2,468 research outputs found
Nucleic acids and growth of \u3cem\u3eCalanus finmarchicus\u3c/em\u3e in the laboratory under different food and temperature conditions
We examined the effects of food concentration and temperature on nucleic acids and protein content of Calanus finmarchicus in order to evaluate the use of RNA as a growth rate index for this species. We measured RNA, DNA, and protein content of copepods reared from egg to adult stage in 5 combinations of food and temperature conditions (25 to 500 ”g C l-1, 4 to 12°C). At 8°C, DNA, RNA and protein content and RNA:DNA differed among food treatments during Stages N6 through to adult female. Protein:DNA ratios and RNA:protein ratios were significantly different among food levels for only 3 of the 8 stages examined. At excess food, DNA, RNA, and protein content and RNA:DNA ratios were inversely related to temperature for most stages from C1 onward, but the effect of temperature was relatively small over the range of temperatures investigated. The RNA:DNA and protein:DNA ratios increased with developmental stage whereas the RNA:protein ratio and growth rates (measured in terms of protein, nitrogen, DNA, and carbon content) declined with increasing stage. Although the relationship of RNA:DNA to growth rates was stage-specific, the two were related when standardized for temperature and developmental stage. RNA:protein ratios were directly related to growth rates regardless of stage, and the slope of the relationship increased with increasing temperature in a nonlinear fashion. Our results emphasize the importance of temperature and developmental stage for the relationship of growth rates to RNA concentration and RNA:DNA ratios. We propose 2 ways to estimate in situ growth rates of C. finmarchicus from RNA:DNA or RNA:protein ratios and environmental temperatur
Relationship between personality change and the onset and course of alcohol dependence in young adulthood
Aimsâ To examine the reciprocal effects between the onset and course of alcohol use disorder (AUD) and normative changes in personality traits of behavioral disinhibition and negative emotionality during the transition between adolescence and young adulthood. Designâ Longitudinalâepidemiological study assessing AUD and personality at ages 17 and 24 years. Settingâ Participants were recruited from the community and took part in a dayâlong, inâperson assessment. Participantsâ Male ( n â=â1161) and female ( n â=â1022) twins participating in the Minnesota Twin Family Study. Measurementsâ The effects of onset (adolescent versus young adult) and course (persistent versus desistent) of AUD on change in personality traits of behavioral disinhibition and negative emotionality from ages 17 to 24 years. Findingsâ Onset and course of AUD moderated personality change from ages 17 to 24 years. Adolescent onset AUD was associated with greater decreases in behavioral disinhibition. Those with an adolescent onset and persistent course failed to exhibit normative declines in negative emotionality. Desistence was associated with a ârecoveryâ towards psychological maturity in young adulthood, while persistence was associated with continued personality dysfunction. Personality traits at age 11 predicted onset and course of AUD, indicating personality differences were not due to active substance abuse. Conclusionsâ Personality differences present prior to initiation of alcohol use increase risk for alcohol use disorder, but the course of alcohol use disorder affects the rate of personality change during emerging adulthood. Examining the reciprocal effects of personality and alcohol use disorder within a developmental context is necessary to improve understanding for theory and intervention.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90257/1/j.1360-0443.2011.03617.x.pd
Goodness-of-Fit Tests for Symmetric Stable Distributions -- Empirical Characteristic Function Approach
We consider goodness-of-fit tests of symmetric stable distributions based on
weighted integrals of the squared distance between the empirical characteristic
function of the standardized data and the characteristic function of the
standard symmetric stable distribution with the characteristic exponent
estimated from the data. We treat as an unknown parameter,
but for theoretical simplicity we also consider the case that is
fixed. For estimation of parameters and the standardization of data we use
maximum likelihood estimator (MLE) and an equivariant integrated squared error
estimator (EISE) which minimizes the weighted integral. We derive the
asymptotic covariance function of the characteristic function process with
parameters estimated by MLE and EISE. For the case of MLE, the eigenvalues of
the covariance function are numerically evaluated and asymptotic distribution
of the test statistic is obtained using complex integration. Simulation studies
show that the asymptotic distribution of the test statistics is very accurate.
