Articles de revues : « Fragmentation secondaire »

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Dufour, Guillaume, Marc Massot et Philippe Villedieu. « Étude d'un modèle de fragmentation secondaire pour les brouillards de gouttelettes ». Comptes Rendus Mathematique 336, n^o 5 (mars 2003) : 447–52. http://dx.doi.org/10.1016/s1631-073x(03)00067-0.

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Lessard, Claude. « Égalité des chances et stratification dans le champ scolaire : quid de l’équité du système d’éducation ? » Éthique en éducation et en formation, n^o 6 (29 avril 2019) : 41–61. http://dx.doi.org/10.7202/1059242ar.

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Le système d’éducation québécois, comme la société qui l’entoure, se fragmente : d’abord, en fonction des facteurs sociaux traditionnels — notamment, le revenu et l’éducation des parents —, ensuite, en fonction de la multiplication de modèles socioculturels. Dans le champ de l’enseignement primaire et secondaire, la première fragmentation s’exprime par la montée de l’enseignement privé, notamment dans les centres urbains; la seconde fragmentation se manifeste, au sein du réseau public, par la multiplication et la variété des projets particuliers, conçus pour retenir des élèves de milieux favorisés, mais aussi pour permettre à des groupes sociaux de transmettre à leurs enfants une éducation distinctive. Ce texte analyse la manifestation de cette double fragmentation dans le champ éducatif et la contextualise dans le cadre de grands changements sociétaux. Nous soutenons qu’ainsi mis sur les rails de la concurrence, le système scolaire québécois est de plus en plus stratifié ou qu’il a plusieurs vitesses. Nous explorons quelques politiques publiques qui permettraient la sortie d’une situation difficile à dépasser.

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Hingrat, Yves, et F. Feer. « Effets de la fragmentation forestière sur l’activité des coléoptères coprophages : dispersion secondaire des graines en Guyane française ». Revue d'Écologie. Supplément 57, n^o 8 (2002) : 165–79. http://dx.doi.org/10.3406/revec.2002.6243.

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Netter, Julien. « Ouverture de l’école et inégalités. Constats et perspectives ». Éducation et sociétés 50, n^o 2 (7 septembre 2023) : 17–31. http://dx.doi.org/10.3917/es.050.0017.

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Dans L’évolution pédagogique en France , Durkheim estime que l’instabilité chronique que l’enseignement secondaire connaît au début du XX e siècle depuis plusieurs décennies traduit la difficulté à trouver le “changement d’esprit et d’orientation qui se trouve nécessaire”. Un constat étonnamment similaire peut être dressé pour l’école primaire française du début du XXI e siècle, en proie à des réformes parfois contradictoires qui se succèdent rapidement. Cette réflexion interroge la difficulté de l’école, dans cette situation, à définir un horizon collectif permettant de se saisir de la question persistante des inégalités scolaires. L’article revient d’abord sur l’évolution générale de l’école vers une plus grande fragmentation, liée à l’accumulation de dispositifs permettant la juxtaposition d’acteurs non coordonnés et de conceptions de l’apprentissage peu discutées. Il cherche ensuite à montrer que le fait de penser l’école en termes de dispositifs amène à négliger la question des pratiques pédagogiques, particulièrement délaissées en France.

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Kodjo, Yawo, Jean-Robert Rwenge Mburano et Hamidou Kone. « Utilisation des Services Obstétricaux Modernes au Togo : Approche par les Modèles Mixtes ». European Scientific Journal, ESJ 18, n^o 40 (31 décembre 2022) : 10. http://dx.doi.org/10.19044/esj.2022.v18n40p10.

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Plusieurs études révèlent que près de 80 % des décès maternels pourraient être évités si les femmes avaient fait un recours adéquat aux soins obstétricaux modernes (Adiko et al., 2018). Au Togo, seulement 33% des femmes ont fait un recours adéquat aux consultations prénatales et 64% ont fait recours à l’accouchement moderne en 2017 (Institut Nationale de Statistique et des Etudes Démographiques(INSEED), 2017). Des modèles mixtes en particulier de la régression logistique multiniveau appliqués aux données de l’enquête par grappes à indicateurs multiples (2017), il ressort que, les femmes faisant recours adéquat aux consultations prénatales uniquement, pratiquaient la contraception moderne, sans union ou en union monogame, vivaient dans des ménages dirigés par une personne ayant un niveau d’instruction secondaire ou plus. Elles habitent dans les communautés à degrés de modernité sanitaire élevé et de fragmentation religieuse homogène. Celles qui ont fait recours uniquement à l’accouchement moderne ont une assurance santé, sont plus épanouies et dirigées par une personne du groupe ethnique Adja/Ewé. Elles résident dans les ménages non loués. Ce sont elles qui habitent dans des communautés plus riches. Tandis que celles qui font les deux recours sont des primipares, plus exposées aux médias, résidant dans un ménage à niveau de vie élevé et dirigé par un chef catholique ou musulman. Au Togo, il serait pertinent d’agir sur le recours adéquat aux consultations prénatales en rendant plus disponibles les soins et sur le recours à l’accouchement moderne par la sensibilisation sur son l’utilité. Several studies show that nearly 80 per cent of maternal deaths could be prevented if women had made adequate use of modern obstetric care (Adiko and al., 2018). In Togo, only 33% of women made adequate use of antenatal consultations and 64% resorted to modern childbirth in 2017 (INSEED, 2017). Mixed models in particular the multilevel logistic regression on data from the Multiple Indicator Cluster Survey (2017), it appears that women making adequate use of antenatal consultations only, has used modern contraception, without a union or in a monogamous union, lived in households headed by a person with secondary education or higher. They live in communities with high degrees of sanitary modernity and homogeneous religious fragmentation. Those who rely solely on modern childbirth have health insurance, are more fulfilled and are led by someone from the Adja/Ewé ethnic group. They reside in non-rented households. They are the ones who live in wealthier communities. While those who make both appeals are primiparous, more exposed to the media, residing in a household with a high standard of living and headed by a chief Catholic or Muslim religious. In Togo, it would be relevant to act on the appropriate use of antenatal cares by making care more available and on the use of modern childbirth by raising public awareness of its usefulness.

