117,602 research outputs found
Not only transposons: the peculiar evolution of olive genome structure.
No full textThe current view of plant genome evolution proposes that genome size is determined by
processes such as polyploidization and amplification and/or loss of transposable elements. Other
types of repeated sequences, including tandem repeats, usually have a minor role in shaping plant
genome structure and size, accounting for a small portion of the genomes sequenced so far.
In the cultivated olive (Olea europaea L. subsp. europaea var. europaea), available data
suggest the occurrence of a singular model of genome evolution, in which polyploidization and
amplification/loss of transposons were accompanied by a massive expansion of the tandem repeated
fraction. This fraction is composed by six major families of satellites, that make almost one third of
the genome. This peculiarity highlights the necessity of further studies about the evolution of the
Olea genus, to shed light on mechanisms of genome expansion and the possible function of the
different types of repeated sequences.
Massively parallel sequencing technologies, advanced bioinformatic analyses and in situ
hybridization, were applied to study in detail the genome structure of cultivated olive and other 4
related species or subspecies (O. europaea subsp. cuspidata, O. europaea subsp. guanchica, O.
exasperata, and O. paniculata). They originated at different times from the common ancestor from
which the cultivated form derived.
Our analysis led to a complete characterization of the repeated fraction of the genomes of the
selected Olea species, with emphasis on the tandem repeats. On average, repetitive DNA in Olea
species ranges from 42% in O. paniculata to 66% in O. europaea subsp. cuspidata, showing
remarkable differences in terms of composition. In fact, the 11 major families of tandem repeats
identified across the analyzed species presented different redundancy levels. Thus, some families
were barely represented in one species and highly redundant in another. A large number of longterminal-repeat (LTR) retrotransposons (of different lineages) were also found in every Olea
species. Interestingly, overall tandem repeat redundancy was inversely correlated to that of
retrotransposons. This trend might implicate a competition in the proliferation of these two classes
of repeats. As a matter of fact, O. paniculata, the closer species to the Olea common ancestor,
presents very few tandemly-repeated sequences (as most plant species) while it is rich in LTRretrotransposons, suggesting that the amplification of tandem repeats occurred after its speciation
from the common ancestor of the other four species (which include the cultivated olive tree).
In conclusion, our research identified the temporal dynamics shaping the genome structure
during the evolution of the genus Olea. This genus represents a very peculiar model of genome
evolution in higher plants. Studies are in progress to estimate the intraspecifc variation of the repeat
component, in order to decipher the possible role that tandem repeats played during the evolution of
the olive genome
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Square Dancing with the Stars to Enhance Dynamic Hirschman Linkages?
No full textIn this Presidential Address, the author takes the reader on a reconnaissance of his life and time as a regional scientist. He points out scenery he found scintillating along the way, hoping that some may pick up the banner and chew on a few of the ideas for a while. He suggests a revisit to Albert O. Hirschman’s notion of key sectors and more empirical analysis related to Marcus Berliant’s and Masahisa Fujita’s notion of knowledge creation and transfer.Presidential Address, San Antonio, Texas, March 29, 2014 (53rd Meetings of the Southern Regional Science Association
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Letter from unknown writer to Jesse L. Boyce
No full textLetter to Jesse L. Boyce from unknown author (possibly Jack) about the investigation into the powder magazine located in the Grand Canyon. Some personal news is included in the letter such as the writer's marriage to the daughter of C.A. Taylor, former Supervisor of Cochise County
The race between retrotransposons and tandem repeats for shaping genome structure. The case of Olea.
No full textGenome size evolution is a process mainly determined by processes as polyploidization and
amplification/loss of transposons, with a minor role played by other repeated sequences such as
tandem repeats.
In the cultivated olive, available data suggest a singular model of genome evolution, in which
a massive expansion of tandem repeated sequences accompanied changes in nuclear architecture.
Focusing on Olea genus evolution, NGS technologies, bioinformatics and in situ hybridization were
applied to study the genome structure of 5 related Olea taxa originated at different times from the
last common ancestor.
On average, repetitive DNA in Olea taxa ranged from ~59% to ~73%, showing remarkable
differences in terms of composition and abundance. We identified 11 major families of tandem
repeats, 5 of which for the first time. Overall, tandem repeat abundance was inversely correlated to
that of retrotransposons, with the exception of O. paniculata which has very few tandem-repeated
sequences being, on the contrary, especially rich in long terminal repeat-retrotransposons,
suggesting that the amplification of tandem repeats occurred after its divergence from the Olea
common ancestor. Furthermore, cytological analyses underlined differences in genome size and
chromatin organization of O. paniculata, whose genome is about 50% larger of that of cultivated
olive compared to O. europaea subsp. europaea. Our results, supported by retrotransposon timing
data and by in situ hybridization, indicates that the genome expansion of O. paniculata may be
derived from massive amplification of major individual retrotransposon families in the last 20 MY.
Our research identified the temporal dynamics shaping Olea genome structure, which
represent a very peculiar model of evolution in higher plants characterized by a preminent role of
tandem repeats in fostering genome structure variation, also suggesting a possible role of
transposons in tandem repeats evolution and mobility
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Sarah L. Blum Author Visit - Warrior Nurse: PTSD and Healing
No full textHear Sarah L. Blum, author of Women Under Fire: Abuse in the Military, discuss her newest book, Warrior Nurse: PTSD and Healing followed by a Q&A and book signing.
Sarah L. Blum is a decorated Vietnam veteran who served as an operating room nurse during the intense fighting of 1967. In recognition of her service, she was awarded the Army Commendation Medal.
Sponsored by CWU Veterans Center and CWU Libraries.https://digitalcommons.cwu.edu/libraryevents/1252/thumbnail.jp
Lillian L. Lambert, Author, Speaker, and Entrepreneur
No full textLillian L. Lambert, Author, Speaker, and Entrepreneu
Letter to Alfred L. Shoemaker, February 10, 1948
No full textA handwritten letter from an unknown author addressed to Alfred L. Shoemaker, dated February 10, 1948. Within, the author discusses the Pennsylvania Dutch word for Ash Wednesday, along with traditions associated with this day.https://digitalcommons.ursinus.edu/shoemaker_documents/1118/thumbnail.jp
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