On the temperature dependence of the enthalpies of mixing in liquid binary (Ag, Cu, Ni)-Sn alloys

The partial and integral enthalpies of mixing of liquid binary alloys in the systems Ag-Sn, Cu-Sn and Ni-Sn were determined at different temperatures from 500 to 1500 °C using drop calorimetry techniques. Generally, our measured values fit well to most of the hitherto reported results. The data were fitted using a Redlich-Kister polynomial and the binary interaction parameters were evaluated. For all three systems the enthalpy curves at various temperatures are discussed focusing on the association theory. C^ass,C^A₁,B₁,C^A₁,A_iB_j,C^B₁,A_iB_j, the interaction parameters and K_AiBj were determined. The general shape and supposed temperature dependence of the enthalpy of mixing in Ag-Sn and Cu-Sn could be confirmed. No significant temperature dependence could be found experimentally for Ni-Sn at temperatures above 1100 °C. Extrapolations into the metastable liquid regions based on the association theory, however, indicate a small drop of Δ_MixH with temperature. A second series of measurements limited to low concentrations of Ag, Cu, or Ni, respectively in Sn has been performed in order to determine the partial enthalpies of mixing at infinite dilution at 500, 600, 700, and 800 °C. Temperature dependence could be observed for all three binary systems, most developed for Ni-Sn.     

Fabrication,rheological analysis,and in vitro characterization of in situ chemically cross‐linkable thermogels as controlled and prolonged drug depot for localized and systemic delivery

5‐Fluorouracil (5‐FU) is widely used against many types of solid cancer in clinics. However, because of its limitations such as short half‐life, poor oral absorption and rapid clearance by dihydropyrimidine dehydrogenase have limited its applications. In current study, new in situ chemically grafted thermogels for prolonged drug release are formed on the basis of poloxamer 407 (PF127) and carboxymethyl chitosan (CMCS) using glutaraldehyde as cross‐linking agent. The phase transition from sol to gel state at body temperature was confirmed by tube titling, rheological analysis, and optical transmittance determinations. Swelling and drug release experiments conducted at various pH and temperature demonstrated that developed formulations are thermoresponsive with maximum swelling and release below critical gelation temperature (CGT) (pH 7.4, 25°C). Cells growth inhibition study confirmed the biocompatibility of thermogels against L929 cell lines. Methyl thiazolyl tetrazolium (MTT) assay confirmed that 5‐FU–loaded thermogels have the potential to cause cells death against HeLa and MCF‐7 cancer lines. The IC₅₀ values calculated for pure 5‐FU solution (27 ± 0.81 μg/mL for HeLa and 24 ± 0.58 μg/mL for MCF‐7) were found higher in comparison with 5‐FU–loaded thermogels, against HeLa (17 ± 0.39 μg/mL) and MCF‐7 (14 ± 0.67 μg/mL). Fourier transform infrared (FTIR) confirmed the new structure formation and chemical grafting between PF127 and CMCS. Thermogravimetric (TG) and differential scanning calorimetry (DSC) analyses proved the phase transition around physiologic temperature range, while scanning electron microscopy (SEM) analysis displayed the presence of connected pores in the cross section of thermogels facilitating the uptake of solvents and drug particles. Altogether, results concluded that developed chemically grafted thermogels can be used in vivo for prolonged drug release after subcutaneous administration.     

Reaction of N‐Nonaflyl and N‐Cyano‐Benzotriazoles with Enamines

N‐Nonaflyl‐benzotriazole 1a reacts with enamines 2 in tetrahydrofurane (THF) at room temperature to afford o‐nonafluorobutansulfonamido‐phenylazo‐enamines 3 in 74–81% yield. Compound 1a reacts with 1‐diethylaminobutadien 2f twice, affording pyridazine derivative 3f in 20% yield. Ringopening of N‐cyano‐benzotriazole 1b with pyrrolidinocyclohexene 2a affords, under cleavage of pyrrolidine 1,2,3,4‐tetrahydro‐dibenzo[4,5:e]imidazo[1,2‐b][1,2,4]triazine 4 in 43% yield.     

Sulfamethoxazole Leaching from Manure-Amended Sandy Loam Soil as Affected by the Application of Jujube Wood Waste-Derived Biochar

Vertical translocation/leaching of sulfamethoxazole (SMZ) through manure-amended sandy loam soil and significance of biochar application on SMZ retention were investigated in this study. Soil was filled in columns and amended with manure spiked with 13.75 mg kg⁻¹ (S1), 27.5 mg kg⁻¹ (S2), and 55 mg kg⁻¹ (S3) of SMZ. Jujube (Ziziphus jujube L.) wood waste was transformed into biochar and mixed with S3 at 0.5% (S3-B1), 1.0% (S3-B2), and 2.0% (S3-B3) ratio. Cumulative SMZ leaching was lowest at pH 3.0, which increased by 16% and 34% at pH 5.0 and 7.0, respectively. A quicker release and translocation of SMZ from manure occurred during the initial 40 h, which gradually reduced over time. Intraparticle diffusion and Elovich kinetic models were the best fitted to leaching data. S3 exhibited the highest release and vertical translocation of SMZ, followed by S2, and S1; however, SMZ leaching was reduced by more than twofold in S3-B3. At pH 3.0, 2.0% biochar resulted in 99% reduction in SMZ leaching within 72 h, while 1.0% and 0.5% biochar applications reduced SMZ leaching to 99% within 120 and 144 h, respectively, in S3. The higher SMZ retention onto biochar could be due to electrostatic interactions, H-bonding, and π-π electron donor acceptor interactions.     

