Recursos de colección

Caltech Authors (137.221 recursos)

Repository of works by Caltech published authors.

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Mostrando recursos 1 - 20 de 6.649

  1. Flower Development: Open Questions and Future Directions

    Wellmer, Frank; Bowman, John L.; Davies, Brendan; Ferrándiz, Cristina; Fletcher, Jennifer C.; Franks, Robert G.; Graciet, Emmanuelle; Gregis, Veronica; Ito, Toshiro; Jack, Thomas P.; Jiao, Yuling; Kater, Martin M.; Ma, Hong; Meyerowitz, Elliot M.; Prunet, Nathanaël; Riechmann, José Luis
    Almost three decades of genetic and molecular analyses have resulted in detailed insights into many of the processes that take place during flower development and in the identification of a large number of key regulatory genes that control these processes. Despite this impressive progress, many questions about how flower development is controlled in different angiosperm species remain unanswered. In this chapter, we discuss some of these open questions and the experimental strategies with which they could be addressed. Specifically, we focus on the areas of floral meristem development and patterning, floral organ specification and differentiation, as well as on the...

  2. MEMS oxygen transport device for islet transplantation in the subcutaneous site

    Kang, Dongyang; Komatsu, Hirotake; Lin, Henry; Cook, Colin A.; Tai, Yu-Chong; Mullen, Yoko; Kandeel, Fouad R.
    This paper presents a new MEMS approach of maintaining islet oxygenation for subcutaneous islet transplantation therapy of type 1 diabetes by engineering a MEMS oxygen transport device. A device is designed and fabricated. Bench-top testing and computational modeling of the device have demonstrated that it would provide sufficient oxygen to prevent hypoxia-induced islet death and maintain the functional metabolic activity of glucose-simulated insulin secretion for islets transplanted subcutaneously.

  3. First Millimeter-Wave Animal In Vivo Measurements of L-Glucose and D-Glucose: Further Steps Towards a Non-Invasive Glucometer

    Siegel, Peter H.; Dai, Wangde; Kloner, Robert A.; Csete, Marie; Pikov, Victor
    The authors present the first in vivo measurements of L-Glucose and D-Glucose concentrations using millimeter waves. Employing direct injection of solutions into the rat jugular vein, we have been able to correlate immediate changes in blood glucose readings with transmission loss through the ears of anesthetized rats at Ka band (27–40 GHz). The sensed changing D-glucose levels are shown to track blood values, but with a delay of approximately 10–15 minutes, which may be due to cellular glucose uptake. Surprisingly, levels of L-glucose, the non-bioactive enantiomer (L-isomer) are also tracked by millimeter-wave transmission through the ear, suggesting that we are...

  4. Alterations in Neuronal Action Potential Shape and Spiking Rate Caused by Pulsed 60 GHz Millimeter Wave Radiation

    Romanenko, Sergii; Siegel, Peter H.; Pikov, Victor; Wallace, Vincent
    This study demonstrates effect of 60 GHz radiation applied in a pulsed mode to the finite neuronal network. Short powerful pulses of 50 to 300 msec duration were applied to leech neuronal ganglion and electrophysiological activity of the Retzius cells were recorded via sharp electrodes. Pulses were applied with respect to the natural activity of the tested cell and preconditioned every recorded action potential. Despite fairly low increase of sample's temperature caused by radiation's heating, clear and instant alteration in action potential parameters occurred. Along with that the prolonged utilization of this mode resulted into decrease of action potential spiking...

  5. Hydraulic supports for polishing TMT M3MP

    Hu, Haifei; Qi, Erhui; Cole, Glen; Hu, Haixiang; Luo, Xiao; Ford, Virginia; Zhang, Xuejun
    For polishing the ultra-thin TMT M3MP, a polishing support system with 18 hydraulic supports (HS) is introduced. This work focuses on the designing and testing of these HSs. Firstly the design concept of HS system is discussed; then mechanical implementation of the HS structure is carried out, with special consideration of fluid cycling, work pressurization and the weight component. Afterward the piping installation and the de-gas process for the working fluid are implemented. Pressurization and stiffness are well checked before system integration for the single HS unit. Finally the support system is integrated for the polishing process.

