Stability Of Mono Research Articles

A sustainable approach for the preparation and stability of mono and hybrid nanofluids in the milling of Nickel based superalloy

This work is focused on enhancing the sustainability and machinability in finish end-milling of Nimonic 90 superalloy using nanofluid-assisted machining. The research deals with the preparation and analysis of the stability of hybrid nanofluids for the machining of Nimonic 90. The UV–visible absorption of prepared mono and hybrid nanofluids are examined and based on the absorption curves, and 1% of the weight of the nanoparticles is chosen. The samples have been used to estimate the ideal ultrasonication time and its behaviour with various ionic and non-ionic surfactants have been determined. By examining the UV–visible absorption curves, the shelf life of the hybrid nanofluid is obtained, and it is found to be equivalent to that of the freshly prepared nanofluid. When preparing nanofluids based on alumina and hBN, tween 80 and Sodium Dodecyl Sulfate (SDS) has proved to be to be superior surfactants, respectively. Furthermore, toxicity test has revealed that the well-dispersed nanofluid are non-toxic in nature, with hybrid nanofluid exhibiting 84% cell viability. The hybrid nanofluid possesses a zeta potential of −30.8 mV. Additionally, has been observed that all the prepared nanofluids exhibited Newtonian behaviour and that their viscosities are 15%–20% higher than those of the base fluid. During the nanofluid assisted machining with hybrid nanofluid, the machining results of Nimonic 90 superalloy demonstrate the synergistic influence of both nanoparticles. Compared to dry machining, the hybrid nanofluid has a 48.80% reduction in cutting forces, 72.66% reduction in cutting temperature, 63.63% reduction in surface roughness, and 46.03% reduction in flank wear. Additionally, a Pugh matrix assessment score of 9 compared to the score of −5 for dry machining indicates that the usage of hybrid nanofluid as a cutting condition has substantial potential for future sustainable machining methods.

Insight into the liposomal encapsulation of mono and bis-naphthalimides.

Mitonafide-loaded liposomes are a promising strategy to overcome the neurotoxicity observed in clinical trials for this drug. This study investigates the influence of loaded mitonafide or a dimer analogue on different liposomal formulations and their therapeutic efficacy in vitro. Physicochemical properties of the liposomes were manipulated using different loading methods (namely bilayer or core loading) and varying the rigidity of the bilayer using distinct phospholipid compositions. Our results demonstrated that the mitonafide dimer analogue had a comparable encapsulation efficiency (EE%) into the liposomes when loaded into rigid or flexible bilayers in contrast to the low mitonafide monomer EE%. A pH gradient core loading method resulted in a more efficient mechanism to load the monomer into the liposomes. DOSY NMR and spectrofluorometric studies revealed key differences in the structure of the vesicles and the arrangement of the monomer or the dimer in the bilayer or the core of the liposomes. The in vitro assessment of the formulations using MDA-MB-231 and RT-112 cells revealed that a flexible lipid bilayer allows a faster drug release, which correlated well with the spectroscopy studies. This study investigated for the first time that the characteristics of the lipid bilayer and the loading method influence the encapsulation efficacy, colloidal properties, photoactivity and stability of mono and bis-naphthalimides loaded in a liposomal carrier, essential factors that will impact the performance of the formulation in a biological scenario.

Reproduction of Nanofluid Synthesis, Thermal Properties and Experiments in Engineering: A Research Paradigm Shift

The suspension of different nanoparticles into various conventional thermal fluids to synthesize nanofluids has been proven to possess superior thermal, optical, tribological, and convective properties, and the heat transfer performance over conventional thermal fluids. This task appears trivial but is complicated and significant to nanofluid synthesis and its subsequent utilization in diverse applications. The stability of mono and hybrid nanofluids is significantly related to stirring duration and speed; volume, density, and base fluid type; weight/volume concentration, density, nano-size, and type of mono or hybrid nanoparticles used; type and weight of surfactant used; and sonication time, frequency, mode, and amplitude. The effects of these parameters on stability consequently affect the thermal, optical, tribological, and convective properties, and the heat transfer performance of nanofluids in various applications, leading to divergent, inaccurate, and suspicious results. Disparities in results have inundated the public domain in this regard. Thus, this study utilized published works in the public domain to highlight the trend in mono or hybrid nanofluid formulation presently documented as the norm, with the possibility of changing the status quo. With the huge progress made in this research area in which a large quantum of different nanoparticles, base fluids, and surfactants have been deployed and more are still emerging in the application of these advanced thermal fluids in diverse areas, there is a need for conformity and better accuracy of results. Reproduction of results of stability, thermal, optical, tribological, anti-wear, and fuel properties; photothermal conversion; and supercooling, lubrication, engine, combustion, emission, thermo-hydraulic, and heat transfer performances of formulated mono or hybrid nanofluids are possible through the optimization and detailed documentation of applicable nanofluid preparation parameters (stirring time and speed, sonication duration, amplitude, mode, frequency, and surfactant concentration) employed in formulating mono or hybrid nanofluids. This proposed approach is expected to project a new frontier in nanofluid research and serve as a veritable working guide to the nanofluid research community.

