• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 4
  • 4
  • 3
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 18
  • 5
  • 3
  • 3
  • 3
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Does environmental variability explain male parental care in a burying beetle?

Noah S Feldman (9183593) 04 August 2020 (has links)
Many animal species invest in extended parental care for their offspring. Parental care is costly, and natural selection favors investment strategies which maximize reproductive success. Biparental care is relatively rare, but when it does occur it has been found to increase success in terms of offspring survival and growth and in terms of future reproductive opportunities. In burying beetles (<i>Nicrophorus</i> spp.), both male and female participate in extended parental care. However, the fitness benefits of biparental care in burying beetles have been difficult to establish, with some studies reporting significantly smaller broods produced when both male and female are present. Variation in environmental conditions, such as temperature, is an important part of the context in which biparental care evolves. I hypothesize that biparental care acts as a buffer against environmental variation. This hypothesis predicts that biparental care will lead to greater reproductive success compared to uniparental care when temperature is increased during a reproductive attempt. I also tested the load-lightening hypothesis, which holds that biparental care benefits future reproduction by lowering the costs of reproduction. This predicts that the additional care by the other parent will allow females to rear higher quality second broods. I conducted a male removal experiment at two temperature treatments, using the species <i>Nicrophorus orbicollis</i>. I measured reproductive success during manipulated first brood and during second broods which females reared without a male, regardless of prior experience. I found that, contrary to my hypothesis, biparental care at the higher temperature resulted in reduced reproductive success compared to uniparental care. I found no effect of biparental care on the success of second broods. Instead, I found evidence of reproductive restraint associated with the higher temperature treatment in delayed egg-laying and increased feeding during second broods.
12

Eclaircissement de la peau chez les femmes africaines à Marseille / The lightening skin of african women living in Marseille

