1,902 research outputs found
Spherical collapse model in agegraphic dark energy cosmologies
Under the commonly used spherical collapse model, we study how dark energy
affects the growth of large scale structures of the Universe in the context of
agegraphic dark energy models. The dynamics of the spherical collapse of dark
matter halos in nonlinear regimes is determined by the properties of the dark
energy model. We show that the main parameters of the spherical collapse model
are directly affected by the evolution of dark energy in the agegraphic dark
energy models. We compute the spherical collapse quantities for different
values of agegraphic model parameter in two different scenarios:
first, when dark energy does not exhibit fluctuations on cluster scales, and
second, when dark energy inside the overdense region collapses similar to dark
matter. Using the Sheth-Tormen and Reed mass functions, we investigate the
abundance of dark matter halos in the framework of agegraphic dark energy
cosmologies. The model parameter is a crucial parameter in order to
count the abundance of dark matter halos. Specifically, the present analysis
suggests that the agegraphic dark energy model with bigger (smaller) value of
predicts less (more) virialized halos with respect to that of
CDM cosmology. We also show that in agegraphic dark energy models, the
number of halos strongly depends on clustered or uniformed distributions of
dark energy.Comment: 14 pages, 7 figures. Accepted in Physical Review
Non-global Structure of the O({\alpha}_s^2) Dijet Soft Function
High energy scattering processes involving jets generically involve matrix
elements of light- like Wilson lines, known as soft functions. These describe
the structure of soft contributions to observables and encode color and
kinematic correlations between jets. We compute the dijet soft function to
O({\alpha}_s^2) as a function of the two jet invariant masses, focusing on
terms not determined by its renormalization group evolution that have a
non-separable dependence on these masses. Our results include non-global single
and double logarithms, and analytic results for the full set of non-logarithmic
contributions as well. Using a recent result for the thrust constant, we
present the complete O({\alpha}_s^2) soft function for dijet production in both
position and momentum space.Comment: 55 pages, 8 figures. v2: extended discussion of double logs in the
hard regime. v3: minor typos corrected, version published in JHEP. v4: typos
in Eq. (3.33), (3.39), (3.43) corrected; this does not affect the main
result, numerical results, or conclusion
Dataset for Response of the Invasive Alliaria Petiolata to Extreme Temperatures and Drought
Alliaria petiolata, a strict biennial in North America, can have annual alternating high abundance of rosettes and flowering plants. We monitored changes in abundance of rosettes and flowering plants in permanent plots (2004 to 2014). Three times during our study the alternating yearly cycle was not observed (2007-2008, 2008-2009, and 2013-2014). We concluded stochastic Extreme Climate Events (ECEs), deviating from long-term climatic data norms (10th or 90th. percentile), likely caused negative organism responses. Long-term data from a local NOAA station located 25 km from our study site included monthly data (1) total precipitation, (2) number of days with \u3e 0.13 cm precipitation, and (3) mean and minimum temperatures. September 2007 met criteria for ECEs for all monthly variables. We first observed A. petiolata on our study site in 1988 and by the early 1990’s it was abundant. To determine if September 2007 significantly differed from other Septembers (1984-2014) we used six variables related to drought: (1) total precipitation, (2) number of days with precipitation, (3) number of contiguous days without precipitation, (4) mean monthly temperature, (5) mean maximum daily temperature, and (6) the number of days with temperatures \u3e 30 o C. The first two variables likely increase plant stress as they decrease, whereas stress declines as the remaining variables decrease. We used the six variables to generate a Principal Component Analysis (PCA) biplot. Axes 1 and 2 accounted for 74.3% of the variance. Record-breaking minimum temperatures (ECEs) for January (2009) and February-March (2014) likely reduced rosette abundance and disrupted reestablishment of alternating high abundance of rosettes and flowering plants. Our data suggest that a single ECE variable, minimum temperature, and multiple ECE variables related to drought likely had negative effects on A. petiolata
Jet Shapes and Jet Algorithms in SCET
Jet shapes are weighted sums over the four-momenta of the constituents of a
jet and reveal details of its internal structure, potentially allowing
discrimination of its partonic origin. In this work we make predictions for
quark and gluon jet shape distributions in N-jet final states in e+e-
collisions, defined with a cone or recombination algorithm, where we measure
some jet shape observable on a subset of these jets. Using the framework of
Soft-Collinear Effective Theory, we prove a factorization theorem for jet shape
