Articles de revues sur le sujet « Cell-Scattering correction »
Pour voir les autres types de publications sur ce sujet consultez le lien suivant : Cell-Scattering correction.
Créez une référence correcte selon les styles APA, MLA, Chicago, Harvard et plusieurs autres
Consultez les 39 meilleurs articles de revues pour votre recherche sur le sujet « Cell-Scattering correction ».
À côté de chaque source dans la liste de références il y a un bouton « Ajouter à la bibliographie ». Cliquez sur ce bouton, et nous générerons automatiquement la référence bibliographique pour la source choisie selon votre style de citation préféré : APA, MLA, Harvard, Vancouver, Chicago, etc.
Vous pouvez aussi télécharger le texte intégral de la publication scolaire au format pdf et consulter son résumé en ligne lorsque ces informations sont inclues dans les métadonnées.
Parcourez les articles de revues sur diverses disciplines et organisez correctement votre bibliographie.
1
Gray, E. MacA, R. I. Smith et M. P. Pitt. « Time-of-flight neutron powder diffraction with a thick-walled sample cell ». Journal of Applied Crystallography 40, no 3 (15 mai 2007) : 399–408. http://dx.doi.org/10.1107/s0021889807006668.
Texte intégralRésumé :
The time-of-flight diffraction techniques that are normally practiced at pulsed neutron sources afford opportunities that are not readily available at continuous fixed-wavelength sources. The present work concerns the increasing trend in materials science to study samples in complex non-ambient environments, such as high gas pressure. Taking the example of a sample cell in which a material is studied under fluid pressure, the optimization of the cell design for best data collection rate is considered. The design of primary- and scattered-beam masks for eliminating background scattering from the sample cell and the correction of the data for cell and sample attenuation are addressed. The outputs of this work include a simple expression for the optimum wall thickness of a thick-walled sample cell, a procedure for accurately determining the required mask aperture width for any scattering angle, more compact expressions for some of the results of the work of Paalman & Pings [J. Appl. Phys.(1962),33, 2635–2639] on absorption corrections, and guidance as to the correction of diffraction profiles for cell and background effects. Examples are given, drawn from studies of materials under hydrogen gas pressures up to 1800 bar in cells constructed from Ti2.1Zr and Inconel.
2
Nettesheim, Florian, Ulf Olsson, Peter Lindner et Walter Richtering. « Correction method for the asymmetry of the tangential beam in Couette (or Searle) geometry used in rheo-small-angle neutron scattering ». Journal of Applied Crystallography 37, no 3 (11 mai 2004) : 438–44. http://dx.doi.org/10.1107/s0021889804006910.
Texte intégralRésumé :
A method of correcting the asymmetry in the scattering of the tangential beam configuration in a rheo-small-angle neutron scattering experiment is proposed. The asymmetry of the scattering in the tangential beam configuration can be attributed to the difference in pathlength for neutrons that are scattered toward compared with those which are scattered away from the axis of rotation of the shear cell. The pathlength problem is solved and a final expression for the two-dimensional scattering intensity is given. The results from these calculations are compared with experimental data, which offer a different option to correct this asymmetry, namely by just measuring the scattering of H2O/D2O mixtures with absolute scattering cross sections identical to those of the respective samples. However, the situation for anisotropic media is more complex and the correction procedure described here is less effective.
3
Kohler, A., J. Sulé-Suso, G. D. Sockalingum, M. Tobin, F. Bahrami, Y. Yang, J. Pijanka et al. « Estimating and Correcting Mie Scattering in Synchrotron-Based Microscopic Fourier Transform Infrared Spectra by Extended Multiplicative Signal Correction ». Applied Spectroscopy 62, no 3 (mars 2008) : 259–66. http://dx.doi.org/10.1366/000370208783759669.
Texte intégralRésumé :
We present an approach for estimating and correcting Mie scattering occurring in infrared spectra of single cells, at diffraction limited probe size, as in synchrotron based microscopy. The Mie scattering is modeled by extended multiplicative signal correction (EMSC) and subtracted from the vibrational absorption. Because the Mie scattering depends non-linearly on α, the product of the radius and the refractive index of the medium/sphere causing it, a new method was developed for estimating the Mie scattering by EMSC for unknown radius and refractive index of the Mie scatterer. The theoretically expected Mie contributions for a range of different α values were computed according to the formulae developed by Van de Hulst (1957). The many simulated spectra were then summarized by a six-dimensional subspace model by principal component analysis (PCA). This subspace model was used in EMSC to estimate and correct for Mie scattering, as well as other additive and multiplicative interference effects. The approach was applied to a set of Fourier transform infrared (FT-IR) absorbance spectra measured for individual lung cancer cells in order to remove unwanted interferences and to estimate ranges of important α values for each spectrum. The results indicate that several cell components may contribute to the Mie scattering.
4
Kato, Minoru, et Tetsuro Fujisawa. « High-Pressure Solution X-ray Scattering of Protein Using a Hydrostatic Cell with Diamond Windows ». Journal of Synchrotron Radiation 5, no 5 (1 septembre 1998) : 1282–86. http://dx.doi.org/10.1107/s0909049598000788.
Texte intégralRésumé :
A hydrostatic high-pressure cell (maximum pressure 700 MPa) with synthetic diamond windows is applied to measure small-angle X-ray scattering of a protein at high pressure. Use of the present cell allows an accurate solvent background correction, providing quantitative analyses. The performance of the present cell for X-ray scattering is shown by using lysozyme as a sample solution. From the Guinier plot, values of the radius of gyration of lysozyme are evaluated to be 15.31 ± 0.09 Å at 1 atm (0.10 MPa) and 14.80 ± 0.15 Å at 400 MPa.
5
Kang, Joon Ho, Teemu P. Miettinen, Lynna Chen, Selim Olcum, Georgios Katsikis, Patrick S. Doyle et Scott R. Manalis. « Publisher Correction : Noninvasive monitoring of single-cell mechanics by acoustic scattering ». Nature Methods 16, no 3 (19 février 2019) : 270. http://dx.doi.org/10.1038/s41592-019-0354-6.
Texte intégral
6
Roth, M. « On absolute scaling in protein crystallography using sums of low-resolution intensities and Wilson statistics at low resolution ». Acta Crystallographica Section A Foundations of Crystallography 42, no 4 (1 juillet 1986) : 230–40. http://dx.doi.org/10.1107/s0108767386099373.
Texte intégralRésumé :
A method of absolute scaling of diffraction data is proposed, based on the calculation of the sum of the intensity diffracted at low resolution (Bragg d spacing > 15 Å). This sum is proportional to the mean-square deviation of the scattering-length density in the unit cell, and this property is used to determine the scale factor. The method is applied to the case of neutron diffraction using contrast variation experiments with biological molecules, and it is used to check the validity of some assumptions concerning the system under study, such as the global rate of H/D exchange or the uniformity of scattering-length density in the molecules. The use of this method requires an asymptotic correction of the sum of intensity. This correction is based on Porod's law, whose application to diffraction experiments is discussed, in particular for contrast variation experiments. An analysis of the spherical average of the diffracted intensity as a function of the scattering vector, compared to isotropic solution scattering, allows the conditions of applicability of Wilson statistics to be specified at low and medium resolution, i.e. the random statistical model underlying the Wilson statistics in this scattering range to be defined.
