Articoli di riviste: "Primitive Earth"

1

Otalora, Fermin, e Juan Manuel García Ruiz. "Investigating the primitive Earth through crystals". Acta Crystallographica Section A Foundations and Advances 74, a2 (22 agosto 2018): e251-e251. http://dx.doi.org/10.1107/s2053273318091398.

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Orò, Juan, e Cristiano B. Cosmovici. "Comets and Life on the Primitive Earth". International Astronomical Union Colloquium 161 (gennaio 1997): 97–120. http://dx.doi.org/10.1017/s0252921100014639.

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AbstractComets may have contributed substantial amounts of water, volatiles and organic precursors such as HCN for the synthesis of biochemical compounds on the primitive Earth. This suggestion followed closely the prebiotic synthesis of adenine, purines and amino acids from HCN. Recent studies on the terrestrial heavy noble gases provide evidence that comets are the principal external source of Earth’s volatiles. During the encounter of comet Halley strong jets of CN, C2, C3and NH2were measured from Earth observatories, and by spacecraft mass spectrometry HCN, formaldehyde, adenine and many other organic compounds were detected, except amino acids. Obviously the latter require liquid water for their formation. Therefore upon capture of comets by the Earth, and melting of the frozen water, the synthesis of most biochemical compounds could take place readily. The detection of water, HCN and other organics of cometary origin after the impact of Comet SL-9 with Jupiter demonstrated the capability of survival of these molecules even after catastrophic events. Thus on the Earth HCN could be converted into purines, cyanacetylene, after hydration and condensation with urea, into pyrimidines, and formaldehyde into monosaccharides. In the presence of phosphates, which have been detected in cometary IDPs, nucleotides could also be synthesized. In conclusion, comets probably provided the necessary molecular precursors for the generation of life on the Earth.

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Rao, M., J. Eichberg e J. Oró. "Synthesis of phosphatidylethanolamine under possible primitive earth conditions". Journal of Molecular Evolution 25, n. 1 (maggio 1987): 1–6. http://dx.doi.org/10.1007/bf02100033.

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Wong, Carlos, J. Carlos Santiago, Lorena Rodriguez-Paez, Miguel Ibánez, Isabel Baeza e J. Oró. "Synthesis of putrescine under possible primitive earth conditions". Origins of Life and Evolution of the Biosphere 21, n. 3 (maggio 1991): 145–56. http://dx.doi.org/10.1007/bf01809443.

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Guo, Dong, Ziyue Zhang, Jichao Sun, Hui Zhao, Wanguo Hou e Na Du. "A Fusion–Growth Protocell Model Based on Vesicle Interactions with Pyrite Particles". Molecules 29, n. 11 (4 giugno 2024): 2664. http://dx.doi.org/10.3390/molecules29112664.

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Protocell models play a pivotal role in the exploration of the origin of life. Vesicles are one type of protocell model that have attracted much attention. Simple single-chain amphiphiles (SACs) and organic small molecules (OSMs) possess primitive relevance and were most likely the building blocks of protocells on the early Earth. OSM@SAC vesicles have been considered to be plausible protocell models. Pyrite (FeS2), a mineral with primitive relevance, is ubiquitous in nature and plays a crucial role in the exploration of the origin of life in the mineral–water interface scenario. “How do protocell models based on OSM@SAC vesicles interact with a mineral–water interface scenario that simulates a primitive Earth environment” remains an unresolved question. Hence, we select primitive relevant sodium monododecyl phosphate (SDP), isopentenol (IPN) and pyrite (FeS2) mineral particles to build a protocell model. The model investigates the basic physical and chemical properties of FeS2 particles and reveals the effects of the size, content and duration of interaction of FeS2 particles on IPN@SDP vesicles. This deepens the understanding of protocell growth mechanisms in scenarios of mineral–water interfaces in primitive Earth environments and provides new information for the exploration of the origin of life.

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von Bloh, W., C. Bounama, M. Cuntz e S. Franck. "Habitability of super-Earths: Gliese 581c & 581d". Proceedings of the International Astronomical Union 3, S249 (ottobre 2007): 503–6. http://dx.doi.org/10.1017/s1743921308017031.

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AbstractThe unexpected diversity of exoplanets includes a growing number of super-Earth planets, i.e., exoplanets with masses smaller than 10 Earth masses. Unlike the larger exoplanets previously found, these smaller planets are more likely to have similar chemical and mineralogical composition to the Earth. We present a thermal evolution model for super-Earth planets to identify the sources and sinks of atmospheric carbon dioxide. The photosynthesis-sustaining habitable zone (pHZ) is determined by the limits of biological productivity on the planetary surface. We apply our model to calculate the habitability of the two super-Earths in the Gliese 581 system. The super-Earth Gl 581c is clearly outside the pHZ, while Gl 581d is at the outer edge of the pHZ. Therefore, it could at least harbor some primitive forms of life.

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YANAGAWA, Hiroshi, Yoko OGAWA e Masahiko ITO. "Construction of protocellular structures under simulated primitive earth conditions." NIPPON KAGAKU KAISHI, n. 11 (1987): 2186–93. http://dx.doi.org/10.1246/nikkashi.1987.2186.

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Chyba, Christopher F. "The cometary contribution to the oceans of primitive Earth". Nature 330, n. 6149 (dicembre 1987): 632–35. http://dx.doi.org/10.1038/330632a0.

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Yanagawa, Hiroshi, Yoko Ogawa, Kiyotsugu Kojima e Masahiko Ito. "Construction of protocellular structures under simulated primitive earth conditions". Origins of Life and Evolution of the Biosphere 18, n. 3 (settembre 1988): 179–207. http://dx.doi.org/10.1007/bf01804670.

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Tsuji, Toru, e Kensei Kobayashi. "Abiotic formation of uracil from simulted primitive Earth atmosphere". Origins of Life and Evolution of the Biosphere 26, n. 3-5 (ottobre 1996): 347–48. http://dx.doi.org/10.1007/bf02459801.

