Hasil untuk "Analytical chemistry"

Oriol Sans-Planell, Nikolay Kardjilov, Ingo Manke et al.

The development of high-energy density solid-state batteries is critical for the achievement of carbon neutrality goals and the advancement of clean energy. Still, the fundamental understanding of lithium transport mechanisms and degradation processes remains limited. Current characterisation methods face significant challenges in studying these complex systems, particularly due to the difficulty of detecting lithium dynamics in three-dimensional battery architectures in operando conditions. Here we present the ANISSA (Advanced Neutron Imaging for Solid-State batteries in Action) project, an integrated experimental framework combining high-resolution neutron and X-ray imaging techniques to research coupled electro-chemo-mechanical processes in lithium-based energy storage systems.

Eman A. Bahgat, Hanaa Saleh, Islam M. Darwish et al.

Esther Santamaría, Naroa Lizarreta, Susana Vílchez et al.

Pullulan is a polysaccharide that has attracted the attention of scientists in recent times as a former of edible films. On the other hand, its use for the preparation of hydrogels needs more study, as well as the formation of pullulan microcapsules as active ingredient release systems for the food industry. Due to the slow gelation kinetics of pullulan with sodium trimetaphosphate (STMP), capsules cannot be formed through the conventional method of dropping into a solution of the gelling agent, as with other polysaccharides, since the pullulan chains migrate to the medium before the capsules can form by gelation. Pullulan microcapsules have been obtained by using inverse water-in-oil emulsions as templates. The emulsion that acts as a template has been characterized by monitoring its stability and by optical microscopy, and the size of the emulsion droplets has been correlated with the size of the microcapsules obtained, demonstrating that it is a good technique for their production. Although some flocs of droplets form, these remain dispersed during the gelation process and two capsule size distributions are obtained: those of the non-flocculated droplets and the flocculated droplets. The microcapsules have been evaluated as vitamin C release systems, showing zero-order release kinetics for acidic pH and Fickian mechanism for neutral pH. On the other hand, the microcapsules offer good protection of vitamin C against oxidation during an evaluation period of 14 days.

Xingchen Zhou, Shengjie Chen, Yanhua Zhang et al.

Manganese dioxide has been significantly utilized in zinc ion batteries (ZIBs). However, in the rechargeable battery system, the manganese dioxide cathode suffers from poor conductivity, volume expansion, and substance dissolution, resulting in low capacity and poor stability. Herein, a 3D frame structure MnO2@CNTs cathode is proposed. In this system, the electrodeposited spherical MnO2 is anchored and interlinked via the in‐situ growth carbon nanotubes (CNTs) onto the carbon cloth. Benefiting the unique 3D frame structure, the MnO2 structure crush problem and the pathway of the electrons and ions are dramatically improved. The optimized MnO2@CNTs cathode demonstrate a high capacity of 256.35 mAh g−1 at 0.1 A g−1 and exceptional cycling stability. Furthermore, in‐situ Raman spectroscopy elucidates the energy storage mechanism of aqueous ZIBs (AZIBs). Moreover, COMSOL finite elements analysis demonstrates that the petal edge‐rich nanostructures of MnO2@CNTs generate a localized high electric field under constant current, accelerating ion/electron transfer. This work explains the rationale for CNTs to improve the properties of MnO2 cathodes, providing a new perspective for the design of high‐performance batteries.

Yiming Hu, Qi Meng, Mengmeng Li et al.

Abstract Historic districts play an important role in urban planning and protection. While previous research on soundscapes has focused on acoustic comfort or preferences in these districts, the aspect of authenticity has been somewhat overlooked. Therefore, this study proposes a methodology for constructing soundscapes that enhance the authenticity of such districts. Using the grounded theory approach, we identified four key components for enhancing authenticity via soundscapes: the aim of soundscape design, physical and cultural characteristics of soundscapes, the effects of soundscapes, and the influence of spatial characteristics on soundscapes. A theoretical framework was developed to illustrate the enhancement of authenticity in historic districts via soundscapes. To verify the applicability and advancement of the proposed framework, it was compared with methodologies and steps obtained from previous soundscape research in historic districts. This study underscores the significance of soundscape design in creating authenticity in historic districts, thereby contributing to the development of soundscape design in historic districts and offering sustainable solutions for the protection and renewal of urban cultural heritage.

Laxmi Suresh Babu, M Janarthanan Pillai

This research aimed to examine the association of job engagement among dental faculties in Kerala with certain sociodemographic and job-related factors. Job engagement levels were assessed using the Utrecht Work Engagement Scale, and comparisons were performed using the Mann–Whitney U-test and Kruskal–Wallis test. The findings revealed significant differences in job engagement based on the type of college, level of autonomy, and provision for time-bound cadre promotions. It also provided insights into the nonsignificant effects of gender, age, experience, and income on job engagement. The study contributes to the existing literature on employee engagement and provides valuable insights for organizations aiming to improve employee productivity and overall performance. Future research can build upon these findings to explore additional factors influencing job engagement and expand the understanding of work engagement in different contexts.

