Relevant bibliographies by topics / Ring formation

Academic literature on the topic 'Ring formation'

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Published: 4 June 2021
Last updated: 19 February 2023

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Journal articles on the topic "Ring formation"

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Guosheng Wang, Guosheng Wang, and Siyu Han and Ronghui Xu Siyu Han and Ronghui Xu. "The Ring Formation Mechanism in Cyclization of Berberine." Journal of the chemical society of pakistan 43, no. 3 (2021): 308. http://dx.doi.org/10.52568/000578/jcsp/43.03.2021.

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Berberine hydrochloride is a natural alkaloid with significant antitumor activities against many types of cancer cells, can be synthesized by cyclic reaction with hydrochloride condensate and glyoxal as raw materials and copper chloride as catalyst. In this study, the transition and energy change for the each reaction step was calculated by the density functional theory program Dmol3 in Materials Studio 2017. and the results testified that there are two ring formation in the cycliztion process, and according to the result we proposed the mechanism of this cyclization reaction. We also use infrared and ultraviolet spectroscopy to monitor the reaction process in real time and prove the ring formation process. The reaction mechanism was firstly proposed at the basic results of above.
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Guosheng Wang, Guosheng Wang, and Siyu Han and Ronghui Xu Siyu Han and Ronghui Xu. "The Ring Formation Mechanism in Cyclization of Berberine." Journal of the chemical society of pakistan 43, no. 3 (2021): 308. http://dx.doi.org/10.52568/000578.

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Berberine hydrochloride is a natural alkaloid with significant antitumor activities against many types of cancer cells, can be synthesized by cyclic reaction with hydrochloride condensate and glyoxal as raw materials and copper chloride as catalyst. In this study, the transition and energy change for the each reaction step was calculated by the density functional theory program Dmol3 in Materials Studio 2017. and the results testified that there are two ring formation in the cycliztion process, and according to the result we proposed the mechanism of this cyclization reaction. We also use infrared and ultraviolet spectroscopy to monitor the reaction process in real time and prove the ring formation process. The reaction mechanism was firstly proposed at the basic results of above.
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Tuma, Rabiya S. "Contractile ring formation." Journal of Cell Biology 174, no. 3 (July 24, 2006): 319b. http://dx.doi.org/10.1083/jcb.1743iti5.

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Pellissier, Hélène. "The Use of Domino Reactions for the Synthesis of Chiral Rings." Synthesis 52, no. 24 (July 22, 2020): 3837–54. http://dx.doi.org/10.1055/s-0040-1707905.

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This short review highlights the recent developments reported in the last four years on the asymmetric construction of chiral rings based on enantioselective domino reactions promoted by chiral metal catalysts.1 Introduction2 Formation of One Ring Containing One Nitrogen Atom3 Formation of One Ring Containing One Oxygen/Sulfur Atom4 Formation of One Ring Containing Several Heterocyclic Atoms5 Formation of One Carbon Ring6 Formation of Two Rings7 Conclusion
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Combes, Françoise. "Ring and Lens Formation." International Astronomical Union Colloquium 157 (1996): 286–98. http://dx.doi.org/10.1017/s0252921100049927.

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AbstractThe dynamical mechanism to form rings at Lindblad resonances in a barred galaxy is now well-known: due to its dissipative character, the gas is forced in a spiral structure, and experiences torques from the bar potential. Angular momentum is transferred until gas accumulates in the resonant rings. Some problems remain however to account for all observations, such as the very different time-scales for nuclear, inner and outer ring formation, while the three are frequently observed in the same galaxy; the shapes, orientations and thickness of the rings, etc... The adequacy of the present gas dynamical modelizations is discussed.Lenses are secondary components of barred galaxies that could originate from bar evolution. No model until now has met the observational constraints, in particular the sharp edge of the lenses, their strong velocity anisotropy, and their small thickness. We propose here that lenses are the result of partial bar destruction, a necessary step in a feedback cycle of bar formation-destruction, a cycle driven by gas accretion.
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Kim, Woong-Tae, Woo-Young Seo, and Yonghwi Kim. "Formation of nuclear rings of barred galaxies and star formation therein." Proceedings of the International Astronomical Union 9, S303 (October 2013): 43–53. http://dx.doi.org/10.1017/s174392131400012x.

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AbstractBarred galaxies contain substructures such as a pair of dust lanes and nuclear rings, with the latter being sites of intense star formation. We study the substructure formation as well as star formation in nuclear rings using numerical simulations. We find that nuclear rings form not by the Lindblad resonances, as previously thought, but by the centrifugal barrier that inflowing gas along dust lanes cannot overcome. This predicts a smaller ring in a more strongly barred galaxy, consistent with observations. Star formation rate (SFR) in a nuclear ring is determined primarily by the mass inflow rate to the ring. In our models, the SFR typically shows a short strong burst associated with the rapid gas infall and stays very small for the rest of the evolution. When the SFR is low, ages of young star clusters exhibit an azimuthal gradient along the ring since star formation takes place mostly near the contact points between the dust lanes and the nuclear ring. When the SFR is large, on the other hand, star formation is widely distributed throughout the whole length of the ring, with no apparent age gradient of star clusters. Since observed ring star formation appears long-lived with episodic bursts, our results suggest that the bar region should be replenished continually with fresh gas from outside.
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Pearce, F. R., and P. A. Thomas. "Ring formation in triaxial potentials." Monthly Notices of the Royal Astronomical Society 248, no. 4 (February 15, 1991): 688–700. http://dx.doi.org/10.1093/mnras/248.4.688.

