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11.
The objective of this paper aims to prove positivity of solutions for the following semilinear partial differential equationu
. This equation represents a generalised model of the so-called porous medium equation. It arises in a variety of meaningful physical situations including gas flows, diffusion of an electron-ion plasma and the dynamics of biological populations whose mobility is density dependent. In all these situations the solutions of the equation must be positive functions. 相似文献
12.
B30.2-like domain proteins: update and new insights into a rapidly expanding family of proteins 总被引:5,自引:0,他引:5
Henry J; Mather IH; McDermott MF; Pontarotti P 《Molecular biology and evolution》1998,15(12):1696-1705
The B30.2 domain is a conserved region of around 170 amino acids associated
with several different protein domains, including the immunoglobulin folds
of butyrophilin and the RING finger domain of ret finger protein. We
recently reported several novel members of this family as well as
previously undescribed protein families possessing the B30.2 domain. Many
proteins have subsequently been found to possess this domain, including
pyrin/marenostrin and the midline 1 (MID1) protein. Mutations in the B30.2
domain of pyrin/marenostrin are implicated in familial Mediterranean fever,
and partial loss of the B30.2 domain of MID1 is responsible for Opitz G/BBB
syndrome, characterized by developmental midline defects. In this study, we
scrutinized the available sequence data bases for the identification of
novel B30.2 domain proteins using highly sensitive database-searching
tools. In addition, we discuss the chromosomal localization of genes in the
B30.2 family, since the encoded proteins are likely to be involved in other
forms of periodic fever, autoimmune, and genetic diseases.
相似文献
13.
Out of Africa and back again: nested cladistic analysis of human Y chromosome variation 总被引:18,自引:3,他引:15
Hammer MF; Karafet T; Rasanayagam A; Wood ET; Altheide TK; Jenkins T; Griffiths RC; Templeton AR; Zegura SL 《Molecular biology and evolution》1998,15(4):427-441
We surveyed nine diallelic polymorphic sites on the Y chromosomes of 1,544
individuals from Africa, Asia, Europe, Oceania, and the New World.
Phylogenetic analyses of these nine sites resulted in a tree for 10
distinct Y haplotypes with a coalescence time of approximately 150,000
years. The 10 haplotypes were unevenly distributed among human populations:
5 were restricted to a particular continent, 2 were shared between Africa
and Europe, 1 was present only in the Old World, and 2 were found in all
geographic regions surveyed. The ancestral haplotype was limited to African
populations. Random permutation procedures revealed statistically
significant patterns of geographical structuring of this paternal genetic
variation. The results of a nested cladistic analysis indicated that these
geographical associations arose through a combination of processes,
including restricted, recurrent gene flow (isolation by distance) and range
expansions. We inferred that one of the oldest events in the nested
cladistic analysis was a range expansion out of Africa which resulted in
the complete replacement of Y chromosomes throughout the Old World, a
finding consistent with many versions of the Out of Africa Replacement
Model. A second and more recent range expansion brought Asian Y chromosomes
back to Africa without replacing the indigenous African male gene pool.
Thus, the previously observed high levels of Y chromosomal genetic
diversity in Africa may be due in part to bidirectional population
movements. Finally, a comparison of our results with those from nested
cladistic analyses of human mtDNA and beta-globin data revealed different
patterns of inferences for males and females concerning the relative roles
of population history (range expansions) and population structure
(recurrent gene flow), thereby adding a new sex-specific component to
models of human evolution.
相似文献
14.
Minard Robert D. Hatcher Patrick G. Gourley Robert C. Matthews Clifford N. 《Origins of life and evolution of the biosphere》1998,28(4-6):461-473
Hydrogen cyanide polymers form spontaneously from HCN and traces of base catalysts. It is probable that these polymers played an important role in the early stages of chemical evolution. Nevertheless, their full structural characterization has still not been accomplished. A number of mass spectrometric methods have now been applied to this structural problem including FAB-MS, thermal desorption EI-MS, ESI-MS, APCI-MS and off-line TMAH thermochemolysis/GC-MS. This latter method causes bond cleavage and in situ methylation producing a suite of products which provides valuable insight into the substructural features of HCN polymers and also promises to serve as a sensitive diagnostic tool for detecting the presence of HCN polymers in samples from diverse sources. 相似文献
15.