Emeriau, Céline 10 September 2010 (has links)
La couleur de la peau est le caractère physique de l’homme possédant la plus grandevariabilité. Originairement répartie selon un gradient géographique, les migrations depopulations sont venues nuancer cette répartition chromatique. La pigmentation caractérisetoutefois un espace géographique et les populations qui y vivent, constituant un marqueuridentitaire selon l’origine géographique des individus. La rencontre de populations d’originesdifférentes a donné naissance à un imaginaire construit autour de la couleur de la peau. Lapigmentation comme marqueur identitaire, qui n’a de sens que dans le domaine social, seconjugue à des mythes et stéréotypes qui ont évolués au cours du temps mais qui restenttoujours présents dans l’imaginaire social.Stigmatisante et chargée symboliquement, la couleur de la peau est soumise au mêmetitre que le reste du corps à un travail des apparences. Pour être jugée esthétiquementconforme aux normes dominantes, la peau doit répondre à des critères. Comme tout travaildes apparences, l’éclaircissement de la peau est un fait social s’inscrivant dans un système dereprésentations propre à l’environnement socio-culturel des populations qui s’éclaircissent.C’est dans ce contexte que cette pratique corporelle prend son sens. Or dans le cas despopulations originaires d’Afrique vivant en France, leur environnement socio-culturel se voitinfluencé à la fois par leur pays d’origine mais aussi par leur pays d’accueil, ainsi que par lesenjeux politiques les liant historiquement, des enjeux pour lesquels la couleur de la peau a putenir un rôle prépondérant, notamment durant la période de la colonisation.Au cours de notre étude, nous cherchons à faire un état des lieux de cette pratique auprèsdes femmes africaines vivant à Marseille. Nous essayons de mettre en évidence comment estréalisée cette pratique et à quels systèmes de représentations elle fait référence. Pour cela nousnous intéresserons aux produits et aux techniques permettant d’éclaircir la peau, au regard desfemmes africaines qu’elles utilisent ou non ces produits, mais également au discours socialsur la pratique émanant des publicités pour produits éclaircissants, des magazines fémininsciblant les femmes africaines mais aussi les vendeurs et les médecins témoins de l’impactnocif des produits.L’analyse globale de ces différents discours montre que la pratique de l’éclaircissementde la peau ne se limite pas à un changement de couleur de peau. En modifiant la teinte, maisaussi la texture et la luminosité de la peau, les femmes répondent à une logique sociale etimaginaire. En effet, la pratique de l’éclaircissement s’inscrit dans une logique imaginaire auxfondements empiriques et dont le résultat imprimé sur la peau des femmes aura un impactdans leur vie sociale. En changeant leur couleur de peau, les femmes rentrent dans uneconstruction bio-socio-subjective. Elles matérialisent ainsi une quête identitaire s’inscrivantdans un référentiel socio-culturel et chromatique.Ce travail a pour particularité d’apporter une analyse originale sur l’éclaircissement chezles femmes africaines à Marseille mais aussi un regard pluridisciplinaire nécessaire à l’étudede l’éclaircissement de la peau, une pratique corporelle qui renvoie à la fois à des fonctionsbiologiques et culturelles. / The skin color is the physical feature of human who has the biggest variability. Originallyspread in fonction a geographic gradient, the migrations of populations came to shade thischromatic distribution. However pigmentation caracterises a goegraphic space andpopulations living there, it is them a tracer of identity in fonction of individual geographicorigin. From the meeting of populations of different origin came forth an imaginary built onthe skin color. The skin pigmentation, as identitary tracer, wich has sens only in the socialdomain, is combined with mythes and stereotypes wich had evolved in the course of time butwich still remain presents in the social imaginary.Stigmatising and symbolically weighty, the skin color is subordinate as the rest of thebody to a work of the appareances. To be judged esthetically coplining dominant norms, skinhas to answer to specific standards. Like all works of appreances, the lightening of skin is asocial fact circumscribing within a system of representation belonging to the socio-culturalenvironment of populations who light itself. It is in this context that this corporal practicetakes sens. Thus, in the cas of populations originating from Africa and living in France, theirsocio-cultural environment is influenced by both the country of origin and the recievingcountry, and also by the political stakes wich historically bind them, stakes for wich skin colorhad taken a preponderant function, in particular during the periode of colonisation.In the course of our study, we try to estimate the situation of this practice by africanwomen living in Marseille. We try to make evident how is realised this practice and to wichsystems of representations it makes reference. In this purpose, we take interest to the productsand techniques enabling to light the skin, to the position of african women using or not thoseproducts, to the social discourse on the practice coming from advertising for lighteningproducts, from feminin magazines targetting african women and also the sellers and thedoctors witness of the harmful impact of the products.The global analyse of these different discourses shows that the practice of lightening skindoes not limite itself to a changing of skin color. Modifing complexion, but also texture andluminosity of the skin, women answer to a social and imaginary logic. Indeed, the practice oflightening lies within an imaginary logic with empirical fondations and whose result printedon the women skin will have an impact in their social life. Changing the skin color, womenbring in a bio-socio-subjective construction. Thus they materialise an identitary questcircumscribing itself in a socio-cultural and chromatic referential.This work has for particularities to bring an original analyse on the lightening of africanwomen living in Marseille but also a pluridisciplinar glance necessary for the study of thelightening skin, a corporal practice wich refer to either biological either cultural functions.
13

Využití nevyhořívajících lehčiv pro lehčení cihlářského střepu / Incombustible ligtweighting agents for brick body

Suk, Vojtěch January 2016 (has links)
This diploma thesis deals with the possibility of reducing the density of the brick body using the chemical additive Vuppor for different types of soil, which are used for the production of thermal insulating products such as type THERM. Describes the availability of suitable additives (starch, carboxymethylcelullose, acrylic dispersion) that are capable of combining with the additive Vuppor to improve the observation properties.
14

"Fair and Lovely": The Concept of Skin Bleaching and Body Image Politics In Kenya

Okango, Joyce Khalibwa 08 August 2017 (has links)
No description available.
15

Puslaidininkinių šviesos šaltinių tyrimas / Semiconductor light sources inquiry

Mačenskas, Marius 10 June 2005 (has links)
The main point: Research light emiting diodes RGB (red, green, blue) matrix with controllable spectrum of light. I have made that matrix, and researching energetic, light and technicality datum. To use that light sources for lightening of emergency. To review other liht sources. Stepping stone and results: There are made review of most popular light sources, quality and limitation. There are overlook of semiconductors light sources and the range where they are using now. Experiments are made with our LED illuminator with minimal number of LED. There are noticed, that LED can take energy from light and that we use to make manage of others light sources. Illuminator are adapted to work in emergency lightening. The result can be use: The result can be use for development LED in Lithuania, to know people more about semiconductor light sources ant to use it ours home.
16

