Charge Carrier Heating Effect in Porous Silicon Structures Investigated by Microwaves

Diode-like samples, containing porous silicon structures, were investigated by microwave radiation pulses. The resistance of the samples and electromotive force arising over the samples placed in a section of waveguide was measured. Reduction of resistance of the samples was observed with increase in microwave power. More complicated shape of the electromotive force dependence on pulse power was found. It is shown that both effects could be explained by models based on a concept of carrier heating by microwave radiation

Photoresponse of Porous Silicon Structures to Infrared Radiation

Photoresponse of silicon samples containing porous structures have been studied under the action of $CO_2$ laser radiation. The signal shape and its behavior under the applied bias voltage revealed the existence of two heterojunctions on the border of porous-crystalline silicon and on the border between the porous layers of different porosity. The photosignal is recognized to be composed of hot hole photoemfs induced across the heterojunctions

Studies of Response of Metal - Porous Silicon Structures to Microwave Radiation

Structures containing layers of porous silicon with two metal contacts are investigated. Porous silicon is manufactured by anodizing p-type crystalline silicon plates of resistivity of 0.4 Ω cm. Contacts for the samples are made by additional boron doping of the surface and by thermal evaporation of aluminium. Resistance and current-voltage characteristics are investigated. Response of the porous silicon layer containing structures under action of pulsed microwave radiation was investigated for the first time. The origin of the response is discussed

Offshore permafrost decay and massive seabed methane escape in water depths >20 m at the South Kara Sea shelf

Since the Last Glacial Maximum (~19 ka), coastal inundation from sea-level rise has been thawing thick subsea permafrost across the Arctic. Although subsea permafrost has been mapped on several Arctic continental shelves, permafrost distribution in the South Kara Sea and the extent to which it is acting as an impermeable seal to seabed methane escape remains poorly understood. Here we use >1300 km of high-resolution seismic data to map hydroacoustic anomalies, interpreted to record seabed gas release, on the West Yamal shelf. Gas flares are widespread over an area of at least 7500 km2 in water depths >20 m. We propose that continuous subsea permafrost extends to water depths of ~20 m offshore and creates a seal through which gas cannot migrate. This Arctic shelf region where seafloor gas release is widespread suggests that permafrost has degraded more significantly than previously thought

Characterization of Iron Dinitrosyl Species Formed in the Reaction of Nitric Oxide with a Biological Rieske Center

Reactions of nitric oxide with cysteine-ligated iron−sulfur cluster proteins typically result in disassembly of the iron−sulfur core and formation of dinitrosyl iron complexes (DNICs). Here we report the first evidence that DNICs also form in the reaction of NO with Rieske-type [2Fe-2S] clusters. Upon treatment of a Rieske protein, component C of toluene/o-xylene monooxygenase from Pseudomonas sp. OX1, with an excess of NO(g) or NO-generators S-nitroso-N-acetyl-d,l-pencillamine and diethylamine NONOate, the absorbance bands of the [2Fe-2S] cluster are extinguished and replaced by a new feature that slowly grows in at 367 nm. Analysis of the reaction products by electron paramagnetic resonance, Mössbauer, and nuclear resonance vibrational spectroscopy reveals that the primary product of the reaction is a thiolate-bridged diiron tetranitrosyl species, [Fe[subscript 2](μ-SCys)[subscript 2](NO)[subscript 4]], having a Roussin’s red ester (RRE) formula, and that mononuclear DNICs account for only a minor fraction of nitrosylated iron. Reduction of this RRE reaction product with sodium dithionite produces the one-electron-reduced RRE, having absorptions at 640 and 960 nm. These results demonstrate that NO reacts readily with a Rieske center in a protein and suggest that dinuclear RRE species, not mononuclear DNICs, may be the primary iron dinitrosyl species responsible for the pathological and physiological effects of nitric oxide in such systems in biology.National Institute of General Medical Sciences (U.S.) (grant GM032134)United States. Dept. of Energy (DOE OBER)National Institute of General Medical Sciences (U.S.) (GM065440)National Institutes of Health (U.S.). Biotechnology Training Fellowship (Grant T32 GM08334)National Institute of General Medical Sciences (U.S.) (1 F32 GM082031-03