scholarly journals Elongated Gravity Sources as an Analytical Limit for Flat Galaxy Rotation Curves

Universe ◽  
2021 ◽  
Vol 7 (9) ◽  
pp. 346
Author(s):  
Felipe J. Llanes-Estrada
Keyword(s):  
Galactic Plane ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Small Scale ◽  
Scaling Exponent ◽  
Rotation Curves ◽  
Central Mass ◽  
Filamentary Structure ◽  
Analytical Limit ◽  
Galaxy Rotation Curves

The flattening of spiral-galaxy rotation curves is unnatural in view of the expectations from Kepler’s third law and a central mass. It is interesting, however, that the radius-independence velocity is what one expects in one less dimension. In our three-dimensional space, the rotation curve is natural if, outside the galaxy’s center, the gravitational potential corresponds to that of a very prolate ellipsoid, filament, string, or otherwise cylindrical structure perpendicular to the galactic plane. While there is observational evidence (and numerical simulations) for filamentary structure at large scales, this has not been discussed at scales commensurable with galactic sizes. If, nevertheless, the hypothesis is tentatively adopted, the scaling exponent of the baryonic Tully–Fisher relation due to accretion of visible matter by the halo comes out to reasonably be 4. At a minimum, this analytical limit would suggest that simulations yielding prolate haloes would provide a better overall fit to small-scale galaxy data.

Large- and small-scale vortical motions in a shear layer perturbed by tabs

1999 ◽  
Vol 382 ◽  
pp. 307-329 ◽  
Author(s):  
JUDITH K. FOSS ◽  
K. B. M. Q. ZAMAN
Keyword(s):  
Shear Layer ◽  
Pitch Angle ◽  
Large Scale ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Small Scale ◽  
Streamwise Vortices ◽  
Streamwise Vorticity ◽  
Cross Sectional ◽  
Scale Population

The large- and small-scale vortical motions produced by ‘delta tabs’ in a two-stream shear layer have been studied experimentally. An increase in mixing was observed when the base of the triangular shaped tab was affixed to the trailing edge of the splitter plate and the apex was pitched at some angle with respect to the flow axis. Such an arrangement produced a pair of counter-rotating streamwise vortices. Hot-wire measurements detailed the velocity, time-averaged vorticity (Ωx) and small-scale turbulence features in the three-dimensional space downstream of the tabs. The small-scale structures, whose scale corresponds to that of the peak in the dissipation spectrum, were identified and counted using the peak-valley-counting technique. The optimal pitch angle, θ, for a single tab and the optimal spanwise spacing, S, for a multiple tab array were identified. Since the goal was to increase mixing, the optimal tab configuration was determined from two properties of the flow field: (i) the large-scale motions with the maximum Ωx, and (ii) the largest number of small-scale motions in a given time period. The peak streamwise vorticity magnitude [mid ]Ωx−max[mid ] was found to have a unique relationship with the tab pitch angle. Furthermore, for all cases examined, the overall small-scale population was found to correlate directly with [mid ]Ωx−max[mid ]. Both quantities peaked at θ≈±45°. It is interesting to note that the peak magnitude of the corresponding circulation in the cross-sectional plane occurred for θ≈±90°. For an array of tabs, the two quantities also depended on the tab spacing. An array of contiguous tabs acted as a solid deflector producing the weakest streamwise vortices and the least small-scale population. For the measurement range covered, the optimal spacing was found to be S≈1.5 tab widths.

scholarly journals The Thinness of the Ocean in S–Θ–p Space and the Implications for Mean Diapycnal Advection

2007 ◽  
Vol 37 (6) ◽  
pp. 1714-1732 ◽  
Author(s):  
Trevor J. McDougall ◽  
David R. Jackett
Keyword(s):  
Dimensional Space ◽  
World Ocean ◽  
Three Dimensional ◽  
Small Scale ◽  
Lateral Motion ◽  
Hydrographic Data ◽  
Mixing Processes ◽  
The World ◽  
The Mean ◽  
Three Dimensional Space