Définition d'une méthodologie d'allègement de structures sous contrainte de rigidité fonctionnelle, cas d'une machine-outil. / Definition of a methodology for lightening structures constrained by a functional rigidity, case of a machine tool

Deneffle, Romain 20 June 2017 (has links)
En réponse à des contraintes écologiques et économiques de plus en plus forte dans l’industrie, la problématique de réduction et de maîtrise de la consommation énergétique est aujourd’hui prise en considération dans le domaine de la machine-outil. Cette thèse s’inscrit dans le cadre du projet Green HSM porté par l’entreprise PCI-SCEMM ayant pour but de réduire la consommation énergétique d’une machine-outil de 30%. L’étude s’est focalisée sur le thème spécifique de l’allègement de structure. L’objectif est de concevoir des structures de machines-outils avec des masses mobiles les plus faibles possibles tout en gardant une rigidité fonctionnelle.Deux méthodes d’allègement de structures sont proposées dans le cadre de cette thèse. La première présente une méthode d’optimisation de structure de machines-outils par analyse de contraintes. Cette méthode a permis un allègement de deux pièces principales de la structure de 6,5% et 9% pour une réduction globale de la consommation énergétique de 3%.Une autre méthode pour concevoir une structure de machines-outils plus légère utilisant l’optimisation topologique est proposée. La méthode s’appuie sur deux paramètres spécifiques : l’espace de conception et DISCRETE. Cette méthode est présentée dans l’optimisation d’un cas simple de poutre encastrée soumise à un effort de flexion et donne de bons résultats. L’utilisation de la méthode sur le chariot X d’une machine-outil met en évidence les limitations de l’optimisation topologique dans le cas d’étude de structures complexes et l’influence du choix de la solution initiale. / In response to the increase of environmental and economic constraints in industry, the issue of reducing and controlling energy consumption is highlighted in machine tool context. This thesis is part of the Green HSM project carried out by the PCI-SCEMM company with the aim of reducing the energy consumption of a machine tool by 30%. The study focused on the specific topic of lightweight design. The objective is to design machine tool structures with the smallest mass while maintaining functional rigidity.Two methods of lightening structures are proposed in the framework of this thesis. The first one presents a method for optimizing the structure of machine tools by stress analysis. This method allows reducing the mass of two main parts of the structure of 6.5% and 9% for an overall reduction in energy consumption of 3%. Another method for designing a lighter machine structure using topological optimization is proposed. The method is based on two specific parameters: the space design and DISCRETE. This method is presented in the optimization of a simple case of embedded beam subjected to a bending effort and gives good results. The use of the method on the X-axis carriage of a machine tool highlights the limitations of topological optimization in the case of complex structure studies and the influence of the initial solution choice.
17

Svetlosni program, gustina naseljenosti i sastav obroka u funkciji proizvodnih parametara,kvaliteta mesa i dobrobiti brojlerskih pilića / Lightening program, stocking density and diet composition in the function of production parameters, meat quality and welfare of broiler chickens

