No abstract

Vertical profiles of virus-like particles (VLPs] and bacteria were determined by near-synoptic sampling through the water column and 15 to 25 cm into the sediment at 5 stations across the mouth of Chesapeake Bay, USA. VLPs were about 10 times more abundant in the pore water (grand mean = 3.6 X 10' VLPs ml-l) than in the water column (grand mean = 3.8 X 107 VLPs ml-l). Similarly, bacteria counts were about 3 tmes higher in the pore water (grand mean = 6.5 X 10' bacteria ml-l) than in the water column (grand mean = 2.4 X 106 bacteria ml-l). The virus to bacteria ratio (VBR) was greater in the pore water (range = 29 to 85) than in the water column (range = 12 to 17). The VBR was lowest in the water-over-boxcore samples and variable in the pore water. Counts of VLPs and bacteria were positively correlated in the water column, although neither was correlated to chlorophyll a. In the water column, VLP and bacteria counts exhibited significant differences among stations, with the highest values on the southern side of the Bay mouth. In the pore water, VLP abundance varied with depth and was negatively correlated to grain size. Bacteria abundance was highest at the sediment-water interface, decreased in the first cm of sediment, was uniform in the deeper horizons, and showed no significant relationship with grain size. Bacteria counts in pore water were not significantly different among stations. In contrast, VLP abundances in pore water were significantly different among stations, although they did not increase in abundance from north to south across the Bay mouth, as did counts of water-column VLPs. These are the first data ind~cating the abundance of VLPs below the surface layer of sediment In aquatic systems and demonstrate that VLPs are components of the sedimentary microbial community to at least 25 cm depth.

In this study, Mo 3 Se 3 − single-chain atomic crystals (SCACs) with atomically small chain diameters of ∼0.6 nm, large surface areas, and mechanical flexibility were synthesized and investigated as an extracellular matrix (ECM)mimicking scaffold material for tissue engineering applications. The proliferation of L-929 and MC3T3-E1 cell lines increased up to 268.4 ± 24.4% and 396.2 ± 8.1%, respectively, after 48 h of culturing with Mo 3 Se 3 − SCACs. More importantly, this extremely high proliferation was observed when the cells were treated with 200 μg mL −1 of Mo 3 Se 3 − SCACs, which is above the cytotoxic concentration of most nanomaterials reported earlier. An ECM-mimicking scaffold film prepared by coating Mo 3 Se 3 − SCACs on a glass substrate enabled the cells to adhere to the surface in a highly stretched manner at the initial stage of cell adhesion. Most cells cultured on the ECM-mimicking scaffold film remained alive; in contrast, a substantial number of cells cultured on glass substrates without the Mo 3 Se 3 − SCAC coating did not survive. This work not only proves the exceptional biocompatible and bioactive characteristics of the Mo 3 Se 3 − SCACs but also suggests that, as an ECM-mimicking scaffold material, Mo 3 Se 3 − SCACs can overcome several critical limitations of most other nanomaterials.

We determined the probability of mating as a function of population density in the estuarine copepod Acartia hudsonica by combining experimental measurements with a simple model. Pairs of unmated copepods were confined in containers of various volumes to simulate variable population density, and experiments were run for 8, 16, and 24 h. Mating frequencies indicated that males search for females at an effective search volume rate of 0.34 6 0.15 L h 21 or 8.2 6 3.5 L d 21 and that males become ready to mate only after ,15 h exposure to the females. We applied these parameters in a simple population model to determine the critical density for zero population growth. With high egg production, zero mortality, and residence time of 60 d, the critical density for A. hudsonica was 0.01 m 23 , at the low end of the range of observed population densities. Critical densities for less favorable conditions were well within the range of observed population densities, even allowing for the effects of aggregation. Thus, mate limitation in sexually reproducing organisms, or Allee effects, can cause negative density dependence in growth rate of these populations at low but realistic population densities. We applied these results to the introduction of exotic zooplankton via ships' ballast water under various scenarios of initial dilution in harbors and subsequent conditions for reproduction and survival. Inocula resulting from the discharge of postexchange ballast water were often high enough to establish new resident populations.

The optimum solvent for Nb2Se9 dispersion, which is a new type of one dimensional (1D) material, is investigated. Among several solvents (16 solvents in total), strong dispersion was observed in benzyl alcohol, isopropyl alcohol, isobutyl alcohol, and diacetone alcohol, which have medium dielectric constants in the range of 10 to 30 and surface tension in the range of 25 to 35 mJ m−2. 1D Nb2Se9 chains, whose size is less than 10 nm, are well dispersed and it is possible to disperse mono-chains of 1 nm or less in a specific dispersion region. The 1D unit chain with dangling bond free surface and high volume to area ratio is expected to be used in applications that utilize the surface of the material. Such dispersion is an important first step towards various potential applications and is an indispensable scientific goal for the practical applications of Nb2Se9.