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Sammes, Peter G., and David J. Weller. "Steric Promotion of Ring Formation." Synthesis 1995, no. 10 (October 1995): 1205–22. http://dx.doi.org/10.1055/s-1995-4099.

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Dutta, Aloke K., and Jared A. Butcher. "Macrocyclic ring formation in micelles." Tetrahedron Letters 27, no. 29 (January 1986): 3343–44. http://dx.doi.org/10.1016/s0040-4039(00)84791-7.

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Spiridonova, Sofya. "Formation dynamics in geostationary ring." Celestial Mechanics and Dynamical Astronomy 125, no. 4 (May 10, 2016): 485–500. http://dx.doi.org/10.1007/s10569-016-9693-0.

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Dissertations / Theses on the topic "Ring formation"

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Olmsted, Susan C. "Star Formation in Ring Galaxies." Digital Commons @ East Tennessee State University, 2016. https://dc.etsu.edu/honors/322.

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Ring galaxies are specific types of interacting galaxies in which a smaller galaxy has passed through the center of the disk of another larger galaxy. The intrusion of the smaller galaxy causes the structure of the larger galaxy to compress as the smaller galaxy falls through, and to recoil back after the smaller galaxy passes through, hence the ring-like shape. In our research, we studied the star-forming regions of a sample of ring galaxies and compared to those of other interacting galaxies and normal galaxies. Using UV, optical, and IR archived images in twelve wavelengths from three telescopes, we analyzed samples of star-forming regions in ring and normal spiral galaxies using photometry. To measure the star formation rates of the star forming regions, we used computer software that picked out the regions and measured their luminosities in all twelve wavelengths, before comparing the luminosities in these wavelengths to determine the rate of star formation. We have determined that ring galaxies have proportionally more clumps with higher star formation rates than spirals, and a similar trend was suggested when comparing ring galaxies to other interacting galaxies (though more data is required for that comparison). These findings can help us understand galaxy evolution, including the evolution of our own galaxy.
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Sutton, Phil J. "Saturn's turbulent F ring." Thesis, Loughborough University, 2015. https://dspace.lboro.ac.uk/2134/18475.

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As our abilities to utilise high performance computing to theoretically probe many astrophysical systems increases, a genuine need to relate to real systems becomes ever more important. Here, Saturn s rings can be used as a nearby laboratory to investigate in real time many astrophysical processes. One such system is the narrow F ring and its interaction with its inner shepherd moon Prometheus. Through numerical modelling and direct observations of the in-situ spacecraft Cassini we find new and exciting dynamics. These might help explain some of the asymmetries witnessed in the distribution of embedded moonlets and azimuthal ring brightness known to exist within the F ring. Spatially we find asymmetry in the Prometheus induced channel edges with regards to density, velocity and acceleration variations of ring particles. Channel edges that show fans (embedded moonlets) are also the locations of highly localised increases in densities, velocity and acceleration changes where opposing edges are considerably less localised in their distribution. As a result of the highly localised nature of the velocity and acceleration changes chaotic fluctuations in density were witnessed. However, this could seek to work in favour of creating coherent objects at this channel edge as density increases were significantly large. Thus, density here had a greater chance of being enhanced beyond the local Roche density. Accompanied with these dynamics was the discovery of a non-zero component to vorticity in the perturbed area of the F ring post encounter. By removal of the background Keplerian flow we find that encounters typically created a large scale rotation of ~10,000 km^2. Within this area a much more rich distribution of local rotations is also seen located in and around the channel edges. Although the real F ring and our models are non-hydrodynamical in nature the existence of a curl in the velocity vector field in the perturbed region could offer some interesting implications for those systems that are gas rich.
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Hylands, Kevin Alexander. "Nitrate ester formation from small ring heterocycles." Thesis, University of Exeter, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337731.

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Harter, Braxton Nicholas. "Lagrangian Coherent Structures in Vortex Ring Formation." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1565828293505214.

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Robertson, Jeremy. "Ring expansion reaction via homolytic pathways." Thesis, University of Oxford, 1990. http://ora.ox.ac.uk/objects/uuid:194ca194-4848-470b-a21f-c16869257b96.

