Academic literature on the topic 'IF3'

Abstract Initiation factor IF3 is an essential protein that enhances the fidelity and speed of bacterial mRNA translation initiation. Here, we describe the dynamic interplay between IF3 domains and their alternative binding sites using pre-steady state kinetics combined with molecular modelling of available structures of initiation complexes. Our results show that IF3 accommodates its domains at velocities ranging over two orders of magnitude, responding to the binding of each 30S ligand. IF1 and IF2 promote IF3 compaction and the movement of the C-terminal domain (IF3C) towards the P site. Concomitantly, the N-terminal domain (IF3N) creates a pocket ready to accept the initiator tRNA. Selection of the initiator tRNA is accompanied by a transient accommodation of IF3N towards the 30S platform. Decoding of the mRNA start codon displaces IF3C away from the P site and rate limits translation initiation. 70S initiation complex formation brings IF3 domains in close proximity to each other prior to dissociation and recycling of the factor for a new round of translation initiation. Altogether, our results describe the kinetic spectrum of IF3 movements and highlight functional transitions of the factor that ensure accurate mRNA translation initiation.

Initiation of translation involves the assembly of a ribosome complex with initiator tRNA bound to the peptidyl site and paired to the start codon of the mRNA. In bacteria, this process is kinetically controlled by three initiation factors—IF1, IF2, and IF3. Here, we show that deletion of helix H69 (∆H69) of 23S rRNA allows rapid 50S docking without concomitant IF3 release and virtually eliminates the dependence of subunit joining on start codon identity. Despite this, overall accuracy of start codon selection, based on rates of formation of elongation-competent 70S ribosomes, is largely uncompromised in the absence of H69. Thus, the fidelity function of IF3 stems primarily from its interplay with initiator tRNA rather than its anti-subunit association activity. While retaining fidelity, ∆H69 ribosomes exhibit much slower rates of overall initiation, due to the delay in IF3 release and impedance of an IF3-independent step, presumably initiator tRNA positioning. These findings clarify the roles of H69 and IF3 in the mechanism of translation initiation and explain the dominant lethal phenotype of the ∆H69 mutation.

Novel therapeutic approaches are much needed for the treatment of osteosarcoma. Targeted radionuclide therapy (TRT) and radioimmunotherapy (RIT) are promising approaches that deliver therapeutic radiation precisely to the tumor site. We have previously developed a fully human antibody, named IF3, that binds to insulin-like growth factor 2 receptor (IGF2R). IF3 was used in TRT to effectively inhibit tumor growth in osteosarcoma preclinical models. However, IF3’s relatively short half-life in mice raised the need for improvement. We generated an Fc-engineered version of IF3, termed IF3δ, with amino acid substitutions known to enhance antibody half-life in human serum. In this study, we confirmed the specific binding of IF3δ to IGF2R with nanomolar affinity, similar to wild-type IF3. Additionally, IF3δ demonstrated binding to human and mouse neonatal Fc receptors (FcRn), indicating the potential for FcRn-mediated endocytosis and recycling. Biodistribution studies in mice showed a higher accumulation of IF3δ in the spleen and bone than wild-type IF3, likely attributed to abnormal spleen expression of IGF2R in mice. Therefore, the pharmacokinetics data from mouse xenograft models may not precisely reflect their behavior in canine and human patients. However, the findings suggest both IF3 and IF3δ as promising options for the RIT of osteosarcoma.

A Bacillus stearothermophilus in vitro translational system has been developed to study the expression of the three cistrons (infC, rpmI, and rplT) constituting the infC operon of this bacterium. When directed by homologous in vitro transcribed infC tricistronic mRNA, this system, which consists of partially purified and purified components of the B. stearothermophilus translational apparatus, synthesizes with high efficiency and specificity the three gene products (IF3, L35, and L20) in a ratio similar to that found in vivo (i.e., about 1:6:6). The three cistrons are translationally coupled and expressed in a specific temporal order: a low level of IF3 synthesis stimulates the expression of L35 which, in turn, greatly stimulates the synthesis of L20 and IF3. Protein L20 and an excess of IF3 were found to act as translational feedback inhibitors of the entire operon. The synthesis of IF3 displayed a strong dependence on IF2. This dependence as well as the repressibility by excess IF3 were found to be due to the presence of the rare AUU initiation triplet at the beginning of infC.Key words: translational coupling, IF3, IF2, L35, L20.

ABSTRACT A primer extension inhibition (toeprint) assay was developed using ribosomes and ribosomal subunits from Streptomyces lividans. This assay allowed the study of ribosome binding to streptomycete leaderless and leadered mRNA. Purified 30S subunits were unable to form a ternary complex on aph leaderless mRNA, whereas 70S ribosomes could form ternary complexes on this mRNA. 30S subunits formed ternary complexes on leadered aph and malE mRNA. The translation initiation factors (IF1, IF2, and IF3) from S. lividans were isolated and included in toeprint and filter binding assays with leadered and leaderless mRNA. Generally, the IFs reduced the toeprint signal on leadered mRNA; however, incubation of IF1 and IF2 with 30S subunits that had been washed under high-salt conditions promoted the formation of a ternary complex on aph leaderless mRNA. Our data suggest that, as reported for Escherichia coli, initiation complexes with leaderless mRNAs might use a novel pathway involving 70S ribosomes or 30S subunits bound by IF1 and IF2 but not IF3. Some mRNA-ribosome-initiator tRNA reactions that yielded weak or no toeprint signals still formed complexes in filter binding assays, suggesting the occurrence of interactions that are not stable in the toeprint assay.