7
Hariri, Sara, Sahar Barzegari B., Kamyar Keshavarz F., Nastaran Nikounezhad, Behnoosh Safaei, Golrokh Farnam et Farshad H. Shirazi. « FTIR bio-spectroscopy scattering correction using natural biological characteristics of different cell lines ». Analyst 144, no 19 (2019) : 5810–28. http://dx.doi.org/10.1039/c9an00811j.
Texte intégralRésumé :
The Mie type scattering makes the FTIR spectra of biological samples unreliable. Here, natural biological characteristics have been used instead of mathematical estimations to solve the scattering problem, which resulted the best corrected spectra of cells.
8
Hoogerheide, David P., Frank Heinrich, Brian B. Maranville et Charles F. Majkrzak. « Accurate background correction in neutron reflectometry studies of soft condensed matter films in contact with fluid reservoirs ». Journal of Applied Crystallography 53, no 1 (1 février 2020) : 15–26. http://dx.doi.org/10.1107/s160057671901481x.
Texte intégralRésumé :
Neutron reflectometry (NR) is a powerful method for looking at the structures of multilayered thin films, including biomolecules on surfaces, particularly proteins at lipid interfaces. The spatial resolution of the film structure obtained through an NR experiment is limited by the maximum wavevector transfer at which the reflectivity can be measured. This maximum is in turn determined primarily by the scattering background, e.g. from incoherent scattering from a liquid reservoir or inelastic scattering from cell materials. Thus, reduction of scattering background is an important part of improving the spatial resolution attainable in NR measurements. Here, the background field generated by scattering from a thin liquid reservoir on a monochromatic reflectometer is measured and calculated. It is shown that background subtraction utilizing the entire background field improves data modeling and reduces experimental uncertainties associated with localized background subtraction.
9
Wheater, R. M., M. D. Hart, M. C. Veale, M. D. Wilson, D. Doblas-Jiménez, M. Turcato, C. Milne, H. Yousef et D. Khakhulin. « Development of data correction for the 1M Large Pixel Detector at the EuXFEL ». Journal of Instrumentation 17, no 04 (1 avril 2022) : P04013. http://dx.doi.org/10.1088/1748-0221/17/04/p04013.
Texte intégralRésumé :
Abstract We present the development of a gain correction process for the Large Pixel Detector (LPD) developed by the Science and Technology Facilities Council (STFC) for the Femtosecond X-Ray Experiment (FXE) instrument based at the European X-ray Free Electron Laser (EuXFEL). LPD operates at 4.5 MHz as necessitated by EuXFEL's pulse timing structure and has a large dynamic range capturing a maximum of 105 photons/pixel @ 12 keV. Experiments at FXE require highly accurate measurements of relative changes in X-ray scattering intensity on the MHz timescale making a correction bringing LPD pixel outputs in line against a common axis essential to understanding experimental results. To facilitate the operational needs of LPD at FXE more than 1.5 billion correction coefficients are required, with corrections generated on a per pixel, per memory cell and per gain stage basis. By comparing output LPD signals to an independent reference diode a linear gain correction has been developed and applied to LPD data. Improvements in image quality have been quantified using the standard deviation in the measured intensity per pixel for a given radius from the beam centre. Improvements to detector uniformity of up to 30.0% are demonstrated in the medium gain stage and 15.9% in the high gain stage. This paper presents an in-depth view of the gain correction development process and further results.
10
Cacocciola, Riccardo, Badreddine Ratni, Nicolas Mielec, Emmanuel Mimoun et Shah Nawaz Burokur. « Metasurfaces for Far-Field Radiation Pattern Correction of Antennas under Dielectric Seamed-Radomes ». Materials 15, no 2 (16 janvier 2022) : 665. http://dx.doi.org/10.3390/ma15020665.
Texte intégralRésumé :
A high-index dielectric radome seam is camouflaged with respect to a low-index dielectric radome panel by tuning the seam with carefully engineered metasurfaces. A transmission-line approach is used to model the metasurface-tuned seam and analytically retrieve the corresponding surface impedance, from which the unit-cell design is then tailored. Full-wave simulations and microwave antenna measurements performed on a proof-of-concept prototype validate the undesired scattering suppression effect in the case of normally and obliquely incident transverse electric and transverse magnetic wave illuminations. Robustness of the proposed solution to fabrication tolerances is also reported. The study presents metasurface-tuning as an easily implementable, frequency adjustable, and polarization insensitive solution to reduce the scattering of dielectric mechanical seams and improve the overall transparency performance of radome structures.
11
INOMATA, K., K. ISHII, H. YAMAZAKI, S. MATSUYAMA, Y. KIKUCHI, Y. WATANABE, A. ISHIZAKI et al. « DEVELOPMENT OF AN IN-AIR ON/OFF AXIS STIM SYSTEM FOR QUANTITATIVE ELEMENTAL MAPPING ». International Journal of PIXE 16, no 03n04 (janvier 2006) : 149–56. http://dx.doi.org/10.1142/s0129083506000939.
Texte intégralRésumé :
We have developed an in-air on/off axis STIM for simultaneous density mapping with PIXE and RBS, which will be useful for damage-monitoring in cell analysis and for yield correction based on the thickness distribution of X-ray self-absorption in samples. The in-air on/off axis STIM system provides a mass concentration map in the cell analysis. In the system, a thin scattering foil is placed downstream of the sample and scattered protons are detected by a Si -PIN photodiode set at 30 degrees with respect to the beam axis. These components are set in a He -gas-filled chamber to reduce energy loss, scattering and sample damage. Using this system, areal density mapping is carried out for RBL-2H3 cells simultaneously with PIXE and RBS. Correction for self-absorption is performed and areal density map of elements is converted into a mass-concentration map using the measured matrix density. The areal density distribution of P corresponds to that of matrix and mass concentration of P is uniform in the cell region. On the other hand, Br is concentrated in the nucleus, even in the mass concentration map. The Br accumulation in the nucleus is first confirmed in mass concentration using the on/off axis STIM and PIXE system. The in-air on/off STIM system will be effective for monitoring changes in cell density during beam irradiation.
12
Chen, Tao, Guanghu Jin et Zhen Dong. « JOINT PROCESSING OF ENVELOPE ALIGNMENT AND PHASE COMPENSATION FOR ISAR IMAGING ». ISPRS Annals of Photogrammetry, Remote Sensing and Spatial Information Sciences IV-3 (23 avril 2018) : 61–64. http://dx.doi.org/10.5194/isprs-annals-iv-3-61-2018.