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Bhandari, N. "Primitive Matter in Meteorites". Symposium - International Astronomical Union 120 (1987): 485–91. http://dx.doi.org/10.1017/s0074180900154506.

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A large number of elements in certain meteorites have isotopic composition different from that existing in rocks of the earth or the moon. Excess amounts of some isotopes, which are radiogenic daughters, are attributed to the in situ decay of their parent nuclide. Material containing radioactive parents is believed to have been injected into the condensing solar nebula, from astrophysical sites of their production shortly before formation of these grains. Other isotopic anomalies do not show mass dependent pattern which is characteristic of chemical fractionation. They must be primary isotopic abundances, if it is assumed that physico-chemical processes in the solar nebula cannot produce non-mass dependent fractionation. In such a case the observed isotopic ratios characterise elements differently synthesised and injected into the solar nebula which condensed before it had enough time to homogenise. Thus the isotopically anomalous matter has extra solar origin and may contain supernovae condensates, interstellar matter or dust from other stars. The evidence for different isotopic anomalies is briefly summarised and discussed in terms of the current ideas regarding chemical processes occurring in the early solar system.

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Jia, Tony Z., Melina Caudan e Irena Mamajanov. "Origin of Species before Origin of Life: The Role of Speciation in Chemical Evolution". Life 11, n. 2 (17 febbraio 2021): 154. http://dx.doi.org/10.3390/life11020154.

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Speciation, an evolutionary process by which new species form, is ultimately responsible for the incredible biodiversity that we observe on Earth every day. Such biodiversity is one of the critical features which contributes to the survivability of biospheres and modern life. While speciation and biodiversity have been amply studied in organismic evolution and modern life, it has not yet been applied to a great extent to understanding the evolutionary dynamics of primitive life. In particular, one unanswered question is at what point in the history of life did speciation as a phenomenon emerge in the first place. Here, we discuss the mechanisms by which speciation could have occurred before the origins of life in the context of chemical evolution. Specifically, we discuss that primitive compartments formed before the emergence of the last universal common ancestor (LUCA) could have provided a mechanism by which primitive chemical systems underwent speciation. In particular, we introduce a variety of primitive compartment structures, and associated functions, that may have plausibly been present on early Earth, followed by examples of both discriminate and indiscriminate speciation affected by primitive modes of compartmentalization. Finally, we discuss modern technologies, in particular, droplet microfluidics, that can be applied to studying speciation phenomena in the laboratory over short timescales. We hope that this discussion highlights the current areas of need in further studies on primitive speciation phenomena while simultaneously proposing directions as important areas of study to the origins of life.

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Imai, Takashi. "Development of Next-Generation Vaccines". Vaccines 10, n. 2 (10 febbraio 2022): 274. http://dx.doi.org/10.3390/vaccines10020274.

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Barbier, Bernard, Marylène Bertrand, François Boillot, Annie Chabin, Didier Chaput, Odile Hénin e André Brack. "Delivery of extraterrestrial amino acids to the primitive Earth. Exposure experiments in Earth orbit." Biological Sciences in Space 12, n. 2 (1998): 92–95. http://dx.doi.org/10.2187/bss.12.92.

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Furukawa, Yoshihiro, Yoshito Chikaraishi, Naohiko Ohkouchi, Nanako O. Ogawa, Daniel P. Glavin, Jason P. Dworkin, Chiaki Abe e Tomoki Nakamura. "Extraterrestrial ribose and other sugars in primitive meteorites". Proceedings of the National Academy of Sciences 116, n. 49 (18 novembre 2019): 24440–45. http://dx.doi.org/10.1073/pnas.1907169116.

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Sugars are essential molecules for all terrestrial biota working in many biological processes. Ribose is particularly essential as a building block of RNA, which could have both stored information and catalyzed reactions in primitive life on Earth. Meteorites contain a number of organic compounds including key building blocks of life, i.e., amino acids, nucleobases, and phosphate. An amino acid has also been identified in a cometary sample. However, the presence of extraterrestrial bioimportant sugars remains unclear. We analyzed sugars in 3 carbonaceous chondrites and show evidence of extraterrestrial ribose and other bioessential sugars in primitive meteorites. The 13C-enriched stable carbon isotope compositions (δ13C vs.VPDB) of the detected sugars show that the sugars are of extraterrestrial origin. We also conducted a laboratory simulation experiment of a potential sugar formation reaction in space. The compositions of pentoses in meteorites and the composition of the products of the laboratory simulation suggest that meteoritic sugars were formed by formose-like processes. The mineral compositions of these meteorites further suggest the formation of these sugars both before and after the accretion of their parent asteroids. Meteorites were carriers of prebiotic organic molecules to the early Earth; thus, the detection of extraterrestrial sugars in meteorites establishes the existence of natural geological routes to make and preserve them as well as raising the possibility that extraterrestrial sugars contributed to forming functional biopolymers like RNA on the early Earth or other primitive worlds.

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Hui, Zhenyang, Zhaochen Cai, Bo Liu, Dajun Li, Hua Liu e Zhuoxuan Li. "A Self-Adaptive Optimization Individual Tree Modeling Method for Terrestrial LiDAR Point Clouds". Remote Sensing 14, n. 11 (26 maggio 2022): 2545. http://dx.doi.org/10.3390/rs14112545.

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Individual tree modeling for terrestrial LiDAR point clouds always involves heavy computation burden and low accuracy toward a complex tree structure. To solve these problems, this paper proposed a self-adaptive optimization individual tree modeling method. In this paper, we first proposed a joint neighboring growing method to segment wood points into object primitives. Subsequently, local object primitives were optimized to alleviate the computation burden. To build the topology relation among branches, branches were separated based on spatial connectivity analysis. And then the nodes corresponding to each object primitive were adopted to construct the graph structure of the tree. Furthermore, each object primitive was fitted as a cylinder. To revise the local abnormal cylinder, a self-adaptive optimization method based on the constructed graph structure was proposed. Finally, the constructed tree model was further optimized globally based on prior knowledge. Twenty-nine field datasets obtained from three forest sites were adopted to evaluate the performance of the proposed method. The experimental results show that the proposed method can achieve satisfying individual tree modeling accuracy. The mean volume deviation of the proposed method is 1.427 m3. In the comparison with two other famous tree modeling methods, the proposed method can achieve the best individual tree modeling result no matter which accuracy indicator is selected.

