Modeling interface shear behavior of granular materials using micro-polar continuum approach

Recently, the authors have focused on the shear behavior of interface between granular soil body and very rough surface of moving bounding structure. For this purpose, they have used finite element method and a micro-polar elasto-plastic continuum model. They have shown that the boundary conditions assumed along the interface have strong influences on the soil behavior. While in the previous studies, only very rough bounding interfaces have been taken into account, the present investigation focuses on the rough, medium rough and relatively smooth interfaces. In this regard, plane monotonic shearing of an infinite extended narrow granular soil layer is simulated under constant vertical pressure and free dilatancy. The soil layer is located between two parallel rigid boundaries of different surface roughness values. Particular attention is paid to the effect of surface roughness of top and bottom boundaries on the shear behavior of granular soil layer. It is shown that the interaction between roughness of bounding structure surface and the rotation resistance of bounding grains can be modeled in a reasonable manner through considered Cosserat boundary conditions. The influence of surface roughness is investigated on the soil shear strength mobilized along the interface as well as on the location and evolution of shear localization formed within the layer. The obtained numerical results have been qualitatively compared with experimental observations as well as DEM simulations, and acceptable agreement is shown.     

A novel and convenient method for synthesis of carbamoyl and thiocarbamoyl phosphonates

A simple, efficient, and general method has been developed for the synthesis of carbamoyl and thiocarbamoyl phosphonic esters using CaCl₂ as an efficient Lewis base catalyst. Carbamoyl and thiocarbamoyl phosphonic esters were obtained in good yield (37%–65%) and purity under mild conditions by the reaction of diethyl phosphite with isocyanates and isothiocyanates in the presence of CaCl₂. This method is easy, rapid, and good‐yielding reaction for the synthesis of carbamoyl and thiocarbamoyl phosphonic esters. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:250–253, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20538     

Density and viscosity of 1-butyl-3-methylimidazolium nitrate with ethanol, 1-propanol, or 1-butanol at several temperatures

Densities and viscosities of 1-butyl-3-methylimidazolium nitrate [Bmim][NO₃], and its binaries with alcohol (ethanol, 1-propanol, or 1-butanol) were measured at different temperatures. The densities and viscosities of pure ionic liquid were correlated successfully by empirical equations. The Vogel–Fulcher–Tammann equations can fit the experimental data of viscosities for pure IL. Excess molar volume and viscosity deviations were calculated for the binaries. The excess molar volumes have negative deviations from the ideal solution.     

A class of supported membranes: formation of fluid phospholipid bilayers on photonic band gap colloidal crystals

We report the formation of a new class of supported membranes consisting of a fluid phospholipid bilayer coupled directly to a broadly tunable colloidal crystal with a well-defined photonic band gap. For nanoscale colloidal crystals exhibiting a band gap at the optical frequencies, substrate-induced vesicle fusion gives rise to a surface bilayer riding onto the crystal surface. The bilayer is two-dimensionally continuous, spanning multiple beads with lateral mobilities which reflect the coupling between the bilayer topography and the curvature of the supporting colloidal surface. In contrast, the spreading of vesicles on micrometer scale colloidal crystals results in the formation of bilayers wrapping individual colloidal beads. We show that simple UV photolithography of colloidal crystals produces binary patterns of crystal wettabilities, photonic stopbands, and corresponding patterns of lipid mono- and bilayer morphologies. We envisage that these approaches will be exploitable for the development of optical transduction assays and microarrays for many membrane-mediated processes, including transport and receptor-ligand interactions.     

Synthesis of the proposed structure of mucoxin via regio- and stereoselective tetrahydrofuran ring-forming strategies

An enantioselective total synthesis of the proposed structure of mucoxin (1) is described. Mucoxin, an annonaceous acetogenin isolated from bioactive leaf extracts of Rollinia mucosa, is the first acetogenin containing a hydroxylated trisubstituted tetrahydrofuran (THF) ring. This natural product is a highly potent and specific antitumor agent against MCF-7 (breast carcinoma) cell lines (ED50 = 3.7 x 10(-3) microg/mL compared to adriamycin, ED50 = 1.0 x 10(-2) microg/mL). The total synthesis described herein features two regio- and stereoselective THF ring-forming reactions. The 2,3,5-trisubstituted THF portion (C13-C17) was accessed using a highly regioselective cyclization of a methylene-interrupted epoxydiol, and the 2,5-disubstituted THF ring (C8-C12) was conveniently assembled via a 1,2-n-triol cyclization strategy. The spectral data of the synthetic material and two of its diastereomers did not match the reported data for the natural product. On the basis of detailed spectroscopic analysis of the synthesized molecule, we reason that the spectral discrepancies are due to stereochemical misassignment of the natural product.     

