Solid-state 13C NMR investigations of cyclophanes: [2.2]paracyclophane and 1,8-dioxa[8](2,7)pyrenophane

Solid-state NMR (ssNMR) and ab initio quantum mechanical calculations are used in order to understand and to better characterize the molecular conformation and properties of [2.2]paracyclophane and 1,8-dioxa[8](2,7)pyrenophane. Both molecules are cyclophanes, consisting of an aromatic ring assembly and a cyclic aliphatic chain connected to both ends of the aromatic portion. The aliphatic chain causes curvature in the six-membered aromatic ring structures. This led us to examine how the ring strain due to curvature affects the chemical shifts. Using X-ray structures of both [2.2]paracyclophane and 1,8-dioxa[8](2,7)pyrenophane as our starting model, we calculate the chemical shielding tensors and compare these data with those collected from the (13)C ssNMR FIREMAT experiment. We define curvature of [2.2]paracyclophane and 1,8-dioxa[8](2,7)pyrenophane using the π-orbital axis vector (POAV) pyramidalization angle (θ(p)).     

Intermolecular gold-catalyzed diastereo- and enantioselective [2+2+3] cycloadditions of 1,6-enynes with nitrones

Going for gold: The title reaction has been developed and demonstrates a wide substrate scope with respect to the 1,6-enynes and nitrones (see scheme; DCE = 1,2-dichloroethane, Tf = trifluoromethanesulfonyl). The results for the enantioselective versions are also presented.     

Regulation of Enzymatic Activity by Deamidation and Their Subsequent Repair by Protein l-isoaspartyl Methyl Transferase

The present study explored both spontaneous and stress-induced deamidation in acid trehalase and endo-xylanase. An alteration in optimum pH by 1.5 units and optimum temperature by 20 °C accelerated the process of deamidation with a rise in isoaspartate formation and ammonia loss. Spontaneous deamidation during an enzyme-substrate reaction at physiological conditions resulted in accretion of isoaspartyl residues within the enzymes which gradually impaired their catalytic efficacy. Deamidation appeared to be more pronounced in endo-xylanase owing to its secondary structure conformation and high asparagine content. The active sites, Ala 549 in acid trehalase and His184 and Trp188 in endo-xylanase contributed to the loss of enzyme activity as they were flanking the deamidation-susceptible Asn residues. Protein l-isoaspartyl methyl transferase seemed to have a repairing capability, which enabled the heat-damaged enzymes to regain their partial activity as evident from there rise in K _cat/K _m. Endo-xylanase could regain 38.1 % of its biological activity while a lesser 17.5 % reactivation was obtained in acid trehalase. A unique protein l-isoaspartyl methyl transferase recognition site, Asn 151 was also identified in acid trehalase. A mass increment of the tryptic peptides of repaired enzyme due to methylation catalyzed by protein l-isoaspartyl methyl transferase substantiated the repair hypothesis.     

o-Iodoxybenzoic acid mediated oxidative desulfurization initiated domino reactions for synthesis of azoles

A systematic exploration of thiophilic ability of o-iodoxybenzoic acid (IBX) for oxidative desulfurization to trigger domino reactions leading to new methodologies for synthesis of different azoles is described. A variety of highly substituted oxadiazoles, thiadiazoles, triazoles, and tetrazoles have been successfully synthesized in good to excellent yields, starting from readily accessible thiosemicarbazides, bis-diarylthiourea, 1,3-disubtituted thiourea, and thioamides.     

Noncommutative effects of charged black hole on holographic superconductors

In this paper, we analytically investigate the noncommutative effects of a charged black hole on holographic superconductors in the probe limit. The effects of charge of the black hole is investigated in our study. Employing the Sturm–Liouville eigenvalue method, the relation between the critical temperature and charge density is analytically investigated. The condensation operator is then computed. It is observed that condensate gets harder to form for large values of charge of the black hole.     