Abstract It is shown that the ocean’s hydrography occupies little volume in the three-dimensional space defined by salinity–temperature–pressure (S–Θ–p), and the implications of this observation for the mean vertical transport across density surfaces are discussed. Although ocean data have frequently been analyzed in the two-dimensional temperature–salinity (S–Θ) diagram where casts of hydrographic data are often locally tight in S–Θ space, the relatively empty nature of the World Ocean in the three-dimensional S–Θ–p space seems not to have received attention. The World Ocean’s data lie close to a single surface in this three-dimensional space, and it is shown that this explains the known smallness of the ambiguity in defining neutral surfaces. The ill-defined nature of neutral surfaces means that lateral motion along neutral trajectories leads to mean vertical advection through density surfaces, even in the absence of small-scale mixing processes. The situation in which the ocean’s hydrography occupies a large volume in S–Θ–p space is also considered, and it is suggested that the consequent vertical diapycnal advection would be sufficiently large that the ocean would not be steady.

Numerical Simulations of Two Coaxial Vortex Rings Head-on Collision

2016 ◽  
Vol 8 (4) ◽  
pp. 616-647 ◽  
Author(s):  
Hui Guan ◽  
Zhi-Jun Wei ◽  
Elizabeth Rumenova Rasolkova ◽  
Chui-Jie Wu
Keyword(s):  
Dimensional Space ◽  
Three Dimensional ◽  
Evaluation Procedure ◽  
Vortex Rings ◽  
Small Scale ◽  
Finite Volume Scheme ◽  
Induced Motion ◽  
Piecewise Parabolic ◽  
Physical Phenomena ◽  
Small Scale Structures

AbstractVortex rings have been a subject of interest in vortex dynamics due to a plethora of physical phenomena revealed by their motions and interactions within a boundary. The present paper is devoted to physics of a head-on collision of two vortex rings in three dimensional space, simulated with a second order finite volume scheme and compressible. The scheme combines non-iterative approximate Riemann-solver and piecewise-parabolic reconstruction used in inviscid flux evaluation procedure. The computational results of vortex ring collisions capture several distinctive phenomena. In the early stages of the simulation, the rings propagate under their own self-induced motion. As the rings approach each other, their radii increase, followed by stretching and merging during the collision. Later, the two rings have merged into a single doughnut-shaped structure. This structure continues to extend in the radial direction, leaving a web of particles around the centers. At a later time, the formation of ringlets propagate radially away from the center of collision, and then the effects of instability involved leads to a reconnection in which small-scale ringlets are generated. In addition, it is shown that the scheme captures several experimentally observed features of the ring collisions, including a turbulent breakdown into small-scale structures and the generation of small-scale radially propagating vortex rings, due to the modification of the vorticity distribution, as a result of the entrainment of background vorticity and helicity by the vortex core, and their subsequent interaction.

scholarly journals Cloud G074.11+00.11: a stellar cluster in formation

2019 ◽  
Vol 630 ◽  
pp. A69
Author(s):  
Mika Saajasto ◽  
Jorma Harju ◽  
Mika Juvela ◽  
Liu Tie ◽  
Qizhou Zhang ◽  
...  
Keyword(s):  
Star Formation ◽  
Large Scale ◽  
Three Dimensional ◽  
Central Star ◽  
Small Scale ◽  
Molecular Line ◽  
Filamentary Structure ◽  
Maser Emission ◽  
Stellar Cluster ◽  
Star Forming

Context. We present molecular line and dust continuum observations of a Planck-detected cold cloud, G074.11+00.11. The cloud consists of a system of curved filaments and a central star-forming clump. The clump is associated with several infrared sources and H2O maser emission. Aims. We aim to determine the mass distribution and gas dynamics within the clump to investigate if the filamentary structure seen around the clump repeats itself on a smaller scale, and to estimate the fractions of mass contained in dense cores and filaments. The velocity distribution of pristine dense gas can be used to investigate the global dynamical state of the clump, the role of filamentary inflows, filament fragmentation, and core accretion. Methods. We used molecular line and continuum observations from single dish observatories and interferometric facilities to study the kinematics of the region. Results. The molecular line observations show that the central clump may have formed as a result of a large-scale filament collision. The central clump contains three compact cores. Assuming a distance of 2.3 kpc, based on Gaia observations and a three-dimensional extinction method of background stars, the mass of the central clump exceeds 700 M⊙, which is roughly ~25% of the total mass of the cloud. Our virial analysis suggests that the central clump and all identified substructures are collapsing. We find no evidence for small-scale filaments associated with the cores. Conclusions. Our observations indicate that the clump is fragmented into three cores with masses in the range [10, 50] M⊙ and that all three are collapsing. The presence of an H2O maser emission suggests active star formation. However, the CO lines show only weak signs of outflows. We suggest that the region is young and any processes leading to star formation have just recently begun.

