Dynamic stability of functionally graded cantilever cylindrical shells under distributed axial follower forces

In this paper, flutter of functionally graded material (FGM) cylindrical shells under distributed axial follower forces is addressed. The first-order shear deformation theory is used to model the shell, and the material properties are assumed to be graded in the thickness direction according to a power law distribution using the properties of two base material phases. The solution is obtained by using the extended Galerkin's method, which accounts for the natural boundary conditions that are not satisfied by the assumed displacement functions. The effect of changing the concentrated (Beck's) follower force into the uniform (Leipholz's) and linear (Hauger's) distributed follower loads on the critical circumferential mode number and the minimum flutter load is investigated. As expected, the flutter load increases as the follower force changes from the so-called Beck's load into the so-called Leipholz's and Hauger's loadings. The increased flutter load was calculated for homogeneous shell with different mechanical properties, and it was found that the difference in elasticity moduli bears the most significant effect on the flutter load increase in short, thick shells. Also, for an FGM shell, the increase in the flutter load was calculated directly, and it was found that it can be derived from the simple power law when the corresponding increase for the two base phases are known.     

A computational study of 1:1 and 1:2 complexes of nitryl halides (O2NX) with HCN and HNC

Quantum calculations at the MP2/cc-pVTZ have been used to examine 1:1 and 1:2 complexes between O₂NX (X = Cl, Br) with HCN and HNC moieties. The interaction of the lone pair of the HCN(HNC) with the σ-hole and π-hole of O₂NX molecules and hydrogen bonding between lone pairs of X and O of O₂NX with H of HCN and HNC have been considered in 1:1 complexes. The 1:1 complexes can easily be differentiated using the stretching frequency of the N–X bond. Thus, those complexes with σ-hole and H···O₂NX interactions show a blue shift of the N-X bond stretching while a red shift is observed in the complexes along the π-hole and H···XNO₂ interactions. In the 1:2 complexes, the cooperative and diminutive energetic effects have been analyzed using the many-body interaction energies. The nature of the interactions has been characterized with the Atoms in Molecules (AIM) and Natural Bond Orbital (NBO) methodologies. Stabilization energies of 1:1 and 1:2 complexes including the variation of the zero-point vibrational energy (ΔZPVE) are in the range 3–9 kJ mol^?1 and 21–40 kJ mol^?1, respectively.     

Synthesis of Novel 1‐(Benzo[d]thiazol‐2‐yl)‐1H‐pyrrol‐2(5H)‐ones

The titled products comprising of two mutually merged bioactive nucleuses, 2‐aminobenzo[d]thiazole and 2,5‐dihydropyrrole rings, were obtained from the reaction between dialkyl acetylenedicarboxylates and alkyl 2‐(benzo[d]thiazol‐2‐yl)amino‐2‐oxoacetates in the presence of triphenylphosphine at RT.     

Radical of filters in BL‐algebras

In this paper, the notion of the radical of a filter in BL‐algebras is defined and several characterizations of the radical of a filter are given. Also we prove that A/F is an MV‐algebra if and only if D_s(A) ? F. After that we define the notion of semi maximal filter in BL‐algebras and we state and prove some theorems which determine the relationship between this notion and the other types of filters of a BL‐algebra. Moreover, we prove that A/F is a semi simple BL‐algebra if and only if F is a semi maximal filter of A. © 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim     

The electrospun poly(ε‐caprolactone)/fluoridated hydroxyapatite nanocomposite for bone tissue engineering

