605 resultados para proceeds


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We consider the concerted evolution of viral genomes in four families of DNA viruses. Given the high rate of horizontal gene transfer among viruses and their hosts, it is an open question as to how representative particular genes are of the evolutionary history of the complete genome. To address the concerted evolution of viral genes, we compared genomic evolution across four distinct, extant viral families. For all four viral families we constructed DNA-dependent DNA polymerase-based (DdDp) phylogenies and in addition, whole genome sequence, as quantitative descriptions of inter-genome relationships. We found that the history of the polymerase gene was highly predictive of the history of the genome as a whole, which we explain in terms of repeated, co-divergence events of the core DdDp gene accompanied by a number of satellite, accessory genetic loci. We also found that the rate of gene gain in baculovirus and poxviruses proceeds significantly more quickly than the rate of gene loss and that there is convergent acquisition of satellite functions promoting contextual adaptation when distinct viral families infect related hosts. The congruence of the genome and polymerase trees suggests that a large set of viral genes, including polymerase, derive from a phylogenetically conserved core of genes of host origin, secondarily reinforced by gene acquisition from common hosts or co-infecting viruses within the host. A single viral genome can be thought of as a mutualistic network, with the core genes acting as an effective host and the satellite genes as effective symbionts. Larger virus genomes show a greater departure from linkage equilibrium between core and satellites functions.

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We present a method to simulate the Magnetic Barkhausen Noise using the Random Field Ising Model with magnetic long-range interaction. The method allows calculating the magnetic flux density behavior in particular sections of the lattice reticule. The results show an internal demagnetizing effect that proceeds from the magnetic long-range interactions. This demagnetizing effect induces the appearing of a magnetic pattern in the region of magnetic avalanches. When compared with the traditional method, the proposed numerical procedure neatly reduces computational costs of simulation. (c) 2008 Published by Elsevier B.V.

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The copper-catalyzed dimerization of alkynyltrifluoroborates proceeds readily with good yields. The homo-coupling reaction can be effected in DMSO, in the open air, using Cu(OAc)(2) as catalyst in the absence of any other additives. A variety of functional groups are tolerated. (C) 2008 Elsevier Ltd. All rights reserved.

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An Ultrasound-assisted preparation of a series of novel 3,5-diaryl-4,5-dihydro-1H-pyrazole-1-carboximidamides that proceeds via the efficient reaction of chalcones with aminoguanidine hydrochloride under clean conditions is described. (C) 2009 Elsevier B.V. All rights reserved.

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The synthesis of potassium 2-substituted-1,3-dithianotrifluoroborate salts and tetra-n-butyl ammonium derivatives is described. The reaction proceeds under mild reaction conditions and the corresponding products were obtained in moderate to good yields. The reactivity of these compounds in rections with chiral cyclic N-acyliminium ions was evaluated.

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Four factors (moisture, light regime, temperature, food type) were examined for their effects on the embryonic diapause of Homichloda (Weiseana) barkeri (Jacoby) (Coleoptera: Chrysomelidae), a biocontrol agent for prickly acacia, Acacia nilotica (L.) Willdenew ex Delile (Mimosaceae). Moisture is critical for termination of diapause. A single wetting of eggs resulted in a low hatch rate while a sequence of wetting events followed by periods of dryness produced a high hatch rate. A relatively constant proportion of embryos within each batch initiated development at each wetting event, with hatching complete after the eighth wetting event in these trials. An extended interval between wetting events, tested at up to 23 days, did not result in a decreased overall hatch rate. A threshold time of exposure to moisture of between 3 to 6 h is required before development proceeds. The response of eggs to the moisture regime is seen as a strategy for taking advantage of available food after rainfall by terminating diapause, rather than merely a quiescent response to the absence of moisture. Temperature affected development time and the proportion of eggs that developed. Experimental manipulations of photoperiod and host-plant availability showed no effect on embryonic development.

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Changes in the physical properties (such as particle density, bulk density of the bed, shrinkage and bed porosity) of fresh green bean particulates were investigated during drying. Three length:diameter ratios (1:1, 2:1 and 3:1) were considered, using drying conditions of 50 +/- 2 degrees C and 13 +/- 2% relative humidity in a heat pump dehumidifier system. The fluidization behaviour was also evaluated at 10 levels of moisture content. The fluidization experiments demonstrated that the minimum fluidization velocity decreases as the drying proceeds due to the reduced moisture content and changes in the physical properties of the bean particulates. Empirical relationships of the following nature were developed for the change in shrinkage [VR = 1 - Be-kMR], particle density [rho(p) = A + BMR + C (exp)(-D MR)], bulk density [rho(b) = a(1) + b(1)MR + c(1)MR(2)] and bed porosity [epsilon = a(2) + b(2)MR + c(2)MR(2)] with the moisture content during fluidized bed drying.