Kinematic Mappings. Part 1: Classification of Algebraic Motions in the Plane

1981 ◽  
Vol 103 (3) ◽  
pp. 585-591 ◽  
Author(s):  
S. De Sa ◽  
B. Roth
Keyword(s):  
Classification Scheme ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Planar Motion ◽  
Rotation Curves ◽  
Planar Motions ◽  
Three Dimensional Space

A classification scheme is developed for algebraic motions in the plane. The method is based upon the study of curves in a special three dimensional space into which the planar motions are mapped. As an example all possible cubic motions are classified. It is shown that this mapping, originally proposed by Blaschke, is based upon the rotation curves and the rotation angles of the planar motion.

scholarly journals Unification of Logistic Demands of Small-scale Enterprises as Solution of Urban Traffic Congestion Problem

2012 ◽  
Vol 23 (4) ◽  
pp. 297-301
Author(s):  
Saša Petar ◽  
Morana Ivaković-Babić
Keyword(s):  
Traffic Congestion ◽  
Urban Areas ◽  
Technological Development ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Urban Traffic ◽  
Small Scale ◽  
Time Dimension ◽  
New Information ◽  
Business Efficiency

The development of information and telecommunication technologies, apart from accelerating the information flows, increasing efficiency on the market and other business changes, results also in the reduction of the number of employees in companies. With the application of new information and telecommunication technologies even companies with a single employee in certain activities (publishing, counselling, tourism, etc.) can successfully compete with larger companies, which leads to an increased number of logistic service demands. A large number of small enterprises create a large number of small orders which have to be delivered in the same unit of time, thus causing increased congestion of roads, especially in urban areas. Although information transport, due to the mentioned technologies, has become to a large extent virtual, the transport of people and cargo continues to operate in a three-dimensional space (recognizing the time dimension as an important factor for calculating the business efficiency). The application of the model from the paper makes it possible to confirm the thesis of increased traffic congestion as consequence of the technological development and to emphasise the need to find a solution in the form of logistic and distribution centres for small and mid-size enterprises. The companies that offer logistic and distribution services may become centres for small and mid-size enterprises, thus offering a solution that maintains the speed and efficiency and avoids costs of congestions and delays.

A Multiscale Model of Plasticity Based on Discrete Dislocation Dynamics

2001 ◽  
Vol 124 (1) ◽  
pp. 78-87 ◽  
Author(s):  
Hussein M. Zbib ◽  
Tomas Diaz de la Rubia ◽  
Vasily Bulatov
Keyword(s):  
Dimensional Space ◽  
Three Dimensional ◽  
Dislocation Dynamics ◽  
Elastic Response ◽  
Small Scale ◽  
Deformation Bands ◽  
Similar Treatment ◽  
Discrete Dislocation Dynamics ◽  
Discrete Dislocation ◽  
Wide Range

We present a framework coupling continuum elasto-viscoplasticity with three-dimensional discrete dislocation dynamics. In this approach, the elastic response is governed by the classical Hooke’s law and the viscoplastic behavior is determined by the motion of curved dislocations in a three-dimensional space. The resulting hybrid continuum-discrete framework is formulated into a standard finite element model where the dislocation-induced stress is homogenized over each element with a similar treatment for the dislocation-induced plastic strain. The model can be used to investigate a wide range of small scale plasticity phenomena, including microshear bands, adiabatic shear bands, stability and formation of dislocation cells, thin films and multiplayer structures. Here we present results pertaining to the formation of deformation bands and surface distortions under dynamic loading conditions and show the capability of the model in analyzing complicated deformation-induced patterns.

