Showing papers by "University of California, Santa Barbara published in 1996"
TL;DR: Comparisons with other multiresolution texture features using the Brodatz texture database indicate that the Gabor features provide the best pattern retrieval accuracy.
Abstract: Image content based retrieval is emerging as an important research area with application to digital libraries and multimedia databases. The focus of this paper is on the image processing aspects and in particular using texture information for browsing and retrieval of large image data. We propose the use of Gabor wavelet features for texture analysis and provide a comprehensive experimental evaluation. Comparisons with other multiresolution texture features using the Brodatz texture database indicate that the Gabor features provide the best pattern retrieval accuracy. An application to browsing large air photos is illustrated.
4,017 citations
TL;DR: The Bekenstein-Hawking area entropy relation S BH = A 4 was derived for a class of five-dimensional extremal black holes in string theory by counting the degeneracy of BPS solition bound states.
3,497 citations
TL;DR: In this article, the current status and trends of approximation methods (local density and generalized gradient approximations, hybrid methods) and the new light which density functional theory has been shedding on important concepts like electronegativity, hardness, and chemical reactivity index are discussed.
Abstract: Density functional theory (DFT) is a (in principle exact) theory of electronic structure, based on the electron density distribution n(r), instead of the many-electron wave function Ψ(r1,r2,r3,...). Having been widely used for over 30 years by physicists working on the electronic structure of solids, surfaces, defects, etc., it has more recently also become popular with theoretical and computational chemists. The present article is directed at the chemical community. It aims to convey the basic concepts and breadth of applications: the current status and trends of approximation methods (local density and generalized gradient approximations, hybrid methods) and the new light which DFT has been shedding on important concepts like electronegativity, hardness, and chemical reactivity index.
2,524 citations
TL;DR: The Bekenstein-Hawking area-entropy relation for extremal black holes in string theory was derived in this paper by counting the degeneracy of BPS soliton bound states.
Abstract: The Bekenstein-Hawking area-entropy relation $S_{BH}=A/4$ is derived for a class of five-dimensional extremal black holes in string theory by counting the degeneracy of BPS soliton bound states.
2,410 citations
TL;DR: In this article, molecular theories of flow and deformation may facilitate the design of branched polymers with tailored rheological properties and improved adhesives, and improved theories relating to associating polymers should aid in the development of thickening agents and coatings.
Abstract: Recent years have brought exciting theoretical advances to understanding the behavior of macromolecular systems under nonequilibrium conditions. Developments in diffusion-controlled reactions of polymers are bringing molecular insights to reactive blending technologies, and improved theories relating to associating polymers should aid in the design of thickening agents and coatings. Recent progress in molecular theories of flow and deformation may facilitate the design of branched polymers with tailored rheological properties and improved adhesives.
2,010 citations
TL;DR: In this paper, it was argued that every Calabi-Yau manifold X with a mirror Y admits a family of supersymmetric toroidal 3-cycles and that the moduli space of such cycles together with their flat connections is precisely the space Y.
1,607 citations
TL;DR: In this article, the authors developed a simple analytic model for the gravitational clustering of dark matter halos to understand how their spatial distribution is biased relative to that of the mass, and showed that this bias function is sufficient to calculate the cross-correlation between dark haloes and mass.
Abstract: We develop a simple analytic model for the gravitational clustering of dark matter haloes to understand how their spatial distribution is biased relative to that of the mass. The statistical distribution of dark haloes within the initial density field (assumed Gaussian) is determined by an extension of the Press-Schechter formalism. Modifications of this distribution caused by gravitationally induced motions are treated using a spherical collapse approximation. We test this model against results from a variety of N-body simulations, and find that it gives an accurate description of a bias function. This bias function is sufficient to calculate the cross-correlation between dark haloes and mass, and again we find excellent agreement between simulation results and analytic predictions. Because haloes are spatially exclusive, the variance in the count of objects within spheres of fixed radius and overdensity is significantly smaller than the Poisson value. This seriously complicates any analytic calculation of the autocorrelation function of dark halos. Our simulation results show that this autocorrelation function is proportional to that of the mass over a wide range in $R$, even including scales where both functions are significantly greater than unity. The constant of proportionality is very close to that predicted on large scales by the analytic model. This result permits an entirely analytic estimate of the autocorrelation function of dark haloes. We use our model to study how the distribution of galaxies may be biased with respect to that of the mass. In conjunction with other data these techniques should make it possible to measure the amplitude of cosmic mass fluctuations and the density of the Universe.
