Stability Of Matrix Research Articles

Co-Assembly of Carbon Nanotube Porins into Biomimetic Peptoid Membranes.

Robust and cost-effective membrane-based separations are essential to solving many global crises, such as the lack of clean water. Even though the current polymer-based membranes are widely used for separations, their performance and precision can be enhanced by using a biomimetic membrane architecture that consists of highly permeable and selective channels embedded in a universal membrane matrix. Researchers have shown that artificial water and ion channels, such as carbon nanotube porins (CNTPs), embedded in lipid membranes can deliver strong separation performance. However, their applications are limited by the relative fragility and low stability of the lipid matrix. In this work,wedemonstrate that CNTPs can co-assemble into twodimension(2D) peptoid membrane nanosheets, opening up a way to produce highly programmable synthetic membranes with superior crystallinity and robustness. A combination of molecular dynamics (MD) simulations, Ramanspectroscopy, X-ray diffraction(XRD), and atomicforcemicroscopy(AFM) measurements to verify the co-assembly of CNTP and peptoids are used and show that it does not disrupt peptoid monomer packing within the membrane. These results provide a new option for designing affordable artificial membranes and highly robust nanoporous solids.

Influence of Microstructural Characteristics on Wear and Corrosion Behaviour of Si3N4-Reinforced Al2219 Composites

The fabrication of the Al2219 + Si3N4 composites was done by means of stir casting process. The specimen was subjected to microstructural studies. The density of Si3N4 employed in the fabrication of the composites has been evaluated. Generally, the density of the composites increases as the weight percent of Si3N4 increases. TGA and DTA were performed at temperatures ranging from 30°C to 800°C, with some mass loss noted as well as the thermal stability of an AA2219 matrix improved. Under various parameters of applied load, operating duration, and speed, the wear behaviour of the produced aluminium matrix composite (AMC) was examined. Corrosion behaviour was examined using potentiodynamic polarization curve data, and it was discovered that the rate of corrosion decreases with increasing Si3N4 content, adding to the AA2219 matrix. The research work is intended to produce a totally new composite material with various compositions of reinforcement and to investigate their mechanical properties and a result of simulation.

A novel Sn/SnOx Ti3C2Tx nanosheet for adsorptive strontium removal in aqueous solution

A novel Sn/SnOx@Ti3C2Tx adsorbent was fabricated via in situ growth of Sn/SnOx particles on layers of Ti3C2Tx nanosheets using facile electrostatic attraction followed by liquid-phase reduction. The characterization results demonstrated that Sn/SnOx particles were uniformly anchored onto the Ti3C2Tx surface and a sandwich-like-structured nanocomposite was formed. The introduction of Sn/SnOx particles increased the space between the Ti3C2Tx nanosheets, thereby increasing the number of active sites for Sr2+ ion removal. Moreover, the incorporated particles served as pillars to strengthen the structural stability of the Ti3C2Tx matrix and inhibited nanolayer restacking during Sr2+ion removal. Experimental results indicated that an initial strontium concentration of 5.0 mg/L was reduced to approximately 0.26 mg/L by Sn/SnOx@Ti3C2Tx within 90 min at pH 7. Furthermore, the Langmuir isotherm best fitted the adsorption data, and the maximum adsorption capacity of Sn/SnOx@Ti3C2Tx for Sr2+ ions was 71.04 mg/g at 298 K. Thus, Sn/SnOx@Ti3C2Tx nanocomposites is a promising adsorbent for the removal of Sr2+ ions from aqueous media.

