@article{Zaehle2004,
  author    = {Z{\"a}hle, Henryk},
  title     = {Heat equation with strongly inhomogeneous noise},
  year      = {2004},
  abstract  = {The author considers the heat equation in dimension one with singular drift and inhomogeneous space-time white noise. In particular, the quadratic variation measure of the white noise is not required to be absolutely continuous w.r.t. the Lebesgue measure, neither in space nor in time. Under some assumptions the author gives statements on strong and weak existence as well as strong and weak uniqueness of continuous solutions.},
  language  = {en}
}
@article{ZollerHolschneiderBenZion2004,
  author    = {Zoller, Gert and Holschneider, Matthias and Ben-Zion, Yehuda},
  title     = {Quasi-static and quasi-dynamic modeling of earthquake failure at intermediate scales},
  year      = {2004},
  abstract  = {We present a model for earthquake failure at intermediate scales (space: 100 m-100 km, time: 100 m/nu(shear},
  language  = {en}
}
@article{ZimmermannRegiererKossmannetal.2004,
  author    = {Zimmermann, P. and Regierer, Babette and Kossmann, Jens and Frossard, Emmanuel and Amrhein, Nikolaus and Bucher, Matthias},
  title     = {Differential expression of three purple acid phosphatases from potato},
  issn      = {1435-8603},
  year      = {2004},
  abstract  = {Three cDNAs encoding purple acid phosphatase (PAP) were cloned from potato (Solanum tuberosum L. cv. Desiree) and expression of the corresponding genes was characterised. StPAP1 encodes a low-molecular weight PAP clustering with mammalian, cyanobacterial, and other plant PAPs. It was highly expressed in stem and root and its expression did not change in response to phosphorus (P) deprivation. StIPAP2 and StPAP3 code for high-molecular weight PAPs typical for plants. Corresponding gene expression was shown to be responsive to the level of P supply, with transcripts of StPAP2 and StPAP3 being most abundant in P-deprived roots or both stem and roots, respectively. Root colonisation by arbuscular mycorrhizal fungi had no effect on the expression of any of the three PAP genes. StIPAP1 mRNA is easily detectable along the root axis, including root hairs, but is barely detectable in root tips. In contrast, both StPAP2 and StPAP3 transcripts are abundant along the root axis, but absent in root hairs, and are most abundant in the root tip. All three PAPs described contain a predicted N-terminal secretion signal and could play a role in extracellular P scavenging, P mobilisation from the rhizosphere, or cell wall regeneration},
  language  = {en}
}
@article{ZiemannSchmidtMirwald2004,
  author    = {Ziemann, Martin Andreas and Schmidt, Christian and Mirwald, Peter W.},
  title     = {Raman spectroscopic study of the liquid-liquid transition in water},
  issn      = {0024-4937},
  year      = {2004},
  language  = {en}
}
@article{ZieheLaskovNolteetal.2004,
  author    = {Ziehe, Andreas and Laskov, Pavel and Nolte, G and M{\"u}ller, Klaus-Robert},
  title     = {A fast algorithm for joint diagonalization with non-orthogonal transformations and its application to blind source separation},
  year      = {2004},
  abstract  = {A new efficient algorithm is presented for joint diagonalization of several matrices. The algorithm is based on the Frobenius-norm formulation of the joint diagonalization problem, and addresses diagonalization with a general, non- orthogonal transformation. The iterative scheme of the algorithm is based on a multiplicative update which ensures the invertibility of the diagonalizer. The algorithm's efficiency stems from the special approximation of the cost function resulting in a sparse, block-diagonal Hessian to be used in the computation of the quasi-Newton update step. Extensive numerical simulations illustrate the performance of the algorithm and provide a comparison to other leading diagonalization methods. The results of such comparison demonstrate that the proposed algorithm is a viable alternative to existing state-of-the-art joint diagonalization algorithms. The practical use of our algorithm is shown for blind source separation problems},
  language  = {en}
}
@article{ZieheKawanabeHarmeling2004,
  author    = {Ziehe, Andreas and Kawanabe, Motoaki and Harmeling, Stefan},
  title     = {Blind separation of post-nonlinear mixtures using linearizing transformations and temporal decorrelation},
  issn      = {1532-4435},
  year      = {2004},
