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971.
972.
We present an experimental demonstration of the power of feedback in quantum metrology, confirming the predicted [H. M. Wiseman, Phys. Rev. Lett. 75, 4587 (1995)]] superior performance of an adaptive homodyne technique for single-shot measurement of optical phase. For measurements performed on weak coherent states with no prior knowledge of the signal phase, adaptive homodyne estimation approaches closer to the intrinsic quantum uncertainty than any previous technique. Our results underscore the importance of real-time feedback for reaching quantum limits in measurement and control. 相似文献
973.
Ahrens J Altieri S Annand JR Anton G Arends HJ Aulenbacher K Beck R Bradtke C Braghieri A Degrande N D'Hose N Drechsel D Dutz H Goertz S Grabmayr P Hansen K Harmsen J Von Harrach D Hasegawa S Hasegawa T Heid E Helbing K Holvoet H Van Hoorebeke L Horikawa N Iwata T Jahn O Jennewein P Kageya T Kamalov S Kiel B Klein F Kondratiev R Kossert K Krimmer J Lang M Lannoy B Leukel R Lisin V Matsuda T McGeorge JC Meier A Menze D Meyer W Michel T Naumann J Panzeri A Pedroni P Pinelli T Preobrajenski I 《Physical review letters》2002,88(23):232002
The helicity dependence of the gamma-->p-->-->ppi(0) reaction has been measured for the first time in the photon-energy range from 550 to 790 MeV. The experiment, performed at the Mainz microtron MAMI, used a 4pi-detector system, a circularly polarized, tagged photon beam, and a longitudinally polarized frozen-spin target. These data are predominantly sensitive to the D13(1520) resonance and are used to determine its helicity amplitudes. 相似文献
974.
We propose that a chain of five-membered rings (polyaminotriazole) should be ferromagnetic with an appropriate doping that is envisaged to be feasible with a field-effect transistor structure. The ferromagnetism is confirmed by a spin density functional calculation, which also shows that ferromagnetism survives the Peierls instability. We explain the magnetism in terms of the Mielke and Tasaki flatband ferromagnetism with the Hubbard model. This opens a new possibility of band ferromagnetism in purely organic polymers. 相似文献
975.
Akutagawa T Hasegawa T Nakamura T Inabe T Saito G 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(19):4402-4411
A novel molecular based proton-electron mixed conductor, (H3BBIM(+))(TCNQ)(Cl(-))(0.5)(H(2)O) (1), where H3BBIM(+) is 2-(2-1H-benzimidazolyl)-1H-benzimidazolium and TCNQ is 7,7,8,8-tetracyano-p-quinodimethane, was synthesized. The salt exhibited peculiar phase transitions as a result of proton-electron coupling phenomena within the crystal. Salt 1 is composed of a closed-shell H3BBIM(+) cation and an open-shell TCNQ anion radical, and was obtained by electrocrystallization in a buffered CH(3)CN solution. Crystal 1 was constructed from the segregated uniform stacks of H3BBIM(+) and TCNQ. The regular stack of partially electron-transferred TCNQ(-0.5) provided a one-dimensional electron-conducting column. Between the regular H3BBIM(+) columns, a channel-like sequence of holes was formed at the side-by-side space that is filled with disordered Cl(-) ions and H(2)O molecules, and which offer a proton-conducting path. The electrical conductivity at room temperature (10 S cm(-1)) was greater by a magnitude of four than the protonic conductivity (1x10(-3) S cm(-1)). Electronic conduction changed from metallic (T>250 K) to semiconducting (250>T>100 K), then insulating (T<100 K). Protonic conductivity was observed above 200 K. The continuous metal-semiconductor transition at 250 K is caused by the formation of the Cl(-) superstructure, whereas the disappearance of protonic conductivity at 200 K is related to the rearrangement of the [Cl(-)-(H(2)O)(2)] sublattice within the channel. The magnetic susceptibility continuously shifted from Pauli paramagnetism (T>250 K) to the one-dimensional linear Heisenberg antiferromagnetic chain (T<250 K). Lattice dimerization in regular TCNQ columns was confirmed by the appearance of vibrational a(g) mode at low temperatures. The strong localization of conduction electrons on each TCNQ dimer caused a Mott transition at 100 K. The melting and freezing of the [Cl(-)-(H(2)O)(2)] sublattice within the channel was correlated to the conduction electrons on the TCNQ stack and the protonic conductivity. 相似文献
976.
