1,499 research outputs found
Choice of discount rate for cost levelization
"September 20, 1991."--ForewordIncludes bibliographical references (page 32
Tidal torques. A critical review of some techniques
We point out that the MacDonald formula for body-tide torques is valid only
in the zeroth order of e/Q, while its time-average is valid in the first order.
So the formula cannot be used for analysis in higher orders of e/Q. This
necessitates corrections in the theory of tidal despinning and libration
damping.
We prove that when the inclination is low and phase lags are linear in
frequency, the Kaula series is equivalent to a corrected version of the
MacDonald method. The correction to MacDonald's approach would be to set the
phase lag of the integral bulge proportional to the instantaneous frequency.
The equivalence of descriptions gets violated by a nonlinear
frequency-dependence of the lag.
We explain that both the MacDonald- and Darwin-torque-based derivations of
the popular formula for the tidal despinning rate are limited to low
inclinations and to the phase lags being linear in frequency. The
Darwin-torque-based derivation, though, is general enough to accommodate both a
finite inclination and the actual rheology.
Although rheologies with Q scaling as the frequency to a positive power make
the torque diverge at a zero frequency, this reveals not the impossible nature
of the rheology, but a flaw in mathematics, i.e., a common misassumption that
damping merely provides lags to the terms of the Fourier series for the tidal
potential. A hydrodynamical treatment (Darwin 1879) had demonstrated that the
magnitudes of the terms, too, get changed. Reinstating of this detail tames the
infinities and rehabilitates the "impossible" scaling law (which happens to be
the actual law the terrestrial planets obey at low frequencies).Comment: arXiv admin note: sections 4 and 9 of this paper contain substantial
text overlap with arXiv:0712.105
Spatiotemporal clustering, social vulnerability and risk of congenital syphilis in northeast Brazil: an ecological study
Background
To investigate the spatial distribution of congenital syphilis (CS) and its association to social vulnerability indexes in northeast Brazil.
Methods
This was an ecological study referring to all cases of CS and CS deaths recorded in the northeast region of Brazil from 2008 to 2015. Data were obtained from three Brazilian information systems. We examined statistical correlations between CS indicators by state and municipality and their socioeconomic and social vulnerability characteristics. We used Bayesian empirical local models to identify fluctuations of the indicators. Spatial statistical tests were used to identify spatial clusters and the municipalities at high risk of CS.
Results
The incidence of CS ranged from 2.1 cases/1000 live births (LB) in 2008 to 6.9/1000 LB in 2015, with an annual increase of 19.9% (p < 0.001). The mortality coefficient of CS ranged from 2.9/1000 LB in 2008 to 6.5/1000 LB in 2015, resulting in an annual increase of 15.1% (p < 0.001). Nine spatial clusters were identified. Cases of congenital syphilis occurred in well-defined spatiotemporal clusters and in areas with high levels of social vulnerability.
Conclusions
CS incidence is associated with social vulnerability. CS control programmes should target spatial clusters and populations with high levels of social vulnerability
The origin of the matter-antimatter asymmetry
Although the origin of matter-antimatter asymmetry remains unknown,
continuing advances in theory and improved experimental limits have ruled out
some scenarios for baryogenesis, for example the sphaleron baryogenesis at the
electroweak phase transition in the standard model. At the same time, the
success of cosmological inflation and the prospects for discovering
supersymmetry at the LHC have put some other models in sharper focus. We review
the current state of our understanding of baryogenesis with the emphasis on
those scenarios that we consider most plausible.Comment: submitted to Reviews of Modern Physics; 38 pages; 9 figure
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Individual common variants exert weak effects on the risk for autism spectrum disorders.
