Direct Determination Research Articles

Theories, models and frameworks to understand barriers to the provision of mobility-assistive technologies: a scoping review

ObjectivesThere is strong evidence that mobility-assistive technologies improve occupational performance, social participation, educational and employment access and overall quality of life in people with disabilities. However, people with disabilities still...

Data-driven modelling makes quantitative predictions regarding bacteria surface motility.

In this work, we quantitatively compare computer simulations and existing cell tracking data of P. aeruginosa surface motility in order to analyse the underlying motility mechanism. We present a three dimensional twitching motility model, that simulates the extension, retraction and surface association of individual Type IV Pili (TFP), and is informed by recent experimental observations of TFP. Sensitivity analysis is implemented to minimise the number of model parameters, and quantitative estimates for the remaining parameters are inferred from tracking data by approximate Bayesian computation. We argue that the motility mechanism is highly sensitive to experimental conditions. We predict a TFP retraction speed for the tracking data we study that is in a good agreement with experimental results obtained under very similar conditions. Furthermore, we examine whether estimates for biologically important parameters, whose direct experimental determination is challenging, can be inferred directly from tracking data. One example is the width of the distribution of TFP on the bacteria body. We predict that the TFP are broadly distributed over the bacteria pole in both walking and crawling motility types. Moreover, we identified specific configurations of TFP that lead to transitions between walking and crawling states.

Direct Determination of Absolute Radical Quantum Yields in Hydroxyl and Sulfate Radical-Based Treatment Processes

Direct Determination of Absolute Radical Quantum Yields in Hydroxyl and Sulfate Radical-Based Treatment Processes

Direct Extraction and Determination of Free Nicotine in Cigarette Smoke.

The accurate determination of the free nicotine content in cigarette smoke is crucial for assessing cigarette quality, studying harm and addiction, and reducing tar levels. Currently, the determination of free nicotine in tobacco products primarily relies on methods such as pH calculation, nuclear magnetic resonance (NMR) spectroscopy, headspace solid-phase microextraction (HS-SPME), and traditional solvent extraction. However, these methods have limitations that restrict their widespread application. In this study, the free nicotine in cigarette smoke was directly extracted by using cyclohexane according to the traditional solvent extraction method and detected via gas chromatography-mass spectrometry. Compared with the traditional two-phase solvent extraction, our experimental method is easy to execute and eliminates the influence of aqueous solutions on the original distribution of nicotine in cigarette smoke particulate matter. Furthermore, the presence of protonated nicotine in tobacco does not affect the determination. Compared with HS-SPME and NMR spectroscopy, our approach, which involves solvent extraction followed by chromatographic separation and instrumental detection, offers simplicity, improved precision, better detection limits, and reduced interference during the instrumental detection stage. The standard addition recoveries in the conducted experiment ranged from 96.2% to 102.5%. The limit of detection was 2.8 μg/cig, and the correlation coefficient (R2) for the quadratic regression of the standard curve exceeded 0.999. The relative standard deviation for parallel samples was between 1.7% and 3.4% (n = 5), fully meeting the requirements for the determination of free nicotine in cigarette smoke. Analysis of cigarette samples from 38 commercially available brands revealed that the content of free nicotine ranged from 0.376 to 0.716 mg/cig, with an average of 0.540 mg/cig, and free nicotine accounted for 39.1%-88.8% of the total nicotine content.

Innovative methods for determination of 90Sr and 137Cs in soil samples based on effective radiochemical separation and beta-counting

– Innovative methods were developed for direct 90Sr and 137Cs determination in soils by radiochemical separation and β-counting. Studies focused on: (1) the suitability of PEG to remove silica by coating, (2) the decontamination effect of Cs from 40K, (3) iron elimination with Microthene-TOA column instead of oxalate complex, and (4) the effective separation of Y and Sr from Pb by a Microthene-TOA column which made the direct 90Sr determination possible in less time with just one resin-column. The methods were validated by analysing the IAEA reference materials, showing good agreement with the recommended values. The methods were used to determine 90Sr and 137Cs in 21 soil samples. The obtained 90Sr concentrations in the soils were in the range of 0.46–2.95 Bq kg−1, while 137Cs 1.24–35.5 Bq kg−1. The yields of yttrium and caesium were 73.4 ± 8.0% and 79.0 ± 9.1%, respectively.

