438 research outputs found
Fingering convection in a spherical shell
We use 120 three dimensional direct numerical simulations to study fingering
convection in non-rotating spherical shells. We investigate the scaling
behaviour of the flow lengthscale, mean velocity and transport of chemical
composition over the fingering convection instability domain defined by , being the ratio of density perturbations of thermal
and compositional origins. We show that the horizontal size of the fingers is
accurately described by a scaling law of the form , where is the shell depth,
the thermal Rayleigh number and the flux ratio. Scaling laws
for mean velocity and chemical transport are derived in two asymptotic regimes
close to the two edges of the instability domain, namely
and . For the former, we show that the transport follows
power laws of a small parameter measuring the distance to
onset. For the latter, we find that the Sherwood number , which quantities
the chemical transport, gradually approaches a scaling
when ; and that the P\'eclet number accordingly follows , being the chemical Rayleigh number. When
the Reynolds number exceeds a few tens, a secondary instability may occur
taking the form of large-scale toroidal jets. Jets distort the fingers
resulting in Reynolds stress correlations, which in turn feed the jet growth
until saturation. This nonlinear phenomenon can yield relaxation oscillation
cycles.Comment: 43 pages, 22 figures, 3 tables, submitted to JF
Recommended from our members
Optical diagnostics for turbulent and multiphase flows: Particle image velocimetry and photorefractive optics
This report summarizes the work performed under the Sandia Laboratory Directed Research and Development (LDRD) project ``Optical Diagnostics for Turbulent and Multiphase Flows.`` Advanced optical diagnostics have been investigated and developed for flow field measurements, including capabilities for measurement in turbulent, multiphase, and heated flows. Particle Image Velocimetry (PIV) includes several techniques for measurement of instantaneous flow field velocities and associated turbulence quantities. Nonlinear photorefractive optical materials have been investigated for the possibility of measuring turbulence quantities (turbulent spectrum) more directly. The two-dimensional PIV techniques developed under this LDRD were shown to work well, and were compared with more traditional laser Doppler velocimetry (LDV). Three-dimensional PIV techniques were developed and tested, but due to several experimental difficulties were not as successful. The photorefractive techniques were tested, and both potential capabilities and possible problem areas were elucidated
Produção de Brachiaria brizantha cv. Marandu quando consorciada com Sorghum bicolor sob perΓodos de estresse hΓdrico.
Verificar o desenvolvimento da Brachiaria brizantha cv. Marandu quando em cultivo consorciado com o sorgo, submetida a perΓodos de dΓ©ficit hΓdrico
Produção de Sorghum bicolor quando consorciada com Brachiaria brizantha cv. Marandu sob perΓodos de estresse hΓdrico.
Graphene plasmonics
Two rich and vibrant fields of investigation, graphene physics and
plasmonics, strongly overlap. Not only does graphene possess intrinsic plasmons
that are tunable and adjustable, but a combination of graphene with noble-metal
nanostructures promises a variety of exciting applications for conventional
plasmonics. The versatility of graphene means that graphene-based plasmonics
may enable the manufacture of novel optical devices working in different
frequency ranges, from terahertz to the visible, with extremely high speed, low
driving voltage, low power consumption and compact sizes. Here we review the
field emerging at the intersection of graphene physics and plasmonics.Comment: Review article; 12 pages, 6 figures, 99 references (final version
available only at publisher's web site
A multi-stage genome-wide association study of bladder cancer identifies multiple susceptibility loci.
We conducted a multi-stage, genome-wide association study of bladder cancer with a primary scan of 591,637 SNPs in 3,532 affected individuals (cases) and 5,120 controls of European descent from five studies followed by a replication strategy, which included 8,382 cases and 48,275 controls from 16 studies. In a combined analysis, we identified three new regions associated with bladder cancer on chromosomes 22q13.1, 19q12 and 2q37.1: rs1014971, (P = 8 Γ 10β»ΒΉΒ²) maps to a non-genic region of chromosome 22q13.1, rs8102137 (P = 2 Γ 10β»ΒΉΒΉ) on 19q12 maps to CCNE1 and rs11892031 (P = 1 Γ 10β»β·) maps to the UGT1A cluster on 2q37.1. We confirmed four previously identified genome-wide associations on chromosomes 3q28, 4p16.3, 8q24.21 and 8q24.3, validated previous candidate associations for the GSTM1 deletion (P = 4 Γ 10β»ΒΉΒΉ) and a tag SNP for NAT2 acetylation status (P = 4 Γ 10β»ΒΉΒΉ), and found interactions with smoking in both regions. Our findings on common variants associated with bladder cancer risk should provide new insights into the mechanisms of carcinogenesis
A multi-stage genome-wide association study of bladder cancer identifies multiple susceptibility loci.
