scholarly journals On the numerical treatment of viscous and convective effects in relative pressure reconstruction methods

2021 ◽  
Author(s):  
Douglas R. Q. Pacheco
Keyword(s):  
Relative Pressure ◽  
Numerical Treatment ◽  
Reconstruction Methods

High-resolution scanning electron microscopy (HRSEM) of mitochondria from various rat tissues

1988 ◽  
Vol 46 ◽  
pp. 14-15
Author(s):  
P.J. Lea ◽  
M.J. Hollenberg
Keyword(s):  
Electron Microscopy ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Rat Hepatocytes ◽  
Three Dimensions ◽  
Objective Lens ◽  
Rat Tissues ◽  
Thin Sections ◽  
Reconstruction Methods ◽  
Scanning Electron

Our current understanding of mitochondrial ultrastructure has been derived primarily from thin sections using transmission electron microscopy (TEM). This information has been extrapolated into three dimensions by artist's impressions (1) or serial sectioning techniques in combination with computer processing (2). The resolution of serial reconstruction methods is limited by section thickness whereas artist's impressions have obvious disadvantages.In contrast, the new techniques of HRSEM used in this study (3) offer the opportunity to view simultaneously both the internal and external structure of mitochondria directly in three dimensions and in detail.The tridimensional ultrastructure of mitochondria from rat hepatocytes, retinal (retinal pigment epithelium), renal (proximal convoluted tubule) and adrenal cortex cells were studied by HRSEM. The specimens were prepared by aldehyde-osmium fixation in combination with freeze cleavage followed by partial extraction of cytosol with a weak solution of osmium tetroxide (4). The specimens were examined with a Hitachi S-570 scanning electron microscope, resolution better than 30 nm, where the secondary electron detector is located in the column directly above the specimen inserted within the objective lens.

3-D reconstruction and analysis of mammalian mitotic spindle structure

1992 ◽  
Vol 50 (1) ◽  
pp. 578-579
Author(s):  
Kent McDonald ◽  
David Mastronarde ◽  
Rubai Ding ◽  
Eileen O'Toole ◽  
J. Richard McIntosh
Keyword(s):  
Cross Sections ◽  
Mitotic Spindle ◽  
Experimental Studies ◽  
Video Camera ◽  
Three Dimensions ◽  
Mitotic Spindles ◽  
Black And White ◽  
Reconstruction Methods ◽  
Spindle Structure ◽  
Tissue Culture Line

Mammalian spindles are generally large and may contain over a thousand microtubules (MTs). For this reason they are difficult to reconstruct in three dimensions and many researchers have chosen to study the smaller and simpler spindles of lower eukaryotes. Nevertheless, the mammalian spindle is used for many experimental studies and it would be useful to know its detailed structure.We have been using serial cross sections and computer reconstruction methods to analyze MT distributions in mitotic spindles of PtK cells, a mammalian tissue culture line. Images from EM negatives are digtized on a light box by a Dage MTI video camera containing a black and white Saticon tube. The signal is digitized by a Parallax 1280 graphics device in a MicroVax III computer. Microtubules are digitized at a magnification such that each is 10-12 pixels in diameter.

Structural Studies on the Eukaryotic Ribosome

1990 ◽  
Vol 48 (1) ◽  
pp. 256-257
Author(s):  
Adriana Verschoor ◽  
Ronald Milligan ◽  
Suman Srivastava ◽  
Joachim Frank
Keyword(s):  
Chick Embryo ◽  
3D Reconstruction ◽  
Single Particle ◽  
Mass Density ◽  
Particle Surface ◽  
Uranyl Acetate ◽  
Electron Microscopic ◽  
Eukaryotic Ribosome ◽  
Negative Stain ◽  
Reconstruction Methods