1,555 citations
TL;DR: A generalized split-window method for retrieving land-surface temperature (LST) from AVHRR and MODIS data is proposed, which is less sensitive to uncertainty in emissivity and to instrument quantization error, and retrieves land- surface temperature more accurately.
Abstract: Proposes a generalized split-window method for retrieving land-surface temperature (LST) from AVHRR and MODIS data. Accurate radiative transfer simulations show that the coefficients in the split-window algorithm for LST must vary with the viewing angle, if the authors are to achieve a LST accuracy of about 1 K for the whole scan swath range (/spl plusmn/55/spl deg/ from nadir) and for the ranges of surface temperature and atmospheric conditions over land, which are much wider than those over oceans. The authors obtain these coefficients from regression analysis of radiative transfer simulations, and they analyze sensitivity and error over wide ranges of surface temperature and emissivity and atmospheric water vapor abundance and temperature. Simulations show that when atmospheric water vapor increases and viewing angle is larger than 45/spl deg/, it is necessary to optimize the split-window method by separating the ranges of the atmospheric water vapor, lower boundary temperature, and the surface temperature into tractable subranges. The atmospheric lower boundary temperature and (vertical) column water vapor values retrieved from HIRS/2 or MODIS atmospheric sounding channels can be used to determine the range for the optimum coefficients of the split-window method. This new algorithm not only retrieves land-surface temperature more accurately, but is also less sensitive to uncertainty in emissivity and to instrument quantization error.
1,553 citations
TL;DR: In this article, the molecular shapes of covalent organosilanes, quaternary ammonium surfactants, and mixed surfactant in various reaction conditions can be used to synthesize silica-based mesophase configurations.
Abstract: The low-temperature formation of liquid-crystal-like arrays made up of molecular complexes formed between molecular inorganic species and amphiphilic organic molecules is a convenient approach for the synthesis of mesostructure materials. This paper examines how the molecular shapes of covalent organosilanes, quaternary ammonium surfactants, and mixed surfactants in various reaction conditions can be used to synthesize silica-based mesophase configurations, MCM-41 (2d hexagonal, p6m), MCM-48 (cubic Ia3d), MCM-50 (lamellar), SBA-1 (cubic Pm3n), SBA-2 (3d hexagonal P63/mmc), and SBA-3 (hexagonal p6m from acidic synthesis media). The structural function of surfactants in mesophase formation can to a first approximation be related to that of classical surfactants in water or other solvents with parallel roles for organic additives. The effective surfactant ion pair packing parameter, g = V/a0l, remains a useful molecular structure-directing index to characterize the geometry of the mesophase products, and pha...
1,428 citations
TL;DR: An alternative interpretation of why hydrophilic surfaces and macromolecules remain well separated in water is suggested, in which hydration forces are either attractive or oscillatory, and where repulsions have a totally different origin.
Abstract: The conventional explanation of why hydrophilic surfaces and macromolecules remain well separated in water is that they experience a monotonically repulsive hydration force owing to structuring of water molecules at the surfaces. A consideration of recent experimental and theoretical results suggests an alternative interpretation in which hydration forces are either attractive or oscillatory, and where repulsions have a totally different origin. Further experiments are needed to distinguish between these possibilities.
1,225 citations
TL;DR: This paper showed that correct Bayesian reasoning can be elicited in 76% of subjects - indeed, 92% in the most ecologically valid condition - simply by expressing the problem in frequentist terms.
