Littérature scientifique sur le sujet « Contrastive Explanat »

Abstract In vitro selection of drought-tolerant cassava varieties is essential for rapid breeding for drought tolerance. The objectives of this study were to determine the response of three contrasting cassava varieties to mannitol-induced drought stress to establish its suitability for in vitro screening and examine relationships among growth parameters. Plantlets were raised from nodal segments on Murashige and Skoog (MS) medium containing 0 (control), 5, 10, 15, 20, 25 and 30 g/l mannitol. Variety CH 140 had the highest survival of explants and frequency of root formation, while MV 99/0395 recorded the highest number of chlorotic leaves and the lowest survival of explants. The lowest numbers of leaves were produced at 25 and 30 g/l mannitol by the three varieties. In CH 140, the highest number of leaves was produced in medium free of mannitol, while the highest number of leaves was produced at 5 and 10 g/l mannitol in MV 99/0395 and TMS 01/1206, respectively. In TMS 01/1206, number of roots produced decreased as the concentration of mannitol in culture media increased, whereas in CH140, number of roots increased as the concentration of mannitol increased before decreasing; while in MV 99/0395, number of roots was not affected by an increase in mannitol concentration. As the concentration of mannitol in the culture media increased shoot height of plantlets decreased with a sharp decline at 20 mg/l mannitol. Concentration of mannitol and survival of explants had significant negative correlation with all parameters. However, frequency of root formation only had significant positive correlation with shoot length. The study concluded that differential responses were expressed by the three varieties to mannitol-induced drought stress and mannitol at 20 g/l concentration was a suitable in vitro drought inducing-agent for screening cassava varieties for drought tolerance.

Abstract In vitro selection of drought-tolerant cassava varieties is essential for rapid breeding for drought tolerance. The objectives of this study were to determine the response of three contrasting cassava varieties to mannitol-induced drought stress to establish its suitability for in vitro screening and examine relationships among growth parameters. Plantlets were raised from nodal segments on Murashige and Skoog (MS) medium containing 0 (control), 5, 10, 15, 20, 25 and 30 g/l mannitol. Variety CH 140 had the highest survival of explants and frequency of root formation, while MV 99/0395 recorded the highest number of chlorotic leaves and the lowest survival of explants. The lowest numbers of leaves were produced at 25 and 30 g/l mannitol by the three varieties. In CH 140, the highest number of leaves was produced in medium free of mannitol, while the highest number of leaves was produced at 5 and 10 g/l mannitol in MV 99/0395 and TMS 01/1206, respectively. In TMS 01/1206, number of roots produced decreased as the concentration of mannitol in culture media increased, whereas in CH140, number of roots increased as the concentration of mannitol increased before decreasing; while in MV 99/0395, number of roots was not affected by an increase in mannitol concentration. As the concentration of mannitol in the culture media increased shoot height of plantlets decreased with a sharp decline at 20 mg/l mannitol. Concentration of mannitol and survival of explants had significant negative correlation with all parameters. However, frequency of root formation only had significant positive correlation with shoot length. The study concluded that differential responses were expressed by the three varieties to mannitol-induced drought stress and mannitol at 20 g/l concentration was a suitable in vitro drought inducing-agent for screening cassava varieties for drought tolerance.

Foodborne pathogens are a public health threat globally. Shiga toxin-producing Escherichia coli (STEC), particularly O26, O111, and O157 STEC, are often associated with foodborne illness in humans. To create effective preharvest interventions, it is critical to understand which factors STEC strains use to colonize the gastrointestinal tract of cattle, which serves as the reservoir for these pathogens. Several colonization factors are known, but little is understood about initial STEC colonization factors. Our objective was to identify these factors via contrasting gene expression between nonpathogenic E. coli and STEC. Colonic explants were inoculated with nonpathogenic E. coli strain MG1655 or STEC strains (O26, O111, or O157), bacterial colonization levels were determined, and RNA was isolated and sequenced. STEC strains adhered to colonic explants at numerically but not significantly higher levels compared to MG1655. After incubation with colonic explants, flagellin (fliC) was upregulated (log2 fold-change = 4.0, p < 0.0001) in O157 STEC, and collectively, Lon protease (lon) was upregulated (log2 fold-change = 3.6, p = 0.0009) in STEC strains compared to MG1655. These results demonstrate that H7 flagellum and Lon protease may play roles in early colonization and could be potential targets to reduce colonization in cattle.