Texte intégralRésumé :
Range envelope alignment and phase compensation are spilt into two isolated parts in the classical methods of translational motion compensation in Inverse Synthetic Aperture Radar (ISAR) imaging. In classic method of the rotating object imaging, the two reference points of the envelope alignment and the Phase Difference (PD) estimation are probably not the same point, making it difficult to uncouple the coupling term by conducting the correction of Migration Through Resolution Cell (MTRC). In this paper, an improved approach of joint processing which chooses certain scattering point as the sole reference point is proposed to perform with utilizing the Prominent Point Processing (PPP) method. With this end in view, we firstly get the initial image using classical methods from which a certain scattering point can be chose. The envelope alignment and phase compensation using the selected scattering point as the same reference point are subsequently conducted. The keystone transform is thus smoothly applied to further improve imaging quality. Both simulation experiments and real data processing are provided to demonstrate the performance of the proposed method compared with classical method.
13
Liu, Yunhong, et Nicolaos G. Alexopoulos. « Correction to “Semianalytical formulation on the scattering of proximity equilibration cell closed ring photonic band gap structures” ». Radio Science 43, no 2 (avril 2008) : n/a. http://dx.doi.org/10.1029/2008rs003833.
Texte intégral
14
Piasecka, Agata, Jolanta Cieśla, Magdalena Koczańska et Izabela Krzemińska. « Correction to : Effectiveness of Parachlorella kessleri cell disruption evaluated with the use of laser light scattering methods ». Journal of Applied Phycology 31, no 1 (30 octobre 2018) : 109. http://dx.doi.org/10.1007/s10811-018-1658-0.
Texte intégral
15
Ståhl, Kenny, Christian G. Frankær, Jakob Petersen et Pernille Harris. « Monitoring protein precipitates by in-house X-ray powder diffraction ». Powder Diffraction 28, S2 (septembre 2013) : S458—S469. http://dx.doi.org/10.1017/s0885715613000833.
Texte intégralRésumé :
Powder diffraction from protein powders using in-house diffractometers is an effective tool for identification and monitoring of protein crystal forms and artifacts. As an alternative to conventional powder diffractometers a single crystal diffractometer equipped with an X-ray micro-source can be used to collect powder patterns from 1 µl samples. Using a small-angle X-ray scattering (SAXS) camera it is possible to collect data within minutes. A streamlined program has been developed for the calculation of powder patterns from pdb-coordinates, and includes correction for bulk-solvent. A number of such calculated powder patterns from insulin and lysozyme have been included in the powder diffraction database and successfully used for search-match identification. However, the fit could be much improved if peak asymmetry and multiple bulk-solvent corrections were included. When including a large number of protein data sets in the database some problems can be foreseen due to the large number of overlapping peaks in the low-angle region, and small differences in unit cell parameters between pdb-data and powder data. It is suggested that protein entries are supplied with more searchable keywords as protein name, protein type, molecular weight, source organism etc. in order to limit possible hits.
16
Pertsov, O. V., et V. P. Berest. « Analysis of kinetics of light scattering by cell suspection during aggregation : mathematical modeling of platelet disaggregation ». 34, no 34 (30 juin 2021) : 70–77. http://dx.doi.org/10.26565/2311-0872-2021-34-08.
Texte intégralRésumé :
Background. Molecular mechanisms of platelet aggregation are actively studied by methods of molecular cell biology, biochemistry, applied physics, but the problem of modeling the dynamics of this process remains open. Mathematical modeling allows to establish quantitative indicators of aggregation kinetics, to analyze the results of scientific research and testing of blood samples in everyday medical practice. Known mathematical models of spontaneous reversible and irreversible platelet aggregation in a shear flow of different intensity are not suitable for analysis of data obtained by the most common laboratory method - light transmission aggregometry. Objectives. The aim of the work was to create a mathematical model of platelet aggregation that can adequately describe the reversible cell aggregation, in particular the disaggregation of platelets in suspension. Materials and methods. A mathematical model of induced platelet aggregation has been developed. The kinetic constants of the model were optimized by experimentally determined average platelet counts in the aggregate measured by light scattering. Kinetic curves of light scattering of platelet suspension during aggregation induced by physiological agonist ADP were obtained using a laser analyzer of platelet aggregation ALAT-2 "Biola". Results. The proposed mathematical model is suitable for modeling reverse aggregation of platelets due to taking into account the inactivation of cells using the time dependence and correction of the disaggregation term. Conclusions. The developed mathematical model complements the models of the dynamics of irreversible platelet aggregation and allows to analyze reversible aggregation. The model satisfactorily describes the experimental time dependences of the size of platelet aggregates obtained by light transmission aggregometry. The introduced additional parameter and the method of setting the term corresponding to inactivation have a much smaller effect on the dependences than the kinetic constants. Calculated by model and optimized according to experimental data at different temperatures rate constants allow to calculate the activation energies of the aggregation process. When using light transmission aggregometry data to optimize the model parameters, it is advised to pre-smooth the input data to remove noise caused by the inhomogeneity of the suspension.
17
Ge, Nan, Stéphane Chevalier, James Hinebaugh, Ronnie Yip, Jongmin Lee, Patrick Antonacci, Toshikazu Kotaka, Yuichiro Tabuchi et Aimy Bazylak. « Calibrating the X-ray attenuation of liquid water and correcting sample movement artefacts duringin operandosynchrotron X-ray radiographic imaging of polymer electrolyte membrane fuel cells ». Journal of Synchrotron Radiation 23, no 2 (10 février 2016) : 590–99. http://dx.doi.org/10.1107/s1600577515023899.
Texte intégralRésumé :
Synchrotron X-ray radiography, due to its high temporal and spatial resolutions, provides a valuable means for understanding thein operandowater transport behaviour in polymer electrolyte membrane fuel cells. The purpose of this study is to address the specific artefact of imaging sample movement, which poses a significant challenge to synchrotron-based imaging for fuel cell diagnostics. Specifically, the impact of the micrometer-scale movement of the sample was determined, and a correction methodology was developed. At a photon energy level of 20 keV, a maximum movement of 7.5 µm resulted in a false water thickness of 0.93 cm (9% higher than the maximum amount of water that the experimental apparatus could physically contain). This artefact was corrected by image translations based on the relationship between the false water thickness value and the distance moved by the sample. The implementation of this correction method led to a significant reduction in false water thickness (to ∼0.04 cm). Furthermore, to account for inaccuracies in pixel intensities due to the scattering effect and higher harmonics, a calibration technique was introduced for the liquid water X-ray attenuation coefficient, which was found to be 0.657 ± 0.023 cm−1at 20 keV. The work presented in this paper provides valuable tools for artefact compensation and accuracy improvements for dynamic synchrotron X-ray imaging of fuel cells.
18
Ross, Frances M. « (Keynote) Developments in Visualizing Electrochemistry in Action with Liquid Cell Electron Microscopy ». ECS Meeting Abstracts MA2022-01, no 23 (7 juillet 2022) : 1138. http://dx.doi.org/10.1149/ma2022-01231138mtgabs.
