On the Insignificance of Photochemical Hydrocarbon Aerosols in the Atmospheres of Close-in Extrasolar Giant Planets

The close-in extrasolar giant planets (CEGPs) reside in irradiated environments much more intense than that of the giant planets in our solar system. The high UV irradiance strongly influences their photochemistry and the general current view believed that this high UV flux will greatly enhance photochemical production of hydrocarbon aerosols. In this letter, we investigate hydrocarbon aerosol formation in the atmospheres of CEGPs. We find that the abundances of hydrocarbons in the atmospheres of CEGPs are significantly less than that of Jupiter except for models in which the CH$_4$ abundance is unreasonably high (as high as CO) for the hot (effective temperatures $\gtrsim 1000$ K) atmospheres. Moreover, the hydrocarbons will be condensed out to form aerosols only when the temperature-pressure profiles of the species intersect with the saturation profiles--a case almost certainly not realized in the hot CEGPs atmospheres. Hence our models show that photochemical hydrocarbon aerosols are insignificant in the atmospheres of CEGPs. In contrast, Jupiter and Saturn have a much higher abundance of hydrocarbon aerosols in their atmospheres which are responsible for strong absorption shortward of 600 nm. Thus the insignificance of photochemical hydrocarbon aerosols in the atmospheres of CEGPs rules out one class of models with low albedos and featureless spectra shortward of 600 nm.Comment: ApJL accepte

Ediacaran Macro Body Fossils

This paper, Ediacaran Macro Body Fossils, reports a new discovery of well preserved three dimensional macro body fossils of the Ediacaran Period in central YunNan province in the People's Republic of China. These body fossils will enable more detailed and in-depth exploration of the evolution of multi-cellular macro organisms on this planet, whereas in the past, researches could only rely on cast or imprint fossils

Phase transition of a one-dimensional Ising model with distance-dependent connections

The critical behavior of Ising model on a one-dimensional network, which has long-range connections at distances $l>1$ with the probability $\Theta(l)\sim l^{-m}$, is studied by using Monte Carlo simulations. Through studying the Ising model on networks with different $m$ values, this paper discusses the impact of the global correlation, which decays with the increase of $m$, on the phase transition of the Ising model. Adding the analysis of the finite-size scaling of the order parameter $[]$, it is observed that in the whole range of $0<m<2$, a finite-temperature transition exists, and the critical exponents show consistence with mean-field values, which indicates a mean-field nature of the phase transition.Comment: 5 pages,8 figure

Arbitrary Dimensional Schwarzschild-FRW Black Holes

The metric of arbitrary dimensional Schwarzschild black hole in the background of Friedman-Robertson-Walker universe is presented in the cosmic coordinates system. In particular, the arbitrary dimensional Schwarzschild-de Sitter metric is rewritten in the Schwarzschild coordinates system and basing on which the even more generalized higher dimensional Schwarzschild-de Sitter metric with another extra dimensions is found. The generalized solution shows that the cosmological constant may roots in the extra dimensions of space.Comment: 10 page

Effects of Zeeman spin splitting on the modular symmetry in the quantum Hall effect

Magnetic-field-induced phase transitions in the integer quantum Hall effect are studied under the formation of paired Landau bands arising from Zeeman spin splitting. By investigating features of modular symmetry, we showed that modifications to the particle-hole transformation should be considered under the coupling between the paired Landau bands. Our study indicates that such a transformation should be modified either when the Zeeman gap is much smaller than the cyclotron gap, or when these two gaps are comparable.Comment: 8 pages, 4 figure

A condition for first order phase transitions in quantum mechanical tunneling models

A criterion is derived for the determination of parameter domains of first order phase transitions in quantum mechanical tunneling models. The criterion is tested by application to various models, in particular to some which have been used recently to explore spin tunneling in macroscopic particles. In each case agreement is found with previously heuristically determined domains.Comment: 13 pages, 5 figure

A high-throughput, quantitative cell-based screen for efficient tailoring of RNA device activity

Recent advances have demonstrated the use of RNA-based control devices to program sophisticated cellular functions; however, the efficiency with which these devices can be quantitatively tailored has limited their broader implementation in cellular networks. Here, we developed a high-efficiency, high-throughput and quantitative two-color fluorescence-activated cell sorting-based screening strategy to support the rapid generation of ribozyme-based control devices with user-specified regulatory activities. The high-efficiency of this screening strategy enabled the isolation of a single functional sequence from a library of over 106 variants within two sorting cycles. We demonstrated the versatility of our approach by screening large libraries generated from randomizing individual components within the ribozyme device platform to efficiently isolate new device sequences that exhibit increased in vitro cleavage rates up to 10.5-fold and increased in vivo activation ratios up to 2-fold. We also identified a titratable window within which in vitro cleavage rates and in vivo gene-regulatory activities are correlated, supporting the importance of optimizing RNA device activity directly in the cellular environment. Our two-color fluorescence-activated cell sorting-based screen provides a generalizable strategy for quantitatively tailoring genetic control elements for broader integration within biological networks

Signature of stratospheric air at the Tibetan Plateau

Current estimates of gross carbon flux tend to ignore the downwelling flux of CO_2 from the stratosphere. Observations showed that there is a phase shift between the time series for the concentration of the standard isotopologue C^16O^16O and C^16O^18O at Waliguan, China (36°17'N, 100° 54'E, 3816 m) and several other places. Previous attempts to explain the shift have not been satisfactory. Here we show that the phase shift could be explained by the downwelling air from the stratosphere, and demonstrate that this source of CO_2 provides a useful tool for constraining the carbon cycle. Using O_3 as a proxy of stratosphere-troposphere exchange, we find excellent correlation between O_3 and C^16O^18O observed at the Waliguan Observatory. The observed variability of C^16O^18O is consistent with model predictions, thus supporting that the surface air has significant contributions from the stratosphere. Quantitative modeling may provide a powerful tool for constraining the sources and sinks of CO_2 using the isotopically enriched CO_2 from the stratosphere as a tracer

The nature of the charge density waves in under-doped YBa2_2Cu3_3O6.54_{6.54} revealed by X-ray measurements of the ionic displacements

All underdoped high-temperature cuprate superconductors appear to exhibit charge density wave (CDW) order, but both the underlying symmetry breaking and the origin of the CDW remain unclear. We use X-ray diffraction to determine the microscopic structure of the CDW in an archetypical cuprate YBa$_2$Cu$_3$O$_{6.54}$ at its superconducting transition temperature Tc ~ 60 K. We find that the CDWs present in this material break the mirror symmetry of the CuO2 bilayers. The ionic displacements in a CDW have two components: one perpendicular to the CuO$_2$ planes, and another parallel to these planes, which is out of phase with the first. The largest displacements are those of the planar oxygen atoms and are perpendicular to the CuO$_2$ planes. Our results allow many electronic properties of the underdoped cuprates to be understood. For instance, the CDW will lead to local variations in the doping (or electronic structure) giving an explicit explanation of the appearance of density-wave states with broken symmetry in scanning tunnelling microscopy (STM) and soft X-ray measurements