Isodon rugosus (Wall. ex Benth.) Codd accumulates large amounts of phenolics and pentacyclic triterpenes. The present study deals with the in vitro callus induction from stem and leaf explants of I. rugosus under various plant growth regulators (PGRs) for the production of antioxidant and anti-ageing compounds. Among all the tested PGRs, thidiazuron (TDZ) used alone or in conjunction with α-napthalene acetic acid (NAA) induced highest callogenesis in stem-derived explants, as compared to leaf-derived explants. Stem-derived callus culture displayed maximum total phenolic content and antioxidant activity under optimum hormonal combination (3.0 mg/L TDZ + 1.0 mg/L NAA). HPLC analysis revealed the presence of plectranthoic acid (373.92 µg/g DW), oleanolic acid (287.58 µg/g DW), betulinic acid (90.51 µg/g DW), caffeic acid (91.71 µg/g DW), and rosmarinic acid (1732.61 µg/g DW). Complete antioxidant and anti-aging potential of extracts with very contrasting phytochemical profiles were investigated. Correlation analyses revealed rosmarinic acid as the main contributor for antioxidant activity and anti-aging hyaluronidase, advance glycation end-products inhibitions and SIRT1 activation, whereas, pentacyclic triterpenoids were correlated with elastase, collagenase, and tyrosinase inhibitions. Altogether, these results clearly evidenced the great valorization potential of I. rugosus calli for the production of antioxidant and anti-aging bioactive extracts for cosmetic applications.

AbstractThe use of idealized scientific theories in explanations of empirical facts and regularities is problematic in two ways: they don’t satisfy the condition that the explanans is true, and they may fail to entail the explanandum. An attempt to deal with the latter problem was proposed by Hempel and Popper with their notion of approximate explanation. A more systematic perspective on idealized explanations was developed with the method of idealization and concretization by the Poznan school (Nowak, Krajewski) in the 1970s. If idealizational laws are treated as counterfactual conditionals, they can be true or truthlike, and the concretizations of such laws may increase their degree of truthlikeness. By replacing Hempel’s truth requirement with the condition that an explanatory theory is truthlike one can distinguish several important types of approximate, corrective, and contrastive explanations by idealized theories. The conclusions have important consequences for the debates about scientific realism and anti-realism.

Tomato explants (fruit with a pedicel and a piece of peduncle), with fruit growth stimulated by treating the flowers with NOA + GA&lt;sub&gt;3&lt;/sub&gt; (NG-series) were used as a model system for studying the effect of high temperature on C-sucrose uptake, its distribution and Ca retranslocation. Two cultivars with contrasting responses to high temperature were compared. In sensitive cv. Roma heat stress during 22h (40&lt;sup&gt;o&lt;/sup&gt;C for 10h and 30&lt;sup&gt;o&lt;/sup&gt;C for 12h), drastically depressed the uptake of ¹⁴C-sucrose coinciding with diminished fruit ¹⁴C-supply. It also decreased the specific activity of soluble acid invertase and the calcium content. All these strong negative responses to high temperature were markedly reduced in the NG-treated series involving remobilization of Ca to the fruits and a higher stability of the invertase activity. This indicates the indirect role of flower treatment with NG in addaptation to heat stress. In tolerant cv. Robin even higher temperatures (42&lt;sup&gt;o&lt;/sup&gt;C for 10h and 34&lt;sup&gt;o&lt;/sup&gt;C for 12h) were not stressful. They did not affect the ¹⁴C-sucrose uptake and stimulated ¹⁴C-supply to the fruit. Increased specific activity of acid invertase and a higher calcium content were also recorded but only in the control explants. In contrast to cv. Roma elevated temperature was slightly stressful for cv. Robin explants of NG-series. The differences in response of both cultivar explants to elevated temperature, based on unequal fruit supply with ¹⁴C-sucrose, seem to be causaly connected with two factors: the invertase activity being more or less sensitive to the heat stress, the ability to translocate Ca to the heated fruits.

