Science.gov

Sample records for accessible conformational space

  1. Mapping the conformational space accessible to catechol-O-methyltransferase.

    PubMed

    Ehler, Andreas; Benz, Jörg; Schlatter, Daniel; Rudolph, Markus G

    2014-08-01

    Methylation catalysed by catechol-O-methyltransferase (COMT) is the main pathway of catechol neurotransmitter deactivation in the prefrontal cortex. Low levels of this class of neurotransmitters are held to be causative of diseases such as schizophrenia, depression and Parkinson's disease. Inhibition of COMT may increase neurotransmitter levels, thus offering a route for treatment. Structure-based drug design hitherto seems to be based on the closed enzyme conformation. Here, a set of apo, semi-holo, holo and Michaelis form crystal structures are described that define the conformational space available to COMT and that include likely intermediates along the catalytic pathway. Domain swaps and sizeable loop movements around the active site testify to the flexibility of this enzyme, rendering COMT a difficult drug target. The low affinity of the co-substrate S-adenosylmethionine and the large conformational changes involved during catalysis highlight significant energetic investment to achieve the closed conformation. Since each conformation of COMT is a bona fide target for inhibitors, other states than the closed conformation may be promising to address. Crystallographic data for an alternative avenue of COMT inhibition, i.e. locking of the apo state by an inhibitor, are presented. The set of COMT structures may prove to be useful for the development of novel classes of inhibitors. PMID:25084335

  2. Conformal bootstrap in embedding space

    NASA Astrophysics Data System (ADS)

    Fortin, Jean-François; Skiba, Witold

    2016-05-01

    It is shown how to obtain conformal blocks from embedding space with the help of the operator product expansion. The minimal conformal block originates from scalar exchange in a four-point correlation function of four scalars. All remaining conformal blocks are simple derivatives of the minimal conformal block. With the help of the orthogonality properties of the conformal blocks, the analytic conformal bootstrap can be implemented directly in embedding space, leading to a Jacobi-like definition of conformal field theories.

  3. Access to space studies

    NASA Technical Reports Server (NTRS)

    Martin, James A.

    1993-01-01

    The National Aeronautics and Space Administration is currently considering possible directions in Earth-to-orbit vehicle development under a study called 'Access to Space.' This agency-wide study is considering commercial launch vehicles, human transportation, space station logistics, and other space transportation requirements over the next 40 years. Three options are being considered for human transportation: continued use of the Space Shuttle; development of a small personnel carrier (personnel logistics system (PLS)); or development of an advanced vehicle such as a single-stage-to-orbit (SSTO). Several studies related to the overall Access to Space study are reported in this document.

  4. Accessing Space Weather Information

    NASA Astrophysics Data System (ADS)

    Morrison, D.; Weiss, M.; Immer, E. A.; Patrone, D.; Potter, M.; Barnes, R. J.; Colclough, C.; Holder, R.

    2009-12-01

    To meet the needs of our technology based society, space weather forecasting needs to be advanced and this will entail collaboration amongst research, military and commercial communities to find new ways to understand, characterize, and forecast. In this presentation VITMO, the Virtual Ionosphere-Thermosphere-Mesosphere Observatory will be used as a prototype for a generalized system as a means to bring together a set of tools to access data, models and online collaboration tools to enable rapid progress. VITMO, available at http://vitmo.jhuapl.edu/, currently provides a data access portal for researchers and scientists to enable finding data products as well as access to tools and models. To further the needs of space weather forecasters, the existing VITMO data holdings need to be expanded to provide additional datasets as well as integrating relevant models and model output. VITMO can easily be adapted for the Space Weather domain in its entirety. In this presentation, we will demonstrate how VITMO and the VITMO architecture can be utilized as a prototype in support of integration of Space Weather forecasting tools, models and data.

  5. Access to space study

    NASA Technical Reports Server (NTRS)

    1994-01-01

    This report summarizes the results of a comprehensive NASA in-house study to identify and assess alternate approaches to access to space through the year 2030, and to select and recommend a preferred cause of action. The goals of the study were to identify the best vehicles and transportation architectures to make major reductions in the cost of space transportation (at least 50%), while at the same time increasing safety for flight crews by at least an order of magnitude. In addition, vehicle reliability was to exceed 0.98 percent, and, as important, the robustness, pad time, turnaround time, and other aspects of operability were to be vastly improved. This study examined three major optional architectures: (1) retain and upgrade the Space Shuttle and expendable launch vehicles; (2) develop new expendable vehicles using conventional technologies and transition from current vehicles beginning in 2005; and (3) develop new reusable vehicles using advanced technology, and transition from current vehicles beginning in 2008. The launch-needs, mission model utilized for for the study was based upon today's projection of civil, defense, and commercial mission payload requirements.

  6. Astronauts Access Web from Space

    NASA Video Gallery

    Aboard the International Space Station, Expedition 22 Commander Jeff Williams and Flight Engineers Soichi Noguchi and T.J. Creamer share their thoughts about Internet access from space and post a r...

  7. Affine conformal vectors in space-time

    NASA Astrophysics Data System (ADS)

    Coley, A. A.; Tupper, B. O. J.

    1992-05-01

    All space-times admitting a proper affine conformal vector (ACV) are found. By using a theorem of Hall and da Costa, it is shown that such space-times either (i) admit a covariantly constant vector (timelike, spacelike, or null) and the ACV is the sum of a proper affine vector and a conformal Killing vector or (ii) the space-time is 2+2 decomposable, in which case it is shown that no ACV can exist (unless the space-time decomposes further). Furthermore, it is proved that all space-times admitting an ACV and a null covariantly constant vector (which are necessarily generalized pp-wave space-times) must have Ricci tensor of Segré type {2,(1,1)}. It follows that, among space-times admitting proper ACV, the Einstein static universe is the only perfect fluid space-time, there are no non-null Einstein-Maxwell space-times, and only the pp-wave space-times are representative of null Einstein-Maxwell solutions. Otherwise, the space-times can represent anisotropic fluids and viscous heat-conducting fluids, but only with restricted equations of state in each case.

  8. Implications of conformal invariance in momentum space

    NASA Astrophysics Data System (ADS)

    Bzowski, Adam; McFadden, Paul; Skenderis, Kostas

    2014-03-01

    We present a comprehensive analysis of the implications of conformal invariance for 3-point functions of the stress-energy tensor, conserved currents and scalar operators in general dimension and in momentum space. Our starting point is a novel and very effective decomposition of tensor correlators which reduces their computation to that of a number of scalar form factors. For example, the most general 3-point function of a conserved and traceless stress-energy tensor is determined by only five form factors. Dilatations and special conformal Ward identities then impose additional conditions on these form factors. The special conformal Ward identities become a set of first and second order differential equations, whose general solution is given in terms of integrals involving a product of three Bessel functions (`triple- K integrals'). All in all, the correlators are completely determined up to a number of constants, in agreement with well-known position space results. In odd dimensions 3-point functions are finite without renormalisation while in even dimensions non-trivial renormalisation in required. In this paper we restrict ourselves to odd dimensions. A comprehensive analysis of renormalisation will be discussed elsewhere. This paper contains two parts that can be read independently of each other. In the first part, we explain the method that leads to the solution for the correlators in terms of triple- K integrals while the second part contains a self-contained presentation of all results. Readers interested only in results may directly consult the second part of the paper.

  9. Securing America's access to space

    SciTech Connect

    Rendine, M.; Wood, L.

    1990-05-23

    We review pertinent aspects of the history of the space launch capabilities of the United States and survey its present status and near-term outlook. Steps which must be taken, pitfalls which much be avoided, and a core set of National options for re-acquiring in the near term the capability to access the space environment with large payloads are discussed. We devote considerable attention to the prospect of creating an interim heavy-lift space launch vehicle of at least 100,000 pound payload-orbiting capacity to serve National needs during the next dozen years, suggesting that such a capability can be demonstrated within 5 years for less than $1 B. Such capability will apparently be essential for meeting the first-phase goals of the President's Space Exploration Initiative. Some other high-leverage aspects of securing American access to space are also noted briefly, emphasizing unconventional technological approaches of presently high promise.

  10. A novel family of space-filling curves in their relation to chromosome conformation in eukaryotes

    NASA Astrophysics Data System (ADS)

    Smrek, Jan; Grosberg, Alexander Y.

    2013-12-01

    Spatial conformation of DNA chains during interphase in eukaryotic cell nucleus is relatively dense, yet unknotted and exhibits self-similar fractal properties. In this respect it resembles the space-filling curves of Hilbert, but differs in the experimentally accessible contact probability of distant loci. Here we construct space-filling curves with fractal domain boundaries of dimension close to that of the embedding space and show how these match the statistical properties and the contact probability of the DNA conformation. The present mathematical model should shed light on the statistical ensemble of unknotted dense polymers and ease the modeling of genome folding and related biological processes.

  11. On the local non-conforming virtual element spaces

    SciTech Connect

    Manzini, Gianmarco; Gyrya, Vitaliy

    2014-11-13

    The construction of the local non-conforming virtual element spaces is discussed and the isomorphism between their functions and the polynomial moments of such functions is established by a formal argument and two different constructive proofs.

  12. Access to space: The Space Shuttle's evolving rolee

    NASA Astrophysics Data System (ADS)

    Duttry, Steven R.

    1993-04-01

    Access to space is of extreme importance to our nation and the world. Military, civil, and commercial space activities all depend on reliable space transportation systems for access to space at a reasonable cost. The Space Transportation System or Space Shuttle was originally planned to provide transportation to and from a manned Earth-orbiting space station. To justify the development and operations costs, the Space Shuttle took on other space transportation requirements to include DoD, civil, and a growing commercial launch market. This research paper or case study examines the evolving role of the Space Shuttle as our nation's means of accessing space. The case study includes a review of the events leading to the development of the Space Shuttle, identifies some of the key players in the decision-making process, examines alternatives developed to mitigate the risks associated with sole reliance on the Space Shuttle, and highlights the impacts of this national space policy following the Challenger accident.

  13. Space Station multiple access communications system

    NASA Technical Reports Server (NTRS)

    Olson, Nanci A.

    1986-01-01

    The development of a multiple access communications system (MACS) for the space-to-space communications on the Space Station is discussed. The communications capabilities of the FHMA, CDMA, TDMA, SDMA, and FDMA techniques are evaluated; FDMA was selected for the space-to-space communications on the Space Station because of its lower complexity and growth capability. The proposed space-to-space multiple access system for the Space Station is a digitally modulated Ku-band FDMA system with a distributed architecture; this system would transmit on frequencies between 13.4 and 13.7 GHz and receive on frequencies between 14.6 and 14.89 GHz, and the bandwidth will support seven high-data-rate users and 12 low-data-rate users. The IF components and antennas for the MACS are examined. A multiple access breadboard design is described.

  14. Small Satellite Access of the Space Network

    NASA Technical Reports Server (NTRS)

    Horan, Stephen; Minnix, Timothy O.; Vigil, J. S.

    1999-01-01

    Small satellites have been perceived as having limited access to NASA's Space Network (SN). The potential for satellite access of the space network when the design utilizes a fixed antenna configuration and low-power, coded transmission is analyzed. From the analysis, satellites using this configuration in high-inclination orbits are shown to have a daily data throughput in the 100 to 1000 Mbit range using the multiple access communications service.

