117,906 research outputs found
Econophysics : a stochastic model for a risk-adjusted market-making strategy. Relation between bid-ask spread, volume and volatility in financial markets
No full textUse of TD-GC–TOF-MS to assess volatile composition during post-harvest storage in seven accessions of rocket salad (Eruca sativa). BELL L, SPADAFORA D.N. contributed equally to the work
No full textAn important step in breeding for nutritionally enhanced varieties is determining the effects of the postharvest
supply chain on phytochemicals and the changes in VOCs produced over time. TD-GC–TOF-MS
was used and a technique for the extraction of VOCs from the headspace using portable tubes is
described. Forty-two compounds were detected; 39 were identified by comparison to NIST libraries.
Thirty-five compounds had not been previously reported in Eruca sativa. Seven accessions were assessed
for changes in headspace VOCs over 7 days. Relative amounts of VOCs across 3 time points were significantly
different – isothiocyanate-containing molecules being abundant on ‘Day 0’. Each accession
showed differences in proportions/types of volatiles produced on each day. PCA revealed a separation
of VOC profiles according to the day of sampling. Changes in VOC profiles over time could provide a tool
for assessment of shelf life
Perturbation of cytokinin and ethylene-signalling pathways explain the strong rooting phenotype exhibited by Arabidopsis expressing the Schizosaccharomyces pombe mitotic inducer, cdc25
No full textBackground
Entry into mitosis is regulated by cyclin dependent kinases that in turn are phosphoregulated. In most eukaryotes, phosphoregulation is through WEE1 kinase and CDC25 phosphatase. In higher plants a homologous CDC25 gene is unconfirmed and hence the mitotic inducer Schizosaccharomyces pombe (Sp) cdc25 has been used as a tool in transgenic plants to probe cell cycle function. Expression of Spcdc25 in tobacco BY-2 cells accelerates entry into mitosis and depletes cytokinins; in whole plants it stimulates lateral root production. Here we show, for the first time, that alterations to cytokinin and ethylene signaling explain the rooting phenotype elicited by Spcdc25 expression in Arabidopsis.
Results
Expressing Spcdc25 in Arabidopsis results in increased formation of lateral and adventitious roots, a reduction of primary root width and more isodiametric cells in the root apical meristem (RAM) compared with wild type. Furthermore it stimulates root morphogenesis from hypocotyls when cultured on two way grids of increasing auxin and cytokinin concentrations. Microarray analysis of seedling roots expressing Spcdc25 reveals that expression of 167 genes is changed by > 2-fold. As well as genes related to stress responses and defence, these include 19 genes related to transcriptional regulation and signaling. Amongst these was the up-regulation of genes associated with ethylene synthesis and signaling. Seedlings expressing Spcdc25 produced 2-fold more ethylene than WT and exhibited a significant reduction in hypocotyl length both in darkness or when exposed to 10 ppm ethylene. Furthermore in Spcdc25 expressing plants, the cytokinin receptor AHK3 was down-regulated, and endogenous levels of iPA were reduced whereas endogeous IAA concentrations in the roots increased.
Conclusions
We suggest that the reduction in root width and change to a more isodiametric cell phenotype in the RAM in Spcdc25 expressing plants is a response to ethylene over-production. The increased rooting phenotype in Spcdc25 expressing plants is due to an increase in the ratio of endogenous auxin to cytokinin that is known to stimulate an increased rate of lateral root production. Overall, our data reveal important cross talk between cell division and plant growth regulators leading to developmental changes
ADIABATIC CONDITIONS FOR FINANCIAL SYSTEMS
No full textIn the Black-Scholes context we consider the probability distribution function (PDF) of financial
returns implied by volatility smile and we study the relation between the decay of its tails and the
fitting parameters of the smile. We show that, considering a scaling law derived from data, it is
possible to get a new fitting procedure of the volatility smile that considers also the exponential
decay of the real PDF of returns observed in the financial markets.
In addiction, we show that this approach based on a volatility smile leads to relative minima for the distribution function
("bad" probabilities) never observed in real data and, in the worst cases, negative probabilities. We
show that these undesirable effects can be eliminated by requiring "adiabatic" conditions on the
volatility smile.