Influence of Preparation Characteristics on Stability, Properties, and Performance of Mono- and Hybrid Nanofluids: Current and Future Perspective

Nanofluids (NFs) synthesized via the suspension of diverse nanoparticles into conventional thermal fluids are known to exhibit better thermal, optical, tribological, and convective properties, photothermal conversion, and heat transfer performance in comparison with traditional thermal fluids. Stability is pivotal to NF preparation, properties, performance, and application. NF preparation is not as easy as it appears, but complex in that obtaining a stable NF comes with the harnessing of different preparation parameters. These parameters include stirring duration and speed, volume, density, base fluid type, weight/volume concentration, density, nano-size, type of mono or hybrid nanoparticles used, type and quantity of surfactant used, and sonication time, temperature, mode, frequency, and amplitude. The effect of these preparation parameters on the stability of mono and hybrid NFs consequently affects the thermal, optical, rheological, and convective properties, and photothermal conversion and heat transfer performances of NFs in various applications. A comprehensive overview of the influence of these preparation characteristics on the thermal, optical, rheological, and properties, photothermal conversion, and heat transfer performance is presented in this paper. This is imperative due to the extensive study on mono and hybrid NFs and their acceptance as advanced thermal fluids along with the critical importance of stability to their properties and performance. The various preparation, characterization, and stability methods deployed in NF studies have been compiled and discussed herein. In addition, the effect of the various preparation characteristics on the properties (thermal, optical, rheological, and convective), photothermal conversion, and heat transfer performances of mono and hybrid NFs have been reviewed. The need to achieve optimum stability of NFs by optimizing the preparation characteristics is observed to be critical to the obtained results for the properties, photothermal conversion, and heat transfer performance studies. As noticed that the preparation characteristics data are not detailed in most of the published works and thus making it mostly impossible to reproduce NF experimental studies, stability, and results; future research is expected to address this gap. In addition, the research community should be concerned about the aging and reusability of NFs (mono and hybrid) in the nearest future.

Axially and Helically Chiral Cationic Radical Bicarbazoles: SOMO-HOMO Level Inversion and Chirality Impact on the Stability of Mono- and Diradical Cations.

We report persistent chiral organic mono- and diradical cations based on bicarbazole molecular design with an unprecedented stability dependence on the type of chirality, namely, axial versus helical. An unusual chemical stability was observed for sterically unprotected axial bicarbazole radical in comparison with monocarbazole and helical bicarbazole ones. Such results were experimentally and theoretically investigated, revealing an inversion in energy of the singly occupied molecular orbital (SOMO) and the highest (doubly) occupied molecular orbital (HOMO) in both axial and helical bicarbazole monoradicals along with a subtle difference of electronic coupling between the two carbazole units, which is modulated by their relative dihedral angle and related to the type of chirality. Such findings allowed us to explore in depth the SOMO-HOMO inversion (SHI) in chiral radical molecular systems and provide new insights regarding its impact on the stability of organic radicals. Finally, these specific electronic properties allowed us to prepare a persistent, intrinsically chiral, diradical which notably displayed near-infrared electronic circular dichroism responses up to 1100 nm and almost degenerate singlet-triplet ground states with weak antiferromagnetic interactions evaluated by magnetometry experiments.

