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Sample records for nouvelles evolutions diagnostiques

  1. Diagnostiquer l’hypertension artérielle

    PubMed Central

    Gelfer, Mark; Dawes, Martin; Kaczorowski, Janusz; Padwal, Raj; Cloutier, Lyne

    2015-01-01

    Résumé Objectif Mettre en lumière les recommandations 2015 du Programme éducatif canadien sur l’hypertension (PECH) sur le diagnostic et l’évaluation de l’hypertension artérielle (HTA). Qualité des données Une recherche systématique remontant à août 2014 a été effectuée par un bibliothécaire de la Collaboration Cochrane dans les banques de données MEDLINE et PubMed. Les résultats de la recherche ont fait l’objet d’une évaluation critique par le sous-comité du PECH sur la mesure de la pression artérielle (PA) et le diagnostic d’HTA, et les recommandations fondées sur les données probantes ont été soumises au Comité central d’examen du PECH aux fins d’examen indépendant et de classement. Finalement, les résultats et recommandations ont été présentés au Groupe de travail sur les recommandations aux fins de discussion, de débat, d’approbation et de vote. Les principales recommandations reposent sur des données probantes de niveau II. Message principal Selon les données probantes les plus récentes, le PECH a formulé 4 nouvelles recommandations classées dans 2 vastes catégories pour améliorer la mesure de la PA et la façon dont l’HTA est diagnostiquée en 2015. Il est fortement recommandé de mesurer la PA à l’aide d’appareils électroniques en clinique plutôt que par auscultation. Chez les patients dont les mesures en clinique sont élevées, le PECH recommande de se tourner précocement vers les mesures ambulatoires, préférablement le monitorage ambulatoire de la PA, afin d’identifier rapidement les patients atteints du syndrome du sarrau blanc. Conclusion Il est crucial d’améliorer la justesse diagnostique afin d’optimiser la prise en charge de l’HTA au Canada. Les mises à jour annuelles du PECH veillent à ce que les praticiens disposent de renseignements fondés sur les données probantes à jour pour éclairer leur pratique.

  2. Le volvulus gastrique idiopathique aigu: à propos d'une nouvelle observation

    PubMed Central

    Abdelilah, Mouhsine; Jihad, Anzaoui; Rachid, Bouchentouf

    2013-01-01

    Le volvulus gastrique est une rotation anormale de l'estomac autour de son axe. La forme aiguë constitue une urgence chirurgicale. Le diagnostic est souvent retardé en raison d'une symptomatologie fréquemment non spécifique. Des signes respiratoires tels la dyspnée et le hoquet peuvent révéler cette pathologie. Les auteurs rapportent une nouvelle observation de volvulus gastrique aigu chez un adolescent de 17 ans, diagnostiqué par la tomodensitométrie, et confirmé par une intervention chirurgicale. Le traitement est chirurgical et consiste à détordre et fixer l'estomac pour prévenir la récidive. PMID:23503200

  3. Exstrophie vésicale : à propos d'un cas diagnostiqué tardivement

    PubMed Central

    Tshimbayi, Michel; Ndua, Danny; Kazadi, Costa; Kwete, Laurent Shamashanga; Bugeme, Marcellin; Mubinda, Patrick Kiopine; Mukuku, Olivier

    2014-01-01

    L'exstrophie vésicale est une forme particulière de malfaçon du tractus génito-urinaire. Son diagnostic est possible par l’échographie dès le premier trimestre de grossesse mais dans la plupart des pays en développement il est diagnostiqué à la naissance faute par manque de surveillance prénatale. Nous rapportons un cas que nous a été amené pour prise en charge d'une plaie hypogastrique depuis la naissance et après une exstrophie vésicale fut diagnostiquée. PMID:25120885

  4. Kyste paratubaire tordu: à propos d'un cas rare de diagnostique difficile

    PubMed Central

    Benkirane, Saad; Alaoui, Fatimazohra Fdili; Chaara, Hekmat; Bougern, Hakima; Melhouf, Moulay Abdelilah

    2014-01-01

    Les kystes para tubaires sont des lésions fréquentes, et peuvent être responsables de complications à type de torsion d'annexe qui est rarissime et difficile à diagnostiquer. Cette pathologie est souvent confondue à une torsion ovarienne, la prise en charge dans les deux cas nécessite une intervention chirurgicale en urgence afin de tenter de conserver l'annexe. Nous rapportons un cas rare d'une jeune patiente opérée d'un kyste para tubaire bénin tordue de diagnostic difficile. PMID:25667687

  5. Prise en charge diagnostique et thérapeutique de la tuberculose ganglionnaire en Tunisie

    PubMed Central

    Ben Brahim, Hajer; Kooli, Ikbel; Aouam, Abir; Toumi, Adnene; Loussaief, Chawki; Koubaa, Jamel; Chakroun, Mohamed

    2014-01-01

    La tuberculose ganglionnaire est la localisation extra-pulmonaire la plus fréquente de la tuberculose. Nous nous proposons dans ce travail d’étudier les modalités diagnostiques, thérapeutiques et évolutives de cette localisation. Il s'agit d'une étude rétrospective portant sur 100 cas de tuberculose ganglionnaire. L’âge moyen était de 35 ± 15 ans (15-85 ans). Aucun malade n’était VIH positif. L'aire cervicale était la plus touchée (93 cas). L'intradermo-réaction à la tuberculine était positive dans 76/91 cas (83,5%). L'examen bactériologique des prélèvements au niveau des ganglions atteints avait mis en évidence des bacilles acido-alcoolo-résistants à l'examen direct dans 2/31 cas (6,4%) et la culture avait isolé Mycobacteruim tuberculosis dans 1/31 cas (3,2%). La cytoponction ganglionnaire (FNAC) était évocatrice de tuberculose dans 35/42 cas (83,3%). La biopsie ganglionnaire était réalisée dans 69 cas et avait permis de retenir le diagnostic de tuberculose dans tous les cas. La FNAC, comparativement à la biopsie, avait permis de raccourcir significativement le délai de la prise en charge (15,1 vs 22,8 jours; p=0,001) et la durée d'hospitalisation (17,3 vs 24,6; p=0,004). La durée moyenne du traitement antituberculeux était de 9,8 ± 4,6 mois (7 à 44 mois). Le traitement chirurgical initial avait raccourci significativement la durée du traitement médical. Il n'avait pas d'impact sur le taux de guérison. Nous avons noté 10 cas de réponse paradoxale aux antituberculeux, quatre cas de résistance clinique et une rechute dans deux cas. La tuberculose ganglionnaire pose un problème diagnostique et thérapeutique. La microbiologie est d'un faible apport. La FNAC est un moyen diagnostique très utiles dans les pays endémiques et à faibles ressources. Un traitement médical seul permet d’éviter les inconvénients de la chirurgie. PMID:25829976

  6. Tuberculose ganglionnaire: aspects épidémiologiques, diagnostiques et thérapeutiques, à propos de 357 cas

    PubMed Central

    Hamzaoui, Ghizlane; Amro, Lamyae; Sajiai, Hafsa; Serhane, Hind; Moumen, Nezha; Ennezari, Abdellah; Yazidi, Abdelhaq Alaoui

    2014-01-01

    La tuberculose ganglionnaire (TG) est la localisation extrapulmonaire la plus fréquente au Maroc. Elle pose encore un problème diagnostique et thérapeutique. Le but du travail est d’ étudier le profil épidémiologique, diagnostique et thérapeutique de la tuberculose ganglionnaire. Il s'agit d'une étude rétrospective portant sur les nouveaux cas de TG suivis au centre spécialisé de tuberculose de Marrakech, entre Janvier 2011 et Décembre 2012. Trois cents cinquante sept cas de TG ont été inclus sur l'ensemble de 1717 cas de tuberculose toute forme confondue, soit une incidence de 20,8%. La moyenne d’âge était de 29,1 ans avec un sex ratio de 0,6 (62,5% de femmes). Le diabète, le contage tuberculeux et l'infection VIH ont été retrouvés respectivement dans 9%, 14,6% et 3,6% des cas. Les adénopathies étaient cervicales dans 95%, médiastinales dans 5,1%, abdominales dans 3,7%, axillaires dans 2,8% et inguinales dans 0,3% des cas. La radiographie du thorax (faite dans 96,4% des cas) a été anormale dans 8,1%. Le diagnostic a été confirmé dans 97,2% des cas. Le régime thérapeutique était 2 RHZE/4RH dans 88% des cas. Dans les cas suivis, l’évolution a été marquée par la disparition des adénopathies dans 95,2% et par l'augmentation du volume ganglionnaire dans 4,8%. 1,4% des cas ont été perdus de vue. La rechute de TG a été notée dans 3,1%. La TG reste fréquente et occupe la 2ème place après l'atteinte pulmonaire et pose un problème diagnostique et thérapeutique. PMID:25767675

  7. Grossesse dans une corne rudimentaire: difficultés diagnostiques et prise en charge thérapeutique

    PubMed Central

    Mamouni, Nisrine; Ghazal, Nabil; Erraghay, Sanaa; Bouchikhi, Chahrazed; Banani, Abdelaziz

    2016-01-01

    La survenue d'une grossesse dans une corne utérine rudimentaire est une situation obstétricale extrêmement rare et potentiellement grave, menaçant le pronostic materno-fœtal. Les auteurs rapportent cinq observations de grossesse dans une corne utérine rudimentaire, à travers lesquelles, ils relatent les difficultés sur le plan diagnostique ainsi que la prise en charge thérapeutique de cette entité pathologique, soulignant l'intérêt de l’échographie endovaginale, de l'IRM pelvienne et de la cœlioscopie dans le diagnostic précoce de ce type de malformation uterine.

  8. Le syndrome des brides amniotiques et ses difficultés diagnostiques et de prise en charge au Burkina Faso

    PubMed Central

    Nagalo, Kisito; Badiel, Roger; Kouéta, Fla; Tall, François Housséini; Yé, Diarra

    2015-01-01

    Le syndrome des brides amniotiques est une embryo-foetopathie rare, d’étiopathogénie encore inconnue, caractérisé par des malformations crânio-faciales, thoraco-abdominales, des membres et des extrémités. Afin de discuter des difficultés diagnostiques et thérapeutiques du syndrome des brides amniotiques, nous rapportons cinq cas de ce syndrome. Ces cas représentaient autant de phénotypes de la maladie mais avec quelques singularités. Les deux premiers étaient des cas de maladie des brides amniotiques caractérisés l'un par une amputation d'un membre inférieur associée à des lésions cutanées et à une surdité, l'autre par des strictions avec amputation des doigts associées à une fente labio-palatine, une cataracte congénitale et un strabisme. Les trois autres cas correspondaient à des formes létales du Limb Body Wall Complex dont deux avec attache placento-crânienne et un avec attache placento-abdominale. Le renforcement du diagnostic anténatal, l'instauration du conseil génétique et la mise en place d'un registre national des malformations devraient permettre d'améliorer la prise en charge des cas du syndrome des brides amniotiques. PMID:26113939

  9. Les tumeurs malignes anorectales en milieu hospitalier à Ouagadougou: aspects épidémiologiques et diagnostiques

    PubMed Central

    Guingané, Alice Nanelin; Sombié, Roger Arsène; Bougouma, Alain

    2014-01-01

    Le but de notre étude était de décrire les caractéristiques épidémiologiques et diagnostiques des tumeurs malignes anorectales en milieu hospitalier à Ouagadougou. Il s'est agi d'une étude rétrospective et transversale qui a concerné les patients vus en endoscopie digestive basse au cours de la période allant du 29/09/1999 au 04/10/2008. À l'aide d'une fiche de collecte, nous avons recueilli, dans 4 structures sanitaires et 3 laboratoires d'anatomie et de cytologie pathologiques de la ville de Ouagadougou, les données à partir des comptes-rendus d'endoscopie digestive basse et des registres d'anatomie et de cytologie pathologiques. Durant la période de notre étude, 645 patients ont été examinés en anorectoscopie et 882 cas d'affections anorectales colligés. Les tumeurs malignes anorectales avec 61 cas (6,9%) occupaient la quatrième place après la maladie hémorroïdaire (45,6%), les anites (21,1%) et les fissures (13,9%). Elles regroupaient les cancers du rectum (4,2%) et les cancers de l'anus (2,7%). Vingt cancers anorectaux ont été histologiquement confirmés parmi lesquels l'adénocarcinome était le type histologique le plus retrouvé avec 17 cas. Les tumeurs malignes, quatrième affection anorectale la plus fréquente au cours de notre étude, constituent une préoccupation du fait de leur fréquence croissante, leur diagnostic souvent tardif et les difficultés liées à leur prise en charge surtout dans nos pays avec une population à faible revenu. La sensibilisation de la population et la prescription plus large de l'endoscopie digestive basse devraient permettre une meilleure prise en charge des patients. PMID:25368715

  10. Evolution.

    ERIC Educational Resources Information Center

    Mayr, Ernst

    1978-01-01

    Traces the history of evolution theory from Lamarck and Darwin to the present. Discusses natural selection in detail. Suggests that, besides biological evolution, there is also a cultural evolution which is more rapid than the former. (MA)

  11. Approche diagnostique d'une dégénérescence maculaire occulte par OCT de type “spectral-domain”: cas Clinique

    PubMed Central

    El Ouafi, Aziz; El Mellaoui, Med; Laktaoui, Abdelkader

    2015-01-01

    Le diagnostic de la dégénérescence maculaire occulte est difficile. Il pourrait être facilité grâce aux nouvelles techniques d'acquisition des images par S-D OCT. L'objectif de ce travail est de discuter de l'intérêt de l'OCT à haute résolution dans le diagnostic d'une dégénérescence maculaire occulte. PMID:26834914

  12. Evolution

    NASA Astrophysics Data System (ADS)

    Peter, Ulmschneider

    When we are looking for intelligent life outside the Earth, there is a fundamental question: Assuming that life has formed on an extraterrestrial planet, will it also develop toward intelligence? As this is hotly debated, we will now describe the development of life on Earth in more detail in order to show that there are good reasons why evolution should culminate in intelligent beings.

  13. Valeur diagnostique de la tomodensitométrie dans la cysticercose cérébrale à Lomé

    PubMed Central

    Sonhaye, Lantam; Tchaou, Mazamaesso; Amadou, Abdoulatif; Assih, Kouméabalo; Kolou, Berésa; Adjenou, Komlavi; N'dakena, Koffi

    2015-01-01

    La cysticercose a une prévalence élevée dans les pays sub-sahariens et son diagnostic reste difficile. Cette étude a pour but de déterminer la valeur diagnostique de la tomodensitométrie dans la cysticercose cérébrale. Recrutement des patients ayant bénéficié d'une tomodensitométrie cérébrale dans l'une des circonstances suivantes: épilepsie, hypertension intracrânienne, syndrome pyramidal, détérioration mentale, ataxie locomotrice ou une diminution de l'acuité visuelle. Les critères de Del Brutto et al. avaient permis de retenir le diagnostic positif de cysticercose cérébrale. Pendant la période, 4193 patients avaient été inclus à l’étude, dont 140 cas de cysticercose cérébrale (3,3%). L’âge moyen des patients de cysticercose cérébrale était de 36 ± 14 ans, avec des extrêmes de 17 ans et 59 ans. La sensibilité et la spécificité de la tomodensitométrie dans la cysticercose cérébrale sont respectivement de 96,4% et 98,3%. La valeur prédictive positive et la valeur prédictive négative de la tomodensitométrie sont respectivement de 65,9% et 99,8%. Les aspects tomodensitométriques chez les vrais positifs sont dominés par des lésions associées, 72 cas (53,3%), suivies d'une hypodensité nodulaire arrondie unique ou multiple sans prise de contraste iodée, 17cas (12,6%). La TDM est une technique d'imagerie qui a une sensibilité et une spécificité élevées dans le diagnostic de la cysticercose cérébrale. Cependant, les autres critères de diagnostic restent utiles du fait de l'existence de nombreux cas de faux positifs à la tomodensitométrie. PMID:26090025

  14. La pneumonie tuberculeuse: une nouvelle série de 27 cas

    PubMed Central

    Bakouh, Ouiam; Aniked, Sarra; Bourkadi, Jamaleddine

    2014-01-01

    Dans le but d’étudier les aspects cliniques, radiologiques et évolutifs de la pneumonie tuberculeuse (PT) au Maroc, pays à forte prévalence de tuberculose, une étude rétrospective s’étalant de Janvier au Septembre 2013 a été menée au service de phtisiologie femme de l'hôpital Moulay Youssef de Rabat. 27 cas de PT ont été diagnostiqués, dont 2 VIH séropositives. La fièvre et l'altération de l’état général étaient rapportées chez toutes les patientes, précédant les signes respiratoires comme La toux et la dyspnée. L'hémoptysie est rapportée chez 7 cas. Diagnostiquées souvent tardivement, du fait de la non spécificité de ses signes, 14 pneumonies sur 27 étaient excavées. Avec prédominance des lésions au lobe supérieur droit. Le traitement antituberculeux était efficace dans la majorité des cas. On a déploré 2 décès. La décision de mise en route du traitement antituberculeux même en l'absence de certitude bactériologique doit être prise dans un délai raisonnable de 15 jours vue la gravité du tableau et les séquelles persistantes. PMID:25745530

  15. Suivi d'une nouvelle UG du Lynx : MASTER OT J072948.66+593824.4

    NASA Astrophysics Data System (ADS)

    Morillon, E.

    2012-03-01

    Suite à la détection, par nos collègues russes, d'une nouvelle variable dans le Lynx mi- février 2012, et à la diffusion de l'alerte sur internet, j'ai pu pointer cette nouvelle cataclysmique de type UGSU, pendant 4h, avant qu'elle ne retourne à son état de repos. Après un rappel sur sa découverte, j'exposerai la façon dont je l'ai suivie 4 jours après la découverte et les quelques résultats que l'on peut en extraire.

  16. Aspects épidémiologiques, diagnostiques et thérapeutiques des ostéosarcomes de l'enfant au CHU Aristide le Dantec de Dakar: à propos de 16 cas

    PubMed Central

    Ndour, Oumar; Alumeti, Desire Munyali; Fall, Mbaye; Fall, Aimée Faye; Diouf, Cheikh; Ndoye, Ndeye Aby; Ngom, Gabriel; Ndoye, Mamadou

    2013-01-01

    Le but de cette étude était de décrire les aspects épidémiologiques, diagnostiques et thérapeutiques des ostéosarcomes de l'enfant. Il s'agissait d'une étude rétrospective sur dix ans qui a colligé 16 dossiers d'ostéosarcome pris en charge au service de Chirurgie Pédiatrique de l'hôpital Aristide Le Dantec de Dakar. Les paramètres étudiés étaient le niveau d'instruction et le niveau socioprofessionnel des parents, l'origine géographique, l’âge, le sexe, les antécédents particuliers, le délai de consultation, les motifs de consultation, les signes physiques, les signes radiologiques, la biologie, les modalités thérapeutiques et l’évolution. Tous les patients avaient bénéficié d'un examen anatomopathologique qui a confirmé le diagnostic d'ostéosarcome. Pour la majeure partie de nos patients (58% des cas) les parents avaient un niveau d'instruction bas. L’âge moyen était de 11ans. Une prédominance masculine était retrouvée avec un sex-ratio de 3,25:1. Le délai de consultation moyen était de 16 mois. Le principal motif de consultation était la tuméfaction (10 cas). Huit patients avaient bénéficié d'un traitement traditionnel. La taille de la tumeur était supérieure à 10cm dans 14 cas. La localisation la plus fréquente était le genou (14 cas). La radiographie standard retrouvait dans 15 cas des images d'ostéolyse. Le bilan d'extension n'avait pas retrouvé de métastases. Les options thérapeutiques étaient dominées par l'amputation seule (43,75% des cas). La survie à 2 ans était de 17%. L'ostéosarcome atteint le plus souvent le garçon après l’âge de 10 ans. Sa prise en charge au Sénégal se heurte à d’énormes difficultés liées au retard diagnostique. La solution repose essentiellement sur une collaboration pluridisciplinaire. PMID:23720705

  17. Evidence of multiple introductions of beak and feather disease virus into the Pacific islands of Nouvelle-Caledonie (New Caledonia).

    PubMed

    Julian, Laurel; Lorenzo, Almudena; Chenuet, Jean-Paul; Bonzon, Marianne; Marchal, Celine; Vignon, Laurent; Collings, David A; Walters, Matthew; Jackson, Bethany; Varsani, Arvind

    2012-11-01

    Beak and feather disease virus (BFDV) is a circular ssDNA virus that causes psittacine beak and feather disease and has almost global presence. Here, we report for the first time the presence of in Nouvelle-Calédonie (New Caledonia). One hundred and sixty-eight exotic and 79 endemic birds were sampled in Nouvelle-Calédonie, 26 were found to be positive for BFDV. We characterized the full genomes of 26 isolates and phylogenetic analysis placed nine of the isolates into the BFDV-J strain, with the remaining 17 isolates from Deplanche's Rainbow Lorikeet (Trichoglossus haematodus deplanchii) forming a novel strain, BFDV-P. Of more concern was the discovery of an infected bird from the vulnerable and endemic New Caledonian Parakeet (Cyanoramphus saisseti). Our results reveal that there have been at least two introductions of BFDV into Nouvelle-Calédonie. PMID:22855782

  18. Les sepsis intra-abdominaux diffus post-operatoires: aspects épidémiologiques, diagnostiques et thérapeutiques au Service de Chirurgie Générale du CHU Aristide Le Dantec de Dakar

    PubMed Central

    Touré, Alpha Oumar; Cissé, Mamadou; Ka, Ibrahima; Dieng, Madieng; Konaté, Ibrahima; Ka, Ousmane; Touré, Cheikh Tidiane

    2014-01-01

    Les sepsis intra-abdominaux diffus postopératoires (SIADPO) ont encore une fréquence alarmante. Ils mettent rapidement en cause l'intégrité des grandes fonctions. Le but de cette étude était d’évaluer leur prise en charge. Il s'agissait d'une étude rétrospective descriptive sur 10 ans (janvier 2000 à décembre 2009) portant sur 45 cas de SIADPO. Nous avons étudié les aspects épidémiologiques, diagnostiques, thérapeutiques et pronostiques. Il s'agissait de 45 cas dont 25 hommes et 20 femmes avec un sex-ratio de 1,25. L’âge moyen des patients était de 34 ans avec des extrêmes de 20 et 70 ans. Le SIADPO survenait au décours d'une intervention septique en urgence dans 68,8% des cas. Le délai moyen de diagnostic était de 10 jours. Les signes cliniques étaient dominés par les troubles du transit (80%), la douleur abdominale (77,7%), la fièvre (66,7%), le météorisme abdominal (33%). Une hyperleucocytose a été retrouvée dans 60% des cas. Le liquide intra-abdominal était polymicrobien. Tous les patients ont bénéficié d'une laparotomie xipho-pubienne dans les 72 heures. Nous avons noté 82,2% de péritonites secondaires notamment post-opératoires et 17,8% de péritonites persistantes. Les étiologies étaient dominées par le lâchage de suture digestive ou gynécologique (66,7% des cas). La stomie digestive a été le geste le plus fréquemment réalisé (41%). La guérison est survenue chez 75,5%. La morbidité opératoire était de 42% faite de suppuration pariétale (10 cas), de fistule entérocutanée (6 cas), d’éviscération (2 cas). La mortalité était de 24,5% en rapport avec le retard diagnostique et les défaillances multi-viscérales. Les interventions septiques en urgence sont les plus grandes pourvoyeuses de SIADPO. La mortalité reste encore élevée en rapport avec la défaillance viscérale. La précocité du diagnostic et de la réintervention conditionnent ainsi le pronostic. PMID:25161748

  19. Qui sera le nouvel Einstein ? Vers une nouvelle theorie de la gravitation

    NASA Astrophysics Data System (ADS)

    Bonnet-Bidaud, J. M.

    1999-10-01

    Un debat de plus d'un siecle a resurgi ces toutes dernieres annees avec une vigueur nouvelle. L'enjeu ? Mettre fin, ni plus ni moins, a l'une des contradictions les plus inouies de la physique fondamentale, en reconciliant mecanique quantique et relativite generale. En effet, a l'heure ou la gravitation semble enfin sur le point de fusionner avec les trois autres forces de la nature. il est certain que la relativite d'Einstein doit etre bientot remplacer par une autre theorie... Reste quye tous les physiciens sont loin de s'accorder sur la marche a suivree. Gravitation quantique, relativite d'echelle, supersymetrie, les candidates ne manquent pas.

  20. Traitement arthroscopique d'une fracture articulaire de la glène: nouvelle astuce

    PubMed Central

    Hamoudi, Samir; Alassaf, Ihab; Boussakri, Hassan; Ntrataze, Philbert; Dumez, Jean François

    2015-01-01

    Le traitement des fractures de la glène scapulaire constitue un sujet de débat dans la littérature. Les auteurs décrivent une observation d'un patient âgé de 22 ans qui présente une fracture articulaire de la glène classée stade III de Ideberg traitée chirurgicalement sous arthroscopie. Nous exposons une nouvelle technique chirurgicale utilisant un matériel simple et nous la recommandons pour ce type de fracture qui constitue une alternative efficace. Globalement, nos résultats cliniques et anatomiques immédiats et à moyen terme, au dernier recul, sont excellents. PMID:26161191

  1. [Rousseau on the couch. "La nouvelle Héloïse as a key to his childhood trauma].

    PubMed

    Niemeyer, C

    1993-05-01

    Whereas many interpreters and biographers of Rousseau tend to present their subject as a pathological figure, Niemeyer will have no truck with such ascriptions. His reading of Rousseau's epistolary novel Julie ou la Nouvelle Héloïse (1761) draws upon the autobiographical Confessions and reveals that Rousseau uses this novel as a species of self-therapy. In the novel the constellations in which certain scenes recur invite their interpretation as complementary scenes to Rousseau's traumatic "Urszene"--the death of his mother when giving birth to him. In Niemeyer's view, the way in which Rousseau turns his re-working of his childhood trauma to literary account qualifies him as a predecessor of psychoanalysis. PMID:8511325

  2. The inventory of botanical curiosities in Pierre-François-Xavier de Charlevoix's Nouvelle France (1744).

    PubMed

    Kobelinski, Michel

    2013-03-01

    The article explores the botanical contributions of Pierre-François-Xavier de Charlevoix's book Histoire et description générale de la Nouvelle France vis-à-vis the contributions of previous researchers, his use of iconographic and discursive representations and its relevance to the project of French colonization. It investigates why he refused Linnaeus' taxonomic model and what he intended with his catalogue of botanical curiosities. The unfolding of his philosophical and religious trajectory allows to understand his stance regarding the classification of nature, the meanings of ethnological information, his forms of intellectual appropriation, and his use of discourse and botanical iconography as political and emotional propaganda to encourage colonial settlement. PMID:23559045

  3. Nouvelle methode pour les etudes des interactions aeroservoelastiques en boucle ouverte sur les avions F/A-18, CL-604 et ATM et en boucle fermee sur l'ATM

    NASA Astrophysics Data System (ADS)

    Dinu, Alin Dorian

    2006-04-01

    Nous avons concu, implemente puis valide une nouvelle methode d'approximation des forces aerodynamiques non stationnaires a l'aide des polynomes orthogonaux de Chebyshev. Cela represente une contribution originale dans l'analyse des interactions aeroservoelastiques. La premiere serie de resultats obtenus par cette nouvelle methode (erreurs d'approximation des forces aerodynamiques non stationnaires) est comparee avec les resultats des methodes LS et de Pade. La deuxieme serie de resultats (vitesses et frequences de battement obtenues avec cette nouvelle methode) est comparee avec celles obtenues par les methodes classiques LS et de Pade. Ces deux series de resultats obtenus par notre methode et par les deux methodes classiques LS et de Pade sont validees sur trois types differents d'avions: l'ATM (Aircraft Test Model), le F/A-18 en collaboration avec les laboratoires de la NASA Dryden Flight Research Center, et enfin le Challenger CL-604 de Bombardier Aeronautique.