Veljić Miljan 30 September 2016 (has links)
<p>Cilj istraţivanja bio je da se ispita uticaj svetlosnog programa (konstantnog &ndash; KS i opadajuĆe- rastuĆeg - ORS), gustine obroka i gustine naseljenosti i njihove interakcije na proizvodne i klaniČne osobine brojlerskih piliĆa, kvalitet mesa i o&scaron;teĆenje tabanskih jastuČiĆa.<br />Istraţivanja su sprovedena na farmi piliĆa Donji Crnci nadomak Podgorice u tri ogleda: u prvom su ispitivani efekti svetlosnog programa i gustine obroka, u drugom programi svetla i gustina naseljenosti piliĆa, a u treĆem program svetla i gustina obroka (sme&scaron;e sa standardnim i poveĆanim sadrţajem energije i proteina, pri Čemu je odnos energija : protein bio konstantan). U svakom ogledu bilo je 320 piliĆa linijskog hibrida Cobb 500, me&scaron;anih po polu, a ogledi su trajali 42 dana. U sva tri ogleda formirane su po Četiri grupe sa Četiri ponavljanja i u svakoj grupi bilo je 80 jednodnevnih piliĆa.<br />Proizvodni parametri (telesna masa, utro&scaron;ak hrane i uginuĆa) praĆeni su u svim ogledima, a izraČunati su konverzija hrane i proizvodni indeks. Telesne mase su merene u uzrastu od 1; 7; 14; 21; 28; 35 i 42 dana. Utro&scaron;ak hrane utvrčivan je na kraju perioda primene pojedinih sme&scaron;a, i to: 14. dana koliČina konzumirane starter sme&scaron;e, 35. dana grovera i 42. dana fini&scaron;er sme&scaron;e. Mortalitet je odrečivan beleţenjem broja uginulih piliĆa u toku trajanja ogleda. Na osnovu telesnih masa, konverzije hrane i mortaliteta izraČunati su proizvodni indeksi.<br />Na kraju svakog ogleda, sa 6 nedelja starosti, piliĆi su izmereni pojedinaČno, izraČunati su proseci tretmana, a zatim je od svakog tretmana izdvojeno 20 piliĆa (10 mu&scaron;kih i 10 ţenskih) radi ispitivanja klaniČnih karakteristika. Pre klanja piliĆi su gladovali 12 sati. Nakon klanja i Či&scaron;Ćenja trupovi su ohlačeni na 40C u toku 24 sata, a potom obračeni kao: &bdquo;klasiČna obrada&rdquo; &bdquo;spremno za peČenje&rdquo; i &bdquo;spremno za ro&scaron;tilj&rdquo;.<br />Pri konfekcioniranju trupova izdvojena je abdominalna mast, izmerene mase obračenih trupova i dobijeni randmani. Radi utvrčivanja prinosa i udela osnovnih i sporednih delova trupa izvr&scaron;eno je rasecanje ohlačenih trupova. Ocena konformacije trupova izvr&scaron;ena je na osnovu utvrčenih apsolutnih mera: duţine piska, duţina kobilice, dubina grudi i obim bataka. Kori&scaron;Ćen je indeks koji predstavlja odnos ţive mase pre klanja i posmatrane mere (g/mm).<br />U ogledu II izvr&scaron;eno je i fiziČko ispitivanje kostiju, na femuru nakon izdvajanja od skeleta brojlera, a u ogledu III odrečeni su sadrţaj vlage, sadrţaj ukupne masti, ukupnog pepela i ukupnih proteina belog i crvenog mesa, na uzorcima mi&scaron;iĆnog tkiva grudi i karabataka od 5 mu&scaron;kih i 5 ţenskih trupova u svakom tretmanu (ukupno 20).</p><p>&nbsp;</p><p>&nbsp;</p><p>Rezultati ukazuju da svetlosni program nije statistiČki znaČajno uticao na zavr&scaron;ne telesne mase u ogledima I i II, dok su u ogledu III veĆe mase utvrčene kod piliĆa tovljenih pri KS. Primena ORS uticala je na usporavanje stope rasta u prvom periodu tova, a kao rezultat kompenzacionog porasta bez uticaja na zavr&scaron;ne mase, sem u treĆem ogledu. Bolju konverziju hrane u periodu ishrane fini&scaron;erom postigli su piliĆi u ogledu I pri ORS nego pri KS, kao i u ishrani starterom u ogledu III. Svetlosni programi u ogledu II nisu uticali na konverziju hrane i mortalitet piliĆa.<br />Gustina obroka nije uticala na zavr&scaron;ne mase, konverziju hrane, mortalitet i proizvodni indeks. Kod piliĆa hranjenih obrocima sa vi&scaron;im sadrţajem proteina i energije utvrčene su veĆe telesne mase na kraju tova (P&lt;0.01). Gustina obroka u ogledima I i III nije imala uticaj na konverziju hrane, mortalitet i proizvodni indeks. Znatno je veĆa zavr&scaron;na masa piliĆa tovljenih pri gustini naseljenosti od 12 grla/m2 (2667,08 g) nego pri 17 grla/m2 (2435,76 g) i razlike su bile statistiČki visoko znaČajne. Nije utvrčen uticaj gustine naseljenosti na konverziju hrane, mortalitet i proizvodni indeks.<br />Ispitivani faktori (svetlo, gustina obroka i gustina naseljenosti) nisu uticali na randmane, ali jesu interakcije nekih od njih. U svim ogledima utvrčen je manji udeo abdominalne masti pri ORS nego pri KS, ali bez statistiČke znaČajnosti. Gustina obroka i gustina naseljenosti nisu uticali na sadrţaj abdominalne masti. VeĆi je sadrţaj abdominalne masti u svim ogledima bio kod ţenskih nego mu&scaron;kih piliĆa. Udeo grudi veĆi je pri KS nego pri ORS, ali su razlike statistiČki znaČajne samo u treĆem ogledu. Gustina obroka i gustina naseljenosti nisu uticale na udeo grudi. Udeo bataka bio je veĆi kod piliĆa tovljenih pri ORS nego pri KS, ali su razlike statistiČki znaČajne samo u prvom ogledu. Udeo karabataka u prvom i drugom ogledu nije se znaČajno razlikovao izmeču svetlosnih programa, dok je u treĆem bio veĆi pri ORS nego pri KS (P&lt;0.01). Nije utvrčen uticaj gustine naseljenosti i gustine obroka na udeo bataka i karabataka. Kod mu&scaron;kih piliĆa utvrčen je veĆi udeo bataka, a kod ţenskih karabataka.