Predictable self-assembled [2×2] Ln(III)4 square grids (Ln = Dy,Tb)-SMM behaviour in a new lanthanide cluster motif

The ditopic carbohydrazone ligand (L1) produces the square, self-assembled [2×2] grids [Dy(4)(L1)(4)(OH)(4)]Cl(2) (1) and [Ln(4)(L1)(4)(μ(4)-O)(μ(2)-1,1-N(3))(4)] (Ln = Dy (2), Tb (3)), with 2 exhibiting SMM behaviour. Two relaxation processes occur with U(eff) = 51 K, 91 K in the absence of an external field, and one with U(eff) = 270 K in the presence of a 1600 Oe optimum field.     

Time discretization and quantization methods for optimal multiple switching problem

In this paper, we study probabilistic numerical methods based on optimal quantization algorithms for computing the solution to optimal multiple switching problems with regime-dependent state process. We first consider a discrete-time approximation of the optimal switching problem, and analyse its rate of convergence. Given a time step h$h$, the error is in general of order (hlog(1/h))^1/2${(hlog(1/h))}^{1/2}$, and of order h^1/2$h^{1/2}$ when the switching costs do not depend on the state process. We next propose quantization numerical schemes for the space discretization of the discrete-time Euler state process. A Markovian quantization approach relying on the optimal quantization of the normal distribution arising in the Euler scheme is analysed. In the particular case of uncontrolled state process, we describe an alternative marginal quantization method, which extends the recursive algorithm for optimal stopping problems as in Bally (2003) [1]. A priori L^p$L^p$-error estimates are stated in terms of quantization errors. Finally, some numerical tests are performed for an optimal switching problem with two regimes.     

Green biosynthesis of silver nanoparticles using Callicarpa maingayi stem bark extraction

Different biological methods are gaining recognition for the production of silver nanoparticles (Ag-NPs) due to their multiple applications. The use of plants in the green synthesis of nanoparticles emerges as a cost effective and eco-friendly approach. In this study the green biosynthesis of silver nanoparticles using Callicarpa maingayi stem bark extract has been reported. Characterizations of nanoparticles were done using different methods, which include; ultraviolet-visible spectroscopy (UV-Vis), powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray fluorescence (EDXF) spectrometry, zeta potential measurements and Fourier transform infrared (FT-IR) spectroscopy. UV-visible spectrum of the aqueous medium containing silver nanoparticles showed absorption peak at around 456 nm. The TEM study showed that mean diameter and standard deviation for the formation of silver nanoparticles were 12.40 ± 3.27 nm. The XRD study showed that the particles are crystalline in nature, with a face centered cubic (fcc) structure. The most needed outcome of this work will be the development of value added products from Callicarpa maingayi for biomedical and nanotechnology based industries.     

Evaluation of Baylis–Hillman Routes to 3-(Aminomethyl)coumarin Derivatives

The relative merits of two different Baylis–Hillman approaches toward the preparation of coumarin derivatives, containing peptide-like side chains, have been explored. In one approach, use of methyl acrylate as the activated alkene requires a protecting group strategy, an approach that is not necessary when using tert-butyl acrylate.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]     

Synthesis of quinazoline based chiral ligands and application in the enantioselective addition of phenylacetylene to aldehydes

Five novel 4-phenylquinazolinols were synthesised in three steps. Their application as ligands in the titanium tetraisopropoxide promoted catalytic enantioselective addition of phenylacetylene to a variety of aldehydes gave propargylic alcohols. Under the optimised reaction conditions, the best enantioselectivity was obtained using l-lactic acid derived 4-phenylquinazolinol and apart from the cyclohexylcarbaldehyde derivative, 16 propargylic alcohols were then synthesised in moderate to excellent enantiomeric excess from 53% to 97%.     

Methyl (SR)‐10‐chloro‐1,2,3,4,5,6‐hexahydro‐6‐hydroxy‐8‐methoxy‐1‐methyl‐1,9‐phenanthroline‐6‐carboxylate

In the title compound, C₁₆H₁₉ClN₂O₄, the pyridine ring is nearly planar, the piperidine ring is non‐planar and the cyclo­hexane ring adopts a screw‐boat conformation. The carboxyl­ate group makes a dihedral angle of 80.9 (2)° with the least‐squares plane through the cyclo­hexane ring.