Significant Degradation Research Articles

HYDROLYTIC DEGRADATION STUDY OF ROXADUSTAT BY RP-HPLC AND HPTLC

Objective: Simple, rapid RP-HPLC and HPTLC methods have been developed in order to study the degradation of Roxadustat under various stress conditions. The Kinetics of hydrolytic degradation is studied. Methods: Optimum separation of Roxadustat and its degradation products was achieved using the following conditions in HPLC, Agilent eclipse XDB-C8 (150×4.6 mm) column, the mobile phase was composed of methanol: phosphate buffer (pH 5, 0.05 M) (70:30 v/v) with UV detection at 262 nm. The flow rate was at 1.0 ml/min. The RT was 4.6±0.02 min. HPTLC work for Roxadustat was performed on Aluminium plates precoated with silica gel 60 F254, (10 cm × 10 cm with 250 μm layer thickness). The mobile phase was composed of Toulene: Ethyl Acetate: Glacial acetic acid (5:5:0.5 v/v/v) and then scanned. The system was found to give a compact spot for Roxadustat (Rf value of 0.58±0.02). Results: In HPLC the calibration curves plotted were found to be linear over the concentration range of 2.5-25μg/ml, with a correlation coefficient of R2=0.9994. In HPTLC the calibration curves plotted were found to be linear over the concentration range of 500-2500 ng/band, with a regression coefficient of R2=0.9957. The analytical performance of the proposed methods was validated as per ICH Q2 (R1) guidelines. The degradant peaks were well resolved from the Roxadustat peak. Significant degradation was observed in acid hydrolysis, alkali hydrolysis, and oxidative degradation. The drug is relatively stable towards photolysis, neutral hydrolysis, and thermal conditions. Conclusion: In the current work, simple RP-HPLC and HPTLC analytical methods for the determination of Roxadustat in the presence of its degradation products have been developed. The information presented herein could be very useful while developing formulation procedures to prevent hydrolytic degradation. It can be used as a routine quality control test.

Annealing effects on Al/polyimide adhesion in flexible optical solar reflectors

Flexible optical solar reflectors are made of single and multi-layered metal thin films on polymer substrates and will encounter around 6000 thermal cycles exceeding +/-100°C during one year of operation in low earth orbit. The candidate thin film system of Inconel/silver (Ag)/Teflon (FEP) recently demonstrated early damage formation (cracks and voids) after only a few thermal cycles, most likely due to the poor interfacial properties between Ag and FEP. An alternative material system that could be used is colourless polyimide, Tormed, instead of FEP. Additionally, aluminium (Al) has demonstrated very good interfacial properties with polyimide even after thermal cycling and has suitable optical properties. The adhesion of the Al/Tormed and Ag/Tormed interfaces were evaluated with tensile induced delamination. Generally, Al/Tormed has a much higher interface adhesion energy compared to Ag/Tormed, and there is no significant degradation after bake-out in vacuum (200°C, 10-6 mbar) for 10 and 24 hrs. Thus, the Al/Tormed system could be a more robust coating system for future flexible solar reflectors.

Identification and characterization of stress degradation products of ibrutinib by LC-UV/PDA and LC-Q/TOF-MS studies.

The anticancer drug ibrutinib was subjected to stress degradation studies under the ICH-prescribed hydrolytic, photolytic, oxidative and thermal stress conditions, and its degradation behavior was studied. A significant degradation was noted for the drug under acidic/alkaline hydrolytic, acid/alkaline photolytic, and oxidative conditions. The UPLC-UV/PDA studies revealed the generation of six degradation products (I-VI), and these were adequately resolved from the drug under the developed chromatographic conditions over a Kinetex® C18 (100 mm×4.6 mm; 2.6 μm) column employing isocratic elution method. Detection wavelength was selected as 289 nm. The UPLC-UV/PDA method conditions were extrapolated to UPLC-MS/TOF studies. All the six degradation products were found to be ionized in the total ion chromatogram, and the products could be identified and characterized from their mass spectral data. The possible degradation route of ibrutinib leading to generation of various products was also postulated.

