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931.
A subexcitable medium of Belousov-Zhabotinsky (BZ) reaction subjected to external Gaussian white noise is studied in experiments and numerical simulations. We observe that at an optimal level of noise the wave sources of excited traveling waves become synchronous, as though there exists a long distance spatial correlation. The synchronous behavior fades if the noise level becomes larger or smaller. Numerical simulations confirm the experimental findings, and point out that the best synchronous behavior takes place when the signal-to-noise ratio of waves becomes largest. 相似文献
932.
Kubo K Akemoto M Anderson S Aoki T Araki S Bane KL Blum P Corlett J Dobashi K Emma P Frisch J Fukuda M Guo Z Hasegawa K Hayano H Higo T Higurashi A Honda Y Iimura T Imai T Jobe K Kamada S Karataev P Kashiwagi S Kim E Kobuki T Kotseroglou T Kurihara Y Kuriki M Kuroda R Kuroda S Lee T Luo X McCormick DJ McKee B Mimashi T Minty M Muto T Naito T Naumenko G Nelson J Nguyen MN Oide K Okugi T Omori T Oshima T Pei G Potylitsyn A Qin Q Raubenheimer T Ross M Sakai H Sakai I Schmidt F Slaton T Smith H 《Physical review letters》2002,88(19):194801
Electron beams with the lowest, normalized transverse emittance recorded so far were produced and confirmed in single-bunch-mode operation of the Accelerator Test Facility at KEK. We established a tuning method of the damping ring which achieves a small vertical dispersion and small x-y orbit coupling. The vertical emittance was less than 1% of the horizontal emittance. At the zero-intensity limit, the vertical normalized emittance was less than 2.8 x 10(-8) rad m at beam energy 1.3 GeV. At high intensity, strong effects of intrabeam scattering were observed, which had been expected in view of the extremely high particle density due to the small transverse emittance. 相似文献
933.
Zhu Y Moodenbaugh AR Schneider G Davenport JW Vogt T Li Q Gu G Fischer DA Tafto J 《Physical review letters》2002,88(24):247002
We use x-ray absorption spectroscopy (XAS) and electron energy loss spectroscopy (EELS) to study the fine structure at the K edge of boron in MgB(2). We observe in XAS a peak of width 0.7 eV at the edge threshold, signaling a narrow energy region with empty boron p states near the Fermi level. The changes in the near edge structure observed in EELS with direction of the momentum transfer imply that these states have p(x)p(y) symmetry. Our observations are consistent with electronic structure calculations indicating a narrow energy window of empty p(x)p(y) states that falls to zero at 0.8 eV above the Fermi level. The disappearance of the p(x)p(y) feature in EELS at grain boundaries suggests that this signature may become powerful in probing superconductivity at nanoscale. 相似文献
934.
The existence of a stripe-liquid phase in a layered nickelate, La(1.725)Sr(0.275)NiO(4), is demonstrated through neutron scattering measurements. We show that incommensurate magnetic fluctuations evolve continuously through the charge-ordering temperature, although an abrupt decrease in the effective damping energy is observed on cooling through the transition. The energy and momentum dependence of the magnetic scattering are parametrized with a damped-harmonic-oscillator model describing overdamped spin waves in the antiferromagnetic domains defined instantaneously by charge stripes. 相似文献
935.
Bai JZ Ban Y Bian JG Chen AD Chen HF Chen HS Chen JC Chen XD Chen YB Cheng BS Chi SP Chu YP Choi JB Cui XZ Dai YS Dong LY Du ZZ Dunwoodie W Fu HY Fu LP Gao CS Gu SD Guo YN Guo ZJ Han SW Han Y Harris FA He J He JT He KL He M He X Hong T Heng YK Hu GY Hu HM Hu QH Hu T Huang GS Huang XP Huang YZ Izen JM Ji XB Jiang CH Jin Y Jones BD Kang JS Ke ZJ Kim HJ Kim SK Kim TY Kong D Lai YF Li D Li HB Li HH Li J Li JC Li PQ Li QJ Li RY Li W Li WG Li XN Li XQ Liu B Liu F Liu F Liu HM Liu J Liu JP Liu TR 《Physical review letters》2002,88(10):101802
We report values of R = sigma(e(+)e(-)-->hadrons)/sigma(e(+)e(-)-->mu(+)mu(-)) for 85 center-of-mass energies between 2 and 5 GeV measured with the upgraded Beijing Spectrometer at the Beijing Electron-Positron Collider. 相似文献
936.
