Aspect ratio dependence of heat transport by turbulent Rayleigh-B\'{e}nard convection in rectangular cells

We report high-precision measurements of the Nusselt number $Nu$ as a function of the Rayleigh number $Ra$ in water-filled rectangular Rayleigh-B\'{e}nard convection cells. The horizontal length $L$ and width $W$ of the cells are 50.0 cm and 15.0 cm, respectively, and the heights $H=49.9$, 25.0, 12.5, 6.9, 3.5, and 2.4 cm, corresponding to the aspect ratios $(\Gamma_x\equiv L/H,\Gamma_y\equiv W/H)=(1,0.3)$, $(2,0.6)$, $(4,1.2)$, $(7.3,2.2)$, $(14.3,4.3)$, and $(20.8,6.3)$. The measurements were carried out over the Rayleigh number range $6\times10^5\lesssim Ra\lesssim10^{11}$ and the Prandtl number range $5.2\lesssim Pr\lesssim7$. Our results show that for rectangular geometry turbulent heat transport is independent of the cells' aspect ratios and hence is insensitive to the nature and structures of the large-scale mean flows of the system. This is slightly different from the observations in cylindrical cells where $Nu$ is found to be in general a decreasing function of $\Gamma$, at least for $\Gamma=1$ and larger. Such a difference is probably a manifestation of the finite plate conductivity effect. Corrections for the influence of the finite conductivity of the top and bottom plates are made to obtain the estimates of $Nu_{\infty}$ for plates with perfect conductivity. The local scaling exponents $\beta_l$ of $Nu_{\infty}\sim Ra^{\beta_l}$ are calculated and found to increase from 0.243 at $Ra\simeq9\times10^5$ to 0.327 at $Ra\simeq4\times10^{10}$.Comment: 15 pages, 7 figures, Accepted by Journal of Fluid Mechanic

Exploiting EST databases for the development and characterization of EST-SSR markers in castor bean (Ricinus communis L.)

<p>Abstract</p> <p>Background</p> <p>The castor bean <it>(Ricinus communis </it>L.), a monotypic species in the spurge family (Euphorbiaceae, 2n = 20), is an important non-edible oilseed crop widely cultivated in tropical, sub-tropical and temperate countries for its high economic value. Because of the high level of ricinoleic acid (over 85%) in its seed oil, the castor bean seed derivatives are often used in aviation oil, lubricants, nylon, dyes, inks, soaps, adhesive and biodiesel. Due to lack of efficient molecular markers, little is known about the population genetic diversity and the genetic relationships among castor bean germplasm. Efficient and robust molecular markers are increasingly needed for breeding and improving varieties in castor bean. The advent of modern genomics has produced large amounts of publicly available DNA sequence data. In particular, expressed sequence tags (ESTs) provide valuable resources to develop gene-associated SSR markers.</p> <p>Results</p> <p>In total, 18,928 publicly available non-redundant castor bean EST sequences, representing approximately 17.03 Mb, were evaluated and 7732 SSR sites in 5,122 ESTs were identified by data mining. Castor bean exhibited considerably high frequency of EST-SSRs. We developed and characterized 118 polymorphic EST-SSR markers from 379 primer pairs flanking repeats by screening 24 castor bean samples collected from different countries. A total of 350 alleles were identified from 118 polymorphic SSR loci, ranging from 2-6 per locus (A) with an average of 2.97. The EST-SSR markers developed displayed moderate gene diversity (<it>H</it>_e) with an average of 0.41. Genetic relationships among 24 germplasms were investigated using the genotypes of 350 alleles, showing geographic pattern of genotypes across genetic diversity centers of castor bean.</p> <p>Conclusion</p> <p>Castor bean EST sequences exhibited considerably high frequency of SSR sites, and were rich resources for developing EST-SSR markers. These EST-SSR markers would be particularly useful for both genetic mapping and population structure analysis, facilitating breeding and crop improvement of castor bean.</p

2-Phenyl-1H-1,3,7,8-tetra­azacyclo­penta­[l]phenanthrene

There are two mol­ecules in the asymmetric unit of the title compound, C19H12N4, with dihedral angles of 2.41 (10) and 10.53 (12)° between the fused ring system and the pendant phenyl ring. In the crystal, mol­ecules are linked into chains by N—H⋯N hydrogen bonds and aromatic π–π stacking inter­actions [shortest centroid–centroid distance = 3.6176 (16) Å] complete the structure

Dichlorido(10,11,12,13-tetra­hydro-4,5,9,14-tetra­azabenzo[b]triphenyl­ene)cadmium(II) hemihydrate

In the title compound, [CdCl2(C18H14N4)2]·0.5H2O, the Cd atom assumes a distorted octa­hedral trans-CdCl2N4 geometry arising from its coordination by two N,N′-bidentate 10,11,12,13-tetra­hydro-4,5,9,14-tetra­azabenzo[b]triphenyl­ene (TBBT) mol­ecules and two chloride ions. In the crystal, π–π aromatic stacking inter­actions between adjacent TTBT rings are seen, with a centroid–centroid distance of 3.604 (3) Å. An O—H⋯Cl hydrogen bond between the half-occupied water molecule and one chloride ion also occurs

Poly[[(μ-benzene-1,4-dicarboxyl­ato)bis­[μ-4-(1H-1,3,7,8-tetra­aza­cyclo­penta­[l]phenanthren-2-yl)benzoato]dizinc] tetra­hydrate]

In the title complex, [Zn2(C8H4O4)(C20H11N4O2)2]·4H2O, the ZnII atom is six-coordinated by two carboxyl­ate O atoms from one bidentate benzene-1,4-dicarboxyl­ate (1,4-BDC) ligand, two carboxyl­ate O atoms from two different monodentate 4-(1H-1,3,7,8-tetra­aza­cyclo­penta­[l]phenanthren-2-yl)benzoate (HNCP) ligands and two HNCP N atoms. The ZnII atoms are bridged by the centrosymmetric 1,4-BDC ligands, forming an extended single-chain structure. Neighbouring single chains are connected by the HNCP ligands from two opposite directions, resulting in a sheet. In addition, there are N—H⋯O hydrogen-bonding inter­actions between adjacent layers. As a result, the polymeric sheets are further extended into a three-dimensional supra­molecular structure

Focal Spot, Winter 1983/84

https://digitalcommons.wustl.edu/focal_spot_archives/1036/thumbnail.jp

2,2′-Dimethyl-1,1′-[2,2-bis­(bromo­methyl)propane-1,3-di­yl]dibenzimidazole hemihydrate

The title compound, C21H22Br2N4·0.5H2O, contains two benzimidazole groups which may provide two potential coordination nodes for the construction of metal–organic frameworks. The mean planes of the two imidazole groups are almost perpendicular, with a dihedral angle of 83.05 (2)°, and adjacent mol­ecules are linked into a one-dimensional chain by π–π stacking inter­actions between imidazole groups of different mol­ecules [centroid-to-centroid distances of 3.834 (2) and 3.522 (2) Å]