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Samulewski, Rafael Block, Josué Martins Gonçalves, Alexandre Urbano, Antônio Carlos Saraiva da Costa, Flávio F. Ivashita, Andrea Paesano e Dimas Augusto Morozin Zaia. "Magnetite Synthesis in the Presence of Cyanide or Thiocyanate under Prebiotic Chemistry Conditions". Life 10, n. 4 (2 aprile 2020): 34. http://dx.doi.org/10.3390/life10040034.

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Magnetite is an iron oxide mineral component of primitive Earth. It is naturally synthesized in different ways, such as magma cooling as well as olivine decomposition under hydrothermal conditions. It is probable magnetite played a significant role in biogenesis. The seawater used in the current work contained high Mg2+, Ca2+ and SO42− concentrations, unlike the seawater of today that has high Na+ and Cl− concentrations. It is likely that this seawater better resembled the ion composition of the seas of the Earth from 4 billion years ago. Cyanide and thiocyanate were common molecules in prebiotic Earth, and especially in primitive oceans, where they could act on the magnetite mechanism synthesis via Fe2+ interaction. In this research, magnetite samples that were synthesized under prebiotic conditions in the presence of cyanide or thiocyanate, (both with and without artificial seawater), showed that, besides magnetite, goethite and ferrihydrite can be produced through different Fe2+-ion interactions. Cyanide apparently acts as a protective agent for magnetite production; however, thiocyanate and seawater 4.0 Gy ions produced goethite and ferrihydrite at different ratios. These results validate that Fe3+ oxides/hydroxides were possibly present in primitive Earth, even under anoxic conditions or in the absence of UV radiation. In addition, the results show that the composition of water in early oceans should not be neglected in prebiotic chemistry experiments, since this composition directly influences mineral formation.

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Harisman, Yulyanti, Difa Aziza, Muchamad Subali Noto, Lukman Harun e Marwia Tamrin Bakar. "“BAGAIMANA ORANG-ORANG DI ZAMAN PRIMITIF BERHITUNG?“ STUDI KASUS PADA MAHASISWA CALON GURU". Teorema: Teori dan Riset Matematika 8, n. 1 (31 marzo 2023): 128. http://dx.doi.org/10.25157/teorema.v8i1.9154.

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Pada zaman primitif perhitungan sudah digunakan dengan cara sederhana. Penelitian ini akan memaparkan bagaimana proses berpikir cara berhitung pada zaman primitif. Selanjutnya proses berpikir yang dilakukan dieksternalisasikan dengan proses berpikir cara berhitung pada siswa zaman sekarang, dan mengetahui sejauh mana pengetahuan mahasiswa calon guru tentang bagaimana orang primitif berhitung. Jenis penelitian ini ialah penelitian kualitatif dengan metode meta analisis dan studi kasus. Meta analisis menggunakan beberapa jurnal dan buku, selanjutnya kurikulum pada sekolah di analisis dan dicari hubungannya dengan proses berpikir cara berhitung zaman primitif. Teknik pengumpulan data dilakukan dengan cara menelaah, menganalisis, dan menghubungkan proses berpikir berhitung zaman primitif dengan materi sekolah. Studi kasus didapat dari mewawancara delapan mahasiswa dari program studi pendidikan matematika 2021. Instrumen penelitian ini adalah 1) ketertarikan peneliti mengenai perhitungan primitif; 2) wawancara terbuka mengenai perhitungan primitif. Analisis data yang digunakan dalam penelitian ini adalah literatur review dan analisis tematik. Hasil penelitian menunjukkan cara-cara orang primitif berhitung dan menunjukkan manusia pada zaman primitif sudah mengenal bilangan, cara berhitungnya masih digunakan untuk pembelajaran berhitung pada saat ini serta studi kasus dengan mahasiswa calon guru menunjukkan bagaimana mahasiswa pendidikan matematika merespon tentang cara berhitung pada zaman primitive dengan kategori respon yaitu: (1) Counting Media Primitive Student yang merupakan kategori mahasiswa yang mendefinisi perhitungan di zaman primitif dengan mengaitkan dengan alat-alat yang digunakan untuk berhitung pada zaman primitif; (2) Symbol Primitif Student adalah kategori mahasiswa yang mendefinisikan perhitungan primitif dengan memperhatikan simbol pada zaman primitif.

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Demongeot, Jacques, e Michel Thellier. "Primitive Oligomeric RNAs at the Origins of Life on Earth". International Journal of Molecular Sciences 24, n. 3 (23 gennaio 2023): 2274. http://dx.doi.org/10.3390/ijms24032274.

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There are several theories on the origin of life, which differ by choosing the preponderant factor of emergence: main function (autocatalysis versus replication), initial location (black smokers versus ponds) or first molecule (RNA versus DNA). Among the two last ones, the first assumes that an RNA world involving a collaboration of small RNAs with amino-acids pre-existed and the second that DNA–enzyme–lipid complexes existed first. The debate between these classic theories is not closed and the arguments for one or the other of these theories have recently fueled a debate in which the two have a high degree of likelihood. It therefore seems interesting to propose a third intermediate way, based on the existence of an RNA that may have existed before the latter stages postulated by these theories, and therefore may be the missing link towards a common origin of them. To search for a possible ancestral structure, we propose as candidate a small RNA existing in ring or hairpin form in the early stages of life, which could have acted as a “proto-ribosome” by favoring the synthesis of the first peptides. Remnants of this putative candidate RNA exist in molecules nowadays involved in the ribosomal factory, the concentrations of these relics depending on the seniority of these molecules within the translation process.

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Rossi, Riikka. "Transgression, Nostalgia, Order: Representation of the Primitive in Émile Zola's La Terre and Knut Hamsun's Markens grøde <\i>". Nordlit 15, n. 2 (27 marzo 2012): 257. http://dx.doi.org/10.7557/13.2282.