R Jayasri Krupa, S Dhivyadharshini, N Aravindha Babu et al.

Tongue print identification has emerged as a promising biometric modality due to the distinctiveness and stability of tongue features. This article provides an in-depth exploration of tongue prints as a viable means of personal identification, emphasizing its anatomical uniqueness and biometric advantages. By examining the anatomy of the tongue, the methodologies for tongue print acquisition, and the technological advancements in tongue print recognition systems, this article highlights the potential applications and contemporary challenges of tongue print biometrics in healthcare, security, and forensic science. It further discusses the accuracy, advantages, limitations, and future directions for the adoption of tongue print technology. This comprehensive analysis aims to contribute to the growing body of knowledge on tongue prints as a significant biometric tool.

D J Williams

Historically, serial homicide has been defined in various ways by experts. Recently, there have been renewed efforts to arrive at a consensus definition, yet these efforts have not yet been resolved. At the heart of the controversy appears to be the prioritization of either qualitative definitional features, such as offenders’ intentions and motives, or more observable quantitative features, specifically a minimum threshold of completed murders. The present technical note briefly summarizes this controversy before considering new empirical and theoretical research developments. These developments support a definition that includes a three-victim minimum threshold of forensically linked murderers by the same person(s), occurring in separate events over time, wherein a primary motive is often personal gratification (leisure experience).

Abdelkarim Chaouiki, Maryam Chafiq, Young Gun Ko et al.

In the present work, we represent two thiazolidinediones, namely (Z)-5-(4-methoxybenzylidene) thiazolidine-2,4-dione (MeOTZD) and (Z)-5-(4-methylbenzylidene) thiazolidine-2,4-dione (MeTZD), as corrosion inhibitors for carbon steel (CS) in 1.0 M HCl solution. Techniques for gravimetric methods, electrochemical measurements, and morphological characterization were used to conduct experimental evaluations. Additionally, calculations based on the fundamental principles of Density Functional Theory (DFT) were employed to simulate inhibitor–iron interactions. Experimental results indicated that investigated inhibitors can significantly enhance the corrosion resistance of CS, reaching a performance of 95% and 87% at 5 × 10⁻³ mol/L of MeOTZ and MeTZD, respectively. According to gravimetric and electrochemical experiments, inhibitor molecules obstruct corrosion reactions by adhering to the CS surface, which follows the Langmuir isotherm model. On the other hand, the morphological analysis showed a well-distinguished difference between unprotected and protected CS surfaces as a result of the inhibitors’ addition to HCl. Projected density of states and interaction energies obtained from first-principles DFT simulations indicate that the studied molecules form covalent bonds with iron atoms through charge transfer.

Dorota Wianowska, Marta Gil

Stefan John Davis, William Robert Wise, Sandro Recchia et al.

The topic of hexavalent chromium (Cr(VI)) in leather has been debated throughout the whole supply chain for years. However, its significance has recently increased due to proposed changes in European legislation concerned with skin-sensitising substances suggesting that acceptable Cr(VI) concentrations in leather goods should be lowered from 3 mg kg⁻¹ to 1 mg kg⁻¹. The proposition of a stricter limit and current analytical difficulties created the need for a review of current standard test methods. The research presented in this paper investigates both the colorimetric (Part 1) and chromatographic (Part 2) methods under BS EN ISO 17075. The focus of the study was to identify possible sources of interference leading to large statistical variance in results and to define the limit of quantification with respect to the proposed new compliance limit. This study into the colorimetric method has shown that the presence of Cr(III), dyes, and proteins can be significant interferences, becoming critical at low Cr(VI) concentrations. Dilution factors worsen the problem of detecting low concentrations: a reliable quantitative detection of 0.01 mg kg⁻¹ and 0.003 mg kg⁻¹ Cr(VI) in solution are required at the 3 mg kg⁻¹ and 1 mg kg⁻¹ compliance limits in leather, respectively. BS EN ISO 17075 part 1 was shown to be incapable of reliably resolving to 3 mg kg⁻¹ or below in leather. Part 2 shows a marked improvement in detection limits and reliability; however, data suggest that 1 mg kg⁻¹ Cr(VI) is not reliably detectable in leather. Suggested improvements to the established test methods and a possible alternative are discussed.