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The preparation of carbocyclic medium rings by two electron processes is reviewed with particular reference to the synthesis of natural products. The formation of medium rings by oxidative and homolytic methods is also reviewed. The synthesis and behaviour of both cis- and tran- ring expansion precursors is described. The 1,4-addition of tributylstannyl lithium to a range of cyclic α,β-unsaturated ketones was performed and procedures found whereby the so-formed enolates could be alkylated with a variety of electrophiles. Using these procedures a range of trans- ring expansion precursors were obtained in moderate to good yield. By the 1,4-addition of tributylstannyl lithium to 2-(ω-phenylselenoalkyl)-cyclohexenones, followed by enolate quenching with either water or methyl iodide, a range of cis- ring expansion precursors were produced. Homolytic ring expansion by either one, three, or four carbon atoms was shown to be possible, producing, respectively, seven, nine, or ten membered functionalised cycloalkenones in high yield except in cases where intramolecular reductive elimination was also possible. Attempts to extend this methodology to the synthesis of exomethylene cycloalkanones is described. The 3-tributylstannyl-3-(ω-phenylselenoalkyl)-cyclohex-2-enone precursors were found not to be successful substrates for ring expansion. The regiospecific alkylation of 2-(tributylstannylmethyl)-cyclohexanone with l-chloro-4-iodo-butane, followed by conversion of the chloride moiety to iodide led to a precursor which, on exposure to homolysis conditions, fragmented to produce the desired exomethylene cyclodecanone in high yield. Work directed towards the synthesis of medium ring cycloalkynones is described. Procedures were developed whereby 2-alkylated cyclohexan-l,3-dione derivatives could be obtained cleanly and in excellent yield on a large scale. The conversion of these derivatives to potential cycloalkynone precursors is described. It is shown that the products obtained after exposure of these precursors to homolysis conditions could, in principle, be derived from the putative cycloalkynones and mechanisms are suggested to explain the formation of these compounds. The homolytic ring expansion reaction was also performed on a substrate possessing an acyl radical precursor in the hope that a medium ring 1,2-dione would be produced. The synthesis of this substrate and its behaviour towards ring expansion is described. It is shown that, again, radical reaction was successful (to the medium ring dione) however subsequent reactions of this product led to the isolation and characterisation of a number of compounds . Attempts to extend this methodology to the synthesis of the natural products curdione and neocurdione is also described. Model reactions with 2,6-dimethylcyclohex-2-enone as the 1,4-addition precursor and 1,4-di-iodobutane as the electrophile led to a ring expansion substrate which fragmented to two ring contracted isomeric compounds in addition to the ring expanded material. Approaches to the preparation of suitable electrophiles for the natural product synthesis are described and their proposed use in subsequent conversion to curdione and neocurdione given.
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Tigges, Sophia E. "The relationship between Centaur activity and ring formation." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/115778.

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Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2018.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 22-25).
Introduction: Centaurs are small bodies whose orbits lie between those of Jupiter and Neptune (Gehrels, 1999). They are thought to be transition objects that originate in the Kuiper belt and occupy the cis-Neptunian region before potentially becoming Jupiter-family or other short-period comets (Dones, Levison, & Duncan, 1996). Their short dynamical lifetimes are on the order of 106 years (Horner, Evans, & Bailey, 2004) due to their unstable, planet-crossing orbits (Horner, Evans, Bailey, & Asher, 2003). Some Centaurs have been observed to be active, and the bodies in the population of active Centaurs have perihelion distances that are statistically smaller than the median perihelion distance for all Centaurs, suggesting that Centaur activity is thermal in nature (Jewitt, 2009). Centaur activity may be observed through changes in the brightness of an object such as those exhibited by the Centaur Chiron (Parker et al., 1997). The presence of a coma around a Centaur may also provide evidence of activity, and dust comae have been detected around several bodies including Chiron (Meech & Belton, 1989; Luu & Jewitt, 1990) and Echeclus (Choi, Weissman, & Polishook, 2006). In addition to comae, other structures have been observed around Centaurs, such as the ring system that was discovered around Chariklo during a stellar occultation (Braga-Ribas et al., 2014). A symmetric feature was observed around Chiron during an occultation (Ruprecht et al., 2015), and some interpret this feature to be possible ring material (Ortiz et al., 2015). Similarly, the trans-Neptunian dwarf planet Haumea was revealed to have a ring during a stellar occultation (Ortiz et al., 2017). The collisional spreading time of Chariklo's rings was calculated to be on the order of 101 years, which is short in comparison to the estimated Centaur lifetime of approximately 106 years (Pan & Wu, 2016), yet Centaur rings are still observed despite this contradiction. Shepherd satellites may serve to increase the lifetime of a Centaur's rings (Pan & Wu, 2016) and maintain distinct ring edges such as those observed in Chariklo's ring system (Charnoz, Canup, Crida, Dones, 2017). Moreover, Centaur activity could supply material to an already present ring system, thus prolonging its lifetime. This study explores the potential connection between Centaur activity and Centaur ring systems by using the N-body integrator REBOUND to model outburst particle interactions and distributions.
by Sophia E. Tigges.
S.B.
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Prasad, Chaturvedula V. "Annulation and cycloaromatization reactions of 3-aryl (alkyl) thio-1-trimethylsiloxy-1-methoxy-1,3-butadienes." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=75442.

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The title compounds were synthesized from methyl 3-aryl(alkyl)thio crotonic acids by deprotonation followed by silylation. The reactions of dienes with a number of carbonyl electrophiles under Lewis-acid catalysed conditions were investigated. The dienes exclusively give $ gamma$-alkylated products. The thio substituent enhances the $ gamma$-selectivity.
The reactions of dienes with a number of 1,3-dicarbonyl equivalents have been studied and a cycloaromatization reaction has been developed for the regiocontrolled synthesis of aryl sulfides in a 3C + 3C combination. The role of dienes in Diels-Alder reactions has also been investigated.
A new 4C + 2C annulation reaction has been developed based on the propensity of dienes to undergo Michael reaction with $ alpha$,$ beta$-unsaturated ketones under Lewis-acid catalysed conditions. These Michael adducts in turn were cyclized either with potassium tert-butoxide or with lithium thiophenoxide. Further, the tandem Michael-Claisen annulation reaction can be controlled to give either cis- or trans-fused 9-methyldecalin system with three carbonyl groups which are differently masked. The chemoselective transformations of the carbonyl groups were also described.
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Lam, Yan-yu Sarah, and 林恩如. "Studies and applications of intermolecular (4+3) cycloaddition reactions of epoxy and aziridinyl enolsilanes." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hdl.handle.net/10722/206359.