<strong>Introduction</strong> Okra (<em>Abelmoschus esculentus</em> L. Moench) is a perennial vegetable of African origin, with production areas expanding throughout the tropical, sub-tropical and warm temperate regions of the world (Benchasri, 2012). Okra is a versatile crop produced forits pods, leaves, seedoil and protein, gums, and fiber in different parts of the world (Lamont,1999). It is produced in Vilanculos primarily for the immature pods, though leaves are consumed to a limited extent in rural communities. Important attributes of okra pods are shape and color, earliness, and totalmarketable yield. Since okra is handharvested, plant height and architecture,as well as the absence of spines are important tofacilitate harvesting (Simonne, et al, 2012).Okra is not only reach in nutrients (fats, proteins, carbohydrates, minerals and vitamins), but it is also believed to have medicinal properties. The climate in much of Mozambique presents favorable conditions for the production of Okra (INE, 2011) and because of the growing preference for Okra among consumers in Mozambique, its area of production had rapidly expanded to every part of the country, mainly in the provinces of Tete, Manica, Sofala and Inhambane. Okra provides a good alternative or supplemental income for smallholder farmers (COSTA <em>et al</em>., 1981) and its production in the district of Vilanculos requires the application of considerable amount of irrigation water to improve productivity. Small farmers-led irrigation in Mozambique takes place in diverse forms, including bucket irrigation, sprinkler and drip systems, furrow and small pumped irrigation systems. However, Mozambique has limited access to raw water supplies and the country as a whole is extremely vulnerable (ranks 3^rd amongst African countries) to extreme weather patterns (i.e. recurring droughts and flood events), which contribute to crop instability, food insecurity and malnutrition (USAID, 2010). However, information on watering (irrigation) frequencies for optimal growth and development of this valuable crop under the edaphic-climatic conditions in the district of Vilanculos is lacking. Climate-smart strategies to increase irrigation efficiency at small-farm level are essential in helping rural smallholders optimize production of okra and other vegetable crops under climate change. <strong>Materials and Methods</strong> <strong>1. Geographical location</strong> The field experiment was carried out between October and December 2016 on the campus of the Universidade Eduardo Mondlane-Escola Superior de Desenvolvimento Rural (UEM-ESUDER) located in the coastal town of Vilanculo within the district of Vilanculos, Province of Inhambane in Mozambique at coordinates 21&ordm;59&rsquo;30.6&rdquo; S, 035&ordm;16&rsquo;14.8&rdquo; E. and an average altitude of 49m. The district of Vilanculosoccupies the northern part of the province of Inhambane, bordering the district of Inhassoro to the north, the district of Massinga to the south, the districts of Mabote and Funhalouro to the west and the Indian Ocean to the east (MAE, 2005). <strong>2. Climatic condition</strong> The climate of the study area is Aw according to the K&ouml;eppen e Geiger, which corresponds to a dry tropical climate with two distinct seasons. A wet season spans from October to March, with an average annual precipitation of 1300 mm; and a dry season from April to September, with an average annual precipitation of 700 to 900 mm (MICOA, 2009 and MAE, 2005).Figure-1 illustrates the average temperature and precipitation patterns in Vilanculos. The driest month is July, which averages 17 mm of rainfall, and the month of February is the wettest with an average precipitation of 166 mm. On average, the temperatures are always high, with an annual average of 24^oC. <strong>3</strong>. <strong>Soils of the study area</strong> The soils in the district of Vilanculos are sandy and permeable in the coastal areas, and sandy-loam to loamy-clay in the interior. The study site was approximatively 10 km from the coastal line and its soils are predominantly sandy and permeable with low organic content (8.55%) and low water holding capacity (less than 5cm/m) (MAE, 2005; Maite, 2014). The growing season averages 120 to 149 days, and because of low precipitation and recurring drought periods during the growing seasons, the area&rsquo;s potential for rain-fed agriculture is marginal (Mafalacusser, 2013.) <em>Figure 1. Monthly temperature and precipitation patterns in the district of Vilanculo, Mozambique.</em> <em>Adapted from Climograma Vilanculos: </em><em>https://pt.climate-data.org/location/52395/</em> &nbsp; <strong>4. Experimental design</strong> The experiment was laid out on an area of 83.375m² within which 3 blocks of equal sizes were setup, each block divided into 4 parcels of 4 m² (2 m x 2 m) for a total of 12 parcels. &nbsp;The blocks were setup at 1m apart and the parcels within each block were spaced at 50cm. Treatments were then randomly assigned to each parcel, resulting in each parcel representing a unique treatment within each block. Table-1 describes the different treatments (irrigation frequencies) used in the experiment. <em>Table 1. Treatments details: Four (4) treatments randomly assigned to the experimental blocks.</em> IF1 <em>Irrigate twice a day in the mornings (5-6 AM), and afternoons (4-5 PM)</em> IF2 <em>Irrigate once a day in the afternoons (4-6PM)</em> IF3 <em>Irrigate once a day in the mornings (5-6 AM)</em> IF4 <em>Irrigate twice a day in the mornings (5-6 AM), and afternoons (4-5 PM) at 1- day intervals.</em> <strong>5. Soil preparation and planting</strong> Soil preparation consisted of removing natural vegetation from the experimental site with a manual hoe without revolving the top soil, and the soil surface was raked and leveled prior to subdivision of the experimental area into parcels, blocks and replications for the study.Seeds of okra (<em>Abelmoschus esculentus</em> L. Moench) variety Clemson Spineless, were soaked in water for 24 hours to stimulate germination, and then sown by placing two (2) seeds in each planting hole at an approximate depth of 5cm in each parcel. Fifteen (15) days following the emergence, the seedlings were thinned by removing the least developed plant in each planting hole, leaving only one (1) okra seedling per hole in each treatment. The seedling selection criteria was based on height, and the number of developed leaves. <strong>6. Soil fertilization</strong> Organic fertilizer in the form of bovine manure was applied seven (7) days prior to sowing and 15 days after seedling emergence, at the rate of 15 tons/ha each. All plants received the same fertilizer application. <strong>7. Irrigation</strong> A hand-held irrigation bucket was used for applying water to the experimental plots, a watering scheme consistent with the most popular irrigation system among smallholders in the study area. All parcels were uniformly irrigated with 13 liters of water, starting from one (1) day prior to seeding until fifteen (15) days after seeding when the okra plants developed up to three (3) fully expanded leaves. Starting from day-15 through the end of the experiment, plants in each parcel were irrigated according to the established watering schedule (Table-1.) <strong>8.</strong> <strong>Pests/Weed Control</strong> Weed control was manual and continuous throughout the study, by hand plucking at the onset of their appearance to avoid perturbation of soil and plants. The most common weeds were <em>amaranthus</em>, <em>commelina benghalensis</em> and cyperus<em> esculentus</em> species, with <em>amaranthus</em>and<em>cyperus esculentus</em> being the most dominants.Observed pests were acarids and caterpillars, and these were treated with pesticides Cipermetrina 25% E.C. and Fords. The occurrence of fungi during the experiment was sparse, but fungi was treated with the fungicide Bravo. <strong>Data Collection</strong> <strong>1. Pre-harvest Data&nbsp;&nbsp; </strong> Pre-harvest plant parameters consisted of plant height and stem diameter. Plant height was determined by measuring the height of the primary stem of random sample of plants in each treatment from the base at soil surface to the apex, using a metric ruler. At the same time, stem diameter was measured with a digital Caliper, within 300mm at 5 cm above the soil surface. Growth Rate of okra plants was determined from height measurements and expressed as <em>Absolute Growth Rate</em> (AGR), based upon increments of measured plant heights between sampling dates (<em>i.e. Height at day2- Height at day1</em>) over the time-period (<em>number of days</em>) between measurement dates. <strong>2. Post-harvest Data</strong> Post-harvest data included Fruit Length, Fruit Diameter, and Fruit Weight. Okra fruits were harvested twice; the first harvest took place 90 days after seeding, and the second harvest 8 days later, or 98 days after seeding. Harvest data were from random fruit samples under each treatment for both harvests. A graduated metric rulerwas used to measure fruit length, while fruit diameter was measured with a digital Caliper within at 5 cm from thebase of each fruit, and fruit weight was determined by weighing sample fruits per treatment from each harvest, with a digital scale equipped with a high precision strain gauge sensor system. <strong>Data Analyses&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </strong> All data collected from the experiment were analyzed with the statistical software SPSS(v.20, IBM SPSS Chicago). Analyses of Variance (ANOVA) were performed to determine differences between treatments, followed by mean comparisons based on Tukey HSD (&alpha; = 0.05). Homogeneity of the variances was verified through the test of Levene (&alpha; = 0.05), and graphical illustrations were produced with the Microsoft Excel program. <strong>Result and Discussion</strong> <strong>1. Plant Height</strong> The different irrigation treatments had no significant effect on plant height at each sampling dates. Okra plants grown in this experiment averaged 4.73cm at 7 days after sowing (DAS), and increased through the study to an average of 49.39 cm at 63 DAS (Fig.2.)