Eco-friendly approach for the construction of biochar-based superhydrophobic membrane for effective oil/water separation

Abstract Researchers are looking at improved oil/water separation techniques due to the industry’s struggles with the separation of oily wastewater. One promising approach is to use superhydrophobic, SHP, membranes to separate oil from oily wastewater. In this study, we developed SHP textile fabric based on biochar, BC. The BC was synthesized from banana leaves by pyrolysis and then modified with nickel metal to produce Ni@BC. The textile fabric, TF, was submerged in an ethanolic solution of Ni@BC, and stearic acid, SA, to produce the SHP coating. The Ni@BC was utilized to improve the roughness of the surface of the pristine TF, and SA was utilized to reduce its surface energy. Scanning electron microscope, SEM, was used to investigate the surface morphology of the pristine and modified TF. The SEM results show that the modified TF shows a micro-nano structure. Atomic force microscopy, AFM, was utilized to study the surface roughness. The results show that the modified TF has a surface roughness greater than the pristine TF. The energy-dispersive x-ray spectroscopy techniques and Fourier transform infrared spectroscopy confirmed the structure of Ni@BC and the grafting of both SA and Ni@BC to the TF. The wettability finding demonstrated that the modified TF had a high degree of superhydrophobicity, with a high-water contact angle of 161° and a low water sliding angle of 1°. The modified TF showed excellent oil/water separation performance, with a separation efficiency of 99.9%. The oil absorption capacity of the TF was also high, with a capacity of 303 g g−1 for silicone oil, and it also has a high flux rate. The modified TF was also found to be mechanically and chemically stable, with no significant degradation after 10 cycles of use. The results of this study demonstrate that the biochar-based SHP TF is a promising material for oil/water separation.

Introduction of a certification procedure for the acoustic response of reference reflectors for ultrasonic testing

This article describes a certification procedure which includes both the qualitative and quantitative characterisation of the acoustic response of reference reflectors. It is dedicated to one-dimensional reference defects such as notches or side drilled holes but can be generalized also to two-dimensional reflectors such as flat bottom holes. At the beginning relevant measured quantities are introduced. This includes the defect homogeneity and the effective defect length which are extracted from the acoustic reflection profile. Afterwards, a setup for the performance of certification measurements is shown and the overall procedure is described. All results are summarized in a standardized protocol. At the end, the reference certification in the daily use is discussed. Due to the large database a statistic evaluation can be presented. It shows that a significant percentage of references do not fulfil the given quality criteria. The importance of a quality monitoring at different time periods is illustrated with an example of a reference notch where measurements before and after commissioning revealed a significant quality degradation. Finally, the presented method can serve as basis for updates of common standards with respect to a more complete specification of reference reflectors which will be needed due to the increasing demands on the accuracy of ultrasonic testing systems.

Bioactive Zn-0.6Cu thin sheet for craniofacial bone repair: In vitro and in vivo evaluations

Millions of craniofacial surgeries are performed annually worldwide, and materials for craniofacial bone repair are widely needed. However, traditionally applied materials, such as titanium and polymethylmethacrylate, have some shortcomings (limited malleability, material-based toxicity, non-biodegradability, lack of bioactivity, etc.). Zinc based biodegradable metals possess superior mechanical properties, biodegradability, and bioactivity, which make them promising candidate materials. Here, we successfully fabricated Zn-0.6Cu thin sheets (thickness ≤0.5 mm, suitable for craniofacial surgery) through combined extrusion and rolling. The in vitro and in vivo performances were generally evaluated and compared to those of a commercially applied pure titanium mesh. The mechanical properties of Zn-0.6Cu sheets were superior to those of clinically used polymethyl methacrylate. They were easy to shape and would not fracture during deformation. The Zn-0.6Cu sheet exhibited a gentle degradation mode, and proper implant-derived Zn improved osteogenic differentiation of rat bone marrow mesenchymal stem cells by up-regulating expression of osteogenesis related genes (alkaline phosphatase, bone morphogenetic protein-2). Thus, it further promoted extracellular matrix mineralization by improving calcium deposition for bone formation. It also improved the expression of angiogenesis-related genes (vascular endothelial growth factor, hypoxia-inducible factor alpha). The Zn-0.6Cu sheet exhibited high osteogenic activity in a cranial defect animal model compared to a non-biodegradable pure titanium mesh. Significant surface degradation occurred after two months in vivo, and degradation products were compatible with surrounding tissues. In general, the Zn-0.6Cu thin sheet seems to be a bioactive material selection for craniofacial bone repair, which might possibly accelerate defect repair and prevent adverse complications.

