Background Intensity Ratio Research Articles

Defect-Engineered Metal-Organic Frameworks as Nanocarriers for Pharmacotherapy: Insights into Intracellular Dynamics at The Single Particle Level.

Nanoscale Metal-Organic Frameworks (nanoMOFs) are widely implemented in a host of assays involving drug delivery, biosensing catalysis, and bioimaging. However, the cell pathways and cell fate remain poorly understood. Here, a new fluorescent nanoMOF integrating ATTO 655 into surface defects of colloidal UiO-66 is synthesized, allowing to track the spatiotemporal localization of Single nanoMOF in live cells. Density functional theory reveals the stronger binding of ATTO 655 to the Zr6 cluster nodes compared with phosphate and Alendronate Sodium. Parallelized tracking of the spatiotemporal localization of thousands of nanoMOFs and analysis using machine learning platforms reveals whether nanoMOFs remain outside as well as their cellular internalization pathways. To quantitatively assess their colocalization with endo/lysosomal compartments, a colocalization proxy approach relying on the nanoMOF detection of particles in one channel to the signal in the corresponding endo/lysosomal compartments channel, considering signal versus local background intensity ratio and signal-to-noise ratio is developed. This strategy mitigates colocalization value inflation from high or low signal expression in endo/lysosomal compartments. The results accurately measure the nanoMOFs' colocalization from early to late endosomes and lysosomes and emphasize the importance of understanding their intracellular dynamics based on single-particle tracking for optimal and safe drug delivery.

Auto-Processing Of Filtered Rayleigh Scattering Images Including Mie And Background Scattering Contributions

Filtered Rayleigh scattering (FRS) is a non-intrusive, optical-based technique that allows for simultaneous, time-averaged, measurements of three-component velocity, static temperature, and static pressure. The method of post-processing the raw images to get these variables is a non-trivial task. The post-processing scheme starts with building a model to generate simulated spectra given known velocity, temperature, and pressure values which can be iterated upon. The model also includes Mie scattering and background scattering contributions that must be taken into account. This iteration scheme allows for the simulated spectra to be matched to the experimental spectra to back out the desired flow variables. This iteration process can be lengthy and so it is important to make spectrum generation/iteration as fast as possible. This is done through the use of support vector spectrum approximation (SVSA), which is a machine learning algorithm, as well as a multivariable minimum error solver based on the least-squares fit between the simulated data and the experimental data. To prove the methodology, simulated results were first compared at different signal-to-noise ratios to determine the expected uncertainty at each SNR level. It was shown that to achieve an error of less than 1\% in all variables (velocity, static temperature, Mie intensity ratio, and background intensity ratio), the SNR must be near 40dB. This kind of SNR level is generally not expected in an experiment. Therefore, a representative experiment was conducted which included Mie and background scattering contributions. It was shown that manually processed data was capable of achieving velocity results that were within 2\% of the probe data. No other variables were achieved. The auto-processing scheme was able to achieve an error of approximately 2.5\% in velocity when compared to probe data. It was also capable of providing static temperature, Mie intensity ratio, and background intensity ratio values. The manual iteration results took several days to achieve while the auto-processing took about an hour. It is clear that this methodology is capable of automatically processing images from experiments with Mie and background scattering contributions while saving time.

Plasmonic features of free-standing chitosan nanocomposite film with silver and graphene oxide for SERS applications

A scalable procedure of SERS substrates design was developed using a novel plasmonic structure based on a freestanding chitosan film, silver nanoparticles, and graphene oxide. Chitosan provides a uniform distribution of silver nanoparticles from a colloidal suspension and, therefore, a reproducible Raman signal from local areas of measurements of several tens of microns. The addition of graphene oxide (GO) to the colloidal solution of silver nanoparticles suppresses the tortuous background fluorescence signal from the analyte and leads to an increase in the signal-to-fluorescence background intensity ratio by up to 6 times as compared to structures without GO. The manufactured plasmonic polymer nanocomposite provides a detection limit of down to 100 pM for R6G using a laser wavelength of 532 nm through a portable ×10 objective. The high colloidal stability of GO in water and the use of an aqueous colloid of silver nanoparticles simplify the procedure for creating a substrate by applying the GO-silver composite on the surface of a chitosan film without a need to form a GO film. Therefore, our approach paves a promising avenue to provide more sensitive detection even for the fluorescent analytes with short-wavelength lasers (532, 633 nm) instead of IR (785, 1024 nm) and foster the practical application of the developed plasmonic composites on portable Raman spectrometers.

