Negative Enthalpy Research Articles

Biosorption of rifampicin from wastewater using cocoa shells product

ABSTRACT Since 1970, the detection of pharmaceutical substances, in the various aquatic systems, became a global health problem. In this study, separation by the adsorption process in the presence of activated carbon cocoa shells (ACCS) as adsorbant was applied for the treatment of effluents containing antibiotic drugs (rifampicin). The influence of process variables such as the adsorption time, initial rifampicin concentration, pH, temperature, and ACCS dose on adsorption performance has been investigated. The general order kinetic model and Freundlich isotherm model provided the best fit to the experimental data. The negative enthalpy indicates an exothermic process that occurs via physisorption. From the experimental results, the values of isosteric heat decreased with increasing the surface coverage, indicating the presence of strong interactions.

Anisotropic elasticity, electronic structure and thermodynamic properties of Al-Fe-Si intermetallic compounds from first principles calculations

In this paper, structural stability, elastic properties, electronic structure and thermodynamic properties of Al-Fe-Si compounds are systematically investigated by first-principles calculations. The negative formation enthalpy indicates that all Al-Fe-Si compounds are thermodynamically stable, and the Al-Fe-Si compounds are determined to be mechanically stable by the stability criteria. The bulk, shear and Young's moduli as well as Poisson's ratio of Al-Fe-Si compounds are also calculated. The results show that Al2Fe3Si3 has the highest shear modulus and Young's modulus, which leads to stronger shear deformation resistance and stiffness. The elastic anisotropy and shear anisotropic factors of Al-Fe-Si compounds are analyzed in this study, and the anisotropy of Al3Fe2Si3 is the greatest among them. Al3Fe2Si3 and Al2Fe3Si4 show metallic character and Al2Fe3Si3 is classified as direct band gap semiconductors. The DOS of Al-Fe-Si compounds are found mainly from Al 3p, Si 3p and Fe 4d states and the Fe-Al/Si bonding is much stronger than that of Al-Si. According to the results, Al2Fe3Si3 has the highest Debye temperature, indicating strong chemical bonding and higher thermal conductivity, which are consistent with the results of Young's modulus and minimum thermal conductivity.

The Effect of Alloying Elements on the Structural Stability, and Mechanical and Electronic Properties of Al3Sc: A First-Principles Study.

The first-principles methods, based on the density function theory, are performed to calculate the properties of pure and doped Al3Sc. The structural stability, and mechanical and electronic properties of L12-Al3Sc1−xMx (M = Zr, Ti, Y, and Li) have been investigated. A negative formation enthalpy for L12-Al3Sc1–xMx indicated that all doped structures were stable, and Al24Sc6Zr2 was found to be the most stable. The elastic constants, elastic moduli and Debye temperatures of Al3Sc, with different doping elements and different doping concentrations, were calculated to explore the influences of doping on the mechanical properties and Debye temperatures of Al3Sc. Furthermore, the calculated results suggested that both Al24Sc6Zr2 and Al24Sc6Ti2 could optimize the mechanical properties. Finally, the electronic properties based on the analyses of densities of states and electron density distributions, have been performed, to explain the underlying mechanisms for the structural and mechanical properties of the L12-Al3Sc1–xMx structures.

Interaction of proflavine with the RNA polynucleotide polyriboadenylic acid–polyribouridylic acid: photophysical and calorimetric studies

The binding of proflavine, an acriflavine derivative, with the RNA polynucletodide polyadenylic acid–polyuridylic acid is investigated here to understand the structural and thermodynamic basis of the binding process. Such binding data are crucial for designing viable theraperutic agents. Spectroscopic studies clearly suggest a strong binding interaction between proflavine and polyadenylic acid–polyuridylic acid leading to efficient energy transfer between the poly AU base pairs and proflavine. The stoichiometry of proflavine polyadenylic acid–polyuridylic acid binding was independently estimated by continuous variation analysis of Job. An intercalative binding model is envisaged for the binding from hydrodynamic studies. Circular dichroism experiments revealed that the binding induced conformational changes in the RNA, and also led to induction of optical activity in the bound dye molecules. The binding affinity of the complex was deduced to be (6.57 ± 0.75) 105 M−1 at (298.15 ± 0.10) K from isothermal titration calorimetry experiment. Positive entropy and negative enthalpy changes characterized the complexation. The binding was observed to be weaker both at higher temperatures and increased [Na+]. The affinity of binding decreased with increasing [Na+]. When the Gibbs energy was parsed between polyelectrolytic and nonpolyelectropytic components, it surprisingly revealed a higher role for the non-polyelectrolytic forces. These results present new data for developing RNA targeted ligands.Communicated by Ramaswamy H. Sarma

