structure in the Chetumal Bay lagoon complex, as a result of human impacts, can be assessed even when community structure data before impact are absent.

Abstract. We investigated surface and vegetation dynamics in the artificial initial ecosystem "Chicken Creek" (Lusatia, Germany) in the years 2006–2011 across a wide spectrum of empirical data. We scrutinized three overarching hypotheses concerning (1) the relations between initial geomorphological and substrate characteristics with surface structure and terrain properties, (2) the effects of the latter on the occurrence of grouped plant species, and (3) vegetation density effects on terrain surface change. Our data comprise and conflate annual vegetation monitoring results, biennial terrestrial laser scans (starting in 2008), annual groundwater levels, and initially measured soil characteristics. The empirical evidence mostly confirms the hypotheses, revealing statistically significant relations for several goal variables: (1) the surface structure properties, local rill density, local relief energy and terrain surface height change; (2) the cover of different plant groups (annual, herbaceous, grass-like, woody, Fabaceae), and local vegetation height; and (3) terrain surface height change showed significant time-dependent relations with a variable that proxies local plant biomass. Additionally, period specific effects (like a calendar-year optimum effect for the occurrence of Fabaceae) were proven. Further and beyond the hypotheses, our findings on the spatiotemporal dynamics during the system's early development grasp processes which generally mark the transition from a geo-hydro-system towards a bio-geo-hydro system (weakening geomorphology effects on substrate surface dynamics, while vegetation effects intensify with time), where pure geomorphology or substrate feedbacks are changing into vegetation–substrate feedback processes.

Demolition products, surplus articles, and designed structures may be placed on the sea floor as habitat for fish and invertebrates or to provide substrate for corals or large attached plants. Such installations should be stable in the long-term, not to be torn apart or swept away during episodes of severe local storms or the onslaught of large swell from distant disturbances. To this end, calculations must be carried out, for a "design wave" deemed appropriate for the site involved, to evaluate applied kinematical loads and seabed reactions. Should the artificial reef appear unstable, then it must be pinned to the bottom unless meaningful redesign is feasible. This paper discusses the various aspects of the whole stability question and provides well more than one hundred pertinent and timely references.

Stem cell fate and behavior are affected by the bidirectional communication of cells and their local microenvironment (the stem cell niche), which includes biochemical cues, as well as physical and mechanical factors. Stem cells are normally cultured in conventional two-dimensional monolayer, with a mechanical environment very different from the physiological one. Here, we compare culture of rat mesenchymal stem cells on flat culture supports and in the “Nichoid”, an innovative three-dimensional substrate micro-engineered to recapitulate the architecture of the physiological niche in vitro. Two versions of the culture substrates Nichoid (single-layered or “2D Nichoid” and multi-layered or “3D Nichoid”) were fabricated via two-photon laser polymerization in a biocompatible hybrid organic-inorganic photoresist (SZ2080). Mesenchymal stem cells, isolated from rat bone marrow, were seeded on flat substrates and on 2D and 3D Nichoid substrates and maintained in culture up to 2 weeks. During cell culture, we evaluated cell morphology, proliferation, cell motility and the expression of a panel of 89 mesenchymal stem cells’ specific genes, as well as intracellular structures organization. Our results show that mesenchymal stem cells adhered and grew in the 3D Nichoid with a comparable proliferation rate as compared to flat substrates. After seeding on flat substrates, cells displayed large and spread nucleus and cytoplasm, while cells cultured in the 3D Nichoid were spatially organized in three dimensions, with smaller and spherical nuclei. Gene expression analysis revealed the upregulation of genes related to stemness and to mesenchymal stem cells’ features in Nichoid-cultured cells, as compared to flat substrates. The observed changes in cytoskeletal organization of cells cultured on 3D Nichoids were also responsible for a different localization of the mechanotransducer transcription factor YAP, with an increase of the cytoplasmic retention in cells cultured in the 3D Nichoid. This difference could be explained by alterations in the import of transcription factors inside the nucleus due to the observed decrease of mean nuclear pore diameter, by transmission electron microscopy. Our data show that 3D distribution of cell volume has a profound effect on mesenchymal stem cells structure and on their mechanobiological response, and highlight the potential use of the 3D Nichoid substrate to strengthen the potential effects of MSC in vitro and in vivo.

