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EDXRF for elemental determination of nanoparticle-related agricultural samples
摘要： The number of studies dealing with nanoparticles (NPs) and plants has increased. They subsidize the advances of agriculture in the 21st century; however, so far, beneficial as well as detrimental results have been reported. In this context, analytical tools for monitoring macronutrients and micronutrients in plants exposed to NPs, with adequate performance and low cost, are required. This work assesses the use of energy-dispersive X-ray fluorescence (EDXRF) spectrometry for elemental content evaluation in NP-containing agricultural samples. For Phaseolus vulgaris (common bean) seedlings treated with ZnO NP, CuO NP, and Fe3O4 NP, the limits of detection (LODs) were 0.4 mg kg?1 for Zn and Cu and 0.6 mg kg?1 for Fe after dry-ashing digestion, thus being suitable for NP oxide monitoring in seed priming. For submicron suspension fertilizers, Mn, Cu, and Zn were quantified as thin films after sample dilution. The LODs for Mn, Cu, and Zn were 0.09, 0.1, and 0.08 mg L?1, respectively. Finally, for P. vulgaris plants exposed to 300-nm ZnO NP, we monitored P, S, K, Ca, and Zn directly in powdered leaves, whose LODs ranged from 1.3 to 27 mg kg?1. No critical spectral interference was observed, and notable repeatability and suitable trueness were found in the cases of studies. EDXRF revealed itself a simple, fast, and reliable alternative to evaluate the elemental content in suspensions or the uptake of NP by plants.
关键词： agriculture,X-ray fluorescence,elemental determination,EDXRF,nanoparticles
更新于2025-09-23 15:22:29
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Ratiometric fluorescence imaging for sodium selenite in living cells
摘要： Sodium selenite as a common selenium-containing agent has been extensively studied for human health, especially cancer prevention and treatment. However, precisely evaluating the dynamic changes of sodium selenite at cellular and molecular level in these pharmacological and pathophysiological studies is still challenging. Developing the chemical tools that enable the quantification of sodium selenite in vivo with high spatial and temporal fidelity thus can provide an efficient solution to this challenge. Here, we report the design, synthesis and biological evaluation of ratiometric sodium selenite fluorescent probe (HBTN-Se) for quantitative ratiometric fluorescence imaging of sodium selenite concentration fluctuations in living cells. A strategy for sodium selenite quantification has been achieved effectively through using a highly selective, rapid and biocompatible hydroxyl-deprotecting reaction. The ratiometric fluorescence imaging with HBTN-Se is constructed to precisely monitor changes in sodium selenite levels in living cells. Moreover, HBTN-Se is capable of visualizing differences in sodium selenite levels between normal cells and cancer cells, establishing the utility of this ratiometric detection platform for assessing the correlation between physiological effects of sodium selenite and its levels in living cells.
关键词： Quantitative determination,Fluorescent probe,Sodium selenite,Ratiometric fluorescence imaging
更新于2025-09-23 15:22:29
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[IEEE 2018 Wave Electronics and its Application in Information and Telecommunication Systems (WECONF) - Saint-Petersburg, Russia (2018.11.26-2018.11.30)] 2018 Wave Electronics and its Application in Information and Telecommunication Systems (WECONF) - The Problem of Determination of Coordinates of Unmanned Aerial Vehicles Using a Two-Position System Ground Radar
摘要： the features of modern methods for detecting and determining the coordinates of small unmanned aerial vehicles using a two-position ground radar system are considered. It is proposed to use the methods developed for multi-sensor radar systems. The limitations and advantages of the two-position radar system are shown. The main potential characteristics of the system and the corresponding restrictions on the conditions of its effective application are determined. Potential characteristics are obtained by simulation methods using mathematical models built on the basis of experimental data.
关键词： two-position system,radar system,detection of objects,trajectory coordinates,unmanned aerial vehicle,determination of coordinates,air object,joint information processing
更新于2025-09-23 15:22:29
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Analysis of Differential Correction Techniques for Orbit Determination Interferometry
摘要： Orbit determination errors are expected to be a major threat for obtaining focused images on Geostationary Synthetic Aperture Radar (GeoSAR) missions. A ground-based interferometer system is presently being under research to determine the satellite orbit with the required precision. However, from that system, it must be addressed which orbit determination techniques offer better results for that purpose. This paper provides a comparison between two differential correction techniques: the least squares (LS) and the extended Kalman filter (EKF) techniques.