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Raftery, MJ, et JH Bowie. « The Collision-Induced Dissociations of Deprotonated Amines in the Gas Phase ». Australian Journal of Chemistry 41, n^o 9 (1988) : 1477. http://dx.doi.org/10.1071/ch9881477.

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The major collision-induced fragmentations of deprotonated primary and secondary amines are best rationalized as proceeding through the intermediacy of ion complexes. For example, the characteristic fragmentation of deprotonated ethylamine isMeCH2NH- → [Me-(CH2=NH)] → CH2N- + CH4 Secondary alkylamines behave in a similar fashion. The occurrence of proton transfer as a prelude to fragmentation is rare: the only example observed in this study is the probable reaction PhNEt →→ PhNHCHMe → [(PhNH=CH)Me-] → C7H6N- + CH4 which is preceded or accompanied by proton transfer between the methylene and phenyl substituents. Deprotonated aniline undergoes specific elimination of CNH from the 1-position to form the cyclopentadienyl anion. Finally, retro reactions are observed for the piperazine anion, e.g. HN(CH2CH2)2N → -CH2CH2N=CH2+CH2NH

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Oz, Ibrahim Ilker, Sevil Ilikhan, Muammer Bilici, Hatice Harmansa, Kemal Karakaya et Yucel Ustundag. « Bezoar-Related Ileus Secondary to Endoscopic Fragmentation ». Istanbul Medical Journal 16, n^o 4 (8 janvier 2016) : 155–57. http://dx.doi.org/10.5152/imj.2015.42104.

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Rudling, Adriana. « What’s Inside the Box ? Mapping Agency and Conflict within Victims’ Organizations ». International Journal of Transitional Justice 13, n^o 3 (26 septembre 2019) : 458–77. http://dx.doi.org/10.1093/ijtj/ijz025.

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Abstract∞ This article provides a better understanding of victims’ individual-level agency and their differences in terms of transitional justice preferences and capabilities by inquiring into intra-organizational conflict. While it is primarily conceptual, it combines secondary literature with case study material from Colombia and Panama, converging on Latin America as a geographical area and the crime of forced disappearance. Tracing the evolution of the 2004/2005 fragmentation of the Colombian Association of Relatives of Detained Disappeared Persons, it argues that victims’ collective action and perceived homogeneity is a performance that builds on much internal negotiation between members. When deliberations have clear winners, they end in adjustments of the mission statement of the group, purges and voluntary member withdrawal, but fragmentations result from situations where the leaders of opposing coalitions are evenly matched and their proposals equally engaging to peers.

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Botrill, Andrew R., Anastassios E. Giannakopulos, Allen Millichope, Ken S. Lee et Peter J. Derrick. « Combination of Time-of-Flight Mass Analysers with Magnetic-Sector Instruments : In-Line and Perpendicular Arrangements. Applications to Poly(Ethylene Glycol) with Long-Chain end Groups ». European Journal of Mass Spectrometry 6, n^o 2 (avril 2000) : 225–32. http://dx.doi.org/10.1255/ejms.341.

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High-energy collision-induced dissociation has been shown to provide extensive and detailed structural information on poly(ethylene glycol) with palmitoyl end-groups. Fragmentation within the end-groups provides direct information on their structures. Both in-line time-of-flight (TOF) and orthogonal TOF have been used for the measurement of fragment ions. Use of TOF as the second stage of mass spectrometry has facilitated exploitation of the pulsed method of ionisation matrix-assisted laser desorption/ionisation (MALDI). The orthogonal TOF instrument is used with a liquid secondary-ion mass spectrometry source. The laboratory-frame collision energies were different for in-line and orthogonal TOF, being 8–12 keV in the former and 800 eV in the latter. The tandem mass spectra were similar for the in-line experiment with either He or Xe collision gas and the orthogonal experiment with Xe. Mechanisms proposed for the fragmentations involve homolytic cleavage (C–H and backbone bonds) and invoke non-ergodicity.

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Phillips, Vaughan T. J., Sachin Patade, Julie Gutierrez et Aaron Bansemer. « Secondary Ice Production by Fragmentation of Freezing Drops : Formulation and Theory ». Journal of the Atmospheric Sciences 75, n^o 9 (16 août 2018) : 3031–70. http://dx.doi.org/10.1175/jas-d-17-0190.1.

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Abstract A numerical formulation is provided for secondary ice production during fragmentation of freezing raindrops or drizzle. This is obtained by pooling laboratory observations from published studies and considering the physics of collisions. There are two modes of the scheme: fragmentation during spherical drop freezing (mode 1) and during collisions of supercooled raindrops with more massive ice (mode 2). The empirical scheme is for atmospheric models. Microphysical simulations with a parcel model of fast ascent (8 m s−1) between −10° and −20°C are validated against aircraft observations of tropical maritime deep convection. Ice enhancement by an order of magnitude is predicted from inclusion of raindrop-freezing fragmentation, as observed. The Hallett–Mossop (HM) process was active too. Both secondary ice mechanisms (HM and raindrop freezing) are accelerated by a positive feedback involving collisional raindrop freezing. An energy-based theory is proposed explaining the laboratory observations of mode 1, both of approximate proportionality between drop size and fragment numbers and of their thermal peak. To illustrate the behavior of the scheme in both modes, the glaciation of idealized monodisperse populations of drops is elucidated with an analytical zero-dimensional (0D) theory treating the freezing in drop–ice collisions by a positive feedback of fragmentation. When drops are too few or too small (≪1 mm), especially at temperatures far from −15°C (mode 1), there is little raindrop-freezing fragmentation on realistic time scales of natural clouds, but otherwise, high ice enhancement (IE) ratios of up to 100–1000 are possible. Theoretical formulas for the glaciation time of such drop populations, and their maximum and initial growth rates of IE ratio, are proposed.

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Gómez, R., R. Castro, F. Betancourt et M. Moncada. « Comparison of normalized and non-normalized block caving comminution models ». Journal of the Southern African Institute of Mining and Metallurgy 121, n^o 11 (30 novembre 2021) : 1–8. http://dx.doi.org/10.17159/2411-9717/1150/2021.

