Prednisolone inhibits phagocytosis by polymorphonuclear leucocytes via steroid receptor mediated events

Prednisolone, at concentrations between 2·78 × 10⁻⁶ M (1 μg/ml) and 1·39 × 10⁻⁸ M (5 × 10⁻³ μg/ml) exerts an inhibitory effect on the phagocytosis of latex particles by normal human polymorphonuclear leucocytes in vitro as assessed by electron microscopical analysis. This inhibition appears to be receptor-mediated, as it is dependent upon RNA and protein synthesis and is glucocorticoid specific.     

Phytosulfokine-α, a sulfated pentapeptide, stimulates the proliferation of rice cells by means of specific high- and low-affinity binding sites

Peptide growth factors were isolated from conditioned medium derived from rice (Oryza sativa L.) suspension cultures and identified to be a sulfated pentapeptide [H-Tyr(SO₃H)-Ile-Tyr(SO₃H)-Thr-Gln-OH] and its C-terminal-truncated tetrapeptide [H-Tyr(SO₃H)-Ile-Tyr(SO₃H)-Thr-OH]. These structures were identical to the phytosulfokines originally found in asparagus (Asparagus officinalis L.) mesophyll cultures. The pentapeptide [phytosulfokine-α (PSK-α)] very strongly stimulated colony formation of rice protoplasts at concentrations above 10⁻⁸ M, indicating a similar mode of action in rice of phytosulfokines. Binding assays using ³⁵S-labeled PSK-α demonstrated the existence of both high- and low-affinity specific saturable binding sites on the surface of rice cells in suspension. Analysis of [³⁵S]PSK-α binding in differential centrifugation fractions suggested association of the binding with a plasma membrane-enriched fraction. The apparent K_d values for [³⁵S]PSK-α binding were found to be 1 × 10⁻⁹ M for the high-affinity type and 1 × 10⁻⁷ M for the low-affinity type, with maximal numbers of binding sites of 1 × 10⁴ sites per cell and 1 × 10⁵ sites per cell, respectively. Competition studies with [³⁵S]PSK-α and several synthetic PSK-α analogs demonstrated that only peptides that possesses mitogenic activity can effectively displace the radioligand. These results suggest that a signal transduction pathway mediated by peptide factors is involved in plant cell proliferation.     

Unliganded gating of acetylcholine receptor channels

We estimated the unliganded opening and closing rate constants of neuromuscular acetylcholine receptor-channels (AChRs) having mutations that increased the gating equilibrium constant. For some mutant combinations, spontaneous openings occurred in clusters. For 25 different constructs, the unliganded gating equilibrium constant (E₀) was correlated with the product of the predicted fold-increase in the diliganded gating equilibrium constant caused by each mutation alone. We estimate that (i) E₀ for mouse, wild-type α₂βδε AChRs is ≈1.15 × 10⁻⁷; (ii) unliganded AChRs open for ≈80 μs, once every ≈15 min; (iii) the affinity for ACh of the O(pen) conformation is ≈10 nM, or ≈15,600 times greater than for the C(losed) conformation; (iv) the ACh-monoliganded gating equilibrium constant is ≈1.7 × 10⁻³; (v) the C→O isomerization reduces substantially ACh dissociation, but only slightly increases association; and (vi) ACh provides only ≈0.9 k_BT more binding energy per site than carbamylcholine but ≈3.1 k_BT more than choline, mainly because of a low O conformation affinity. Most mutations of binding site residue αW149 increase E₀. We estimate that the mutation αW149F reduces the ACh affinity of C only by 13-fold, but of O by 190-fold. Rate–equilibrium free-energy relationships for different regions of the protein show similar slopes (Φ values) for un- vs. diliganded gating, which suggests that the conformational pathway of the gating structural change is fundamentally the same with and without agonists. Agonist binding is a perturbation that (like most mutations) changes the energy, but not the mechanism, of the gating conformational change.     

