Recent progress in NMR microscopy towards cellular imaging

1990 ◽  
Vol 333 (1632) ◽  
pp. 469-475 ◽  
Keyword(s):  
Molecular Diffusion ◽  
Signal To Noise Ratio ◽  
Pulse Sequences ◽  
Cell Lineage ◽  
Experimental System ◽  
Cellular Imaging ◽  
Physical Parameters ◽  
Nmr Microscopy ◽  
Resolution Limits ◽  
Finite Line

Recent advances in NMR microscopy based on fundamental physical parameters and experimental factors are discussed. We consider fundamental resolution limits due to molecular diffusion and the experimental system bandwidth, as well as practical resolution limits arising from poor signal-to-noise ratio due to small imaging voxel size and finite line broadening due to signal attenuation brought about by diffusion. Several microscopic imaging pulse sequences are presented and applied to elucidating cellular imaging problems such as the cell lineage patterns in Xenopus laevis embryos. Experimental results obtained with 7.0 T NMR microscopy system are presented.

A Study of Clustering for the Enhancement of Image Resolution in Dynamic Photon Emission

2019 ◽  
Author(s):  
S. Chef ◽  
C. T. Chua ◽  
C. L. Gan
Keyword(s):  
Signal To Noise Ratio ◽  
Photon Emission ◽  
Optical Signal ◽  
Image Resolution ◽  
Time Dimension ◽  
Processing Scheme ◽  
3D Space ◽  
Initial Acquisition ◽  
Resolution Limits ◽  
Emission Microscopy

Abstract Limited spatial resolution and low signal to noise ratio are some of the main challenges in optical signal observation, especially for photon emission microscopy. As dynamic emission signals are generated in a 3D space, the use of the time dimension in addition to space enables a better localization of switching events. It can actually be used to infer information with a precision above the resolution limits of the acquired signals. Taking advantage of this property, we report on a post-acquisition processing scheme to generate emission images with a better image resolution than the initial acquisition.

Tomographic resolution limits for diffraction imaging

2015 ◽  
Vol 3 (1) ◽  
pp. SF15-SF20 ◽  
Author(s):  
Yunsong Huang ◽  
Dongliang Zhang ◽  
Gerard T. Schuster
Keyword(s):  
Numerical Simulations ◽  
Diffraction Data ◽  
Signal To Noise Ratio ◽  
Signal To Noise ◽  
Specular Reflections ◽  
Data Resolution ◽  
Resolution Limits ◽  
Diffraction Imaging ◽  
Noise Ratio

We derived formulas for the tomographic resolution limits [Formula: see text] of diffraction data. Resolution limits exhibited that diffractions can provide twice or more the tomographic resolution of specular reflections and therefore led to more accurate reconstructions of velocities between layers. Numerical simulations supported this claim in which the tomogram inverted from diffraction data was noticeably more resolved compared to that inverted from specular data. The specular synthetics were generated by sources on the surface, and the diffraction data were generated by buried diffractors. However, this advantage is nullified if the intensity and signal-to-noise ratio of the diffractions are much less than those of the pervasive specular reflections.

scholarly journals A new and homogeneous metallicity scale for Galactic classical Cepheids

2018 ◽  
Vol 616 ◽  
pp. A82 ◽  
Author(s):  
B. Proxauf ◽  
R. da Silva ◽  
V. V. Kovtyukh ◽  
G. Bono ◽  
L. Inno ◽  
...  
Keyword(s):  
Effective Temperature ◽  
Signal To Noise Ratio ◽  
High Signal ◽  
Physical Parameters ◽  
Classical Cepheids ◽  
Microturbulent Velocity ◽  
Metal Abundances ◽  
Pulsation Cycle ◽  
Intrinsic Error ◽  
Better Than