Biodegradable cell‐incorporated scaffolds can guide the regeneration process of bone defects such as physiological resorption, tooth loss, and trauma which medically, socially, and economically hurt patients. Here, 0, 5, 10, and 15 wt% fluoridated hydroxyapatite (FHA) nanoparticles containing 25 wt% F^? and 75 wt% OH^? were incorporated into poly(ε‐caprolactone) (PCL) matrix to produce PCL/FHA nanocomposite scaffolds using electrospinning method. Then, scanning electron microscopy (SEM), X‐ray diffraction (XRD) pattern, and Fourier transform infrared spectroscopy (FTIR) were used to evaluate the morphology, phase structure, and functional groups of prepared electrospun scaffolds, respectively. Furthermore, the tensile strength and elastic modulus of electrospun scaffolds were investigated using the tensile test. Moreover, the biodegradation behavior of electrospun PCL/FHA scaffolds was studied by the evaluation of weight loss of mats and the alternation of pH in phosphate buffer saline (PBS) up to 30 days of incubation. Then, the biocompatibility of prepared mats was investigated by culturing MG‐63 osteoblast cell line and performing MTT assay. In addition, the adhesion of osteoblast cells on prepared electrospun scaffolds was studied using their SEM images. Results revealed that the fiber diameter of prepared electrospun PCL/FHA scaffolds alters between 700 and 900 nm. The mechanical assay illustrated the mat with 10 wt% FHA nanoparticles revealed the highest tensile strength and elastic modulus. The weight loss alternation of mats determined around 1% to 8% after 30 days of incubation. The biocompatibility and cell adhesion of mats improved by increasing the amounts of FHA nanoparticles.     

Analyzing solubility of acid gas and light alkanes in triethylene glycol

Physical solvents such as ethylene glycol （EG）, diethylene glycol （DEG）, and triethylene glycol （TEG） are commonly used in wet gas dehydration processes with TEG being the most popular due to ease of regeneration and low solvent losses. Unfortunately, TEG absorbs significantly more hydrocarbons and acid gases than EG or DEG. Quantifying this amount of absorption is therefore critical in order to minimize hydrocarbon losses or to optimize hydrocarbon recovery depending on the objective of the process. In this article, a new correlation that fully covers the operating ranges of TEG dehydration units is developed in order to determine the solubility of light alkanes and acid gases in TEG solvent. The influence of several parameters on hydrocarbon and acid gas solubility including temperature, pressure, and solvent content is also examined.     

Adsorption of hydrogen and methane on intrinsic and alkali metal cations-doped Zn<Subscript>2</Subscript>(NDC)<Subscript>2</Subscript>(diPyTz) metal–organic framework using GCMC simulations

In this study, the adsorption of hydrogen and methane on the Zn₂(NDC)₂(diPyTz) [(NDC = 2,6-naphthalenedicarboxylate, diPyTz = di-3,6-(4-pyridyl)-1,2,4,5-tetrazine)] metal–organic framework (MOF) and the effect of its doping with alkali metal cations (Li⁺, Na⁺, K⁺) were investigated using Grand Canonical Monte Carlo simulations. The results indicated that the triply catenating Zn₂(NDC)₂(diPyTz), possessing small pores preferentially adsorbed hydrogen. Doping of Zn₂(NDC)₂(diPyTz) with alkali metal cations enhanced the hydrogen adsorption on the MOF. However, this enhancement became weaker as the atomic number of metal cation increased. The simulation results showed that the hydrogen adsorption on the Li⁺-doped Zn₂(NDC)₂(diPyTz) was almost 2.35 times greater than that of the corresponding undoped MOF at low pressure and room temperature. This suggests that the doping of MOFs with alkali metal cations especially lithium is a desired strategy for hydrogen storage. Furthermore, the results revealed that the adsorption of hydrogen on the Zn₂(NDC)₂(diPyTz) was higher than that of methane at room temperature.     

