Optical trapping of particles has become a powerful non-mechanical and non-destructive technique for precise particle positioning. The manipulation of particles in the evanescent field of a channel waveguide potentially allows for sorting and trapping of several particles and cells simultaneously. Channel waveguide designs can be further optimized to increase evanescent field prior to the fabrication process. This is crucial in order to make sure that the surface intensity is sufficient for optical trapping. Simulation configurations are explained in detail with specific simulation flow. Discussion on parameters optimization; physical geometry, optical polarization and wavelength is included in this paper. The effect of physical, optical parameters and beam spot size on evanescent field has been thoroughly discussed. These studies will continue toward the development of a novel copper ion-exchanged waveguide as a method of particle sorting, with biological cell propulsion studies presently underway.
- MeSH
- Equipment Failure Analysis MeSH
- Computer-Aided Design MeSH
- Equipment Design MeSH
- Ions chemistry MeSH
- Copper chemistry MeSH
- Optical Tweezers * MeSH
- Computer Simulation MeSH
- Surface Plasmon Resonance instrumentation MeSH
- Scattering, Radiation MeSH
- Light MeSH
- Models, Theoretical * MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Review MeSH
Vibrational optical activity (VOA) such as vibrational circular dichroism and Raman optical activity comprises developing spectroscopic techniques providing additional information on molecules. The information depends on theoretical modeling of the spectra. The review deals with the physics of the phenomena, their advantages and problems in experiments and spectral interpretation, applications and simulation methods. Application potentials in large, hydrated and flexible systems are documented on insuline, lactamide and a recently discovered natural molecule, "SynoxA". VOA is able to afford unique structural information; however, better instruments as well as more accurate simulations are still desirable.
- MeSH
- Amides MeSH
- Circular Dichroism * MeSH
- Cell Physiological Phenomena MeSH
- Insulin physiology MeSH
- Quantum Theory MeSH
- Molecular Structure MeSH
- Oxazolidinones MeSH
- Computer Simulation * MeSH
- Spectrum Analysis, Raman * MeSH
- Fluorescence Resonance Energy Transfer MeSH
- Molecular Dynamics Simulation MeSH
- Spectrum Analysis * MeSH
- Vibration MeSH
- Diffusion Tensor Imaging MeSH
Cíl: Cílem studie bylo analyzovat předozadní poměr optické mohutnosti rohovky (AP poměr), provést komparaci výsledných hodnot s hodnotami teoretických modelů oka a definovat vliv použití individuální hodnoty poměru na aproximaci celkové mohutnosti rohovky. Materiál a metody: Do souboru bylo zařazeno celkem 406 očí. Každý pacient podstoupil vyšetření na OCT (RTVue XR) s TCP módem, dle kterého byl stanoven AP poměr rohovky, dále byly stanoveny biometrické parametry oka (Lenstar LS900). Vzájemný vztah biometrických parametrů oka a individuální hodnoty AP poměru byl hodnocen pomocí Pearsonova korelačního koeficientu. V analýze byly výsledky AP poměru komparovány s vybranými schématickými modely oka. Za využití Gaussových vztahů byla dosazením hodnoty AP poměru realizována teoretická kalkulace celkové optické mohutnosti rohovky (KG), která byla komparována s reálně naměřenou celkovou optickou mohutností (TCP). Výsledky: Průměrná hodnota z individuálně stanovených AP poměrů byla rovna 1,17 ±0,02. Nejčetněji zastoupeným intervalem (33,74 %) byl 1,17–1,18 hodnoty AP poměru, přičemž naprostá většina očí (79,56 %) byla v rozsahu 1,15–1,20. Teoretické hodnoty celkové optické mohutnosti rohovky se statisticky významně lišily (p < 0,05) od TCP (kromě modelu oka dle Liou-Brennana, kdy p = 0,06). Nejnižší průměrná diference hodnot byla nalezena pro schématický model dle Navarra. Závislost hodnot měřeného AP poměru a biometrických parametrů dosáhla střední negativní korelace (r = -0,50 pro p < 0,05) s parametrem zakřivení zadní plochy rohovky (Rp) a dále slabá negativní korelace s průměrem limbu WtW (r = -0,26 pro p < 0,05) a slabá pozitivní s centrální tloušťkou rohovky CCT (r = 0,17 pro p < 0,05). Závěr: Předpoklad konstantní hodnoty AP poměru dle vybraných schématických modelů oka se statisticky významně liší od reálně naměřených hodnot a byla pro něj definována pouze negativní slabá korelace s velikostí průměru limbu. Použitím výsledné průměrné hodnoty stanoveného AP poměru (1,17 ±0,02) bylo docíleno nižší diference reálné a kalkulované celkové optické mohutnosti rohovky.