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Schaefer, Anthony G. "Part 1, stereoselection in (4+2) cycloadditions ; Part 2, synthesis of 14-epiupial /." The Ohio State University, 1987. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487585645577956.

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Olcay, Ali Bahadir. "Measurement of ambient fluid entrainment and calculation of vortex ring impulse during vortex ring formation." Ann Arbor, Mich. : ProQuest, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3258314.

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Thesis (Ph.D. in Mechanical Engineering)--S.M.U., 2007.
Title from PDF title page (viewed Mar. 18, 2008). Source: Dissertation Abstracts International, Volume: 68-03, Section: B, page: 1890. Adviser: Paul Krueger. Includes bibliographical references.
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Books on the topic "Ring formation"

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Jack, Li Jie, ed. Name reactions for carbocyclic ring formations. Hoboken, N.J: Wiley, 2010.

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1933-, Tebby John C., ed. Alkynes in cycloadditions. Chichester, West Sussex: Wiley, 2014.

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1930-, Hassner Alfred, ed. Synthesis of heterocycles via cycloadditions II. Berlin: Springer, 2008.

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Appelbe, Ruth. Synthetic applications of cationic arene-alkene cyclisations. Dublin: University College Dublin, 1997.

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Manus, Eileen Mc. Oxazolidine and thiazolidine ring opening reactions. Dublin: University College Dublin, 1996.

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Valters, Raimonds E. Ring-chain tautomerism. New York: Plenum, 1985.

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Wilhelm, Flitsch, and Katritzky Alan R, eds. Ring-chain tautomerism. New York: Plenum Press, 1985.

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Margetic, Davor. Microwave assisted cycloaddition reactions. Hauppauge, N.Y: Nova Science Publishers, 2012.

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Harmata, Michael. Advances in cycloaddition. Stamford, Conn: JAI Press, 1999.

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Horst, Kunz, ed. Chiral auxiliaries in cycloadditions. Weinheim: Wiley-VCH, 1999.

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Book chapters on the topic "Ring formation"

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Akhmetov, D. G. "Vortex Ring Formation." In Vortex Rings, 89–103. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-642-05016-9_5.

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Danaila, Ionut, Felix Kaplanski, and Sergei S. Sazhin. "Formation Number of Vortex Rings." In Vortex Ring Models, 121–39. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-68150-0_6.

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Schmidt, Johann Friedrich Julius. "The Ring mountain Formation." In Historical & Cultural Astronomy, 67–76. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-37269-9_18.

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Mayya, Y. D., and R. Romano. "Star Formation in Ring Galaxies." In New Quests in Stellar Astrophysics: The Link Between Stars and Cosmology, 155–56. Dordrecht: Springer Netherlands, 2002. http://dx.doi.org/10.1007/978-94-010-0393-3_32.

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Cater, J., J. Soria, and T. T. Lim. "Vortex Ring Formation at an Orifice." In Fluid Mechanics and Its Applications, 15–18. Dordrecht: Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-011-5118-4_4.

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Ehresmann, Anne-Laure, Manuel Lafond, Lata Narayanan, and Jaroslav Opatrny. "Distributed Pattern Formation in a Ring." In Structural Information and Communication Complexity, 215–29. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-24922-9_15.

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Rathgeber, Cyrille B. K., Gonzalo Pérez-de-Lis, Laura Fernández-de-Uña, Patrick Fonti, Sergio Rossi, Kerstin Treydte, Arthur Gessler, Annie Deslauriers, Marina V. Fonti, and Stéphane Ponton. "Anatomical, Developmental and Physiological Bases of Tree-Ring Formation in Relation to Environmental Factors." In Stable Isotopes in Tree Rings, 61–99. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-92698-4_3.

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AbstractUnderstanding the process of wood formation and its dynamics over the growing season is fundamental to interpret the isotopic signature of tree rings. Indeed, the isotopic signal recorded in wood does not only depend on the conditions influencing carbon, water, and nitrogen uptake in the leaves and roots, but also on how these elements are translocated to the stem and incorporated into the developing xylem. Depending on environmental conditions, tree developmental stage, and physiological status, wood formation dynamics can vary greatly and produce tree-ring structures carrying specific isotopic signatures. In this chapter, we present the physiological processes involved in wood formation, along with their relationships with anatomical, developmental, and environmental factors, to understand when and how photosynthetic assimilates are progressively incorporated into the forming xylem, creating the final isotopic signature of a tree ring. First, we review current knowledge on the structure and functions of wood. Then we describe the xylogenesis process (how and when the new xylem cells produced by the cambium develop through successive differentiation phases), and its relationships with physiological, developmental, and environmental factors. Finally, we explain the kinetics of xylemcell differentiation and show why the knowledge recently acquired in this field allows us to better understand the isotopic signals in tree rings.
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Curir, Anna, and Paola Mazzei. "Chemo-Photometric Models of Ring Galaxies." In Multiwavelength Mapping of Galaxy Formation and Evolution, 372–73. Berlin, Heidelberg: Springer Berlin Heidelberg, 2006. http://dx.doi.org/10.1007/10995020_66.