(Invited) Β-SnSb for Sodium Ion Battery Anodes: Phase Transformations Responsible for Enhanced Cycling Stability Revealed By in Situ TEM

The alloy β-SnSb is known to be a highly stable anode for sodium ion batteries during cycling, but its sodiation−desodiation alloying reactions are poorly understood. Combining in situ TEM with electroanalytical methods, we demonstrate that β-SnSb forms Na3Sb and Na15Sn4 in sequence upon sodiation and re-forms as β- SnSb upon desodiation. The negative enthalpy of mixing for Sn and Sb is sufficient to cause sequentially deposited bilayers of Sn/Sb to transform into β-SnSb, resulting in comparable cycling stability. The good cycling stability of β-SnSb results from the complex two-phase amorphous−nanocrystalline microstructure in the partially charged− discharged states, as well as the intrinsic mechanical toughness of the β phase. Per the in situ TEM results, the sequential phase transformation shows minimal fracturing of the β-SnSb, indicating facile buffering of stresses. Extensively cycled specimens eventually show crystalline Sn phase segregation, which may be the source of the ultimate capacity fade in the alloy and bilayers.

Solvation Structure of Poly(benzyl methacrylate) in a Solvate Ionic Liquid: Preferential Solvation of Li-Glyme Complex Cation.

We report the solvation structure of a lower critical solution temperature (LCST)-type thermoresponsive polymer in a solvate ionic liquid (SIL, i.e., an ionic liquid comprising solvate ions) to elucidate the predominant interaction for the dissolution of the thermoresponsive polymer in SIL at low temperatures. The solvation structure of poly(benzyl methacrylate) (PBnMA) and a model compound of its monomer in a typical glyme-based SIL, [Li(G4)][TFSA] (G4: tetraglyme; TFSA: bis(trifluoromethanesulfonyl)amide), have been investigated using high-energy X-ray total scattering and all-atom molecular dynamics simulations. In the model compound/SIL system, the intermolecular components extracted from the total G( r)s revealed that the ester moiety of BnMA is preferentially solvated by Li cations through a cation-dipole interaction, which induces slight desolvation of the G4 molecules, and the aromatic ring of BnMA is secondarily solvated by the [Li(G4)] cation complex through a cation-π interaction with maintaining the complex structure. In contrast, TFSA anions are attracted only by the [Li(G4)] cation. These interactions result in the formation of a solvation layer of SILs around the aromatic ring, which plays a key role in the negative entropy and enthalpy of mixing. Meanwhile, in the polymer solution, the coordination number of the Li cation around the ester moiety significantly decreased. This could be ascribed to the steric effect of the bulky side chains, preventing the approach of the [Li(G4)] cation complex to the ester moiety located near the main chain. These solvation structures lead to small absolute values of negative entropy and enthalpy of mixing, which together are key factors to understand the LCST-type phase behavior in the IL system.