Aims: The aim of the study was to analyse the values of the anteroposterior corneal optical power ratio (AP ratio), to compare the resulting values with those of theoretical models of the eye, and to define the effect of using an individual ratio value on the approximation of the total corneal power. Material and Methods: A total of 406 eyes were included. Each patient underwent an OCT (RTVue XR) examination, according to which the AP ratio of the cornea was determined, as well as the biometric parameters of the eye (Lenstar LS900). The correlation between the biometric parameters of the eye and the individual AP ratio values was evaluated using Pearson’s correlation coefficient. In the analysis, the AP ratio results were compared with selected schematic models of the eye. Using Gaussian equations, a theoretical calculation of the total corneal optical power (KG) was performed, by fitting the AP ratio value and comparing it with the actually measured total corneal power (TCP). Results: The mean value of the individually determined AP ratio was 1.17 ±0.02. The most frequently represented interval (33.74 %) was 1.17 to 1.18 AP ratio values, with the vast majority of eyes (79.56 %) in the range of 1.15 to 1.20. Individual values of total corneal optical power were statistically significantly different (p < 0.05) from the theoretical values of TCP (except in the Liu-Brennan eye model, where p = 0.06). The lowest mean difference of values was found for the Navarro schematic model. The dependence of the measured AP ratio values and biometric parameters reached a moderate negative correlation (r = -0.50 for p < 0.05) with the parameter corneal posterior surface curvature (Rp), as well as a weak negative correlation with limbal diameter WtW (r = -0.26 for p < 0.05) and a weak positive correlation with central corneal thickness CCT (r = 0.17 for p < 0.05). Conclusion: The assumption of a constant value of the AP ratio according to the selected schematic models of the eye is statistically significantly different from the actual measured values and was defined to have only a negative weak correlation with the size of the limbus diameter. Using the resulting average value of the determined AP ratio (1.17 ±0.02), a lower difference between real and calculated total corneal optical power was achieved.
BACKGROUND: Optical coherence tomography (OCT) is a well established imaging technique with different applications in preclinical research and clinical practice. The main potential for its application lies in the possibility of noninvasively performing "optical biopsy". Nevertheless, functional OCT imaging is also developing, in which perfusion imaging is an important approach in tissue function study. In spite of its great potential in preclinical research, advanced perfusion imaging using OCT has not been studied. Perfusion analysis is based on administration of a contrast agent (nanoparticles in the case of OCT) into the bloodstream, where during time it specifically changes the image contrast. Through analysing the concentration-intensity curves we are then able to find out further information about the examined tissue. METHODS: We have designed and manufactured a tissue mimicking phantom that provides the possibility of measuring dilution curves in OCT sequence with flow rates 200, 500, 1000 and 2000 μL/min. The methodology comprised of using bolus of 50 μL of gold nanorods as a contrast agent (with flow rate 5000 μL/min) and continuous imaging by an OCT system. After data acquisition, dilution curves were extracted from OCT intensity images and were subjected to a deconvolution method using an input-output system description. The aim of this was to obtain impulse response characteristics for our model phantom within the tissue mimicking environment. Four mathematical tissue models were used and compared: exponential, gamma, lagged and LDRW. RESULTS: We have shown that every model has a linearly dependent parameter on flow ([Formula: see text] values from 0.4914 to 0.9996). We have also shown that using different models can lead to a better understanding of the examined model or tissue. The lagged model surpassed other models in terms of the minimisation criterion and [Formula: see text] value. CONCLUSIONS: We used a tissue mimicking phantom in our study and showed that OCT can be used for advanced perfusion analysis using mathematical model and deconvolution approach. The lagged model with three parameters is the most appropriate model. Nevertheless, further research have to be performed, particularly with real tissue.