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This article examines the representation of the primitive in two peasant novels, Émile Zola's La Terre (1887, trans. as The Earth) and Knut Hamsun's Markens grøde (1917, trans. as Growth of the Soil). The concept of the primitive crosses a wide range of issues that were central to naturalist and decadent literature at the turn of the twentieth century, from unconscious instincts to the fascination with exotic cultures. It thus offers a fruitful medium for the comparative reading of French and Nordic fiction of the era. I especially focus on analysing the diverse, representative practices of Zola's and Hamsun's works, which betray stylistic differences in their portrayal of the primitive. I suggest that by describing the primitive as a vital, transgressive force that even turns against itself - against nature - Zola's La Terre creates a decadent version of the primitive, which, instead of a "serious", naturalistic portrayal of everyday life, is drawn to the brutal, instinctive primitive and uses the primitive to create vital forces of transgression. Hamsun's neo-naturalist novel, in turn, reconfigures the naturalist themes in a new form and envisions a fusion of the Darwinian, naturalistic primitive and the Romantic cult of innocent primordiality, suggesting the primitive lifestyle as a nostalgic return to a pre-modern lifestyle and a turn away from the degeneration of modernity.

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Michel, Patrick. "MarcoPolo-R: Near Earth Asteroid Sample Return Mission candidate as ESA-M3 class mission". Proceedings of the International Astronomical Union 10, H16 (agosto 2012): 483. http://dx.doi.org/10.1017/s1743921314011879.

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AbstractMarcoPolo-R is a sample return mission to a primitive Near-Earth Asteroid (NEA) selected in 2011 for the Assessment Study Phase of M3-class missions in the framework of ESAs Cosmic Vision (CV) 2015-2025 programme. The phase A study started at the end of 2012 and will proceed throughout 2013. The final selection by ESA will occur in February 2014. MarcoPolo-R is a European-led mission with a possible contribution from other agencies. MarcoPolo-R will rendez-vous with the primitive NEA 2008 EV5. Before returning a unique sample to Earth, the asteroid will be scientifically characterized at multiple scales. MarcoPolo-R will provide detailed knowledge of the physical and compositional properties of a member of the population of Potentially Hazardous Asteroids (PHA), which is an important contribution to mitigation studies.

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Michel, Patrick, Luisa-M. Lara, Bernard Marty, Detlef Koschny, Maria Antonietta Barucci, Andy Cheng, Hermann Bohnhardt et al. "MarcoPolo-R: Near Earth Asteroid Sample Return Mission candidate as ESA-M3 class mission". Proceedings of the International Astronomical Union 10, H16 (agosto 2012): 163. http://dx.doi.org/10.1017/s1743921314005183.

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AbstractMarcoPolo-R is a sample return mission to a primitive Near-Earth Asteroid (NEA) selected in February 2011 for the Assessment Study Phase at ESA in the framework of ESAfs Cosmic Vision 2 program. MarcoPolo-R is a European-led mission with a proposed NASA contribution. MarcoPolo-R takes advantage of three industrial studies completed as part of the previous Marco Polo mission (see ESA/SRE (2009)3). The aim of the new Assessment Study is to reduce the cost of the mission while maintaining its high science level, on the basis of advanced studies and technologies, as well as optimization of the mission. MarcoPolo-R will rendezvous with a unique kind of target, a primitive binary NEA, scientifically characterize it at multiple scales, and return a unique pristine sample to Earth unaltered by the atmospheric entry process or terrestrial weathering. The baseline target of MarcoPolo-R is the primitive binary NEA (175706) 1996 FG3, which offers a very efficient operational and technical mission profile. A binary target also provides enhanced science return: the choice of this target will allow new investigations to be performed more easily compared to a single object, and also enables investigations of the fascinating geology and geophysics of asteroids that are impossible to obtain from a single object. Precise measurements of the mutual orbit and rotation state of both components can be used to probe higher-level harmonics of the gravitational potential, and therefore the internal structure. A unique opportunity is offered to study the dynamical evolution driven by the YORP/Yarkovsky thermal effects. Possible migration of regolith on the primary from poles to equator allows the increasing maturity of asteroidal regolith with time to be expressed as a latitude-dependent trend, with the most-weathered material at the equator matching what is seen in the secondary. MarcoPolo-R will allow us to study the most primitive materials available to investigate early solar system formation processes. Moreover, MarcoPolo-R will provide a sample from a known target with known geological context. Direct investigation of both the regolith and fresh interior fragments is also impossible by any means other than sample return. The main goal of the MarcoPolo-R mission is to return unaltered NEA material for detailed analysis in ground-based laboratories. The limited sampling provided by meteorites does not offer the most primitive material available in near-Earth space. More primitive material, having experienced less alteration on the asteroid, will be more friable and would not survive atmospheric entry in any discernible amount. Only in the laboratory can instruments with the necessary precision and sensitivity be applied to individual components of the complex mixture of materials that forms an asteroid regolith, to determine their precise chemical and isotopic composition. Such measurements are vital for revealing the evidence of stellar, interstellar medium, pre-solar nebula and parent body processes that are retained in primitive asteroidal material, unaltered by atmospheric entry or terrestrial contamination. It is no surprise therefore that sample return missions are considered a priority by a number of the leading space agencies.

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Towe, Kenneth M. "Biochemical Innovations, Oxygen and Earth History". Short Courses in Paleontology 1 (1988): 114–29. http://dx.doi.org/10.1017/s2475263000000714.

