Transition to Chaos in the Floating Half Zone Convection

The transition process from steady convection to chaos is experimentally studied in thermocapillary convections of floating half zone. The onset of temperature oscillations in the liquid bridge of floating half zone and further transitions of the temporal convective behaviour are detected by measuring the temperature in the liquid bridge. The fast Fourier transform reveals the frequency and amplitude characteristics of the flow transition. The experimental results indicate the existence of a sequence of period-doubling bifurcations that culminate in chaos. The measured Feigenbaum numbers are δ2 =4.69 and δ4 = 4.6, which are comparable with the theoretical asymptotic value δ=4.669.     

Multivariate experimental design: towards more reliable electrochemical detection

Design of an experiment approach has recently become an urgent requirement for different experimental measurements. Not only owing to the increased expenses for purchasing chemicals and equipment but also to reduce time required to conduct several one-variable at a time experiments to optimize the operating conditions of an experimental design. Design of experiments has excellent applicability in the analytical process related to method development based on multiple variants used for pharmaceutical, food, and environmental analysis. Application of experimental design has become effective to identify and optimize the significant factors and to achieve adequate results using few experimental trials. Electrochemical sensors represent a class of fast, reliable, and economic tools in analytical chemistry, with vast applicability to different fields. This review aims at presenting the most recently used screening and optimization designs during (2019–2021) for the fabrication and operation variables of electrochemical sensors and how can they be efficiently correlated.     

Synthetic studies using unsaturated and active phosphonium salts. A convenient preparation of furano‐ and pyrano[2,3‐c]pyridazines and substituted quinolines

By applying vinyl‐ ( 3 ) and allyltriphenylphosphonium bromides ( 9 ) to 4‐cyano‐5,6‐difur‐2′yl‐2H‐pyridazin‐3‐one ( 1 ) the corresponding fused 5,8‐oxazolo‐ 6, 12 (∼37%) and pyrano‐ 8 , 13 , 14 (∼20%) derivatives are isolated whereas with alkylphosphonium bromides 15a,b fused furans 17a,b (22%) and isopyrroles 18a,b (∼45%) are obtained. On the other hand, the reaction of 2‐[(benzylidene)amino]‐benzonitrile ( 2 ) with 3 and 9 yielded benzoazepines 20 and 21 (∼56%). With 15a,b , quinolines 23a,b (∼46%) and quinazoline 25 (∼24%) are obtained. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:56–64, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20065     

The effect of initial stress and inhomogeneity on the thermoelastic stresses in a rotating anisotropic solid

The present paper presents a general treatment of the transient thermoelastic stresses in a rotating nonhomogeneous anisotropic solid under compressive initial stress. The system of fundamental equations is solved by means of a boundary element method (BEM) and the numerical calculations are carried out for the temperature, displacement components and stress components. The results indicate that the effects of inhomogeneity and initial stress are very pronounced.     

Construction and Implementation of NMR Quantum Logic Gates for Two Spin Systems

The implementation of small prototype quantum computers has been studied through ensemble quantum computing via NMR measurements. In such laboratory studies it is convenient to have access to a wide array of logic gates. Here a systematic approach to reduce the logic gate to an NMR pulse sequence is introduced. This approach views the truth table for a quantum logic operation as a permutation matrix that corresponds to a propagator for an NMR transition. This propagator is then used as the starting point for the derivation of a pulse sequence. Pulse sequences for all the permutations of a four level system are reported along with implementations of representative examples on a two spin-1/2 system, 13C-labeled chloroform.     

Natural Products in Mitigation of Bisphenol A Toxicity: Future Therapeutic Use

Bisphenol A (BPA) is a ubiquitous environmental toxin with deleterious endocrine-disrupting effects. It is widely used in producing epoxy resins, polycarbonate plastics, and polyvinyl chloride plastics. Human beings are regularly exposed to BPA through inhalation, ingestion, and topical absorption routes. The prevalence of BPA exposure has considerably increased over the past decades. Previous research studies have found a plethora of evidence of BPA’s harmful effects. Interestingly, even at a lower concentration, this industrial product was found to be harmful at cellular and tissue levels, affecting various body functions. A noble and possible treatment could be made plausible by using natural products (NPs). In this review, we highlight existing experimental evidence of NPs against BPA exposure-induced adverse effects, which involve the body’s reproductive, neurological, hepatic, renal, cardiovascular, and endocrine systems. The review also focuses on the targeted signaling pathways of NPs involved in BPA-induced toxicity. Although potential molecular mechanisms underlying BPA-induced toxicity have been investigated, there is currently no specific targeted treatment for BPA-induced toxicity. Hence, natural products could be considered for future therapeutic use against adverse and harmful effects of BPA exposure.     

