Nanocarbons, especially two-dimensional carbons, have received considerable attention due to their unique structure and physical and chemical properties, which make them promising candidate materials ...for biomedical applications. In this study, we focus on graphene oxide (GO), which has many oxygenated functional groups and high affinity with water and biomaterials, and the synthesis of GO complexes with antibacterial agents, like cetylpyridinium chloride (CPC) and its derivatives. We found that the sustained release of CPCs from GO can be controlled by changing the terminal functional group of CPC. The prepared GO-CPC complexes were subjected to antibacterial tests against S. mutans. CPC with the carboxy group was degraded by the oxidizing property of GO, resulting in the loss of antibacterial properties. On the other hand, the other CPC derivatives were released from GO and showed antibacterial activities. Finally, we propose a new mechanism describing how GO and CPC form a functional complex, and how CPC is released from this complex. These findings will lead to pioneering the carbon-based functional antibacterial agents designed at the molecular level.
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MicroRNAs (miRNAs) are approximately 21-25 nt long and interact with mRNAs to lead to either translational repression or RNA cleavage through RNA interference. A previous study showed that human ...immunodeficiency virus 1 (HIV-1) nef dsRNA from AIDS patients who are long-term non-progressors inhibited HIV-1 transcription. In the study reported here, nef-derived miRNAs in HIV-1-infected and nef transduced cells were identified, and showed that HIV-1 transcription was suppressed by nef-expressing miRNA, miR-N367, in human T cells. The miR-N367 could reduce HIV-1 LTR promoter activity through the negative responsive element of the U3 region in the 5'-LTR. Therefore, nef miRNA produced in HIV-1-infected cells may downregulate HIV-1 transcription through both a post-transcriptional pathway and a transcriptional neo-pathway.
The brightness of aurorae in Earth's polar region often beats with periods ranging from sub-second to a few tens of a second. Past observations showed that the beat of the aurora is composed of a ...superposition of two independent periodicities that co-exist hierarchically. However, the origin of such multiple time-scale beats in aurora remains poorly understood due to a lack of measurements with sufficiently high temporal resolution. By coordinating experiments using ultrafast auroral imagers deployed in the Arctic with the newly-launched magnetospheric satellite Arase, we succeeded in identifying an excellent agreement between the beats in aurorae and intensity modulations of natural electromagnetic waves in space called "chorus". In particular, sub-second scintillations of aurorae are precisely controlled by fine-scale chirping rhythms in chorus. The observation of this striking correlation demonstrates that resonant interaction between energetic electrons and chorus waves in magnetospheres orchestrates the complex behavior of aurora on Earth and other magnetized planets.
Pulsating auroras (PsAs) are thought to be generated by precipitating electrons scattered by lower‐band chorus (LBC) waves near the magnetic equator. One‐to‐one correlation between the LBC intensity ...and the PsA intensity has been reported. Electrostatic electron cyclotron harmonic (ECH) waves can also scatter electrons. However, direct correlation between ECH and PsA has not been reported yet. In this study, using a coordinated Exploration of energization and Radiation in Geospace (Arase) satellite and ground‐based imager observation, we report that not only LBC but also ECH have correlation with PsA. We estimated the precipitating electron energy by assuming that the time lag when the cross‐correlation coefficient became the highest was travel time of electrons from the modulation region. We found that the estimated energies show reasonable values as the cyclotron resonance energy of each wave.
Plain Language Summary
Pulsating auroras (PsAs), which have quasiperiodic on‐off switching emission, are caused by the intermittent electron precipitation from the magnetosphere. Such electrons are precipitated by wave‐particle interactions. The candidate waves to interact with electrons are lower‐band chorus (LBC) and electrostatic electron cyclotron harmonic (ECH) waves. One‐to‐one correspondence between the LBC wave intensity and the PsA intensity has been reported by previous studies. However, the correlation between ECH and PsA has not been reported yet. In this study, using a coordinated Exploration of energization and Radiation in Geospace (Arase) satellite and ground‐based all‐sky imager observation, we report that not only LBC but also ECH waves have correlation with PsAs.
