1,862 research outputs found
Brane Inflation from Rotation of D4 Brane
In this paper, a inflationary model from the rotation of D4-brane is
constructed. We show that for a very wide rage of parameter, this model
satisfies the observation and find that regarded as inflaton, the rotation of
branes may be more nature than the distance between branes. Our model offers a
new avenue for brane inflation.Comment: 6 pages, no figure
Dominance of climate warming effects on recent drying trends over wet monsoon regions
Understanding changes in background dryness over land is key information for
adapting to climate change because of its critical socioeconomic
consequences. However, causes of continental dryness changes remain uncertain
because various climate parameters control dryness. Here, we verify dominant
climate variables determining dryness trends over continental eastern Asia,
which is characterized by diverse hydroclimate regimes ranging from arid to
humid, by quantifying the relative effects of changes in precipitation, solar
radiation, wind speed, surface air temperature, and relative humidity on
trends in the aridity index based on observed data from 189 weather stations
for the period of 1961–2010. Before the early 1980s (1961–1983), change in
precipitation is a primary condition for determining aridity trends. In the
later period (1984–2010), the dominant climate parameter for aridity trends
varies according to the hydroclimate regime. Drying trends in arid regions
are mostly explained by reduced precipitation. In contrast, the increase in
potential evapotranspiration due to increased atmospheric water-holding
capacity, a secondary impact of warming, works to increase aridity over the
humid monsoon region despite an enhanced water supply and relatively less
warming. Our results show significant drying effects of warming over the
humid monsoon region in recent decades; this also supports the drying trends
over warm and water-sufficient regions in future climate
A Single Scalar Field Model of Dark Energy with Equation of State Crossing -1
In this paper we study the possibility of building models of dark energy with
equation of state across -1 and propose explicitly a model with a single scalar
field which gives rise to an equation of state larger than -1 in the past and
less than -1 at the present time, consistent with the current observations.Comment: 4 pages, 1 figure, the version accepted by JCAP, presentation
improved and references adde
Bayesian dissection for genetic architecture of traits associated with nitrogen utilization efficiency in rice
Nitrogen is one of the key important nutrients in rice production. High rice grain yield is greatly dependent upon economic nitrogen input and genetic factors. In order to locate quantitative loci for traits associated with nitrogen utilization efficiency in rice, F9 recombinant inbred lines derived from a Korean tongil type Dasanbyeo and a Chinese japonica variety TR22183 was genetically designed. The six traits of interest were observed on 155 RILs, along with 105 SSR and 103 STS markers. Bayesian model selection technique was used to dissect genetic architecture for traits of interest. A total of 28 main-effect QTLs and 23 pairs of epistatic QTLs were detected for traits associated with nitrogen utilization efficiency. The proportions of phenotypic variation explained by the detected QTLs ranged from 0.09 to 16.90% and from 0.19 to 12.76% for main-effect and epistatic QTLs, respectively. Sixteen of main-effect QTLs interacted with nitrogen level. One pleiotropic QTL was found, governing simultaneously nitrogen dry matter production efficiency and Nitrogen grain production efficiency
Reconstruction of a Nonminimal Coupling Theory with Scale-invariant Power Spectrum
A nonminimal coupling single scalar field theory, when transformed from
Jordan frame to Einstein frame, can act like a minimal coupling one. Making use
of this property, we investigate how a nonminimal coupling theory with
scale-invariant power spectrum could be reconstructed from its minimal coupling
counterpart, which can be applied in the early universe. Thanks to the coupling
to gravity, the equation of state of our universe for a scale-invariant power
spectrum can be relaxed, and the relation between the parameters in the action
can be obtained. This approach also provides a means to address the Big-Bang
puzzles and anisotropy problem in the nonminimal coupling model within Jordan
frame. Due to the equivalence between the two frames, one may be able to find
models that are free of the horizon, flatness, singularity as well as
anisotropy problems.Comment: 31 pages, 4 figure
Modeling stand-level mortality based on maximum stem number and seasonal temperature