Yoshino A Matsudaira H Asato E Koikawa M Shiga T Ohba M Okawa H 《Chemical communications (Cambridge, England)》2002,(12):1258-1259
Four Zn(II) ions arranged within a pyridine-modified large phenolate-containing macrocyle Lpy2- encapsulate two chloranilate ions in a double bis-didentate bridging fashion; the ligands are strongly pi-pi stacked with each other with a short distance of 3.27 A and are electrochemically reduced at the same potential of -1.00 V to produce a reasonably stable biradical species with T1/2 = 60 min at 25 degrees C. 相似文献
977.
Ohtaka A Kuniyasu H Kinomoto M Kurosawa H 《Journal of the American Chemical Society》2002,124(48):14324-14325
The photo-and-thiol-driven trans insertion of phenylacetylene into H-Pt bonds of Pt(X)(H)(PPh3)2 (X = SAr, Cl, Br, and I) took place to afford Pt[(Z)-C(H)=CH(Ph)](X)(PPh3)2 in good yields. 相似文献
978.
Furukawa S Takagi N Ikeda T Ono M Nafady AM Nohara T Sugimoto H Doi S Yamada H 《Chemical & pharmaceutical bulletin》2002,50(3):439-440
Two new long-chain alkanoic acid esters of lupeol were isolated together with known triterpenoids, alpha-amyrin, beta-amyrin, cycloartenol, lanosta-7,24-diene-3beta-ol and lupeol from Alecrim-propolis collected in Brazil. The structures were characterized by spectroscopic means. 相似文献
979.
Psilocin analogs having either a formyl group (9-12) or a bromine atom (13-18) at the 5- or 7-position have been prepared for the first time. Syntheses of 5- and 7-bromo derivatives of 4-hydroxy- (23, 24, 28) and 4-benzyloxyindole-3-carbaldehyde (19, 25, 29, 30), 4-benzyloxyindole-3-acetonitriles (20, 31), and 4-benzyloxy-N,N-dimethyltryptamine (32, 34, 35) have also been established. 相似文献
980.
Koji Kano Hideki Hasegawa 《Journal of inclusion phenomena and macrocyclic chemistry》2001,41(1-4):41-47
Anionic N-acetylated -aminoacids (AcTrp-, AcPhe-, AcLeu- and AcVal-) are bound to protonatedheptakis(6-amino-6-deoxy)--cyclodextrin(per-NH3
+--CD) by a cooperative work of inclusion and Coulomb interactions.Such complexation occurs enantioselectively ((S)-selective)and is accompanied bypositive entropy changes. Similar (S)-selectivecomplexation occurs in the oppositelycharged system. Namely, cationic -aminoacid methyl esters are enantioselectivelybound to dissociatedheptakis(6-carboxymethylthio-6-deoxy)--cyclodextrin(per-COO---CD). In order to obtain thegeneral mechanism for complexationof a charged host with an oppositely charged guest,we examined the 1H NMR spectra oncomplexation of simple carboxylate anions suchas p-methylbenzoate anion andalkanoate anions with per-NH3
+--CD.Both Coulomb interactions andinclusion are essential to form stable complexesof these carboxylate anions. In allcases, positive entropy changes promote thecomplexation between the carboxylateanions and per-NH3
+--CD. Dehydrationfrom both charged host and guestis the origin of entropic gains. The mechanism forcomplexation of a charged host withan oppositely charged guest involving the cooperativework of inclusion and Coulombinteractions and positive entropy change due todehydration upon complexation isgenerally applied for related systems such asenantioselective complexation ofRu(phen)3
2+ with per-COO---CDand of Ru(phen)3
2+with DNA. 相似文献