Alloxylon flammeum is a rare and threatened Australian rainforest species that features spectacular red flowers and contrasting dark green foliage giving it potential as a cut flower crop. It also has potential as a rootstock for difficult to grow tree waratah species. There is, however, little published information on the propagation of Alloxylon spp. Here we show that A. flammeum can be propagated by vegetative cuttings and in vitro. The most commercially viable option is to propagate by cuttings using 8000 mg indole-3-butyric acid/L under intermittent mist with a root zone temperature of 24 ± 2˚C. Pre-treatment of A. flammeum stock plants with gibberellin (A4 and A7) spray before initiation into culture increased the success of initiation. The use of tip material resulted in minimal explant contamination and 1% sodium hypochlorite for 15 min was adequate for surface disinfection of material. Well elongated shoots were multiplied using 6-benzyladenine and 6-dimethylallyaminopurine (isopentyladenine), whilst thidiazuron-cultured shoots were numerous but short and unusable.

The role of protein synthesis in apoptosis was investigated in the retina of developing rats. In the neonatal retina, a ganglion cell layer, containing neurons with long, centrally projecting axons, is separated from an immature neuroblastic layer by a plexiform layer. This trilaminar pattern subsequently evolves to five alternating cell and plexiform layers that constitute the mature retina and a wave of programmed neuron death sweeps through the layers. Apoptosis due to axon damage was found in ganglion cells of retinal explants within 2 days in vitro and was prevented by inhibition of protein synthesis. Simultaneously, protein synthesis blockade induced apoptosis among the undamaged cells of the neuroblastic layer, which could be selectively prevented by an increase in intracellular cyclic AMP. Both the prevention and the induction of apoptosis among ganglion cells or neuroblastic cells, respectively, occurred after inhibition of protein synthesis in vivo. The results show the coexistence of two mechanisms of apoptosis within the organized retinal tissue. One mechanism is triggered in ganglion cells by direct damage and depends on the synthesis of proteins acting as positive modulators of apoptosis. A distinct, latent mechanism is found among immature neuroblasts and may be repressed by continuously synthesized negative modulators, or by an increase in intracellular cyclic AMP.

This interview with Jack Katz offers an inspiring statement about how to study social life. It starts with a discussion of Katz’s three-dimensional social ontology; social life is constituted in embodied interactions in which people adjust to others and create transcendent meanings. Contrasting the ontology with anthropology’s ontological turn, we note that social ontology is about generating empirically accurate descriptions capturing the flow of social life. This leads to a critical discussion of sociology’s pre-occupation with explanans-driven theorizing. Touching upon macro–micro relationships, we consider what a phenomenology of collective emotions would look like. This brings us to emotional transformations, notably the notion of ‘falling’, an important theme in Katz’s work. The interview continues with advice of how to think beyond given categories, to consider the validity of ethnographic description and to look for the absurd. Finally, we conclude that ethnography has the potential to appeal to mass audiences.

Cardiac vessel density (β-actin immunolabeling) and angiogenic capacity of coronary artery explants (culture in collagen gel) was determined in hypertrophied heart obtained by exercise training (10 wk) or ANG II infusion for 10 days. A group of rats received ANG II the last 10 days of training. The heart weight index was similarly elevated after exercise, and ANG II-hypertension compared with controls (3.16 ± 0.09 and 3.11 ± 0.11 vs. 2.68 ± 0.08 mg/g, respectively), whereas tail cuff pressure (TCP) increased only in sedentary rats infused with ANG II. Vessel density was increased by 36% in trained rats and reduced by 30% in ANG II-infused rats. The number of sprouts generated by coronary rings was reduced by 50% in ANG II-infused rats and increased by 50% in exercise trained rats compared with controls (35 ± 4 and 113 ± 5 vs. 71 ± 1 sprouts per ring, respectively). Exercise-training partly prevented the hypertensive effect of ANG II (TCP of 141 ± 5 mmHg), whereas heart weight index (3.66 ± 0.06 mg/g body wt) was not lowered. Myocardial vessel density was normalized, and sprouting from coronary rings increased by 50% in trained rats infused with ANG II compared with sedentary normotensive rats. Cardiac VEGF (Western blot analysis) was higher in hypertensive rats and not affected by exercise. Facing a similar increase in cardiac mass, intense training, but not ANG II hypertension, is accompanied by an increase in vascular density of the heart. The effect of training is unlikely related to changes in resting VEGF and may represent enhanced angiogenic capacity of the coronary vascular bed.