While it is apparent that rare variation can play an important role in the genetic architecture of autism spectrum disorders (ASDs), the contribution of common variation to the risk of developing ASD is less clear. To produce a more comprehensive picture, we report Stage 2 of the Autism Genome Project genome-wide association study, adding 1301 ASD families and bringing the total to 2705 families analysed (Stages 1 and 2). In addition to evaluating the association of individual single nucleotide polymorphisms (SNPs), we also sought evidence that common variants, en masse, might affect the risk. Despite genotyping over a million SNPs covering the genome, no single SNP shows significant association with ASD or selected phenotypes at a genome-wide level. The SNP that achieves the smallest P-value from secondary analyses is rs1718101. It falls in CNTNAP2, a gene previously implicated in susceptibility for ASD. This SNP also shows modest association with age of word/phrase acquisition in ASD subjects, of interest because features of language development are also associated with other variation in CNTNAP2. In contrast, allele scores derived from the transmission of common alleles to Stage 1 cases significantly predict case status in the independent Stage 2 sample. Despite being significant, the variance explained by these allele scores was small (Vm< 1%). Based on results from individual SNPs and their en masse effect on risk, as inferred from the allele score results, it is reasonable to conclude that common variants affect the risk for ASD but their individual effects are modest
Worldwide Patterns of Ancestry, Divergence, and Admixture in Domesticated Cattle
The domestication and development of cattle has considerably impacted human
societies, but the histories of cattle breeds have been poorly understood
especially for African, Asian, and American breeds. Using genotypes from 43,043
autosomal single nucleotide polymorphism markers scored in 1,543 animals, we
evaluate the population structure of 134 domesticated bovid breeds. Regardless
of the analytical method or sample subset, the three major groups of Asian
indicine, Eurasian taurine, and African taurine were consistently observed.
Patterns of geographic dispersal resulting from co-migration with humans and
exportation are recognizable in phylogenetic networks. All analytical methods
reveal patterns of hybridization which occurred after divergence. Using 19
breeds, we map the cline of indicine introgression into Africa. We infer that
African taurine possess a large portion of wild African auroch ancestry,
causing their divergence from Eurasian taurine. We detect exportation patterns
in Asia and identify a cline of Eurasian taurine/indicine hybridization in
Asia. We also identify the influence of species other than Bos taurus in the
formation of Asian breeds. We detect the pronounced influence of Shorthorn
cattle in the formation of European breeds. Iberian and Italian cattle possess
introgression from African taurine. American Criollo cattle are shown to be of
Iberian, and not African, decent. Indicine introgression into American cattle
occurred in the Americas, and not Europe. We argue that cattle migration,
movement and trading followed by admixture have been important forces in
shaping modern bovine genomic variation.Comment: 38 pages, 15 figures. Various changes made to respond to peer
reviews. Mostly, arguments were clarified and additional f-statistics were
adde
Bodily tides near spin-orbit resonances
Spin-orbit coupling can be described in two approaches. The method known as
"the MacDonald torque" is often combined with an assumption that the quality
factor Q is frequency-independent. This makes the method inconsistent, because
the MacDonald theory tacitly fixes the rheology by making Q scale as the
inverse tidal frequency.
Spin-orbit coupling can be treated also in an approach called "the Darwin
torque". While this theory is general enough to accommodate an arbitrary
frequency-dependence of Q, this advantage has not yet been exploited in the
literature, where Q is assumed constant or is set to scale as inverse tidal
frequency, the latter assertion making the Darwin torque equivalent to a
corrected version of the MacDonald torque.
However neither a constant nor an inverse-frequency Q reflect the properties
of realistic mantles and crusts, because the actual frequency-dependence is
more complex. Hence the necessity to enrich the theory of spin-orbit
interaction with the right frequency-dependence. We accomplish this programme
for the Darwin-torque-based model near resonances. We derive the
frequency-dependence of the tidal torque from the first principles, i.e., from
the expression for the mantle's compliance in the time domain. We also explain
that the tidal torque includes not only the secular part, but also an
oscillating part.
We demonstrate that the lmpq term of the Darwin-Kaula expansion for the tidal
torque smoothly goes through zero, when the secondary traverses the lmpq
resonance (e.g., the principal tidal torque smoothly goes through nil as the
secondary crosses the synchronous orbit).
We also offer a possible explanation for the unexpected frequency-dependence
of the tidal dissipation rate in the Moon, discovered by LLR
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