Texte intégralRésumé :
In situ transmission electron microscopy (TEM) can provide unparalleled structural and compositional information with high spatial and temporal resolution and is a standard tool for understanding and quantifying electrochemical nucleation and growth processes. Both solid state reactions and processes involving liquids can be examined. However, liquid phase reactions require particular care since the liquid needs to be confined in a thin layer and protected from the vacuum in the microscope. This problem is solved in the technique of electrochemical liquid cell TEM by confining the liquid between microfabricated electron transparent membranes on which the electrodes are patterned. Electrochemical liquid cell TEM has enabled quantification of nucleation and growth phenomena, dendrite formation, additive effects on morphology and SEI formation. Recent experimental developments have broadened the application space, but many more opportunities remain to be explored. Here we discuss how the existing strategies for electrochemical liquid cell TEM experiments can be adapted to allow quantitative data acquisition under an expanded range of electrochemical conditions. We first discuss the control of temperature, an important parameter in electrochemical systems such as batteries and fuel cells. Increasing the temperature while simultaneously applying a bias is achieved by customizing liquid cell chips to incorporate an electrically isolated heater strip beneath the electrodes. We find, as expected, that elevated temperature increases the rates of deposition and etching reactions and we discuss potential applications in electrocatalysis and codeposition. We then address the limitations of image resolution in liquid cell experiments. For nucleation and growth processes that take place on the surface of the electrode, the electrode materials such as Au or Pt often used in microfabricated liquid cells contribute strongly to electron scattering and thereby reduce the signal to noise ratio in the images. We show how few-layer graphene can be added to liquid cell chips to produce electrodes with minimal scattering, resulting in nucleation and growth movies with improved discrimination between nucleus shapes. We next consider the exciting consequences of instrumental improvements in microscopy - aberration correction, energy filtering and efficient electron detectors - in improving the resolution and lowering the dose required for imaging. Electron beam effects are unavoidable, however, and we discuss how the chemical changes caused by the beam can be modeled and perhaps mitigated for different electrolyte compositions and as a function of temperature. More speculative developments in liquid cell technique may allow us to measure stress, electrolyte composition and even the electrochemical double layer. Although a lot of work remains to be done, I hope to convince you that electrochemical TEM of liquids can address grand challenge questions in nucleation and growth through its unique view of electrochemical processes.
19
Orlova, Elena D., Aleksandra A. Savina, Sergey A. Abakumov, Anatolii V. Morozov et Artem M. Abakumov. « Comprehensive Study of Li+/Ni2+ Disorder in Ni-Rich NMCs Cathodes for Li-Ion Batteries ». Symmetry 13, no 9 (3 septembre 2021) : 1628. http://dx.doi.org/10.3390/sym13091628.
Texte intégralRésumé :
The layered oxides LiNixMnyCozO2 (NMCs, x + y + z = 1) with high nickel content (x ≥ 0.6, Ni-rich NMCs) are promising high-energy density-positive electrode materials for Li-ion batteries. Their electrochemical properties depend on Li+/Ni2+ cation disordering originating from the proximity of the Li+ and Ni2+ ionic radii. We synthesized a series of the LiNi0.8Mn0.1Co0.1O2 NMC811 adopting two different disordering schemes: Ni for Li substitution at the Li site in the samples finally annealed in air, and close to Ni↔Li antisite disorder in the oxygen-annealed samples. The defect formation scenario was revealed with Rietveld refinement from powder X-ray diffraction data, and then the reliability of semi-quantitative parameters, such as I003/I104 integral intensity ratio and c/(2√6a) ratio of pseudocubic subcell parameters, was verified against the refined defect concentrations. The I003/I104 ratio can serve as a quantitative measure of g(NiLi) only after explicit correction of intensities for preferred orientation. Being normalized by the total scattering power of the unit cell, the I003/I104 ratio depends linearly on g(NiLi) for each disordering scheme. The c/(2√6a) ratio appears to be not reliable and cannot be used for a quantitative estimate of g(NiLi). In turn, the volume of the R3¯m unit cell correlates linearly with g(NiLi), at least for defect concentrations not exceeding 5%. The microscopy techniques such as high-resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and electron diffraction tomography (EDT) allow us to study the materials locally, still, there is no proper quantitative approach for comprehensive analysis of defects. In the present work, the TEM-assisted quantitative Li+/Ni2+ disordering analysis with EDT and HAADF-STEM in six Ni-rich NMC samples with various defects content is demonstrated. Noteworthy, while PXRD and EDT methods demonstrate overall defect amounts, HAADF-STEM allows us to quantitatively distinguish regions with various disordering extents. Therefore, the combination of mentioned PXRD and TEM methods gives the full picture of Li+/Ni2+ mixing defects in Ni-rich NMCs.
20
Liu, Rui, Lena Zheng, Denis M. Dwyre, Fabrizia Urbinati, Donald B. Kohn, Dennis Matthews, James Chan et Noriko Satake. « Laser Tweezers Raman Spectroscopy As a Novel Red Blood Cell Functional Assay for Sickle Cell Disease ». Blood 118, no 21 (18 novembre 2011) : 4847. http://dx.doi.org/10.1182/blood.v118.21.4847.4847.
Texte intégralRésumé :
Abstract Abstract 4847 The number of individuals with sickle cell disease (SCD) in the U.S. is estimated to be over 70,000, and the average life span of a SCD patient is 39 years. Despite the high incidence of SCD in the U.S. and its significant negative effects on patient health, there are currently only limited treatment options for this disease. Also, although a single mutation in the globin gene is known to cause SCD, there is significant clinical diversity. As technology advances, many studies, including genome-wide analyses and proteomics, have been conducted to understand the disease mechanism and find better treatments. However, none has yet led to the development of novel therapies. We need a practical approach to study red blood cells (RBCs) to increase our knowledge of this heterogeneous disease. Laser tweezers Raman spectroscopy (LTRS) is a label-free, laser-based method for the biochemical analysis of single living cells. Based on the phenomenon of inelastic light scattering of photons by molecular bonds, Raman spectroscopy can provide detailed information, in the form of a Raman spectrum, about the molecular structure and conformations inside single living cells. Moreover, the integration of laser tweezers enables 1) simple, convenient analysis of single suspension cells such as RBCs and 2) a method to impart a mechanical force on a cell (via the optical forces) and simultaneously monitor the biochemical response of that cell to the applied force. Previous studies using optical tweezers have shown different RBC elasticity between samples from SCD patients treated with hydroxyurea and those that were not treated with hydroxyurea. Raman spectroscopy has been applied to both normal and pathological RBCs in previous studies, but the results were limited to the identification of characteristic signatures. Our integration of the two methods, Raman spectroscopy and laser tweezers, is a new biophotonic approach for studying the intricate relationship between the biochemical and mechanical properties of a single cell that was not previously possible and is not easily carried out with existing methods. As such, we believe that this recent emerging single cell-based technology can be developed and used as an RBC functional assay. We have previously shown that LTRS can detect a force dependent oxygenation state transition in individual RBCs trapped at different laser powers, presumably due to the optical forces stretching the cell and inducing changes in the hemoglobin-hemoglobin and hemoglobin-membrane interactions that change the oxygen content of the cell. We have also shown characteristic Raman signatures indicating different oxygen content in different RBC samples at specific applied forces. Signatures were different among RBCs from cord, normal adult, and SCD patient blood, suggesting laser tweezers Raman spectroscopy can be used to measure the different force dependent oxygen content in a single RBC. We are currently validating our system to determine whether Raman spectroscopy can be used to identify and distinguish gene-corrected RBCs from normal and sickle RBCs. Our preliminary results showed distinct Raman fingerprints associated with the membrane structure of RBCs. Spectral fingerprints were observed to be different between normal and sickle RBCs, and gene-corrected RBCs were observed to have Raman profiles similar to those of normal RBCs. We speculate that the signature overlap between normal and gene-corrected samples is due to partial gene correction. These results are encouraging and strongly suggest that Raman spectroscopy can not only identify molecular structures but also be used as a functional assay. Disclosures: No relevant conflicts of interest to declare.