Mohd Faiz Abd Ghani, Rozana Othman, Noraziah Nordin

The naturally derived flavonoids are well known to have anticarcinogenic effects. Flavonoids could be an alternative strategy for ovarian cancer treatment, due to existing platinum-based drugs are reported to develop resistance with low survival rates. Inhibition of antiapoptotic proteins, namely B-cell lymphoma (Bcl-2) and B-cell lymphoma-extra large (Bcl-xl), is the key target to stimulate apoptosis process in cancer cells. This study aimed to determine the binding interaction of five naturally derived flavonoids (biochanin A, myricetin, apigenin, galangin, and fisetin) with potential antiapoptotic target proteins (Bcl-2 and Bcl-xl). The molecular docking study was conducted using AutoDock Vina program. The binding affinity and the presence of hydrogen bonds between the flavonoids and target proteins were predicted. Our findings showed that all the flavonoids showed better binding affinity with Bcl-xl than that of Bcl-2 proteins. The highest binding affinity was recorded in fisetin–Bcl-xl protein complex (−8.8 kcal/mol). Meanwhile, the other flavonoids docked with Bcl-xl protein showed binding affinities, ranging from –8.0 to –8.6 kcal/mol. A total of four hydrogen bonds, four hydrophobic contacts, and one electrostatic interaction were detected in the docked fisetin–Bcl-xl complex, explaining its high binding affinity with Bcl-xl. The present results indicate that all flavonoids could potentially serve as Bcl-xl protein inhibitors, which would consequently lead to apoptotic process in ovarian cancers.

Hua Jin, Ge Tang, Jin Li et al.

A sensitive and accurate method was developed for the simultaneous determination of twelve components including phenolic acids (gallic acid, protocatechuic aldehyde, protocatechuic acid, and ferulic acid), flavonoids (catechin, epicatechin, rutin, luteolin, luteolin-7-glucoside, and epicatechin gallate), anthraquinones (emodin), and triterpenes (ursolic acid) in Cynomorii herba in different harvest times by liquid chromatography tandem mass spectrometry (LC-MS/MS). The chromatographic separation was achieved on an Eclipse plus C18 (3.0 mm × 50 mm, 1.8 μm) column at 40°C. The mobile phase consisted of acetonitrile and 0.05% formic acid with a gradient elution at a flow rate of 0.4 mL·min −1. Under the optimized conditions, there was good linear relation (r ≥ 0.9944) and satisfactory precision (RSD values less than 5.65%). The recoveries of the twelve components were in the range of 93.5–105%. Moreover, the limits of detection (LOD) ranged from 0.003 to 21 ng mL−1 for the twelve analytes. In conclusion, the validated method was successfully applied to analyze the change regularity of the twelve components of Cynomorii herba in different harvest times. It provides a theoretical basis for choosing the suitable harvesting time of Cynomorii herba.

M. P. Ali, M. N. Bari, S. S. Haque et al.

Abstract Background Increases in global mean temperature, changes in rainfall patterns, and extreme climatic events are expected results of climate change. The individual effects of elevated temperature and precipitation on insect pests due to the impact of climate change have been widely modeled individually but their combined effects are poorly understood. Results Ten years of monthly abundance of an important economic rice insect pest, the rice yellow stem borer (YSB), Scirpophaga incertulas Walker (Lepidoptera: Pyralidae), was modeled in relation to temperature and rainfall using cross-correlation functions, general linear models, ARIMA models and simple linear regressions. The results suggested that increasing temperature and rainfall separately had a positive effect on growth rate of YSB. However, the combined effect of high temperature and rainfall was negative Temperature affected abundance of YSB negatively at high rainfall, but positively at intermediate to low rainfall level. The growth rate of YSB was found to be high at relatively low temperature and abundant rainfall. Conclusion The combined effects of temperature and rainfall showed a quadratic response of YSB abundance, which indicated that outbreak risk of YSB may be reduced if climate change results in increasing temperature and rainfall. It should be noted that we could address only a few of the important factors which could influence our model prediction.

Etsuo Uchida, Yuichiro Sakurai, Rathborith Cheng et al.

An amendment to this paper has been published and can be accessed via the original article.

Jeroen van Roy, Niels Wouters, Bart De Ketelaere et al.