Stability study of germanene vacancies: The first-principles calculations

By using the first-principles density functional theory, stability of mono- and divacancies of germanene is studied. We simulate two configurations of monovacancies (Mo1, and Mo2) and three configurations of divacancies (Di1, Di2, and Di3). The calculated formation energies are 2.03, 2.34, 2.54, 3.38, 3.68 eV for Mo1, Mo2, Di1, Di2, and Di3, respectively. In the case of monovacancies, Mo1 has no broken-bond stabilizing its geometry and forming a fourfold configuration with tetrahedral symmetry. Meanwhile Mo2 forms a C2v symmetry leaving two broken-bonds that make Mo2 less stable than Mo1. As for the divacancies, Di1 and Di2 are more stable than Di3, originating from the absence of broken-bonds. Meanwhile, Di1 is the most stable configuration maintaining the sp2 hybridization. The metastability of Di2 compared with Di1 is that there are two fourfold configurations in Di2 replacing the sp2 by sp3 hybridization which requires higher energies.

Delivery and Release of Small-Molecule Probes in Mitochondria Using Traceless Linkers.

Mitochondria-penetrating peptides (MPPs) are specific targeting vectors for the localization of small molecules to the mitochondrial matrix. Mitochondrial targeting of small molecules has enabled the development of a number of potential therapeutics and chemical probes. However, the need for covalent conjugation of small molecules to MPPs can negatively affect the activity of the appended cargo against its cellular target. Here, we describe cleavable linkers designed for the traceless release of chemical cargo from MPPs following mitochondrial transit. The cleavage kinetics of a number of disulfides were investigated using a fluorescent reporter system in order to optimize linker stability for mitochondrial release. The stability of mono- and disubstituted disulfides was determined to be sufficient during transit through the cytosol while still allowing for release of the cargo within 24 h. This linker system successfully released the compound Luminespib, an HSP90 inhibitor, which was deactivated by direct MPP conjugation. The releasable conjugate regenerated Luminespib activity and induced mitochondrial phenotypes of HSP90 inhibition. This linker may prove useful in expanding the repertoire of small molecules that can be used with mitochondrial targeting vectors.

Effect of the composition of dimethyl sulfoxide–acetonitrile solvent on the stability of silver(I) complexes with 2,2'-bipyridyl

The effect of composition of the dimethyl sulfoxide–acetonitrile solvent on the shift in complexation equilibrium of silver(I) and 2,2'-bipyridyl was studied potentiometrically at 298.15 K. The stability of mono- and bis(bipyridyl) complexes of silver(I) was found to rise with increasing acetonitrile content in the mixed solvent. The difference in changes in the solvation state of the central and complex ions (the solvation effect of ions) was found to make a major contribution to the changes in stability of silver(I) complexes with 2,2'-bipyridyl in dimethyl sulfoxide–acetonitrile binary solvent.

Electronic Structure and Stability of Mono- and Bimetallic Borohydrides and Their Underlying Hydrogen-Storage Properties: A Cluster Study

Using gradient corrected density functional theory and a cluster-based model we have studied the stability and hydrogen-storage properties of monometallic borohydrides, M(BH4)3, and bimetallic borohydrides, KM(BH4)4 (M = Al, Ga, Sc). A systematic study of BHx (x = 1–4), M(BH4)n (M = Al, Ga, Sc; n = 1–4), and KM(BH4)4 reveals many interesting results. (i) The vertical detachment energy of BH4– is larger than that of any halogen atom; hence, BH4 can be classified as a superhalogen. (ii) When a metal atom, M, is surrounded with BH4 moieties whose number exceed the valence of the metal atom by one, a new class of highly electronegative molecules referred to as hyperhalogens can be formed. (iii) Both BH4– and M(BH4)4– can serve as the building blocks of super- and hyper-salts, respectively, when counterbalanced with a metal cation such as K+. (iv) The energy required to remove a hydrogen atom from a bimetallic borohydride such as KAl(BH4)4 is found to be less than that from the corresponding monometallic borohydride, namely Al(BH4)3, thus making bimetallic borohydrides potential candidates for hydrogen-storage materials. We hope these results will stimulate experimental investigation into new super- and hyperhalogens and their corresponding salts as potential hydrogen-storage materials.

Quantum-chemical calculations on the stability and mobility of vacancies in graphene

Thermodynamic stabilities of mono- and bivacancies in graphene for deformed and nondeformed lattices are estimated by means of quantum-chemical calculations. Monovacancy hopping constants are evaluated in dependence on the applied uniaxial deformations.

