Constraints on the Abundance of Highly Ionized Proto-Cluster Regions from the Absence of Large Voids in the Lyman Alpha Forest

Energetic feedback processes during the formation of galaxy clusters may have heated and ionized a large fraction of the intergalactic gas in proto-cluster regions. When such a highly ionized hot ``super-bubble'' falls along the sightline to a background quasar, it would be seen as a large void, with little or no absorption, in the Lyman alpha forest. We examine the spectra of 137 quasars in the Sloan Digital Sky Survey, to search for such voids, and find no clear evidence of their existence. The size distribution of voids in the range 5-70 Angstrom (corresponding to physical sizes of approximately 3-35 comoving Mpc/h) is consistent with the standard model for the Lyman alpha forest without additional hot bubbles. We adapt a physical model for HII bubble growth during cosmological reionization (Furlanetto, Zaldarriaga and Hernquist 2004), to describe the expected size-distribution of hot super-bubbles at redshift around z = 3. This model incorporates the conjoining of bubbles around individual neighboring galaxies. Using the non-detection of voids, we find that models in which the volume filling factor of hot bubbles exceeds approximately 20 percent at z=3 can be ruled out, primarily because they overproduce the number of large (40-50 Angstrom) voids. We conclude that any pre-heating mechanism that explains galaxy cluster observations must avoid heating the low-density gas in the proto-cluster regions, either by operating relatively recently (z<3) or by depositing entropy in the high-density regions.Comment: submitted to ApJ, 9 emulateapj pages with 3 figure

1/m_Q Corrections to the Heavy-to-Light-Vector Transitions in the HQET

Within the HQET, the heavy to light vector meson transitions are systematically analyzed to the order of 1/m_Q. Besides the four universal functions at the leading order, there are twenty-two independent universal form factors at the order of 1/m_Q. Both the semileptonic decay B->\rho which is relevant to the |V_{ub}| extraction, and the penguin induced decay B -> K^* which is important to new physics discovering, depend on these form factors. Phenomenological implications are discussed.Comment: RevTeX, 9 pages, no figure

Towards a Deterministic Model of Planetary Formation I: a Desert in the Mass and Semi Major Axis Distributions of Extra Solar Planets

We examine the accretion of cores of giant planets from planetesimals, gas accretion onto the cores, and their orbital migration. We adopt a working model for nascent protostellar disks with a wide variety of surface density distributions in order to explore the range of diversity among extra solar planetary systems. If some cores can acquire more mass than a critical value of several Earth masses during the persistence of the disk gas, they would be able to rapidly accrete gas and evolve into gas giant planets. The gas accretion process is initially regulated by the Kelvin-Helmholtz contraction of the planets' gas envelope. Based on the assumption that the exponential decay of the disk-gas mass occurs on the time scales $\sim 10^{6}-10^{7}$ years and that the disk mass distribution is comparable to those inferred from the observations of circumstellar disks of T Tauri stars, we carry out simulations to predict the distributions of masses and semi major axes of extra solar planets. Since planets' masses grow rapidly from $10 M_{\oplus}$ to $100 M_{\oplus}$, the gas giant planets rarely form with asymptotic masses in this intermediate range. Our model predicts a paucity of extra solar planets with mass in the range 10-$100 M_{\oplus}$ and semi major axis less than 3AU. We refer to this deficit as a ``planet desert''. The effect of migration is to sharpen the boundaries and to enhance the contrast of the planet desert. The mass and semi major axis distributions generated in our simulations for the gas giants are consistent with those of the known extra solar planets.Comment: 55 pages, 12 figure

Opinion formation in multiplex networks with general initial distributions

We study opinion dynamics over multiplex networks where agents interact with bounded confidence. Namely, two neighbouring individuals exchange opinions and compromise if their opinions do not differ by more than a given threshold. In literature, agents are generally assumed to have a homogeneous confidence bound. Here, we study analytically and numerically opinion evolution over structured networks characterised by multiple layers with respective confidence thresholds and general initial opinion distributions. Through rigorous probability analysis, we show analytically the critical thresholds at which a phase transition takes place in the long-term consensus behaviour, over multiplex networks with some regularity conditions. Our results reveal the quantitative relation between the critical threshold and initial distribution. Further, our numerical simulations illustrate the consensus behaviour of the agents in network topologies including lattices and, small-world and scale-free networks, as well as for structure-dependent convergence parameters accommodating node heterogeneity. We find that the critical thresholds for consensus tend to agree with the predicted upper bounds in Theorems 4 and 5 in this paper. Finally, our results indicate that multiplexity hinders consensus formation when the initial opinion configuration is within a bounded range and, provide insight into information diffusion and social dynamics in multiplex systems modeled by networks

From Plasmodium vivax outbreak to elimination: lessons learnt from a retrospective analysis of data from Guantang

BACKGROUND: Malaria was once a serious public health problem in China, with Plasmodium vivax the major species responsible for more than 90% of local transmission. Following significant integrated malaria control and elimination programmes, malaria burden declined, and since 2017 China has not recorded any indigenous case. To understand the historical malaria transmission patterns and epidemic characteristics in China and insights useful to guide P. vivax malaria control and elimination elsewhere, a retrospective study was carried out. METHODS: Historical data from a pilot study conducted in Guantang, Luyi in central China from 1971-1995, were digitized. The data included monthly numbers of reported cases, febrile cases, parasite carriage rates, the neonatal infection rate, and entomological data regarding Anopheles sinensis. RESULTS: Following 25 years of continuous integrated malaria control activities, malaria incidence in Guantang decreased from 4,333 cases per 10,000 in 1970 before integrated implementation to 0.23 cases per 10,000 in 1991, and no cases in 1992-1995. Some fluctuations in incidence were observed between 1977 and 1981. During the period parasite rates, antibody levels and the neonatal infection rate also decreased. The pattern of seasonality confirmed that P. vivax in Henan Province was primarily of the long incubation type (temperate) during non-transmission period. The findings retrospectively provide a scientific basis for the implementation of mass campaigns of liver stage hypnozoite clearance. Entomological studies indicated that An. sinensis was the only vector, and it preferred bovine to human hosts, predominantly biting and resting outdoors. Mosquito densities declined between 1971 and 1984. CONCLUSION: The integrated malaria control approach in Guantang effectively controlled malaria and achieved elimination. Analysis of the effectiveness of the programme can provide guidance to other regions or countries with similar ecological settings aiming to move from malaria control to elimination. There is a potential challenge in the maintenance of non-transmission status owing to imported cases and the long dormancy of liver stage hypnozoites