We gathered more than 1130 high-resolution optical spectra for more than 250 Galactic classical Cepheids. The spectra were collected with the optical spectrographs UVES at VLT, HARPS at 3.6 m, FEROS at 2.2 m MPG/ESO, and STELLA. To improve the effective temperature estimates, we present more than 150 new line depth ratio (LDR) calibrations that together with similar calibrations already available in the literature allowed us to cover a broad range in wavelength (5348 ≤ λ ≤ 8427 Å) and in effective temperature (3500 ≤ Teff ≤ 7700 K). This gives us the unique opportunity to cover both the hottest and coolest phases along the Cepheid pulsation cycle and to limit the intrinsic error on individual measurements at the level of ~100 K. As a consequence of the high signal-to-noise ratio of individual spectra, we identified and measured hundreds of neutral and ionized lines of heavy elements, and in turn, have the opportunity to trace the variation of both surface gravity and microturbulent velocity along the pulsation cycle. The accuracy of the physical parameters and the number of Fe I (more than one hundred) and Fe II (more than ten) lines measured allowed us to estimate mean iron abundances with a precision better than 0.1 dex. We focus on 14 calibrating Cepheids for which the current spectra cover either the entire or a significant portion of the pulsation cycle. The current estimates of the variation of the physical parameters along the pulsation cycle and of the iron abundances agree very well with similar estimates available in the literature. Independent homogeneous estimates of both physical parameters and metal abundances based on different approaches that can constrain possible systematics are highly encouraged.

The evolution of cell lineage in nematodes

Development ◽  
1994 ◽  
Vol 1994 (Supplement) ◽  
pp. 85-95
Author(s):  
Ralf J. Sommer ◽  
Lynn K. Carta ◽  
Paul W. Sternberg
Keyword(s):  
Cell Lineage ◽  
Experimental System ◽  
Nematode Species ◽  
Cell Fates ◽  
Equivalence Group ◽  
Vulval Development ◽  
C Elegans ◽  
Somatic Gonad ◽  
Vulval Precursor Cell ◽  
P Cells

The invariant development of free-living nematodes combined with the extensive knowledge of Caenorhabditis elegans developmental biology provides an experimental system for an analysis of the evolution of developmental mechanisms. We have collected a number of new nematode species from soil samples. Most are easily cultured and their development can be analyzed at the level of individual cells using techniques standard to Caenorhabditis. So far, we have focused on differences in the development of the vulva among species of the families Rhabditidae and Panagrolaimidae. Preceding vulval development, twelve Pn cells migrate into the ventral cord and divide to produce posterior daughters [Pn.p cells] whose fates vary in a position specific manner [from P1.p anterior to P12.p posterior]. In C. elegans hermaphrodites, P(3-8).p are tripotent and form an equivalence group. These cells can express either of two vulval fates (1° or 2°) in response to a signal from the anchor cell of the somatic gonad, or a non-vulval fate (3°), resulting in a 3°-3°-2°-1°-2°-3° pattern of cell fates. Evolutionary differences in vulval development include the number of cells in the vulval equivalence group, the number of 1° cells, the number of progeny generated by each vulval precursor cell, and the position of VPCs before morphogenesis. Examples of three Rhabditidae genera have a posterior vulva in the position of P9-P11 ectoblasts. In Cruznema tripartitum, P(5-7).p form the vulva as in Caenorhabditis, but they migrate posteriorly before dividing. Induction occurs after the gonad grows posteriorly to the position of P(5-7).p cells. In two other species, Mesorhabditis sp. PS 1179 and Teratorhabditis palmarum, we have found changes in induction and competence with respect to their presumably more C. elegans-like ancestor. In Mesorhabditis, P(5-7).p form the vulva after migrating to a posterior position. However, the gonad is not required to specify the pattern of cell fates 3°-2°-1°-2°-3°. Moreover, the Pn.p cells are not equivalent in their potentials to form the vulva. A regulatory constraint in this family thus forces the same set of precursors to generate the vulva, rather than more appropriately positioned Pn.p cells.