  6. Apodized vortex coronagraph designs for segmented aperture telescopes

    Ruane, Garreth; Jewell, Jeffrey; Mawet, Dimitri; Pueyo, Laurent; Shaklan, Stuart
    Current state-of-the-art high contrast imaging instruments take advantage of a number of elegant coronagraph designs to suppress starlight and image nearby faint objects, such as exoplanets and circumstellar disks. The ideal performance and complexity of the optical systems depends strongly on the shape of the telescope aperture. Unfortunately, large primary mirrors tend to be segmented and have various obstructions, which limit the performance of most conventional coronagraph designs. We present a new family of vortex coronagraphs with numerically-optimized gray-scale apodizers that provide the sensitivity needed to directly image faint exoplanets with large, segmented aperture telescopes, including the Thirty Meter Telescope...

  7. The Application of Pentaprism Scanning Technology on the Manufacturing of M3MP

    Qi, Erhui; Hu, Haixiang; Hu, Haifei; Cole, Glen; Luo, Xiao; Ford, Virginia; Zhang, Xuejun
    The PSS (pentaprism scanning system) has advantages of simple structure, needless of reference flat, be able of on-site testing, etc, it plays an important role in large flat reflective mirror’s manufacturing, especially the high accuracy testing of low order aberrations. The PSS system measures directly the slope information of the tested flat surface. Aimed at the unique requirement of M3MP, which is the prototype mirror of the tertiary mirror in TMT (Thirty Meter Telescope) project, this paper analyzed the slope distribution of low order aberrations, power and astigmatism, which is very important in the manufacturing process of M3MP. Then the...

  8. The policy analysis market: an electronic commerce application of a combinatorial information market

    Polk, Charles; Hanson, Robin; Ledyard, John; Ishikida, Takahi
    [no abstract]

  9. Plasma fusion code coupling using scalable I/O services and scientific workflows

    Podhorszki, Norbert; Klasky, Scott; Liu, Qing; Docan, Ciprian; Parashar, Manish; Abbasi, Hasan; Lofstead, Jay; Schwan, Karsten; Wolf, Matthew; Zheng, Fang; Cummings, Julian
    In order to understand the complex physics of mother nature, physicist often use many approximations to understand one area of physics and then write a simulation to reduce these equations to ones that can be solved on a computer. Different approximations lead to different equations that model different physics, which can often lead to a completely different simulation code. As computers become more powerful, scientists can either write one simulation that models all of the physics or they produce several codes each for different portions of the physics and then 'couple' these codes together. In this paper, we concentrate on...

  10. Constraints methods for flexible models

    Platt, John C.; Barr, Alan H.
    Simulating flexible models can create aesthetic motion for computer animation. Animators can control these motions through the use of constraints on the physical behavior of the models. This paper shows how to use mathematical constraint methods based on physics and on optimization theory to create controlled, realistic animation of physically-based flexible models. Two types of constraints are presented in this paper: reaction constraints (RCs) and augrmented Lagrangian constraints (ALCs). RCs allow the fast computation of collisions of flexible models with polygonal models. In addition, RCs allow flexible models to be pushed and pulled under the control of an animator. ALCs...

  11. Online convex optimization with ramp constraints

    Badiei, Masoud; Li, Na; Wierman, Adam
    We study a novel variation of online convex optimization where the algorithm is subject to ramp constraints limiting the distance between consecutive actions. Our contribution is results providing asymptotically tight bounds on the worst-case performance, as measured by the competitive difference, of a variant of Model Predictive Control termed Averaging Fixed Horizon Control (AFHC). Additionally, we prove that AFHC achieves the asymptotically optimal achievable competitive difference within a general class of “forward looking” online algorithms. Furthermore, we illustrate that the performance of AFHC in practice is often much better than indicated by the (worst-case) competitive difference using a case study...

  12. An Iterative Abstraction Algorithm for Reactive Correct-by-Construction Controller Synthesis

    Mattila, Robert; Mo, Yilin; Murray, Richard M.
    In this paper, we consider the problem of synthesizing correct-by-construction controllers for discrete-time dynamical systems. A commonly adopted approach in the literature is to abstract the dynamical system into a Finite Transition System (FTS) and thus convert the problem into a two player game between the environment and the system on the FTS. The controller design problem can then be solved using synthesis tools for general linear temporal logic or generalized reactivity(1) specifications. In this article, we propose a new abstraction algorithm. Instead of generating a single FTS to represent the system, we generate two FTSs, which are under- and...

