Size-frequency distribution of boulders ≥7 m on comet 67P/Churyumov-Gerasimenko

Aims. We derive for the first time the size-frequency distribution of boulders on a comet, 67P/Churyumov-Gerasimenko (67P), computed from the images taken by the Rosetta/OSIRIS imaging system. We highlight the possible physical processes that lead to these boulder size distributions. Methods. We used images acquired by the OSIRIS Narrow Angle Camera, NAC, on 5 and 6 August 2014. The scale of these images (2.44−2.03 m/px) is such that boulders ≥7 m can be identified and manually extracted from the datasets with the software ArcGIS. We derived both global and localized size-frequency distributions. The three-pixel sampling detection, coupled with the favorable shadowing of the surface (observation phase angle ranging from 48° to 53°), enables unequivocally detecting boulders scattered all over the illuminated side of 67P. Results. We identify 3546 boulders larger than 7 m on the imaged surface (36.4 km2), with a global number density of nearly 100/km2 and a cumulative size-frequency distribution represented by a power-law with index of −3.6 +0.2/−0.3. The two lobes of 67P appear to have slightly different distributions, with an index of −3.5 +0.2/−0.3 for the main lobe (body) and −4.0 +0.3/−0.2 for the small lobe (head). The steeper distribution of the small lobe might be due to a more pervasive fracturing. The difference of the distribution for the connecting region (neck) is much more significant, with an index value of −2.2 +0.2/−0.2. We propose that the boulder field located in the neck area is the result of blocks falling from the contiguous Hathor cliff. The lower slope of the size-frequency distribution we see today in the neck area might be due to the concurrent processes acting on the smallest boulders, such as i) disintegration or fragmentation and vanishing through sublimation; ii) uplifting by gas drag and consequent redistribution; and iii) burial beneath a debris blanket. We also derived the cumulative size-frequency distribution per km2 of localized areas on 67P. By comparing the cumulative size-frequency distributions of similar geomorphological settings, we derived similar power-law index values. This suggests that despite the selected locations on different and often opposite sides of the comet, similar sublimation or activity processes, pit formation or collapses, as well as thermal stresses or fracturing events occurred on multiple areas of the comet, shaping its surface into the appearance we see today.

The morphological diversity of comet 67P/Churyumov-Gerasimenko

Images of comet 67P/Churyumov-Gerasimenko acquired by the OSIRIS (Optical, Spectroscopic and Infrared Remote Imaging System) imaging system onboard the European Space Agency's Rosetta spacecraft at scales of better than 0.8 meter per pixel show a wide variety of different structures and textures. The data show the importance of airfall, surface dust transport, mass wasting, and insolation weathering for cometary surface evolution, and they offer some support for subsurface fluidization models and mass loss through the ejection of large chunks of material.

Histoire naturelle des animaux sans vertèbres ... Troisieme Edition

3

Erasmus Darwin e os seres vivos: concepções de \'evolução\' e herança

Erasmus Darwin (1731-1802) apresentou suas ideias evolutivas principalmente no fim do século XVIII. No entanto, elas não foram consideradas na época. Seu neto, Charles Darwin (1809-1882), na 6ª edição do Origin of species as avaliou de modo negativo, comparando-as às concepções equivocadas de Lamarck. O objetivo desta dissertação é inicialmente, descrever as concepções de hereditariedade e evolução de Erasmus, considerando o contexto de sua época. Além disso, procura esclarecer se o tratamento recebido se deveu a uma proposta fraca ou se ela mereceria uma maior consideração. Esta dissertação contém uma Introdução e quatro capítulos. O Capítulo 1 discute a vida, trabalhos e contexto em que Erasmus apresentou suas ideias. O Capítulo 2 lida com as concepções de herança e evolução presentes em Zoonomia. O Capítulo 3 discute sobre as concepções de Erasmus sobre a transformação das espécies nas plantas. O Capítulo 4 compara as concepções evolutivas de Erasmus com as de Lamarck. O Capítulo 5 procura responder às perguntas colocadas no início desta pesquisa e apresenta algumas considerações finais sobre o assunto discutido. Esta pesquisa leva à conclusão de que a transmutação das espécies não era o principal interesse de Erasmus. Ele não ofereceu uma fundamentação empírica para suas ideias. Este fato, juntamente com a situação sócio-político-religiosa da época, muito provavelmente contribuiu para a recepção sofrida. Além disso, embora existam algumas semelhanças entre as propostas de Erasmus e Lamarck, existem também grandes diferenças tais como a abrangência da pesquisa, o espaço dedicado à discussão das ideias, a fundamentação oferecida, dentre outras. Erasmus não propôs uma teoria coerente lidando com desde a origem da vida até o aparecimento do homem como Lamarck. Ele somente apresentou algumas ideias a esse respeito em obras dedicadas a outros assuntos.