Characterization of Rotating Gantry Micro-CT Configuration for theIn VivoEvaluation of Murine Trabecular Bone

2013 ◽  
Vol 19 (4) ◽  
pp. 907-913 ◽  
Author(s):  
Luke Arentsen ◽  
Susanta Hui
Keyword(s):  
Trabecular Bone ◽  
Signal To Noise Ratio ◽  
Hounsfield Unit ◽  
Rate Of Change ◽  
Physical Parameters ◽  
Micro Ct ◽  
Detector Geometry ◽  
Ct System ◽  
Filter Thickness

AbstractThe objective of this study is to determine the optimal physical parameters of a rotating gantry micro-CT system to assessin vivochanges to the trabecular bone of mice. Magnification, binning, peak kilovoltage, beam filtration, and tissue thickness are examined on a commercially available micro-CT system. The X-ray source and detector geometry provides 1.3×, 1.8×, or 3.3× magnification. Binning is examined from no binning to 2 to 4. Energy is varied from 40 to 80 kVp in 10 kVp increments and filter thickness is increased from no filtration to 1.5 mmAl in 0.5 mmAl increments. Mice are imaged at different magnifications and binning combinations to evaluate changes to image quality and microstructure estimation. Increasing magnification from 1.3× to 3.3× and lowering binning from 4 to 1 varies the spatial resolution from 2.5 to 11.8 lp/mm. Increasing the beam energy or filtration thickness decreases Hounsfield unit (HU) estimation, with a maximum rate of change being −286 HU/kVp for 80 kVp. Images for murine trabecular bone are blurred at effective pixel sizes above 60 μm. By comparing resolution, signal-to-noise ratio, and radiation dose, we find that a 3.3× magnification, binning of 2.80 kVp beam with a 0.5 mmAl filter comprises the optimal parameters to evaluate murine trabecular bone for this rotating gantry micro-CT.

Three Dimensional NMR Microscopy Towards In Vivo Cellular Imaging

2005 ◽  
Author(s):  
Z.H. Cho ◽  
C.B. Ahn ◽  
S.C. Juh ◽  
W.C. Chu ◽  
R.M. Friedenberg ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Cellular Imaging ◽  
Nmr Microscopy

scholarly journals Three-Dimensional Microwave Holographic Imaging Employing Forward-Scattered Waves Only

2013 ◽  
Vol 2013 ◽  
pp. 1-15 ◽  
Author(s):  
Reza K. Amineh ◽  
Maryam Ravan ◽  
Justin McCombe ◽  
Natalia K. Nikolova
Keyword(s):  
Signal To Noise Ratio ◽  
Three Dimensional ◽  
Imaging Method ◽  
Two Dimensional ◽  
Signal To Noise ◽  
High Loss ◽  
Holographic Imaging ◽  
Multiple Receivers ◽  
Satisfactory Performance ◽  
Resolution Limits

We propose a three-dimensional microwave holographic imaging method based on the forward-scattered waves only. In the proposed method, one transmitter and multiple receivers perform together a two-dimensional scan on two planar apertures on opposite sides of the inspected domain. The ability to achieve three-dimensional imaging without back-scattered waves enables the imaging of high-loss objects, for example, tissues, where the back-scattered waves may not be available due to low signal-to-noise ratio or nonreciprocal measurement setup. The simulation and experimental results demonstrate the satisfactory performance of the proposed method in providing three-dimensional images. Resolution limits are derived and confirmed with simulation examples.

scholarly journals Soret and Radiation Effects on Mixture of Ethylene Glycol-Water (50%-50%) Based Maxwell Nanofluid Flow in an Upright Channel

Complexity ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Kashif Sadiq ◽  
Fahd Jarad ◽  
Imran Siddique ◽  
Bagh Ali
Keyword(s):  
Ethylene Glycol ◽  
Radiation Effects ◽  
Molecular Diffusion ◽  
Volume Fraction ◽  
Thermal Flux ◽  
Physical Parameters ◽  
Parallel Plates ◽  
Maxwell Nanofluid ◽  
Energy And Momentum ◽  
Nanoparticles Of Silver

