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1.
In this work, density functional theory (DFT) combined with the finite field (FF) method has been adopted to analyze the second-order nonlinear optical (NLO) properties of the triarylborane (TAB) derivatives obtained by introducing different inductive electron groups into the phenylene ring of the TAB (RTAB, where R=2-C6H5-C2B10H10(1),R=F(2), R=Me(3),R=NO2(4),R=NH2(5)). The static first hyperpolarizabilities (βtot) of the RTAB molecules can be switched by binding one F- to the boron center (RTAB′) or one-electron reduction (RTAB"). The DFT-FF calculations show that the βtot values of 2′, 3′ and 5′ decrease while those of 1′ and 4′ increase compared with the values of their neutral molecules, which was attributed to the fact that the charge transfers of 2, 3 and 5 become smaller and those of 1 and 4 become larger by binding one F- ion to the boron center, according to time-domain DFT (TD-DFT) analysis. However, the incorporation of one electron enhances the second-order NLO properties of the RTAB molecules remarkably, especially for system 1. It is notable that the βtot value of reduced form 1″ is 508.69×10-30 esu, i.e. about 578 times larger than that of system 1. Frontier molecular orbital (FMO) and natural bond orbital (NBO) analyses suggest that the reversal of the charge distribution between the neutral molecules and their reduced forms leads to low HOMO-LUMO energy gaps (E0) and thus large βtot values for the reduced forms. 相似文献
2.
LIU Ruiyuan LIU Shunlin XU Zhonghua WU Jian WANG Xianyi ZHANG Beichen HU Hongqiao 《科学通报(英文版)》2006,51(3):352-357
IONOSPHERIC MOTIONS AND VARIATIONS ARE AFFECTED BY THE SOLAR WIND AND THE MAGNETOSPHERE FROM THE UPPER AND THE MESOSPHERE FROM THE LOWER. APART FROM DIURNAL, SEASONAL AND SOLAR CYCLE VARIATIONS, THE IONOSPHERE EX- PERIENCES AN OBVIOUS DAY-TO-DAY VARIATION… 相似文献
3.
SiCN thin films were synthesized by a radio frequency chemical vapor deposition (RFCVD) system on P-type Si (1 0 0) wafers
using C2H4, SiH4 and N2 as raw materials, In order to get rid of the oxygen absorbed on the surface and improve the characteristics of electron field
emission, Ar+ ions of low energy were used to bombard the samples. The field emission characteristics of SiCN thin films before and after
Ar+ bombardment were studied in the super vacuum environment of 10−6 Pa. It was showed that the turn-on field (defined as the point where the current-voltage curve shows a sharp increase in
the current density) decreased from 38 V/μm before bombardment to 25 V/μm after bombardment. And the maximum emission current
density increased from 159.2 to 267.4 μA/cm2. The composition before and after Ar+ bombardment was compared using X-ray photoelectron spectroscopy (XPS). Our results illustrated that the field emission characteristics
were improved after the bombardment of Ar+.
Foundation item: Supported by the National Natural Science Foundation of China (19975035)
Biography: Ma You-peng (1978), male, Master candidate, research direction: novel functional materials film and ion beam modification
of materials. 相似文献
4.
Discovery of C<Subscript>4</Subscript> species at high altitude in Qinghai-Tibetan Plateau 总被引:1,自引:0,他引:1
WANG Luo LU Houyuan WU Naigin CHU Duo HAN Jiamao WU Yuhu WU Haibin & GU Zhaoyan Institute of Geology Geophysics Chinese Academy of Sciences Beijing ChinaTibet Institute of Plateau Atmospheric Environmental Sciences Lhasa China Northwest Institute of Plateau Biology Chinese Academy of Sciences Xining China Institute of Earth Environment Chinese Academy of Sciences Xi''''an China 《科学通报(英文版)》2004,49(13):1392-1396
Plant specimens are collected from the areas between latitude 27°?2′N and 40°57′N, and longitude 88°93°E and 103°24′E, with an altitudinal range from 2210 to 5050 m above the sea level in Qinghai-Tibetan Plateau. The stable carbon isotope analysis indicates that two of Chenopodiaceae and six of Poaceae in the samples are C4 plants. Four of the C4 plants are found in 11 spots with altitudes above 3800 m, and Pennisetum centrasiaticum, Arundinella yunnanensis and Orinus thoroldii are present in six spots above 4000 m, even up to 4520 m. At low CO2 partial pressure, that sufficient energy of high light improving C4 plant's tolerance of low temperature and precipitations concentrating in growing season probably are favorable for C4 plants growing at high altitude in Qinghai-Tibetan Plateau. 相似文献
5.