21
Wiberg, Gustav K. H., Rebecca K. Pittkowski, Stefanie Punke, Olivia Aalling-Frederiksen, Kirsten M. Ø. Jensen et Matthias Arenz. « Design and Application of a Gas Diffusion Electrode (GDE) Cell for Operando and In Situ Studies ». CHIMIA 78, no 5 (29 mai 2024) : 344–48. http://dx.doi.org/10.2533/chimia.2024.344.
Texte intégralRésumé :
Presented here is an electrochemical three-electrode Gas Diffusion Electrode (GDE) cell tailored for operandoand in situ investigations of electrocatalytic processes, with a particular focus on X-ray scattering studies. The optimized cell is engineered to accommodate the minimal sample-detector distances requisite for comprehensive X-ray total scattering investigations. An in-depth understanding of catalytic processes requires their study under ‘working’ conditions. Configured as a flow-cell, the setup therefore enables the examination of electrocatalysts under high current densities and associated gas evolution phenomena, particularly pertinent for reactions like the oxygen evolution reaction (OER). Notably, its transparency simplifies cell alignment, troubleshooting, and facilitates scans through the catalyst layer, crucial for background corrections. Demonstrating its versatility, we showcase its utility through Small Angle X-ray Scattering (SAXS), X-ray Diffraction (XRD), and X-ray Pair Distribution Function (PDF) analyses of total scattering data.
22
Konevskikh, Tatiana, Rozalia Lukacs, Reinhold Blümel, Arkadi Ponossov et Achim Kohler. « Mie scatter corrections in single cell infrared microspectroscopy ». Faraday Discussions 187 (2016) : 235–57. http://dx.doi.org/10.1039/c5fd00171d.
Texte intégralRésumé :
Strong Mie scattering signatures hamper the chemical interpretation and multivariate analysis of the infrared microscopy spectra of single cells and tissues. During recent years, several numerical Mie scatter correction algorithms for the infrared spectroscopy of single cells have been published. In the paper at hand, we critically reviewed existing algorithms for the correction of Mie scattering and suggest improvements. We developed an iterative algorithm based on Extended Multiplicative Scatter Correction (EMSC), for the retrieval of pure absorbance spectra from highly distorted infrared spectra of single cells. The new algorithm uses the van de Hulst approximation formula for the extinction efficiency employing a complex refractive index. The iterative algorithm involves the establishment of an EMSC meta-model. While existing iterative algorithms for the correction of resonant Mie scattering employ three independent parameters for establishing a meta-model, we could decrease the number of parameters from three to two independent parameters, which reduced the calculation time for the Mie scattering curves for the iterative EMSC meta-model by a factor of 10. Moreover, by employing the Hilbert transform for evaluating the Kramers–Kronig relations based on a FFT algorithm in Matlab, we further improved the speed of the algorithm by a factor of 100. For testing the algorithm we simulate distorted apparent absorbance spectra by utilizing the exact theory for the scattering of infrared light at absorbing spheres, taking into account the high numerical aperture of infrared microscopes employed for the analysis of single cells and tissues. In addition, the algorithm was applied to measured absorbance spectra of single lung cancer cells.
23
Rossouw, C. J., L. J. Allen et P. R. Miller. « LACBED with Quantitative Anomalous Absorption Corrections ». Proceedings, annual meeting, Electron Microscopy Society of America 48, no 2 (12 août 1990) : 528–29. http://dx.doi.org/10.1017/s0424820100136246.
Texte intégralRésumé :
An Einstein model for thermal diffuse scattering (TDS) has enabled quantitative calculation of the absorptive potential V'(r). This allows anomalous absorption to be accounted for in LACBED contrast. Fourier coefficients Vg-h of the absorptive component from each atom α are calculated from integrals of the formwhere fα is the scattering amplitude and M(Q) the Debye-Waller factor. Integration over the Ewald sphere (dΩ) requires the momentum transfer q to have values up to 2ko (the incident beam momentum). Dynamical ‘dechannelling’ is accounted for by the terms g ≠ h. The crystal absorptive potential is obtained by coherently summing over these atomic absorptive potentials within the unit cell. Unlike the elastic potential, the absorptive potential is a strong function of incident beam energy Eo, since the range of momentum transfer q and associated solid angles dΩ change with the Ewald sphere radius.Fig. 1 shows a LACBED pattern of the zeroth order beam from Si aligned along a <001> zone axis.
24
French, Stephanie A., Paul R. Territo et Robert S. Balaban. « Correction for inner filter effects in turbid samples : fluorescence assays of mitochondrial NADH ». American Journal of Physiology-Cell Physiology 275, no 3 (1 septembre 1998) : C900—C909. http://dx.doi.org/10.1152/ajpcell.1998.275.3.c900.
Texte intégralRésumé :
Fluorescent determinations of NADH in porcine heart mitochondria were subject to significant errors caused by alterations in inner filter effects during numerous metabolic perturbations. These inner filter effects were primarily associated with changes in mitochondrial volume and accompanying light scattering. The observed effects were detected in a standard commercial fluorometer with emission orthogonal to the excitation light path and, to a lesser extent, in a light path geometry detecting only the surface fluorescence. A method was developed to detect and correct for inner filter effects on mitochondrial NADH fluorescence measurements that were independent of the optical path geometry using an internal fluorescent standard and linear least-squares spectral analysis. A simple linear correction with the inner fluorescence reference was found to adequately correct for inner filter effects. This approach may be useful for other fluorescence probes in isolated mitochondria or other light-scattering media.
25
Cervellino, Antonio, Ruggero Frison, Giuseppe Cernuto, Antonietta Guagliardi et Norberto Masciocchi. « Lattice parameters and site occupancy factors of magnetite–maghemite core–shell nanoparticles. A critical study ». Journal of Applied Crystallography 47, no 5 (30 septembre 2014) : 1755–61. http://dx.doi.org/10.1107/s1600576714019840.
