Parametric imaging of attenuation by optical coherence tomography: review of models, methods, and clinical translation

SIGNIFICANCE: Optical coherence tomography (OCT) provides cross-sectional and volumetric images of backscattering from biological tissue that reveal the tissue morphology. The strength of the scattering, characterized by an attenuation coefficient, represents an alternative and complementary tissue optical property, which can be characterized by parametric imaging of the OCT attenuation coefficient. Over the last 15 years, a multitude of studies have been reported seeking to advance methods to determine the OCT attenuation coefficient and developing them toward clinical applications. AIM: Our review provides an overview of the main models and methods, their assumptions and applicability, together with a survey of preclinical and clinical demonstrations and their translation potential. RESULTS: The use of the attenuation coefficient, particularly when presented in the form of parametric en face images, is shown to be applicable in various medical fields. Most studies show the promise of the OCT attenuation coefficient in differentiating between tissues of clinical interest but vary widely in approach. CONCLUSIONS: As a future step, a consensus on the model and method used for the determination of the attenuation coefficient is an important precursor to large-scale studies. With our review, we hope to provide a basis for discussion toward establishing this consensus

Fabrication of UV/ TiO2 nanotubes / Pd system by electrochemical anodization for furfural photocatalytic degradation

The aim of this study was to degrade furfural by a new nanotube system. To degrade some organic pollutants as well as to reduce the amount of furfural which is a well-known pollutant in oil industry, the photocatalytic process along with ultraviolet (UV) irradiation may be employed. In this study, the UV/TiO2/Pd system in which the nanoparticles of palladium doped into the titanium dioxide was proposed for degradation of furfural. The rate of furfural decomposition in the proposed system was more than that of the system without TiO2 foils due to the degradable reactions. The experimental results demonstrate that the maximum degradation occurs at a distinct pH and specific temperature under the UV irradiation. After 100-minute UV-irradiation duration, the maximum and minimum degradations were 97.8% (pH 3), and 95.8% (pH 12), respectively. Also, the degradation values were as parabolic function at the pH values. The values of efficiency of decomposition for this irradiation duration at optimum pH 3 were 96.7% and 98.5% at 30◦C and 40◦C, respectively. Also, the minimum degradation under photolysis was 93.52% at 30oC under 20-minute UV-irradiation duration. Furthermore, while the irradiation duration was 70-75 min, the degradation values were independent of pH approximately. The difference between the degradation values at 30 and 40◦C was decreased with increasing the UV-irradiation duration till 60min, and then this difference was increased with increasing the UV-irradiation duration

Excited state dynamics of Photoactive Yellow Protein chromophores elucidated by high-resolution spectroscopy and ab initio calculations

We report on experimental high-resolution spectroscopic studies in combination with advanced theoretical calculations that focus on the excited-state dynamics of various forms of the chromophore of the Photoactive Yellow Protein (PYP), and the dependence of these dynamics on conformational and isosteric structure, as well as the biological environment. Three-colour nanosecond multiphoton ionization pump-probe studies confirm and extend previous conclusions that the dominant decay channel of the lowest excited pi pi* state (the so-called V' state) of methyl-4-hydroxycinnamate is picosecond internal conversion to the adiabatically lower n pi* state, and enable us to resolve apparent contradictions with picosecond pump-probe studies. Comparison of multiphoton ionization and laser induced fluorescence excitation spectra leads to the assignment of the hitherto elusive excitation spectrum of the V(pp*) state. Complexation of methyl-4-hydroxycinnamate with water radically changes the excited-state dynamics; internal conversion to the np* state is absent, and bond isomerization channels instead play a prominent role. Excited states of the thio-ester compound, the form in which the chromophore is present in PYP, have till the present study remained out of reach of gas-phase studies. The excitation spectra obtained here show a broad, almost structureless band system, giving evidence for enhanced nonradiative decay channels. The gas-phase results will be discussed in the context of results from ultrafast studies on these two chromophores in solution

From sample structure to optical properties and back:A theoretical framework for quantitative OCT and its clinical application

The aim of this thesis is to provide a methodology to extract quantitative parameters from optical coherence tomography (OCT) images and to relate these parameters to sample properties such as structure, organization and flow. OCT uses near-infrared light to acquire 3D images of biological tissue, with a resolution around 5-15 μm and an imaging depth of approximately 2 mm. OCT can be a useful clinical tool for minimally-invasive, high-resolution imaging of tissue structures and morphology. In addition to morphological imaging, quantification of scattering properties from OCT images is a potential complementary source of information on microscopic tissue properties, which can be used clinically for tissue characterization. Quantitative parameters can be extracted from OCT data using an appropriate model for the OCT signal. However, the extracted parameters strongly depend on the applied methodology, and are sensitive to the selected input parameters. In order to establish the clinical value of quantitative OCT, the extracted parameters should be reliable and robust. Furthermore, the sensitivity of these parameters to clinically relevant changes in tissue should be determined. In the first part of this thesis a model describing the OCT signal and the relation of quantitative OCT-parameters to sample properties of discrete random media is derived and validated. Furthermore, a robust method to extract quantitative parameters from OCT data is presented. The second part of this thesis covers two in vivo pilot studies on the feasibility of quantitative OCT during surgery, in which the obtained quantitative OCT-parameters are related to structural tissue properties and flow