Exploring the effects of AI literacy in teacher learning: an empirical study

As most practitioners (including teachers) do not know how AI functions and cannot make full use of AI in education, there is an urgent need to investigate teachers’ intentions to learn AI and related determinants so as to promote their AI learning. This study collected survey data from a total of 318 K-12 teachers from sixteen provinces or municipalities in China. A two-step structural equation modeling approach was performed to analyze the data. Our findings show that K-12 teachers’ perceptions of the use of AI for social good and self-efficacy in learning AI are two direct determinants of behavioral intentions to learn AI, while awareness of AI ethics and AI literacy are two indirect ones. AI literacy has a direct impact on perceptions of the use of AI for social good, self-efficacy in learning AI and awareness of AI ethics and has an indirect impact on behavioral intentions to learn AI. This study represents one of the earliest attempts to empirically examine the power of AI literacy and explore the determinants of behavioral intentions to learn AI among K-12 teachers. Our findings can theoretically and practically contribute to the virgin field of K-12 teachers’ AI learning.

An enhanced direct position determination of non-circular sources via sparse Bayesian inference and grid refinement strategy

In this study, an off-grid sparse Bayesian inference (OGSBI) based direct position determination (DPD) algorithm is investigated. Existing SBI-based DPD algorithms are confronted with the challenge of excessive computational loads and lack of consideration for non-circular (NC) signals. To address these limitations, we present an enhanced OGSBI-based DPD algorithm for multiple non-circular sources. By utilizing the conjugate information of the NC signals, we expand the dimensionality of the data matrix to achieve a significant improvement in the localization performance. Additionally, a grid refinement strategy is developed to alleviate the computational loads, which involves an initial search to determine the approximate source locations, followed by fine localization using a denser grid. Moreover, the computational complexity and Cramér-Rao lower bound are derived to provide a comprehensive analysis of the proposed algorithm. Numerical simulations demonstrate the superiority of the proposed algorithm in terms of both localization accuracy and computational efficiency.

Study on Influencing Factors of Two-Body Parallel Separation

In the parallel separation process of two bodies, the initial velocity state and the surrounding flow field environment jointly determine the motion state of the two bodies, which is a direct determinant of the separation process safety. To study the two-body parallel separation process and the influencing factors, this paper adopts the dynamic mesh technique and finite volume method to solve the Navier-Stokes equations and study the influence of the initial separation clearance and velocity state on the separation process. The results show that: with the increase of the initial separation clearance, the separation process safety of two bodies under the action of complex flow field may decrease; the effect is poor when the two bodies are separated at rest, and a suitable initial velocity state is beneficial to improve the separation safety to achieve the purpose of safe separation, and the two bodies show different separation processes under different initial velocity states.

Multiline observations of hydrogen, helium, and carbon radio-recombination lines toward Orion A: A detailed dynamical study and direct determination of physical conditions

