The Hubble Constant from Observations of the Brightest Red Giant Stars in a Virgo-Cluster Galaxy

The Virgo and Fornax clusters of galaxies play central roles in determining the Hubble constant H_0. A powerful and direct way of establishing distances for elliptical galaxies is to use the luminosities of the brightest red-giant stars (the TRGB luminosity, at M_I = -4.2). Here we report the direct observation of the TRGB stars in a dwarf elliptical galaxy in the Virgo cluster. We find its distance to be 15.7 +- 1.5 Megaparsecs, from which we estimate a Hubble constant of H_0 = 77 +- 8 km/s/Mpc. Under the assumption of a low-density Universe with the simplest cosmology, the age of the Universe is no more than 12-13 billion years.Comment: 12 pages, LaTeX, with 2 postscript figures; in press for Nature, July 199

Neutralino relic density in supersymmetric GUTs with no-scale boundary conditions above the unification scale

We investigate SU(5) and SO(10) GUTs with vanishing scalar masses and trilinear scalar couplings at a scale higher than the unification scale. The parameter space of the models, further constrained by b-\tau Yukawa coupling unification, consists of a common gaugino mass and of \tan\beta. We analyze the low energy phenomenology, finding that A-pole annihilations of neutralinos and/or coannihilations with the lightest stau drive the relic density within the cosmologically preferred range in a significant region of the allowed parameter space. Implications for neutralino direct detection and for CERN LHC experiments are also discussed.Comment: 14 pages, 5 figures, JHEP style. Version accepted for publication in JHE

The luminosity of supernovae of type Ia from TRGB distances and the value of H_0

Distances from the tip of the red-giant branch (TRGB) in the halo Population of galaxies - calibrated through RR Lyr stars as well as tied to Hipparcos parallaxes and further supported by stellar models - are used to determine the luminosity of six nearby type Ia supernovae (SN 2011fe, 2007sr, 1998bu, 1989B, 1972E, and 1937C). The result is M_V^corr = -19.41 +/- 0.05. If this value is applied to 62 SNe Ia with 3000< v < 20,000 km/s a large-scale value of the Hubble constant follows of H_0 = 64.0 +/- 1.6 +/- 2.0. The SN HST Project gave H_0 = 62.3 +/- 1.3 +/- 5.0 from ten Cepheid-calibrated SNe Ia (Sandage et al. 2006). The agreement of young Population I (Cepheids) and old, metal-poor Population II (TRGB) distance indicators is satisfactory. The combined weighted result is H_0 = 63.7 +/- 2.3 (i.e. +/-3.6%). The result can also be reconciled with WMAP5 data (Reid et al. 2010).Comment: 9 pages, 3 figures, 3 tables, accepted for publication in Astronomy and Astrophysic

Linking Adult Reproduction and Larval Density of Invasive Carp in a Large River

Identifying how temporal variation in the environment affects reproductive success of invasive alien species will aid in predicting future establishment and tracking dynamics of established populations. Asian carp Hypophthalmichthys spp. have become a nuisance in recent years in the Mississippi River basin. Their populations are apparently expanding, indicating favorable conditions for reproduction. During 2004 and 2005, we quantified mean density of Asian carp larvae, mean monthly gonadosomatic index (GSI) of adult males and females, and number of eggs within mature females in the lower Illinois River, a major tributary of the Mississippi River. A flood (water velocity ≥ 0.7 m/s) and drought (\u3c0.2 m/s) occurred during apparent spawning in 2004 and 2005, respectively. During 2004, Asian carp larvae were found during 32% of sampling weeks; mean GSI and fecundity were relatively low for adults, probably reflecting partially spawned individuals and perhaps low reproductive investment. During the drought of 2005, larval stages were present during only one (5%) of the sampling weeks, whereas mean GSI and fecundity of adults were high through summer. Females resorbed their eggs instead of spawning during this year. Spawning conditions during low water periods appear to be unsuitable for Asian carps, inhibiting adult spawning and yielding few larvae. Spawning conditions during 2004 were better but still yielded low densities of larvae relative to native fishes. Reproduction in the lower Illinois River appears to be linked to river flow and its impact on adult spawning decisions, but conditions for strong year-class production (i.e., high larval densities) may be rarer than previously expected