Gastric motility is an important factor in the pathogenesis of indomethacin-induced gastric mucosal lesions in rats

Effects of atropine, cimetidine, and 16,16-dimethyl prostaglandin E₂ (16,16-dmPGE₂) on indomethacin-induced gastric lesions were investigated in rats by correlating their effects on gastric acid and HCO^}-₃ secretion and motility. Subcutaneously administered indomethacin (25 mg/kg) produced gastric mucosal lesions within 4 hr. In parallel studies, an equivalent dose of indomethacin inhibited gastric HCO^}-₃ secretion, and stimulated gastric motor activity measured as intraluminal pressure recordings, whereas acid secretion was unaffected. The lesions induced by indomethacin were significantly prevented by three agents: cimetidine (100 mg/kg), which reduced acid secretion; atropine (1 mg/kg), which reduced acid secretion and gastric motility; and 16,16-dmPGE₂ (10 g/kg), which reduced acid secretion and motility and increased gastric HCO^– ₃ secretion. If acid (150 mM HCl) was infused into the stomach (1.2 ml/hr) during indomethacin treatment, only the latter two agents significantly prevented the formation of gastric lesions in response to indomethacin. Since only the effect on gastric motility was common to these two agents (atropine and 16,16-dmPGE₂), the increased gastric motility may be an important pathogenetic factor in indomethacin-induced gastric lesions. The presence of acid as well as a deficiency of endogenous PGs may be prerequisite for later extension of the lesions but cannot account for the induction of mucosal lesions in rats following administration of indomethacin.     

Low Temperature Synthesis and Characterization of AlScMo3O12

Recent interest in low and negative thermal expansion materials has led to significant research on compounds that exhibit this property, much of which has targeted the A₂M₃O₁₂ family (A = trivalent cation, M = Mo, W). The expansion and phase transition behavior in this family can be tuned through the choice of the metals incorporated into the structure. An undesired phase transition to a monoclinic structure with large positive expansion can be suppressed in some solid solutions by substituting the A-site by a mixture of two cations. One such material, AlScMo₃O₁₂, was successfully synthesized using non-hydrolytic sol-gel chemistry. Depending on the reaction conditions, phase separation into Al₂Mo₃O₁₂ and Sc₂Mo₃O₁₂ or single-phase AlScMo₃O₁₂ could be obtained. Optimized conditions for the reproducible synthesis of stoichiometric, homogeneous AlScMo₃O₁₂ were established. High resolution synchrotron diffraction experiments were carried out to confirm whether samples were homogeneous and to estimate the Al:Sc ratio through Rietveld refinement and Vegard’s law. Single-phase samples were found to adopt the orthorhombic Sc₂W₃O₁₂ structure at 100 to 460 K. In contrast to all previously-reported A₂M₃O₁₂ compositions, AlScMo₃O₁₂ exhibited positive thermal expansion along all unit cell axes instead of contraction along one or two axes, with expansion coefficients (200–460 K) of α_a = 1.7 × 10⁻⁶ K⁻¹, α_b = 6.2 × 10⁻⁶ K⁻¹, α_c = 2.9 × 10⁻⁶ K⁻¹ and α_V = 10.8 × 10⁻⁶ K⁻¹, respectively.     

Electrochemically Activated Screen-Printed Carbon Sensor Modified with Anionic Surfactant (aSPCE/SDS) for Simultaneous Determination of Paracetamol,Diclofenac and Tramadol

In this work, an electrochemically activated screen-printed carbon electrode modified with sodium dodecyl sulfate (aSPCE/SDS) was proposed for the simultaneous determination of paracetamol (PA), diclofenac (DF), and tramadol (TR). Changes of surface morphology and electrochemical behaviour of the electrode after the electrochemical activation with H₂O₂ and SDS surface modification were studied by scanning electron microscopy (SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The influence of various parameters on the responses of the aSPCE/SDS such as pH and concentration of the buffer, SDS concentration, and techniques parameters were investigated. Using optimised conditions (E_acc. of −0.4 V, t_acc. of 120 s, ΔE_A of 150 mV, ν of 250 mV s⁻¹, and t_m of 10 ms), the aSPCE/SDS showed a good linear response in the concentration ranges of 5.0 × 10⁻⁸–2.0 × 10⁻⁵ for PA, 1.0 × 10⁻⁹–2.0 × 10⁻⁷ for DF, and 1.0 × 10⁻⁸–2.0 × 10⁻⁷ and 2.0 × 10⁻⁷–2.0 × 10⁻⁶ mol L⁻¹ for TR. The limits of detection obtained during the simultaneous determination of PA, DF, and TR are 1.49 × 10⁻⁸ mol L⁻¹, 2.10 × 10⁻¹⁰ mol L⁻¹, and 1.71 × 10⁻⁹ mol L⁻¹, respectively. The selectivity of the aSPCE/SDS was evaluated by examination of the impact of some inorganic and organic substances that are commonly present in environmental and biological samples on the responses of PA, DF, and TR. Finally, the differential pulse adsorptive stripping voltammetric (DPAdSV) procedure using the aSPCE/SDS was successfully applied for the determination of PA, DF, and TR in river water and serum samples as well as pharmaceuticals.     