Vera MF da Silva Anthony M Carter Carlos E Ambrosio Ana F Carvalho Marina Bonatelli Marcelo C Lima Angelica Maria Miglino 《Reproductive biology and endocrinology : RB&E》2007,5(1):26-6
A recent reassessment of the phylogenetic affinities of cetaceans makes it timely to compare their placentation with that
of the artiodactyls. We studied the placentae of two sympatric species of dolphin from the Amazon River Basin, representing
two distinct families. The umbilical cord branched to supply a bilobed allantoic sac. Small blood vessels and smooth muscle
bundles were found within the stroma of the cord. Foci of squamous metaplasia occurred in the allanto-amnion and allantochorion.
The interhemal membrane of the placenta was of the epitheliochorial type. Two different types of trophoblastic epithelium
were seen. Most was of the simple columnar type and indented by fetal capillaries. However, there were also areolar regions
with tall columnar trophoblast and these were more sparsely supplied with capillaries. The endometrium was well vascularised
and richly supplied with actively secreting glands. These findings are consistent with the current view that Cetacea are nested
within Artiodactyla as sister group to the hippopotamids. 相似文献
16.
Germano Siqueira Adriane MF Milagres Walter Carvalho Gerald Koch André Ferraz 《Biotechnology for biofuels》2011,4(1):7
Background
Lignin and hemicelluloses are the major components limiting enzyme infiltration into cell walls. Determination of the topochemical distribution of lignin and aromatics in sugar cane might provide important data on the recalcitrance of specific cells. We used cellular ultraviolet (UV) microspectrophotometry (UMSP) to topochemically detect lignin and hydroxycinnamic acids in individual fiber, vessel and parenchyma cell walls of untreated and chlorite-treated sugar cane. Internodes, presenting typical vascular bundles and sucrose-storing parenchyma cells, were divided into rind and pith fractions. 相似文献17.
Brief overview of BioMicroNano technologies 总被引:2,自引:0,他引:2
Gourley PL 《Biotechnology progress》2005,21(1):2-10
This paper provides a brief overview of the fields of biological micro-electromechanical systems (bioMEMs) and associated nanobiotechnologies, collectively denoted as BioMicroNano. Although they are developing at a very rapid pace and still redefining themselves, several stabilized areas of research and development can be identified. Six major areas are delineated, and specific examples are discussed and illustrated. Various applications of the technologies are noted, and potential market sizes are compared. 相似文献
18.
19.
Background
The tear film is a thin layer of fluid that covers the ocular surface and is involved in lubrication and protection of the eye. Little is known about the protein composition of tear fluid but its deregulation is associated with disease states, such as diabetic dry eyes. This makes this body fluid an interesting candidate for in-depth proteomic analysis. 相似文献20.
Murine intraepithelial lymphocytes (IEL) express c-kit, the receptor for stem cell factor (SCF). SCF induced a low but significant proliferative response in IEL, but not in splenic T cells. SCF stimulation of IEL resulted in an expansion of the c-kit(+), TCRgammadelta(+)cell population. SCF-induced proliferation was dependent upon SCF-c-kit interactions, since antibody to c-kit blocked this response, and IEL obtained from c-kit mutant (W/W(v)) mice failed to respond to SCF. SCF acted synergistically with anti-TCRgammadelta and with concavalin A (Con A) to induce proliferation and interferon gamma (IFN-gamma) production in IEL. Finally, mice injected with SCF had a significant increase in the number of IEL in the small intestine. SCF-treated mice had increased numbers of TCRalphabeta(+)and TCRgammadelta(+)cell populations, as well as increased numbers of c-kit(+)and c-kit(-)IEL. These data suggest that SCF-c-kit interactions play an important role in regulating IEL expansion and activation. 相似文献