  4. Languages in Canada 1996 Census. New Canadian Perspectives = Les langues au Canada Recensement de 1996. Nouvelles Perspectives Canadiennes.

    ERIC Educational Resources Information Center

    Marmen, Louise; Corbeil, Jean-Pierre

    This book analyzes the evolution of the language situation in Canada over the last 45 years, drawing heavily from census data taken between 1951 and 1996. Chapters discuss: the evolution of the English language in Canada, including the size and distribution of the English native-language population, use of English as a home language, knowledge of…

  5. FTS evolution

    NASA Technical Reports Server (NTRS)

    Provost, David E.

    1990-01-01

    Viewgraphs on flight telerobotic servicer evolution are presented. Topics covered include: paths for FTS evolution; frequently performed actions; primary task states; EPS radiator panel installation; generic task definitions; path planning; non-contact alignment; contact planning and control; and human operator interface.

  6. Teaching Evolution

    ERIC Educational Resources Information Center

    Bryner, Jeanna

    2005-01-01

    Eighty years after the famous 1925 Scopes "monkey trial," which tested a teacher's right to discuss the theory of evolution in the classroom, evolution--and its most recent counterview, called "intelligent design"--are in the headlines again, and just about everyone seems to have an opinion. This past July, President Bush weighed in, telling…

  7. Stellar evolution.

    NASA Technical Reports Server (NTRS)

    Chiu, H.-Y. (Editor); Muriel, A.

    1972-01-01

    Aspects of normal stellar evolution are discussed together with evolution near the main sequence, stellar evolution from main sequence to white dwarf or carbon ignition, the structure of massive main-sequence stars, and problems of stellar stability and stellar pulsation. Other subjects considered include variable stars, white dwarfs, close binaries, novae, early supernova luminosity, neutron stars, the photometry of field horizontal-branch stars, and stellar opacity. Transport mechanisms in stars are examined together with thermonuclear reactions and nucleosynthesis, the instability problem in nuclear burning shells, stellar coalescence, and intense magnetic fields in astrophysics. Individual items are announced in this issue.

  8. Security Evolution.

    ERIC Educational Resources Information Center

    De Patta, Joe

    2003-01-01

    Examines how to evaluate school security, begin making schools safe, secure schools without turning them into fortresses, and secure schools easily and affordably; the evolution of security systems into information technology systems; using schools' high-speed network lines; how one specific security system was developed; pros and cons of the…

  9. Art & Evolution

    ERIC Educational Resources Information Center

    Terry, Mark

    2005-01-01

    In this article, the author presents a two-week evolution unit for his biology class. He uses Maria Sybilla Merian (1647-1717) as an example of an Enlightenment mind at work--in this case a woman recognized as one of the great artists and natural scientists of her time. Her representations of butterflies, caterpillars and their pupae, and the…

  10. Mitochondrial Evolution

    PubMed Central

    Gray, Michael W.

    2012-01-01

    Viewed through the lens of the genome it contains, the mitochondrion is of unquestioned bacterial ancestry, originating from within the bacterial phylum α-Proteobacteria (Alphaproteobacteria). Accordingly, the endosymbiont hypothesis—the idea that the mitochondrion evolved from a bacterial progenitor via symbiosis within an essentially eukaryotic host cell—has assumed the status of a theory. Yet mitochondrial genome evolution has taken radically different pathways in diverse eukaryotic lineages, and the organelle itself is increasingly viewed as a genetic and functional mosaic, with the bulk of the mitochondrial proteome having an evolutionary origin outside Alphaproteobacteria. New data continue to reshape our views regarding mitochondrial evolution, particularly raising the question of whether the mitochondrion originated after the eukaryotic cell arose, as assumed in the classical endosymbiont hypothesis, or whether this organelle had its beginning at the same time as the cell containing it. PMID:22952398

  11. Insect evolution.

    PubMed

    Engel, Michael S

    2015-10-01

    It goes without saying that insects epitomize diversity, and with over a million documented species they stand out as one of the most remarkable lineages in the 3.5-billion-year history of life on earth (Figure 1). This reality is passé to even the layperson and is taken for granted in the same way none of us think much of our breathing as we go about our day, and yet insects are just as vital to our existence. Insects are simultaneously familiar and foreign to us, and while a small fraction are beloved or reviled, most are simply ignored. These inexorable evolutionary overachievers outnumber us all, their segmented body plan is remarkably labile, they combine a capacity for high rates of speciation with low levels of natural extinction, and their history of successes eclipses those of the more familiar ages of dinosaurs and mammals alike. It is their evolution - persisting over vast expanses of geological time and inextricably implicated in the diversification of other lineages - that stands as one of the most expansive subjects in biology. PMID:26439349

  12. Viral evolution

    PubMed Central

    Nasir, Arshan; Kim, Kyung Mo; Caetano-Anollés, Gustavo

    2012-01-01

    Explaining the origin of viruses remains an important challenge for evolutionary biology. Previous explanatory frameworks described viruses as founders of cellular life, as parasitic reductive products of ancient cellular organisms or as escapees of modern genomes. Each of these frameworks endow viruses with distinct molecular, cellular, dynamic and emergent properties that carry broad and important implications for many disciplines, including biology, ecology and epidemiology. In a recent genome-wide structural phylogenomic analysis, we have shown that large-to-medium-sized viruses coevolved with cellular ancestors and have chosen the evolutionary reductive route. Here we interpret these results and provide a parsimonious hypothesis for the origin of viruses that is supported by molecular data and objective evolutionary bioinformatic approaches. Results suggest two important phases in the evolution of viruses: (1) origin from primordial cells and coexistence with cellular ancestors, and (2) prolonged pressure of genome reduction and relatively late adaptation to the parasitic lifestyle once virions and diversified cellular life took over the planet. Under this evolutionary model, new viral lineages can evolve from existing cellular parasites and enhance the diversity of the world’s virosphere. PMID:23550145

  13. EMU evolution

    NASA Technical Reports Server (NTRS)

    Rouen, M.

    1991-01-01

    Evolution of Extravehicular Mobility Unit (EMU) technology is necessary to support the Extravehicular Activity (EVA) requirements of the Space Station Freedom Program and those of the Space Exploration Initiative (SEI). Key qualities supporting long-duration missions include technologies that are highly reliable, durable, minimize logistics requirements, and are in-flight maintainable and serviceable. While these qualities are common to SSF and SEI EVA, development paths will differ where specific mission requirements impose different constraints. Development of reusable, regenerative technologies is necessary to minimize the logistics penalties. Increased battery discharge/recharge cycle life and usable wet life, compact high current density fuel cells, reusable CO2 absorbing media, and thermal radiation coupled with venting heat rejection technologies are just some methods of reducing consumables. Development must strive for durable, reliable systems that are in-flight serviceable and maintainable, which are vital for missions where logistics capabilities are extremely constrained. Key areas include suit components (e.g., gloves, boots, and cooling garments), and life support hardware such as fans, pumps, instrumentation, and emergency O2 systems. Higher pressure suits will reduce EVA prebreathe requirements and pre-EVA operations overall. Many challenges of higher pressure suits have been addressed by on-going development. Emphasis on glove development is necessary to provide low fatigue, dexterous glove mobility at higher suit pressures. Minimum impact hooks and scars which support an advanced SSF EMU have been identified. These accommodations permit upgrades that support servicing of low volume, high pressure oxygen systems, and hydrogen technologies such as fuel cell, and venting hydrogen heat rejection systems.

  14. Evolution: Help for the Confused.

    ERIC Educational Resources Information Center

    Scheer, Bradley T.

    1979-01-01

    Written in response to an earlier article questioning certain aspects of evolution theory. Discusses ontogeny and phylogeny, the basis of evolution, chance or purpose in evolution, micro and macro-evolution, reversibility, and the evolution processes today. (MA)

  15. Understanding Evolution: An Evolution Website for Teachers

    ERIC Educational Resources Information Center

    Scotchmoor, Judy; Janulaw, Al

    2005-01-01

    While many states are facing challenges to the teaching of evolution in their science classrooms, the University of California Museum of Paleontology, working with the National Center for Science Education, has developed a useful web-based resource for science teachers of all grade- and experience-levels. Understanding Evolution (UE) was developed…

  16. The Evolution of Design

    ERIC Educational Resources Information Center

    Stebbins, G. Ledyard

    1973-01-01

    Describes the basic logic behind the modern view of evolution theory. Despite gaps in fossil records, evidence is indicative of the origin of life from nonliving molecules and evolution of higher forms of life from simpler forms. (PS)

  17. Evolution and Probability.

    ERIC Educational Resources Information Center

    Bailey, David H.

    2000-01-01

    Some of the most impressive-sounding criticisms of the conventional theory of biological evolution involve probability. Presents a few examples of how probability should and should not be used in discussing evolution. (ASK)

  18. Oxygen and Biological Evolution.

    ERIC Educational Resources Information Center

    Baugh, Mark A.

    1990-01-01

    Discussed is the evolution of aerobic organisms from anaerobic organisms and the accompanying biochemistry that developed to motivate and enable this evolution. Uses of oxygen by aerobic organisms are described. (CW)

  19. Mistakes and Molecular Evolution.

    ERIC Educational Resources Information Center

    Trevors, J. T.

    1998-01-01

    Examines the role mistakes play in the molecular evolution of bacteria. Discusses the interacting physical, chemical, and biological factors that cause changes in DNA and play a role in prokaryotic evolution. (DDR)

  20. HIV Evolution and Escape.

    PubMed Central

    Richman, Douglas D.; Little, Susan J.; Smith, Davey M.; Wrin, Terri; Petropoulos, Christos; Wong, Joseph K.

    2004-01-01

    Human immunodeficiency virus (HIV) exemplifies the principles of Darwinian evolution with a telescoped chronology. Because of its high mutation rate and remarkably high rates of replication, evolution can be appreciated over periods of days in contrast to the durations conceived of by Darwin. Certain selective pressures that drive the evolution of HIV include chemotherapy, anatomic compartmentalization and the immune response. Examples of these selective forces on HIV evolution are described. Images Fig. 5 PMID:17060974

  1. Arguing for Evolution.

    ERIC Educational Resources Information Center

    Ayala, Francisco J.

    2000-01-01

    Discusses the Kansas State Board of Education's decision to remove references to evolution and cosmology from the state's education standards and assessment. Advocates the need to teach evolution in high schools for a meaningful biology education. Addresses the question whether the teaching of evolution poses a threat to Christianity or other…

  2. A Shuttle evolution strategy

    NASA Technical Reports Server (NTRS)

    Teixeira, Charles; Mallini, Charles

    1989-01-01

    An overview of a potential Space Shuttle evolution strategy is presented. A Shuttle development study which reviews past and ongoing studies, implements a Shuttle Enhancement Data Base, and develops a methodology and a strawman evolution strategy is discussed. The long-term goals of a Shuttle evolution strategy, including increased reliability, lower cost, robustness, resiliency, increased capability, and assured access are addressed.

  3. Evolution & Diversity in Plants.

    ERIC Educational Resources Information Center

    Pearson, Lorentz C.

    1988-01-01

    Summarizes recent findings that help in understanding how evolution has brought about the diversity of plant life that presently exists. Discusses basic concepts of evolution, diversity and classification, the three-line hypothesis of plant evolution, the origin of fungi, and the geologic time table. Included are 31 references. (CW)

  4. Old Perspectives on Evolution

    ERIC Educational Resources Information Center

    De Blacquiere-Clarkson, John

    1976-01-01

    Presents a perspective on evolution which includes an explanation of the textbook theory of evolution, a review of evolutionary theory before Darwin, and an outline of Darwin's early theories. Describes a rethinking of evolutionary theory to include natural selection, conservative selection, discontinous evolution, catastrophism, and the…

  5. Evolution for Young Victorians

    NASA Astrophysics Data System (ADS)

    Lightman, Bernard

    2012-07-01

    Evolution was a difficult topic to tackle when writing books for the young in the wake of the controversies over Darwin's Origin of Species. Authors who wrote about evolution for the young experimented with different ways of making the complex concepts of evolutionary theory accessible and less controversial. Many authors depicted presented evolution in a non-Darwinian form amenable to religious interpretation.

  6. Frontiers of stellar evolution

    NASA Technical Reports Server (NTRS)

    Lambert, David L. (Editor)

    1991-01-01

    The present conference discusses theoretical and observational views of star formation, spectroscopic constraints on the evolution of massive stars, very low mass stars and brown dwarfs, asteroseismology, globular clusters as tests of stellar evolution, observational tests of stellar evolution, and mass loss from cool evolved giant stars. Also discussed are white dwarfs and hot subdwarfs, neutron stars and black holes, supernovae from single stars, close binaries with evolved components, accretion disks in interacting binaries, supernovae in binary systems, stellar evolution and galactic chemical evolution, and interacting binaries containing compact components.

  7. Has Human Evolution Stopped?

    PubMed Central

    Templeton, Alan R.

    2010-01-01

    It has been argued that human evolution has stopped because humans now adapt to their environment via cultural evolution and not biological evolution. However, all organisms adapt to their environment, and humans are no exception. Culture defines much of the human environment, so cultural evolution has actually led to adaptive evolution in humans. Examples are given to illustrate the rapid pace of adaptive evolution in response to cultural innovations. These adaptive responses have important implications for infectious diseases, Mendelian genetic diseases, and systemic diseases in current human populations. Moreover, evolution proceeds by mechanisms other than natural selection. The recent growth in human population size has greatly increased the reservoir of mutational variants in the human gene pool, thereby enhancing the potential for human evolution. The increase in human population size coupled with our increased capacity to move across the globe has induced a rapid and ongoing evolutionary shift in how genetic variation is distributed within and among local human populations. In particular, genetic differences between human populations are rapidly diminishing and individual heterozygosity is increasing, with beneficial health effects. Finally, even when cultural evolution eliminates selection on a trait, the trait can still evolve due to natural selection on other traits. Our traits are not isolated, independent units, but rather are integrated into a functional whole, so selection on one trait can cause evolution to occur on another trait, sometimes with mildly maladaptive consequences. PMID:23908778

  8. Nouvelles approches en theorie du champ moyen dynamique: le cas du pouvoir thermoelectrique et celui de l'effet orbital d'un champ magnetique

    NASA Astrophysics Data System (ADS)

    Arsenault, Louis-Francois

    , cette approche donne une bonne representation de S lorsque le systeme devient coherent. Les calculs montrent aussi que la formule Kelvin est precise lorsque la fonction spectrale des electrons devient incoherente, soit a plus haute temperature. Dans la limite Kelvin, S est essentiellement l'entropie par particule, tel que propose il y a longtemps. Nos resultats demontrent ainsi que la vision purement entropique de S est la bonne dans le regime incoherent, alors que dans le regime coherent, l'approche a frequence infinie est meilleure. Nous avons utilise une methode a la fine pointe, soit le Monte-Carlo quantique en temps continu pour resoudre la DMFT. Pour permettre une exploration rapide du diagramme de phase, nous avons du developper une nouvelle version de la methode des perturbations iterees pour qu'elle soit applicable aussi a forte interaction au-dela de la valeur critique de la transition de Mott. Un autre sujet a aussi ete aborde. L'effet orbital du champ magnetique dans les systemes electroniques fortement correles est une question tres importante et peu developpee. Cela est d'autant plus essentiel depuis la decouverte des oscillations quantiques dans les supraconducteurs a haute temperature (haut- Tc). Par desir de developper une methode la moins biaisee possible, nous avons derive la DMFT lorsqu'un champ se couplant a l'operateur energie cinetique par la substitution de Peierls est present. Ce type d'approche est necessaire pour comprendre entre autres l'effet de la physique de Mott sur des phenomenes tels que les oscillations quantiques. Nous avons obtenu un resultat tres important en demontrant rigoureusement que la relation d'auto-coherence de la DMFT et le systeme intermediaire d'impurete quantique restent les memes. L'effet du champ peut etre contenu dans la fonction de Green locale, ce qui constitue la grande difference avec le cas habituel. Ceci permet de continuer a utiliser les solutionneurs d'impuretes standards, qui sont de plus en plus puissants

  9. Oxygen evolution reaction catalysis

    DOEpatents

    Haber, Joel A.; Jin, Jian; Xiang, Chengxiang; Gregoire, John M.; Jones, Ryan J.; Guevarra, Dan W.; Shinde, Aniketa A.

    2016-09-06

    An Oxygen Evolution Reaction (OER) catalyst includes a metal oxide that includes oxygen, cerium, and one or more second metals. In some instances, the cerium is 10 to 80 molar % of the metals in the metal oxide and/or the catalyst includes two or more second metals. The OER catalyst can be included in or on an electrode. The electrode can be arranged in an oxygen evolution system such that the Oxygen Evolution Reaction occurs at the electrode.

  10. Museums teach evolution.

    PubMed

    Diamond, Judy; Evans, E Margaret

    2007-06-01

    Natural history museums play a significant role in educating the general public about evolution. This article describes Explore Evolution, one of the largest evolution education projects funded by the National Science Foundation. A group of regional museums from the Midwestern United States worked with leading evolutionary scientists to create multiple permanent exhibit galleries and a curriculum book for youth. This program invites the public to experience current evolutionary research on organisms that range in size from HIV to whales. Learning research is being conducted on museum visitors to understand how they reason about evolution and to determine what influences the process of conceptual change. PMID:17542857

  11. Speeding up evolution

    NASA Astrophysics Data System (ADS)

    Hoff, Wouter

    Proteins and cells offer great opportunities for green chemistry and renewable energy. However, few of these possible applications have been put into practice because of details that turn out to be major barriers to cost-efficient implementation and that prove difficult to solve by genetic engineering. A better understanding of molecular evolution promises a novel approach to addressing these important challenges. While major advances have been made, major gaps remain in understanding the evolution of proteins. Different approaches to accelerating molecular evolution into targeted directions will be discussed, including recent progress on evolution in non-homogeneous environments.

  12. Entropy and evolution

    NASA Astrophysics Data System (ADS)

    Styer, Daniel F.

    2008-11-01

    Quantitative estimates of the entropy involved in biological evolution demonstrate that there is no conflict between evolution and the second law of thermodynamics. The calculations are elementary and could be used to enliven the thermodynamics portion of a high school or introductory college physics course.

  13. Evolution: Theory or Dogma?

    ERIC Educational Resources Information Center

    Mayer, William V.

    In this paper the author examines the question of whether evolution is a theory or a dogma. He refutes the contention that there is a monolithic scientific conspiracy to present evolution as dogma and suggests that his own presentation might be more appropriately entitled "Creationism: Theory or Dogma." (PEB)

  14. Reconciling Evolution and Creation.

    ERIC Educational Resources Information Center

    Tax, Sol

    1983-01-01

    Proposes a way to reconcile evolution with creationism by hypothesizing that the universe was created when the scientific evidence shows, speculating that this was when God began the series of creations described in Genesis, and assuming that God gave humans intelligence to uncover the methods by which he ordained scientific evolution. (Author/MJL)

  15. Evolution - A Theory Evolving

    ERIC Educational Resources Information Center

    Weinberg, Janet H.

    1975-01-01

    Presented is an explanation of a non-Darwinian theory of evolution based on the premise that functional differences are the result of many small mutations such as the substitution of one amino acid for another in a large protein molecule. A brief overview of Darwinian evolution and other theories are presented. (EB)

  16. State Standards and Evolution

    ERIC Educational Resources Information Center

    Moore, Randy

    2004-01-01

    Throughout the United States various individuals and groups have tried to subvert science education by removing or weakening the treatment of evolution in state science-education standards. Most states' science-education standards support the teaching of evolution, but many in the general public and some policymakers want science classrooms to…

  17. Evolution for Young Victorians

    ERIC Educational Resources Information Center

    Lightman, Bernard

    2012-01-01

    Evolution was a difficult topic to tackle when writing books for the young in the wake of the controversies over Darwin's "Origin of Species." Authors who wrote about evolution for the young experimented with different ways of making the complex concepts of evolutionary theory accessible and less controversial. Many authors depicted presented…

  18. Hydrogen evolution reaction catalyst

    DOEpatents

    Subbaraman, Ram; Stamenkovic, Vojislav; Markovic, Nenad; Tripkovic, Dusan

    2016-02-09

    Systems and methods for a hydrogen evolution reaction catalyst are provided. Electrode material includes a plurality of clusters. The electrode exhibits bifunctionality with respect to the hydrogen evolution reaction. The electrode with clusters exhibits improved performance with respect to the intrinsic material of the electrode absent the clusters.

  19. Framing Evolution Discussion Intellectually

    ERIC Educational Resources Information Center

    Oliveira, Alandeom W.; Cook, Kristin; Buck, Gayle A.

    2011-01-01

    This study examines how a first-year biology teacher facilitates a series of whole-class discussions about evolution during the implementation of a problem-based unit. A communicative theoretical perspective is adopted wherein evolution discussions are viewed as social events that the teacher can frame intellectually (i.e., present or organize as…

  20. Evolution of Constructivism

    ERIC Educational Resources Information Center

    Liu, Chu Chih; Chen, I Ju

    2010-01-01

    The contrast between social constructivism and cognitive constructivism are depicted in different ways in many studies. The purpose of this paper is to summarize the evolution of constructivism and put a focus on social constructivism from the perception of Vygotsky. This study provides a general idea of the evolution of constructivism for people…

  1. Treatment of Evolution Inconsistent

    ERIC Educational Resources Information Center

    Cavanagh, Sean

    2005-01-01

    State standards for academic content vary enormously in how well they cover the topic of evolution, with many of those documents either ignoring or giving scant treatment to the core principles of that established scientific theory. This article presents the analysis of Education Week on state's standards treatment of evolution. Nearly all the…

  2. Evolution & Intelligent Design

    ERIC Educational Resources Information Center

    Staver, John R.

    2003-01-01

    Advocates of Intelligent Design (ID) theory argue that evolution is a theory in crisis, ID is a legitimate scientific theory, and biology teachers should teach the controversy. Supporters of evolutionary theory testify that ID is a religious, not scientific, concept, and evolution is in no danger of bankruptcy, having survived 140 years of…

  3. Science, Evolution, and Creationism

    ERIC Educational Resources Information Center

    National Academies Press, 2008

    2008-01-01

    How did life evolve on Earth? The answer to this question can help us understand our past and prepare for our future. Although evolution provides credible and reliable answers, polls show that many people turn away from science, seeking other explanations with which they are more comfortable. In the book "Science, Evolution, and…

  4. Evolution Under Attack

    ERIC Educational Resources Information Center

    Muench, David; Newell, Norman D.

    1974-01-01

    The article points out the growing attempts by creationists to have special creation presented with evolution in any educational discussion of the origin of life. The evolution theory is shown to be consistent with known scientific facts while the theory of special creation does not adequately account for these facts. (LS)

  5. How Can Evolution Learn?

    PubMed

    Watson, Richard A; Szathmáry, Eörs

    2016-02-01

    The theory of evolution links random variation and selection to incremental adaptation. In a different intellectual domain, learning theory links incremental adaptation (e.g., from positive and/or negative reinforcement) to intelligent behaviour. Specifically, learning theory explains how incremental adaptation can acquire knowledge from past experience and use it to direct future behaviours toward favourable outcomes. Until recently such cognitive learning seemed irrelevant to the 'uninformed' process of evolution. In our opinion, however, new results formally linking evolutionary processes to the principles of learning might provide solutions to several evolutionary puzzles - the evolution of evolvability, the evolution of ecological organisation, and evolutionary transitions in individuality. If so, the ability for evolution to learn might explain how it produces such apparently intelligent designs. PMID:26705684

  6. Organic chemical evolution

    NASA Technical Reports Server (NTRS)

    Chang, S.

    1981-01-01

    The course of organic chemical evolution preceding the emergence of life on earth is discussed based on evidence of processes occurring in interstellar space, the solar system and the primitive earth. Following a brief review of the equilibrium condensation model for the origin and evolution of the solar system, consideration is given to the nature and organic chemistry of interstellar clouds, comets, Jupiter, meteorites, Venus and Mars, and the prebiotic earth. Major issues to be resolved in the study of organic chemical evolution on earth are identified regarding condensation and accretion in the solar nebula, early geological evolution, the origin and evolution of the atmosphere, organic production rates, organic-inorganic interactions, environmental fluctuations, phase separation and molecular selectivity.

  7. The evolution of airplanes

    NASA Astrophysics Data System (ADS)

    Bejan, A.; Charles, J. D.; Lorente, S.

    2014-07-01

    The prevailing view is that we cannot witness biological evolution because it occurred on a time scale immensely greater than our lifetime. Here, we show that we can witness evolution in our lifetime by watching the evolution of the flying human-and-machine species: the airplane. We document this evolution, and we also predict it based on a physics principle: the constructal law. We show that the airplanes must obey theoretical allometric rules that unite them with the birds and other animals. For example, the larger airplanes are faster, more efficient as vehicles, and have greater range. The engine mass is proportional to the body size: this scaling is analogous to animal design, where the mass of the motive organs (muscle, heart, lung) is proportional to the body size. Large or small, airplanes exhibit a proportionality between wing span and fuselage length, and between fuel load and body size. The animal-design counterparts of these features are evident. The view that emerges is that the evolution phenomenon is broader than biological evolution. The evolution of technology, river basins, and animal design is one phenomenon, and it belongs in physics.

  8. Cultural Evolution and SETI

    NASA Astrophysics Data System (ADS)

    Dick, S. J.