Effects of nondenumerable fixed points in finite dynamical systems

The motion of a spinning soccer ball brings forth the possible existence of a whole class of finite dynamical systems where there may be a nondenumerably infinite number of fixed points. They defy the very traditional meaning of the fixed point that a point on the fixed point in the phase space should remain there forever, for, a fixed point can evolve as well! Under such considerations one can argue that a free-kicked soccer ball should be nonchaotic.     

On the applicability of low-dimensional models for convective flow reversals at extreme Prandtl numbers

Constructing simpler models, either stochastic or deterministic, for exploring the phenomenon of flow reversals in fluid systems is in vogue across disciplines. Using direct numerical simulations and nonlinear time series analysis, we illustrate that the basic nature of flow reversals in convecting fluids can depend on the dimensionless parameters describing the system. Specifically, we find evidence of low-dimensional behavior in flow reversals occurring at zero Prandtl number, whereas we fail to find such signatures for reversals at infinite Prandtl number. Thus, even in a single system, as one varies the system parameters, one can encounter reversals that are fundamentally different in nature. Consequently, we conclude that a single general low-dimensional deterministic model cannot faithfully characterize flow reversals for every set of parameter values.     

A New Group Decision-Making Technique under Picture Fuzzy Soft Expert Information

As an extension of intuitionistic fuzzy sets, the theory of picture fuzzy sets not only deals with the degrees of rejection and acceptance but also considers the degree of refusal during a decision-making process; therefore, by incorporating this competency of picture fuzzy sets, the goal of this study is to propose a novel hybrid model called picture fuzzy soft expert sets by combining picture fuzzy sets with soft expert sets for dealing with uncertainties in different real-world group decision-making problems. The proposed hybrid model is a more generalized form of intuitionistic fuzzy soft expert sets. Some novel desirable properties of the proposed model, namely, subset, equality, complement, union and intersection, are investigated together with their corresponding examples. Two well-known operations AND and OR are also studied for the developed model. Further, a decision-making method supporting by an algorithmic format under the proposed approach is presented. Moreover, an illustrative application is provided for its better demonstration, which is subjected to the selection of a suitable company of virtual reality devices. Finally, a comparison of the initiated method is explored with some existing models, including intuitionistic fuzzy soft expert sets.     

Acoustic field and array response uncertainties in stratified ocean media

The change-of-variables theorem of probability theory is applied to compute acoustic field and array beam power probability density functions (pdfs) in uncertain ocean environments represented by stratified, attenuating ocean waveguide models. Computational studies for one and two-layer waveguides investigate the functional properties of the acoustic field and array beam power pdfs. For the studies, the acoustic parameter uncertainties are represented by parametric pdfs. The field and beam response pdfs are computed directly from the parameter pdfs using the normal-mode representation and the change-of-variables theorem. For two-dimensional acoustic parameter uncertainties of sound speed and attenuation, the field and beam power pdfs exhibit irregular functional behavior and singularities associated with stationary points of the mapping, defined by acoustic propagation, from the parameter space to the field or beam power space. Implications for the assessment of orthogonal polynomial expansion and other methods for computing acoustic field pdfs are discussed.     

Substitutional effect of Cr ions on the properties of Mg–Zn ferrite nanoparticles

The effect of Cr³⁺ substitution in Mg–Zn ferrite, with a chemical formula Mg_0.5Zn_0.5Cr_xFe_2−xO₄ (x=0.0–1.0), synthesized by a sol–gel auto-combustion reaction is presented in this paper. The resultant powders were investigated by various techniques, including X-ray diffractometry (XRD), transmission electron microscopy (TEM), infrared spectroscopy (IR), vibrating sample magnetometry (VSM), and DC resistivity. The XRD pattern revealed that the cubic spinel structure is maintained for the all the compositions. The particle sizes measured from XRD and TEM are in good agreement with each other. The cation distribution suggests that Mg²⁺, Cr³⁺ and Fe³⁺ have strong preference towards octahedral B-site. The theoretical lattice constant and experimental lattice constant match each other very well. The IR analysis supports the presently accepted cation distribution. The saturation magnetization decreases linearly with increasing Cr³⁺ content. Curie temperatures are obtained by the Laoria and AC susceptibility techniques. The dc resistivity has been investigated as a function of temperature and composition.