1,720,993 research outputs found
The rolB oncogene improves photosynthesis efficiency and chlorophyll content in transgenic tomato (Solanum Lycopersicum L.) plants.
Full text linkTomato is a well-known model organism both at the genetic and molecular level, and one of
the most important commercial food crops in the world.
Transgenic tomato plants, transformed with the rolB oncogene, have been studied in order to
evaluate genes differentially expressed in respect of untransformed plants.
By Suppression Subtractive Hybridization method (SSH) and cDNA sequencing analyses, 20
clones have been found to be upregulated following transformation, and their putative functions
have been characterised by homology searches against the GenBank database. All cDNAs matched
with high significance to sequences involved in stress response, basal metabolism, signal
transduction and gene expression.
Among these, five genes engaged in chloroplast function have been identified. These genes,
directly or indirectly induced by rolB, participate in protection from light and oxidative stress, in
capture and transfer of light energy, CO2 diffusion, and cytochrome involvement in chloroplast
electron transport chain.
Photosynthesis efficiency measurement by three different photosynthetic parameters (Fv/Fm,
rETR, NPQ) showed in rolB plants a significant increase in non-photochemical quenching and a, b
chlorophyll content.
Our results add a new competence for rolB when integrated into the tomato plant genome.
Transgenic plants alter their response to the environment, regulating a primary and central plant
metabolism such as photosynthesis.
Assays are currently in progress to verify the effect on transgenic tomato of specific light
wavelengths
LIGHT ENVIRONMENT AND SEASONAL DYNAMICS OF MICROALGAE IN THE ANNUAL SEA ICE AT TERRA NOVA BAY ROSS SEA
No full textWe investigated the physical conditions of the Spring pack ice environment at Terra Nova Bay to understand their influence on the structure and physiology of sympagic microalgae. Bio-optical methods were used to study the availability and spectral quality of solar radiation, both inside and underneath the ice cover. Pack ice thickness was around 2.5 m, with a temperature between -2 and -7°C. On average, only 1.4% of surface PAR penetrated to the bottom ice and less than 0.6% below platelet ice level. Surface UV-B radiation under the bottom ice was 0.20.4%. Biomass concentrations up to 2400 mg Chl a m-3, dominated
by two species of diatoms (Entomoneis kjellmannii and Nitschia cf. stellata), showed marked spatial and temporal patterns. Maximum values were in the platelet ice during the first half of November, and in the bottom ice two weeks later. Strong shade adaptation characteristics emerged clearly and explained the
relevant abundance of microalgae within the sea ice, with specific absorption coefficients (a*) as low as 0.005 m2 (mg Chl a)-1 and the photo-acclimation index (Ek) in the range of in situ irradiance. The biomass specific production values were low, around 0.120.13 mg C mg Chl a-1 h -1. The hypothesis suggesting
bottom ice colonization by platelet ice microalgae is supported here
LIGHT ENVIRONMENT AND SEASONAL DYNAMICS OF MICROALGAE IN THE ANNUAL SEA ICE AT TERRA NOVA BAY ROSS SEA
No full textWe investigated the physical conditions of the Spring pack ice environment at Terra Nova Bay to understand their influence on the structure and physiology of sympagic microalgae. Bio-optical methods were used to study the availability and spectral quality of solar radiation, both inside and underneath the ice cover. Pack ice thickness was around 2.5 m, with a temperature between -2 and -7°C. On average, only 1.4% of surface PAR penetrated to the bottom ice and less than 0.6% below platelet ice level. Surface UV-B radiation under the bottom ice was 0.20.4%. Biomass concentrations up to 2400 mg Chl a m-3, dominated
by two species of diatoms (Entomoneis kjellmannii and Nitschia cf. stellata), showed marked spatial and temporal patterns. Maximum values were in the platelet ice during the first half of November, and in the bottom ice two weeks later. Strong shade adaptation characteristics emerged clearly and explained the
relevant abundance of microalgae within the sea ice, with specific absorption coefficients (a*) as low as 0.005 m2 (mg Chl a)-1 and the photo-acclimation index (Ek) in the range of in situ irradiance. The biomass specific production values were low, around 0.120.13 mg C mg Chl a-1 h -1. The hypothesis suggesting
bottom ice colonization by platelet ice microalgae is supported here
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe 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
Parametri fotosintetici da fluorescenza variabile modulata (PAM)
No full textIl metodo prevede l'utilizzo di fluorimetri ad impulsi modulati misurano i parametri Fo, Fm, Ft, Fm’ e consentono di calcolare i parametri di fluorescenza e di conseguenza quelli fotosintetici.
Il campione è mantenuto al buio fino al momento della misura, l’intensità della measuring light, scelta attraverso la regolazione del settaggio, deve essere < 1 μE m-2 sec-1. Dopo tale esposizione viene inviato il primo impulso saturante, quindi misurati Fo ed Fm. Il campione è poi illuminato con luce attinica e mantenuto a tale intensità luminosa per un determinato periodo di tempo, segue il secondo impulso saturante e la simultanea misura di Ft e Fm’ a quella PAR, poi l’esposizione ad una terza intensità luminosa, e così via per l’intero gradiente previsto. I valori di ETR misurati ad una serie di 6-10 PAR di intensità crescente comprese generalmente tra 0 e 2000 μE m-2sec-1 consentono la costruzione di una curva PE
Parametri fotosintetici: curve fotosintesi-irradianza (PvsE - metodo 14C)
No full textEsistono metodi per determinare il tasso fotosintetico per la costruzione delle curve P vs. E, tuttavia, data la maggiore sensibilità, il metodo più utilizzato è basato sull’incubazione dell’isotopo radioattivo del carbonio (14C). Per le misure di produzione primaria a diverse intensità luminose (curve P vs. E) è, in genere, utilizzato un “fotosintetron” radiale, costituito da un numero variabile di camere d’incubazione (da 1 a 10) che poggiano su un piano in alluminio (o in PVC) e da una fonte luminosa posta in posizione centrale. Ciascuna camera deve contenere circa 10-12 flask, disposte l’una dietro l’altra. Il campione, raccolto ad una determinata profondità, è conservato sin dal momento del prelievo in bottiglie scure in PVC (1 lt), e poi suddiviso nelle flasks in 12 sub-campioni tramite un dispenser.
In ciascun subcampione è inoculato un quantitativo di NaH14CO3 in saluzione acquosa tale che l’attività sia 10-20 μCi. La durata dell’incubazione è breve (max 120 minuti, ma in genere 30-60 min) in maniera da ridurre l’effetto dei fenomeni di fotoacclimatazione
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
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