Tuning the glass forming ability and mechanical properties of Ti-based bulk metallic glasses by Ga additions

A new series of Ti40Zr10Cu36−xPd14Gax (x = 2, 4, 8 and 10) alloys with improved plasticity and glass-forming ability (GFA) are produced. The strategy is to create local structural heterogeneity in Ti-based bulk metallic glasses (BMGs) by alloying with a soft element which has high negative enthalpy of mixing with Ti-atoms. The GFA of Ti40Zr10Cu36−xPd14Gax rods increases with increasing Ga content up to 4 at.%, and for more Ga it decreases. Minor addition of Ga (x = 2) is beneficial to improve the strength and ductility of the TiZrCuPd-based BMG due to the formation of local structural heterogeneities which facilitate the formation of a highly organized pattern of multiple shear bands under quasi-static compression. Ti40Zr10Cu34Pd14Ga2 BMG shows the best combination of compressive global strain and maximum compressive strength of ∼4.5% and ∼2000 MPa, respectively. Comparing the Young's modulus of Ga-containing alloys in amorphous and crystalline state we find that the amorphous state shows significant elastic softening (40–48% smaller) which is useful to reduce stress shielding effect for biomedical applications. The alloys show a remarkable thermoplastic formability as the viscosity decreases sharply by an order of magnitude in the supercooled liquid region.

Mechanism for asymmetric atmospheric responses in the western North Pacific to El Niño and La Niña

The cause of asymmetric atmospheric circulation responses over the tropical western North Pacific (WNP) to El Nino and La Nina was investigated through observational analyses and idealized modeling experiments. Firstly, column integrated moisture and moist static energy budget analyses were carried out to reveal the cause of asymmetric precipitation anomalies over the WNP. The result indicates that negative nonlinear moist enthalpy advection anomalies occur in both El Nino and La Nina, and they tend to induce a negative precipitation anomaly in the key WNP region and thus an anomalous anticyclone during both El Nino and La Nina winters. This, together with linear moist enthalpy advection, results in an asymmetric atmospheric circulation response. Secondly, the relative roles of the nonlinear moist enthalpy advection and the zonal shift of longitudinal location of anomalous heating over the central-eastern Pacific between El Nino and La Nina were investigated through an anomaly general circulation model. It is found that both the nonlinear advection and the zonally asymmetric heating contribute equally to the observed zonal shift of the anomalous WNP anticyclonic and cyclonic circulation centers between El Nino and La Nina.

Magnetic orders and electronic behaviours of new chalcogenides Cu3MnCh4 (Ch = S, Se and Te): An ab initio study

ABSTRACTThe ternary copper-based chalcogenides Cu3MnCh4 (Ch = S, Se and Te), which have simple cubic (SC) crystal structure and conform to space group with 215 space number, have been investigated by spin-polarised Generalised Gradient Approximation (GGA) in the framework of Density Functional Theory (DFT). First, all systems have been considered in ferromagnetic (FM) and three different type antiferromagnetic (AFM) orders which are A-type (A-AFM), G-type (G-AFM) and C-type (C-AFM) to investigate most stable magnetic phase for each system. The energetically favoured magnetic phase is A-type AFM for Cu3MnS4 and Cu3MnSe4 compounds, while Cu3MnTe4 compound has FM ground state. The electronic band structures of these systems have been investigated, after the well-optimised structural parameters in their stable magnetic phase have been obtained. The calculated spin-polarised electronic band structure of FM Cu3MnTe4 compound exhibits half-metallic behaviour with a band gap in minority spin channel (Eg = 0.99 eV) while metallic band structure is observed for majority spin. The calculated electronic band structures in A-type AFM phase for Cu3MnS4 and Cu3MnSe4 systems show that Cu3MnS4 compound has semiconducting behaviour with a small band gap (Eg = 0.21 eV) whereas Cu3MnSe4 compound has metallic character. The calculated negative formation enthalpies indicate the thermodynamic stability and structural synthesisability of these compounds.

First principles study on new half-metallic ferromagnetic ternary zinc-based sulfide and telluride (Zn3VS4 and Zn3VTe4)