  15. Superintegrability in a non-conformally-flat space

    NASA Astrophysics Data System (ADS)

    Kalnins, E. G.; Kress, J. M.; Miller, W., Jr.

    2013-01-01

    Superintegrable systems in two- and three-dimensional spaces of constant curvature have been extensively studied. From these, superintegrable systems in conformally flat spaces can be constructed by Stäckel transform. In this paper a method developed to establish the superintegrability of the Tremblay-Turbiner-Winternitz system in two dimensions is extended to higher dimensions and a superintegrable system on a non-conformally-flat four-dimensional space is found. In doing so, curvature corrections to the corresponding classical potential are found to be necessary. It is found that some subalgebras of the symmetry algebra close polynomially.

  16. Entanglement entropy from the truncated conformal space

    NASA Astrophysics Data System (ADS)

    Palmai, T.

    2016-08-01

    A new numerical approach to entanglement entropies of the Rényi type is proposed for one-dimensional quantum field theories. The method extends the truncated conformal spectrum approach and we will demonstrate that it is especially suited to study the crossover from massless to massive behavior when the subsystem size is comparable to the correlation length. We apply it to different deformations of massless free fermions, corresponding to the scaling limit of the Ising model in transverse and longitudinal fields. For massive free fermions the exactly known crossover function is reproduced already in very small system sizes. The new method treats ground states and excited states on the same footing, and the applicability for excited states is illustrated by reproducing Rényi entropies of low-lying states in the transverse field Ising model.

  17. Mapping the Accessible Conformational Landscape of an Insect Carboxylesterase Using Conformational Ensemble Analysis and Kinetic Crystallography.

    PubMed

    Correy, Galen J; Carr, Paul D; Meirelles, Tamara; Mabbitt, Peter D; Fraser, Nicholas J; Weik, Martin; Jackson, Colin J

    2016-06-01

    The proper function of enzymes often depends upon their efficient interconversion between particular conformational sub-states on a free-energy landscape. Experimentally characterizing these sub-states is challenging, which has limited our understanding of the role of protein dynamics in many enzymes. Here, we have used a combination of kinetic crystallography and detailed analysis of crystallographic protein ensembles to map the accessible conformational landscape of an insect carboxylesterase (LcαE7) as it traverses all steps in its catalytic cycle. LcαE7 is of special interest because of its evolving role in organophosphate insecticide resistance. Our results reveal that a dynamically coupled network of residues extends from the substrate-binding site to a surface loop. Interestingly, the coupling of this network that is apparent in the apoenzyme appears to be reduced in the phosphorylated enzyme intermediate. Altogether, the results of this work highlight the importance of protein dynamics to enzyme function and the evolution of new activity. PMID:27210287

  18. Twisted conformal algebra related to κ -Minkowski space

    NASA Astrophysics Data System (ADS)

    Meljanac, Stjepan; Pachoł, Anna; Pikutić, Danijel

    2015-11-01

    Twisted deformations of the conformal symmetry in the Hopf algebraic framework are constructed. The first one is obtained by a Jordanian twist built up from dilatation and momenta generators. The second is the lightlike κ -deformation of the Poincaré algebra extended to the conformal algebra, obtained by a twist corresponding to the extended Jordanian r -matrix. The κ -Minkowski spacetime is covariant quantum space under both of these deformations. The extension of the conformal algebra by the noncommutative coordinates is presented in two cases. The differential realizations for κ -Minkowski coordinates, as well as their left-right dual counterparts, are also included.

  19. Conformal algebra on Fock space and conjugate pairs of operators

    SciTech Connect

    Sibold, Klaus; Burkhard, Eden

    2010-11-15

    Using the moment construction, we represent the generators of the conformal algebra as bilinear products of creation and annihiliation operators on the Fock space of the massless real scalar field in four dimensions. A complete set of one-particle eigenstates of the dilatation generator is given. Next, a complete set of one-particle eigenstates of the conformal generator is constructed in two distinct ways, once directly and once through an expansion in terms of dilatation eigenstates. The second approach uses an analytic continuation of the dilatation eigenvalue away from the real axis; the validity of the method is illustrated by the consistency with the first approach. Drawing upon this technique, we finally ponder the idea of building conjugates to the four components of the momentum operator by suitably modifying the action of the conformal generators on dilatation eigenstates. The construction of eigenstates of these new operators proceeds as for the conformal generator itself.

  20. Enhancing Access to Space Science Literature

    NASA Astrophysics Data System (ADS)

    Bigwood, D. P.

    2006-03-01

    By participating in the Name Authority Program Component and Subject Authority Cooperative Program of the Program for Cooperative Cataloging of the Library of Congress even the smallest libraries can enhance access to the space science literature.

  1. Space division multiplexing in access networks

    NASA Astrophysics Data System (ADS)

    Effenberger, Frank J.

    2015-01-01

    Space division multiplexing (SDM) has received a lot of attention in the past years, as it is seen as the final frontier of fiber optic capacity improvement for long haul transmission. Its use in access networks is even more interesting, due to the different design optimization goals in access versus transport. This paper explores some of the applications of SDM in access that have the potential for early adoption.

  2. Fast Access to Space Tourism

    NASA Astrophysics Data System (ADS)

    Favata', P.; Martineau, N.

    2002-01-01

    creating a revolutionary space-orbiting habitat dedicated to tourism. Up to now, such proposals have focused on two approaches. The first accounts for financial and technological constraints on space flight and living, and sacrifices creativity for practicality. The second is more utopic in nature and proposes projects, which are imaginative but unfeasible in the near future. This proposal is innovative because it considers the current obstacles to space tourism and utilizes existing technologies and infrastructures, but also includes the forethinking of futuristic commercial projects. Project Objectives: NASA claims that commercialization of space activities is so difficult that it will require decades more funding of so-called space-technology development. The benefits of this project show that this is not true. First, safety has been addressed because this proposal utilizes already space tested and assured technologies. Second, the project demonstrates potential for significant economic profit within the near future. Because we are using the least expensive technology available, we have limited start up costs. We forecast up to forty flights per year, with a potential capacity of eighty tourists. The design objectives focus on the proposal of a new approach to space tourism. These include: the expansion of the living space in the interiors, innovative and creative interior design, increased concern for the physiological and psychological comfort of tourists, and attention to entertainment possibilities. Project Content: The efficiency of the launch and configuration phase is one of the strengths of the proposed project. We propose the use of the Zenith 2 launcher, a large two-stage vehicle developed in the Soviet Union in the early 1980s, for the configuration of the orbiting platform. Following the Russian outfitting philosophy, once in orbit, the platform is already functional. The interior design is based on advanced lightweight inflatable technologies which

  3. Fast Access to Space Tourism

    NASA Astrophysics Data System (ADS)

    Favata', P.; Martineau, N.

    2002-01-01

    creating a revolutionary space-orbiting habitat dedicated to tourism. Up to now, such proposals have focused on two approaches. The first accounts for financial and technological constraints on space flight and living, and sacrifices creativity for practicality. The second is more utopic in nature and proposes projects, which are imaginative but unfeasible in the near future. This proposal is innovative because it considers the current obstacles to space tourism and utilizes existing technologies and infrastructures, but also includes the forethinking of futuristic commercial projects. Project Objectives: NASA claims that commercialization of space activities is so difficult that it will require decades more funding of so-called space-technology development. The benefits of this project show that this is not true. First, safety has been addressed because this proposal utilizes already space tested and assured technologies. Second, the project demonstrates potential for significant economic profit within the near future. Because we are using the least expensive technology available, we have limited start up costs. We forecast up to forty flights per year, with a potential capacity of eighty tourists. The design objectives focus on the proposal of a new approach to space tourism. These include: the expansion of the living space in the interiors, innovative and creative interior design, increased concern for the physiological and psychological comfort of tourists, and attention to entertainment possibilities. Project Content: The efficiency of the launch and configuration phase is one of the strengths of the proposed project. We propose the use of the Zenith 2 launcher, a large two-stage vehicle developed in the Soviet Union in the early 1980s, for the configuration of the orbiting platform. Following the Russian outfitting philosophy, once in orbit, the platform is already functional. The interior design is based on advanced lightweight inflatable technologies which

  4. Access to Space Interactive Design Web Site

    NASA Technical Reports Server (NTRS)

    Leon, John; Cutlip, William; Hametz, Mark

    2000-01-01

    The Access To Space (ATS) Group at NASA's Goddard Space Flight Center (GSFC) supports the science and technology community at GSFC by facilitating frequent and affordable opportunities for access to space. Through partnerships established with access mode suppliers, the ATS Group has developed an interactive Mission Design web site. The ATS web site provides both the information and the tools necessary to assist mission planners in selecting and planning their ride to space. This includes the evaluation of single payloads vs. ride-sharing opportunities to reduce the cost of access to space. Features of this site include the following: (1) Mission Database. Our mission database contains a listing of missions ranging from proposed missions to manifested. Missions can be entered by our user community through data input tools. Data is then accessed by users through various search engines: orbit parameters, ride-share opportunities, spacecraft parameters, other mission notes, launch vehicle, and contact information. (2) Launch Vehicle Toolboxes. The launch vehicle toolboxes provide the user a full range of information on vehicle classes and individual configurations. Topics include: general information, environments, performance, payload interface, available volume, and launch sites.

  5. Global Trends in Space Access and Utilization

    NASA Technical Reports Server (NTRS)

    Rahman, Shamim A.; Keim, Nicholas S.; Zeender, Peter E.

    2010-01-01

    In the not-so-distant past, space access and air/space technology superiority were within the purview of the U.S. and former Soviet Union's respective space agencies, both vying for global leadership in space exploitation. In more recent years, with the emergence of the European Space Agency (ESA) member countries and Asian countries joining the family of space-faring nations, it is truer now more than ever that space access and utilization has become a truly global enterprise. In fact, according to the Space Report 2007, this enterprise is a $251-billion economy. It is possible to gauge the vitality of worldwide efforts from open sources in today's transparent, media-based society. In particular, print and web broadcasters regularly report and catalog global space activities for defense and civil purposes. For the purposes of this paper, a representative catalog of missions is used to illustrate the nature of the emerging "globalization." This paper highlights global trends in terms of not only the providers of space access, but also the end-users for the various recently accomplished missions. With well over 50 launches per year, in recent years, the launch-log reveals a surprising percentage of "cooperative or co-dependent missions" where different agencies, countries, and/or commercial entities are so engaged presumably to the benefit of all who participate. Statistics are cited and used to show that recently over d0% of the 50-plus missions involved multiple nations working collectively to deliver payloads to orbit. Observers, space policy professionals, and space agency leaders have eloquently proposed that it might require the combined resources and talents of multiple nations to advance human exploration goals beyond low earth orbit. This paper does not intend to offer new information with respect to whether international collaboration is necessary but to observe that, in continuing to monitor global trends, the results seem to support the thesis that a

  6. Molecular conformational space analysis using computer graphics: going beyond FRODO.

    PubMed

    Nilsson, O

    1990-12-01

    The molecular graphics program FRODO has been modified to support analytical animation of molecular dynamics trajectories. The enhanced program, mdFRODO, supports all features available in FRODO and is interfaced to GROMOS. A variety of analytical animation modes is included. Extensive coloring and atom selection features are implemented to aid the user in distinguishing features of interest in a set of conformations. Molecular conformational space can be analyzed efficiently and comprehended. Animations may be viewed in stereo, and the animated object can be overlaid with any of the standard FRODO objects. The mdFRODO program is of wide use in molecular dynamics, X-ray crystallography and two-dimensional NMR work. Examples illustrating various aspects of collective motion in protein molecules are given and discussed. PMID:2282358

  7. The cost of access to space

    NASA Technical Reports Server (NTRS)

    Griffin, Michael D.; Claybaugh, William R., II

    1994-01-01

    Nearly four decades into the space age, our biggest problem is still the high cost of transportation to space. Close behind are the relatively infrequent flight opportunities and high risk of the transportation systems we have. These problems are of course not independent; rather, they are interrelated measures of the difficulty of accelerating a payload through an ideal velocity increment of over 9 km/s and a height of 200 km or more in just a few minutes. These difficulties are not unrecognized, and the demand for newer, cheaper, more reliable, more frequently flying launch systems has been unending. Hundreds, maybe thousands of studies have been done on various approaches offering improved access to space, and each approach has its ardent supporters, convinced that no other approach can work as well. In the government, hardly a year passes without the attempted initiation of a new program to lower the cost and improve the reliability of space transportation. This paper does not attempt to decide the merits and demerits of various transportation concepts but examines the cost of access to space from a slightly different perspective, and attempts to use that perspective to reach some conclusions about characteristics that a next-generation system must have to yield lower cost, regardless of its design.