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In block cave mining, rock fragmentation is a key parameter that influences the production level design and mine planning. Fragmentation occurs mainly by natural breakage during the caving process and in the draw column. The breakage that occurs within the column is known as secondary fragmentation. Secondary fragmentation has been successfully described using the block caving comminution model, which replicates the fragmentation mechanics between particles under drawn and vertical loads in a draw column. This model is based on a kinetic and population balance approach, in which non-normalized and normalized assumptions can be used depending on material and comminution system behaviour. In this paper, the non-normalized and normalized approaches are applied and compared to laboratory data to determine which assumption should be used for secondary breakage in block caving. Approaches are compared graphically, with the mean square error and the Fisher test with a false-rejection probability of 0.05. Based on a statistical analysis, the results show that the normalized model can be applied to all the rock types tested.

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Korolev, Alexei, et Thomas Leisner. « Review of experimental studies of secondary ice production ». Atmospheric Chemistry and Physics 20, n^o 20 (19 octobre 2020) : 11767–97. http://dx.doi.org/10.5194/acp-20-11767-2020.

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Abstract. Secondary ice production (SIP) plays a key role in the formation of ice particles in tropospheric clouds. Future improvement of the accuracy of weather prediction and climate models relies on a proper description of SIP in numerical simulations. For now, laboratory studies remain a primary tool for developing physically based parameterizations for cloud modeling. Over the past 7 decades, six different SIP-identifying mechanisms have emerged: (1) shattering during droplet freezing, (2) the rime-splintering (Hallett–Mossop) process, (3) fragmentation due to ice–ice collision, (4) ice particle fragmentation due to thermal shock, (5) fragmentation of sublimating ice, and (6) activation of ice-nucleating particles in transient supersaturation around freezing drops. This work presents a critical review of the laboratory studies related to secondary ice production. While some of the six mechanisms have received little research attention, for others contradictory results have been obtained by different research groups. Unfortunately, despite vast investigative efforts, the lack of consistency and the gaps in the accumulated knowledge hinder the development of quantitative descriptions of any of the six SIP mechanisms. The present work aims to identify gaps in our knowledge of SIP as well as to stimulate further laboratory studies focused on obtaining a quantitative description of efficiencies for each SIP mechanism.

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Антонов, Д. В., К. Ю. Вершинина et Р. М. Федоренко. « Микровзрывная фрагментация двухжидкостных капель на основе таллового масла ». Письма в журнал технической физики 49, n^o 14 (2023) : 3. http://dx.doi.org/10.21883/pjtf.2023.14.55816.19575.

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The paper presents the results of experimental study of the micro-explosive fragmentation of two-liquid drops during heating in a high-temperature medium. The characteristics of secondary fragments during micro-explosive fragmentation of single droplets based on tall oil were studied. With micro-explosive fragmentation of droplets based on crude tall oil, it is possible to increase the evaporation surface area by more than 70 times. It has been established that during the secondary grinding of drops based on crude tall oil due to micro-explosive effects, it is possible to obtain 2–3 times more secondary fragments than when fragmenting drops based on kerosene and filtered tall oil under identical heating conditions.

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Petersen, Allan C., Steen Hammerum, Zhigang Li, Paul Meenan, Patti A. Parziale, Kirsi Ranta et Teófilo Rojo. « Isomerization and Fragmentation of Metastable Secondary Amine Radical Cations. » Acta Chemica Scandinavica 52 (1998) : 1045–50. http://dx.doi.org/10.3891/acta.chem.scand.52-1045.

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Karkanorachaki, Katerina, Panagiota Tsiota, Giorgos Dasenakis, Evdokia Syranidou et Nicolas Kalogerakis. « Nanoplastic Generation from Secondary PE Microplastics : Microorganism-Induced Fragmentation ». Microplastics 1, n^o 1 (21 janvier 2022) : 85–101. http://dx.doi.org/10.3390/microplastics1010006.

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Concern regarding the pollution of the marine environment with plastics has been rising in recent years. Plastic waste residing in and interacting with the environment fragments into secondary particles in the micro- and nanoscale, whose negative impacts on the environment are even greater than those of the parent items. In this work, secondary high density polyethylene (HDPE) and low density polyethylene (LDPE) microplastics were produced by irradiation of virgin films following mechanical fragmentation. The fragments with size ranging from 250 μm to 2 mm were selected for subsequent microcosm experiments. Incubation for 120 days in seawater inoculated with two marine communities, Agios, acclimatized to utilizing plastics as a carbon source, and Souda, as was collected at the Souda bay (Crete, Greece), resulted in biofilm formation by polyethylene (PE) degraders. Monthly FTIR (Fourier-transform infrared spectroscopy) examination of the samples revealed changes in the chemical structure of the surface of the polymers. Dynamic light scattering (DLS) was employed and nano- and microparticles with sizes in the range between 56 nm and 4.5 μm were detected in the seawater of inoculated microcosms. It was thus demonstrated that weathered plastics particles can biodeteriorate and biofragment as a result of biofilm attachment, resulting in the production of nanoplastics due to microbial activity.

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McIlwraith, C. W. « Patellar fragmentation secondary to bilateral medial patellar ligament desmotomy ». Equine Veterinary Education 17, n^o 4 (5 janvier 2010) : 205–6. http://dx.doi.org/10.1111/j.2042-3292.2005.tb00371.x.

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Jones, Thomas J., Keri McNamara, Julia Eychenne, Alison C. Rust, Katharine V. Cashman, Bettina Scheu et Robyn Edwards. « Primary and secondary fragmentation of crystal-bearing intermediate magma ». Journal of Volcanology and Geothermal Research 327 (novembre 2016) : 70–83. http://dx.doi.org/10.1016/j.jvolgeores.2016.06.022.

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Jarosz, Sławomir, Katarzyna Szewczyk, Jerzy Sitkowski et Anna Gaweł. « Mechanism of the fragmentation of secondary sugar allyltin derivatives ». Tetrahedron : Asymmetry 15, n^o 17 (septembre 2004) : 2653–56. http://dx.doi.org/10.1016/j.tetasy.2004.07.023.

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Cooper, Helen J., Robert R. Hudgins, Kristina Håkansson et Alan G. Marshall. « Secondary fragmentation of linear peptides in electron capture dissociation ». International Journal of Mass Spectrometry 228, n^o 2-3 (août 2003) : 723–28. http://dx.doi.org/10.1016/s1387-3806(03)00202-1.

