The influence of ultrasonic waves on the hydrogen ion concentration and the stability of colloidal solutions

Summary The ultrasonic waves causes the cerie hydroxide sol to set to a gel. This change has been followed by measuring viscosity, conductivity and hydrogen ion concentration. It has been shown that the extent of hydrogen peroxide formed under the action of ultrasonic waves on water is not alone sufficient to explain for the increase in viscosity, nor at such concentrations it would set the sol to a gel.

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Zusammenfassung Ultraschall verursacht in Cerhydroxyd-Solen Gelierung. Dieses Ver?nderung wurde durch Messen der Viskosit?t, Leitf?higkeit und der Wasserstoffkonzentration verfolgt. Es hat sich gezeigt, da? der Betrag an Wasserstoffperoxydbildung unter Einwirkung des Ultraschalles auf Wasser nicht allein ausreichend ist, den Anstieg in der Viskosit?t oder hinsichtlich der Konzentration zu erkl?ren, um die Gelierung zu deuten.

     

Preparation and characterization of silver-poly(vinylidene fluoride) nanocomposites: formation of piezoelectric polymorph of poly(vinylidene fluoride)

In situ Ag nanoparticles are produced on reduction of Ag+ with N,N-dimethylformamide in the presence of poly(vinylidene fluoride) (PVF2). The plasmon band transition is monitored with time in the reaction mixture for three sets of experiments by UV-vis spectroscopy. The plasmon band absorbance increases sigmoidally with log(time). Analysis of the data with the Avrami equation yields an exponent n value between 1.5 and 2.0, indicating two-dimensional nucleation with linear or diffusion controlled growth. The TEM study of the polymer nanocomposites (PNC) indicates both spherical and rodlike morphology for PNC0.5 and PNC2.5 samples, whereas the PNC11 sample has spherical and agglomerated structures (the numerical number associated with PNC indicates percentage (w/w) of Ag in the nanocomposite). The WAXS and FTIR studies indicate the formation of piezoelectric beta-polymorphic PVF2 in the nanocomposites. The DSC study indicates some increase of the melting point and enthalpy of fusion of PVF2 in the nanocomposite, although with increase in Ag nanoparticle concentration the increase is smaller. The crystallization temperatures of PNCs also increased, indicating nucleating effect of Ag nanoparticles in the composite. In the TGA curves, the PNCs exhibit a three-step degradation process. The degradation temperatures of PNCs are lower than that of PVF2. The storage modulus data indicate a significant reinforcement of the mechanical property in the PNCs where also the reinforcement effect decreases with increasing nanoparticle concentration. Both the loss modulus and tan delta plots indicate two peaks; the lower temperature peak has been attributed for glass transition temperature, whereas the higher one has been attributed to a similar type relaxation process for the crystalline-amorphous interface. The increase in the glass transition is marginal for the PNCs, but the increase of later transition temperature is somewhat higher. The FTIR study shows that the dipolar interaction of the >CF2 dipole with the surface charges of Ag nanoparticle stabilizes the nanoparticle in the nanocomposite.     

First-principles calculations to investigate structural,electronic, optical,and transport properties of half-Heusler VFeZ (Z = N and P) compounds

This research work investigates the structural, electronic, optical, and thermoelectric characteristics of VFeZ (Z = N and P) half-Heusler compounds. The study employs the full-potential linearized augmented plane wave (FP-LAPW) method integrated into the WIEN2K algorithm, serving as the underpinning framework for density functional theory (DFT) analysis. In the study, we use the PBE generalized gradient approximation (PBE-GGA) to identify numerous parameters associated with structural and elastic properties. Lattice parameter results are in agreement with previous outcomes. Moreover, computed elastic parameters satisfy the criterion for stability. In the cubic structure VFeZ (Z = N and P) is ductile, to enhance the computations of electronic characteristics, Tran and Blaha's modified Becke-Johnson potential (TB-mBJ) is used. Our simulations demonstrate that the materials exhibit semiconductor behavior, with a direct band gap for VFeZ (Z = N and P). Strong UV absorption is found via optical experiments suggest compounds are suitable for optical application. Furthermore, study of the thermoelectric properties suggests its application in the thermoelectric generators.     