Texte intégralRésumé :
The size-driven expansion and oxidation-driven contraction phenomena of nonstoichiometric magnetite–maghemite core–shell nanoparticles have been investigated by the total scattering Debye function approach. Results from a large set of samples are discussed in terms of significant effects on the sample average lattice parameter and on the possibility of deriving the sample average oxidation level from accurate, diffraction-based, cell values. Controlling subtle experimental effects affecting the measurement of diffraction angles and correcting for extra-sample scattering contributions to the pattern intensity are crucial issues for accurately estimating lattice parameters and cation vacancies. The average nanoparticle stoichiometry appears to be controlled mainly by iron depletion of octahedral sites. A simple law with a single adjustable parameter, well correlating lattice parameter, stoichiometry and size effects of all the nanoparticles present in the whole set of samples used in this study, is proposed.
26
Remer, Itay, Roni Shaashoua, Netta Shemesh, Anat Ben-Zvi et Alberto Bilenca. « Publisher Correction : High-sensitivity and high-specificity biomechanical imaging by stimulated Brillouin scattering microscopy ». Nature Methods 17, no 10 (20 août 2020) : 1060. http://dx.doi.org/10.1038/s41592-020-0956-z.
Texte intégral
27
Streich, Lina, Juan Carlos Boffi, Ling Wang, Khaleel Alhalaseh, Matteo Barbieri, Ronja Rehm, Senthilkumar Deivasigamani, Cornelius T. Gross, Amit Agarwal et Robert Prevedel. « High-resolution structural and functional deep brain imaging using adaptive optics three-photon microscopy ». Nature Methods 18, no 10 (30 septembre 2021) : 1253–58. http://dx.doi.org/10.1038/s41592-021-01257-6.
Texte intégralRésumé :
AbstractMultiphoton microscopy has become a powerful tool with which to visualize the morphology and function of neural cells and circuits in the intact mammalian brain. However, tissue scattering, optical aberrations and motion artifacts degrade the imaging performance at depth. Here we describe a minimally invasive intravital imaging methodology based on three-photon excitation, indirect adaptive optics (AO) and active electrocardiogram gating to advance deep-tissue imaging. Our modal-based, sensorless AO approach is robust to low signal-to-noise ratios as commonly encountered in deep scattering tissues such as the mouse brain, and permits AO correction over large axial fields of view. We demonstrate near-diffraction-limited imaging of deep cortical spines and (sub)cortical dendrites up to a depth of 1.4 mm (the edge of the mouse CA1 hippocampus). In addition, we show applications to deep-layer calcium imaging of astrocytes, including fibrous astrocytes that reside in the highly scattering corpus callosum.
28
Ungar, P. Jeffrey, Kari Laasonen et Michael L. Klein. « Ab initio simulation of the structure and dynamics of white phosphorus (P4) at low temperatures ». Canadian Journal of Physics 73, no 11-12 (1 novembre 1995) : 710–17. http://dx.doi.org/10.1139/p95-105.
Texte intégralRésumé :
Ab initio simulations of low-temperature white phosphorus (β-P4) were performed using Car–Parrinello density-functional-theory molecular dynamics and a plane-wave basis set. Gradient corrections to the local density approximation were used to obtain a better description of the weak intermolecular forces. Starting with unit-cell parameters and atomic coordinates recently verified using neutron scattering, molecular dynamics trajectories over 9–10 ps were obtained for temperatures of 50 and 145 K. The computations show that the distortions from ideal tetrahedral P4 molecules found in the reduction of the neutron data may be a finite-temperature effect and not an artifact of the data analysis. Examination of the molecular reorientational dynamics shows that orientational order persists throughout the simulations, which suggests that β-P4 is an orientational crystal.
29
Suchaneck, Gunnar, et Evgenii Artiukh. « Absence of Weak Localization Effects in Strontium Ferromolybdate ». Applied Sciences 13, no 12 (13 juin 2023) : 7096. http://dx.doi.org/10.3390/app13127096.
Texte intégralRésumé :
Sr2FeMoO6-δ (SFMO) double perovskite is a promising candidate for room-temperature spintronic applications, since it possesses a half-metallic character (with theoretically 100% spin polarization), a high Curie temperature of about 415 K and a low-field magnetoresistance (LFMR). The magnetic, resistive and catalytic properties of the double perovskite SFMO are excellent for spintronic (non-volatile memory), sensing, fuel cell and microwave absorber applications. However, due to different synthesis conditions of ceramics and thin films, different mechanisms of electrical conductivity and magnetoresistance prevail. In this work, we consider the occurrence of a weak localization effect in SFMO commonly obtained in disordered metallic or semiconducting systems at very low temperatures due to quantum interference of backscattered electrons. We calculate the quantum corrections to conductivity and the contribution of electron scattering to the resistivity of SFMO. We attribute the temperature dependence of SFMO ceramic resistivity in the absence of a magnetic field to the fluctuation-induced tunneling model. We also attribute the decreasing resistivity in the temperature range from 409 K to 590 K to adiabatic small polaron hopping and not to localization effects. Neither fluctuation-induced tunneling nor adiabatic small polaron hopping favors quantum interference. Additionally, we demonstrate that the resistivity upturn behavior of SFMO cannot be explained by weak localization. Here, the fitted model parameters have no physically meaningful values, i.e., the fitted weak localization coefficient (B′) was three orders of magnitude lower than the theoretical coefficient, while the fitted exponent (n) of the electron–electron interaction term (CnTn) could not be assigned to a specific electron-scattering mechanism. Consequently, to the best of our knowledge, there is still no convincing evidence for the presence of weak localization in SFMO.
30
Svane, Bjarke, Kasper Tolborg, Kenichi Kato et Bo Brummerstedt Iversen. « Multipole electron densities and structural parameters from synchrotron powder X-ray diffraction data obtained with a MYTHEN detector system (OHGI) ». Acta Crystallographica Section A Foundations and Advances 77, no 2 (28 janvier 2021) : 85–95. http://dx.doi.org/10.1107/s2053273320016605.
Texte intégralRésumé :
Powder X-ray diffraction has some inherent advantages over traditional single-crystal X-ray diffraction in accurately determining electron densities and structural parameters due to the lower requirements for sample crystallinity, simpler corrections and measurement simultaneity. For some simple inorganic materials, it has been shown that these advantages can compensate for disadvantages such as peak overlap and error-prone background subtraction. Although it is challenging to extend powder X-ray diffraction-based electron-density studies to organic materials with significant peak overlap, previous results using a dedicated vacuum diffractometer with a large image-plate camera (AVID) demonstrated that it can be done. However, the vacuum setup with the off-line detector system was found to prohibit a widespread use. Fast microstrip detectors, which have been employed at a number of powder diffraction beamlines, have the potential to facilitate electron-density studies. Nevertheless, no electron-density studies even for materials with slight peak overlap have been performed with microstrip detectors. One of the most critical problems has been a difference in sensitivity between microstrip channels, which substantially defines the dynamic range of a detector. Recently, a robust approach to this problem has been developed and applied to a total scattering measurement system (OHGI) with 15 MYTHEN microstrip modules. In the present study, synchrotron powder X-ray diffraction data obtained with OHGI are evaulated in terms of multipole electron densities and structural parameters (atomic positions and displacement parameters). These results show that, even without a dedicated setup and perfect samples, electron-density modelling can be carried out on high-quality powder X-ray diffraction data. However, it was also found that the required prior information about the sample prohibits widespread use of the method. With the presently obtainable data quality, electron densities of molecular crystals in general are not reliably obtained from powder data, but it is an excellent, possibly superior, alternative to single-crystal measurements for small-unit-cell inorganic solids. If aspherical atomic scattering factors can be obtained from other means (multipole databases, theoretical calculations), then atomic positions (including for hydrogen) and anisotropic atomic displacement parameters (non-hydrogen atoms) of excellent accuracy can be refined from synchrotron powder X-ray diffraction data on organic crystals.
