| 1. |
- Jansson, T, et al.
(författare)
-
Automated correction of linear deformation due to sectioning in serial micrographs.
- 1995
-
Ingår i: Journal of microscopy. - 0022-2720. ; 177:Pt 2, s. 119-27
-
Tidskriftsartikel (refereegranskat)abstract
- This paper describes an objective and automatic method for detection and correction of sectioning deformations in digitized micrographs, as well as an evaluation of the method applied to light and electron microscopic images of semi-thin and ultra-thin serial sections from brain cortex. The detection is based on matching of image subregions and the deformation model is bi-linear, i.e. two first-order polynomials are used for modelling compression/expansion in perpendicular directions. The procedure is applicable to prealigned serial two-dimensional sections and is primarily aimed at three-dimensional reconstruction of tissue samples consisting of a large number of cells with random distribution and morphology.
|
|
| 2. |
|
|
| 3. |
- Kim, Jae-Young, et al.
(författare)
-
Event Horizon Telescope imaging of the archetypal blazar 3C 279 at an extreme 20 microarcsecond resolution
- 2020
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 640
-
Tidskriftsartikel (refereegranskat)abstract
- 3C 279 is an archetypal blazar with a prominent radio jet that show broadband flux density variability across the entire electromagnetic spectrum. We use an ultra-high angular resolution technique - global Very Long Baseline Interferometry (VLBI) at 1.3mm (230 GHz) - to resolve the innermost jet of 3C 279 in order to study its fine-scale morphology close to the jet base where highly variable-ray emission is thought to originate, according to various models. The source was observed during four days in April 2017 with the Event Horizon Telescope at 230 GHz, including the phased Atacama Large Millimeter/submillimeter Array, at an angular resolution of ∼20 μas (at a redshift of z = 0:536 this corresponds to ∼0:13 pc ∼ 1700 Schwarzschild radii with a black hole mass MBH = 8 × 108 M⊙). Imaging and model-fitting techniques were applied to the data to parameterize the fine-scale source structure and its variation.We find a multicomponent inner jet morphology with the northernmost component elongated perpendicular to the direction of the jet, as imaged at longer wavelengths. The elongated nuclear structure is consistent on all four observing days and across diffierent imaging methods and model-fitting techniques, and therefore appears robust. Owing to its compactness and brightness, we associate the northern nuclear structure as the VLBI "core". This morphology can be interpreted as either a broad resolved jet base or a spatially bent jet.We also find significant day-to-day variations in the closure phases, which appear most pronounced on the triangles with the longest baselines. Our analysis shows that this variation is related to a systematic change of the source structure. Two inner jet components move non-radially at apparent speeds of ∼15 c and ∼20 c (∼1:3 and ∼1:7 μas day-1, respectively), which more strongly supports the scenario of traveling shocks or instabilities in a bent, possibly rotating jet. The observed apparent speeds are also coincident with the 3C 279 large-scale jet kinematics observed at longer (cm) wavelengths, suggesting no significant jet acceleration between the 1.3mm core and the outer jet. The intrinsic brightness temperature of the jet components are ≤1010 K, a magnitude or more lower than typical values seen at ≥7mm wavelengths. The low brightness temperature and morphological complexity suggest that the core region of 3C 279 becomes optically thin at short (mm) wavelengths.
|
|
| 4. |
- Pascher, R, et al.
(författare)
-
Computer-assisted 3D analysis of cell distributions in the normal and epileptic cerebral cortex: description of a methodology in progress.
- 1993
-
Ingår i: Computerized medical imaging and graphics : the official journal of the Computerized Medical Imaging Society. - 0895-6111. ; 17:4-5, s. 405-10
-
Tidskriftsartikel (refereegranskat)abstract
- This paper describes software routines that (a) visualizes a stack of several thousands of aligned sequential photographic two-dimensional (2D) images stored in an image processing system; (b) creates a data base containing information about objects identified sequentially from the 2D images; (c) transfers the data base to a graphical terminal; (d) reconstructs a three-dimensional (3D) object space; and (e) supports on-line interaction between the image processing system and the graphical terminal. As an application example, the cell content of a prism of motor cerebral cortex of the cat is reconstructed. Preliminary results from reconstructing human epileptic temporal cortex (cortical microdysgenesia) are also reported.
|
|
| 5. |
- Skoglund, Thomas, 1969, et al.
(författare)
-
3D reconstruction of biological objects from sequential image planes--applied on cerebral cortex from cat.
