713 research outputs found
An atlas of endohedral Sc2S cluster fullerenes
Structural identification is a difficult task in the study of metallofullerenes, but understanding of the mechanism of formation of these structures is a pre-requisite for new high-yield synthetic methods. Here, systematic density functional theory calculations demonstrate that metal sulfide fullerenes Sc2S@Cn have similar cage geometries from C70 to C84 and form a close-knit family of structures related by Endo-Kroto insertion/extrusion of C2 units and Stone-Wales isomerization transformations. The stabilities predicted for favoured isomers by DFT calculations are in good agreement with available experimental observations, have implications for the formation of metallofullerenes, and will aid structural identification from within the combinatorially vast pool of conceivable isomers
Observations of Coronal Mass Ejections with the Coronal Multichannel Polarimeter
The Coronal Multichannel Polarimeter (CoMP) measures not only the
polarization of coronal emission, but also the full radiance profiles of
coronal emission lines. For the first time, CoMP observations provide
high-cadence image sequences of the coronal line intensity, Doppler shift and
line width simultaneously in a large field of view. By studying the Doppler
shift and line width we may explore more of the physical processes of CME
initiation and propagation. Here we identify a list of CMEs observed by CoMP
and present the first results of these observations. Our preliminary analysis
shows that CMEs are usually associated with greatly increased Doppler shift and
enhanced line width. These new observations provide not only valuable
information to constrain CME models and probe various processes during the
initial propagation of CMEs in the low corona, but also offer a possible
cost-effective and low-risk means of space weather monitoring.Comment: 6 figures. Will appear in the special issue of Coronal Magnetism,
Sol. Phy
Possible Role of Protein CPG15 in Hippocampal Mossy Fiber Sprouting Under Conditions of Pentylenetetrazole Kindling
We examined changes in expression of the candidate plasticity-related gene 15 (CPG15) in
the dentate gyrus (DG) and hippocampal CA3 region in the pentylenetetrazole (PTZ) kindling
model and investigated the role of this gene in the phenomenon of mossy fiber sprouting
(MFS). Experimental rats were divided into the control and PTZ groups. The epileptic model
was created by intraperitoneal PTZ injection, while control rats were injected with saline.
At days 3, 7, 14, 28, and 42 after the first PTZ injection, Timm staining was scored in the
CA3 hippocampal area, and a product of CPG15 (protein CPG15) was labeled in the DG
stratum granulosum and in the CA3 area using immunohistochemistry. The Timm scores in
the CA3 region increased gradually from day 3 and were significantly higher than those in
the control within the subsequent period. The level of CPG15 protein in the DG and CA3
area decreased gradually until day 14 and returned to the normal level at day 28. The results
obtained indicate, for the first time, that CPG15 may be involved in the process of MFS.
Understanding the molecular mechanisms underlying this phenomenon may lead to successful
therapeutic interventions that limit epileptogenesis.Ми досліджували зміни експресії продукту гена CPG15
у зубчастій звивині (ЗЗ) та зоні CA3 гіпокампа в моделі
пентилентетразолового (ПТЗ-) кіндлінгу та можливу роль цього гена у феномені спрутингу моховитих волокон
(СМВ). Піддослідні щури були поділені на групи контролю та ПТЗ-кіндлінгу. Модель епілепсії створювали за допомогою внутрішньоочеревинних ін’єкцій пентилентетразолу
(ПТЗ); контрольним щурам ін’єкували фізіологічний
розчин. На третю, сьому, 14-ту, 28-му та 42-гу добу після
першої ін’єкції ПТЗ оцінювали забарвлення, за Тіммом, у
зоні CA3. Локалізацію протеїну CPG15 у stratum granulosum ЗЗ та зоні CA3 гіпокампа визначали з використанням
імуногістохімічної методики. Інтенсивність забарвлення, за
Тіммом, у зоні CA3 поступово збільшувалася починаючи з
третьої доби та була вірогідно вищою, ніж така в контролі,
протягом усього наступного періоду. Рівень протеїну CPG15
у ЗЗ та полі CA3 поступово зменшувався до 14-ї доби та
повертався до нормальних значень на 28-му добу. Отримані
результати вперше вказують на те, що CPG15 може бути
залученим у процес СМВ. Зрозуміння молекулярних механізмів, на яких базується цей феномен, може призвести до розробки успішних терапевтичних заходів, котрі обмежували б епілептогенез
Quantifying atmospheric nitrogen deposition through a nationwide monitoring network across China
A Nationwide Nitrogen Deposition Monitoring Network (NNDMN) containing 43 monitoring sites was established in China to measure gaseous NH3, NO2, and HNO3 and particulate NH4+ and NO3− in air and/or precipitation from 2010 to 2014. Wet/bulk deposition fluxes of Nr species were collected by precipitation gauge method and measured by continuous-flow analyzer; dry deposition fluxes were estimated using airborne concentration measurements and inferential models. Our observations reveal large spatial variations of atmospheric Nr concentrations and dry and wet/bulk Nr deposition. On a national basis, the annual average concentrations (1.3–47.0 μg N m−3) and dry plus wet/bulk deposition fluxes (2.9–83.3 kg N ha−1 yr−1) of inorganic Nr species are ranked by land use as urban > rural > background sites and by regions as north China > southeast China > southwest China > northeast China > northwest China > Tibetan Plateau, reflecting the impact of anthropogenic Nr emission. Average dry and wet/bulk N deposition fluxes were 20.6 ± 11.2 (mean ± standard deviation) and 19.3 ± 9.2 kg N ha−1 yr−1 across China, with reduced N deposition dominating both dry and wet/bulk deposition. Our results suggest atmospheric dry N deposition is equally important to wet/bulk N deposition at the national scale. Therefore, both deposition forms should be included when considering the impacts of N deposition on environment and ecosystem health
Multi-plateau magnetization curves of one-dimensional Heisenberg ferrimagnets
Ground-state magnetization curves of ferrimagnetic Heisenberg chains of
alternating spins and are numerically investigated. Calculating several
cases of , we conclude that the spin- chain generally exhibits
magnetization plateaux even at the most symmetric point. In the double- or
more-plateau structure, the initial plateau is generated on a classical basis,
whereas the higher ones are based on a quantum mechanism.Comment: 6 pages, 6 figures embedded, to appear in Phys. Rev. B 01 August 200
Coherent electron-phonon coupling and polaron-like transport in molecular wires
We present a technique to calculate the transport properties through
one-dimensional models of molecular wires. The calculations include inelastic
electron scattering due to electron-lattice interaction. The coupling between
the electron and the lattice is crucial to determine the transport properties
in one-dimensional systems subject to Peierls transition since it drives the
transition itself. The electron-phonon coupling is treated as a quantum
coherent process, in the sense that no random dephasing due to electron-phonon
interactions is introduced in the scattering wave functions. We show that
charge carrier injection, even in the tunneling regime, induces lattice
distortions localized around the tunneling electron. The transport in the
molecular wire is due to polaron-like propagation. We show typical examples of
the lattice distortions induced by charge injection into the wire. In the
tunneling regime, the electron transmission is strongly enhanced in comparison
with the case of elastic scattering through the undistorted molecular wire. We
also show that although lattice fluctuations modify the electron transmission
through the wire, the modifications are qualitatively different from those
obtained by the quantum electron-phonon inelastic scattering technique. Our
results should hold in principle for other one-dimensional atomic-scale wires
subject to Peierls transitions.Comment: 21 pages, 8 figures, accepted for publication in Phys. Rev. B (to
appear march 2001
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