The impacts of renewable energy production, economic growth, and economic globalization on CO2 emissions: evidence from Fourier ADL co-integration and Fourier-Granger causality test for Turkey.

Along with the growth and globalization of the whole world economy since the First Industrial Revolution, the production and use of fossil fuels have led to increased CO2 emissions and, ultimately, significant environmental degradation. The impact of globalization, economic growth, and renewable energy sources on CO2 may show trends with different turning points in developing countries, and estimations may need to follow Fourier-type functions to capture the frequency domain. Therefore, the aim of this study is to examine the effects of renewable energy production, economic globalization, and economic growth on CO2 emissions for Turkey in the period 1971-2006 with Fourier autoregressive distribution lag (ADL) cointegration, DOLS, and Fourier-Granger causality tests. The originality of this study is the estimation of a model of CO2 emissions with a Fourier-type function for the first time. The findings indicate a negative relationship between renewable energy production and CO2 emissions and a positive relationship between economic globalization and economic growth and CO2 emissions. In addition, according to the empirical results, there exists a one-way causality relationship between economic globalization to CO2 and economic globalization to renewable energy production, and there is evidence of a bidirectional causality relationship between economic globalization and economic growth in this study.

Hybrid Graph Convolutional Network With Online Masked Autoencoder for Robust Multimodal Cancer Survival Prediction.

Cancer survival prediction requires exploiting related multimodal information (e.g., pathological, clinical and genomic features, etc.) and it is even more challenging in clinical practices due to the incompleteness of patient's multimodal data. Furthermore, existing methods lack sufficient intra- and inter-modal interactions, and suffer from significant performance degradation caused by missing modalities. This manuscript proposes a novel hybrid graph convolutional network, entitled HGCN, which is equipped with an online masked autoencoder paradigm for robust multimodal cancer survival prediction. Particularly, we pioneer modeling the patient's multimodal data into flexible and interpretable multimodal graphs with modality-specific preprocessing. HGCN integrates the advantages of graph convolutional networks (GCNs) and a hypergraph convolutional network (HCN) through node message passing and a hyperedge mixing mechanism to facilitate intra-modal and inter-modal interactions between multimodal graphs. With HGCN, the potential for multimodal data to create more reliable predictions of patient's survival risk is dramatically increased compared to prior methods. Most importantly, to compensate for missing patient modalities in clinical scenarios, we incorporated an online masked autoencoder paradigm into HGCN, which can effectively capture intrinsic dependence between modalities and seamlessly generate missing hyperedges for model inference. Extensive experiments and analysis on six cancer cohorts from TCGA show that our method significantly outperforms the state-of-the-arts in both complete and missing modal settings. Our codes are made available at https://github.com/lin-lcx/HGCN.

A Macromechanical Constitutive Model for Rebar Buckling

Rebar buckling and fracture have been experimentally observed to cause significant degradation of the mechanical properties of reinforced concrete (RC) elements and should be accounted for in the analysis of RC structures. While data on the material properties of steel rebar are widely available, test data on rebar buckling remain scarce. This paper proposes a macromechanical model capable of predicting rebar buckling responses solely on the basis of steel material properties and the rebar geometry, even when rebar buckling experimental data are not available. This is achieved by computationally building the uniaxial stress-strain constitutive response at each analysis step through the equilibrium in the deformed configuration of the buckled rebar and through the cross-sectional constitutive response. The equilibrium in the deformed configuration is treated in a manner consistent with the corotational formulation, while the cross-sectional constitutive response is built through integration of a uniaxial damage plasticity model over the cross-section area. Rebar buckling is triggered by an initial imperfection, while low-cycle fatigue effects are reproduced through the uniaxial damage plasticity steel material model, without the need for cycle-counting algorithms. The proposed model is translated to a computer code, calibrated to a set of experimental data, validated to separate test data, and subsequently used in the analysis of an experimentally studied RC column that experienced rebar buckling under cyclic loading. Using the proposed model, the analysis captured the response of the RC column and the experimentally observed strength deterioration due to rebar buckling.

