Comprehensive Study Of Stability Research Articles

Ensuring Stability of Anode Catalysts in PEMWE: From Material Design to Practical Application.

Proton Exchange Membrane Water Electrolysis (PEMWE) has emerged as a clean and effective approach for the conversion and storage of renewable electricity, particularly due to its compatibility with fluctuating photovoltaic and wind power. However, the high cost and limited performance of iridium oxide catalysts (i.e. IrO2) used as anode catalyst in industrial PEM electrolyzers remain significant obstacles to widespread application. Although numerous low-cost and efficient alternative catalysts have been developed in laboratory research, comprehensive stability studies critical for industrial use are often overlooked. This leads to the failure of performance transfer from catalysts tested in liquid half-cell systems to those employed in PEM electrolyzers. This concept presents a thorough overview for the stability issues of anode catalysts in PEMWE, and discuss their degradation mechanisms in both liquid half-cell systems and PEM electrolyzers. We summarize comprehensive protocol for the assessment and characterization, analyze the effective strategies for stability optimization, and explore the opportunities for designing viable anode catalysts for PEM electrolyzers.

Comprehensive study of stability and thermo-physical properties of water-based CaCO3/SiO2 dual hybrid nanofluid

Comprehensive study of stability and thermo-physical properties of water-based CaCO3/SiO2 dual hybrid nanofluid

Quantification of endogenous Angiotensin 1-10, 1-9, 1-8, 1-7, and 1-5 in human plasma using micro-UHPLC-MS/MS: Outlining the importance of the pre-analytics for reliable results

Angiotensin peptides (ANGs) play a central role in the renin–angiotensin–aldosterone system, rendering them interesting biomarkers associated with hypertension. Precise quantification of circulating ANGs holds the potential to assess the activity of angiotensin-converting enzyme (ACE), a key protease targeted by widely prescribed drugs, namely ACE inhibitors. This ability could pave the way for personalised medicine, offering insights into the prescription of inhibitors targeting either the proteases or the receptors within the system. Despite recent developments in liquid chromatography–mass spectrometry (LC-MS) methods for measuring circulating ANG concentrations, comprehensive stability studies of ANGs in human plasma are absent in the literature, raising concerns about the reliability of measured concentrations and their link to clinical conditions. To address this critical gap, we conducted an exhaustive evaluation of the pre-analytical stability of ANG1–10, ANG1–9, ANG1–8, ANG1–7, and ANG1–5. By employing surfactants to mitigate non-specific adsorption and a dedicated mix of protease inhibitors to limit protease activity, we established an MS-based assay for these five peptides. We used this method to quantify circulating concentrations of ANGs in the plasma of 11 healthy donors and 3 patients under kidney dialysis. Our findings revealed that ANG1–10 and ANG1–8 circulate at concentrations ranging from 1 to 10 pM in healthy subjects and exhibit a high degree of correlation. Notably, ANG1–9, ANG1–7, and ANG1–5 were undetectable in any of the 14 patients, despite a sub-picomolar limit of detection. This strikingly contrasts with the reference concentrations reported in the literature, which typically fall within the picomolar range. In light of these discrepancies, we strongly advocate for rigorous pre-analytical considerations and comprehensive stability studies to ensure reliable results. We emphasise the pivotal role of heightened pre-analytical awareness within the clinical chemistry community, and we hope for continued growth in this critical area.

Preparation and Characterization of Theophylline Controlled Release Matrix System Incorporating Poloxamer 407, Stearyl Alcohol, and Hydroxypropyl Methylcellulose: A Novel Formulation and Development Study.