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Andreu-Hayles, Laia, Mathieu Lévesque, Rossella Guerrieri, Rolf T. W. Siegwolf, and Christian Körner. "Limits and Strengths of Tree-Ring Stable Isotopes." In Stable Isotopes in Tree Rings, 399–428. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-92698-4_14.

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AbstractThis chapter aims at summarizing strengths and caveats on the suitability of stable carbon and oxygen isotopes in tree rings as recorders for fingerprints of environmental influences. First, environmental constraints limiting tree growth and shaping tree species distribution worldwide are discussed. Second, examples are presented for environmental conditions under which tree-ring isotopes record environmental signals particularly well, but also cases where physiological processes can mask climate signals. Third, the link between leaf-level carbon assimilation and the investment of assimilates in the stem during the annual ring formation are discussed in light of the resulting deviations of the isotopic values between leaves and tree rings. Finally, difficulties and pitfalls in the interpretation of stable isotope signals in tree rings are reviewed. These problems often result from a poor understanding of when and how the tree canopy, stems and roots are physiologically interconnected. Current literature suggests that photosynthesis and radial growth are only loosely coupled, if at all, challenging the interpretation of environmental signals recorded in tree-ring isotopes. Harsh environmental conditions (e.g. low temperatures, drought) often result in a decoupling of carbon assimilation and growth. The chapter closes by providing possible solutions on how to improve the detection of environmental information from stable isotope signals by integrating scales and different methodological approaches.
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Frank, David, Keyan Fang, and Patrick Fonti. "Dendrochronology: Fundamentals and Innovations." In Stable Isotopes in Tree Rings, 21–59. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-92698-4_2.

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AbstractThis chapter overviews long-standing foundations, methods, and concepts of dendrochronology, yet also pays attention to a few related paradigm shifts driven by isotope measurements in tree-rings. The basics of annual ring formation are first reviewed, followed by structural descriptions of tree-rings at the macroscopic-to-microscopic scale including earlywoodandlatewoodin conifers (gymnosperms) and hardwoods (angiosperms), as well as wood anatomical features. Numerous examples of inter-disciplinary applications connected to various tree-ring parameters are provided. With the foundation of tree-rings established, this chapter then describes the process and necessity for crossdating—the process by which each and every ring is assigned to a specific year. Methods and terminology related to field sampling also briefly described. The long-standing paradigm of site selection criteria—well shown to maximize common signals in tree-ring width datasets—is challenged in a brief discussion of newer tree-ring isotope literature demonstrating that robust chronologies with high signal-to-noise ratios can be obtained at non-ecotonal locations. Opportunities for isotope measurements to enable crossdating in otherwise challenging contexts are likewise highlighted. The chapter reviews a conceptual framework to disaggregate tree-ring time-series, with special attention to detrending and standardization methods used to mitigate tree-age/size related noise common to many applications such as dendroclimatic reconstruction. Some of the drivers of long-term trends in tree-ring isotope data such as the increase in the atmospheric concentration of CO2, age/size/height trends, and climate variation are presented along with related debates/uncertainties evident in literature in order to establish priorities for future investigations. The development of tree-ring chronologies and related quality control metrics used to assess the common signal and the variance of tree-ring data are described, along with the limitations in correlation based statistics to determine the robustness of tree-ring datasets particularly in the low frequency domain. These statistical methods will gain relevance as tree-ring isotope datasets increasingly approach sample replications and dataset structures typical for tree-ring width measurements.
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Conference papers on the topic "Ring formation"

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Gharib, Morteza. "Optimal Vortex Ring Formation: A Study of Vortex Ring Formation in Starting and Pulsed Jets (Keynote)." In ASME/JSME 2003 4th Joint Fluids Summer Engineering Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/fedsm2003-45813.

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Pulsatile jet flows are found in many industrially relevant fluid mechanical problems. A common feature of these flows is that they are fundamentally a series of fluid pulses. This aspect of pulsatile jets implies vortex rings are a basic element of the resulting flow. The significance of this observation is based in part on the tendency of vortex rings to entrain ambient fluid during their formation, but more so on the recent discovery of the phenomenon of vortex ring pinch off. This phenomenon was characterized for starting jets (individual pulses) showing that for pulses sufficiently long with respect to the nozzle diameter (i.e., sufficiently large L/D), the vortex ring stops forming and pinches off from the generating jet. This represents a maximization principle for vortex ring formation and suggests that any effects associated with vortex ring formation in pulsatile jets (e.g., enhanced entrainment), might be able to be optimized by properly selecting the L/D for each pulse.
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Stewart, Kelley C., and Pavlos P. Vlachos. "Vortex Ring Formation in Wall-Bounded Domains." In ASME 2010 3rd Joint US-European Fluids Engineering Summer Meeting collocated with 8th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2010. http://dx.doi.org/10.1115/fedsm-icnmm2010-31055.

