Heterotricyclodecane IX. 2, 7-Dioxa-isotwistan, 2, 7-Dioxatwistan und 2, 8-Dioxa-homotwistbrendan sowie Derivate

The synthesis of 2, 7-dioxa-isotwistane ( 10 ), 2, 7-dioxa-twistane ( 17 ), and 2, 8-dioxa-homotwistbrendane ( 36 ) and several of their derivatives is described starting from endo-2-hydroxy-9-oxabicyclo[3.3.1]non-6-ene ( 1 ). The 10^O(7)-isotwistane iodide 7 and the corresponding tosylate 15 as well as the 10^O(2)-iodide 9 were treated under reaction conditions suitable for molecular rearrangements involving oxonium ions g and i , respectively, by neighbouring group participation leading to 2, 7-dioxa-twistanes and 2, 8-dioxa-homotwistbrendanes, respectively.     

Oxymercuration. Substituted 9-oxabicyclo[4.2.1]- and 9- oxabicyclo[3.3.1]nonanes

Oxymercuration of cis, cis-1, 5-cyclooctadiene ( 1 ), followed by treatment with potassium iodide and subsequent reaction with iodine, leads to six isomeric diiodides which represent the three possible stereoisomers 2 , 3 , and 4 of 2, 5-diiodo-9-oxabicyclo[4.2.1]nonane as well as 5 , 6 , and 7 of 2, 6-diiodo-9-oxabicyclo[3.3.1]nonane. The isolation, structure determination and some reactions of these diiodo compounds 2 – 7 are described.     

Mathematical modeling of the temperature fields during the solidification of metal in molds of complicated profile

We present a computational model of the process of solidification of metal in molds of complicated configuration. The model is based on the theory of R-functions, which makes it possible to construct the normal equations of drawings and introduce additional parameters into these equations, by means of which one can assure the required behavior of the solution corresponding to the technological implementation of the process. Computational experiments were carried out using thePOLE system. Translated fromMatematichni Metodi i Fiziko-mekhanichni Polya, Vol. 40, No. 1, 1997, pp. 59–65.     

Lewis acid stabilized methylidene and oxoscandium complexes

The methylidene scandium complex (PNP)Sc(mu3-CH2)(mu2-CH3)2[Al(CH3)2]2 (PNP = N[2-P(CHMe2)2-4-methylphenyl]2-) can be prepared from the reaction of (PNP)Sc(CH3)2 and 2 equiv of Al(CH3)3. The Lewis acid stabilized methylidenes candium complex has been crystallographically characterized, and its bonding scheme analyzed by DFT. In addition, we report preliminary reactivity studies of the Sc-CH2 ligand with substrates such as H2NAr and OCPh2. While the former results in an Br?nsted acid-base reaction, the latter reagent produces the olefin H2C CPh2 along with the novel oxoscandium complex (PNP)Sc(mu3-O)(mu2-CH3)2[Al(CH3)2]2, quantitatively.     

Synthesis of VO2 (B) nanorods for Li battery application

Vanadium dioxide nanorods were synthesized through a hydrothermal reaction from V₂O₅ xerogel, poly(vinyl pyrrolidone) (PVP) and lithium perchlorate (LiClO₄). The prepared samples were characterized by X-ray diffraction, infrared spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electrochemical discharge–charge cycling in lithium battery. SEM images reveal the nanorods to have dimensions on the order of 1–3 μm in length and 10–50 nm in diameter. The measured initial discharge capacity of the lithium battery with a cathode made of VO₂ (B) nanorods was 152 mA h/g.     

Characterization of MoO3 nanorods for lithium battery using PVP as a surfactant

We synthesized MoO₃ nanorods using poly (vinyl pyrrolidone) (PVP) as a surfactant through the hydrothermal route for making a cathode for a lithium battery. Scanning electron microscopy images reveal the structures to have dimensions on the order of 1–10 μm in length and 50–200 nm in diameter. Analytical techniques such as X-ray diffractometry, Fourier transformation infrared spectroscopy, thermogravimetric analysis, and cyclic voltammetry were used to characterize the nanorods. The measured specific charge of MoO₃ nanorods prepared through a 15-day hydrothermal reaction was 156 mAhg⁻¹ during the initial discharge process.     