EFFECT OF GRANULATION, MECHANICAL ACTIVATION, THERMOVACUUM TREATMENT AND AMBIENT GAS PRESSURE ON TI–0,5C SYSTEM SYNTHESIS REGULARITIES

This paper studies dependences of combustion velocities and changes in sample relative lengths from ambient pressure and thermovacuum degassing (TVD) time for the Ti + 0,5C mixture. It was shown that Ti + 0,5C mixture TVD significantly (doubly) increase combustion velocity as well as sample shrinkage. Sample shrinkage occurs under the influence of surface tension due the sufficient quantity of a liquid phase in combustion products that ensure their low viscosity. It was not possible before to obtain pressed samples from the mechanically activated (MA) Ti + C mixture because of their low strength, and therefore to investigate their combustion regularities. To solve this problem, the authors used preliminary granulation of the initial Ti + 0,5C mixture before MA. As a result, dependences of combustion velocity and post-combustion changes in sample lengths from MA time were obtained for the first time ever for the Ti + 0,5C preliminary granulated mixture. It was found that mechanical activation decreases mixture combustion velocity and significantly (triply) increases sample elongation after combustion. Combustion velocity after MA mixture TVD reaches combustion velocity of initial mixtures at the same TVD time. The samples of condensed reaction products from the MA mixture retained a slight elongation (within 8 %) after TVD. X-ray phase analysis revealed no reaction products formed during MA. Combustion products of all mixtures (initial, activated mixture and activated granules) contain the Ti2C phase and Ti traces. X-ray analysis of the initial and MA mixtures shows peaks intensity broadening and reduction of peak intensity to the background intensity ratio after MA thus indicating a higher defect rate in the crystal structure of the components of mixtures. This effect intensifies with an increase in activation time. The study results are interpreted based on the conduction – convection model of reaction wave propagation.

Delineation of Biological Tumor Volume from Positron Emission Tomography Images in Nasopharyngeal Carcinoma

Objective: To develop an auto-segmentation method for delineating the biological tumor volume of nasopharyngeal carcinoma from positron emission tomography images. Methods: A phantom consisting of a water tank with fixed background fluorodeoxyglucose [18F-FDG] activity and spheres with diameters ranging from 2.1 to 5 cm with varying activities of FDG were used to simulate tumors of different sizes and FDG uptake. The phantom was scanned with a PET/CT scan at different sphere to background intensity ratios. An optimum fixed percentage threshold (FT) approach and a signal-to-background ratio (SBR) approach were developed to estimate the true size of the spheres from the PET images. Both approaches were further evaluated in patient images for validation. Twenty-two patients with NPC from stage T1 to T4 were included. The PET based biological tumor volumes (BTV) were delineated with both FT (BTVFT) and SBR (BTVSBR) approaches and compared with the gross tumor volume localized from MRI (GTVMR). The mean volumes of BTVFT and BTVSBR were compared and the degree of overlap between GTVMR and both BTVs was evaluated. Paired t-tests were used for statistical analysis. Results: The optimal FT value was 36.5% of maximal intensity, and SBR approach was represented by an inverse linear regression model. The estimated volume of spheres segmented by both approaches shows no significant difference from the true volume of spheres (p > 0.05), but the average absolute errors were smaller from SBR approach than FT approach (p = 0.008). GTVMR was larger than both BTVFT (p = 0.003) and BTVSBR (p SBR with GTVMR is significantly larger than with BTVFT (0.52 and 0.42 respectively, p MR for radiotherapy planning purpose.