Rh–Ni/CeO2–Al2O3 catalysts for methane dry reforming

A series of Ni and Rh–Ni catalysts supported on Al2O3 modified by CeO2 (3 and 5wt%, Ce) was studied for CO2 reforming of methane. Catalysts were characterized by hydrogen chemisorption, TPR, XRD, XPS, BET, TEM and dry reforming reaction tests. The influence of calcination temperature and Ce loading on activity and stability of mono and bimetallic samples was studied. The effect of Rh and Ce addition to Ni/a-Al2O3 catalyst improves the activity. Results show that the catalyst content 3%w/w Ce calcined at 650°C, present higher reforming activity and stability than the unpromoted catalyst. The higher catalytic activity is attributed to the interaction between Rh and Ce phases, which has been verified by TPR experiments that improve the Rh dispersion and increase the catalyst active surface. The Rh addition on Ce–Al2O3 support increases the resistance to deactivation by carbon deposition.

Geometrical Isomerism and Stability of Mono- and Dichalcogenide Analogs of Carbamic Acid H2NC(=X)YH (X, Y = O, S, Se)

Abstract Activation barriers for geometrical isomerism and tautomerization have been studied for carbamic acid and its mono- and dichalcogenide analogs at B3LYP/6-31+G*, MP2/6-31+G*, and G2MP2 theoretical levels. The studies indicate that carbamic acid with higher chalcogen prefers chalcogen at the chalcogenol position. Proton affinities, gas-phase acidities and atomic charges for these molecules have also been evaluated. Unimolecular, bimolecular, and two-step pathways for the decomposition of carbamic acid and its analogs are also analyzed, from which it was concluded that the two step mechanism is the more plausible pathway.

Atomic Geometry and Stability of Mono-, Di-, and Trivacancies in Graphene

Stability and atomic geometry of mono-, di-, and trivacancies in graphene sheets are studied by using first-principles calculations. We find that the atomic relaxation substantially contributes to the stability of the vacancies. The monovacancy is found to have a nonplanar structure, i.e., its symmetry is C1h, while the ideal monovacancy has D3h symmetry. The divacancy is found to have a 5-8-5 membered ring structure. The trivacancy is also found to have two five membered rings. The energetics of these vacancies are not explained by the conventional dangling-bond counting model, which does not include lattice relaxation. Our calculations show that the divacancy is very stable and is thus expected to be detected under some experimental conditions.

Interaction of methyltin(IV) compounds with carboxylate ligands. Part 1: formation and stability of methyltin(IV)–carboxylate complexes and their relevance in speciation studies of natural waters

AbstractQuantitative data on the stability of mono‐, di‐ and trimethyltin(IV)‐carboxylate complexes (acetate, malonate, succinate, malate, oxydiacetate, diethylenetrioxydiacetate, tricarballylate, citrate, butanetetracarboxylate and mellitate) are reported at t = 25 °C and I→ 0 mol l−1. Several mononuclear, mixed proton, mixed hydroxo and polynuclear species are formed in these systems. As expected, the stability trend is mono‐ > di‐ > trimethyltin(IV) and mono < di < tri < tetra < hexa for the organotin moieties and carboxylate ligands investigated, respectively. Moreover, ligands containing, in addition to carboxylic,OandOH groups show a significantly higher stability with respect to analogous ligands with the same number of carboxylic binding sites. The results obtained from all the systems investigated allowed us to formulate the following empirical predictive equation for correlation between complex stability and some simple structural parameters, where ncarb and nOH are the number of carboxylic and alcoholic groups in the ligand, respectively, r is the stoichiometric coefficient of H+ (positive) or OH− (negative) and zcat is the methyltin cation charge (CH3)xSnz+ (z+ = 4 − x). Distribution diagrams for some representative systems are also reported and are discussed in the light of speciation studies in natural waters. A literature data comparison is made with carboxylate complexes of other metal ions with the same charge as the organotin cations investigated here. Copyright © 2005 John Wiley & Sons, Ltd.

Thermal Stability of Peroxyalkynes

The thermal stability of mono- and disubstituted peroxyalkynes was compared. The reaction order and the apparent activation energy for the first step of decomposition of the peroxides were determined. The strength of the O-O bond in 3-tert-alkyl(cycloalkyl, aralkyl)peroxy-3-methyl-1-butynes and 2-tert-alkylperoxy-2-methyl-2-alkynes was estimated.

