2,212 research outputs found
Presidents and Mummies and Patents, Oh My: Why Patenting Special Effects Technology Is like a Box of Chocolates, You Never Know What You\u27re Going to Get
Towards the graviton from spinfoams: the 3d toy model
Recently, a proposal has appeared for the extraction of the 2-point function
of linearised quantum gravity, within the spinfoam formalism. This relies on
the use of a boundary state, which introduces a semi-classical flat geometry on
the boundary. In this paper, we investigate this proposal considering a toy
model in the (Riemannian) 3d case, where the semi-classical limit is better
understood. We show that in this limit the propagation kernel of the model is
the one for the harmonic oscillator. This is at the origin of the expected 1/L
behaviour of the 2-point function. Furthermore, we numerically study the short
scales regime, where deviations from this behaviour occur.Comment: 8 pages, 2 figures; v3 revised versio
Leaf morphology in cowpea [Vigna unguiculata (L.) Walp]: QTL analysis, physical mapping and identifying a candidate gene using synteny with model legume species
Cowpea [Vigna unguiculata (L.) Walp] exhibits a considerable variation in leaf shape. Although cowpea is mostly utilized as a dry grain and animal fodder crop, cowpea leaves are also used as a high-protein pot herb in many countries of Africa
Identification of markers associated with bacterial blight resistance loci in cowpea (Vigna unguiculata (L.) Walp.)
Cowpea bacterial blight (CoBB), caused by Xanthomonas axonopodis pv. vignicola (Xav), is a worldwide major disease of cowpea [Vigna unguiculata (L.) Walp.]. Among different strategies to control the disease including cultural practices, intercropping, application of chemicals, and sowing pathogen-free seeds, planting of cowpea genotypes with resistance to the pathogen would be the most attractive option to the resource poor cowpea farmers in sub-Saharan Africa. Breeding resistance cultivars would be facilitated by marker-assisted selection (MAS). In order to identify loci with effects on resistance to this pathogen and map QTLs controlling resistance to CoBB, eleven cowpea genotypes were screened for resistance to bacterial blight using 2 virulent Xav18 and Xav19 strains isolated from Kano (Nigeria). Two cowpea genotypes Danila and Tvu7778 were identified to contrast in their responses to foliar disease expression following leaf infection with pathogen. A set of recombinant inbred lines (RILs) comprising 113 individuals derived from Danila (resistant parent) and Tvu7778 (susceptible parent) were infected with CoBB using leaf inoculation method. The experiments were conducted under greenhouse conditions (2007 and 2008) and disease severity was visually assessed using a scale where 0 = no disease and 4 = maximum susceptibility with leaf drop. A single nucleotide polymorphism (SNP) genetic map with 282 SNP markers constructed from the same RIL population was used to perform QTL analysis. Using Kruskall-Wallis and Multiple-QTL model of MapQTL 5, three QTLs, CoBB-1, CoBB-2 and CoBB-3 were identified on linkage group LG3, LG5 and LG9 respectively showing that potential resistance candidate genes cosegregated with CoBB resistance phenotypes. Two of the QTLs CoBB-1, CoBB-2 were consistently confirmed in the two experiments accounting for up to 22.1 and to 17.4% respectively for the first and second experiments. Whereas CoBB-3 was only discovered for the first experiment (2007) with less phenotypic variation explained of about 10%. Our results represent a resource for molecular marker development that can be used for marker assisted selection of bacterial blight resistance in cowpe
Ecological model of extinctions
We present numerical results based on a simplified ecological system in
evolution, showing features of extinction similar to that claimed for the
biosystem on Earth. In the model each species consists of a population in
interaction with the others, that reproduces and evolves in time. Each species
is simultaneously a predator and a prey in a food chain. Mutations that change
the interactions are supposed to occur randomly at a low rate. Extinctions of
populations result naturally from the predator-prey dynamics. The model is not
pinned in a fitness variable, and natural selection arises from the dynamics.Comment: 16 pages (LaTeX type, RevTeX style), including 6 figures in gif
format. To be published in Phys. Rev. E (prob. Dic. 96
Mineral exploration in the Lower Palaeozoic rocks of south-west Cumbria. Part 1, regional surveys
The results of geochemical, geological and geophysical surveys over Lower Palaeozoic rocks in the
south-western part of Cumbria are given in two reports. This report (Part 1) describes the results of a
geochemical drainage survey and an examination of mineralised sites, and relates them to information
from new geological mapping and an assessment of regional geophysical data. Part 2 contains details
of follow-up surveys in the Black Combe inlier.