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P>The Toll-like receptor (TLR) signalling pathway is the first system that defends against Leishmania. After recognising Leishmania as nonself, TLRs trigger NF-kappa B expression. NF-kappa B proceeds to the nucleus and promotes the transcription of pro-inflammatory cytokines. TLR9 is thus an important factor in the induction of an effective immune response against Leishmania. We examined the pattern of TLR9 expression in 12 patients with cutaneous leishmaniasis caused by Leishmania braziliensis detected by polymerase chain reaction. Normal skin was analysed as a negative control. TLR9 expression was examined in the dermis and epidermis by immunohistochemical analysis of paraffin-embedded biopsy tissue. TLR9 expression was primarily observed in the granuloma. The protein was detected in a few cells in the dermis. A lower expression level was detected in the epidermis of patients with leishmaniasis when compared with normal skin. The presence of TLR9 in the skin of patients with cutaneous leishmaniasis is associated with granuloma and expressed by macrophages.

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To investigate bone mineral accretion in growing children, the Saskatchewan Pediatric Bone Mineral Accrual Study was initiated in 1991. The study involves the collection of dietary and physical activity information along with anthropometric growth and maturity measurements every 6 months and dual-energy X-ray absorptiometer (DXA) bone scans of the whole body, AP lumbar spine and proximal femur taken annually, The study has now finished its 6th year and 68 males and 72 females from an original sample of 228 elementary schoolchildren are still involved, To investigate how bone mineral at clinically important sites proceeds in relation to maturation we developed distance and velocity growth curves for height and bone mineral content (BMC) for the AP lumbar spine, the femoral neck and the whole body, In both boys and girls, over 35% of total body and AP spine bone mineral and over 27% of the bone mineral at the femoral neck was laid down during the 4-year adolescent period surrounding peak linear growth velocity. The clinical significance of these values can be appreciated by consideration of the fact that as much bone mineral will be laid down during these 4 adolescent growing years as most people will lose during all of adult life.

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The reaction of the bis(1,2-diamine) copper(II) complexes of racemic propane-1,2-diamine (pn) and 2-methylpropane-1,2-diamine (dmen) with formaldehyde and nitroethane in methanol under basic conditions yields minor macrocyclic condensation products in addition to the major acyclic products. Where C-pendant methyl groups on the pair of coordinated diamines are in cis dispositions, the first -NH-CH2-C(CH3)(NO2)-CH2-NH- ring formation occurs at amine pairs distant from these C-methyl substituents, and further reaction to yield a macrocycle is not observed. However, where the C-methyl substituents are in trans dispositions, the chemistry proceeds to yield the macrocycle. Commencing with pn, trans-(6,13-diammonio-2,6,9,13-tetramethyl-1,4,7,10-tetraazacyclotetradecane)copper(II) perchlorate formed and crystallized in the space group P2(1)/n, with a 9.782(2), b 9.2794(6), c 17.017(4) Angstrom, beta 103.24(1)degrees. The copper ion is found in a square-planar environment, with the two methyl groups of the pn residues and the pairs of introduced pendant groups all in trans arrangements.

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This work reports the first ultrastructural investigation into the degradation process that starch granules isolated from bananas (cv. Nanicao) undergo during ripening. Starch granules from green bananas had a smooth surface, while granules from ripe bananas were more elongated with parallel striations, as revealed by CSLM and SEM. AFM images revealed that the first layer covering the granule surface is composed of a hard material and, as degradation proceeds, hard and soft regions seem to be repeated at regular intervals. WAXD patterns of banana starches were C-type, and the crystalline index was reduced during ripening. The B-/A-type ratio was increased, indicating the preferential degradation of the A-type allomorph. The branch-chain length distribution showed predominantly short chains of amylopectin (A and B1-chain). The fa/fb ratio was reduced during degradation, while amylose content was increased. The results allowed a detailed understanding of the changes that starch granules undergo during banana ripening. (C) 2010 Elsevier Ltd. All rights reserved.

