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Caltech Authors (127.665 recursos)

Repository of works by Caltech published authors.

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Mostrando recursos 1 - 20 de 5.872

  1. Geologic Map of the San Emigdio Mountains, Southern California

    Chapman, Alan D.; Saleeby, Jason B.
    New and existing geologic mapping and geochronology of the San Emigdio Mountains are compiled in a 1:40,000 scale map, establishing the framework for recently published and ongoing studies of Cretaceous assemblages belonging to the Sierra Nevada batholith and the Late Cretaceous San Emigdio Schist. Basement exposures of the San Emigdio Mountains are subdivided into four principal fault-bounded assemblages: (1) mid- to Late Cretaceous shallow-level granitoids and Paleozoic to Mesozoic metamorphic pendant rocks of the Pastoria plate; (2) Early to mid-Cretaceous deep-level intrusives of the Tehachapi-San Emigdio complex; (3) mid-to Late Jurassic gabbro, tonalite, ultramafic rocks, and framework basalts of the Western San Emigdio mafic complex; and (4) the Late...

  2. Campanella and the Disciplines from Obscurity to Concealment

    Haugen, Kristine Louise
    During 27 years in prison, Tommaso Campanella became a European celebrity by publishing natural philosophy, political philosophy, and more. What was it like to write in prison in the 17th century, and did those conditions leave any traces in his books? By comparison with the chaotic style of his earlier career, Campanella usually became clearer and more appealing, relying much less on books and more on original argument. On the other hand, his abiding interest in republican political thought demanded an alert and even sympathetic reader as Campanella ostensibly opposed republicanism with disputations and authorities that recalled his youth.

  3. Quantum Proofs

    Vidick, Thomas; Watrous, John
    Quantum information and computation provide a fascinating twist on the notion of proofs in computational complexity theory. For instance, one may consider a quantum computational analogue of the complexity class NP, known as QMA, in which a quantum state plays the role of a proof (also called a certificate or witness), and is checked by a polynomial-time quantum computation. For some problems, the fact that a quantum proof state could be a superposition over exponentially many classical states appears to offer computational advantages over classical proof strings. In the interactive proof system setting, one may consider a verifier and one...

  4. High-speed photoacoustic tomography

    Song, Liang; Guo, Zijian; Wang, Lihong V.
    Traditional diagnostic imaging technologies—including ultrasound, x-ray computed tomography, and magnetic resonance imaging—have dramatically improved patient care in the clinic. However, these technologies still have limited ability to detect small lesions. In most cases, the detectable lesions are ~1 cm in dimeter, corresponding to ~10^9 cells (including circulating and microscopic metastatic deposits) and representing ~2/3 of the natural history of a cancer [1]. Consequently, the window of opportunity for treatment before a tumor reaches its lethal state is narrow. Hence, it is imperative to develop novel technologies capable of detecting neoplasia early. Non ionizing biomedical optical imaging is highly desirable because of...

  5. A Dual-Modality Photoacoustic and Ultrasound Imaging System for Noninvasive Sentinel Lymph Node Detection: Preliminary Clinical Results

    Erpelding, Todd N.; Garcia-Uribe, Alejandro; Krumholz, Arie; Ke, Haixin; Maslov, Konstantin; Appleton, Catherine; Margenthaler, Julie; Wang, Lihong V.
    Sentinel lymph node biopsy (SLNB) has emerged as an accurate, less invasive alternative to axillary lymph node dissection, and it has rapidly become the standard of care for patients with clinically node-negative breast cancer. The sentinel lymph node (SLN) hypothesis states that the pathological status of the axilla can be accurately predicted by determining the status of the first (i.e., sentinel) lymph nodes that drain from the primary tumor. Physicians use radio-labeled sulfur colloid and/or methylene blue dye to identify the SLN, which is most likely to contain metastatic cancer cells. However, the surgical procedure causes morbidity and associated expenses. To overcome these limitations, we developed a...

  6. Probability 1 Computation with Chemical Reaction Networks

    Cummings, Rachel; Doty, David; Soloveichik, David
    The computational power of stochastic chemical reaction networks (CRNs) varies significantly with the output convention and whether or not error is permitted. Focusing on probability 1 computation, we demonstrate a striking difference between stable computation that converges to a state where the output cannot change, and the notion of limit-stable computation where the output eventually stops changing with probability 1. While stable computation is known to be restricted to semilinear predicates (essentially piecewise linear), we show that limitstable computation encompasses the set of predicates in Δ^0_2 in the arithmetical hierarchy (a superset of Turing-computable). In finite time, our construction achieves...