L' Europe galante: ballet : représenté en l'an 1697 par l'Academie royale de musique

de la composition de Monsieur Campra, maître de musique de la chapelle du Roy ; les paroles de cette piece sont de Monsieur de La Motte, de l'Academie françoise.

Histoire naturelle des animaux sans vertèbres ... précédée d'une introduction offrant la détermination des caractères essentiels de l'animal, sa distinction du végétal et des autres corps naturels, enfin, l'exposition des principes fondamentaux de la zoologie.

3 & 5

Histoire naturelle des animaux sans vertèbres ... précédée d'une introduction offrant la détermination des caractères essentiels de l'animal, sa distinction du végétal et des autres corps naturels, enfin, l'exposition des principes fondamentaux de la zoologie.

7

Histoire naturelle des animaux sans vertèbres ... précédée d'une introduction offrant la détermination des caractères essentiels de l'animal, sa distinction du végétal et des autres corps naturels, enfin, l'exposition des principes fondamentaux de la zoologie.

6

Histoire naturelle des animaux sans vertèbres ... Troisieme Edition

1

L' Euphrate et le Tigre

par le Sr. d'Anville ; Guill. De La Haye.

Nouvel atlas de la Chine, de la Tartarie chinoise et du Thibet : contenant les cartes générales & particulieres de ces pays, ainsi que la carte du royaume de Corée : la plupart levées sur les lieux par ordre de l'empereur Cang-Hi avec toute l'exactitude imaginable, soit par les PP. Jésuites missionaires à la Chine, soit par des Tartares du Tribunal des mathématiques, & toutes revûës par les mêmes peres /

Title page in red and black; tailpiece.

Monumens de l'histoire de France, en estampes et dessins ...

The present 30 volumes seem to have remained with the Dukes of Leuchtenberg, until the ducal library was acquired for sale in 1935 by the dealers Ulrich Hoepli (Milan) and Braus-Riggenbach (Basel). The volumes are not complete, as leaves have been wholly or partly removed throughout; this is particularly evident in preliminary volumes 2 and 10 and volume 75. Prints and the relatively small number of drawings are mostly French, with some German, Dutch and English, and are mostly of the 17th or 18th centuries. They are mounted generally on rectos of leaves, often with hand-written captions. Large prints are occasionally bound in directly; these are often folded. The engraved general title page (bearing the date 1788) appears at the beginning of each volume; below the printed title a hand-written volume number and brief title describing the volume's contents usually appear. In many volumes the title leaf is followed by a hand-written contents leaf listing the section titles, which are also written individually throughout the volume on leaves with etched decorative frames. Sections are numbered continuously throughout the work as a whole. Numbering of the leaves, when present, appears in black ink within each volume at top center recto. Printmakers include B. & J. Audran, Francesco Bartolozzi, Abraham Bosse, Stefano della Bella, Jacques Callot, François Chéreau, Wenceslaus Hollar, Romeyn de Hooghe, Raymond La Fage, Sébastien Le Clerc, Pierre Lepautre, Claude Mellan, Bernard Picart, and Simon Thomassin. There are also early color prints by Gautier-Dagoty and Jean-Baptiste Morret.

Essai général de fortification et d'attaque et défense des places, dans lequel ces deux sciences sont expliquées et mises l'une par l'autre à la portée de tout le monde ...

Mode of access: Internet.

Le géneral Kléber,

Siége de Mayence. Guerre de Vendée. Appendice.--Allemagne.--Expédition d'Egypte. Appendice.

Extrait du cours de zoologie du Muséum d'histoire naturelle, sur les animaux sans vert̀bres; présentant la distribution et la classification de ces animaux, les caractères des principales divisions, et une simple liste des genres; a l'usage de ceux qui suivent ce cours.

Mode of access: Internet.