Spectroscopic,thermal and biological studies of coordination compounds of sulfasalazine drug: Mn(II), Hg(II), Cr(III), ZrO(II), VO(II) and Y(III) transition metal complexes

The complexations of sulfasalazine (H₃Suz) with some of transition metals have been investigated. Three types of complexes, [Mn(HSuz)⁻²(H₂O)₄]·2H₂O, [M(HSuz)⁻²(H₂O)₂]·xH₂O (M = Hg(II), ZrO(II) and VO(II), x = 4, 8 and 6, respectively) and [M(HSuz)⁻²(Cl)(H₂O)₃]·xH₂O (M = Cr(III) and Y(III), x = 5 and 6, respectively) were obtained and characterized by physicochemical and spectroscopic methods. The IR spectra of the complexes suggest that the sulfasalazine behaves as a monoanionic bidentate ligand. The thermal decomposition of the complexes as well as thermodynamic parameters (δE*, δH*, δS* and δG*) were estimated using Coats-Redfern and Horowitz-Metzger equations. In vitro antimicrobial activities of the H₃Suz and the complexes were tested.     

Selective Recovery of Chromium from Precipitates Containing d Elements and Actinides: III. Effect of S2O82-

Reaction of Cr(III) hydroxides and mixed Fe(III)-Cr(III) and Ni(II)-Cr(III) hydroxides with persulfate ion in alkaline solutions was studied by spectrophotometry. The Cr(VI) yield (at oxidant deficiency) corresponds to the S₂O₈ ^{2 -} : Cr(VI) molar ratio close to 1.5. The initial reaction rate V ₀ is described by the kinetic equation -d[Cr(III)]/d = k[Cr(III)][S₂O₈ ^{2 -}][NaOH]. The activation energy is 53 kJ mol^{- 1} within the 41.5-95°C range. V ₀ is higher than the rate of thermal decomposition of persulfate ion, i.e., Cr(III) reacts directly with S₂O₈ ^{2 -}. Oxidation of NiCr₂O₄·nH₂O and mixed Fe(III)-Cr(III) hydroxides proceeds faster than oxidation of pure Cr(III) hydroxide. This is due to the catalytic effect of Fe(III) and Ni(II). Additions of Co(II) and Cu(II) also accelerate the process. Pu(IV) in alkali solution under the action of persulfate is converted into a more soluble oxidized species, which can be reduced back to Pu(IV) with appropriate reductants.     

Synthesis and properties of poly (organophosphazenes) ionomers [NP(HNC6H5)2−(x+y)(HNC6H4SO3H) x (HNC6H4SO3Li) y ] n

Poly(anilino sulphamicphosphazenes) such as [NP(HNC₆H₅)_2–x (HNC₆H₄SO₃H) _x ] _n for polymer (I) x=0.3 and for polymer (II) x=0.8 were prepared by the reaction of poly(anilinophosphazene) [NP(HNC₆H₅)₂] _n and sulphonic chloride HSO₃Cl in tetrachloroethane solvent several timeS. Also, H protons in the polymer (I) and (II) were prepared from lithum hydroxide in aqueous solution. It was found, by chemical analysis, that the product prepared with (I) and (II) had compositions such as [NP(HNC₆H₅)_1.7 (HNC₆H₄SO₃H)_0.1(HNC₆H₄SO₃Li)_0.2] _n (III) and [NP(HNC₆H₅)_1.2(HN-C₆H₄SO₃Li)_0.8] _n (IV). Also, the resistivity of products (III) and (IV) were determined and found to be 3.3×10⁷ and 1.5×10⁷ cm^–1, respectively.     