Using a new ground-state ab initio potential energy surface reported by Deskevich et al., the product polarizations in the reactions F+HCl→HF+Cl and F+DCl→DF+Cl
were studied by employing the quasi-classical trajectory method. At a collision energy of 10 kcal/mol, the four generalized
polarization-dependent differential cross-sections (2π/σ)(dσ00/dω
t
), (2π/σ)(dσ20/dω
t
), (2π/σ)(dσ22+/dω
t
) and (2π/σ)(dσ21−/dω
t
) were calculated in the center-of-mass frame. The distribution of the angle between k and j′, P(θ
r
), the distribution of the dihedral angle denoting the k-k′-j′ correlation, P(φ
r
), and the angular distribution of the product rotational vectors in the form of polar plots P(θ
r
, φ
r
) were also calculated. The evident influence of isotope substitution on the product polarization is revealed. This effect
may result from the different mass factors of the two reactions. 相似文献
6.
THe effects of strong convection electric field on the electron density in the auroral ionosphericF-region have been simulated numerically by means of a physical model. It is found that an enhancement of electric field directed
west-northward in post-noon or west-southward in pre-noon results in an ionization depletion with its maximum at altitudes
40–50 km higher than that of theF
2 peak. When the enhanced electric field lasts for 45 min and has a maximum about 32 mV/m, the resulted ionization depletions
reach their maximum at the time just ∼10 min behind the time when the convection electric field and ion temperature enhancements
reach their maximum. This is consistent well with EISCAT observations. The magnitudes of the percentage ionization depletions
and their recovery time are dependent not only on the intensity of the electric field, but also on the diurnal variation phase
of the background electron density.
Foundation item: Supported by the National Natural Science Foundation of China (49674241, 40074039) and the Research Fund
for the Doctoral Program of Higher Education in China
Biography: Cai Hong-tao (1976-), male, Ph. D. candidate, research direction: polar ionospheric modeling. 相似文献
7.
测量Fe28Al和Fe40Al合金的正电子寿命谱参数,计算合金基体和缺陷处的价电子密度。Fe28Al和Fe40Al合金基体的价电子密度(nb)分别为410×10-2au和236×10-2au,表明当Al和Fe结合形成Fe28Al或Fe40Al合金时,Al原子提供价电子与Fe原子的3d电子形成局域的共价键,Fe28Al和Fe40Al合金中金属键和共价键共存。两种合金均有开空间大的缺陷,晶界缺陷处价电子密度(nd)〔132×10-3au(Fe28Al),470×10-3au(Fe40Al)〕比基体的低,表明晶界处的键合力较弱。Fe40Al合金晶界缺陷的开空间比Fe28Al的大。 相似文献
8.
LI PanLai GUO QingLin WANG ZhiJun PANG LiBin LIANG BaoLai 《科学通报(英文版)》2007,52(8):1024-1028
A non-synchronously-numerating experimental system is applied in this research.The effect of the incident beam intensity I and the beam incident angleθon beam fanning effect is investigated with a singular beam incident on Ce:KNSBN crystal.The results show that the beam fanning effect strongly depends on I andθ.The threshold effect of I for the beam fanning in Ce:KNSBN crystal is observed,and the threshold intensity of incident beam keeps the same value of 38.2 mW/cm 2 for differentθ,and the steady beam fanning intensity Ifsat reaches a peak atθ=15°under the same I.In addition,the effect of the incident beam modulated on the beam fanning noise and holographic storage in Ce:KNSBN crystal is studied.And the results suggest that the beam fanning noise is effectively suppressed,and the quality of the reappearance image is greatly improved. 相似文献
9.
On March 11, 2011, a large earthquake of Mw=9.0 occurred near the east coast of Honshu, Japan. This paper investigates preearthquake ionospheric anomalies during the earthquake period, using data from global navigation satellite systems and ionosonde stations near the epicenter. A clear anomaly that occurred on March 8 lasted 6 hours. Eliminating ionospheric anomalies that may have been caused by solar activities and magnetic storms, we believe that a positive anomaly on March 8 was very possibly an ionospheric precursor. The affected ionospheric area on March 8, which is evident on a vertical total electron content distribution map, extended to 50° in longitude and 20° in latitude, with length ratio approximately 3:1. The anomaly peak arose from 15:00-19:00 LT, and its location did not coincide with the vertical projection of the epicenter, but was instead to its south. Corresponding ionospheric anomalies are also observed in the magnetically conjugated region. There were no obvious ionospheric anomalies in other parts of the world. To analyze changes in the ionospheric anomaly, computerized ionospheric tomography technology was used to invert the spatial and temporal distribution of electron density in the ionosphere. The ionospheric anomaly on March 8, 2011 is suggested to be an ionospheric precursor of the March 11 earthquake in Japan. 相似文献
10.
