A Pore-Scale Numerical Simulation Method for Estimating the Permeability of Sand Sediment

A numerical method system to estimate the permeability of sand sediments, at a microscopic scale, was developed. Initially, 3D geometrical representations of the sand grains are reconstructed from a series of 2D X-ray CT scans of real sand grains. 2D cross-sectional slices of the grain outlines are combined together to produce 3D objects via spherical harmonics series expansions. Then, the reconstructed sand grains are packed randomly inside a cubic, microscopic, domain by a combination of a growth method and a simulated annealing method to achieve a predefined porosity. Finally, a single-phase water flow within the domain was simulated numerically, using the lattice Boltzmann method. The calculated permeability of these systems compares well with the values provided by conventional theoretical models. One of the contributions of this study is to show that it is possible to predict the permeability of sand sediments of variable porosities, using sand grains from CT images with changing size distributions and orientations.     

Synthesis of a new poly(carboxybetaine) with peptide main chain

A new poly(carboxybetaine) whose main chain is composed of peptide bonds was synthesized from poly(γ-methyl L -glutamate). The side chains of poly(γ-methyl L -glutamate) were exchanged to carboxybetaine structures by three reactions. Our new poly(carboxybetaine) has 84% carboxybetaine structures in the side chains, as determined by ¹H NMR measurements. The presence of betaine structures in the side chains was confirmed by viscosity measurements.     

Autoxidation of acridanyl and benzhydryl carbanions adjacent to sulfur groups leading to C?S bond cleavage with weak chemiluminescence

Autoxidation of acridanyl and benzhydryl carbanions stabilized by sulfur groups gave the corresponding ketones via radical intermediates, being accompanied by a weak light emission. While oxidation of 9‐sulfenylacridanes ( 1a and 1b ) in the presence of tert‐BuOK showed direct chemiluminescence (CL) due to excited 10‐methylacridone, that of benzhydryl phenyl sulfide ( 2 ) and benzhydryldimethylsulfomium bromide ( 3 ) displayed CL in the presence of a fluorescer, 9,10‐dibromoanthracene (DBA), due to excited benzophenone. The yields of excited species in the present oxidation are low but comparable to acyclic peroxide systems. The bimolecular energy transfer from triplet benzophenone to DBA was established in CL of the sulfonium ylide from 3 . © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:252–257, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/hc.10025     

Selective transport of D,L‐tryptophan through poly(L‐glutamic acid) membranes

Permeability coefficients of D ‐ and L ‐tryptophan (D ‐, L ‐Trp) were estimated for poly(L ‐glutamic acid) (PLG) membranes immersed in aqueous ethanol. D ‐tryptophan was selectively transported (the maximum permeability ratio was 2.6) depending on the amount and the species of crosslinking agent, and on the composition of immersing solvent. It is suggested that hydrogen bonding between uncharged permeates and carboxyl and/or amide groups of PLG is an essential factor for the selective transport. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1035–1041, 1999     

A new cyano-substituted fluorescamine superior to its original form as a fluorescent probe for amino acid detection

Synthesis and spectral study of two new cyano-substituted fluorescamine as the fluorescent probes for amino acid detection have been carried out comparing with the original fluorescamine. Of the three compounds, the derivative with a cyano group at the meta-position on the 4-phenyl group was found to be superior to the original one in the reactivity toward some amino acids as well as the fluorescence intensity of the adducts. The fluorescent amino acid adducts were also applied to the peroxyoxalate chemiluminescence system as the fluorophores, in which the derivative described above was found to be more effective also in chemiluminescence than the original one.     

The molecular basis of myeloid malignancies

Myeloid malignancies consist of acute myeloid leukemia (AML), myelodysplastic syndromes (MDS) and myeloproliferative neoplasm (MPN). The latter two diseases have preleukemic features and frequently evolve to AML. As with solid tumors, multiple mutations are required for leukemogenesis. A decade ago, these gene alterations were subdivided into two categories: class I mutations stimulating cell growth or inhibiting apoptosis; and class II mutations that hamper differentiation of hematopoietic cells. In mouse models, class I mutations such as the Bcr-Abl fusion kinase induce MPN by themselves and some class II mutations such as Runx1 mutations induce MDS. Combinations of class I and class II mutations induce AML in a variety of mouse models. Thus, it was postulated that hematopoietic cells whose differentiation is blocked by class II mutations would autonomously proliferate with class I mutations leading to the development of leukemia. Recent progress in high-speed sequencing has enabled efficient identification of novel mutations in a variety of molecules including epigenetic factors, splicing factors, signaling molecules and proteins in the cohesin complex; most of these are not categorized as either class I or class II mutations. The functional consequences of these mutations are now being extensively investigated. In this article, we will review the molecular basis of hematological malignancies, focusing on mouse models and the interfaces between these models and clinical findings, and revisit the classical class I/II hypothesis.     

Chemically-induced geometrical isomerization of stilbenes during peroxyoxalate chemiluminescence reaction: revisit to ‘photochemistry without light’

The chemically-induced isomerization of stilbenes during the peroxyoxalate chemiluminescence (PO-CL) reactions was reinvestigated. The PO-CL reactions using bis(2,4,6-trichlorophenyl) oxalate in the presence of several stilbenes (type A reaction) produced cis-stilbenes in 0–4% yields, which was dependent on the singlet excitation energy of the stilbenes. On the other hand, the PO-CL reactions of the oxalates, containing the stilbene moieties in the molecules (type B reaction), produced cis-stilbenes 0–9.3% yields, some of which were much more effective than the type A reactions considering the amount of the oxalate moiety as the energy supplier.     

Cleavage of esters under nearly neutral conditions at high pressure

Abstract

Hydrolysis of esters proceeded at room temperature under high pressure in the presence of iPr₂, NEt or N-methylmorpholine using CH₃CN—H₂O (60:1) as the solvent. This very mild procedure enables the smooth hydrolysis of biologically important compounds such as amino esters, aliphatic unsaturated fatty esters, and β-hydroxy ester; no racemization, no isomerization, and no side reactions take place. Selective hydrolysis of two ester groups is also accomplished with alcohol exchange reactions. This new synthetic technique can be utilized for the mild and selective hydrolysis of sophisticated molecules.

Hydrolysis of esters is one of the most essential transformations in organic synthesis. Normally, a basic or acidic aqueous solution is used for ester hydrolysis. However, the hydrolysis of biologically related molecules such as amino esters, peptides, …, or unstaturated fatty esters, under such conditions is accompanied by side reactions, loss of chirality, or isomerization.¹ We report an entirely new approach to this problem via high pressure induced hydrolysis. Hydrolysis is carried out at room temperature under > 8 Kbar in CH₃CN—H₂, O.²     

Three-Dimensional H-Bonded Networks Based on Mono- and Tetranuclear Metal-Pteridine Complexes

Abstract

The crystal structure of the transition metal-pteridine complexes having three-dimensional hydrogen-bonded (H-bonded) network and stacking interactions between pteridine ligands are described; (1) Mononuclear copper(II)-pteridine complex and (2) Tetranuclear palladium(II)-pteridine complex.