  8. Cargo Assured Access to International Space Station

    NASA Technical Reports Server (NTRS)

    Smith, David A.

    2004-01-01

    Boeing's Cargo Assured Access logistics delivery system will provide a means to transport cargo to/from the International Space Station, Low Earth Orbit and the moon using Expendable Launch Vehicles. For Space Station, this capability will reduce cargo resupply backlog during nominal operations (e.g., supplement Shuttle, Progress, ATV and HTV) and augment cargo resupply capability during contingency operations (e.g., Shuttle delay and/or unavailability of International Partner launch or transfer vehicles). This capability can also provide an autonomous means to deliver cargo to lunar orbit, a lunar orbit refueling and work platform, and a contingency crew safe haven in support of NASA's new Exploration Initiative.

  9. A Demand Access Protocol for Space Applications

    NASA Technical Reports Server (NTRS)

    Gao, Jay L.; Leang, Dee

    2007-01-01

    This paper describes a demand access protocol for space communications, which is a messaging procedure that facilitates the exchange of resource requests and grants between users and service providers. A minimal set of operational and environmental needs and constraints are assumed since the intent is to keep the protocol flexible and efficient for a wide-range of envisioned NASA robotic and human exploration missions. The protocol described in this document defines the message format and procedures used to ensure proper and correct functioning of a demand access communications system, which must operate under customized resource management policies applied by the users and service providers. This protocol also assumes a minimal set of capabilities from the underlying communications system so that no unique requirements are imposed on the communications sub-systems.

  10. Stratospheric Balloon Platforms for Near Space Access

    NASA Astrophysics Data System (ADS)

    Dewey, R. G.

    2012-12-01

    For over five decades, high altitude aerospace balloon platforms have provided a unique vantage point for space and geophysical research by exposing scientific instrument packages and experiments to space-like conditions above 99% of Earth's atmosphere. Reaching altitudes in excess of 30 km for durations ranging from hours to weeks, high altitude balloons offer longer flight durations than both traditional sounding rockets and emerging suborbital reusable launch vehicles. For instruments and experiments requiring access to high altitudes, engineered balloon systems provide a timely, responsive, flexible, and cost-effective vehicle for reaching near space conditions. Moreover, high altitude balloon platforms serve as an early means of testing and validating hardware bound for suborbital or orbital space without imposing space vehicle qualifications and certification requirements on hardware in development. From float altitudes above 30 km visible obscuration of the sky is greatly reduced and telescopes and other sensors function in an orbit-like environment, but in 1g. Down-facing sensors can take long-exposure atmospheric measurements and images of Earth's surface from oblique and nadir perspectives. Payload support subsystems such as telemetry equipment and command, control, and communication (C3) interfaces can also be tested and operationally verified in this space-analog environment. For scientific payloads requiring over-flight of specific areas of interests, such as an active volcano or forest region, advanced mission planning software allows flight trajectories to be accurately modeled. Using both line-of-sight and satellite-based communication systems, payloads can be tracked and controlled throughout the entire mission duration. Under NASA's Flight Opportunities Program, NSC can provide a range of high altitude flight options to support space and geophysical research: High Altitude Shuttle System (HASS) - A balloon-borne semi-autonomous glider carries

  11. Predictive Sampling of Rare Conformational Events in Aqueous Solution: Designing a Generalized Orthogonal Space Tempering Method.

    PubMed

    Lu, Chao; Li, Xubin; Wu, Dongsheng; Zheng, Lianqing; Yang, Wei

    2016-01-12

    In aqueous solution, solute conformational transitions are governed by intimate interplays of the fluctuations of solute-solute, solute-water, and water-water interactions. To promote molecular fluctuations to enhance sampling of essential conformational changes, a common strategy is to construct an expanded Hamiltonian through a series of Hamiltonian perturbations and thereby broaden the distribution of certain interactions of focus. Due to a lack of active sampling of configuration response to Hamiltonian transitions, it is challenging for common expanded Hamiltonian methods to robustly explore solvent mediated rare conformational events. The orthogonal space sampling (OSS) scheme, as exemplified by the orthogonal space random walk and orthogonal space tempering methods, provides a general framework for synchronous acceleration of slow configuration responses. To more effectively sample conformational transitions in aqueous solution, in this work, we devised a generalized orthogonal space tempering (gOST) algorithm. Specifically, in the Hamiltonian perturbation part, a solvent-accessible-surface-area-dependent term is introduced to implicitly perturb near-solute water-water fluctuations; more importantly in the orthogonal space response part, the generalized force order parameter is generalized as a two-dimension order parameter set, in which essential solute-solvent and solute-solute components are separately treated. The gOST algorithm is evaluated through a molecular dynamics simulation study on the explicitly solvated deca-alanine (Ala10) peptide. On the basis of a fully automated sampling protocol, the gOST simulation enabled repetitive folding and unfolding of the solvated peptide within a single continuous trajectory and allowed for detailed constructions of Ala10 folding/unfolding free energy surfaces. The gOST result reveals that solvent cooperative fluctuations play a pivotal role in Ala10 folding/unfolding transitions. In addition, our assessment

  12. Conformational dynamics of ligand-dependent alternating access in LeuT.

    PubMed

    Kazmier, Kelli; Sharma, Shruti; Quick, Matthias; Islam, Shahidul M; Roux, Benoît; Weinstein, Harel; Javitch, Jonathan A; McHaourab, Hassane S

    2014-05-01

    The leucine transporter (LeuT) from Aquifex aeolicus is a bacterial homolog of neurotransmitter/sodium symporters (NSSs) that catalyze reuptake of neurotransmitters at the synapse. Crystal structures of wild-type and mutants of LeuT have been interpreted as conformational states in the coupled transport cycle. However, the mechanistic identities inferred from these structures have not been validated, and the ligand-dependent conformational equilibrium of LeuT has not been defined. Here, we used distance measurements between spin-label pairs to elucidate Na(+)- and leucine-dependent conformational changes on the intracellular and extracellular sides of the transporter. The results identify structural motifs that underlie the isomerization of LeuT between outward-facing, inward-facing and occluded states. The conformational changes reported here present a dynamic picture of the alternating-access mechanism of LeuT and NSSs that is different from the inferences reached from currently available structural models. PMID:24747939

  13. Korn's inequality and Donati's theorem for the conformal Killing operator on pseudo-Euclidean space

    NASA Astrophysics Data System (ADS)

    Wang, Wei

    2008-09-01

    We prove the Korn's inequality for the conformal Killing operator on pseudo-Euclidean space , and an existence theorem for solutions to the non-homogeneous conformal Killing equation, which is a pseudo-Euclidean conformal generalization of Donati's theorem for Euclidean Killing operator.

  14. Ares Launch Vehicles Overview: Space Access Society

    NASA Technical Reports Server (NTRS)

    Cook, Steve

    2007-01-01

    America is returning to the Moon in preparation for the first human footprint on Mars, guided by the U.S. Vision for Space Exploration. This presentation will discuss NASA's mission, the reasons for returning to the Moon and going to Mars, and how NASA will accomplish that mission in ways that promote leadership in space and economic expansion on the new frontier. The primary goals of the Vision for Space Exploration are to finish the International Space Station, retire the Space Shuttle, and build the new spacecraft needed to return people to the Moon and go to Mars. The Vision commits NASA and the nation to an agenda of exploration that also includes robotic exploration and technology development, while building on lessons learned over 50 years of hard-won experience. NASA is building on common hardware, shared knowledge, and unique experience derived from the Apollo Saturn, Space Shuttle, and contemporary commercial launch vehicle programs. The journeys to the Moon and Mars will require a variety of vehicles, including the Ares I Crew Launch Vehicle, which transports the Orion Crew Exploration Vehicle, and the Ares V Cargo Launch Vehicle, which transports the Lunar Surface Access Module. The architecture for the lunar missions will use one launch to ferry the crew into orbit, where it will rendezvous with the Lunar Module in the Earth Departure Stage, which will then propel the combination into lunar orbit. The imperative to explore space with the combination of astronauts and robots will be the impetus for inventions such as solar power and water and waste recycling. This next chapter in NASA's history promises to write the next chapter in American history, as well. It will require this nation to provide the talent to develop tools, machines, materials, processes, technologies, and capabilities that can benefit nearly all aspects of life on Earth. Roles and responsibilities are shared between a nationwide Government and industry team. The Exploration Launch

  15. Making Space Science and Exploration Accessible

    NASA Astrophysics Data System (ADS)

    Runyon, C. J.; Guimond, K. A.; Hurd, D.; Heinrich, G.

    There are currently 28 million hard of hearing and deaf Americans, approximately 10 to 11 million blind and visually impaired people in North America, and more than 50 million Americans with disabilities, approximately half of whom are students. The majority of students with disabilities in the US are required to achieve the same academic levels as their non-impaired peers. Unfortunately, there are few specialized materials to help these exceptional students in the formal and informal settings. To assist educators in meeting their goals and engage the students, we are working with NASA product developers, scientists and education and outreach personnel in concert with teachers from exceptional classrooms to identify the types of materials they need and which mediums work best for the different student capabilities. Our goal is to make the wonders of space science and exploration accessible to all. As such, over the last four years we have been hosting interactive workshops, observing classroom settings, talking and working with professional educators, product developers, museum and science center personnel and parents to synthesize the most effective media and method for presenting earth and space science materials to audiences with exceptional needs. We will present a list of suggested best practices and example activities that can help engage and encourage a person with special needs to study the sciences, technology, engineering, and mathematics.

  16. National Report Norway: Arctic Access to Space

    NASA Astrophysics Data System (ADS)

    Brekke, P.