关键词： Interferometer,GeoSAR,Differential Correction Techniques,Orbit Determination
更新于2025-09-23 15:22:29
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Enzymatic method of urea determination in LTCC microfluidic system based on absorption photometry
摘要： In this paper a novel microanalytical system based on absorption photometry for urea determination in small-volume biological samples is described. The developed microsystem with built-in microreactor with urease immobilised on its surface was fabricated using low temperature co-fired ceramics (LTCC) technology. For detection of the ammonium ions – product of urea hydrolysis, the modified Berthelot’s reaction was applied and conditions of this reaction were optimised in a way to be suitable for analysis in microsystems and for particular application, with special regards to very small alternation of urea concentration in culture medium. The best results were obtained for reagent R1 composed of: 180 mM sodium salicylate, 15 mM sodium nitroprusside, 2 mM EDTA in phosphate buffer solution of pH 7 and reagent R2 containing 16.9 mM sodium hypochlorite in phosphate buffer solution of pH 12. Linear concentration range of urea detection with the use of the developed LTCC microfluidic system for the selected flow rate of 4 μl/min, was in the range up to 1 mM, and the calculated lower limit of detection – 0.002 mM. The developed microsystem enables urea determination in samples of post-culture medium and of cells lysates of minimised volume c.a. 1 μl. Preliminary studies related to determination of urea in real samples, performed using hepatic cells lysates and post-culture medium were successful. As reference methods, commercially available tests were applied. The determined urea concentration measured by means of the QuantiChrom? and BioMaxima test and by the developed method based on the LTCC microanalytical system differs by c.a. 9% and 2% respectively. To the best of our knowledge, this is the first urea analysis microsystem for use in cells culture studies characterised by: the smallest volume of sample – 1 μl, long lifetime with stable response - reduced by 14%, through experimental time span of 30 days as well as suitability for quasi-monitoring of cells in vitro with sampling rate - 6 samples per hour.
关键词： LTCC technology,enzymatic microreactor,microfluidic systems,lab-on-a-chip,enzymatic urea determination,absorption photometry
更新于2025-09-23 15:22:29
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Structural identification of silicene on the Ag(111) surface by atomic force microscopy
摘要： Silicene is a two-dimensional atomic layer material with buckled honeycomb arrangements of Si atoms. The diversity of those arrangements, which expands its potential applications, makes it dif?cult to determine its structure in any particular case. In this paper, we show that atomic force microscopy (AFM) has the capability of structural determination of unknown phases of silicene. We carried out an AFM observation of (√13×√13)R13.9? silicene of unknown structures on Ag(111). Remarkably, it was shown that all constituent Si atoms forming a honeycomb lattice can be resolved by AFM whereas scanning tunneling microscopy (STM) can image only the topmost Si atoms. High-resolution AFM imaging allowed us to identify two types of buckled structure of (√13×√13)R13.9? silicene on Ag(111), which had not been previously discriminated. The structure models obtained by theoretical simulation reproduced AFM images as well as previous STM images. In addition, the mechanism of high-resolution AFM imaging was elucidated by force spectroscopy combined with ?rst-principles calculations. Namely, attractive interaction with the tip pulls up buckled down Si atoms, causing local ?ips of the buckled structures.
关键词： structural determination,buckled structures,Ag(111) surface,silicene,atomic force microscopy
更新于2025-09-23 15:21:21
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Speciation and Determination of Ionic and Trace-Level Colloidal Silver in Selected Personal Care Products by Thermal Lens Spectrometry
摘要： The collinear dual beam thermal lens spectrometric (TLS) detection in batch mode (BM), as well as combined with the flow injection analysis (FIA), was applied to determine the colloidal silver in personal care products available in the public pharmacies and declared by producers to contain nanosilver at the level of 5-30 μg ml-1. It was found, that the examined samples contain mainly ionic silver (99% or more), whereas the colloidal form of silver is at the level of less than 1 μg ml-1. The TLS methods were confirmed to be fast, precise, highly accurate and highly sensitive with limits of quantitation of 0.30 ng ml-1 and 1.50 ng ml-1 and relative standard deviations not higher than 1.2% and 6.0% for BM- and FIA-TLS configuration, respectively. The developed TLS methods have nearly 60 times lower LOQ values concerning the colloidal silver determination than the classical spectrophotometric method. To verify the obtained results of the real sample analysis the total amount of ionic silver was determined by the use of ICP-OES technique.