High-field ESR on Light-Induced Transition of Spin Multiplicity in FeCo Complex

Cyanide-bridged Fe-Co complex [Fe(Tp)(CN)₃]₂Co(bpe)?5H₂O (1?5H₂O; Tp = hydro-tris(pyrazolyl)borate; bpe = 1,2-bis(4-pyridyl)ethane) shows temperature- and light- induced metal-to-metal charge transfer (MMCT) involving spin state changes between magnetic $\mathrm{Fe}^{\mathrm{III}}_{\phantom{\mathrm{III}}\mathrm{LS}}\mbox{--}\mathrm{Co}^{\mathrm{II}}_{\phantom{\mathrm{II}}\mathrm{HS}}$ (HS = high spin, LS = low spin) state and nonmagnetic $\mathrm{Fe}^{\mathrm{II}}_{\phantom{\mathrm{II}}\mathrm{LS}}\mbox{--}\mathrm{Co}^{\mathrm{III}}_{\phantom{\mathrm{III}}\mathrm{LS}}$ state, while the dehydrated material 1 does not show any MMCT and holds $\mathrm{Fe}^{\mathrm{III}}_{\phantom{\mathrm{III}}\mathrm{LS}}\mbox{--}\mathrm{Co}^{\mathrm{II}}_{\phantom{\mathrm{II}}\mathrm{HS}}$ state. We have investigated the magnetic properties of each spin state in 1 and 1?5H₂O by means of magnetization and ESR measurement under pulsed high magnetic field. At low temperature below T _N, in both 1 and 1?5H₂O, the saturation magnetization in the induced ferromagnetic phase is well explained by S and g values derived from the magnetic susceptibility study. In the ESR of 1, we observed characteristic modes corresponding to a spin excitation in the induced ferromagnetic phase where its temperature dependence shows an evolution of spin correlation in the $\mathrm{Fe}^{\mathrm{III}}_{\phantom{\mathrm{III}}\mathrm{LS}}\mbox{--}\mathrm{Co}^{\mathrm{II}}_{\phantom{\mathrm{II}}\mathrm{HS}}$ state at low temperature. We further found that the similar ESR modes grow in the light-induced state of 1?5H₂O. The results strongly suggest that the light-induced magnetization in 1?5H₂O is driven by a light-induced MMCT, which involves transition of spin multiplicity from the nonmagnetic $\mathrm{Fe}^{\mathrm{II}}_{\phantom{\mathrm{II}}\mathrm{LS}}\mbox{--}\mathrm{Co}^{\mathrm{III}}_{\phantom{\mathrm{III}}\mathrm{LS}}$ to the magnetic $\mathrm{Fe}^{\mathrm{III}}_{\phantom{\mathrm{III}}\mathrm{LS}}\mbox{--}\mathrm{Co}^{\mathrm{II}}_{\phantom{\mathrm{\mathrm{II}}}\mathrm{HS}}$ pair.     

Mechanisms of Photochemical Reactions of Europium Ions in Aqueous Acid Solutions

Published data on photochemical reactions of Eu(II), Eu(III) ions in aqueous solutions wereconsidered. Previously proposed mechanisms of these reactions are unlikely. We suggest that photoexcited Euion forms with the unexcited ion a dimer (so-called excimer), which decomposes with liberation of H₂ and two Eu(III) ions in the case of Eu(II) oxidation and with liberation of H₂O₂ and two Eu(II) ions in Eu(III) reduction.     

Interaction parameter, k12, for non-azeotropic refrigerant mixtures

The interaction parameter, k₁₂, is determined from the experimental equilibrium data obtained by other authors. Vapour-liquid equilibria for binary mixtures of halocarbon refrigerants are predicted using the Redlich-Kwong-Soave equation of state. The mixtures considered are: R14-R23, R23-R12, R13-R12, R13-R11, R13B1-R22, R13B1-R152a, R22-RC318, R12-RC318, R12-R11.     

Selectively Potentiating Hypoxia Levels by Combretastatin A4 Nanomedicine: Toward Highly Enhanced Hypoxia‐Activated Prodrug Tirapazamine Therapy for Metastatic Tumors

Hypoxia‐activated prodrugs (HAPs) have the potential to selectively kill hypoxic cells and convert tumor hypoxia from a problem to a selective treatment advantage. However, HAPs are unsuccessful in most clinical trials owing to inadequate hypoxia within the treated tumors, as implied by a further substudy of a phase II clinical trial. Here, a novel strategy for the combination of HAPs plus vascular disrupting agent (VDA) nanomedicine for efficacious solid tumor therapy is developed. An effective VDA nanomedicine of poly(l ‐glutamic acid)‐graft‐methoxy poly(ethylene glycol)/combretastatin A4 (CA4‐NPs) is prepared and can selectively enhance tumor hypoxia and boost a typical HAP tirapazamine (TPZ) therapy against metastatic 4T1 breast tumors. After treatment with the combination of TPZ plus CA4‐NPs, complete tumor reduction is observed in 4T1 xenograft mice (initial tumor volume is 180 mm³), and significant tumor shrinkage and antimetastatic effects are observed in challenging large tumors with initial volume of 500 mm³. The report here highlights the potential of using a combination of HAPs plus VDA nanomedicine in solid tumor therapy.     