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Zaikin, Vladimir G., Roman S. Borisov et Vladislav V. Luzhnov. « Specific Electron Ionization-Induced Fragmentation of Secondary Alcohol Methoxyacetates ». European Journal of Mass Spectrometry 7, n^o 1 (février 2001) : 63–67. http://dx.doi.org/10.1255/ejms.391.

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Cool, T., et P. W. Voorhees. « Dendrite fragmentation : an experiment-driven simulation ». Philosophical Transactions of the Royal Society A : Mathematical, Physical and Engineering Sciences 376, n^o 2113 (8 janvier 2018) : 20170213. http://dx.doi.org/10.1098/rsta.2017.0213.

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The processes leading to the fragmentation of secondary dendrite arms are studied using a three-dimensional Sn dendritic structure that was measured experimentally as an initial condition in a phase-field simulation. The phase-field model replicates the kinetics of the coarsening process seen experimentally. Consistent with the experiment, the simulations of the Sn-rich dendrite show that secondary dendrite arm coalescence is prevalent and that fragmentation is not. The lack of fragmentation is due to the non-axisymmetric morphology and comparatively small spacing of the dendrite arms. A model for the coalescence process is proposed, and, consistent with the model, the radius of the contact region following coalescence increases as t 1/3 . We find that small changes in the width and spacing of the dendrite arms can lead to a very different fragmentation-dominated coarsening process. Thus, the alloy system and growth conditions of the dendrite can have a major impact on the fragmentation process. This article is part of the theme issue ‘From atomistic interfaces to dendritic patterns’.

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Saravanan, Lakshamanan, Mahalakshmi Saravanan, Ramya Harish et Nidhi Sharma. « Effect of sperm DNA fragmentation on ICSI outcome : A prospective study ». Clinical Journal of Obstetrics and Gynecology 3, n^o 2 (14 octobre 2020) : 127–31. http://dx.doi.org/10.29328/journal.cjog.1001065.

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Aim and objectives: The primary aim was to measure the sperm DNA damage and to study the magnitude of sperm DNA damage. Secondary objective was to study the effect of sperm DNA fragmentation on Day 5 Blastocyst expansion (graded 1-5). Results: There is an increase in sperm DNA fragmentation with an increase in age. Increased sperm DNA fragmentation is also associated with abnormal motility and morphology in semen samples. However, there is no reduction in expansion or grade of blastocyst. Conclusion: Sperm DNA fragmentation testing is a useful investigation in unexplained infertility. However, Sperm DNA fragmentation has no significant association with Day 5 embryo grade in ICSI cycles. Thesis work of Fellowship in Reproductive Medicine student: Dr. Ramya Harish

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Saha, Shivnetra, et Shashank Deep. « Glycerol inhibits the primary pathways and transforms the secondary pathway of insulin aggregation ». Physical Chemistry Chemical Physics 18, n^o 28 (2016) : 18934–48. http://dx.doi.org/10.1039/c6cp02906j.

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Eshun, P. A., B. O. Affum et A. Boakye. « Drill and Blast Performance Evaluation at the Obra Pit of Chirano Gold Mines Ltd, Ghana ». Ghana Mining Journal 16, n^o 2 (20 décembre 2016) : 28–35. http://dx.doi.org/10.4314/gm.v16i2.4.

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This paper investigates the causes of inefficient fragmentation and formation of toes in the Obra pit of Chirano Gold Mines Ltd and recommends best practices in order to produce optimum fragmentation to feed the crusher at a reduced cost and to provide good working pit floors. The methods employed included: drilling performance analysis using statistical methods; fragmentation analysis of blasting performance using Kuz-Ram Model and Wipfrag software; determination of the velocity of detonation of the bulk explosive using MREL Micro Trap VOD/Data Recorder; and estimation of the cost of secondary drilling and blasting using Mine Management Reporting Software. From the analyses, it was observed that the blast designed parameters and blasting practices were acceptable to produce good fragmentation but the actual drilling parameters deviated from the designed parameters by about 25%, 24% and 26% in hole depth, burden and spacing respectively. It was concluded that the cause of the ineffective fragmentation leading to high cost of secondary breakage and uneven pit floors was due to operational errors during drilling. It is therefore recommended that in order to reduce excessive deviations in the drilling parameters, periodic training of operators must be conducted, supervision of drilling and blasting operations must be enhanced, and inclinometers should be used during drilling activities to ensure the accuracy and precision of all blast holes. Keywords: Drilling, Blasting, Fragmentation, Kuz-Ram Model, Wipfrag Software

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Tsaprailis, George, Hari Nair, Árpád Somogyi, Vicki H. Wysocki, Wenqing Zhong, Jean H. Futrell, Scott G. Summerfield et Simon J. Gaskell. « Influence of Secondary Structure on the Fragmentation of Protonated Peptides ». Journal of the American Chemical Society 121, n^o 22 (juin 1999) : 5142–54. http://dx.doi.org/10.1021/ja982980h.

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Evans, James D., Christopher M. Halloran, Paul Mansour et Michael R. Zeiderman. « Fatal Intestinal Perforation Secondary to Fragmentation of a Celestin Tube ». Digestive Surgery 17, n^o 4 (2000) : 400–402. http://dx.doi.org/10.1159/000018886.

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Fu, Yu, Guanglu Li, Tenghui Zheng, Yingsong Zhao et Mingxi Yang. « Fragmentation of soil aggregates induced by secondary raindrop splash erosion ». CATENA 185 (février 2020) : 104342. http://dx.doi.org/10.1016/j.catena.2019.104342.

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Gómez, René, Raúl L. Castro, Aldo Casali, Sergio Palma et Asieh Hekmat. « A Comminution Model for Secondary Fragmentation Assessment for Block Caving ». Rock Mechanics and Rock Engineering 50, n^o 11 (3 juillet 2017) : 3073–84. http://dx.doi.org/10.1007/s00603-017-1267-2.

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DOORNENBAL, PIETER. « SHELL STRUCTURE, COLLECTIVITY AND NUCLEAR SHAPES — RISING IN-BEAM EXPERIMENTS AT RELATIVISTIC ENERGIES ». International Journal of Modern Physics E 15, n^o 07 (octobre 2006) : 1495–503. http://dx.doi.org/10.1142/s0218301306005083.

