scholarly journals Two‐Dimensional Reconstruction of a Time‐Dependent Mirror Structure from Double‐Polytropic MHD simulation

2020 ◽  
Author(s):  
Wai‐Leong Teh ◽  
Seiji Zenitani
1980 ◽  
Vol 19 (1) ◽  
pp. 1-15
Author(s):  
M. DRYER ◽  
S. T. WU ◽  
S. M. HAN

Un modelo numérico bidimensional magnetohidrodinámico (MHD) es usado para simular diferentes tipos de interacciones de corrientes de plasma de alta velocidad con un flujo ambiental no perturbado de viento solar. Los orígenes físicos de estos tipos de interacción se especifican suponiendo que las corrientes de plasma de alta velocidad se generan por medio de dos fenómenos forzados: (i) una liberación de energía limitada en el tiempo y representada por un destello solar transitorio; (ii) una corriente de plasma de alta velocidad generada en un agujero coronal recién creado, la cual continúa, sin disminuir, entregando energía al flujo original del viento solar. Debido a la diferencia en la escala de tiempo del destello solar y del agujero coronal, el desarrollo del flujo perturbado detrás de los frentes de choque generados en el destello y en el agujero coronal es distinto. Esto es, el último puede iniciarse en una escala de tiempo de un día, pero puede continuarse por una o más rotaciones solares. Por otra parte, el primero puede iniciarse solamente en una escala de tiempo de minutos o hasta una hora, después del cual su decaimiento se mide en una hora o dos más. Por lo tanto, hemos iniciado un estudio de estas dos causas variando simplemente la duración temporal de los disturbios en el cálculo del valor inicial. Varias diferencias en el comportamiento dinámico de la interacción del viento solar con un frente de choque generado en un agujero coronal, y con el generado en un destello solar se hacen notar en este estudio. En el primer caso, un resultado único es el desarrollado de una burbuja magnética que viaja hacia afuera.


1989 ◽  
Vol 25 (1) ◽  
pp. 238-242 ◽  
Author(s):  
M.A. Huerta ◽  
G.C. Boynton

Author(s):  
A.M. Jones ◽  
A. Max Fiskin

If the tilt of a specimen can be varied either by the strategy of observing identical particles orientated randomly or by use of a eucentric goniometer stage, three dimensional reconstruction procedures are available (l). If the specimens, such as small protein aggregates, lack periodicity, direct space methods compete favorably in ease of implementation with reconstruction by the Fourier (transform) space approach (2). Regardless of method, reconstruction is possible because useful specimen thicknesses are always much less than the depth of field in an electron microscope. Thus electron images record the amount of stain in columns of the object normal to the recording plates. For single particles, practical considerations dictate that the specimen be tilted precisely about a single axis. In so doing a reconstructed image is achieved serially from two-dimensional sections which in turn are generated by a series of back-to-front lines of projection data.


Author(s):  
José L. Carrascosa ◽  
José M. Valpuesta ◽  
Hisao Fujisawa

The head to tail connector of bacteriophages plays a fundamental role in the assembly of viral heads and DNA packaging. In spite of the absence of sequence homology, the structure of connectors from different viruses (T4, Ø29, T3, P22, etc) share common morphological features, that are most clearly revealed in their three-dimensional structure. We have studied the three-dimensional reconstruction of the connector protein from phage T3 (gp 8) from tilted view of two dimensional crystals obtained from this protein after cloning and purification.DNA sequences including gene 8 from phage T3 were cloned, into Bam Hl-Eco Rl sites down stream of lambda promotor PL, in the expression vector pNT45 under the control of cI857. E R204 (pNT89) cells were incubated at 42°C for 2h, harvested and resuspended in 20 mM Tris HC1 (pH 7.4), 7mM 2 mercaptoethanol, ImM EDTA. The cells were lysed by freezing and thawing in the presence of lysozyme (lmg/ml) and ligthly sonicated. The low speed supernatant was precipitated by ammonium sulfate (60% saturated) and dissolved in the original buffer to be subjected to gel nitration through Sepharose 6B, followed by phosphocellulose colum (Pll) and DEAE cellulose colum (DE52). Purified gp8 appeared at 0.3M NaCl and formed crystals when its concentration increased above 1.5 mg/ml.


Author(s):  
J.L. Carrascosa ◽  
G. Abella ◽  
S. Marco ◽  
M. Muyal ◽  
J.M. Carazo

Chaperonins are a class of proteins characterized by their role as morphogenetic factors. They trantsiently interact with the structural components of certain biological aggregates (viruses, enzymes etc), promoting their correct folding, assembly and, eventually transport. The groEL factor from E. coli is a conspicuous member of the chaperonins, as it promotes the assembly and morphogenesis of bacterial oligomers and/viral structures.We have studied groEL-like factors from two different bacteria:E. coli and B.subtilis. These factors share common morphological features , showing two different views: one is 6-fold, while the other shows 7 morphological units. There is also a correlation between the presence of a dominant 6-fold view and the fact of both bacteria been grown at low temperature (32°C), while the 7-fold is the main view at higher temperatures (42°C). As the two-dimensional projections of groEL were difficult to interprete, we studied their three-dimensional reconstruction by the random conical tilt series method from negatively stained particles.


1998 ◽  
Vol 5 (3) ◽  
pp. 145-151
Author(s):  
A. D. Kirwan, Jr. ◽  
B. L. Lipphardt, Jr.

Abstract. Application of the Brown-Samelson theorem, which shows that particle motion is integrable in a class of vorticity-conserving, two-dimensional incompressible flows, is extended here to a class of explicit time dependent dynamically balanced flows in multilayered systems. Particle motion for nonsteady two-dimensional flows with discontinuities in the vorticity or potential vorticity fields (modon solutions) is shown to be integrable. An example of a two-layer modon solution constrained by observations of a Gulf Stream ring system is discussed.


1977 ◽  
Vol 48 (1) ◽  
pp. 270-278 ◽  
Author(s):  
Shih‐Pei Hu ◽  
Benjamin M. Rabinovici

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