Superplastic behaviour of as received superplastic forming grade IN718 superalloy

Abstract

Tensile specimens of superplastic forming grade IN718 superalloy, containing banded microstructure in the as received state, were deformed at high temperatures T to investigate the stress σ versus strain rate ? · behaviour, the nature of the stress versus strain ? curves, ductility, and microstructure upon failure. The log σ–log ? · plot for the ? · range ～5 × 10^-6–3 × 10^-2 s^-1 at T = 1173–1248 K exhibited a strain rate sensitivity index m = 0·62 at low strain rates and m = 0·26 at high strain rates, representing region II and III behaviour, respectively. The activation energies were estimated to be 308 and 353 kJ mol^-1, respectively. All the σ–? curves, obtained at ? · = 1 × 10^-4 s^-1 for the temperature range 1173–1273 K, and at T = 1198 K for the strain rate range 1 × 10^-4–1 × 10^-2 s^-1, exhibited initial flow hardening, followed by flow softening. The microstructures revealed dynamic recrystallisation, grain growth, cavitation, and a variation in the amount of second phase particles. Grain growth and cavitation were found to increase with temperature in region II. Excessive grain growth at 1273 K led to the elimination of region II. Grain growth and cavitation were both found to be less pronounced as the strain rate increased in region III.     

Threshold and growth mechanism of fatigue cracks under mode II and III loadings

ABSTRACT The fatigue crack growth behaviour of 0.47% carbon steel was studied under mode II and III loadings. Mode II fatigue crack growth tests were carried out using specially designed double cantilever (DC) type specimens in order to measure the mode II threshold stress intensity factor range, ΔK_IIth. The relationship ΔK_IIth > ΔK_Ith caused crack branching from mode II to I after a crack reached the mode II threshold. Torsion fatigue tests on circumferentially cracked specimens were carried out to study the mechanisms of both mode III crack growth and of the formation of the factory‐roof crack surface morphology. A change in microstructure occurred at a crack tip during crack growth in both mode II and mode III shear cracks. It is presumed that the crack growth mechanisms in mode II and in mode III are essentially the same. Detailed fractographic investigation showed that factory‐roofs were formed by crack branching into mode I. Crack branching started from small semi‐elliptical cracks nucleated by shear at the tip of the original circumferential crack.     

Spectroscopic Studies of p-H2 to Above 200 GPa

Raman and infrared vibrational spectra of H ₂ have been measured to pressures in excess of 200 GPa and at liquid helium temperatures using new high sensitivity techniques. Detailed study of the pressure dependence of o-p conversion rate reveals an initial increase followed by a decrease above 1 GPa. The conversion rate then increases dramatically with pressure, and this continues to above 50 GPa. New sets of vibron, phonon, roton, and libron excitations in converted para samples are documented as a function of pressure through phases I, II, and III. The results provide important information on the crystal structures, molecular orientational state, and vibrational dynamics of the high-pressure phases.     

Engineered Bacterial Bioreactor for Tumor Therapy via Fenton‐Like Reaction with Localized H2O2 Generation

Synthetic biology based on bacteria has been displayed in antitumor therapy and shown good performance. In this study, an engineered bacterium Escherichia coli MG1655 is designed with NDH‐2 enzyme (respiratory chain enzyme II) overexpression (Ec‐pE), which can colonize in tumor regions and increase localized H₂O₂ generation. Following from this, magnetic Fe₃O₄ nanoparticles are covalently linked to bacteria to act as a catalyst for a Fenton‐like reaction, which converts H₂O₂ to toxic hydroxyl radicals (?OH) for tumor therapy. In this constructed bioreactor, the Fenton‐like reaction occurs with sustainably synthesized H₂O₂ produced by engineered bacteria, and severe tumor apoptosis is induced via the produced toxic ?OH. These results show that this bioreactor can achieve effective tumor colonization, and realize a self‐supplied therapeutic Fenton‐like reaction without additional H₂O₂ provision.     