- MeSH
- Printing, Three-Dimensional MeSH
- Equipment Design MeSH
- Phantoms, Imaging * MeSH
- Contrast Media chemistry MeSH
- Metal Nanoparticles chemistry MeSH
- Nanotubes chemistry MeSH
- Tomography, Optical Coherence methods MeSH
- Image Processing, Computer-Assisted MeSH
- Models, Theoretical * MeSH
- Tissue Scaffolds chemistry MeSH
- Gold chemistry MeSH
- Publication type
- Journal Article MeSH
Optická koherenční tomografie je bezkontaktní, rychlá a dobře reprodukovatelná zobrazovací metoda, jejíž pomocí získáváme detailní obraz struktury sítnice. Patologické změny na sítnici v souvislosti s roztroušenou sklerózou (RS) zahrnují jak následky zánětu očního nervu, tak i odraz difuzních neurodegenerativních změn. Úbytek vrstvy retinálních nervových vláken, atrofie makuly a specifické ubývání vrstvy gangliových buněk korelují se změnou zrakové ostrosti, s atrofií mozku a s kognitivními změnami u pacientů s RS. Přední část zrakové dráhy se stala modelem neuroaxonálního poškození u RS a začíná být využívána k monitoraci progrese RS a k testování neuroprotektivního účinku léků. Článek shrnuje principy optické koherenční tomografie a jejího použití u RS.
Optical coherence tomography is fast, non-invasive and reproducible imaging technique that provides detailed measurements of retinal structures. Retinal pathology in multiple sclerosis (MS) includes consequences of optic neuritis as well as diffuse degenerative changes. Thinning of retinal nerve fiber layer, decrease in total macular volume and loss of retinal ganglion cell layer correlate with visual acuity, brain atrophy measures and cognitive changes. Anterior visual pathway became a model of neuroaxonal injury in MS and is used to test neuroprotective effects of new therapies. The paper provides an overview of the physics of optical coherence tomography and its application in MS. Key words: optical coherence tomography – multiple sclerosis – retinal nerve fibre layer – total macular volume The authors declare they have no potential conflicts of interest concerning drugs, products, or services used in the study. The Editorial Board declares that the manuscript met the ICMJE “uniform requirements” for biomedical papers.
The authors tested the diagnostic potential of the portable autofluorescence optical system that was developed in the preoperative evaluation of resection margins, and thus of the resection line safety in patients with low-positioned colorectal carcinoma. A total of 217 spectral measurements of the fluorescence properties of normal (117) and malignant (100) tissues in 19 patients with colorectal carcinoma were accomplished. The measured spectra thus acquired were then evaluated using logistic regression. Using the principal component method, the authors selected the 30 and 40 most significant wavelengths, respectively, which they then used to construct the logistic model. The model met the basic criteria of statistical significance. The classification power of the model was 79.7% (for 30 wavelengths) and 82.5% (for 40). Statistical discrimination was 0.88 and 0.91, respectively. These results confirm that the optical setup that we selected is suitable for the peroperative testing of the distal resection line. It is capable of differentiating with 90% confidence pathological tissue and thus of reliably guiding further histological processing.