Stability of mono- and trivalent meningococcal outer membrane vesicle vaccines

The stability during storage of outer membrane vesicles (OMVs) of Neisseria meningitidis group B was studied. Three types of OMVs were compared for their stability, containing either one (monovalent) or three different PorA subtypes (trivalent), the latter with and without class 4 outer membrane protein (OMO, RmpM).Aqueous formulations were stored freeze-dried (4°C), frozen (−70°C) and in liquid form at 4, 37 and 56°C. Physico-chemical properties and immunogenicity of the OMVs as well as PorA conformation and antigenicity (P1.7-2,4, the subtype present in all formulations) were monitored during 1 year. At −70 or 4°C, the structure and immunogenicity of OMVs was preserved. Storage of OMVs at high temperatures (37 or 56°C) induced destruction of the OMV structure and denaturation of PorA, followed by chemical degradation. Immunogenicity decreased or was lost completely. Changes observed in the fluorescence spectra of degraded OMVs were also seen in tryptophan (Trp) and tyrosine (Tyr) derivatives incubated at 56°C, indicating the occurrence of chemical degradation of tryptophan and tyrosine residues in PorA. Trivalent OMVs were slightly more stable at 37°C than monovalent OMVs as assessed by in vitro methods, but these differences did not result in differences in the immunogenicity. The stability of trivalent OMVs was not affected by the presence of RmpM. Both trivalent and monovalent OMVs could be freeze-dried with preservation of their immunogenicity.In conclusion, OMVs are sensitive to elevated temperatures, but are stable in the frozen or freeze-dried state or when stored at 4°C in the liquid state.

Thermal Stability of Mono- and Polycyclic Peroxyalcohols and Their Derivatives by Thermal Analysis

A comparative study of the thermal stability of 33 mono- and polycyclic peroxyalcohols, as well as ethers and esters derived from them was performed by thermal analysis. Reaction orders and apparent rate constants of the first stage of peroxide decomposition were determined from the DTA curves. Semiempirical quantum-chemical calculations of the strength of the O-O bond in peroxycycloalkanols and peroxyalcohols of the adamantane series and their derived esters were performed.

Perfluorophenyl-containing verdazyl radicals

New formazans, tetrazines, and verdazyl radicals containing perfluorophenyl substituents were obtained on the basis of perfluorophenylhydrazides. The stabilities of mono-, bis-, and tris(perfluorophenyl)verdazyl radicals and their leuco compounds are compared qualitatively. The stabilities of the free radicals obtained considerably exceed the stability of the diphenylpicrylhydrazyl (DPPH) radical.

Über Reaktionen oxygenierter Kobalt(II)‐Chelate. VII. Zur Stabilität einfach und doppelt verbrückter μ‐Peroxo‐dikobalt(III)‐Komplexe

On reactions of oxygenated Cobalt(II) Chelates. VII. Stability of mono and doubly bridged μ‐Peroxo‐dicobalt(III) Complexes.The oxygen carrier properties of the cobalt(II) chelates of symmetrical diethylenetriamine‐4‐acetic acid (dtma) and unsymmetrical ethylenediamine‐1,1‐diacetic acid (edda) have been investigated by O2 equilibrium measurements in alkaline solution. Maximum O2 uptake is at pH = pKH (4), indicating that μ‐peroxo‐μ‐hydroxodicobalt(III) ion is the only oxygenated species formed in aqueous solution. Relationships between stability and structural factors are discussed.

Studies on 1,3-dithiolium cations—IV : Syntheses, physiochemical properties and stabilities of mono-, di-, and triphenyl- and 2- p-substituted phenyl-1,3-dithiolium cations

In order to investigate the changes in the properties of 1.3-dithiolium cations when aryl groups are introduced into various positions, a number of 2- p-substituted phenyl-4-phenyl-1.3-dithiolium salts were prepared and their UV and NMR spectra and pK R+ values determined. Results showed that a phenyl group introduced to the C-2 position largely stabilized the 1.3-dithiolium cation by conjugation. Substituent effects in 2- p-substituted phenyl-4-phenyl-1.3-dithiolium cations indicated that the positive charge is largely localized on the S-C-S grouping in the 1.3-dithiolium ring.