Design Optimization, Cabling and Stability of Large-Diameter High Jc Nb3Sn Wires

In the framework of the High Field Magnets (HFM) program, CERN is developing and qualifying Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn Rutherford cables to support magnet development towards the requirements of a future energy-frontier collider, using both state-of-the-art commercial wires and experimental wires under development with industrial partners. The trend towards higher current density and larger diameter wires imposes challenges for magneto-thermal stability. In this study, rolling trials and Rutherford cabling have been performed at CERN for two designs of a 1 mm diameter distributed tin Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn wire produced by KAT, and for 1 mm and 1.1 mm diameter RRP Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn wires procured from Bruker OST, and the self-field stability and cabling degradation have been analyzed. The 1 mm RRP wire shows significant degradation in <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I_c</i> and stability on cabling. Although the latter is not expected to impact the performance of research magnets, the potential of heat treatment optimization to improve stability has also been quantified. The distributed tin wire shows substantially poorer stability, but promising indications of low cabling degradation. The influence of wire design characteristics on cabling behavior and stability have been assessed, and the implications for future wire optimization towards high field accelerator magnet applications have been discussed.

Significant Degradation Reduction in Metal Oxide Thin-Film Transistors via the Interaction of Ionized Oxygen Vacancy Redistribution, Self-Heating Effect, and Hot Carrier Effect

In this work, device degradation of metal oxide (MO) thin-film transistors (TFTs) under positive bias stress, linear stress, and saturation stress is systematically investigated. A significant degradation reduction in InGaZnO TFTs is observed for the first time under saturation stress. Incorporated with electric field simulations and temperature simulations, a degradation model, considering the interaction of ionized oxygen vacancy redistribution, self-heating effect, and hot carrier effect, is tentatively proposed to understand the degradation behaviors under various stress combinations. Moreover, a similar degradation reduction phenomenon is also reproduced in InSnZnO TFTs, demonstrating the applicability of the proposed degradation model in MO TFTs.

An Experimental Study on Manipulation of Individual Coil Current in Parallel-Connected HTS Pancake Coils

This paper reports experimental results of individual coil current manipulation by heater operation in parallel-connected three no-insulation (NI) high-temperature superconductor (HTS) pancake coils. The resistive heater was installed at the coil terminal of the lowermost pancake coil. During magnet operation with a power supply current held constant in a bath of liquid nitrogen at 77 K, the heater was operated to reduce the coil current of the lowermost pancake coil. Due to the heater operation, the coil currents of the uppermost and the middle pancake coil increased as a result of the coil-to-coil current sharing mechanism. The result demonstrates the potential of handling the unstable magnet operation in a parallel-connected magnet by taking action to each coil individually such as coil current reduction without significant degradation of the magnetic field intensity.

Synergistic effect of stirring and marigold shaped Cu2FeSnS4 nanostructure for the enhanced performance of Rhodamine B degradation under visible light

The success of Photocatalysis for environmental applications strongly relies upon the availability of suitable energy spectrum as well as absorption of photon energy by the photocatalyst to generate reactive oxygen species (ROS) which are deemed necessary for dye removal. Present work report the solvothermally synthesized Cu2FeSnS4 (CFTS) marigold flower shaped nanostructures which demonstrates significant degradation efficiency against rhodamine B (RhB) dye. The formation of single-phase tetragonal stannite structure of CFTS nanoparticles with lattice constant values a = b = 5.48 Å and c = 10.61 Å was confirmed by XRD analysis. FESEM studies reveals the formation of self-assembled thin sheets of nanoflakes with uniform average thickness 25-30 nm and fringe spacing between adjacent lattice for 〈204〉 atomic plane is found to be 0.19 nm calculated by HR-TEM. The excellent RhB degradation efficiency of 92.1% under visible light within 05 minutes was achieved under synergetic effect of stirring and synthesized CFTS material.

