Molecular-dynamics simulations of organic polymer etching by hydrocarbon beams

Molecular-dynamics simulations of hydrocarbon beam injections into a poly (1,4-phenylene) substrate surface are carried out with the use of classical potential functions for covalent bonds of carbon and hydrogen atoms. Van der Waals interactions among carbon atoms are also taken into account. In the low injection energy (50 eV) regime, we have observed that injected carbon atoms tend to be deposited on the surface, whereas hydrogen atoms tend to chemically break carbon bonds in the substrate. With the combination of chemical effects by hydrogen with large momenta carried by the injected carbon atoms, hydrogen-rich carbon clusters can etch organic polymer surfaces with relatively high efficiency. Implications of our simulation results on etching processes of low-dielectric-constant organic polymers by hydrogen-nitrogen plasmas are also discussed. © 2004 American Institute of Physics.H. Yamada et al., Journal of Applied Physics 96, 6147 (2004) https://doi.org/10.1063/1.180890

Overview of research on tuna thermo-physiology using electric tags

The behavioral physiology of bigeye tuna was investigated using acoustic tags in the 1990s. They spend most of the daylight hours below the thermocline but make regular brief excursions into the mixed layer. In doing so, they reduce the efficacy of their vascular countercurrent heat exchangers while gaining heat from the warmer environment and then increase it again when they return below the thermocline. Recently, archival tags have been used on a range of tuna species including bluefin. This tag, recovered when the tuna is harvested, yields time-series data over longer periods than acoustic tags. Although immature Pacific bluefin spend most of their time at the surface, they often dive below the thermocline, maintaining a peritoneal temperature. This might be due either to heat conservation or high heat production. Further, while giant Atlantic bluefin show an ability to maintain their temperature above the ambient, there are occasions in cold water when some physiological process is clearly limiting their dive time. Solution of the growth conundrum that their warm body temperature may pose an ecological problem as they grow in body mass, should be clarified by using tag data. This will lead to investigation of their adaptation mechanisms to their habitats

Pb2+ reduces the current from NMDA receptors expressed in Xenopus oocytes

AbstractWe compared the effects of Pb2+ on four types of NMDA receptors expressed in Xenopus ooeytes. Pb2+ reduced the currents evoked by glutamate and glycine. The Ki values of the receptors, ε1/ζ1, ε2/ζ1, ε3/ζ1 and ε4/ζ1, were 39, 34, 54 and 42 μM, respectively, and their Hill coefficients were 0.53, 4.6, 0.52 and 0.37, respectively. The ε2/ζ1 receptor that was inhibited in the presence of over 30 μM Pb2+ was not recovered to the control level after a Pb2+ washout for over 30 min, suggesting that ε2/ζ1 is responsible for the chronic Pb2+ intoxication in the nervous system

Numerical Analysis of Jets Produced by Intense Laser

In this paper we present a numerical study of plasma jets produced by intense laser matter interactions. Through this study we hope to better understand astrophysical jets and their recent experimental simulations in the laboratory. We paid special attention to radiation cooling and the interaction of the jet with ambient gas. Four cases are presented in this paper; two of them deal with the propagation of jets in vacuum, while in the other two the propagation takes place in the ambient gas. Available experimental results are reproduced to good accuracy in the vacuum case. For jets in ambient gas, we find that the existence of the surrounding gas confines the jet into a narrow cylindrical shape so that both the density and temperature of the jet remain high enough for effective radiation cooling. As a result, a collimated plasma jet is formed in these cases. The dimensionless parameters characterizing the laboratory jets and protostellar jets have overlapping domains. We also discuss the cooling lengths for our model and compare them with the corresponding values in the astrophysical jets. A plasma jet in the ambient gas experiment is proposed which is within the reach of present day technology, and can be relevant to astrophysical phenomena.Comment: Accepted for publication in Ap