The effects of hydrogen on dynamic fracture toughness of high-strength low-carbon medium manganese steel

The effect of retained austenite (RA) stability and dislocation density of martensite matrix on low-temperature dynamic fracture toughness and the hydrogen embrittlement (HE) susceptibility was investigated in a high-strength low-carbon medium manganese steel subjected to three different heat treatments, i.e., the inter-critical annealing at 630 °C (QHA), inter-critical annealing at 610 °C (QLA), and direct quenching (DQ). Dynamic cracked three-point bending tests were performed at 20 °C and −40 °C with and without hydrogen charging. The RA volume fraction and the martensite matrix's dislocation density significantly affected the dynamic fracture toughness and HE behavior. All QHA and QLA tested at 20 °C fractured in the ductile mode, but all DQ and QLA tested at −40 °C fractured in the brittle mode. Dynamic fracture toughness decreases with RA volume fraction under the same tested temperature. The HE mechanism in the ductile region is HELP, and that in the brittle region is HEDE.

A Selective and Accurate LC-MS/MS Method for Simultaneous Quantification of Valsartan and Hydrochlorothiazide in Human Plasma

The fixed dose combination of valsartan (VAL) and hydrochlorothiazide (HCTZ) is the most commonly prescribed medicine for the effective treatment of hypertension. In this study, a simple sensitive and accurate liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the simultaneous quantitation of VAL and HCTZ in human plasma by using irbesartan (IRB) and hydroflumethiazide (HFMZ) as their specific internal standards (ISs). HLB cartridge-based solid-phase extraction was used for the extraction of analytes and ISs. The chromatographic separation was achieved on Lichrocart RP Select (125 × 4 mm), 5 nm with the mobile phase composition of acetonitrile: 10 mM ammonium acetate buffer: 95:05, v/v, at flow rate of 0.5 mL/min. The turbo ion electrospray ionization in negative mode was used as ion source for the sample ionization. The precursor to product ion transitions were 434.10 > 179.10 (VAL), 295.70 > 204.90 (HCTZ), 427.10 > 192.90 (IRB), and 329.90 > 302.40 (HFMZ) for detection and quantification of analytes and their ISs. The retention times of VAL and HCTZ were 1.90 min and 2.30 min, respectively. The range for the calibration curves of VAL and HCTZ were 50.2–6018.6 ng/mL and 1.25–507.63 ng/mL, respectively, with good linearity having correlation coefficient values of ≥0.995 for both VAL and HCTZ. All validation parameter results (selectivity, precision and accuracy, matrix effects and stabilities) were within the acceptable range as per USFDA guideline for bioanalytical method validation. The intra-day and inter-day accuracy data for VAL were within the range of 105.68–114.22% and 98.41–108.16%, respectively, whereas for HCTZ they were 87.01–101.18% and 95.16–99.37%, respectively. The ion suppression effects produced for VAL and ion enhancement effects produced for HCTZ were insignificant according to the proposed sample cleanup procedure. The developed LC-MS/MS method was successfully applied to bioequivalence study on healthy volunteers.

First-principles calculation and experimental study on the effect of rare earth Ce and Nd on the corrosion behavior of Mg alloys

In this study, the influence mechanism of rare earth elements Ce and Nd on the corrosion behavior of Mg alloy was studied by combining experimental characterization with the first-principles calculation. The changes of work function and surface energy of the rare Earth phase and matrix phase in binary rare Earth Mg alloys Mg-0.3%Ce and Mg-0.3%Nd. In addition, the electronic properties of the second rare Earth phase and matrix phase, and the correlation between the interface energy of the second rare Earth phase and matrix and the corrosion behavior of Mg alloys were investigated. The experimental results show that Mg12Ce and Mg12Nd as the second phases of Mg-0.3%Ce and Mg-0.3%Nd, respectively, have not obvious roles in the galvanic corrosion of the alloys. The corrosion morphology of the two alloys is similar, the matrix undergoes filamentary corrosion through the grain to a large area. The results of the first-principles calculation show that the binding energy of the rare Earth phase is higher than that of the matrix phase, this implied the addition of light rare Earth elements Ce and Nd can improve the stability of the second phase. The work function of different surfaces of the second phase is similar to that of the matrix phase, so limited effect of the rare Earth phase on corrosion behavior has been found. In addition, the addition of rare Earth Ce and Nd will decrease the surface stability of Mg matrix, this result reaffirms the higher corrosion rates of Mg-0.3%Ce and Mg-0.3%Nd over that of the pure Mg.