    2009-12-01

    The Drake Equation for the number of radio communicative technological civilizations in the Galaxy encompasses three components of cosmic evolution: astronomical, biological and cultural. Of these three, cultural evolution totally dominates in terms of the rapidity of its effects. Yet, SETI scientists do not take cultural evolution into account, perhaps for understandable reasons, since cultural evolution is not well-understood even on Earth and is unpredictable in its outcome. But the one certainty for technical civilizations billions, millions, or even thousands of years older than ours is that they will have undergone cultural evolution. Cultural evolution potentially takes place in many directions, but this paper argues that its central driving force is the maintenance, improvement and perpetuation of knowledge and intelligence, and that to the extent intelligence can be improved, it will be improved. Applying this principle to life in the universe, extraterrestrials will have sought the best way to improve their intelligence. One possibility is that they may have long ago advanced beyond flesh-and-blood to artificial intelligence, constituting a postbiological universe. Although this subject has been broached, it has not been given the attention it is due from its foundation in cultural evolution. Nor has the idea of a postbiological universe been carried to its logical conclusion, including a careful analysis of the implications for SETI. SETI scientists, social scientists, and experts in AI should consider the strengths and weaknesses of this new paradigm.

  9. Is genetic evolution predictable?

    PubMed

    Stern, David L; Orgogozo, Virginie

    2009-02-01

    Ever since the integration of Mendelian genetics into evolutionary biology in the early 20th century, evolutionary geneticists have for the most part treated genes and mutations as generic entities. However, recent observations indicate that all genes are not equal in the eyes of evolution. Evolutionarily relevant mutations tend to accumulate in hotspot genes and at specific positions within genes. Genetic evolution is constrained by gene function, the structure of genetic networks, and population biology. The genetic basis of evolution may be predictable to some extent, and further understanding of this predictability requires incorporation of the specific functions and characteristics of genes into evolutionary theory. PMID:19197055

  10. Evolution in the Bacillaceae.

    PubMed

    Fajardo-Cavazos, Patricia; Maughan, Heather; Nicholson, Wayne L

    2014-10-01

    The family Bacillaceae constitutes a phenotypically diverse and globally ubiquitous assemblage of bacteria. Investigation into how evolution has shaped, and continues to shape, this family has relied on several widely ranging approaches from classical taxonomy, ecological field studies, and evolution in soil microcosms to genomic-scale phylogenetics, laboratory, and directed evolution experiments. One unifying characteristic of the Bacillaceae, the endospore, poses unique challenges to answering questions regarding both the calculation of evolutionary rates and claims of extreme longevity in ancient environmental samples. PMID:26104365

  11. Heredity in Evolution & Evolution of Heredity

    NASA Astrophysics Data System (ADS)

    Rivoire, Olivier

    2015-03-01

    The inheritance of characteristics induced by the environment has often been opposed to the theory of evolution by natural selection. However, although evolution by natural selection requires new heritable traits to be produced and transmitted, it does not prescribe, per se, the mechanisms by which this is operated. The mechanisms of inheritance are not, however, unconstrained, because they are themselves subject to natural selection. We introduce a schematic, analytically solvable mathematical model to compare the adaptive value of different schemes of inheritance. Our model allows for variations to be inherited, randomly produced, or environmentally induced, and, irrespectively, to be either transmitted or not during reproduction. The adaptation of the different schemes for processing variations is quantified for a range of fluctuating environments, following an approach that links quantitative genetics with stochastic control theory.

  12. Nouvelle structure de capteur à courants de Foucault et algorithme associé pour la mesure des propriétés électrique et magnétique d'un métal

    NASA Astrophysics Data System (ADS)

    Lê, Minh-Quang; Placko, Dominique

    1995-06-01

    This paper describes a new structure for eddy-current transducers which improves sensitivity while maintaining high lateral resolution. We have developed an analytical model to allow a model-based inversion from transducers signals to estimate thick and homogeneous plates electrical conductivity, magnetic permeability and/or lift-off. The inversion procedure is described and shows the possibility of a precise simultaneous estimation of the three parameters. Experiments were conducted with magnetic and non magnetic metals. Cet article décrit une nouvelle structure de capteur à courants de Foucault qui permet d'améliorer la sensibilité du capteur tout en conservant sa résolution latérale. Nous avons développé un modèle analytique de ce capteur qui peut être inversé pour estimer la conductivité électrique, la perméabilité magnétique d'une cible homogène et/ou la distance capteur-cible. La procédure d'inversion a été décrite et montre une possibilité d'estimer ces trois paramètres avec précision. L'expérience a été effectuée sur des métaux magnétiques et amagnétiques.

  13. Evolution of models for evolution. [of life

    NASA Technical Reports Server (NTRS)

    Rohlfing, D. L.

    1974-01-01

    The paper discusses models of evolution and their values, and some critiques of these models and the value of these critiques. A model is investigated which involves the formation of prebiotic protein from amino acids. Its formation by four theoretical critiques that suggest alternative environmental conditions is discussed. Experiments are reviewed so as to illustrate the experimental testing of the possible weaknesses of a model for a single molecular evolutionary phase and to suggest some necessary changes in the model.

  14. Stellar evolution. VI.

    NASA Technical Reports Server (NTRS)

    Iben, I., Jr.

    1967-01-01

    Evolution of low mass Population I stars from main sequence to red giant branch in Hertzsprung- Russell diagram, through energy generation phases of p-p chain reactions /dominating over C-N cycle reactions/ and hydrogen burning

  15. Co-Evolution.

    ERIC Educational Resources Information Center

    McGhee, Robert

    2002-01-01

    Discusses the role of techniques of DNA analysis in assessing the genetic relationships between various species. Focuses on wolf-dog evolution using DNA evidence and historical data about human/wolf-dog relationships. (DDR)

  16. Experimental evolution gone wild.

    PubMed

    Scheinin, M; Riebesell, U; Rynearson, T A; Lohbeck, K T; Collins, S

    2015-05-01

    Because of their large population sizes and rapid cell division rates, marine microbes have, or can generate, ample variation to fuel evolution over a few weeks or months, and subsequently have the potential to evolve in response to global change. Here we measure evolution in the marine diatom Skeletonema marinoi evolved in a natural plankton community in CO2-enriched mesocosms deployed in situ. Mesocosm enclosures are typically used to study how the species composition and biogeochemistry of marine communities respond to environmental shifts, but have not been used for experimental evolution to date. Using this approach, we detect a large evolutionary response to CO2 enrichment in a focal marine diatom, where population growth rate increased by 1.3-fold in high CO2-evolved lineages. This study opens an exciting new possibility of carrying out in situ evolution experiments to understand how marine microbial communities evolve in response to environmental change. PMID:25833241

  17. Evolution: Always New

    ERIC Educational Resources Information Center

    Flannery, Maura C.

    2005-01-01

    The changes in the evolution due to changes in science are explored. These changes are frustrating to paleontologists, especially when they are trying to date a singular event, like a cataclysm that precipitated a mass extinction.

  18. Experimental evolution gone wild

    PubMed Central

    Scheinin, M.; Riebesell, U.; Rynearson, T. A.; Lohbeck, K. T.; Collins, S.

    2015-01-01

    Because of their large population sizes and rapid cell division rates, marine microbes have, or can generate, ample variation to fuel evolution over a few weeks or months, and subsequently have the potential to evolve in response to global change. Here we measure evolution in the marine diatom Skeletonema marinoi evolved in a natural plankton community in CO2-enriched mesocosms deployed in situ. Mesocosm enclosures are typically used to study how the species composition and biogeochemistry of marine communities respond to environmental shifts, but have not been used for experimental evolution to date. Using this approach, we detect a large evolutionary response to CO2 enrichment in a focal marine diatom, where population growth rate increased by 1.3-fold in high CO2-evolved lineages. This study opens an exciting new possibility of carrying out in situ evolution experiments to understand how marine microbial communities evolve in response to environmental change. PMID:25833241

  19. Physical Principles of Evolution

    NASA Astrophysics Data System (ADS)

    Schuster, Peter

    Theoretical biology is incomplete without a comprehensive theory of evolution, since evolution is at the core of biological thought. Evolution is visualized as a migration process in genotype or sequence space that is either an adaptive walk driven by some fitness gradient or a random walk in the absence of (sufficiently large) fitness differences. The Darwinian concept of natural selection consisting in the interplay of variation and selection is based on a dichotomy: All variations occur on genotypes whereas selection operates on phenotypes, and relations between genotypes and phenotypes, as encapsulated in a mapping from genotype space into phenotype space, are central to an understanding of evolution. Fitness is conceived as a function of the phenotype, represented by a second mapping from phenotype space into nonnegative real numbers. In the biology of organisms, genotype-phenotype maps are enormously complex and relevant information on them is exceedingly scarce. The situation is better in the case of viruses but so far only one example of a genotype-phenotype map, the mapping of RNA sequences into RNA secondary structures, has been investigated in sufficient detail. It provides direct information on RNA selection in vitro and test-tube evolution, and it is a basis for testing in silico evolution on a realistic fitness landscape. Most of the modeling efforts in theoretical and mathematical biology today are done by means of differential equations but stochastic effects are of undeniably great importance for evolution. Population sizes are much smaller than the numbers of genotypes constituting sequence space. Every mutant, after all, has to begin with a single copy. Evolution can be modeled by a chemical master equation, which (in principle) can be approximated by a stochastic differential equation. In addition, simulation tools are available that compute trajectories for master equations. The accessible population sizes in the range of 10^7le Nle 10

  20. Manipulation of quantum evolution

    NASA Technical Reports Server (NTRS)

    Cabera, David Jose Fernandez; Mielnik, Bogdan

    1994-01-01

    The free evolution of a non-relativistic charged particle is manipulated using time-dependent magnetic fields. It is shown that the application of a programmed sequence of magnetic pulses can invert the free evolution process, forcing an arbitrary wave packet to 'go back in time' to recover its past shape. The possibility of more general operations upon the Schrodinger wave packet is discussed.

  1. Evolution in Revolution

    PubMed Central

    2011-01-01

    Biological evolution represents one of the most successful, but also controversial scientific concepts. Ever since Charles Darwin formulated his version of evolution via natural selection, biological sciences experienced explosive development and progress. First of all, although Darwin could not explain how traits of organisms, selected via natural selection, are inherited and passed down along generations; his theory stimulated research in this respect and resulted in the establishment of genetics and still later in the discovery of DNA and genome sequencing some hundred years after his evolutionary theory. Nevertheless, there are several weaknesses in classical Darwinian as well as Neodarwinian gene-centric views of biological evolution. The most serious drawback is its narrow focus: the modern evolutionary synthesis, as formulated in the 20th Century, is based on the concept of gene and on the mathematical/statistical analysis of populations. While Neodarwinism is still generally considered a valid theory of biological evolution, its narrow focus and incompatibility with several new findings and discoveries calls for its update and/or transformation. Either it will be replaced with an updated version or, if not flexible enough, it will be replaced by a new theory. In his book “Evolution — A New View from the 21st Century,”1 James A. Shapiro discusses these problems as well as newly emerging results which are changing our understanding of biological evolution. This new book joins a row of several other recent books highlighting the same issues.2–13

  2. Energy and Evolution

    NASA Astrophysics Data System (ADS)

    Porter, George

    I have called my lecture Energy and Evolution, and that embraces Physics and Biology. I suppose that what I have in mind are the great things that have happened in the last 135 years since Charles Darwin; and the great problems that we have in this field today. In 1859 Charles Darwin wrote history on a grand scale and he gave mankind an intellectual shock which changed our concept of ourselves and our place in the world. Rather suddenly we have come to realize that the process of natural evolution which he described and which has served the world for three billion years may be about to cease or least to change in a profound way. The Darwinian changes of evolution occurred slowly, unnoticed by participants who had very little to say about the forms that their descendants would take. They merely flocked to survive and if they survived they had one privilege only and that was the privilege of handing on their genes. The situation has changed drastically in the last few years. One species, man now so dominates the earth that it is in his part to eliminate most of the other species if he so wishes. Those who do survive do so only because man finds them interesting and useful and he is busy with the natural evolution even of these. It is the end of the evolution, as Darwin knew it. Far greater powers to play God will soon be in our hands. Genetic Engineering will enable us to eliminate conquered genes and other unfavorable genetic information and even to change the nature of mankind. We may not wish to do this but it will become possible. What we see happening is a rapid transfer of responsibility for the future evolution into the hands of ourselves, the hands of one species, homosapiens. We are no longer pawns in the game of evolution. We are not even the kings and queens, we are the players.

  3. Creationism, Evolution, and Science Education

    SciTech Connect

    Scott, Eugenie C.

    2005-06-22

    Many topics in the curriculum of American schools are controversial, but perhaps the one with the longest tenure is evolution. Three arguments are made against evolution: that it is allegedly weak science ('evolution is a theory in crisis'); that it is incompatible with religion; and that it is only 'fair' to 'balance' evolution with creationism. Regardless of the appropriateness of their application to science education, all three of the arguments are made to try to restrict the teaching of evolution. Variants of the fairness argument such as balancing evolution with 'scientific alternatives to evolution' or balancing evolution with 'arguments against evolution' have in fact become the current predominant antievolutionist strategy. Current events in the creationism/evolution controversy will be reviewed, and suggestions made for how to promote sound science education in the schools.

  4. Evolution of Metabolism

    NASA Astrophysics Data System (ADS)

    Nealson, K. H.; Rye, R.

    2003-12-01

    This chapter is devoted to the discussion of the evolution of metabolism, with a particular focus towards redox metabolism and the utilization of redox energy by life. We will deal with various aspects of metabolism that involve direct interaction with, and the extraction of energy from, the environment (catabolic metabolism) and will talk briefly of the reactions that affect mineral formation and dissolution. However, we will de-emphasize the aspects related to the formation of complex molecules and organisms. To some, it will be refreshingly brief; to others, somewhat superficial. This is unavoidable, as our knowledge of the details of the evolution of metabolism is at best slim. However, by piecing together aspects of the properties and history of the Earth and coupling these with what we know of today's metabolism, it is possible to at least frame several different hypotheses that, with time, should be possible to test and modify so that the next writing of this chapter might contain some intellectual entrees and not just the appetizers. Any discussion of metabolic evolution must occur in concert with a consideration of the Earth - the understanding of the forces that drove the co-evolution of life and Earth can be achieved only by considering them together. This theme will pervade this chapter, and any real understanding of the evolution of metabolism must be inexorably coupled to, and consistent with, the geological record of the Earth.The first aspect of evolution concerns the metabolic participants as we know them now (i.e., a definition of metabolic diversity), and the second concerns the sequence of events that have led to this remarkable metabolic diversity. The first part is fairly straightforward: a discussion of the domains of life, and the metabolic achievements that are expressed in the various domains, and relating metabolism to biogeochemical processes whenever possible. The second part is much more problematic. While it is possible to make up

  5. Workshop on Molecular Evolution

    NASA Technical Reports Server (NTRS)

    Cummings, Michael P.

    2004-01-01

    Molecular evolution has become the nexus of many areas of biological research. It both brings together and enriches such areas as biochemistry, molecular biology, microbiology, population genetics, systematics, developmental biology, genomics, bioinformatics, in vitro evolution, and molecular ecology. The Workshop provides an important contribution to these fields in that it promotes interdisciplinary research and interaction, and thus provides a glue that sticks together disparate fields. Due to the wide range of fields addressed by the study of molecular evolution, it is difficult to offer a comprehensive course in a university setting. It is rare for a single institution to maintain expertise in all necessary areas. In contrast, the Workshop is uniquely able to provide necessary breadth and depth by utilizing a large number of faculty with appropriate expertise. Furthermore, the flexible nature of the Workshop allows for rapid adaptation to changes in the dynamic field of molecular evolution. For example, the 2003 Workshop included recently emergent research areas of molecular evolution of development and genomics.

  6. Evolution of Active Regions

    NASA Astrophysics Data System (ADS)

    van Driel-Gesztelyi, Lidia; Green, Lucie May

    2015-09-01

    The evolution of active regions (AR) from their emergence through their long decay process is of fundamental importance in solar physics. Since large-scale flux is generated by the deep-seated dynamo, the observed characteristics of flux emergence and that of the subsequent decay provide vital clues as well as boundary conditions for dynamo models. Throughout their evolution, ARs are centres of magnetic activity, with the level and type of activity phenomena being dependent on the evolutionary stage of the AR. As new flux emerges into a pre-existing magnetic environment, its evolution leads to re-configuration of small-and large-scale magnetic connectivities. The decay process of ARs spreads the once-concentrated magnetic flux over an ever-increasing area. Though most of the flux disappears through small-scale cancellation processes, it is the remnant of large-scale AR fields that is able to reverse the polarity of the poles and build up new polar fields. In this Living Review the emphasis is put on what we have learned from observations, which is put in the context of modelling and simulation efforts when interpreting them. For another, modelling-focused Living Review on the sub-surface evolution and emergence of magnetic flux see Fan (2009). In this first version we focus on the evolution of dominantly bipolar ARs.

  7. Données nouvelles sur le contenu organique des dépôts phosphatés du gisement de Ras-Draâ (Tunisie)

    NASA Astrophysics Data System (ADS)

    Ben Hassen, Aida; Trichet, Jean; Disnar, Jean-Robert; Belayouni, Habib

    2009-04-01

    The study of the organic matter (OM) content of phosphatic sediments from the Ras-Draâ deposit, Tunisia, was carried on the two separated lithological fractions constituting the bulk sediments, namely phosphatic grains (pellets) and their associated matrices. The geochemical characterization of the OM present in pellets and in their matrices by CNS elemental analysis and RE pyrolysis indicates that: (i) the TOC content is higher in matrices (where it reaches 4.00%), than in pellets in the same strata where it does not exceed 1.62%; (ii) the presence of more or less oxidized marine planktonic OM in both fractions; (iii) a low degree of diagenetic evolution of the OM in both fractions (RE Tmax globally < than 430 °C). The chemical extraction of the humic substances (HS) from both fractions followed by the separation of fractions according to the IHSS procedure, systematically indicates a higher abundance of extractable humic compounds (HC) in the pellets (C HC ˜ 70% of the sum of TOC in the separated fractions, TOCfr) and a variable but lower extraction yield in matrices (C HC ˜ 18% TOCfr). This significant difference between both fractions excludes the possibility that pellets formed authigenically from, and within, their matrix. This is consistent with recent findings suggesting that these pellets could be fish feces.

  8. Galactic chemical evolution

    NASA Astrophysics Data System (ADS)

    Chiappini, C.; Matteucci, F.

    2001-11-01

    In this paper we review the current ideas about the formation of our Galaxy. In particular, the main ingredients necessary to build chemical evolution models (star formation, initial mass function and stellar yields) are described and discussed. A critical discussion about the main observational constraints available is also presented. Finally, our model predictions concerning the evolution of the abundances of several chemical elements (H, D, He, C, N, O, Ne, Mg, Si, Ca and Fe) are compared with observations relative to the solar neighborhood and the whole disk. We show that from this comparison we can constrain the history of the formation and evolution of the Milky Way as well as the nucleosynthesis theories concerning the Big Bang and the stars. .

  9. Plant sex chromosome evolution.

    PubMed

    Charlesworth, Deborah

    2013-01-01

    It is now well established that plants have an important place in studies of sex chromosome evolution because of the repeated independent evolution of separate sexes and sex chromosomes. There has been considerable recent progress in studying plant sex chromosomes. In this review, I focus on how these recent studies have helped clarify or answer several important questions about sex chromosome evolution, and I shall also try to clarify some common misconceptions. I also outline future work that will be needed to make further progress, including testing some important ideas by genetic, molecular, and developmental approaches. Systems with different ages can clearly help show the time course of events during changes from an ancestral co-sexual state (hermaphroditism or monoecy), and I will also explain how different questions can be studied in lineages whose dioecy or sex chromosomes evolved at different times in the past. PMID:23125359

  10. Evolution and Christian Faith

    NASA Astrophysics Data System (ADS)

    Roughgarden, J. E.

    2006-12-01

    My recent book, Evolution and Christian Faith explores how evolutionary biology can be portrayed from the religious perspective of Christianity. The principal metaphors for evolutionary biology---differential success at breeding and random mutation, probably originate with the dawn of agriculture and clearly occur in the Bible. The central narrative of evolutionary biology can be presented using Biblical passages, providing an account of evolution that is inherently friendly to a Christian perspective. Still, evolutionary biology is far from complete, and problematic areas pertain to species in which the concept of an individual is poorly defined, and to species in which the expression of gender and sexuality depart from Darwin's sexual-selection templates. The present- day controversy in the US about teaching evolution in the schools provides an opportunity to engage the public about science education.

  11. B-chromosome evolution.

    PubMed Central

    Camacho, J P; Sharbel, T F; Beukeboom, L W

    2000-01-01

    B chromosomes are extra chromosomes to the standard complement that occur in many organisms. They can originate in a number of ways including derivation from autosomes and sex chromosomes in intra- and interspecies crosses. Their subsequent molecular evolution resembles that of univalent sex chromosomes, which involves gene silencing, heterochromatinization and the accumulation of repetitive DNA and transposons. B-chromosome frequencies in populations result from a balance between their transmission rates and their effects on host fitness. Their long-term evolution is considered to be the outcome of selection on the host genome to eliminate B chromosomes or suppress their effects and on the B chromosome's ability to escape through the generation of new variants. Because B chromosomes interact with the standard chromosomes, they can play an important role in genome evolution and may be useful for studying molecular evolutionary processes. PMID:10724453

  12. Computational evolution: taking liberties.

    PubMed

    Correia, Luís

    2010-09-01

    Evolution has, for a long time, inspired computer scientists to produce computer models mimicking its behavior. Evolutionary algorithm (EA) is one of the areas where this approach has flourished. EAs have been used to model and study evolution, but they have been especially developed for their aptitude as optimization tools for engineering. Developed models are quite simple in comparison with their natural sources of inspiration. However, since EAs run on computers, we have the freedom, especially in optimization models, to test approaches both realistic and outright speculative, from the biological point of view. In this article, we discuss different common evolutionary algorithm models, and then present some alternatives of interest. These include biologically inspired models, such as co-evolution and, in particular, symbiogenetics and outright artificial operators and representations. In each case, the advantages of the modifications to the standard model are identified. The other area of computational evolution, which has allowed us to study basic principles of evolution and ecology dynamics, is the development of artificial life platforms for open-ended evolution of artificial organisms. With these platforms, biologists can test theories by directly manipulating individuals and operators, observing the resulting effects in a realistic way. An overview of the most prominent of such environments is also presented. If instead of artificial platforms we use the real world for evolving artificial life, then we are dealing with evolutionary robotics (ERs). A brief description of this area is presented, analyzing its relations to biology. Finally, we present the conclusions and identify future research avenues in the frontier of computation and biology. Hopefully, this will help to draw the attention of more biologists and computer scientists to the benefits of such interdisciplinary research. PMID:20532997

  13. TMDs: Evolution, modeling, precision

    NASA Astrophysics Data System (ADS)

    D'Alesio, Umberto; Echevarría, Miguel G.; Melis, Stefano; Scimemi, Ignazio

    2015-01-01

    The factorization theorem for qT spectra in Drell-Yan processes, boson production and semi-inclusive deep inelastic scattering allows for the determination of the non-perturbative parts of transverse momentum dependent parton distribution functions. Here we discuss the fit of Drell-Yan and Z-production data using the transverse momentum dependent formalism and the resummation of the evolution kernel. We find a good theoretical stability of the results and a final χ2/points ≲ 1. We show how the fixing of the non-perturbative pieces of the evolution can be used to make predictions at present and future colliders.

  14. Evolution of proteins.

    NASA Technical Reports Server (NTRS)

    Dayhoff, M. O.

    1971-01-01

    The amino acid sequences of proteins from living organisms are dealt with. The structure of proteins is first discussed; the variation in this structure from one biological group to another is illustrated by the first halves of the sequences of cytochrome c, and a phylogenetic tree is derived from the cytochrome c data. The relative geological times associated with the events of this tree are discussed. Errors which occur in the duplication of cells during the evolutionary process are examined. Particular attention is given to evolution of mutant proteins, globins, ferredoxin, and transfer ribonucleic acids (tRNA's). Finally, a general outline of biological evolution is presented.

  15. Macrothermodynamics of Biological Evolution:

    NASA Astrophysics Data System (ADS)

    Gladyshev, Georgi P.

    The author sets forth general considerations pertaining to the thermodynamic theory of biological evolution and the aging of living organisms. It becomes much easier to comprehend the phenomenon of life scrutinizing the formation of structural hierarchies of biological matter applying different temporal scales. These scales are 'identified' by nature itself, and this is reflected in the law of temporal hierarchies. The author discusses some misunderstandings in thermodynamics and evolutionary biology. A simple physicochemical model of biological evolution and the development of living beings is proposed. The considered theory makes it possible to use physicochemical evaluations to develop effective anti-aging diets.

  16. Evolution and social epidemiology.

    PubMed

    Nishi, Akihiro

    2015-11-01

    Evolutionary biology, which aims to explain the dynamic process of shaping the diversity of life, has not yet significantly affected thinking in social epidemiology. Current challenges in social epidemiology include understanding how social exposures can affect our biology, explaining the dynamics of society and health, and designing better interventions that are mindful of the impact of exposures during critical periods. I review how evolutionary concepts and tools, such as fitness gradient in cultural evolution, evolutionary game theory, and contemporary evolution in cancer, can provide helpful insights regarding social epidemiology. PMID:26319950

  17. Overview of TMD Evolution

    NASA Astrophysics Data System (ADS)

    Boer, Daniël

    2016-02-01

    Transverse momentum dependent parton distributions (TMDs) appear in many scattering processes at high energy, from the semi-inclusive DIS experiments at a few GeV to the Higgs transverse momentum distribution at the LHC. Predictions for TMD observables crucially depend on TMD factorization, which in turn determines the TMD evolution of the observables with energy. In this contribution to SPIN2014 TMD factorization is outlined, including a discussion of the treatment of the nonperturbative region, followed by a summary of results on TMD evolution, mostly applied to azimuthal asymmetries.

  18. Software evolution. What kind of evolution?

    NASA Astrophysics Data System (ADS)

    Torres-Carbonell, J. J.; Parets-Llorca, J.

    2001-06-01

    Most Software Systems capable of adapting to the environment or of performing some kind of adaptive activity (such as pattern learning, behavior simulations and the like) use concepts and models from Biology. Nevertheless, such approaches are based on the Modern Synthesis, i.e., Darwinism plus Mendelism, and this implies preadaptive mutations in, and subsequent selection of the better adapted individuals. These pre-adaptive changes usually do not produce the desired effect, are virtually useless and require some kind of backtracking for the system to obtain profit from adaptation. It is our contention that an evolutionary approach in Software Systems development cannot be based on pre-adaptive mutations, but rather on post-adaptive ones, that is, anticipatory mutations and modifications (Lamarkism). A novel way of understanding evolution in Software Systems based on applied Lamarkism is presented and a framework that allows the incorporation of modifications according to the necessities of the system and the will of the modeller is proposed.