In this resear, we have investigated electronic and magnetic behavior and also some mechanical properties of ternary zinc-based chalcogenides Zn3VCh4 (Ch = S and Te) conform to space group with 215 space number, which have simple cubic (SC) crystal structure, by spin-polarized Generalized Gradient Approximation (GGA) within Density Functional Theory (DFT). To make extensive study within ab initio methods, after the optimization process to get optimal structural parameters in most suitable magnetic phase, the electronic band structures with the total density of electronic states and second order elastic constants to predict some thermal and elastic features have been calculated. The calculated negative formation enthalpy values indicate that, our materials are thermodynamically stable and structurally synthesizable. The observed minority (down) band gaps in the calculated electronic band structures, Eg = 2.62 eV for Zn3VS4 and Eg = 1.75 eV for Zn3VTe4, show that our crystal systems have half-metallic character. Also, the calculated elastic constants prove that our compounds are mechanically stable due to satisfy the Born-Huang criteria. Moreover, the anisotropic elastic properties have been visualized in two-dimensional (2D) and three-dimensional (3D) surfaces for Young’s modulus, linear compressibility, shear modulus and Poisson’s ratio as well as with the calculation of the anisotropic factors.

Lead binding to wild metal-resistant bacteria analyzed by ITC and XAFS spectroscopy

Metal-resistant bacteria can survive exposure to high metal concentrations without any negative impact on their growth. Biosorption is considered to be one of the more effective detoxification mechanisms acting in most bacteria. However, molecular-scale characterization of metal biosorption by wild metal-resistant bacteria has been limited. In this study, the Pb(II) biosorption behavior of Serratia Se1998 isolated from Pb-contaminated soil was investigated through macroscopic and microscopic techniques. A four discrete site non-electrostatic model fit the potentiometric titration data best, suggesting a distribution of phosphodiester, carboxyl, phosphoryl, and amino or hydroxyl groups on the cell surface. The presence of these functional groups was verified by the attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, which also indicated that carboxyl and phosphoryl sites participated in Pb(II) binding simultaneously. The negative enthalpy (−9.11 kJ mol−1) and large positive entropy (81.52 J mol−1 K−1) of Pb(II) binding with the bacteria suggested the formation of inner-sphere complexes by an exothermic process. X-ray absorption fine structure (XAFS) analysis further indicated monodentate inner-sphere binding of Pb(II) through formation of C−O−Pb and P−O−Pb bonds. We inferred that C−O−Pb bonds formed on the flagellar surfaces, establishing a self-protective barrier against exterior metal stressors. This study has important implications for an improved understanding of metal-resistance mechanisms in wild bacteria and provides guidance for the construction of genetically engineered bacteria for remediation purposes.

Size- and ion-dose-dependent microstructural evolution and hardening in He-irradiated miscible Cu/Zr crystalline/crystalline nanolaminates

The microstructural features and hardness of He-irradiated miscible Cu/Zr crystalline/crystalline nanolaminates with a negative enthalpy of mixing were investigated at room temperature. The distribution of He bubbles within the Cu layers exhibits a high dependence on both layer thickness (h) and ion dose (Φ), while that at the Cu-Zr interfaces is only affected by ion dose. Compared with their as-deposited counterparts, the He-irradiated Cu/Zr nanolaminates tend to manifest radiation-induced solid-state amorphization (RSA), which was induced by ion beam mixing and initiated from crystalline interfaces. The size-dependent hardness of the as-deposited Cu/Zr nanolaminates is elucidated by a transition in the strengthening mechanism from the interfacial barrier strengthening mechanism to the confined layer slip of partials when h is increased. In the He-irradiated Cu/Zr samples, however, the size-dependent hardness is highly related to Φ. Under lower Φ, a nonmonotonically h-dependent irradiation hardening is evident and is associated with a transition from irradiation hardening at large h (≥10 nm) to softening at small h (<10 nm), and the maximum hardening occurs at a critical value of h ≈ 25 nm. In contrast, under higher Φ, the Cu/Zr nanolaminates merely display irradiation softening behavior, with the minimum softening at the critical value of h ≈ 25 nm. The underlying mechanisms are highlighted in terms of dislocation-bubble interactions and RSA. These findings indicate the effects of He ion dose and layer thickness on the He bubble distribution and the interface-mixing of Cu/Zr nanolaminates as well as provide thorough insight into how to tune the He ion dose to manipulate the mechanical response of nanolaminated FCC/HCP materials on a small scale.

