Search

Metal organic frameworks (MOFs) with marvelous properties have aroused enormous attention for different application especially gas adsorption and separation. In this regard, fabrication of MOF hybrids with carbon based materials is new strategy to upgrade MOF performance. In this study CuBTC (Copper benzene-1,3,5-tricarboxylic acid)/graphene oxide (GO) composite was synthesized and characterized by BET, SEM, TGA, XRD and FT-IR techniques. Then CuBTC and CuBTC/GO composite were incorporated into polysulfone (PSF) polymer to construct mixed matrix membranes (MMMs). The obtained membranes were characterized by SEM, TGA, XRD and tensile tests and their gas permeability was measured. The results were compared to those of CuBTC/PSF MMMs. It was revealed that CuBTC/GO composite as filler showed superior performance relative to CuBTC. For instance, 15 wt% loading of CuBTC/GO in PSF represented outstanding gas separation behavior while the same loading of CuBTC in PSF deteriorated performance of MMM. Well particle dispersion and favorable polymer-filler interaction were responsible for such observed difference. A high H2/CH4 and H2/N2 selectivity of 80.03 and 70.46 were recorded for CuBTC/GO in PSF (15 wt%) compared to 44.56 and 40.92 for CuBTC in PSF (15 wt%).

This research is focused on the development of a new starch-based nanocomposite films reinforced with cellulose nanofibrils (CNFs) for food packaging purposes. A series of starch films were produced by the solution casting method with various concentrations of glycerin, CNF, and citric acid (CA). Mechanical properties of the films were investigated using tensile tests. Based on the results, the best formulation with optimal mechanical properties was introduced by different amounts of various gums to study the effects of the gums on tensile properties of the samples. Fourier-transform infrared analysis was performed to study posttreatment chemical structure of the sample to confirm the cross-linking and esterifying of the nanocomposite films. Results revealed that the tragacanth gum had a negative impact on the mechanical properties, while the frankincense gum (F-gum) and Arabic gum positively influenced the mechanical properties through strengthening the network structure. The sample containing 0.3 g of F-gum (10% w/w, relative to the starch weight) showed the best results compared to the control films.

In this investigation we set out to understand the origins of non-nuclear attractors (NNAs) found for neutral lithium clusters Lim (m = 2-5) on the QTAIM molecular graph but not on the Ehrenfest force F(r) molecular graph. Therefore, we pursued the stress tensor σ(r) without using the dependency on the QTAIM partitioning, since previously σ(r) was only calculated within the QTAIM partitioning, to see if any indication of NNA character can be determined. Because the stress tensor σ(r) lacks an associated scalar- or vector-field as is the case for QTAIM and the Ehrenfest F(r) partitioning schemes respectively, a stress tensor σ(r) partitioning scheme cannot be constructed. Therefore, to overcome this difficulty we use next generation QTAIM, constructed from the most preferred directions of electronic charge density accumulation, to calculate the stress tensor σ(r) 3-D bond-paths on the Ehrenfest force F(r) molecular graph. Using next generation 3-D bond-paths within the Ehrenfest force F(r) partitioning, we can classify the degree of NNA character in the absence of NNAs. A much higher degree of NNA character is found to be present for the stress tensor σ(r) 3-D bond-paths than for the corresponding QTAIM or Ehrenfest force F(r) 3-D bond-paths. The stabilizing effect of the NNA is demonstrated by undertaking Li2 bond-path compression and stretching distortions sufficient to cause the annihilation of the NNA. The compression and stretching distortions also lead to a large increase in the 3-D bond-path asymmetry and persistent bond-path torsion respectively.