  abstract  = {We propose two methods that reduce the post-nonlinear blind source separation problem (PNL-BSS) to a linear BSS problem. The first method is based on the concept of maximal correlation: we apply the alternating conditional expectation (ACE) algorithm-a powerful technique from nonparametric statistics-to approximately invert the componentwise nonlinear functions. The second method is a Gaussianizing transformation, which is motivated by the fact that linearly mixed signals before nonlinear transformation are approximately Gaussian distributed. This heuristic, but simple and efficient procedure works as good as the ACE method. Using the framework provided by ACE, convergence can be proven. The optimal transformations obtained by ACE coincide with the sought-after inverse functions of the nonlinearitics. After equalizing the nonlinearities, temporal decorrelation separation (TDSEP) allows us to recover the source signals. Numerical simulations testing "ACE-TD" and "Gauss-TD" on realistic examples are performed with excellent results},
  language  = {en}
}
@article{ZhukGunther2004,
  author    = {Zhuk, Alexandre and Gunther, U.},
  title     = {Massive scalar fields in the early universe},
  issn      = {0218-2718},
  year      = {2004},
  abstract  = {We discuss the role of gravitational excitons/radions in different cosmological scenarios. Gravitational excitons are massive moduli fields which describe conformal excitations of the internal spaces and which, due to their Planck-scale suppressed coupling to matter fields, are WIMPs. It is demonstrated that, depending on the concrete scenario, observational cosmological data set strong restrictions on the allowed masses and initial oscillation amplitudes of these particles},
  language  = {en}
}
@article{ZhouKurths2004,
  author    = {Zhou, Changsong and Kurths, J{\"u}rgen},
  title     = {Resonant patterns in noisy active media},
  issn      = {1063-651X},
  year      = {2004},
  abstract  = {We investigate noise-controlled resonant response of active media to weak periodic forcing, both in excitable and oscillatory regimes. In the excitable regime, we find that noise-induced irregular wave structures can be reorganized into frequency-locked resonant patterns by weak signals with suitable frequencies. The resonance occurs due to a matching condition between the signal frequency and the noise-induced inherent time scale of the media. m:1 resonant regions similar to the Arnold tongues in frequency locking of self-sustained oscillatory media are observed. In the self-sustained oscillatory regime, noise also controls the oscillation frequency and reshapes significantly the Arnold tongues. The combination of noise and weak signal thus could provide an efficient tool to manipulate active extended systems in experiments},
  language  = {en}
}
@article{ZentelBehlNeheretal.2004,
  author    = {Zentel, Rudolf and Behl, Marc and Neher, Dieter and Zen, Achmad and Lucht, Sylvia},
  title     = {Nanostructured polytriarylamines : orientation layers for polyfluorene},
  issn      = {0065-7727},
  year      = {2004},
  language  = {en}
}
@article{ZenPflaumHirschmannetal.2004,
  author    = {Zen, Achmad and Pflaum, J. and Hirschmann, S. and Zhuang, W. and Jaiser, Frank and Asawapirom, Udom and Rabe, J. P. and Scherf, Ullrich and Neher, Dieter},
  title     = {Effect of molecular weight and annealing of poly (3-hexylthiophene)s on the performance of organic field-effect transistors},
  year      = {2004},
  abstract  = {The optical, structural, and electrical properties of thin layers made from poly(3-hexylthiophene) (P3HT) samples of different molecular weights are presented. As reported in a previous paper by Kline et al., Adv. Mater 2003, 15, 1519, the mobilities of these layers are a strong function of the molecular weight, with the largest mobility found for the largest molecular weight. Atomic force microscopy studies reveal a complex polycrystalline morphology which changes considerably upon annealing. X-ray studies show the occurrence of a layered phase for all P3HT fractions, especially after annealing at 1.50 degreesC . However, there is no clear correlation between the differences in the transport properties and the data from structural investigations. In order to reveal the processes limiting the mobility in these layers, the transistor properties were investigated as a function of temperature. The mobility decreases continuously with increasing temperatures; with the same trend pronounced thermochromic effects of the P3HT films occur. Apparently, the polymer chains adopt a more twisted, disordered conformation at higher temperatures, leading to interchain transport barriers. We conclude that the backbone conformation of the majority of the bulk material rather than the crystallinity of the layer is the most crucial parameter controlling the charge transport in these P3HT layers. This interpretation is supported by the significant blue-shift of the solid-state absorption spectra with decreasing molecular weight, which is indicative of a larger distortion of the P3HT backbone in the low-molecular weight P3HT layers},
  language  = {en}
}