Optimization of arsenite removal by adsorption onto organically modified montmorillonite clay: Experimental & theoretical approaches

Arsenic is a critical contaminant for aqueous environments as it poses harmful health risks. To meet the stringent regulations regarding the presence of arsenic in aqueous solutions, the feasibility of montmorillonite clay modified with hexadecyltrimethyl ammonium chloride as the adsorbent was tested for the removal of arsenic ions from aqueous solutions. A scanning electron microscopy (SEM) study confirmed that the organically modified nanoclay (ONC) adsorbent had a porous structure with a vast adsorbent surface.The x-ray fluorescence (XRF) analysis proved the presence of carbon in the structure of the modified nanoclay that can be evidence for the creation of ONC. The x-ray diffraction (XRD) analysis results confirm the existence of four main groups of minerals, carbonate (Calcite), clay (Askmtyt and Kandyt), silicate (Quartz), and phyllosilicate (Kaolinite), in the ONC structure.The influence of various parameters such as solution pH, adsorbent dosage, initial arsenite concentration, and contact time on arsenic adsorption onto ONC was investigated. A 2(5) full factorial central composite experimental design was applied. A central composite design under response surface methodology (RSM) was employed to investigate the effects of independent variables on arsenite removal and to determine the optimum condition. The experimental values were in a good fit with the ones predicted by the model. The optimal operating points (adsorbent dosage: 3.7 g L-1, surfactant dosage: 3 g L-1 and the contact time: 37.2min) giving maximum arsenite removal (95.95) were found using Solver "Add-ins" in Microsoft Excel 2010

Anal tuberculosis: A non–Healing anal lesion

Anal tuberculosis is an extremely rare extrapulmonary presentation of tuberculosis (TB). Less than 1% of the individuals who contract TB manifests as gastrointestinal TB, and anoperineal TB is much less frequently encountered, 1% of the TB cases of the digestive tract. A rare case of anal tuberculosis is reported in a 37-year-old male patient with a recent anal fistula surgery and relapsing anal lesions. AFB were detected by biopsy and culture. In total, the treatment course lasted 6 months and the patient showed signs of recovery in the early stages of the treatment (after 2 weeks), and complete remission was achieved. In conclusion, it is recommended that in case of encountering Non-healing and recurrent anal lesions, especially in regions endemic for TB, should be evaluated for tuberculosis. Keywords: Anal, Tuberculosis, Fistula surger

Synthesis and characterization of novel antibacterial PdDA/ honey nanofiber against Gram-positive and Gram-negative bacteria

Nanomaterials are increasingly used to the targeting of gram-positive and gram-negative bacteria as an alternative to antibiotics. Bacterial infections are a major cause of chronic infections and mortality. People requirement for new materials for pathogenic bacteria treatment. It seems that nanomaterial-based strategies can be resolving this problem. In this research, improved antibacterial nanofibrous material using the synthesis of novel blend nanofibers by electrospinning method against gram-positive and gram-negative bacteria. First, Honey as a natural, biocompatible and antimicrobial compound (with different percentages) was added to the PDDA solution and the influence of processing parameters on the morphology of the electrospun blend nanofibers were investigated. The results showed that a bead-free morphology of nanofibers with uniform diameter achieved at the concentration ratio of 40/60 (PDDA/honey), the flow rate of 0.8 mL/h and the high voltage of 17kV. The sample with optimum morphology was cross-linked by glutaraldehyde at different crosslinking times. Evaluation of the water absorption property of nanofibers showed the absorption capacity of 4.9 g/g. Then, the in-vitro antibacterial activity of nanofiber investigated against gram-positive and gram-negative strains, Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). Afterward, novel nanofiber antibacterial activity studied against pathogenic Pseudomonas aeruginosa (P. aeruginosa). The MIC values indicated that the ratio of 40/60 PDDA/honey nanofiber induced about 99.9 bacterial death for both strains. Moreover, the novel PDDA/honey nanofibers showed suitable antibacterial activity (98.89 ) against pathogenic Pseudomonas aeruginosa. Moreover, the results showed a large reduction of bacterial numbers and evidently presented novel nanofibers as new antimicrobial agents. © 2020 Nanomedicine Research Journal. All rights reserved