Effects of mixing enthalpy and cooling rate on phase formation of AlxCoCrCuFeNi high-entropy alloys

We investigated the influence of mixing enthalpy and cooling rate on phase formation and selected the melt-spun AlxCoCrCuFeNi (x = 0, 0.1, 0.5, 0.8 and 1.0 in molar ratios) high-entropy alloys (HEAs) as a model system. The mean mixing enthalpy (ΔHmix) of the alloy system is tuned from positive to negative by increasing Al molar ratios while the mixing entropy (ΔSmix) only has an insignificant variation. Microstructure analyses revealed that the dominant phase in the AlxCoCrCuFeNi HEAs changes from a face-centered cubic (FCC) to body-centered cubic (BCC) structure with the variation of the ΔHmix. Accompanying with phase changing, the lattice constant of the FCC phase increases linearly with Al molar ratio regardless of cooling rate, indicating that the lattice expansion caused by the substitutional alloying of Al plays an important role in the phase evolution, in addition to the effect of the ΔHmix. The increasingly negative enthalpy ΔHmix with Al addition also leads to more pronounced phase separation with the formation of ordered intermetallic phases in the BCC-dominant HEAs than the FCC-dominant ones. Interestingly, when the magnitude of the mean ΔHmix is small, both the coarsening of Cu-rich nanophase and decomposition of the solid-solution phase in the Al0.5CoCrCuFeNi HEA are suppressed. This observation is in line with thermodynamic predictions that a weak ΔHmix benefits the stabilization of the solid-solution phase.

Thermodynamic Modelling and Experimental Validation of CO2 Mineral Sequestration in Mandla Basalt of the Eastern Deccan Volcanic Province, India

Abstract Deccan basalt contains primary silicates rich in Ca, Mg, and Fe ions, suitable for CO2 sequestration. Previous, basalt-water-CO2 interaction studies were focused on other than Deccan basalt types. However, such studies on the Deccan basalt are rare. Thus, present basalt-CO2 water saturated interaction modelling under hydrothermal-like conditions was carried out on the Deccan basalt of the Mandla area to understand apposite pCO2 and time parameters. Modelling results were further validated by experiments run in a laboratory time framework. Present results show negative entropy (ΔS) and enthalpy (ΔfH) that suggest feasibility of plagioclase, pyroxene and magnetite dissolution. Obtained negative Gibb’s free energy (ΔfG), ΔfH and ΔS values for calcite, dolomite and magnesite indicate spontaneous reaction, whereas, positive ΔfG and negative ΔfH and ΔS values of the siderite suggest non-spontaneous and opposing reactions. Calcite is the first carbonate mineral to form, but, at a faster rate. Magnetite dissolution begins after a time lag (not initiated along with the plagioclase and pyroxene). X-ray Powder Diffraction results of post-experiment residues revealed formation of calcite, aragonite, ankerite, huntite, siderite, smectite, chlorite, smectite/chlorite mixed layers and chabazite. Scanning electron microscopic images show tiny calcite crystal growth over the larger calcite crystal and incipient-disordered calcite with imperfections on crystal faces. Thus, basalt carbonation is mainly controlled by time, but temperature, pCO2 and pH played sub-ordinate role. Largely, thermodynamic models do not agree well with the experimental results as numerical models indicate larger carbonate growth. Additionally, transition state theory based models work well to predict dissolution rates for most of the minerals, but, they overpredict growth of the secondary minerals.

Noncovalent interactions between fluoroquinolone antibiotics with dissolved organic matter: A 1H NMR binding site study and multi-spectroscopic methods