TL;DR: In this paper, the authors showed that soluble polyanionic proteins alone are sufficient to control the crystal phase of calcite and calcite without the need for deposition of an intervening protein sheet.
Abstract: IN the initial stages of the biomineralization of abalone shells, a primer layer of oriented calcite crystals grows on a nucleating protein sheet1,2. The deposition of this primer is followed by an abrupt transition to c-axis-oriented crystals of aragonite, another crystalline form of calcium carbonate. The formation of each of the two crystal types is accompanied by the synthesis of specific polyanionic proteins1–3, suggesting that cooperative interactions between these proteins and the inorganic ions during crystal nucleation and growth control the phase of the deposited mineral and that differential expression of the proteins allows the organism to induce phase changes. It is known that soluble shell proteins can control crystal morphology4–10, but it has been suspected that the switch in phase—from calcite to aragonite—might require the deposition of a new nucleating protein sheet. Here we describe in vitro studies of the crystallization of calcium carbonate in the presence of soluble polyanionic proteins extracted from abalone shell. We find that these proteins alone are sufficient to control the crystal phase, allowing us to switch abruptly and sequentially between aragonite and calcite without the need for deposition of an intervening protein sheet. These results show that soluble organic components can exert greater control over hierarchical biomineral growth than hitherto suspected, offering the prospect of similar phase control in materials chemistry.
TL;DR: This article found that individual level factors (i.e., self construals and values) are better predictors of low and high-context communication styles across cultures than cultural individualism-collectivism.
Abstract: Individualism-collectivism has a direct effect on communication styles and an indirect effect that is mediated through self construals and values. It was hypothesized that cultural individualism-collectivism, self construals, and values would have separate effects on individuals’use of low- and high-context communication styles. As predicted, the results of this study suggest that independent self construals and individualistic values mediate the influence of cultural individualism-collectivism on the use of low-context communication, and interdependent self construals and collectivistic values mediate the influence of cultural individualism-collectivism on the use of high-context communication. The patterns for cultural individualism-collectivism were not as clear-cut. The findings suggest that individual level factors (i.e., self construals and values) are better predictors of low- and high-context communication styles across cultures than cultural individualism-collectivism.
TL;DR: A cross-phase modulation scheme that exhibits a giant, resonantly enhanced nonlinearity, along with vanishing linear susceptibilities, is analyzed and has possible applications in quantum nondemolition measurements and for quantum logic gates.
Abstract: We analyze a cross-phase modulation (XPM) scheme that exhibits a giant, resonantly enhanced nonlinearity, along with vanishing linear susceptibilities The proposed atomic system uses an electromagnetically induced transparency and is limited only by two-photon absorption We predict dramatic improvement by several orders of magnitude for conditional phase shifts in XPM, and the system has possible applications in quantum nondemolition measurements and for quantum logic gates
TL;DR: In this paper, the authors considered the existence problem for the IVP (1.1) problem in H(R) = L(R), where R is the energy space.
Abstract: u(x, 0) = u0(x), where u0 ∈ H(R). Our principal aim here is to lower the best index s for which one has local well posedness in H(R), i.e. existence, uniqueness, persistence and continuous dependence on the data, for a finite time interval, whose size depends on ‖u0‖Hs . Equation in (1.1) was derived by Korteweg and de Vries [21] as a model for long wave propagating in a channel. A large amount of work has been devoted to the existence problem for the IVP (1.1). For instance, (see [9], [10]), the inverse scattering method applies to this problem, and, under appropriate decay assumptions on the data, several existence results have been established, see [5],[6],[14],[28],[33]. Another approach, inherited from hyperbolic problems, relies on the energy estimates, and, in particular shows that (1.1) is locally well posed in H(R) for s > 3/2, (see [2],[3],[12],[29],[30],[31]). Using these results and conservation laws, global (in time) well posedness in H(R), s ≥ 2 was established, (see [3],[12],[30]). Also, global in time weak solutions in the energy space H(R) were constructed in [34]. In [13] and [22] a “local smoothing” effect for solutions of (1.1) was discovered. This, combined with the conservation laws, was used in [13] and [22] to construct global in time weak solutions with data in H(R), and even in L(R). In [16], we introduced oscillatory integral techniques, to establish local well posedness of (1.1) in H(R), s > 3/4, and hence, global (in time) well posedness in H(R), s ≥ 1. (In [16] we showed how to obtain the above mentioned result by Picard iteration in an appropriate function space.) In [4] J. Bourgain introduced new function spaces, adapted to the linear operator ∂t+∂ 3 x, for which there are good “bilinear” estimates for the nonlinear term ∂x(u /2). Using these spaces, Bourgain was able to establish local well posedness of (1.1) in H(R) = L(R), and hence, by a conservation
TL;DR: A variational principle for $n({r,r}^{\ensuremath{'}})$ is derived in which, by the use of a penalty functional, the (difficult) idempotency of $n(r, r)$ need not be assured in advance but is automatically achieved.