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It is conventional to view the origin and early evolution of life as having taken place beneath an atmosphere devoid of free oxygen. Of primary concern is the fact that experiments designed to produce simple prebiotic compounds as precursor “building-blocks” for life are generally successful only if free oxygen is lacking from the starting mixture of gases. Clearly, life could hardly have evolved in the absence of suitable starting materials. Secondly, organic compounds are thermodynamically susceptible to oxygen and, given enough time, will become oxidized, ultimately to carbon dioxide. A centerpiece of biochemical evidence commonly invoked to support early anoxic conditions is the fact that almost all of the metabolic pathways for respiratory electron transfer in aerobic organisms take place anaerobically. Only the last step in the process requires free oxygen. It is easy to argue that this last step was an evolutionary response to the development of oxygenic conditions and was a later addition to the less energy-efficient pathways found in primitive anaerobes. The assumption in arguments of this type is that the present-day descendants of these early, primitive organisms are using similar biochemical pathways today that they used billions of years ago. For paleobiologists the meagre early Precambrian fossil record is of minimal help and such a uniformitarian approach toward deciphering early evolution is, together with the protein and nucleic acid sequence studies, one of the few methodologies available to go on.

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Bhakuni, D. S. "Prebiotic organic chemistry and the origin of life". Journal of Palaeosciences 41 (31 dicembre 1992): 9–17. http://dx.doi.org/10.54991/jop.1992.1100.

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Prebiotic synthesis of organic compounds such as amino, hydroxyl and aliphatic acids, urea, imidazoles and synthesis of amino acids, co-enzymes, nucleosides under primitive earth conditions have been reviewed.

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Ringwood, A. E. "The Earth-Moon Connection". Zeitschrift für Naturforschung A 44, n. 10 (1 ottobre 1989): 891–923. http://dx.doi.org/10.1515/zna-1989-1004.

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Abstract The early thermal state of the Earth provides important constraints on hypotheses relating to its origin and its connection with the Moon. The currently popular giant impact hypothesis of lunar origin requires the Earth’s mantle to have been completely melted during the impact. Differentiation of a molten mantle would have produced strong chemical and mineralogical stratification, causing the mantle to become gravitationally stable and resistant to convective rehomogenization. The resulting composition and mineralogy of the upper mantle and primitive crust would have been dramatically different from those which have existed during the past 3.8 b. y. It is concluded that the Earth’s mantle was not extensively melted at the conclusion of accretion of the planet and therefore the hypothesis that the Moon was formed by the impact of a martian-sized planetesimal on the proto-Earth is probably incorrect. Nevertheless, a wide range of geochemical evidence demonstrates the existence of a close genetic relationship between the Moon and the Earth’s mantle. The key evidence relates to the processes of core formation in planetary bodies and resultant abundance patterns of siderophile elements which remain in their silicate mantles. Because of the complexity of the core formation process within a given body and the multiplicity of chemical and physical processes involved, the mantle siderophile signature is expected to be a unique characteristic. Thus, the siderophile signatures of Mars and of the eucrite parent body are quite distinct from that of the Earth’s mantle. Lunar siderophile geochemistry is reviewed in detail. It is demonstrated that a large group of siderophile elements display similar abundances in the terrestrial and lunar mantles. The similarity implies that a major proportion of the material now in the Moon was derived from the Earth’s mantle after core formation. This implication, however, does not require that the bulk compositions of the lunar and terrestrial mantles should be essentially identical, as is often assumed. Factors which may contribute to significant compositional differences between the two bodies within the context of a close genetic relationship are reviewed. The most promising mechanism for removing terrestrial material from the Earth’s mantle arises from the impacts of a number of large (0.001 to 0.01 ME) but not giant (≥ 0.1 ME) planetesimals after core formation and at the terminal stage of the Earth’s accretion. These impacts evaporated several times their own masses of mantle material and shock-melted considerably more. However, they did not lead to complete or extensive (e.g. > 50%) melting of the entire mantle. Impact-generated clouds of shock-melted spray and vapours were accelerated to high velocities in the presence of a primitive terrestrial atmosphere that co-rotated with the Earth. This provided an effective means of transferring angular momentum from the Earth to the ejected material which condensed to form a ring of Earth-orbiting planetesimals and moonlets. The Moon was formed by coagulation from material derived from the outer regions of this ring. Accretion of the Earth in the presence of the gases of the solar nebula and the co-rotating primitive terrestrial atmosphere may also have provided a mechanism for generating the rapid prograde spin of the proto-Earth.

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Ishigami, Masahiro, Hideshi Ihara e Hiroyuki Shinoda. "Molecular Evolution of Aminoacyl tRNA Synthetases and Origin of Universal Genetic Code". International Astronomical Union Colloquium 161 (gennaio 1997): 483–89. http://dx.doi.org/10.1017/s0252921100015013.

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AbstractIt is thought that living things first appeared on the primitive earth 35 hundred million years ago. At that time, a primitive protein synthesis mechanism was thought to have been established, a genetic code system evolved, and a universal genetic code system developed. Aminoacyl tRNA synthetase must have evolved with the genetic code system. The aim of the present study is to clarify the evolution of aminoacyl tRNA synthetase and the process and era of the establishment of the universal genetic code system.

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Chisholm, Michael, e Richard Hodges. "Primitive and Peasant Markets". Geographical Journal 155, n. 2 (luglio 1989): 270. http://dx.doi.org/10.2307/635097.

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Pettitt, Paul B., e Mark J. White. "Cave men: Stone tools, Victorian science, and the ‘primitive mind’ of deep time". Notes and Records of the Royal Society 65, n. 1 (22 dicembre 2010): 25–42. http://dx.doi.org/10.1098/rsnr.2010.0100.

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Palaeoanthropology, the study of the evolution of humanity, arose in the nineteenth century. Excavations in Europe uncovered a series of archaeological sediments which provided proof that the antiquity of human life on Earth was far longer than the biblical six thousand years, and by the 1880s authors had constructed a basic paradigm of what ‘primitive’ human life was like. Here we examine the development of Victorian palaeoanthropology for what it reveals of the development of notions of cognitive evolution. It seems that Victorian specialists rarely addressed cognitive evolution explicitly, although several assumptions were generally made that arose from preconceptions derived from contemporary ‘primitive’ peoples. We identify three main phases of development of notions of the primitive mind in the period.

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Hanczyc, Martin M. "Metabolism and motility in prebiotic structures". Philosophical Transactions of the Royal Society B: Biological Sciences 366, n. 1580 (27 ottobre 2011): 2885–93. http://dx.doi.org/10.1098/rstb.2011.0141.