11.
Conclusions The transition from natural Al-enstatite to garnet and Al-poor pyroxene has taken place under the condition of about 1000°C
and 4.5–5.5 GPa, and new phases of garnet and corundum have formed when 15% Al2O3 was added to the initial natural Al-enstatite. This experimental result has explained the ultrahigh pressure (3.5–5.0 GPa)
and relatively low temperature (< 1000°C) genesis of the ultramafic rock of high-pressure metamorphic zone in Dabieshan-northern
Jiangsu-Jiaodong and of red corundum garnetite coexisting with garnet peridotite. From the genetic mineralogy, petrology andP-T equilibrium conditions of garnet peridotite of the high-pressure metamorphic zone, kimberlite and Cenozoic basalt and the
ultrahigh pressure experimental result, it is inferred that the upper mantle garnet peridotite is transformed with the increase
of depth from Al-rich pyroxene garnet peridotite (80–120 km) to Al-poor pyroxene garnet peridotite (greater than 120–150 km). 相似文献
12.
Photocatalytic degradation of trace-level of MicrocystinLR by nano-film of titanium dioxide 总被引:1,自引:0,他引:1
FENG Xiaogang RONG Fei FU Degang YUAN Chunwei HU Yan 《科学通报(英文版)》2006,51(10):1191-1198
The occurrence of toxic water bloom of cyanobacte-ria algae, widely reported in eutrophic freshwater, hasbeen a serious pollution problem in recent years[1]. Mi-crocystins (MCs), the most common cyanobacteriatoxin with a cyclic heptapeptide structure (Fig… 相似文献
13.
DANG Ge MA ShuYing ZHOU YunLiang 《科学通报(英文版)》2007,52(24):3403-3415
With energetic ion measurements on FAST satellite, the morphologic features of quiet-time ionospheric O ion upflowing at altitudes of 2000 to 4000 km are drawn out for the first time. The pre-noon cusp/cleft is the predominant region of upflowing occurrence for O with lower energy. Meanwhile the pre-dawn sector near the equatorward edge of the plasma convection dominates the occurrence for the higher energy O ions. No matter whether the energy is lower or higher, the upflows occur often over a wide MLT range of lower latitudes outside the auroral oval. The upflowing within the pre-midnight (21:00― 22:00 MLT) auroral oval carrys larger energy fluxes, with extremely large fluxes for higher energy O appearing near the polar cap boundary. For altitudes of 2000―4200 km under observation, the ion conics occur much more frequently than ion beams. Ion beams are rarely found below 3000 km, while the conics occur uniformly over the observed altitudes. 相似文献
14.
A new method on constructing analytical potential energy functions is presented, and then a relatively universal analytical
potential energy function for precisely calculating the spectra of diatomic molecules and ions is derived. Furthermore, six
kinds of common potential energy curves containing three main potential curves i.e. steady state, metastable state and repulsive
state are obtained from this potential energy function. Finally, spectroscopic parameters of thirteen diatomic molecules and
ions including BeD-X
2
Σ
+, BeT-X
2
Σ
+ and Na2-X
1
Σ
g
+ etc are calculated by using the potential function, as a consequence, all calculation results are in good agreement with
experimental data.
Biography: YU Changfeng (1962–), male, Associate professor, research direction: theoretical physics. 相似文献
15.
Distribution characteristics of soil organic matter(SOM) and total nitrogen(TN) were studied in different plant communities of the Yajiageng vertical belt in Gongga Mountain around the Dadu River banks. The results show: (1) the contents of SOM and TN of the plant communities gradually decreased with the following order: subalpine coniferous forest (3 027 m), subalpine meadow (3 873 m), coniferous broadleaved mixed forest(2 737 m), subalpine shrub(3 565 m) and treeline(3 564 m). (2) With soil profile depth increasing, the contents of SOM and TN gradually decreased. For different vegetation types, the contents of SOM and TN in sub-alpine coniferous forest were higher than that of other vegetational types. (3)The ratio of the content of carbon to the content of total nitrogen (Cc/CTN)WaS 13.5-27.6, which was relatively lower than the appropriate Cc/CTN of 25-30, and indicated that the soil in favor of the organic matter decomposed and nutrients released. Cc/CTN in the soil had no correlation with sea level altitude. However, its distribution in the soil x, aried with different vegetation types. (4) Nitrogen in SOM existed mainly in the form of organic nitrogen, and Cc/CTN in the soil was not obvious correlated with SOM and TN. 相似文献
16.