Synergistic effect of silica nanoparticles assisted by rosemary powder in the stabilization of styrene-isoprene-styrene triblock copolymer

The synergistic efficiency in the improvement of thermal and radiation stabilities of polymer substrate (styrene-isoprene-styrene triblock copolymer) is studied by isothermal and nonisothermal chemiluminescence, when silica nanoparticles loaded in various proportions (1, 2, and 3 wt%) are coupled with rosemary in the dropping down the degradation rate. The measurements of chemiluminescence emission intensities at various degradation degrees obtained by accelerated ageing with γ-radiation provide the evidences for a synergistic action of n-silica nanoparticles/rosemary extract upon the stability of polymer matrix. The main kinetic parameter, oxidation induction time (OIT), which describes the stabilization efficiency of additives by the hindering of oxidation presents illustrative values for the co-operation factors between the two prevention components. The synergistic effect is evident: the OIT of couple action is much higher than the values that characterize component activities. This feature has much higher values than unity. The contribution of this inorganic/organic antioxidant couple is discussed based on the activation energy values calculated by Arrhenius method. The effects of silica nanoparticles on the delay of degradation is also analyzed by means of nonisothermal chemiluminescence measurements, which prove the increase of protection activity when the silica loading is enhanced from 1 to 3 wt%. The applications of this stabilization couple may be found in the areas of food handling, pharmaceutics, medical wear, dentistry, nuclear sealing, commodities, and many suitable others.

Synthesis of sustainable flame retarded polypropylene by using waste material

The use of a waste material as flame retardant for polypropylene (PP), i.e. flue gas desulfurization (FGD) gypsum, has been studied. FGD gypsum has been used alone or in combination with melamine cyanurate (MC) and a phosphate ester (SolDP), which acts also as polymer plasticizer. Several formulations have been investigated in order to obtain UL94-V2 rated PP at 3.2 mm thickness.The results have demonstrated that 20 wt% of FGD is the optimal amount to be used together with 15 wt% MC and 3 wt% SolDP to get UL94-V2 PP material. The flame retardancy action of MC and SolDP can be, indeed, further strengthen by the presence of FGD filler, which is essential to guarantee the good fire reaction obtained. The results have also shown that the control of the dripping phenomena is essential and therefore a suitable plasticizer, acting also as flame retardant, shall be used in this system. The content of the plasticizer shall be optimized since, from one side, it favours dripping but, on the other side, it tends to decrease the heat stability of the polymeric matrix when used at high content (>5%). Finally, a synergy between this phosphate ester plasticizer and MC has also been revealed.

Determination of valproic acid and its six metabolites in human serum using LC-MS/MS and application to interaction with carbapenems in epileptic patients.

Valproic acid (VPA) is a classic medication for several types of epilepsy and mood disorders, and some of its effectiveness and toxicity is associated with metabolites. Although many reports have reported the drug-drug interactions of VPA, no study has focused on the influence of carbapenems (CBPMs) on VPA's active metabolites. An LC-MS/MS method for determining VPA and its six metabolites (3-hydroxy valproic acid, 4-hydroxy valproic acid, 2-propyl-2-pentenoic acid, 2-propyl-4-pentenoic acid, 3-keto valproic acid, and 2-propylglutaric acid) in human serum was established and applied to evaluate the drug-drug interaction with CBPMs in epileptic patients. The stable isotope valproic acid-d6 was used as an internal standard. Analytes in serum samples (50 μl) were isolated using a Kinetex C18 column (3× 100 mm, 2.6μm) and detected via negative electrospray ionization after protein precipitation. It was linear (r> 0.99) over the calibration range for different analytes. The accuracy was 91.44-110.92%, and the precision was less than 9.98%. The matrix effect, recovery, and stability met the acceptance criteria. According to the data collected from 150 epileptic patients, the concentration-dose ratio for VPA and its metabolites decreased with CBPM polytherapy. This method is simple and rapid with great accuracy and precision. It is suitable for routine clinical analysis of VPA and its metabolites in human serum.