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Easily accessible, primitive chemical structures produced by self-assembly of hydrophobic substances into oil droplets may result in self-moving agents able to sense their environment and move to avoid equilibrium. These structures would constitute very primitive examples of life on the Earth, even more primitive than simple bilayer vesicle structures. A few examples of simple chemical systems are presented that self-organize to produce oil droplets capable of movement, environment remodelling and primitive chemotaxis. These chemical agents are powered by an internal chemical reaction based on the hydrolysis of an oleic anhydride precursor or on the hydrolysis of hydrogen cyanide (HCN) polymer, a plausible prebiotic chemistry. Results are presented on both the behaviour of such droplets and the surface-active properties of HCN polymer products. Such motile agents would be capable of finding resources while escaping equilibrium and sustaining themselves through an internal metabolism, thus providing a working chemical model for a possible origin of life.

30

Gururani, Kavita. "Acetonitrile: A Plausible Source of Amino Acids on the Primitive Earth." IOSR Journal of Applied Chemistry 2, n. 2 (2012): 43–48. http://dx.doi.org/10.9790/5736-0224348.

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Wade, Jon, Brendan Dyck, Richard M. Palin, James D. P. Moore e Andrew J. Smye. "The divergent fates of primitive hydrospheric water on Earth and Mars". Nature 552, n. 7685 (dicembre 2017): 391–94. http://dx.doi.org/10.1038/nature25031.

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KOBAYASHI, Tetsuo. "Metabolic Properties of Marine Hyperthermophiles, The Most Primitive Organisms on Earth." Kagaku To Seibutsu 33, n. 12 (1995): 796–802. http://dx.doi.org/10.1271/kagakutoseibutsu1962.33.796.

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Shimizu, Mikio. "Violent Primitive Earth Might have Harmonized with the Origin of Life". International Astronomical Union Colloquium 161 (gennaio 1997): 431–36. http://dx.doi.org/10.1017/s0252921100014949.

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AbstractAt the end of the planetesimal infall on the surface of the primitive earth, hot dry beaches might have been useful for the formation of various activated monomers and oligomers (peptides and small RNAs). We discuss the possibility that a small system composed of small RNAs (∼ 10 mers) and dipeptides might have mimicked the contemporary biosystem, based on experimental results suggesting the presence of previously overlooked weak but specific interactions between three bases and one amino acid (of genetic code type) and also those between a dipeptide and a biosubstrate (of ligase, transferase, hydrolase, lyase, isomerase and dehydrogenase type). The Kms obtained for these dipeptide enzymes were of the order of 1M, in accord with the association constant for the binding of guanosine to cytocine in water. In this oligomer world, the genotype and phenotype evolution was closely coupled, resulting in a very rapid rate of evolution.

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KAWAKATSU, Yasuhiro, Masanao ABE e Jun'ichiro KAWAGUCHI. "Mission Analysis for Sample Retrieval from a Primitive Near-Earth Asteroid". TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, SPACE TECHNOLOGY JAPAN 7 (2009): 33–41. http://dx.doi.org/10.2322/tstj.7.33.

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Coustenis, A. "Titan's atmosphere and surface: Parallels and differences with the primitive Earth". Earth, Moon, and Planets 67, n. 1-3 (1994): 95–100. http://dx.doi.org/10.1007/bf00613295.

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Estévez, Carles. "Alkyl chlorides in the primitive Earth: Implications for prebiotic chemical evolution". Origins of Life and Evolution of the Biosphere 26, n. 3-5 (ottobre 1996): 338–39. http://dx.doi.org/10.1007/bf02459795.

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37

Gregory, C. A., e Richard Hodges. "Primitive and Peasant Markets." Man 24, n. 2 (giugno 1989): 358. http://dx.doi.org/10.2307/2803326.

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Ge, Xuming, Bo Wu, Yuan Li e Han Hu. "A Multi-Primitive-Based Hierarchical Optimal Approach for Semantic Labeling of ALS Point Clouds". Remote Sensing 11, n. 10 (24 maggio 2019): 1243. http://dx.doi.org/10.3390/rs11101243.

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There are normally three main steps to carrying out the labeling of airborne laser scanning (ALS) point clouds. The first step is to use appropriate primitives to represent the scanning scenes, the second is to calculate the discriminative features of each primitive, and the third is to introduce a classifier to label the point clouds. This paper investigates multiple primitives to effectively represent scenes and exploit their geometric relationships. Relationships are graded according to the properties of related primitives. Then, based on initial labeling results, a novel, hierarchical, and optimal strategy is developed to optimize semantic labeling results. The proposed approach was tested using two sets of representative ALS point clouds, namely the Vaihingen datasets and Hong Kong’s Central District dataset. The results were compared with those generated by other typical methods in previous work. Quantitative assessments for the two experimental datasets showed that the performance of the proposed approach was superior to reference methods in both datasets. The scores for correctness attained over 98% in all cases of the Vaihingen datasets and up to 96% in the Hong Kong dataset. The results reveal that our approach of labeling different classes in terms of ALS point clouds is robust and bears significance for future applications, such as 3D modeling and change detection from point clouds.

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Huang, Liu, Wang, Zheng, Wang e Ming. "Change Detection of High Spatial Resolution Images Based on Region-Line Primitive Association Analysis and Evidence Fusion". Remote Sensing 11, n. 21 (24 ottobre 2019): 2484. http://dx.doi.org/10.3390/rs11212484.