Selective Recovery of Chromium from Precipitates Containing d Elements and Actinides: II. Effect of H2O2

Oxidation of various Cr(III) hydroxides and mixed Cr(III)-Ni(II) and Cr(III)-Fe(III) hydroxides with hydrogen peroxide was studied. The initial reaction rate increases as the Cr(III) content in the suspension and H₂O₂ concentration are increased and nonmonotonicaly decreases with increasing NaOH concentration within the 0.2-2.0 M range. The activation energy in 0.5 M NaOH is equal to 82 kJ mol^{- 1} (30-90°C). The oxidant consumption substantially exceeds the stoichiometry.     

Novel Nanogels Loaded with Mn(II) Chelates as Effective and Biologically Stable MRI Probes

Here it is described nanogels (NG) based on a chitosan matrix, which are covalently stabilized by a bisamide derivative of Mn-t-CDTA (t–CDTA = trans-1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid). the Mn(II) complex acts both as a contrast medium and as a cross-linking agent. These nanogels are proposed as an alternative to the less stable paramagnetic nanogels obtained by electrostatic interactions between the polymeric matrix and paramagnetic Gd(III) chelates. The present novel nanogels show: i) relaxivity values seven times higher than that of typical monohydrated Mn(II) chelates at the clinical fields, thanks to the combination of a restricted mobility of the complex with a fast exchange of the metal-bound water molecule; ii) high stability of the formulation over time at pH 5 and under physiological conditions, thus excluding metal leaking or particles aggregation; iii) good extravasation and accumulation, with a maximum contrast achieved at 24 h post-injection in mice bearing subcutaneous breast cancer tumor; iv) high T₁ contrast (1 T) in the tumor 24 h post-injection. These improved properties pave the way for the use of these paramagnetic nanogels as promising magnetic resonance imaging (MRI) probes for in vitro and in vivo preclinical applications.     

Depolymerization of Pu(IV) Polymer in 0.5-3 M HNO3 in the Presence of Reductants and Oxidants

Methods of depolymerization of polymeric Pu(IV) in 0.5-3 M HNO₃ in the presence of reductants [hydroquinone, H₂O₂, hydroxylamine, U(IV)] and oxidants [KMnO₄, H₂O₂ + Fe(NO₃)₃, Na₂S₂O₈ + catalysts, Co(III)] were studied. The ratios of various oxidation states and complex species of plutonium in such systems were determined by electronic absorption spectroscopy. A mechanism of depolymerization of Pu(IV) by sodium persulfate in 0.5-3 M HNO₃ in the presence of Co(II) salts was proposed. The stepwise stability constant of the PuO₂SO₄ complex K ₁ was estimated.     

Pressure of the Saturated Vapor of Nickel at High Temperatures

Two series of measurements of the saturated vapor pressure of crystalline and liquid nickel are carried out in the temperature range of 1270–1896 K using the integral version of the effusion method and Knudsen mass spectrometry. The enthalpy of sublimation of Ni at 0 K is calculated from the measurement results in accordance with the second _s H ₀ ⁰(II) and the third _s H ₀ ⁰(III) laws of thermodynamics. Good agreement between the vapor pressure values, determined by different methods under different experimental conditions, makes possible their joint treatment for crystalline and liquid nickel and leads one to recommend the value of _s H ₀ ⁰ = 425.3 ± 2.0 kJ/mol. The results obtained are compared with the available data of other authors.     

Reduction of Np(V) with Fe(II) in weakly acidic solutions containing H<Subscript>2</Subscript>C<Subscript>2</Subscript>O<Subscript>4</Subscript>

The kinetics of the reaction of Np(V) with Fe(II) in dilute perchloric and nitric acid solutions containing H₂C₂O₄ was studied by spectrophotometry. In the range pH 1–2, the reaction rate is described by the equation d[Np(V)]/dt = k[Np(V)][Fe(II)][H₂C₂O₄]²[H⁺]^−1.6, k = 182 mol^−1.4 l^1.4 s⁻¹. The activation energy in the range 25–45°C is 26 kJ mol⁻¹. The reaction mechanism involves formation of Fe(II) and Np(V) oxalate complexes, followed by their reaction with the participation of the H⁺ ion.     