Improvement of UV stability of thermoplastic starch matrix by addition of selected lignin fraction - Photooxidative degradation

This paper examines the additivation of thermoplastic starch (TPS) matrix by selected fractions of kraft lignin (KL) and correlates its structure-performance when exposed to photooxidative degradation. KL from Eucalyptus urograndis wood was refined by a sequential fractionation process in ethyl acetate (EtOAc). Films were prepared by mixing lignin fractions as additive in TPS matrix by casting and pressing. The lignin employed were KL, fraction of KL insoluble in EtOAc (INS) and fraction of KL soluble in EtOAc (SOL). The samples were exposed to accelerated aging with Ultraviolet-C light (UV-C) for 432 h. Structural changes were measured by FTIR (Fourier-Transform Infrared) spectra. Thermal properties, such as melting enthalpy, glass transition temperature and thermal decomposition, were evaluated by DSC (Differential Scanning Calorimetry) and TG (Thermogravimetry). Morphology of the films was obtained by SEM (Scanning Electron Microscopy). Surface property of wettability was measured by contact angle. Mechanical properties were explored before and after exposure to UV-C light. It was observed that the least photodegraded films were those resulting from the addition of the lignin fraction with higher phenolic hydroxyl group content. According to structural and morphological observations, the soluble fraction (TSOL) presented the highest photoprotection and stabilizing effect as an UV-C light blocker additive on TPS matrix.

Distributed Stabilization of Signed Networks via Self-loop Compensation

The positive semidefiniteness of Laplacian matrices is a critical guarantee of the consensus of unsigned multi-agent networks, which is not valid for signed Laplacian matrices. In this paper, we first analyze the stability of signed networks by introducing a novel graph-theoretic concept called <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">negative cut set</i> , which indicates that the existence of negative edges in signed networks can easily render the network unstable. This fact hinders the applicability of consensus protocol on signed networks. To this end, inspired by the interplay between diagonal dominance and matrix stability, a local state damping mechanism is introduced using <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">self-loop compensation</i> , which is activated only for those agents who are incident to negative edges and can stabilize signed networks in a distributed manner. Quantitative connections between self-loop compensation and the stability of the compensated signed network are established for a tradeoff between compensation efforts and the stability/consensus of signed networks. The optimality of self-loop compensation is discussed. Furthermore, we extend our results to directed signed networks where the symmetry of signed Laplacian is not free. The correlation between the stability of the compensated dynamics obtained by self-loop compensation and eventually positivity is further discussed. Simulation examples are given to demonstrate the theoretical results.

The role of Eudragit® as a component of hydrogel formulations for medical devices.

Over the last decade, significant progress has been made in developing hydrogels as medical devices. By physically cross-linking pharmaceutically approved polymers into three-dimensional matrices, we can ensure their biocompatibility and facilitate their seamless transition from the laboratory to clinical applications. Moreover, the reversible nature of their physical cross-links allows hydrogels to dissolve in the presence of external stimuli. Particularly, their high degree of hydration, high molecular weight, and superior flexibility of the polymer chains facilitate their interaction with complex biological barriers (e.g., mucus layer), making them ideal candidates for mucosal drug delivery. However, fine-tuning the composition of the hydrogel formulations is of great importance to optimize the performance of the medical device and its therapeutic cargo. Herein, we investigated the influence of different Eudragits® on the properties of hydrogels based on polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), and polyethylene glycol (PEG), which were originally proposed as ocular inserts in previous reports. Our research aims to determine the effects that including different Eudragits® have on the structure and protein ocular delivery ability of various hydrogel formulations. Properties such as matrix stability, protein encapsulation, release kinetics, mucoadhesion, and biocompatibility have been analyzed in detail. Our study represents a guideline of the features that Eudragits® have to exhibit to endow hydrogels with good adhesion to the eye's conjunctiva, biocompatibility, and structural strength to cope with the ocular biointerface and allow sustained protein release. This work has important implications for the design of new hydrogel materials containing Eudragits® in their composition, particularly in mucosal drug delivery.