Mechanism and kinetics of solid-state amorphization by mechanical alloying of Al65Cu 35−x Nb x

In the present study, we have synthesized a number of Al-based Al₆₅Cu_35???x Nb_x ternary alloys by mechanical alloying and undertaken a detailed characterization of their microstructural evolution by X-ray diffraction, high-resolution transmission electron microscopy and positron annihilation spectroscopy. To predict the phase-equilibrium in a given ternary powder blend subjected to mechanical alloying, we have modified the Miedema model to incorporate the influence of interfacial energy contribution in solid-state amorphization and analytically calculate the enthalpy and Gibbs energy of ternary amorphous and nanocrystalline solid solutions. The predicted trend compares well with the experimental data. Finally, an attempt has been made to determine the mechanism of solid-state amorphization in Al₆₅Cu_35?xNb_x alloys utilizing both experimental results and model-based thermodynamic calculations.     

Performance of a 80 W copper vapor laser with “alignment free” unstable CAT-EYE resonator and other configurations using intra-cavity apertures

Performance of a kinetically enhanced copper vapor laser (KE-CVL) with various stable/unstable “alignment free” CAT-EYE resonator configurations are presented here in this paper. The laser used in the experiment was a 45 mm bore (∼2 l discharge volume) kinetically enhanced copper vapor laser developed in our laboratory and capable of generating maximum power of ∼80 W (at ∼9.8 kHz). The efficiency of the laser was ∼1.4% and beam divergence of ∼3.5 mrad in a plane-plane standard multimode cavity. For the first time performance of unstable CAT-EYE resonator is demonstrated with a CVL/KE-CVL. On using unstable CAT-EYE resonator the divergence of the laser beam reduced to ∼0.22 mrad (∼20-fold reduction as compared to conventional plane-plane cavity), ∼40 W output power and with excellent misalignment tolerance. The laser output power was found to be within ∼5% drift/decline with misalignment angle of about 4 mrad between the mirrors. This is a significant improvement in comparison to standard conventional unstable resonator (M ∼ 50) CVL where ∼0.5 mrad divergence is achieved with power drift/decline of about 45% at ∼4 mrad misalignment angle.Off-axis unstable CAT-EYE unstable resonator was also demonstrated for the first time with further reduction in beam divergence to ∼0.13 mrad and with output power of ∼28 W. The misalignment tolerance was found to be highest in case of off-axis unstable CAT-EYE resonator with decline/drift in laser power of only ∼10% for misalignment angle as high as ∼8 mrad. Performance with intra-cavity apertures in plane-plane type CAT-EYE resonator for transverse mode control is also presented for the first time in CVLs. It is observed that the laser beam divergence reduces significantly to 1.25 mrad (a factor of 2) on using an aperture of ∼3.5 mm at the CAT-EYE reflector as compared to its normal (R = F = d) configuration without aperture. In case of stable CAT-EYE resonator the average beam divergence reduces from 8 mrad to 4 mrad (factor of 2) on using intra-cavity aperture of about 3 mm. It was also observed that high misalignment tolerance was retained on using intra-cavity apertures in almost all the CAT-EYE resonators. Use of intra-cavity mesh was also demonstrated for the first time with stable CAT-EYE resonator for improving the beam focus-ability. Average beam divergence was reduced by a factor of 2.5 (from 8 mrad to 3 mrad) on using intra-cavity mesh. These new configurations in CAT-EYE resonators in KE-CVLs are found to be effective in improving and controlling the laser beam divergence significantly with additional characteristic of high misalignment tolerance.     