We present a study of hydrogen, helium, and carbon millimeter-wave radio-recombination lines (RRLs) toward ten representative positions throughout the Orion Nebula complex, using the Yebes 40m telescope in the Q band (31.3 GHz to 50.6 GHz) at an angular resolution of about $45 (sim 0.09\,pc). The observed positions include the Orion Nebula (M42) with the Orion Molecular Core 1, M43, and the Orion Molecular Core 3 bordering on NGC 1973, 1975, and 1977. While hydrogen and helium RRLs arise in the ionized gas surrounding the massive stars in the Orion Nebula complex, carbon RRLs stem from the neutral gas of the adjacent photo-dissociation regions (PDRs). The high velocity resolution ($0.3\ $) enables us to discern the detailed dynamics of the RRL emitting neutral and ionized gas. We compare the carbon RRLs with SOFIA/upGREAT observations of the ii m $ line and IRAM 30m observations of the 13CO (J=2-1) line (the complete map is presented here for the first time). We observe small differences in peak velocities between the different tracers, which cannot always be attributed to geometry but potentially to shear motions. Using the far-infrared ii and ii intensities with the carbon RRL intensities, we can infer physical conditions (electron temperature $T_ e $ and electron density $n_ e $, converted to hydrogen nuclei density $n_ H $ by dividing by the carbon gas-phase abundance $ A C $) in the PDR gas using nonlocal thermal equilibrium excitation models. For positions in OMC1, we infer $n_ e cm^ $ and $T_ e K $. On the border between OMC1 and M43, we observe two gas components with $n_ e cm^ $ and $n_ e cm^ $, and $T_ e K $ and $T_ e K $. In M43, we infer $n_ e cm^ $ and $T_ e K $. The Extended Orion Nebula southeast of OMC1 is characterized by $n_ e cm^ $ and $T_ e K $, while OMC3 has $n_ e cm^ $ and $T_ e K $. Our observations are sensitive enough to detect faint lines toward two positions in OMC1, in the BN/KL PDR and the PDR close to the Trapezium stars, that may be attributed to RRLs of C$^+$ or O$^+$. In general, the RRL line widths of both the ionized and neutral gas, as well as the ii and 13CO line widths, are broader than thermal, indicating significant turbulence in the interstellar medium, which transitions from super-Alfv\'enic and subsonic in the ionized gas to sub-Alfv\'enic and supersonic in the molecular gas. At the scales probed by our observations, the turbulent pressure dominates the pressure balance in the neutral and molecular gas, while in the ionized gas the turbulent pressure is much smaller than the thermal pressure.

Cross-border Product Payments in Sub-Saharan Africa! How MSMEs React to PAPSS as E-payment Innovation: Moderating Role of Experience

The purpose of the study is to evaluate micro, small and medium enterprises’ (MSMEs) reaction to the pan-African payment and settlement system (PAPSS). The new cross-border e-payment technology is designed to facilitate cross- border instant payments, motivate cross-border businesses and promote sub-Saharan African trades which have been a real problem following the involvement of third currency, untimely payment and regulations that impact payments across borders. The study is important because of the non-existence of empirical results on what motivates MSMEs’ intention to use it and how the experience might impact the intention to use PAPSS. Thus, the study considered the impact of MSMEs’ previous experience on e-payment as a moderating influence on intention to use PAPSS. An adapted questionnaire that was structured on 7-point Likert scale was used in the survey to collect data from MSMEs in Nigeria. Structural equation modelling and the Hayes process for moderation were used in the analysis. The authors learned that ease of use is the strongest indirect determinant of intention to use PAPSS while perceived compatibility is the strongest direct determinant of intention to use PAPSS. Further, the authors discovered the important role of the simplicity of the innovation and its compatibility with users’ characteristics in promoting intention to use. The level of experience is confirmed to be significant in moderating intention to use PAPSS. Therefore, deeper involvement of the apex banks and commercial banks in communicating simplicity is paramount to achieve significant progress, while the services of tech experts and professionals can be utilised to provide periodic information to business owners through organised TV and radio programmes. Notably, this is a novel study that focuses on new cross-border payments in sub-Saharan Africa.

Two novel iterative approaches for improved LSPIA convergence

This paper introduces two improved variants of the least squares progressive-iterative approximation (LSPIA) by leveraging momentum techniques. Specifically, based on the Polyak's and Nesterov's momentum techniques, the proposed methods utilize the previous iteration information to update the control points. We name these two methods PmLSPIA and NmLSPIA, respectively. The introduction of momentum enhances the determination of the search directions, leading to a significant improvement in convergence rate. The geometric interpretations of PmLSPIA and NmLSPIA are elucidated, providing insights into the underlying principles of these accelerated algorithms. Rigorous convergence analyses are conducted, revealing that both PmLSPIA and NmLSPIA exhibit faster convergence than LSPIA. Numerical results further validate the efficacy of the proposed algorithms.

