Acoustic Observation of the Spawning Aggregation of Megalobrama hoffmanni in the Pearl River

Using the Simrad EY60 split-beam echosounder, the spawning aggregation of Megalobrama hoffmanni was observed at the Luopang spawning grounds in the Pearl River, China, from April 19 to 22 2006. With the boat anchored, the transducer was stationary and was aimed horizontally to monitor the migration of the fish. Using fishery information, the echoes of M. hoffmanni were identified. The results showed that the spawning aggregation of M. hoffmanni at Luopang was obvious and easy to discriminate. The target strength of M hoffmanni in situ ranged from -33.8 dB to -52.3 dB (average 42.2dB). The aggregation of M. hoffmanni was obviously affected by light. With a speed of -0.31 m/s, 88.9% of the spawning stocks migrated upstream. Most M hoffmanni were recorded moving near the bottom. Their distinctive acoustic signature demonstrated the suitability of the stationary acoustic observation for M. hoffmanni identification and discrimination.

Aggregation and precipitation in high dose as ion implanted Ge0.5Si0.5 alloy

Thermally stimulated redistribution and precipitation of excess arsenic in Ge0.5Si0.5 alloy has been studied by X-ray photoelectron spectroscopy (XPS), cross sectional transmission electron microscopy (XTEM) and X-ray energy disperse spectrometry (EDS). Samples were prepared by the implantation of 6 X 10(6) As+ cm(-2) and 100 keV with subsequent thermal processing at 800 degrees C and 1000 degrees C for 1 h. The XPS depth profiles from the implanted samples before and after the thermal annealing indicate that there is marked redistribution of the elements in heavily arsenic-implanted Ge0.5Si0.5 alloys during the annealing, including: (1) diffusion of As from the implanted region to the surface; (2) aggregation of Ge in the vicinity of the surface. A high density of precipitates was observed near the surface which were by XTEM and EDS identified as an arsenide. It is suggested that most of the implanted As in Ge0.5Si0.5 alloy exists in the form of GeAs.

Comparison of aggregation behaviors between branched and linear block polyethers: MesoDyn simulation study

The comparison of aggregation behaviors between the branched block polyether T1107 (polyether A) and linear polyether (EO)(60)(PO)(40)(EO)(60) (polyether B) in aqueous solution are investigated by the MesoDyn simulation. Polyether A forms micelles at lower concentration and has a smaller aggregation number than B. Both the polyethers show the time-dependent micellar growth behaviors. The spherical micelles appear and then change to rod-like micelles with time evolution in the 10 vol% solution of polyether A. The micellar cluster appears and changes to pseudo-spherical micelles with time evolution in the 20 vol% solution of polyether A. However, the spherical micelles appear and change to micellar cluster with time evolution in the 20 vol% polyether B solution. The shear can induce the micellar transition of both block polyethers. When the shear rate is 1x10(5) s(-1), the shear can induce the sphere-to-rod transition of both polyethers at the concentration of 10 and 20 vol%. When the shear rate is lower than 1x10(5) s(-1), the huge micelles and micellar clusters can be formed in the 10 and 20 vol% polyether A systems under the shear, while the huge micelles are formed and then disaggregated with the time evolution in the 20 vol% polyether B system.

A simple and sensitive colorimetric pH meter based on DNA conformational switch and gold nanoparticle aggregation

A simple and rapid colorimetric pH meter has been developed based on the conformational switch of i-motif DNA and non-crosslinking AuNP aggregation, the average accuracy of the nano-meter was found to be +/- 0.04 pH unit across the physiological operating range.

Rapid label-free detection of metal-induced Alzheimer's amyloid beta peptide aggregation by electrochemical method

Amyloid beta peptide plays a critical role in the pathogenesis of Alzheimer's disease (AD). Metal ions are highly enriched in cerebral amyloid deposits in AD and are proposed to be able to mediate A beta conformation. Therefore, a rapid, low-cost, and sensitive detection of metal-induced A beta aggregation and their relation to AD is clearly needed for the clinical diagnosis and treatment. In this report, we study metal-induced A beta aggregation by a rapid, label-free electrochemical method and monitor both the aggregation kinetics and the morphology in the absence or presence of Zn (II) and Cu (II).

