Formation of Relativistic Axion Stars

Axions and axion-like particles are compelling candidates for the missing dark matter of the universe. As they undergo gravitational collapse, they can form compact objects such as axion stars or even black holes. In this paper, we study the formation and distribution of such objects. First, we simulate the formation of compact axion stars using numerical relativity with aspherical initial conditions that could represent the final stages of axion dark matter structure formation. We show that the final states of such collapse closely follow the known relationship of initial mass and axion decay constant $f_a$. Second, we demonstrate with a toy model how this information can be used to scan a model density field to predict the number densities and masses of such compact objects. In addition to being detectable by the LIGO/VIRGO gravitational wave interferometer network for axion mass of $10^{-9} < m_a < 10^{-11}$ eV, we show using peak statistics that for $f_a < 0.2M_{pl}$, there exists a "mass gap" between the masses of axion stars and black holes formed from collapse

Report on the public archives of Florida.

A report covering subject matter, condition, and availability of archival materials (exluding Spanish materials) relating to the history of Florida.https://stars.library.ucf.edu/floridaheritage/1132/thumbnail.jp

Expression, purification, and characterization of the yeast KEX1 gene product, a polypeptide precursor processing carboxypeptidase.

The Saccharomyces cerevisiae KEX1 gene encodes a protease with carboxypeptidase B-like activity involved in K1 and K2 killer toxins and alpha-factor (mating pheromone) precursors processing. The gene has been expressed using the baculovirus/insect cell system, and the KEX1 encoded protein (Kex1p) was purified to apparent homogeneity from detergent-solubilized membrane preparations of insect cells infected with the recombinant virus. The specific activity of the enzyme was enriched 126-fold as compared with the cell lysate, with a recovery of 29%. The NH2-terminal sequence of the purified active enzyme was identical to the predicted sequence after the removal of the signal peptide. This provides evidence that Kex1p, at least in insect cells, is not made as a proenzyme. The optimum pH for activity was 6.0, and the apparent pI value of the protein was below pH 3.0. The enzyme cleaves arginine or lysine from the COOH terminus of synthetic peptides: benzoyl-Phe-Ala-Arg (Km = 284 microM), furylacryloyl (fa)-Ala-Arg (Km = 516 microM), and fa-Ala-Lys (Km = 962 microM). The kinetic data obtained reveals that Kex1p preferentially cleaves the COOH-terminal arginine of peptides over the COOH-terminal lysine. Insect-derived Kex1p processes alpha-factor-Lys-Arg, its known natural substrate, to mature active alpha-factor, and this maturation event takes place in a sequential manner. Furthermore, the enzyme expresses very high affinity for the 15-amino acid-long peptide, alpha-factor-Lys-Arg (Ki = 22 microM), and somewhat lower affinity for the heptapeptides [Leu]enkephalin-Arg-Arg,-Arg-Lys, and [Met]enkephalin-Lys-Lys (Ki = 45, 57, and 81 microM, respectively). The data demonstrate that processing at the COOH terminus of the peptides tested stops after the cleavage of the Arg and/or Lys residues. The specificity of the enzyme for COOH-terminal basic amino acid residues of the peptides used in this study and its high affinity for alpha-factor-Lys-Arg confirms the role that Kex1p plays in polypeptide precursor processing in yeast

Advanced aeroservoelastic stabilization techniques for hypersonic flight vehicles

Advanced high performance vehicles, including Single-Stage-To-Orbit (SSTO) hypersonic flight vehicles, that are statically unstable, require higher bandwidth flight control systems to compensate for the instability resulting in interactions between the flight control system, the engine/propulsion dynamics, and the low frequency structural modes. Military specifications, such as MIL-F-9490D and MIL-F-87242, tend to limit treatment of structural modes to conventional gain stabilization techniques. The conventional gain stabilization techniques, however, introduce low frequency effective time delays which can be troublesome from a flying qualities standpoint. These time delays can be alleviated by appropriate blending of gain and phase stabilization techniques (referred to as Hybrid Phase Stabilization or HPS) for the low frequency structural modes. The potential of using HPS for compensating structural mode interaction was previously explored. It was shown that effective time delay was significantly reduced with the use of HPS; however, the HPS design was seen to have greater residual response than a conventional gain stablized design. Additional work performed to advance and refine the HPS design procedure, to further develop residual response metrics as a basis for alternative structural stability specifications, and to develop strategies for validating HPS design and specification concepts in manned simulation is presented. Stabilization design sensitivity to structural uncertainties and aircraft-centered requirements are also assessed

Ischemic volvulus of the transverse colon: A case report and review of literature

A 75-year old male presented to the emergency room with worsening abdominal pain and distension. Plain radiographs were suggestive of a large bowel obstruction due to volvulus. An attempt to detorse the volvulus and decompress the colon endoscopically failed, after which the patient was taken for an exploratory laparotomy. A transverse colon volvulus was found, and an extended right hemicolectomy and ileostomy was performed. We discuss the diagnosis and management of transverse colon volvulus and review the pertinent literature

A Sustained Dietary Change Increases Epigenetic Variation in Isogenic Mice

Epigenetic changes can be induced by adverse environmental exposures, such as nutritional imbalance, but little is known about the nature or extent of these changes. Here we have explored the epigenomic effects of a sustained nutritional change, excess dietary methyl donors, by assessing genomic CpG methylation patterns in isogenic mice exposed for one or six generations. We find stochastic variation in methylation levels at many loci; exposure to methyl donors increases the magnitude of this variation and the number of variable loci. Several gene ontology categories are significantly overrepresented in genes proximal to these methylation-variable loci, suggesting that certain pathways are susceptible to environmental influence on their epigenetic states. Long-term exposure to the diet (six generations) results in a larger number of loci exhibiting epigenetic variability, suggesting that some of the induced changes are heritable. This finding presents the possibility that epigenetic variation within populations can be induced by environmental change, providing a vehicle for disease predisposition and possibly a substrate for natural selection.This work was supported by the Australian Research Council (DP0771859) and the National Health and Medical Research Council (#459412, #635510)

Reverse genetics in Candida albicans predicts ARF cycling is essential for drug resistance and virulence

Peer reviewedPublisher PD

Habitable Climate Scenarios for Proxima Centauri b With a Dynamic Ocean

The nearby exoplanet Proxima Centauri b will be a prime future target for characterization, despite questions about its retention of water. Climate models with static oceans suggest that an Earth-like Proxima b could harbor a small dayside region of surface liquid water at fairly warm temperatures despite its weak instellation. We present the first 3-dimensional climate simulations of Proxima b with a dynamic ocean. We find that an ocean-covered Proxima b could have a much broader area of surface liquid water but at much colder temperatures than previously suggested, due to ocean heat transport and depression of the freezing point by salinity. Elevated greenhouse gas concentrations do not necessarily produce more open ocean area because of possible dynamic regime transitions. For an evolutionary path leading to a highly saline present ocean, Proxima b could conceivably be an inhabited, mostly open ocean planet dominated by halophilic life. For an ocean planet in 3:2 spin-orbit resonance, a permanent tropical waterbelt exists for moderate eccentricity. Simulations of Proxima Centauri b may also be a model for the habitability of planets receiving similar instellation from slightly cooler or warmer stars, e.g., in the TRAPPIST-1, LHS 1140, GJ 273, and GJ 3293 systems.Comment: Submitted to Astrobiology; 38 pages, 12 figures, 5 table