Theophylline (THN), a bronchodilator with potential applications in emerging conditions like COVID-19, requires a controlled-release delivery system due to its narrow therapeutic range and short half-life. This need is particularly crucial as some existing formulations demonstrate impaired functionality. This study aims to develop a new 12-h controlled-release matrix system (CRMS) in the form of a capsule to optimize dosing intervals. CRMSs were developed using varying proportions of poloxamer 407 (P-407), stearyl alcohol (STA), and hydroxypropyl methylcellulose (HPMC) through the fusion technique. Their in vitro dissolution profiles were then compared with an FDA-approved THN drug across different pH media. The candidate formulation underwent characterization using X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. Additionally, a comprehensive stability study was conducted. In vitro studies showed that adjusting the concentrations of excipients effectively controlled drug release. Notably, the CRMS formulation 15 (CRMS-F15), which was composed of 30% P-407, 30% STA, and 10% HPMC, closely matched the 12 h controlled-release profile of an FDA-approved drug across various pH media. Characterization techniques verified the successful dispersion of the drug within the matrix. Furthermore, CRMS-F15 maintained a consistent controlled drug release and demonstrated stability under a range of storage conditions. The newly developed CRMS-F15 achieved a 12 h controlled release, comparable to its FDA-approved counterpart.

Formulation And Evaluation Of Herbal Cream For The Treatment Of Wound Healing

This study was to formulate and evaluate an herbal cream for wound healing using natural plant extracts known for their therapeutic properties. The selected herbs included Centella asiatica, which was chosen based on their well-documented efficacy in promoting skin repair and regeneration. Herbal extracts were prepared using ethanol and water as solvents, followed by standardization to ensure consistent active compound concentrations. The cream base was developed as an oil-in-water emulsion, optimized for pH, viscosity, and Spreadability to ensure suitability for topical application. Comprehensive stability studies were conducted to assess the formulation's physical, chemical, and microbial stability. The wound healing efficacy was evaluated through in vitro scratch assays and in vivo studies using a rat model, demonstrating significant improvements in wound contraction and re-epithelialization compared to controls. Additionally, dermal irritation tests confirmed the formulation’s safety for skin application. This research highlights the potential of combining traditional herbal medicine with modern formulation techniques to create effective and safe wound-healing products. The findings suggest that the developed herbal cream is a promising alternative to conventional treatments, offering natural and accessible solutions for wound care.

Microbiological quality and efficacy of preservatives in marigold-based skin care products

<p>The microbiological stability of cosmetic products is crucial, especially in products with high water content, such as creams. Therefore, preservatives are used in order to protect consumers from harmful pathogens that would otherwise invade the cosmetics. Despite their function, the addition of preservatives can be considered controversial in the cosmetics industry. Parabens are frequently used synthetic preservatives in various industries. According to regulatory directives concerning cosmetics (Cosmetic Directive by the European Commission) usage of some parabens (methylparaben, propylparaben, butylparaben, and ethylparaben) is safe and permitted in allowed concentrations. On the other hand, the European Commission prohibited the use of isopropylparaben, isobutylparaben, phenylparaben, benzylparaben and pentylparaben. Therefore, a comprehensive stability study was conducted to evaluate the influence of paraben-based preservative (Gujsol-1<sup>®</sup>, INCI name: Phenoxyethanol, Methylparaben, Ethylparaben, Propylparaben, Butylparaben) and potassium sorbate in order to preserve plant extracts-based skin-care products, Day and Night creams with marigold extract. Previously, mentioned skin-care products were preserved with the preservative Dekaben C<sup>®</sup>, which contained paraben mixture with banned isobutylparaben. All tested formulations showed favorable texture and sensory characteristics, desirable mild acidic pH values, satisfactory physical stability and appropriate microbiological quality at the initial point, as well as after storage at elevated temperature or at cyclic stress test conditions and at room temperature during two years. In addition, both preservatives significantly reduced the number of inoculated microorganisms during the challenge test. It can be concluded that potassium sorbate in plant-based creams could be an efficient alternative to paraben-based preservatives.</p>