Three Dimensional structure and organization of diploid chromosomes by optical section microscopy

1987 ◽  
Vol 45 ◽  
pp. 633-635
Author(s):  
David A. Agard ◽  
Yasushi Hiraoka ◽  
John W. Sedat
Keyword(s):  
Dimensional Space ◽  
Three Dimensional ◽  
Developmental State ◽  
Mitotic Cell ◽  
Biological Properties ◽  
Dimensional Structure ◽  
Specific Gene ◽  
Three Dimensional Structure ◽  
Complementary Techniques ◽  
Dynamic Structures

In an effort to understand the complex relationship between structure and biological function within the nucleus, we have embarked on a program to examine the three-dimensional structure and organization of Drosophila melanogaster embryonic chromosomes. Our overall goal is to determine how DNA and proteins are organized into complex and highly dynamic structures (chromosomes) and how these chromosomes are arranged in three dimensional space within the cell nucleus. Futher, we hope to be able to correlate structual data with such fundamental biological properties as stage in the mitotic cell cycle, developmental state and transcription at specific gene loci.Towards this end, we have been developing methodologies for the three-dimensional analysis of non-crystalline biological specimens using optical and electron microscopy. We feel that the combination of these two complementary techniques allows an unprecedented look at the structural organization of cellular components ranging in size from 100A to 100 microns.

Diffraction contrast of dislocations in icosahedral quasicrystals

1990 ◽  
Vol 48 (4) ◽  
pp. 454-455
Author(s):  
K. Urban ◽  
Z. Zhang ◽  
M. Wollgarten ◽  
D. Gratias
Keyword(s):  
Dimensional Space ◽  
Three Dimensional ◽  
Complete Characterization ◽  
Extinction Condition ◽  
Burgers Vector ◽  
Diffraction Contrast ◽  
Lattice Geometry ◽  
Reference Space ◽  
Icosahedral Quasicrystals ◽  
The One

Recently dislocations have been observed by electron microscopy in the icosahedral quasicrystalline (IQ) phase of Al65Cu20Fe15. These dislocations exhibit diffraction contrast similar to that known for dislocations in conventional crystals. The contrast becomes extinct for certain diffraction vectors g. In the following the basis of electron diffraction contrast of dislocations in the IQ phase is described. Taking account of the six-dimensional nature of the Burgers vector a “strong” and a “weak” extinction condition are found.Dislocations in quasicrystals canot be described on the basis of simple shear or insertion of a lattice plane only. In order to achieve a complete characterization of these dislocations it is advantageous to make use of the one to one correspondence of the lattice geometry in our three-dimensional space (R3) and that in the six-dimensional reference space (R6) where full periodicity is recovered . Therefore the contrast extinction condition has to be written as gpbp + gobo = 0 (1). The diffraction vector g and the Burgers vector b decompose into two vectors gp, bp and go, bo in, respectively, the physical and the orthogonal three-dimensional sub-spaces of R6.

Flavin radicals, conformational sampling and robust design principles in interprotein electron transfer: the trimethylamine dehydrogenase-electron-transferring flavoprotein complex

2004 ◽  
Vol 71 ◽  
pp. 1-14
Author(s):  
David Leys ◽  
Jaswir Basran ◽  
François Talfournier ◽  
Kamaldeep K. Chohan ◽  
Andrew W. Munro ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Kinetic Studies ◽  
Molecular Assembly ◽  
Conformational Sampling ◽  
Trimethylamine Dehydrogenase ◽  
Key Residues ◽  
Electron Transferring Flavoprotein ◽  
Electron Transfer Complex

TMADH (trimethylamine dehydrogenase) is a complex iron-sulphur flavoprotein that forms a soluble electron-transfer complex with ETF (electron-transferring flavoprotein). The mechanism of electron transfer between TMADH and ETF has been studied using stopped-flow kinetic and mutagenesis methods, and more recently by X-ray crystallography. Potentiometric methods have also been used to identify key residues involved in the stabilization of the flavin radical semiquinone species in ETF. These studies have demonstrated a key role for 'conformational sampling' in the electron-transfer complex, facilitated by two-site contact of ETF with TMADH. Exploration of three-dimensional space in the complex allows the FAD of ETF to find conformations compatible with enhanced electronic coupling with the 4Fe-4S centre of TMADH. This mechanism of electron transfer provides for a more robust and accessible design principle for interprotein electron transfer compared with simpler models that invoke the collision of redox partners followed by electron transfer. The structure of the TMADH-ETF complex confirms the role of key residues in electron transfer and molecular assembly, originally suggested from detailed kinetic studies in wild-type and mutant complexes, and from molecular modelling.

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