The availability of nesting resources influences the persistence and survival of bee communities. Although a positive effect of artificial nesting structures has frequently been shown for aboveground cavity-nesting wild bees, studies on below ground-nesting bees are rare. Artificial nesting hills designed to provide nesting habitats for ground-nesting bees were therefore established within the BienABest project in 20 regions across Germany. Wild bee communities were monitored for two consecutive years, accompanied by recordings of landscape and abiotic nest site variables. Bee activity and species richness increased from the first to the second year after establishment; this was particularly pronounced in landscapes with a low cover of semi-natural habitat. The nesting hills were successively colonized, indicating that they should exist for many years, thereby promoting a species-rich bee community. We recommend the construction of nesting hills on sun-exposed sites with a high thermal gain of the substrate because the bees prefer south-facing sites with high soil temperatures. Although the soil composition of the nesting hills plays a minor role, we suggest using local soil to match the needs of the local bee community. We conclude that artificial nesting structures for ground-nesting bees act as a valuable nesting resource for various bee species, particularly in highly degraded landscapes. We offer a construction and maintenance guide for the successful establishment of nesting hills for bee conservation.

The worm Dendronereis pinnaticirris is used as feed of shrimp broodstock in a hatchery, mainly because of its availability in the local market, and its nutritional content required for improving gonad maturation and post larvae production. The important economic value of the worm and the increasing demand for feed in shrimp hatcheries have led to an intense exploitation that suppers its population and the sustainability of the whole estuarine ecosystem. The study, which represents the starting point of large-scale production of the polychaete worm by culture in the artificial system, shall be undertaken. Accordingly, a production study using D. pinnaticirris juvenile was carried out under controlled conditions fed with two different feed (feed contains mainly plant protein and animal protein, respectively), and kept in three different substrates (substrate consists of mud and 8.78%, 37.34%, 39.17% sand, respectively). The treatments were arranged according to randomized completely block design in 8 (eight) replicates. The survival rate, body weight increment and growth, oxygen consumption, proximate body chemical, and fatty acid contents were measured. The results showed that growth and oxygen consumption was significantly influenced by a substrate and feed type (P<0.05). Worms on the mud substrate with 39.17% sand, and feed containing vegetable protein showed the highest oxygen consumption. Survival rate and chemical body content were not significantly influenced by the type of substrate and feed (P<0.05). The protein content of the worm was 32.02-43.81%, while fat content was 2.41-9.89%. Twenty different fatty acids were identified in the worm of all treatment groups.

Extensive green roofs (GRs) often appear as pollution sources during actual rainfall events; therefore, it is necessary to study the control of nutrient leaching in the substrate layer. In this study, four extensive GR experimental devices are built: two with artificial granular structure substrate layers improved with kaolin as a binder, one with a commercial substrate layer, and one with a standard roof (SR). Based on the simulated rainfall conditions in different local recurrence periods, the delayed outflow time, rainfall retention rate, event mean concentration (EMC), and cumulative pollutant quality of NH4+, NO3−, NO2−, and PO43− in the effluents were measured and evaluated. The results of the study indicate that under simulated rainfall in all the experimental design recurrence periods, the kaolin-modified substrate layer does not exhibit a more significant retention capacity than the commercial substrate. However, it does show some suppression of the leaching effect of NO3− and PO43− in the runoff. The reduction rate of cumulative NO3− quality is 6.56%, and PO43− is 10.54%. In future practical engineering and related research, attention should be paid to the influence of the type and addition amount of the substrate layer modifier on the stability of the granular structure to prevent nutrient loss caused by soil erosion.

The integration of III-V devices on Si substrates would allow the fabrication of specialized devices for optoelectronics and photonics directly on the highly refined silicon infrastructure, based on CMOS technology. In this work of thesis, Droplet Epitaxy technique is used for the low thermal budget fabrication of GaAs quantum nanostructures on silicon substrates through a Ge layer and for the fabrication of GaAs local artificial substrates directly on Si substrate. Quantum nanostructures grown on Si substrate through a Ge layer showed an intense photoluminescence emission, detectable up to room temperature and with a ratio between number of photon emitted and photogenerated carriers similar to the one obtained for GaAs quantum nanostructures grown by droplet epitaxy on GaAs substrate. GaAs local artificial substrates fabricated on Si showed high tunability in size and density, a size dispersion below 10%, a good crystalline quality and well defined shapes with a high aspect ratio.

