5,318 research outputs found
Larger testes are associated with a higher level of polyandry, but a smaller ejaculate volume, across bushcricket species (Tettigoniidae)
While early models of ejaculate allocation predicted that both relative testes and ejaculate size should increase with sperm competition intensity across species, recent models predict that ejaculate size may actually decrease as testes size and sperm competition intensity increase, owing to the confounding effect of potential male mating rate. A recent study demonstrated that ejaculate volume decreased in relation to increased polyandry across bushcricket species, but testes mass was not measured. Here, we recorded testis mass for 21 bushcricket species, while ejaculate ( ampulla) mass, nuptial gift mass, sperm number and polyandry data were largely obtained from the literature. Using phylogenetic-comparative analyses, we found that testis mass increased with the degree of polyandry, but decreased with increasing ejaculate mass. We found no significant relationship between testis mass and either sperm number or nuptial gift mass. While these results are consistent with recent models of ejaculate allocation, they could alternatively be driven by substances in the ejaculate that affect the degree of polyandry and/or by a trade-off between resources spent on testes mass versus non-sperm components of the ejaculate
An experimental study of the dual-fuel performance of a small compression ignition diesel engine operating with three gaseous fuels
A dual-fuel engine is a compression ignition (CI) engine where the primary gaseous fuel source is premixed with air as it enters the combustion chamber. This homogenous mixture is ignited by a small quantity of diesel, the âpilotâ, that is injected towards the end of the compression stroke. In the present study, a direct-injection CI engine, was fuelled with three different gaseous fuels: methane, propane, and butane. The engine performance at various gaseous concentrations was recorded at 1500 r/min and quarter, half, and three-quarters relative to full a load of 18.7 kW. In order to investigate the combustion performance, a novel three-zone heat release rate analysis was applied to the data. The resulting heat release rate data are used to aid understanding of the performance characteristics of the engine in dual-fuel mode.
Data are presented for the heat release rates, effects of engine load and speed, brake specific energy consumption of the engine, and combustion phasing of the three different primary gaseous fuels.
Methane permitted the maximum energy substitution, relative to diesel, and yielded the most significant reductions in CO2. However, propane also had significant reductions in CO2 but had an increased diffusional combustion stage which may lend itself to the modern high-speed direct-injection engine
Penning trap and vacuum noise
A number of comments are provided on Rogers's model experiment to measure the
circular Unruh vacuum noise by means of a hyperbolic Penning trap inside a
microwave cavity. It is suggested that cylindrical Penning traps, being
geometrically simpler, and controlled almost at the same level of accuracy as
the hyperbolic trap, might be a better choice for such an experiment. Besides,
the microwave modes of the trap itself, of known analytical structure, can be
directly used in trying to obtain measurable results for such a tiny noise
effect.Comment: 7 LaTex pages, published text and references with title
Fair Value Accounting: A Historical Review Of The Most Controversial Accounting Issue In Decades
Historically, there have been many disputes in the area of corporate financial reporting. However, one of the primary issues of disagreement between practitioners, regulators, and theoreticians is that of valuation of financial statement components. The latest twist in the evolution of valuation is the push for (and against) the use of a fair value approach. The purpose of this paper is to examine the history and evolution of how the most critical elements of an entity’s financial statements are valued. We provide a history of valuation of financial statement components, and identify the issues involved. Further, we examine the criticisms of actions taken by the regulatory bodies in their efforts to standardize and advance accounting practices. Particularly, we focus on the evolution of fair value measurements. Arguments both for and against the implementation of fair value accounting are provided
POEM: Pricing Longer for Edge Computing in the Device Cloud
Multiple access mobile edge computing has been proposed as a promising
technology to bring computation services close to end users, by making good use
of edge cloud servers. In mobile device clouds (MDC), idle end devices may act
as edge servers to offer computation services for busy end devices. Most
existing auction based incentive mechanisms in MDC focus on only one round
auction without considering the time correlation. Moreover, although existing
single round auctions can also be used for multiple times, users should trade
with higher bids to get more resources in the cascading rounds of auctions,
then their budgets will run out too early to participate in the next auction,
leading to auction failures and the whole benefit may suffer. In this paper, we
formulate the computation offloading problem as a social welfare optimization
problem with given budgets of mobile devices, and consider pricing longer of
mobile devices. This problem is a multiple-choice multi-dimensional 0-1
knapsack problem, which is a NP-hard problem. We propose an auction framework
named MAFL for long-term benefits that runs a single round resource auction in
each round. Extensive simulation results show that the proposed auction
mechanism outperforms the single round by about 55.6% on the revenue on average
and MAFL outperforms existing double auction by about 68.6% in terms of the
revenue.Comment: 8 pages, 1 figure, Accepted by the 18th International Conference on
