Search results for "Variation"

How does academic achievement come about: cross-cultural and methodological notes

2001

Abstract This chapter discusses the possible impact of cross-national diversity in academic institutions, in the selection of students, in the importance of national achievement tests, and cross-national differences in the variation of social background factors. It ends with the strengths and limitations of using path modeling in cross-sectional research. It is of particular interest to note whether study behaviors mediate the impact of students’ abilities on college success, or whether students’ abilities mediate the effect of study behaviors on achievement. A secondary concern is the extent to which the same causal model applies equally to different universities in different countries.

Geographical variation of land mineral composition

2015

Comparing biological classifications of freshwater phytoplankton: a case study from South China

2012

The use of ecological classification systems is becoming more and more widely used when studying phytoplankton. Grouping phytoplankton species into ecologically coherent groups allow to reduce redundancy and in this way, to handle a minor number of biological variables when investigating the ecological status of aquatic ecosystems. Three ecological classifications are mostly used when freshwater phytoplankton is studied: functional groups or coda, morpho-functional groups (MFGs) and morphology-based functional groups (MBFGs). In this study, these three ecological classifications were comparatively used along with two taxonomic classifications based on species and genera to analyse phytoplan…

An integrated dialect analysis tool using phonetics and acoustics

2019

This study aimed to verify a computational phonetic and acoustic analysis tool created in the MATLAB environment. A dataset was obtained containing 3 broad American dialects (Northern, Western and New England) from the TIMIT database using words that also appeared in the Swadesh list. Each dialect consisted of 20 speakers uttering 10 sentences. Verification using phonetic comparisons between dialects was made by calculating the Levenshtein distance in Gabmap and the proposed software tool. Agreement between the linguistic distances using each analysis method was found. Each tool showed increasing linguistic distance as a function of increasing geographic distance, in a similar shape to Segu…

The evolutionary history of the Arabidopsis arenosa complex: diverse tetraploids mask the Western Carpathian center of species and genetic diversity.

2012

The Arabidopsis arenosa complex is closely related to the model plant Arabidopsis thaliana. Species and subspecies in the complex are mainly biennial, predominantly outcrossing, herbaceous, and with a distribution range covering most parts of latitudes and the eastern reaches of Europe. In this study we present the first comprehensive evolutionary history of the A. arenosa species complex, covering its natural range, by using chromosome counts, nuclear AFLP data, and a maternally inherited marker from the chloroplast genome [trnL intron (trnL) and trnL/F intergenic spacer (trnL/F-IGS) of tRNA(Leu) and tRNA(Phe), respectively]. We unravel the broad-scale cytogeographic and phylogeographic pa…

Characterizing a hybrid zone between a cryptic species pair of freshwater snails.

2015

Characterizing hybrid zones and their dynamics is a central goal in evolutionary biology, but this is particularly challenging for morphologically cryptic species. The lack of conspicuous divergence between parental types means intermediate hybrid forms often go undetected. We aimed to detect and characterize a suspected hybrid zone between a pair of morphologically cryptic lineages of the freshwater snail, Radix. We sampled Radix from across a contact zone between two mitochondrial lineages (Radix balthica and an undescribed lineage termed 'MOTU3') and detected admixture between two nuclear genotype clusters, which were significantly but not categorically associated with the mitochondrial …

Mitochondrial DNA variation and the evolutionary history of cryptic Gammarus fossarum types.

2000

The evolutionary history of the cryptic Gammarus fossarum species complex (Crustacea, Amphipoda) in Central Europe was approached by investigating the genetic variation in populations of a natural contact zone. Nucleotide sequence variation of a 395-bp segment of the mitochondrial 16S rRNA gene was compared to that of six nuclear allozyme loci. Three major mtDNA lineages were found, the eastern clade being consistent with the former allozyme type A. The two western clades (types B and C) were not distinguished previously. Strong sequence divergence and correlation with nuclear genetic isolation in syntopic populations, however, justifies the specific status of the three G. fossarum types. T…

Genetic contribution in sporadic thoracic aortic aneurysm? Emerging evidence of genetic variants related to TLR-4-mediated signaling pathway as risk …

2015

Abstract Sporadic thoracic aortic aneurysms (TAA) and dissections are one of the major causes of morbidity and mortality worldwide, especially in those older than 65 years. The presentation of TAA is varied and often silent. Thus, sporadic TAA detection is often fortuitous, with identification occurring during a routine physical examination or during an unrelated medical evaluation. Once suspected, confirmation by imaging clinical approaches is needed to allow the choose of the unique treatments for TAA, namely the surgery procedures, including elective surgery or endovascular repair before the onset of catastrophic and fatal complications, such as dissection or rupture. At present, there a…

Standardvarietäten in finnischen DaF- und EFL-Lehrwerken : Ein Vergleich zwischen Deutsch-Lehrwerken und Englisch-Lehrwerken

2010

Englanti ja saksa ovat kieliä, jotka ovat virallisia kieliä useammassa maassa eli niillä on useampi standardivarieteetti. Tällöin puhutaan kielen plurisentrisyydestä. Standardivarieteettien tunteminen on oleellinen osa kommunikatiivista kompetenssia ja oppilaan kielitaitoa. Tässä työssä tutkittiin, miten suomalaiset englannin ja saksan vieraankielen oppikirjat ottavat huomioon kielen plurisentrisyyden ja sen eri standardivarieteetit. Tavoitteena oli tutkia, millainen rooli kullakin standardivarieteetilla oppikirjassa on, missä järjestyksessä varieteetit tulevat opinpolulla esiin, mitä kielen aspekteja, esim. sanasto ja ääntäminen, oppikirjat standardivarieteeteista esittelevät. Tavoitteena …

Photometric and spectroscopic variability of the B5IIIe star HD 171219

2017

We analyzed the star HD 171219, one of the relatively bright Be stars observed in the seismo field of the CoRoT satellite, in order to determine its physical and pulsation characteristics. Classical Be stars are main-sequence objects of mainly B-type, whose spectra show, or have shown at some epoch, Balmer lines in emission and an infrared excess. Both characteristics are attributed to an equatorially concentrated circumstellar disk fed by non-periodic mass-loss episodes (outbursts). Be stars often show nonradial pulsation gravity modes and, as more recently discovered, stochastically excited oscillations. Applying the CLEANEST algorithm to the high-cadence and highly photometrically precis…