Key Points
The lower‐band chorus and electrostatic electron cyclotron harmonic wave intensities had correlation with the pulsating auroral intensity
Taking advantage of high sampling rate of the imager, we estimated the energy of precipitating electrons
The energy of precipitating electrons was reasonable compared with the cyclotron resonance energy of each wave
Over‐Darkening of Pulsating Aurora Hosokawa, K.; Miyoshi, Y.; Oyama, S.‐I. ...
Journal of geophysical research. Space physics,
April 2021, Letnik:
126, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Recent analyses of high‐time resolution ground‐based optical observations of pulsating aurora (PsA) have reported that the brightness of PsA sometimes decreases below the diffuse background level ...immediately after the ON phase of the main pulsation finishes. To date, however, the generation mechanism of such an “over‐darkening PsA” is still unclarified. In this study, we investigated the characteristics of the over‐darkening PsA by using simultaneous observations of PsA with an electron multiplying charge coupled device all‐sky camera in Sodankylä, Finland and the Arase satellite. During one of the conjunction events in Scandinavia on March 29, 2017, almost all the PsA pulses showed clear over‐darkening characteristics. By analyzing the 2D all‐sky images at the times of over‐darkening we discovered that over‐darkening areas appeared in the trailing edge of PsA patches and moved in tandem with the poleward propagating patches. It was also found that similar over‐decreasing characteristics were not seen in the chorus data from the wave instruments onboard Arase located at the magnetospheric counterpart of PsA. These results indicate that the over‐darkening PsA is not caused by a temporal variation of chorus at a fixed point, but is produced by a propagation of over‐darkening area with PsA patches. That is, the over‐darkening PsA is a result of compounding effects of spatial structure and recurrent propagation of PsA. The mechanism creating the dark area is still unknown, but the existence of over‐darkening PsA suggests that the temporal variation of PsA is not always a perfect copy of the modulation of lower‐band chorus waves in the magnetosphere.
Plain Language Summary
Pulsating auroras (PsAs) are characterized by quasi‐periodic variations in the brightness whose period typically ranges from a few to a few tens of second. Coordinated ground/satellite observations in the last decade demonstrated that the main optical pulsation well correlates with the intensity modulation of electromagnetic wave called “chorus” in the magnetosphere. Recent optical observations of PsA using high‐speed cameras have reported that the brightness of PsA often decreases below the diffuse background level immediately after the ON phase of the optical pulsation. In this study, we investigate the characteristics of such “over‐darkening PsAs” by using simultaneous observations of PsA with an all‐sky camera in Finland and the magnetospheric satellite Arase. By analyzing the 2D all‐sky images of over‐darkening PsA on March 29, 2017, we discovered that over‐darkening areas appeared in the trailing edge of PsA patches and moved in tandem with the poleward propagating patches. Similar over‐decreasing characteristics were not identified in the chorus data from Arase located at the magnetospheric counterpart of PsA. These results indicate that the over‐darkening PsA is not a pure temporal variation of chorus at a fixed point, but a result of compounding effects of spatial structure and dynamical motion of PsA.
Key Points
Over‐darkening of pulsating aurora (PsA) was observed during an interval of conjugate observation with the Arase satellite
Corresponding over‐decreasing of chorus wave intensity was not seen in the wave data from Arase
Over‐darkening is caused by a passage of dark region on the trailing edge of the PsA patch across the sensing area
A specialized ground‐based system has been developed for simultaneous observations of pulsating aurora (PsA) and related magnetospheric phenomena with the Arase satellite. The instrument suite is ...composed of (a) six 100 Hz sampling high‐speed all‐sky imagers (ASIs), (b) two 10 Hz sampling monochromatic ASIs observing 427.8 and 844.6 nm auroral emissions, (c) a 20 Hz sampling fluxgate magnetometer. The 100 Hz ASIs were deployed in four stations in Scandinavia and two stations in Alaska, which have been used for capturing the main pulsations and quasi 3 Hz internal modulations of PsA at the same time. The 10 Hz sampling monochromatic ASIs have been operative in Tromsø, Norway with the 20 Hz sampling magnetometer. Combination of these multiple instruments with the European Incoherent SCATter (EISCAT) radar enables us to detect the low‐altitude ionization due to energetic electron precipitation during PsA and further to reveal the ionospheric electrodynamics behind PsA. Since the launch of the Arase satellite, the data from these instruments have been examined in comparison with the wave and particle data from the satellite in the magnetosphere. In the future, the system can be utilized not only for studies of PsA but also for other classes of aurora in close collaboration with the planned EISCAT_3D project.