Yukawa coupling unification and non-universal gaugino mediation of supersymmetry breaking

The requirement of Yukawa coupling unification highly constrains the SUSY parameter space. In several SUSY breaking scenarios it is hard to reconcile Yukawa coupling unification with experimental constraints from B(b->s gamma) and the muon anomalous magnetic moment a_mu. We show that b-tau or even t-b-tau Yukawa unification can be satisfied simultaneously with b->s gamma and a_mu in the non-universal gaugino mediation scenario. Non-universal gaugino masses naturally appear in higher dimensional grand unified models in which gauge symmetry is broken by orbifold compactification. Relations between SUSY contributions to fermion masses, b->s gamma and a_mu which are typical for models with universal gaugino masses are relaxed. Consequently, these phenomenological constraints can be satisfied simultaneously with a relatively light SUSY spectrum, compared to models with universal gaugino masses.Comment: 20 pages, 8 figures. References added. A copy of the paper with better resolution figures can be found at http://www.hep.fsu.edu/~balazs/Physics/Papers/2003

Effects of SO(10) D-Term on Yukawa Unification and Unstable Minima of the Supersymmetric Scalar Potential

We study the effects of SO(10) D-terms on the allowed parameter space (APS) in models with $t - b - \tau$ and $b - \tau$ Yukawa unifiction. The former is allowed only for moderate values of the D-term, if very precise ($\le$ 5%) unification is required. Next we constrain the parameter space by looking for different dangerous directions where the scalar potential may be unbounded from below (UFB1 and UFB3). The common trilinear coupling $A_0$ plays a significant role in constraing the APS. For very precise $t - b - \tau$ Yukawa unification, $-m_{16} < or \approx A_0 < or \approx m_{16}$ can be probed at the LHC, where $m_{16}$ is the common soft breaking mass for the sfermions. Moreover, an interesting mass hierarchy with very heavy sfermions but light gauginos, which is strongly disfavoured in models without D-terms, becomes fairly common in the presence of the D-terms. The APS exhibits interesting characteristics if $m_{16}$ is not the same as the soft breaking mass $m_{10}$ for the Higgs sector. In $b - \tau$ unification models with D-terms, the APS consistent with Yukawa unification and radiative electroweak symmetry breaking, increases as the UFB1 constraint becomes weaker. However for $A_0 \leq 0$, a stronger UFB3 condition still puts, for a given $m_{16}$, a stringent upper bound on the common gaugino mass ($m_{1/2}$) and a lower bound on $m_{16}$ for a given $m_{1/2}$. The effects of sign of $\mu$ on Yukawa unification and UFB constraints are also discussed.Comment: Plain Latex, 22 pages, 11 figures. Small changes in the abstract, the pattern of discussion changed signifiantly, no change in the figures and results, a few new references added, version published in JP

An Integrated Ecosystem Approach for Assessing the Potential Role of Cultivated Bivalve Shells as Part of the Carbon Trading System

The role of bivalve mariculture in the CO2 cycle has been commonly evaluated as the balance between respiration, shell calcium carbonate sequestration and CO2 release during biogenic calcification. However, this approach neglects the ecosystem implications of cultivating bivalves at high densities, e.g. the impact on phytoplankton dynamics and benthic-pelagic coupling, which can significantly contribute to the CO2 cycle. Therefore, an ecosystem approach that accounts for the trophic interactions of bivalve aquaculture, including dissolved and particulate organic and inorganic carbon cycling, is needed to provide a rigorous assessment of the role of bivalve mariculture in the CO2 cycle. On the other hand, the discussion about the inclusion of shells of cultured bivalves into the carbon trading system should be framed within the context of ecosystem goods and services. Humans culture bivalves with the aim of producing food, not sequestering CO2 in their shells, therefore the main ecosystem good provided by bivalve aquaculture is meat production, and shells should be considered as by-products of this human activity. This reasoning provides justification for dividing up respired CO2 between meat and shell when constructing a specific bivalve CO2 budget for potential use of bivalve shells in the carbon trading system. Thus, an integrated ecosystem approach, as well as an understanding of the ecosystems goods and services of bivalve aquaculture, are 2 essential requisites for providing a reliable assessment of the role of bivalve shells in the CO2 cycle