  7. Coarse-Grained Molecular Dynamics Simulations of the Bacterial Cell Wall

    Nguyen, Lam T.; Gumbart, James C.; Jensen, Grant J.
    Understanding mechanisms of bacterial sacculus growth is challenging due to the time and length scales involved. Enzymes three orders of magnitude smaller than the sacculus somehow coordinate and regulate their processes to double the length of the sacculus while preserving its shape and integrity, all over a period of tens of minutes to hours. Decades of effort using techniques ranging from biochemical analysis to microscopy have produced vast amounts of data on the structural and chemical properties of the cell wall, remodeling enzymes and regulatory proteins. The overall mechanism of cell wall synthesis, however, remains elusive. To approach this problem...

  8. Super-A Polynomial

    Fuji, Hiroyuki; Sułkowski, Piotr
    We review a construction of a new class of algebraic curves, called super-A-polynomials, and their quantum generalizations. The super-A-polynomial is a two-parameter deformation of the A-polynomial known from knot theory or Chern-Simons theory with SL(2,C) gauge group. The two parameters of the super-A-polynomial encode, respectively, the t-deformation which leads to the "refined A-polynomial", and the Q-deformation which leads to the augmentation polynomial of knot contact homology. For a given knot, the super-A-polynomial encodes the asymptotics of the corresponding S^r-colored HOMFLY homology for large r, while the quantum super-A-polynomial provides recursion relations for such homology theories for each r. The super-A-polynomial...

  9. Introduction to Light Scattering by Biological Objects. Part 1. Extinction and Scattering of Light in Disperse Systems

    Khlebtsov, Nikolai G.; Maksimova, Irena L.; Tuchin, Valery V.; Wang, Lihong V.
    [no abstract]

  10. Medical Imaging with Microwave: Thermoacoustic Tomography

    Xu, Yuan; Wang, Lihong V.
    After introducing the principles of thermoacoustic tomography and pure microwave imaging, we summarize the mechanisms attributable to the dielectrical properties of biological tissues in the microwave frequency range. Next, we introduce some theoretical results from studies of thermoacoustic tomography, including information about optimal microwave frequencies, effects of acoustical heterogeneity on breast thermoacoustic tomography, limited-view thermoacoustic tomography, reconstruction algorithms, and spatial resolution. The experimental setups and the results of thermoacoustic tomography in planar and circular geometries are discussed. Finally, in vivo and in vitro results of both thermoacoustic tomography and pure microwave imaging are presented.

  11. Photoacoustic Tomography of Microcirculation

    Leahy, Martin J.; Hu, Song; Wang, Lihong V.
    Photoacoustic tomography (PAT), a hybrid technology combining optical excitation and ultrasonic detection, senses functional or molecular optical absorption contrasts and enables high‐resolution imaging as deep as the optical diffusive regime. PAT for label‐free microvascular imaging is highly desirable because of the presence of hemoglobin as an endogenous chromophore. In this chapter, we first review two major embodiments of PAT (photoacoustic microscopy and photoacoustic computed tomography). Then, we introduce methods for in vivo quantification of total hemoglobin concentration, blood oxygenation, and blood flow. After that, we show a few recent biomedical applications, including angiogenesis monitoring, brain and ocular imaging, and in...

  12. Photoacoustic Tomography of the Brain

    Xia, Jun; Wang, Lihong V.
    Photoacoustic tomography (PAT) is an emerging hybrid imaging technique with great potential for a wide range of brain imaging applications. A unique feature of PAT is the capability of sensing optical contrasts ultrasonically. Because of the low ultrasonic scattering in tissue, PAT generates high resolution images in both the ballistic and diffusive regimes. With a rich choice of endogenous and exogenous optical contrasts, PAT can provide neurovascular, structural, functional, and molecular brain images at multiple spatial scales. In this chapter, we review the principles and imaging capability of various photoacoustic brain tomography systems and highlight studies published in the past...

  13. Three-Dimensional Optical-Resolution Photoacoustic Microscopy

    Hu, Song; Maslov, Konstantin; Wang, Lihong V.
    Three-dimensional optical-resolution photoacoustic microscopy (OR-PAM), an emerging optical-acoustic hybrid technology capable of imaging optical absorption contrasts with subcellular resolution and sensitivity, has been recognized as a valuable complement to existing optical microscopy technologies. In this chapter, we provide detailed discussion on the design and operation of OR-PAM, including the principle, system design, system configuration, system alignment, experimental procedures, laser safety, functional imaging scheme, recent technical advances, and sample biomedical applications. Future directions of OR-PAM development are also discussed at the end of this chapter.