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Vortex ring formation and propagation have been studied extensively in quiescent semi-infinite volumes. However, very little is known about the dynamics of vortex-ring formation in wall-bounded domains where vortex wall interaction will affect both the vortex ring pinch-off and propagation velocity. This study addresses this limitation and studies vortex formation in radially confined domains to analyze the effect of vortex-ring wall interaction on the formation and propagation of the vortex ring. Vortex rings were produced using a pneumatically driven piston cylinder arrangement and were ejected into a long cylindrical tube parallel to the piston cylinder arrangement which defined the confined downstream domain. Two different domains were studied with diameters twice and four times the size of the piston cylinder. A semi-infinite unbounded volume with no downstream cylinder was also investigated for comparison. The piston stroke-to-diameter ratio (L/D0) for the studied vortex rings was varied between 0.75 and 3 with corresponding Reynolds numbers, based on circulation, of approximately 500 to 8,000. Velocity field measurements were performed using planar Time Resolved Digital Particle Image Velocimetry (TRDPIV). The TRDPIV data were processed using an in-house developed cross-correlation PIV algorithm and post processed using Proper Orthogonal Decomposition to remove high frequency noise. The propagation velocity and vorticity were investigated and vortex identification was used to track the changing size, location, and circulation of the vortices. The combination of these parameters was used to investigate the effects of wall interaction on vortex ring formation and propagation.
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Tran, Dzung M., David Casbeer, Eloy Garcia, Isaac E. Weintraub, Dejan Milutinovic, and Satyanarayana G. Manyam. "Ring Formation Maneuver: Single-Integrator Kinematics." In AIAA Scitech 2021 Forum. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2021. http://dx.doi.org/10.2514/6.2021-0978.

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Ray, Bahni, Gautam Biswas, and Ashutosh Sharma. "Vortex Ring Formation on Drop Coalescence With Underlying Liquid." In ASME 2013 Heat Transfer Summer Conference collocated with the ASME 2013 7th International Conference on Energy Sustainability and the ASME 2013 11th International Conference on Fuel Cell Science, Engineering and Technology. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/ht2013-17711.

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Numerical simulations using coupled level-set and volume-of-fluid (CLSVOF) method has been carried out to capture the vortex ring when a drop coalesces on a pool of liquid. A study has been done for the formation and motion of vortex rings generated when drops of liquid are allowed to come into contact at zero velocity with a quiescent flat surface of the same liquid.
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Leung, S. M., K. S. Cheng, W. Y. Chau, and K. L. Chan. "Formation and origin of asymmetric ring galaxies." In Back to the Galaxy. AIP, 1992. http://dx.doi.org/10.1063/1.43939.

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BARRIO, R. A., C. VAREA, T. ALARCÓN, C. B. PICALLO, and A. HERNANDEZ-MACHADO. "DYNAMICS OF Z-RING FORMATION IN LIPOSOMES." In International Symposium on Mathematical and Computational Biology. WORLD SCIENTIFIC, 2015. http://dx.doi.org/10.1142/9789814667944_0001.

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Tran, Dzung, David Casbeer, Eloy Garcia, Isaac E. Weintraub, and Dejan Milutinovic. "Ring Formation Maneuvering with Double Integrator Dynamics*." In 2021 International Conference on Unmanned Aircraft Systems (ICUAS). IEEE, 2021. http://dx.doi.org/10.1109/icuas51884.2021.9476770.

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Remeika, M., A. T. Hammack, S. Poltavtsev, L. V. Butov, J. Wilkes, A. L. Ivanov, K. L. Campman, M. Hanson, and A. C. Gossard. "Pattern Formation in the Exciton Inner Ring." In CLEO: QELS_Fundamental Science. Washington, D.C.: OSA, 2013. http://dx.doi.org/10.1364/cleo_qels.2013.qm2d.6.

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Bagnato, V. S., L. G. Marcassa, M. Oriá, G. I. Surdutovich, and S. C. Zilio. "Observations on Ring Formation in Magneto-Optically Trapped Sodium Atoms." In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1991. http://dx.doi.org/10.1364/oam.1991.pd19.

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In this report we present the experimental observation of rings of sodium atoms in a cold vapor cell and a theoretical model based in the existence of vortex forces leading to stable circular orbits. The apparatus for this experiment consists of a Zeeman-shift spontaneous-force trap(1), similar to the one used for Cs atoms(2). The magnetic field is produced by a pair of anti-Helmholtz coils and the three circularly polarized retro-reflected laser beams are tuned to the 3S1/2 (F=2) → 3P3/2 (F=3) transition of sodium. All laser beams carry a 1712 Mz sideband frequency working as a repumper for atoms in the 3S1/2 (F=1) ground state. When all beams are well aligned with respect to the retro-reflection and magnetic field and are detuned 10 MHz below resonance, we observe a bright ball with 1 to 2 mm at the trap center. If one of the beams is misaligned by a small rotation of the retro-reflector, the initially spheric ball deforms to a dwell shape. When a second beam is also misaligned, the formation of a ring is observed. The ring increases its radius and keeps the same width as the laser is scanned to larger values of red detunings, as shown in Fig. 1. For detunings larger than Δ = 25 MHz the ring disappears. By adding a small misalignment to the third orthogonal beam we observed a change of the plane where the ring is formed.
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Liu, Xiaobing, Lin Chen, Yury Kachanov, and Chaoqun Liu. "DNS for Ring - Like Vortices Formation and Roles in Positive Spikes Formation." In 48th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2010. http://dx.doi.org/10.2514/6.2010-1471.

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Reports on the topic "Ring formation"

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Boatz, J. A., and J. D. Mills. Theoretical Determination of the Heats of Formation of Prospective Strained-Ring Rocket Fuels. Fort Belvoir, VA: Defense Technical Information Center, February 1998. http://dx.doi.org/10.21236/ada397872.