<br />Relativne vrednosti mera konformacije nisu bile pod uticajem svetlosnih programa i gustine obroka, osim &scaron;to je pri manjoj gustini naseljenosti relativna vrednost dubine grudi bila veĆa (P&lt;0.05). Na o&scaron;teĆenje tabanskih jastuČiĆa nije utvrčen uticaj svetla i gustine obroka, ali su piliĆi pri veĆim gustinama naseljenosti, poČev od 28. dana, imali znatno veĆa o&scaron;teĆenja tabanskih jastuČiĆa nego pri manjoj gustini.<br />Svetlosni program i gustina naseljenosti nisu uticali na fiziČke osobine femura: povr&scaron;inu preseka, silu loma i specifiČnu silu loma. Mu&scaron;ki piliĆi imali su veĆi povr&scaron;inu preseka i silu loma femura, razlike za povr&scaron;inu preseka su statistiČki znaČajne, ali ne i za silu loma.<br />Procenat masti u tamnom mesu bio je veĆi, a proteina niţi pri ORS nego pri KS. Ostali parametri hemijske analize tamnog i belog mesa nisu bili pod uticajem svetlosnih programa. Gustina obroka nije imala uticaj na hemijski sastav mesa grudi i karabataka.<br />Na osnovu svega iznesenog moţe se zakljuČiti da su sva tri faktora (svetlosni program, gustina obroka i gustina naseljenosti), kao i njihove interakcije, uticali na brojne proizvodne parametre i kvalitet mesa brojlera, pa i na njihovu dobrobit u razliČitim fazama tova. ImajuĆi u vidu ogromne razlike u efektima koji se mogu postiĆi pri razliČitim kombinacijama ovih Činilaca, rezultati ovih i sliČnih istraţivanja treba da olak&scaron;aju izbor tehnologije koja Će davati najbolje ekonomske efekte u tovu piliĆa. Takoče, tamo gde su rezultati nejasni ili kontradiktorni, treba nastaviti istraţivanja na veĆem broju jedinki i fokusirati se na ekonomski vaţnije proizvodne i klaniČne osobine piliĆa.</p> / <p>The purpose of the research was to investigate the effect of the lighting program (constant &ndash; KS and intermittent &ndash; ORS), feed density and stocking density and their interaction with production and slaughterhouse characteristics of broiler chicken, meat quality and feet pad damage.<br />The research was conducted on a chicken farm Donji Crnci in the vicinity of Podgorica, in three trials: the first trial focused on effects of the lighting program and feed density, the second on the lighting program and stocking density and the third on the lighting program and the feed density (mixes with standard and increased content of energy and protein, with a constant energy:protein ratio). Each of the trials included 320 chicken of the Cobb 500 hybrid line, mixed sexes; trials lasted for 42 days. In all three trials, four groups were formed with four repetitions and each group included 80 one-day chickens.<br />Production parameters (weight, feed consumption and deaths) were monitored in all trials and feed conversion ratio and production index were calculated. Weight was measured when broilers were 1; 7; 14; 21; 28; 35 and 42 days old. Feed consumption was determined at the end of the use of specific mixes, as follows: 14th day the quantity of starter mix consumed, 35th day the quantity of grower mix consumed and 42nd day quantity of the finisher mix. Mortality rate was determined by recording the number of chicken that died during the trial. Production indices were calculated based on weight, food conversion ratio and mortality.<br />At the end of all trials, at 6 weeks of age, the chickens were measured individually, group averages were calculated and then by random sampling, 20 chicken were taken from each group (10 males and 10 females) in order to analyse slaughter characteristics. Pre-slaughter fasting lasted for 12 hours. After slaughter and cleaning, the carcasses were cooled to 40C over 24 hours and then processed as: &ldquo;classical processing&rdquo;, &ldquo;ready to grill&rdquo; and &ldquo;barbecue ready&rdquo;.<br />In carcass processing, abdominal fat was taken out, weight of processed carcases measured and carcass yield values were obtained. In order to determine the yield and share of the main and secondary parts of the carcass, cooled carcasses were cut out. Evaluation of carcass conformation was done on the basis of absolute measures of the following: metatarsus length, keel length, breast depth and drumsticks circumference. Index representing the ratio of live weight before slaughter and measure observed was used (g/mm).