  19. Hemangiopericytome nasosinusien: difficulté diagnostique et thérapeutique

    PubMed Central

    Roubal, Mohamed; Horra, Aziza; Bajja, Mohamed Yahya; El Ettar, Hicham; Abada, Reda; Rouadi, Sami; Mahtar, Mohamed; Janah, Abdelaziz; Kadiri, Fatmi

    2014-01-01

    L'hemangiopericytome est une tumeur vasculaire rare, développée à partir des pericytes des capillaires, dans sa localisation nasosinusienne elle ne représente que 0 .5% de l'ensemble des tumeurs de cette région. Une jeune de 35ans a présenté une tumeur rapidement évolutive au cours du bilan diagnostic, l’étude anatomopathologique a conclu à un hémangiopericytome. PMID:26113887

  20. Schwannome cervical du nerf vague: Stratégies diagnostique et thérapeutique

    PubMed Central

    Benmansour, Najib; Elfadl, Yasine; Bennani, Amal; Maaroufi, Mustapha; Chbani, Leila; Amarti, Afaf; Tizniti, Siham; Elalami, Mohamed Noureddine

    2013-01-01

    Les schwannomes cervicaux sont des tumeurs bénignes des nerfs périphériques développées exclusivement à partir des cellules de Schwann. L'atteinte du nerf vague cervical est relativement rare, et les auteurs en rappellent, à partir d'un cas, les signes radiologiques évocateurs ainsi que les caractéristiques histologiques. Le traitement de ces tumeurs est chirurgical. Un patient de 32 ans consultait pour une masse latéro-cervicale supérieure droite isolée, évoluant depuis trois ans. Une imagerie médicale (TDM et IRM) cervicale mettait en évidence une masse vascularisée au temps retardé, refoulant la veine jugulaire interne en dehors et l'axe carotidien en dedans. Un examen cytologique non contributif conduisait à réaliser une exérèse chirurgicale extracapsulaire de la masse par voie de cervicotomie. Il s'agissait d'une tumeur rétro-jugulo-carotidienne développée aux dépens du nerf vague cervical droit. L'analyse histologique concluait à un schwannome. Les suites opératoires étaient simples. Le schwannome du nerf vague est une tumeur bénigne rare, qui doit être évoquée devant toute masse latérocervicale isolée. L'imagerie médicale (TDM et IRM) cervicale préopératoire représente les examens de choix indispensable pour évoquer le diagnostic. Le traitement est chirurgical, afin de confirmer le diagnostic histologique. L'exérèse chirurgical complète extracapsulaire est possible et est le seul garant de la non récidive. PMID:23646212

  1. Apport diagnostique de la cervicotomie exploratrice: étude rétrospective de 300 cas

    PubMed Central

    Darouassi, Youssef; Chihani, Mehdi; Touati, Mohamed Mliha; Ammar, Haddou; Bouaity, Brahim

    2015-01-01

    Les tuméfactions cervicales représentent un motif fréquent de consultation, et les adénopathies en constituent l’étiologie la plus fréquente. L'examen clinique et les bilans paracliniques permettent, dans la majorité des cas de retrouver une étiologie. Néanmoins certaines de ces tuméfactions restent d'origine non précisée, portant donc l'indication d'une cervicotomie exploratrice. Il s'agit d'une étude rétrospective d'une série de 300 cas de tuméfactions cervicales isolées colligées au service d'ORL de l'hôpital militaire Avicenne de Marrakech entre 2001 et 2014. Tous nos patients ont bénéficié d'une cervicotomie exploratrice avec étude anatomo-pathologique. L’âge des patients varie entre 1 et 76 ans avec un âge moyen de 32,57 ans et une légère prédominance masculine de 52%. La symptomatologie qui a motivé une consultation chez 81% des patients était la tuméfaction latérocervicale. La localisation la plus fréquente était sous mandibulaire (33,34%). Les tuméfactions d'installation progressive ont été retrouvées chez 93,34% des patients. Les principales étiologies retrouvées dans notre étude après examen anatomopathologique étaient de deux types: soit d'origine ganglionnaire dominées par la tuberculose ganglionnaire cervicale (53,66%), le lymphome malin non hodgkinien (6,66%), les adénites réactionnelles non spécifiques (4,66%), la maladie deHodgkin (4,33%) et les métastases ganglionnaires cervicales (3,33%); soit d'origine non ganglionnaire dont le lipome cervicale (17,66%), les kystes branchiaux (6%), les kystes du tractus thyréoglosse (1,66%) et le lymphangiome kystique (1,66%). A la lumière des résultats obtenus et des données de la littérature, nous allons discuter l'intérêt et l'utilité de la cervicotomie exploratrice dans le diagnostic étiologique des tuméfactions cervicales lorsque les examens cliniques et paracliniques ne sont pas concluants, et ainsi d'analyser les aspects épidémiologiques, cliniques et paracliniques des différentes étiologies retrouvées. La cervicotomie exploratrice reste, avec l’étude anatomo-pathologique, un outil nécessaire pour le diagnostic de certitude de certaines tuméfactions cervicales malgré son caractère invasif. PMID:27022424

  2. Technologies for ECLSS Evolution

    NASA Technical Reports Server (NTRS)

    Diamant, Bryce L.

    1990-01-01

    Viewgraphs and discussion on technologies for Environmental Control and Life Support System (ECLSS) evolution are presented. Topics covered include: atmosphere revitalization including CO2 removal, CO2 reduction, O2 generation, and trace contaminant control; water recovery and management including urine processing, hygiene water processing, and potable water processing; and waste management. ECLSS technology schematics, process diagrams, and fluid interfaces are included.

  3. Evolution and the Law

    ERIC Educational Resources Information Center

    Mayer, William V.

    1973-01-01

    Some court cases and legislative bills have been filed in states to legalize the use of the creationist view (of life forms on earth) in biology textbooks superseding the organic theory of evolution. The law has not yet accepted the religious viewpoint. (PS)

  4. Human Development, Human Evolution.

    ERIC Educational Resources Information Center

    Smillie, David

    One of the truly remarkable events in human evolution is the unprecedented increase in the size of the brain of "Homo" over a brief span of 2 million years. It would appear that some significant selective pressure or opportunity presented itself to this branch of the hominid line and caused a rapid increase in the brain, introducing a wholly new…

  5. Evolution in Action

    ERIC Educational Resources Information Center

    Dennis, Mike; Duggan, Adrienne; McGregor, Deb

    2014-01-01

    Evolution and inheritance appear in the new National Science Curriculum for England, which comes into effect from September 2014. In the curriculum documents, it is expected that pupils in year 6 (ages 10-11) should be taught to: (1) recognise that living things have changed over time; (2) recognise that living things produce offspring of the same…

  6. Evolution and Friendship

    ERIC Educational Resources Information Center

    Mena-Werth, Jose

    2005-01-01

    In 1925, Williams Jennings Bryan, a former congressman from Nebraska and a former Secretary of State under Woodrow Wilson, spent two agonizing weeks defending his religious faith that cost him his life a month after. Bryan was a prosecutor of high school teacher John Scopes, who had violated Tennessee state law by teaching the theory of evolution.…

  7. Evolution of Osmolyte Systems.

    ERIC Educational Resources Information Center

    Banfalvi, Gaspar

    1991-01-01

    Osmotic aspects of aqueous solutions that are usually disregarded in biochemistry textbooks are presented. This article discusses the osmolarity of seawater, evolution of organisms over geological time, ionic adaptation of cells, ionic concentrations in bacteria, osmolytes and blood electrolytes in water-stressed organisms and land vertebrates,…

  8. Evolution of lifespan.

    PubMed

    Neill, David

    2014-10-01

    Present-day evolutionary theory, modern synthesis and evo-devo, appear to explain evolution. There remain however several points of contention. These include: biological time, direction, macroevolution verses microevolution, ageing and the extent of internal as opposed to external mediation. A new theoretical model for the control of biological time in vertebrates/bilaterians is introduced. Rather than biological time being controlled solely by a molecular cascade domino effect, it is suggested there is also an intracellular oscillatory clock. This clock (life's timekeeper) is synchronised across all cells in an organism and runs at a constant frequency throughout life. Slower frequencies extend lifespan, increase body/brain size and advance behaviour. They also create a time void which could aid additional evolutionary change. Faster frequencies shorten lifespan, reduce body/brain size and diminish behaviour. They are therefore less likely to mediate evolution in vertebrates/mammals. It is concluded that in vertebrates, especially mammals, there is a direction in evolution towards longer lifespan/advanced behaviour. Lifespan extension could equate with macroevolution and subsequent modifications with microevolution. As life's timekeeper controls the rate of ageing it constitutes a new genetic theory of ageing. Finally, as lifespan extension is internally mediated, this suggests a major role for internal mediation in evolution. PMID:24992233

  9. Tectonic Evolution of Mars

    NASA Technical Reports Server (NTRS)

    Phillips, Roger J.

    1992-01-01

    The Final Technical Report on tectonic evolution of Mars is presented. Two papers and an abstract are included. Topics addressed include: scientific rationale and requirements for a global seismic network on Mars, permanent uplift in magmatic systems with application to the Tharsis Region of Mars, and the geophysical signal of the Martian global dichotomy.

  10. Evolution Perception with Metaphors

    ERIC Educational Resources Information Center

    Yilmaz, Fatih

    2016-01-01

    The main objective of this research is to find out how the teacher candidates who graduated from the Faculty of Theology and study in pedagogical formation program perceive the theory of evolution. Having a descriptive characteristic, this research is conducted with 63 Faculty of Theology graduate teacher candidates of which 36 is women and 27 is…

  11. Evolution Projects Yield Results

    ERIC Educational Resources Information Center

    Sparks, Sarah D.

    2010-01-01

    When a federal court in 2005 rejected an attempt by the Dover, Pennsylvania, school board to introduce intelligent design as an alternative to evolution to explain the development of life on Earth, it sparked a renaissance in involvement among scientists in K-12 science instruction. Now, some of those teaching programs, studies, and research…

  12. Crustal Evolution Introduced.

    ERIC Educational Resources Information Center

    Stoever, Edward C., Jr.; Korporaal, Arie R.

    1979-01-01

    Detailed are the origins, development, and implementation of the Crustal Evolution Education Project (CEEP). This group has produced, for use in earth science and other classes in grades 8-10, a series of instructional modules based on current scientific research in the composition, history, and processes of the earth's crust. (BT)

  13. On Multiobjective Evolution Model

    NASA Astrophysics Data System (ADS)

    Ahmed, E.; Elettreby, M. F.

    Self-Organized Criticality (SOC) phenomena could have a significant effect on the dynamics of ecosystems. The Bak-Sneppen (BS) model is a simple and robust model of biological evolution that exhibits punctuated equilibrium behavior. Here, we will introduce random version of BS model. We also generalize the single objective BS model to a multiobjective one.

  14. Evolution. Teacher's Guide.

    ERIC Educational Resources Information Center

    Bershad, Carol

    This teacher's guide was developed to assist teachers in the use of multimedia resources for the Public Broadcasting System (PBS) program, "Evolution." Each unit uses an inquiry-based approach to meet the National Science Education Standards. Units include: (1) "What is the Nature of Science?"; (2) "Who Was Charles Darwin?"; (3) "What is the…

  15. The Evolution of Darwinism.

    ERIC Educational Resources Information Center

    Stebbins, G. Ledyard; Ayala, Francisco J.

    1985-01-01

    Recent developments in molecular biology and new interpretations of the fossil record are gradually altering and adding to Charles Darwin's theory, which has been the standard view of the process of evolution for 40 years. Several of these developments and interpretations are identified and discussed. (JN)

  16. Evolution of an operation.

    PubMed

    Shumacker, H B

    1981-01-01

    The story of the origin of Matas' endoaneurysmorrhaphy with suggestions for maintaining or restoring arterial continuity and their gradual evolution into the technique of intrasaccular interpolation of grafts in managing aneurysms provides another example of the increased utility of an operative procedure by its modification and expansion. PMID:7217191

  17. Evolution and Religion

    ERIC Educational Resources Information Center

    Strickberger, Monroe W.

    1973-01-01

    The relationship between the two concepts (evolution, religion) from an historical and social view is discussed. The concepts are seen to respond differently to the various needs of society, with considerable conflict between them in areas which involve the justification of religious beliefs. (Author/EB)

  18. Software Architecture Evolution

    ERIC Educational Resources Information Center

    Barnes, Jeffrey M.

    2013-01-01

    Many software systems eventually undergo changes to their basic architectural structure. Such changes may be prompted by new feature requests, new quality attribute requirements, changing technology, or other reasons. Whatever the causes, architecture evolution is commonplace in real-world software projects. Today's software architects, however,…

  19. Darwinism: Evolution or Revolution?

    ERIC Educational Resources Information Center

    Holt, Niles R.

    1989-01-01

    Maintains that Darwin's theory of evolution was more than a science versus religion debate; rather it was a revolutionary concept that influenced numerous social and political ideologies and movements throughout western history. Traces the impact of Darwin's work historically, utilizing a holistic approach. (RW)

  20. The Evolution of Behavior.

    ERIC Educational Resources Information Center

    Smith, John Maynard

    1978-01-01

    The topic of altruistic behavior is an important one in studying the evolution of behavior. It is questioned whether natural selection can actually favor patterns of behavior that apparently do not favor the survival of the individual. Game theory models are presented to help explore the problem. (MA)

  1. Evolution: Skipping School

    PubMed Central

    Bell, Alison M.

    2014-01-01

    Some individual fish like to be close together in ‘schools’, while other individuals like to be alone. A pair of recent papers dissects the genetic basis of schooling behavior, showing that genetic changes in sensory systems are involved when this social behavior is lost during evolution. PMID:24112981

  2. Early cellular evolution.

    NASA Technical Reports Server (NTRS)

    Margulis, L.

    1972-01-01

    Study of the evolutionary developments that occurred subsequent to the origin of ancestral cells. Microbial physiology and ecology are potential sharp tools for shaping concepts of microbial evolution. Some popular unjustified assumptions are discussed. It is considered that certain principles derived mainly from the advances of molecular biology can be used to order the natural groups (genera) of extant prokaryotes and their patterns phylogenetically.

  3. Animal evolution: trilobites on speed.

    PubMed

    Budd, Graham E

    2013-10-01

    A new study quantifies rates of morphological and molecular evolution for arthropods during the critical Cambrian explosion. Both morphological and molecular evolution are accelerated--but not so much to break any speed limits. PMID:24112983

  4. "New" Persuasive Evidence for Evolution.

    ERIC Educational Resources Information Center

    Max, Edward E.

    1998-01-01

    Discusses some new evidence for evolution that might be useful in persuading students who question the scientific basis for evolution. Draws on findings from the fields of molecular biology and genetics. (DDR)

  5. Evolution as Fact and Theory.

    ERIC Educational Resources Information Center

    Gould, Stephen Jay

    1981-01-01

    This essay by a Harvard evolutionist presents viewpoints concerning the creationists' arguments against evolutionary biology. Semantics regarding "facts" and "theory" of evolution are examined, examples are cited of creationist argument, and arguments for evolution are presented. (CS)

  6. The physics of evolution

    NASA Astrophysics Data System (ADS)

    Eigen, Manfred

    1988-12-01

    The Darwinian concept of evolution through natural selection has been revised and put on a solid physical basis, in a form which applies to self-replicable macromolecules. Two new concepts are introduced: sequence space and quasi-species. Evolutionary change in the DNA- or RNA-sequence of a gene can be mapped as a trajectory in a sequence space of dimension ν, where ν corresponds to the number of changeable positions in the genomic sequence. Emphasis, however, is shifted from the single surviving wildtype, a single point in the sequence space, to the complex structure of the mutant distribution that constitutes the quasi-species. Selection is equivalent to an establishment of the quasi-species in a localized region of sequence space, subject to threshold conditions for the error rate and sequence length. Arrival of a new mutant may violate the local threshold condition and thereby lead to a displacement of the quasi-species into a different region of sequence space. This transformation is similar to a phase transition; the dynamical equations that describe the quase-species have been shown to be analogous to those of the two-dimensional Ising model of ferromagnetism. The occurrence of a selectively advantageous mutant is biased by the particulars of the quasi-species distribution, whose mutants are populated according to their fitness relative to that of the wild-type. Inasmuch as fitness regions are connected (like mountain ridges) the evolutionary trajectory is guided to regions of optimal fitness. Evolution experiments in test tubes confirm this modification of the simple chance and law nature of the Darwinian concept. The results of the theory can also be applied to the construction of a machine that provides optimal conditions for a rapid evolution of functionally active macromolecules. An introduction to the physics of molecular evolution by the author has appeared recently.1 Detailed studies of the kinetics and mechanisms of replication of RNA, the most

  7. Phenotypic Evolution With and Beyond Genome Evolution.

    PubMed

    Félix, M-A

    2016-01-01

    DNA does not make phenotypes on its own. In this volume entitled "Genes and Phenotypic Evolution," the present review draws the attention on the process of phenotype construction-including development of multicellular organisms-and the multiple interactions and feedbacks between DNA, organism, and environment at various levels and timescales in the evolutionary process. First, during the construction of an individual's phenotype, DNA is recruited as a template for building blocks within the cellular context and may in addition be involved in dynamical feedback loops that depend on the environmental and organismal context. Second, in the production of phenotypic variation among individuals, stochastic, environmental, genetic, and parental sources of variation act jointly. While in controlled laboratory settings, various genetic and environmental factors can be tested one at a time or in various combinations, they cannot be separated in natural populations because the environment is not controlled and the genotype can rarely be replicated. Third, along generations, genotype and environment each have specific properties concerning the origin of their variation, the hereditary transmission of this variation, and the evolutionary feedbacks. Natural selection acts as a feedback from phenotype and environment to genotype. This review integrates recent results and concrete examples that illustrate these three points. Although some themes are shared with recent calls and claims to a new conceptual framework in evolutionary biology, the viewpoint presented here only means to add flesh to the standard evolutionary synthesis. PMID:27282029

  8. Fla. Panel's Evolution Vote Hailed

    ERIC Educational Resources Information Center

    Cavanagh, Sean

    2008-01-01

    This article reports on how the compromise hammered out in Florida recently over the treatment of evolution in the state's science classrooms is winning praise from scientists and educators. The new science standards will refer to evolution as the "scientific theory of evolution." These changes will replace more-general language in the previous…

  9. Expanding the Understanding of Evolution

    ERIC Educational Resources Information Center

    Musante, Susan

    2011-01-01

    Originally designed for K-12 teachers, the Understanding Evolution (UE) Web site ("www.understandingevolution.org") is a one-stop shop for all of a teacher's evolution education needs, with lesson plans, teaching tips, lists of common evolution misconceptions, and much more. However, during the past five years, the UE project team learned that…

  10. Evolution of Brain and Language

    ERIC Educational Resources Information Center

    Schoenemann, P. Thomas

    2009-01-01

    The evolution of language and the evolution of the brain are tightly interlinked. Language evolution represents a special kind of adaptation, in part because language is a complex behavior (as opposed to a physical feature) but also because changes are adaptive only to the extent that they increase either one's understanding of others, or one's…

  11. Evolution of intrafamilial interactions.

    PubMed Central

    Lynch, M

    1987-01-01

    A theory for the evolution of behavioral interactions among relatives is developed that allows for genetic correlations between the types of behavior that are expressed in different social contexts. Both theoretical and empirical considerations indicate that such genetic constraints will almost certainly be common in natural populations. It is shown that when genetic correlations between elements of social behavior exist, Hamilton's rule inaccurately describes the conditions for evolution by way of kin selection. The direction in which social organization evolves is a delicate function of the genetic covariance structure among behaviors expressed as an offspring, sibling, parent, etc. A change in this covariance structure caused by random genetic drift or by a change in environment for a population exhibiting genotype-environment interaction can cause the population to suddenly cross a threshold into a new selective domain. Consequently, radical changes in social organization may arise between closely related species without any major shift in selective pressures external to the population. Images PMID:3479804

  12. Relative constraints and evolution

    NASA Astrophysics Data System (ADS)

    Ochoa, Juan G. Diaz

    2014-03-01

    Several mathematical models of evolving systems assume that changes in the micro-states are constrained to the search of an optimal value in a local or global objective function. However, the concept of evolution requires a continuous change in the environment and species, making difficult the definition of absolute optimal values in objective functions. In this paper, we define constraints that are not absolute but relative to local micro-states, introducing a rupture in the invariance of the phase space of the system. This conceptual basis is useful to define alternative mathematical models for biological (or in general complex) evolving systems. We illustrate this concept with a modified Ising model, which can be useful to understand and model problems like the somatic evolution of cancer.

  13. Algorithms, games, and evolution

    PubMed Central

    Chastain, Erick; Livnat, Adi; Papadimitriou, Christos; Vazirani, Umesh

    2014-01-01

    Even the most seasoned students of evolution, starting with Darwin himself, have occasionally expressed amazement that the mechanism of natural selection has produced the whole of Life as we see it around us. There is a computational way to articulate the same amazement: “What algorithm could possibly achieve all this in a mere three and a half billion years?” In this paper we propose an answer: We demonstrate that in the regime of weak selection, the standard equations of population genetics describing natural selection in the presence of sex become identical to those of a repeated game between genes played according to multiplicative weight updates (MWUA), an algorithm known in computer science to be surprisingly powerful and versatile. MWUA maximizes a tradeoff between cumulative performance and entropy, which suggests a new view on the maintenance of diversity in evolution. PMID:24979793

  14. The evolution of pregnancy.

    PubMed

    Bainbridge, David R J

    2014-11-01

    Although viviparity has evolved many times in the animal kingdom, it remains relatively uncommon-scorpions and therian mammals being rare examples of entirely viviparous major taxa. Viviparity is a specialised form of intra-species parasitism which biases parental investment towards fertilised eggs, temporally spreads that investment, and also temporarily protects offspring from many selection pressures. Importantly, the mammalian viviparity appeared at a relatively late stage in the process of vertebrate evolution. Because of this, viviparity was 'superimposed' on complex pre-existing cardiovascular, respiratory, metabolic and immune systems, and has altered them dramatically. Also, pregnancy has exerted pervasive effects on gene expression in mammals, including genetic imprinting, X inactivation, sex determination, and the ectopic expression in the extra-embryonic membranes of many genes previously expressed in the gonads, brain, pituitary and immune system. Finally, although lactation probably pre-dated viviparity in mammalian evolution, the two have co-evolved as alternative strategies of offspring nutrition ever since. PMID:25242206

  15. Evolutions from extremality

    NASA Astrophysics Data System (ADS)

    Booth, Ivan

    2016-04-01

    We examine the evolution of extremal spherically symmetric black holes, developing both general theory as well as the specific cases of (charged) null dust and massless scalar field spacetimes. As matter accretes onto extremal marginally trapped tubes, they generically evolve to become nonextremal, with the initial extremal horizon bifurcating into inner and outer nonextremal horizons. At the start of this process arbitrarily slow matter accretion can cause a geometrically invariant measure of horizon growth to jump from zero to infinity. We also consider dynamical horizons that are extremal throughout their evolution and see that such spacetimes contain two extremal black hole horizons: an inner isolated one and an outer dynamical one. We compare these extremal dynamical horizons with the dynamical extreme event horizon spacetimes of Murata, Reall and Tanahashi.

  16. Evolution of mycorrhiza systems

    NASA Astrophysics Data System (ADS)

    Cairney, J. W. G.

    Most terrestrial plants live in mutualistic symbiosis with root-infecting mycorrhizal fungi. Fossil records and molecular clock dating suggest that all extant land plants have arisen from an ancestral arbuscular mycorrhizal condition. Arbuscular mycorrhizas evolved concurrently with the first colonisation of land by plants some 450-500 million years ago and persist in most extant plant taxa. Ectomycorrhizas (about 200million years ago) and ericoid mycorrhizas (about 100million years ago) evolved subsequently as the organic matter content of some ancient soils increased and sclerophyllous vegetation arose as a response to nutrient-poor soils respectively. Mycorrhizal associations appear to be the result of relatively diffuse coevolutionary processes. While early events in the evolution of mycorrhizal symbioses may have involved reciprocal genetic changes in ancestral plants and free-living fungi, available evidence points largely to ongoing parallel evolution of the partners in response to environmental change.

  17. Evolution of mycorrhiza systems.

    PubMed

    Cairney, J W

    2000-11-01

    Most terrestrial plants live in mutualistic symbiosis with root-infecting mycorrhizal fungi. Fossil records and molecular clock dating suggest that all extant land plants have arisen from an ancestral arbuscular mycorrhizal condition. Arbuscular mycorrhizas evolved concurrently with the first colonisation of land by plants some 450-500 million years ago and persist in most extant plant taxa. Ectomycorrhizas (about 200 million years ago) and ericoid mycorrhizas (about 100 million years ago) evolved subsequently as the organic matter content of some ancient soils increased and sclerophyllous vegetation arose as a response to nutrient-poor soils respectively. Mycorrhizal associations appear to be the result of relatively diffuse coevolutionary processes. While early events in the evolution of mycorrhizal symbioses may have involved reciprocal genetic changes in ancestral plants and free-living fungi, available evidence points largely to ongoing parallel evolution of the partners in response to environmental change. PMID:11151665

  18. Interactive evolution of camouflage.

    PubMed

    Reynolds, Craig

    2011-01-01

    This article presents an abstract computation model of the evolution of camouflage in nature. The 2D model uses evolved textures for prey, a background texture representing the environment, and a visual predator. A human observer, acting as the predator, is shown a cohort of 10 evolved textures overlaid on the background texture. The observer clicks on the five most conspicuous prey to remove ("eat") them. These lower-fitness textures are removed from the population and replaced with newly bred textures. Biological morphogenesis is represented in this model by procedural texture synthesis. Nested expressions of generators and operators form a texture description language. Natural evolution is represented by genetic programming (GP), a variant of the genetic algorithm. GP searches the space of texture description programs for those that appear least conspicuous to the predator. PMID:21370960

  19. Emergence and Evolution

    PubMed Central

    Bullwinkle, Tammy J.

    2013-01-01

    The aminoacyl-tRNA synthetases (aaRSs) are essential components of the protein synthesis machinery responsible for defining the genetic code by pairing the correct amino acids to their cognate tRNAs. The aaRSs are an ancient enzyme family believed to have origins that may predate the last common ancestor and as such they provide insights into the evolution and development of the extant genetic code. Although the aaRSs have long been viewed as a highly conserved group of enzymes, findings within the last couple of decades have started to demonstrate how diverse and versatile these enzymes really are. Beyond their central role in translation, aaRSs and their numerous homologs have evolved a wide array of alternative functions both inside and outside translation. Current understanding of the emergence of the aaRSs, and their subsequent evolution into a functionally diverse enzyme family, are discussed in this chapter. PMID:23478877

  20. QCD Evolution 2015

    NASA Astrophysics Data System (ADS)

    These are the proceedings of the QCD Evolution 2015 Workshop which was held 26-30 May, 2015 at Jefferson Lab, Newport News, Virginia, USA. The workshop is a continuation of a series of workshops held during four consecutive years 2011, 2012, 2013 at Jefferson Lab, and in 2014 in Santa Fe, NM. With the rapid developments in our understanding of the evolution of parton distributions including low-x, TMDs, GPDs, higher-twist correlation functions, and the associated progress in perturbative QCD, lattice QCD and effective field theory techniques we look forward with great enthusiasm to the 2015 meeting. A special attention was also paid to participation of experimentalists as the topics discussed are of immediate importance for the JLab 12 experimental program and a future Electron Ion Collider.