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In the light of Gary Becker's economic theory of the family, considers how economic cost and benefit factors can influence the size of families that parents decide to have. Some support for the importance of such factors is found from results of structured interviews with wives in Kondh-dominated villages in western Orissa. These results are at variance with the hypothesis of Malthus about population growth. Factors that may alter the optimal family size as development proceeds are discussed. It is found in our sampling that, on the whole, there is a preference for daughters rather than sons although this is not as strong in the Kondh-dominated villages as in poor villages in the Santal tribal belt of West Bengal. While in the Kondh-dominated villages some discrimination in access to education in favour of boys compared to girls is present, little such or no such discrimination occurs in relation to access to food and medical attention. In the villages surveyed in the West Bengal Santal tribal belt, discrimination in favour of boys is more pronounced than in the Kondh-dominated area in Orissa. While economic considerations help to explain gender discrimination between boys and girls, we find that social and cultural factors also play a major role. Parents in a similar economic situation seem to display substantially different patterns of gender discrimination between children depending on their social and cultural content. It seems that the extent to which economic theories of the family explain family preferences and behaviour depend significantly on the social and cultural context in which they are to be applied.

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We develop a new iterative filter diagonalization (FD) scheme based on Lanczos subspaces and demonstrate its application to the calculation of bound-state and resonance eigenvalues. The new scheme combines the Lanczos three-term vector recursion for the generation of a tridiagonal representation of the Hamiltonian with a three-term scalar recursion to generate filtered states within the Lanczos representation. Eigenstates in the energy windows of interest can then be obtained by solving a small generalized eigenvalue problem in the subspace spanned by the filtered states. The scalar filtering recursion is based on the homogeneous eigenvalue equation of the tridiagonal representation of the Hamiltonian, and is simpler and more efficient than our previous quasi-minimum-residual filter diagonalization (QMRFD) scheme (H. G. Yu and S. C. Smith, Chem. Phys. Lett., 1998, 283, 69), which was based on solving for the action of the Green operator via an inhomogeneous equation. A low-storage method for the construction of Hamiltonian and overlap matrix elements in the filtered-basis representation is devised, in which contributions to the matrix elements are computed simultaneously as the recursion proceeds, allowing coefficients of the filtered states to be discarded once their contribution has been evaluated. Application to the HO2 system shows that the new scheme is highly efficient and can generate eigenvalues with the same numerical accuracy as the basic Lanczos algorithm.

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Stomatogenesis and the cell division cycle was investigated for Macropodinium yalanbense Dehority, 1996 from Macropus giganteus using light and electron microscopy. Macropodinium spp. are endosymbiotic ciliates found only in the stomachs of macropodid marsupials. Stomatogenesis proceeds through 4 stages: initial formation of a transverse division suture; formation of the preoral field and formation of vestibular kineties in an internal pouch; extension of vestibulum posteriorly and external formation of new adoral kineties; and extension of somatic and adoral kineties accompanying dorsal and ventral constriction of the cell. Karyokinesis and formation of the new cytoproct occur immediately prior to cytokinesis. Comparison with other litostome ciliates shows that the formation of new vestibular kineties is most similar to that of the entodiniomorphs, formation of adoral kineties is most similar to that of the haptorians and formation of the somatic kineties to that of the vestibuliferans. The phylogenetic affinities of Macropodinium are thus difficult to infer from the ontogeny of organelle systems. Stomatogenesis of the adoral kineties is either epiapokinetal or a new type of cryptotelokinetal whereas the vestibular kineties are formed by either endoapokinetal or cryptotelokinetal processes. No other ciliate has been observed to utilise 2 types of stomatogenesis in its division cycle.

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The extant lungfish, including three genera, the Australian, South American and African lungfishes, retain a dentition that appeared first in the Devonian, in some of the oldest members of this group. The dentition consists of permanent tooth plates with persistent cusps that appear early in development of the fish. The cusps, separate early in development, form ridges that are arranged in a radiating pattern, and fusion of the cusps to each other and to the underlying jaw bone produces a tooth plate. The lungfish dentition is based on a template of mantle dentine that surrounds bone trabeculae enclosed in the tooth plate. The mantle layer is covered by enamel. In most derived dipnoans, this framework encloses two further forms of dentine, known as interdenteonal and circumdenteonal dentines. The tooth plates grow in area and in depth without evidence of macroscopic resorption of dentines or of enamel. Increase in size and changes in shape of lungfish tooth plates is actually achieved by a process involving microscopic remodelling of the bone contained within the margin of each tooth plate, and the later addition of new dentines and enamel within and around the bone. This is accomplished without creating weakness in the structural integrity of the tooth plate and bone complex, and proceeds in line with growth and remodelling of the jaw bones attached to the tooth plates.