Stability Analysis: Two-Area Power System with Wind Power Integration

This paper focuses on a comprehensive stability study of a two-area power system with wind power integration and synthetic inertia control in each area, considering the effects of varying the interconnection link. Normally, synthetic inertia proposals are analyzed in one-area systems, in which stability is tested without considering transmission system phenomena, such as coherency. As modern power systems are progressively becoming interconnected, the possibility of forming two or more non-coherent areas is likely, which poses a challenge to synthetic inertia control techniques that use system frequency as a main feedback signal. In this context, this work addresses a crucial gap in the existing literature and provides a valuable starting point for studying more complex interconnected power systems with wind power integration. Simulations were performed in Matlab-Simulink considering a data-driven frequency dynamics model of the Chilean Electric System, and a wind power model with synthetic inertia control H2 norm minimization in each area. The results showed that it is possible to find local optimal feedback gains, preserving the stability of the global system under significant variations in the interconnection link. RoCoF and Nadir indicators are provided, highlighting the benefits of synthetic inertia control, particularly in low-inertia situations.

Stability of polymeric cationic niosomes and their plasmid DNA-based complexes as gene delivery carriers

This study aims to explore the stability of lipo-polymeric niosomes/niosome-based pCMS-EGFP complexes under different storage temperatures (25 °C, 4 °C, and −20 °C). To date, the question of nucleic acid-complex stability is one of the most vital issues in gene delivery applications. The need for stable vaccines during the COVID-19 pandemic has merely highlighted it. In the case of niosomes as gene carriers, the scientific literature still lacks comprehensive stability studies. In this study, the physicochemical features of niosomes/nioplexes in terms of size, surface charge, and polydispersity index (PDI), along with transfection efficiency, and cytotoxicity in NT2 cells were evaluated for 8 weeks. Compared to day 0, the physicochemical features of the niosomes stored at 25 °C and −20 °C changed dramatically in terms of size, zeta potential, and PDI, while remaining in reasonable values when stored at 4 °C. However, niosomes and nioplexes stored at 4 °C and −20 °C showed nearly stable transfection efficiency values, yet an obvious decrease at 25 °C. This article provides a proof of concept into the stability of polymeric cationic niosomes and their nioplexes as promising gene delivery vehicles. Moreover, it highlights the practical possibility of storing nioplexes at 4 °C for up to 2 months, as an alternative to niosomes, for gene delivery purposes.

Comprehensive stability study of benzimidazole drug residues in standard solution, muscle and milk

The performance criteria of analytical methods and the necessity for stability analysis to provide the accuracy of the results of the analyzed samples are explained in European Commission Decision 2021/808/EC and the guidance document SANTE/2021/11312. Detection of time-dependent changes in drug concentrations during storage or transport and re-analysis of samples are crucial to obtain high-quality results and reliable data. In this way, it allows toxicologists to interpret the analytical results accurately in drug analyses. The aim of this study was comprehensively to investigate the stability of benzimidazoles (levamisole hydrochloride, albendazole, albendazole-sulfone, albendazole-2-amino sulfone, albendazole sulfoxide, oxfendazole, 5-hydroxythiabendazole, triclabendazole, ketotriclabendazole, thiabendazole, flubendazole, fenbendazole sulfone) in working solutions, muscle and milk samples. For this purpose, long-term stability was evaluated over 6 months and under four different storage conditions (4 °C, −20 °C, 20 °C light and 20 °C dark) in the matrix. The influences of three freeze-thaw cycles, autosampler stability, and 60 min storage at 40 °C were investigated for short-term stability. Simultaneously, the stability of the working solutions were established over 6 months and under five different conditions (4 °C, −20 °C, −80 °C, 20 °C light, and 20 °C dark). It was found that working solutions can be stored at −80 °C or −20 °C, and it is appropriate to prepare the standard working solution freshly once a month. Storage of milk at 4 °C is suitable for some analytes (ABZ-SO, FBZ-SO2, FLUBZ, ABZ, ABZ-NH2-SO2) whereas for the muscle almost all substances were stable only at −20 °C. Some freeze-thaw and short-term stability changes were detected.

