Exact solutions of solid-liquid phase-change heat transfer when subjected to convective boundary conditions

A closed-form expression is presented to find the location of solid-liquid interface motion in convection-dominated solidification and melting problems. In this regard, the solutions are expressed in terms of the generalized representations of error functions,E (u, v) andF (u, v), which are useful to heat-conduction problems with convective-type boundary conditions. It is demonstrated that for constant surface temperature, the interface solution reduces to the classical Neumann solution.     

Measurement and prediction of solubilities and diffusion coefficients of carbon dioxide in starch–water mixtures at elevated pressures

The solubility and diffusion coefficient of carbon dioxide in intermediate‐moisture starch–water mixtures were determined both experimentally and theoretically at elevated pressures up to 16 MPa at 50 °C. A high‐pressure decay sorption system was assembled to measure the equilibrium CO₂ mass uptake by the starch–water system. The experimentally measured solubilities accounted for the estimated swollen volume by Sanchez–Lacombe equation of state (S‐L EOS) were found to increase almost linearly with pressure, yielding 4.0 g CO₂/g starch–water system at 16 MPa. Moreover, CO₂ solubilities above 5 MPa displayed a solubility increase, which was not contributed by the water fraction in the starch–water mixture. The solubilities, however, showed no dependence on the degree of gelatinization (DG) of starch. The diffusion coefficient of CO₂ was found to increase with concentration of dissolved CO₂, which is pressure‐dependent, and decrease with increasing DG in the range of 50–100%. A free‐volume‐based diffusion model proposed by Areerat was employed to predict the CO₂ diffusivity in terms of pressure, temperature, and the concentration of dissolved CO₂. S‐L EOS was once more used to determine the specific free volume of the mixture system. The predicted diffusion coefficients showed to correlate well with the measured values for all starch–water mixtures. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 607–621, 2006     

Synthesis and antimycobacterial activity of some beta-carboline alkaloids

In view of the attributed medicinal properties of beta-carboline alkaloids, some new O-acyl derivatives of beta-carboline alkaloid--harmol, were prepared and tested for possible antimycobacterial activity against Mycobacterium tuberculosis H37Rv.     

Parametric study of catalytic reforming process?

Summary A parametric study of catalytic reforming process in a pilot plant was carried out by varying the pressure, H₂/HC ratio, and space velocity. The results show that lower aromatics and higher hydrogen yields can be accomplished by increasing the space velocity in existing reformers, which will also result in better C₅⁺yield.     

NMR spectroscopic study of the inclusion complex of desloratadine with β-cyclodextrin in solution

Desloratadine (DES) is an antihistamine used in the treatment of allergies and chronic urticaria. ¹H NMR spectroscopic study of varying ratios of DES and β-Cyclodextrin (β-CD) in D₂O suggests the formation of a 1:1 inclusion complex formed by the penetration of Cl-substituted aromatic ring into the β-CD cavity. The stoichiometry and binding constant of the complex were determined by Scott’s method.     

Chemische Vitamin D<Subscript>3</Subscript>-Bestimmung in Lebertran

The different aspects of Vitamin D₃ determination and the data reported in the literature are discussed. The spectrophotometric determination of Vitamin D₃ in cod-liver oil is carried out after the alkaline saponification, extraction of unsaponified parts, precipitation of accompanying sterols and the column- and thin-layer chromatographic purification and separation of vitamin D₃ on 40 cm plates from other vitamins. The dyestuff α-naphtholbenzein is suited well as standard substance for the better location and identification of vitamin D₃ zone on the thin-layer plate. The results obtained from the chemical method were checked through the simultaneous biological determination.     

Synthesis of PDMAEMA-PCL-PDMAEMA triblock copolymers

The synthesis of ABA triblock copolymers of the type PDMAEMA-PCL-PDMAEMA was achieved by atom transfer radical polymerization (ATRP) of DMAEMA using difunctional polycaprolactone (PCL) as macroinitiator. First, ring-opening polymerization (ROP) of ε-caprolactone (ε-CL) was carried out in the presence of 1,2-diaminoethane/tin (II) octanoate. Dihydroxy PCL thus obtained was end-functionalized in a quantitative manner using 2-bromoisobutyryl bromide. The resulting Br-PCL-Br was used as macroinitiator in the ATRP of DMAEMA leading to triblock copolymers with PCL as the central block and PDMAEMA sequences of different lengths. NMR and SEC analyses confirmed the formation of ABA triblocks.     

Characterization of oligosaccharide moieties of intact glycoproteins by microwave-assisted partial acid hydrolysis and mass spectrometry

A method, which utilizes microwave-assisted partial acid hydrolysis and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS), to elucidate oligosaccharide composition of intact glycoproteins is presented here. Glycoproteins, such as ribonuclease B, avidin, alpha1-acid glycoprotein, and fetuin, are used as model systems to demonstrate this technique. Partial cleavage of oligosaccharides from whole intact glycoproteins with trifluoroacetic acid was observed after a short exposure to microwaves. Due to the high-resolution mass spectra obtained by MALDI-TOFMS from glycoproteins with molecular weights less than 20 kDa, the compositions of oligosaccharides are readily derived for ribonuclease B and avidin. The data agree with the proposed oligosaccharide structures of ribonuclease B (five glycoforms) and avidin (eight glycoforms). Larger glycoproteins such as alpha1-acid glycoprotein (many glycoforms) and fetuin (many glycoforms) exhibited only broad peaks with no glycoform resolution. Nevertheless, this method can be used successfully for analysis of glycoproteins with molecular weights greater than 20 kDa to determine the presence or absence of glycosylation.     

Studies of tetracene- and pentacene-based organic thin-film transistors fabricated by the neutral cluster beam deposition method

The neutral cluster beam deposition (NCBD) method has been applied to produce and characterize organic thin-film transistors (OTFTs) based upon tetracene and pentacene molecules as active layers. Organic thin films were prepared by the NCBD method on hexamethyldisilazane (HMDS)-untreated and -pretreated silicon dioxide (SiO2) substrates at room temperature. The surface morphology and structures for the tetracene and pentacene thin films were examined by atomic force microscopy (AFM) and X-ray diffraction (XRD). The measurements demonstrate that the weakly bound and highly directional neutral cluster beams are efficient in producing high-quality single-crystalline thin films with uniform, smooth surfaces and that SiO2 surface treatment with HMDS enhances the crystallinity of the pentacene thin-film phase. Tetracene- and pentacene-based OTFTs with the top-contact structure showed typical source-drain current modulation behavior with different gate voltages. Device parameters such as hole carrier mobility, current on/off ratio, threshold voltage, and subthreshold slope have been derived from the current-voltage characteristics together with the effects of surface treatment with HMDS. In particular, the high field-effect room-temperature mobilities for the HMDS-untreated OTFTs are found to be comparable to the most widely reported values for the respective untreated tetracene and pentacene thin-film transistors. The device performance strongly correlates with the surface morphology, and the structural properties of the organic thin films are discussed.