Spreading and recoil of a surfactant-containing water drop on glass-supported alcohol films

In this paper we report the experimental observation of spreading and recoil of surfactant-containing water drops on various alcohol films supported on glass slides. The time evolution of spreading and recoil behavior was recorded by placing a web camera above the drop. We observed that the drop spread the fastest on CH3OH, followed by C2H5OH, and the slowest on i-PrOH. On the other hand, the recoil behavior was just the opposite. The drop recoiled the slowest on CH3OH and fastest on i-PrOH, while it recoiled in an intermediate time on C2H5OH. In addition, concentration of surfactant in the drop played a prominent role in the spreading and recoil time of the drop, with higher surfactant concentration making the drop spread and recoil faster. The time evolution of spreading velocity of the drop on different alcohol films at various surfactant concentrations occurred with a Gaussian distribution and the peak velocity was reached earliest on CH3OH followed by C2H5OH, while on i-PrOH it took the longest time. The recoil behavior was similar. The variation of velocity as a function of radius exhibited oscillatory behavior, indicating the existence of an interfacial phenomenon. We also report the observation that spreading of the drop occurred without observable fingering instability. Further, we observed by Fourier transform infrared (FTIR) spectroscopic measurements that the drop had mixed with the alcohol films as it spread. Miscibility of the alcohol in the film with the drop, alcohol evaporation cooling-induced temperature gradient, and Marangoni effect probably play important roles in the spreading and recoil behavior of the drop.     

Microspectrometric Investigation of Petrified Wood from South-Eastern Poland

 The investigation of the interesting collection of the petrified wood from Bondyrz, Roztocze, south-eastern Poland, has been continued. Two kinds of microprobes such as electron microprobe from the Catholic University of Lublin and synchrotron-based X-ray microprobe from LURE, Orsay, were applied to detect the elements associated with the main component – silica and their spatial distribution and interrelations. The distribution of carbon in the petrified material has been established, which is important since that element is the main remains from the history of the trees. The carbon distribution was characteristic – it concentrated on a place of primordial dark wood. The distribution patterns of the other elements were either similar to that of carbon (Cu, Pb) or they concentrated in separate inclusions (Fe, Al, K, Na, Ca). The replicating mode of the original wood pattern in silica and carbon-containing material was explained. Some indications about the composition of the primordial petrifying solution, the rate of the petrifaction process and the recent coloration of the sample could be concluded from the compositional patterns of silica. The boundary between totally and partially petrified zones could be well observed. Received October 2000. Revision March 6, 2001.     

New peroxovanadium compounds containing biogenic co-ligands: synthesis,stability and effect on alkaline phosphatase activity

A set of new diperoxovanadate(V) complexes with the dipeptides glycyl–glycine or glycyl–leucine as ancillary ligands of the type, A[VO(O₂)₂(peptide)(H₂O)] · H₂O, A = Na or K have been synthesized and characterized by elemental analysis, thermal analysis, magnetic susceptibility and spectral studies. The complexes contain side-on bound peroxo groups and a dipeptide zwitterion as co-ligand, binding the metal center unidentately through O (carboxylate) atom. The compounds are highly stable toward decomposition in solutions of acidic as well as physiological pH and serve as weak substrates to catalase, undergoing degradation in the presence of the enzyme at a rate much slower than H₂O₂. The compounds stoichiometrically oxidize GSH to GSSG. On comparing the GSH oxidizing ability of these compounds with those of previously reported peroxotungsten compounds containing similar co-ligands, a significant difference was noted. The compounds induce a strong inhibitory effect on alkaline phosphatase activity with a potency higher than that of the free peptides, vanadate, or peroxovanadate.     

Measurements of elastic scattering for 7Be, 7Li + 9Be systems and fusion cross sections for 7Li + 9Be system

Elastic scattering angular distributions have been measured for ⁷Be + ⁹Be system at E_lab = 17, 19 and 21 MeV in the angular range θ_cm=26^○–58°, and for ⁷Li + ⁹Be system at E_lab= 15.75, 24 and 30 MeV. An optical model (OM) analysis of these data have been carried out. For the ⁷Li + ⁹Be system fusion cross sections were obtained at E_lab = 15.75, 24 and 30 MeV by measuring the α-evaporation spectra from the compound nucleus at backward angles. The measured α-evaporation spectra were reproduced by the statistical model calculations and fusion cross sections were extracted therefrom. The ratios of the experimental fusion cross sections to the total reaction cross sections (obtained form OM analysis) were found to be rather small. This result suggests that break-up process has a strong influence on fusion process leading to a reduction in fusion cross section.     

