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91.
Experiments in quasi-two-dimensional geometry (Hele-Shaw cells) in which a fluid is injected into a viscoelastic medium (foam, clay, or associating polymers) show patterns akin to fracture in brittle materials, very different from standard Laplacian growth patterns of viscous fingering. An analytic theory is lacking since a prerequisite to describing the fracture of elastic material is the solution of the bi-Laplace rather than the Laplace equation. In this Letter we close this gap, offering a theory of bi-Laplacian growth patterns based on the method of iterated conformal maps. 相似文献
92.
Sikharulidze I Dolbnya IP Fera A Madsen A Ostrovskii BI de Jeu WH 《Physical review letters》2002,88(11):115503
The dynamics of the layer-displacement fluctuations in smectic membranes have been studied by x-ray photon correlation spectroscopy (XPCS). We report transitions from an oscillatory damping regime to simple exponential decay of the fluctuations, both as a function of membrane thickness and upon changing from specular to off-specular scattering. This behavior is in agreement with recent theories. Employing avalanche photodiode detectors and the uniform filling mode of the synchrotron storage ring, the fast limits of XPCS have been explored down to 50 ns. 相似文献
93.
Modh P Backlund J Eriksson N Bengtsson J Kristjánsson S Larsson A 《Optics letters》2002,27(8):574-576
We experimentally demonstrate that a grating outcoupler used for complex beam shaping (spot-array generation) can produce unintentional optical feedback that severely disturbs the integrated in-plane laser that illuminates the coupler. Simulations show that these outcouplers, in contrast to conventional collimating or focusing outcouplers, tend to produce high levels of feedback in spite of the detuning used to suppress feedback. Further, this feedback is focused to high intensity in the laser gain medium. This focused light acts as a seed for the nonlinear self-focusing that causes wave-front distortion and filamentation, which degrades the beam quality. 相似文献
94.
Bertram HC Rasmussen M Busk H Oksbjerg N Karlsson AH Andersen HJ 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2002,157(2):267-276
This study investigates the effects of developmental stage and muscle type on the mobility and distribution of water within skeletal muscles, using low-field (1)H-NMR transverse relaxation measurements in vitro on four different porcine muscles (M. longissimus dorsi, M. semitendinosus, M. biceps femoris, M. vastus intermedius) from a total of 48 pigs slaughtered at various weight classes between 25 kg and 150 kg. Principal component analysis (PCA) revealed effects of both slaughter weight and muscle type on the transverse relaxation decay. Independent of developmental stage and muscle type, distributed exponential analysis of the NMR T(2) relaxation data imparted the existence of three distinct water populations, T(2b), T(21), and T(22), with relaxation times of approximately 1-10, 45-120, and 200-500 ms, respectively. The most profound change during muscle growth was a shift toward faster relaxation in the intermediate time constant, T(21). It decreased by approx. 24% in all four muscle types during the period from 25 to 150 kg live weight. Determination of dry matter, fat, and protein content in the muscles showed that the changes in relaxation time of the intermediate time constant, T(21), during growth should be ascribed mainly to a change in protein content, as the protein content explained 77% of the variation in the T(21) time constant. Partial least squares (PLS) regression revealed validated correlations in the region of 0.58 to 0.77 between NMR transverse relaxation data and muscle development for all the four muscle types, which indicates that NMR relaxation measurements may be used in the prediction of muscle developmental stage. 相似文献
95.
Anders Melin 《Journal d'Analyse Mathématique》1992,59(1):133-160
Dedicated to Professor Shmuel Agmon 相似文献
96.
Anders Martin-Löf 《Communications in Mathematical Physics》1972,24(4):253-259
The equality between the spontaneous magnetization and the long range order is established for the Ising model with nearest neighbour interactions for low and high temperatures. The proof is presented for the two-dimensional lattice but works also in higher dimensions. The result verifies that the valuem*=(1–(Sh)–4)1/8 of the spontaneous magnetization below the critical point calculated by Onsager and Yang is the true value, which has been a long standing open question. 相似文献
97.
98.
Roy Nilsson Ralf Nyholm Anders Berndtsson Jan Hedman Carl Nordling 《Journal of Electron Spectroscopy and Related Phenomena》1976,9(4):337-353
A new source for producing YMξ radiation in an ESCA spectrometer is described. The system makes use of continuous evaporation of yttrium on a rotating anode. It is demonstrated that this scheme allows YMξ-excited electron spectra to be recorded without gradual loss of resolution and intensity due to anode oxidation. Electron spectra of Ar, Hg and N2 excited by YMξ radiation are studied. Relative photoelectric cross-sections of the 5d, 5d and 6s orbitals in Hg and the four valence orbitals in N2 are measured. The valence electron shake-up spectrum of N2 is discussed. 相似文献
99.
100.
B. Anders U. Berghaus H. Brückmann P. Lara C. Pegel H. Salehi A. Schütte K. Sinram K. Wick 《Physics letters. [Part B]》1979,87(4):346-348
At the Hamburger Isochronous Cyclotron the formation of the particle unstable ground state of has been investigated in the reaction α + d → α + p + n at Eα = 28.3 MeV. The neutrons were detected in two liquid scintillation counters, while a large Si (Li) detector was used to observe the α-particles. In a first analysis, the tensor polarization parameters of the five-nucleon system 5Li are determined from the experimental data. The results are in quite good agreement with theoretical predictions of Hackenbroich et al. 相似文献