<br />In Trial II, physical examination of bones was done, on femur, upon separation from the broiler skeleton, and in Trial III moisture content, total fat content, total ash content and total protein of white and red meat was determined on samples of muscle tissue of breasts and thighs of 5 male and 5 female carcasses in each of the treatments (20 in total).<br />The results show that lighting program had no statistically significant effect on final body weight in Trials I and II, while in Trial III, higher weights were recorded in chicken fattened under KS. ORS resulted in slowing down of the growth rate in the first fattening period, and as a result of compensatory growth it had no effect on final weights, except in the third trial. Better food conversion ratio in the period of finisher mix diet was achieved by chicken in Trial I under ORS than those under KS, as well as in starter mix diet in Trial III. Lighting program in Trial II had no effect on food conversion ratio and mortality of chicken. Feed density did not have an effect on final weights, feed conversion, mortality and production index. In chicken fed with meals with higher protein and energy content, higher weight was recorded at the end of the fattening period (P&lt;0.01). Feed density in Trials I and III did not have an effect on feed conversion ratio, mortality and production index. Significantly higher weight was recorded in chicken fattened at the stocking density of 12 animals/m2 (2667.08 g) than at the density of 17 animals/m2 (2435.76<br />8<br />g) and differences had statistically high significance. No effect of stocking density was identified in terms of feed conversion, mortality and production index.<br />Factors analysed (light, feed density and stocking population) did not have an effect on carcass yield, but interactions of some of them did. In all the trials, a smaller share of abdominal fat was established under ORS than under KS, but it was not statistically significant. Feed density and stocking density had no effect on abdominal fat content. Higher abdominal fat content in all trials was found in female than in male chicken. The share of breasts is larger under KS than under ORS, but differences are statistically significant only in the Trial III. Feed density and stocking density had no effect on the share of breasts in the carcass. The share of drumsticks was higher in chicken fattened under ORS than those under KS, but differences were statistically significant only in the Trial I. The share of thighs in Trials I and II did not differ significantly between lighting programs, while in the Trial III it was higher under ORS than under KS (P&lt;0.01). Effect of stocking density and feed density on the share of drumsticks and thighs was not determined. Higher share of drumsticks was determined in male chicken while in female, the share of thighs was higher.<br />Relative values of conformation measures were not influenced by the light programs and feed density, except that in lower stocking density the relative value of the breast depth was higher (P&lt;0.05). Effect of light and feed density on feet pads damage was not determined, but chicken in higher stocking density, as of 28th day, had significantly higher feet pad damage than those in lower stocking density.<br />Light program and stocking density did not have an effect on physical properties of femur: cross-sectional area, breaking force and specific breaking force. Male chicken had larger cross-sectional area and femur breaking force, differences in cross-sectional area were statistically significant, but this was not the case with the breaking force.<br />Percentage of fat in dark meat was higher and that of proteins lower under ORS than under KS. Other parameters of the chemical analysis of dark and white meat were not under the influence of the light programs. Feed density had no effect on chemical composition of breasts and thighs meat.<br />Based on all stated above, it can be concluded that all three factors (light program, feed density and stocking density) as well as their interactions had effect on numerous production parameters and quality of broiler meat, including on their welfare in different fattening phases. Taking into account enormous differences in effects that may be achieved in different combinations of these factors, the results of these and similar researches should make easier the selection of the technology that would yield the best economic effects in chicken fattening. Furthermore, where results are unclear or contradictory, further research should be conducted on a larger number of animals and focus on economically more significant production and slaughterhouse characteristics of chicken.</p>
18

