A novel and efficient solvent-free and heterogeneous method for the synthesis of primary, secondary and bis-N-acylsulfonamides using metal hydrogen sulfate catalysts

Some metal hydrogen sulfates were used as acid catalysts in the N-acylation of different sulfonamides using carboxylic acid chlorides and anhydrides as acylating agents under both heterogeneous and solvent-free conditions. Al(HSO₄)₃ and Zr(HSO₄)₄ were found to have the highest activity and catalyze the reactions efficiently to furnish the primary N-acyl sulfonamides (RCONHSO₂R′), secondary N-acylsulfonamides (RCONR″SO₂R′) and bis-N-acylsulfonamnides [RCO(SO₂R′)N-R″-N(SO₂R′)COR] in good to high yield. The mild reaction conditions, inexpensive and low toxicity of catalysts and easy work-up procedure make this method attractive.     

Recombination System Based on Cre α Complementation and Leucine Zipper Fusions

A gene encoding β-1,3-1,4-glucanase was cloned by polymerase chain reaction (PCR) from Bacillus subtilis MA139. Sequencing result showed 97% homology to the corresponding gene from Bacillus licheniformis. The open reading frame (ORF) of the gene contained 690 bp coding for a 226 amino-acid matured protein with the estimated molecular weight of 24.44 kDa. The β-1,3-1,4-glucanase gene was subcloned into an expression vector of pET28a and expressed in Escherichia coli BL21 and then purified by metal affinity chromatography using a nickel–nitrilotriacetic acid (Ni–NTA) column. The purified β-1,3-1,4-glucanase demonstrated 24.05 and 12.52 U ml^-1 activities for the substrates of barley β-glucan and lichenan, respectively, and the specific activities were 728.79 and 379.1 U mg^-1 for them, respectively. The optimal temperature and pH of the purified enzyme were 40°C and 6.4, respectively. When barley β-glucan was used as the substrate, K _m was 5.34 mg ml^-1, and K _cat showed 7,206.71 S^-1, thus the ratio of K _cat and K _m was 1,349.67 ml s^-1 mg^-1. The activity of β-1,3-1,4-glucanase was affected by a range of metal ions or ethylenediaminetetraacetic acid (EDTA).     

Acetone Adsorption on Pristine and Pt-doped Graphene: A First-Principles vdW-DF Study

Using van der Waals corrected density functional theory (vdW-DF) method we have investigated the adsorption of acetone molecule on pristine and Pt-doped graphene. Several active sites for both the interacting systems have been considered in the adsorption process including full geometry optimization. We have analyzed the structural and electrical properties of energetically favorable configurations. The results show that adsorption of acetone molecule on the Pt-doped graphene is energetically preferable. The binding energy and bonding distance are determined to be -5.277 eV and 2.206 Å, respectively, accompanying with charge transfer of 1.11 e. Furthermore, the Pt-O bond is rather significantly elongated when acetone is adsorbed on Pt-doped graphene. Compared to pristine graphene, the Pt-doped graphene has stronger interaction with the acetone and may provide more sensitive signal for a single acetone molecule. Meanwhile, practically, the band gap of Pt-doped graphene would become reduced after acetone adsorption. Consequently, our first-principles study presents evidence for a coherent benchmark for the applicability of Pt-doped graphene for acetone adsorption and detection.     

Property preserving reformulation of constitutive laws for the conformation tensor

The challenge for computational rheologists is to develop efficient and stable numerical schemes in order to obtain accurate numerical solutions for the governing equations at values of practical interest of the Weissenberg number. This study presents a new approach to preserve the symmetric positive definiteness of the conformation tensor and to bound the magnitude of its eigenvalues. The idea behind this transformation lies with the matrix logarithm formulation. Under the logarithmic transformation, the eigenvalue spectrum of the new conformation tensor varies from infinite positive to infinite negative. However reconstructing the classical formulation from unbounded eigenvalues does not achieve meaningful results. This enhanced formulation, expressed in terms of the hyperbolic tangent, overcomes the failure of alternative formulations by bounding the magnitude of eigenvalues in a manner that positive definite is always satisfied. In order to evaluate the capability of the hyperbolic tangent formulation, we performed a numerical simulation of FENE-P fluid in a rectangular channel in the context of the finite element method. Under this new transformation, the maximum attainable Weissenberg number increases by 21.4% and 112.5% compared to the standard log-conformation and classical constitutive equation, respectively.     

Numerical Investigation of Drug Delivery to Cancerous Solid Tumors by Magnetic Nanoparticles Using External Magnet

Chemotherapy as one of the most utilized cancerous tumor treatment methods introduces undesired side effects due to penetrating toxic drugs into the healthy organs. Delivery of anticancer therapeutic agents to solid tumors is also problematic. The purpose of current study is to investigate the penetration of magnetic drug carriers (MDCs) within the cancerous solid tumor tissue under the influence of external magnet. Capillary wall and tumor tissue is modeled as a saturated porous media. In order to solve the coupled governing equations, mass, momentum and concentration, an in-house finite volume-based code is developed and utilized. Results show the penetration of MDCs into the tumor in the absence of magnetic field is minimal and is limited to the surface of the tumor. On the other hand, under the influence of external magnet the penetration of MDCs within the tumor increases exponentially. They also penetrate deep into the tumor and cover the entire tumor which increase the effectivity and decrease the side effect of the treatment.     

The impact of customer behavior models on revenue management systems

Computational Management Science - Revenue management (RM) can be considered an application of operations research in the transportation industry. For these service companies, it is a difficult...     

Gliclazide as novel carrier in construction of PVC-based La(III)-selective membrane sensor

A PVC-based sensor for La³⁺ ions based on N-[hexahydrocyclopentapyrol-2((1H)yl)amino]carbonyl]-4-methyl benzene sulfonamide (gliclazide) as a novel carrier was prepared. The electrode exhibits a Nernstian response for La³⁺ over a wide concentration range (1.0×10⁻¹-1.0×10⁻⁶ M) with a slope of 20.1 mV per decade. The limit of detection is 8.0×10⁻⁷ M. The sensor has a very short response time (<15 s) and a useful working pH range of 4.0-8.0. The proposed membrane sensor shows excellent discriminating ability towards La³⁺ ions with regard to several alkali, alkaline earth, transition and heavy metal ions. The electrode was successfully applied for determination of La³⁺ in binary mixtures.     

Novel ferrocene modified poly(amide ether amide)s and investigation of physical and thermal properties

A new diamine containing ferrocene group with preformed ether and amide units was prepared via reaction of 1,1′-ferrocenedicarbonyl chloride with two moles of 2,6-bis(5-amino-1-naphthoxy)pyridine. Polycondensation reactions of the prepared diamine with different aromatic and aliphatic diacid chlorides in the presence of trimethylchlorosilane (TMSCl) resulted in preparation of novel ferrocene modified poly(amide ether amide)s. The monomer and polyamides were characterized and the effect of trimethylchlorosilane (TMSCl) as activating agent on the polymerization reaction was studied. The physical and thermal properties of the polyamides including inherent viscosity, solubility, thermal stability and behavior, flame-retardancy and crystallinity of the polymers were studied. The polymers showed good thermal stability and flame-retardancy, and also improved solubility in polar aprotic solvents.