National Key Research and DevelopmentProgram of China, Grant/Award Number:2019YFC1907805 The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link. This study aims to investigate the phenomenon of torquoselectivity through four thermal cyclobutenes ring-opening reactions including 1-chlorocyclobut-1-ene (Reaction 1), 3-chloro-4-methylcyclobut-1-ene (Reaction 2), 3-methoxy-4-methylcyclobut-1-ene (Reaction 3), and finally 3-chloro-4-methoxycyclobut-1-ene (Reaction 4). Despite the limitation of conventional methods in which just considers activation energies within transition state theory, this research focuses on the nature of the chemical bond, electronic reorganization, and predicting either non-competitive or competitive reactions within quantum theory of atoms in molecules (QTAIM) and stress tensor frameworks. Various theoretical analyses for these reactions such as metallicity ξ(rb), ellipticity ε, total local energy density H(rb), stress tensor polarizability ℙσ, stress tensor eigenvalue λ3σ, bond-path length, and path lengths H display differently for non-competitive and competitive reactions as well as for the conrotatory preferences either it is the transition state outward conrotatory (TSOC) or transition state inward conrotatory (TSIC) directions by presenting degeneracy or non-degeneracy in their results. Results illustrate that the preference of TSOC or TSIC of these thermal ring-opening reactions could obtain from path lengths H of the ring-opening bonds, where the longer one apparently predicts the preference. In addition, examinations indicate that Reaction 1 is competitive and Reactions (2–4) are non-competitive reactions with TSOC, TSOC, and TSIC preference directions respectively. The concordant results of stress tensor and QTAIM scalar and vectors with experimental results provide a better understanding of all reactions mechanism.

In this investigation, we considered both the scalar and 3-D vector-based measures of bonding using next generation quantum theory of atoms in molecules (QTAIM), constructed from the preferred direction of electronic charge density accumulation, to better understand the photochemical reaction associated with of the formation of benzvalene from benzene. The formation of benzvalene from benzene resulted in two additional C-C bonds forming compared with the benzene. The creation of the additional C-C bonds was explained in terms of an increasing the favorability of the reaction process by maximizing the bonding density. The topological instability of the benzvalene structure was determined using the scalar and vector-based measures to explain the short chemical half-life of benzvalene in terms of the competition between the formation of unstable new C-C bonding that also destabilizes nearest neighbor C-C bonds. The explosive character of benzvalene is indicated by the unusual tendency of the C-C bonds to rupture as easily as weak bonding. The topological instability of the short strong C-C bonds was explained by the existence of measures from conventional and next generation QTAIM that previously have only been observed in weak interactions; such measures included twisted 3-D bonding descriptors.

Condensation is an important regime of heat transfer which has wide applications in different industries such as power plants, heating, ventilating and air conditioning, and refrigeration. Condensation occurs in two different modes including filmwise (FWC) and dropwise (DWC) condensation. DWC occurring on hydrophobic and superhydrophobic surfaces has a much higher heat transfer capacity than FWC. Therefore, wide investigations have been done to produce DWC in recent years. Superhydrophobic surfaces have micro/nano structures with low surface energy. In this study, a two-step electrodeposition process is used to produce micro/nano structures on copper specimens. The surface energy of specimens is reduced by a self-assembled monolayer using ethanol and 1-octadecanethiol solution. The results show that there is an optimum condition for electrodeposition parameters. For example, a surface prepared by 2000 s step time has 5 times greater heat transfer than FWC while a surface with 4000 s step time has nearly the same heat transfer as FWC. The surfaces of the fabricated specimens are examined using XRD and SEM analyses. The SEM analyses of the surfaces show that there are some micro-structures on the surfaces and the surface porosities are reduced by increasing the second step electrodeposition time.

We seek to explain why the hydrogen bond possesses unusual strength in small water clusters that account for many of the complex behaviors of water. We have investigated and visualized the donation of covalent character from covalent (sigma) to hydrogen-bonds, by calculating the eigenvector coupling properties of QTAIM, stress tensor σ(r) and Ehrenfest Force F(r) on the F(r) molecular graph. The next generation 3-D bond-path framework sets are presented and only the F(r) bond-path framework sets reproduce the earlier finding on the coupling between covalent (sigma) and hydrogen-bonds that possess a degree of covalent character. The directional character of the covalent (sigma) and hydrogen-bonds 3-D bond-path framework sets for the F(r) explains differences found in the earlier results from QTAIM and the stress tensor σ(r).

