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1.
Cyclic arylene ethynylene hexamer 1 , composed of alternating 2,7‐anthrylene ethynylene units and meta‐phenylene ethynylene units, was synthesized. It shows C3 symmetry and possesses a flat and rigid conformation with a large equilateral triangle‐like cavity. Macrocycle 1 self‐associates through π–π stacking interactions between the anthracene‐containing macrocyclic aromatic cores with indefinite‐association constant KE=6980 m ?1 in CDCl3 at 303 K. Macrocycle 1 also self‐assembles into π‐stacked nanofibers in the drop‐cast film.  相似文献   
2.
To prepare cross‐linked silicone (silicone rubber) particles in an aqueous medium, we investigated two synthesis methods involving a miniemulsion system. The first method was based on cationic ring‐opening polymerization of cyclic siloxane, which is a common synthetic route for linear silicone oil and uses octamethylcyclotetrasiloxane (D4) as the monomer and dimeric D4 (bis‐D4) as the cross‐linker. Although this method produces silicone particles, the particles do not remain in the particulate state after drying because of low cross‐linking density. The polymerization mechanism of this method was also investigated, which proceeds under the ring‐opening reaction of D4 in monomer droplets and upon polycondensation of hydrolyzed D4, which occurs in the water phase (ie, outside the monomer droplets). This mechanism implied that introducing the cross‐linking structure into particles is difficult because of the low solubility of bis‐D4 in water. To overcome these difficulties, we demonstrated a second method of preparing silicone particles based on the thiol‐Michael addition reaction between thiol‐terminated silicone oil and triacrylate in miniemulsion systems. Transmission electron microscopy images indicated that the silicone particles obtained in the particulate state upon drying and the aggregates of these particles showed elasticity.  相似文献   
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1.IntroductionInthispaper,wewillinvestigatethenumericalsolutionsofthefollowinginitialvalueproblemsforDDEswithmanyvariabledelayswherea,bl,b2,...,bmandcoEC,0相似文献   
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A diversity‐oriented synthetic strategy allowed us to design a series of conjugated molecules containing multiple benzosilole units that can be utilized as efficient hole‐blocking materials for phosphorescent organic light emitting diodes (OLEDs). Some of these compounds showed a performance surpassing that of the current standard, bathocuproine. The new compounds were easily synthesized in a modular fashion from a previously reported 3‐stannyl benzosilole building unit. Studies on the properties of these compounds in solution and in the solid state indicate that they possess high electron affinity, high ionization potential, and form stable amorphous films that show high electron‐drift mobility. The correlation between their molecular properties and the efficiency of the OLED device performance is also investigated.  相似文献   
6.
A simple and highly sensitive method for the determination of free and total (free + conjugated) catecholamines (norepinephrine, epinephrine and dopamine) in human urine is described which employs HPLC with fluorescence detection. Conjugated catecholamines (sulfate form) are hydrolyzed by a sulfatase-mediated reaction to the corresponding free amines. After cation exchange chromatography on a Toyopak IC-SP S cartridge, catecholamines and isoproterenol (internal standard) in urine samples were converted into the corresponding fluorescent compounds by reaction with 1,2-diphenylethylenediamine. These compounds were separated within 8 min on a reversed phase column with isocratic elution using a mixture of water, methanol and acetonitrile containing a Tris-hydrochloric acid buffer (pH 7.0). The detection limit for each catecholamine is ca 2 fmol per 100 microL injection volume.  相似文献   
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Lax et al. [Phys. Rev. 11 (1975) 1365] discovered that a light beam in vacuum is not a transverse wave but does have a longitudinal field component. We investigate atomic and molecular electric dipole transitions induced by such a light beam, in particular, linearly polarized in a transverse plane. We derive the selection rules and the transition rates for various quantization axes using the paraxial approximation up to the first order of 1/kw, where k is the wave number and w is the transverse size of the light beam. The light beam is able to yield atomic spin polarization in the direction perpendicular to both the optical axis and the transverse electric field, and its magnitude is approximately 1/kw times that generated by a circularly polarized light wave with the similar intensity.  相似文献   
9.