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The RISING fast beam campaign aims at high resolution γ-ray spectroscopy experiments with relativistic radioactive beams at GSI. The secondary beams produced by fragmentation or fission are used for Coulomb excitation or secondary fragmentation experiments to perform studies of nuclei far off stability. The physics phenomena studied with this method include nuclear structure experiments targeting at the evolution of shell structure toward the drip lines, mirror symmetry, collectivity and electromagnetic transition strengths. Example results of this fast beam campaign are presented and compared to various shell model calculations and nuclear structure models.

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Lin, Chih-Lung, Aaron S. Dumont, Yu-Feng Su, Yee-Jean Tsai, Jih-Hui Huang, Kao-Ping Chang, Shen-Long Howng, Aij-Lie Kwan, Neal F. Kassell et Cheng-Hsing Kao. « Attenuation of cerebral vasospasm and secondary injury by 17β-estradiol following experimental subarachnoid hemorrhage ». Journal of Neurosurgery 110, n^o 3 (mars 2009) : 457–61. http://dx.doi.org/10.3171/2008.6.17622.

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Object Cerebral vasospasm remains a major complication in patients who have suffered a subarachnoid hemorrhage (SAH). Previous studies have shown that 17β-estradiol (E2) attenuates experimental SAH–induced cerebral vasospasm. Moreover, E2 has been shown to reduce neuronal apoptosis and secondary injury following cerebral ischemia. Adenosine A1 receptor (AR-A1) expression is increased following ischemia and may represent an endogenous neuroprotective effect. This study was designed to evaluate the efficacy of E2 in preventing cerebral vasospasm and reducing secondary injury, as evidenced by DNA fragmentation and AR-A1 expression, following SAH. Methods A double-hemorrhage model of SAH in rats was used, and the degree of vasospasm was determined by averaging the cross-sectional areas of the basilar artery 7 days after the first SAH. A cell death assay was used to detect apoptosis. Changes in the protein expression of AR-A1 in the cerebral cortex, hippocampus, and dentate gyrus were compared with levels in normal controls and E2-treated groups (subcutaneous E2, 0.3 mg/ml). Results The administration of E2 prevented vasospasm (p < 0.05). Seven days after the first SAH, DNA fragmentation and protein levels of AR-A1 were significantly increased in the dentate gyrus. The E2 treatment decreased DNA fragmentation and prevented the increase in AR-A1 expression in the dentate gyrus. There were no significant changes in DNA fragmentation and the expression of AR-A1 after SAH in the cerebral cortex and hippocampus in the animals in the control and E2-treated groups. Conclusions The E2 was effective in attenuating SAH-induced cerebral vasospasm, decreasing apoptosis in the dentate gyrus, and reducing the expression of AR-A1 in the dentate gyrus after SAH. Interestingly, E2 appears to effectively prevent cerebral vasospasm subsequent to SAH as well as attenuate secondary injury by reducing both apoptosis and a compensatory increase in AR-A1 expression in the dentate gyrus.

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Chiaki, Gen, et Naoki Yoshida. « Disc fragmentation and oligarchic growth of protostellar systems in low-metallicity gas clouds ». Monthly Notices of the Royal Astronomical Society 510, n^o 4 (2 octobre 2021) : 5199–219. http://dx.doi.org/10.1093/mnras/stab2799.

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ABSTRACT We study low-metallicity star formation with a set of high-resolution hydrodynamics simulations for various gas metallicities over a wide range 0–$10^{-3} \ {\rm Z_{\bigodot }}$. Our simulations follow non-equilibrium chemistry and radiative cooling by adopting realistic elemental abundance and dust size distribution. We examine the condition for the fragmentation of collapsing clouds (cloud fragmentation; CF) and of accretion discs (disc fragmentation; DF). We find that CF is suppressed due to rapid gas heating accompanied with molecular hydrogen formation even with efficient dust cooling for metallicities ${\gtrsim}10^{-5} \ {\rm Z_{\bigodot }}$. Instead, DF occurs in almost all runs regardless of metallicity. We also find that, in the accretion discs, the growth of the protostellar systems is overall oligarchic. The primary protostar grows through the accretion of gas, and secondary protostars form through the interaction of spiral arms or the break-up of a rapidly rotating protostar. Despite vigorous fragmentation, a large fraction of secondary protostars are destroyed through mergers or tidal disruption events. For a few hundred years after the first adiabatic core formation, only several protostars survive in the disc, and the total mass of protostars is 0.52–$3.8 \ {\rm M_{\bigodot }}$.

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KOIZUMI, Yu, Kimikazu TSUSAKA, Chikaosa TANIMOTO et Yasuyuki MIYAJIMA. « DISC CUTTER WEAR AND SECONDARY FRAGMENTATION IN HARD ROCK TBM TUNNELING ». Doboku Gakkai Ronbunshuu C 65, n^o 4 (2009) : 951–62. http://dx.doi.org/10.2208/jscejc.65.951.

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Marban, Gregorio, José J. Pis et Antonio B. Fuertes. « Simulation of secondary fragmentation during fluidized bed combustion of char particles ». Powder Technology 89, n^o 1 (octobre 1996) : 71–78. http://dx.doi.org/10.1016/s0032-5910(96)03157-9.

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Arena, Umberto, Antonio Cammarota, Riccardo Chirone et Leopoldo Massimilla. « Secondary fragmentation of a char in a circulating fluidized bed combustor ». Symposium (International) on Combustion 24, n^o 1 (janvier 1992) : 1341–48. http://dx.doi.org/10.1016/s0082-0784(06)80156-6.

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Chirone, R., P. Salatino et L. Massimilla. « Secondary fragmentation of char particles during combustion in a fluidized bed ». Combustion and Flame 77, n^o 1 (juillet 1989) : 79–90. http://dx.doi.org/10.1016/0010-2180(89)90106-5.

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Fleury, A., R. Del Moral, J. P. Dufour, H. Emmermann, F. Hubert, C. Poinot, M. S. Pravikoff, H. Delagrange et R. Bimbot. « Production of 17N and 16C secondary beams via projectile nuclear fragmentation ». Nuclear Instruments and Methods in Physics Research Section B : Beam Interactions with Materials and Atoms 10-11 (mai 1985) : 369–72. http://dx.doi.org/10.1016/0168-583x(85)90271-x.