Abstract: A widely applicable ``nearsightedness'' principle is first discussed as the physical basis for the existence of computational methods scaling linearly with the number of atoms. This principle applies to the one particle density matrix $n({r,r}^{\ensuremath{'}})$ but not to individual eigenfunctions. A variational principle for $n({r,r}^{\ensuremath{'}})$ is derived in which, by the use of a penalty functional $P[n({r,r}^{\ensuremath{'}})]$, the (difficult) idempotency of $n({r,r}^{\ensuremath{'}})$ need not be assured in advance but is automatically achieved. The method applies to both insulators and metals.
TL;DR: An inversion procedure is introduced for nonlinear systems which constructs a bounded input trajectory in the preimage of a desired output trajectory which leads to a simple geometric connection between the unstable manifold of the system zero dynamics and noncausality in the nonminimum phase case.
Abstract: An inversion procedure is introduced for nonlinear systems which constructs a bounded input trajectory in the preimage of a desired output trajectory. In the case of minimum phase systems, the trajectory produced agrees with that generated by Hirschorn's inverse dynamic system; however, the preimage trajectory is noncausal (rather than unstable) in the nonminimum phase case. In addition, the analysis leads to a simple geometric connection between the unstable manifold of the system zero dynamics and noncausality in the nonminimum phase case. With the addition of stabilizing feedback to the preimage trajectory, asymptotically exact output tracking is achieved. Tracking is demonstrated with a numerical example and compared to the well-known Byrnes-Isidori regulator. Rather than solving a partial differential equation to construct a regulator, the inverse is calculated using a Picard-like interaction. When preactuation is not possible, noncausal inverse trajectories can be truncated resulting in the tracking-error transients found in other control schemes.
TL;DR: The elastic modulus of the platelet was determined with a lateral resolution of approximately 100 nm by measuring force curves as a function of the lateral position on top of human platelets with the atomic force microscope.
Journal Article•
TL;DR: The results support the hypothesis that the most potent chemotherapeutic mechanism of paclitaxel is kinetic stabilization of spindle microtubule dynamics.
Abstract: Paclitaxel at low concentrations (10 nm for 20 h) induces ∼90% mitotic block at the metaphase/anaphase transition in HeLa cells, apparently by suppressing dynamics of spindle microtubules (M. A. Jordan et al., Proc. Natl. Acad. Sci. USA, 90: 9552–9556, 1993). It is not known, however, whether inhibition of mitosis by such low paclitaxel concentrations results in cell death. In the present work, we found that after removal of pacli-taxel (10 nm-1 µm), blocked cells did not resume proliferation. Instead, cells exited mitosis abnormally within 24 h. They did not progress through anaphase or cytokinesis but entered an interphase-like state (chromatin decondensed, and an interphase-like microtubule array and nuclear membranes reformed). Many cells (≥55%) contained multiple nuclei. Additional DNA synthesis and polyploidy did not occur. DNA degradation into nucleosome-sized fragments characteristic of apoptosis began during drug incubation and increased after drug removal. Cells died within 48–72 h. Incubation with paclitaxel (10 nm for 20 h) resulted in high intracellular drug accumulation (8.3 µm) and little efflux after paclitaxel removal; intracellular retention of paclitaxel may contribute to its efficacy. The results support the hypothesis that the most potent chemotherapeutic mechanism of paclitaxel is kinetic stabilization of spindle microtubule dynamics.