In this paper the microstructure of different polyethylenes was characterized via FTIR spectroscopy. Two commercial low density polyethylenes (PE) (L1 and L2) and one commercial high density polyethylene were characterized. For comparison, one branched metallocene-PE and one linear metallocene-PE were also used. Test specimens were prepared in the form of film through hot compression molding of the polymers. Based on the FTIR spectra the exact position of the methyl deformation band for L1 and L2, was located at 1379.1 cm−1, which has a position between the ethyl branch (1379.1 cm−1) and the butyl (1377.8 cm−1) and for mLCB-PE, the absorbance band is at 1377.5, which indicates that most of its branches are of the hexyl type. Absorbance bands in the 790–700 cm−1 region correspond to the branches of ethyl, butyl and hexyl or longer groups, indicating the presence of ethyl branches in LDPE samples, butyl but not any ethyl branch in mLCB-PE, and no ethyl and butyl branches in the HDPE. According to the absorption bands of 888 and 910 cm−1 unsaturated species in the microstructure of polyethylene samples, mainly vinylidene and vinyl end groups, were investigated.

This study aims to promote the epoxy systems' mechanical attributes (especially toughness) using surface-treated graphene oxide nanosheets. To this end, the graphene oxide nanoplatelets were synthesized and then surface-modified. 3-amino propyl triethoxy silane (APTES) and hyperbranched polyester amide (HBP) were employed via a serial approach. The results of different characterizing techniques (FTIR, TGA, XRD, Raman, and FE-SEM) approved the leading role of dual modification in expanding the inter-layer distance of nanoplatelets and significantly improving the filler dispersion within organic media. All unmodified and variously modified nanosheets were introduced into the epoxy at three loading levels (0.25, 0.5, and 1 wt%). While almost all modified nanoparticles could considerably enhance the hardness and toughness, the highest enhancement (2.6 times in toughness and 2.28 times in micro-hardness) was achieved with 1 wt% graphene oxide sequentially treated with APTES and HBP. Simultaneous promotion of hardness and toughness, which usually have an inverse relationship, was a highly desirable achievement. Our structural studies, utilizing the DMTA technique, revealed that such promotion was indebted to the simultaneous reinforcement in the physical (uniform filler distribution) and chemical (increased crosslinking density without any Tg elevation) aspects of the resultant network.

In this investigation we explore the function and existence of the non-nuclear attractor (NNA) for a series of small charged lithium clusters Limq (m = 2-5, q = ±1) using QTAIM and the Ehrenfest force F(r) partitioning schemes. The NNAs were found to be present in all of the Limq (m = 2-5, q = ±1) clusters for QTAIM, in contrast none were found for F(r). We discovered that the anionic and cationic lithium dimers are limiting cases for minimal and maximal impact of the NNA related to the relative sparseness of total charge density ρ(r) distributions respectively. Evidence is found that the NNA in the anionic dimer is in the process of being annihilated by two neighboring BCPs. We provide a measure of the size of the NNA and find for Limq (m = 2-5, q = ±1) that larger NNAs correlate with increased Li-Li separations. The NNA was determined to be a persistent feature by varying the Li separations for the cationic and anionic dimers. Very large Li separations failed to induce an NNA in the F(r) anionic dimer and therefore we conclude that F(r) is unable to detect NNAs. The metallicity ξ(rb) was also used to measure the sparseness of the distribution of ρ(r) and significant metallic character, on the basis of ξ(rb) > 1, was present for QTAIM but not for F(r), providing further evidence that F(r) cannot detect NNAs. Advantages of the use of Ehrenfest force F(r) partitioning scheme are discussed that include the design of nano-devices through tuning of the Ehrenfest potential VF(b) by the application of external forces such as a constant electric or strain field.

