Observing Growth and Division of Large Numbers of Individual Bacteria by Image Analysis

We describe a method that enabled us to observe large numbers of individual bacterial cells during a long period of cell growth and proliferation. We designed a flow chamber in which the cells attached to a transparent solid surface. The flow chamber was mounted on a microscope equipped with a digital camera. The shear force of the flow removed the daughter cells, making it possible to monitor the consecutive divisions of a single cell. In this way, kinetic parameters and their distributions, as well as some physiological characteristics of the bacteria, could be analyzed based on more than 1,000 single-cell observations. The method which we developed enabled us to study the history effect on the distribution of the lag times of single cells.     

Light Trapping with Dielectric Scatterers in Single‐ and Tandem‐Junction Organic Solar Cells

Efficient dielectric scatterers based on a mixture of TiO₂ nanoparticles and polydimethylsiloxane are demonstrated for light trapping in semitransparent organic solar cells. An improvement of 80% in the photocurrent of an optimized semitransparent solar cell is achieved with the dielectric scatterer with ≈100% diffuse reflectance for wavelengths larger than 400 nm. For a parallel tandem solar cell, the dielectric scatterer generates 20% more photocurrent compared with a silver mirror beneath the cell; for a series tandem solar cell, the dielectric scatterer can be used as a photocurrent balancer between the subcells with different photoabsorbing materials. The power conversion efficiency of the tandem cell in series configuration with balanced photocurrent in the subcells exceeds that of an optimized standard solar cell with a reflective electrode. The characteristics of polydimethylsiloxane, such as flexibility and the ability to stick conformably to surfaces, also remain in the dielectric scatterers, which makes the demonstrated light trapping configuration highly suitable for large scale module manufacturing of roll‐to‐roll printed organic single‐ or tandem‐junction solar cells.     

Charge Storage Capacity of Renewable Biopolymer/Conjugated Polymer Interpenetrating Networks Enhanced by Electroactive Dopants

Renewable materials are requested for large scale electrical storage, a coming necessity with the growth of intermittent solar and wind renewable electricity generation. Biopolymers are a source of inexpensive materials, in particular through the use of black liquor from paper production, a waste product. Interpenetrating networks of the biopolymer lignosulfonate (Lig) and conjugated polymer polypyrrole (Ppy) are synthesized by galvanostatic polymerization from pyrrole/lignosulfonate mixture in acidic aqueous electrolyte. Methoxy and phenolic functional group present in the non‐conducting lignosulfonate are converted to quinone groups. The redox chemistry of quinones is used for charge storage, along with charge storage in polypyrrole. A large variation of the electrochemical activity between lignosulfonates obtained from different sources is observed. The charge storage capacities are significantly enhanced by also including another electroactive dopant, anthraquinone sulfonate (AQS). AQS redox peaks act as an internal reference (standard) to probe the redox electrochemistry of Lig. The synthesized Ppy(Lig) and Ppy(Lig‐AQS) electrodes are characterized by cyclic voltammetry, galvanostatic charge‐discharge cycling, electrochemical quartz crystal microbalance, and atomic force microscopy.     

Responses to temperature,heavy metal and sediment stress by the giant clam Tridacna squamosa

Increasing seawater temperature, heavy metal concentration and sediment load, all represent environmental stress factors found in the Gulf of Thailand. In the present study we investigate and compare the physiological responses of exposure to increased water temperature (+ 3°C) and copper (50 μg Cu/l) by the giant clam Tridacna squamosa, and the behavioural response to sedimentation.

Both temperature and copper caused significant decrease in P_g: R ratios, although by different physiological responses. In clams exposed to copper, the decrease in P_g: R is caused by reduced photosynthesis, whereas the clams exposed to increased temperature maintained a high photosynthetic rate, but significantly increased their respiration.

Clams responded to additional sediment with increased activity. This augmented activity was further increased for clams previously stressed by copper.