Feature selection for a continental-scale geospatial model of environmental sound levels.

Modeling environmental sound levels over continental scales is difficult due to the variety of geospatial environments. Moreover, current continental-scale models depend upon machine learning and therefore face additional challenges due to limited acoustic training data. In previous work, an ensemble of machine learning models was used to predict environmental sound levels in the contiguous United States using a training set composed of 51 geospatial layers (downselected from 120) and acoustic data from 496 geographic sites from Pedersen, Transtrum, Gee, Lympany, James, and Salton [JASA Express Lett. 1(12), 122401 (2021)]. In this paper, the downselection process, which is based on factors such as data quality and inter-feature correlations, is described in further detail. To investigate additional dimensionality reduction, four different feature selection methods are applied to the 51 layers. Leave-one-out median absolute deviation cross-validation errors suggest that the number of geospatial features can be reduced to 15 without significant degradation of the model's predictive error. However, ensemble predictions demonstrate that feature selection results are sensitive to variations in details of the problem formulation and, therefore, should elicit some skepticism. These results suggest that more sophisticated dimensionality reduction techniques are necessary for problems with limited training data and different training and testing distributions.

Study of electrical and fatigue properties of copper micro-alloyed wires in IGBT subject to chloride corrosion

In this study, the corrosion resistance and electrical and mechanical properties of 20 mil pure copper (Cu) and copper–phosphorus (CP) micro-alloyed wires were investigated. The experimental results show that both wires are equiaxed crystals containing twinning boundaries, and their similar grain sizes result in similar tensile properties and hardness values. In addition, both wires exhibit similar electrical performance characteristics; however, the CP wire has a more stable dynamic resistance and electrothermal impedance. The chloride corrosion tests showed that both wires experience pitting corrosion on the surface; chloride ions mainly corrode the twin boundaries and then the grain boundaries, which delays the corrosion process and prevents the significant degradation of the wire’s electrical properties after chlorination. Considering the application of wires in insulated gate bipolar transistors (IGBTs), the wire failure mechanism was evaluated through electrical and mechanical tests, including tests of the electrothermal fatigue mechanism to determine the electrical properties and bending fatigue tests to determine the mechanical properties. When subjected to chloride corrosion, the CP wire has fewer twin boundaries and a lower boundary corrosion resistance, resulting in a better basal effect that improves the corrosion resistance and promotes work hardening during bending. As a result, the CP wire has a longer current cycle life and better bending fatigue properties than the Cu wire. This confirms the excellent application reliability of CP wires subject to corrosion.

PH-Responsive Dynaplexes as Potent Apoptosis Inductors by Intracellular Delivery of Survivin siRNA.

Gene knockdown by siRNA offers an unrestricted choice of targets and specificity based on the principle of complementary Watson-Crick base pairing with mRNA. However, the negative charge, large molecular size, and susceptibility to enzymatic degradation of siRNA impede its successful transfection, hence limiting its potential for therapeutic use. The development of efficient and safe siRNA transfection agents is, therefore, critical for siRNA-based therapy. Herein, we developed a protein-based biodynamic polymer (biodynamer) that showed potential as a siRNA transfection vector, owing to its excellent biocompatibility, easy tunability, and dynamic polymerization under acidic environments. The positively charged biodynamers formed stable dynamic nanocomplexes (XL-DPs, hydrodynamic diameter of approximately 104 nm) with siRNA via electrostatic interactions and chemical cross-linking. As a proof of concept, the optimized XL-DPs were stable in physiological conditions with serum proteins and demonstrated significant pH-dependent size change and degradability, as well as siRNA release capability. The minimal cytotoxicity and excellent cellular uptake of XL-DPs effectively supported the intracellular delivery of siRNA. Our study demonstrated that the XL-DPs in survivin siRNA delivery enabled potent knockdown of survivin mRNA and induced notable apoptosis of carcinoma cells (2.2 times higher than a lipid-based transfection agent, Lipofectamine 2000). These findings suggested that our XL-DPs hold immense potential as a promising platform for siRNA delivery and can be considered strong candidates in the advancement of next-generation transfection agents.