Study of Thermal, Phase Morphological and Mechanical Properties of Poly(L-lactide)-b-Poly(ethylene glycol)-b-Poly(L-lactide)/Poly(ethylene glycol) Blend Bioplastics

A poly(L-lactide)-b-poly(ethylene glycol)-b-poly(L-lactide)(PLLA-PEG-PLLA) block copolymer has great potential for use as a flexible bioplastic. Highly flexible bioplastics are required for flexible packaging applications. In this work, a PEG was incorporated into block copolymer as a plasticizer by solvent casting. PLLA-PEG-PLLA/ PEG blends with different blend ratios were prepared, and the plasticizing effect and miscibility of PEG in block copolymer were intensively investigated compared to PLLA/PEG blends. The results indicated that the PEG was an effective plasticizer for the block copolymer. The blending of PEG decreased glass-transition temperature and accelerated the crystallization of both the PLLA and PLLA-PEG-PLLA matrices. The PEG was completely miscible when blended with block copolymer and it improved thermal stability of the block copolymer matrix but not of the PLLA matrix. Film extensibility of PLLA-PEG-PLLA/PEG blends steadily increased as the PEG ratio increased. These non-toxic and highly flexible PLLA-PEG-PLLA/PEG bioplastics are promising candidates for several applications such as biomedical devices, tissue scaffolds and packaging materials.

One-Pot Hydrothermal Preparation of Hydroxyapatite/Zinc Oxide Nanorod Nanocomposites and Their Cytotoxicity Evaluation against MG-63 Osteoblast-like Cells.

In the present study, HAp-ZnO nanorod nanocomposites were successfully prepared using a customized hydrothermal reactor and studied for their compatibility against MG-63 osteoblast-like cells. The crystallinity, morphology, presence of chemical elements, and surface area properties were studied by XRD (X-ray diffraction), FE-SEM (field emission scanning electron microscopy), TEM (transmission electron microscopy), EDS (energy dispersive spectrum) and N2 adsorption/desorption isotherm techniques, respectively. Further, the mechanical strength and thermal analysis were carried out using the nanoindentation method and thermogravimetric/differential scanning calorimeter (TG/DSC) methods, respectively. Moreover, in vitro biocompatibility studies for the prepared samples were carried out against human osteosarcoma cell lines (MG-63). The crystalline nature of the samples without any impurity phases was notified from XRD results. The formation of composites with the morphology of nanorods and the presence of desired elements in the intended ratio were verified using FE-SEM and EDS spectra, respectively. The TG/DSC results revealed the improved thermal stability of the HAp matrix, promoted by the reinforcement of the ZnO nanorods. The nanoindentation study ensured a significant enhancement in the mechanical stability of the prepared composite material. Finally, it demonstrated that the HAp matrix's mechanical strength and thermal stability were improved by the reinforcement of ZnO, and the cytotoxicity evaluation affirmed the biocompatible nature of the biomimetic hydroxyapatite in the composite.