We also present a formula of the asymptotic covariance function of the
characteristic function process with parameters estimated by an efficient
estimator for general distributions
The variant call format and VCFtools
Summary: The variant call format (VCF) is a generic format for storing DNA polymorphism data such as SNPs, insertions, deletions and structural variants, together with rich annotations. VCF is usually stored in a compressed manner and can be indexed for fast data retrieval of variants from a range of positions on the reference genome. The format was developed for the 1000 Genomes Project, and has also been adopted by other projects such as UK10K, dbSNP and the NHLBI Exome Project. VCFtools is a software suite that implements various utilities for processing VCF files, including validation, merging, comparing and also provides a general Perl API
Growth and development rates of the copepod \u3cem\u3eCalanus finmarchicus\u3c/em\u3e reared in the laboratory
Development rates, nitrogen- and carbon-specific growth rates, size, and condition were determined for the copepod Calanus finmarchicus reared at 3 temperatures (4, 8, and 12°C) at non-limiting food concentrations and 2 limiting food concentrations at 8°C in the laboratory. Development rates were equiproportional, but not isochronal. Naupliar stage durations were similar, except for non-feeding stages, which were of short duration, and the first feeding stage, which was prolonged, while copepodite stage durations increased with increasing stage of development. Under limiting food concentrations at 8°C, development rates were prolonged but similar relative patterns in stage durations were observed. Body size (length and weight) was inversely related to temperature and positively related to food concentration. Condition measurements were not affected by temperature, but were positively related to food concentration. Growth rates increased with increasing temperature and increased asymptotically with increasing food concentration. At high food concentrations, growth rates of naupliar stages were high (except for individuals molting from the final naupliar stage to the first copepodite stage, in which growth rates were depressed), while growth of copepodites decreased with increasing stage of development. Neither nitrogen nor carbon growth rates, the former a proxy for structural growth, were exponential over the entire life cycle, but rather sigmoidal. Carbon-specific growth rates were greater than nitrogen-specific growth rates, and this difference increased with increasing stage of development, reflecting an augmentation in lipid deposition in the older stages. However, nitrogen and carbon growth rates were more similar under food-limited conditions. Based on this study, we recommend that secondary production rates of Calanus finmarchicus and possibly other lipid-storing copepods not be estimated from egg production measurements alone, as has been suggested for other species of copepods, because growth, including structural growth, is not equivalent for all stages
Reorientation of Spin Density Waves in Cr(001) Films induced by Fe(001) Cap Layers
Proximity effects of 20 \AA thin Fe layers on the spin density waves (SDWs)
in epitaxial Cr(001) films are revealed by neutron scattering. Unlike in bulk
Cr we observe a SDW with its wave vector Q pointing along only one {100}
direction which depends dramatically on the film thickness t_{Cr}. For t_{Cr} <
250 \AA the SDW propagates out-of-plane with the spins in the film plane. For
t_{Cr} > 1000 \AA the SDW propagates in the film plane with the spins
out-of-plane perpendicular to the in-plane Fe moments. This reorientation
transition is explained by frustration effects in the antiferromagnetic
interaction between Fe and Cr across the Fe/Cr interface due to steps at the
interface.Comment: 4 pages (RevTeX), 3 figures (EPS
Polarization rotation via a monoclinic phase in the piezoelectric 92%PbZn1/3Nb2/3O3-8%PbTiO3
The origin of ultrahigh piezoelectricity in the relaxor ferroelectric
PbZn1/3Nb2/3O3-PbTiO3 was studied with an electric field applied along the
[001] direction. The zero-field rhombohedral R phase starts to follow the
direct polarization path to tetragonal symmetry via an intermediate monoclinic
M phase, but then jumps irreversibly to an alternate path involving a different
type of monoclinic distortion. Details of the structure and domain
configuration of this novel phase are described. This result suggests that
there is a nearby R-M phase boundary as found in the Pb(Ti,Zr)O3 system.Comment: REVTeX file. 4 pages. New version after referees' comment
Genetic Correlations in Mutation Processes
We study the role of phylogenetic trees on correlations in mutation
processes. Generally, correlations decay exponentially with the generation
number. We find that two distinct regimes of behavior exist. For mutation rates
smaller than a critical rate, the underlying tree morphology is almost
irrelevant, while mutation rates higher than this critical rate lead to strong
tree-dependent correlations. We show analytically that identical critical
behavior underlies all multiple point correlations. This behavior generally
characterizes branching processes undergoing mutation.Comment: revtex, 8 pages, 2 fig
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