The Unsteady Wake of a Circular Cylinder near a Free Surface

The behaviour of the wake Strouhal number for flow past a cylinder close to a free surface at both low and moderate Froude numbers is investigated numerically. For the low Froude number case (i.e., gravity-dominated), the results obtained are similar to those for flow past a cylinder close to an adjacent no-slip boundary. As the distance between the wall and the cylinder is reduced, the Strouhal number, as measured from the time varying lift, increases to a maximum at a gap ratio of 0.70. Further gap reduction leads to a rapid decrease in the Strouhal number, with shedding finally ceasing altogether at gap ratios below 0.16. The agreement between the results for a free surface and a no-slip boundary suggests that the mechanism behind the suppression of vortex shedding is common. For flow at a fixed gap ratio and a moderate Froude number, two distinctly different wake states are observed with the flow passing over the cylinder tending to switch from a state of attachment to the free surface, to one of separation from it, and then back again in a pseudo-periodic fashion. Even though there is a significant difference in Reynolds number, the predicted numerical two-dimensional behaviour is found to compare favourably with the experimental observations at higher Reynolds number.     

An economic analysis of microbial reduction of sulfur dioxide with anaerobically digested sewage biosolids as electron donor

Applied Biochemistry and Biotechnology - In summary, it appears that the microbial reduction process is not competitive with conventional SO2-reduction techniques when AD-MSS medium is used as the...     

Microbial stabilization of active-sulfide sludges

Applied Biochemistry and Biotechnology - It has been demonstrated that a sulfide-tolerant strain of T.denitrificans (strain F) can oxidize under moderate conditions at least part of the acid-labile...     

Structure and biosynthesis of the jamaicamides, new mixed polyketide-peptide neurotoxins from the marine cyanobacterium Lyngbya majuscula

A screening program for bioactive compounds from marine cyanobacteria led to the isolation of jamaicamides A-C. Jamaicamide A is a novel and highly functionalized lipopeptide containing an alkynyl bromide, vinyl chloride, beta-methoxy eneone system, and pyrrolinone ring. The jamaicamides show sodium channelblocking activity and fish toxicity. Precursor feeding to jamaicamide-producing cultures mapped out the series of acetate and amino acid residues and helped develop an effective cloning strategy for the biosynthetic gene cluster. The 58 kbp gene cluster is composed of 17 open reading frames that show an exact colinearity with their expected utilization. A novel cassette of genes appears to form a pendent carbon atom possessing the vinyl chloride functionality; at its core this contains an HMG-CoA synthase-like motif, giving insight into the mechanism by which this functional group is created.     

Degradation of munition wastes byPhanerochaete chrysosporium

“Pink water” is a waste-water stream generated by munitions LAP (loading, assembly, and packing) operations. The major components of this waste water are trinitrotoluene (TNT) and cyclotrimethylene trinitramine (RDX) at concentrations of 120-175 mg/L and 25 mg/L, respectively. Currently, pink water is treated by activated carbon adsorption. Removal efficiencies of >99.5% have been reported. However, this treatment method suffers a serious limitation in that the carbon cannot be safely regenerated. Loaded carbon is disposed of by incineration after a single use.

We have demonstrated that TNT, RDX, simulated, and actual pink water can be effectively treated byPhanerochaete chrysosporium immobilized on the disks of a rotating biological contractor (RBC) in both batch and continuous modes. Greater than 90% removal of TNT from a simulated pink water was observed in a continuous RBC with a residence time of about 24 h. The disk area required was about 10,000 ft²/gpm (4091 m²/m³h) feed. RDX was amenable to treatment, but RDX removal rates were somewhat slower. A full-scale treatment system was designed on the basis of laboratory data, and a cost analysis was performed. This analysis has shown that biotreatment of pink water can be a cost-effective alternative to carbon adsorption.

     

Modal spectroscopy of optoexcited vibrations of a micron-scale on-chip resonator at greater than 1 GHz frequency

We analyze experimentally and theoretically >1 GHz optoexcited mechanical vibration in an on-chip micron-scaled sphere. Different eigen-mechanical modes are excited upon demand by the centrifugal radiation pressure of the optical whispering-gallery-mode, enabling an optomechanical modal spectroscopy investigation of many vibrational modes. Spectral analysis of the light emitted from the device enables deduction of its natural vibrational modes in analogy with spectroscopy of a molecule's vibrational levels, and its eccentricity perturbation is shown to induce spectral splitting.     

Structure-based design of 2-arylamino-4-cyclohexylmethoxy-5-nitroso-6-aminopyrimidine inhibitors of cyclin-dependent kinase 2

An efficient synthesis of 2-substituted O(4)-cyclohexylmethyl-5-nitroso-6-aminopyrimidines from 6-amino-2-mercaptopyrimidin-4-ol has been developed and used to prepare a range of derivatives for evaluation as inhibitors of cyclin-dependent kinase 2 (CDK2). The structure-activity relationships (SARs) are similar to those observed for the corresponding O(6)-cyclohexylmethoxypurine series with the 2-arylsulfonamide and 2-arylcarboxamide derivatives showing excellent potency. Two compounds, 4-(6-amino-4-cyclohexylmethoxy-5-nitrosopyrimidin-2-ylamino)-N-(2-hydroxyethyl)benzenesulfonamide (7q) and 4-(6-amino-4-cyclohexylmethoxy-5-nitrosopyrimidin-2-ylamino)-N-(2,3-dihydroxypropyl)benzenesulfonamide (7s), were the most potent with IC50 values of 0.7 +/- 0.1 and 0.8 +/- 0.0 nM against CDK2, respectively. The SARs determined in this study are discussed with reference to the crystal structure of 4-(6-amino-4-cyclohexylmethoxy-5-nitrosopyrimidin-2-ylamino)-N-(2,3-dihydroxypropyl)benzenesulfonamide (7j) bound to phosphorylated CDK2/cyclin A.     

Experimental study of simultaneous measurement of velocity and surface topography: in the wake of a circular cylinder at low Reynolds number

A technique to provide simultaneous measurement on both free surface topography and the velocity vector field of free surface flows is further developed and validated. Testing was performed on the topography measurement by imaging static plastic wave samples over a wide range of amplitudes. Analysis on the accuracy of the topography reconstruction, the sensitivity to noise and the dependence on spatial resolution are presented. The displacement of the free surface is insensitive to noisy input and the sensitivity shows a linear dependence with the sample spacing. Simultaneous measurements of the free surface and associated velocity field in the wake of a circular cylinder are presented for Reynolds numbers between 55 and 100.     

The effect of reagent charge state on the charge inversion efficiency of singly charged polyatomic ions in the gas phase

A variety of combinations of oppositely charged ions have been reacted to examine the role of the charge state from a multiply protonated or multiply deprotonated reagent ion on the efficiency of conversion of a singly charged ion of opposite polarity to a singly charged ion of the same polarity as the reagent. Maximum efficiencies on the order of tens of percent were observed. A threshold for charge inversion was noted in all cases and, with one exception, a clear decrease in efficiency was also noted at high charge states. A model was developed to predict charge inversion efficiency based on charge states, cross-sections of the reactants, and relevant thermodynamic ion affinity values for the reactants and products. The model predicts a threshold for charge inversion, although the prediction does not match the observed threshold quantitatively. This discrepancy is likely due to a simplifying assumption that is not justified on a quantitative basis but which does reproduce the qualitative trend. The model does not predict the major decrease in efficiency at high charge states. However, calculations show that the kinetic energies of the charge inversion products can lead to significant scattering losses at high charge states of the ion-ion collision complex.