A Novel Thermosensitive Gel Adsorbent for Phosphate Ions

Summary: A novel thermosensitive gel adsorbent for phosphate ions was developed and its adsorption/desorption properties were investigated. The gel adsorbent was made by the copolymerization of N-isopropylacrylamide (NIPA) and N-[3-(dimethylamino)propyl]acrylamide (DMAPAA). The adsorbent has a volume phase transition temperature (VPTT), below which it becomes hydrophilic. The tertiary amino groups of DMAPAA were ionized and showed a cationic state when the gel swelled. Phosphate ions were adsorbed onto the ionized tertiary amino groups in the gel network below the VPTT and were desorbed above the VPTT because of the suppression of the ionization of the tertiary amino groups of gel and the shrinkage of the gel.     

Potentiality of IMAC as Sample Pretreatment Tool in Food Analysis for Veterinary Drugs

Immobilized metal ion affinity chromatography (IMAC) was evaluated as a sample pretreatment tool for residual veterinary drugs (VDs) in food. A test of six cations for the IMAC efficiency revealed that Cu²⁺ and Fe³⁺ were suitable in retaining tetracyclines, quinolones (QLs: fluoroquinolones, acid quinolones), macrolides, β-lactams, and aminoglycosides, but ineffective for sulfonamides and hormones. These results showed the IMAC had great potential for a multiclass multiresidual VDs analysis in a simple and selective way. This methodology was applied on milk analysis for eleven QLs, involving extraction with (1:1) acetonitrile/methanol and IMAC with Fe³⁺. Averaged recoveries ranged from 68 to 93% and limits of quantitation from 2 to 26 ng mL^?1. Ten commercial milk samples were found to be free from the QLs.     

Synthesis of the Methyl α-Glycoside of the Intracatenary Disaccharide Repeating Unit of the O-Polysaccharide of Vibrio Cholerae O:1. A Comparison of two Assembly Strategies

Abstract

The two strategies engaged in the construction of the title disaccharide 17 comprise: 1. assembly of a diamino disaccharide and its N-acylation using chiral reagents to introduce the 4-(3-deoxy-l-glycero-tetronyl) group, followed by deprotection, and 2. preparation of a glycosyl acceptor and a glycosyl donor both having the chiral 3-deoxy-l-glycero-tetronamido group already in place, their condensation to give a fully substituted disaccharide, and deprotection. Accordingly, the crystalline diamino disaccharide methyl 2-O-(4-amino-3-O-benzyl-4, 6-dideoxy-α-d-mannopyranosyl)-4-amino-3-O-benzyl-4, 6-dideoxy-α-d-mannopyranoside, (14), was prepared from the known [Bundle, D. R. et al., Carbohydr. Res. 174, 239 (1988)] diazido disaccharide 12, and treated with the lactone 30, or its acetylated or benzylated analogs 31 and 32, respectively, as the N-acylating reagents. Subsequent deprotection of the respective products applying standard chemistry gave 17. Alternatively, the methyl α-glycoside of the monomeric intracatenary repeating unit of Vibrio cholerae 0:1 (2) was converted to the fully benzoylated glycosyl chloride 26, and the latter glycosyl donor was condensed with methyl 3-O-benzyl-4,6-dideoxy-4-(2,4-di-O-benzoyl-3-deoxy- l-glycero-tetronamido)-α-d-mannopyranoside (24), to give the corresponding, fully protected derivative 27. Deprotection then readily gave 17. It appears that the title disaccharide can be most efficiently synthesized using synthons 24 and 26. The lactones 30 and 32 appear to be promising acylating reagents for the introduction of the 3-deoxy-l-glycero-tetronamido group when higher oligosaccharides in this series will be synthesized via their (poly)amino precursors.     

Spin-inversion mechanisms in O2 binding to a model heme complex revisited by density function theory calculations

Spin-inversion mechanisms in O₂ binding to a model heme complex, consisting of Fe(II)-porphyrin and imidazole, were investigated using density-functional theory calculations. First, we applied the recently proposed mixed-spin Hamiltonian method to locate spin-inversion structures between different total spin multiplicities. Nine spin-inversion structures were successfully optimized for the singlet–triplet, singlet–quintet, triplet–quintet, and quintet–septet spin-inversion processes. We found that the singlet–triplet spin-inversion points are located around the potential energy surface region at short Fe–O distances, whereas the singlet–quintet and quintet–septet spin-inversion points are located at longer Fe–O distances. This suggests that both narrow and broad crossing models play roles in O₂ binding to the Fe-porphyrin complex. To further understand spin-inversion mechanisms, we performed on-the-fly Born-Oppenheimer molecular dynamics calculations. The reaction coordinates, which are correlated to the spin-inversion dynamics between different spin multiplicities, are also discussed.     