&nbsp; In contrast with other studies, okra plant height at the end of this experiment was relatively shorter than heights observed elsewhere. For example, Saifullah and Rabbani (2009) reported from evaluation of different genotypes that okra plant height at final harvest ranged from 81.80cm to 196.17cm. It is probable that the conditions under which the present study was carried out did not favor greater shoot elongation of the okra plants. However, significant differences in plant heights were observed between sampling dates according to the growth progression of plants through the study period, and between treatments across sampling dates. As illustrated in Figure 2, plant heights during the first three (3) sampling dates (7-21 DAS) were significantly lower than plant heights at other sampling dates. <em>Figure 2. Average plant height per treatment per sampling date</em> &nbsp; Furthermore, plant heights at 28-35 DAS was significantly lower than heights at 63 DAS. Overall, plant heights continuously increased during the study period, except under IF2 (<em>watering once a day in the afternoons</em>), where plant height leveled off between 28 and 35 DAS, before increasing again through the end of the study period (Fig.2.) Starting from 35 DAS to 63 DAS, okra plants height under IF2 increased rapidly to match heights of plants under IF1 and surpass heights of plants under IF3 and IF4 at 63 DAS. Figure-3 further shows okra plant height averaged across treatments at each sampling date.&nbsp; Okra plant height followed a rather exponential pattern from 7 DAS until 35 DAS, and then the growth pattern became linear thereafter. Significant differences in plant heights were observed during the first phases of plant growth between 7 DAS and 21 DAS, and between the set of 7 DAS - 21 DAS and the remainder DAS. However, no significant differences in plant height were observed between sampling dates from 28 DAS through 63 DAS (Fig.3.) &nbsp; &nbsp; <em>Figure 3.Average plant height per sampling date across the treatments</em> &nbsp; Figure 4 illustrates the average plant height per treatment across sampling dates. Plants grown under IF3 (<em>watering once a day in the mornings</em>) were significantly taller (P&lt;0.05) than those under IF2 and IF4. Although watering plants twice a day (IF1) resulted in plant heights similar to those under IF3, these results suggest that in terms of okra plant growth, watering once a day in the mornings (IF3) was more efficient in promoting plant growth with less use of irrigation water, compared with IF1 (<em>watering twice a day</em>.) <em>Figure 4.Average plant height per treatment across sampling dates</em> &nbsp; Moreover, plants grown under IF4 which received irrigation water twice a day but at one-day intervals, significantly outperformed those under IF2 (<em>watering once a day in the afternoons</em>) in terms of plant height. Given equal amounts of irrigation water applied but at different intervals in or IF2 and IF4, the treatment IF4 appeared to be more efficient in promoting okra plant growth as compared with IF2 (Fig.4.) <strong>2. Plant Growth Rate&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </strong> Growth Rate of okra plants was determined from height measurements and expressed as <em>Absolute Growth Rate</em> (AGR), based upon increments of measured plant heights between sampling dates (<em>i.e. Height at day2- Height at day1</em>) over the time-period (<em>number of days</em>) between measurement dates.&nbsp; Figure 5 illustrates the AGR pattern of okra plants under each treatment at each sampling date, with dates expressed in number of days after sowing (DAS). <em>Figure 5. Average Plant Growth Rate (cm/day) per sampling date across the treatments</em> &nbsp; As illustrated in Fig.5, okra plants grown under IF1 and IF3 exhibited relatively similar AGR pattern during much of the study period, while those under IF2 and IF4 constitute the other pair of similar AGR. Averaged across treatments, the AGR of okra plants under this study was 0.568 cm/day at 14 DAS and then increased significantly (P&lt;0.05) to a maximum rate of 2.346 cm/day at 28 DAS. After 28 days or so of growth have passed, the AGR dropped to a low of 0.309 cm/day at 35 DAS, before leveling off to an average rate 0.536 cm/day for the remainder of the growth period (Fig.6.)&nbsp; <em>Figure 6. Average Growth Rate per sampling date across treatments</em> &nbsp; Not many studies appear to have been carried out on okra growth rate, but the AGR pattern exhibited under this study was similar to those observed in previous experiments (Hunt, 1978; Tarassoum and Lovane, 2019.) Similar to previous studies, the reduction in AGR after 28 DAS have passed was attributable to Phenology and/or resource allocation to functions other than plant height.Comparisons of AGR between treatments across sampling dates showed that the average AGR was significantly faster (P&lt;0.05) under IF2 and IF4 when compared with IF1 and IF3 (Fig.7), with no significant differences observed between the respective pairs of treatments.Strikingly, the two treatments (IF1 &amp; IF3) which produced taller plants (Fig.4) resulted in relatively lower overall AGR during the study period, compared with the pair of IF2 and IF4, which resulted in shorter plants. While plant height under IF2 and IF4 were lower during the first 21 days and after 35 DAS have passed (Fig. 3), the significantly rapid increase in their heights between 21 and 28 DAS resulted in an overall greater AGR compared with the other treatments. <em>Figure 7. Average Growth Rate per treatment across sampling date</em> &nbsp; &nbsp; <strong>3. Plant Diameter</strong> Table 5 presents the average plant diameter under each treatment. The different irrigation frequencies had no significant effects on okra plant diameter, which averaged from 7.83 cm to 7.86 cm across the treatments. <em>Table 5. Average plant diameter per treatment across sampling dates</em> Treatments (Irrigation Frequency) Average Plant Diameter (cm) IF1 7.83&ordf; IF2 7.83&ordf; IF3 7.86&ordf; IF4 7.83&ordf; <strong>Average Treatments</strong> <strong>7.85</strong> <em>Means followed by the same letters are not significantly different (P&gt;=0.05)</em> The average stem diameter of okra plants under IF3 was slightly above the diameter under other treatments, but the difference was not significant (P&gt;0.05.) However, like plant height, plant diameter also increased exponentially from an average of 2.5cm on the first sampling date (7 DAS), to about 10.0cm on the fourth sampling date (28 DAS) and remained constant for the remainder of the study period (Fig.8.)&nbsp; <em>Figure 8: Average plant diameter per sampling date across treatments</em> <strong>4. Fruit Characteristics</strong> Summarized in Table-6 are the okra fruit characteristics under the different irrigation frequencies. Fruit diameter, length and weight under this experiment averaged 0.1852 cm, 11.83 cm and 0.04625 kg per pod across the treatments. Mateus (2011) reported that fruit characteristics of Okra (<em>Abelmoschus Esculentus</em>) Clemson variety, averaged 1.7 cm in diameter, 7.5 cm in length and 10g in weight. Other studies reported fruit diameter from 1.26 to 2.86cm, fruit length from 5.46 to 17.25 cm, and individual fruit weights from 0.01528 to 0.02615kg (Owolarafe and Shotonde, 2004; Saifullah and Rabbani, 2009.) Considering data from these previous studies, it appeared that okra plants under the present experiment were shorter but produced heavier and taller fruits compared with the above referenced study results. The variability in okra fruit characteristics is attributable to genotypes, experimental designs or climate variances amongst study areas. <em>Table 6. Average fruit length, diameter and weight under different irrigation frequencies.</em> IRRIGATION FREQUENCIES VARIABLES Fruit Length (cm) Fruit Diameter (cm) Fruit Weight (kg) IF1 13.0208a 0.2000a 0.060a IF2 11.3542b 0.1913ab 0.041ab IF3 11.2417b 0.1704b 0.046ab IF4 11.7083 b 0. 1813b 0.038b <strong>AVERAGE</strong> <strong>11.83125b</strong> <strong>0.1852ab</strong> <strong>0.04625ab</strong> <em>Means followed by the same letters in a column are not significantly different (P&gt;=0.05)</em> As shown on the Table-6, irrigating plants twice a day (IF1) resulted in significantly longer pods (P&lt; 0.05) compared with all the other treatments. IF4 resulted in a slightly longer fruits when compared with plants grown under IF2 and IF3, but the differences were not statistically significant. Fruit diameter was similar under IF1 and IF2, with no significant differences observed between IF2, IF3 and IF4, although IF4 resulted in a slightly larger fruit diameter than IF3. As for fruit weight, plants grown under IF1, IF2 &amp; IF3 produced fruits of similar weights. The only statistical difference observed was between IF1 and IF4, with the later treatment resulting in significantly lower fruit weight. The results from this study suggest that even though IF1 resulted in longer fruits, the non-significant differences between IF1 &amp; IF2 in terms of fruit diameterand between IF1, IF2 &amp; IF3 in terms of fruit weight, irrigating okra plants once a day (IF2 or IF3) could yield marketable fruits while at the same time reduce the amount of irrigation water. <strong>Conclusions</strong> Okra is produced in the district of Vilanculos primarily for its immature pods, which are either sold in local market or consumed by the producing households. Smallholders comprise the vast majority of okra producers in the study area, growing small plots of various sizes under bucket or furrow irrigation systems to improve growth and yield. Differences in Okra plant characteristics (height and growth rate) under this study appeared to show variation between pairs of treatments, with IF1 &amp; IF3 constituting one pair, and IF2 &amp; IF4 constituting the other pair. Interestingly, the taller plants exhibited lower average growth rate when compared with the shorter plants (Fig.3 &amp; 6.) Differences in fruit characteristics were also observed between plants grown under different watering frequencies. While IF1 resulted in longer okra pods compared with the other treatments, fruit diameter was similar under IF1 and IF2, and fruit weight similar under IF1, IF2 &amp;IF3. These results seemed to suggest that watering okra plants once a day in the mornings (IF3) offer better alternatives for irrigation water-saving strategy for optimal plant height and fruit weight. Additional studies will further assess the once-a-day irrigation schedules at different day-intervals to determine optimal water-saving irrigation schedule for okra production in the district of Vilanculos.

