Search results for " density"
showing 10 items of 2709 documents
A multiscale X-ray phase-contrast tomography dataset of whole human left lung
2021
ABSTRACTTechnological advancements in X-ray imaging using bright and coherent synchrotron sources now allows to decouple sample size and resolution, while maintaining high sensitivity to the microstructure of soft, partially dehydrated tissues. The recently developed imaging technique, hierarchical phase-contrast tomography, is a comprehensive approach to address the challenge of organ-scale (up to tens of centimeters) soft tissue imaging with resolution and sensitivity down to the cellular level. Using this technique, we imaged ex vivo an entire human left lung at an isotropic voxel size of 25.08 μm along with local zooms down to 6.05 - 6.5 μm and 2.45 - 2.5 μm in voxel size. The high tiss…
What about computational super-resolution in fluorescence Fourier light field microscopy?
2020
Recently, Fourier light field microscopy was proposed to overcome the limitations in conventional light field microscopy by placing a micro-lens array at the aperture stop of the microscope objective instead of the image plane. In this way, a collection of orthographic views from different perspectives are directly captured. When inspecting fluorescent samples, the sensitivity and noise of the sensors are a major concern and large sensor pixels are required to cope with low-light conditions, which implies under-sampling issues. In this context, we analyze the sampling patterns in Fourier light field microscopy to understand to what extent computational super-resolution can be triggered duri…
Super-Resolution Scanning Near-Field Optical Microscopy
2007
Scanning near-field optical microscopy (SNOM) is a method to obtain information about the optical properties of a sample at a lateral resolution below the diffraction limit of far-field microscopy. In SNOM, a light source of a dimension which is small compared to the wavelength of light and which is held at a small distance from the sample is scanned across the surface of the sample. The modulation by the sample of the light emitted from the source is recorded as a signal. As a general rule one may say that the size of the source and the distance to the sample limit the resolution of SNOM. A radiating self-emitting point dipole may be regarded as an idealized SNOM source. With such a source…
Fourier-domain lightfield microscopy: a new paradigm in 3D microscopy
2020
Recently, integral (also known as lightfield or plenoptic) imaging concept has been applied successfully to microscopy. The main advantage of lightfield microscopy when compared with conventional 3D imaging techniques is that it offers the possibility of capturing the 3D information of the sample after a single shot. However, integral microscopy is now facing many challenges, like improving the resolution and depth of field of the reconstructed specimens or the development and optimization of specially-adapted reconstruction algorithms. This contribution is devoted to review a new paradigm in lightfield microscopy, namely, the Fourier-domain integral microscope (FiMic), that improves the ca…
Superresolution imaging of biological nanostructures by spectral precision distance microscopy
2011
For the improved understanding of biological systems on the nanoscale, it is necessary to enhance the resolution of light microscopy in the visible wavelength range beyond the limits of conventional epifluorescence microscopy (optical resolution of about 200 nm laterally, 600 nm axially). Recently, various far-field methods have been developed allowing a substantial increase of resolution ("superresolution microscopy", or "lightoptical nanoscopy"). This opens an avenue to 'nano-image' intact and even living cells, as well as other biostructures like viruses, down to the molecular detail. Thus, it is possible to combine light optical spatial nanoscale information with ultrastructure analyses…
Hybrid DFT calculations of the atomic and electronic structure for ABO3 perovskite (001) surfaces
2005
Abstract We present the results of first-principles calculations on two possible terminations of the (0 0 1) surfaces of SrTiO3, BaTiO3, and PbTiO3 perovskite crystals. Atomic structure and the electronic configurations were calculated for different 2D slabs, both stoichiometric and non-stoichiometric, using hybrid (B3PW) exchange-correlation technique and re-optimized basis sets of atomic (Gaussian) orbitals. Results are compared with previous calculations and available experimental data. The electronic density distribution near the surface and covalency effects are discussed in details for all three perovskites. Both SrTiO3 and BaTiO3 (0 0 1) surfaces demonstrate reduction of the optical …
Effect of clenching on biomechanical response of human mandible and temporomandibular joint to traumatic force analyzed by finite element method
2013
Purpose: The purpose of the present study was to analyze the effect of clenching on the biomechanical response of human mandible and temporomandibular joint (TMJ) to traumatic force by the finite element (FE) method. Material and Methods: FE models of the mandible and the TMJ in resting and clenching positions were prepared. Distribution and magnitude of von Mises stress were analyzed by applying force as a point load in the symphyseal, canine, body and angle regions of the mandible. In addition, strain energy density (SED) at the articular disc and in posterior connective tissue of TMJ was analyzed. Results: In the resting position, von Mises stress was mainly concentrated at the condylar …
Intraosseous monitoring of drilling in lumbar vertebrae by ultrasound: An experimental feasibility study.
2016
The rationale for this project is to evaluate the efficiency of a novel sonographic method for measurements of interosseous distances. The method utilizes a propagating ultrasonic beam through aqueous milieu which is directed as a jet into a drilled tract. We used a plastic model of human L5 vertebra and ex vivo specimen of L5 porcine vertebra and generated 2 mm in diameter tracts in vertebral pedicles. The tracts were created in the "desired" central direction and in the "wrong" medial and lateral directions. The drilled tracts and the residual, up to opposite cortex, distances were measured sonographically and mechanically and compared statistically. We show that "true" mechanical measure…
The use of low-resolution phasing followed by phase extension from 7.6 to 2.5 Å resolution with noncrystallographic symmetry to solve the structure o…
2011
P2, the major capsid protein of bacteriophage PM2, adopts the double β-barrel fold characteristic of the PRD1-adenoviral lineage. The 2.5 Å resolution X-ray data obtained by analysis of the two major lattices of a multiple crystal of P2 were phased by molecular replacement, using as a search model structure factors to 7.6 Å resolution obtained from electron density cut from the map of the entire PM2 virion. Phase extension to 2.5 Å resolution used solely sixfold cycling averaging and solvent flattening. This represents an atypical example of an oligomeric protein for which the structure has been determined at high resolution by bootstrapping from low-resolution initial phases.
A TDDFT-based Study on the Proton-DNA Collision
2019
The interaction of heavy charged particles with DNA is of interest for several areas, from hadrontherapy to aero-space industry. In this paper, a TD-DFT study on the interaction of a 4 keV proton with an isolated DNA base pair was carried out. Ehrenfest dynamics was used to study the evolution of the system during and after the proton impact up to about 193 fs. This time was long enough to observe the dissociation of the target, which occurs between 80-100 fs. The effect of base pair linking to the DNA double helix was emulated by fixing the four O3' atoms responsible for the attachment. The base pair tends to dissociate into its main components, namely the phosphate groups, sugars and nitr…