Enhancement of stability and accuracy of the moving particle semi-implicit method

As a Lagrangian gridless particle method, the MPS (Moving Particle Semi-implicit) method has been proven useful in a wide range of engineering applications. Up to now, most of MPS applications have been limited to problems with compressive stress states. This paper investigates the performance and stability of MPS method in simulation of more general hydrodynamic problems, including those characterized by tensile stresses or by changes in the stress states. It is shown that MPS-based simulations are prone to become destabilized in presence of attractive interparticle forces. This instability appears to be similar to the so-called tensile instability in SPH method. Two new modifications, namely, a modified Poisson Pressure Equation and a corrective matrix for pressure gradient model, are proposed to resolve this shortcoming. These two new modifications together with two previously proposed improvements are shown to stabilize and enhance the performance of MPS method.     

Hydrogen bonding in two solid phases of phenazine–chloranilic acid (1/1) determined at 170 and 93 K

The crystal structures in two solid phases, i.e. phase II stable between 146 and 253 K and phase IV below 136 K, of the title compound [phenazine–chloranilic acid (1/1), C₁₂H₈N₂·C₆H₂Cl₂O₄, in phase II, and phenazinium hydrogen chloranilate, C₁₂H₉N₂⁺·C₆HCl₂O₄⁻, in phase IV], have been determined. Both phases crystallize in P2₁, and each structure was refined as an inversion twin. In phase II, the phenazine and chloranilic acid mol­ecules are arranged alternately through two kinds of O—H⋯N hydrogen bonds. In phase IV, salt formation occurs by donation of one H atom from the chloranilic acid molecule to the phenazine mol­ecule; the resulting monocation and monoanion are linked by N—H⋯O and O—H⋯N hydrogen bonds.     

Newsvendor solutions via conditional value-at-risk minimization

In this paper, we consider the minimization of the conditional value-at-risk (CVaR), a most preferable risk measure in financial risk management, in the context of the well-known single-period newsvendor problem, which is originally formulated as the maximization of the expected profit or the minimization of the expected cost. We show that downside risk measures including the CVaR are tractable in the problem due to their convexity, and consequently, under mild assumptions on the probability distribution of products’ demand, we provide analytical solutions or linear programming (LP) formulation of the minimization of the CVaR measures defined with two different loss functions. Numerical examples are also exhibited, clarifying the difference among the models analyzed in this paper, and demonstrating the efficiency of the LP solutions.     

Highly stereoselective radical carbonylations of gem-dihalocyclopropane derivatives with CO

A couple of radical carbonylations of gem-dihalocyclopropanes 1 using CO and Bu3SnH (formylation) or Bu3Sn(CH2CH=CH2) (allylacylation) successfully proceeded to give trans and cis adducts (2 and 3) with good to excellent stereoselectivity (trans/cis = >99/1-75/25 or 17/83-1/99). The formylation of 2,3-cis-disubstituted 1,1-dihalocyclopropanes enhanced trans selectivity (trans/cis = >99/1-95/5), whereas both 2,3-cis-disubstituted and 2-monosubstituted 1,1-dihalocyclopropanes underwent allylacylation with nearly complete trans selectivity (trans/cis = >99/1). Inherently less reactive gem-dichloro- and bromochlorocyclopropanes than gem-dibromocyclopropanes served as favorable substrates. [reaction: see text].     

Role of Pressure in Turbulence

There is very limited knowledge of the kinematical relations for the velocity structure functions higher than three. Instead, the dynamical equations for the structure functions of the velocity increment are obtained from the Navier–Stokes equation under the assumption of the local homogeneity and isotropy. These equations contain the correlation between the velocity and pressure gradient increments, which is very difficult to know theoretically and experimentally. We have examined these dynamical relations by using direct numerical simulation data at very high resolution at large Reynolds numbers, and found that the contribution of the pressure term is important to the dynamics of the longitudinal velocity with large amplitudes. The pressure term is examined from the view point of the conditional average and the role of the pressure term in the turbulence dynamics is discussed.