    2015-09-01

    Norway has long traditions as a space nation, much due to our northern latitude. Our space science activities are concentrated into relatively few areas. This concentration is necessary due to limited resources, both in funding and personnel. The main scientific activities are within Solar-terrestrial physics and cosmology. The first field has been a priority since before the space age and is still the major priority. The usage of the ground infrastructure in Northern Norway and on Svalbard is essential in studying the middle and upper atmosphere and the interaction with the Sun. This includes the utilization of sounding rockets, both small and large, and ground based installations like radars, lidars and other optical instrumentation. The planned use of Svalbard as a launch site for large stratospheric balloons may allow the cosmology community access to our northern infrastructure. The solar physics community is also heavily involved in the HINODE and IRIS missions and Norway is supporting downlink of data via the Svalbard Station for these missions. The sounding rocket program is in close collaboration with many countries like Germany, USA, France, Canada and Japan. Two scientific sounding rocket programs are currently being pursued: The ICI series (from Svalbard) and MaxiDusty (from Andoya). A series of scientific publications have recently appeared from the ECOMA campaign a few years ago. A significant improvement of today's polar and ionospheric research infrastructure in Northern Norway and Svalbard has recently been put on the ESFRI roadmap for European research infrastructure through the 5105 and EISCAT 3D initiatives. The Norwegian government has recently decided to upgrade the VLBI facilities at Svalbard.

  17. Flexibility unleashed in acyclic monoterpenes: conformational space of citronellal revealed by broadband rotational spectroscopy.

    PubMed

    Domingos, Sérgio R; Pérez, Cristóbal; Medcraft, Chris; Pinacho, Pablo; Schnell, Melanie

    2016-06-22

    Conformational flexibility is intrinsically related to the functionality of biomolecules. Elucidation of the potential energy surface is thus a necessary step towards understanding the mechanisms for molecular recognition such as docking of small organic molecules to larger macromolecular systems. In this work, we use broadband rotational spectroscopy in a molecular jet experiment to unravel the complex conformational space of citronellal. We observe fifteen conformations in the experimental conditions of the molecular jet, the highest number of conformers reported to date for a chiral molecule of this size using microwave spectroscopy. Studies of relative stability using different carrier gases in the supersonic expansion reveal conformational relaxation pathways that strongly favour ground-state structures with globular conformations. This study provides a blueprint of the complex conformational space of an important biosynthetic precursor and gives insights on the relation between its structure and biological functionality. PMID:27298210

  18. Locally accessible conformations of proteins: multiple molecular dynamics simulations of crambin.

    PubMed Central

    Caves, L. S.; Evanseck, J. D.; Karplus, M.

    1998-01-01

    Multiple molecular dynamics (MD) simulations of crambin with different initial atomic velocities are used to sample conformations in the vicinity of the native structure. Individual trajectories of length up to 5 ns sample only a fraction of the conformational distribution generated by ten independent 120 ps trajectories at 300 K. The backbone atom conformational space distribution is analyzed using principal components analysis (PCA). Four different major conformational regions are found. In general, a trajectory samples only one region and few transitions between the regions are observed. Consequently, the averages of structural and dynamic properties over the ten trajectories differ significantly from those obtained from individual trajectories. The nature of the conformational sampling has important consequences for the utilization of MD simulations for a wide range of problems, such as comparisons with X-ray or NMR data. The overall average structure is significantly closer to the X-ray structure than any of the individual trajectory average structures. The high frequency (less than 10 ps) atomic fluctuations from the ten trajectories tend to be similar, but the lower frequency (100 ps) motions are different. To improve conformational sampling in molecular dynamics simulations of proteins, as in nucleic acids, multiple trajectories with different initial conditions should be used rather than a single long trajectory. PMID:9541397

  19. 29 CFR 1915.76 - Access to cargo spaces and confined spaces.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 29 Labor 7 2010-07-01 2010-07-01 false Access to cargo spaces and confined spaces. 1915.76 Section..., Ladders and Other Working Surfaces § 1915.76 Access to cargo spaces and confined spaces. The provisions of... this section applies to ship repairing only. (a) Cargo spaces. (1) There shall be at least one safe...

  20. 29 CFR 1915.76 - Access to cargo spaces and confined spaces.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 29 Labor 7 2013-07-01 2013-07-01 false Access to cargo spaces and confined spaces. 1915.76 Section..., Ladders and Other Working Surfaces § 1915.76 Access to cargo spaces and confined spaces. The provisions of... this section applies to ship repairing only. (a) Cargo spaces. (1) There shall be at least one safe...

  1. 29 CFR 1915.76 - Access to cargo spaces and confined spaces.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 29 Labor 7 2014-07-01 2014-07-01 false Access to cargo spaces and confined spaces. 1915.76 Section..., Ladders and Other Working Surfaces § 1915.76 Access to cargo spaces and confined spaces. The provisions of... this section applies to ship repairing only. (a) Cargo spaces. (1) There shall be at least one safe...

  2. 29 CFR 1915.76 - Access to cargo spaces and confined spaces.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 29 Labor 7 2012-07-01 2012-07-01 false Access to cargo spaces and confined spaces. 1915.76 Section..., Ladders and Other Working Surfaces § 1915.76 Access to cargo spaces and confined spaces. The provisions of... this section applies to ship repairing only. (a) Cargo spaces. (1) There shall be at least one safe...

  3. 29 CFR 1915.76 - Access to cargo spaces and confined spaces.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 29 Labor 7 2011-07-01 2011-07-01 false Access to cargo spaces and confined spaces. 1915.76 Section..., Ladders and Other Working Surfaces § 1915.76 Access to cargo spaces and confined spaces. The provisions of... this section applies to ship repairing only. (a) Cargo spaces. (1) There shall be at least one safe...

  4. Efficient conformational space exploration in ab initio protein folding simulation.

    PubMed

    Ullah, Ahammed; Ahmed, Nasif; Pappu, Subrata Dey; Shatabda, Swakkhar; Ullah, A Z M Dayem; Rahman, M Sohel

    2015-08-01

    Ab initio protein folding simulation largely depends on knowledge-based energy functions that are derived from known protein structures using statistical methods. These knowledge-based energy functions provide us with a good approximation of real protein energetics. However, these energy functions are not very informative for search algorithms and fail to distinguish the types of amino acid interactions that contribute largely to the energy function from those that do not. As a result, search algorithms frequently get trapped into the local minima. On the other hand, the hydrophobic-polar (HP) model considers hydrophobic interactions only. The simplified nature of HP energy function makes it limited only to a low-resolution model. In this paper, we present a strategy to derive a non-uniform scaled version of the real 20×20 pairwise energy function. The non-uniform scaling helps tackle the difficulty faced by a real energy function, whereas the integration of 20×20 pairwise information overcomes the limitations faced by the HP energy function. Here, we have applied a derived energy function with a genetic algorithm on discrete lattices. On a standard set of benchmark protein sequences, our approach significantly outperforms the state-of-the-art methods for similar models. Our approach has been able to explore regions of the conformational space which all the previous methods have failed to explore. Effectiveness of the derived energy function is presented by showing qualitative differences and similarities of the sampled structures to the native structures. Number of objective function evaluation in a single run of the algorithm is used as a comparison metric to demonstrate efficiency. PMID:26361554

  5. Efficient conformational space exploration in ab initio protein folding simulation

    PubMed Central

    Ullah, Ahammed; Ahmed, Nasif; Pappu, Subrata Dey; Shatabda, Swakkhar; Ullah, A. Z. M. Dayem; Rahman, M. Sohel

    2015-01-01

    Ab initio protein folding simulation largely depends on knowledge-based energy functions that are derived from known protein structures using statistical methods. These knowledge-based energy functions provide us with a good approximation of real protein energetics. However, these energy functions are not very informative for search algorithms and fail to distinguish the types of amino acid interactions that contribute largely to the energy function from those that do not. As a result, search algorithms frequently get trapped into the local minima. On the other hand, the hydrophobic–polar (HP) model considers hydrophobic interactions only. The simplified nature of HP energy function makes it limited only to a low-resolution model. In this paper, we present a strategy to derive a non-uniform scaled version of the real 20×20 pairwise energy function. The non-uniform scaling helps tackle the difficulty faced by a real energy function, whereas the integration of 20×20 pairwise information overcomes the limitations faced by the HP energy function. Here, we have applied a derived energy function with a genetic algorithm on discrete lattices. On a standard set of benchmark protein sequences, our approach significantly outperforms the state-of-the-art methods for similar models. Our approach has been able to explore regions of the conformational space which all the previous methods have failed to explore. Effectiveness of the derived energy function is presented by showing qualitative differences and similarities of the sampled structures to the native structures. Number of objective function evaluation in a single run of the algorithm is used as a comparison metric to demonstrate efficiency. PMID:26361554

  6. Exploring the conformational space of bridge-substituted dithienylcyclopentenes.

    PubMed

    Fredersdorf, Maic; Göstl, Robert; Kolmer, Andreas; Schmidts, Volker; Monecke, Peter; Hecht, Stefan; Thiele, Christina M

    2015-10-01

    Stimuli responsive compounds and materials are of high interest in synthetic chemistry and materials science, with light being the most intriguing stimulus due to the possibility to remote control the physicochemical properties of a molecule or a material. There is a constant quest to design photoswitches with improved switching efficiency and especially diarylethene-type switches promise photo cyclization quantum yields up to unity. However, only limited attention has been paid towards the influence of the solution conformation on the switching efficiency. Here, we describe a detailed NMR spectroscopic investigation on the conformational distribution of bridge-substituted dithienylcyclopentenes in solution. We could discriminate between several photoactive and photoinactive as well as two diastereomorphous conformations and show that the trends observed in the switching efficiency match the conformer populations obtained from state of the art NMR parameters in solution. PMID:26298451

  7. Predictive Sampling of Rare Conformational Events in Aqueous Solution: Designing a Generalized Orthogonal Space Tempering Method

    PubMed Central

    Lv, Chao; Li, Xubin; Wu, Dongsheng; Zheng, Lianqing; Yang, Wei

    2016-01-01

    In aqueous solution, solute conformational transitions are governed by intimate interplays of the fluctuations of solute-solute, solute-water, and water-water interactions. To promote essential fluctuations to enhance sampling, a common strategy is to construct an expanded Hamiltonian through a series of Hamiltonian perturbations, for instance on certain interactions of focus. Due to lack of active sampling of configuration response to perturbation transitions, it is challenging for common expanded Hamiltonian methods to robustly explore solvent mediated rare conformational events. The orthogonal space sampling (OSS) scheme, as exemplified by the orthogonal space random walk and orthogonal space tempering methods, provides a general framework for synchronous acceleration of slow configuration responses. To more effectively sample conformational transitions in aqueous solution, in this work, we devised a generalized orthogonal space tempering (gOST) algorithm. Specifically, in the Hamiltonian perturbation part, a solvent-accessible-surface-area-dependent term is introduced to implicitly perturb near-solute water-water fluctuations; and in the orthogonal space response part, the generalized force order parameter is generalized as a two-dimension order parameter set, in which the solute-solvent and solute-solute components are separately treated. The gOST algorithm is evaluated through a molecular dynamics simulation study on the explicitly-solvated deca-alanine (Ala10) peptide. Based on a fully automated sampling protocol, the gOST simulation enabled repetitive folding and unfolding of the solvated peptide within a single continuous trajectory and allowed for detailed constructions of Ala10 folding/unfolding free energy surfaces. The gOST result reveals that solvent cooperative fluctuations play a pivotal role in Ala10 folding/unfolding transitions. In addition, our assessment analysis suggests that because essential rare events are mainly driven by the compensating

  8. 46 CFR 111.01-7 - Accessibility and spacing.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 4 2012-10-01 2012-10-01 false Accessibility and spacing. 111.01-7 Section 111.01-7 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS-GENERAL REQUIREMENTS General § 111.01-7 Accessibility and spacing. (a) The design and arrangement...

