3 results match your criteria erratic year-to-year

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Heroin use cannot be measured adequately with a general population survey.

Addiction 2021 Mar 2. Epub 2021 Mar 2.

University of Maryland, Department of Criminology and Criminal Justice, College Park, MD, USA.

Background: Globally, heroin and other opioids account for more than half of deaths and years-of-life-lost due to drug use and comprise one of the four major markets for illegal drugs. Having sound estimates of the number of problematic heroin users is fundamental to formulating sound health and criminal justice policies. Researchers and policymakers rely heavily upon general population surveys (GPS), such as the US National Survey on Drug Use and Health (NSDUH), to estimate heroin use, without confronting their limitations. Read More

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Regularity underlies erratic population abundances in marine ecosystems.

J R Soc Interface 2015 Jun;12(107)

Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208, USA Northwestern Institute on Complex Systems, Northwestern University, Evanston, IL 60208, USA

The abundance of a species' population in an ecosystem is rarely stationary, often exhibiting large fluctuations over time. Using historical data on marine species, we show that the year-to-year fluctuations of population growth rate obey a well-defined double-exponential (Laplace) distribution. This striking regularity allows us to devise a stochastic model despite seemingly irregular variations in population abundances. Read More

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Long-term and seasonal changes in composition and richness of intestinal helminth communities in eels Anguilla anguilla of an isolated English river.

Authors:
C R Kennedy

Folia Parasitol (Praha) 1997 ;44(4):267-73

Department of Biological Sciences, University of Exeter, UK.

The need for more long-term studies on helminth communities was addressed by examining changes in composition and diversity of the intestinal helminth component and infracommunities in eels of a small isolated river over 12 years. Examination of samples over one summer season indicated that single samples were representative of community richness in that year. In 1985 the community was species poor (1 species only) and with zero diversity, but by 1996 it comprised six species and all parameters at both levels indicated that it was the richest community yet reported from eels. Read More

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February 1998
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