Alkylation of Benzene with Propylene in a Flow-Through Membrane Reactor and Fixed-Bed Reactor: Preliminary Results

Benzene alkylation with propylene was studied in the gas phase using a catalytic membrane reactor and a fixed-bed reactor in the temperature range of 200–300 °C and with a weight hourly space velocity (WHSV) of 51 h⁻¹. β-zeolite was prepared by hydrothermal synthesis using silica, aluminum metal and TEAOH as precursors. The membrane’s XRD patterns showed good crystallinity for the β-zeolite film, while scanning electron microscopy SEM results indicated that its random polycrystalline film was approximately 1 μm thick. The powders’ specific area was determined to be 400 m²·g⁻¹ by N₂ adsorption/desorption, and the TPD results indicated an overall acidity of 3.4 mmol NH₃·g⁻¹. Relative to the powdered catalyst, the catalytic membrane showed good activity and product selectivity for cumene.     

Peculiarities of DRX in a Highly-Alloyed Austenitic Stainless Steel

The features of discontinuous dynamic recrystallization (DRX) in a highly-alloyed austenitic stainless steel were studied at temperatures of 800 °C to 1100 °C. Hot deformation accompanied by DRX was characterized by an activation energy of 415 kJ/mol. The frequency of the sequential DRX cycles depended on the deformation conditions; and the largest fraction of DRX grains with small grain orientation spread below 1° was observed at a temperature of around 1000 °C and a strain rate of about 10⁻³ s⁻¹. The following power law relationships were obtained for DRX grain size (D_DRX) and dislocation density (ρ) vs. temperature-compensated strain rate (Z) or peak flow stress (σ_P): D_DRX ~ Z^−0.25, ρ ~ Z^0.1, σ_P ~ D_DRX^−0.9, σ_P ~ ρ^1.4. The latter, i.e., σ_P ~ ρ^1.4, was valid in the flow stress range below 300 MPa and changed to σ_P ~ ρ^0.5 on increasing the stress. The obtained dependencies suggest a unique power law function between the dislocation density and the DRX grain size with an exponent of −0.5.     

Improved Electrical Characteristics of Gallium Oxide/P-Epi Silicon Carbide Static Induction Transistors with UV/Ozone Treatment Fabricated by RF Sputter

In this study, static induction transistors (SITs) with beta gallium oxide (β-Ga₂O₃) channels are grown on a p-epi silicon carbide (SiC) layer via radio frequency sputtering. The Ga₂O₃ films are subjected to UV/ozone treatment, which results in reduced oxygen vacancies in the X-ray photoelectron spectroscopy data, lower surface roughness (3.51 nm) and resistivity (319 Ω·cm), and higher mobility (4.01 cm²V⁻¹s⁻¹). The gate leakage current is as low as 1.0 × 10⁻¹¹ A at V_GS = 10 V by the depletion layer formed between n-Ga₂O₃ and p-epi SiC at the gate region with a PN heterojunction. The UV/O₃-treated SITs exhibit higher (approximately 1.64 × 10² times) drain current (V_DS = 12 V) and on/off ratio (4.32 × 10⁵) than non-treated control devices.     

