167 research outputs found
SCABBARD: single-node fault-tolerant stream processing
Single-node multi-core stream processing engines (SPEs) can process hundreds of millions of tuples per second. Yet making them fault-tolerant with exactly-once semantics while retaining this performance is an open challenge: due to the limited I/O bandwidth of a single-node, it becomes infeasible to persist all stream data and operator state during execution. Instead, single-node SPEs rely on upstream distributed systems, such as Apache Kafka, to recover stream data after failure, necessitating complex cluster-based deployments. This lack of built-in fault-tolerance features has hindered the adoption of single-node SPEs.We describe Scabbard, the first single-node SPE that supports exactly-once fault-tolerance semantics despite limited local I/O bandwidth. Scabbard achieves this by integrating persistence operations with the query workload. Within the operator graph, Scabbard determines when to persist streams based on the selectivity of operators: by persisting streams after operators that discard data, it can substantially reduce the required I/O bandwidth. As part of the operator graph, Scabbard supports parallel persistence operations and uses markers to decide when to discard persisted data. The persisted data volume is further reduced using workload-specific compression: Scabbard monitors stream statistics and dynamically generates computationally efficient compression operators. Our experiments show that Scabbard can execute stream queries that process over 200 million tuples per second while recovering from failures with sub-second latencies
Hadamard States and Adiabatic Vacua
Reversing a slight detrimental effect of the mailer related to TeXabilityComment: 10pages, LaTeX (RevTeX-preprint style
Reproductive Biology of the Cape Honeybee: A Critique of Beekman et al: A critique of "Asexually Produced Cape Honeybee Queens (Apis mellifera capensis) Reproduce Sexually,â authors: Madeleine Beekman, Michael H. Allsopp, Julianne Lim, Frances Goudie, and Benjamin P. Oldroyd. Journal of Heredity. 2011:102(5):562-566
Laying workers of the Cape honeybee parthenogenetically produce female offspring, whereas queens typically produce males. Beekman et al. confirm this observation, which has repeatedly been reported over the last 100 years including the notion that natural selection should favor asexual reproduction in Apis mellifera capensis. They attempt to support their arguments with an exceptionally surprising finding that A. m. capensis queens can parthenogenetically produce diploid homozygous queen offspring (homozygous diploid individuals develop into diploid males in the honeybee). Beekman et al. suggest that these homozygous queens are not viable because they did not find any homozygous individuals beyond the third larval instar. Even if this were true, such a lethal trait should be quickly eliminated by natural selection. The identification of sex (both with molecular and morphological markers) is possible but notoriously difficult in honeybees at the early larval stages. Ploidy is however a reliable indicator, and we therefore suggest that these "homozygousâ larvae found in queen cells are actually drones reared from unfertilized eggs, a phenomenon well known by honeybee queen breeder
Floral turnover and climate drive seasonal bee diversity along a tropical elevation gradient
The contribution of seasonality in species communities to elevational diversity
of tropical insects remains poorly understood. We here assessed seasonal patterns
and drivers of bee diversity in the Eastern Afromontane Biodiversity
Hotspot, Kenya, to understand the contribution of seasonality to elevational
biodiversity patterns. Bee species and plant species visited by bees were
recorded on 50 study plots in regrowth vegetation across four major seasons
along two elevation gradients from 525 to 2530 m above sea level. Bees were
sampled by transect walks using sweep nets and aspirators. We examined how
local species richness (α-diversity) and seasonal changes in local species communities
(ÎČ-diversity) contribute to species richness across seasons (Îł-diversity)
along elevation gradients. Using a multimodel inference framework, we identified
the contribution of climate and floral seasonality to elevational patterns in
bee diversity. We found that both α- and γ-diversity decreased with elevation.
Seasonal ÎČ-diversity decreased with elevation and the high turnover of species
across seasons contributed to a considerably higher γ- than α-diversity on
study plots. A combination of seasonality in climate and the seasonal turnover of floral resources best explained the seasonality in bee species communities
(seasonal ÎČ-diversity). We, therefore, conclude that, despite the more stable,
and favorable climatic conditions in the tropics (in comparison to temperate
regions), climatic seasonality and its influence on beesâ floral resources largely
determined seasonal patterns of bee species diversity along elevation gradients
on tropical mountains.JRS Biodiversity Foundation (grant number: 60610), UKâs Foreign, Commonwealth & Development Office (FCDO), the Swedish International Development Cooperation Agency (Sida), the Swiss Agency for Development and Cooperation (SDC), the Federal Democratic Republic of Ethiopia, and the Government of the Republic of Kenya.https://onlinelibrary.wiley.com/r/ecs2am2023Zoology and Entomolog
Reproductive Biology of the Cape Honeybee: A Critique of Beekman et al.