We have studied the eukaryotic ribosome from two vertebrate species (rabbit reticulocyte and chick embryo ribosomes) in several different electron microscopic preparations (Fig. 1a-d), and we have applied image processing methods to two of the types of images. Reticulocyte ribosomes were examined in both negative stain (0.5% uranyl acetate, in a double-carbon preparation) and frozen hydrated preparation as single-particle specimens. In addition, chick embryo ribosomes in tetrameric and crystalline assemblies in frozen hydrated preparation have been examined. 2D averaging, multivariate statistical analysis, and classification methods have been applied to the negatively stained single-particle micrographs and the frozen hydrated tetramer micrographs to obtain statistically well defined projection images of the ribosome (Fig. 2a,c). 3D reconstruction methods, the random conical reconstruction scheme and weighted back projection, were applied to the negative-stain data, and several closely related reconstructions were obtained. The principal 3D reconstruction (Fig. 2b), which has a resolution of 3.7 nm according to the differential phase residual criterion, can be compared to the images of individual ribosomes in a 2D tetramer average (Fig. 2c) at a similar resolution, and a good agreement of the general morphology and of many of the characteristic features is seen.Both data sets show the ribosome in roughly the same ’view’ or orientation, with respect to the adsorptive surface in the electron microscopic preparation, as judged by the agreement in both the projected form and the distribution of characteristic density features. The negative-stain reconstruction reveals details of the ribosome morphology; the 2D frozen-hydrated average provides projection information on the native mass-density distribution within the structure. The 40S subunit appears to have an elongate core of higher density, while the 60S subunit shows a more complex pattern of dense features, comprising a rather globular core, locally extending close to the particle surface.

Effects of Neoadjuvant Chemio-Radiation Therapy on the Anal Sphincter Function in Patients with Low Rectal Cancers

2020 ◽  
Vol 10 (3) ◽  
pp. 190-197
Author(s):  
A. B. Baichorov ◽  
A. O. Rasulov
Keyword(s):  
Anal Sphincter ◽  
Neoadjuvant Chemoradiotherapy ◽  
Functional Results ◽  
Neoadjuvant Chemoradiation ◽  
Chemoradiation Therapy ◽  
Preoperative Treatment ◽  
Neoadjuvant Chemoradiation Therapy ◽  
Reconstruction Methods ◽  
Anterior Rectal Resection ◽  
Significant Difference

The aim of the study was to compare functional results prior to and following neoadjuvant chemoradiation therapy.Materials and methods. An analysis of the functional results of a prospective clinical study was carried out. The study included 90 patients who underwent low anterior rectal resection for cancer of the lower or middle ampullar rectum with T1-4aN0-2M0 using various reconstruction methods.Results and discussion. Group A included 22 patients with J-shaped reservoirs; group B — 30 patients with side-to-end anastomoses; group C — 38 patients with end-to-end anastomoses. Out of the total study group (n = 90), 43 patients underwent neoadjuvant chemoradiotherapy vs. 47 patients without any preoperative treatment. No statistically significant difference was observed in the frequency of applied reconstructive techniques (р = 0.725) and the incidence of postoperative complications (p = 0.103) in the groups with and without neoadjuvant chemoradiotherapy. The baseline scores of the Wexner scale and the results of anorectal manometry in the comparison groups were comparable (p > 0.05). However, upon completion of neoadjuvant chemoradiotherapy and during the period from the moment of surgery up to 12 months after the closure of preventive intestinal stomas, the functional results were less satisfactory in the group of patients having received neoadjuvant chemoradiotherapy (n = 43) with regard to the comparison group (n =  47). Nevertheless, a statistically significant difference in the results was observed from the end of neoadjuvant chemoradiotherapy up to 3 months after closure of the stoma (p <0.05).Conclusions. Neoadjuvant chemoradiation therapy has a negative effect on the function of the anal sphincter, thus requiring concomitant therapy and physiotherapy both at the stages of neoadjuvant chemoradiotherapy and at long intervals after the main surgical stage. 

Analysis on Three NDVI Time-series Reconstruction Methods and Their Applications in North Tibet

2011 ◽  
Vol 13 (1) ◽  
pp. 133-143 ◽  
Author(s):  
Chunqiao SONG ◽  
Songcai YOU ◽  
Linghong KE ◽  
Gaohuan LIU
Keyword(s):  
Time Series ◽  
Reconstruction Methods ◽  
Ndvi Time Series
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