The file attached to this record is the Publisher's final version. This study aims to investigate the phenomenon of torquoselectivity through three thermal cyclobutene ring-opening reactions (N1–N3). This research focuses on the nature of the chemical bond, electronic reorganization, predicting non-competitive or competitive reactions, and torquoselectivity preference within Quantum Theory of Atoms in Molecules (QTAIM) and stress tensor frameworks. Various theoretical analyses for these reactions, such as metallicity ξ(rb), ellipticity ε, total local energy density H(rb), stress tensor polarizability Pσ , stress tensor eigenvalue λ3σ , and bond-path length, display differently for non-competitive and competitive reactions as well as for the conrotatory preferences either it is the transition state outward conrotatory (TSout) or transition state inward conrotatory (TSin) directions by presenting degeneracy or non-degeneracy in their results. The ellipticity profile provides the motion of the bond critical point locations due to the different substituents of cyclobutene. In agreement with experimental results, examinations demonstrated that N1 is a competitive reaction and N2–N3 are non-competitive reactions with TSout and TSin preference directions, respectively. The concordant results of QTAIM and stress tensor scalar and vectors with experimental results provide a better understanding of reaction mechanisms

A QTAIM investigation of the [Sb 3 Au 3 Sb 3 ] 3− sandwich complex is consistent with a previous investigation and reveals all of the bond critical points ( BCP s) to be closed-shell BCP s with a degree of covalent character. All of the Sb--Au BCP s and Sb--Sb BCP s are found to possess metallicity. From the stress tensor analysis a topological instability in the Sb--Au BCP s and Sb--Sb BCP s is revealed highlighting the need for an improved charge density. The topological instability is removed by using the SR-ZORA method to describe relativistic effects.

A QTAIM investigation of the torsion in both the clockwise and counter-clockwise directions about the π bonds of the retinal protonated Schiff base chromophore in the lowest electronically excited state provided a detailed description of the changing bonding topology that was sensitive to both the torsion and the direction of torsion. Analysis of the separate torsion calculations demonstrated a clear order of preferred bonding torsion in terms of principles of maximizing bonding. Unusual behavior of the bond ellipticity in the S 1 state was found for the two less favorable bonds for torsion and explained in terms of the presence of weak bonding interactions.

A quantum theory of atoms in molecules (QTAIM) and stress tensor analysis was applied to analyze intramolecular interactions influencing the photoisomerization dynamics of a light-driven rotary molecular motor. For selected nonadiabatic molecular dynamics trajectories characterized by markedly different S1 state lifetimes, the electron densities were obtained using the ensemble density functional theory method. The analysis revealed that torsional motion of the molecular motor blades from the Franck–Condon point to the S1 energy minimum and the S1/S0 conical intersection is controlled by two factors: greater numbers of intramolecular bonds before the hop-time and unusually strongly coupled bonds between the atoms of the rotor and the stator blades. This results in the effective stalling of the progress along the torsional path for an extended period of time. This finding suggests a possibility of chemical tuning of the speed of photoisomerization of molecular motors and related molecular switches by resha...

A QTAIM and Stress tensor eigenvector projection U σ space formalism has been used to provide a detailed description of the participation of each of the bonds of the four infrared active normal modes of benzene. Analysis of the maximum U σ space trajectory projections revealed a mixture of C C and C H bonding characteristics. The four infrared active U σ space trajectories were found to be unique. The normal mode with the highest infrared intensity was the only mode with non-zero maximum U σ space trajectory projections in the most preferred and least preferred directions for the C C and C H bond critical points respectively.

In the present study, ethylbenzene dehydrogenation to styrene monomer over a potassium-promoted iron oxide catalyst in radial fixed bed reactor was simulated. The pseudo-heterogeneous model was employed to predict ethylbenzene conversion and selectivity of styrene monomer, toluene, and benzene. The simulation results showed that deactivation of catalysts causes reduction in the reaction zone; therefore, the ethylbenzene conversion decreases. It is proposed that, for compensating the conversion reduction, the feed temperature is increased 1 °C per 5 cm of deactivated length. Simulation results are in good agreement with the experimental data obtained from real plant.

In Saccharomyces cerevisiae, los1 encodes a nuclear tRNA exporter. Despite the non-essentiality, the deletion of los1 has been shown to extend replicative life span in yeast. Here, we characterized AfuXpot, the los1 homologue in human pathogen Aspergillus fumigatus and found that it is continuously expressed during fungal growth. Microscopic examination of an AfuXpot-GFP-expressing transformant confirmed the nuclear localization of the fusion protein. The targeted gene deletion affirmed the non-essential role of AfuXpot in hyphal growth and sporulation. However, the growth of the deletion mutant was affected by amino acid, but not glucose, deprivation. The susceptibility of the deletant strain to protein and DNA/RNA synthesis inhibitors was also altered. Using bioinformatics tools, some transcription factor binding sites were predicted in AfuXpot promoter. Expression analyses of potential AfuXpot-interacting genes showed a marked down-regulation of sfp1 and mtr10 homologues in ΔAfuXpot strain. Our data demonstrates some conserved aspects of AfuXpot as a tRNA exporter in A. fumigatus.