- 1993
-
Ingår i: Computerized medical imaging and graphics : the official journal of the Computerized Medical Imaging Society. - 0895-6111. ; 17:3, s. 165-74
-
Tidskriftsartikel (refereegranskat)abstract
- A prism of cat cerebral cortex was reconstructed with a method for three-dimensional (3D) representation of biological objects. A series of 918 semithin sections were digitized into an image analysis system. The images were aligned and analyzed, and a data base with the coordinates and a classification of the cells was created. The data base (i.e., the cortical prism) was visualized in a 3D graphic terminal, and parameters such as columnar and lamellar organization, clustering, and cell density were analyzed. A neuronal perikaryon and its neurites was reconstructed and shown together with the cortical prism.
|
|
| 6. |
- Skoglund, Thomas, 1969, et al.
(författare)
-
A method for 3D reconstruction of neuronal processes using semithin serial sections displayed as a cinematographic sequence.
- 1995
-
Ingår i: Journal of neuroscience methods. - 0165-0270. ; 61:1-2, s. 105-11
-
Tidskriftsartikel (refereegranskat)abstract
- In order to study the organization and distribution of dendrites and axons in the cerebral cortex, we have developed a computer-assisted method for 3D reconstruction of neuronal processes based on serial light microscopic images displayed as a continuous sequence. A series of tangential sections (0.65 micron thick) through rat parietal cortex was aligned, digitized into the computer and then used to build a sequence (stack) of images which was stored to a digital real-time video disk. Apical dendrites located in dendritic bundles in laminae III and IV were traced through the sequence. Two tracing modes were tested: (1) cinematographic mode, in which the image stack was displayed continuously and automatically by the computer at various preset speeds (max. speed: 25 images/s) and (2) stepping mode, in which the interval between each image was varied manually according to the choice of the operator. Coordinates were stored in a database and used to build a 3D reconstruction where apical dendrites were displayed as wires or tubes. Tracing in cinematographic mode was about 3 times faster than tracing in stepping mode. We believe that the former mode exploits the built in 'filtering' capacity of the visual system to perform temporal averaging.
|
|
| 7. |
- Skoglund, Thomas, 1969, et al.
(författare)
-
Heterogeneity in the columnar number of neurons in different neocortical areas in the rat.
- 1996
-
Ingår i: Neuroscience letters. - 0304-3940. ; 208:2, s. 97-100
-
Tidskriftsartikel (refereegranskat)abstract
- We have investigated the number of neurons in three neocortical areas of the rat brain. Our results challenge the uniformity concept proposed by Rockel et al. [Brain, 103 (1980) 221-244]. Area Fr1, HL and Oc2 (primary motor, primary somatosensory and secondary visual cortex) from Sprague-Dawley rats were examined. The brains were glutaraldehyde fixed, sectioned in 50 mu m thick sagittal slices and stained in Richardson's solution. The counting was carried out using a computerized system based on the optical disector. The cortical thickness was measured to be 1.9 mm, 1.9 mm, and 1.4 mm in area Fr1, HL, and Oc2, respectively. The number of neurons under 1 mm2 cortical surface was calculated to be 91 100 in Fr1, 133 500 in HL and 106 100 in Oc2. The number of neurons in a volume of tissue 30 x 25 mu m through the depth of the cortex was calculated to be 68 in Fr1, 100 in HL and 80 in Oc2. The density of neurons was calculated to be 48 500 neurons/mm3 in Fr1, 69 400 neurons/mm3 in HL and 76,900 neurons/mm3 in Oc2. There were significant (P < 0.01) differences between all areas regarding both the number of neurons under a certain area of surface as well as the neuron density. The results indicate that there is no basic uniformity in the number of neurons under a certain area of cortical surface.
|
|
| 8. |
- Skoglund, Thomas, 1969, et al.
(författare)
-
The existence of a layer IV in the rat motor cortex.
- 1997
-
Ingår i: Cerebral cortex (New York, N.Y. : 1991). - 1047-3211. ; 7:2, s. 178-80
-
Tidskriftsartikel (refereegranskat)abstract
- We have reconstructed the laminar pattern of rat primary motor cortex (Fr1) using a computerized analysis system based on the so-called 'optical dissector'. Data were visualized on a graphics terminal. In contrast to current views, which state that there is no prominent layer IV in the motor cortex of the rat, our method of analysis revealed a genuine layer IV consisting of densely packed small neurons.
|
|
