Lagoonal littorinids: Shell shape and speciation

Variables related to shell shape have been measured in littorinids from brackish lagoons and coastal sites. After removal of size related effects, the data were analyzed using multivariate techniques. On Canonical Variate 1 there was good separation of the shells of the lagoonal animals from those of animals from the coast and a tidal lagoon. The former, for example, had lighter, and therefore thinner, shells for any given shell size and a smaller jugosity of the aperture lip. The lagoonal shells from Golam Head and the coastal animals from Robin Hood's Bay could each be separated clearly from the other samples. Although there are clear morphometric differences in the shells, it is not possible without appropriate breeding experiments to raise the lagoonal animals from L. saxatilis var. lagunae (L. tenebrosa) to species status. The importance of conserving lagoonal habitats is considered in terms of the preservation of biodiversit

Infrared light excites cells by changing their electrical capacitance

Optical stimulation has enabled important advances in the study of brain function and other biological processes, and holds promise for medical applications ranging from hearing restoration to cardiac pace making. In particular, pulsed laser stimulation using infrared wavelengths >1.5 μm has therapeutic potential based on its ability to directly stimulate nerves and muscles without any genetic or chemical pre-treatment. However, the mechanism of infrared stimulation has been a mystery, hindering its path to the clinic. Here we show that infrared light excites cells through a novel, highly general electrostatic mechanism. Infrared pulses are absorbed by water, producing a rapid local increase in temperature. This heating reversibly alters the electrical capacitance of the plasma membrane, depolarizing the target cell. This mechanism is fully reversible and requires only the most basic properties of cell membranes. Our findings underscore the generality of pulsed infrared stimulation and its medical potential

Role of Surface Area, Primary Particle Size, and Crystal Phase on Titanium Dioxide Nanoparticle Dispersion Properties

Characterizing nanoparticle dispersions and understanding the effect of parameters that alter dispersion properties are important for both environmental applications and toxicity investigations. The role of particle surface area, primary particle size, and crystal phase on TiO2 nanoparticle dispersion properties is reported. Hydrodynamic size, zeta potential, and isoelectric point (IEP) of ten laboratory synthesized TiO2 samples, and one commercial Degussa TiO2 sample (P25) dispersed in different solutions were characterized. Solution ionic strength and pH affect titania dispersion properties. The effect of monovalent (NaCl) and divalent (MgCl2) inert electrolytes on dispersion properties was quantified through their contribution to ionic strength. Increasing titania particle surface area resulted in a decrease in solution pH. At fixed pH, increasing the particle surface area enhanced the collision frequency between particles and led to a higher degree of agglomeration. In addition to the synthesis method, TiO2 isoelectric point was found to be dependent on particle size. As anatase TiO2 primary particle size increased from 6 nm to 104 nm, its IEP decreased from 6.0 to 3.8 that also results in changes in dispersion zeta potential and hydrodynamic size. In contrast to particle size, TiO2 nanoparticle IEP was found to be insensitive to particle crystal structure

Long-term decline of the Amazon carbon sink

Atmospheric carbon dioxide records indicate that the land surface has acted as a strong global carbon sink over recent decades1, 2, with a substantial fraction of this sink probably located in the tropics3, particularly in the Amazon4. Nevertheless, it is unclear how the terrestrial carbon sink will evolve as climate and atmospheric composition continue to change. Here we analyse the historical evolution of the biomass dynamics of the Amazon rainforest over three decades using a distributed network of 321 plots. While this analysis confirms that Amazon forests have acted as a long-term net biomass sink, we find a long-term decreasing trend of carbon accumulation. Rates of net increase in above-ground biomass declined by one-third during the past decade compared to the 1990s. This is a consequence of growth rate increases levelling off recently, while biomass mortality persistently increased throughout, leading to a shortening of carbon residence times. Potential drivers for the mortality increase include greater climate variability, and feedbacks of faster growth on mortality, resulting in shortened tree longevity5. The observed decline of the Amazon sink diverges markedly from the recent increase in terrestrial carbon uptake at the global scale1, 2, and is contrary to expectations based on models6

Method for studying the physical effect of extracellular matrix on voltage-dependent ion channel gating

Divalent cations can change the actual electrical potential at the outer surface of the plasma membrane. They do so by the so-called Gouy-Chapman-Stern effect which is due to the electrical \u201cmasking\u201d that certain ions, especially divalents, can exert onto the electrically negative charged polar heads of the membrane phospholipids. Chondroitin sulfates can chelate free calcium ions to a different extent based on the spatial arrangement of their sulfate groups and can thus alter the actual availability of screening divalent ions at the outer membrane surface. Voltage-dependent ion channels sense the actual potential difference between the two sides of the plasma membrane and are thus exquisite and extremely sensitive \u201cdevices\u201d able to react to changes in the electrical potential across the membrane. Hence, by recording the shift in the activation curve of well-known voltage-dependent ionic channels it will be possible to study the physical effect of ECM chondroitin sulfates on membrane conductances