Modelling the effects of water diversion and combined sewer overflow on urban inland river quality.

In order to assist and optimize the operation of a clean water diversion project for the medium-sized inland rivers in Chaohu, China, an integrated hydrodynamic and water quality model was used in this study. Sixteen diversion scenarios and five sewage interception scenarios were defined to assess the improvement of water quality parameters including ammonia nitrogen (NH3-N), total phosphorus (TP) and chemical oxygen demand (COD) under different diverted water flows, diverting times, diverting points, diverting routines and sewage interception proportions. An index of pollutant removal rate per unit diverted water flow (PRUWF) was proposed to evaluate the effect of the clean water diversion. Results show that operating conditions played important roles in water quality improvement of medium-sized inland rivers. The optimal clean water diversion was operated under the conditions of a flow rate of 5 m3/s for 48 h with an additional constructed bridge sluice. A global sensitivity analysis using the Latin Hypercube One-Factor-at-a-Time (LH-OAT) method was conducted to distinguish the contributions of various driving forces to inland river water restoration. Results show that sewage interception was more important than diverted water flow and diverting time with respect to water quality improvement, especially for COD.

Tuning the Spectroscopic Properties of Ratiometric Fluorescent Metal Indicators: Experimental and Computational Studies on Mag-fura-2 and Analogues.

In this joint theoretical and experimental work, we investigate the properties of Mag-fura-2 and seven structurally related fluorescent sensors designed for the ratiometric detection of Mg2+ cations. The synthesis of three new compounds is described, and the absorption and emission spectra of all of the sensors in both their free and metal-bound forms are reported. A time-dependent density functional theory approach accounting for hydration effects using a hybrid implicit/explicit model is employed to calculate the absorption and fluorescence emission wavelengths, study the origins of the hypsochromic shift caused by metal binding for all of the sensors in this family, and investigate the auxochromic effects of various modifications of the "fura" core. The metal-free forms of the sensors are shown to undergo a strong intramolecular charge transfer upon light absorption, which is largely suppressed by metal complexation, resulting in predominantly locally excited states upon excitation of the metal complexes. Our computational protocol might aid in the design of new generations of fluorescent sensors with low-energy excitation and enhanced properties for ratiometric imaging of metal cations in biological samples.

Visualizing Compartmentalized Cellular Mg2+ on Demand with Small-Molecule Fluorescent Sensors.

The study of intracellular metal ion compartmentalization and trafficking involved in cellular processes demands sensors with controllable localization for the measurement of organelle-specific levels of cations with subcellular resolution. We introduce herein a new two-step strategy for in situ anchoring and activation of a fluorescent Mg2+ sensor within an organelle of choice, using a fast fluorogenic reaction between a tetrazine-functionalized pro-sensor, Mag-S-Tz, and a strained bicyclononyne conjugated to a genetically encoded HaloTag fusion protein of known cellular localization. Protein conjugation does not affect the metal-binding properties of the o-aminophenol-N,N,O-triacetic acid (APTRA)-based fluorescent indicator, which displays a dissociation constant Kd = 3.1 mM suitable for the detection of low millimolar concentrations of chelatable Mg2+ typical of the intracellular environment. We demonstrate the application of our sensing system for the ratiometric detection of Mg2+ in target organelles in HEK 293T cells, providing the first direct comparison of subcellular pools of the metal without interfering signal from other compartments. Activation of the fluorescence in situ through a fluorogenic conjugation step effectively constrains the fluorescence signal to the locale of interest, thus improving the spatial resolution in imaging applications and eliminating the need for washout of mislocalized sensor. The labeling strategy is fully compatible with live cell imaging, and provides a valuable tool for tracking changes in metal distribution that to date have been an unsolved mystery in magnesium biology.

Scheduling jobs with variable job processing times on unrelated parallel machines.

m unrelated parallel machines scheduling problems with variable job processing times are considered, where the processing time of a job is a function of its position in a sequence, its starting time, and its resource allocation. The objective is to determine the optimal resource allocation and the optimal schedule to minimize a total cost function that dependents on the total completion (waiting) time, the total machine load, the total absolute differences in completion (waiting) times on all machines, and total resource cost. If the number of machines is a given constant number, we propose a polynomial time algorithm to solve the problem.

Ligand-free palladium-catalyzed intramolecular Heck reaction of secondary benzylic bromides.

A facile ligand-free palladium-catalyzed intramolecular Heck reaction of ß-hydrogen-containing secondary benzylic bromides was developed, which affords pyrroline derivatives with good regioselectivities.

Study the formation mechanism of silicon carbide polytype by silicon carbide nanobelts sintered under high pressure.

In this paper, in order to reveal the formation mechanism of SiC polytype, four SiC specimens sintered under high pressure has been investigated, after being prepared from SiC nanobelts as initial powders. The structure and morphology variation dependence of SiC specimens with temperature and pressure was studied based on experimental data obtained by XRD, SEM, and Raman. The results show that SiC lattice structure and the crystallite size are greatly affected by pressure between 2 and 4 GPa under different sintering temperatures of 800 and 1200 degrees C. At the largest applied pressure and temperature, 4 GPa and 1200 degrees C, 3C-SiC crystal structure can be changed into to R-SiC due to the stress resulted in dislocations instead of planar defects. Based on our results, the multiquantum-well structure based a single one-dimensional nanostructure can be achieved by applying high pressure at certain sintered temperature.

Palladium-catalyzed tandem diperoxidation/C-H activation resulting in diperoxy-oxindole in air.

A highly efficient and facile palladium-catalyzed tandem diperoxidation and C-H activation process was reported, which provides a new pathway for the synthesis of biologically active diperoxides as well as oxindole derivatives from readily available starting materials in excellent chemical yields.

Copper-catalyzed aminobromination/elimination process: an efficient access to alpha,beta-unsaturated vicinal haloamino ketones and esters.

A novel copper-catalyzed aminobromination-elimination process has been developed, which provides an easy access to alpha,beta-unsaturated vicinal haloamindes derivatives from readily available alpha,beta-unsaturated ketones and esters in good to excellent yields. The isolated intermediate discloses that the current system proceeds through the aminobromination process.

New catalytic system for aminohalogenation of beta-methyl-beta-nitrostyrenes to give opposite regiochemistry.

A new combination of catalyst and co-additive has been found for aminohalogenation reaction of beta-methyl-beta-nitrostyrenes with N,N-dichloro-p-tolunesulfonamide (4-TsNCl(2)). The reaction was achieved by using MnSO(4) as the catalyst together with tolunesulfonamide to give vicinal haloamino nitroalkanes with opposite regiochemistry to that generated from other electron-deficient olefins observed previously. The reaction proceeded smoothly at room temperature under nitrogen atmosphere to give useful to good yields and excellent regio and stereoselectivity. A mechanism involving the formation of chloronium intermediate was proposed to explain the resulting regio and stereochemistry.