Formulation de mélanges de polyoléfines à l’aide d’une extrudeuse à très haute vitesse : Application à la dispersion de particules de traceurs, détectables par fluorescence X ou UV, en vue du tri de déchets polymères post-consommation / Formulation of polyolefin blends using high shear extruder : Application of this technique to the dispersion of particles of tracers detectable by X or UV fluorescence for sorting polymers from post-consumer waste

Louizi, Molka 04 December 2013 (has links)
Cette thèse, qui s’inscrit dans le cadre du projet ANR Eco-Tech TRIPTIC, a eu comme objectif de contribuer au tri industriel en cadence de polymères contenant des traceurs détectables grâce à leurs propriétés en fluorescence X ou UV. Dans un premier temps, étant donné que le coût des traceurs choisis pour l’étude TRIPTIC est assez élevé, nous avons réalisé une étude préliminaire, avec des particules modèles de silice, visant à optimiser la dispersion de charges dans une matrice polypropylène/éthylène propylène rubber (PP/EPR). Nous avons montré que l’extrusion à taux de cisaillement élevé est une technologie efficace permettant une dispersion homogène de charges de tailles micro ou nanométriques. Dans un deuxième temps, après optimisation des conditions de dispersion, nous avons extrapolé nos résultats à la dispersion de particules de traceurs UV dans différentes matrices thermoplastiques. Nous avons montré que la dispersion de 1000 ppm de particules de traceurs, de tailles micrométriques, dans des matrices polypropylènes, en extrusion à haute vitesse (N= 800 rpm), n’a pas d’impact sur les propriétés mécaniques et physico-chimiques des mélanges tracés, ainsi que sur la photo-dégradation sous rayonnement UV. Cette fine dispersion a non seulement permis la conservation des propriétés des polymères tracés mais aussi une bonne détection dynamique, tant en fluorescence X qu’UV, sur un prototype conçu par des partenaires du projet (Pellenc Selective Technologies, CEA-LITT et ENSAM- LCPI). Enfin, nous avons validé l’extrusion à haute vitesse pour compatibiliser des mélanges de polymères ternaires (PP/EPR)/PE (polyéthylène) pouvant correspondre à la valorisation de polymères post-consommation, par exemple dans l’hypothèse où on souhaite recycler (PP/EPR) et PE ensembles. Les propriétés prometteuses des mélanges obtenus doivent leur permettre de trouver des applications dans l’industrie automobile, par exemple. Cette voie est d’un grand intérêt pour les applications industrielles, car elle permet d’envisager des propriétés mécaniques élevées pour les polymères recyclés. Elle ouvre aussi de nouvelles perspectives pour l’élaboration de matériaux allégés, obtenus à partir de matières vierges ou recyclées. / This thesis, which is part of the ANR Eco-Tech TRIPTIC project, had the objective of contributing to industrial sorting rate of polymers containing tracers detectable by their fluorescence X or UV properties. At first, given that the cost of tracers selected for TRIPTIC study is quite high, a preliminary study is conducted with models of silica particles to optimize the dispersion of fillers in polypropylene / ethylene-propylene rubber (PP / EPR) matrix. It was found that processing under high shear rate is an effective technology for accomplishing a homogeneous dispersion of micro or nanoscale fillers. In a second step, after optimization of dispersion conditions, our results are extrapolated to the dispersion of UV tracer in different thermoplastic matrices. It was shown that the dispersion of 1000 ppm of micrometer tracer particles, in polypropylene matrices, extruded at high shear rates (N = 800 rpm), has no impact on the mechanical and physico-chemical properties as well as in the photo-degradation of the polymer after UV irradiation exposure. This fine dispersion was beneficial not only for the conservation of the properties of traced polymers but also for achieving a good dynamic detection of UV or X tracers using a prototype developed by the project partners ( Pellenc Selective Technologies , CEA- LITT and ENSAM - RPI ). Finally, high shear processing has successfully used to the compatibilization of ternary blends ( PP / EPR ) / PE (polyethylene) which may correspond to the post-consumer polymers. This technique has proved to be an effective method to produce polymer blends with unique mechanical properties. This novel strategy of compatibilization is of a particular interest, especially for industrial application prospects. It also opens new perspectives for materials lightening as well as “high shear recycling” of immiscible polymers.

Page generated in 0.0615 seconds