A Comprehensive Stability Study of Glucose Concentrations Measured in Sodium Fluoride, Heparin and Serum Separator Tubes: A Cross-sectional Study

Introduction: Sodium fluoride mixed vacutainers were once viewed as the gold standard tubes for glucose analysis. However, their ineffectiveness in inhibiting glycolysis, especially in the first one to four hours has been reported in several studies. The accurate blood glucose estimation is crucial for the diagnosis and management of diabetes mellitus. Aim: To find out a cost effective and feasible alternative blood collection vacutainer for the estimation of accurate blood glucose. Materials and Methods: A cross-sectional study was conducted at the Blood Collection Centre of HAH Centenary Hospital, New Delhi, India, from December 2019 to July 2020. A blood sample was collected from 155 subjects in each-sodium fluoride [Na2EDTA], heparin [sodium heparin] and Serum Separator Tube (SST). To find out the glucose reduction during blood coagulation in SST tubes, the glucose levels (n=25) of sodium fluoride (plasma) at 0 hr and 30 mins after coagulation in SST tubes were compared. The remaining study subjects (n=130) were categorised into two groups (65 subjects in each group) and assessed for the reduction of glucose at 4°C and 25°C. Further, the reduction of glucose was also studied in both the groups as per glucose concentrations <100 mg/dL (n=25), 100-200 mg/dL (n=25) and >200 mg/dL (n=15) in each group. Results: The inter assay coefficient of variation of quality control samples of glucose (n=61) was 3.0%. The highest percentage of glucose reduction was found in the green vacutainers (p<0.05) at 4°C and 25°C storage temperatures. There was no significant reduction of glucose level in SST vacutainers at 4°C up to 96 hrs of analysis (p>0.05) and the result was comparable to grey vacutainers. Further, there was no haemolysis in the SST vacutainers up to 96 hrs of analysis, however, green and grey vacutainers showed enormous haemolysis. Conclusion: The glucose analysis in SST vacutainers can reduce the loss of sample, cost of analysis, and interferences in the analysis due to haemolysis. The study strongly suggests that all the analytical laboratories should do glucose analysis in SST vacutainers.

A Comprehensive Stability Study of Vardenafil Using Quality by Design Approach

A Comprehensive Stability Study of Vardenafil Using Quality by Design Approach

Comprehensive Stability Study of Vitamin D3 in Aqueous Solutions and Liquid Commercial Products.

Vitamin D3 has numerous beneficial effects, such as musculoskeletal, immunomodulatory, and neuroprotective. However, its instability is the main obstacle to formulating quality products. Despite increased attention and growing use, data on vitamin D3 stability is scarce because data from individual studies is inconclusive and mostly qualitative. Therefore, we have systematically investigated the influence of various factors (temperature, light, oxygen, pH, concentration, and metal ions) on its stability in aqueous media using a stability-indicating HPLC-UV method. First-order kinetics fitted its degradation under all tested conditions except light and oxygen. In both cases, the established models in chemical kinetics were inappropriate and upgraded with the Weibull model. Metal ions and acidic conditions had the main destabilizing effect on vitamin D3 in aqueous media, but these solutions were successfully stabilized after the addition of ethylenediaminetetraacetic acid (EDTA), ascorbic acid, and citric acid, individually and in combination. EDTA showed the most significant stabilizing effect. Synergism among antioxidants was not observed. Our findings on vitamin D3 instability in aqueous media also correlated with its instability in commercial products. Vitamin D3 aqueous products require proper stabilization, thereby signifying the importance and contribution of the obtained results to the formulation of stable and quality products.

Comprehensive study of stability of copper oxide nanoparticles in complex biological media

