Phosphate Removal Through Nano-Zero-Valent Iron Permeable Reactive Barrier; Column Experiment and Reactive Solute Transport Modeling

The stability of natural penetrative convection arising due to a uniform internal heat source in a vertical porous layer saturated with an Oldroyd-B fluid is investigated. The vertical walls of the porous layer are impermeable and maintained at different uniform temperatures. The energy stability analysis performed reveals that the system is unconditionally stable even in the presence of internal heating in the case of Newtonian fluids, while for viscoelastic fluids the base flow is found to be unstable. As the energy stability analysis of Gill type is unable to decide the stability of the system, the Galerkin method is used to solve the complex eigenvalue problem. The internal heating introduces asymmetry in the basic flow and amounts to the existence of different set of onset modes. The internal heating and stress relaxation parameter facilitates instability of the system while increasing strain retardation parameter discloses stabilizing effect on the system. Moreover, the critical Darcy–Rayleigh number, wave number and wave speed become invariant as Ns becomes large. The streamlines and isotherms presented herein demonstrate the development of complex dynamics at the critical state.     

Fusopoltides B–E,new polyketides isolated from Fusarium solani B-18

Four new polyketides, fusopoltides B–E, were isolated, along with four known compounds, from Fusarium solani B-18 cultured on brown-rice. Fusopoltide B is a diastereomer of its co-isolated known compound, fusopoltide A, featuring a pentaleno[1,2-c]pyran ring system. Fusopoltide C and fusopoltides D–E are incorporated the first natural polyketides featured decahydro-pentaleno[1,2-c]pyran and pentaleno[1,2-c]furan ring systems, respectively. The structural assignments were established using comprehensive spectroscopic techniques, the modified Mosher's ester method, and electronic circular dichroism (ECD) calculations.     

Sr substitution effects on atomic and local electronic structure of Ca2AlMnO5+δ

We performed the first-principle calculations based on spin-polarized density functional theory to investigate the Sr substitution effects on the atomic and local electronic structure of Ca₂AlMnO_5+δ. The ionic radius of Sr²⁺ is larger than that of Ca²⁺; thus, the lattice expansion occurs with Sr substitution. From the total energy calculations, we found that Sr substitution makes the oxygen-absorbed phase unstable and realizes the lower operation temperature. From the point of atomic structure, Sr substitution lengthens the bond length between Mn and O atoms connecting Mn and Al atoms in Al tetrahedral (O_Mn-Alt) in oxygen-absorbed phase, because the large Sr²⁺ prevents the release of the Jahn-Teller distortion. We also found that the covalent bonding between Mn and O_Mn-Alt atoms weaken with Sr substitution by the local electronic structure analysis, which results in the unstable oxygen-absorbed phase and weak prepeak and main peak intensity near the onset of O-K edge ELNES of O_Mn-Alt atoms.     

Repeatability and reproducibility of measurements of low dissolved radiocesium concentrations in freshwater using different pre-concentration methods

Journal of Radioanalytical and Nuclear Chemistry - We assessed the repeatability and reproducibility of methods for determining low dissolved radiocesium concentrations in freshwater in Fukushima....     

Polymer Structure‐Guided Self‐Assisted Preparation of Poly(ester‐thioether)‐Based Hollow Porous Microspheres and Hierarchically Interconnected Microcages for Drug Release

Porous polymer microspheres (PPMs) have been widely applied in various biomedical fields. Herein, the self‐assisted preparation of poly(ester‐thioether)‐based porous microspheres and hierarchical microcages, whose pore sizes can be controlled by varying the polymer structures, is reported. Poly(ester‐thioether)s with alkyl side chains (carbon atom numbers were 2, 4, and 8) can generate hollow porous microspheres; the longer alkyl chain length, the larger pore size of microspheres. The allyl‐modified poly(ester‐thioether) (PHBDT‐g‐C₃) can form highly open, hierarchically interconnected microcages. A formation mechanism of these PPMs is proposed; the hydrophobic side chains‐mediated stabilization of oil droplets dictate the droplet aggregation and following solvent evaporation, which is the key to the formation of PPMs. The hierarchically interconnected microcages of PHBDT‐g‐C₃ are due to the partially crosslinking of polymers. Pore sizes of PPMs can be further tuned by a simple mixing strategy of poly(ester‐thioether)s with different pore‐forming abilities. The potential application of these PPMs as H₂O₂‐responsive vehicles for delivery of hydrophobic (Nile Red) and hydrophilic (doxorubicin hydrochloride) cargos is also investigated. The microspheres with larger pore sizes show faster in vitro drug release. The poly(ester‐thioether)‐based polymer microspheres can open a new avenue for the design of PPMs and provide a H₂O₂‐responsive drug delivery platform.     