Nowadays, quality inspection of fruit and vegetables is typically accomplished through visual inspection. Automation of this inspection is desirable to make it more objective. For this, hyperspectral imaging has been identified as a promising technique. When the field of view includes multiple objects, hypercubes should be segmented to assign individual pixels to different objects. Unsupervised and supervised methods have been proposed. While the latter are labour intensive as they require masking of the training images, the former are too computationally intensive for in-line use and may provide different results for different hypercubes. Therefore, a semi-supervised method is proposed to train a computationally efficient segmentation algorithm with minimal human interaction. As a first step, an unsupervised classification model is used to cluster spectra in similar groups. In the second step, a pixel selection algorithm applied to the output of the unsupervised classification is used to build a supervised model which is fast enough for in-line use. To evaluate this approach, it is applied to hypercubes of vine tomatoes and table grapes. After first derivative spectral preprocessing to remove intensity variation due to curvature and gloss effects, the unsupervised models segmented 86.11% of the vine tomato images correctly. Considering overall accuracy, sensitivity, specificity and time needed to segment one hypercube, partial least squares discriminant analysis (PLS-DA) was found to be the best choice for in-line use, when using one training image. By adding a second image, the segmentation results improved considerably, yielding an overall accuracy of 96.95% for segmentation of vine tomatoes and 98.52% for segmentation of table grapes, demonstrating the added value of the learning phase in the algorithm.

M. Dall´Osto, D. C. S. Beddows, P. Tunved et al.

Abstract Atmospheric new particle formation (NPF) and growth significantly influences climate by supplying new seeds for cloud condensation and brightness. Currently, there is a lack of understanding of whether and how marine biota emissions affect aerosol-cloud-climate interactions in the Arctic. Here, the aerosol population was categorised via cluster analysis of aerosol size distributions taken at Mt Zeppelin (Svalbard) during a 11 year record. The daily temporal occurrence of NPF events likely caused by nucleation in the polar marine boundary layer was quantified annually as 18%, with a peak of 51% during summer months. Air mass trajectory analysis and atmospheric nitrogen and sulphur tracers link these frequent nucleation events to biogenic precursors released by open water and melting sea ice regions. The occurrence of such events across a full decade was anti-correlated with sea ice extent. New particles originating from open water and open pack ice increased the cloud condensation nuclei concentration background by at least ca. 20%, supporting a marine biosphere-climate link through sea ice melt and low altitude clouds that may have contributed to accelerate Arctic warming. Our results prompt a better representation of biogenic aerosol sources in Arctic climate models.

Tsung-Heng Tsai, Zhiqi Hao, Qiuting Hong et al.

Abstract Peptide mapping with liquid chromatography–tandem mass spectrometry (LC-MS/MS) is an important analytical method for characterization of post-translational and chemical modifications in therapeutic proteins. Despite its importance, there is currently no consensus on the statistical analysis of the resulting data. In this manuscript, we distinguish three statistical goals for therapeutic protein characterization: (1) estimation of site occupancy of modifications in one condition, (2) detection of differential site occupancy between conditions, and (3) estimation of combined site occupancy across multiple modification sites. We propose an approach, which addresses these goals in terms of summarizing the quantitative information from the mass spectra, statistical modeling, and model-based analysis of LC-MS/MS data. We illustrate the approach using an LC-MS/MS experiment from an antibody-drug conjugate and its monoclonal antibody intermediate. The performance was compared to a ‘naïve’ data analysis approach, by using computer simulation, evaluation of differential site occupancy in positive and negative controls, and comparisons of estimated site occupancy with orthogonal experimental measurements of N-linked glycoforms and total oxidation. The results demonstrated the importance of replicated studies of protein characterization, and of appropriate statistical modeling, for reproducible, accurate and efficient site occupancy estimation and differential analysis.

Niina Ronkainen

Studies have shown that the more ownership students take of their academic work, the greater the level of information retained, knowledge acquired, and general cognitive development. Many teaching techniques that span across sciences, and go beyond standard techniques such as: merely lecturing at students or following written procedures for “cook book-style” laboratory experiments, have surfaced in the last decade. One such method, known as Course Preparation Assignments (CPAs), requires students to read and analyze course material prior to attending class. This approach gives students their first exposure to new content outside of the classroom, while also engaging them in responding to a series of questions that they must answer individually. This prior exposure to course material allows the students to not only complete written assignments with the incentive of earning points, but also forces them to reflect on what they are learning. Prior to adopting the CPA teaching practice, I discovered that very few of my chemistry and biochemistry students completed the reading and homework problems until a few days prior to an examination. Each class or unit that includes a CPA follows a predictable pattern which students adjust to quickly: Read – Think –Write/Draw/Calculate – Discuss the course content. The impact of incorporating CPAs into undergraduate Analytical Chemistry and Principles of Biochemistry lecture courses will be described from this instructor’s point of view. In addition, the advantages and challenges of utilizing this teaching approach at a Primarily Undergraduate Institution, within classes made up of 8-45 students, will be described. Furthermore, the development and use of CPAs for teaching various Chemistry courses, the leading and facilitating of course discussions in class, the grading of assignments, and student perceptions of the approach will be discussed. Indeed, the pedagogical approach generally promotes timely completion of assignments, helps create a more interactive classroom setting, encourages students to ask more questions, facilitates involvement in discussions all of which result in an improved ability to think and reason critically.