Accelerated Chemical Reactions and Organic Synthesis in Leidenfrost Droplets

Leidenfrost levitated droplets can be used to accelerate chemical reactions in processes that appear similar to reaction acceleration in charged microdroplets produced by electrospray ionization. Reaction acceleration in Leidenfrost droplets is demonstrated for a base‐catalyzed Claisen–Schmidt condensation, hydrazone formation from precharged and neutral ketones, and for the Katritzky pyrylium into pyridinium conversion under various reaction conditions. Comparisons with bulk reactions gave intermediate acceleration factors (2–50). By keeping the volume of the Leidenfrost droplets constant, it was shown that interfacial effects contribute to acceleration; this was confirmed by decreased reaction rates in the presence of a surfactant. The ability to multiplex Leidenfrost microreactors, to extract product into an immiscible solvent during reaction, and to use Leidenfrost droplets as reaction vessels to synthesize milligram quantities of product is also demonstrated.     

Eccentricity modulation of a close-in planet by a companion: Application to GJ 436 system

GJ 436b is a Neptune-size planet with 23.2 Earth masses in an elliptical orbit of period 2.64 days and eccentricity 0.16. With a typical tidal dissipation factor (Q′∼10⁶) as that of a giant planet with convective envelope, its orbital circularization timescale under internal tidal dissipation is around 1 Ga, at least two times less than the stellar age (> 3 Ga). A plausible mechanism is that the eccentricity of GJ 436b is modulated by a planetary companion due to their mutual perturbation. Here we investigate this possibility from the dynamical viewpoint. A general method is given to predict the possible locations of the dynamically coupled companions, including nearby/distance non-resonant or mean motion resonance orbits with the first planet. Applying the method to GJ 436 system, we find it is very unlikely that the eccentricity of GJ 436b is maintained at the present location by a nearby/distance companion through secular perturbation or mean motion resonance. In fact, in all these simulated cases, GJ 436b will undergo eccentricity damp and orbital decay, leaving the present location within the stellar age. However, these results do not rule out the possible existence of planet companions in nearby/distance orbits, although they are not able to maintain the eccentricity of GJ 436b. Supported by the National Natural Science Foundation of China (Grant Nos. 10833001 and 10778603) and the National Basic Research Program of China (Grant No. 2007CB4800)     

Strange stars properties calculated in the framework of the Field Correlator Method

We calculate the strange star properties in the framework of the Field Correlator Method. We find that for gluon condensate values G₂$G_2$ in the range 0.006–0.007 GeV⁴$0.006\text{–}0.007{\text{GeV}}^4$, which give a critical temperature Tc∼170 MeV$T_c\sim 170\text{MeV}$ at μc=0${\mu }_c=0$, the sequences of strange stars are compatible with some of the semi-empirical mass–radius relations and data obtained from astrophysical observations.     

Numerical methods for computing ground states and dynamics of nonlinear relativistic Hartree equation for boson stars

Efficient and accurate numerical methods are presented for computing ground states and dynamics of the three-dimensional (3D) nonlinear relativistic Hartree equation both without and with an external potential. This equation was derived recently for describing the mean field dynamics of boson stars. In its numerics, due to the appearance of pseudodifferential operator which is defined in phase space via symbol, spectral method is more suitable for the discretization in space than other numerical methods such as finite difference method, etc. For computing ground states, a backward Euler sine pseudospectral (BESP) method is proposed based on a gradient flow with discrete normalization; and respectively, for computing dynamics, a time-splitting sine pseudospectral (TSSP) method is presented based on a splitting technique to decouple the nonlinearity. Both BESP and TSSP are efficient in computation via discrete sine transform, and are of spectral accuracy in spatial discretization. TSSP is of second-order accuracy in temporal discretization and conserves the normalization in discretized level. In addition, when the external potential and initial data for dynamics are spherically symmetric, the original 3D problem collapses to a quasi-1D problem, for which both BESP and TSSP methods are extended successfully with a proper change of variables. Finally, extensive numerical results are reported to demonstrate the spectral accuracy of the methods and to show very interesting and complicated phenomena in the mean field dynamics of boson stars.     

Surface structure of quark stars with magnetic fields

We investigate the impact of magnetic fields on the electron distribution of the electrosphere of quark stars. For moderately strong magnetic fields of B ∼ 10¹³ G, quantization effects are generally weak due to the large number density of electrons at surface, but can nevertheless affect the photon emission properties of quark stars. We outline the main observational characteristics of quark stars as determined by their surface emission, and briefly discuss their formation in explosive events termed as quark-novae, which may be connected to the r-process.     

On diquark clustering in quark—gluon plasma

The possibility that pairs of quarks will form diquark clusters in the regime above deconfinement transition for hadron matter at finite density is revisited. Here we present the results on the diquark-diquark (dq-dq) interaction in the framework of constituent quark model taking account of spin, isospin and color degrees of freedom in the spirit of generalized Pauli principle. By constructing the appropriate spin and color states of the dq-dq clusters we compute the expectation values of the interaction Hamiltonian involving pairwise quark—quark interaction. We find that the effective interaction between two diquark clusters is quite sensitive to different configurations characterized by color and spin states, obtained after the coupling of two diquark states. The value of the coupling parameter for a particular color—spin state, i.e., -3, 1 is compared to the one obtained earlier by Donoghue and Sateesh,Phys. Rev. D38, 360 (1988) based on the effective Φ⁴-theory. This new value of λ derived for different color-spin dq-dq states, may lead to several important implications in the studies of diquark star and diquark gas.