31
Dohn, A. O., V. Markmann, A. Nimmrich, K. Haldrup, K. B. Møller et M. M. Nielsen. « Eliminating finite-size effects on the calculation of x-ray scattering from molecular dynamics simulations ». Journal of Chemical Physics 159, no 12 (27 septembre 2023). http://dx.doi.org/10.1063/5.0164365.
Texte intégralRésumé :
Structural studies using x-ray scattering methods for investigating molecules in solution are shifting focus toward describing the role and effects of the surrounding solvent. However, forward models based on molecular dynamics (MD) simulations to simulate structure factors and x-ray scattering from interatomic distributions such as radial distribution functions (RDFs) face limitations imposed by simulations, particularly at low values of the scattering vector q. In this work, we show how the value of the structure factor at q = 0 calculated from RDFs sampled from finite MD simulations is effectively dependent on the size of the simulation cell. To eliminate this error, we derive a new scheme to renormalize the sampled RDFs based on a model of the excluded volume of the particle-pairs they were sampled from, to emulate sampling from an infinite system. We compare this new correction method to two previous RDF-correction methods, developed for Kirkwood–Buff theory applications. We present a quantitative test to assess the reliability of the simulated low-q scattering signal and show that our RDF-correction successfully recovers the correct q = 0 limit for neat water. We investigate the effect of MD-sampling time on the RDF-corrections, before advancing to a molecular example system, comprised of a transition metal complex solvated in a series of water cells with varying densities. We show that our correction recovers the correct q = 0 behavior for all densities. Furthermore, we employ a simple continuum scattering model to dissect the total scattering signal from the solvent–solvent structural correlations in a solute–solvent model system to find two distinct contributions: a non-local density-contribution from the finite, fixed cell size in NVT simulations, and a local contribution from the solvent shell. We show how the second contribution can be approximated without also including the finite-size contribution. Finally, we provide a “best-practices”-checklist for experimentalists planning to incorporate explicit solvation MD simulations in future work, offering guidance for improving the accuracy and reliability of structural studies using x-ray scattering methods in solution.
32
Song, Qian, Qing Huo Liu et Wen Chen. « High-resolution ghost imaging through dynamic and complex scattering media with adaptive moving average correction ». Applied Physics Letters 124, no 21 (20 mai 2024). http://dx.doi.org/10.1063/5.0211930.
Texte intégralRésumé :
Optical imaging through dynamic and complex scattering media has attracted various applications, e.g., ranging from scene imaging to cell imaging. Nevertheless, imaging through complex media is full of challenges attributed to the inhomogeneous scattering, leading to nonlinear effects. Although ghost imaging (GI) has proven effective in solving some scattering problems, dynamic and complex scattering still requires an efficient solution. In this Letter, we report a model based on adaptive moving average (AMA) to correct the influence of dynamic scattering media from a statistical perspective for high-resolution GI. The developed AMA correction method selects an appropriate time window based on the changing trend of measured single-pixel light intensities to accurately correct a series of dynamic scaling factors. Then, the corrected single-pixel light intensities are used for ghost reconstruction using a second-order correlation algorithm. A series of optical experiments are conducted to verify superiority of the proposed method. Moreover, the proposed method can be applied with other algorithms to enhance the quality of the reconstructed ghost images. By leveraging a statistical model based on the measured data, the proposed scheme offers an enhanced solution to solving dynamic and complex scattering problems in GI.
33
Zhao, Minmin, Binbin Wu, Jingyi Liu et Li Lei. « Anti-Stokes/Stokes temperature calibration and its application in laser-heating diamond anvil cell ». Chinese Physics B, 17 avril 2023. http://dx.doi.org/10.1088/1674-1056/accd55.
Texte intégralRésumé :
Abstract Anti-Stokes/Stokes Raman peak intensity ratio was used to infer sample temperature, but the influence factors of system correction factors were not clear. Non-contact in-situ anti-Stokes/Stokes temperature calibration was carried out up to 1500 K based on six different samples under two excitation light sources (±50 K within 1000 K, ±100 K above 1000 K), and the system correction factor γ was systematically investigated. The results show that the correction factor γ of anti-Stokes/Stokes thermometry is affected by the wavelength of the excitation light source, Raman mode peak position, temperature measurement region and other factors. The anti-Stokes/Stokes thermometry was applied to the laser-heating diamond anvil cell (LHDAC) experiment to investigate the anharmonic effect of hBN under high temperature and high pressure. It is concluded that the strong anharmonic effect caused by phonon scattering at low pressure gradually changes into the predominance of localized molecular lattice thermal expansion at high pressure.
34
Matsui, Tsutomu, Ivan Rajkovic, Blaine H. M. Mooers, Ping Liu et Thomas M. Weiss. « Adaptable SEC‐SAXS data collection for higher quality structure analysis in solution ». Protein Science 33, no 4 (19 mars 2024). http://dx.doi.org/10.1002/pro.4946.
Texte intégralRésumé :
AbstractThe two major challenges in synchrotron size‐exclusion chromatography coupled in‐line with small‐angle x‐ray scattering (SEC‐SAXS) experiments are the overlapping peaks in the elution profile and the fouling of radiation‐damaged materials on the walls of the sample cell. In recent years, many post‐experimental analyses techniques have been developed and applied to extract scattering profiles from these problematic SEC‐SAXS data. Here, we present three modes of data collection at the BioSAXS Beamline 4–2 of the Stanford Synchrotron Radiation Lightsource (SSRL BL4‐2). The first mode, the High‐Resolution mode, enables SEC‐SAXS data collection with excellent sample separation and virtually no additional peak broadening from the UHPLC UV detector to the x‐ray position by taking advantage of the low system dispersion of the UHPLC. The small bed volume of the analytical SEC column minimizes sample dilution in the column and facilitates data collection at higher sample concentrations with excellent sample economy equal to or even less than that of the conventional equilibrium SAXS method. Radiation damage problems during SEC‐SAXS data collection are evaded by additional cleaning of the sample cell after buffer data collection and avoidance of unnecessary exposures through the use of the x‐ray shutter control options, allowing sample data collection with a clean sample cell. Therefore, accurate background subtraction can be performed at a level equivalent to the conventional equilibrium SAXS method without requiring baseline correction, thereby leading to more reliable downstream structural analysis and quicker access to new science. The two other data collection modes, the High‐Throughput mode and the Co‐Flow mode, add agility to the planning and execution of experiments to efficiently achieve the user's scientific objectives at the SSRL BL4‐2.