Summary The energy spectrum of cosmic-ray neutrinos in the atmosphere has been calculated for the neutrino energy from 0.2 GeV to 108 GeV by taking into account the results of p-p collision, p-nucleus collision, nucleus-nucleus collision, the energy spectrum of primary cosmic rays, momentum spectrum and charge ratio of cosmic-ray muons measured by MUTRON, and the production of prompt neutrinos in the decay of charmed particles. Our result on neutrino intensity is in good agreement with the result of Osborneet al. for the horizontal direction if their muon spectrum has been corrected, and also with the result of Volkova for the vertical direction except for the lower energies. For the horizontal direction the intensity of prompt muon-neutrinos exceeds that of muonneutrinos from the conventional processes at the neutrino energy of 106 GeV and also the intensity of prompt electron-neutrinos exceeds that of electron-neutrinos from the conventional processes at the energy of 105 GeV. The corresponding values for the vertical direction are 105 GeV and 104 GeV, respectively. In the energy region from 0.3 GeV to 3 GeV, the expected value for the ratio of intensity of electron-neutrino to that of muon-neutrino is obtained as 0.42±0.08 and this is excellent agreement with the experimental value 0.36±0.13 of NUSEX group.
Riassunto è stato calcolato lo spettro d’energia dei neutrini dei raggi cosmici nell’atmosfera per un’energia neutrinica da 0.2 a 108 GeV tenendo conto dei risultati delle collisioni p-p, p-nucleo, nucleo-nucleo, dello spettro d’energia dei raggi cosmici primari, dello spettro dell’impulso e del rapporto di carica dei muoni dei raggi cosmici misurato da MUTRON e dalla produzione di neutrini pronti nel decadimento di particelle con charm. Il nostro risultato sull’intensità dei neutrini è in buon accordo con il risultato di Osborneet al. per la direzione orizzontale se il loro spettro muonico viene corretto, ed anche con il risultato di Volkova per la direzione verticale tranne che per le energie piú basse. Per la direzione orizzontale l’intensità dei neutrini muonici pronti è maggiore di quella dei neutrini muonici che derivano dai processi convenzionali ad energia neutrinica di 106 GeV ed anche l’intensità dei neutrini elettronici pronti è maggiore di quella dei neutrini elettronici che derivano dai processi convenzionali all’energia di 105 GeV. I valori corrispondenti per la direzione verticale sono rispettivamente 105 e 104 GeV. Nella regione d’energia tra 0.3 e 3 GeV, il valore atteso ottenuto per il rapporto tra l’intensità dei neutrini elettronici e quella dei neutrini muonici è 0.42±0.08 e questo è in accordo eccellente con il valore sperimentale 0.36±0.13 del gruppo NUSEX.

Ёнергетический спектр нейтрино космических лучей в атмосфере
Резюме Вычисляется Энергетический спектр нейтрино космических лучей в атмосфере для Энергий нейтрино от 0.2 ГЭВ до 108 ГЭВ, учитывая р-р соударения, р-ядерные соударения, ядерно-ядерные соударения, Энергетический спектр первичных космических лучей, импульсный спектр и зарядовое отнощение мюонов космических лучей, измеренных с помошью МUTRON, и образование нейтрино в распадах очарованных частиц. Нащ результат для интенсивности нейтрино хорощо согласуется с результатом Осборна и др. для горизонтального направления, если их мюонный спектр является правильным, а также с результатом Волковой для вертикального направления, за исключением низких Энергий. Для горизонтального направления интенсивность мгновенных мюонных нейтрино превыщает интенсивность мюон-ных нейтрино из обычных процессов при Энергиях нейтрино 106 ГЭВ. Йнтенсивность мгновенных Электронных нейтрино превыщает интенсивность Электронных нейтрино из обычных процессов при Энергии 105 ГЭВ. Соответствуюшие величины для вертикального направления соответственно равны 105 ГЭВ и ДО4 ГЭВ. В области Энергий от 0.3 ГЭВ до 3 ГЭВ ожидаемая величина отнощения интенсивностей Электронных нейтрино к интенсивности мюонных нейтрино составляет 0.42±0.08. Ёта величина прекрасно согласуется с Экспериментальным результатом 0.36±0.13, полученным группой
  相似文献   
10.
Drastic reduction of irregular defect density in molecular beam epitaxy (MBE) grown GaAs is obtained by using a novel arsenic Knudsen effusion cell with a cracking furnace. A surface defect density of less than 10 cm−2 is routinely achieved for continuously grown three 3-inch diameter, 1.7 μm thick, metal-semiconductor-field effect transistor (MESFET) structures when the cracking is carried out at about 700°C, which is the critical temperature for the conduction type change, and with the group III Knudsen cell only heated near the orifice of the crucible (top heat cell). These optimized cracking conditions also lead to successful mass production of some microwave devices with not only ultra-low defect density but suitable electrical performances.  相似文献   
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