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Bedo, D. G. « Nucleolar fragmentation in polytene trichogen cells of Lucilia cuprina and Chrysomya bezziana (Diptera : Calliphoridae) ». Genome 35, n^o 2 (1 avril 1992) : 283–93. http://dx.doi.org/10.1139/g92-044.

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The location of genes coding for 18S and 28S ribosomal RNA in mitotic and polytene cells of Lucilia cuprina and Chrysomya bezziana was investigated using in situ hybridization of an 18 + 28S ribosomal gene probe and silver staining. In both species ribosomal genes were localized to secondary constriction regions in sex chromosome heterochromatin. In L. cuprina mitotic cells the probe hybridizes to a distal secondary constriction region in the short arms of the X and Y chromosomes. In C. bezziana mitotic chromosomes ribosomal genes were located in distal secondary constriction regions in the long arms of the X and Y chromosomes. In polytene trichogen cells of both species, hybridization results varied with the level of polyteny. Cells of low polyteny have a single hybridization site, but with greater polytenization, increasing numbers of extrachromosomal fragments strongly hybridize to the ribosomal gene probe. No hybridization occurs in structures representing the sex chromosomes or in the autosomes. These results indicate that fragmentation and dispersal of the nucleolus occurs during polytenization. Silver staining of both unsquashed and squashed polytene nuclei show identical behaviour of multiple, varied-sized nucleolar bodies, thus confirming the in situ hybridization results. Uridine incorporation studies in L. cuprina indicate that transcription occurs in extrachromosomal bodies similar to nucleolar fragments. Nucleolar fragmentation is more pronounced in L. cuprina males, particularly in those with the translocation T(Y;2)540. Chromosomally normal C. bezziana show nucleolar fragmentation levels similar to that in L. cuprina males. Ribosomal genes are disproportionately replicated in trichogen cells to a much greater extent than surrounding heterochromatin. Nucleolar fragmentation may be a gene amplification system, but it is not known to what degree, relative to diploid amounts, ribosomal genes replicate in trichogen cells.Key words: Lucilia cuprina, Chrysomya bezziana, polytene cells, ribosomal genes, nucleolar fragmentation, disproportionate replication, heterochromatin.

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Zhang, Jie, Jieqiong Tan, Zhiping Hu, Chunli Chen et Liuwang Zeng. « HDAC6 Inhibition Protects against OGDR-Induced Golgi Fragmentation and Apoptosis ». Oxidative Medicine and Cellular Longevity 2019 (2 juillet 2019) : 1–12. http://dx.doi.org/10.1155/2019/6507537.

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The Golgi apparatus (GA) is a pivotal organelle, and its fragmentation is an essential process in the development of apoptosis. GA is a potential target in the treatment of cerebral ischemia-reperfusion injury. Histone deacetylase 6 (HDAC6) catalyzes the removal of functional acetyl groups from proteins and plays an important role in cell homeostasis. In this study, the neuroprotective effects and the underlying mechanisms of HDAC6 inhibition were assessed in an ischemia-reperfusion injury model. Mouse neuroblastoma N2a cells and cultured neurons were subjected to oxygen-glucose deprivation/reperfusion (OGDR) insult. OGDR induces Golgi fragmentation and reduces tubulin acetylation in N2a cells and cultured neurons. Golgi fragmentation is prior to nuclear chromatin condensation after OGDR injury. Overexpression of GBF1 not only protects against OGDR-induced Golgi fragmentation but also protects against OGDR-induced apoptosis, suggesting that Golgi fragmentation is not secondary to apoptosis but plays a causal role for subsequent apoptosis. HDAC6 inhibition suppresses OGDR-induced tubulin deacetylation, p115 cleavage, and caspase 3 activation and protects against OGDR-induced Golgi fragmentation and apoptosis. This work opens a new avenue for potential clinical application of HDAC6 inhibitors for cerebral ischemia-reperfusion-related disorders.

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Wohlleben, Wendel, Jessica Meyer, Julie Muller, Philipp Müller, Klaus Vilsmeier, Burkard Stahlmecke et Thomas A. J. Kuhlbusch. « Release from nanomaterials during their use phase : combined mechanical and chemical stresses applied to simple and multi-filler nanocomposites mimicking wear of nano-reinforced tires ». Environmental Science : Nano 3, n^o 5 (2016) : 1036–51. http://dx.doi.org/10.1039/c6en00094k.

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Inoue, Shigeki, et Naoki Yoshida. « Spiral-arm instability – III. Fragmentation of primordial protostellar discs ». Monthly Notices of the Royal Astronomical Society : Letters 491, n^o 1 (23 octobre 2019) : L24—L28. http://dx.doi.org/10.1093/mnrasl/slz160.

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ABSTRACT We study the gravitational instability and fragmentation of primordial protostellar discs by using high-resolution cosmological hydrodynamics simulations. We follow the formation and evolution of spiral arms in protostellar discs, examine the dynamical stability, and identify a physical mechanism of secondary protostar formation. We use linear perturbation theory based on the spiral-arm instability (SAI) analysis in our previous studies. We improve the analysis by incorporating the effects of finite thickness and shearing motion of arms, and derive the physical conditions for SAI in protostellar discs. Our analysis predicts accurately the stability and the onset of arm fragmentation that is determined by the balance between self-gravity and gas pressure plus the Coriolis force. Formation of secondary and multiple protostars in the discs is explained by the SAI, which is driven by self-gravity and thus can operate without rapid gas cooling. We can also predict the typical mass of the fragments, which is found to be in good agreement with the actual masses of secondary protostars formed in the simulation.

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Loza, C. L., J. S. Craven, L. D. Yee, M. M. Coggon, R. H. Schwantes, M. Shiraiwa, X. Zhang et al. « Secondary organic aerosol yields of 12-carbon alkanes ». Atmospheric Chemistry and Physics Discussions 13, n^o 8 (7 août 2013) : 20677–727. http://dx.doi.org/10.5194/acpd-13-20677-2013.