35
Wu Dan-Dan, Pan Li, Zhou Zhe, Fu Wei-Wei, Zhu Hai-Long et Dong Yue-Fang. « Research of NIR-II small animal living fluorescence imaging system ». Acta Physica Sinica, 2024, 0. http://dx.doi.org/10.7498/aps.73.20231910.
Texte intégralRésumé :
Fluorescence imaging technology can dynamically monitor gene and cell changes in live animals in real-time, with advantages such as high sensitivity, high resolution, and non-invasive. In recent years, it has been widely used in tumor research, gene expression research, drug development research, etc. The imaging wavelength of traditional fluorescence imaging technology is located in the visible and near-infrared-I region. Due to the absorption and scattering effects of light propagation within biological tissues, as well as the inherent fluorescence of biological tissues, traditional fluorescence imaging techniques still have significant limitations in penetration depth and image signal-to-noise ratio. In this paper, a highly integrated near-infrared-II (NIR-II, 900~1880 nm) small animal living fluorescence imaging system is developed, by utilizing the advantages of NIR-II fluorescence imaging technology, such as low absorption, low scattering, and deep penetration depth in biological tissues. And a fluorescence image enhancement and correction method is proposed to optimize fluorescence images. This article designs biological tissue simulation experiments and live animal experiments to test the performance and imaging effect of the system. The experimental results show that the system has the advantages of deep penetration depth, high signal-to-noise ratio, and high sensitivity. Combined with commercial indocyanine green reagents and aggregation-induced emission dyes, this system can monitor the distribution of blood vessels in real time and continuously monitor deep tissues and organs in mice, achieving dynamic monitoring research in living mice in a conscious state. This helps to promote tumor research and drug development research in the field of biomedical imaging to enter a new stage.
36
Kaushik, Vineeta, Michał Dąbrowski, Luca Gessa, Nelam Kumar et Humberto Fernandes. « Two-photon excitation fluorescence in ophthalmology : safety and improved imaging for functional diagnostics ». Frontiers in Medicine 10 (3 janvier 2024). http://dx.doi.org/10.3389/fmed.2023.1293640.
Texte intégralRésumé :
Two-photon excitation fluorescence (TPEF) is emerging as a powerful imaging technique with superior penetration power in scattering media, allowing for functional imaging of biological tissues at a subcellular level. TPEF is commonly used in cancer diagnostics, as it enables the direct observation of metabolism within living cells. The technique is now widely used in various medical fields, including ophthalmology. The eye is a complex and delicate organ with multiple layers of different cell types and tissues. Although this structure is ideal for visual perception, it generates aberrations in TPEF eye imaging. However, adaptive optics can now compensate for these aberrations, allowing for improved imaging of the eyes of animal models for human diseases. The eye is naturally built to filter out harmful wavelengths, but these wavelengths can be mimicked and thereby utilized in diagnostics via two-photon (2Ph) excitation. Recent advances in laser-source manufacturing have made it possible to minimize the exposure of in vivo measurements within safety, while achieving sufficient signals to detect for functional images, making TPEF a viable option for human application. This review explores recent advances in wavefront-distortion correction in animal models and the safety of use of TPEF on human subjects, both of which make TPEF a potentially powerful tool for ophthalmological diagnostics.
37
Hervey, John R. D., Paolo Bombelli, David J. Lea-Smith, Alan K. Hulme, Nathan R. Hulme, Atvinder K. Rullay, Robert Keighley et Christopher J. Howe. « A dual compartment cuvette system for correcting scattering in whole-cell absorbance spectroscopy of photosynthetic microorganisms ». Photosynthesis Research, 14 août 2021. http://dx.doi.org/10.1007/s11120-021-00866-8.
Texte intégralRésumé :
AbstractAbsorption spectroscopy is widely used to determine absorption and transmission spectra of chromophores in solution, in addition to suspensions of particles, including micro-organisms. Light scattering, caused by photons deflected from part or all of the cells or other particles in suspension, results in distortions to the absorption spectra, lost information and poor resolution. A spectrophotometer with an integrating sphere may be used to alleviate this problem. However, these instruments are not universally available in biology laboratories, for reasons such as cost. Here, we describe a novel, rapid, and inexpensive technique that minimises the effect of light scattering when performing whole-cell spectroscopy. This method involves using a custom made dual compartment cuvette containing titanium dioxide in one chamber as a scattering agent. Measurements were conducted of a range of different photosynthetic micro-organisms of varying cell size and morphology, including cyanobacteria, eukaryotic microalgae and a purple non-sulphur bacterium. A concentration of 1 mg ml−1 titanium dioxide, using a spectrophotometer with a slit width of 5 nm, produced spectra for cyanobacteria and microalgae similar (1–4% difference) to those obtained using an integrating sphere. The spectrum > 520 nm was similar to that with an integrating sphere with the purple non-sulphur bacterium. This system produced superior results to those obtained using a recently reported method, the application of the diffusing agent, Scotch™ Magic tape, to the side of the cuvette. The protocol can be completed in an equivalent period of time to standard whole-cell absorbance spectroscopy techniques, and is, in principle, suitable for any dual-beam spectrophotometer.
38
Santamaría-Sanz, Lucía. « Quantum field theory at finite temperature for 3D periodic backgrounds ». Journal of Physics A : Mathematical and Theoretical, 3 mai 2024. http://dx.doi.org/10.1088/1751-8121/ad4754.
Texte intégralRésumé :
Abstract The one-loop quantum corrections to the internal energy of some lattices due to the quantum fluctuations of the scalar field of phonons are studied. The band spectrum of the lattice is characterised in terms of the scattering data, allowing to compute the quantum vacuum interaction energy between nodes at zero temperature, as well as the total Helmholtz free energy, the entropy, and the Casimir pressure between nodes at finite non-zero temperature. Some examples of periodic potentials built from the repetition in one of the three spatial dimensions of the same punctual or compact supported potential are addressed: a stack of parallel plates constructed by positioning $\delta\delta'$-functions at the lattice nodes, and an ``upside-down tiled roof" of parallel two-dimensional P"oschl-Teller wells centred at the nodes. They will be called \textit{generalised Dirac comb} and \textit{P"oschl-Teller comb}, respectively. Positive one-loop quantum corrections to the entropy appear for both combs at non-zero temperatures. Moreover, the Casimir force between the lattice nodes is always repulsive for both chains when non-trivial temperatures are considered, implying that the primitive cell increases its size due to the quantum interaction of the phonon field.
39
« Correction : Volume 250, No. 2 (1998) : Examining F-actin interaction with intact talin and talin head and tail fragment using static and dynamic light scattering ». European Journal of Biochemistry 254, no 1 (15 mai 1998) : 207. http://dx.doi.org/10.1046/j.1432-1327.1998.2540207.x.
Texte intégral