Tese de Doutoramento em Ciência, Tecnologia e Gestão do Mar
Degradation and loss of coastal habitats affects all components of species diversity and ecosystem functions and services. For this reason, greater attention is needed to these ecosystems to assess and eventually control the disturbances to which they have been subjected and their consequences. Monitoring of marine communities is an essential procedure for environmental management, provided for by the European Marine Strategy Framework Directive (MSFD; 2008/56 / EC), with species composition being a basic descriptor for assessing 'Good Environmental Status' (GES). However, the scientific uncertainties about the benthic processes and the difficulties of sampling and monitoring them make the assessment of what constitutes the GES for the integrity of the seabed a difficult task. Furthermore, obtaining comparable data in benthic rock environments, which are often complex in nature, is not an easy task. The rocky bottoms pose particular difficulties for carrying out comprehensive surveys of the biodiversity patterns, since they present a great spatial complexity and local variability that affects the macrofauna communities. In the sampling of benthic macrofauna, macroalgae that inhabit rocky bottoms are good targets for monitoring studies based on colonization processes, because through these it is possible to sample the epifauna that uses them as habitat. However, the collection of macroalgae may not be sustainable, as it may compromise the survival of the populations of the target macroalgae and destroy fragile or threatened communities. As rocky habitats are relatively difficult to sample because they are heterogeneous and complex, many questions arise as to what methods should be used to sample these spatially variable communities. In this context, Artificial Substrates (AS) appear as a simple and non-destructive solution that can solve the main environmental and manmade problems associated with sampling in rocky environments, as they are easy to implement and their cost can be kept within reasonable values. The main objective of this thesis was to search for non-destructive standard methodologies using AS that can be colonized by a representative sample of the surrounding benthic assemblages. As a complementary objective, it was also sought to differentiate between different locations and times, as well as between fauna associated either with macroalgae or cryptofauna over time and at local and regional scales. This thesis is structured in five chapters based on analyzes of macrofauna assemblies, associated with SA with different types of structure. Through the use of several approaches, the validity of artificial substrates as sampling devices has been tested on a local and regional scale. The major objectives of this thesis were: - To investigate the viability of using AS for epifaunal comunities monitoring as an alternative to macroalgae collection. - To investigate the viability of using AS to distinguish dendritic and crevice epifaunal assemblages as an alternative to non-standard sampling methods. - To investigate the viability of using AS for epifaunal assemblages monitoring as an alternative to destructive methodologies overtime on a regional scale. - To investigate the viability of using the Taxonomic Sufficienci (TS) approach to optimize the costs and time constraints in marine monitoring studies based on AS. The results of the different approaches primarily display that the use of methodologies based on artificial substrates to assess macrobenthic communities must be standardized from the very beginning. Therefore, after evaluating the results of the tested approaches in this work, the proposed methodology is summarized below: - Artificial Substrate units: to nearshore hard-bottoms monitoring a combination of dendritic (ASMS) and crevice artificial substrates (ACMS) is the best approach. - Deployment period: 3 months must be the standard. - Long-term monitoring: an annual deployment at the beginning of the winter and retrieval of the AS every 3 months, combined with the additional deployment of uncolonized ASMS as replacements and its retrieval after 3 months, is the recommended approach. - Faunal identification level: species-level should be considered as the standard. Even so, depending on the specific goals of the study, family-level identification can be a usable strategy. Overall, AS with known structural complexity and volume were adequate to remove the variability of the sampling processes from the equation in quantitative sampling. In addition, the use of AS for monitoring purposes does not compromise algae stands or natural rocky reefs and can be used globally, as they are not limited by the natural life cycles inherent in algae and the natural distribution of the type of macroalgae or the reefs. Although SA appear as a simple solution that can solve the main environmental and man-made problems, as they are “low cost” and easily implementable, this methodology based on the identification of macrobenthic assemblies suffers from the temporal limitations in obtaining high taxonomic resolution data. Thus, under particular conditions and with a very well defined set of questions in mind, the (TS) approach can be a way to optimize costs and time constraints in marine monitoring studies.