MO Zhongxi ZENG Tao 《武汉大学学报:自然科学英文版》2006,11(3):498-502
In view of the fact that the problem of sorting unsigned permutation by reversal is NP-hard, while the problem of sorting signed permutation by reversal can be solved easily, in this paper, we first transform an unsigned permutation of length n,π (π1 ,… ,πn), into a set S(π) containing 2^n signed permutations, so that the reversal distance of π is equal to the reversal distance of the optimal signed permutation in S(π). Then analyze the structural features of S(π) by creating a directed graph and induce a new computing model of this question. Finally, an improved genetic algorithm for solving the new model is proposed. Experimental results show that the proposed model and algorithm is very efficient in practice. 相似文献
17.
Yong Wei QiuGang Zong ZuYin Pu WeiXing Wan JianJun Liu SuiYan Fu QuanQi Shi 《科学通报(英文版)》2011,56(11):1117-1122
It is believed that a southward interplanetary magnetic field (IMF) is mainly responsible for the energy input from solar
wind into the magnetosphere. This paper presents an unusual case of strong anti-sunward plasma flow (up to 2 km/s) in the
polar cap ionosphere and large cross-polar cap potential (CPCP) during a period of horizontal IMF (|B
Z
| < 2 nT) observed by both ACE (at the L1 point) and Geotail (on the dusk flank of the magnetosheath). The CPCP is even higher
than that under preceding B
Z
≈ −23 nT. Furthermore, GOES8 observed that the magnetosheath field turns northward as the anti-sunward plasma flow and CPCP
start to increase, which implies that the magnetosheath field interacting with the Earth’s magnetopause has significantly
rotated and differs from the IMF observed by ACE and Geotail. In accordance with previous theoretical work, we suggest that
the magnetic field line draping produces a southward magnetosheath field and enhances anti-sunward plasma flow and the CPCP. 相似文献
18.
JIANG Huiming ZHANG Shubiao JIN Rongchao MA Yunhua 《武汉大学学报:自然科学英文版》2007,12(6):1099-1104
Piperidine absorbs CO2 and H2O in air to form a molecular complex: piperidium-l-piperidinecarboxylate-H2O. The structure of the complex was characterized by X-ray single crystal diffraction. The crystal structure was determined to be triclinic, space group P1^-with a=0.648 6(8) nm, b=0.809 200) nm, c= 1.357 1(16) nm, a=96.96706)°, β =102.506(15)°,γ=104.202 05)°, Z=2. The complex is stabilized via five hydrogen bonds between the three components, N-O electrostatic interaction and O-O interaction (electron transfer) betweenl-piperidinecarboxylate and H2O. Due to electron transference of carbamate ion, the oxygen atom in water molecule is strongly negatively charged and the O-H bond is considerably shorter than that of the free molecule of water. The formation of the molecular complex is a reversible process and will decompose upon heating. The mechanism of formation and stabilization is further investigated herein. 相似文献
19.
LI Kaiyang LIU ShenglinSchool of Physics Science Technology Wuhan University Wuhan Hubei China 《武汉大学学报:自然科学英文版》2006,11(2):373-376
0Introduction Near infrared(NIR)techniquesarebasedonsensitive,quantitativemeasurementsoffunctionalcontrastbe tweenhealthyanddiseasedtissue.Recently,researchersshowgreatinterestinmeasuringfunctionalpropertiesofbreasttis suesuchashemoglobinconcentrationoroxygensaturationbyNIRspectroscopyandNIRimaging[1,2].NIRlightcanpene trateseveralcentimetersintotissuebeforeitisattenuatedbe lowdetection.ThemainintrinsicmechanismsofNIRlightat tenuationintissuearethescatteringduetoindexofrefractionvariatio… 相似文献
20.
CHEN Gang~ FAN Yun~ YUAN Yuan~ . School of Mathematics Statistics Wuhan University Wuhan Hubei China . School of Mathematics Statistics Central China Normal University Wuhan Hubei China . School of Computer Wuhan University Wuhan Hubei China 《武汉大学学报:自然科学英文版》2006,11(2):339-342
0Introduction LetGbeafinitegroupoforder|G|=g,andletR(G)denotethecharacterringofG,whichisgeneratedbyalltheirreduciblecomplexcharactersofG.LetZbetherationalintegerringandNthesetofnatural numbers,andletZ[ω]betheintegralextensiongeneratedbyaprimitiveg throotωofunity.SupposethatSisasubringof thealgebraicnumberfieldsuchthatZ[ω]S.πisasetofra tionalprimenumbersdefinedasfollowsπ={p|pisarationalprimenumbersuchthatp-1S}.Definition1WecallthataconjugacyclassCofthefinite groupGisaπregularconju… 相似文献