Disentangling the Peak and Background Signals in Surface-Enhanced Raman Scattering

Understanding the complex relationship between peak enhancement and the underlying broad continuum (called the “background”) is crucial for developing reliable and quantitative applications of surface-enhanced Raman scattering (SERS). Here we use a gentle mechanochemical (“snow jet”) process to perturb molecules on a SERS active substrate to track the dynamics of the different contributions to SERS. By use of the snow jet process we are able to increase SERS signals on substrates by 500% or more while simultaneously increasing the peak:background intensity ratio. We identify components of the signal arising from changes in molecular distribution and surface morphology using a multiplexed time-varied exposure technique developed in-house. This allows us to distinguish between processes decaying over time and those decaying due to laser heating. Our study goes a long way toward disentangling the different contributions to SERS peak and background continuum signals and points to the different origins of these two co-occurring processes on nanostructured plasmonic substrates. This deeper understanding of the SERS process is crucial to allow SERS to reach its full potential.

Regional expression of epithelial MDR1/P‐glycoprotein in chronic rhinosinusitis with and without nasal polyposis

P-glycoprotein (P-gp) is a 170-kDa transmembrane glycoprotein encoded by the MDR1 (ABCB1) gene and is constitutively expressed on lower airway epithelium. P-gp has been shown to function as an immunomodulator regulating efflux of T-helper 1/T-helper 2 (Th1/Th2) cytokines from its host cell; however, its association with sinonasal inflammation has not been described. The purpose of this study is to determine the pattern and degree of epithelial P-gp expression in chronic rhinosinusitis (CRS) with nasal polyposis (CRSwNP) or CRS without nasal polyposis (CRSsNP). Institutional Review Board (IRB)-approved study utilizing sinus, septal, and inferior turbinate mucosa in patients with no disease, CRS, and CRSwNP (n = 4 each). Quantitative fluorescent immunohistochemistry (Q-FIHC) was performed using an anti-P-gp antibody and a secondary fluorescein isothiocyanate (FITC)-conjugated Fc specific fragment. Protein expression was quantified by calculating the epithelial to nonspecific background intensity ratio (4 images/subsite). Scores less than 1 suggested negligible expression. Staining ratios between patient groups and subsites were compared using a 2-tailed Student t test. Among the sinus mucosa, P-gp expression in CRSwNP (1.570 ± 0.354) was significantly greater than both CRS (1.224 ± 0.248) and control (0.762 ± 0.128) (p < 0.001, p = 0.002; respectively). CRS scores were significantly greater than control (p = 0.002). Among the septal mucosa, there was no significant difference between CRSwNP (0.914 ± 0.264), CRS (1.126 ± 0.476), or control (0.966 ± 0.327). Among the inferior turbinate mucosa, there was no significant difference between CRSwNP (1.047 ± 0.157), CRS (1.099 ± 0.362), or control (0.824 ± 0.181). MDR1/P-gp is overexpressed in the epithelial layer of sinus mucosa in patients with both CRSwNP and CRS relative to other sinonasal subsites. Expression in healthy mucosa is negligible. Given its known immunomodulatory function this suggests that P-gp may play a role in the pathogenesis or maintenance of chronic sinonasal inflammation.

Assembly of Graphene Oxide and Au0.7Ag0.3 Alloy Nanoparticles on SiO2: A New Raman Substrate with Ultrahigh Signal-to-Background Ratio

Resonance Raman spectroscopy (RRS) often suffers from the large fluorescence background which obscures the much weaker Raman scattering. To address this fundamental problem, a novel Raman substrate has been fabricated by adsorption of Au0.7Ag0.3 alloy nanoparticles (NPs) on a graphene oxide (GO) coated SiO2 surface, which offers both excellent Raman enhancement and fluorescence quenching. Our experimental data reveal that a Raman to fluorescence background intensity ratio of 1.6 can be obtained for a highly fluorescent dye like Alexa fluor 488. Moreover, we demonstrate that the Raman enhancement mainly originates from the Au0.7Ag0.3 alloy NPs and that the fluorescence quenching mainly arises from the underlying functionalized GO (FGO) substrate.