  9. 46 CFR 111.01-7 - Accessibility and spacing.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 4 2013-10-01 2013-10-01 false Accessibility and spacing. 111.01-7 Section 111.01-7 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS-GENERAL REQUIREMENTS General § 111.01-7 Accessibility and spacing. (a) The design and arrangement...

  10. Pilot Non-Conformance to Alerting System Commands During Closely Spaced Parallel Approaches

    NASA Technical Reports Server (NTRS)

    Pritchett, Amy R.; Hansman, R. John

    1997-01-01

    Pilot non-conformance to alerting system commands has been noted in general and to a TCAS-like collision avoidance system in a previous experiment. This paper details two experiments studying collision avoidance during closely-spaced parallel approaches in instrument meteorological conditions (IMC), and specifically examining possible causal factors of, and design solutions to, pilot non-conformance.

  11. Bounds for the moduli of continuity for conformal mappings of domains near their accessible boundary arcs

    SciTech Connect

    Dolzhenko, Evgenii P

    2011-12-31

    The paper presents bounds for the moduli of continuity {omega}(f, G-bar ,{delta}) of conformal mappings w=f(z) of a bounded simply connected domain G with an arbitrary Jordan boundary onto a bounded simply connected domain with an arbitrary Jordan boundary, the 'quality' of boundaries being taken into account. For a Jordan curve (simple arc or a closed contour), its quality is characterized in general by its modulus of oscillation, and if it has finite length, by a more sensitive modulus of rectifiability-these purely metric concepts were introduced by the author in 1996. Theorems on the behaviour of conformal mappings of simply connected domains of arbitrary nature near open accessible boundary arcs are established. Bibliography: 18 titles.

  12. Virtual states introduced for overcoming entropic barriers in conformational space

    PubMed Central

    Higo, Junichi; Nakamura, Haruki

    2012-01-01

    Free-energy landscape is an important quantity to study large-scale motions of a biomolecular system because it maps possible pathways for the motions. When the landscape consists of thermodynamically stable states (low-energy basins), which are connected by narrow conformational pathways (i.e., bottlenecks), the narrowness slows the inter-basin round trips in conformational sampling. This results in inaccuracy of free energies for the basins. This difficulty is not cleared out even when an enhanced conformational sampling is fairly performed along a reaction coordinate. In this study, to enhance the inter-basin round trips we introduced a virtual state that covers the narrow pathways. The probability distribution function for the virtual state was controlled based on detailed balance condition for the inter-state transitions (transitions between the real-state basins and the virtual state). To mimic the free-energy landscape of a real biological system, we introduced a simple model where a wall separates two basins and a narrow hole is pierced in the wall to connect the basins. The sampling was done based on Monte Carlo (MC). We examined several hole-sizes and inter-state transition probabilities. For a small hole-size, a small inter-state transition probability produced a sampling efficiency 100 times higher than a conventional MC does. This result goes against ones intuition, because one considers generally that the sampling efficiency increases with increasing the transition probability. The present method is readily applicable to enhanced conformational sampling such as multi-canonical or adaptive umbrella sampling, and extendable to molecular dynamics.

  13. Conformal symmetry and pion form factor: Space- and timelike region

    SciTech Connect

    Choi, Ho-Meoyng; Ji, Chueng-Ryong

    2008-06-01

    We extend a recent analysis of the pion electromagnetic form factor constrained by the conformal symmetry to explore the timelike region. We show explicitly that the timelike form factor obtained by the analytic continuation of the spacelike form factor correctly satisfies the dispersion relation. Our results indicate that the quark spin and dynamical mass effects are crucial to yield the realistic features of the vector meson dominance phenomena.

  14. Transforming Community Access to Space Science Models

    NASA Technical Reports Server (NTRS)

    MacNeice, Peter; Heese, Michael; Kunetsova, Maria; Maddox, Marlo; Rastaetter, Lutz; Berrios, David; Pulkkinen, Antti

    2012-01-01

    Researching and forecasting the ever changing space environment (often referred to as space weather) and its influence on humans and their activities are model-intensive disciplines. This is true because the physical processes involved are complex, but, in contrast to terrestrial weather, the supporting observations are typically sparse. Models play a vital role in establishing a physically meaningful context for interpreting limited observations, testing theory, and producing both nowcasts and forecasts. For example, with accurate forecasting of hazardous space weather conditions, spacecraft operators can place sensitive systems in safe modes, and power utilities can protect critical network components from damage caused by large currents induced in transmission lines by geomagnetic storms.

  15. Transforming community access to space science models

    NASA Astrophysics Data System (ADS)

    MacNeice, Peter; Hesse, Michael; Kuznetsova, Maria; Maddox, Marlo; Rastaetter, Lutz; Berrios, David; Pulkkinen, Antti

    2012-04-01

    Researching and forecasting the ever changing space environment (often referred to as space weather) and its influence on humans and their activities are model-intensive disciplines. This is true because the physical processes involved are complex, but, in contrast to terrestrial weather, the supporting observations are typically sparse. Models play a vital role in establishing a physically meaningful context for interpreting limited observations, testing theory, and producing both nowcasts and forecasts. For example, with accurate forecasting of hazardous space weather conditions, spacecraft operators can place sensitive systems in safe modes, and power utilities can protect critical network components from damage caused by large currents induced in transmission lines by geomagnetic storms.

  16. Beamforming of Joint Polarization-Space Matched Filtering for Conformal Array

    PubMed Central

    Liu, Lutao; Jiang, Yilin; Tian, Zuoxi

    2013-01-01

    Due to the polarization mismatch of the antenna, the received signal suffers from energy loss. The conventional beamforming algorithms could not be applied to the conformal array because of the varying curvature. In order to overcome the energy loss of the received signal, a novel joint polarization-space matched filtering algorithm for cylindrical conformal array is proposed. First, the snapshot data model of the conformal polarization sensitive array is analyzed. Second, the analytical expression of polarization sensitive array beamforming is derived. Linearly constrained minimum variance (LCMV) beamforming technique is facilitated for the cylindrical conformal array. Third, the idea of joint polarization-space matched filtering is presented, and the principle of joint polarization-space matched filtering is discussed in detail. Theoretical analysis and computer simulation results verify that the conformal polarization sensitive array is more robust than the ordinary conformal array. The proposed algorithm can improve the performance when signal and interference are too close. It can enhance the signal-to-noise ratio (SNR) by adjusting the polarization of the elements of the conformal array, which matches the polarization of the incident signal. PMID:24501582

  17. 46 CFR 111.01-7 - Accessibility and spacing.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 4 2011-10-01 2011-10-01 false Accessibility and spacing. 111.01-7 Section 111.01-7 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS... electric apparatus must afford accessibility to each part as needed to facilitate proper...

  18. 46 CFR 111.01-7 - Accessibility and spacing.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Accessibility and spacing. 111.01-7 Section 111.01-7 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS... electric apparatus must afford accessibility to each part as needed to facilitate proper...

  19. 46 CFR 111.01-7 - Accessibility and spacing.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 4 2014-10-01 2014-10-01 false Accessibility and spacing. 111.01-7 Section 111.01-7 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS... electric apparatus must afford accessibility to each part as needed to facilitate proper...

  20. Develop and test a solvent accessible surface area-based model in conformational entropy calculations.

    PubMed

    Wang, Junmei; Hou, Tingjun

    2012-05-25

    It is of great interest in modern drug design to accurately calculate the free energies of protein-ligand or nucleic acid-ligand binding. MM-PBSA (molecular mechanics Poisson-Boltzmann surface area) and MM-GBSA (molecular mechanics generalized Born surface area) have gained popularity in this field. For both methods, the conformational entropy, which is usually calculated through normal-mode analysis (NMA), is needed to calculate the absolute binding free energies. Unfortunately, NMA is computationally demanding and becomes a bottleneck of the MM-PB/GBSA-NMA methods. In this work, we have developed a fast approach to estimate the conformational entropy based upon solvent accessible surface area calculations. In our approach, the conformational entropy of a molecule, S, can be obtained by summing up the contributions of all atoms, no matter they are buried or exposed. Each atom has two types of surface areas, solvent accessible surface area (SAS) and buried SAS (BSAS). The two types of surface areas are weighted to estimate the contribution of an atom to S. Atoms having the same atom type share the same weight and a general parameter k is applied to balance the contributions of the two types of surface areas. This entropy model was parametrized using a large set of small molecules for which their conformational entropies were calculated at the B3LYP/6-31G* level taking the solvent effect into account. The weighted solvent accessible surface area (WSAS) model was extensively evaluated in three tests. For convenience, TS values, the product of temperature T and conformational entropy S, were calculated in those tests. T was always set to 298.15 K through the text. First of all, good correlations were achieved between WSAS TS and NMA TS for 44 protein or nucleic acid systems sampled with molecular dynamics simulations (10 snapshots were collected for postentropy calculations): the mean correlation coefficient squares (R²) was 0.56. As to the 20 complexes, the TS

  1. Conformal foliations by circles and complex isoparametric functions on Euclidean 3-space

    NASA Astrophysics Data System (ADS)

    Baird, P.

    1998-03-01

    The space of circles in S3 completed to include points is identified with a complex quadric hypersurface [script H] of CP4. A conformal foliation by arcs of circles of a domain in R3 now corresponds to a complex holomorphic curve in [script H]. The space [script H] minus a hyperplane section fibres in a natural way over the space of lines in R3, each fibre consisting of the well known family of circles of Villarceau transformed by a homothety. As a consequence we show that there is a correspondence between harmonic morphisms on the 3-dimensional space forms and demonstrate the existence of a distinguished surface associated to a conformal foliation by arcs of circles.We generalize Cartan's isoparametric functions to complex valued functions and classify all those horizontally conformal complex isoparametric functions defined on domains of R3 with arcs of circles or lines as fibres.

  2. Describing the Conformational Landscape of Small Organic Molecules through Gaussian Mixtures in Dihedral Space.

    PubMed

    Pisani, Pasquale; Piro, Paolo; Decherchi, Sergio; Bottegoni, Giovanni; Sona, Diego; Murino, Vittorio; Rocchia, Walter; Cavalli, Andrea

    2014-06-10

    Due to the well-known structure-function paradigm, conformational equilibrium plays a major role in molecular recognition. Therefore, a deep understanding of the conformational profile of small organic molecules is an essential prerequisite to modern computer-assisted drug design. However, a thorough analysis and a meaningful representation of the conformational landscape of drug-like molecules remains a challenge. The thermodynamic equilibrium of conformational states can be described in terms of probability density function (PDF) defined in the space of the relevant degrees of freedom of the system. In principle, this PDF could be estimated by traditional histogram methods, which are, however, hampered by several limitations when the variables forming the space are more than two or three. Here, we present an unsupervised parametric fitting procedure based on cluster analysis, aimed at estimating the PDF in the conformational space of small drug-like molecules with low sensitivity to data dimensionality. Indeed, data are represented in the dihedral space of the molecule and clustered using a simple adaptation of the standard k-means algorithm for periodic data. In the final step of the analysis, the PDF is derived as a linear combination of multivariate circular Gaussian distributions. We show that exploiting the analytic properties of Gaussian distributions, the proposed approach makes it possible to analyze the conformational ensemble in higher dimensional spaces with several advantages over the histogram-based methods. The posterior analysis of the PDF also helps identify a minimal subset of variables able to provide a meaningful representation of the conformational space. We tested our approach on alanine dipeptide, alanine tetrapeptide, and rilpivirine with satisfactory results compared to standard histogram-based methods and to those based on chemical intuition. PMID:26580776

  3. System, cost, and risk analysis for access to space

    NASA Technical Reports Server (NTRS)

    Chase, James P.; Carter, Rebecca L.; Smith, Jeffrey L.