Fickian-Based Empirical Approach for Diffusivity Determination in Hollow Alginate-Based Microfibers Using 2D Fluorescence Microscopy and Comparison with Theoretical Predictions

Hollow alginate microfibers (od = 1.3 mm, id = 0.9 mm, th = 400 µm, L = 3.5 cm) comprised of 2% (w/v) medium molecular weight alginate cross-linked with 0.9 M CaCl₂ were fabricated to model outward diffusion capture by 2D fluorescent microscopy. A two-fold comparison of diffusivity determination based on real-time diffusion of Fluorescein isothiocyanate molecular weight (FITC MW) markers was conducted using a proposed Fickian-based approach in conjunction with a previously established numerical model developed based on spectrophotometric data. Computed empirical/numerical (D_empiricial/D_numerical) diffusivities characterized by small standard deviations for the 4-, 70- and 500-kDa markers expressed in m²/s are (1.06 × 10⁻⁹ ± 1.96 × 10⁻¹⁰)/(2.03 × 10⁻¹¹), (5.89 × 10⁻¹¹ ± 2.83 × 10⁻¹²)/(4.6 × 10⁻¹²) and (4.89 × 10⁻¹² ± 3.94 × 10⁻¹³)/(1.27 × 10⁻¹²), respectively, with the discrimination between the computation techniques narrowing down as a function of MW. The use of the numerical approach is recommended for fluorescence-based measurements as the standard computational method for effective diffusivity determination until capture rates (minimum 12 fps for the 4-kDa marker) and the use of linear instead of polynomial interpolating functions to model temporal intensity gradients have been proven to minimize the extent of systematic errors associated with the proposed empirical method.     

Kinetics of the Organic Compounds and Ammonium Nitrogen Electrochemical Oxidation in Landfill Leachates at Boron-Doped Diamond Anodes

Electrochemical oxidation (EO) of organic compounds and ammonium in the complex matrix of landfill leachates (LLs) was investigated using three different boron-doped diamond electrodes produced on silicon substrate (BDD/Si)(levels of boron doping [B]/[C] = 500, 10,000, and 15,000 ppm—0.5 k; 10 k, and 15 k, respectively) during 8-h tests. The LLs were collected from an old landfill in the Pomerania region (Northern Poland) and were characterized by a high concentration of N-NH₄⁺ (2069 ± 103 mg·L⁻¹), chemical oxygen demand (COD) (3608 ± 123 mg·L⁻¹), high salinity (2690 ± 70 mg Cl⁻·L⁻¹, 1353 ± 70 mg SO₄²⁻·L⁻¹), and poor biodegradability. The experiments revealed that electrochemical oxidation of LLs using BDD 0.5 k and current density (j) = 100 mA·cm⁻² was the most effective amongst those tested (C_8h/C₀: COD = 0.09 ± 0.14 mg·L⁻¹, N-NH₄⁺ = 0.39 ± 0.05 mg·L⁻¹). COD removal fits the model of pseudo-first-order reactions and N-NH₄⁺ removal in most cases follows second-order kinetics. The double increase in biodegradability index—to 0.22 ± 0.05 (BDD 0.5 k, j = 50 mA·cm⁻²) shows the potential application of EO prior biological treatment. Despite EO still being an energy consuming process, optimum conditions (COD removal > 70%) might be achieved after 4 h of treatment with an energy consumption of 200 kW·m⁻³ (BDD 0.5 k, j = 100 mA·cm⁻²).     

Fast events in protein folding: Relaxation dynamics of secondary and tertiary structure in native apomyoglobin

We report the fast relaxation dynamics of “native” apomyoglobin (pH 5.3) following a 10-ns, laser-induced temperature jump. The structural dynamics are probed using time-resolved infrared spectroscopy. The infrared kinetics monitored within the amide I absorbance of the polypeptide backbone exhibit two distinct relaxation phases which have different spectral signatures and occur on very different time scales (ν = 1633 cm⁻¹, τ = 48 ns; ν = 1650 cm⁻¹, τ = 132 μs). We assign these two spectral components to discrete substructures in the protein: helical structure that is solvated (1633 cm⁻¹) and native helix that is protected from solvation by interhelix tertiary interactions (1650 cm⁻¹). Folding rate coefficients inferred from the observed relaxations at 60°C are k_f(solvated) = (7 to 20) × 10⁶ s⁻¹ and k_f(native) = 3.6 × 10³ s⁻¹, respectively. The faster rate is interpreted as the intrinsic rate of solvated helix formation, whereas the slower rate is interpreted as the rate of formation of tertiary contacts that determine a native helix. Thus, at 60°C helix formation precedes the formation of tertiary structure by over three orders of magnitude in this protein. Furthermore, the distinct thermodynamics and kinetics observed for the apomyoglobin substructures suggest that they fold independently, or quasi-independently. The observation of inhomogeneous folding for apomyoglobin is remarkable, given the relatively small size and structural simplicity of this protein.     