distributions and demonstrate the consistent renormalization-group running of
the functions in the factorization theorem for any number of measured and
unmeasured jets, any number of quark and gluon jets, and any angular size R of
the jets, as long as R is much smaller than the angular separation between
jets. We calculate the jet and soft functions for angularity jet shapes \tau_a
to one-loop order (O(alpha_s)) and resum a subset of the large logarithms of
\tau_a needed for next-to-leading logarithmic (NLL) accuracy for both cone and
kT-type jets. We compare our predictions for the resummed \tau_a distribution
of a quark or a gluon jet produced in a 3-jet final state in e+e- annihilation
to the output of a Monte Carlo event generator and find that the dependence on
a and R is very similar.Comment: 62 pages plus 21 pages of Appendices, 13 figures, uses JHEP3.cls. v2:
corrections to finite parts of NLO jet functions, minor changes to plots,
clarified discussion of power corrections. v3: Journal version. Introductory
sections significantly reorganized for clarity, classification of logarithmic
accuracy clarified, results for non-Mercedes-Benz configurations adde
Late Miocene-Quaternary fault evolution and interaction in the southern California Inner Continental Borderland
Changing conditions along plate boundaries are thought to result in the reactivation of preexisting structures. The offshore southern California Borderland has undergone dramatic adjustments as conditions changed from subduction tectonics to transform tectonics, including major Miocene oblique extension, followed by transpressional fault reactivation. However, consensus is still lacking about stratigraphic age models, fault geometry, and slip history for the near-offshore area between southern Los Angeles and San Diego (California, USA). We interpret an extensive data set of seismic reflection, bathymetric, and stratigraphic data from that area to determine the three-dimensional geometry and kinematic evolution of the faults and folds and document how preexisting structures have changed their activity and type of slip through time. The resulting structural representation reveals a moderately landward-dipping San Mateo–Carlsbad fault that converges downward with the steeper, right-lateral Newport-Inglewood fault, forming a fault wedge affected by Quaternary contractional folding. This fault wedge deformed in transtension during late Miocene through Pliocene time. Subsequently, the San Mateo–Carlsbad fault underwent 0.6–1.0 km displacement, spatially varying between reverse right lateral and transtensional right lateral. In contrast, shallow parts of the previously identified gently dipping Oceanside detachment and the faults above it appear to have been inactive since the early Pliocene. These observations, together with new and revised geometric representations of additional steeper faults, and the evidence for a pervasive strike-slip component on these nearshore faults, suggest a need to revise the earthquake hazard estimates for the coastal region
The Goddard and Saturn Genes Are Essential for Drosophila Male Fertility and May Have Arisen de Novo
© 2017 The Author. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution. All rights reserved. New genes arise through a variety of mechanisms, including the duplication of existing genes and the de novo birth of genes from noncoding DNA sequences. While there are numerous examples of duplicated genes with important functional roles, the functions of de novo genes remain largely unexplored. Many newly evolved genes are expressed in the male reproductive tract, suggesting that these evolutionary innovations may provide advantages to males experiencing sexual selection. Using testis-specific RNA interference, we screened 11 putative de novo genes in Drosophila melanogaster for effects on male fertility and identified two, goddard and saturn, that are essential for spermatogenesis and sperm function. Goddard knockdown (KD) males fail to produce mature sperm, while saturn KD males produce few sperm, and these function inefficiently once transferred to females. Consistent with a de novo origin, both genes are identifiable only in Drosophila and are predicted to encode proteins with no sequence similarity to any annotated protein. However, since high levels of divergence prevented the unambiguous identification of the noncoding sequences fromwhich each gene arose, we consider goddard and saturn to be putative de novo genes. Within Drosophila, both genes have been lost in certain lineages, but show conserved, male-specific patterns of expression in the species in which they are found. Goddard is consistently found in single-copy and evolves under purifying selection. In contrast, saturn has diversified through gene duplication and positive selection. These data suggest that de novo genes can acquire essential roles in male reproduction
Globally, plant-soil feedbacks are weak predictors of plant abundance