A degradação e perda de habitats costeiros afetam todos os componentes da diversidade de espécies e funções e serviços do ecossistema. Por esse motivo, é necessário maior atenção a esses ecossistemas para avaliar e eventualmente controlar as perturbações a que estes estiveram sujeitos e suas consequências. A monitorização das comunidades marinhas é um procedimento essencial para a gestão ambiental, prevista pela Diretiva Quadro Estratégia Marinha Europeia (MSFD; 2008/56 / CE), sendo a composição em espécies um descritor básico para avaliar o 'Bom Estado Ambiental' (GES). No entanto, as incertezas científicas sobre os processos bentónicos e as dificuldades de amostragem e monitorização dos mesmos tornam a avaliação do que constitui o GES para integridade do fundo do mar uma tarefa difícil. Além disso, a obtenção de dados comparáveis em ambientes rochosos bentónicos, frequentemente complexos por natureza, não é uma tarefa fácil. Os fundos rochosos colocam dificuldades particulares para a realização de levantamentos abrangentes dos padrões da biodiversidade, uma vez que apresentam uma grande complexidade espacial e variabilidade local que afeta as comunidades de macrofauna. Na amostragem da macrofauna bentónica, as macroalgas que habitam fundos rochosos são bons alvos para estudos de monitorização baseados em processos de colonização, pois através destas é possível amostrar a epifauna que as utiliza como habitat. No entanto, a recolha de macroalgas pode não ser sustentável, pode comprometer a sobrevivência das populações das macroalgas alvo e destruir comunidades frágeis ou ameaçadas. Como os habitats rochosos são relativamente difíceis de amostrar porque são heterogéneos e complexos, levantam-se muitas questões sobre que métodos devem ser usados para amostrar essas comunidades espacialmente variáveis. Nesse contexto, os Substratos Artificiais (AS) surgem como uma solução simples e não destrutiva que pode resolver os principais problemas ambientais e antrópicos associados às amostragens em ambiente rochoso, pois são de fácil implementação e o seu custo pode ser mantido dentro de valores razoáveis. O objetivo geral desta tese foi investigar metodologias padrão não destrutivas usando AS que possam ser colonizadas por uma amostra representativa das comunidades bentónicas circundantes. Como objetivo complementar, procurou-se ainda diferenciar entre locais e épocas distintas, bem como entre faunas associadas tanto a macroalgas como à criptofauna ao longo do tempo e em escalas locais e regionais. Esta tese está estruturada em cinco capítulos, tendo como base análises de amostragens da macrofauna, associadas a SA com diferentes tipos de estrutura. Através do uso de várias abordagens, a validade dos substratos artificiais como amostradores foi testada à escala local e regional. Os principais objetivos desta tese foram: - Investigar a viabilidade do uso de AS para monitorização de comunidades epifaunais como alternativa à recolha de macroalgas. - Investigar a viabilidade do uso de AS para distinguir assembleias epifaunais dendríticas e associadas a fendas como uma alternativa aos métodos de amostragem não padronizados. - Investigar a viabilidade do uso de AS para monitorização de assembleias epifaunais como alternativa às metodologias destrutivas ao longo do tempo em escala regional. - Investigar a viabilidade do uso da abordagem de Suficiência Taxonómica (TS) para otimizar os custos e as limitações de tempo em estudos de monitorização marinha baseados em AS. Os resultados das diferentes abordagens mostraram que o uso de metodologias baseadas em substratos artificiais para avaliar as comunidades macrobentónicas deve ser padronizado desde o início. Portanto, após avaliação dos resultados das abordagens testadas neste trabalho, a metodologia proposta é resumida a seguir: - Unidades de substrato artificial: para monitorizar fundos duros próximos da costa, uma combinação de substratos dendríticos (ASMS) e de fendas artificiais (ACMS) é a melhor abordagem. - Período de implantação: 3 meses deve ser o padrão. - Monitorização de longo prazo: uma implantação anual no início do inverno e recuperação dos AS a cada 3 meses, combinada com a implantação adicional de ASMS não colonizados como substitutos e sua recuperação após 3 meses, é a abordagem recomendada. - Nível de identificação da fauna: o nível de espécie deve ser considerado como o padrão. Mesmo assim, dependendo dos objetivos específicos do estudo, a identificação ao nível familiar pode ser uma estratégia a considerar. No geral, AS com complexidade estrutural e volume conhecidos foram adequados para remover a variabilidade dos processos de amostragem da equação na amostragem quantitativa. Além disso, o uso de AS para fins de monitorização não compromete os povoamentos de algas ou os recifes rochosos naturais e pode ser usado globalmente, uma vez que não são limitados pelos ciclos de vida naturais inerentes às algas e à distribuição natural do tipo de macroalga ou dos recifes. Embora os SA apareçam como uma solução simples que pode resolver os principais problemas ambientais e antrópicos, por serem de “baixo custo” e facilmente implementáveis, esta metodologia baseada na identificação de assembleias macrobentónicas sofre com as limitações temporais em obter alta resolução taxonôómica dados. Assim, em condições particulares e com um conjunto de questões muito bem definido em mente, a abordagem (TS) pode ser uma forma de otimizar os custos e as restrições de tempo em estudos de monitorização marinha.

