Experimental investigation of the streamer zone of long‐spark positive leader using high‐speed photography and microwave probing
The streamer zone of positive leader during the breakthrough phase of long sparks was
experimentally investigated with two methods. One of the methods is the analysis of streamer‐zone
images obtained with a high‐speed framing camera with image enhancement. This method allowed us to
estimate the spatial distribution of streamer density and low‐frequency conductivity in the streamer zone.
The other method is the microwave probing, which we applied for the first time to long sparks. The
attenuation of microwave beam in the streamer zone in our experiments is proportional to the total number
of free electrons inside the microwave beam. Experimental data on the microwave attenuation combined
with the streamer density found using the first method allowed us to estimate the total number of free
electrons in one streamer. The following parameters were obtained. The streamer density in the center of the
streamer zone is (0.6–1)·10^5m^−3, and the total number of streamers in the streamer zone is 4·10^5–10^6. The
average total number of free electrons in one streamer is about 3·10^10. Low‐frequency conductivity
on the axis of streamer zone was estimated to be typically 2·10^−5 S/m, which is similar to that estimated for
corona sheath in lightning. Both methods are based on the assumption of constancy of electric field and
similarity of all streamers inside the streamer zone. The overall results of this study are generally consistent
with this assumption.
The last few decades saw serious changes in the scientific community’s understanding of the nature of lightning discharges in the Earth atmosphere, which, in particular, had to do with the use for such studies of the new scientific equipment installed on spacecraft. The existence of a physical process previously unknown to science, which was given the name of Terrestrial Gamma Flushes, was discovered in the early 1990s. It is characterized by extremely powerful gamma-bursts and radio-frequency pulses generated in the Earth’s upper atmosphere that are observable in a wide range of electromagnetic spectrum frequencies. In order to study this kind of processes and mechanisms generating gamma-bursts, electromagnetic emissions in a wide range of frequencies (including infrared and ultraviolet regions) during high-altitude atmospheric lightning discharges, it is necessary to be able to take ionospheric measurements with a very high time resolution (at the level of a few microseconds), as well as to take simultaneous measurements in the optical, radio and gamma bands.
To address these important scientific problems, on January 25, 2012, using a cargo transportation spacecraft Progress-M, which had performed a mission for the infrastructure of the Iternational Space Station Russian Segment, an academic microsatellite Chibis-M was put into a standalone 513 km circular orbit with an inclination of 52°.
One of the key advances in genome assembly that has led to a significant improvement in contig lengths has been improved algorithms for utilization of paired reads (mate-pairs). While in most assemblers, mate-pair information is used in a post-processing step, the recently proposed Paired de Bruijn Graph (PDBG) approach incorporates the mate-pair information directly in the assembly graph structure. However, the PDBG approach faces difficulties when the variation in the insert sizes is high. To address this problem, we first transform mate-pairs into edge-pair histograms that allow one to better estimate the distance between edges in the assembly graph that represent regions linked by multiple mate-pairs. Further, we combine the ideas of mate-pair transformation and PDBGs to construct new data structures for genome assembly: pathsets and pathset graphs.
Papers about natural protection territories
Many environmental stimuli present a quasi-rhythmic structure at different timescales that the brain needs to decompose and integrate. Cortical oscillations have been proposed as instruments of sensory de-multiplexing, i.e., the parallel processing of different frequency streams in sensory signals. Yet their causal role in such a process has never been demonstrated. Here, we used a neural microcircuit model to address whether coupled theta–gamma oscillations, as observed in human auditory cortex, could underpin the multiscale sensory analysis of speech. We show that, in continuous speech, theta oscillations can flexibly track the syllabic rhythm and temporally organize the phoneme-level response of gamma neurons into a code that enables syllable identification. The tracking of slow speech fluctuations by theta oscillations, and its coupling to gamma-spiking activity both appeared as critical features for accurate speech encoding. These results demonstrate that cortical oscillations can be a key instrument of speech de-multiplexing, parsing, and encoding.
Neuronal nicotinic acetylcholine receptors (NNRs) of the α7 subtype have been shown to contribute to the release of dopamine in the nucleus accumbens. The site of action and the underlying mechanism, however, are unclear. Here we applied a circuit modeling approach, supported by electrochemical in vivo recordings, to clarify this issue. Modeling revealed two potential mechanisms for the drop in accumbal dopamine efflux evoked by the selective α7 partial agonist TC-7020. TC-7020 could desensitize α7 NNRs located predominantly on dopamine neurons or glutamatergic afferents to them or, alternatively, activate α7 NNRs located on the glutamatergic afferents to GABAergic interneurons in the ventral tegmental area. Only the model based on desensitization, however, was able to explain the neutralizing effect of coapplied PNU-120596, a positive allosteric modulator. According to our results, the most likely sites of action are the preterminal α7 NNRs controlling glutamate release from cortical afferents to the nucleus accumbens. These findings offer a rationale for the further investigation of α7 NNR agonists as therapy for diseases associated with enhanced mesolimbic dopaminergic tone, such as schizophrenia and addiction
The paper provides a number of proposed draft operational guidelines for technology measurement and includes a number of tentative technology definitions to be used for statistical purposes, principles for identification and classification of potentially growing technology areas, suggestions on the survey strategies and indicators. These are the key components of an internationally harmonized framework for collecting and interpreting technology data that would need to be further developed through a broader consultation process. A summary of definitions of technology already available in OECD manuals and the stocktaking results are provided in the Annex section.