TL;DR: In this paper, the implications of T -duality and extended gauge symmetry for the conjectured equivalence of heterotic and Type I superstrings were studied. But the results of the study were limited to the Dirichlet one-brane of Type I string theory.
TL;DR: Gain narrowing in optically pumped thin films, both neat and undiluted, of luminescent conjugated polymers with different molecular structures was demonstrated in this paper, showing that the polymers studied have large cross sections for stimulated emission, that population inversion can be achieved at low pump energies, and that the emitted photons travel distances greater than the gain length within the gain medium.
Abstract: Gain narrowing in optically pumped thin films, both neat and undiluted, of luminescent conjugated polymers with different molecular structures was demonstrated. These results indicate that the polymers studied have large cross sections for stimulated emission, that population inversion can be achieved at low pump energies, and that the emitted photons travel distances greater than the gain length within the gain medium. The use of simple waveguide structures is sufficient to cause low gain narrowing thresholds in submicrometer-thick films.
TL;DR: Ordered mesostructured porous silicas that are also macroscopically structured were created by control of the interface on two different length scales simultaneously, and might have implications for technical applications, such as slow drug-release systems or membranes, and in biomineralization, where many processes are also interface-controlled.
Abstract: Ordered mesostructured porous silicas that are also macroscopically structured were created by control of the interface on two different length scales simultaneously. Micellar arrays controlled the nanometer-scale assembly, and at the static boundary between an aqueous phase and an organic phase, control was achieved on the micrometer to centimeter scale. Acid-prepared mesostructures of silica were made with the p6, Pm3n, and the P63/mmc structures in the form of porous fibers 50 to 1000 micrometers in length, hollow spheres with diameters of 1 to 100 micrometers, and thin sheets up to 10 centimeters in diameter and about 10 to 500 micrometers in thickness. These results might have implications for technical applications, such as slow drug-release systems or membranes, and in biomineralization, where many processes are also interface-controlled.
TL;DR: In this paper, a comparison of 14C (carbon-14) in archived (pre-1963) and contemporary soils taken along an elevation gradient in the Sierra Nevada, California, demonstrates rapid (7 to 65 years) turnover for 50 to 90 percent of carbon in the upper 20 centimeters of soil (A horizon soil carbon).
Abstract: Comparison of 14C (carbon-14) in archived (pre-1963) and contemporary soils taken along an elevation gradient in the Sierra Nevada, California, demonstrates rapid (7 to 65 years) turnover for 50 to 90 percent of carbon in the upper 20 centimeters of soil (A horizon soil carbon). Carbon turnover times increased with elevation (decreasing temperature) along the Sierra transect. This trend was consistent with results from other locations, which indicates that temperature is a dominant control of soil carbon dynamics. When extrapolated to large regions, the observed relation between carbon turnover and temperature suggests that soils should act as significant sources or sinks of atmospheric carbon dioxide in response to global temperature changes.
TL;DR: It is argued that the {ital K}3 orbifold with spin connection embedded in gauge connection corresponds to an interacting conformal field theory in the type I theory.
Abstract: We study superstrings with orientifold projections and with generalized open string boundary conditions (D branes). We find two types of consistency condition, one related to the algebra of Chan-Paton factors and the other to cancellation of divergences. One consequence is that the Dirichlet five branes of the type I theory carry a symplectic gauge group, as required by string duality. As another application we study the type I theory on a $K3$ ${Z}_{2}$ orbifold, finding a family of consistent theories with various unitary and symplectic subgroups of U(16)\ifmmode\times\else\texttimes\fi{}U(16). We argue that the $K3$ orbifold with spin connection embedded in gauge connection corresponds to an interacting conformal field theory in the type I theory.