Targeting Apoptosis for Optical Imaging of Infection

Infection is ubiquitous and a major cause of morbidity and mortality. The most reliable method for localizing infection requires radiolabeling autologous white blood cells ex vivo. A compound that can be injected directly into a patient and can selectively image infectious foci will eliminate the drawbacks. The resolution of infection is associated with neutrophil apoptosis and necrosis presenting phosphatidylserine (PS) on the neutrophil outer leaflet. Targeting PS with intravenous administration of a PS-specific, near-infrared (NIR) fluorophore will permit localization of infectious foci by optical imaging. Bacterial infection and sterile inflammation were induced in separate groups (n = 5) of mice. PS was targeted with a NIR fluorophore, PSVue(®)794 (2.7 pmol). Imaging was performed (ex = 730 nm, em = 830 nm) using Kodak Multispectral FX-Pro system. The contralateral normal thigh served as an individualized control. Confocal microscopy of normal and apoptotic neutrophils and bacteria confirmed PS specificity. Lesions, with a 10-s image acquisition, were unequivocally visible at 5 min post-injection. At 3 h post-injection, the lesion to background intensity ratios in the foci of infection (6.6 ± 0.2) were greater than those in inflammation (3.2 ± 0.5). Image fusions confirmed anatomical locations of the lesions. Confocal microscopy determined the fluorophore specificity for PS. Targeting PS presented on the outer leaflet of apoptotic or necrotic neutrophils as well as gram-positive microorganism with PS-specific NIR fluorophore provides a sensitive means of imaging infection. Literature indicates that NIR fluorophores can be detected 7-14 cm deep in tissue. This observation together with the excellent results and the continued development of versatile imaging devices could make optical imaging a simple, specific, and rapid modality for imaging infection.

When should one subtract background fluorescence in 2-color microarrays?

Two-color microarrays are a powerful tool for genomic analysis, but have noise components that make inferences regarding gene expression inefficient and potentially misleading. Background fluorescence, whether attributable to nonspecific binding or other sources, is an important component of noise. The decision to subtract fluorescence surrounding spots of hybridization from spot fluorescence has been controversial, with no clear criteria for determining circumstances that may favor, or disfavor, background subtraction. While it is generally accepted that subtracting background reduces bias but increases variance in the estimates of the ratios of interest, no formal analysis of the bias-variance trade off of background subtraction has been undertaken. In this paper, we use simulation to systematically examine the bias-variance trade off under a variety of possible experimental conditions. Our simulation is based on data obtained from 2 self versus self microarray experiments and is free of distributional assumptions. Our results identify factors that are important for determining whether to background subtract, including the correlation of foreground to background intensity ratios. Using these results, we develop recommendations for diagnostic visualizations that can help decisions about background subtraction.

A high-contrast all-glass ps-terawatt CPA laser system

We report on a compact, all-glass laser using a fiberless CPA technique as a potential system for the generation of extreme high-contrast picosecond pulses in the terawatt power range. New exciting experiments in the field of laser-matter interaction at extremely high intensities require both a high output energy and a very high peak to background intensity ratio (contrast). At present the system delivers 1.5 ps-pulses of 1.5-J energy with an intensity contrast of 4.109.

Topographic compensation in Auger electron spectroscopy

AbstractThe scanning Auger microprobe (SAM) produces Auger images which provide information on the elemental distribution of specimen surfaces. However specimen topography affects the data obtained. To eliminate the topographical effect, the peak‐to‐background ratio, (P − B)/B ( = R), is often used instead of the net peak intensity, P − B. It was found that this method would provide reasonable quantitative results when the tilting angle of the facet plane against the primary electron beam incidence is less than approximately 50°. Over 50°, R would generally give higher values. At 80° R would be 1.2–3.7 times larger than that at 0°. In this paper we propose a new method to compensate for this deviation. Through specimen tilting experiments using a flat surface, we found a deformation of total background shape at high tilting angles. It is interpreted by γ, a background intensity ratio at two energies (ex. 2000 eV and 3000 eV). It was found that γ obeys a simple equation of tilt angle θ, . Then, θ can be derived from the values of the background intensity ratios. The following relationship was also found between R0 and R where R0 and Rθ are peak‐to‐background ratios at 0 and θ degrees, respectively, and E is the Auger transition energy. Since θ can be derived, we can always connect the peak‐to‐background ratio at θ to that in the horizontal state. Thus, elimination of topographic effect would be possible.We believe that this scheme would contribute to quantitative Auger imaging.