Plant-soil feedbacks (PSFs) have been shown to strongly affect plant performance under controlled conditions, and PSFs are thought to have far reaching consequences for plant population dynamics and the structuring of plant communities. However, thus far the relationship between PSF and plant species abundance in the field is not consistent. Here, we synthesize PSF experiments from tropical forests to semiarid grasslands, and test for a positive relationship between plant abundance in the field and PSFs estimated from controlled bioassays. We meta-analyzed results from 22 PSF experiments and found an overall positive correlation (0.12 <= r over bar <= 0.32) between plant abundance in the field and PSFs across plant functional types (herbaceous and woody plants) but also variation by plant functional type. Thus, our analysis provides quantitative support that plant abundance has a general albeit weak positive relationship with PSFs across ecosystems. Overall, our results suggest that harmful soil biota tend to accumulate around and disproportionately impact species that are rare. However, data for the herbaceous species, which are most common in the literature, had no significant abundance-PSFs relationship. Therefore, we conclude that further work is needed within and across biomes, succession stages and plant types, both under controlled and field conditions, while separating PSF effects from other drivers (e.g., herbivory, competition, disturbance) of plant abundance to tease apart the role of soil biota in causing patterns of plant rarity versus commonness
Double Non-Global Logarithms In-N-Out of Jets
We derive the leading non-global logarithms (NGLs) of ratios of jet masses
m_{1,2} and a jet energy veto \Lambda due to soft gluons splitting into regions
in and out of jets. Such NGLs appear in any exclusive jet cross section with
multiple jet measurements or with a veto imposed on additional jets. Here, we
consider back-to-back jets of radius R produced in e^+e^- collisions, found
with a cone or recombination algorithm. The leading NGLs are of the form
\alpha_s^2 \ln^2(\Lambda/m_{1,2}) or \alpha_s^2\ln^2(m_1/m_2). Their
coefficients depend both on the algorithm and on R. We consider cone, \kt,
anti-\kt, and Cambridge-Aachen algorithms. In addition to determining the full
algorithmic and R dependence of the leading NGLs, we derive new relations among
their coefficients. We also derive to all orders in \alpha_s a factorized form
for the soft function S(k_L,k_R,\Lambda) in the cross section
\sigma(m_1,m_2,\Lambda) in which dependence on each of the global logs of
\mu/k_L, \mu/k_R and \mu/\Lambda determined by the renormalization group are
separated from one another and from the non-global logs. The same kind of soft
function, its associated non-global structure, and the algorithmic dependence
we derive here will also arise in exclusive jet cross sections at hadron
colliders, and must be understood and brought under control to achieve precise
theoretical predictions.Comment: 19 pages, 10 figures. v2: minor edits, additional discussion in
Introduction. v3: version published in JHE
Broken SU(3) Symmetry in Two-Body B Decays
The decays of mesons to two-body hadronic final states are analyzed
within the context of broken flavor SU(3) symmetry, extending a previous
analysis involving pairs of light pseudoscalars to decays involving one or two
charmed quarks in the final state. A systematic program is described for
learning information {}from decay rates regarding (i) SU(3)-violating
contributions, (ii) the magnitude of exchange and annihilation diagrams
(effects involving the spectator quark), and (iii) strong final-state
interactions. The implication of SU(3)-breaking effects for the extraction of
weak phases is also examined. The present status of data on these questions is
reviewed and suggestions for further experimental study are made.Comment: 38 pages, 8 figures, LaTeX file. The full postscript manuscript is
available by anon ftp at
ftp://lpsvsh.lps.umontreal.ca/theorie/hep-ph/SU3break.ps (a VAX so use the
format theorie.hep-ph if you change by more than one directory at a time
Application of Fluorescence-Guided Surgery to Subsurface Cancers Requiring Wide Local Excision: Literature Review and Novel Developments Toward Indirect Visualization.
The excision of tumors by wide local excision is challenging because the mass must be removed entirely without ever viewing it directly. Positive margin rates in sarcoma resection remain in the range of 20% to 35% and are associated with increased recurrence and decreased survival. Fluorescence-guided surgery (FGS) may improve surgical accuracy and has been utilized in other surgical specialties. ABY-029, an anti-epidermal growth factor receptor Affibody molecule covalently bound to the near-infrared fluorophore IRDye 800CW, is an excellent candidate for future FGS applications in sarcoma resection; however, conventional methods with direct surface tumor visualization are not immediately applicable. A novel technique involving imaging through a margin of normal tissue is needed. We review the past and present applications of FGS and present a novel concept of indirect FGS for visualizing tumor through a margin of normal tissue and aiding in excising the entire lesion as a single, complete mass with tumor-free margins
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