Milk from different cattle breeds can present different casein and fat contents, which are reflected in different cheese yields (CY). However, CY is also related to some breed-related molecular characteristics. The aim of the present work was to quantify the effect of these characteristics by comparing a series of Parmigiano Reggiano (PR) cheese-making trials made with milks from Italian Brown (IB) and Italian Friesian (IF) cattle herds. Twelve trials were carried out in a cheese factory in one year (one trial per month), each one consisting of four vats processed in parallel: three vats contained milk from three different IF cattle herds (IF1, IF2 and IF3) and one contained milk from a single IB cattle herd. A 24-h CY prediction formula was developed with data from IF1, IF2 and IF3 trials (calibration) and successively validated by applying it to 12 PR trials made with IF milk in six different cheese factories (external validation). The predicted values of 24-h CY were no different to the actual ones in both calibration and external validation. Finally, the formula was tested on trials made with IB milk. In this case, the predicted values were lower than the actual ones. The quantity of IF milk casein necessary to give the same CY of IB milk was 0.20 g/100 g.

According to the standard model of bacterial translation initiation, the small ribosomal 30S subunit binds to the initiation site of an mRNA with the help of three initiation factors (IF1–IF3). Here, we describe a novel type of initiation termed “70S-scanning initiation,” where the 70S ribosome does not necessarily dissociate after translation of a cistron, but rather scans to the initiation site of the downstream cistron. We detailed the mechanism of 70S-scanning initiation by designing unique monocistronic and polycistronic mRNAs harboring translation reporters, and by reconstituting systems to characterize each distinct mode of initiation. Results show that 70S scanning is triggered by fMet-tRNA and does not require energy; the Shine–Dalgarno sequence is an essential recognition element of the initiation site. IF1 and IF3 requirements for the various initiation modes were assessed by the formation of productive initiation complexes leading to synthesis of active proteins. IF3 is essential and IF1 is highly stimulating for the 70S-scanning mode. The task of IF1 appears to be the prevention of untimely interference by ternary aminoacyl (aa)-tRNA•elongation factor thermo unstable (EF-Tu)•GTP complexes. Evidence indicates that at least 50% of bacterial initiation events use the 70S-scanning mode, underscoring the relative importance of this translation initiation mechanism.

SUMMARY Valuable information on translation initiation is available from biochemical data and recently solved structures. We present a detailed description of current knowledge about the structure, function, and interactions of the individual components involved in bacterial translation initiation. The first section describes the ribosomal features relevant to the initiation process. Subsequent sections describe the structure, function, and interactions of the mRNA, the initiator tRNA, and the initiation factors IF1, IF2, and IF3. Finally, we provide an overview of mechanisms of regulation of the translation initiation event. Translation occurs on ribonucleoprotein complexes called ribosomes. The ribosome is composed of a large subunit and a small subunit that hold the activities of peptidyltransfer and decode the triplet code of the mRNA, respectively. Translation initiation is promoted by IF1, IF2, and IF3, which mediate base pairing of the initiator tRNA anticodon to the mRNA initiation codon located in the ribosomal P-site. The mechanism of translation initiation differs for canonical and leaderless mRNAs, since the latter is dependent on the relative level of the initiation factors. Regulation of translation occurs primarily in the initiation phase. Secondary structures at the mRNA ribosomal binding site (RBS) inhibit translation initiation. The accessibility of the RBS is regulated by temperature and binding of small metabolites, proteins, or antisense RNAs. The future challenge is to obtain atomic-resolution structures of complete initiation complexes in order to understand the mechanism of translation initiation in molecular detail.