    2004-01-01

    This paper proposes the use of a new tool more quickly develop initial cost and risk estimates of alternative flight options for both single missions and the partnering of missions into a single space flight. this work is particularly useful for small missions that require low-cost opportunities for accessing space.

  4. Anthranilic acid-containing cyclic tetrapeptides: at the crossroads of conformational rigidity and synthetic accessibility.

    PubMed

    Xin, Dongyue; Burgess, Kevin

    2016-06-14

    Each amino acid in a peptide contributes three atom units to main-chains, hence natural cyclic peptides can be 9, 12, 15, …. i.e. 3n membered-rings, where n is the number of amino acids. Cyclic peptides that are 9 or 12-membered ring compounds tend to be hard to prepare because of strain, while their one amino acid homologs (15-membered cyclic pentapeptides) are not conformationally homogeneous unless constrained by strategically placed proline or d-amino acid residues. We hypothesized that replacing one genetically encoded amino acid in a cyclic tetrapeptide with a rigid β-amino acid would render peptidomimetic designs that rest at a useful crossroads between synthetic accessibility and conformational rigidity. Thus this research explored non-proline containing 13-membered ring peptides 1 featuring one anthranilic acid (Anth) residue. Twelve cyclic peptides of this type were prepared, and in doing so the viability of both solution- and solid-phase methods was demonstrated. The library produced contained a complete set of four diastereoisomers of the sequence 1aaf (i.e. cyclo-AlaAlaPheAnth). Without exception, these four diastereoisomers each adopted one predominant conformation in solution; basically these conformations feature amide N-H vectors puckering above and below the equatorial plane, and approximately oriented their N-H[combining low line] atoms towards the polar axis. Moreover, the shapes of these conformers varied in a logical and predictable way (NOE, temperature coefficient, D/H exchange, circular dichroism). Comparisons were made of the side-chain orientations presented by compounds 1aaa in solution with ideal secondary structures and protein-protein interaction interfaces. Various 1aaa stereoisomers in solution present side-chains in similar orientations to regular and inverse γ-turns, and to the most common β-turns (types I and II). Consistent with this, compounds 1aaa have a tendency to mimic various turns and bends at protein

  5. Access to Space for Technology Validation Missions: A Practical Guide

    NASA Technical Reports Server (NTRS)

    Herrell, Linda M.

    2007-01-01

    Space technology experiments and validation missions share a common dilemma with the aerospace industry in general: the high cost of access to space. Whether the experiment is a so-called university cubesat, a university measurement experiment, or a NASA New Millennium Program (NMP) technology validation mission, the access to space option can be scaled appropriately for the particular constraints. A cubesat might fly as one of a number of cubesats that negotiate a flight on an experimental vehicle. A university experiment might do the same. A NASA flight validation might partner with an Air Force experimental mission.

  6. An overview of the EASE/ACCESS space construction demonstration

    NASA Technical Reports Server (NTRS)

    Levin, George M.; Ross, Jerry L.; Spring, Sherwood C.

    1988-01-01

    Consideration is given to the development of the Experimental Assembly of Structures in EVA/Assembly Concept for Construction of Erectable Space Structures (EASE/ACCESS) space construction demonstration, which was performed during Space Shuttle mission 61-B. The mission equipment is described and illustrated and the EASE/ACCESS mission management structure is outlined. Simulations of the assembly and disassembly in the NASA neutral buoyancy simulators were used to test the mission plans. In addition, EVA training and crew performance for the mission are discussed.

  7. The National Aerospace Initiative (NAI): Technologies For Responsive Space Access

    NASA Technical Reports Server (NTRS)

    Culbertson, Andrew; Bhat, Biliyar N.

    2003-01-01

    The Secretary of Defense has set new goals for the Department of Defense (DOD) to transform our nation's military forces. The Director for Defense Research and Engineering (DDR&E) has responded to this challenge by defining and sponsoring a transformational initiative in Science and Technology (S&T) - the National Aerospace Initiative (NAI) - which will have a fundamental impact on our nation's military capabilities and on the aerospace industry in general. The NAI is planned as a joint effort among the tri-services, DOD agencies and National Aeronautics and Space Administration (NASA). It is comprised of three major focus areas or pillars: 1) High Speed Hypersonics (HSH), 2) Space Access (SA), and 3) Space Technology (ST). This paper addresses the Space Access pillar. The NAI-SA team has employed a unique approach to identifying critical technologies and demonstrations for satisfying both military and civilian space access capabilities needed in the future. For planning and implementation purposes the NAI-SA is divided into five technology subsystem areas: Airframe, Propulsion, Flight Subsystems, Operations and Payloads. Detailed technology roadmaps were developed under each subsystem area using a time-phased, goal oriented approach that provides critical space access capabilities in a timely manner and involves subsystem ground and flight demonstrations. This S&T plan addresses near-term (2009), mid-term (2016), and long-term (2025) goals and objectives for space access. In addition, system engineering and integration approach was used to make sure that the plan addresses the requirements of the end users. This paper describes in some detail the technologies in NAI-Space Access pillar. Some areas of emphasis are: high temperature materials, thermal protection systems, long life, lightweight, highly efficient airframes, metallic and composite cryotanks, advanced liquid rocket engines, integrated vehicle health monitoring and management, highly operable systems and

  8. Low-cost access to space

    NASA Astrophysics Data System (ADS)

    Slayton, Donald K.; Daniels, Mark; Grimes, David

    1992-03-01

    The paper discusses the wide range of orbital launch capabilities of the Conestoga series and the suborbital sounding rocket services of the Starfire family. Both launchers are designed with flight-proven components and offer low cost and a high degree of reliability. Current information on the market for small-sized space payloads and the ability of the above launchers to support these requirements are addressed. The Conestoga orbital launch design embodies the concept of achieving payload growth flexibility without the need to change either the basic vehicle design or the operational approach. Low technical, schedule, and cost risk is achieved with the Conestoga design due to the high degree of previously flight-proven hardware utilized. The Conestoga launch vehicle series performance curves are illustrated. The various Starfire configurations and their microgravity performance are shown.

  9. Titan III - Commercial access to space

    NASA Astrophysics Data System (ADS)

    Gizinski, Stephen J., III; Herrington, Douglas B.

    1988-06-01

    The commercial Titan III launch vehicle is discussed, reviewing the history of the Titan program, the technical aspects of the launcher, and the market outlook. The solid rocket motors of the boost vehicle, core, attitude control system, and payload carrier are described. The vehicle can carry one or two payloads taking up a space of up to 3.65 m in diameter and 10.7 m in length. The avionics, communications, and electrical power systems of the vehicle are examined and the range of perigree stages with which the vehicle is compatible is given. An overview of the mission and the launch facilities is presented and future markets for commercial satellites are considered.

  10. Conformally invariant spin-3/2 field equation in de Sitter space-time

    NASA Astrophysics Data System (ADS)

    Fatahi, N.

    2015-09-01

    In the previous paper (Behroozi et al., Phys Rev D 74:124014, 2006; Dehghani et al., Phys Rev D 77:064028, 2008), conformal invariance for massless tensor fields (scalar, vector and spin-2 fields) was studied and the solutions of their wave equations and two-point functions were obtained. In the present paper, conformally invariant wave equation for massless spinor field in de Sitter space-time has been obtained. For this propose, we use Dirac's six-cone formalism. The solutions of massless spin-1/2 and -3/2 equations, in the ambient space notation, have been calculated.

  11. On the measure of conformal difference between Euclidean and Lobachevsky spaces

    NASA Astrophysics Data System (ADS)

    Zorich, Vladimir A.

    2011-12-01

    Euclidean space R^n and Lobachevsky space H^n are known to be not equivalent either conformally or quasiconformally. In this work we give exact asymptotics of the critical order of growth at infinity for the quasiconformality coefficient of a diffeomorphism f\\colon R^n\\to H^n for which such a mapping f is possible. We also consider the general case of immersions f\\colon M^n\\to N^n of conformally parabolic Riemannian manifolds. Bibliography: 17 titles.

  12. Real-space visualization of conformation-independent oligothiophene electronic structure

    NASA Astrophysics Data System (ADS)

    Taber, Benjamen N.; Kislitsyn, Dmitry A.; Gervasi, Christian F.; Mills, Jon M.; Rosenfield, Ariel E.; Zhang, Lei; Mannsfeld, Stefan C. B.; Prell, James S.; Briseno, Alejandro L.; Nazin, George V.

    2016-05-01

    We present scanning tunneling microscopy and spectroscopy (STM/STS) investigations of the electronic structures of different alkyl-substituted oligothiophenes on the Au(111) surface. STM imaging showed that on Au(111), oligothiophenes adopted distinct straight and bent conformations. By combining STS maps with STM images, we visualize, in real space, particle-in-a-box-like oligothiophene molecular orbitals. We demonstrate that different planar conformers with significant geometrical distortions of oligothiophene backbones surprisingly exhibit very similar electronic structures, indicating a low degree of conformation-induced electronic disorder. The agreement of these results with gas-phase density functional theory calculations implies that the oligothiophene interaction with the Au(111) surface is generally insensitive to molecular conformation.