In this article, ethylene glycol (EG) + waterbased Maxwell nanofluid with radiation and Soret effects within two parallel plates has been investigated. The problem is formulated in the form of partial differential equations. The dimensionless governing equations for concentration, energy, and momentum are generalized by the fractional molecular diffusion, thermal flux, and shear stress defined by the Caputo–Fabrizio time fractional derivatives. The solutions of the problems are obtained via Laplace inversion numerical algorithm, namely, Stehfest’s. Nanoparticles of silver (Ag) are suspended in a mixture of EG + water to have a nanofluid. It is observed that the thermal conductivity of fluid is enhanced by increasing the values of time and volume fraction. The temperature and velocity of water-silver nanofluid are higher than those of ethylene glycol (EG) + water (H2O)-silver (Ag) nanofluid. The results are discussed at 2% of volume fraction. The results justified the thermo-physical characteristics of base fluids and nanoparticles shown in the tables. The effects of major physical parameters are illustrated graphically and discussed in detail.

Télémètre à détection coherente avec un laser CO2 à ondes entretenues : étude et conception

1983 ◽  
Vol 61 (2) ◽  
pp. 318-331 ◽  
Author(s):  
Denis Vincent ◽  
Gabriel Otis
Keyword(s):  
Detection System ◽  
Signal To Noise Ratio ◽  
Optical Power ◽  
Experimental System ◽  
Intermediate Frequency ◽  
Local Oscillator ◽  
Heterodyne Detection ◽  
Signal To Noise ◽  
Noise Ratio ◽  
Rotating Target

We performed a theoretical and experimental study of a 10.6 μm heterodyne detection system with nonlinear postdetection. A single laser serves as both transmitter and local oscillator; the intermediate frequency is given by the Doppler effect due to a rotating target. An electrooptic crystal modulates the amplitude of the laser beam at a frequency of 15 kHz; a synchronous voltmeter measures the return signal after the nonlinear element. Values of the signal-to-noise ratio with respect to incident optical power agree with the results of the theoretical model. In particular, experimentally measured target-induced frequency spreading effects on the signal-to-noise ratio correspond to the predictions of the model. We also describe an experimental system.

Relief effects correction on frequency-domain electromagnetic data

Geophysics ◽  
2019 ◽  
Vol 84 (1) ◽  
pp. E1-E11
Author(s):  
Rimary Valera Sifontes ◽  
Hédison Kiuity Sato
Keyword(s):  
Frequency Domain ◽  
Magnetic Dipole ◽  
Signal To Noise Ratio ◽  
Physical Parameters ◽  
Correction Procedure ◽  
Dipole Axis ◽  
Electromagnetic Data ◽  
Limited Effectiveness ◽  
Land Survey ◽  
Coil Size

During a frequency-domain electromagnetic (FDEM) land survey using transmitter-receiver distances of kilometer order, the receiver and transmitter may be at different altitudes. To increase the signal-to-noise ratio, the transmitting coil size must be increased to the order of a hundred meters and its geometry will be determined by the terrain roughness. Therefore, the equivalent magnetic dipole axis may be neither vertical nor normal to the mean plane representing the terrain surface. Considering the perpendicular loop-loop arrangement, these factors modify the expected secondary magnetic field in two ways: (1) A horizontal primary field arises at the receiving coil position as well as (2) the secondary fields induced by the abnormal currents in the subsurface caused by the tilting of the transmitter dipole axis. A correction procedure is proposed to remove these effects on field FDEM data and tested by using simulated FDEM data with two- or three-layered tilted models to represent the earth with a dipping surface and a nonvertically oriented transmitter magnetic dipole representing a large coil laid on rough terrain. The results demonstrate that the proposed correction procedure has a limited effectiveness, but it can be applied to the FDEM data collected on terrain surfaces having small dipping angles. It is observed that maximum values of the transmitter dipole or surficial plane tilt angle should be 2° to ensure error values in the apparent conductivity less than 10%. Even for the said value, in some combinations of geometric and physical parameters, the tilting and dipping angles can be increased to the order of 5°.

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