  13. Localization of disturbances in transportation systems

    Sivaranjani, S.; Wang, Yuh-Shyang; Gupta, Vijay; Savla, Ketan
    We present a control strategy for localization and attenuation of disturbances in transportation systems. Sudden and large disturbances in a transportation network can lead to the creation and propagation of shock waves which spread throughout the system causing jams and decreasing system throughput. By considering the Cell Transmission Model of traffic flow, we design a minimum-energy controller that exploits inter-vehicle communication to localize shock waves to small sections of the highway and attenuate them within a specified period of time. The control design is illustrated through simulations on realistic data from the I-210 highway in California.

  14. Networking for high energy physics

    Newman, H. B.; Mughal, A.; Kassymkhanova, I.; Bunn, J.; Voicu, R.; Lápádátescu, V.; Kcira, D.
    This report, and the accompanying reports of the Standing Committee on Inter-regional Connectivity (SCIC), a technical panel of the International Committee on Future Accelerators (ICFA), serve as comprehensive lecture notes, updated to February 2015, for the lectures on Global Networking delivered at the Varenna Summer School in July 2014. The full set of reports including the accompanying Annexes, Monitoring Working Group report and presentation slide deck may be found at http://cern.ch.icfa-scic.

  15. Monitoring and control of large-scale distributed systems

    Legrand, I. C.
    An important part of managing large-scale, distributed computing systems is a monitoring service that is able to monitor and track in real-time many site facilities, networks, and tasks in progress. The monitoring information gathered is essential for developing the required higher level services, the components that provide decision support and some degree of automated decisions and for maintaining and optimizing workflow in large-scale distributed systems. Our strategy in trying to satisfy the demands of data intensive applications was to move to more synergetic relationships between the applications, computing and storage facilities and the network infrastructure. These orchestration and global optimization...

  16. Advanced networking for scientific applications

    Barczyk, A.
    This paper provides an overview of recent ideas and novel paradigms in data networking, with some discussion on how they can be leveraged in modern scientific applications. In it, we discuss the dynamic circuit services providing bandwidth guarantees to the application, the Software Defined Networking principle and the OpenFlow protocol, showing a number of possible application scenarios. We conclude with a glimpse of the Information Centric Networking paradigm, one of the Future Internet Architecture directions being researched today.

  17. The virtual hospital: the emergence of telemedicine

    Petrasek, Danny; Barr, Alan; Palem, Krishna V.
    The current practice of medicine, while utilizing the advances in biological and physical science, still takes place in the physician office or hospital. Unfortunately, traditional practice as integrated into the current Healthcare system is unsustainable. Accommodating the increase demand for medical services with the attendant rising costs has caused a crisis in healthcare. Telemedicine, the practice of medicine by means of mobile/internet is a transformative process that will impact healthcare globally. Already, teleradiology (diagnostic radiology remotely by means of digital images that are electronically exported) and electronic medical records are gaining wide acceptance. The ability to distribute medical services by means...

  18. Wildfire Wally: a volunteer computing game

    Peck, Evan; Riolo, Maria; Cusack, Charles
    Online casual games can be used to significantly enhance the productivity of volunteer computing. We call games which perform volunteer computing volunteer computing games. We introduce Wildfire Wally, a volunteer computing game capable of solving the maximum clique problem.

  19. Transistor sizing of energy-delay-efficient circuits

    Pénzes, Paul I.; Nyström, Mika; Martin, Alain J.
    This paper studies the problem of transistor sizing of CMOS circuits optimized for energy-delay efficiency, i.e., for optimal Etn where E is the energy consumption and t is the delay of the circuit, while n is a fixed positive optimization index that reflects the chosen trade-off between energy and delay. We propose a set of analytical formulas that closely approximate the optimal transistor sizes. We then study an efficient iteration procedure that can further improve the original analytical solution. Based on these results, we introduce a novel transistor sizing algorithm for energy-delay efficiency.

  20. Energy-Delay Efficiency of VLSI Computations

    Pénzes, Paul I.; Martin, Alain J.
    In this paper we introduce an energy-delay efficiency metric that captures any trade-off between the energy and the delay of the computation. We apply this new concept to the parallel and sequential composition of circuits in general and in particular to circuits optimized through transistor sizing. We bound the delay and energy of the optimized circuit and we give necessary and sufficient conditions under which these bounds are reached. We also give necessary and sufficient conditions under which subcomponents of a design can be optimized independently so as to yield global optimum when recomposed. We demonstrate the utility of a...

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