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In recent years, toxic Microcystis blooms have occurred annually in Lake Taihu, China. In order to elucidate the relationships between photosynthetic activity of Microcystis , Microcystis genotypic composition, microcystin (MC) production and environmental factors, water samples and associated environmental data were collected from January to December 2014 in Lake Taihu. Seasonal variations in photosynthetic activity were measured using a Phyto-PAM Analyzer, abundances of total and toxic Microcystis genotypes were determined by quantitative real-time PCR (qPCR), and MC concentrations were quantified by HPLC. The maximum quantum yield of photosystem II ( F v / F m ) of Microcystis cells changed on a seasonal basis. F v / F m was not detectable in the winter, but increased from spring to early summer, after which, it gradually decreased until the winter. The level of non-photochemical quenching ( NPQ ) increased from March to August and then decreased until December. qPCR data showed that the abundances of total Microcystis genotypes ranged from 1.91 × 10 5 to 8.64 × 10 7 copies/mL and toxic Microcystis genotypes ranged from 2.38 × 10 4 to 5.67 × 10 7 copies/mL. The toxic proportion varied from 12.5 to 65.6%, with an average value of 27.9%. Correlation analysis revealed that there was a positive correlation between photosynthetic activity, genotypic composition and MC production. Water temperature was the only environmental factor that was positively correlated with F v / F m , NPQ , total and toxic Microcystis and intracellular MC. Additionally, total phosphorus was also significantly correlated with intracellular MC. These results indicate that future global warming, in addition to eutrophication, could promote Microcystis blooms in Lake Taihu and that blooms may increase in intensity and toxicity.

The generalized tight-binding model is developed to largely reduce the numerical computation time in calculating optical properties. Modulated electric potentials can control the low-frequency magneto-optical absorption spectra of monolayer graphene. They induce the oscillatory energy dispersions of Landau subbands and the spatial symmetry breaking of the wave function; therefore, the original peaks and extra peaks of different selection rules come into existence simultaneously. Such peaks mainly arise from the band-edge states and/or the middle states. Their number, intensities, frequencies and structures are dominated by the modulation strength and period. More absorption peaks appear with an increase in potential. The extra peaks can relatively easily be observed for higher frequencies and stronger potentials. However, the absorption spectra remain unchanged for a fixed ratio of strength over period.

Electronic structures of nanotube–graphene hybrid carbon systems are calculated by the tight-binding model. The Lennard-Jones potential is used to determine the optimal geometry between nanotubes and a monolayer graphene. The periodic alignment of nanotubes on graphene results in quasi-one-dimensional physical phenomena. The low-frequency energy dispersions are significantly influenced by the interlayer interactions, such as the removal of subband degeneracy, creation of extra band-edge states, and modulation of energy gaps. The composite systems could be either metals or semiconductors according to the alignment and geometry of nanotubes.

The mechanical behavior of multi-walled carbon nanotubes (MWNTs), being fixed at both ends under uniaxial tensile loading, is investigated via the molecular dynamics (MD) simulation with the Tersoff interatomic potential. It is found that Young's modulus of the MWNTs is in the range between 0.85 and 1.16 TPa via the curvature method based on strain energy density calculations. Anharmonicity in the energy curves is observed, and it may be responsible for the time-dependent properties of the nanotubes. Moreover, the number of atomic layers that is fixed at the boundaries of the MWNTs will affect the critical strain for jumps in strain energy density vs. strain curves. In addition, the boundary conditions may affect “yielding” strength in tension. The van der Waals interaction of the double-walled carbon nanotube (DWNT) is studied to quantify its effects in terms of the chosen potential.

Molecular dynamics simulation was carried out to investigate the behavior of (5,5) and (10,10) armchair carbon nanotubes in water under tensile loading. The water molecules inside a nanoscale tube, unlike inside a bulk tube, have a confined effect. The local density distributions of oxygen and hydrogen atoms inside the carbon nanotubes were calculated to find the confinement effect. Moreover, the mechanical behavior of carbon nanotubes in water was studied under tensile loading. The results show that the Young's modulus of nano-tubes in water remains the same as that in vacuum. However, the tensile stress of nanotube in water is less than that in vacuum.

Buckling strengths, in terms of compressive strain, of single-, double- and triple-walled carbon nanotubes (CNTs) are investigated to study the effects of slenderness ratio (S R ) via the molecular dynamics (MD) simulations with the Tersoff potential. Under constant ratio of slenderness, the CNTs with small S R behave like a continuum shell object. For large S R 'S, multi-walled CNTs exhibit the characteristics of the Euler columns. In addition, smaller nanotubes possess higher buckling-resistance. The buckling strength of multi-walled nanotubes is controlled by the size of their outermost shell.

This paper employs molecular dynamics (MD) simulations to investigate the influence of the Ar ion incident energy and incident angle on the surface roughness of Cu films fabricated using the ion assisted deposition (IAD) process. The MD simulations use the tight-binding potential and the Moliere potential to simulate the Cu–Cu and Cu–Ar+ interactions, respectively. The numerical results indicate that the dependency of the surface roughness on the incident angle of the ions is a function of the ion incident energy. At lower incident energies, a weaker dependency exists, and the surface roughness is improved irrespective of the ion incident angle. However, at intermediate and higher ion incident energies, the dependency of the surface roughness on the incident angle becomes more apparent. Under these conditions, a higher incident angle yields an improved surface roughness. Increasing the ion assisted ratio has a similar effect on the surface roughness as increasing the ion incident energy. The results indicate that an excessive ion assisted ratio leads to the formation of a rougher surface; particularly at higher ion incident energies.