Investigation of hydrazine addition to functionalized furans: synthesis of new functionalized 4,4′-bipyrazole derivatives

The addition of hydrazine to functionalized furans 2a-d leads to a variety of 4,4′-bipyrazoles 4a-c depending on the structure of the starting materials. In one example, compound 2c was first converted to an intermediate, furo[3,4-d]pyridazine 3c which was then transformed into 4,4′-bipyrazole 4c on reacting with hydrazine.     

A novel method for the separation of bis(alpha-hydroxyalkyl)phosphinic acid diastereoisomers via formation of novel cyclic phosphinic acids

The reaction of aromatic and aliphatic aldehydes with hypophosphorus acid under microwave irradiation was examined. The reaction gave a mixture of a racemic pair of bis(alpha-hydroxyalkyl)phosphinic acids and acetal derivatives from the corresponding bis(alpha-hydroxyalkyl)phosphinic acids of meso-stereochemistry in good yield. The difference in solubility in organic solvents due to polarity allowed us to readily separate these compounds. This method constitutes an easy, rapid, and good-yielding preparation and separation of bis(alpha-hydroxyalkyl) phosphinic acid diastereoisomers from simple starting materials using microwave irradiation.     

Biodegradable microfabricated plug-filters for glaucoma drainage devices

We report on the development of a batch fabricated biodegradable truncated-cone-shaped plug filter to overcome the postoperative hypotony in nonvalved glaucoma drainage devices. Plug filters are composed of biodegradable polymers that disappear once wound healing and bleb formation has progressed past the stage where hypotony from overfiltration may cause complications in the human eye. The biodegradable nature of device eliminates the risks associated with permanent valves that may become blocked or influence the aqueous fluid flow rate in the long term. The plug-filter geometry simplifies its integration with commercial shunts. Aqueous humor outflow regulation is achieved by controlling the diameter of a laser-drilled through-hole. The batch compatible fabrication involves a modified SU-8 molding to achieve truncated-cone-shaped pillars, polydimethylsiloxane micromolding, and hot embossing of biodegradable polymers. The developed plug filter is 500?μm long with base and apex plane diameters of 500 and 300?μm, respectively, and incorporates a laser-drilled through-hole with 44-μm effective diameter in the center.     

A signal subspace approach for modeling the hemodynamic response function in fMRI

Many fMRI analysis methods use a model for the hemodynamic response function (HRF). Common models of the HRF, such as the Gaussian or Gamma functions, have parameters that are usually selected a priori by the data analyst. A new method is presented that characterizes the HRF over a wide range of parameters via three basis signals derived using principal component analysis (PCA). Covering the HRF variability, these three basis signals together with the stimulation pattern define signal subspaces which are applicable to both linear and nonlinear modeling and identification of the HRF and for various activation detection strategies. Analysis of simulated fMRI data using the proposed signal subspace showed increased detection sensitivity compared to the case of using a previously proposed trigonometric subspace. The methodology was also applied to activation detection in both event-related and block design experimental fMRI data using both linear and nonlinear modeling of the HRF. The activated regions were consistent with previous studies, indicating the ability of the proposed approach in detecting brain activation without a priori assumptions about the shape parameters of the HRF. The utility of the proposed basis functions in identifying the HRF is demonstrated by estimating the HRF in different activated regions.     

Hydrangenone, a new isoprenoid with an unprecedented skeleton from Salvia hydrangea

Hydrangenone, a new heptacyclic isoprenoid with a 6/7/6/5/5 membered carbon ring skeleton, was isolated from the aerial parts of Salvia hydrangea. The structure was established by extensive NMR spectroscopic methods. The relative and absolute configuration of 1 was assigned by NOESY and X-ray crystallographic analysis and by comparison of experimental and calculated electronic circular dichroism (ECD) spectra. Compound 1 showed in vitro antiplasmodial activity, with an IC(50) value of 1.4 μM against P. falciparum. A plausible biosynthetic pathway of 1 was also proposed.