关键词： Thermal lens spectrometric determination,Personal care products,Flow injection analysis,Silver nanoparticles,Colloidal silver
更新于2025-09-23 15:21:21
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Analysis of High-Temperature Carrier Transport Mechanisms for High Al-Content Al <sub/>0.6</sub> Ga <sub/>0.4</sub> N MSM Photodetectors
摘要： We propose a generative model for robust tensor factorization in the presence of both missing data and outliers. The objective is to explicitly infer the underlying low-CANDECOMP/PARAFAC (CP)-rank tensor capturing the global information and a sparse tensor capturing the local information (also considered as outliers), thus providing the robust predictive distribution over missing entries. The low-CP-rank tensor is modeled by multilinear interactions between multiple latent factors on which the column sparsity is enforced by a hierarchical prior, while the sparse tensor is modeled by a hierarchical view of Student-t distribution that associates an individual hyperparameter with each element independently. For model inference under a fully Bayesian treatment, which can effectively prevent the overfitting problem and scales linearly with data size. In contrast to existing related works, our method can perform model selection automatically and implicitly without the need of tuning parameters. More specifically, it can discover the groundtruth of CP rank and automatically adapt the sparsity inducing priors to various types of outliers. In addition, the tradeoff between the low-rank approximation and the sparse representation can be optimized in the sense of maximum model evidence. The extensive experiments and comparisons with many state-of-the-art algorithms on both synthetic and real-world data sets demonstrate the superiorities of our method from several perspectives.
关键词： tensor factorization,robust factorization,tensor completion,video background modeling,variational Bayesian (VB) inference,Rank determination
更新于2025-09-23 15:21:01
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On the imprecisions that may be induced when applying the Blaugrund approximation for the analysis of Doppler-shift attenuation lifetime measurements
摘要： It is shown that the Blaugrund approximation could have led to some imprecise lifetime determinations in the past which used the Doppler-shift attenuation method (DSAM). Comparison with Monte Carlo simulations of the slowing-down process show that there is not an easy way to judge using them on the reliability of old data.
关键词： Lineshapes analysis in DSAM measurements,Monte Carlo simulations,Lifetime determination,Blaugrund approximation
更新于2025-09-23 15:21:01
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Carbon quantum dots originated from chicken blood as peroxidase mimics for colorimetric detection of biothiols
摘要： Carbon quantum dots (CQDs) were prepared from chicken blood by hydrothermal method, which could catalyze the oxidation of 3, 3′, 5, 5′-tetramethylbenzidine (TMB) in the presence of H2O2 to generate the blue oxidized TMB (ox-TMB) with a strong absorption peak at 652 nm. However, the introduction of biothiols could induce the reduction of ox-TMB, leading to shallower blueness and lower absorbance. Based on this fact, a convenient and sensitive colorimetric method for detection of biothiols using CQDs as peroxidase mimics was established. Several factors, such as acidity, temperature, incubating time, CQDs dosage, H2O2 and TMB concentrations, which might influence the response of the analysis signal, were optimized by taking cysteine (CySH) as an example. Under the selected conditions, sensitive detection of biothiols was achieved, and the limits of detection (LOD) for CySH, glutathione (GSH), and homocysteine (HcySH) were 0.4, 0.6, and 0.9 μM respectively. This method was successfully applied for the determination of CySH in human serum samples with the recovery of 91.5%–109.3%, indicating the potential application of this method for biothiols sensing in real samples.
关键词： Determination,Carbon quantum dots,Peroxidase mimics,Colorimetry
更新于2025-09-23 15:21:01