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TL;DR: In this paper, it was shown that many of the p -branes of type II string theory and d = 11 supergravity can have boundaries on other p-branes, and the rules for when this can and cannot occur are derived from charge conservation.
TL;DR: This article discusses the results of three studies done with 160 university German students using CyberBuch, a hypermedia application for reading German texts that contains a variety of annotations for words in the form of text, pictures, and video that showed a higher rate of incidental learning than expected, and a correlation between looking up a certain annotation type and using this type as the retrieval cue for remembering words.
Abstract: Research on second language (L2) vocabulary acquisition has revealed that words associated with actual objects or imagery techniques are learned more easily than those without. With multimedia applications, it is possible to provide, in addition to traditional definitions of words, different types of information, such as pictures and videos. Thus, one of the fundamental research questions posed in the use of multimedia systems is: How effective are annotations with different media types for vocabulary acquisition? This article discusses the results of three studies done with 160 university German students using CyberBuch, a hypermedia application for reading German texts that contains a variety of annotations for words in the form of text, pictures, and video. The issues examined are related to (a) how well vocabulary is learned incidentally when the goal is reading comprehension, (b) the effectiveness of different types of annotations for vocabulary acquisition, and (c) the relationship between look-up behavior and performance on vocabulary tests. The results showed a higher rate of incidental learning than expected (25% accuracy on production tests, 77% on recognition tests), significantly higher scores for words that were annotated with pictures + text than for those with video + text or text only, and a correlation between looking up a certain annotation type and using this type as the retrieval cue for remembering words.
TL;DR: In this paper, the authors give a derivation of the gravitational Hamiltonian starting from the Einstein-Hilbert action, keeping track of all surface terms, which can be applied to any spacetime that asymptotically approaches a static background solution.
Abstract: We give a derivation of the gravitational Hamiltonian starting from the Einstein - Hilbert action, keeping track of all surface terms. This derivation can be applied to any spacetime that asymptotically approaches a static background solution. The surface term that arises in the Hamiltonian can be taken as the definition of the `total energy', even for spacetimes that are not asymptotically flat. (In the asymptotically flat case, it agrees with the usual ADM energy.) We also discuss the relation between the Euclidean action and the Hamiltonian when there are horizons of infinite area (e.g. acceleration horizons) as well as the usual finite area black hole horizons. Acceleration horizons seem to be more analogous to extreme than nonextreme black holes, since we find evidence that their horizon area is not related to the total entropy.
TL;DR: In this paper, Ferrara, Kallosh and the author derived a universal formula for the Bekenstein-Hawking entropy in terms of the charges and the moduli space geometry at X Λ ( q ( m, q ( e ) ).
TL;DR: A new framework for removing impulse noise from images is presented in which the nature of the filtering operation is conditioned on a state variable defined as the output of a classifier that operates on the differences between the input pixel and the remaining rank-ordered pixels in a sliding window.
Abstract: A new framework for removing impulse noise from images is presented in which the nature of the filtering operation is conditioned on a state variable defined as the output of a classifier that operates on the differences between the input pixel and the remaining rank-ordered pixels in a sliding window. As part of this framework, several algorithms are examined, each of which is applicable to fixed and random-valued impulse noise models. First, a simple two-state approach is described in which the algorithm switches between the output of an identity filter and a rank-ordered mean (ROM) filter. The technique achieves an excellent tradeoff between noise suppression and detail preservation with little increase in computational complexity over the simple median filter. For a small additional cost in memory, this simple strategy is easily generalized into a multistate approach using weighted combinations of the identity and ROM filter in which the weighting coefficients can be optimized using image training data. Extensive simulations indicate that these methods perform significantly better in terms of noise suppression and detail preservation than a number of existing nonlinear techniques with as much as 40% impulse noise corruption. Moreover, the method can effectively restore images corrupted with Gaussian noise and mixed Gaussian and impulse noise. Finally, the method is shown to be extremely robust with respect to the training data and the percentage of impulse noise.