A Chemometric–Assisted Voltammetric Method for Simultaneous Determination of Acetaminophen and Diclofenac

AbstractDiclofenac (DCF) and Acetaminophen (ACT) are among the most important nonsteroidal anti–inflammatory drugs (NSAIDs) that sought after for their antipyretic, analgesic, and anti‐inflammatory properties. In addition, ACT and DCF show synergistic activity toward pain relief. Therefore, appropriate analytical strategies are required for the simultaneous quantification of these NSAIDs in prescription drugs. This study introduces a method for the direct and simultaneous determination of ACT and DCF using the voltammetric approach in conjunction with chemometric tools such as partial least squares (PLS) and genetic algorithm–multiple linear regressions (GA−MLR). The calibration set was established using differential pulse voltammetry for 25 distinct mixtures of ACT and DCF. The calibration curve exhibited linearity within the concentration ranges of 0.1–1000 μM for ACT and 0.1–100 and 100–1000 for DCF. The effectiveness of chemometric methods was evaluated by analyzing synthetic mixtures of ACT and DCF and applying these methods to real samples containing a commercial pharmaceutical preparation of the specified drugs. Both methods yielded favorable results.

General minimum velocity threshold for one-repetition maximum prediction in two squat variations: does the load–velocity profiling approach matter?

Abstract Purpose Most studies examining the predictive value of the load–velocity relationship in determining one-repetition maximum (1RM) in the back squat implemented its direct determination to enable testing movement velocity within a predetermined set of relative loads (e.g., 50, 60, 70, 80, and 90% 1RM). We determined whether a different approach of load–velocity profiling affects the accuracy of estimating 1RM. Methods Predictions based on a practical 2-point approach (no pre-determination of 1RM) were compared to those obtained with the conventional multipoint and 2-point approach (pre-determination of 1RM). 1RM was estimated relying on a reference minimum velocity threshold (MVT) of 0.3 ms−1. Analyses were conducted for separate back-squat variations (n = 13 Smith machine; n = 13 free-weight). Slopes and y-intercepts were compared. The accuracy of 1RM prediction was determined by contrasting actual vs. predicted 1RM values. Results The individual MVT did not differ from the general 0.3 ms−1 value in either back-squat variation. Slopes and y-intercepts were similar between all determination approaches. For the Smith machine, estimated 1RM did not differ from the actual value with either approach (mean misestimate: −1.83 to 0.02 kg). However, the limits of agreement were wide (~ 12 kg) and the absolute percent error was significantly different from 0 with all approaches (p < 0.05). Conclusion 1RM can be estimated with similar accuracy with all profiling methods, irrespectively of the back squat variation. However, the free-weight variation displays higher systematic and random errors. It can be concluded that the wide limits of agreement preclude accurate 1RM estimations on an individual basis.

Highly sensitive and accurate measurement of underivatized phosphoenolpyruvate in plasma and serum via EDTA-facilitated hydrophilic interaction liquid chromatography–tandem mass spectrometry

Phosphoenolpyruvate (PEP) is an essential intermediate metabolite that is involved in various vital biochemical reactions. However, achieving the direct and accurate quantification of PEP in plasma or serum poses a significant challenge owing to its strong polarity and metal affinity. In this study, a sensitive method for the direct determination of PEP in plasma and serum based on ethylenediaminetetraacetic acid (EDTA)-facilitated hydrophilic interaction liquid chromatography–tandem mass spectrometry was developed. Superior chromatographic retention and peak shapes were achieved using a zwitterionic stationary-phase HILIC column with a metal-inert inner surface. Efficient dechelation of PEP–metal complexes in serum/plasma samples was achieved through the introduction of EDTA, resulting in a significant enhancement of the PEP signal. A PEP isotopically labelled standard was employed as a surrogate analyte for the determination of endogenous PEP, and validation assessments proved the sensitivity, selectivity, and reproducibility of this method. The method was applied to the comparative quantification of PEP in plasma and serum samples from mice and rats, as well as in HepG2 cells, HEK293T cells, and erythrocytes; the results confirmed its applicability in PEP-related biomedical research. The developed method can quantify PEP in diverse biological matrices, providing a feasible opportunity to investigate the role of PEP in relevant biomedical research.