Laser-induced fluorescence is used to characterize the axial velocity and temperature field at the exit plane of a low-power
helium arcjet. Two cases were examined, one in which the mass-flow rate was changed at a constant current, and the other where
the current was changed at a constant mass-flow rate. At constant mass-flow rate, the velocity scales with the increase in
power. At constant current, a higher specific energy results in an unexpected lower mean exit velocity. The temperature profiles
show that the nozzle-wall temperature is greater than the mean exit temperature. Along the axis of the arcjet, these measurements
indicate the presence of a shock less than one nozzle diameter downstream of the exit.
Received: 10 July 2002 / Published online: 22 November 2002
RID="*"
ID="*"Corresponding author. Fax: +1-650-723-1748, E-mail: qwalker@stanford.edu 相似文献
937.
As a kind of intermediates, a-oxo ketene dithioacetals I are important in organicsynthesis"'. In our recent studies, we found that the difference of dialkythio group canbestow various properties on these kinds of compounds"'. To exploit the reactivityadjusted by the dialkythio groups in l, a-oxo ketene dibenzylthioacetals 2 were chosenand studied. Some interesting new results were obtained in these experiments. Here wereport the new results.When studying the reaction of a-oxo ketene dibenzylt… 相似文献
938.
LaIl{1Tussalivlts(L.salivus)isleguminouscropcultivatedinlndia,BangladeshandEthiopia,whereitisamajorproteinsourceforpeopleinthelowestincomegroups"'.However,excessiveingestionofthispulsecanleadtoirreversibleparalysisofthelegs-adiseaseknownasneurolathyrisn1orlathyrism.Thecausativeagentwasreportedtobethenon-proteinaminoacid,3-N-L-oxalyl-2,3-diaminopropioniacid(o-ODAP,sometimes,referredtoasBOAA)','.Thea-isomerofODAP,2-N-oxalyl-2,3-diaminopropionicacid,hasbeenshowntobenontoxictochicksandmice… 相似文献
939.
Tezuka Y Stampoulis P Banskota AH Awale S Tran KQ Saiki I Kadota S 《Chemical & pharmaceutical bulletin》2000,48(11):1711-1719
From the MeOH extract of the aerial part of Vietnamese Orthosiphon stamineus, five new isopimarane-type diterpenes [orthosiphols F-J (1-5)] and two new diterpenes [staminols A (6) and B (7)] with a novel carbon-framework, to which we proposed the name "staminane", and three new highly-oxygenated staminane-type diterpenes [staminolactones A (8) and B (9) and norstaminol A (10)1 were isolated. Moreover, staminolactone A (8) is 8,14-secostaminane-type and staminolactone B (9) is 13,14-secostaminane-type, while norstaminol A (10) is 14-norstaminen-type. Together with these new diterpenes, sixteen known compounds were also isolated and identified to be: 7,3',4'-tri-O-methylluteolin (11), eupatorin (12), sinensetin (13), 5-hydroxy-6,7,3',4'-tetramethoxyflavone (14), salvigenin (15), ladanein (16), tetramethylscutellarein (17), 6-hydroxy-5,7,4'-trimethoxyflavone (18), vomifoliol (19), aurantiamide acetate (20), rosmarinic acid (21), caffeic acid (22), oleanolic acid (23), ursolic acid (24), betulinic acid (25), and beta-sitosterol (26). All the isolated compounds were tested for their cytotoxicity towards highly liver metastatic murine colon 26-L5 carcinoma cells, and the new diterpenes, except for 4, and flavonoids (11, 12, 16, 18) showed cytotoxicity with an ED50 value between 10 and 90 microg/ml. 相似文献
940.