  1. Anatomy of Scientific Evolution

    PubMed Central

    Yun, Jinhyuk; Kim, Pan-Jun; Jeong, Hawoong

    2015-01-01

    The quest for historically impactful science and technology provides invaluable insight into the innovation dynamics of human society, yet many studies are limited to qualitative and small-scale approaches. Here, we investigate scientific evolution through systematic analysis of a massive corpus of digitized English texts between 1800 and 2008. Our analysis reveals great predictability for long-prevailing scientific concepts based on the levels of their prior usage. Interestingly, once a threshold of early adoption rates is passed even slightly, scientific concepts can exhibit sudden leaps in their eventual lifetimes. We developed a mechanistic model to account for such results, indicating that slowly-but-commonly adopted science and technology surprisingly tend to have higher innate strength than fast-and-commonly adopted ones. The model prediction for disciplines other than science was also well verified. Our approach sheds light on unbiased and quantitative analysis of scientific evolution in society, and may provide a useful basis for policy-making. PMID:25671617

  2. The evolution of helicopters

    NASA Astrophysics Data System (ADS)

    Chen, R.; Wen, C. Y.; Lorente, S.; Bejan, A.

    2016-07-01

    Here, we show that during their half-century history, helicopters have been evolving into geometrically similar architectures with surprisingly sharp correlations between dimensions, performance, and body size. For example, proportionalities emerge between body size, engine size, and the fuel load. Furthermore, the engine efficiency increases with the engine size, and the propeller radius is roughly the same as the length scale of the whole body. These trends are in accord with the constructal law, which accounts for the engine efficiency trend and the proportionality between "motor" size and body size in animals and vehicles. These body-size effects are qualitatively the same as those uncovered earlier for the evolution of aircraft. The present study adds to this theoretical body of research the evolutionary design of all technologies [A. Bejan, The Physics of Life: The Evolution of Everything (St. Martin's Press, New York, 2016)].

  3. Histones in protistan evolution.

    PubMed

    Rizzo, P J

    1985-01-01

    The potential of comparative studies on histones for use in protistan evolution is discussed, using algal histones as specific examples. A basic premise for the importance of histones in protistan evolution is the observation that these proteins are completely absent in prokaryotes (and cytoplasmic organelles), but with few exceptions, the same five major histone types are found in all higher plants and animals. Since the histone content of the algae and other protists is not constant, some of these organisms may represent transition forms between the prokaryotic and eukaryotic modes of packaging the genetic material. Comparative studies of protistan histones may thus be of help in determining evolutionary relationships. However, several problems are encounter with protistan histones, including difficulties in isolating nuclei, proteolytic degradation, anomalous gel migration of histones, and difficulties in histone identification. Because of the above problems, and the observed variability in protistan histones, it is suggested that several criteria be employed for histone identification in protists. PMID:3910133

  4. Thermal evolution of Venus

    NASA Astrophysics Data System (ADS)

    Arkani-Hamed, J.; Toksoz, M. N.

    1984-09-01

    A modification of the Boussinesq fluid assumption is the basis of the present theory of three-dimensional and finite amplitude convection in a viscous spherical shell with temperature- and pressure-dependent physical parameters. The theory is applied to the definition of thermal evolution models for Venus which emphasize the effects of certain physical parameters on thermal evolution, rather than the specific thermal history of the planet. It is suggested that a significant portion of the present temperature in the mantle and surface heat flux of Venus is due to the decay of a high temperature that was established in the planet at the completion of its core formation, and that Venus has been highly convective over the course of its history, until about 0.5 Ga ago.

  5. Evolution of catalytic function

    NASA Technical Reports Server (NTRS)

    Joyce, G. F.

    1993-01-01

    An RNA-based evolution system was constructed in the laboratory and used to develop RNA enzymes with novel catalytic function. By controlling the nature of the catalytic task that the molecules must perform in order to survive, it is possible to direct the evolving population toward the expression of some desired catalytic behavior. More recently, this system has been coupled to an in vitro translation procedure, raising the possibility of evolving protein enzymes in the laboratory to produce novel proteins with desired catalytic properties. The aim of this line of research is to reduce darwinian evolution, the fundamental process of biology, to a laboratory procedure that can be made to operate in the service of organic synthesis.

  6. Nonperturbative Quantum Field Evolution

    NASA Astrophysics Data System (ADS)

    Zhao, Xingbo; Ilderton, Anton; Maris, Pieter; Vary, James P.

    2014-06-01

    We introduce a nonperturbative, first-principles approach to time-dependent problems in quantum field theory. In this approach, the time-evolution of quantum field configurations is calculated in real time and at the amplitude level. This method is particularly suitable for treating systems interacting with a time-dependent background field. As a test problem, we apply this approach to QED and study electron acceleration and the associated photon emission in a time- and space-dependent electromagnetic background field.

  7. Evolution and ageing

    NASA Astrophysics Data System (ADS)

    de Oliveira, S. Moss; Alves, Domingos; Martins, J. S. Sá

    2000-09-01

    The idea of this review is to connect the different models of evolution to those of biological ageing through Darwin's theory. We start with the Eigen model of quasispecies for microevolution, then introduce the Bak-Sneppen model for macroevolution and, finally, present the Penna model for biological ageing and some of its most important results. We also explore the concept of coevolution using this model.

  8. Evolution of Virtual Communities

    NASA Astrophysics Data System (ADS)

    Cheon, Eunyoung; Ahn, Joongho

    As the capabilities of technologies are enhanced and users become diversified, virtual communities have evolved from BBS to a new phenomena—virtual world. This study describes the evolution of VCs in three generations by three dimensions. Facing new challenges in new VC generation, VC platform providers need to adopt new approaches. The authors discuss important factors of future VCs. The field for VCs in the future will become more sophisticated and competitive.

  9. Evolution of stellar entropy

    NASA Astrophysics Data System (ADS)

    de Souza, R. A.; de Avellar, M. G. B.; Horvath, J. E.

    2015-11-01

    An appraisal of the behavior of stellar entropy along stellar evolution is made. It is shown that the entropy per baryon of a star of a fixed baryon number decreases monotonically with increasing compactness of the star. The same entropy per baryon increases only whenever an irreversible collapse of the star happens. The recent proposals for a gravitational entropy related to curvature may justify the huge increase of the entropy in the ultimate collapse to a black hole.

  10. Space Station evolution study

    NASA Technical Reports Server (NTRS)

    Evans, David B.

    1993-01-01

    This is the Space Station Freedom (SSF) Evolution Study 1993 Final Report, performed under NASA Contract NAS8-38783, Task Order 5.1. This task examined: (1) the feasibility of launching current National Space Transportation System (NSTS) compatible logistics elements on expendable launch vehicles (ELV's) and the associated modifications, and (2) new, non-NSTS logistics elements for launch on ELV's to augment current SSF logistics capability.

  11. Epistasis in protein evolution.

    PubMed

    Starr, Tyler N; Thornton, Joseph W

    2016-07-01

    The structure, function, and evolution of proteins depend on physical and genetic interactions among amino acids. Recent studies have used new strategies to explore the prevalence, biochemical mechanisms, and evolutionary implications of these interactions-called epistasis-within proteins. Here we describe an emerging picture of pervasive epistasis in which the physical and biological effects of mutations change over the course of evolution in a lineage-specific fashion. Epistasis can restrict the trajectories available to an evolving protein or open new paths to sequences and functions that would otherwise have been inaccessible. We describe two broad classes of epistatic interactions, which arise from different physical mechanisms and have different effects on evolutionary processes. Specific epistasis-in which one mutation influences the phenotypic effect of few other mutations-is caused by direct and indirect physical interactions between mutations, which nonadditively change the protein's physical properties, such as conformation, stability, or affinity for ligands. In contrast, nonspecific epistasis describes mutations that modify the effect of many others; these typically behave additively with respect to the physical properties of a protein but exhibit epistasis because of a nonlinear relationship between the physical properties and their biological effects, such as function or fitness. Both types of interaction are rampant, but specific epistasis has stronger effects on the rate and outcomes of evolution, because it imposes stricter constraints and modulates evolutionary potential more dramatically; it therefore makes evolution more contingent on low-probability historical events and leaves stronger marks on the sequences, structures, and functions of protein families. PMID:26833806

  12. Darwinian Evolution and Fractals

    NASA Astrophysics Data System (ADS)

    Carr, Paul H.

    2009-05-01

    Did nature's beauty emerge by chance or was it intelligently designed? Richard Dawkins asserts that evolution is blind aimless chance. Michael Behe believes, on the contrary, that the first cell was intelligently designed. The scientific evidence is that nature's creativity arises from the interplay between chance AND design (laws). Darwin's ``Origin of the Species,'' published 150 years ago in 1859, characterized evolution as the interplay between variations (symbolized by dice) and the natural selection law (design). This is evident in recent discoveries in DNA, Madelbrot's Fractal Geometry of Nature, and the success of the genetic design algorithm. Algorithms for generating fractals have the same interplay between randomness and law as evolution. Fractal statistics, which are not completely random, characterize such phenomena such as fluctuations in the stock market, the Nile River, rainfall, and tree rings. As chaos theorist Joseph Ford put it: God plays dice, but the dice are loaded. Thus Darwin, in discovering the evolutionary interplay between variations and natural selection, was throwing God's dice!

  13. Evolution of Metabolic Dependency

    NASA Astrophysics Data System (ADS)

    Shou, Wenying

    Microbes are often found to have lost their ability to make essential metabolites (auxotrophs) and instead rely on other individuals for these metabolites. How might metabolic dependency evolve to be so common? When microbes live inside a host (endosymbionts), amply host metabolites support auxotrophic endosymbionts. If the host transmits only a small number of endosymbionts to its offspring, then auxotrophic endosymbionts can rise to high frequency simply by chance. On the other hand, auxotrophs have also been observed in abundant free-living bacteria found in ocean water where nutrient supply is low. How might auxotrophs rise to an appreciable frequency in a large population when nutrient supply is low? We have found commonly-encountered conditions that facilitate the evolution of metabolic dependency. Metabolic interactions can in turn shape spatial organization of microbial communities (Momeni et al. (2013) eLife 2, 00230; Momeni et al. (2013) eLife 2, 00960; Estrela and Brown (2013) PLoS Comput Biol 9, e1003398; Muller et al. (2014) PNAS 111, 1037-1042). Rapid evolution of metabolic dependency can contribute to the complexity of microbial communities. Evolution of metabolic dependency.

  14. The evolution within us

    PubMed Central

    Cobey, Sarah; Wilson, Patrick; Matsen, Frederick A.

    2015-01-01

    The B-cell immune response is a remarkable evolutionary system found in jawed vertebrates. B-cell receptors, the membrane-bound form of antibodies, are capable of evolving high affinity to almost any foreign protein. High germline diversity and rapid evolution upon encounter with antigen explain the general adaptability of B-cell populations, but the dynamics of repertoires are less well understood. These dynamics are scientifically and clinically important. After highlighting the remarkable characteristics of naive and experienced B-cell repertoires, especially biased usage of genes encoding the B-cell receptors, we contrast methods of sequence analysis and their attempts to explain patterns of B-cell evolution. These phylogenetic approaches are currently unlinked to explicit models of B-cell competition, which analyse repertoire evolution at the level of phenotype, the affinities and specificities to particular antigenic sites. The models, in turn, suggest how chance, infection history and other factors contribute to different patterns of immunodominance and protection between people. Challenges in rational vaccine design, specifically vaccines to induce broadly neutralizing antibodies to HIV, underscore critical gaps in our understanding of B cells' evolutionary and ecological dynamics. PMID:26194749

  15. Dynamics of secular evolution

    NASA Astrophysics Data System (ADS)

    Binney, James

    2013-10-01

    The material in this article was presented in five hours of lectures to the 2011 Canary Islands Winter School. The School’s theme was ‘Secular Evolution of Galaxies’ and my task was to present the underlying stellar-dynamical theory. Other lecturers were speaking on the role of bars and chemical evolution, so these topics are avoided here. The material starts with an account of the connections between isolating integrals, quasiperiodicity and angle-action variables - these variables played a prominent and unifying role throughout the lectures. This leads on to the phenomenon of resonant trap- ping and how this can lead to chaos in cuspy potentials and phase-space mixing in slowly evolving potentials. Surfaces of section and frequency analysis are introduced as diagnostics of phase-space structure. Real galactic potentials include a fluctuating part that drives the system towards unattainable thermal equilibrium. Two-body encounters are only one source of fluctuations, and all fluctuations will drive similar evolution. The orbit-averaged Fokker-Planck equation is derived, as are relations that hold between the second-order diffusion coefficients and both the power spectrum of the fluctuations and the first-order diffusion coefficients. From the observed heating of the solar neighbourhood we show that the second-order diffusion coefficients must scale as ˜ J1/2. We show that periodic spiral structure shifts angular momentum outwards, heating at the Lindblad resonances and mixing at corotation. The equation that would yield the normal modes of a stellar disk is first derived and then used to discuss the propagation of tightly wound spiral waves. The winding up of such waves is described and explains why cool stellar disks are responsive systems that amplify ambient noise. An explanation is offered of why the Lin-Shu-Kalnajs dispersion relation and even global normal-mode calculations provide a very incomplete understanding of the dynamics of stellar disks.

  16. Evolution before genes

    PubMed Central

    2012-01-01

    Background Our current understanding of evolution is so tightly linked to template-dependent replication of DNA and RNA molecules that the old idea from Oparin of a self-reproducing 'garbage bag' ('coacervate') of chemicals that predated fully-fledged cell-like entities seems to be farfetched to most scientists today. However, this is exactly the kind of scheme we propose for how Darwinian evolution could have occurred prior to template replication. Results We cannot confirm previous claims that autocatalytic sets of organic polymer molecules could undergo evolution in any interesting sense by themselves. While we and others have previously imagined inhibition would result in selectability, we found that it produced multiple attractors in an autocatalytic set that cannot be selected for. Instead, we discovered that if general conditions are satisfied, the accumulation of adaptations in chemical reaction networks can occur. These conditions are the existence of rare reactions producing viable cores (analogous to a genotype), that sustains a molecular periphery (analogous to a phenotype). Conclusions We conclude that only when a chemical reaction network consists of many such viable cores, can it be evolvable. When many cores are enclosed in a compartment there is competition between cores within the same compartment, and when there are many compartments, there is between-compartment competition due to the phenotypic effects of cores and their periphery at the compartment level. Acquisition of cores by rare chemical events, and loss of cores at division, allows macromutation, limited heredity and selectability, thus explaining how a poor man's natural selection could have operated prior to genetic templates. This is the only demonstration to date of a mechanism by which pre-template accumulation of adaptation could occur. Reviewers This article was reviewed by William Martin and Eugene Koonin. PMID:22221860

  17. Evolution and human sexuality.

    PubMed

    Gray, Peter B

    2013-12-01

    The aim of this review is to put core features of human sexuality in an evolutionary light. Toward that end, I address five topics concerning the evolution of human sexuality. First, I address theoretical foundations, including recent critiques and developments. While much traces back to Darwin and his view of sexual selection, more recent work helps refine the theoretical bases to sex differences and life history allocations to mating effort. Second, I consider central models attempting to specify the phylogenetic details regarding how hominin sexuality might have changed, with most of those models honing in on transitions from a possible chimpanzee-like ancestor to the slightly polygynous and long-term bonded sociosexual partnerships observed among most recently studied hunter-gatherers. Third, I address recent genetic and physiological data contributing to a refined understanding of human sexuality. As examples, the availability of rapidly increasing genomic information aids comparative approaches to discern signals of selection in sexuality-related phenotypes, and neuroendocrine studies of human responses to sexual stimuli provide insight into homologous and derived mechanisms. Fourth, I consider some of the most recent, large, and rigorous studies of human sexuality. These provide insights into sexual behavior across other national samples and on the Internet. Fifth, I discuss the relevance of a life course perspective to understanding the evolution of human sexuality. Most research on the evolution of human sexuality focuses on young adults. Yet humans are sexual beings from gestation to death, albeit in different ways across the life course, and in ways that can be theoretically couched within life history theory. PMID:24151100

  18. Evolution of Sedimentary Rocks

    NASA Astrophysics Data System (ADS)

    Veizer, J.; MacKenzie, F. T.

    2003-12-01

    For almost a century, it has been recognized that the present-day thickness and areal extent of Phanerozoic sedimentary strata increase progressively with decreasing geologic age. This pattern has been interpreted either as reflecting an increase in the rate of sedimentation toward the present (Barrell, 1917; Schuchert, 1931; Ronov, 1976) or as resulting from better preservation of the younger part of the geologic record ( Gilluly, 1949; Gregor, 1968; Garrels and Mackenzie, 1971a; Veizer and Jansen, 1979, 1985).Study of the rocks themselves led to similarly opposing conclusions. The observed secular (=age) variations in relative proportions of lithological types and in chemistry of sedimentary rocks (Daly, 1909; Vinogradov et al., 1952; Nanz, 1953; Engel, 1963; Strakhov, 1964, 1969; Ronov, 1964, 1982) were mostly given an evolutionary interpretation. An opposing, uniformitarian, approach was proposed by Garrels and Mackenzie (1971a). For most isotopes, the consensus favors deviations from the present-day steady state as the likely cause of secular trends.This chapter attempts to show that recycling and evolution are not opposing, but complementary, concepts. It will concentrate on the lithological and chemical attributes of sediments, but not deal with the evolution of sedimentary mineral deposits (Veizer et al., 1989) and of life ( Sepkoski, 1989), both well amenable to the outlined conceptual treatment. The chapter relies heavily on Veizer (1988a) for the sections dealing with general recycling concepts, on Veizer (2003) for the discussion of isotopic evolution of seawater, and on Morse and Mackenzie (1990) and Mackenzie and Morse (1992) for discussion of carbonate rock recycling and environmental attributes.

  19. Orbital Evolution of Asteroids

    NASA Astrophysics Data System (ADS)

    Dermott, S. F.; Kehoe, T. J. J.

    2011-10-01

    The synthetic orbital frequencies and eccentricities of main belt asteroids computed by Knezevic and Milani [2] show evidence that the structure of the asteroid belt has been determined by a dense of web of high-order resonances. By examining the orbital frequency distribution at high resolution, we discover a correlation between asteroid number density, mean orbital eccentricity and Lyapunov Characteristic Exponent. In particular, the orbital eccentricities of asteroids trapped in resonance tend to be higher than those of non-resonant asteroids and we argue that this is observational evidence for orbital evolution due to chaotic diffusion.

  20. Evolution of Atmospheres

    SciTech Connect

    Hanson, B.

    1993-02-12

    An atmosphere is the dynamic gaseous boundary layer between a planet and space. Many complex interactions affect the composition and time evolution of an atmosphere and control the environment - or climate - at a planet's surface. These include both reactions within the atmosphere as well as exchange of energy, gases, and dust with the planet below and the solar system above; for Earth today, interactions with the biosphere and oceans are paramount. In view of the large changes in inputs of energy and gases that have occurred since planets began to form and the complexity of the chemistry, it is not surprising that planetary climates have changed greatly and are continuing to change.

  1. Evolution was chemically constrained.

    PubMed

    Williams, R J P; Fraústo Da Silva, J J R

    2003-02-01

    The objective of this paper is to present a systems view of the major features of biological evolution based upon changes in internal chemistry and uses of cellular space, both of which it will be stated were dependent on the changing chemical environment. The account concerns the major developments from prokaryotes to eukaryotes, to multi-cellular organisms, to animals with nervous systems and a brain, and finally to human beings and their uses of chemical elements in space outside themselves. It will be stated that the changes were in an inevitable progression, and were not just due to blind chance, so that "random searching" by a coded system to give species had a fixed overall route. The chemical sequence is from a reducing to an ever-increasingly oxidizing environment, while organisms retained reduced chemicals. The process was furthered recently by human beings who have also increased the range of reduced products trapped on Earth in novel forms. All the developments are brought about from the nature of the chemicals which organisms accumulate using the environment and its changes. The relationship to the manner in which particular species (gene sequences) were coincidentally changed, the molecular view of evolution, is left for additional examination. There is a further issue in that the changes of the chemistry of the environment developed largely at equilibrium due to the relatively fast reactions there of the available inorganic chemicals. Inside cells, some of these same chemicals also came to equilibrium within compounds. All such equilibria reduced the variance (degrees of freedom) of the total environmental/biological system and its possible development. However, the more sophisticated organic chemistry, almost totally inside cells until humans evolved, is kinetically controlled and limited by the demands of cellular reduction necessary to produce essential chemicals and by the availability of certain elements and energy. Hence the variability of

  2. The evolution of nucleotides

    NASA Technical Reports Server (NTRS)

    Usher, D. A.; Needels, M. C.

    1986-01-01

    Examples of chiral selection in nonenzymatic aminoacylation of internal 2-prime hydroxyl groups of oligo- and polynucleotides are discussed as an evidence for the early evolution of bionucleotides. Some factors that could influence the degree of this chiral selection and its direction are discussed. These include the structure of the aminoacyl component, the structure of the nucleoside component, and the reaction conditions. Investigation of the mechanism of this reaction was aided by the use of 3-prime inosine methyl phosphate (as a simplified model for a dinucleoside monophosphate) and proton NMR spectroscopy of t-butoxycarbonyl-alanyl esters of nucleosides as models for the transition state of the aminoacylation reaction itself.

  3. Galaxy evolution. Galactic paleontology.

    PubMed

    Tolstoy, Eline

    2011-07-01

    Individual low-mass stars have very long lives, comparable to the age of the universe, and can thus be used to probe ancient star formation. At present, such stars can be identified and studied only in the Milky Way and in the very closest of our neighboring galaxies, which are predominantly small dwarf galaxies. These nearby ancient stars are a fossil record that can provide detailed information about the physical processes that dominated the epoch of galaxy formation and subsequent evolution. PMID:21737732

  4. Is evolution finished?

    PubMed

    Davison, John A

    2004-01-01

    Since speciation seems to be no longer in progress, one is compelled to conclude that sexual reproduction is incompetent as a macroevolutionary device. I propose that the reason some might insist that evolution is still in progress stems primarily from the influence of two authorities, the geologist Charles Lyell, with his doctrine of uniformitarianism and Gregor Mendel, the discoverer of sexually mediated transmission genetics. William Bateson, the father of modern genetics, clearly foresaw the failure of Mendelism to explain macroevolutionary change, a perspective with which I am in full agreement. PMID:15648214

  5. Glossogeny and phylogeny: cultural evolution meets genetic evolution.

    PubMed

    Fitch, W Tecumseh

    2008-08-01

    Evolutionary theorists since Darwin have been interested in the parallels and interactions between biological and cultural evolution. Recent applications of empirical techniques originally developed to analyze molecular genetic data to linguistic data offer new insights into the historical evolution of language, revealing fascinating parallels between language change and biological evolution. This work offers considerable potential toward unified theories of genetic and cultural change. PMID:18585817

  6. Intron Evolution in Saccharomycetaceae

    PubMed Central

    Hooks, Katarzyna B.; Delneri, Daniela; Griffiths-Jones, Sam

    2014-01-01

    Introns in protein-coding genes are very rare in hemiascomycetous yeast genomes. It has been suggested that these species have experienced extensive intron loss during their evolution from the postulated intron-rich fungal ancestor. However, no intron-devoid yeast species have been identified and some of the introns remaining within the genomes of intron-poor species, such as Saccharomyces cerevisiae, appear to be beneficial during growth under stress conditions. In order to reveal the pattern of intron retention within intron-poor yeast species and better understand the mechanisms of intron evolution, we generated a comprehensive set of 250 orthologous introns in the 20 species that comprise the Saccharomycetaceae, by analyzing RNA deep-sequencing data and alignments of intron-containing genes. Analysis of these intron sets shows that intron loss is at least two orders of magnitude more frequent than intron gain. Fine mapping of intron positions shows that intron sliding is rare, and that introns are almost always removed without changing the primary sequence of the encoded protein. The latter finding is consistent with the prevailing view that homologous recombination between reverse-transcribed mature mRNAs and the corresponding genomic locus is the primary mechanism of intron loss. However, we also find evidence that loss of a small number of introns is mediated by micro-homology, and that the number of intron losses is diminished in yeast species that have lost the microhomology end joining and nonhomologous end joining machinery. PMID:25364803

  7. Introns in gene evolution.

    PubMed

    Fedorova, Larisa; Fedorov, Alexei

    2003-07-01

    Introns are integral elements of eukaryotic genomes that perform various important functions and actively participate in gene evolution. We review six distinct roles of spliceosomal introns: (1) sources of non-coding RNA; (2) carriers of transcription regulatory elements; (3) actors in alternative and trans-splicing; (4) enhancers of meiotic crossing over within coding sequences; (5) substrates for exon shuffling; and (6) signals for mRNA export from the nucleus and nonsense-mediated decay. We consider transposable capacities of introns and the current state of the long-lasting debate on the 'early-or-late' origin of introns. Cumulative data on known types of contemporary exon shuffling and the estimation of the size of the underlying exon universe are also discussed. We argue that the processes central to introns-early (exon shuffling) and introns-late (intron insertion) theories are entirely compatible. Each has provided insight: the latter through elucidating the transposon capabilities of introns, and the former through understanding the importance of introns in genomic recombination leading to gene rearrangements and evolution. PMID:12868603

  8. Evolution of molecular clouds

    NASA Technical Reports Server (NTRS)

    Sevenster, M.

    1993-01-01

    The evolution of interstellar molecular hydrogen was studied, with a special interest for the formation and evolution of molecular clouds and star formation within them, by a two-dimensional hydrodynamical simulation performed on a rectangular grid of physical sizes on the order of 100 pc. It is filled with an initial density of approx. 1 cm(exp -3), except for one cell (approx. 1 pc(exp 2)) at the center of the grid where an accretion core of 1-10(exp 3) solar masses is placed. The grid is co-moving with the gridcenter that is on a circular orbit around the Galactic center and that also is the guiding center of epicyclic approximation of orbits of the matter surrounding it. The initial radial velocity is zero; to account for differential rotation the initial tangential velocity (i.e. the movement around the galactic center) is proportional to the radial distance to the grid center. The rate is comparable to the rotation rate at the Local Standard of Rest. The influence of galactic rotation is noticed by spiral or elliptical forms, but on much longer time scales than self gravitation and cooling processes. Density and temperature are kept constant at the boundaries and no inflow is allowed along the tangential boundaries.

  9. Evolution of Oxygenic Photosynthesis

    NASA Astrophysics Data System (ADS)

    Fischer, Woodward W.; Hemp, James; Johnson, Jena E.