Aggregation-based growth of silver nanowires at room temperature

We describe an aggregation-based growth mechanism for formation of silver nanowires at room temperature. It is found that the pH of solution and the concentration of L-cysteine capping molecules have an important effect on the formation and growth of nanowires. Characterization by atomic force microscopy (AFM) and UV-vis spectroscopy recorded as time clearly shows that the silver nanowires are grown at the expense of nanoparticles.

Nucleic Acid-Induced Aggregation and Pyrene Excimer Formation

Nucleic acid was found to induce the aggregation of the positively charged pyrene probe (compound 1); as a result, strong pyrene excimer emission was observed. The intensity of the excimer emission was dependent on the concentration of the pyrene probe and the oligonucleotide length, sequence, and concentration. These results suggest a new strategy for label-free nucleic acid-based biosensing applications.

Tight intermolecular packing through supramolecular interactions in crystals of cyano substituted oligo(para-phenylene vinylene): a key factor for aggregation-induced emission

Strong supramolecular interactions, which induced tight packing and rigid molecules in crystals of cyano substituent oligo(para-phenylene vinylene) (CN-DPDSB), are the key factor for the high luminescence efficiency of its crystals; opposite to its isolated molecules in solution which have very low luminescence efficiency.

Study of controllable aggregation morphology of ABA amphiphilic triblock copolymer in dilute solution by changing the solvent property

We have studied, both experimentally and theoretically, the aggregation morphology of the ABA amphiphilic triblock copolymer in dilute solution by changing the solvent property. Experimental results showed that the micellar morphology changed from spheres to rods and then to vesicles by changing the common solvent from N-N-dimethylformamide (DMF) to dioxane and then to tetrahydrofuran (THF). These controllable aggregates were also obtained by Monte Carlo simulation. The simulative results showed that the solvent property is a key factor that determines the copolymer aggregation morphology. The morphology changed from spheres to rods and then to vesicles by increasing the solvent solubility, corresponding to the change of stretched of the copolymer chains in the micellar cores. This result is in good agreement with the experimental one. Moreover, the simulative results revealed that the end-to-end distant of the ABA triblock copolymer in the vesicle was larger than that in the spheres and rods, indicating that the copolymer chains were more stretched in vesicles than in the spheres and rods. Furthermore, we gave the distribution of the fraction of the chain number with the end-to-end distance. The results indicated that the amount of folded chains is almost the same as that of stretched chains in the vesicle. Although most chains were folded, stretched chains could be found in the rod and sphere micelles.

Monte Carlo simulation of the aggregation of rod-flexible triblock copolymers in a thin film

The aggregation of rod-flexible ABA and BAB triblock (A was rod block and repulsive with block B) copolymers in a thin film was studied as a function of varying the rigidity (eta) and the length of the rod block by Monte Carlo simulation. The rigidity of block A was defined as eta = R-c/R-max in this study. R-c, was the end-to-end distance below which the conformation of the block was not allowed, whereas R-max, was the longest end-to-end distance that the block could be. If eta = 0 the block was flexible, whereas if eta = 1 the block was a straight rod. The simulation results showed that the ABA triblock copolymer film were likely to form lamella structure with increasing the rigidity (eta) of block A. The lamellas were parallel each other and perpendicular to the film surface. However, the aggregation of BAB triblock copolymers tended to change from lamella to cylinder structure with increasing the rigidity (eta) of block A. Typical lamella and cylinder co-exist structure was obtained at eta = 0.504 for the BAB copolymer film. On the other hand, the simulation results indicated that the film changed from disorder to order, then to disorder structure with increasing the relative length of B block for both ABA and BAB copolymer films.