Temperature dependence of dc photoconductivity in CdTe thin films

The temperature dependence of dc photoconductivity in the measuring range 303–417 K has been studied in CdTe thin films having thicknesst < 4000 Å. The photoactivation energy decreases in dark which is explained on the basis of grain boundary (GB) effect. The current lost to recombination at GB space charge region causes a negative effect on the photosensitivity of the films. A decrease in photosensitivity with increase in temperature is attributed to the reduction of photoexcitation process. It is observed that the minority carrier lifetime varies inversely with light intensity which supports the sublinear relationship of photoconductivity with the intensity of light and thereby confirms the defect-controlled photoconductivity in CdTe thin films     

Temperature-induced magnetic phase transitions in crystals with competing single-ion and interionic magnetic anisotropies

Temperature-induced phase transitions in a uniaxial ferromagnetic system of spins S = 1 with competing one-particle and two-particle anisotropies are studied. It is shown that, in the case where easy-plane single-ion anisotropy dominates over easy-axis two-particle anisotropy, the transition from the paramagnetic state to a ferromagnetic state with magnetization perpendicular to the anisotropy axis is a second-order displacive magnetic phase transition. In the opposite case, where two-particle anisotropy dominates over single-particle anisotropy, the transition to a ferromagnetic state with magnetization perpendicular to the anisotropy axis is also continuous but of the order-disorder type. In a system with competing second-order one-and two-particle anisotropies, the orientational first-order phase transition can occur to a state with the magnetization directed along or perpendicular to the anisotropy axis.     

Synthesis of Vegetable Oil‐Based Polyurethane: A Study on Curing Kinetics Behavior

In the present study, biobased polyurethane (BPU) samples were synthesized from three different polyols along with polymeric hexamethylene diisocyanate. The three different polyols were synthesized by reacting castor oil with ethylene glycol, triethylene glycol, and triethanolamine. The synthesized polyols were confirmed using proton nuclear magnetic resonance (¹H NMR) spectra analysis. BPU samples were confirmed by the disappearance of isocyanate peak in the FTIR spectra. The cross‐linking densities of all BPU samples were determined using swelling studies. Curing kinetics behavior of all BPU samples were analyzed using differential scanning calorimetry at three different heating rates (5, 7.5, and 10°C/min). The curing kinetic parameters were studied using three nonisothermal methods such as Kissinger, Flynn–Wall–Ozawa, and Ozawa, respectively. The activation energies were found to increase with increasing degree of cure (α). Surface properties of all the synthesized BPU samples were evaluated by dynamic mechanical analysis and scanning electron microscopy.     

Synthesis and properties of 3,4-dioxythiophene and 1,4-dialkoxybenzene based copolymers via direct C?H arylation: Dopant-free hole transport material for perovskite solar cells

Direct C H arylation coupling reaction has gained significant importance in synthesis of conjugated polymers for organic electronic applications. We report here a facile and straightforward method called “direct C H arylation” reaction to synthesize conjugated 3,4-dioxythiophene and 1,4-dialkoxybenzene based copolymers as hole transport material (HTM) for perovskite solar cells. Two electron-rich conjugated polymers P1-2 were synthesized, in which 1,4-dibromo-2,5-bis(dodecyloxy)benzene and 3,4-dialkoxy-thiophene units were used for polymerization. The resulting polymers were characterized and exhibited high solubility in organic solvents. Electrochemical and optical characterizations were carried out by cyclic voltammetry and UV–Vis–NIR absorption spectroscopy and found that these polymers show higher-lying HOMO energy levels with wide band gap. Density functional theory calculation was performed on these polymers ( P1-2 ) and correlated with our experimental results. Finally, perovskite solar cells were fabricated by solution-processable deposition of P1-2 as dopant-free HTM with device geometry ITO/SnO₂/Perovskite/HTM( P1 / P2 )/Ag and achieved a maximum power conversion efficiency of 5.28%. This study provides information on designing and simple preparation by direct C H arylation reaction of higher-lying HOMO energy level polymer as HTM for perovskite solar cells.     

Efficient Synthesis of Homoallylic Alcohols/Amines from Allyltributylstannane and Carbonyl Compounds/Imines Using Iodine as Catalyst Under Acetic Acid–Water Medium

This paper describes a general method for the synthesis of homoallylic alcohols and amines by nucleophilic addition reaction of allyltributylstannane to carbonyl compounds and aldimines where iodine acts as a catalyst in H₂O/acetic acid (1:1) medium. Only 10 mol% of I₂ is required for various organic transformations. By using this process, various homoallylic alcohols and amines are produced in good to excellent yields.