INAUGURAL ARTICLE by a Recently Elected Academy Member:In vitro evolution of horse heart myoglobin to increase peroxidase activity

Random mutagenesis and screening for enzymatic activity has been used to engineer horse heart myoglobin to enhance its intrinsic peroxidase activity. A chemically synthesized gene encoding horse heart myoglobin was subjected to successive cycles of PCR random mutagenesis. The mutated myoglobin gene was expressed in Escherichia coli LE392, and the variants were screened for peroxidase activity with a plate assay. Four cycles of mutagenesis and screening produced a series of single, double, triple, and quadruple variants with enhanced peroxidase activity. Steady-state kinetics analysis demonstrated that the quadruple variant T39I/K45D/F46L/I107F exhibits peroxidase activity significantly greater than that of the wild-type protein with k₁ (for H₂O₂ oxidation of metmyoglobin) of 1.34 × 10⁴ M⁻¹ s⁻¹ (≈25-fold that of wild-type myoglobin) and k₃ [for reducing the substrate (2, 2′-azino-di-(3-ethyl)benzthiazoline-6-sulfonic acid] of 1.4 × 10⁶ M⁻¹ s⁻¹ (1.6-fold that of wild-type myoglobin). Thermal stability of these variants as measured with circular dichroism spectroscopy demonstrated that the T_m of the quadruple variant is decreased only slightly compared with wild-type (74.1°C vs. 76.5°C). The rate constants for binding of dioxygen exhibited by the quadruple variant are identical to the those observed for wild-type myoglobin (k_on, 22.2 × 10⁻⁶ M⁻¹ s⁻¹ vs. 22.3 × 10⁻⁶ M⁻¹ s⁻¹; k_off, 24.3 s⁻¹ vs. 24.2 s⁻¹; K_O2, 0.91 × 10⁻⁶ M⁻¹ vs. 0.92 × 10⁻⁶ M⁻¹). The affinity of the quadruple variant for CO is increased slightly (k_on, 0.90 × 10⁻⁶ M⁻¹s⁻¹ vs. 0.51 × 10⁻⁶ M⁻¹s⁻¹; k_off, 5.08 s⁻¹ vs. 3.51 s⁻¹; K_CO, 1.77 × 10⁻⁷ M⁻¹ vs. 1.45 × 10⁻⁷ M⁻¹). All four substitutions are in the heme pocket and within 5 Å of the heme group.     

Fatty acids suppress voltage-gated Na+ currents in HEK293t cells transfected with the α-subunit of the human cardiac Na+ channel

Studies have shown that fish oils, containing n-3 fatty acids, have protective effects against ischemia-induced, fatal cardiac arrhythmias in animals and perhaps in humans. In this study we used the whole-cell voltage-clamp technique to assess the effects of dietary, free long-chain fatty acids on the Na⁺ current (I_Na,α) in human embryonic kidney (HEK293t) cells transfected with the α-subunit of the human cardiac Na⁺ channel (hH1_α). Extracellular application of 0.01 to 30 μM eicosapentaenoic acid (EPA, C20:5n-3) significantly reduced I_Na,α with an IC₅₀ of 0.51 ± 0.06 μM. The EPA-induced suppression of I_Na,α was concentration- and voltage-dependent. EPA at 5 μM significantly shifted the steady-state inactivation relationship by −27.8 ± 1.2 mV (n = 6, P < 0.0001) at the V_1/2 point. In addition, EPA blocked I_Na,α with a higher “binding affinity” to hH1_α channels in the inactivated state than in the resting state. The transition from the resting state to the inactivated state was markedly accelerated in the presence of 5 μM EPA. The time for 50% recovery from the inactivation state was significantly slower in the presence of 5 μM EPA, from 2.1 ± 0.8 ms for control to 34.8 ± 2.1 ms (n = 5, P < 0.001). The effects of EPA on I_Na,α were reversible. Furthermore, docosahexaenoic acid (C22:6n-3), α-linolenic acid (C18:3n-3), conjugated linoleic acid (C18:2n-7), and oleic acid (C18:1n-9) at 5 μM and all-trans-retinoic acid at 10 μM had similar effects on I_Na,α as EPA. Even 5 μM of stearic acid (C18:0) or palmitic acid (C16:0) also significantly inhibited I_Na,α. In contrast, 5 μM EPA ethyl ester did not alter I_Na,α (8 ± 4%, n = 8, P > 0.05). The present data demonstrate that free fatty acids suppress I_Na,α with high “binding affinity” to hH1_α channels in the inactivated state and prolong the duration of recovery from inactivation.     