Comparative analysis of kinetic model-fitting methods and selection priority for horse manure pyrolysis

The diverse origins of biomass wastes provide a constraint on the practical application of pyrolysis, as it leads to uncertain chemical reactions, feedstock conversion, and energy consumption. Various model-fit methods are available to identify the decomposition kinetics, however, limited studies have compared the reliability and accuracy of those kinetic models. This work compared five different kinetic models, two based on model-fit methods (Coats–Redfern (CR), Kennedy-Clark (KC) and three based on the application forms of Criado Master Plots (CMP I, CMP II and CMP III). The mass loss data from the pyrolysis of horse manure (HM) through a thermogravimetric analyser was used as a biomass sample for evaluation. Results demonstrated that all five model-fit methods report different kinetics data. Although the model-fit methods (CR and KC) allow a direct determination of kinetic triplets, the accuracy of data is lower. The CMP-II and CMP-III methods (incorporating model-free data in the model-fit methods) showcase multi-step chemical kinetics and better describe the decomposition behavior of HM due to its multi-compositional properties. To obtain kinetic triplets with enhanced accuracy, it is recommended to incorporate model-free data into the model-fit method. Improved precision of the kinetics data is essential for developing experimental parameters and optimizing the process. Future research should include the selection criteria of model-fit methods shown in this study to improve the accuracy of kinetic data.

Rapid and sensitive determination of trace Cd in carbonate samples using direct solid sampling electrothermal vaporization atomic absorption spectrometry

The accurate determination of cadmium (Cd) hosted and accumulated in sedimentary carbonate remains challenging due to its low concentration (ng·g−1) and complex matrix. Conventional methods, such as inductively coupled plasma mass spectrometry (ICP-MS) and graphite furnace atomic absorption spectrometry (GF-AAS), which typically rely on liquid sampling and sample digestion, are tedious, labor-intensive and time-consuming. In this study, a rapid and sensitive method for the direct determination of carbonate-hosted Cd was developed based on solid sampling electrothermal atomic absorption spectrometry (SS-ETV-AAS). This method eliminates the need of acid digestion procedure, allowing the entire analysis, including sample preparation, to be completed within 10 min. To minimize the carbonate matrix effect, ethylene diamine tetra acetic acid disodium salt (EDTA-2Na) was proposed as matrix modifier to facilitate the release of Cd, enabling fast and accurate determination of trace Cd in carbonate samples. Under optimized conditions, the Cd detection limits was found to be as low as 0.17 ng·g−1, and repeatability (relative standard deviation, RSD) was better than 8 % (n = 7). The accuracy of the proposed SS-ETV-AAS was verified by analyzing five carbonate certified reference materials (GBW07127, GBW07129, GBW07130, GBW07135 and JDo-1), two soil certified reference materials (GBW07404a, GBW07405), as well as several actual carbonate samples. All these results demonstrate that the proposed SS-ETV-AAS method provides a simple, rapid and sensitive approach for measuring trace Cd in carbonates.

High sensitivity atomic fluorescence spectroscopy for the detection of AsIII by selective electrolysis of arsenic on nanoflowers-like Fe/NFE

Modified electrosynthetic sample introduction technique is a reliable means of solving the problem of high sensitivity analysis of trace arsenite. This article attempts to achieve selective electroreduction of AsIII through the construction of electrode surfaces with different structures and materials from the perspective of interface reactions. Among the four transition metal modifiers, the iron modified nickel foam electrode with nano-flower structure documented higher efficiency in inducing arsenic reduction and better species selectivity. Systematic electrochemical and spectroscopic tests suggest that strong adsorption effect between Fe and AsIII, appropriate hydrogen evolution potential, and catalytic activity jointly promote efficient electroreduction of AsIII. Optimization based on electrode materials and electrolysis conditions, with high sensitivity, wide linear range (0.1–50 μg L−1), and excellent species selectivity, this paper offers an efficient and economic sample introduction method for trace AsIII/V selective atomic spectroscopy direct determination.

