Intermittency in the joint cascade of energy and helicity

The statistics of the energy and helicity fluxes in isotropic turbulence are studied using high resolution direct numerical simulation. The scaling exponents of the energy flux agree with those of the transverse velocity structure functions through refined similarity hypothesis, consistent with Kraichnan's prediction. The helicity flux is even more intermittent than the energy flux. Consistent with this observation, the spatial helicity-flux structures are finer than those of energy flux and more tubelike in geometry.     

Rapidity dependence of charged antihadron to hadron ratios in Au+Au collisions at sqrt[s(NN)]=200 GeV

We present ratios of the numbers of charged antihadrons to hadrons (pions, kaons, and protons) in Au+Au collisions at sqrt[s(NN)]=200 GeV as a function of rapidity in the range y=0-3. While the ratios at midrapidity are approaching unity, the K(-)/K(+) and p;/p ratios decrease significantly at forward rapidities. An interpretation of the results within the statistical model indicates a reduction of the baryon chemical potential from mu(B) approximately 130 MeV at y=3 to mu(B) approximately 25 MeV at y=0.     

High-throughput screening of pKa values of pharmaceuticals by pressure-assisted capillary electrophoresis and mass spectrometry

A high-throughput pKa screening method based on pressure-assisted capillary electrophoresis (CE) and mass spectrometry (MS) is presented. Effects of buffer type and ionic strength on sensitivity and pKa values were investigated. Influence of dimethyl sulfoxide (DMSO) concentration present in the sample on effective mobility measurement was examined. A series of ten volatile buffers, covering a pH range from 2.5 to 10.5 with the same ionic strength, was employed. The application of volatile background electrolytes resulted in significant signal increase as compared with commonly used non-volatile phosphate buffers. In general, the CE/MS system provided a ten-fold higher sensitivity than conventional UV detection. The newly developed CE/MS method offers high-throughput capacity by pooling a number of compounds into a single sample. Simultaneous measurement of more than 50 compounds was readily achieved in less than 150 min. The measured pKa values are consistent with the published data obtained from the CE/UV method and are also in good agreement with data generated by other methods. Other advantages of using CE/MS for pKa screening are illustrated with typical examples, including poorly soluble compounds and non-UV-absorbing compounds.     

Stereoselective synthesis of several azido/amino- and diazido/diamino-myo-inositols and their phosphates from p-benzoquinone

A practical route is described for the preparation of azido-myo-inositols, amino-myo-inositols and azido-conduritol B derivatives. Starting from p-benzoquinone, optically pure compounds in both forms can be prepared via enzymatic resolution of a derived diacetoxy conduritol B derivative. Selective introduction of nitrogen-containing functional groups in four of the six possible positions in the cyclitol moiety is followed by further functionalization to yield the target compounds.     

Tablets of functionalized polystyrene beads alone and in combination with solid reagents or catalysts. Preparation and applications in parallel solution and solid phase synthesis

Pretreatment of polystyrene beads with a nonpolar organic solvent is the key for the generation of mechanically robust tablets consisting of neat functionalized polystyrene beads, both alone and in combination with solid reagents or catalysts. The novel dosing methodology provides accurately preweighed tablets in virtually any shape and size and with excellent disintegration properties, speeding up parallel solution and solid phase synthesis. The use of tablets is demonstrated in parallel Mitsunobu and acylation reactions.     

Nonintegrability of a Fifth-Order Equation with Integrable Two-Body Dynamics

We consider a fifth-order partial differential equation (PDE) that is a generalization of the integrable Camassa–Holm equation. This fifth-order PDE has exact solutions in terms of an arbitrary number of superposed pulsons with a geodesic Hamiltonian dynamics that is known to be integrable in the two-body case N==2. Numerical simulations show that the pulsons are stable, dominate the initial value problem, and scatter elastically. These characteristics are reminiscent of solitons in integrable systems. But after demonstrating the nonexistence of a suitable Lagrangian or bi-Hamiltonian structure and obtaining negative results from Painlevé analysis and the Wahlquist–Estabrook method, we assert that this fifth-order PDE is not integrable.     

Strong attraction between charged spheres due to metastable ionized states

We report a mechanism which can lead to long-range attractions between like-charged spherical macroions, stemming from the existence of metastable ionized states. We show that the ground state of a single highly charged colloid plus a few excess counterions is overcharged. For the case of two highly charged macroions in their neutralizing divalent counterion solution we demonstrate that, in the regime of strong Coulomb coupling, the counterion clouds are very likely to be unevenly distributed, leading to one overcharged and one undercharged macroion. This long-living metastable configuration in turn leads to a long-range Coulomb attraction.     

Theoretical investigation of high pressure phases of carbon dioxide

The recent discovery of a new solid phase of carbon dioxide ( CO2-V) has made it apparent that the properties of this vital chemical species are drastically altered under high pressure conditions. The reported transition at around 40 GPa from the Cmca phase ( CO2-III), which is a molecular solid, into the novel phase, which was observed to be quartzlike, clearly suggests a dramatic change of the chemical, electronic, and structural properties. We here present a theoretical analysis of the implications of this metamorphosis. At even higher pressures, we predict the existence of a very hard phase of the stishovite type.