Analysis of a series of chlorogenic acid isomers using differential ion mobility and tandem mass spectrometry

Chlorogenic acids are among the most abundant phenolics found in the human diet. Of these, the mono-caffeoylquinic acids are the predominant phenolics found in fruits, such as apples and pears, and products derived from them. In this research, a comprehensive study of the electrospray ionization (ESI) tandem mass spectrometric (MS/MS) dissociation behavior of the three most common mono-caffeoylquinic acids, namely 5-O-caffeoylquinic acid (5-CQA), 3-O-caffeoylquinic acid (3-CQA) and 4-O-caffeoylquinic acid (4-CQA), were determined using both positive and negative ionization. All proposed structures of the observed product ions were confirmed with second-generation MS³ experiments. Similarities and differences between the dissociation pathways in the positive and negative ion modes are discussed, confirming the proposed structures and the established MS/MS fingerprints. MS/MS dissociation was primarily driven via the cleavage of the ester bond linking the quinic acid moiety to the caffeic acid moiety within tested molecules. Despite being structural isomers with the same m/z values and dissociation behaviors, the MS/MS data in the negative ion mode was able to differentiate the three isomers based on ion intensity for the major product ions, observed at m/z 191, 179 and 173. This differentiation was consistent among various MS instruments. In addition, ESI coupled with high-field asymmetric waveform ion mobility spectrometry-mass spectrometry (ESI-FAIMS-MS) was employed for the separation of these compounds for the first time. By combining MS/MS data and differential ion mobility, a method for the separation and identification of mono-caffeoylquinic in apple/pear juice samples was developed with a run time of less than 1 min. It is envisaged that this methodology could be used to identify pure juices based on their chlorogenic acid profile (i.e., metabolomics), and could also be used to detect juice-to-juice adulteration (e.g., apple juice addition to pear juice).     

Practical and theoretical study on the α-substituent effect on α-diimine Nickel(II) and Cobalt(II)-based catalysts for polymerization of ethylene

The Late transition metal catalysts based on Ni(II) and Co(II) were synthesized and their structure and activity in polymerization of ethylene were compared. Methylaluminoxane (MAO) was used as a co-catalyst. To discover the optimum polymerization conditions, the effect of polymerization temperature, monomer pressure, [Al]: [Ni] molar ratio and time of polymerization were studied. Activity of the catalysts was promoted by increasing of the monomer pressure. The viscosity average molecular weights M_v of the synthesized polymers using 1,2-bis(2,4,6-trimethyl phenyl imino) acenaphthene Nickel(II) dibromide were increased with increasing of the monomer pressure from 1 up to 6 bar which studied. Explicitly, the ortho-substituent has a significant effect on the catalyst behavior. Melting point and crystallinity of the obtained polyethylene using 1,2-bis(2,4,6-trimethyl phenyl imino) acenaphthene Nickel(II) dibromide catalyst were increased with enhancing monomer pressure. The optimum and stable structures were computed and some factors related to the activity were studied. Catalyst 1,2-bis(2,4,6-trimethyl phenyl imino) acenaphthene Nickel(II) dibromide had the highest activity with the highest quantities of dipole moment (18.29 Debye), charge of Mullikan on metal atom (1.48) and Sum of electronic and thermal Energies (–7906.52 e.u.).     

Electromembrane extraction of tartrazine from food samples: Effects of nano‐sorbents on membrane performance

In the present study, for the first time electromembrane extraction followed by high‐performance liquid chromatography coupled with ultraviolet detection was developed and validated for the determination of tartrazine in some food samples. The parameters influencing electromembrane extraction were evaluated and optimized. The membrane consists of 1‐octanol immobilized in the pores of a hollow fiber. As a driving force, a 30 V electrical field was applied to make the analyte migrate from sample solution with pH 3, through the supported liquid membrane into an acceptor solution with pH 10. Best preconcentration (enrichment factor >21) was obtained in extraction duration of 15 min. Effects of some solid nano‐sorbents like carbon nanotubes and molecularly imprinted polymers on membrane performance and electromembrane extraction efficiency were evaluated. The method provided the linearity in the range 25–1000 ng/mL for tartrazine (R² > 0.9996) with repeatability range (RSD) between 3.8 and 8.5% (n = 3). The limits of detection and quantitation were 7.5 and 25 ng/mL, respectively. Finally, the method was applied to the determination and quantification of tartrazine from some food samples with relative recoveries in the range between 90 and 98%.