ExplorEnz: a MySQL database of the IUBMB enzyme nomenclature

Background  

We describe the database ExplorEnz, which is the primary repository for EC numbers and enzyme data that are being curated on behalf of the IUBMB. The enzyme nomenclature is incorporated into many other resources, including the ExPASy-ENZYME, BRENDA and KEGG bioinformatics databases.     

Full-field measurements of flow through a scaled metal foam replica

Open-celled foam geometries show great promise in heat/mass transfer, chemical treatment, and enhanced mixing applications. Flow measurements on these geometries have consisted primarily of observations of the upstream and downstream effects the foam has on the velocity field. Unfortunately, these observations give little insight into the flow inside the foam. We have performed quantitative flow measurements inside a scaled replica of a metal foam, ϕ = 0.921, D _Cell = 2.5 mm, by Magnetic Resonance Velocimetry to better understand the fluid motion inside the foam and give an alternative method to determine the foam cell and pore sizes. Through these 3-D, spatially resolved measurements of the flow field for a cell Reynolds number of 840, we have shown that the transverse motion of the fluid has velocities 20–30% of the superficial velocity passing through the foam. This strong transverse motion creates and dissipates streamwise jets with peak velocities 2–3 times the superficial velocity and whose coherence length is strongly correlated to the cell size of the foam. This complex fluid motion is described as “mechanical mixing” and is attributed to the geometry of the foam. A mechanical dispersion coefficient, D _M, was formed which demonstrates the transverse dispersion of this geometry to be 14 times the kinematic viscosity and 10 times the thermal diffusivity of air at 20°C and 1 atm.     

Isocyanide insertion and cyclization reactions to form indolines using pincer-type complexes of scandium

The addition of 2,6-dimethylphenyl isocyanide (CN[DMeP], two equivalents) to previously reported (PNP)Sc(III) pyridyl complexes resulted in the formation of novel indoline complexes of scandium. By varying the nature of the pyridyl moiety one can intercept an intermediate prior to methyl migration. In addition to structural studies of two indolene complexes, we also propose a mechanism for the insertion and indolene ring closure.     

Release of electrolytes from W/O/W double emulsions stabilized by a soluble complex of modified pectin and whey protein isolate

W/O/W double emulsions (DEs) stabilized by charged soluble complexes of whey protein isolate (WPI) and modified pectins were investigated in relation to their stability and the release of two types of electrolytes, NaCl and sodium ascorbate.WPI alone cannot properly stabilize the DEs. The droplet size is relatively large (100 μm) and increases with time. However, addition of modified pectin to form a soluble complex with WPI significantly improved the stability.DEs prepared with two types of oils (medium chain triglycerides (MCT) and R(+)-limonene) were studied by measuring droplet size, creaming, viscosity, and electrolyte release. Irrespective of their very different oil phase nature, both emulsions were stable against coalescence, but R(+)-limonene formed smaller droplets (25 μm) than MCT (35 μm). The electrolyte release rate was significantly higher from the R(+)-limonene that formed DEs with much lower viscosity. R(+)-limonene-DE released 75% of the NaCl after 28 days, while MCT-DE released only 50%. NaCl was released more slowly than sodium ascorbate.Apparently, the release mechanism from R(+)-limonene-DE was found to be “thinning the outer interface and release of the entire inner droplets” while it seems that the release from MCT-DE was slower and “diffusion controlled”.DEs stabilized by WPI/C63 released 12% of the sodium ascorbate after 1 day in milk and remained stable for at least 8 days. However, DEs stabilized with only WPI released about 50% of the sodium ascorbate after 1 day, and phase separated after 8 days.