Dropwise condensation (DWC) is one of the phase change heat transfer regimes, which due to its high capacity has received much attention from investigators. To produce DWC, it is necessary to have hydrophobic surfaces. Low surface energy coatings have been usually used to produce hydrophobic surfaces. These coatings due to their low thermal conductivities must have the minimum thickness. Therefore, self-assembled monolayers coatings like stearic acid or 1-octadecanethiol coatings (with thicknesses as high as a few nanometers) have been used in the literature. To create hydrophobic coatings by these materials, the surfaces are immersed in hydrophobic solutions with particular concentrations and in a specific time. There is not any general investigation on the effects of the time and concentration of these coatings on DWC in the literature. In this study, first, a proper apparatus for DWC experiments is designed and fabricated. Then, the effects of concentration and immersing time of the two mentioned materials on DWC phenomena have been studied. Between four coating times and solution concentrations of 1-octadecanethiol, concentration of 0.025 M at coating time of 30 min increases DWC heat transfer coefficient by about 4–7 times with respect to filmwise condensation in different subcooling temperatures. Concentration of 0.0025 M at coating time of 1 hour of stearic acid also increases the heat transfer coefficient by about 3–4 times. As well as the 1-octadecanethiol coating has a more uniform structure and higher heat transfer coefficient with respect to stearic acid coating.

Here we have determined the precessions K and K’ of the {p,p′} and {q,q′} path-packets for the excited state deactivation reaction of fulvene in terms of bond-flexing, bond-torsion and bond-anharmonicity that includes the tendencies towards bond-path-rigidity and bond-path-flexibility. An asymmetry is found for the S1 state resulting in an unpredictable variation in the direction of the bond-path-rigidity as a function of the torsion coordinate. Uniquely, the S1 state at torsion θ = 0.0° possesses the possible maximum bond-path-rigidity, along the entire bond-path but then drops lower than for the S0 state at the conical intersection indicating photo-excitation facilitates the torsion.

Graphene oxide (GO) nanoplatelets are synthesized via modified Hummer method. Then, GO is surface functionalized using (3-aminopropyl) triethoxysilane, i.e. APTES, to substitute its functionalities with primary amine groups. Chemical, structural and morphological analyses reveal that APTES molecules have successfully been grafted on the GO flakes, interlayer d -spacing in the stacks has increased, an intercalated/exfoliated morphology with smaller agglomerations has obtained and number of flakes in the stacks has been reduced. Subsequently, various concentrations, i.e. 0.25 %, 0.5 % and 1%, are impregnated into a low molecular weight Bisphenol-A liquid epoxy resin which is then cured by a polyamidoamine hardener. The effects of the nano fillers on mechanical characteristics of the cured epoxy films are investigated by universal tensile test, dynamic mechanical analysis and morphology assessment of the ruptured cross sectional area. The results show significant increases in elastic modulus (24 %), maximum stress (12 %), maximum strain (24 %) and work of fracture (69 %) for the nanocomposite containing 1 wt.% silane-modified GO compared to blank epoxy. DMA outcomes also show that highest Tg and maximized crosslinking density belongs to this sample. Fractured-surface morphology studies describe the mechanical properties enhancement. Such enhancement in mechanical properties empowers the prospective of this coating as a heavy-duty protective coating in various industries.

We present, for the first time, the S0 → S1 (S01) and S0 → S2 (S02) natural transition orbital (NTO) densities for fulvene, using the 3-D next generation QTAIM that can visualize and quantify the rearrangement of the charge density that occurs in response to the applied torsion and as a consequence of the preferred direction of electron density accumulation. A symmetrization of the position of the bond critical point (BCP) of the torsional C2-C6 BCP along the containing bond-path was determined to be characteristic of the presence of a conical intersection (CI) for the S0 → S1 (S01) transition.