The geochemical drainage survey, involving the collection and analysis of heavy mineral concentrates
and stream sediment samples from 119 sites, found substantial antimony, arsenic, barium, bismuth,
copper, iron, lead, tin, tungsten and zinc anomalies. Gold was reported for the first time from this part
of the Lake District: small amounts were noted in panned concentrates from five sites. Other minerals
identified in panned concentrates included arsenopyrite, baryte, bismutite, bismuthinite, cassiterite,
chalcopyrite, cerussite, pyrite, pyromorphite, scheelite, sphalerite, stolzite and wolfram&e.
The examination of old workings and outcrops revealed many undocumented occurrences of quartzsulphide
vein-style mineralisation. The chemical analysis of samples taken from old workings and
other occurrences confirmed field observations that locally, particularly in the Black Combe area, this
mineralisation is polymetallic with variable amounts of arsenic, gold, bismuth, copper, lead, zinc and
in a few cases antimony, barium, cobalt, nickel, tungsten and tin. Iron mineralisation occurs both as
oxide (hematite) and sulphide deposits. Mercury was present in appreciable amounts in samples from
the High Brow pyrite mine.
The distribution of panned concentrate anomalies suggests that the vein-style mineralisation is
polyphase and that individual phases may be zoned. Highest zinc anomalies occur near Torver and the
highest lead on the west side of Black Combe. Tin and tungsten are restricted largely to the central
part of Black Combe, and the most prominent arsenic and bismuth anomalies are found in the same
area. Copper anomalies are widespread over the Skiddaw Group and the Borrowdale Volcanic Group.
Barium anomalies indicate that baryte mineralisation is weak and localised, occurring principally
within the Black Combe area and close to the Windermere Supergroup basal unconformity. Iron
oxides from host rocks and hematite mineralisation are responsible for local enrichments of iron,
antimony, arsenic and molybdenum in panned concentrates
Gravitational Equilibrium in the Presence of a Positive Cosmological Constant
We reconsider the virial theorem in the presence of a positive cosmological
constant Lambda. Assuming steady state, we derive an inequality of the form rho
>= A (Lambda / 4 pi GN) for the mean density rho of the astrophysical object.
With a minimum at Asphere = 2, its value can increase by several orders of
magnitude as the shape of the object deviates from a spherically symmetric one.
This, among others, indicates that flattened matter distributions like e.g.
clusters or superclusters, with low density, cannot be in gravitational
equilibrium.Comment: 7 pages, no figure
Genetic architecture of delayed senescence, biomass, and grain yield under drought stress in cowpea
CowpeaThe stay-green phenomenon is a key plant trait with wide usage in managing crop production under limited water conditions. This trait enhances delayed senescence, biomass, and grain yield under drought stress. In this study we sought to identify QTLs in cowpea (Vigna unguiculata) consistent across experiments conducted in Burkina Faso, Nigeria, Senegal, and the United States of America under limited water conditions. A panel of 383 diverse cowpea accessions and a
recombinant inbred line population (RIL) were SNP genotyped using an Illumina 1536 GoldenGate assay. Phenotypic data from thirteen experiments conducted across the four countries were used to identify SNP-trait associations based on linkage disequilibrium association mapping, with bi-parental QTL mapping as a complementary strategy. We identified seven loci, five of which exhibited evidence suggesting pleiotropic effects (stay-green) between delayed senescence, biomass, and grain yield. Further, we provide evidence suggesting the existence of positive pleiotropy in cowpea based on positively correlated mean phenotypic values (0.34, r ,0.87) and allele effects (0.07, r ,0.86) for delayed senescence and grain yield across three African environments. Three of the five putative stay-green QTLs, Dro-1, 3, and 7 were identified in both RILs and diverse germplasm with resolutions of 3.2 cM or less for each of the three loci, suggesting that these may be valuable targets for marker-assisted breeding in cowpea. Also, the co-location of early vegetative delayed senescence with biomass and grain yield QTLs suggests the possibility of using delayed senescence at the seedling stage as a rapid screening tool for post-flowering drought tolerance in cowpea breeding. BLAST analysis using EST sequences harboring SNPs with the highest associations provided a genomic context for loci identified in this study in closely related common bean (Phaseolus vulgaris) and soybean (Glycine max) reference genomes
Scenario of Accelerating Universe from the Phenomenological \Lambda- Models
Dark matter, the major component of the matter content of the Universe,
played a significant role at early stages during structure formation. But at
present the Universe is dark energy dominated as well as accelerating. Here,
the presence of dark energy has been established by including a time-dependent
term in the Einstein's field equations. This model is compatible with
the idea of an accelerating Universe so far as the value of the deceleration
parameter is concerned. Possibility of a change in sign of the deceleration
parameter is also discussed. The impact of considering the speed of light as
variable in the field equations has also been investigated by using a well
known time-dependent model.Comment: Latex, 9 pages, Major change
- …