Movement and Habitat Selection by Invasive Asian Carps in a Large River

We evaluated the habitat use and movements of 50 adult bighead carp Hypophthalmichthys nobilis and 50 silver carp H. molitrix by means of ultrasonic telemetry during spring–summer 2004 and 2005 to gain insight into the conditions that facilitate their establishment, persistence, and dispersal in the lower Illinois River (river kilometer 0–130). Movement and habitat use were monitored with stationary receivers and boat-mounted tracking. The relative availability of four macrohabitat categories (main channel, island side channel, channel border, and connected backwater) was quantified to determine selection; discriminant function analysis was used to evaluate changes in physical characteristics within each category. A flood pulse occurred in spring through early summer of 2004 but not 2005. Movement rates (km/week) of both species were positively correlated with flow but not with temperature. Including data from stationary receivers greatly increased estimates of daily movement. During low summer flow, both species typically selected channel borders and avoided the main channel and backwaters. Both species rarely occupied depths over 4 m, regardless of abiotic conditions. Flood pulses appear to trigger dispersal, while habitat use is only specific during low summer flow. Thus, movement prevention efforts (e.g., dispersal barriers) will require particular vigilance during late-winter or spring flooding, and controlled removal (e.g., harvest) should be directed toward selected habitats during summer

A deeply branching thermophilic bacterium with an ancient acetyl-CoA pathway dominates a subsurface ecosystem

<div><p>A nearly complete genome sequence of <em>Candidatus</em> ‘Acetothermum autotrophicum’, a presently uncultivated bacterium in candidate division OP1, was revealed by metagenomic analysis of a subsurface thermophilic microbial mat community. Phylogenetic analysis based on the concatenated sequences of proteins common among 367 prokaryotes suggests that <em>Ca.</em> ‘A. autotrophicum’ is one of the earliest diverging bacterial lineages. It possesses a folate-dependent Wood-Ljungdahl (acetyl-CoA) pathway of CO₂ fixation, is predicted to have an acetogenic lifestyle, and possesses the newly discovered archaeal-autotrophic type of bifunctional fructose 1,6-bisphosphate aldolase/phosphatase. A phylogenetic analysis of the core gene cluster of the acethyl-CoA pathway, shared by acetogens, methanogens, some sulfur- and iron-reducers and dechlorinators, supports the hypothesis that the core gene cluster of <em>Ca.</em> ‘A. autotrophicum’ is a particularly ancient bacterial pathway. The habitat, physiology and phylogenetic position of <em>Ca.</em> ‘A. autotrophicum’ support the view that the first bacterial and archaeal lineages were H₂-dependent acetogens and methanogenes living in hydrothermal environments.</p> </div

Growth, Fecundity, and Diets of Newly Established Silver Carp in the Middle Mississippi River

The silver carp Hypophthalmichthys molitrix has spread throughout the Mississippi River drainage. During 2003, we determined its population status and potential impact in the middle Mississippi River (MMR), the conduit between the lower Mississippi River and the upper Mississippi, Missouri, and Illinois rivers. We quantified growth, age structure, fecundity, and diets of silver carp sampled with trammel nets and AC electrofishing in main-channel areas. Mean length at age in the MMR exceeded that of populations in Asia by as much as 26%. Individuals were typically more than 1 year old and 230 mm total length, suggesting that small, young fish were absent. Individuals in this population matured earlier (age 2) than in the species\u27 native range. Regardless of phytoplankton variation (using chlorophyll a as a surrogate) and zooplankton concentration at MMR sites, phytoplankton was consistently most abundant in diets. Silver carp are finding suitable resources within the MMR, allowing individuals to grow rapidly during early life, persist as adults, and successfully disperse upstream