Our study finds application in the Risk Management activities where the tails characterization of financial returns PDF has a
central role for the risk estimation
Detection of Protein–Protein Interactions in Tobacco BY-2 Cells Using Bimolecular Fluorescence Complementation
No full textKnowledge of protein–protein interactions in the plant cell is invaluable for furthering our understanding
of the functions of these proteins. Many of the methods available for the study of these interactions, such
as yeast two-hybrid and co-immunoprecipitation assays, rely on in vitro techniques. Here we describe the
use of bimolecular fl uorescence complementation for the study of protein–protein interactions in vivo,
using simple techniques and accessible materials
Spare Parts Management: an Optimized Service Level-based Model for Inventory Control
No full textSpare parts optimization can significantly reduce inventory costs while avoiding compromising equipment availability. However, the distinctive trend of spare parts demand makes it difficult to establish the optimal stock level. Many literature studies address and classify the different criticalities of spare parts, but there is a lack of workable and structured tools related to the effective management of these items. For this reason, this paper proposes a practical approach to compute the stock quantities by setting a target service level, which is pre-defined by considering some critical factors, ad-hoc tuned to the company’s needs. The presented approach is composed of three sequential steps: the first aims at classifying the demand time series behavior as intermittent, lumpy, erratic, or smooth; then, forecasting methods are applied to predict consumption events, and the forecasting accuracy metrics are compared to identify the optimal one, per each item; lastly, reorder strategies are selected according to the results of the previous steps and reorder events are triggered by the probability of achieving the target service level for the next time bucket. This model has been validated in a pharmaceutical manufacturing facility, leading to excellent results in reducing stockholding costs
Italian Tailored Assessment Of Lung Indeterminate Accidental Nodule By Proposing A Segmental Pet/Computed Tomography (S-Pet/Ct): Rationale And Study Design Of A Retrospective, Multicenter Trial
No full text
Determination of 2-Methyisoborneol and Geosmin as Malodours in Catfish for Quality Control Using a Fully Automated Sample Prep Platform Coupled with Gas Chromatography and Mass Spectrometry
No full textAccumulation of off-flavours and odours in fish flesh are a major contributor towards a decrease in fish meat quality because of the dislike by consumers. This is typically caused by two compounds, geosmin (GM) and 2-methylisoborneol (2-MIB),
produced as secondary by-products of bacterial metabolism in water. These compounds have very low human sensory detection limits (or odour thresholds), which means that they can be present at trace-levels and still be detected with a
human nose. Due to the lipophilic properties of these compounds their extraction from the fish tissue and subsequent
analysis can be hindered due to simultaneous extraction of other volatile organic compounds (VOCs) which are present at
much higher concentration levels. Lengthy extraction techniques such as steam distillation are typically required to extract
the target compounds from the other VOCs present, producing cleaner chromatography. However, this is time consuming
and manually labour-intensive for the analyst.
Here we demonstrate a simple, solvent-free and fully-automated technique using high-capacity sorptive extraction (HiSorb)
coupled with Gas Chromatography and Mass Spectrometry for the identification of GM and 2-MIB at ppt-levels (pg/g) in
catfish samples. The ‘prep-ahead’ functionality of the extraction and enrichment platform, Centri, provided enhanced
sample management for increased sample throughput without compromising analytical sensitivity
Developmental stimuli and stress factors affect expression of ClGLP1, an emerging allergen-related gene in Citrus limon.
No full textbe involved in many developmental and stress related processes. A novel GLP cDNA was isolated from
Citrus limon and structural features and genomic organization were investigated by in silico and Southern
blots analysis. In lemon, the ClGLP1 encodes a 24.38 kDa which possesses a conserved motif of plant GLPs
proteins. A phylogetic analysis mapped ClGLP1 as belonging to the GER3 subfamily into the GLP1 group of
large GLP family. ClGLP1 was differentially expressed in the various organs and was highest in mature
fruit. Moreover, expression in the fruit was tissue- and stage-related as well as dependent on agricultural
practice (organic vs conventional). ClGLP1 transcripts increased during the transition from the green (180
days after blooming) to the yellow (240 days after blooming) mature fruit and were strongly enhanced in
yellow mature fruit from organic compared with conventional culture. A sudden and systemic increase in
ClGLP1 expression level was observed in leaves injured by wounding, together with an increase of
endogenous H2O2 amount. Notably, an enhancement of H202 was observed in fruit peel during transition
from green to yellow fruit stage. All together our data showed that ClGLP1 expression can be modulated
in relation to both developmental stimuli and culture practices; evidence is also provided that through
an oxidase activity this gene could play a role in fruit maturation as well as in stress responses
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