Fluoroquinolone antibiotics (FQs) are considered to be emerging environmental contaminants that have been detected extensively in aquatic environment. It is of quite importance to explore FQs interacting with dissolved organic matter (DOM). The interactions of FQs with DOM were examined by nuclear magnetic resonance (NMR) spectroscopy, fluorescence quenching, UV–vis, Fourier transform infrared (FT-IR) spectroscopic techniques. The bindings of FQs to DOM had one single binding site and their quenching mechanisms were static, which were evaluated by the Stern-Volmer and Site-binding equations. Addition of DOM could result in micro-environmental changes of fluorophores groups in FQs. The location adjacent oxygen right of Ofloxacin (OFL) and the aromatic ring (the adjacency replaced by two nitrogen-containing groups) of Ciprofloxacin (CIP), Enrofloxacin (ENR), Norfloxacin (NOR) might be highly affected by DOM molecule. The negative enthalpy change (ΔH0), negative entropy change (ΔS0) and the positive Gibbs' energy change (ΔG0) figured out that the binding processes were exothermic but not thermodynamic favorable, the formation of HA-FQs complexes would be powered chiefly by the ΔS0. H-bonding, electrostatic effect, van der Waals force were the acting force in the binding reactions and the π-π stacking effect was the major binding force under alkaline conditions. Moreover, the protonated, deprotonated, or partially protonated state of FQs were found to have different binding capacity to DOM, and the binding reactions for FQs-HA system were suppressed as the ionic strength increased. Meanwhile, alterations of FQs conformation in the presence of DOM were evaluated by FT-IR and UV–vis spectra.

Effect of minor Si additions and cooling rate on the phase formation and properties of glass former Ni57Nb33Zr5Co5 alloy

Ni57Nb33Zr5Co5 metallic glass is a promising candidate to be used as bipolar plates in Proton Exchange Membrane Fuel Cells. Nevertheless, this alloy presents a low glass-forming ability (GFA) and a relatively low supercooled liquid stability. A method well-known to improve the GFA of metallic glasses is via minor additions of alloying elements with a large difference in size and negative enthalpy of mixing relative to the elements in the glass. Using this approach, Si was identified to be a potentially good candidate to improve the GFA of the Ni57Nb33Zr5Co5. The aim of this work was to investigate the effect of Si additions and cooling rate on the formation and properties of this alloy. Ribbons and wedge shape samples of(Ni57Nb33Zr5Co5)100-xSix (x = 0.5, 1, 2 and 3 at.%) were prepared by melt spinning and suction casting, respectively, and characterized by X-ray diffraction, optical and scanning electron microscopy, differential scanning calorimetry and microhardness. The results show the addition of Si increases the supercooled region up to 84% mainly because of a significant decrease in the glass transition temperature but the additions do not improve the GFA of the Ni57Nb33Zr5Co5. The wedge samples showed that the critical diameter for amorphization is below 1 mm thickness and for larger sections, eutectic colonies of NiNb and Ni3Nb form together with primary Ni3Nb. It was observed that the addition of Si favors the formation of this primary phase, which increases in amount and size. High hardness values around 1150 HV were measured for regions with a fine eutectic structure and low amount of the primary phase.

Adsorption of paraquat from water by insoluble cyclodextrin polymer crosslinked with 1,2,3,4-butanetetracarboxylic acid

An insoluble polymer was elaborated by crosslinking reaction between β-CD (β-cyclodextrin) and BTCA (1,2,3,4-butanetetracarboxylic acid) and it was firstly applied in adsorption of paraquat (PQ) from water. This insoluble polymer was synthesized at 180 °C for 30 min which displayed 74.1% of reaction yield, 3.80 mmol g− 1 of ion exchange capacity (IEC) and 0.18 mmol g− 1 of β-CD content. Physicochemical properties were evaluated by attenuated total reflection–Fourier transform infrared spectroscopy (ATR-FTIR), carbon-13 nuclear magnetic resonance (13C NMR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) method and stereoscopic microscopy. The optimal pH was 8 and the equilibrium time was 120 min. At 30 °C, the adsorption capacity was enhanced (10.8, 19.7, and 25.8 mg g− 1) when the initial concentration of paraquat was increased (25, 50 and 200 mg L− 1, respectively). Adsorption kinetics was described by the pseudo-second-order model and adsorption isotherm was appropriated to the Langmuir model. The negative standard enthalpy change (∆Ho) showed an exothermic process, the positive standard entropy change (∆So) displayed an increased disorder and the negative standard Gibbs free energy change (∆Go) indicated a spontaneous adsorption method. Ultimately, the regeneration efficiency of polymer in methanol was 87.3% after four cycles. This polymer could be used as a potential adsorbent for removal of other cationic pesticides.