Rational Design of a Cocktail of Inhibitors against Aβ Aggregation

It has been reported that many molecules could inhibit the aggregation of Aβ (amyloid-β) through suppressing either primary nucleation, secondary nucleation, or elongation processes. In order to suppress multiple pathways of Aβ aggregation, we screened 23 small molecules and found two types of inhibitors with different inhibiting mechanisms based on chemical kinetics analysis. Trp-glucose conjugates ( AS2 ) could bind with fibril ends while natural products ( D3 and D4 ) could associate with monomers. A cocktail of these two kinds of molecules achieved co-inhibition of various fibrillar species and avoid unwanted interference.     

Coordination and Hydroboration of Ru(II)-Borate Complexes: Dihydridoborate vs. Bis(dihydridoborate)

Treatment of [Cp*RuCl₂]₂, 1 , [(COD)IrCl]₂, 2 or [(p-cymene)RuCl₂]_2, 3 (Cp*=η⁵-C₅Me_5, COD= 1,5-cyclooctadiene and p-cymene=η⁶-ⁱPrC₆H₄Me) with heterocyclic borate ligands [Na[(H₃B)L], L₁ and L₂ ( L₁ : L=amt, L₂ : L=mp; amt=2-amino-5-mercapto-1,3,4-thiadiazole, mp=2-mercaptopyridine) led to the formation of borate complexes having uncommon coordination. For example, complexes 1 and 2 on reaction with L₁ and L₂ afforded dihydridoborate species [L^AM(μ-H)₂BHL] 4 – 6 ( 4 : L^A=Cp*, M=Ru, L=amt; 5 : L^A=Cp*, M=Ru, L=mp; 6 : L^A=COD, M=Ir, L=mp). On the other hand, treatment of 3 with L₂ yielded cis- and trans-bis(dihydridoborate) species, [Ru{(μ-H)₂BH(mp)}₂], cis- 7 and trans- 7 . The isolation and structural characterization of fac- and mer-[Ru{(μ-H)₂BH(mp)}{(μ-H)BH(mp)₂}], 8 from the same reaction offered an insight into the behaviour of these dihydridoborate species in solution. Fascinatingly, despite having reduced natural charges on Ru centres both at cis-and trans- 7 , they underwent hydroboration reaction with alkynes that yielded both Markovnikov and anti-Markovnikov addition products, 10 a – d .     

Ethynylation of Cysteine Residues: From Peptides to Proteins in Vitro and in Living Cells

Current approaches to introduce terminal alkynes for bioorthogonal reactions into biomolecules still present limitations in terms of either reactivity, selectivity, or adduct stability. We present a method for the ethynylation of cysteine residues based on the use of ethynylbenziodoxolone (EBX) reagents. The acetylene group is directly introduced onto the thiol group of cysteine and can be used for copper‐catalyzed alkyne‐azide cycloaddition (CuAAC) without further processing. Labeling proceeded with reaction rates comparable to or higher than the most often used iodoacetamide on peptides or maleimide on the antibody trastuzumab, and high cysteine selectivity was observed. The reagents were also used in living cells for cysteine proteomic profiling and displayed improved coverage of the cysteinome compared to previously reported iodoacetamide or hypervalent iodine reagents. Fine‐tuning of the EBX reagents allows optimization of their reactivity and physical properties.     

Further results on the Drazin inverse of even‐order tensors

The notion of the Drazin inverse of an even‐order tensors with the Einstein product was introduced, very recently [J. Ji and Y. Wei. Comput. Math. Appl., 75(9), (2018), pp. 3402‐3413]. In this article, we further elaborate this theory by establishing a few characterizations of the Drazin inverse and $\mathrm{??}$‐weighted Drazin inverse of tensors. In addition to these, we compute the Drazin inverse of tensors using different types of generalized inverses and full rank decomposition of tensors. We also address the solution of multilinear systems by using the Drazin inverse and iterative (higher order Gauss‐Seidel) method of tensors. Besides these, the convergence analysis of the iterative technique is also investigated within the framework of the Einstein product.