220 research outputs found
On the Super-Additivity and Estimation Biases of Quantile Contributions
Sample measures of top centile contributions to the total (concentration) are
downward biased, unstable estimators, extremely sensitive to sample size and
concave in accounting for large deviations. It makes them particularly unfit in
domains with power law tails, especially for low values of the exponent. These
estimators can vary over time and increase with the population size, as shown
in this article, thus providing the illusion of structural changes in
concentration. They are also inconsistent under aggregation and mixing
distributions, as the weighted average of concentration measures for A and B
will tend to be lower than that from A U B. In addition, it can be shown that
under such fat tails, increases in the total sum need to be accompanied by
increased sample size of the concentration measurement. We examine the
estimation superadditivity and bias under homogeneous and mixed distributions
The Future Has Thicker Tails than the Past: Model Error As Branching Counterfactuals
Abstract Ex ante forecast outcomes should be interpreted as counterfactuals (potential histories), with errors as the spread between outcomes. We reapply measurements of uncertainty about the estimation errors of the estimation errors of an estimation treated as branching counterfactuals. Such recursions of epistemic uncertainty have markedly different distributial properties from conventional sampling error, and lead to fatter tails in the projections than in past realizations. Counterfactuals of error rates always lead to fat tails, regardless of the probability distribution used. A mere .01% branching error rate about the STD (itself an error rate), and .01% branching error rate about that error rate, etc. (recursing all the way) results in explosive (and infinite) moments higher than 1. Missing any degree of regress leads to the underestimation of small probabilities and concave payoffs (a standard example of which is Fukushima). The paper states the conditions under which higher order rates of uncertainty (expressed in spreads of counterfactuals) alters the shapes the of final distribution and shows which a priori beliefs about conterfactuals are needed to accept the reliability of conventional probabilistic methods (thin tails or mildly fat tails)
Channeling in direct dark matter detection I: channeling fraction in NaI (Tl) crystals
The channeling of the ion recoiling after a collision with a WIMP changes the
ionization signal in direct detection experiments, producing a larger signal
than otherwise expected. We give estimates of the fraction of channeled
recoiling ions in NaI (Tl) crystals using analytic models produced since the
1960's and 70's to describe channeling and blocking effects. We find that the
channeling fraction of recoiling lattice nuclei is smaller than that of ions
that are injected into the crystal and that it is strongly temperature
dependent.Comment: 37 pages, 35 figures, Accepted for publication in JCAP on 27 October
2010, Minor revisions: added an appendix, updated references, updated Fig. 9,
corrected a few typo
Channeling Effects in Direct Dark Matter Detectors
The channeling of the ion recoiling after a collision with a WIMP changes the
ionization signal in direct detection experiments, producing a larger signal
than otherwise expected. We give estimates of the fraction of channeled
recoiling ions in NaI (Tl), Si and Ge crystals using analytic models produced
since the 1960's and 70's to describe channeling and blocking effects. We find
that the channeling fraction of recoiling lattice nuclei is smaller than that
of ions that are injected into the crystal and that it is strongly temperature
dependent.Comment: 8 pages, 12 figures, To appear in the Proceedings of the sixth
International Workshop on the Dark Side of the Universe (DSU2010) Leon,
Guanajuato, Mexico 1-6 June 201
Quantitative errors in the Cochrane review on "Physical interventions to interrupt or reduce the spread of respiratory viruses"
The COVID-19 pandemic has heightened the urgency to understand and prevent
pathogen transmission, specifically regarding infectious airborne particles.
Extensive studies validate the understanding of larger (droplets) and smaller
(aerosols) particles in disease transmission. Similarly, N95 respirators, and
other forms of respiratory protection, have proven efficacy in reducing the
risk of infection across various environments. Even though multiple studies
confirm their protective effect when adopted in healthcare and public settings
for infection prevention, studies on their adoption over the last several
decades in both clinical trials and observational studies have not provided as
clear an understanding. Here we show that the standard analytical equations
used in the analysis of these studies do not accurately represent the random
variables impacting study results. By correcting these equations, it is
demonstrated that conclusions drawn from these studies are heavily biased and
uncertain, providing little useful information. Despite these limitations, we
show that when outcome measures are properly analyzed, existing results
consistently point to the benefit of N95 respirators over medical masks, and
masking over its absence. Correcting errors in widely reported meta-analyses
also yields statistically significant estimates. These findings have important
implications for study design and using existing evidence for infection control
policy guidelines.Comment: 23 pages, 8 figure
Morphological characterization of indigenous goats in the region of laghouat in algeria
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Deportation Stigma and Re-migration
Many, if not most, of those who are forcibly expelled from the country to which they have migrated will not settle in the country to which they have been returned but will leave again. A recent article examined some of the reasons why this should be so. It was argued that in addition to the factors that had caused the original migration, such as fear of persecution, continuing conflict, insecurity, poverty and lack of opportunity, deportation creates at least three additional reasons that make re-migration the most likely outcome. These were debt, family commitments and the shame of failure and or ‘contamination’ leading to stigmatisation. In this article, we explore the stigma of failure and of contamination attached to those deported, and the ways in which they respond to and manage this stigmatisation, including by re-migrating. We use Goffman's concept of stigma and the refinement offered by to further nuance understanding of the impact of deportation
Characterization of the Hamra sheep breed in western Algeria
editorial reviewedThe present work is a part of a National Research Project (PNR Algeria 2022) dedicated to the
development of the Hamra sheep breed in his cradle western Algeria. The aim of this study is to
characterize the morphology, growth and reproductive performance of this ovine breed. A sample of
15 rams and 30 ewes were used for the morphological characterization versus a total of 1,328 head
for the growth and reproduction performance carried out at the technical livestock institute in Saida
area located in the western Algeria. Hamra sheep breed is small compared to other Algerian breeds.
It has a dark brown (mahogany) head and legs, a blackish-blue tongue, white wool, spiral horns,
and a fine, medium-length tail. Total body length is 124.5 cm for males and 110.5 cm for females,
with a trunk length of 78.6 cm for males and 67.7 cm for females. Depth, width and circumference
of chest are respectively 40.3 cm; 30 cm; 116.4 cm for males, and 34.2 cm; 22 cm; 99.8 cm for
females. Growth monitoring showed an average birth weight of 3 to 3.6kg, depending on sex (male
or female) and litter size (single or double). Live weights reached an average of 17.9kg for males
and 16.2kg for females at 90th day of age. The ewes' reproductive performances are as follows:
82.2% for fertility, 97% for fecundity and 118% for prolificacy at birth and weaning. In conclusion,
the Hamra breed has shown promise performances in terms of growth, but its butchering potential
needs more assessments. Further studies are required to establish a conservation strategy becoming
urgent by the uncontrolled introduction of genetics from other sheep breeds.PNR- Algérie12. Responsible consumption and productio
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