    2016-06-01

    The origin of oxygenic photosynthesis was the most important metabolic innovation in Earth history. It allowed life to generate energy and reducing power directly from sunlight and water, freeing it from the limited resources of geochemically derived reductants. This greatly increased global primary productivity and restructured ecosystems. The release of O2 as an end product of water oxidation led to the rise of oxygen, which dramatically altered the redox state of Earth's atmosphere and oceans and permanently changed all major biogeochemical cycles. Furthermore, the biological availability of O2 allowed for the evolution of aerobic respiration and novel biosynthetic pathways, facilitating much of the richness we associate with modern biology, including complex multicellularity. Here we critically review and synthesize information from the geological and biological records for the origin and evolution of oxygenic photosynthesis. Data from both of these archives illustrate that this metabolism first appeared in early Paleoproterozoic time and, despite its biogeochemical prominence, is a relatively late invention in the context of our planet's history.

  10. Nucleosynthesis and Stellar Evolution

    NASA Astrophysics Data System (ADS)

    Woosley, S. E.

    Preface I. Nuclear Astrophysics Nuclear cross sections Nuclear reaction rates Approximations to reaction rates for heavy nuclei Nuclear reaction networks II. Nuclear Reactions During Advanced Burning Stages of Massive Stars Carbon burning Neon burning Oxygen burning Silicon burning Nuclear statistical equilibrium (NSE) NSE network calculations Equilibrium at high densities III. Approximate Thermodynamic Conditions for Advanced Burning Stages in Massive Stars Burning in hydrostatic equilibrium Explosive burning conditions IV. Parametrized Network Calculations of Nucleosynthesis Helium Burning Carbon burning Neon burning Oxygen burning Silicon burning Summary V. Classical Novae and X-ray Bursts Classical novae Parametrized nucleosynthesis calculations Numerical calculations of a model nova Type I X-ray bursts VI. The Evolution of Massive Stars; M >= 8 Msun Stars that become type II supernovae Computer results Nucleosynthesis in pre-supernova stars The evolution to instability of more massive stars VII. Type II Supernovae Light curves and spectra of type II supernovae The type II explosion mechanism: core collapse and bounce "Delayed" explosions The role of rotation Nucleosynthesis in type II supernovae Unusual type II supernovae and "type III" supernovae VIII. Type I Supernovae General thermonuclear models The current standard model Nucleosynthesis in the standard model Spectral synthesis in type I supernovae Peculiar Type I's More on the physics of carbon ignition: flame propagation the conductive velocity the "turbulent" flame velocity Carbon detonation: The phase velocity and "spontaneous combustion" Initial conditions References

  11. Archaeology and cognitive evolution.

    PubMed

    Wynn, Thomas

    2002-06-01

    Archaeology can provide two bodies of information relevant to the understanding of the evolution of human cognition--the timing of developments, and the evolutionary context of these developments. The challenge is methodological. Archaeology must document attributes that have direct implications for underlying cognitive mechanisms. One example of such a cognitive archaeology is found in spatial cognition. The archaeological record documents an evolutionary sequence that begins with ape-equivalent spatial abilities 2.5 million years ago and ends with the appearance of modern abilities in the still remote past of 400,000 years ago. The timing of these developments reveals two major episodes in the evolution in spatial ability, one, 1.5 million years ago and the other, one million years later. The two episodes of development in spatial cognition had very different evolutionary contexts. The first was associated with the shift to an open country adaptive niche that occurred early in the time range of Homo erectus. The second was associated with no clear adaptive shift, though it does appear to have coincided with the invasion of more hostile environments and the appearance of systematic hunting of large mammals. Neither, however, occurred in a context of modern hunting and gathering. PMID:12879699

  12. Hox genes and evolution

    PubMed Central

    Hrycaj, Steven M.; Wellik, Deneen M.

    2016-01-01

    Hox proteins are a deeply conserved group of transcription factors originally defined for their critical roles in governing segmental identity along the antero-posterior (AP) axis in Drosophila. Over the last 30 years, numerous data generated in evolutionarily diverse taxa have clearly shown that changes in the expression patterns of these genes are closely associated with the regionalization of the AP axis, suggesting that Hox genes have played a critical role in the evolution of novel body plans within Bilateria. Despite this deep functional conservation and the importance of these genes in AP patterning, key questions remain regarding many aspects of Hox biology. In this commentary, we highlight recent reports that have provided novel insight into the origins of the mammalian Hox cluster, the role of Hox genes in the generation of a limbless body plan, and a novel putative mechanism in which Hox genes may encode specificity along the AP axis. Although the data discussed here offer a fresh perspective, it is clear that there is still much to learn about Hox biology and the roles it has played in the evolution of the Bilaterian body plan. PMID:27239281

  13. Geometry Genetics and Evolution

    NASA Astrophysics Data System (ADS)

    Siggia, Eric

    2011-03-01

    Darwin argued that highly perfected organs such as the vertebrate eye could evolve by a series of small changes, each of which conferred a selective advantage. In the context of gene networks, this idea can be recast into a predictive algorithm, namely find networks that can be built by incremental adaptation (gradient search) to perform some task. It embodies a ``kinetic'' view of evolution where a solution that is quick to evolve is preferred over a global optimum. Examples of biochemical kinetic networks were evolved for temporal adaptation, temperature compensated entrainable clocks, explore-exploit trade off in signal discrimination, will be presented as well as networks that model the spatially periodic somites (vertebrae) and HOX gene expression in the vertebrate embryo. These models appear complex by the criterion of 19th century applied mathematics since there is no separation of time or spatial scales, yet they are all derivable by gradient optimization of simple functions (several in the Pareto evolution) often based on the Shannon entropy of the time or spatial response. Joint work with P. Francois, Physics Dept. McGill University. With P. Francois, Physics Dept. McGill University

  14. Heat freezes niche evolution.

    PubMed

    Araújo, Miguel B; Ferri-Yáñez, Francisco; Bozinovic, Francisco; Marquet, Pablo A; Valladares, Fernando; Chown, Steven L

    2013-09-01

    Climate change is altering phenology and distributions of many species and further changes are projected. Can species physiologically adapt to climate warming? We analyse thermal tolerances of a large number of terrestrial ectotherm (n = 697), endotherm (n = 227) and plant (n = 1816) species worldwide, and show that tolerance to heat is largely conserved across lineages, while tolerance to cold varies between and within species. This pattern, previously documented for ectotherms, is apparent for this group and for endotherms and plants, challenging the longstanding view that physiological tolerances of species change continuously across climatic gradients. An alternative view is proposed in which the thermal component of climatic niches would overlap across species more than expected. We argue that hard physiological boundaries exist that constrain evolution of tolerances of terrestrial organisms to high temperatures. In contrast, evolution of tolerances to cold should be more frequent. One consequence of conservatism of upper thermal tolerances is that estimated niches for cold-adapted species will tend to underestimate their upper thermal limits, thereby potentially inflating assessments of risk from climate change. In contrast, species whose climatic preferences are close to their upper thermal limits will unlikely evolve physiological tolerances to increased heat, thereby being predictably more affected by warming. PMID:23869696

  15. Modeling Protein Evolution

    NASA Astrophysics Data System (ADS)

    Goldstein, Richard; Pollock, David

    The study of biology is fundamentally different from many other scientific pursuits, such as geology or astrophysics. This difference stems from the ubiquitous questions that arise about function and purpose. These are questions concerning why biological objects operate the way they do: what is the function of a polymerase? What is the role of the immune system? No one, aside from the most dedicated anthropist or interventionist theist, would attempt to determine the purpose of the earth's mantle or the function of a binary star. Among the sciences, it is only biology in which the details of what an object does can be said to be part of the reason for its existence. This is because the process of evolution is capable of improving an object to better carry out a function; that is, it adapts an object within the constraints of mechanics and history (i.e., what has come before). Thus, the ultimate basis of these biological questions is the process of evolution; generally, the function of an enzyme, cell type, organ, system, or trait is the thing that it does that contributes to the fitness (i.e., reproductive success) of the organism of which it is a part or characteristic. Our investigations cannot escape the simple fact that all things in biology (including ourselves) are, ultimately, the result of an evolutionary process.

  16. Concrete Chemical Evolution

    SciTech Connect

    D.H. Tang

    1998-07-31

    The objectives of this analysis are to discuss and evaluate testing results that were performed for the M&O by the Pennsylvania State University (PSU) to evaluate the potential long-term evolution of organic admixtures in cementitious materials at elevated temperatures. The testing was designed to help provide a basis for a determination by the Performance Assessment group (PA) of the long-term acceptability and longevity of cementitious materials for repository use. The main purpose of the testing was to assess the evolution of gases (especially CO{sub 2}) from hydrated cement paste at elevated temperatures and to determine the impact on alkalinity, i.e., the pH value of cement paste pore solution. This information in turn can be used as scoping information to determine if further tests of this nature are needed to support PA. As part of this discussion and evaluation of the PSU results, an assessment of alkalinity in a ''cementitious repository'' and an evaluation of organic materials are presented.

  17. Student Visual Communication of Evolution

    NASA Astrophysics Data System (ADS)

    Oliveira, Alandeom W.; Cook, Kristin

    2016-05-01

    Despite growing recognition of the importance of visual representations to science education, previous research has given attention mostly to verbal modalities of evolution instruction. Visual aspects of classroom learning of evolution are yet to be systematically examined by science educators. The present study attends to this issue by exploring the types of evolutionary imagery deployed by secondary students. Our visual design analysis revealed that students resorted to two larger categories of images when visually communicating evolution: spatial metaphors (images that provided a spatio-temporal account of human evolution as a metaphorical "walk" across time and space) and symbolic representations ("icons of evolution" such as personal portraits of Charles Darwin that simply evoked evolutionary theory rather than metaphorically conveying its conceptual contents). It is argued that students need opportunities to collaboratively critique evolutionary imagery and to extend their visual perception of evolution beyond dominant images.

  18. Evolution across the Curriculum: Microbiology.

    PubMed

    Burmeister, Alita R; Smith, James J

    2016-05-01

    An integrated understanding of microbiology and evolutionary biology is essential for students pursuing careers in microbiology and healthcare fields. In this Perspective, we discuss the usefulness of evolutionary concepts and an overall evolutionary framework for students enrolled in microbiology courses. Further, we propose a set of learning goals for students studying microbial evolution concepts. We then describe some barriers to microbial evolution teaching and learning and encourage the continued incorporation of evidence-based teaching practices into microbiology courses at all levels. Next, we review the current status of microbial evolution assessment tools and describe some education resources available for teaching microbial evolution. Successful microbial evolution education will require that evolution be taught across the undergraduate biology curriculum, with a continued focus on applications and applied careers, while aligning with national biology education reform initiatives. Journal of Microbiology & Biology Education. PMID:27158306

  19. Evolution across the Curriculum: Microbiology

    PubMed Central

    Burmeister, Alita R.; Smith, James J.

    2016-01-01

    An integrated understanding of microbiology and evolutionary biology is essential for students pursuing careers in microbiology and healthcare fields. In this Perspective, we discuss the usefulness of evolutionary concepts and an overall evolutionary framework for students enrolled in microbiology courses. Further, we propose a set of learning goals for students studying microbial evolution concepts. We then describe some barriers to microbial evolution teaching and learning and encourage the continued incorporation of evidence-based teaching practices into microbiology courses at all levels. Next, we review the current status of microbial evolution assessment tools and describe some education resources available for teaching microbial evolution. Successful microbial evolution education will require that evolution be taught across the undergraduate biology curriculum, with a continued focus on applications and applied careers, while aligning with national biology education reform initiatives. Journal of Microbiology & Biology Education PMID:27158306

  20. The evolution of dominance.

    PubMed

    Bourguet, D

    1999-07-01

    The evolution of dominance has been subject to intensive debate since Fisher first argued that modifiers would be selected for if they made wild-type alleles more dominant over mutant alleles. An alternative explanation, put forward by Wright, is that the commonly observed dominance of wild-type alleles is simply a physiological consequence of metabolic pathways. Wright's explanation has gained support over the years, largely ending the debate over the general recessivity of deleterious mutations. Nevertheless there is reason to believe that dominance relationships have been moulded by natural selection to some extent. First, the metabolic pathways are themselves products of evolutionary processes that may have led them to be more stable to perturbations, including mutations. Secondly, theoretical models and empirical experiments suggest that substantial selection for dominance modifiers exists during the spread of adaptive alleles or when a polymorphism is maintained either by overdominant selection or by migration-selection balance. PMID:10447697

  1. Evolution of microbial markets

    PubMed Central

    Werner, Gijsbert D. A.; Strassmann, Joan E.; Ivens, Aniek B. F.; Engelmoer, Daniel J. P.; Verbruggen, Erik; Queller, David C.; Noë, Ronald; Johnson, Nancy Collins; Hammerstein, Peter; Kiers, E. Toby

    2014-01-01

    Biological market theory has been used successfully to explain cooperative behavior in many animal species. Microbes also engage in cooperative behaviors, both with hosts and other microbes, that can be described in economic terms. However, a market approach is not traditionally used to analyze these interactions. Here, we extend the biological market framework to ask whether this theory is of use to evolutionary biologists studying microbes. We consider six economic strategies used by microbes to optimize their success in markets. We argue that an economic market framework is a useful tool to generate specific and interesting predictions about microbial interactions, including the evolution of partner discrimination, hoarding strategies, specialized versus diversified mutualistic services, and the role of spatial structures, such as flocks and consortia. There is untapped potential for studying the evolutionary dynamics of microbial systems. Market theory can help structure this potential by characterizing strategic investment of microbes across a diversity of conditions. PMID:24474743

  2. Evolution and climate variability

    SciTech Connect

    Potts, R.

    1996-08-16

    Variations in organisms are preserved and accrue if there is a consistent bias in selection over many generations. This idea of long-term directional selection has been embraced to explain major adaptive change. It is widely thought that important adaptive shifts in hominids corresponded with directional environmental change. This view, which echoes the savanna scenario of hominid evolution, has strongly been supported by paleontologists and paleoclimatologists over the past decade. The origin of the hominids, bipedality, stone toolmaking, and brain size increase have all been related to cooling, aridification, and savanna expansion. However there appears to be a more prominent signal than the aridity trend: an increase in the range of climatic variation over time. This article discusses the possible reprocussions of this interpertation. 13 refs.

  3. Evolution of Metals

    NASA Astrophysics Data System (ADS)

    Shull, J. M.

    1998-05-01

    This review will cover a mystery story. Actually, two mysteries of the Structure and Evolution of the Universe involving the history of the baryons and the chemical elements synthesized in the first stars. When did the gas and metals first form? How did they evolve to their current distribution? The original crime scene is unknown, but evidence has been collected in the diffuse intergalactic medium and in hot intracluster gas. In these scattered locales, large amounts of gas has accumulated, contaminated by heavy elements from the first stars. Unfortunately, some of the evidence has been destroyed by gravity. Also, the earliest quasars, massive stars, and supernovae altered the physical state of the gas and transported the elements far from the original scene. I will briefly review current observations and theories relevant to these processes and suggest ways in which future NASA missions could constrain the many speculative ideas on this subject.

  4. Evolution of working memory.

    PubMed

    Carruthers, Peter

    2013-06-18

    Working memory (WM) is fundamental to many aspects of human life, including learning, speech and text comprehension, prospection and future planning, and explicit "system 2" forms of reasoning, as well as overlapping heavily with fluid general intelligence. WM has been intensively studied for many decades, and there is a growing consensus about its nature, its components, and its signature limits. Remarkably, given its central importance in human life, there has been very little comparative investigation of WM abilities across species. Consequently, much remains unknown about the evolution of this important human capacity. Some questions can be tentatively answered from the existing comparative literature. Even studies that were not intended to do so can nonetheless shed light on the WM capacities of nonhuman animals. However, many questions remain. PMID:23754428

  5. Early stellar evolution

    NASA Technical Reports Server (NTRS)

    Stahler, Steven W.

    1994-01-01

    Research into the formation and early evolution of stars is currently an area of great interest and activity. The theoretical and observational foundations for this development are reviewed in this paper. By now, the basic physics governing cloud collapse is well understood, as is the structure of the resulting protostars. However, the theory predicts protostellar luminosities that are greater than those of most infrared sources. Observationally, it is thought that protostars emit powerful winds that push away remnant cloud gas, but both the origin of these winds and the nature of their interaction with ambient gas are controversial. Finally, the theory of pre-main-sequence stars has been modified to incorporate more realistic initial conditions. This improvement helps to explain the distribution of such stars in the H-R diagram. Many important issues, such as the origin of binary stars and stellar clusters, remain as challenges for future research.

  6. Evolution and public health

    PubMed Central

    Omenn, Gilbert S.

    2009-01-01

    Evolution and its elements of natural selection, population migration, genetic drift, and founder effects have shaped the world in which we practice public health. Human cultures and technologies have modified life on this planet and have coevolved with myriad other species, including microorganisms; plant and animal sources of food; invertebrate vectors of disease; and intermediate hosts among birds, mammals, and nonhuman primates. Molecular mechanisms of differential resistance or susceptibility to infectious agents or diets have evolved and are being discovered with modern methods. Some of these evolutionary relations require a perspective of tens of thousands of years, whereas other changes are observable in real time. The implications and applications of evolutionary understanding are important to our current programs and policies for infectious disease surveillance, gene–environment interactions, and health disparities globally. PMID:19966311

  7. Evolution of Biological Complexity

    NASA Astrophysics Data System (ADS)

    Goldstein, Raymond E.

    It is a general rule of nature that larger organisms are more complex, at least as measured by the number of distinct types of cells present. This reflects the fitness advantage conferred by a division of labor among specialized cells over homogeneous totipotency. Yet, increasing size has both costs and benefits, and the search for understanding the driving forces behind the evolution of multicellularity is becoming a very active area of research. This article presents an overview of recent experimental and theoretical work aimed at understanding this biological problem from the perspective of physics. For a class of model organisms, the Volvocine green algae, an emerging hypothesis connects the transition from organisms with totipotent cells to those with terminal germ-soma differentiation to the competition between diffusion and fluid advection created by beating flagella. A number of challenging problems in fluid dynamics, nonlinear dynamics, and control theory emerge when one probes the workings of the simplest multicellular organisms.

  8. Evolution of working memory

    PubMed Central

    Carruthers, Peter

    2013-01-01

    Working memory (WM) is fundamental to many aspects of human life, including learning, speech and text comprehension, prospection and future planning, and explicit “system 2” forms of reasoning, as well as overlapping heavily with fluid general intelligence. WM has been intensively studied for many decades, and there is a growing consensus about its nature, its components, and its signature limits. Remarkably, given its central importance in human life, there has been very little comparative investigation of WM abilities across species. Consequently, much remains unknown about the evolution of this important human capacity. Some questions can be tentatively answered from the existing comparative literature. Even studies that were not intended to do so can nonetheless shed light on the WM capacities of nonhuman animals. However, many questions remain. PMID:23754428

  9. Evolution and Impartiality*

    PubMed Central

    Kahane, Guy

    2014-01-01

    Lazari-Radek and Singer argue that evolutionary considerations can resolve Sidgwick’s dualism of practical reason, because such considerations debunk moral views that give weight to self-interested or partial considerations, but cannot threaten the principle Universal Benevolence. I argue that even if we grant these claims, this appeal to evolution is ultimately self-defeating. Lazari-Radek and Singer face a dilemma. Either their evolutionary argument against partial morality succeeds, but then we need to also give up our conviction that suffering is bad; or there is a way to defend this conviction, but then their argument against partiality fails. Utilitarians, I suggest, should resist the temptation to appeal to evolutionary debunking arguments. PMID:24711673

  10. [Metalworking industry management evolution].

    PubMed

    Mattucci, Massimo

    2011-01-01

    Analysis of the evolution drivers of the management systems in the metalworking industry, mainly characterized as "automotive", starting with the "mass production" model, followed for the development of Italian industry in the '50. Through the socio-economic changes of the '90/10, the metalworking plants were deeply restructured with the introduction of computers in the production systems, and then with the first global benchmarks such as the "lean production", towards the needed operational flexibility to respond to the market dynamics. Plants change radically, company networks become real, ICT services are fundamental elements for the integration. These trends help visualizing a new "Factory of the Future" for the years 2020/30, where the competition will be based on the socio-economical, technological and environmental factors included in the "Competitive Sustainable Manufacturing" paradigm. PMID:22073665

  11. Evolution of biological information.

    PubMed

    Schneider, T D

    2000-07-15

    How do genetic systems gain information by evolutionary processes? Answering this question precisely requires a robust, quantitative measure of information. Fortunately, 50 years ago Claude Shannon defined information as a decrease in the uncertainty of a receiver. For molecular systems, uncertainty is closely related to entropy and hence has clear connections to the Second Law of Thermodynamics. These aspects of information theory have allowed the development of a straightforward and practical method of measuring information in genetic control systems. Here this method is used to observe information gain in the binding sites for an artificial 'protein' in a computer simulation of evolution. The simulation begins with zero information and, as in naturally occurring genetic systems, the information measured in the fully evolved binding sites is close to that needed to locate the sites in the genome. The transition is rapid, demonstrating that information gain can occur by punctuated equilibrium. PMID:10908337

  12. SIM Configuration Evolution

    NASA Technical Reports Server (NTRS)

    Aaron, Kim M.

    2000-01-01

    The Space Interferometry Mission (SIM) is a space-based 10 m baseline Michelson interferometer. Planned for launch in 2005 aboard a Delta III launch vehicle, or equivalent, its primary objective is to measure the positions of stars and other celestial objects with an unprecedented accuracy of 4 micro arc seconds. With such an instrument, tremendous advancement can be expected in our understanding of stellar and galactic dynamics. Using triangulation from opposite sides of the orbit around the sun (i.e. by using parallax) one can measure the distance to any observable object in our galaxy. By directly measuring the orbital wobble of nearby stars, the mass and orbit of planets can be determined over a wide range of parameters. The distribution of velocity within nearby galaxies will be measurable. Observations of these and other objects will improve the calibration of distance estimators by more than an order of magnitude. This will permit a much better determination of the Hubble Constant as well as improving our overall understanding of the evolution of the universe. SIM has undergone several transformations, especially over the past year and a half since the start of Phase A. During this phase of a project, it is desirable to perform system-level trade studies, so the substantial evolution of the design that has occurred is quite appropriate. Part of the trade-off process has addressed two major underlying architectures: SIM Classic; and Son of SIM. The difference between these two architectures is related to the overall arrangement of the optical elements and the associated metrology system. Several different configurations have been developed for each architecture. Each configuration is the result of design choices that are influenced by many competing considerations. Some of the more important aspects will be discussed. The Space Interferometry Mission has some extremely challenging goals: millikelvin thermal stability, nanometer stabilization of optics

  13. Evolution of filament barbs.

    NASA Astrophysics Data System (ADS)

    Liu, R.; Xu, Y.; Wang, H.

    We present a selected few cases in which the sense of chirality of filament barbs changed within periods as short as hours. We investigate in detail a quiescent filament on 2003 September 10 and 11. Of its four barbs displaying such changes, only one overlays a small polarity inversion line inside the EUV filament channel (EFC). No magnetic elements with magnitude above the noise level were detected at the endpoints of all barbs. In particular, a pair of barbs first approached toward, and then departed from, each other in Halpha , with the barb endpoints migrating as far as ˜ 10 arcsec. We conclude that the evolution of the barbs was driven by flux emergence and cancellation of small bipolar units at the EFC border.

  14. Viral Quasispecies Evolution

    PubMed Central

    Sheldon, Julie; Perales, Celia

    2012-01-01

    Summary: Evolution of RNA viruses occurs through disequilibria of collections of closely related mutant spectra or mutant clouds termed viral quasispecies. Here we review the origin of the quasispecies concept and some biological implications of quasispecies dynamics. Two main aspects are addressed: (i) mutant clouds as reservoirs of phenotypic variants for virus adaptability and (ii) the internal interactions that are established within mutant spectra that render a virus ensemble the unit of selection. The understanding of viruses as quasispecies has led to new antiviral designs, such as lethal mutagenesis, whose aim is to drive viruses toward low fitness values with limited chances of fitness recovery. The impact of quasispecies for three salient human pathogens, human immunodeficiency virus and the hepatitis B and C viruses, is reviewed, with emphasis on antiviral treatment strategies. Finally, extensions of quasispecies to nonviral systems are briefly mentioned to emphasize the broad applicability of quasispecies theory. PMID:22688811

  15. Evolution and Impartiality.

    PubMed

    Kahane, Guy

    2014-01-01

    Lazari-Radek and Singer argue that evolutionary considerations can resolve Sidgwick's dualism of practical reason, because such considerations debunk moral views that give weight to self-interested or partial considerations, but cannot threaten the principle Universal Benevolence. I argue that even if we grant these claims, this appeal to evolution is ultimately self-defeating. Lazari-Radek and Singer face a dilemma. Either their evolutionary argument against partial morality succeeds, but then we need to also give up our conviction that suffering is bad; or there is a way to defend this conviction, but then their argument against partiality fails. Utilitarians, I suggest, should resist the temptation to appeal to evolutionary debunking arguments. PMID:24711673

  16. The evolution of inequality.

    PubMed

    Mattison, Siobhán M; Smith, Eric A; Shenk, Mary K; Cochrane, Ethan E

    2016-07-01

    Understanding how systems of political and economic inequality evolved from relatively egalitarian origins has long been a focus of anthropological inquiry. Many hypotheses have been suggested to link socio-ecological features with the rise and spread of inequality, and empirical tests of these hypotheses in prehistoric and extant societies are increasing. In this review, we synthesize several streams of theory relevant to understanding the evolutionary origins, spread, and adaptive significance of inequality. We argue that while inequality may be produced by a variety of localized processes, its evolution is fundamentally dependent on the economic defensibility and transmissibility of wealth. Furthermore, these properties of wealth could become persistent drivers of inequality only following a shift to a more stable climate in the Holocene. We conclude by noting several key areas for future empirical research, emphasizing the need for more analyses of contemporary shifts toward institutionalized inequality as well as prehistoric cases. PMID:27519458

  17. Evolution of microbial markets.

    PubMed

    Werner, Gijsbert D A; Strassmann, Joan E; Ivens, Aniek B F; Engelmoer, Daniel J P; Verbruggen, Erik; Queller, David C; Noë, Ronald; Johnson, Nancy Collins; Hammerstein, Peter; Kiers, E Toby

    2014-01-28

    Biological market theory has been used successfully to explain cooperative behavior in many animal species. Microbes also engage in cooperative behaviors, both with hosts and other microbes, that can be described in economic terms. However, a market approach is not traditionally used to analyze these interactions. Here, we extend the biological market framework to ask whether this theory is of use to evolutionary biologists studying microbes. We consider six economic strategies used by microbes to optimize their success in markets. We argue that an economic market framework is a useful tool to generate specific and interesting predictions about microbial interactions, including the evolution of partner discrimination, hoarding strategies, specialized versus diversified mutualistic services, and the role of spatial structures, such as flocks and consortia. There is untapped potential for studying the evolutionary dynamics of microbial systems. Market theory can help structure this potential by characterizing strategic investment of microbes across a diversity of conditions. PMID:24474743

  18. Chemical evolution in space

    NASA Technical Reports Server (NTRS)

    Greenberg, J. M.