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Hughes, Joseph B. Novel Pathways of Nitroaromatic Metabolism: Hydroxylamine Formation, Reactivity and Potential for Ring Fission for Destruction of TNT-CU1214. Fort Belvoir, VA: Defense Technical Information Center, August 2005. http://dx.doi.org/10.21236/ada462163.

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Brenan, J. M., K. Woods, J. E. Mungall, and R. Weston. Origin of chromitites in the Esker Intrusive Complex, Ring of Fire Intrusive Suite, as revealed by chromite trace element chemistry and simple crystallization models. Natural Resources Canada/CMSS/Information Management, 2021. http://dx.doi.org/10.4095/328981.

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To better constrain the origin of the chromitites associated with the Esker Intrusive Complex (EIC) of the Ring of Fire Intrusive Suite (RoFIS), a total of 50 chromite-bearing samples from the Black Thor, Big Daddy, Blackbird, and Black Label chromite deposits have been analysed for major and trace elements. The samples represent three textural groups, as defined by the relative abundance of cumulate silicate phases and chromite. To provide deposit-specific partition coefficients for modeling, we also report on the results of laboratory experiments to measure olivine- and chromite-melt partitioning of V and Ga, which are two elements readily detectable in the chromites analysed. Comparison of the Cr/Cr+Al and Fe/Fe+Mg of the EIC chromites and compositions from previous experimental studies indicates overlap in Cr/Cr+Al between the natural samples and experiments done at >1400oC, but significant offset of the natural samples to higher Fe/Fe+Mg. This is interpreted to be the result of subsolidus Fe-Mg exchange between chromite and the silicate matrix. However, little change in Cr/Cr+Al from magmatic values, owing to the lack of an exchangeable reservoir for these elements. A comparison of the composition of the EIC chromites and a subset of samples from other tectonic settings reveals a strong similarity to chromites from the similarly-aged Munro Township komatiites. Partition coefficients for V and Ga are consistent with past results in that both elements are compatible in chromite (DV = 2-4; DGa ~ 3), and incompatible in olivine (DV = 0.01-0.14; DGa ~ 0.02), with values for V increasing with decreasing fO2. Simple fractional crystallization models that use these partition coefficients are developed that monitor the change in element behaviour based on the relative proportions of olivine to chromite in the crystallizing assemblage; from 'normal' cotectic proportions involving predominantly olivine, to chromite-only crystallization. Comparison of models to the natural chromite V-Ga array suggests that the overall positive correlation between these two elements is consistent with chromite formed from a Munro Township-like komatiitic magma crystallizing olivine and chromite in 'normal' cotectic proportions, with no evidence of the strong depletion in these elements expected for chromite-only crystallization. The V-Ga array can be explained if the initial magma responsible for chromite formation is slightly reduced with respect to the FMQ oxygen buffer (~FMQ- 0.5), and has assimilated up to ~20% of wall-rock banded iron formation or granodiorite. Despite the evidence for contamination, results indicate that the EIC chromitites crystallized from 'normal' cotectic proportions of olivine to chromite, and therefore no specific causative link is made between contamination and chromitite formation. Instead, the development of near- monomineralic chromite layers likely involves the preferential removal of olivine relative to chromite by physical segregation during magma flow. As suggested for some other chromitite-forming systems, the specific fluid dynamic regime during magma emplacement may therefore be responsible for crystal sorting and chromite accumulation.
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KRUPINA, E. A. OLD ENGLISH LEXEME “RINC” IN IN THE GLOSSARIES AND IN THE TEXT OF THE POEM “BEOWULF”. Science and Innovation Center Publishing House, April 2022. http://dx.doi.org/10.12731/2077-1770-2021-14-1-3-51-56.

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The article considers the Old English lexeme “rinc” with the help of etymology and word formation, the author uses contrastive-comparative analysis of the headword in the glossaries and contextual analysis of the lexeme.
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Шестопалова (Бондар), Катерина Миколаївна, and Олена Петрівна Шестопалова. Support of Inclusive Education in Kryvyi Rig. Padua, Italy, 2019. http://dx.doi.org/10.31812/123456789/3234.

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An analysis of the system of training, the implementation of a pilot project "SUPPORT OF INCLUSIVE EDUCATION IN KRYVYI RIG". The team that worked in project by GIZ (Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ) GmbH) create strategy for training teachers that include 6 modules: 1) regulatory and legislative framework for inclusive education; 2) inclusion ethics and philosophy; universal design and reasonable accommodation of educational space; 3) support team: interdisciplinary interation; algorithm of provision of psycho-pedagogical, corrective and development services; 4) individualization of the educational process; 5) competences of the teacher in inclusive education: strategies of teaching in inclusive education, method of collaborative learning, integration of technology into the discipline teaching methods, peculiarities of formation of mathematical concepts in children with special needs, difficulties with reading mastering and correction of dyslexia in children with special educational needs, correction and development of sense side of reading, development of intelligence of a child with SEN with the help of kinesiology methods, cooperation of teacher, psychologist and parents of a child with special educational needs, five levels can be associated with parents engagement; 6) work with children with behavior problems; resource room as the method of a child specific sensor needs satisfaction.
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Gantt, Elisabeth, Avigad Vonshak, Sammy Boussiba, Zvi Cohen, and Amos Richmond. Carotenoid-Rich Algal Biomass for Aquaculture: Astaxanthin Production by Haematococcus Pluvialis. United States Department of Agriculture, August 1996. http://dx.doi.org/10.32747/1996.7613036.bard.