One-Step Synthesis of Metal/Oxide Nanocomposites by Gas Phase Condensation.

Metallic nanoparticles (NPs), either supported on a porous oxide framework or finely dispersed within an oxide matrix, find applications in catalysis, plasmonics, nanomagnetism and energy conversion, among others. The development of synthetic routes that enable to control the morphology, chemical composition, crystal structure and mutual interaction of metallic and oxide phases is necessary in order to tailor the properties of this class of nanomaterials. With this work, we aim at developing a novel method for the synthesis of metal/oxide nanocomposites based on the assembly of NPs formed by gas phase condensation of metal vapors in a He/O2 atmosphere. This new approach relies on the independent evaporation of two metallic precursors with strongly different oxidation enthalpies. Our goal is to show that the precursor with less negative enthalpy gives birth to metallic NPs, while the other to oxide NPs. The selected case study for this work is the synthesis of a Fe-Co/TiOx nanocomposite, a system of great interest for its catalytic and magnetic properties. By exploiting the new concept, we achieve the desired target, i.e., a nanoscale dispersion of metallic alloy NPs within titanium oxide NPs, the structure of which can be tailored into TiO1-δ or TiO2 by controlling the synthesis and processing atmosphere. The proposed synthesis technique is versatile and scalable for the production of many NPs-assembled metal/oxide nanocomposites.

Elemental Distribution in CrNbTaTiW-C High Entropy Alloy Thin Films.

The microstructure and distribution of the elements have been studied in thin films of a near-equimolar CrNbTaTiW high entropy alloy (HEA) and films with 8 at.% carbon added to the alloy. The films were deposited by magnetron sputtering at 300°C. X-ray diffraction shows that the near-equimolar metallic film crystallizes in a single-phase body centered cubic (bcc) structure with a strong (110) texture. However, more detailed analyses with transmission electron microscopy (TEM) and atom probe tomography (APT) show a strong segregation of Ti to the grain boundaries forming a very thin Ti-Cr rich interfacial layer. The effect can be explained by the large negative formation enthalpy of Ti-Cr compounds and shows that CrNbTaTiW is not a true HEA at lower temperatures. The addition of 8 at.% carbon leads to the formation of an amorphous structure, which can be explained by the limited solubility of carbon in bcc alloys. TEM energy-dispersive X-ray spectroscopy indicated that all metallic elements are randomly distributed in the film. The APT investigation, however, revealed that carbide-like clusters are present in the amorphous film.

Alizarin interaction with sickle hemoglobin: elucidation of their anti-sickling properties by multi-spectroscopic and molecular modeling techniques

Polymerization of hemoglobin S is a major cause of morbidity and mortality in sickle cell disease, which leads to sickling and destruction of red blood cell. Alizarin, a bioactive compound from Rubia cordifolia, is reported to be blood purifier. This study investigates the potential of alizarin as an anti-sickling agent, showing a significant decrease in the rate of polymerization, therefore inhibiting the rate of sickling with increasing concentration. Interaction studies indicated that the fluorescence intensity of sickle hemoglobin (Hb S) decreases gradually with increasing alizarin concentration. This suggests the static quenching, where binding constant and the number of binding sites were deduced at different temperatures. The negative values of Gibbs energy change (ΔG0) strongly suggest that it is entropy-driven spontaneous and exothermic reaction. Negative enthalpy (ΔH0) and positive entropy (ΔS0) stipulated that hydrogen and hydrophobic bonding forces were interfering in a hydrophobic micro-environment of β6Val leading to Hb S polymerization inhibition. In circular dichroism (CD) spectra, Hb S in the presence of alizarin shows helical structural changes leading to destabilization of Hb S polymer. These findings were also supported by molecular docking simulation studies using DOCK6 and GROMACS. So, from these findings, we may conclude that alizarin interacts with Hb S through hydrogen bonding and leading to inhibition of Hb S polymerization. Consequently, alizarin may have potential use as an anti-sickle cell medication for sickle cell disorder.Communicated by Ramaswamy H. Sarma