    1984-01-01

    Most of the complex molecules in interstellar space ar probably contained in small, frozen interstellar dust grains which are about as old as the earth and have been photochemically converted into large organic molecules. These molecules' maximum molecular weight is limited only by the approximately 0.1-micron grain size. Their evolution leads from cool, evolved stellar atmospheres' formation of seedlings to destruction through incorporation into the material of new stars. Organic dust constitutes about 0.1 percent of the total mass of the Milky Way, far outweighing any estimates of total planetary mass in the Galaxy. Because comets may be virtually pure, aggregated interstellar dust, they offer a source of interstellar organic material for detailed study.

  19. Evolution education in Canada's museums: Where is human evolution?

    NASA Astrophysics Data System (ADS)

    Bean, Sarah

    While an interest in the origin of human beings may be a cultural universal, there are various views and beliefs about how this event took place. In Canada, a recent (2010) Angus Reid survey revealed that only 61% of Canadians accepted that humans evolved over millions of years; 39% of the population either believed in creationism or did not accept evolution as a scientific fact. These statistics suggest that human evolution education is a topic that needs to be addressed. This thesis investigates the role of museums in public education about human evolution. Prior to this study, the number of Canadian museums with exhibits about this topic was unknown. Sixteen Canadian museums participated in this study, and the results demonstrated that only two had permanent exhibits on human evolution, and one creationist museum presented a biblically-based account of human origins. Here, it is argued that more of Canada's museums should consider incorporating human evolution education into their mandates.

  20. Palaeoenvironments and hominoid evolution.

    PubMed

    Pickford, Martin

    2002-03-01

    One of the key features that separates humans and their closest relatives (extinct species of the genus Homo and Praeanthropus and the australopithecines Australopithecus and Paranthropus) on the one hand, from the other hominoids, on the other, is their obligate bipedal locomotion when on the ground. This major difference from the generally quadrupedal locomotion practiced by other hominoids (Pan, Gorilla, Pongo and many extinct lineages) is reflected in many parts of the body, including all the major bones in the legs, arms, trunk and cranium. Locomotion has thus been of major interest to those interested in human origins, evolution, classification and phylogeny. A major hurdle to studies of the origins of bipedalism concerns the paucity of African hominoid fossils between 15 Ma, when all the adequately known hominoids were quadrupedal (most were pronograde, but at least one lineage was orthograde), and 4.2 Ma by which time fully bipedal hominids were established in Africa. Examination of Old World geology and palaeontology reveals a great deal about the evolution of palaeoenvironments and faunas during this period, and it is suggested that hominids evolved bipedal locomotion at the same time that there was a fundamental reorganisation of faunas towards the end of the Miocene. This faunal turnover resulted in the establishment of faunal lineages of "modern" aspect in Africa at the expense of "archaic" lineages which either went extinct or suffered a diminution of diversity. Many of the "modern" lineages were adapted to open country habitats in which grass became a major component of the diet as shown by modifications in the cheek teeth. Hominoids, in contrast, retained their traditional diet but were obliged to forage over greater and greater areas in order to do so, and this tactic led to pressures to modify the locomotor system rather than the diet. If bipedal hominids originated during this period, then the family Hominidae (sensu stricto) dates from about 8

  1. Early bioenergetic evolution

    PubMed Central

    Sousa, Filipa L.; Thiergart, Thorsten; Landan, Giddy; Nelson-Sathi, Shijulal; Pereira, Inês A. C.; Allen, John F.; Lane, Nick; Martin, William F.

    2013-01-01

    Life is the harnessing of chemical energy in such a way that the energy-harnessing device makes a copy of itself. This paper outlines an energetically feasible path from a particular inorganic setting for the origin of life to the first free-living cells. The sources of energy available to early organic synthesis, early evolving systems and early cells stand in the foreground, as do the possible mechanisms of their conversion into harnessable chemical energy for synthetic reactions. With regard to the possible temporal sequence of events, we focus on: (i) alkaline hydrothermal vents as the far-from-equilibrium setting, (ii) the Wood–Ljungdahl (acetyl-CoA) pathway as the route that could have underpinned carbon assimilation for these processes, (iii) biochemical divergence, within the naturally formed inorganic compartments at a hydrothermal mound, of geochemically confined replicating entities with a complexity below that of free-living prokaryotes, and (iv) acetogenesis and methanogenesis as the ancestral forms of carbon and energy metabolism in the first free-living ancestors of the eubacteria and archaebacteria, respectively. In terms of the main evolutionary transitions in early bioenergetic evolution, we focus on: (i) thioester-dependent substrate-level phosphorylations, (ii) harnessing of naturally existing proton gradients at the vent–ocean interface via the ATP synthase, (iii) harnessing of Na+ gradients generated by H+/Na+ antiporters, (iv) flavin-based bifurcation-dependent gradient generation, and finally (v) quinone-based (and Q-cycle-dependent) proton gradient generation. Of those five transitions, the first four are posited to have taken place at the vent. Ultimately, all of these bioenergetic processes depend, even today, upon CO2 reduction with low-potential ferredoxin (Fd), generated either chemosynthetically or photosynthetically, suggesting a reaction of the type ‘reduced iron → reduced carbon’ at the beginning of bioenergetic evolution

  2. Case A Binary Evolution

    SciTech Connect

    Nelson, C A; Eggleton, P P

    2001-03-28

    We undertake a comparison of observed Algol-type binaries with a library of computed Case A binary evolution tracks. The library consists of 5500 binary tracks with various values of initial primary mass M{sub 10}, mass ratio q{sub 0}, and period P{sub 0}, designed to sample the phase-space of Case A binaries in the range -0.10 {le} log M{sub 10} {le} 1.7. Each binary is evolved using a standard code with the assumption that both total mass and orbital angular momentum are conserved. This code follows the evolution of both stars until the point where contact or reverse mass transfer occurs. The resulting binary tracks show a rich variety of behavior which we sort into several subclasses of Case A and Case B. We present the results of this classification, the final mass ratio and the fraction of time spent in Roche Lobe overflow for each binary system. The conservative assumption under which we created this library is expected to hold for a broad range of binaries, where both components have spectra in the range G0 to B1 and luminosity class III - V. We gather a list of relatively well-determined observed hot Algol-type binaries meeting this criterion, as well as a list of cooler Algol-type binaries where we expect significant dynamo-driven mass loss and angular momentum loss. We fit each observed binary to our library of tracks using a {chi}{sup 2}-minimizing procedure. We find that the hot Algols display overall acceptable {chi}{sup 2}, confirming the conservative assumption, while the cool Algols show much less acceptable {chi}{sup 2} suggesting the need for more free parameters, such as mass and angular momentum loss.

  3. Galaxy Formation and Evolution

    NASA Astrophysics Data System (ADS)

    Nagamine, Kentaro; Reddy, Naveen; Daddi, Emanuele; Sargent, Mark T.

    2016-07-01

    In this chapter, we discuss the current status of observational and computational studies on galaxy formation and evolution. In particular, a joint analysis of star-formation rates (SFRs), stellar masses, and metallicities of galaxies throughout cosmic time can shed light on the processes by which galaxies build up their stellar mass and enrich the environment with heavy elements. Comparison of such observations and the results of numerical simulations can give us insights on the physical importance of various feedback effects by supernovae and active galactic nuclei. In Sect. 1, we first discuss the primary methods used to deduce the SFRs, stellar masses, and (primarily) gas-phase metallicities in high-redshift galaxies. Then, we show how these quantities are related to each other and evolve with time. In Sect. 2, we further examine the distribution of SFRs in galaxies following the `Main Sequence' paradigm. We show how the so-called `starbursts' display higher specific SFRs and SF efficiencies by an order of magnitude. We use this to devise a simple description of the evolution of the star-forming galaxy population since z ˜3 that can successfully reproduce some of the observed statistics in the infrared (IR) wavelength. We also discuss the properties of molecular gas. In Sect. 3, we highlight some of the recent studies of high-redshift galaxy formation using cosmological hydrodynamic simulations. We discuss the physical properties of simulated galaxies such as luminosity function and escape fraction of ionizing photons, which are important statistics for reionization of the Universe. In particular the escape fraction of ionizing photons has large uncertainties, and studying gamma-ray bursts (which is the main topic of this conference) can also set observational constraints on this uncertain physical parameter as well as cosmic star formation rate density.

  4. Evolution of entomopathogenicity in fungi

    Technology Transfer Automated Retrieval System (TEKTRAN)

    As with all great and complex questions, no definitive answers are possible about the evolution of pathogenicity in general (an eternal question for mycologists!), much less about the evolution of fungal specialization to attack and to kill living insects or other arthropods. It does seem certain, h...

  5. Prolegomenon to patterns in evolution.

    PubMed

    Kauffman, Stuart A

    2014-09-01

    Despite Darwin, we remain children of Newton and dream of a grand theory that is epistemologically complete and would allow prediction of the evolution of the biosphere. The main purpose of this article is to show that this dream is false, and bears on studying patterns of evolution. To do so, I must justify the use of the word "function" in biology, when physics has only happenings. The concept of "function" lifts biology irreducibly above physics, for as we shall see, we cannot prestate the ever new biological functions that arise and constitute the very phase space of evolution. Hence, we cannot mathematize the detailed becoming of the biosphere, nor write differential equations for functional variables we do not know ahead of time, nor integrate those equations, so no laws "entail" evolution. The dream of a grand theory fails. In place of entailing laws, I propose a post-entailing law explanatory framework in which Actuals arise in evolution that constitute new boundary conditions that are enabling constraints that create new, typically unprestatable, adjacent possible opportunities for further evolution, in which new Actuals arise, in a persistent becoming. Evolution flows into a typically unprestatable succession of adjacent possibles. Given the concept of function, the concept of functional closure of an organism making a living in its world becomes central. Implications for patterns in evolution include historical reconstruction, and statistical laws such as the distribution of extinction events, or species per genus, and the use of formal cause, not efficient cause, laws. PMID:24704211

  6. America's Anti-Evolution Movement

    ERIC Educational Resources Information Center

    Moore, Randy

    2002-01-01

    Evolution is the cornerstone of biology and one of the most powerful, exciting, and well-supported laws in modern science. Evolution transforms biology from a collection of unrelated observations and definitions into a coherent discipline that, among other things, helps people understand life's history and predict answers to important research…

  7. Enzyme catalysis: Evolution made easy

    NASA Astrophysics Data System (ADS)

    Wee, Eugene J. H.; Trau, Matt

    2014-09-01

    Directed evolution is a powerful tool for the development of improved enzyme catalysts. Now, a method that enables an enzyme, its encoding DNA and a fluorescent reaction product to be encapsulated in a gel bead enables the application of directed evolution in an ultra-high-throughput format.

  8. The Molecular Basis of Evolution.

    ERIC Educational Resources Information Center

    Wilson, Allan C.

    1985-01-01

    Discovery that mutations accumulate at steady rates over time in the genes of all lineages of plants and animals has led to new insights into evolution at the molecular and organismal levels. Discusses molecular evolution, examining deoxyribonuclei acid (DNA) sequences, morphological distances, and codon rate of change. (DH)

  9. A Teaching Guide to Evolution

    ERIC Educational Resources Information Center

    Gregg, Thomas G.; Janssen, Gary R.; Bhattacharjee, J.K.

    2003-01-01

    Evolution is considered by virtually all biologists to be the central unifying principle of biology, yet its fundamental concepts are not widely understood or widely disseminated. Teaching evolution--defined as descent with modification from a common ancestor as a result of natural selection acting on genetic variation--has traditionally been a…

  10. Evolution: Understanding Life on Earth.

    ERIC Educational Resources Information Center

    Dybas, Cheryl Lyn

    2002-01-01

    Reports on presentations representing evolution at the 53rd annual meeting of the American Institute of Biological Sciences (AIBS) which was held March 22-24, 2002. Explains evolutionary patterns, phylogenetic pageantry, molecular clocks, speciation and biogeography, speciation and macroevolution, and human-induced evolution of drugs-resistant…

  11. Evolution & the Cesarean Section Rate

    ERIC Educational Resources Information Center

    Walsh, Joseph A.

    2008-01-01

    "Nothing in biology makes sense except in the light of evolution." This was the title of an essay by geneticist Theodosius Dobzhansky writing in 1973. Many causes have been given for the increased Cesarean section rate in developed countries, but biologic evolution has not been one of them. The C-section rate will continue to rise, because the…

  12. Visualizing Clonal Evolution in Cancer.

    PubMed

    Krzywinski, Martin

    2016-06-01

    Rapid and inexpensive single-cell sequencing is driving new visualizations of cancer instability and evolution. Krzywinski discusses how to present clone evolution plots in order to visualize temporal, phylogenetic, and spatial aspects of a tumor in a single static image. PMID:27259197

  13. Major transitions in human evolution.

    PubMed

    Foley, Robert A; Martin, Lawrence; Mirazón Lahr, Marta; Stringer, Chris

    2016-07-01

    Evolutionary problems are often considered in terms of 'origins', and research in human evolution seen as a search for human origins. However, evolution, including human evolution, is a process of transitions from one state to another, and so questions are best put in terms of understanding the nature of those transitions. This paper discusses how the contributions to the themed issue 'Major transitions in human evolution' throw light on the pattern of change in hominin evolution. Four questions are addressed: (1) Is there a major divide between early (australopithecine) and later (Homo) evolution? (2) Does the pattern of change fit a model of short transformations, or gradual evolution? (3) Why is the role of Africa so prominent? (4) How are different aspects of adaptation-genes, phenotypes and behaviour-integrated across the transitions? The importance of developing technologies and approaches and the enduring role of fieldwork are emphasized.This article is part of the themed issue 'Major transitions in human evolution'. PMID:27298461

  14. Two Level Parallel Grammatical Evolution

    NASA Astrophysics Data System (ADS)

    Ošmera, Pavel

    This paper describes a Two Level Parallel Grammatical Evolution (TLPGE) that can evolve complete programs using a variable length linear genome to govern the mapping of a Backus Naur Form grammar definition. To increase the efficiency of Grammatical Evolution (GE) the influence of backward processing was tested and a second level with differential evolution was added. The significance of backward coding (BC) and the comparison with standard coding of GEs is presented. The new method is based on parallel grammatical evolution (PGE) with a backward processing algorithm, which is further extended with a differential evolution algorithm. Thus a two-level optimization method was formed in attempt to take advantage of the benefits of both original methods and avoid their difficulties. Both methods used are discussed and the architecture of their combination is described. Also application is discussed and results on a real-word application are described.

  15. Molecular imprint of dust evolution

    NASA Astrophysics Data System (ADS)

    Akimkin, Vitaly; Zhukovska, Svitlana; Wiebe, Dmitri; Semenov, Dmitry; Pavlyuchenkov, Yaroslav; Vasyunin, Anton; Birnstiel, Til; Henning, Thomas

    2013-07-01

    Evolution of sub-micron grains is an essential process during early stages of planet formation. The dust growth and sedimentation to the midplane affect a spectral energy distribution. At the same time dust evolution can alter significantly the distribution of gas that is a factor of 100 more massive than dust and can be traced with molecular line observations. We present simulations of protoplanetary disk structure with grain evolution using the ANDES code ("AccretioN disk with Dust Evolution and Sedimentation"). ANDES comprises (1) a 1+1D frequency-dependent continuum radiative transfer module, (2) a module to calculate the chemical evolution using an extended gas-grain chemical network with UV/X-ray-driven processes and surface reactions, (3) a module to calculate the gas thermal energy balance, and (4) a 1+1D module that simulates dust grain evolution. Such a set of physical processes allows us to assess the impact of dust evolution on the gas component, which is primarily related to radiation field and total available surface for chemical reactions. Considering cases of (i) evolved dust (2 Myr of grain coagulation, fragmentation and sedimentation) and (ii) pristine dust (well- mixed 0.1 micron grains), we found a sufficient changes in disk physical and chemical structure caused by the dust evolution. Due to higher transparency of the evolved disk model UV-shielded molecular layer is shifted closer to the midplane. The presence of big grains in the disk midplane delays the freeze-out of volatile gas-phase species such as CO, while the depletion is still effective in adjacent upper layers. Molecular concentrations of many species are enhanced in the disk model with dust evolution (CO2, NH2CN, HNO, H2O, HCOOH, HCN, CO) which provides an opportunity to use these molecules as tracers of dust evolution.

  16. Evolution of genome architecture.

    PubMed

    Koonin, Eugene V

    2009-02-01

    Charles Darwin believed that all traits of organisms have been honed to near perfection by natural selection. The empirical basis underlying Darwin's conclusions consisted of numerous observations made by him and other naturalists on the exquisite adaptations of animals and plants to their natural habitats and on the impressive results of artificial selection. Darwin fully appreciated the importance of heredity but was unaware of the nature and, in fact, the very existence of genomes. A century and a half after the publication of the "Origin", we have the opportunity to draw conclusions from the comparisons of hundreds of genome sequences from all walks of life. These comparisons suggest that the dominant mode of genome evolution is quite different from that of the phenotypic evolution. The genomes of vertebrates, those purported paragons of biological perfection, turned out to be veritable junkyards of selfish genetic elements where only a small fraction of the genetic material is dedicated to encoding biologically relevant information. In sharp contrast, genomes of microbes and viruses are incomparably more compact, with most of the genetic material assigned to distinct biological functions. However, even in these genomes, the specific genome organization (gene order) is poorly conserved. The results of comparative genomics lead to the conclusion that the genome architecture is not a straightforward result of continuous adaptation but rather is determined by the balance between the selection pressure, that is itself dependent on the effective population size and mutation rate, the level of recombination, and the activity of selfish elements. Although genes and, in many cases, multigene regions of genomes possess elaborate architectures that ensure regulation of expression, these arrangements are evolutionarily volatile and typically change substantially even on short evolutionary scales when gene sequences diverge minimally. Thus, the observed genome

  17. Evolution of the Insects

    NASA Astrophysics Data System (ADS)

    Grimaldi, David; Engel, Michael S.

    2005-05-01

    This book chronicles the complete evolutionary history of insects--their living diversity and relationships as well as 400 million years of fossils. Introductory sections cover the living species diversity of insects, methods of reconstructing evolutionary relationships, basic insect structure, and the diverse modes of insect fossilization and major fossil deposits. Major sections then explore the relationships and evolution of each order of hexapods. The volume also chronicles major episodes in the evolutionary history of insects from their modest beginnings in the Devonian and the origin of wings hundreds of millions of years before pterosaurs and birds to the impact of mass extinctions and the explosive radiation of angiosperms on insects, and how they evolved into the most complex societies in nature. Whereas other volumes focus on either living species or fossils, this is the first comprehensive synthesis of all aspects of insect evolution. Illustrated with 955 photo- and electron- micrographs, drawings, diagrams, and field photos, many in full color and virtually all of them original, this reference will appeal to anyone engaged with insect diversity--professional entomologists and students, insect and fossil collectors, and naturalists. David Grimaldi and Michael S. Engel have collectively published over 200 scientific articles and monographs on the relationships and fossil record of insects, including 10 articles in the journals Science, Nature, and Proceedings of the National Academy of Sciences. David Grimaldi is curator in the Division of Invertebrate Zoology, American Museum of Natural History and adjunct professor at Cornell University, Columbia University, and the City University of New York. David Grimaldi has traveled in 40 countries on 6 continents, collecting and studying recent species of insects and conducting fossil excavations. He is the author of Amber: Window to the Past (Abrams, 2003). Michael S. Engel is an assistant professor in the

  18. Lakes, Lagerstaetten, and Evolution

    NASA Astrophysics Data System (ADS)

    Kordesch, E. G.; Park, L. E.

    2001-12-01

    nonmarine organisms, and thus the evolution of freshwater organisms, can occur in a short geologic timespan. Because of their unique and varied conditions, the evolution of nonmarine organisms may be linked to lake basin type as well as lake longevity.

  19. Evolution of Interstellar Grains

    NASA Technical Reports Server (NTRS)

    Allamandola, Lou J.; DeVincenzi, Donald L. (Technical Monitor)

    1998-01-01

    During the past two decades observations combined with laboratory simulations, have revolutionized our understanding of interstellar ice and dust, the raw materials from which planets, comets and stars form. Most interstellar material is concentrated in large molecular clouds where simple molecules are formed by dust-grain and gas-phase reactions. Gaseous species striking the cold (10K) dust stick, forming an icy grain mantle. This accretion, coupled with UV photolysis, produces a complex chemical mixture containing volatile, non-volatile, and isotopically fractionated species. Ices in molecular clouds contain the very simple molecules H2O, CH3OH, CO, CO2, H2, and perhaps some NH3 and H2CO, as well as more complex species. The evidence for these compounds, as well as carbon-rich materials, will be reviewed and the possible connections with comets and meteorites will be presented in the first part of the talk . The second part of the presentation will focus on interstellar/precometary ice photochemical evolution and the species likely to be found in comets. The chemical composition and photochemical evolution of realistic interstellar/pre-cometary ice analogs will be discussed. Ultraviolet photolysis of these ices produces H2, H2CO, CO2, CO, CH4, HCO, and more complex molecules. When ices representative of interstellar grains and comets are exposed to UV radiation at low temperature a series of moderately complex organic molecules are formed in the ice including: CH3CH2OH (ethanol), HC(=O)NH2 (formamide), CH3C(=O)NH2 (acetamide), and R-C=N (nitriles). Several of these are already known to be in the interstellar medium, and their presence indicates the importance of grain processing. After warming to room temperature an organic residue remains. This is composed primarily of hexamethylenetetramine (HMT, C6H12N4), with lesser amounts of polyoxymethylene-related species (POMs), amides, and ketones. This is in sharp contrast to the organic residues produced by

  20. The evolution of replicators.

    PubMed Central

    Szathmáry, E

    2000-01-01

    Replicators of interest in chemistry, biology and culture are briefly surveyed from a conceptual point of view. Systems with limited heredity have only a limited evolutionary potential because the number of available types is too low. Chemical cycles, such as the formose reaction, are holistic replicators since replication is not based on the successive addition of modules. Replicator networks consisting of catalytic molecules (such as reflexively autocatalytic sets of proteins, or reproducing lipid vesicles) are hypothetical ensemble replicators, and their functioning rests on attractors of their dynamics. Ensemble replicators suffer from the paradox of specificity: while their abstract feasibility seems to require a high number of molecular types, the harmful effect of side reactions calls for a small system size. No satisfactory solution to this problem is known. Phenotypic replicators do not pass on their genotypes, only some aspects of the phenotype are transmitted. Phenotypic replicators with limited heredity include genetic membranes, prions and simple memetic systems. Memes in human culture are unlimited hereditary, phenotypic replicators, based on language. The typical path of evolution goes from limited to unlimited heredity, and from attractor-based to modular (digital) replicators. PMID:11127914

  1. Evolution of coalitionary killing.

    PubMed

    Wrangham, R W

    1999-01-01

    Warfare has traditionally been considered unique to humans. It has, therefore, often been explained as deriving from features that are unique to humans, such as the possession of weapons or the adoption of a patriarchal ideology. Mounting evidence suggests, however, that coalitional killing of adults in neighboring groups also occurs regularly in other species, including wolves and chimpanzees. This implies that selection can favor components of intergroup aggression important to human warfare, including lethal raiding. Here I present the principal adaptive hypothesis for explaining the species distribution of intergroup coalitional killing. This is the "imbalance-of-power hypothesis," which suggests that coalitional killing is the expression of a drive for dominance over neighbors. Two conditions are proposed to be both necessary and sufficient to account for coalitional killing of neighbors: (1) a state of intergroup hostility; (2) sufficient imbalances of power between parties that one party can attack the other with impunity. Under these conditions, it is suggested, selection favors the tendency to hunt and kill rivals when the costs are sufficiently low. The imbalance-of-power hypothesis has been criticized on a variety of empirical and theoretical grounds which are discussed. To be further tested, studies of the proximate determinants of aggression are needed. However, current evidence supports the hypothesis that selection has favored a hunt-and-kill propensity in chimpanzees and humans, and that coalitional killing has a long history in the evolution of both species. PMID:10601982

  2. Active region coronal evolution

    NASA Technical Reports Server (NTRS)

    Golub, L.; Noci, G.; Poletto, G.; Vaiana, G. S.

    1982-01-01

    Scaling relations between coronal base pressure and longitudinal photospheric magnetic field strength are tested for the case of a single active region observed for five solar rotations from Skylab. The evolution of measureable quantities, such as coronal thermal energy content, total longitudinal photospheric magnetic flux, region scale size, and peak energy density, is traced throughout the five rotations observed. The theoretically derived scaling law of Golub et al. (1980) is found to provide an acceptable fit to the data throughout the entire evolutionary history of the region from an age of about 3 days to the fully evolved state in which the mature active region merges into the general large-scale structure of the quiet corona. An alternative scaling law obtained by including the results of Galeev et al. (1981), however, is found to provide a somewhat better fit to the data. The study is seen as providing additional justification for the belief that magnetic field-related heating is the operative mechanism in the solar corona.

  3. Nanosciences: Evolution or revolution?

    NASA Astrophysics Data System (ADS)

    Pautrat, Jean-Louis

    2011-09-01

    In miniaturized objects fabricated by modern technology the smallest linear size may be of a few nanometers. In the field of microelectronics, the advantages of such a miniaturization are huge (increased complexity and reliability, reduced costs). The technology is now approaching the limits where further size reduction will be impossible, except for very novel techniques such as molecular electronics. Miniaturization research has also led to the discovery of nanometric objects such as carbon nanotubes, which turn out to be particularly appropriate for inventing new materials. Miniaturization techniques have been progressively applied in other fields, with the hope of obtaining improvements similar to those encountered in microelectronics. Examples are biochips, which concentrate on a few cm 2 the recognition of ADN sequences, or 'lab-on-a-chip' devices, each of which constitutes a whole laboratory of chemical analysis, or MEMs (Micro Electro Mechanical Systems). New therapies will use miniaturized objects with multiple functions: For instance a nanoparticle can both recognize the target organ thanks to an appropriate protein, and deliver the therapeutic molecule to this target. These results have only been possible through new observation instruments, able to observe and manipulate nano objects. Is the observed evolution really a revolution of science and techniques? This is a point discussed in the conclusion, which also deals with risks associated to nanotechnologies, while the need for a social regulation is stressed.

  4. Evolution of Titan's atmosphere

    NASA Astrophysics Data System (ADS)

    Lammer, H.; Povoden, G.; Selsis, F.; Ribas, I.; Tehrany, M. G.; Guinan, E. F.; Hanslmeier, A.; Bauer, S. J.