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Abstract. Secondary organic aerosol (SOA) yields were measured for cyclododecane, hexylcyclohexane, n-dodecane, and 2-methylundecane under high- and low-NOx conditions, in which alkyl peroxy radicals (RO2) react primarily with NO and HO2, respectively, for multiple initial alkane concentrations. Experiments were run until 95–100% of the initial alkane had reacted. Particle wall loss was evaluated as two limiting cases. SOA yield differed by 2 orders of magnitude between the two limiting cases, but the same trends among alkane precursors were observed for both limiting cases. Vapor-phase wall losses were addressed through a modeling study and increased SOA yield uncertainty by approximately 30%. SOA yields were highest from cyclododecane under both NOx conditions. Under high-NOx conditions, SOA yields increased from 2-methylundecane < dodecane ~ hexylcyclohexane < cyclododecane, consistent with previous studies. Under low-NOx conditions, SOA yields increased from 2-methylundecane ~ dodecane < hexylcyclohexane < cyclododecane. The presence of cyclization in the parent alkane structure increased SOA yields, whereas the presence of branch points decreased SOA yields due to increased vapor-phase fragmentation. Vapor-phase fragmentation was found to be more prevalent under high-NOx conditions than under low-NOx conditions. For different initial concentrations of the same alkane and same NOx conditions, SOA yield did not correlate with SOA mass throughout SOA growth, suggesting kinetically limited SOA growth for these systems.

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Yang, Jiong, et Kristina Håkansson. « Characterization of Oligodeoxynucleotide Fragmentation Pathways in Infrared Multiphoton Dissociation and Electron Detachment Dissociation by Fourier Transform Ion Cyclotron Double Resonance ». European Journal of Mass Spectrometry 15, n^o 2 (avril 2009) : 293–304. http://dx.doi.org/10.1255/ejms.966.

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Infrared multiphoton dissociation (IRMPD) is a vibrational excitation tandem mass spectrometric fragmentation method valuable for sequencing of oligonucleotides. For oligodeoxynucleotides, typical product ions correspond to sequence-specific 5′ ( a-base) and their complementary 3′ w-type ions from carbon–oxygen bond cleavage at the 3′ position of the deoxyribose from which a nucleobase is lost. Such fragmentation patterns are also observed in collision activated dissociation (CAD). The CAD oligodeoxynucleotide fragmentation mechanism has been characterized in detail. By contrast, fragmentation schemes in IRMPD have not been rigorously established. In this paper, we apply, for the first time, Fourier transform ion cyclotron double resonance (DR) experiments to characterize IRMPD fragmentation pathways of oligodeoxynucleotide anions. Our results suggest that neutral base loss precedes backbone fragmentation but that T-rich oligodeoxynucleotides fragment via a different mechanism, similar to the mechanisms proposed for CAD. We also extend the DR approach to characterize intermediates in electron detachment dissociation of hexamer oligodeoxynucleotides. Here, we found that charge reduced radical precursor ions constitute major intermediates for dT6, d(GCATAC) and d(GCATGC). Furthermore, ( a/ z–T) ions ( z ions correspond to C–O bond cleavage on the other side of a backbone phosphate group as compared to the formation of a ions) mainly originate from secondary fragmentation of a/ z radical ions for the oligodeoxynucleotide dT6.

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Zolotorevsky, N. « Patterns of Grain Fragmentation During Plastic Deformation of Metals at Small to Medium Strains (Brief Review) ». Reviews on Advanced Materials and Technologies 6, n^o 1 (31 mars 2024) : 1–11. http://dx.doi.org/10.17586/2687-0568-2024-6-1-1-11.

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The review is devoted to the phenomenon of fragmentation: the subdivision of initial grains into highly misoriented crystallites in the process of plastic deformation. The investigations performed mostly during last two decades were considered and, in doing so, the early stages of fragmented microstructure evolution were of interest. Characteristics of regular cell block structure, described repeatedly before, were specified on the basis of more recent investigations, in particular, its orientation dependence and the development of primary and secondary microbands. The large-scale manifestations of grain subdivision, zones of intense fragmentation as well as the evolution of misorientation angle distribution with increasing strain and changing deformation conditions were also considered. Finally, the modeling of fragmentation is discussed briefly.

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TRAUTMANN, W., P. ADRICH, T. AUMANN, C. O. BACRI, T. BARCZYK, R. BASSINI, S. BIANCHIN et al. « N/Z DEPENDENCE OF PROJECTILE FRAGMENTATION ». International Journal of Modern Physics E 17, n^o 09 (octobre 2008) : 1838–49. http://dx.doi.org/10.1142/s0218301308010829.

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The N/Z dependence of projectile fragmentation at relativistic energies has been studied in a recent experiment at the GSI laboratory with the ALADiN forward spectrometer coupled to the LAND neutron detector. Besides a primary beam of 124 Sn , also secondary beams of 124 La and 107 Sn delivered by the FRS fragment separator have been used in order to extend the range of isotopic compositions of the produced spectator sources. With the achieved mass resolution of ΔA/A ≈ 1.5%, lighter isotopes with atomic numbers Z ≤ 10 are individually resolved. The presently ongoing analyses of the measured isotope yields focus on isoscaling and its relation to the properties of hot fragments at freeze-out and on the derivation of chemical freeze-out temperatures which are found to be independent of the isotopic composition of the studied systems. The latter result is at variance with the predictions for limiting temperatures as obtained with finite-temperature Hartree-Fock calculations.

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Nasirov, U. F., Sh Sh Zairov, M. R. Mekhmonov et A. U. Fatkhiddinov. « Controlling blast energy parameters to ensure intensive open-pit rock fragmentation ». Gornye nauki i tekhnologii = Mining Science and Technology (Russia) 7, n^o 2 (20 juillet 2022) : 137–49. http://dx.doi.org/10.17073/2500-0632-2022-2-137-149.

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Controlling blast action, in order to increase its energy efficiency in a production blasthole is quite an important issue. This is because it enables the formation of broken rock mass with preset coarseness parameters. Increasing the blast pressure and the time of the blast impact on a rock mass is traditionally recommended as one of the ways to improve the blast action on the rock mass, thus reducing the oversize yield in open pits. One device which enables this approach to a certain extent is a turbulator. The turbulator is fabricated of aluminum plate twisted in a helical fashion around its longitudinal axis. It is mounted in a production blasthole according to a specially designed scheme. The methodology developed to study the stress and strain state of a rock mass when using a turbulator in a blasthole explosive charge allows the size of radial fracture zone and the radius of rock fragmentation to be defined. A method was developed to initiate blasthole charges in a pit blasting block. It includes drilling blastholes, filling them with explosive, installing downhole blasting caps, and blasting using non-electric initiation system. A blasting block is divided into two equal parts (sections), which in turn contain three series of blastholes for short-delay blasting. Blasthole charges are initiated simultaneously in the two parts of the block based on a trapezoidal blasting pattern, thus ensuring meeting detonation waves. In the first series, instantaneous blasting of blastholes located on both ends of the blasting block and forming a trapezoid (in plan view) is carried out. Then after 42 ms, the second series of blastholes (also forming a trapezoid) is detonated. After another 42 ms, the remaining blastholes are detanoated along the perimeter of the blast block in the third series. Implementation of this design with the effect of turbo-blasting for rock fragmentations by blasthole charges at the Kalmakyr deposit of JSC “Almalyk Mining and Metallurgical Complex” has led to the reduction of consumption of explosives, volume of drilling, secondary fragmentation costs, and increased productivity of excavators and mining safety.

