Adsorption studies of β-naphthol by untreated and treated activated carbon [optimizing of adsorption by central composite design (CCD)]

In the present work the adsorption of aromatic compound, namely ??-naphthol (BN) by two granular activated carbons, one untreated and the other treated with HNO₃ carried out under controlled conditions. The effects of experimental parameters on adsorption process such as pH, contact time and adsorbent dosage have been investigated. Experimental design methodology was applied to optimize the removal of ??-naphthol. The effect of various experimental parameters was investigated using five-level three-factorial central composite design (CCD). The relationship between the parameters and the response for model optimization was found and optimum conditions were obtained by CCD. In the optimum conditions obtained by response surface modeling, 100% BN was adsorbed on the carbons. Treatment with HNO₃ led to a decrease in the point of zero charge and the adsorption capacity (Q _max) of the activated carbon. The adsorption capacity of the carbons was determined using Freundlich and Langmuir homogenous equation. The variation of the model parameters with the solution pH was also studied. The fitted parameters obtained from both models showed the Q _max value decrease with increasing of pH.     

Nanofibrous Scaffolds with Biomimetic Composition for Skin Regeneration

Applied Biochemistry and Biotechnology - Treatments of skin injuries caused by trauma and diseases are among the most considerable medical problems. The use of scaffolds that can cover the wound...     

Effect of orifice shape on bubble formation mechanism

The effect of orifice shape on the mechanism of bubble formation in gas–liquid two-phase flow is investigated experimentally with three different orifice geometries regarding a circle, a square, and a triangle with same cross-sectional areas. The liquid and gas phases are purified water at 20 °C and air at room temperature, respectively. Gas is injected at the rate of 50–1200 mlph into a stagnant pool of liquid in distances of 5, 10, and 15 cm below the liquid surface. The position, velocity, and acceleration of bubbles are measured at bubbles’ centers of mass (CM) and the effects of these parameters on the bubble volume are investigated. Moreover, the forces acting on a bubble are balanced and the effects of geometry and gas flow rate on each force are presented. In addition, the changes of the acting forces versus time are plotted and discussed for a specific condition. Results show the bubbles formed with the square and circular orifice cross-sectional areas have the most and least volumes at detachment, respectively.     

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.     

Streamers in gas discharge devices

Streamers are ionization waves in gas discharge devices, modelled here as travelling wave solutions of a drift-diffusion model for the transport of electrons and ions. The existence of a certain type of small amplitude streamers is proved by applying results from the theory of singularly perturbed ordinary differential equations. Global information is obtained from a large activation energy analysis.

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Zusammenfassung Streamer sind lonisierungswellen in Gasentladungsröhren, die hier durch wandernde Wellenlösungen eines Drift-Diffusionsmodelles für den Transport von Elektronen und Ionen beschrieben werden. Die Existenz von Wellen eines bestimmten Typs mit kleiner Amplitude wird mit Hilfe von Resultaten über singulär gestörte gewöhnliche Differentialgleichungen bewiesen. Globale Information liefert eine Störungsanalyse für große Aktivierungsenergie.

     

The combined use of high performance liquid chromatography and immuno-biochemical techniques for protein isolation: a new approach for identification of an individual protein from a pool of proteins

HPLC was used in combination with immuno-bead separation technique for identification of an individual protein from a pool of proteins. This was carried out using an in-house monoclonal antibody (ATC2) specific for placental alkaline phosphatase (PLAP) as a primary antibody for conjugation to CNBr beads. The phosphatase activity (ALP) of PLAP was measured by colorimetric assay (MEDC). The data from this study has so far indicated that: 1. HPLC analysis of molecules following isolation with ATC2-conjugated beads showed high degree of purity. This could be achieved using protein mixtures prepared from lysates of tumour cell lines or tumour fragments. 2. HPLC-isolated PLAP maintained phosphatase activity. 3. Out of the four dissociation reagents used, diethyl amine (DEA) was found to be the best reagent for dissociation of antigen, ie PLAP, but not mAb from CNBr beads. 4. The profile of ALP activity was different for samples prepared from testis and kidney fragments, both in terms of the HPLC peak profile as well as the sensitivity. These data confirmed that the immuno-bead separation technique in conjunction with HPLC were powerful tools for identifying an individual protein from a pool of proteins. These approaches are being used for the identification of PLAP molecules, as a tumour marker in patients suspected of testicular malignancies with equivocal ultrasound.     

Synthesis of new 1-C-(2-furyl)-and 3-C-(2-furyl)-hexopyranosides and 3-C-(2-furyl)-daunorubicin analogs

Summary Reaction of furan with 3,4-di-O-acetyl-L-rhamnal (1) afforded a mixture of epimeric 3-C-(2-furyl) glycals3 and4 and 1-C-(2-furyl)-hex-2-enopyranoses5 and6. Glycals3 and4 were transformed to 2-deoxy-glycosides9–13 and 3-deamino-3-C-(2-furyl)daunorubicines15 and16. Hex-2-enopyranosyl5 wascis hydroxylated with osmium tetroxide/N-methylmorpholine N-oxide to C-glycoside14.On leave from Pharmaceutical Research Institute, Warsaw, Poland     

Evaluation of semiquantitative analysis mode in ICP-MS

Semiquantitative analysis mode in inductively coupled plasma mass spectrometry (ICP-MS) has been popularly used for fast screening purposes. Although the benefit of it has been studied by many researchers, its performance of application in real-world routine analyses has not been reported.

In this study, we evaluated the reliability of semiquantitative analysis mode through inter-laboratory comparison using two different ICP-MS systems with one multi-element calibration standard. The suitability of semiquantitative analysis mode in routine analysis laboratory was demonstrated by evaluating its application in different laboratories and in real production laboratory practices. Twenty one elements were measured, namely, Be, B, Al, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, As, Sr, Mo, Ag, Cd, Sn, Sb, Ba, Tl, and Pb in various fresh water reference samples. Good results concerning accuracy (relative percentage error within 10%) and reproducibility (relative standard deviation lower than 5%) were obtained in more than 90% analyzed samples at concentrations equal to or greater than 10 times the detection limit (DL). Semiquantitative analysis mode also enabled the determination of elements that are not present in the calibration standard. The results demonstrated the potential of semiquantitative analysis mode as a reliable approach in routine laboratory determination of simple matrices, where high throughput and cost-effectiveness are desired, as well as in emergency situations where speed of analysis is critical and quite often limited sample information is available.     

The cationic cascade route to longifolene

W. S. Johnson's total synthesis of the sesquiterpenoid longifolene is a classic example of the power of cationic polycyclizations for constructing complex molecular architectures. Herein we revisit the key polycyclization step of this synthesis using hybrid Hartree-Fock/density functional theory calculations and validate the feasibility of Johnson's proposed mechanism. We also explore perturbations to the 3-center 2-electron bonding array in a key intermediate that result from changing the polycyclic framework in which it is embedded.     

Boltzmann asymptotics with diffuse reflection boundary conditions

StrongL ¹-convergence towards a stationary solution when time tends to infinity is established for the solutions of the time-dependent nonlinear Boltzmann equation in a bounded domain ³ with constant temperature on the boundary. The collisionless case is first investigated in the varying temperature case.