In response to the rapid development of nanomaterials in the biomedical field, especially in advanced cancer therapy, more comprehensive studies regarding the safety of nanomaterials are continuously required. Currently, several fundamental studies concerning the fate of nanoparticles in the biological media are needed, especially before in vivo studies. Inspired by these approaches, and the wide variation on result in the literature regarding copper (I) oxide nanoparticles (Cu2O NPs), in this article we modified sulfobetaine-stabilzed Cu2O NPs with glutathione (GSH) and hyaluronic acid (HA) tumor targeting ligands to investigate the effects of nanoparticles design on their stability in four different biological fluids: simulated saliva, human blood plasma, gastric and intestinal fluids. In addition, we examined the kinetics of copper ions release under physiological conditions, and according to mathematical models, we proposed the most probable mechanism of mass transport. The GSH- and HA-modified, as well as unmodified sulfobetaine-stabilized Cu2O NPs suspended in all tested biological fluids, formed agglomerates with sizes varying from 150 to 700 nm. The highest copper ions content was observed for Cu2O NPs in simulated gastric fluid. The formation of aggregates and copper ions release in contact with biological fluids influenced the Cu2O NPs cytotoxicity. The results indicated that cancer cells were more susceptible to HA-modified copper oxide NPs action.

Comprehensive and quantitative stability study of ascorbic acid using capillary zone electrophoresis with ultraviolet detection and high-resolution tandem mass spectrometry.

Ascorbic acid is a powerful antioxidant compound involved in many biological functions, and a chronic deficiency is at the origin of scurvy disease. A simple, rapid, and cost-effective capillary electrophoresis method was developed for the separation and simultaneous quantification of ascorbic acid and the major degradation products: dehydroascorbic acid, furfural, and furoic acid. Systematic optimization of the conditions was performed that enabled baseline separation of the compounds in less than 10min. In addition to simultaneous quantification of ascorbic acid alongside to the degradation products, stability studies demonstrated the possibility using capillary electrophoresis to separate and identify the major degradation products. Thus, high-resolution tandem mass spectrometry experiments were conducted in order to identify an unknown degradation product separated by capillary electrophoresis and significantly present in degraded samples. Comparison of mass spectrometry data and capillary electrophoresis electropherograms allowed to identify unambiguously trihydroxy-keto-valeraldehyde. Finally, capillary electrophoresis was successfully applied to evaluate the composition of different pharmaceutical preparation of ascorbic acid. Results showed the excellent performance of the capillary electrophoresis method due to the separation of excipients from the compounds of interest, which demonstrated the relevance of using an electrophoretic separation in order to perform comprehensive stability studies of ascorbic acid.

Single-atom vacancy in monolayer phosphorene: A comprehensive study of stability and magnetism under applied strain

Using first-principles calculations based on density-functional theory we systematically investigate the effect of applied strain on the stability and on the electronic and magnetic properties of monolayer phosphorene with single-atom vacancy. We consider two types of single vacancies: the symmetric SV-55|66, which has a metallic and non-magnetic ground state, and the asymmetric SV-5|9, which is energetically more favorable and exhibits a semiconducting and magnetic character. Our results show that compressive strain up to 10%, both biaxial and uniaxial along the zigzag direction, reduces the formation energy of both single-atom vacancies with respect to the pristine configuration and can stabilize these defects in phosphorene. We found that the magnetic moment of the SV-5|9 system is robust under uniaxial strain in the range of −10 to +10%, and it is only destroyed under biaxial compressive strain larger than 8%, when the system also suffers a semiconductor-to-metal transition. Additionally, we found that magnetism can be induced in the SV-55|66 system under uniaxial compressive strain larger than 4% along the zigzag direction and under biaxial tensile strain larger than 6%. Our findings of small formation energies and non-zero magnetic moments for both SV-5|9 and SV-55|66 systems under zigzag uniaxial compressive strain larger than 4% strongly suggest that a magnetic configuration in monolayer phosphorene can be easily realized by single-vacancy formation under uniaxial compressive strain.