Topographic compensation in auger electron spectroscopy.

Scanning Auger microprobe (SAM) images provide information on the elemental distribution of specimen sdurfaces, but the data are influenced by specimen topography. To climinate this effect, the peak to background ratio, (P-B)/B(=R), is often used instead of the net peak intensity, P-B. It was found that these mothods would provide reasonable quantitative results when the tilting angle of the facet plane against the primary electron beam incidence is less than approx. 50 degrees. Over 50 deg., the R would generally give higher values, and at 80 deg., the value is 1.23.7 times larger than that at 0 deg. We propose a new method to compensate for this deviation. Through spcimen tilting experiments, we found a deformation in total background shape at high tilting angles. It is interpreted by γ, a background intensity ratio at two energies (ex. 2000 eV and 3000 eV). Since, γ obeys a simple equation of tilt angle θ, γ(θ)=7×10-5θ2-2.92×10-3θ+1Then the θ can be derived the background intensity values. The following relationship was also found between R0 and RθR0=Rθ/[(1.47×10-3E+0.06) exp {6.1 × 10-4(θ-45)2} + 1]where R0 and Rθ are peak to background ratios at 0 and θ deg., respectively, and E is the Auger transition energy. Since θ can known, we can always get the peak to background ratio values converted to the horizontal state. Elimination of topographic effect would thus be possible.We believe that this scheme would contribute to quantitative Auger imaging.

Optical emission spectrometry with an inductively coupled radiofrequency argon plasma source and direct sample introduction from a graphite rod

Preliminary studies of analytical performance are described for an instrumental assembly in which microlitre volumes of liquid samples are applied to a graphite rod, desolvated and the rod is inserted axially directly into a continuously operating low-power inductively coupled argon plasma. Simplex optimisation of operating parameters has been undertaken for manganese to determine the most favourable signal to background intensity ratios and detection limits are reported for manganese, cadmium, cobalt, copper, iron, nickel and lead.

Application of the Grimm magnetic field glow-discharge source to the analysis of mild and alloyed steel

The magnetic field glow-discharge source (MFGDS) has been evaluated in the analysis of mild and alloyed steels. Its performance, as described by precision, line—background intensity ratio and the quality of calibration curves, was compared to results obtainable with the conventional Grimm glow-discharge source (GDS). The analytical performance was found to be comparable in the analysis of mild steels but difficulties, exhibiting themselves as the splitting of calibration curves, were encountered in the analysis of alloyed steels on account of their differing magnetic properties.

The nuclear reactor as a high intensity source for discrete gamma rays up to 11 MeV

Abstract The use of a nuclear reactor as a potential high-intensity source of discrete gamma rays for energies up to 11 MeV is discussed in the light of investigations undertaken. The advantages and disadvantages inherent in such sources are compared with those associated with other gamma sources for this energy region, such as, in particular, proton capture reactions. The following features indicate interesting possibilities in employment of sources: (a) a large variety of discrete gamma rays of various energies exists (there are about 10 lines between 3 and 11 MeV); (b) background is low (for background quanta above 4 MeV, the line to background intensity ratio ranges up to about 10); (c) collimation is good (the beam can be collimated along a 4 m path) and (d) intensity is very high (about a 1000-fold that of (p, γ)-sources in practice). The absolute intensity can with ease be calibrated to within 10%. Experimental details are given, e.g. of collimation, target container and target material, and an arrangement is proposed whereby an appreciable increase of line to background intensity can be attained.