The aim of this chapter is to report the perception of artisanal fishers regarding long-term implementation impacts of artificial reefs in the northern coast of Rio de Janeiro, Brazil. Data was collected through 60 interviews with local and regional artisanal fishers. The fishers stated an increase in fish abundance and species richness around the reef complex and consider it very important for local fisheries due to its ability to attract commercial species. These findings were clearly supported by their positive perception regarding the installation of reef balls and how these structures have benefited the local and regional fishing community over time (>25 years). In addition, the data confirms that the presence of different species in the reef complex is due to an increase of consolidated and stable substrate, which provides several types of prey and habitat for recruitment and shelter.

<em>Abstract</em>.—Artificial reefs quickly became important in Malaysian fisheries management after their introduction in the 1970s. Their popularity lies in their potential for rehabilitating and enhancing coastal resources, particularly after the establishment of legal protection for coastal resources via regulations regarding fishing zonation in 1985. These human-made substrates were created from various materials, from tires to concrete structures. These structures were meant to create permanent sites conceptually similar to traditional artificial reefs deployed by local fishers that were more temporary in nature. Studies conducted up to the 1990s indicated that artificial reefs had the potential to bring resource users and managers together to establish a community-based management of small-scale coastal fisheries. However, the degree of progress made toward using artificial reefs to bring together users and managers remained obscure. Subsequently, a case study conducted between 2008 and 2010 used the sustainable livelihood approach to gain the perspectives of small-scale fishers on artificial reefs in Terengganu. This paper revisits the potential and challenges of using artificial reefs to implement a community-based fishery management approach. Focus is given to the institutional arrangements, both indigenous and official, that mediate the use of artificial reefs by small-scale fishers in Setiu. While many enabling factors exist, institutional weaknesses that impede a more inclusive management structure also persist. The importance of leveraging traditional fishing codes of conduct to manage access to artificial reefs is highlighted as the key to realizing the potential of deploying artificial reefs to enhance livelihoods based on sustainable fisheries resources.

One of the challenges in engineering complex artificial tissue constructs, with defined matrix and cellular architecture, is the formation of a viable microcirculation within them, that inosculates with the host vasculature and matures into a functional microvascular bed. Current methods based on complex cell patterning in 2-D or 3-D matrix systems rely on ‘printing’ cells or patterns of cells on/ in a substrate, direct culture on patterned substrates, or endothelialization of decellularized vessels. We are now beginning to understand the effects of the microenvironment on microvascular constructs. Flow induced remodeling and maturation of angiogenic microvasculature and changes in functional characteristics when co-implanted with astrocyte precursors strongly suggests a role for the local environment in determining characteristics of the microvascular bed [1, 2]. Chang et al. have shown that neovascular networks from microvessels pre-aligned by direct-bioprinting in a collagen matrix, retain alignment when cultured in vitro, but lose alignment on implantation in vivo [3]. Though unloading of mechanically loaded tissue influences cell behavior [4], it does not explain this loss of orientation after implantation, of previously unloaded constructs. Implanted constructs have an additional level of complexity in the form of network revision and maturation with blood flow. We hypothesize that the local mechanical microenvironment, in addition to flow, dictates network morphology in vivo. This study compares the changes in pre-aligned microvascular networks implanted with and without anchorage.

This work examines the microscale physics of heat transfer processes in flow boiling of FC-72 in a single microchannel. Experimental results discussed in this paper provide new physical insight on the nature of heat transfer events. The study is enabled through development of a device with a composite substrate that consists of a high thermal conductivity material coated by a thin layer of a low thermal conductivity material with embedded temperature sensors. This novel arrangement enables measurement of local heat flux with a spatial resolution of 40–65 μm and a temporal resolution of 50 μs. The device generates isolated bubbles from a 300 nm in diameter artificial cavity fabricated at the center of a pulsed function micro-heater. Analysis of the temperature and heat flux data along with synchronized images of bubbles show that four mechanisms of heat transfer are active as a bubble grows and flows through the channel. These mechanisms of heat transfer are 1) microlayer evaporation, 2) interline evaporation, 3) transient conduction, and 4) micro-convection. The magnitude and time period of activation of these mechanisms of heat transfer are determined and their characteristics are discussed in details.