Oxygen excess nonstoichiometry and thermodynamic quantities of La2NiO4?+?δ

The oxygen excess nonstoichiometry of La₂NiO_4 + δ is measured as a function of temperature and oxygen partial pressure (pO₂) by coulometric titration method. A positive deviation from the ideal dilution solution behavior is exhibited, and the partial molar thermodynamic quantities of La₂NiO_4 + δ are calculated from the Gibbs–Helmholtz equation for regular solution by introducing the activity coefficient of the charge carriers. The activity coefficient of holes is successfully calculated by using the Joyce–Dixon approximation of the Fermi–Dirac integral. The effective mass of holes ( m_\texth^* m_{\text{h}}^{{*}} ) is 1.27–1.29 times the rest mass (m _h), which indicate the action of band-like conduction and allow the effect of the small degree of polaron hopping to be ignored. The activity coefficient of holes calculated against the oxygen nonstoichiometry clearly illustrates the early positive deviation of the activity coefficient of holes from unit, leading to g_{\texth ^·} \gamma_{{{\text{h}}^{ \bullet }}}  ≈ 14 at δ ≈ 0.08, which is quite close to the literature value of g_{\texth ^·} \gamma_{{{\text{h}}^{ \bullet }}}  ≈ 10 at δ ≈ 0.08. All the evaluated thermodynamic quantities are in good agreement with the experimental literature values.     

Spontaneously aggregated chiral nanostructures from achiral tripod-terpyridine

A chiral tripod-terpyridine ligand is known to coordinate with Ag+. These complexes self-assemble into chiral aggregates at room temperature. Molecular dynamic simulation reveals the cooperation of tripodal ligand structures with Ag(I) cations, which leads to the formation of helical aggregations, thus the chirality.     

EFFECTS OF IONOPHORES AND RUTHENIUM RED ON THE PHOTOTAXIS OF STENTOR COERULEUS AS MEASURED BY SIMPLE DEVICES

Abstract— Two simple methods of phototaxis measurements have been applied to study the effects of ionophores on the negative phototactic response in Stentor coeruleus. The inhibitory effects of Ca²⁺-ionophore (A23187), Ca²⁺-blocking agent (Ruthenium Red), and K⁺ -ionophore (valinomycin) on photo-taxis have been determined. Results suggest that the influx of Ca²⁺ plays a transducing role in the phototaxis of Stentor.     

Depolymerization of Free‐Radical Polymers with Spin Migrations

The mechanism of depolymerization is one of the most essential issues in chemical engineering and materials science. In this work, we investigate the depolymerization reactions of three typical free‐radical poly(alpha‐methylstyrene) tetramers by using first‐principles density functional theory. The calculated results show that these reactions all need to overcome the energy barriers in the range of 0.58 to 0.77 eV, and that breaking the C?C bond at the chain end leads to the dissociation of alpha‐methylstyrene monomers from the polymers. Electronic‐structure analysis indicates that the reactions occur easily at the CR₃ unsaturated end, and that the frontier molecular orbitals that participate in the reactions are mainly localized at the unsaturated ends. Meanwhile, spin population analysis presents the unique net spin‐transfer process in free‐radical depolymerization reactions. We hope the current findings can contribute to understanding the free‐radical depolymerization mechanism and help guide future experiments.     

Terpenoids from the Stems of Drypetes congestiflora

Two new eremophilane‐type sesquiterpenoids, 1α‐hydroxyeremophila‐6,9,11‐trien‐8‐one ( 1 ), 4α‐hydroxyeremophila‐1,9‐diene‐3,8‐dione ( 2 ), and a new friedelane‐type triterpenoid, friedelane‐3α,16β‐diol ( 4 ), along with six known terpenoids, 3 and 5 – 9 , have been isolated from the stems of Drypetes congestiflora. Their structures and relative configurations were elucidated on the basis of detailed spectroscopic analyses and by comparison of their NMR data with those reported in the literature. All of the compounds, 1 – 9 , were isolated for the first time from this species. Compound 3 exhibited moderate cytotoxic activities against the A549 and B16F10 cell lines.     

Simultaneous determination of cadmium(II), lead(II) and copper(II) by using a screen-printed electrode modified with mercury nano-droplets

We are presenting a strategy for the fabrication of disposable screen-printed electrodes modified with mercury nano-droplets and capable of sensing heavy metal ions. They were prepared by coating electrodes with a mixture of multi-walled carbon nanotubes and chitosan, this followed by adsorption of mercury. The resulting sensor was characterized by cyclic voltammetry and impedance spectroscopy. Also the effects caused by adsorption of mercury were investigated. It is shown that square wave anodic stripping voltammetry enables simultaneous determination of cadmium(II), lead(II) and copper(II), for which detection limits of 12, 23 and 20 nM, respectively, are found. Relative standard deviations for ten determinations at 0.6 µM concentrations of these ions are in the range of 3.0 to 5.7%. The applicability was tested by analyzing river water and showed recoveries between 94.1 and 104.6%, thus demonstrating its utility for in-field monitoring of these heavy metal ions.     