Calibration of reaction parameters for the improvement of thermal stability and crystalline quality of multi-walled carbon nanotubes

The results of Raman analysis on multi-walled carbon nanotubes, prepared by catalysed chemical vapour deposition, are used as a guide for the calibration of the growth parameters, directed to improve crystalline quality and resulting thermal stability of nanotubes. Under selective growth conditions, the resistance to oxidation in air, as assessed by thermogravimetry measurements, is found to increase with the establishment of the long-range graphitic order in radial tube direction, as signalled by the Raman G′/G intensity ratio enhancement. In the range of parameters explored (synthesis temperature: 500–700 °C; growth atmosphere: 120 cc/min i-C₄H₁₀–H₂–He mixture with He at 0–25%; i-C₄H₁₀/H₂ flow ratio: 1–3; metal load and reduction temperature of Fe/Al₂O₃ catalysts: 17–40 wt%, and 500 and 700 °C, respectively), the best crystalline quality and the highest oxidative resistance are achieved by carrying out the synthesis reaction at 700 °C in 1:1:0 i-C₄H₁₀–H₂–He atmosphere over 29 wt% Fe catalysts reduced at 700 °C. An additional relevant finding is the strong correlation evidenced between results of thermogravimetry and Raman analyses, suggesting the use of Raman spectroscopy for non-destructively evaluating the thermal stability of any graphitically ordered carbon species.     

An Investigation of Evaporation of Lithium

The Knudsen effusion method with mass-spectrometric analysis of evaporation products is used to determine the composition and pressure of saturated vapor over liquid lithium in the temperature range from 627 to 893 K. The Li(l) = Li(g), 2Li(l) = Li₂(g), and Li₂(g) = 2Li(g) reactions are investigated. The measured values of partial pressure for Li and Li₂are used to calculate the values of enthalpy for these reactions at 0 K by the second, _r H ₀ ⁰(II), and third, _r H ₀ ⁰(III), laws of thermodynamics: _r H ₀ ⁰(II) = 157.9 ± 0.5, 214.2 ± 0.6, and 101.4 ± 1.1 kJ/mol, and _r H ₀ ⁰(III) = 157.5 ± 0.3, 213.9 ± 0.3, and 101.1 ± 0.6 kJ/mol, respectively.     

Determination of the oxidizing ability of HTSC materials containing two elements with a variable degree of oxidation

The presence of mixed valence states of elements is supposed to be a common characteristic feature of the high-T _c superconductors, based on copper oxides. Methods have been suggested for the determination of Cu(III) in the Y-Ba-Cu-O ceramics and separate determination of two oxidants: Bi(V) and Cu(III), Tl(III) and Cu(III) in the corresponding materials. Compounds of Bi(V) oxidize in the ions of Mn(II) to MnO ₄ ⁻ in the acidic medium. Active oxygen, bound to Cu(III) is isolated, not oxidizing Mn(II). MnO ₄ ⁻ is titrated then with a solution of Fe(II) sulphate. For the determination of Tl(III) the sample is dissolved in the acid, Cu(III) is reduced to Cu(II) and Tl(III) is titrated with the hydroquinone solution. The compounds of Bi(V), Tl(III) and Cu(III), having high oxidation-reduction potentials can oxidize the complex Co(II)-EDTA to Co(III)-EDTA. The colour intensity of the latter is proportional to the content of Cu(III) or to the sum of Bi(V) and Cu(III) or Tl(III) and Cu(III). The content of Cu(III) in Bi- and Tl-containing materials is determined by the difference.     

Heats of Solution,Transition, and Formation of Three Crystalline Forms of Metaboric Acid

The three crystalline forms of metaboric acid HBO₂ were prepared, purified, and analyzed. Heats of solution in water or of reaction with sodium hydroxide solution were compared with those of orthoboric acid H₃BO₃(c). The best values for the heats of transition at 25 °C are: (c,I) to (c,II), 2.33±0.23 kcal/mole; (c,II) to (c,III), 1.30±0.05 kcal/mole; (c,I) to (c,III), 3.63±0.24 kcal/mole. The following heats of formation at 25 °C were derived: −192.77 ± 0.35 kcal/mole for the cubic HBO₂(c,I), −190.43 ±0.34 kcal/mole for the monoclinic HBO₂ (c,II), and −189.13 ± 0.34 kcal/mole for the orthorhombic HBO₂(c,III).