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Mahajan, R. K., Neelam Gupta et Satinder K. Uppal. « Mass spectral studies of aromatic aza analogues of juvabione ». Collection of Czechoslovak Chemical Communications 51, n^o 12 (1986) : 2879–83. http://dx.doi.org/10.1135/cccc19862879.

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ITO, H., T. SAKURAI, T. MATSUO, T. ICHIHARA et I. KATAKUSE. « MASS SPECTRA AND DISSOCIATION PATTERNS OF TELLURIUM CLUSTERS USING POSITIVE AND NEGATIVE SECONDARY-ION MASS SPECTROMETRY ». Surface Review and Letters 03, n^o 01 (février 1996) : 577–82. http://dx.doi.org/10.1142/s0218625x96001042.

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Size distribution of positive and negative tellurium clusters in the size range from 2 to 56 atoms was investigated by secondary-ion mass spectrometry (SIMS). Cluster ions were produced by the 12-keV Xe+ ions bombardment of a sample tellurium sheet and were mass-analyzed using sector-type double-focusing mass spectrometers. It was found that a discontinuous variation of cluster-ion intensity appeared at specific numbers of n. These numbers were 5, 8, 12, 15, 19, and 23 for positive clusters and 6, 10, 13, and 16 for negative clusters. The dissociation pattern was also investigated by an acceleration-voltage scanning method. It was found that Te2, Te5, and Te6 fragmentation events occurred at a large probability. Observation of specific fragmentation patterns suggested the existence of nonsequential fragment channels.

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Geisthoff, Urban, et Steffen Maune. « Ultrasound-Guided Mechanical Fragmentation of Sialoliths ». Otolaryngology–Head and Neck Surgery 139, n^o 2_suppl (août 2008) : P48. http://dx.doi.org/10.1016/j.otohns.2008.05.154.

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Objective Assess the efficacy of ultrasound-guided mechanical intraductal stone fragmentation and removal of sialoliths (SonoFragmentation). SonoFragmentation has been described recently as a new technique for the treatment of sialolithiasis (Surg Endosc 2006;20(4):690–4). Methods Retrospective analysis of cases treated within the last 3 years. Results SonoFragmentation was used as a 2nd line treatment in 22/28 cases. 10 patients were free of stones (parotid gland [PG]: 2x, submandibular gland [SMG]: 7x, sublingual gland: 1x; in 2 cases sialendoscopy was additionally used). Residual stones persisted in 12 patients (PG: 2x, SMG: 10x). 6 patients with sialolithiasis of the GP were primarily treated with the technique. 4 of those patients were cured. Reasons for failure were lacking accessibility of the stone by the forceps (9x), impossibility to grasp the stone (5x) and/or the concomitant grabbing of soft tissue together with the stone (3x). Conclusions The efficacy of SonoFragmentation as a secondary treatment after failure of other minimally invasive methods is about 50% (10/22). Additionally, it is a promising primary therapeutic option (cure: 4/6 patients).

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Dhakal, Bhola Nath, et Narendra Raj Khanal. « Causes and Consequences of Fragmentation of Agricultural Land : A Case of Nawalparasi District, Nepal ». Geographical Journal of Nepal 11 (3 avril 2018) : 95–112. http://dx.doi.org/10.3126/gjn.v11i0.19551.

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This paper discusses the causes and consequences of agricultural land fragmentation in Nawalparasi district. Primary and secondary sources of information at District and Village Development Committees (Now Municipalities and Rural Municipalities) levels are used. A total of 93 households were interviewed in three VDCs from Nawalparasi district of Nepal. Socio-economic, legal and infrastructure development factors are responsible for fragmentation of agricultural land. Results showed that there has been decreasing productivity of land due to fragmentation of agricultural land. It is mainly due to increasing time of labor input, less opportunity of using modern chemical fertilizer on the one hand and the problem in using modern agricultural equipment such as tractors on the other.The Geographical Journal of NepalVol. 11: 95-112, 2018

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Taylor, Michael J., Hoshin Kim, William Kew, Amity Andersen, Arunima Bhattacharjee, Mark H. Engelhard et Christopher R. Anderton. « Atomistic simulations for investigation of substrate effects on lipid in-source fragmentation in secondary ion mass spectrometry ». Biointerphases 18, n^o 1 (janvier 2023) : 011003. http://dx.doi.org/10.1116/6.0002298.

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In beam-based ionization methods, the substrate plays an important role on the desorption mechanism of molecules from surfaces. Both the specific orientation that a molecule adopts at a surface and the strength of the molecule-surface interaction can greatly influence desorption processes, which in turn will affect the ion yield and the degree of in-source fragmentation of a molecule. In the beam-based method of secondary ion mass spectrometry (SIMS), in-source fragmentation can be significant and molecule specific due to the hard ionization method of using a primary ion beam for molecule desorption. To investigate the role of the substrate on orientation and in-source fragmentation, we have used atomistic simulations—molecular dynamics in combination with density functional theory calculations—to explore the desorption of a sphingolipid (palmitoylsphingomyelin) from a model surface (gold). We then compare SIMS data from this model system to our modeling findings. Using this approach, we found that the combined adsorption and binding energy of certain bonds associated with the headgroup fragments (C3H8N+, C5H12N+, C5H14NO+, and C5H15PNO4+) was a good predictor for fragment intensities (as indicated by relative ion yields). This is the first example where atomistic simulations have been applied in beam-based ionization of lipids, and it presents a new approach to study biointerfacial lipid ordering effects on SIMS imaging.

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