Effects of adding B element on amorphous forming ability, magnetic properties, and mechanical properties of FePBCCu alloy

Fe-based amorphous alloys are widely used in power electronics fields such as transformers and reactors due to their low coercivity, high permeability and low loss. However, the relatively low saturation magnetization (&lt;i&gt;B&lt;/i&gt;&lt;sub&gt;s&lt;/sub&gt;) limits their further applications. Generally speaking, the adjustable magnetic Fe content as an effective strategy can ameliorate the magnetic properties, and the higher the Fe content, the higher the obtained &lt;i&gt;B&lt;/i&gt;&lt;sub&gt;s&lt;/sub&gt; is, but the decrease of the corresponding non-magnetic element content will result in the drop of the ability of alloys to form amorphous phase, leading to the deterioration of the magnetic softness and bending ductility of nanocrystalline alloys. To address this critical issue, in this work, based on the metal-metalloid hybridization, the FePBCCu amorphous ribbons, each with a thickness of ~25 μm, are prepared by the single-roller melt spinning method via 7% (atomic percent) B substitution for P, and the effects of B element addition on the ability to form amorphous phase, magnetic properties and mechanical properties of ribbons are investigated. Thermodynamic behavior shows that the addition of small quantities of B element can reduce the structural heterogeneity of alloy and the crystallization driving force as well, thus effectively improving the thermal stability of the amorphous matrix. The melting and solidification curves show that the addition of B can promote alloy to approach to the eutectic composition, and there is a large degree of undercooling. As a result, the critical thickness of ribbons increases from ~21 μm for B-free alloy to ~30 μm for B-added alloy due to the micro-alloying effect. The addition of B increases the effective magnetic moment of magnetic atoms in alloy, resulting in the increase of the saturation magnetization. Furthermore, the results of nanoindentation tests show that the modulus value of the B-added alloy decreases greatlyr and fluctuates in a smaller range than that of the B-free alloy, which is closely associated with the structural uniformity of the alloy.

A liquid chromatography-miniature mass spectrometry (LC-Mini MS) method for quantitative analysis of risperidone and 9-hydroxyrisperidone in plasma.

Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is a universal method for the quantitative analysis of small molecular drugs in therapeutic drug monitoring (TDM). Alternatively, liquid chromatography-miniature mass spectrometry (LC-Mini MS) is a simple operating technique for quantitative analysis. However, the wide chromatographic peaks and long retention times of TDM samples using the LC-Mini MS system deteriorated the accuracy and efficiency of quantitative analysis. Here, an optimized electrospray ionization (ESI) interface setup with a splitter valve and a capillary needle (I.D. 30 μm and O.D. 150 μm) of the LC-Mini MS system was acquired. The chromatographic peaks were narrower and smoother and the retention time was shorter for TDM compounds. Furthermore, a quantitative analysis method for risperidone and the active metabolite 9-hydroxyrisperidone in plasma was developed based on this optimal LC-Mini MS setup. The results showed that the calibration curves of risperidone and 9-hydroxyrisperidone had good linear ranges of 2-100 ng mL-1 (R2 = 0.9931) and 2-100 ng mL-1 (R2 = 0.9915), respectively. Finally, the matrix effects, recoveries and stability of risperidone and 9-hydroxyrisperidone samples were analyzed. The results satisfied the requirements of quantitative validation in routine TDM procedures.

Optimal Control and Bifurcation Analysis of HIV Model.

In this study, a very crucial stage of HIV extinction and invisibility stages are considered and a modified mathematical model is developed to describe the dynamics of infection. Moreover, the basic reproduction number R 0 is computed using the next-generation matrix method whereas the stability of disease-free equilibrium is investigated using the eigenvalue matrix stability theory. Furthermore, if R 0 ≤ 1, the disease-free equilibrium is stable both locally and globally whereas if R 0 > 1, based on the forward bifurcation behavior, the endemic equilibrium is locally and globally asymptotically stable. Particularly, at the critical point R 0 = 1, the model exhibits forward bifurcation behavior. On the other hand, the optimal control problem is constructed and Pontryagin's maximum principle is applied to form an optimality system. Further, forward fourth-order Runge-Kutta's method is applied to obtain the solution of state variables whereas Runge-Kutta's fourth-order backward sweep method is applied to obtain solution of adjoint variables. Finally, three control strategies are considered and a cost-effective analysis is performed to identify the better strategies for HIV transmission and progression. In advance, prevention control measure is identified to be the better strategy over treatment control if applied earlier and effectively. Additionally, MATLAB simulations were performed to describe the population's dynamic behavior.

