Heat transfer delay method for the fluid velocity evaluation in a multi-turn pulsating heat pipe

A multi-turn closed loop pulsating heat pipe made of aluminium is tested in vertical bottom heated mode and different condenser temperatures with the aim of providing quantitative information regarding its flow dynamics through a novel post-processing technique on the local wall-to-fluid heat flux, evaluated within the adiabatic section. The studied device is made of an annealed aluminium tube (inner/outer diameter: 3/5 mm), folded in 14 turns and partially filled with methanol (volumetric filling ratio: 50%). The aluminium channels are coated with a high-emissivity opaque paint, thus allowing thermographic measurements on the outer wall by means of a high-resolution medium wave infrared camera. The proposed method, named Heat Transfer Delay Method, is validated by means of a dedicated experimental approach. Then, the acquired time-space temperature maps are used as input data for the inverse heat conduction problem resolution approach to estimate the local convective heat flux locally exchanged at the inner wall-fluid interface. The resulting wall-to-fluid heat fluxes are then post- processed by applying the Heat Transfer Delay Method to the oscillatory and circulatory flow modes. The average fluid velocity is assessed at varying working conditions during the circulatory flow, finding values up to 0.77 m/s and 0.3 m/s for condenser temperature equal to 20 ◦C and 10 ◦ C, respectivel

Genome elimination during microsporogenesis in two pentaploid accessions of Brachiaria decumbens (Poaceae)

Polyploidy is a prominent and significant force in plant evolution, taking place since ancient times and continuing until today. Recent cytogenetic studies in the genus Brachiaria using germplasm collected from wild African savannas in the 1980s revealed that most species and accessions within species are polyploid. Diploid, tetraploid, and pentaploid accessions have been found. We found asynchronous meiosis during microsporogenesis, followed by genome elimination, in two pentaploid (2n = 5x = 45) accessions (D53 and D71) of a hardy, invasive pasture grass, introduced from Africa to Brazil, Brachiaria decumbens. In these accessions, chromosomes paired as 18 bivalents and nine univalents during diakinesis, suggesting that these accessions resulted from a recent event of natural hybridization. The lack of chromosome associations in the genomes suggests that these accessions resulted from hybridization between two genotypes that are not closely related, with low genome affinity and with different meiotic rhythms. This supposition is reinforced by the meiotic behavior of the nine univalents, which were always laggard in relation to the other chromosomes and eliminated as micronucleiin microspores. The behavior of these accessions, which have an odd level of ploidy and confirmed genome elimination, supports the general assumption that a polyploid accession can undergo a new event of polyploidization by natural hybridization (neopolyploidyzation). This evidence for natural hybridization in Brachiaria shows that this is a wild genus in an ongoing evolutionary process

A new and distinctive male-sterile, female-fertile desynaptic mutant in soybean (Glycine max).

A spontaneous desynaptic mutation, affecting only microsporogenesis and causing pollen sterility, has been detected in BR97-12986H, a line of the official Brazilian soybean breeding program. In this male-sterile, female-fertile mutant, up to metaphase II, the meiotic behavior was similar to that described for the st series of synaptic mutants previously reported in soybean. Besides many univalents, few or total absence of bivalents were recorded in diakinesis. Bivalents presented one or two terminal chiasmata, while univalents retained the sister chromatid cohesion. Bivalents and most univalents congregated at the equatorial metaphase plate, although univalents frequently migrated to the poles prematurely. Laggards resulting from delay in chiasmata terminalization were also recorded. Distinctly different in their behavior from st series soybean mutants, telophase I-originated micronuclei of different sizes organized their own spindle in the second division. This behavior contributed towards an increase in genome fractionation. Several microspores and microcytes of different sizes were recorded at the end of meiosis. Pollen sterility was estimated at 91.2 %. Segregation ratio for sterility in this line and its progenies reached 3:1. Allelism tests with st series of synaptic mutants are in progress. The importance of male-sterile, female-fertile mutations for soybean breeding programs is discussed

Thermal characterization of intumescent fire retardant paints

Intumescent coatings are now the dominant passive fire protection materials used in industrial and commercial buildings. The coatings, which usually are composed of inorganic components contained in a polymer matrix, are inert at low temperatures and at higher temperatures, they expand and degrade to provide a charred layer of low conductivity materials. The charred layer, which acts as thermal barrier, will prevent heat transfer to underlying substrate. The thermal properties of intumescent paints are often unknown and difficult to be estimated since they vary significantly during the expansion process; for this reason the fire resistance validation of a commercial coatings is based on expensive, large-scale methods where each commercial coating-beam configuration has to be tested one by one. Adopting, instead, approaches based on a thermal modelling of the intumescent paint coating could provide an helpful tool to make easier the test procedure and to support the design of fire resistant structures as well. The present investigation is focused on the assessment of a methodology intended to the restoration of the equivalent thermal conductivity of the intumescent layer produced under the action of a cone calorimetric apparatus. The estimation procedure is based on the inverse heat conduction problem approach, where the temperature values measured at some locations inside the layer during the expansion process are used as input known data. The results point out that the equivalent thermal conductivity reached by the intumescent material at the end of the expansion process significantly depends on the temperature while the initial thickness of the paint does not seem to have much effect

Cytogenetic data about some Brazilian accessions of Paspalum.

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Nitric oxide-driven modifications of lipoic arm inhibit α-ketoacid dehydrogenases

Pyruvate dehydrogenase complex (PDHC) and oxoglutarate dehydrogenase complex (OGDC), which belong to the mitochondrial α-ketoacid dehydrogenase family, play crucial roles in cellular metabolism. These multi-subunit enzyme complexes use lipoic arms covalently attached to their E2 subunits to transfer an acyl group to coenzyme A (CoA). Here, we report a novel mechanism capable of substantially inhibiting PDHC and OGDC: reactive nitrogen species (RNS) can covalently modify the thiols on their lipoic arms, generating a series of adducts that block catalytic activity. S-Nitroso-CoA, a product between RNS and the E2 subunit\u27s natural substrate, CoA, can efficiently deliver these modifications onto the lipoic arm. We found RNS-mediated inhibition of PDHC and OGDC occurs during classical macrophage activation, driving significant rewiring of cellular metabolism over time. This work provides a new mechanistic link between RNS and mitochondrial metabolism with potential relevance for numerous physiological and pathological conditions in which RNS accumulate

Uso de testes colorimétricos na determinação da viabilidade do grão de pólen de acessos da grama-do-cerrado, Pantanal.

A principal economia do Pantanal é a bovinocultura de corte, criada em sistemas extensivos, com uso dos recursos forrageiros nativos. No entanto, há carência de estudos básicos da reprodução indicativos do potencial de acessos para futuros programas de seleção e melhoramento. Nesse contexto, objetivou-se avaliar a viabilidade do pólen de 10 acessos, presentes do Banco Ativo de Germoplasma, implantado pela Embrapa Pantanal na fazenda Nhumirim, sub-região da Nhecolândia, Pantanal, Corumbá, MS