Abstract Recently, there has been a shortage of baby formula due to the COVID-19-related supply chain, unsanitary conditions, and contamination in the manufacturing company. There is genuine concern that contaminated baby formulas may have been inadvertently imported worldwide. For this purpose, five commercially available infant formulas were selected and coded as IF1, IF2, IF3, IF4, and IF5. Physicochemical, nutritional compositions, toxic element (Pb), microbial content, and identification of isolates in the infant formula were determined using standard methods. The pH and total titratable acidity ranged from 6.50±0.00 to 6.90±0.0 and 0.05±0.01 to 0.07±0.00 %, respectively. Moisture, ash, and protein ranged from 2.4±0.1 to 8.00±0.3 %; 1.9±0.01 to 2.7±0.4 %; 1.8±0.0 to 3.8±0.3 %, respectively. Crude fat ranged from 22.0±0.0 to 28.30±0.0 %, and fibre was not detected. Toxic element Pb was detected in all the samples, ranging from 1.2±0.1 to 13.51±0.9 mg/kg. Microbial counts ranged from 2.0×10 to 8.0×104 CFU/g for total viable, enterobacteriaceae 3.0×104 to 13.5×105 CFU/g; staphylococcal 5×103 to 1.0×104 CFU/g and fungal 1.1×10 to 2.4×105 CFU/g. Although the standard is that no pathogen should be in infant formula, several were identified including Klebsiella spp., Escherichia spp., and Staphylococcus spp. In conclusion, the nutritional composition obtained correlated with the product description. Manufacturers should work assiduously on taking steps to ensure the safety of their products by limiting the level of toxic elements and microbial contaminants which negatively affect the health of infants.

Le facteur de demarrage de la traduction if3 est une proteine specifique des eubacteries, essentielle a la viabilite cellulaire. Elle intervient dans la reconnaissance du codon de demarrage d'un gene par le ribosome et garantit la concentration en sous-unites 30s libres alors susceptibles d'interagir avec l'arn messager. Son role, dans la cascade d'evenements se produisant sur le complexe de demarrage de la traduction, est encore mal compris. Au cours de ce travail, nous nous sommes particulierement interesses au domaine c-terminal d'if3 qui est responsable de la fixation d'if3 sur la sous-unite 30s et au domaine de fixation de ce dernier dans l'arn 16s. Ainsi, nous avons mis en evidence que la region centrale de l'arn 16s (556-884) serait responsable de la fixation d'if3. Par rmn, nous avons observe que la face d'interaction d'if3c avec le domaine central de l'arn 16s etait constituee de l'helice 1 du brin 1 et de la boucle 130 (residus 130-139). Nous avons alors mis en evidence l'importance du residu d106 qui joue un role dans la specificite de l'interaction, cet acide amine serait un antideterminant. Pour comprendre le role d'if3 dans la fidelite du demarrage, nous avons etudie l'importance du peptide de connexion qui relie le domaine n-terminal au domaine c-terminal d'if3. Une approche combinant des etudes in vitro (biochimiques, biologie moleculaire), in vivo (tests de fonctionnalite) et structurales (rmn) a ete retenue. Nous avons montre que le domaine n-terminal ne pouvait pas assurer seul la fidelite du demarrage. Le peptide de connexion n'a, semble-t-il, pas de role a jouer dans la fonction d'if3 mais il garantit l'action concomitante des deux domaines de la proteine. La fixation des deux domaines d'if3 pourrait induire un changement de conformation dans la sous-unite 30s qui serait a l'origine de la discrimination par celle-ci des complexes ternaires de composition non canonique.

Deux etapes fondamentales de la synthese d'une proteine chez escherichia coli ont ete etudiees: (1) l'interaction entre le facteur d'initiation if3 et la sous-unite ribosomique 30s; (2) la regulation de la traduction d'un arn messager: l'arnm de la threonyl-arnt synthetase. Le role de if3 a ete etudie en analysant son site de fixation sur la sous-unite 30s, au moyen d'un reactif de pontage: le trans-diaminodichloro platine (ii). If3 a ete ponte majoritairement a l'arn ribosomique 16s au niveau de deux sites distincts. L'analyse de ces sites nous a permis de proposer un mecanisme d'action de if3 permettant d'expliquer son role dans la stimulation de la fixation de l'arnm sur la sous-unite 30s. Ce mecanisme est supporte par la phylogenie et par l'effet de if3 sur la conformation de l'arnr 16s. L'expression de la threonyl-arnt synthetase de e. Coli est autoregulee negativement au niveau traductionnel. La conformation de la region de l'arnm necessaire au controle et son interaction avec la synthetase ont ete analysees en utilisant des sondes de structure enzymatiques et chimiques. La synthetase interagit avec son propre arnm au niveau de deux sites: un site "mimant" le bras de l'anticodon de l'arnt et un site, localise en amont du premier, correspondant a une structure tige/boucle tres stable. Ces deux sites sont independants structuralement et fonctionnellement. Le premier site est indispensable pour le controle, le deuxieme ne l'est pas mais il le favorise. Le controle s'exerce sous la forme d'une competition entre la synthetase et le ribosome dans la reconnaissance de leurs sites respectifs sur l'arnm. L'arnt #t#h#r qui a un effet anti-represseur sur la synthese de sa propre synthetase permet ainsi d'ajuster la concentration d'enzyme a celle de trna dans la cellule. Une modelisation graphique de cette region de l'arnm est proposee

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2016-08-23T14:06:23Z No. of bitstreams: 2 Dissertação - Weslei Silva de Araújo - 2016.pdf: 1398500 bytes, checksum: f28b00fa1bf2094ab7d357e829733e78 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5)<br>Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2016-08-23T14:07:36Z (GMT) No. of bitstreams: 2 Dissertação - Weslei Silva de Araújo - 2016.pdf: 1398500 bytes, checksum: f28b00fa1bf2094ab7d357e829733e78 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5)<br>Made available in DSpace on 2016-08-23T14:07:36Z (GMT). No. of bitstreams: 2 Dissertação - Weslei Silva de Araújo - 2016.pdf: 1398500 bytes, checksum: f28b00fa1bf2094ab7d357e829733e78 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-07-25<br>In this paper we sought to understand how the Degree in Physics in IFG Goiânia campus is structured and what the perspective of teachers in the area, specifically in the implementation of degree in Physics, and forward the changes in the institution. The choice of this theme is due to the requirement stipulated by law 11.892 of December 29, 2008, the Federal Institutes of Education, Science and Technology, in offering undergraduate courses, especially in the areas of Science and Mathematics, despite its recognized expertise in professional education. Some research has dealt with the theme of the presence of the degrees in FIs, discussing the profile, the deployment and the challenges that they are consoli dated. However, here we seek teachers' perception of the process. Characterized as a qualitative study we used bibliographical research to survey the changes via legal documents in the institution, as well as research on the site e -MEC for recognizing the quantity of courses offered in this mode before and after the creation of the IFs. For analysis of the survey responses a nd interviews with teachers of Physical area of Goiânia the IFG campus, we used content analysis, according to Bardin (2002). It was identified as perceived by teachers who: (i) changes in the institution provided an expansion and internalization, even disorderly; (Ii) the change in the teaching profession and school mischaracterization with devaluation of technical education; (Iii) the course designed to meet the law, structure and operation in construction, has a focus on specific knowledge at the expense of teaching; (Iv) teachers work almost exclusively in the classroom, with little or no research and extension activities. These aspects lead to understand that there is still a lack of identity in I Fs after implantation of degrees and forward the changes in this institutions.<br>Neste trabalho buscou-se compreender de que forma a Licenciatur a em Física no campus Goiânia do IFG se estrutura e qual a perspectiva dos professores da área , especificamente, na implantação da licenciatura em Física , e frente as mudanças ocorridas na instituição. A escolha deste tema se deve pela obrigatoriedade, estipulada pela lei 11.892 de 29 de dezembro de 2008, dos Institutos Federais de Educação, Ciência e Tecnologia, em ofertar cursos de licenciaturas, principalmente nas áreas de Ciências e Matemática, apesar de sua reconhecida competência na área de educação p rofissional. Algumas pesquisas têm tratado da temática sobre a presença das licenciaturas nos IFs, discutindo o perfil, a implantação e os desafios para que os mesmos sejam consolidados. No entanto, aqui buscamos a percepção dos professores sobre todo o pr ocesso. Caracterizado como um trabalho de abordagem qualitativa utilizou-se inicialmente de pesquisa bibliográfica para levantamento das alterações ocorridas via documentos legais na instituição, assim como pesquisa no site e -MEC para o reconhecimento do quantitativo de cursos ofertados nesta modalidade antes e depois da cria ção dos IFs. Para análise das respostas do questionário e das entrevistas realizadas com os professores da área de Física, do campus Goiânia do IFG, utilizou-se a Análise de Conteúdo, segundo Bardin (2002). Identificou-se, segundo a percepção dos professores que: (i) as mudanças na instituição proporciona ram uma expansão e interiorização, mesmo que desordenada ; (ii) a alteração na carreira do professor e a descaracterização da escola com desvalorização do ensino técnico; (iii) o curso criado para atender a lei, com estrutura e funcionamento em construção, possui um enfoque no conhecimento específico em detrimento do pedagógico; (iv) os professores atuam quase que exclusivamente em sala de aula, com poucas ou nenhuma atividade de pesquisa e de extensão. Estes aspectos levam a entender que há ainda uma falta de identidade nos IFs após a implantação das licenciaturas e frente as mudanças ocorridas nesta s instituições.