Mortality is a key process in forest stand dynamics. However, tree mortality is not well understood, particularly in relation to climatic factors. The objectives of this study were to: (i) determine the patterns of maximum stem number per ha (MSN) over dominant tree height from 5-year remeasurements of the permanent sample plots for temperate forests [Red pine (Pinus densiflora), Japanese larch (Larix kaempferi), Korean pine (Pinus koraiensis), Chinese cork oak (Quercus variabilis), and Mongolian oak (Quercus mongolica)] using Sterba’s theory and Korean National Forest Inventory (NFI) data, (ii) develop a stand-level mortality (self-thinning) model using the MSN curve, and (iii) assess the impact of temperature on tree mortality in semi-variogram and linear regression models. The MSN curve represents the upper boundary of observed stem numbers per ha. The developed mortality model with our results showed a high degree of reliability (R2 = 0.55–0.81) and no obvious dependencies or patterns in residuals. However, spatial autocorrelation was detected from residuals of coniferous species (Red pine, Japanese larch and Korean pine), but not for oak species (Chinese cork oak and Mongolian oak). Based on the linear regression analysis of residuals, we found that the mortality of coniferous forests tended to increase with the rising seasonal temperature. This is more evident during winter and spring months. Conversely, oak mortality did not significantly vary with increasing temperature. These findings indicate that enhanced tree mortality due to rising temperatures in response to climate change is possible, especially in coniferous forests, and is expected to contribute to forest management decisions
Inflationary universe in loop quantum cosmology
Loop quantum cosmology provides a nice solution of avoiding the big bang
singularity through a big bounce mechanism in the high energy region. In loop
quantum cosmology an inflationary universe is emergent after the big bounce, no
matter what matter component is filled in the universe. A super-inflation phase
without phantom matter will appear in a certain way in the initial stage after
the bounce; then the universe will undergo a normal inflation stage. We discuss
the condition of inflation in detail in this framework. Also, for slow-roll
inflation, we expect the imprint from the effects of the loop quantum cosmology
should be left in the primordial perturbation power spectrum. However, we show
that this imprint is too weak to be observed.Comment: 21 pages, 4 figures; accepted for publication in JCA
Deletion mapping of chromosome 16q in hepatocellular carcinoma
Hepatocellular carcinoma (HCC) frequently shows an allelic imbalance (AI) on chromosome 16q. In order to define the commonly affected regions on chromosome 16q, we assessed AI studies in 41 HCCs using a panel of 37 microsatellite markers. Thirty-five cases (85%) showed AI at one or more loci. Among the 35 cases with AI, 21 cases showed multiple AI, suggesting the wide scope of deletion on the long arm of chromosome 16, and the remaining 14 cases showed partial AI. Detailed deletion mapping identified two independent commonly deleted regions on this chromosome arm. These included the D16S3106 locus and D16S498 locus. In conclusion, we have demonstrated frequent AI on 16q in HCCs and identified two loci with frequent AI, which may harbour new tumour suppressor genes.ope
F-term, D-term and hybrid brane inflation
We study inflation and reheating in models for the brane universe,
considering hybrid brane inflation without tachyon condensation. We expect that
some fields that are localized on different branes interact with O(1) coupling
when branes are on top of each other, while the interaction vanishes when
branes are separated at a distance. If the interaction is needed to avoid
spontaneous breaking of supersymmetry on the brane, our idea for hybrid brane
inflation works. In our model, when branes are far apart, supersymmetry is
spontaneously broken by the fields on a brane, which induces inflation. The
inflaton field is the moduli for the brane distance. At the end of inflation,
when branes come close, supersymmetry is restored by the interaction between
fields on the branes, then the oscillation starts to reheat the Universe. In
this paper we construct explicit models for F-term and D-term inflation. There
are at least two major advantages. The most attractive point is that reheating
is natural in our model, because the trigger field is not the tachyon but a
conventional field on the brane. The serious constraint from the loop
correction, which always appears in conventional models for hybrid inflation,
is avoided.Comment: 13pages, latex2e, final version, to appear in JCA
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