Effect of Renewable Energy Consumption on Environmental Degradation in ASEAN Countries

This study focused on estimating the long-run and short-run relationship of dross domestic savings, development of the industrial sector, and renewable energy consumption towards the environmental degradation in Association of Southeast Asian (ASEAN) countries. We conducted the Pooled Mean Group (PMG) estimation techniques developed by Pesaran et al.(1999). The results highlighted that all the variables present significant environmental degradation while using renewable energy has abolished environmental pollution in ASEAN countries. Therefore, policymakers must take action to design sustainable economic development mechanisms and convert industrial investments to environmentally friendly projects to improve green technology.

A review on method development and validation of stability indicating RP HPLC Method for metformin and Empagliflozin

Metformin HCl and empagliflozin are oral antidiabetic medications that help control blood sugar levels. A simple, precise, rapid, accurate, sensitive, specific, and stable RP-HPLC method was developed and validated for the simultaneous determination of Metformin and Empagliflozin in drug bulk form and drug dosage. This new RP-HPLC method is superior to formal reversed-phase HPLC with reduced solvent usage, retention time, resolution, and cost. Upper region separation was performed on a Waters HPLC system equipped with a PDA detector and autosampler. Both Metformin and Empagliflozin undergo stress conditions including acid, alkali, oxidative, thermal, and photodegradation, but significant degradation was observed in acid studies. The newly developed RP HPLC chromatographic method was validated for system compatibility, linearity, robustness, accuracy, and precision.

Surface plasmon resonance effects of Ti3C2 MXene for degradation of antibiotics under full spectrum

The ML-(Ti1−X2+TiX3+)3C2VAlX(ML-Ti3C2) crystal was exfoliated into the crystal Ti3C2 MXene with coexistence of (Ti1−X2+TiX3+)3C2VAlX MXene and Ti2CVAlX MXene by HF etching Ti3AlC2 and ultrasonic crushing in water. Ti3C2 MXene exhibits the surface plasmon effects of transverse and longitudinal surface plasmon resonance due to its surface holes and internal bound electrons. When excited by the simulated sunlight, the high energy hot holes on the surface of plasma Ti3C2 MXene crystal directly oxidize the antibiotics and the organic pollutants. The electrons bound in the crystal lag behind the excitation of holes and migrate to the surface to further degradation. After 150 min of near infrared light irradiation, the degradation rates of tetracycline (TC) and ciprofloxacin (CIP) by Ti3C2 MXene are 78.91% and 99.26%, respectively. They are 1.35/1.00 and 1.53/3.11 times of ML-Ti3C2 and (001)TiO2/Ti3C2. This study indicates that Ti3C2 MXene has significant degradation effects on antibiotics in the full spectral range. Our work intends to provide a valuable reference for the design of the MXene full spectral photocatalyst.

An advanced analytical approach to assess the long-term degradation of microplastics in the marine environment

Determining the hazards posed by microplastics (MPs, <5 mm) requires an understanding of plastic degradation processes when exposed to environmental weathering forces. However, despite their perceived risks, limited information exists on the natural weathering progression of microplastics in marine environments. Our findings from environmentally realistic conditions reveal that long-term marine weathering resulted in significant degradation of plastic surfaces and bulk-phases, which varied by time and plastic polymer type. Plastics displayed biofouling, and an altered surface morphology, thermal stability and chemical signature. Secondary micronanoplastics (MNPs, <1 µm) were formed from weathered plastic surfaces, supported by a significant reduction in the size of PCL and PVC pellets. Using real world data, we reveal that plastic surfaces can degrade at a rate of up to 469.73 µm per year, 12 times greater than previous estimates. Our time-series data contributes valuable information towards developing plastic specific risk assessment frameworks and future plastics policy.