    2003-04-01

    We show that anomalies of heavy isotopes in Titan's atmosphere can be explained by using observational data of the radiation and particle environment of solar proxies. These observations indicate a larger solar wind flux and high solar EUV radiation of the early Sun during the first billion years are responsible for a fractionated atmospheric loss. For studying the evolution of the thermal escape of Titan's atmosphere we use a scaling law based on an approximate solution of the heat balance equation in the exosphere. Further, isotope fractionation by non-thermal atmospheric escape processes like dissociative recombination, impact dissociation, atmospheric sputtering and ion pick-up processes. We show that Titan lost an atmospheric mass We discuss also possible chemical reactions of methane and other out-gassing substances due to the high solar EUV fluxes powered thermospheric temperature 4 Gyr ago. This could have lead to molecules of higher mass like ethane and other organic compounds. The efficient production of such molecules was reduced by the decrease of the solar activity resulting in a kind of frozen state. At present only high energy processes like lightning discharges may give similar reactions.

  5. The Galaxy Evolution Explorer

    NASA Astrophysics Data System (ADS)

    Martin, Christopher; Barlow, Thomas; Barnhart, William; Bianchi, Luciana; Blakkolb, Brian K.; Bruno, Dominique; Bushman, Joseph; Byun, Yong-Ik; Chiville, Michael; Conrow, Timothy; Cooke, Brian; Donas, Jose; Fanson, James L.; Forster, Karl; Friedman, Peter G.; Grange, Robert; Griffiths, David; Heckman, Timothy; Lee, James; Jelinsky, Patrick N.; Kim, Sug-Whan; Lee, Siu-Chun; Lee, Young-Wook; Liu, Dankai; Madore, Barry F.; Malina, Roger; Mazer, Alan; McLean, Ryan; Milliard, Bruno; Mitchell, William; Morais, Marco; Morrissey, Patrick F.; Neff, Susan G.; Raison, Frederic; Randall, David; Rich, Michael; Schiminovich, David; Schmitigal, Wes; Sen, Amit; Siegmund, Oswald H. W.; Small, Todd; Stock, Joseph M.; Surber, Frank; Szalay, Alexander; Vaughan, Arthur H.; Weigand, Timothy; Welsh, Barry Y.; Wu, Patrick; Wyder, Ted; Xu, C. Kevin; Zsoldas, Jennifer

    2003-02-01

    The Galaxy Evolution Explorer (GALEX), a NASA Small Explorer Mission planned for launch in Fall 2002, will perform the first Space Ultraviolet sky survey. Five imaging surveys in each of two bands (1350-1750Å and 1750-2800Å) will range from an all-sky survey (limit mAB~20-21) to an ultra-deep survey of 4 square degrees (limit mAB~26). Three spectroscopic grism surveys (R=100-300) will be performed with various depths (mAB~20-25) and sky coverage (100 to 2 square degrees) over the 1350-2800Å band. The instrument includes a 50 cm modified Ritchey-Chrétien telescope, a dichroic beam splitter and astigmatism corrector, two large sealed tube microchannel plate detectors to simultaneously cover the two bands and the 1.2 degree field of view. A rotating wheel provides either imaging or grism spectroscopy with transmitting optics. We will use the measured UV properties of local galaxies, along with corollary observations, to calibrate the UV-global star formation rate relationship in galaxies. We will apply this calibration to distant galaxies discovered in the deep imaging and spectroscopic surveys to map the history of star formation in the universe over the red shift range zero to two. The GALEX mission will include an Associate Investigator program for additional observations and supporting data analysis. This will support a wide variety of investigations made possible by the first UV sky survey.

  6. Evolution of optogenetic microdevices.

    PubMed

    Kale, Rajas P; Kouzani, Abbas Z; Walder, Ken; Berk, Michael; Tye, Susannah J

    2015-07-01

    Implementation of optogenetic techniques is a recent addition to the neuroscientists' preclinical research arsenal, helping to expose the intricate connectivity of the brain and allowing for on-demand direct modulation of specific neural pathways. Developing an optogenetic system requires thorough investigation of the optogenetic technique and of previously fabricated devices, which this review accommodates. Many experiments utilize bench-top systems that are bulky, expensive, and necessitate tethering to the animal. However, these bench-top systems can make use of power-demanding technologies, such as concurrent electrical recording. Newer portable microdevices and implantable systems carried by freely moving animals are being fabricated that take advantage of wireless energy harvesting to power a system and allow for natural movements that are vital for behavioral testing and analysis. An investigation of the evolution of tethered, portable, and implantable optogenetic microdevices is presented, and an analysis of benefits and detriments of each system, including optical power output, device dimensions, electrode width, and weight is given. Opsins, light sources, and optical fiber coupling are also discussed to optimize device parameters and maximize efficiency from the light source to the fiber, respectively. These attributes are important considerations when designing and developing improved optogenetic microdevices. PMID:26158015

  7. Thioredoxin and evolution

    NASA Technical Reports Server (NTRS)

    Buchanan, B. B.

    1991-01-01

    Comparisons of primary structure have revealed significant homology between the m type thioredoxins of chloroplasts and the thioredoxins from a variety of bacteria. Chloroplast thioredoxin f, by comparison, remains an enigma: certain residues are invariant with those of the other thioredoxins, but a phylogenetic relationship to bacterial or m thioredoxins seems distant. Knowledge of the evolutionary history of thioredoxin f is, nevertheless, of interest because of its role in photosynthesis. Therefore, we have attempted to gain information on the evolutionary history of chloroplast thioredoxin f, as well as m. Our goal was first to establish the utility of thioredoxin as a phylogenetic marker, and, if found suitable, to deduce the evolutionary histories of the chloroplast thioredoxins. To this end, we have constructed phylogenetic (minimal replacement) trees using computer analysis. The results show that the thioredoxins of bacteria and animals fall into distinct phylogenetic groups - the bacterial group resembling that derived from earlier 16s RNA analysis and the animal group showing a cluster consistent with known relationships. The chloroplast thioredoxins show a novel type of phylogenetic arrangement: one m type aligns with its counterpart of eukaryotic algae, cyanobacteria and other bacteria, whereas the second type (f type) tracks with animal thioredoxin. The results give new insight into the evolution of photosynthesis.

  8. Monitoring Evolution at CERN

    NASA Astrophysics Data System (ADS)

    Andrade, P.; Fiorini, B.; Murphy, S.; Pigueiras, L.; Santos, M.

    2015-12-01

    Over the past two years, the operation of the CERN Data Centres went through significant changes with the introduction of new mechanisms for hardware procurement, new services for cloud provisioning and configuration management, among other improvements. These changes resulted in an increase of resources being operated in a more dynamic environment. Today, the CERN Data Centres provide over 11000 multi-core processor servers, 130 PB disk servers, 100 PB tape robots, and 150 high performance tape drives. To cope with these developments, an evolution of the data centre monitoring tools was also required. This modernisation was based on a number of guiding rules: sustain the increase of resources, adapt to the new dynamic nature of the data centres, make monitoring data easier to share, give more flexibility to Service Managers on how they publish and consume monitoring metrics and logs, establish a common repository of monitoring data, optimise the handling of monitoring notifications, and replace the previous toolset by new open source technologies with large adoption and community support. This contribution describes how these improvements were delivered, present the architecture and technologies of the new monitoring tools, and review the experience of its production deployment.

  9. The evolution of language.

    PubMed

    Corballis, Michael C

    2009-03-01

    Language, whether spoken or signed, can be viewed as a gestural system, evolving from the so-called mirror system in the primate brain. In nonhuman primates the gestural system is well developed for the productions and perception of manual action, especially transitive acts involving the grasping of objects. The emergence of bipedalism in the hominins freed the hands for the adaptation of the mirror system for intransitive acts for communication, initially through the miming of events. With the emergence of the genus Homo from some 2 million years ago, pressures for more complex communication and increased vocabulary size led to the conventionalization of gestures, the loss of iconic representation, and a gradual shift to vocal gestures replacing manual ones-although signed languages are still composed of manual and facial gestures. In parallel with the conventionalization of symbols, languages gained grammatical complexity, perhaps driven by the evolution of episodic memory and mental time travel, which involve combinations of familiar elements--Who did what to whom, when, where, and why? Language is thus adapted to allow us to share episodic structures, whether past, planned, or fictional, and so increase survival fitness. PMID:19338501

  10. Evolution of optogenetic microdevices

    PubMed Central

    Kale, Rajas P.; Kouzani, Abbas Z.; Walder, Ken; Berk, Michael; Tye, Susannah J.

    2015-01-01

    Abstract. Implementation of optogenetic techniques is a recent addition to the neuroscientists’ preclinical research arsenal, helping to expose the intricate connectivity of the brain and allowing for on-demand direct modulation of specific neural pathways. Developing an optogenetic system requires thorough investigation of the optogenetic technique and of previously fabricated devices, which this review accommodates. Many experiments utilize bench-top systems that are bulky, expensive, and necessitate tethering to the animal. However, these bench-top systems can make use of power-demanding technologies, such as concurrent electrical recording. Newer portable microdevices and implantable systems carried by freely moving animals are being fabricated that take advantage of wireless energy harvesting to power a system and allow for natural movements that are vital for behavioral testing and analysis. An investigation of the evolution of tethered, portable, and implantable optogenetic microdevices is presented, and an analysis of benefits and detriments of each system, including optical power output, device dimensions, electrode width, and weight is given. Opsins, light sources, and optical fiber coupling are also discussed to optimize device parameters and maximize efficiency from the light source to the fiber, respectively. These attributes are important considerations when designing and developing improved optogenetic microdevices. PMID:26158015

  11. Landscape evolution (A Review)

    PubMed Central

    Sharp, Robert P.

    1982-01-01

    Landscapes are created by exogenic and endogenic processes acting along the interface between the lithosphere and the atmosphere and hydrosphere. Various landforms result from the attack of weathering and erosion upon the highly heterogeneous lithospheric surface. Landscapes are dynamic, acutely sensitive to natural and artificial perturbation. Undisturbed, they can evolve through a succession of stages to a plain of low relief. Often, the progression of an erosion cycle is interrupted by tectonic or environmental changes; thus, many landscapes preserve vestiges of earlier cycles useful in reconstructing the recent history of Earth's surface. Landforms are bounded by slopes, so their evolution is best understood through study of slopes and the complex of factors controlling slope character and development. The substrate, biosphere, climatic environment, and erosive processes are principal factors. Creep of the disintegrated substrate and surface wash by water are preeminent. Some slopes attain a quasisteady form and recede parallel to themselves (backwearing); others become ever gentler with time (downwearing). The lovely convex/rectilinear/concave profile of many debris-mantled slopes reflects an interplay between creep and surface wash. Landscapes of greatest scenic attraction are usually those in which one or two genetic factors have strongly dominated or those perturbed by special events. Nature has been perturbing landscapes for billions of years, so mankind can learn about landscape perturbation from natural examples. Images

  12. Evolution of VCSELs

    NASA Astrophysics Data System (ADS)

    Tatum, Jim A.

    2014-02-01

    Over the last 20 years, nearly 1 billion VCSELs have been shipped, the vast majority of them emitting at 850nm using GaAs active regions, and primarily used in data communications and optical tracking applications. Looking to the future, the ever increasing speed of data communications is driving the VCSEL to evolve with more complex active regions, optical mode control, and alternate wavelengths to meet the more stringent requirements. We will discuss the current state of VCSELs for 28Gbps, and higher speeds, focusing on evolution to more complex active regions and alternate wavelength approaches, particularly as the market evolves to more active optical cables. Other high volume applications for VCSELs are driving improvements in single mode and optical power characteristics. We will present several evolving market trends and applications, and the specific VCSEL requirements that are imposed. The ubiquitous 850nm, GaAs active region VCSEL is evolving in multiple ways, and will continue to be a viable optical source well in to the future.

  13. EVOLUTION OF MYELOID CELLS

    PubMed Central

    Barreda, Daniel R.; Neely, Harold R.; Flajnik, Martin F.

    2015-01-01

    In 1882, Elie Metchnikoff identified myeloid-like cells from starfish larvae responding to the invasion by a foreign body (rose thorn). This marked the origins of the study of innate immunity, and an appreciation that cellular immunity is already well established in these “primitive” organisms. This chapter focuses on these myeloid cells as well as the newest members of this family, the dendritic cells (DC), and explores their evolutionary origins. Our goal is to provide evolutionary context for the development of the multilayered immune system of mammals, where myeloid cells now serve as central effectors of innate immunity and regulators of adaptive immunity. Overall, we find that core contributions of myeloid cells to the regulation of inflammation are based on mechanisms that have been honed over hundreds of millions of years of evolution. Using phagocytosis as a platform, we show how fairly simple beginnings have offered a robust foundation onto which additional control features have been integrated, resulting in central regulatory nodes that now manage multi-factorial aspects of homeostasis and immunity. PMID:27337471

  14. Tooth patterning and evolution.

    PubMed

    Salazar-Ciudad, Isaac

    2012-12-01

    Teeth are a good system for studying development and evolution. Tooth development is largely independent of the rest of the body and teeth can be grown in culture to attain almost normal morphology. Their development is not affected by the patterns of movement or sensorial perception in the embryo. Teeth are hard and easily preserved. Thus, there is plenty of easily accessible information about the patterns of morphological variation occurring between and within species. This review summarises recent work and describes how tooth development can be understood as the coupling between a reaction-diffusion system and differential growth produced by diffusible growth factors: which growth factors are involved, how they affect each other's expression and how they affect the spatial patterns of proliferation that lead to final morphology. There are some aspects of tooth development, however, that do not conform to some common assumptions in many reaction-diffusion models. Those are discussed here since they provide clues about how reaction-diffusion systems may work in actual developmental systems. Mathematical models implementing what we know about tooth development are discussed. PMID:23266218

  15. Evolution of galaxy habitability

    NASA Astrophysics Data System (ADS)

    Gobat, R.; Hong, S. E.

    2016-08-01

    We combine a semi-analytic model of galaxy evolution with constraints on circumstellar habitable zones and the distribution of terrestrial planets in order to probe the suitability of galaxies of different mass and type to host habitable planets, and how it evolves with time. We find that the fraction of stars with terrestrial planets in their habitable zone (known as habitability) depends only weakly on galaxy mass, with a maximum around 4 × 1010M⊙. We estimate that 0.7% of all stars in Milky Way-type galaxies to host a terrestrial planet within their habitable zone, consistent with the value derived from Kepler observations. On the other hand, the habitability of passive galaxies is slightly but systematically higher, unless we assume an unrealistically high sensitivity of planets to supernovae. We find that the overall habitability of galaxies has not changed significantly in the last ~8 Gyr, with most of the habitable planets in local disk galaxies having formed ~1.5 Gyr before our own solar system. Finally, we expect that ~1.4 ×109 planets similar to present-day Earth have existed so far in our galaxy.

  16. Flies, clocks and evolution.

    PubMed Central

    Rosato, E; Kyriacou, C P

    2001-01-01

    The negative feedback model for gene regulation of the circadian mechanism is described for the fruitfly, Drosophila melanogaster. The conservation of function of clock molecules is illustrated by comparison with the mammalian circadian system, and the apparent swapping of roles between various canonical clock gene components is highlighted. The role of clock gene duplications and divergence of function is introduced via the timeless gene. The impressive similarities in clock gene regulation between flies and mammals could suggest that variation between more closely related species within insects might be minimal. However, this is not borne out because the expression of clock molecules in the brain of the giant silk moth, Antheraea pernyi, is not easy to reconcile with the negative feedback roles of the period and timeless genes. Variation in clock gene sequences between and within fly species is examined and the role of co-evolution between and within clock molecules is described, particularly with reference to adaptive functions of the circadian phenotype. PMID:11710984

  17. Extraterrestrial civilizations: Problems of their evolution

    NASA Technical Reports Server (NTRS)

    Leskov, L. V.

    1987-01-01

    The problem of finding extraterrestrial civilizations and establishing contact with them is directly related to the problem of their evolution. Possible patterns in this evolution and the stages in the evolution of extraterrestrial civilizations are examined.

  18. Gas evolution from geopressured brines

    SciTech Connect

    Matthews, C.S.

    1980-06-01

    The process of gas evolution from geopressured brine is examined using as a basis the many past studies of gas evolution from liquids in porous media. A discussion of a number of speculations that have been made concerning gas evolution from geopressured brines is provided. According to one, rapid pressure reduction will cause methane gas to evolve as when one opens a champagne bottle. It has been further speculated that evolved methane gas would migrate up to form an easily producible cap. As a result of detailed analyses, it can be concluded that methane gas evolution from geopressured brines is far too small to ever form a connected gas saturation except very near to the producing well. Thus, no significant gas cap could ever form. Because of the very low solubility of methaned in brine, the process of methane gas evolution is not at all analogous to evolution of carbon dioxide from champagne. A number of other speculations and questions on gas evolution are analyzed, and procedures for completing wells and testing geopressured brine reservoirs are discussed, with the conclusion that presently used procedures will provide adequate data to enable a good evaluation of this resource.

  19. Statistical limitations on molecular evolution.

    PubMed

    Perlovsky, Leonid I

    2002-06-01

    Complexity of functions evolving in an evolution process are expected to be limited by the time length of an evolution process among other factors. This paper outlines a general method of deriving function-complexity limitations based on mathematical statistics and independent from details of a biological or genetic mechanism of the evolution of the function. Limitations on the emergence of life are derived, these limitations indicate a possibility of a very fast evolution and are consistent with "RNA world" hypothesis. The discussed method is general and can be used to characterize evolution of more specific biological organism functions and relate functions to genetic structures. The derived general limitations indicate that a co-evolution of multiple functions and species could be a slow process, whereas an evolution of a specific function might proceed very fast, so that no trace of intermediate forms (species) is preserved in fossil records of phenotype or DNA structure; this is consistent with a picture of "punctuated equilibrium". PMID:12023805

  20. On the evolution of development

    PubMed Central

    Torday, John S.

    2015-01-01

    Perhaps development is more than just morphogenesis. We now recognize that the conceptus expresses epigenetic marks that heritably affect it phenotypically, indicating that the offspring are to some degree genetically autonomous, and that ontogeny and phylogeny may coordinately determine the fate of such marks. This scenario mechanistically links ecology, ontogeny and phylogeny together as an integrated mechanism for evolution for the first time. As a functional example, the Parathyroid Hormone-related Protein (PTHrP) signaling duplicated during the Phanerozoic water-land transition. The PTHrP signaling pathway was critical for the evolution of the skeleton, skin barrier, and lung function, based on experimental evidence, inferring that physiologic stress can profoundly affect adaptation through internal selection, giving seminal insights to how and why vertebrates were able to evolve from water to land. By viewing evolution from its inception in unicellular organisms, driven by competition between pro- and eukaryotes, the emergence of complex biologic traits from the unicellular cell membrane offers a novel way of thinking about the process of evolution from its beginnings, rather than from its consequences as is traditionally done. And by focusing on the epistatic balancing mechanisms for calcium and lipid homeostasis, the evolution of unicellular organisms, driven by competition between pro- and eukaryotes, gave rise to the emergence of complex biologic traits derived from the unicellular plasma lemma, offering a unique way of thinking about the process of evolution. By exploiting the cellular-molecular mechanisms of lung evolution as ontogeny and phylogeny, the sequence of events for the evolution of the skin, kidney and skeleton become more transparent. This novel approach to the evolution question offers equally novel insights to the primacy of the unicellular state, hologenomics and even a priori bioethical decisions. PMID:25729239

  1. Confronting the Evolution Education Abyss

    NASA Astrophysics Data System (ADS)

    Zook, Douglas

    This article discusses recent evolution education literature and highlights key themes and perspectives recognized in the scientific community but only minimally exposed within either the science classroom or the science education research agenda. Examples include: macroevolution, expressed as the history of life on earth; the microbial dominance of most of earth time as a learning tool and theme organizer; sym-biogenesis and frequently accompanying horizontal gene transfer; Lamarck and the roles of others traditionally ridiculed in evolution study; and new views of fundamental evolution topics such as speciation. Several recommendations are given to address these important omissions within the science educator community.Received: 7 October 1994; Revised: 11 April 1995;

  2. The Evolution of Cataclysmic Variables

    NASA Astrophysics Data System (ADS)

    Li, Lifang; Zhang, Fenghui; Han, Zhanwen

    2013-02-01

    Using Eggletons code the evolution of cataclysmic variables (CVs) is investigated. CVs might suffer the loss of mass and angular momentum during their evolution, we present the models of CVs with mass loss and angular momentum loss (AML) due to gravitation wave radiation (GR) and/or magnetic braking (MB). It is found that the loss of mass and angular momentum has significant influence on the evolution of CVs, and that the change of the star structure or their atmosphere properties is a possible mechanism which underlies a sudden change in the rate of AML owing to MB.

  3. Experimental evolution in budding yeast

    NASA Astrophysics Data System (ADS)

    Murray, Andrew

    2012-02-01

    I will discuss our progress in analyzing evolution in the budding yeast, Saccharomyces cerevisiae. We take two basic approaches. The first is to try and examine quantitative aspects of evolution, for example by determining how the rate of evolution depends on the mutation rate and the population size or asking whether the rate of mutation is uniform throughout the genome. The second is to try to evolve qualitatively novel, cell biologically interesting phenotypes and track the mutations that are responsible for the phenotype. Our efforts include trying to alter cell morphology, evolve multicellularity, and produce a biological oscillator.

  4. Evolution of the ventricles.

    PubMed Central

    Victor, S; Nayak, V M; Rajasingh, R

    1999-01-01

    We studied the evolution of ventricles by macroscopic examination of the hearts of marine cartilaginous and bony fish, and by angiocardiography and gross examination of the hearts of air-breathing freshwater fish, frogs, turtles, snakes, and crocodiles. A right-sided, thin-walled ventricular lumen is seen in the fish, frog, turtle, and snake. In fish, there is external symmetry of the ventricle, internal asymmetry, and a thick-walled left ventricle with a small inlet chamber. In animals such as frogs, turtles, and snakes, the left ventricle exists as a small-cavitied contractile sponge. The high pressure generated by this spongy left ventricle, the direction of the jet, the ventriculoarterial orientation, and the bulbar spiral valve in the frog help to separate the systemic and pulmonary circulations. In the crocodile, the right aorta is connected to the left ventricle, and there is a complete interventricular septum and an improved left ventricular lumen when compared with turtles and snakes. The heart is housed in a rigid pericardial cavity in the shark, possibly to protect it from changing underwater pressure. The pericardial cavity in various species permits movements of the heart-which vary depending on the ventriculoarterial orientation and need for the ventricle to generate torque or spin on the ejected blood- that favor run-off into the appropriate arteries and their branches. In the lower species, it is not clear whether the spongy myocardium contributes to myocardial oxygenation. In human beings, spongy myocardium constitutes a rare form of congenital heart disease. Images PMID:10524737

  5. Stratocumulus cloud evolution

    SciTech Connect

    Yang, X.; Rogers, D.P.; Norris, P.M.; Johnson, D.W.; Martin, G.M.

    1994-12-31

    The structure and evolution of the extra-tropical marine atmospheric boundary layer (MABL) depends largely on the variability of stratus and stratocumulus clouds. The typical boundary-layer is capped by a temperature inversion that limits exchange with the free atmosphere. Cloud-top is usually coincident with the base of the inversion. Stratus clouds are generally associated with a well-mixed MABL, whereas daytime observations of stratocumulus-topped boundary-layers indicate that the cloud and subcloud layers are often decoupled due to shortwave radiative heating of the cloud layer. In this case the surface-based mixed layer is separated from the base of the stratocumulus (Sc) by a layer that is stable to dry turbulent mixing. This is sometimes referred to as the transition layer. Often cumulus clouds (Cu) develop in the transition layer. The cumulus tops may remain below the Sc base or they may penetrate into the Sc layer and occasionally through the capping temperature inversion. While this cloud structure is characteristic of the daytime MABL, it may persist at night also. The Cu play an important role in connecting the mixed layer to the Sc layer. If the Cu are active they transport water vapor from the sea surface that maintains the Sc against the dissipating effects of shortwave heating. The Cu, however, are very sensitive to small changes in the heat and moisture in the boundary-layer and are transient features. Here the authors discuss the effect of these small Cu on the turbulent structure of the MABL.

  6. Evolution of rhinology.

    PubMed

    Kaluskar, S K

    2008-06-01

    The study of the nose is as old as civilisation. Various conditions affecting its structure and function has been documented in Edwin Smith Papyrus in hieroglyphic script, an Egyptian writing system of the mid -4th Millennium BC.The major contribution for the complete reconstruction of the nose originated in India by Sushruta in around 600 BC. Writing in Sanskrit in the form of verses he described in detail the technique of total reconstruction, which is still being practiced today as Indian Rhinoplasty. This surgical reconstruction paved the way to modern plastic surgery in Europe and United States in 18th century. Sushruta contributed not only to the plastic surgery of the nose, but described entire philosophy of Head and Neck and other surgery as well. Other notable contributors were Greek physicians, Hippocrate and Galen, and at the birth of the Christianity, Celsus wrote eight books of medical encyclopaedia, which described various conditions affecting nose.Septal and Sinus surgery, in comparison to rhinoplasty did not develop until 17th century. Septal surgery began with total septectomy, sub mucous resection by Killian & Freer in early 20th century and later septoplasty by Cottle in middle of 20th century.Sinus surgery probably originated in Egypt, where instruments were used to remove brain through the ethmoid sinuses as part of the mummification process. In 18th century, empyema of the maxillary sinus was drained through the tooth socket or anterior wall of the sinus, which lead to the evolution of radical procedures of removal of mucous membrane and inferior meatal antrostomy. In the late 20th century, improved understanding of the mucociliary mechanism described by Prof. Messerklinger and Nasal Endoscopy described by Prof. Draf with the development of fibre optics and CT imaging, heralded a new era, which evolved in functional endoscopic sinus surgery. New technology further enhanced the scope of endoscope being used "around and beyond" the nose. PMID

  7. Fire Control and Human Evolution.

    ERIC Educational Resources Information Center

    Russell, Claire

    1978-01-01

    Briefly outlines some aspects of the discovery of fire control by primitive people, such as the preadaptation for speech, the evolution of the human brain, and natural selection for human nakedness or loss of hair. (CS)

  8. Weak interactions and presupernova evolution

    SciTech Connect

    Aufderheide, M.B. State Univ. of New York . Dept. of Physics)

    1991-02-19

    The role of weak interactions, particularly electron capture and {beta}{sup {minus}} decay, in presupernova evolution is discussed. The present uncertainty in these rates is examined and the possibility of improving the situation is addressed. 12 refs., 4 figs.

  9. Marine microbiology: Evolution on acid

    NASA Astrophysics Data System (ADS)

    Collins, Sinéad

    2012-05-01

    The prediction of marine microbial responses to ocean acidification is a key challenge for marine biologists. Experimental evolution offers a powerful tool for understanding the forces that will shape tomorrow's microbial communities under global change.

  10. Evolution of the Solar System

    NASA Technical Reports Server (NTRS)

    Alfven, H.; Arrhenius, G.

    1976-01-01

    The origin and evolution of the solar system are analyzed. Physical processes are first discussed, followed by experimental studies of plasma-solid reactions and chemical and mineralogical analyses of meteorites and lunar and terrestrial samples.