The Effect of Backbone Stereochemistry on the Folding of Acyclic β2, 3‐Aminoxy Peptides

As a new type of foldamer, β‐aminoxy peptides have the ability to adopt novel β N? O turns or β N? O helices in solution. Herein, we describe a new subclass of β‐aminoxy peptide, that is, peptides of acyclic β^{2, 3}‐aminoxy acids (NH₂OCHR₁CHR₂COOH), in which the presence of two chiral centers provides insight into the effect of backbone stereochemistry on the folding of β‐aminoxy peptides. Acyclic β^{2, 3}‐aminoxy peptides with syn and anti configurations have been synthesized and their conformations investigated by NMR, IR, and circular dichroism (CD) spectroscopic, and X‐ray crystallographic analysis. The β N? O turns or β N? O helices, which feature nine‐membered rings with intramolecular hydrogen bonds and have been identified previously in peptides of β³‐ and β^{2, 2}‐aminoxy acids, are also predominantly present in the acyclic β^{2, 3}‐aminoxy peptides with a syn configuration and N? O bonds gauche to the C_α? C_β bonds in both solution and the solid state. In the acyclic β^{2, 3}‐aminoxy peptides with an anti configuration, an extended strand (i.e., non‐hydrogen‐bonded state) is found in the solid state, and several conformations including non‐hydrogen‐bonded and intramolecular hydrogen‐bonded states are present simultaneously in nonpolar solvents. These results suggest that the backbone stereochemistry does affect the folding of the acyclic β^{2, 3}‐aminoxy peptides. Theoretical calculations on the conformations of model acyclic β^{2, 3}‐aminoxy peptides with different backbone stereochemistry were also conducted to elucidate structural characteristics. Our present work may provide useful guidelines for the design and construction of new foldamers with predicable structures.     

Counting bacteria on a microfluidic chip

This paper reports a lab-on-a-chip device that counts the number of bacteria flowing through a microchannel. The bacteria number counting is realized by a microfluidic differential Resistive Pulse Sensor (RPS). By using a single microfluidic channel with two detecting arm channels placed at the two ends of the sensing section, the microfluidic differential RPS can achieve a high signal-to-noise ratio. This method is applied to detect and count bacteria in aqueous solution. The detected RPS signals amplitude for Pseudomonas aeruginosa ranges from 0.05 V to 0.17 V and the signal-to-noise ratio is 5-17. The number rate of the bacteria flowing through the sensing gate per minute is a linear function of the sample concentration. Using this experimentally obtained correlation curve, the concentration of bacteria in the sample solution can be evaluated within several minutes by measuring the number rate of the bacteria flowing through the sensing gate of this microfluidic differential RPS chip. The method described in this paper is simple and automatic, and have wide applications in determining the bacteria and cell concentrations for microbiological and other biological applications.     

Cobalt(II)‐Catalyzed C?H Alkynylation/Annulation with Terminal Alkynes: Selective Access to 3‐Methyleneisoindolin‐1‐one

A highly efficient cobalt(II)‐catalyzed alkynylation/annulation of terminal alkynes assisted by an N,O‐bidentate directing group is described. This protocol is characterized by wide substrate scope utilizing cheap cobalt catalysts, and offers a new approach to 3‐methyleneisoindolin‐1‐one, which can be converted into an oxadiazine salt in one step. Moreover, the directing group could be removed in three steps.     

Effect of flow rate on the sorption breakthrough behaviors of uranium(VI), phosphate,and fulvic acid onto a silica column

Five column experiments have been carried out to investigate the effect of flow rate on the breakthrough curves (BTCs) of phosphate, fulvic acid, and uranium(VI) onto a silica column. Both BTCs of phosphate and fulvic acid, and three BTCs of uranium(VI) in the presence and absence of phosphate or fulvic acid at high flow rate published in the previous paper [1] were compared with corresponding initial parts of BTCs at low flow rate in this paper. Each BTC in this paper was expressed as both C/C_o–t and C/C_o–V/V_o plots, where C and C_o are the concentrations in the influent and the effluent respectively, t and V are the time and the effluent volume from the start of injection of pulse solution respectively, V_o is the pore volume of the SiO₂ column. Based on the experimental results and the relationship among V, t, and flow rate F, it was found that there are advantages to using C/C_o–V/V_o plot as BTC to study the effect of flow rate. Based on these comparisons of C/C_o–V/V_o plots at different flow rates and the theoretical analysis from the Bohart–Adams sorption model, it was found that the right shift (increase in V/V_o of breakthrough), the left shift (decrease in V/V_o of breakthrough), and the non-shift (non-change in V/V_o of breakthrough) of initial parts of BTCs with increasing flow rate are certain to occur instead of only left shift and that three different trends of shifts can be mainly attributed to different rate-controlling mechanisms of sorption process.