- MeSH
- Biopsy instrumentation methods statistics & numerical data MeSH
- Fluorescence MeSH
- Spectrometry, Fluorescence MeSH
- Colorectal Neoplasms diagnosis surgery MeSH
- Middle Aged MeSH
- Humans MeSH
- Optical Fibers MeSH
- Optical Phenomena MeSH
- Optical Devices MeSH
- Intraoperative Period MeSH
- Aged, 80 and over MeSH
- Aged MeSH
- Check Tag
- Middle Aged MeSH
- Humans MeSH
- Male MeSH
- Aged, 80 and over MeSH
- Aged MeSH
- Female MeSH
- Publication type
- Journal Article MeSH
- Evaluation Study MeSH
Design and development of scale-down approaches, such as microbioreactor (μBR) technologies with integrated sensors, are an adequate solution for rapid, high-throughput and cost-effective screening of valuable reactions and/or production strains, with considerably reduced use of reagents and generation of waste. A significant challenge in the successful and widespread application of μBRs in biotechnology remains the lack of appropriate software and automated data interpretation of μBR experiments. Here, it is demonstrated how mathematical models can be usedas helpful tools, not only to exploit the capabilities of microfluidic platforms, but also to reveal the critical experimental conditions when monitoring cascade enzymatic reactions. A simplified mechanistic model was developed to describe the enzymatic reaction of glucose oxidase and glucose in the presence of catalase inside a commercial microfluidic platform with integrated oxygen sensor spots. The proposed model allowed an easy and rapid identification of the reaction mechanism, kinetics and limiting factors. The effect of fluid flow and enzyme adsorption inside the microfluidic chip on the optical sensor response and overall monitoring capabilities of the presented platform was evaluated via computational fluid dynamics (CFD) simulations. Remarkably, the model predictions were independently confirmed for μL- and mL- scale experiments. It is expected that the mechanistic models will significantly contribute to the further promotion of μBRs in biocatalysis research and that the overall study will create a framework for screening and evaluation of critical system parameters, including sensor response, operating conditions, experimental and microbioreactor designs.
Mammalian bodies are hierarchical systems whose internal cooperation and coherent activity require high capacity information transfer between the central control unit--the brain--and the periphery--the organs. A communication system capable of meeting information capacity requirements should be based on transmission of electromagnetic signals. Structures that fulfill requirements for such information transfer have not yet been analyzed. Acupuncture meridians have been demonstrated experimentally in some animals. They might represent systems of information transfer between the brain and the peripheral organs. The ducts of the meridians may correspond to optical fibers operating from the far infrared to the visible wavelength region. The main features of a model of the duct as an optical fiber are delineated and its properties outlined. However, to analyze essentials of the transmission capabilities, the whole meridian structure should be mapped and a more comprehensive set of physical parameters measured. In particular, experimental data concerning morphological arrangements of ordered water in the ducts and corpuscles, and a complete content of the biological particles in the flowing water and its permittivity are missing.
- MeSH
- Acupuncture MeSH
- Meridians MeSH
- Acupuncture Therapy MeSH
- Models, Biological MeSH
- Information Theory MeSH
- Humans MeSH
- Brain MeSH
- Optical Fibers MeSH
- Mammals MeSH
- Systems Biology MeSH
- Animals MeSH
- Check Tag
- Humans MeSH
- Animals MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
Interpretation of the Raman optical activity (ROA) of peptides is difficult because of molecular flexibility and interaction with the solvent. Typically, simulations and experiments are compared in terms of a qualitative agreement between the spectra. However, on a series of the Pro-Gly, Gly-Pro, Pro-Ala, and Ala-Pro dipeptides more precise conformer ratios could be obtained with the aid of the density functional computations and numerical decomposition of the spectral shapes. All observed transitions were assigned, and the computed transition frequencies were scaled accordingly. Then the populations predicted by the optical spectroscopy agreed within a few percent with an analysis of the spin-spin coupling constants based on the Karplus equations, which was confirmed also by a comparison of calculated and experimental NMR couplings. The results are supported by molecular dynamics simulations and related to the previous conformational studies of similar molecules.
- MeSH
- Models, Chemical MeSH
- Dipeptides chemistry MeSH
- Financing, Organized MeSH
- Quantum Theory MeSH
- Magnetic Resonance Spectroscopy methods standards MeSH
- Molecular Conformation MeSH
- Computer Simulation MeSH
- Spectrum Analysis, Raman methods standards MeSH
- Reference Standards MeSH
- Reproducibility of Results MeSH
- Vibration MeSH
- Publication type
- Comparative Study MeSH