Les interférons (IFN) constituent une famille de cytokines aux propriétés antiprolifératives et antivirales. Ils activent, via la voie Jak/STAT, des gènes spécifiques dont les produits sont les médiateurs des effets biologiques des IFN. C’est le cas de PML (Promyelocytic leukemia), appelée aussi TRIM19, qui joue un rôle central dans la défense antivirale. PML appartenant à la famille des protéines Tripartite Motif (TRIM), caractérisée par la présence en N-terminal d’un motif RBCC, constitué d’un domaine RING, d’une ou de deux boites B et d’un domaine coiled-coil. PML a été identifiée dans la leucémie aiguë promyélocytaire, une pathologie causée par la translocation chromosomique t(15 ;17) qui fusionne les gènes PML et RARA, aboutissant à la synthèse d'une protéine chimère PML-RARA. Le trioxyde d'arsenic (As2O3) cible la portion PML de la protéine oncogénique, entraînant sa dégradation et la rémission complète des patients. Dans les cellules saines, les transcrits PML issus d’un gène unique génèrent par épissage alternatif 7 isoformes principales de PML, dont six sont nucléaires (PMLI à PMLVI) et une cytoplasmique (PMLVIIb). Toutes possèdent la même extrémité N-terminale mais diffèrent au niveau de leur extrémité C-terminale, conférant à chaque isoforme des fonctions spécifiques.PML est l’organisatrice d’une structure multi-protéique appelée corps nucléaires (CN), impliquée dans divers processus cellulaires tels que l’apoptose, la dégradation des protéines ou encore la défense antivirale.PML est modifiée par SUMO de façon covalente au niveau de trois sites lysines (K65, K160, K490) et de façon non covalente, via son domaine SIM (pour « SUMO Interacting Motif »). Ces modifications sont requises pour la formation de CN fonctionnels et le recrutement de protéines partenaires au sein de ceux-ci. Le but de ma thèse a été d’étudier le rôle différentiel des différentes isoformes de PML en réponse à l’As2O3 et suite à l’infection virale. Nous avons montré que le SIM de PML est nécessaire à sa dégradation en réponse à l'As2O3. Ce motif est présent dans toutes les isoformes de PML, hormis l’isoforme nucléaire PMLVI et l’isoforme cytoplasmique PMLVIIb. Le SIM de PML n’est pas requis pour sa SUMOylation et son interaction avec RNF4 (une E3 ubiquitine ligase responsable de la dégradation de PML via le protéasome). En revanche, ce motif est requis pour l’ubiquitination de PML, le recrutement des composants du protéasome et sa dégradation en réponse à l’As2O3. Concernant les propriétés antivirales de PML, l’étude que nous avons menée avec toutes les isoformes de PML a permis de montrer que seules PMLIII et PMLIV confèrent une résistance au Virus de la Stomatite Vésiculaire (VSV). L’effet antiviral de PMLIII n'est observé qu'à faible multiplicité d’infection (MOI) et est indépendant de la production d’IFN. Par contre, PMLIV exerce une puissante activité anti-VSV, y compris à forte MOI et s'exerce selon deux mécanismes distincts : (i) PMLIV inhibe la réplication du VSV par un mécanisme précoce indépendant de l’IFN, (ii) PMLIV augmente tardivement la production d’IFN-β via une plus forte activation d’IRF3 qui est due à la séquestration spécifique de Pin1 au sein des CN par PMLIV. Ces deux processus nécessitent la SUMOylation de PMLIV. Ces résultats montrent que PMLIV exerce une activité antivirale intrinsèque et est impliquée dans l’immunité innée en régulant positivement la voie de transduction conduisant à la synthèse d’IFN-β<br>Interferons (IFNs) are a family of cytokines with antiproliferative and antiviral properties.They activate, via the Jak/Stat pathway, specific genes whose products are the mediators of the biological effects of IFNs. This is the case of PML (Promyelocytic leukemia), also known as TRIM19, which plays a central role in antiviral defense.PML belongs to the Tripartite Motif (TRIM) protein family, characterized by the presence of an N- terminal RBCC pattern, consisting of a RING domain, one or two B-boxes and a coiled-coil domain. PML was identified in acute promyelocytic leukemia, a disease caused by the chromosomal translocation t(15 ;17), which fuses the PML and RARA genes, leading to the synthesis of a chimeric protein PML-RARA . Arsenic trioxide (As2O3) targets the PML moiety of the oncogenic protein, resulting in its degradation and in the complete remission of patients.In healthy cells, PML transcripts derived from a single gene generate seven major isoforms of PML by alternative splicing, including six nuclear (PMLI to PMLVI) and one cytoplasmic (PMLVIIb). All share the same N-terminus but differ at their C-terminus, giving each isoform specific functions.PML is the organizer of a multi-protein structure called nuclear bodies (NBs) that are involved in various cellular processes such as apoptosis, protein degradation or antiviral defense.PML is covalently modified by SUMO at three lysine residues (K65, K160, K490) but also non-covalently via its SIM domain (for « SUMO Interacting Motif »). These modifications are required for the formation of functional NBs and the recruitment of partner proteins within them.The aim of my thesis was to study the differential role of the different PML isoforms in response to As2O3 and during viral infection.We have shown that the SIM PML SIM is necessary for its degradation in response to As2O3. This motif is present in all PML isoforms, except the nuclear PMLVI and the cytoplasmic PMLVIIb isoforms. The SIM of PML is not required for its SUMOylation and its interaction with RNF4 (the E3 ubiquitin ligase responsible for PML proteasome-dependent degradation). However, this motif is required for the ubiquitination of PML, the recruitment of proteasome components and the degradation of PML in response to As2O3.Concerning the antiviral properties of PML, the study that we conducted with all PML isoforms allowed us to show that only PMLIII and PMLIV confer resistance to Vesicular Stomatitis Virus (VSV). Whereas the antiviral activity of PMLIII is only observed at low multiplicity of infection (MOI) and is independent of IFN production, PMLIV has a potent anti-VSV activity, including at high MOI, which is mediated through two distinct mechanisms: (i) PMLIV inhibits the replication of VSV by an early and IFN-independent mechanism, (ii) PMLIV later increases the production of IFN-β via a stronger activation of IRF3, which is due to the specific sequestration of Pin1 by PMLIV within NBs. Both processes require the PMLIV SUMOylation. These results show that PMLIV has an intrinsic antiviral activity and is also involved in innate immunity by positively regulating the transduction pathway leading to IFN-β synthesis