  14. Translational Photoacoustic Microscopy

    Zhou, Yong; Wang, Lihong V.
    Photoacoustic microscopy (PAM), combining the advantages of optical excitation and of acoustic detection, has been widely used for both structural and functional imaging with scalable resolution and penetration in biological tissues. In this chapter, we provide a detailed discussion on PAM in translational studies. We first summarize the principles and major implementations of this technology. Then we introduce the state of the art in translational PAM, including studies on burns, peripheral arterial occlusive disease, eye disease, diabetic microvascular complications, pain, melanoma, gastrointestinal tract disease, and the brain. Finally, we discuss the major challenges and future directions of translational PAM.

  15. Clipping using homogeneous coordinates

    Blinn, James F.; Newell, Martin E.
    Clipping is the process of determining how much of a given line segment lies within the boundaries of the display screen. Homogeneous coordinates are a convenient mathematical device for representing and transforming objects. The space represented by homogeneous coordinates is not, however, a simple Euclidean 3-space. It is, in fact, analagous to a topological shape called a “projective plane”. The clipping problem is usually solved without consideration for the differences between Euclidean space and the space represented by homogeneous coordinates. For some constructions, this leads to errors in picture generation which show up as lines marked invisible when they should...

  16. Light reflection functions for simulation of clouds and dusty surfaces

    Blinn, James F.
    The study of the physical process of light interacting with matter is an important part of computer image synthesis since it forms the basis for calculations of intensities in the picture. The simpler models used in the past are being augmented by more complex models gleaned from the physics literature. This paper is another step in the direction of assimilating such knowledge. It concerns the statistical simulation of light passing through and being reflected by clouds of similar small particles. (It does not, however, address the cloud structure modeling problem). By extension it can be applied to surfaces completely covered...

  17. A generalization of algebraic surface drawing

    Blinn, James F.
    The mathematical description of three dimensional surfaces usually falls in one of two classifications: parametric and algebraic. The form is defined as all points which satisfy some equation: F(x,y,z)=0. This form is ideally suited for image space shaded picture drawing, the pixel coordinates are substituted for x and y and the equation is solved for z. Algorithms for drawing such objects have been developed primarily for first and second order polynomial functions. This paper presents a new algorithm applicable to other functional forms, in particular to the summation of several gaussian density distributions. The algorithm was created to model electron...

  18. Simulation of wrinkled surfaces

    Blinn, James F.
    Computer generated shaded images have reached an impressive degree of realism with the current state of the art. They are not so realistic, however, that they would fool many people into believing they are real. One problem is that the surfaces tend to look artificial due to their extreme smoothness. What is needed is a means of simulating the surface irregularities that are on real surfaces. In 1973 Ed Catmull introduced the idea of using the parameter values of parametrically defined surfaces to index into a texture definition function which scales the intensity of the reflected light. By tying the...

  19. Correlation transfer and diffusion of ultrasound-modulated multiply scattered light

    Sakadžić, Sava; Wang, Lihong V.
    We develop a temporal correlation transfer equation (CTE) and a temporal correlation diffusion equation (CDE) for ultrasound-modulated multiply scattered light, which can be used to calculate the ultrasound-modulated optical intensity in an optically scattering medium with a nonuniform ultrasound field and a heterogeneous distribution of optical parameters. We present an analytical solution based on the CDE for scattering of the temporal autocorrelation function from a cylinder of ultrasound in an optically scattering slab. The CDE is valid for moderate ultrasound pressures on a scale comparable with the optical transport mean free path, which must be greater than the ultrasound wavelength...

  20. Reduced dynamical equations for barycentric spherical robots

    Burkhardt, Matt; Burdick, Joel W.
    Barycentric spherical robots (BSRs) rely on a noncollocated center of mass and center of rotation for propulsion. Unique challenges inherent to BSRs include a nontrivial correlation between internal actuation, momentum, and net vehicle motion. A new method is presented for deriving reduced dynamical equations of motion (EOM) for a general class of BSRs which extends and synthesizes prior efforts in geometric mechanics. Our method is an extension of the BKMM approach [1], allowing Lagrangian reduction and reconstruction to be applied to dynamical systems with symmetry-breaking potential energies, such as those encountered by BSRs rolling on a surface. The resulting dynamical...

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