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Change detection (CD) remains an important issue in remote sensing applications, especially for high spatial resolution (HSR) images, but it has yet to be fully resolved. This work proposes a novel object-based change detection (OBCD) method for HSR images that is based on region–line primitive association analysis and evidence fusion. In the proposed method, bitemporal images are separately segmented, and the segmentation results are overlapped to obtain the temporal region primitives (TRPs). The temporal line primitives (TLPs) are obtained by straight line detection on bitemporal images. In the initial CD stage, Dempster–Shafer evidence theory fuses the multiple items of evidence of the TRPs’ spectrum, edge, and gradient changes, and obtains the initial changed areas. In the refining CD stage, the association between the TRPs and their contacting TLPs in the unchanged areas is established on the basis of the region–line primitive association framework, and the TRPs’ main line directions (MLDs) are calculated. Some changed TRPs omitted in the initial CD stage are recovered by their MLD changes, thereby refining the initial CD results. Different from common OBCD methods, the proposed method considers the change evidence of TRPs’ internal and boundary information simultaneously via information complementation between TRPs and TLPs. The proposed method can significantly reduce missed alarms while maintaining a low level of false alarms in OBCD, thereby improving total accuracy. In our experiments, our method is superior to common CD methods, including change vector analysis (CVA), PCA-k-means, and iterative reweighted multivariate alteration detection (IRMAD), in terms of overall accuracy, missed alarms, and Kappa coefficient.

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Mulder, Thomas E., Heiko Goelzer, Fred W. Wubs e Henk A. Dijkstra. "Snowball Earth Bifurcations in a Fully-Implicit Earth System Model". International Journal of Bifurcation and Chaos 31, n. 06 (maggio 2021): 2130017. http://dx.doi.org/10.1142/s0218127421300172.

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There is now much geological evidence that the Earth was fully glaciated during several periods in the geological past (about 700[Formula: see text]Myr ago) and attained a so-called Snowball Earth (SBE) state. Additional support for this idea has come from climate models of varying complexity that show transitions to SBE states and undergo hysteresis under changes in solar radiation. In this paper, we apply large-scale bifurcation analyses to a novel, fully-implicit Earth System Model of Intermediate Complexity (I-EMIC) to study SBE transitions. The I-EMIC contains a primitive equation ocean model, a model for atmospheric heat and moisture transport, a sea ice component and formulations for the adjustment of albedo over snow and ice. With the I-EMIC, high-dimensional branches of the SBE bifurcation diagram are obtained through parameter continuation. We are able to identify stable and unstable equilibria and uncover an intricate bifurcation structure associated with the ice-albedo feedback. Moreover, large-scale linear stability analyses are performed near major bifurcations, revealing the spatial nature of destabilizing perturbations.

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Arai, Noriyoshi, Yusei Kobayashi e Kenji Yasuoka. "A biointerface effect on the self-assembly of ribonucleic acids: a possible mechanism of RNA polymerisation in the self-replication cycle". Nanoscale 12, n. 12 (2020): 6691–98. http://dx.doi.org/10.1039/c9nr09537c.

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The self-assembly was found to be more favoured in a vesicle-cell membrane, rather than in the bulk system. The result will contribute to a better understanding of the origin of life on the primitive Earth.

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Martins, Zita, e Matthew A. Pasek. "Delivery of Organic Matter to the Early Earth". Elements 20, n. 1 (1 febbraio 2024): 19–23. http://dx.doi.org/10.2138/gselements.20.1.19.

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The inner Solar System—including the planet Earth—was heavily bombarded by comets, asteroids, and their fragments (i.e., meteorites, micrometeorites, and interplanetary dust particles) from 4.56 to about 3.5 billion years ago. This bombardment resulted in a rich assortment of organics delivered to the Earth, as comets and many asteroids contain carbonaceous material. These organic compounds were likely further processed on the early Earth (e.g., by impact-shock reactions), providing a feedstock of prebiotic molecules to the crust and oceans. In this chapter, we review the mechanisms of organic matter delivery to the primitive Earth, further reactions and processing, and the importance of exogenous material in the evolution of our planet and life.

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Cary, Francesca C. A., David W. Deamer, Bruce F. Damer, Sarah A. Fagents, Kathleen C. Ruttenberg e Stuart P. Donachie. "Could Life Have Started on Mars? Planetary Conditions That Assemble and Destroy Protocells". Life 14, n. 3 (20 marzo 2024): 415. http://dx.doi.org/10.3390/life14030415.

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Early Mars was likely habitable, but could life actually have started there? While cellular life emerged from prebiotic chemistry through a pre-Darwinian selection process relevant to both Earth and Mars, each planet posed unique selection ‘hurdles’ to this process. We focus on drivers of selection in prebiotic chemistry generic to Earth-like worlds and specific to Mars, such as an iron-rich surface. Iron, calcium, and magnesium cations are abundant in hydrothermal settings on Earth and Mars, a promising environment for an origin of life. We investigated the impact of cations on the stability and disruption of different primitive cell membranes under different pH conditions. The relative destabilizing effect of cations on membranes observed in this study is Ca2+ > Fe2+ > Mg2+. Cation concentrations in Earth systems today are too low to disrupt primitive membranes, but on Mars concentrations could have been elevated enough to disrupt membranes during surface dehydration. Membranes and RNA interact during dehydration–rehydration cycles to mutually stabilize each other in cation-rich solutions, and optimal membrane composition can be ‘selected’ by environmental factors such as pH and cation concentrations. We introduce an approach that considers how life may have evolved differently under the Martian planetary conditions and selective pressures.

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Nicholls, Elizabeth L., e Donald Brinkman. "A new specimen of Utatsusaurus (Reptilia: Ichthyosauria) from the Lower Triassic Sulphur Mountain Formation of British Columbia". Canadian Journal of Earth Sciences 30, n. 3 (1 marzo 1993): 486–90. http://dx.doi.org/10.1139/e93-037.

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An incomplete skull and mandible of the primitive ichthyosaur Utatsusaurus is described from the Lower Triassic Vega Phroso Member of the Sulphur Mountain Formation of British Columbia. The specimen contributes to our knowledge of the cranial anatomy of the genus, which was previously known primarily from postcranial material, and extends its geographic range to Canada. The presence of an isodont dentition in this primitive genus suggests that isodonty rather than heterodonty may be the primitive character state for the Ichthyosauria.