Combustion performance of hybrid rocket fuels loaded with MgB2 and carbon black additives

Paraffin-based fuel has a great potential for several innovative missions, including space tourism, due to its safety, low environmental impact, high performance and low cost. Despite the fact that liquefying solid fuels increases the regression rate of hybrid rocket motors, incorporating energetic materials into solid fuel can still improve the performance. The objective and scope of this study is to increase the performance characteristics of the paraffin-based fuel by using magnesium diboride (MgB2) and carbon black (CB) additives. The cylindrical-port fuel grains were manufactured with various additives percentages in mass (wt%: CB-2% and MgB2-10%) and tested using a laboratory-scale ballistic hybrid motor under gaseous oxygen. The mechanical performance results revealed that adding CB and MgB2 improved the ultimate strength and elastic modulus of paraffin-based fuels. The addition of these fillers increased the hardness of fuel by developing a strong interaction in the paraffin matrix. Thermogravimetry (TG) results showed that CB inclusion improved the thermal stability of the paraffin matrix. The average regression rates of fuels loaded with CB and MgB2 were 32% and 52% higher than those of unmodified paraffin wax, respectively. The characteristic velocity efficiency was found in the range of 68%–79% at an O/F ratio of 1.5–2.6. The MgB2 oxidation/combustion in the paraffin matrix was described by a four-step oxidation process ranging from 473 K to 1723 K. Finally, a combustion model of MgB2 in the paraffin matrix was proposed, and four-step oxidation processes were discussed in detail.

Green composites from vanillin-based benzoxazine and silane surface modified chopped carbon fibers

By following the rules of green chemistry, a novel composite is developed from a renewable and ecofriendly resource, namely, vanillin. The latter was used as a phenolic precursor for the microwave synthesis of a bio-based benzoxazine resin (Va-BZ). Afterward, high-performance green composites were developed by reinforcing Va-BZ with various amounts of chopped silane surface modified carbon fibers (CFs). The chemical structure of the Va-BZ monomers was confirmed by 1H NMR and Fourier transform infrared spectroscopy. The grafting of the silane moiety on the CF surface was assessed by FTIR and TGA analyses. The autocatalytic ring opening polymerization of the Va-BZ monomers was confirmed by DSC analysis. The mechanical performances of the developed green composites were studied by flexural and tensile investigations. The findings suggested that the maximum amount of 20 wt. CFs afforded the best results, with flexural and tensile strengths of 450 and 462 MPa, respectively. The SEM was used to study the fractured tensile surfaces and elucidated the toughening mechanism. Meanwhile, the TGA showed that the introduction of the CFs markedly improved the thermal stability of the benzoxazine matrix. Overall, this study confirmed that greener approaches can also result in high-performance composites satisfying the needs of exigent applications.

On the selection of a better radial basis function and its shape parameter in interpolation problems

A traditional criterion to calculate the numerical stability of the interpolation matrix is its standard condition number. In this paper, it is observed that the effective condition number (κeff) is more informative than the standard condition number (κ) in investigating the numerical stability of the interpolation problem. While the κeff considers the function to be interpolated, the standard condition number only depends on the interpolation matrix. We propose using the shape parameter corresponding to the maximum κeff to obtain a small error in RBF interpolation. It is also observed that the κeff helps to predict the error behavior with respect to the type of the RBF, where the basis function with a higher effective condition number yields a smaller error. In the end, we conclude that the effective condition number links to the error with respect to the selection of a radial basis function, choosing its shape parameter, number of collocation points, and test function. To this end, ten test functions are interpolated using the multiquadric, Matern family, and Gaussian basis functions to show the advantage of the proposed method.