Aqueous coordination chemistry and photochemistry of uranyl(VI) oxalate revisited: a density functional theory study

Using density functional theory (DFT) calculations, we revisited a classical problem of uranyl(VI) oxalate photochemical decomposition. Photoreactivities of uranyl(VI) oxalate complexes are found to correlate largely with ligand-structural arrangements. Importantly, the intramolecular photochemical reaction is inhibited when oxalate is bound to uranium exclusively in chelate binding mode. Previously proposed mechanisms involving a UO(2)(C(2)O(4))(2)(2-) (1:2) complex as the main photoreactive species are thus unlikely to apply, because the two oxalic acids are bound to uranium in a chelating binding mode. Our DFT results suggest that the relevant photoreactive species are UO(2)(C(2)O(4))(3)(4-) (1:3) and (UO(2))(2)(C(2)O(4))(5)(6-) (2:5) complexes binding uranium in an unidentate fashion. These species go through decarboxylation upon excitation to the triplet state, which ensues the release of CO(2) and reduction of U(vi) to U(v). The calculations also suggest an alternative intermolecular pathway at low pH via an electron transfer between the excited state *UO(2)(2+) and hydrogen oxalate (HC(2)O(4)(-)) which eventually leads to the production of CO and OH(-) with no net reduction of U(VI). The calculated results are consistent with previous experimental findings that CO is only detected at low pH while U(IV) is detected only at high pH.     

Structure–Property Relationship of Thin Plasma Deposited Poly(allyl alcohol) Films

Poly(allyl alcohol) films with a thickness of about 150 nm were deposited by pulse plasma polymerization onto different substrates (inorganic and organic). The structure/property relationships of these samples were studied in dependence on the duty cycle (DC) of the plasma by a broad combination of different techniques and probes. For the first time volume sensitive methods (FTIR and dielectric spectroscopy) are combined with surface analytics by employing XPS for that system. FTIR spectroscopy gives qualitatively the same dependence of the concentration of the OH groups on DC like XPS. The observed differences are discussed considering the different analytical depths of both the methods. The dielectric measurements show that the plasma deposited films are not thermally stable but undergo a post plasma chemical reaction during heating. The results obtained by dielectric spectroscopy are discussed in detail with the data from FTIR and XPS measurements.     

Advanced binderless board-like green nanocomposites from undebarked cotton stalks and mechanism of self-bonding

Self-bonding of air-dried undebarked cotton stalks during hot pressing in a closely fitting mold was studied. Advanced board-like green nanocomposites from ground undebarked cotton stalks were introduced for the first time in the present work. The dry forming process was adopted. Moderate molding pressure and temperature were selected and applied in a tight die, thus saving water and energy and avoiding the use of any binders to achieve an environment-friendly green product. Green nanocomposites having densities in the range of 1.27–1.29 g/cm³ and 1.03–1.06 g/cm³ were prepared. Particle size and cell wall morphological structure were found to play a major role in self-bonding. Properties of composites prepared from the fine fraction of cotton stalks were superior to those prepared from the cotton stalk coarse fraction at the same conditions. This is attributed—among other things—to the dominance of pith (parenchymal cells) in the fine fraction. Such cells possess a high lumen-to-cell wall ratio, which renders them more deformable under pressure, leading to more intercellular or interparticle bonding. Advanced binderless green nanocomposites having bending strength as high as 637 kg/cm² and water absorption as low as 12.1 % were obtained from the ground undebarked cotton stalks. The results show clearly that the advanced green nanocomposite obtained by the dry forming process, without the addition of any binders, is superior to hardboard obtained from cotton stalks by the conventional wet web formation process. The mechanism of self-bonding is discussed.