La necessità di spiegazioni sui sistemi di Machine Learning (ML) sta crescendo man mano che i nuovi modelli superano in performance i loro predecessori, diventando più complessi e meno comprensibili per gli utenti finali. Un passaggio essenziale nella ricerca in ambito eXplainable Artificial Intelligence (XAI) è la creazione di modelli interpretabili che mirano ad approssimare la funzione decisionale di un algoritmo black box. Sebbene negli ultimi anni siano stati proposti diversi metodi di XAI, non è stata prestata sufficiente attenzione alla spiegazione di come i modelli modificano il loro comportamento in contrasto con altre versioni (ad esempio, a causa di nuovi addestramenti dei modelli o modifica dei dati sottostanti). In questi casi, un sistema XAI dovrebbe spiegare perché il modello cambia le sue previsioni sui risultati passati. In diverse situazioni pratiche, i decisori umani si confrontano con più di un modello di apprendimento automatico. Di conseguenza, sta crescendo l'importanza di capire come funzionano due modelli di Machine Learning al di là delle loro performance predittive, per comprendere il loro comportamento, le loro differenze e la loro somiglianza. Ad oggi, i modelli interpretabili sono sintetizzati per spiegare i cosiddetti modelli black-box e le loro previsioni, e possono essere utili per rappresentare formalmente e misurare le differenze nel comportamento del modello ri-addestrato nel trattare dati nuovi e diversi. Catturare e comprendere tali differenze è fondamentale, poiché la necessità di fiducia è fondamentale in qualsiasi applicazione a supporto dei processi decisionali umani-IA. Questa è l'idea di ContrXT, un nuovo approccio che (i) traccia i criteri decisionali di un classificatore black box codificando i cambiamenti nella logica decisionale attraverso Binary Decision Diagrams. Quindi (ii) fornisce spiegazioni globali, agnostici dalla tipologia di modello, Model-Contrastive (M-contrast) in linguaggio naturale, stimando perché -e in quale misura- il modello ha modificato il suo comportamento nel tempo. Abbiamo implementato e valutato questo approccio su diversi modelli ML supervisionati addestrati su set di dati di benchmark e un'applicazione reale, dimostrando che è efficace nel rilevare classi notevolmente modificate e nello spiegare la loro variazione attraverso un user study. L'approccio è stato implementato ed è disponibile per la comunità sia come pacchetto Python che tramite API REST, fornendo contrastive explanations as a service.
The need for explanations of Machine Learning (ML) systems is growing as new models outperform their predecessors while becoming more complex and less comprehensible for their end-users. An essential step in eXplainable Artificial Intelligence (XAI) research is to create interpretable models that aim at approximating the decision function of a black box algorithm. Though several XAI methods have been proposed in recent years, not enough attention was paid to explaining how models change their behaviour in contrast with other versions (e.g., due to retraining or data shifts). In such cases, an XAI system should explain why the model changes its predictions concerning past outcomes. In several practical situations, human decision-makers deal with more than one machine learning model. Consequently, the importance of understanding how two machine learning models work beyond their prediction performances is growing, to understand their behavior, their differences, and their likeness. To date, interpretable models are synthesised for explaining black boxes and their predictions and can be beneficial for formally representing and measuring the differences in the retrained model's behaviour in dealing with new and different data. Capturing and understanding such differences is crucial, as the need for trust is key in any application to support human-Artificial Intelligence (AI) decision-making processes. This is the idea of ContrXT, a novel approach that (i) traces the decision criteria of a black box classifier by encoding the changes in the decision logic through Binary Decision Diagrams. Then (ii) it provides global, model-agnostic, Model-Contrastive (M-contrast) explanations in natural language, estimating why -and to what extent- the model has modified its behaviour over time. We implemented and evaluated this approach over several supervised ML models trained on benchmark datasets and a real-life application, showing it is effective in catching majorly changed classes and in explaining their variation through a user study. The approach has been implemented, and it is available to the community both as a python package and through REST API, providing contrastive explanations as a service.