Structural,Physical, and Mechanical Analysis of ZnO and TiO2 Nanoparticle-Reinforced Self-Adhesive Coating Restorative Material

This study aimed to modify an EQUIA coat (EC; GC, Japan) by incorporating 1 and 2 wt.% of zinc oxide (ZnO; EC-Z1 and EC-Z2) and titanium dioxide (TiO₂; EC-T1 and EC-T2) nanoparticles, whereby structural and phase analyses were assessed using Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD), respectively. Thermogravimetric analysis/differential scanning calorimetry, micro-hardness, and water absorption analyses were conducted, and the microstructure was studied by scanning electron microscopy/energy-dispersive spectroscopy. FTIR spectra showed a reduction in peak heights of amide (1521 cm⁻¹) and carbonyl (1716 cm⁻¹) groups. XRD showed peaks of ZnO (2θ ~ 31.3°, 34.0°, 35.8°, 47.1°, 56.2°, 62.5°, 67.6°, and 68.7°) and TiO₂ (2θ ~ 25.3°, 37.8°, 47.9, 54.5°, 62.8°, 69.5°, and 75.1°) corresponding to a hexagonal phase with a wurtzite structure and an anatase phase, respectively. Thermal stability was improved in newly modified materials in comparison to the control group. The sequence of obtained glass transitions was EC-T2 (111 °C), EC-T1 (102 °C), EC-Z2 (98 °C), EC-Z1 (92 °C), and EC-C (90 °C). EC-T2 and EC-T1 showed the highest (43.76 ± 2.78) and lowest (29.58 ± 3.2) micro-hardness values. EC showed the maximum water absorption (1.6%) at day 7 followed by EC-T1 (0.82%) and EC-Z1 (0.61%). These results suggest that EC with ZnO and TiO₂ nanoparticles has the potential to be used clinically as a coating material.     

Hysteresis in Lanthanide Zirconium Oxides Observed Using a Pulse CV Technique and including the Effect of High Temperature Annealing

A powerful characterization technique, pulse capacitance-voltage (CV) technique, was used to investigate oxide traps before and after annealing for lanthanide zirconium oxide thin films deposited on n-type Si (111) substrates at 300 °C by liquid injection Atomic Layer Deposition (ALD). The results indicated that: (1) more traps were observed compared to the conventional capacitance-voltage characterization method in LaZrO_x; (2) the time-dependent trapping/de-trapping was influenced by the edge time, width and peak-to-peak voltage of a gate voltage pulse. Post deposition annealing was performed at 700 °C, 800 °C and 900 °C in N₂ ambient for 15 s to the samples with 200 ALD cycles. The effect of the high temperature annealing on oxide traps and leakage current were subsequently explored. It showed that more traps were generated after annealing with the trap density increasing from 1.41 × 10¹² cm⁻² for as-deposited sample to 4.55 × 10¹² cm⁻² for the 800 °C annealed one. In addition, the leakage current density increase from about 10⁻⁶ A/cm² at V_g = +0.5 V for the as-deposited sample to 10⁻³ A/cm² at V_g = +0.5 V for the 900 °C annealed one.     

