Vibrational assignment, structure and intramolecular hydrogen bond study of 3-amino-1-phenyl-2-buten-1-one

Fourier transform infrared and Fourier transform Raman spectra of 3-amino-1-phenyl-2-buten-1-one and its deuterated analogue were recorded in the regions 400-4,000 and 150-4,000 cm(-1), respectively. Furthermore, the molecular structure and vibrational frequencies of title compound were investigated by a series of density functional theoretical, DFT, and ab initio calculations at the post-Hartree-Fock (MP2) level. Although, the calculated frequencies are generally in agreement with the observed spectra but the DFT results are in much better quantitative agreement with the observed spectra than the MP2 results. The observed wavenumbers were analyzed and assigned to different normal modes of vibration of the molecule. The calculated geometrical parameters show a strong intramolecular hydrogen bond with a N...O distance of 2.621-2.668 A. This bond length is shorter than that of its parent, 4-amino-3-penten-2-one (with two methyl groups in the beta-position), which is in agreement with spectroscopic results. The topological properties of the electron density contributions for intramolecular hydrogen bond in 3-amino-1-phenyl-2-buten-1-one and 4-amino-3-penten-2-one have been analyzed in term of the Bader theory of atoms in molecules (AIM). These results also support the stronger hydrogen bond in the title compound with respect to the parent molecule.     

Superhydrophobic and icephobic surfaces prepared by RF-sputtered polytetrafluoroethylene coatings

A superhydrophobic and icephobic surface were investigated on aluminum alloy substrate. Anodizing was used first to create a micro-nanostructured aluminum oxide underlayer on the alloy substrate. In a second step, the rough surface was coated with RF-sputtered polytetrafluoroethylene (PTFE or Teflon^®). Scanning electron microscopy images showed a “bird's nest”-like structure on the anodized surface. The RF-sputtered PTFE coating exhibited a high static contact angle of ∼165° with a very low contact angle hysteresis of ∼3°. X-ray photoelectron spectroscopy (XPS) results showed high quantities of CF₃ and CF₂ groups, which are responsible for the hydrophobic behavior of the coatings. The performance of this superhydrophobic film was studied under atmospheric icing conditions. These results showed that on superhydrophobic surfaces ice-adhesion strength was 3.5 times lower than on the polished aluminum substrate.     

Equimatchable claw-free graphs

A graph is equimatchable if all of its maximal matchings have the same size. A graph is claw-free if it does not have a claw as an induced subgraph. In this paper, we provide the first characterization of claw-free equimatchable graphs by identifying the equimatchable claw-free graph families. This characterization implies an efficient recognition algorithm.     

Positive semidefinite indicator property for norm-numerical range

In this paper, using an elementary method, we prove that if norm-numerical range related to an absolute norm \(\Vert .\Vert \) on \(\mathbb {C}^n\) satisfies the positive semidefinite indicator property, then \(\Vert .\Vert \) will be a multiple of Euclidian norm.     

Shape-Constrained Estimation Using Nonnegative Splines

We consider the problem of nonparametric estimation of unknown smooth functions in the presence of restrictions on the shape of the estimator and on its support using polynomial splines. We provide a general computational framework that treats these estimation problems in a unified manner, without the limitations of the existing methods. Applications of our approach include computing optimal spline estimators for regression, density estimation, and arrival rate estimation problems in the presence of various shape constraints. Our approach can also handle multiple simultaneous shape constraints. The approach is based on a characterization of nonnegative polynomials that leads to semidefinite programming (SDP) and second-order cone programming (SOCP) formulations of the problems. These formulations extend and generalize a number of previous approaches in the literature, including those with piecewise linear and B-spline estimators. We also consider a simpler approach in which nonnegative splines are approximated by splines whose pieces are polynomials with nonnegative coefficients in a nonnegative basis. A condition is presented to test whether a given nonnegative basis gives rise to a spline cone that is dense in the space of nonnegative continuous functions. The optimization models formulated in the article are solvable with minimal running time using off-the-shelf software. We provide numerical illustrations for density estimation and regression problems. These examples show that the proposed approach requires minimal computational time, and that the estimators obtained using our approach often match and frequently outperform kernel methods and spline smoothing without shape constraints. Supplementary materials for this article are provided online.     

Encapsulation of small fullerenes into nitrogenated holey nanotubes: a density functional theory study

Encapsulation of fullerene into nanotubes based on a C₂N sheet, known as nitrogenated holey graphene, was investigated using density functional theory. The structural and electronic properties of these carbon hybrid materials, consisting of nitrogenated holey nanotubes and a small C₂₀ fullerene, were studied. The formation energies showed that encapsulation of the fullerene into the nitrogenated holey nanotube is an exothermic process. To characterise the electronic properties, the electronic band structure and density of states of armchair and zigzag nitrogenated holey nanotubes were calculated. Filling these nanotubes with the C₂₀ fullerene resulted in a p-type semiconducting character. The energy band gap of the nitrogenated holey nanotubes decreased with fullerene encapsulation. The results are indicative of the possibility of band gap engineering by encapsulation of small fullerenes into nitrogenated holey nanotubes.     

Structural Snapshots of Cluster Growth from {U6} to {U38} During the Hydrolysis of UCl4

Herein we report the assembly of large uranium(IV) clusters with novel nuclearities and/or shapes from the controlled hydrolysis of UCl₄ in organic solution and in the presence of the benzoate ligands. {U₆}, {U₁₃}, {U₁₆}, {U₂₄}, {U₃₈} oxo and oxo/hydroxo clusters were isolated and crystallographically characterized. These structural snapshots indicate that larger clusters are slowly built from the condensation of octahedral {U₆} building blocks. The uranium/benzoate ligand ratio, the reaction temperature and the presence of base play an important role in determining the structure of the final assembly. Moreover, the isolation of different size cluster {U₆} (few hours), {U₁₆} (3 days), {U₂₄} (21 days) from the same solution in a chosen set of conditions shows that the assembly of uranium oxo clusters in hydrolytic conditions is time dependent.     

Numerical analysis of the internal flow and the mixing chamber length effects on the liquid film thickness exiting from the effervescent atomizer

Journal of Thermal Analysis and Calorimetry - Two-phase flow was simulated within the effervescent atomizer by the volume of fluid interface tracing model. Different gas-to-liquid mass ratios...     

Fabrication of PECVD-grown fluorinated hydrocarbon nanoparticles and circular nanoring arrays using nanosphere lithography

Nanosphere lithography (NSL) masks were created by spin-coating of polystyrene particles onto silicon surfaces. Fluorinated hydrocarbon films were coated on the nanosphere lithography masks using plasma-enhanced chemical vapor deposition (PECVD) to obtain ordered arrays of fluorinated hydrocarbon. Atomic force microscope images show hexagonally ordered nanodots of dimension 225 ± 11 nm with a height of 23 ± 4 nm. Every hexagon encloses a circular ring of diameter 540 ± 24 nm having a height and width of 13.5 ± 0.6 nm and 203 ± 16 nm, respectively. FTIR analysis shows two distinct zones of atomic bonding of CH_x and CF_x in the plasma coated ordered fluorinated hydrocarbon films.