Effect of sulfate on Cu(II) sorption to polymer-supported nano-iron oxides: behavior and XPS study

Iron oxides tend to be immobilized within nanoporous supports to improve their feasibility for practical environmental remediation including arsenic and heavy metal removal. Contrary to the co-ions, little is known concerning the effect of counter ions on the performance of the resultant composites. In this study, two hybrid sorbents (denoted as HFO-PS(-) and HFO-PS(0), respectively) were prepared by loading hydrous ferric oxide (HFO) nanoparticles onto two polystyrene beads: PS(-), negatively charged with sulfonic acid groups, and PS(0), covalently bonded with neutral chloromethyl groups. Effects of sulfate on their sorption toward Cu ions were investigated. Consistent with the case in bulky HFO particles, the amount of Cu adsorbed on HFO-PS(0) was markedly promoted by introducing sulfate. As for HFO-PS(-), with monovalent cation as background (Na(+)), it exhibited an apparent decrease in Cu sorption as a result of the competing effect of Na ions and the Cu-SO(4) complexation in solution. Contrarily, the adsorbed Cu was increased by introducing sulfate in the divalent cation background (Ca), because sulfate ions were allowed to access to the loaded HFO nanoparticles due to the screening of the sulfonic acid groups caused by Ca ions. XPS spectroscopy further demonstrated that besides the electrostatic effects, the formation of Cu-SO(4) ternary complexes also accounted for the enhanced Cu sorption on both bulky HFO and hybrid HFO sorbents in the presence of sulfate. These results indicated that the effect of counter-ion ligands on metal adsorption to hybrid iron oxides was largely dependent on the surface properties of the host materials.     

Catalytic enantioselective tert-aminocyclization by asymmetric binary acid catalysis (ABC): stereospecific 1,5-hydrogen transfer

Selective H transfer by ABC: A new asymmetric binary acid catalyst was developed to promote 1,5-H transfer specifically and stereoselectively in tert-aminocyclization reactions with excellent activity, high enantioselectivity, and broad substrate scope. The H atom (in red) was proven to transfer through a stereospecific suprafacial pathway (see scheme).     

Attenuation auto-correction method in Raman distributed temperature measurement system

A novel method to auto-correct and compensate the attenuation in Raman distributed temperature sensors is proposed. This method utilizes a fiber in loop configuration combined with a reference temperature in the front section to cancel out the impact of attenuation generated by different wavelengths, local external perturbations and environment changes. The conception is successfully verified by theory and experiments. Rapid measurements are shown, with 1,250 m fiber in loop configuration, allowing for a $2.5\,^{\circ }\text{ C }$ 2.5 ° C improved temperature accuracy compared to the conventional method.     

Recent Progress in Chemiluminescence for Gas Analysis

Abstract

Chemiluminescence is frequently used as a powerful analytical tool for gas analysis. In this mini-review with 102 references, we summarize the recent advances in chemiluminescence-based analytical methodologies and their application in gas/volatile species analysis, mainly including applications of ozone-induced chemiluminescence, cataluminescence-based gas sensors and arrays, and dielectric barrier discharge–induced chemiluminescence for gas analysis. Efforts in the innovation of the methodologies, the exploration of new sensing materials, and the mechanism studies are discussed in detail.     

The optimal harvesting policy for non-autonomous populations with discount

Infinite horizon and non-autonomous optimal harvesting problems with discounted instantaneous utility are considered in this work. We first show that the optimal harvesting policy exists for a class of single populations by using the maximum principle. Second, the explicit expressions for the optimal harvesting policy and the maximum yields of logistic, Gompertz and Gilpin–Ayahs systems are obtained.     

Finite p-groups with small subgroups generated by two conjugate elements

In this paper, we study the properties of a finite p-group G such that ${|\langle x, x^y \rangle:\langle x \rangle| \leq p}$ for all ${x,y \in G}$ . Such groups relate to a problem posed by Berkovich and Janko (Groups of prime order, Walter de Gruyter, Berlin, vol. 3, 2011) (Problem 1762). For such a group G, we mainly get the exponent of G′ and the nilpotent class of G.     

On Hypercentral Groups G With |G:G n |<∞

In 1960, Baumslag, following up on work of Cernikov for the 1940s, proved that a hypercentral p-group G with G = G ^p is a divisible Abelian group. In this article, we provide an interesting generalization of this 45 year old result: If a hypercentral p-group G satisfies |G:G ^p |<∞ (of course, it contains G = G ^p ), there exists a normal divisible Abelian subgroup D such that |G:D|<∞.     

Recoil proton tagged knockout reaction for He

We report for the first time the discrimination of the core fragment knockout and valence nucleon knockout reaction mechanisms at medium energy range, by the use of the recoil proton tagging technique. Intense ⁸He beams at 82.3 MeV/u were supplied by the RIPS beam line at RIKEN, and impinged on both hydrogen and carbon targets. Recoil protons were detected in coincidence with the forward moving core fragments and neutrons. The core fragment knockout mechanism is identified through the polar angle correlation and checked by various kinematics relations. This mechanism may be used to extract the cluster structure information of unstable nuclei. On the other hand, with the selection of the tagged valence nucleon knockout mechanism, a narrower peak of ⁷He ground state is obtained. The extracted neutron spectroscopic factor Sn=0.512(18) is relatively smaller than the no-tagged one, and is in good agreement with the prediction of ab initio Green?s function Monte Carlo calculations.     

A fluorescence chemosensor based on peptidase for detecting nickel(II) with high selectivity and high sensitivity

We report herein a new class of metal ion chemosensors and give the first example of a metal-dependent peptidase chemosensor for metal ions. The chemosensor contains the basic specific Ni(II)-dependent peptide bond hydrolysis sequence (Gly-Ala-Ser-Arg-His-Trp-Lys-Phe-Lys). The substrate was labeled with a fluorophore at the N-terminal and a quencher at the C-terminal Lys side chain. Initially, the MOCAc ((7-methoxycoumarin-4-yl)acetyl-) emission was quenched by the nearby quencher. In the presence of Ni(II), the substrate was irreversibly cleaved at the cleavage site, leading to a 20-fold increase in fluorescence intensity. The chemosensor combines the high selectivity of a peptidase (at least greater than tenfold for Ni(II) over other metal ions) with the high sensitivity of fluorescence detection limit of 50 nM and can be applied for the quantitative detection of Ni(II) over a concentration range of three orders of magnitude. Given this degree of selectivity and sensitivity, our molecular engineering design may prove useful in the future development of other peptidase-based probes for different metal ions in toxicological and environmental monitoring.