Submitted by Jaqueline Vilas Boas Talga (jtalga@yahoo.com.br) on 2018-11-14T13:16:32Z No. of bitstreams: 1 Tese_Jaqueline Vilas Boas Talga_Linhagens em movimento_reflexões a partir das culturas iorubas.pdf: 5584361 bytes, checksum: 9d6226c92bd0fecd707d6fe6b4a32b4d (MD5)<br>Approved for entry into archive by Milena Maria Rodrigues null (milena@fclar.unesp.br) on 2018-11-21T18:51:44Z (GMT) No. of bitstreams: 1 talga_jvb_dr_arafcl.pdf: 5584361 bytes, checksum: 9d6226c92bd0fecd707d6fe6b4a32b4d (MD5)<br>Made available in DSpace on 2018-11-21T18:51:44Z (GMT). No. of bitstreams: 1 talga_jvb_dr_arafcl.pdf: 5584361 bytes, checksum: 9d6226c92bd0fecd707d6fe6b4a32b4d (MD5) Previous issue date: 2018-09-19<br>Este trabalho tem por propósito apreender e discutir as concepções e práticas dos movimentos de adeptos e sacerdotes dos cultos ancestrais iorubas, entre o Golfo de Benin e o Brasil. Trata-se de um relato etnográfico focado nos movimentos atuais, cuja notável recorrência, inscrita em sucessivas trajetórias de vida, conduz ao questionamento de sua profundidade temporal, como de sua própria inteligibilidade na tessitura de laços linhageiros. A partir do cotejamento de esparsas referências disponíveis a trajetórias de vida que remontam à constituição de cidades estados em território ioruba em África e terreiros de Cambomblés no Brasil, ainda à vigência do regime escravagista, distinguimos uma parcela de africanos livres, libertos e seus descendentes que forjaram, ora por vontade, ora por imposições, as movimentações de retorno ao continente africano, ou mesmo, de contínuas viagens dos dois lados do oceano Atlântico. Consideramos a seguir, de modo particular, dentre os retornados e os viajantes, os que irão formar redes sociorreligiosas de transeuntes, e redes sociorreligiosas de matrimônios transatlânticos. Já no início do século XX passamos a notar nas movimentações estabelecidas por simpatizantes, iniciados ou não no culto dos Orixás, a participação destacada de intelectuais e artistas que passam a intermediar trocas entre adeptos dos dois lados do Atlântico. No período mais recente das movimentações, percebemos novas nuances incidentes nas motivações para a travessia do Atlântico Sul, dentre elas algumas promovidas pelos desdobramentos não esperados de convênios bilaterais entre Brasil e Nigéria, e de modo especial, as incitadas pelo movimento de africanização dos cultos brasileiros que reacende a busca direta dos ritos dirigidos por sacerdotes iorubas nigerianos, tanto no Brasil como em África<br>The purpose of this work is to apprehend and discuss the conceptions and practices of movements made by addherents, religious people of Ifá between the Benins Gulf and Brazil. It is an ethnographic study focused on current movents, which are frequently reveiling life trajectories and it leads to the question of temporal deepness of the lineages. It departs from the scattered literature available and from the life trajectories that resembles to the constitution of State cities in ioruba territory in Africa and Camdomblés terreiros in Brasil. We distinguish different groups, such as free Africans, former-saves and their descendents who constructed the movements of return to the African continent, connenting the both sides of the Atlantic Ocean. In the most recent period of the movements, we noticed new characteristics in the motivs for the journey, among them some promoted by unexpected consequences of the official bilateral projects between Brazil and Nigeria. Specially, we emphacize the movement of the Africanization of Brazilian worships that pushes the direct search for rituals led by Nigerian iorubas both in Brazil and in Africa.

Dans le cadre de cette thèse, une approche de calcul de couplage multi-échelle et multi-physique en 2D et en 3D est présentée. La modélisation multi-échelle d’une structure consiste de l’échelle macro qui représente la réponse homogénéisée de la structure entière, tandis que l’échelle micro peut capturer les détails du comportement à la petite échelle du matériau, où des mécanismes inélastiques, tels que la plasticité ou l’endommagement, peuvent être pris en compte. L’intérieur de chaque macro-élément est rempli par le maillage à l’échelle micro qui s’y adapte entièrement. Les deux échelles sont couplées à travers le champ de déplacements imposé à l’interface. Le calcul par éléments finis est effectué, en utilisant une procédure de solution operator-split sur les deux échelles. En 2D, une discontinuité dans le champ de déplacements est introduite à l’échelle macro dans un élément fini Q4, pour pouvoir capturer l’adoucissement comportement d’un matériau piézoélectrique. Un degré de liberté supplémentaire qui représente le voltage est ajouté aux noeuds des macro-éléments de tétraèdre et d’hexaèdre en 3D. La poutre de Timoshenko comportant un modèle de commutation de polarisation est utilisée à l’échelle micro. Également, une formulation multi-échelle de Hellinger-Reissner a été développée et implémentée pour un simple patch test en électrostatique. La procédure proposée est mise en œuvre dans le logiciel de calcul par éléments finis FEAP - Finite Element Analysis Program. Pour simuler le comportement aux deux échelles, FEAP est modifié, et deux versions différentes du code sont obtenues - macroFEAP et microFEAP. Le couplage de ces codes est réalisé avec Component Template Library - CTL qui rend possible l’échange d’informations entre les deux échelles. Les capacités de cette approche multi-échelle en 2D et en 3D sont démontrées dans un environnement purement mécanique, mais aussi multi-physique. La formulation théorique et l’application algorithmique sont présentées, et les avantages de la méthode multi-échelle pour la modélisation des matériaux hétérogènes sont illustrés avec plusieurs exemples numériques<br>In this thesis, a multi-scale and multi-physics coupling computation procedure for a 2D and 3D setting is presented. When modeling the behavior of a structure by a multi-scale method, the macro-scale is used to describe the homogenized response of the structure, and the micro-scale to describe the details of the behavior on the smaller scale of the material where some inelastic mechanisms, like damage or plasticity, can be taken into account. The micro-scale mesh is defined for each macro-scale element in a way to fit entirely inside it. The two scales are coupled by imposing a constraint on the displacement field over their interface. The computation is performed using the operator split solution procedure on both scales, using the standard finite element method. In a 2D setting, an embedded discontinuity is implemented in the Q4 macroscale element to capture the softening behavior happening on the micro-scale. For the micro-scale element, a constant strain triangle (CST) is used. In a 3D setting, a macro-scale tetrahedral and hexahedral elements are developed, while on the micro-scale Timoshenko beam finite elements are used. This multi-scale methodology is extended with a multi-physics functionality, to simulate the behavior of a piezoelectric material. An additional degree of freedom (voltage) is added on the nodes of the 3D macro-scale tetrahedral and hexahedral elements. For the micro-scale element, a Timoshenko beam element with added polarization switching model is used. Also, a multi-scale Hellinger- Reissner formulation for electrostatics has been developed and implemented for a simple electrostatic patch test. For implementing the proposed procedure, Finite Element Analysis Program (FEAP) is used. To simulate the behavior on both macro and micro-scale, FEAP is modified and two different version of FEAP code are implemented – macroFEAP and microFEAP. For coupling, the two codes are exchanging information between them, and Component Template Library (CTL) is used. The capabilities of the proposed multi-scale approach in a 2D and 3D pure mechanics settings, but also multi-physics environment have been shown. The theoretical formulation and algorithmic implementation are described, and the advantages of the multi-scale approach for modeling heterogeneous materials are shown on several numerical examples