β‐Selective Glycosylation by Using O‐Aryl‐Protected Glycosyl Donors

New glycosyl donors have been developed that contained several para‐substituted O‐aryl protecting groups and their stereoselectivity for the glycosylation reaction was evaluated. A highly β‐selective glycosylation reaction was achieved by using thioglycosides that were protected by 4‐nitrophenyl (NP) groups, which were introduced by using the corresponding diaryliodonium triflate. Analysis of the stereoselectivities of several glycosyl donors indicated that the β‐glycosides were obtained through an S_N2‐type displacement from the corresponding α‐glycosyl triflate. The NP group could be removed by reduction of the nitro group and acylation, followed by oxidation with ceric ammonium nitrate (CAN).     

Enantioselective N‐Heterocyclic Carbene Catalysis that Exploits Imine Umpolung

The catalytic umpolung of imines remains an underdeveloped approach to reaction discovery. Herein we report an enantioselective aza‐Stetter reaction that proceeds via imine umpolung using N‐heterocyclic carbene catalysis. The reaction proceeds with high levels of enantioselectivity (all ≥96:4 er) and good generality (21 examples). Mechanistic studies are reported and are consistent with turnover‐limiting addition of the NHC to the imine.     

Electret properties of ethylene–propylene random co-polymer

Thermally stimulated current (TSC) spectra were examined for ethylene–propylene (EP) random co-polymer at different charging voltages V_p with positive and negative polarities. Observed TSC spectra showed two well-separated TSC bands, B_L and B_H, which respectively appeared in the temperature regions below and above 100 °C. Observed V_p dependence of B_L was quite different from that of typical polypropylene homo-polymer: As V_p increased, B_L band grew keeping its peak position same at 65 °C, and the band shape unchanged, as if the traps responsible for the B_L band are a single set of traps with the same trap depth and capture cross section. The trap depth of B_L was about 1.9 eV and 1.7 eV for positively charged EP and talc-containing EP samples, respectively. EP samples also showed unique TSC bands above 100 °C: one is a narrow TSC band peaked at 120 °C and the other is an unusual TSC band which was non-vanishing even at 165 °C just before destruction of samples by their melting. Consequently, the utmost stable charge density in EP co-polymer above 100 °C was found to be 3.5 × 10^?4 C/m² and 6.0 × 10 ^?4 C/m² for positively and negatively charged samples, respectively. These equivalent surface charge densities are much larger than those of usual polypropylene homo-polymer.     

Combinatorics of Dispersionless Integrable Systems and Universality in Random Matrix Theory

It is well-known that the partition function of the unitary ensembles of random matrices is given by a τ-function of the Toda lattice hierarchy and those of the orthogonal and symplectic ensembles are τ-functions of the Pfaff lattice hierarchy. In these cases the asymptotic expansions of the free energies given by the logarithm of the partition functions lead to the dispersionless (i.e. continuous) limits for the Toda and Pfaff lattice hierarchies. There is a universality between all three ensembles of random matrices, one consequence of which is that the leading orders of the free energy for large matrices agree. In this paper, this universality, in the case of Gaussian ensembles, is explicitly demonstrated by computing the leading orders of the free energies in the expansions. We also show that the free energy as the solution of the dispersionless Toda lattice hierarchy gives a solution of the dispersionless Pfaff lattice hierarchy, which implies that this universality holds in general for the leading orders of the unitary, orthogonal, and symplectic ensembles. We also find an explicit formula for the two point function F _nm which represents the number of connected ribbon graphs with two vertices of degrees n and m on a sphere. The derivation is based on the Faber polynomials defined on the spectral curve of the dispersionless Toda lattice hierarchy, and \frac1nmF_nm{\frac{1}{nm}F_{nm}} are the Grunsky coefficients of the Faber polynomials.