Key Points
An integrated package of instruments for high‐time resolution measurements of pulsating aurora was deployed in Scandinavia and Alaska
The system has enabled us to capture the fine‐scale spatio‐temporal variations of pulsating aurora in a wide area
Data from those instruments have also been used for simultaneous observations of pulsating aurora with the Arase satellite
Five-lamina (C3-7) procedure is the most popular cervical laminoplasty and there have been no studies on the most appropriate number of laminae to be opened. We prospectively reduced the range of ...laminoplasty from C3-7 to C3-6 in 2002 and compared the outcome of C3-6 laminoplasty (n=37) to that of C3-7 laminoplasty (n=28). In both groups, neurological gain was satisfactory, radiographic changes were minimal, and postoperative MRI indicated sufficient expansion of the dura and the spinal cord. Average operating period was significantly shorter, and length of the operative wound was significantly less in the C3-6 group than in the C3-7 group. Postoperative axial neck pain was significantly rarer after C3-6 laminoplasty than after C3-7 laminoplasty (5.4% vs. 29%, P=0.015). Due to its simplicity and various benefits, C3-6 laminoplasty is a promising alternative to conventional C3-7 laminoplasty for treatment of multisegmental compression myelopathy.
We analyzed neutral winds, ambipolar diffusion coefficients, and neutral temperatures observed by the Nippon/Norway Tromsø Meteor Radar (NTMR) and ion temperatures observed by the European Incoherent ...Scatter (EISCAT) UHF radar at Tromsø (69.6°N, 19.2°E), during a major stratospheric sudden warming (SSW) that occurred in January 2009. The zonal winds at 80–100 km height reversed approximately 10 days earlier than the zonal wind reversal in the stratosphere and the neutral temperature at 90 km decreased simultaneously with the zonal wind reversal at the same altitude. We found different variations between geomagnetically quiet nighttime ion temperatures at 101–110 km and 120–142 km for about 10 days around the SSW. Our results from the ground‐based observations agree well with the satellite observations shown in an accompanying paper. Thus, this study indicates that a SSW is strongly linked to thermal structure and dynamics in the high‐latitude mesosphere, lower thermosphere, and ionosphere.
Although proteins may be artificially improved by random insertion and deletion mutagenesis methods, these procedures are technically difficult, and the mutations introduced are no more variable than ...those introduced by the introduction of random point mutations. We describe here a three-step method called RAISE, which is based on gene shuffling and can introduce a wide variety of insertions, deletions and substitutions. To test the efficacy of this method, we used it to mutate TEM β-lactamase to generate improved antibiotic resistance. Some unique insertion or deletion mutations were observed in the improved mutants, some of which caused higher activities than point mutations. Our findings indicate that the RAISE method can yield unique mutants and may be a powerful technique of protein engineering.
The question to which extent the divergence of the Hall current can be connected to the Pedersen current or to the closure current in the magnetosphere through field‐aligned currents (FACs), that is, ...the Cowling channel process in the polar region, has long been debated but not fully understood. The present study reformulates the Cowling channel by introducing a two‐layer model consisting of Hall and Pedersen conductivity layers with channel boundaries not only in the direction perpendicular to the channel but also in the direction along it. This new model enables us to better and more physically understand the connection between the Hall current, Pedersen current, and FAC. In particular, the finiteness of the channel along its direction enables us to understand that the primary nonzero electric field along the channel and FACs at the channel boundaries that faced each other in the channel direction carries the necessary energy for the Hall current to set up the secondary electric field from the magnetosphere. A case for a possible connection between the Pedersen and Hall currents is shown based on a polar current system derived from the Kamide‐Richmond‐Matsushita method. A more comprehensive analysis based on data is presented in the companion paper.
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