A New Homogeneous Catalyst for the Dehydrogenation of Dimethylamine Borane Starting with Ruthenium(III) Acetylacetonate

The catalytic activity of ruthenium(III) acetylacetonate was investigated for the first time in the dehydrogenation of dimethylamine borane. During catalytic reaction, a new ruthenium(II) species is formed in situ from the reduction of ruthenium(III) and characterized using UV-Visible, Fourier transform infrared (FTIR), ¹H NMR, and mass spectroscopy. The most likely structure suggested for the ruthenium(II) species is mer-[Ru(N₂Me₄)₃(acac)H]. Mercury poisoning experiment indicates that the catalytic dehydrogenation of dimethylamine-borane is homogeneous catalysis. The kinetics of the catalytic dehydrogenation of dimethylamine borane starting with Ru(acac)₃ were studied depending on the catalyst concentration, substrate concentration and temperature. The hydrogen generation was found to be first-order with respect to catalyst concentration and zero-order regarding the substrate concentration. Evaluation of the kinetic data provides the activation parameters for the dehydrogenation reaction: the activation energy E_a = 85 ± 2 kJ·mol⁻¹, the enthalpy of activation ∆H^# = 82 ± 2 kJ·mol⁻¹ and the entropy of activation; ∆S^# = −85 ± 5 J·mol⁻¹·K⁻¹. The ruthenium(II) catalyst formed from the reduction of ruthenium(III) acetylacetonate provides 1700 turnovers over 100 hours in hydrogen generation from the dehydrogenation of dimethylamine borane before deactivation at 60 °C.     

Sustainable Chitosan-Dialdehyde Cellulose Nanocrystal Film

In this study, we incorporated 2,3-dialdehyde nanocrystalline cellulose (DANC) into chitosan as a reinforcing agent and manufactured biodegradable films with enhanced gas barrier properties. DANC generated via periodate oxidation of cellulose nanocrystal (CNC) was blended at various concentrations with chitosan, and bionanocomposite films were prepared via casting and characterized systematically. The results showed that DANC developed Schiff based bond with chitosan that improved its properties significantly. The addition of DANC dramatically improved the gas barrier performance of the composite film, with water vapor permeability (WVP) value decreasing from 62.94 g·mm·m⁻²·atm⁻¹·day⁻¹ to 27.97 g·mm·m⁻²·atm⁻¹·day⁻¹ and oxygen permeability (OP) value decreasing from 0.14 cm³·mm·m⁻²·day⁻¹·atm⁻¹ to 0.026 cm³·mm·m⁻²·day⁻¹·atm⁻¹. Meanwhile, the maximum decomposition temperature (Td_max) of the film increased from 286 °C to 354 °C, and the tensile strength of the film was increased from 23.60 MPa to 41.12 MPa when incorporating 25 wt.% of DANC. In addition, the chitosan/DANC (75/25, wt/wt) films exhibited superior thermal stability, gas barrier, and mechanical strength compared to the chitosan/CNC (75/25, wt/wt) film. These results confirm that the DANC and chitosan induced films with improved gas barrier, mechanical, and thermal properties for possible use in film packaging.     

Linking the Electrical Conductivity and Non-Stoichiometry of Thin Film Ce1−xZrxO2−δ by a Resonant Nanobalance Approach

Bulk ceria-zirconia solid solutions (Ce_1−xZr_xO_2−δ, CZO) are highly suited for application as oxygen storage materials in automotive three-way catalytic converters (TWC) due to the high levels of achievable oxygen non-stoichiometry δ. In thin film CZO, the oxygen storage properties are expected to be further enhanced. The present study addresses this aspect. CZO thin films with 0 ≤ x ≤ 1 were investigated. A unique nano-thermogravimetric method for thin films that is based on the resonant nanobalance approach for high-temperature characterization of oxygen non-stoichiometry in CZO was implemented. The high-temperature electrical conductivity and the non-stoichiometry δ of CZO were measured under oxygen partial pressures pO₂ in the range of 10⁻²⁴–0.2 bar. Markedly enhanced reducibility and electronic conductivity of CeO₂-ZrO₂ as compared to CeO_2−δ and ZrO₂ were observed. A comparison of temperature- and pO₂-dependences of the non-stoichiometry of thin films with literature data for bulk Ce_1−xZr_xO_2−δ shows enhanced reducibility in the former. The maximum conductivity was found for Ce_0.8Zr_0.2O_2−δ, whereas Ce_0.5Zr_0.5O_2-δ showed the highest non-stoichiometry, yielding δ = 0.16 at 900 °C and pO₂ of 10⁻¹⁴ bar. The defect interactions in Ce_1−xZr_xO_2−δ are analyzed in the framework of defect models for ceria and zirconia.