Ternary blends of polypropylene/polycarbonate/poly(styrene-b-(ethylene-co-butylene)-b-styrene) (PP/PC/SEBS) with varying SEBS contents were produced via melt blending in a co-rotating twin-screw extruder. The phase morphology of the resulting ternary blends and its relationship with bending and impact behaviors were studied. Transmission optical microscopy (TOM) of the crack tip damage zone and scanning electron microscopy (SEM) of impact fractured surfaces were performed to characterize the fracture mechanism. With increasing SEBS content in the PP/PC/SEBS ternary blends, the number of PC/SEBS core-shell particles increased and the size of the core-shell particles enlarged. It was shown that with an SEBS content of 5%, the crack initiation resistance decreased and then was almost unchanged with further increase of SEBS content, while resistance to crack growth increased continuously with increasing of SEBS content. Preliminary analysis of the micromechanical deformation suggested that the high impact tou...

PP/PC, PP/SEBS binary blends and a PP/PC/SEBS ternary blend were produced via melt blending in a co-rotating twin-screw extruder. The phase morphology, bending and impact behaviors of the blends were studied. Transmission optical microscopy (TOM) of the crack tip damage zone, scanning electron microscopy (SEM) of impact fractured surfaces and transmission electron microscope (TEM) were performed to characterize the fracture mechanism. The core-shell particles in PP/PC/SEBS ternary blends do not have a significant influence on the crack initiation resistance but SEBS particles in PP/SEBS binary blend cause reduction of the crack initiation resistance and PC particles in PP/PC binary blend cause the greatest reduction of the crack initiation resistance. In PP and PP/PC binary blend samples no sign of plastic deformation was observed, while TOM micrographs in R30 and BR30 samples indicates that shear yielding mechanisms have also occurred around the crack tip and crack wake, also the fracture surfaces of R30...

The Ramachandran plot is a potent way to understand structures of biomolecules, however, the original formulation of the Ramachandran plot only considers backbone conformations. We formulate a new interpretation of the original Ramachandran plot ($\phi-\psi$) that can include a description of the weaker interactions including both the hydrogen bonds and H$---$H bonds as a new way to derive insights into the phenomenon of peptide folding. We use QTAIM (quantum theory of atoms in molecules) to interpret the Ramachandran plot. Specifically, we show that QTAIM analysis permits identifying key regions of the Ramachandran plot without the need for massive data sets. A highly non-linear relationship is found between the QTAIM vector-derived interpreted Ramachandran plot and the conventional Ramachandran plot ($\phi-\psi$) demonstrating that this new approach is not a trivial coordinate transformation. An investigation of both the backbone and the weaker bonds within the framework of the QTAIM interpreted Ramachandran plot was found to be in line with physical intuition. The least-preferred directions calculated for the hydrogen bonds and H$---$H bonds were found to coincide with the 'unlikely' regions of the Ramachandran plot., Comment: Submitted to IJQC

Tumor and especially breast cancer is among the most common causes of death worldwide. Finding novel nanosized therapeutic compounds have important role to decrease the chance of death and increase the survival. Cancer cells are highly attractive to glucose [with a nanosize bimolecular structure 1nm] as an energy source more than normal cell and nanosized therapeutics due to possessing different pharmacokinetic and pharmacodynamic have advantageous over classical dosage forms in cancer therapy. The aim of the study was to synthesize Glucosamin-Porphyrin-Tamoxifen [TPG] nanosized complex as a novel selective biocompatible anti breast cancer agent. After the synthesis procedure, this complex was purified and then tested In Vitro on breast cancer cells [MCF-7] in the absence or presence of the red light and found totally successful. The results showed a good anti breast cancer activity mediated by the activation of TNF-α and necrosis/apoptosis pathways for the nanosized complex with no alteration effects on blood PT/APTT and glucose or hexokinase levels/ activity. TPG nanoconjugate seems to be very good opponents to current anti breast cancer drugs and needs to be further investigated in near future.