Dans le contexte de la micro-robotique, cette thèse vise à développer une méthode de localisation et de suivi optique de micro-convoyeurs se déplaçant sur une surface. Le principe de la méthode de localisation proposée consiste à détecter un faisceau réfléchi sur le micro-convoyeur et à analyser ce signal optique pour obtenir les positions correspondantes. Les principaux éléments du système sont un rétroréflecteur à coin cube placé sur un micro-convoyeur et qui permet de réfléchir le signal optique dans sa direction incidente, un miroir MEMS qui permet de balayer la surface avec un éclairement laser, un séparateur de faisceau qui est un composant optique utilisé pour guider la lumière réfléchie vers un photodétecteur utilisé pour assurer la localisation et le suivi à travers l’exploitation du signal détecté par ce dernier. L’importance de la localisation est d’optimiser la trajectoire suivie par les micro-convoyeurs en contrôlant leur position et leur vitesse pour finalement pouvoir localiser les micro-convoyeurs avec une grande précision et éviter d’éventuelles collisions entre eux. Pour faire des tests expérimentaux et évaluer le capteur développé, la surface utilisée est une surface de micro-convoyage basée sur un principe électromagnétique, développée au laboratoire Roberval. Une calibration du système, en utilisant l’homographie, a été effectuée afin d’assurer la localisation et le suivi du micro-convoyeur pour après contrôler sa trajectoire et sa vitesse. Une localisation et un suivi simultané de deux micro-convoyeurs en utilisant un multiplexage temporel a été également développé et validé dans ce travail<br>This thesis aims to develop a method for optical localization and tracking of microconveyors moving over a surface in the context of micro-robotics. The principle of the proposed localization method consists of detecting a beam that is reflected on the micro-conveyor and analyzing this optical received signal to obtain the corresponding positions. The main elements of the system are a corner cube reflector, a MEMS mirror and a beam splitter. The corner cube is placed on the micro-conveyor in order to allow the optical signal to be reflected in its incident direction. The MEMS mirror allows the surface to be scanned with the laser. As for the beam splitter, it is an optical component used to guide the reflected light to a photodetector which is in turn used for localization and tracking through the exploitation of the signal that it detects. The important role of localization is to optimize the trajectory followed by the micro-conveyors. This could be achieved by controlling the respective position and speed of each of them in order to be finally able to localize the micro-conveyor with high precision and to avoid possible collisions between them. The surface used is a micro-conveying surface based on an electromagnetic principle, developed at the Roberval laboratory. The surface is used to perform experimental tests and to evaluate the developed sensor. A system calibration, using homography, was carried out in order to ensure the localization and tracking of the micro-conveyor, and then to control its trajectory and speed. Simultaneous localization and tracking of two micro-conveyors using time division multiplexing was also developed and validated in this work. An application of the thesis at the macroscopic scale is presented as well through applying free space optical communication between two mobile systems controlled by closed-loop optical tracking. Each system includes an active transmitter and a receiver (instead of a passive corner cube reflector in the case of the micro-conveyor). The system is driven by two servomotors which permit it to have free movement in three-dimensional space. The two modules must be aligned in order to be able to send and receive information by laser and thus communicate. In this case, a high-precision tracking system which is capable of aligning the two moving modules is required

La modélisation des matériaux nano-renforcés nécessite de prendre en compte l’effet de taille induit par les phénomènes locaux à l’interface entre la nanoinclusion et la matrice. Cet effet de taille est interprété par une augmentation du rapport interface/volume et peut être pris en compte en introduisant une élasticité surfacique à l’interface. Alors que de nombreux travaux ont été développés du point de vue analytique, peu de contributions ont trait à la description numérique et à la mise en œuvre de cette élasticité surfacique dans la méthode des éléments finis (FEM). Nos études visent à développer des outils numériques efficaces basés sur la FEM pour la modélisation de nanocomposites. Dans un premier temps, nous évaluons les deux stratégies numériques existantes, à savoir l’approche XFEM et l’approche des éléments d’interface, dans la reproduction de l’effet de taille dans le processus d’homogénéisation. Deuxièmement, sur la base d’un test de performance des trois types de formulations d’E-FEM dans le cas de discontinuités faibles, nous proposons une formulation améliorée de SKON permettant d’intégrer l’effet d’une interface cohérente. Enfin, la modélisation numérique du comportement non linéaire des nanocomposites est étudiée. Lors de la première étape, une loi élastoplastique de type von Mises avec durcissement linéaire isotrope est considérée pour le volume, tandis que l’interface est considérée comme élastique linéaire<br>The modelization of nano-reinforced material requires to take into account the size effect caused by the local phenomena at the interface between the nano-inclusion and the matrix. This size effect is interpreted through an increase in the ratio interface/volume and can be taken into account by introducing a surface elasticity at the interface. Whereas a lot of works have been developed from the analytical point of view, few contributions are related to numerical description and implementation of such surface elasticity in Finite Element Method (FEM). Our studies aim to develop efficient numerical tools based on FEM for the modeling of nanocomposites. Firstly, we evaluate the two existent numerical strategies namely the XFEM approach and the Interface element approach in reproducing the size effect in the homogenization process. Secondly, based on a performance test on the three types of formulations of E-FEM for the case of weak discontinuity, we propose an enhanced SKON formulation allowing to incorporate the effect of a coherent interface. Finally, the numerical modeling on the nonlinear behavior of nanocomposites is investigated. In the first step, a von Mises type elastoplastic law with linear isotropic hardening is considered for the bulk while the interface is considered as linear elastic