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The synthesis of carotenoids has been studied toward enhancing the production of ketocarotenoids, since fish and crustaceans raised by aquaculture require astaxanthin and other ketocaroteinoids in their feed for desirable pigmentation. Notable progress has been made in attaining the goals of determining improved conditions for ketocarotenoid production in Haematococcus pluvialis and in elucidating the carotenoid biosynthetic pathway. For production of astaxanthin a number of strains of the green alga Haematococcus were evaluated, a strain CCAG was found to be optimal for photoautotrophic growth. Of four mutants, selected for enhanced carotenoid production, two hold considerable promise because caroteinoid accumulation occurs without encystment. The biosynthetic pathway of carotenoids was elucidated in photosynthetic organisms by characterizing novel genes encoding carotenoid enzymes and by examining the function of these enzymes in a bacterial complementation system. Two cyclases (b- and e-) were cloned that are at a critical branch point in the pathway. One branch leads to the formation of b-carotene and zeaxanthin and astaxanthin, and the other to the production of a-carotene and lutein. Cyclization of both endgroups of lycopene to yield b-carotene was shown to be catalyzed by a single gene product, b-lycopene cyclase in cyanobacteria and plants. The formation of a-carotene was found to require the e-cyclase gene product in addition to the b-cyclase. By cloning a b-hydroxylase gene we showed that a single gene product forms zeaxanthin by hydroxylatin of both b-carotene rings. It is expected that a second hydroxylase is required in the synthesis of astaxanthin, since canthaxanthin rather than zeaxanthin is the precursor. Evidence, from inhibitor studies, suggests that astaxanthin is formed from canthaxanthin and that b-carotene is a major precursor. Feasibility studies with the photobioreactors have shown that a two-stage system is the most practical, where Haematococcus cultures are first grown to high cell density and are then switched to high light for maximal astaxanthin production. The basic knowledge and molecular tools generated from this study will significantly enhance Haematococcus as a viable model for enhanced astaxanthin production.
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Brophy, Kenny, and Alison Sheridan, eds. Neolithic Scotland: ScARF Panel Report. Society of Antiquaries of Scotland, June 2012. http://dx.doi.org/10.9750/scarf.06.2012.196.

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The main recommendations of the Panel report can be summarised as follows: The Overall Picture: more needs to be understood about the process of acculturation of indigenous communities; about the Atlantic, Breton strand of Neolithisation; about the ‘how and why’ of the spread of Grooved Ware use and its associated practices and traditions; and about reactions to Continental Beaker novelties which appeared from the 25th century. The Detailed Picture: Our understanding of developments in different parts of Scotland is very uneven, with Shetland and the north-west mainland being in particular need of targeted research. Also, here and elsewhere in Scotland, the chronology of developments needs to be clarified, especially as regards developments in the Hebrides. Lifeways and Lifestyles: Research needs to be directed towards filling the substantial gaps in our understanding of: i) subsistence strategies; ii) landscape use (including issues of population size and distribution); iii) environmental change and its consequences – and in particular issues of sea level rise, peat formation and woodland regeneration; and iv) the nature and organisation of the places where people lived; and to track changes over time in all of these. Material Culture and Use of Resources: In addition to fine-tuning our characterisation of material culture and resource use (and its changes over the course of the Neolithic), we need to apply a wider range of analytical approaches in order to discover more about manufacture and use.Some basic questions still need to be addressed (e.g. the chronology of felsite use in Shetland; what kind of pottery was in use, c 3000–2500, in areas where Grooved Ware was not used, etc.) and are outlined in the relevant section of the document. Our knowledge of organic artefacts is very limited, so research in waterlogged contexts is desirable. Identity, Society, Belief Systems: Basic questions about the organisation of society need to be addressed: are we dealing with communities that started out as egalitarian, but (in some regions) became socially differentiated? Can we identify acculturated indigenous people? How much mobility, and what kind of mobility, was there at different times during the Neolithic? And our chronology of certain monument types and key sites (including the Ring of Brodgar, despite its recent excavation) requires to be clarified, especially since we now know that certain types of monument (including Clava cairns) were not built during the Neolithic. The way in which certain types of site (e.g. large palisaded enclosures) were used remains to be clarified. Research and methodological issues: There is still much ignorance of the results of past and current research, so more effective means of dissemination are required. Basic inventory information (e.g. the Scottish Human Remains Database) needs to be compiled, and Canmore and museum database information needs to be updated and expanded – and, where not already available online, placed online, preferably with a Scottish Neolithic e-hub that directs the enquirer to all the available sources of information. The Historic Scotland on-line radiocarbon date inventory needs to be resurrected and kept up to date. Under-used resources, including the rich aerial photography archive in the NMRS, need to have their potential fully exploited. Multi-disciplinary, collaborative research (and the application of GIS modelling to spatial data in order to process the results) is vital if we are to escape from the current ‘silo’ approach and address key research questions from a range of perspectives; and awareness of relevant research outside Scotland is essential if we are to avoid reinventing the wheel. Our perspective needs to encompass multi-scale approaches, so that ScARF Neolithic Panel Report iv developments within Scotland can be understood at a local, regional and wider level. Most importantly, the right questions need to be framed, and the right research strategies need to be developed, in order to extract the maximum amount of information about the Scottish Neolithic.
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