  13. Real-space visualization of conformation-independent oligothiophene electronic structure.

    PubMed

    Taber, Benjamen N; Kislitsyn, Dmitry A; Gervasi, Christian F; Mills, Jon M; Rosenfield, Ariel E; Zhang, Lei; Mannsfeld, Stefan C B; Prell, James S; Briseno, Alejandro L; Nazin, George V

    2016-05-21

    We present scanning tunneling microscopy and spectroscopy (STM/STS) investigations of the electronic structures of different alkyl-substituted oligothiophenes on the Au(111) surface. STM imaging showed that on Au(111), oligothiophenes adopted distinct straight and bent conformations. By combining STS maps with STM images, we visualize, in real space, particle-in-a-box-like oligothiophene molecular orbitals. We demonstrate that different planar conformers with significant geometrical distortions of oligothiophene backbones surprisingly exhibit very similar electronic structures, indicating a low degree of conformation-induced electronic disorder. The agreement of these results with gas-phase density functional theory calculations implies that the oligothiophene interaction with the Au(111) surface is generally insensitive to molecular conformation. PMID:27208961

  14. Pilot Non-Conformance to Alerting System Commands During Closely Spaced Parallel Approaches

    NASA Technical Reports Server (NTRS)

    Pritchett, Amy Ruth; Hansman, R. John; Corker, Kevin (Technical Monitor)

    1997-01-01

    Cockpit alerting systems monitor potentially hazardous situations, both inside and outside the aircraft. When a hazard is projected to occur, the alerting system displays alerts and/or command decisions to the pilot. However, pilots have been observed to not conform to alerting system commands by delaying their response or by not following the automatic commands exactly. This non-conformance to the automatic alerting system can reduce its benefit. Therefore, a need exists to understand the causes and effects of pilot non-conformance in order to develop automatic alerting systems whose commands the pilots are more likely to follow. These considerations were examined through flight simulator evaluations of the collision avoidance task during closely spaced parallel approaches. This task provided a useful case-study because the effects of non-conformance can be significant, given the time-critical nature of the task. A preliminary evaluation of alerting systems identified non-conformance in over 40% of the cases and a corresponding drop in collision avoidance performance. A follow-on experiment found subjects' alerting and maneuver selection criteria were consistent with different strategies than those used by automatic systems, indicating the pilot may potentially disagree with the alerting system if the pilot attempts to verify automatic alerts and commanded avoidance maneuvers. A final experiment found supporting automatic alerts with the explicit display of its underlying criteria resulted in more consistent subject reactions. In light of these experimental results, a general discussion of pilot non-conformance is provided. Contributing factors in pilot non-conformance include a lack of confidence in the automatic system and mismatches between the alerting system's commands and the pilots' own decisions based on the information available to them. The effects of non-conformance on system performance are discussed. Possible methods of reconciling mismatches are

  15. GOES-R Space Weather Data: Ensuring Access and Usability

    NASA Astrophysics Data System (ADS)

    Tilton, M.; Rowland, W. F.; Wilkinson, D. C.; Denig, W. F.; Darnel, J.; Kress, B. T.; Loto'aniu, P. T. M.; Machol, J. L.; Redmon, R. J.; Rodriguez, J. V.

    2015-12-01

    The upcoming Geostationary Operational Environmental Satellite series, GOES-R, will provide critical space weather data. These data are used to prevent communication outages, mitigate the damage solar weather causes to satellites and power grids, and reduce astronaut radiation exposure. The space weather instruments aboard GOES-R will deliver an operational dataset of unprecedented breadth. However, NOAA's National Centers for Environmental Information (NCEI)—the organization that provides access to archived GOES-R data—has faced several challenges in delivering this information to customers in usable form. For instance, the GOES-R ground system was contracted to develop higher-level products for terrestrial data but not space weather data. Variations in GOES-R data file formats and archive locations have also threatened to create an inconsistent user experience. This presentation will examine the ways in which NCEI is making GOES-R space weather data more accessible and actionable for customers. These efforts include NCEI's development of high-level data products to meet the requirements of NOAA's Space Weather Prediction Center—a role NCEI has not previously played. In addition, NCEI is creating a demonstration system to show how these products can be produced in real-time. The organization is also examining customer usage of the GOES-NOP data access system and using these access patterns to drive decisions about the GOES-R user interface.

  16. Access from Space: A New Perspective on NASA's Space Transportation Technology Requirements and Opportunities

    NASA Technical Reports Server (NTRS)

    Rasky, Daniel J.

    2004-01-01

    The need for robust and reliable access from space is clearly demonstrated by the recent loss of the Space Shuttle Columbia; as well as the NASA s goals to get the Shuttle re-flying and extend its life, build new vehicles for space access, produce successful robotic landers and s a q k retrr? llisrions, and maximize the science content of ambitious outer planets missions that contain nuclear reactors which must be safe for re-entry after possible launch aborts. The technology lynch pin of access from space is hypersonic entry systems such the thermal protection system, along with navigation, guidance and control (NG&C). But it also extends to descent and landing systems such as parachutes, airbags and their control systems. Current space access technology maturation programs such as NASA s Next Generation Launch Technology (NGLT) program or the In-Space Propulsion (ISP) program focus on maturing laboratory demonstrated technologies for potential adoption by specific mission applications. A key requirement for these programs success is a suitable queue of innovative technologies and advanced concepts to mature, including mission concepts enabled by innovative, cross cutting technology advancements. When considering space access, propulsion often dominates the capability requirements, as well as the attention and resources. From the perspective of access from space some new cross cutting technology drivers come into view, along with some new capability opportunities. These include new miniature vehicles (micro, nano, and picosats), advanced automated systems (providing autonomous on-orbit inspection or landing site selection), and transformable aeroshells (to maximize capabilities and minimize weight). This paper provides an assessment of the technology drivers needed to meet future access from space mission requirements, along with the mission capabilities that can be envisioned from innovative, cross cutting access from space technology developments.

  17. Conformal prediction for anomaly detection and collision alert in space surveillance

    NASA Astrophysics Data System (ADS)

    Chen, Huimin; Chen, Genshe; Blasch, Erik; Pham, Khanh

    2013-05-01

    Anomaly detection has been considered as an important technique for detecting critical events in a wide range of data rich applications where a majority of the data is inconsequential and/or uninteresting. We study the detection of anomalous behaviors among space objects using the theory of conformal prediction for distribution-independent on-line learning to provide collision alerts with a desirable confidence level. We exploit the fact that conformal predictors provide valid forecasted sets at specified confidence levels under the relatively weak assumption that the normal training data, together with the normal testing data, are generated from the same distribution. If the actual observation is not included in the conformal prediction set, it is classified as anomalous at the corresponding significance level. Interpreting the significance level as an upper bound of the probability that a normal observation is mistakenly classified as anomalous, we can conveniently adjust the sensitivity to anomalies while controlling the false alarm rate without having to find the application specific threshold. The proposed conformal prediction method was evaluated for a space surveillance application using the open source North American Aerospace Defense Command (NORAD) catalog data. The validity of the prediction sets is justified by the empirical error rate that matches the significance level. In addition, experiments with simulated anomalous data indicate that anomaly detection sensitivity with conformal prediction is superior to that of the existing methods in declaring potential collision events.

  18. Ka-band geostationary satellite spacing requirements and access schemes

    NASA Technical Reports Server (NTRS)

    Caron, Mario; Hindson, Daniel J.

    1995-01-01

    Geostationary satellite systems for wideband personal communications applications have been proposed. This paper looks at the geostationary satellite spacing requirement to meet the ITU-R sharing criterion for FDMA and CDMA access schemes. CDMA capacity equation is first developed. Then the basis for the interference analysis between two systems with an overlapping coverage area is developed for the cases of identical and different access schemes and for bandwidth and power limited systems. An example of an interference analysis between two systems is fully carried out. The paper also points out the inherent problems when comparing systems with different access schemes. It is found that under certain scenarios, CDMA can allow a closer spacing between satellites.

  19. Advanced Cosmic-Ray Composition Experiment for Space Station (ACCESS): ACCESS Accommodation Study Report

    NASA Technical Reports Server (NTRS)

    Wilson, Thomas L. (Editor); Wefel, John P. (Editor)

    1999-01-01

    In 1994 NASA Administrator selected the first high-energy particle physics experiment for the Space Station, the Alpha Magnetic Spectrometer (AMS), to place a magnetic spectrometer in Earth orbit and search for cosmic antimatter. A natural consequence of this decision was that NASA would begin to explore cost-effective ways through which the design and implementation of AMS might benefit other promising payload experiments. The first such experiment to come forward was Advanced Cosmic-Ray Composition Experiment for Space Station (ACCESS) in 1996. It was proposed as a new mission concept in space physics to attach a cosmic-ray experiment of weight, volume, and geometry similar to the AMS on the International Space Station (ISS), and replace the latter as its successor when the AMS is returned to Earth. This was to be an extension of NASA's suborbital balloon program, with balloon payloads serving as the precursor flights and heritage for ACCESS. The balloon programs have always been a cost-effective NASA resource since the particle physics instrumentation for balloon and space applications are directly related. The next step was to expand the process, pooling together expertise from various NASA centers and universities while opening up definition of the ACCESS science goals to the international community through the standard practice of peer review. This process is still ongoing, and the accommodation study presented here will discuss the baseline definition of ACCESS as we understand it today.

  20. Quasilocal conformal Killing horizons: Classical phase space and the first law

    NASA Astrophysics Data System (ADS)

    Chatterjee, Ayan; Ghosh, Avirup

    2015-03-01

    In realistic situations, black hole spacetimes do not admit a global timelike Killing vector field. However, it is possible to describe the horizon in a quasilocal setting by introducing the notion of a quasilocal boundary with certain properties which mimic the properties of a black hole inner boundary. Isolated horizons and Killing horizons are examples of such a kind. In this paper, we construct such a boundary of spacetime which is null and admits a conformal Killing vector field. Furthermore we construct the space of solutions (in general relativity) which admits such quasilocal conformal Killing boundaries. We also establish a form of the first law for these quasilocal horizons.

  1. Integrated Ground Operations Demonstration for Responsive Space Access

    NASA Technical Reports Server (NTRS)

    Johnson, Robert G.; Notardonato, William U.

    2014-01-01

    The NASA Advanced Exploration Systems (AES) program has a three year project to develop and demonstrate technologies to fundamentally change the way ground servicing activities support future access to space architectures. The AES Integrated Ground Operation Demonstration Units (IGODU) project has created two test beds for investigating and maturing two key elements of spaceport processing activities. The first is the GODU Integrated Refrigeration and Storage test bed that is demonstrating zero-loss storage of liquid hydrogen propellants and studying the storage and transfer of densified propellants. The second activity is the GODU Autonomous Control test bed that is implementing health management technologies and autonomous control capability of the propellant loading process to reduce the standing army of experts historically needed to ensure safe propellant loading operations. This presentation will give an overview of the activities at the Kennedy Space Center on these two test beds and its potential impact on future access to space programs.

  2. Structural Propensities of Human Ubiquitination Sites: Accessibility, Centrality and Local Conformation

    PubMed Central

    Song, Jiangning; Zhang, Ziding

    2013-01-01

    The existence and function of most proteins in the human proteome are regulated by the ubiquitination process. To date, tens of thousands human ubiquitination sites have been identified from high-throughput proteomic studies. However, the mechanism of ubiquitination site selection remains elusive because of the complicated sequence pattern flanking the ubiquitination sites. In this study, we perform a systematic analysis of 1,330 ubiquitination sites in 505 protein structures and quantify the significantly high accessibility and unexpectedly high centrality of human ubiquitination sites. Further analysis suggests that the higher centrality of ubiquitination sites is associated with the multi-functionality of ubiquitination sites, among which protein-protein interaction sites are common targets of ubiquitination. Moreover, we demonstrate that ubiquitination sites are flanked by residues with non-random local conformation. Finally, we provide quantitative and unambiguous evidence that most of the structural propensities contain specific information about ubiquitination site selection that is not represented by the sequence pattern. Therefore, the hypothesis about the structural level of the ubiquitination site selection mechanism has been substantially approved. PMID:24349449

  3. Lectins as probes for assessing the accessibility of N-linked glycans in relation to the conformational changes of fibronectin.