Eco-friendly assessment of turmeric-assisted approach in developing and validating a method for the quantification of atropine sulphate in bulk and tablet dosage form using UV–Visible spectrophotometry

The literature review uncovers the quantitative analysis of atropine sulfate using either direct determination methods or chemical derivatization techniques. However, in order to innovate upon traditional analytical approaches, an alternative method for estimating atropine sulfate was developed using the natural pH indicator turmeric. An economical and accurate chemical derivatization technique utilizing turmeric powder was devised for the quantification of atropine sulphate in both bulk and tablet dosage forms. The maximum absorption was identified at 600 nm, with a linear range spanning 0.5 – 2.5 µg/ml. The correlation coefficient (r) was calculated to be 0.9997±0.0006, demonstrating an exceptional level of linearity. Rigorous validation of the proposed method affirmed its simplicity, precision, accuracy, and rapidity in determining atropine sulphate in both its pure form and dosage forms. Additionally, the developed approach underwent assessment through the Analytical GREEnness Metric (AGREE), Green Analytical Procedure Index (GAPI), and Analytical Eco-scale Assessment (AES). The AGREE and AES scores were observed to be 0.78 and 96, respectively, signaling highly favorable eco-friendly outcomes.

Rapid elucidation of agonist-driven regulation of the neurokinin 1 receptor using a GPCR phosphorylation immunoassay

Agonist-induced phosphorylation is a crucial step in the activation/deactivation cycle of G protein-coupled receptors (GPCRs), but direct determination of individual phosphorylation events has remained a major challenge. We have recently developed a bead-based immunoassay for the quantitative assessment of agonist-induced GPCR phosphorylation that can be performed entirely in 96-well plates, thus eliminating the need for western blot analysis. In the present study, we adapted this assay to three novel phosphosite-specific antibodies directed against the neurokinin 1 (NK1) receptor, namely pS338/pT339-NK1, pT344/pS347-NK1, and pT356/pT357-NK1. We found that substance P (SP) stimulated concentration-dependent phosphorylation of all three sites, which could be completely blocked in the presence of the NK1 receptor antagonist aprepitant. The other two endogenous ligands of the tachykinin family, neurokinin A (NKA) and neurokinin B (NKB), were also able to induce NK1 receptor phosphorylation, but to a much lesser extent than substance P. Interestingly, substance P promoted phosphorylation of the two distal sites more efficiently than that of the proximal site. The proximal site was identified as a substrate for phosphorylation by protein kinase C. Analysis of GPCR kinase (GRK)-knockout cells revealed that phosphorylation was mediated by all four GRK isoforms to similar extents at the T344/S347 and the T356/T357 cluster. Knockout of all GRKs resulted in abolition of all phosphorylation signals highlighting the importance of these kinases in agonist-mediated receptor phosphorylation. Thus, the 7TM phosphorylation assay technology allows for rapid and detailed analyses of GPCR phosphorylation.

Effect of Co-adsorbed Guest Adsorbates on the Separation of Ethylene/Ethane Mixtures on Metal-Organic Frameworks with Open Metal Sites.

Direct determination of the equilibrium adsorption and spectroscopic observation of adsorbent-adsorbate interaction is crucial to evaluate the olefin/paraffin separation performance of porous adsorbents. However, the experimental characterization of competitive adsorption of various adsorbates at atomic-molecular level in the purification of multicomponent gas mixtures is challenging but rarely conducted. Herein, solid-state NMR spectroscopy is employed to examine the effect of co-adsorbed guest adsorbates on the separation of ethylene/ethane mixtures on Mg-MOF-74, Zn-MOF-74 and UTSA-74. 1H MAS NMR spectra facilitates the determination of equilibrium uptake and adsorption selectivity of ethylene/ethane in ternary mixture systems. The co-adsorption of H2O and CO2 significantly leads to the degradation of the ethylene uptake and ethylene/ethane selectivity. The detailed host-guest and guest-guest interactions are unraveled by 2D 1H-1H spin diffusion homo-nuclear correlation and static 25Mg NMR experiments. The experimental results verify H2O coordinated on the open metal sites can supply a new adsorption site for ethylene and ethane. The effects of guest adsorbates on the adsorption capacity and adsorption selectivity of the ethylene/ethane mixtures are in the following order: H2O > CO2 > O2. This work provides a direct approach for exploring the equilibrium adsorption and detailed separation mechanism of multicomponent gas mixtures using MOFs adsorbents.