Small-signal stability analysis, and predictive control of Z-Source Matrix Converter feeding a PMSG-WECS

The modeling, small-signal stability analysis, and control of quasi-Z-Source Matrix Converter (qZSMC), and also its application in Wind Energy Conversion System (WECS) are discussed. First, the small-signal model of the qZSMC, composed of an input filter, a Three-Phase Quasi-Z-Source Network (TPQZSN), and a Matrix Converter (MC), is derived. Then, a comprehensive stability study is carried out and it is shown that, unlike the conventional MC, the qZSMC does not have problem working stable for its entire range of operation. The small-signal model is used to obtain system transfer functions and perform a frequency domain analysis. A guide to choose proper passive components of qZSMC is also presented. The qZSMC is further employed as grid interface by a Permanent Magnet Synchronous Generator (PMSG) based WECS (PMSG-WECS). A modified predictive control (MPC) is developed, allowing shoot-through states to be inserted within the deliberately made sequences of zero switching states in MC switching pulses. The proposed MPC is then compared to its conventional version, showing that by the MPC, the grid-current ripples are reduced considerably. Simulation study is used to assess the effectiveness of proposed WECS and MPC, and to highlight the promising features of the proposed WECS in comparison to Conventional MC-based PMSG-WECS (CMC-WECS).

The stability of poly(2,2′-(m-phenylene)-5,5′-bibenzimidazole) membranes in aqueous potassium hydroxide

In the form of membranes, poly(2,2′-(m-phenylene)-5,5′-bibenzimidazole) (mPBI) is known to exhibit high ionic conductivity when doped with aqueous KOH, which makes it interesting as electrolyte in e.g. alkaline fuel cells and water electrolyzers. The conductivity peaks at KOH concentrations around 25wt%. This work is devoted to a comprehensive stability study of mPBI in aqueous KOH of different concentrations for up to 200 days under conditions relevant for electrochemical energy conversion technologies. The polymer membranes were kept at 88°C in aqueous KOH with concentrations ranging from 0 to 50wt%, and the chemical and physicochemical changes were monitored. The degradation was connected to the hydrolysis of the polymer backbone and the degradation rate increased with increasing KOH concentration. In the lower concentration range mPBI proved to be stable but exhibited low ionic conductivity (10−4Scm−1). The preparation of a porous mPBI matrix was demonstrated as an effective approach to increase the ionic conductivity in the lower KOH concentration range, with great potential for further improvement through optimization of the porous structure.

A comprehensive study of stability in an electro-statically actuated micro-beam

This paper studies the mechanical and bifurcation behavior of a capacitive micro-beam suspended between two conductive stationary plates, which can be used as a micro-switch or as a RF resonator. The equation of dynamic motion of the micro-switch is obtained using Euler–Bernoulli beam theorem. The equilibrium positions or the fixed points of the micro-switch are obtained by solving the equation of the static deflection using the step-by-step linearization method (SSLM) and discretizing by Galerkin weighted residual method. In order to study the global stability of the obtained fixed points a modified non-linear mass–spring model is used. Non-linear motion trajectories in phase portraits are given and regions of bounded and unbounded solutions separated by a homoclinic or heteroclinic orbits and positions of the stationary conductive plates are illustrated. Critical values of the applied voltage leading to qualitative changes in the micro-beam behavior through a saddle node or pitch fork bifurcations for different values of the gap and voltage ratios are obtained. The effects of different gaps and voltage ratios also are investigated.

An investigation into the sample preparation procedure and analysis of cyanoacrylate adhesives using capillary electrophoresis

In this study, the trace acid profile of cyanoacrylate adhesives was studied using capillary electrophoresis. Liquid–liquid extraction was employed as the sample preparation step before separation by capillary electrophoresis. The solubility of the adhesives was investigated using various organic solvents, e.g. hexane and dichloromethane, and chloroform was determined to be the optimum solvent as it enabled the full dissolution of the adhesive. A comprehensive stability study was performed over a 3-year period and results indicate that the adhesives were stable for 2 years after which their stability and performance degraded.

Stabilizing an atom laser using spatially selective pumping and feedback

We perform a comprehensive study of stability of a pumped atom laser in the presence of pumping, damping, and outcoupling. We also introduce a realistic feedback scheme to improve stability by extracting energy from the condensate and determine its effectiveness. We find that while the feedback scheme is highly efficient in reducing condensate fluctuations, it usually does not alter the stability class of a particular set of pumping, damping, and outcoupling parameters.