Algorithms and Architectures for Parallel Processing (ICA3PP
Estimating the amount of vorticity generated by cosmological perturbations in the early universe
We estimate the amount of vorticity generated at second order in cosmological
perturbation theory from the coupling between first order energy density and
non-adiabatic pressure, or entropy, perturbations. Assuming power law input
spectra for the source terms, and working in a radiation background, we
calculate the wave number dependence of the vorticity power spectrum and its
amplitude. We show that the vorticity generated by this mechanism is
non-negligible on small scales, and hence should be taken into consideration in
current and future CMB experiments.Comment: 9 pages, revtex4, 1 figure; v2: typos and minor error corrected,
result unchange
Genetic Targeting of ERK1 Suggests a Predominant Role for ERK2 in Murine Pain Models
The extracellular signal-regulated kinase (ERK) isoforms, ERK1 and ERK2, are believed to be key signaling molecules in nociception and nociceptive sensitization. Studies utilizing inhibitors targeting the shared ERK1/2 upstream activator, mitogen-activated protein kinase kinase (MEK), and transgenic mice expressing a dominant negative form of MEK have established the importance of ERK1/2 signaling. However, these techniques do not discriminate between ERK1 and ERK2. To dissect the function of each isoform in pain, we utilized mice with a targeted genetic deletion of ERK1 (ERK1 KO) to test the hypothesis that ERK1 is required for behavioral sensitization in rodent pain models. Despite activation (phosphorylation) of ERK1 following acute noxious stimulation and in models of chronic pain, we found that ERK1 was not required for formalin-induced spontaneous behaviors, complete Freundâs adjuvant-induced heat and mechanical hypersensitivity, and spared nerve injury-induced mechanical hypersensitivity. However, ERK1 deletion did delay formalin-induced long-term heat hypersensitivity, without affecting formalin-induced mechanical hypersensitivity, suggesting that ERK1 partially shapes long-term responses to formalin. Interestingly, ERK1 deletion resulted in elevated basal ERK2 phosphorylation. However, this did not appear to influence nociceptive processing, since inflammation-induced ERK2 phosphorylation and pERK1/2 immunoreactivity in spinal cord were not elevated in ERK1 KO mice. Additionally, systemic MEK inhibition with SL327 attenuated formalin-induced spontaneous behaviors similarly in WT and ERK1 KO mice, indicating that unrelated signaling pathways do not functionally compensate for the loss of ERK1. Taken together, these results suggest that ERK1 plays a limited role in nociceptive sensitization and supports a predominant role for ERK2 in these processes
Modelling non-dust fluids in cosmology
Currently, most of the numerical simulations of structure formation use
Newtonian gravity. When modelling pressureless dark matter, or `dust', this
approach gives the correct results for scales much smaller than the
cosmological horizon, but for scenarios in which the fluid has pressure this is
no longer the case. In this article, we present the correspondence of
perturbations in Newtonian and cosmological perturbation theory, showing exact
mathematical equivalence for pressureless matter, and giving the relativistic
corrections for matter with pressure. As an example, we study the case of
scalar field dark matter which features non-zero pressure perturbations. We
discuss some problems which may arise when evolving the perturbations in this
model with Newtonian numerical simulations and with CMB Boltzmann codes.Comment: 5 pages; v2: typos corrected and refs added, submitted version; v3:
version to appear in JCA
Sub-millimeter galaxies as progenitors of compact quiescent galaxies
Three billion years after the big bang (at redshift z=2), half of the most
massive galaxies were already old, quiescent systems with little to no residual
star formation and extremely compact with stellar mass densities at least an
order of magnitude larger than in low redshift ellipticals, their descendants.
Little is known about how they formed, but their evolved, dense stellar
populations suggest formation within intense, compact starbursts 1-2 Gyr
earlier (at 3<z<6). Simulations show that gas-rich major mergers can give rise
to such starbursts which produce dense remnants. Sub-millimeter selected
galaxies (SMGs) are prime examples of intense, gas-rich, starbursts. With a
new, representative spectroscopic sample of compact quiescent galaxies at z=2
and a statistically well-understood sample of SMGs, we show that z=3-6 SMGs are
consistent with being the progenitors of z=2 quiescent galaxies, matching their
formation redshifts and their distributions of sizes, stellar masses and
internal velocities. Assuming an evolutionary connection, their space densities
also match if the mean duty cycle of SMG starbursts is 42 (+40/-29) Myr
(consistent with independent estimates), which indicates that the bulk of stars
in these massive galaxies were formed in a major, early surge of
star-formation. These results suggests a coherent picture of the formation
history of the most massive galaxies in the universe, from their initial burst
of violent star-formation through their appearance as high stellar-density
galaxy cores and to their ultimate fate as giant ellipticals.Comment: ApJ (in press
Weighing the Milky Way
We describe an experiment to measure the mass of the Milky Way galaxy. The
experiment is based on calculated light travel times along orthogonal
directions in the Schwarzschild metric of the Galactic center. We show that the
difference is proportional to the Galactic mass. We apply the result to light
travel times in a 10cm Michelson type interferometer located on Earth. The mass
of the Galactic center is shown to contribute 10^-6 to the flat space component
of the metric. An experiment is proposed to measure the effect.Comment: 10 pages, 1 figur
- âŠ