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Zhou, Hao, Zheng Ji, Xiangyu You, Yuchen Liu, Lingfeng Chen, Kun Zhao, Shan Lin e Xiangxiang Huang. "Geometric Primitive-Guided UAV Path Planning for High-Quality Image-Based Reconstruction". Remote Sensing 15, n. 10 (18 maggio 2023): 2632. http://dx.doi.org/10.3390/rs15102632.

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Image-based refined 3D reconstruction relies on high-resolution and multi-angle images of scenes. The assistance of multi-rotor drones and gimbal provides great convenience for image acquisition. However, capturing images with manual control generally takes a long time. It could easily lead to redundant or insufficient local area coverage, resulting in poor quality of the reconstructed model. We propose a surface geometric primitive-guided UAV path planning method (SGP-G) that aims to automatically and quickly plan a collision-free path to capture fewer images, based on which high-quality models can be obtained. The geometric primitives are extracted by plane segmentation on the proxy, which performs three main functions. First, a more representative evaluation of the reconstructability of the whole scene is realized. Second, two optimization strategies for different geometric primitives are executed to quickly generate a near-global optimized set of viewpoints. Third, regularly arranged viewpoints are generated to improve the efficiency of image acquisition. Experiments on virtual and real scenes demonstrate the remarkable performance of our method. Compared with the state of the art, we accomplish the planning of the photographic path with higher efficiency in a relatively simple way, achieving equivalent and even higher quality of the reconstructed model with fewer images.

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Brazeau, Martin D. "A new genus of rhizodontid (Sarcopterygii, Tetrapodomorpha) from the Lower Carboniferous Horton Bluff Formation of Nova Scotia, and the evolution of the lower jaws in this group". Canadian Journal of Earth Sciences 42, n. 8 (1 agosto 2005): 1481–99. http://dx.doi.org/10.1139/e05-041.

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Letognathus gen. nov. is described from the Lower Carboniferous (Tournaisian) Horton Bluff Formation. Included in this genus is the species Letognathus hardingi (Dawson 1868), which was originally assigned toRhizodus and later toStrepsodus, but it is distinct from these genera in tooth morphology and the presence of several more primitive rhizodontid characters. By contrast with these latter more derived genera, the parasymphysial plate contacts the first coronoid; the first coronoid bears a row of lingually deflected teeth, the tooth striations occur around the entire circumference of the crown and are much finer and less regular than those ofStrepsodus, and marginal tooth row reaches anteriorly to the dentary symphysis. Phylogenetic analysis indicates that rhizodontid jaws primitively bear symphysial tusks; slender recumbent teeth; an anterior projection of the dentary over the anteromesial depression for the median symphysial plate and shows the highly derived jaws ofStrepsodus andRhizodus evolved within the Rhizodontida, rather than as primitive characters for the group. This new jaw material supports earlier models of mandibular kinesis and shows that the coronoid fangs were oriented such as to facilitate kinesis. Rhizodontid jaw evolution seems to be marked by parallelisms with tristichopterids and early tetrapods.

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Tazaki, Kazue, e W. S. Fyfe. "Primitive clay precursors formed on feldspar". Canadian Journal of Earth Sciences 24, n. 3 (1 marzo 1987): 506–27. http://dx.doi.org/10.1139/e87-051.

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High-resolution transmission electron microscopy of clay formation on K-feldspar has revealed the existence of intermediate states between feldspar and crystalline clay products. During the earliest weathering stages of K-feldspar, a primitive clay precursor forms on the feldspar surface that is spotted by ion oxides. This reactive iron is incorporated into the primitive clay precursors, which have an ultrathin 150–200 Å (1 Å = 0.1 nm) circular form and 14–20 Å lattice images or long, curled fiber forms with varied lattice image spacings. The electron diffraction patterns of primitive clay precursors show diffuse rings at 2.65, 2.04, and 1.51 Å, suggesting low crystallinity, random orientation, and partial inheritance of the original structure. EDX step scanning analysis showed that the major-element concentrations of Si, Al, and K tend to decrease from unaltered parts to altered parts of precursors with substantial increase in Fe. Auger depth profiling showed the thickness of the primitive clay layers is 150–300 Å. The primitive clay precursors may well precede formation of spheroidal particles of halloysite, squat cylinders of halloysite or hexagonal crystalline, and tabuler halloysite (7 Å). SEM, XRD, SIMS, and SAM data support the TEM results.

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Bouvier, A., e M. Boyet. "Primitive Solar System materials and Earth share a common initial 142Nd abundance". Nature 537, n. 7620 (14 settembre 2016): 399–402. http://dx.doi.org/10.1038/nature19351.

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Honda, Yasuhiro, Rafael Navarro-González e Cyril Ponnamperuma. "A quantitative assay of biologically important compounds in simulated primitive earth experiments". Advances in Space Research 9, n. 6 (gennaio 1989): 63–66. http://dx.doi.org/10.1016/0273-1177(89)90209-3.

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Saha, Arpita, Ruiqin Yi, Albert C. Fahrenbach, Anna Wang e Tony Z. Jia. "A Physicochemical Consideration of Prebiotic Microenvironments for Self-Assembly and Prebiotic Chemistry". Life 12, n. 10 (13 ottobre 2022): 1595. http://dx.doi.org/10.3390/life12101595.

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The origin of life on Earth required myriads of chemical and physical processes. These include the formation of the planet and its geological structures, the formation of the first primitive chemicals, reaction, and assembly of these primitive chemicals to form more complex or functional products and assemblies, and finally the formation of the first cells (or protocells) on early Earth, which eventually evolved into modern cells. Each of these processes presumably occurred within specific prebiotic reaction environments, which could have been diverse in physical and chemical properties. While there are resources that describe prebiotically plausible environments or nutrient availability, here, we attempt to aggregate the literature for the various physicochemical properties of different prebiotic reaction microenvironments on early Earth. We introduce a handful of properties that can be quantified through physical or chemical techniques. The values for these physicochemical properties, if they are known, are then presented for each reaction environment, giving the reader a sense of the environmental variability of such properties. Such a resource may be useful for prebiotic chemists to understand the range of conditions in each reaction environment, or to select the medium most applicable for their targeted reaction of interest for exploratory studies.

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