A critique of âAsexually Produced Cape Honeybee Queens (Apis mellifera capensis) Reproduce Sexuallyâ: Laying workers of the Cape honeybee parthenogenetically produce female offspring whereas queens typically produce males. Beekman et al. confirm this observation, which has repeatedly been reported over the last 100 years including the notion that natural selection should favor asexual reproduction in A. m. capensis. They attempt to support their arguments with an exceptionally surprising finding that A. m. capensis queens can parthenogenetically produce diploid homozygous queen offspring (homozygous diploid individuals develop into diploid males in the honeybee). Beekman et al. suggest that these homozygous queens are not viable because they did not find any homozygous individuals beyond the third larval instar. Even if this were true, such a lethal trait should be quickly eliminated by natural selection. The identification of sex (both with molecular and morphological markers) is possible but notoriously difficult in honeybees at the early larval stages. Ploidy is however a reliable indicator and we therefore suggest that these âhomozygousâ larvae found in queen cells are actually drones reared from unfertilized eggs, a phenomenon well known by honeybee queen breeders.http://www.ncbi.nlm.nih.gov/pubmed/22581844ab201
Search for Relativistic Magnetic Monopoles with IceCube
We present the first results in the search for relativistic magnetic
monopoles with the IceCube detector, a subsurface neutrino telescope located in
the South Polar ice cap containing a volume of 1 km. This analysis
searches data taken on the partially completed detector during 2007 when
roughly 0.2 km of ice was instrumented. The lack of candidate events
leads to an upper limit on the flux of relativistic magnetic monopoles of
\Phi_{\mathrm{90%C.L.}}\sim 3\e{-18}\fluxunits for . This is a
factor of 4 improvement over the previous best experimental flux limits up to a
Lorentz boost below . This result is then interpreted for a
wide range of mass and kinetic energy values.Comment: 11 pages, 11 figures. v2 is minor text edits, no changes to resul
Lateral Distribution of Muons in IceCube Cosmic Ray Events
In cosmic ray air showers, the muon lateral separation from the center of the
shower is a measure of the transverse momentum that the muon parent acquired in
the cosmic ray interaction. IceCube has observed cosmic ray interactions that
produce muons laterally separated by up to 400 m from the shower core, a factor
of 6 larger distance than previous measurements. These muons originate in high
pT (> 2 GeV/c) interactions from the incident cosmic ray, or high-energy
secondary interactions. The separation distribution shows a transition to a
power law at large values, indicating the presence of a hard pT component that
can be described by perturbative quantum chromodynamics. However, the rates and
the zenith angle distributions of these events are not well reproduced with the
cosmic ray models tested here, even those that include charm interactions. This
discrepancy may be explained by a larger fraction of kaons and charmed
particles than is currently incorporated in the simulations
An improved method for measuring muon energy using the truncated mean of dE/dx
The measurement of muon energy is critical for many analyses in large
Cherenkov detectors, particularly those that involve separating
extraterrestrial neutrinos from the atmospheric neutrino background. Muon
energy has traditionally been determined by measuring the specific energy loss
(dE/dx) along the muon's path and relating the dE/dx to the muon energy.
Because high-energy muons (E_mu > 1 TeV) lose energy randomly, the spread in
dE/dx values is quite large, leading to a typical energy resolution of 0.29 in
log10(E_mu) for a muon observed over a 1 km path length in the IceCube
detector. In this paper, we present an improved method that uses a truncated
mean and other techniques to determine the muon energy. The muon track is
divided into separate segments with individual dE/dx values. The elimination of
segments with the highest dE/dx results in an overall dE/dx that is more
closely correlated to the muon energy. This method results in an energy
resolution of 0.22 in log10(E_mu), which gives a 26% improvement. This
technique is applicable to any large water or ice detector and potentially to
large scintillator or liquid argon detectors.Comment: 12 pages, 16 figure
ORCHIDEE-PEAT (revision 4596), a model for northern peatland CO2, water, and energy fluxes on daily to annual scales
Peatlands store substantial amounts of carbon and are vulnerable to climate change. We present a modified version of the Organising Carbon and Hydrology In Dynamic Ecosystems (ORCHIDEE) land surface model for simulating the hydrology, surface energy, and CO2 fluxes of peatlands on daily to annual timescales. The model includes a separate soil tile in each 0.5 degrees grid cell, defined from a global peatland map and identified with peat-specific soil hydraulic properties. Runoff from non-peat vegetation within a grid cell containing a fraction of peat is routed to this peat soil tile, which maintains shallow water tables. The water table position separates oxic from anoxic decomposition. The model was evaluated against eddy-covariance (EC) observations from 30 northern peatland sites, with the maximum rate of carboxylation (V-cmax) being optimized at each site. Regarding short-term day-to-day variations, the model performance was good for gross primary production (GPP) (r(2) = 0.76; Nash-Sutcliffe modeling efficiency, MEF = 0.76) and ecosystem respiration (ER, r(2) = 0.78, MEF = 0.75), with lesser accuracy for latent heat fluxes (LE, r(2) = 0.42, MEF = 0.14) and and net ecosystem CO2 exchange (NEE, r(2) = 0.38, MEF = 0.26). Seasonal variations in GPP, ER, NEE, and energy fluxes on monthly scales showed moderate to high r(2) values (0.57-0.86). For spatial across-site gradients of annual mean GPP, ER, NEE, and LE, r(2) values of 0.93, 0.89, 0.27, and 0.71 were achieved, respectively. Water table (WT) variation was not well predicted (r(2) <0.1), likely due to the uncertain water input to the peat from surrounding areas. However, the poor performance of WT simulation did not greatly affect predictions of ER and NEE. We found a significant relationship between optimized V-cmax and latitude (temperature), which better reflects the spatial gradients of annual NEE than using an average V-cmax value.Peer reviewe
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