We conducted a multi-stage, genome-wide association study of bladder cancer with a primary scan of 591,637 SNPs in 3,532 affected individuals (cases) and 5,120 controls of European descent from five studies followed by a replication strategy, which included 8,382 cases and 48,275 controls from 16 studies. In a combined analysis, we identified three new regions associated with bladder cancer on chromosomes 22q13.1, 19q12 and 2q37.1: rs1014971, (P = 8 Γ 10β»ΒΉΒ²) maps to a non-genic region of chromosome 22q13.1, rs8102137 (P = 2 Γ 10β»ΒΉΒΉ) on 19q12 maps to CCNE1 and rs11892031 (P = 1 Γ 10β»β·) maps to the UGT1A cluster on 2q37.1. We confirmed four previously identified genome-wide associations on chromosomes 3q28, 4p16.3, 8q24.21 and 8q24.3, validated previous candidate associations for the GSTM1 deletion (P = 4 Γ 10β»ΒΉΒΉ) and a tag SNP for NAT2 acetylation status (P = 4 Γ 10β»ΒΉΒΉ), and found interactions with smoking in both regions. Our findings on common variants associated with bladder cancer risk should provide new insights into the mechanisms of carcinogenesis
Who Needs Microtubules? Myogenic Reorganization of MTOC, Golgi Complex and ER Exit Sites Persists Despite Lack of Normal Microtubule Tracks
A wave of structural reorganization involving centrosomes, microtubules, Golgi complex and ER exit sites takes place early during skeletal muscle differentiation and completely remodels the secretory pathway. The mechanism of these changes and their functional implications are still poorly understood, in large part because all changes occur seemingly simultaneously. In an effort to uncouple the reorganizations, we have used taxol, nocodazole, and the specific GSK3-Ξ² inhibitor DW12, to disrupt the dynamic microtubule network of differentiating cultures of the mouse skeletal muscle cell line C2. Despite strong effects on microtubules, cell shape and cell fusion, none of the treatments prevented early differentiation. Redistribution of centrosomal proteins, conditional on differentiation, was in fact increased by taxol and nocodazole and normal in DW12. Redistributions of Golgi complex and ER exit sites were incomplete but remained tightly linked under all circumstances, and conditional on centrosomal reorganization. We were therefore able to uncouple microtubule reorganization from the other events and to determine that centrosomal proteins lead the reorganization hierarchy. In addition, we have gained new insight into structural and functional aspects of the reorganization of microtubule nucleation during myogenesis
LKB1 Destabilizes Microtubules in Myoblasts and Contributes to Myoblast Differentiation
Background: Skeletal muscle myoblast differentiation and fusion into multinucleate myotubes is associated with dramatic cytoskeletal changes. We find that microtubules in differentiated myotubes are highly stabilized, but premature microtubule stabilization blocks differentiation. Factors responsible for microtubule destabilization in myoblasts have not been identified. Findings: We find that a transient decrease in microtubule stabilization early during myoblast differentiation precedes the ultimate microtubule stabilization seen in differentiated myotubes. We report a role for the serine-threonine kinase LKB1 in both microtubule destabilization and myoblast differentiation. LKB1 overexpression reduced microtubule elongation in a Nocodazole washout assay, and LKB1 RNAi increased it, showing LKB1 destabilizes microtubule assembly in myoblasts. LKB1 levels and activity increased during myoblast differentiation, along with activation of the known LKB1 substrates AMPactivated protein kinase (AMPK) and microtubule affinity regulating kinases (MARKs). LKB1 overexpression accelerated differentiation, whereas RNAi impaired it. Conclusions: Reduced microtubule stability precedes myoblast differentiation and the associated ultimate microtubule stabilization seen in myotubes. LKB1 plays a positive role in microtubule destabilization in myoblasts and in myoblast differentiation. This work suggests a model by which LKB1-induced microtubule destabilization facilitates the cytoskeleta
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