    PubMed

    Agniel, Rémy; Vendrely, Charlotte; Poulouin, Laurent; Bascetin, Rümeyza; Benachour, Hamanou; Gallet, Olivier; Leroy-Dudal, Johanne

    2015-12-01

    Fibronectin, a ≈ 450-kDa protein with 4-9% (w/w) glycosylation, is a key component of extracellular matrices and has a high conformational lability regarding its functions. However, the accessibility and the role of glycosylated moieties associated with the conformational changes of fibronectin are poorly understood. Using lectins as probes, we developed an approach comprising dynamic light scattering, turbidimetry measurements, and isothermal titration calorimetry to assess the accessibility of glycosylated moieties of fibronectin undergoing thermal-induced conformational changes. Among a set of 14 lectins, fibronectin mainly reacted with mannose-binding lectins, specifically concanavalin A. When temperature was raised from 25 to 50 °C, fibronectin underwent progressive unfolding, but the conformation of concanavalin A was unaffected. Dynamic light scattering, turbidimetry measurements, and isothermal titration calorimetry showed increased concanavalin A binding to fibronectin during progressive thermal-induced unfolding of the protein core. Such data suggest that mannosylated residues are progressively exposed as fibronectin unfolds. Because oligosaccharide moieties can be differently exposed to cells, and the cell's responses could be modified physiologically or pathologically, modulation of fibronectin sugar chains could be relevant to its biological functions. Thus, lectins might be useful tools to probe the glycosylation accessibility accompanying changes in protein core folding, for which a better understanding would be of value for biological and biomedical research. PMID:26148749

  4. Conformally Coupled Scalars, Instantons, and Vacuum Instability in 4D Anti-de Sitter Space

    SciTech Connect

    Haro, Sebastian de; Papadimitriou, Ioannis; Petkou, Anastasios C.

    2007-06-08

    We show that a scalar field conformally coupled to AdS gravity in four dimensions with a quartic self-interaction can be embedded into M theory. The holographic effective potential is exactly calculated, allowing us to study nonperturbatively the stability of AdS{sub 4} in the presence of the conformally coupled scalar. It is shown that there exists a one-parameter family of conformal scalar boundary conditions for which the boundary theory has an unstable vacuum. In this case, the bulk theory has instanton solutions that mediate the decay of the AdS{sub 4} space. These results match nicely with the vacuum structure and the existence of instantons in an effective three-dimensional boundary model.

  5. Fluorine Substitution in Neurotransmitters: Microwave Spectroscopy and Modelling of the Conformational Space and Non Bonding Interactions

    NASA Astrophysics Data System (ADS)

    Melandri, S.; Maris, A.; Merloni, A.

    2011-06-01

    Fluorine substitution in molecules is a common practice in bio-organic chemistry in order to modulate physicochemical properties and biological activity of molecules and an increasing number of drugs on the market contain fluorine, the presence of which is often of major importance to modify pharmacokinetics properties and molecular activity. The rationale for such a strategy is that fluorine is generally a stronger electron acceptor than the other halogen atoms and its size is intermediate between that of hydrogen and oxygen. We have studied two fluorinated analogs of 2-phenylethylamine (PEA), the prototype molecule for adrenergic neurotransmitters, namely: 4-Fluoro (4FPEA) and 2-Fluoro-2-phenylethylamine (2FPEA) by Molecular Beam Fourier Transform Microwave Spectroscopy in the frequency range 6-18 GHz and ab initio calculations at the MP2/6311++G** level. The aim is to obtain information on the spatial arrangement of the ethylamine side chain and the effects of fluorination on the energy landscape. The conformational space is dominated by low energy gauche conformations stabilized by weak interactions between the aminic hydrogens and the electron cloud of the benzene ring and anti conformations higher in energy. In 2FPEA the presence of the fluorine atom almost duplicate the number of possible conformation with respect to 4FPEA. We observed two conformers of 4FPEA and five conformers of 2FPEA which have been classified with the guide provided by accurate ab initio calculations. The identification of the conformational species was helped by the analysis of the quadrupole hyperfine pattern which is greatly influenced by the orientation of the amino group and acts as a fingerprint for each conformation. The orientation of the dipole moment within the principal axis frame and the order of stability of the different conformations are other independent pieces of evidence for the unambiguous assignment and identification of the conformers. The order of stability was

  6. Conformational Transition of Giant DNA in a Confined Space Surrounded by a Phospholipid Membrane

    PubMed Central

    Kato, Ayako; Shindo, Eri; Sakaue, Takahiro; Tsuji, Akihiko; Yoshikawa, Kenichi

    2009-01-01

    It has been established that a long DNA molecule exhibits a large discrete conformational change from a coiled state to a highly folded state in aqueous solution, depending on the presence of various condensing agents such as polyamines. In this study, T4 DNA labeled with fluorescent dyes was encapsulated in a cell-sized microdroplet covered with a phospholipid membrane to investigate the conformational behavior of a DNA molecule in such a confined space. Fluorescence microscopy showed that the presence of Mg2+ induced the adsorption of DNA onto the membrane inner-surface of a droplet composed of phosphatidylethanolamine, while no adsorption was observed onto a phosphatidylcholine membrane. Under the presence of spermine (tetravalent amine), DNA had a folded conformation in the bulk solution. However, when these molecules were encapsulated in the microdroplet, DNA adsorbed onto the membrane surface accompanied by unfolding of its structure into an extended coil conformation under high concentrations of Mg2+. In addition, DNA molecules trapped in large droplets tended not to be adsorbed on the membrane, i.e., no conformational transition occurred. A thermodynamic analysis suggests that the translational entropy loss of a DNA molecule that is accompanied by adsorption is a key factor in these phenomena under micrometer-scale confinement. PMID:19751673

  7. Conformational space annealing scheme in the inverse design of functional materials

    NASA Astrophysics Data System (ADS)

    Kim, Sunghyun; Lee, In-Ho; Lee, Jooyoung; Oh, Young Jun; Chang, Kee Joo

    2015-03-01

    Recently, the so-called inverse method has drawn much attention, in which specific electronic properties are initially assigned and target materials are subsequently searched. In this work, we develop a new scheme for the inverse design of functional materials, in which the conformational space annealing (CSA) algorithm for global optimization is combined with first-principles density functional calculations. To implement the CSA, we need a series of ingredients, (i) an objective function to minimize, (ii) a 'distance' measure between two conformations, (iii) a local enthalpy minimizer of a given conformation, (iv) ways to combine two parent conformations to generate a daughter one, (v) a special conformation update scheme, and (vi) an annealing method in the 'distance' parameter axis. We show the results of applications for searching for Si crystals with direct band gaps and the lowest-enthalpy phase of boron at a finite pressure and discuss the efficiency of the present scheme. This work is supported by the National Research Foundation of Korea (NRF) under Grant No. NRF-2005-0093845 and by Samsung Science and Technology Foundation under Grant No. SSTFBA1401-08.

  8. Entanglement entropy of black holes and anti-de Sitter space/conformal-field-theory correspondence.

    PubMed

    Solodukhin, Sergey N

    2006-11-17

    A recent proposal by Ryu and Takayanagi for a holographic interpretation of entanglement entropy in conformal field theories dual to supergravity on anti-de Sitter space is generalized to include entanglement entropy of black holes living on the boundary of anti-de Sitter space. The generalized proposal is verified in boundary dimensions d=2 and d=4 for both the uv-divergent and uv-finite terms. In dimension d=4 an expansion of entanglement entropy in terms of size L of the subsystem outside the black hole is considered. A new term in the entropy of dual strongly coupled conformal-field theory, which universally grows as L(2)lnL and is proportional to the value of the obstruction tensor at the black hole horizon, is predicted. PMID:17155672

  9. Advanced Cosmic Ray Composition Experiment for Space Station (ACCESS)

    NASA Technical Reports Server (NTRS)

    Wilson, Thomas L.; Wefel, John P.

    1999-01-01

    In 1994 the first high-energy particle physics experiment for the Space Station, the Alpha Magnetic Spectrometer (AMS), was selected by NASA's Administrator as a joint collaboration with the U.S. Department of Energy (DOE). The AMS program was chartered to place a magnetic spectrometer in Earth orbit and search for cosmic antimatter. A natural consequence of this decision was that NASA would begin to explore cost-effective ways through which the design and implementation of AMS might benefit other promising payload experiments which were evolving from the Office of Space Science. The first such experiment to come forward was ACCESS in 1996. It was proposed as a new mission concept in space physics to place a cosmic-ray experiment of weight, volume, and geometry similar to the AMS on the ISS, and replace the latter as its successor when the AMS is returned to Earth. This was to be an extension of NASA's sub-orbital balloon program, with balloon payloads serving as the precursor flights and heritage for ACCESS. The balloon programs have always been a cost-effective NASA resource since the particle physics instrumentation for balloon and space applications are directly related. The next step was to expand the process, pooling together expertise from various NASA centers and universities while opening up definition of the ACCESS science goals to the international community through the standard practice of peer-review. This process is still on-going and the Accommodation Study presented here will discuss the baseline definition of ACCESS as we understand it today. Further detail on the history, scope, and background of the study is provided in Appendix A.

  10. Segmented proportional spacing medium access control protocol for APONs

    NASA Astrophysics Data System (ADS)

    Wang, Hongbin; Yu, Yiqing; Zhou, Dongru; Meng, Bo

    2004-04-01

    Combining asynchronous transfer mode (ATM) over a passive optical network (APON) can provide broadband services as defined by the international telecommunications union (ITU). The medium access control (MAC) layer is of primary importance to the access scheme as in controls the flow of traffic in the access network. This paper presents a novel MAC protocol-segmented proportional spacing MAC protocol, which complies with ITU-T recommendations, is firstly designed for APON system based on the analysis of different type of bandwidth allocation algorithms. The main idea of protocol is: frame structure adopts the structure regulated by ITU; fine time division for the optical network unit (ONU) to apply bandwidth; the bandwidth"s application is not based on the T-interface but ONU, the bandwidth allocation algorithm uses segmented proportional spacing algorithm. At last, we compare our protocol to other MAC protocols, the results show that proportional spacing and segmented bandwidth allocation control the cell jitter with satisfactory and improve the system bandwidth efficiency at same time, the correlative conclusions are given finally.

  11. Conformally de Sitter space from anisotropic space-like D3-brane of type IIB string theory

    NASA Astrophysics Data System (ADS)

    Roy, Shibaji

    2014-05-01

    We construct a four-dimensional de Sitter space up to a conformal transformation by compactifying the anisotropic SD3-brane solution of type IIB string theory on a six-dimensional product space of the form H5×S1, where H5 is a five-dimensional hyperbolic space and S1 is a circle. The radius of the hyperbolic space is chosen to be constant. The radius of the circle and the dilaton in four dimensions are time dependent and not constant in general. By different choices of parameters characterizing the SD3-brane solution, either the dilaton or the radius of the circle can be made constant but not both. The form field is also nonvanishing in general, but it can be made to vanish without affecting the solution. This construction might be useful for a better understanding of dS/CFT correspondence as well as for cosmology.

  12. Time and dark matter from the conformal symmetries of Euclidean space

    NASA Astrophysics Data System (ADS)

    Hazboun, Jeffrey S.; Wheeler, James T.

    2014-11-01

    Starting with the conformal symmetries of Euclidean space, we construct a manifold where time manifests as a part of the geometry. Though there is no matter present in the geometry studied here, geometric terms analogous to dark energy and dark matter appear when we write down the Einstein tensor. Specifically, the quotient of the conformal group of Euclidean four-space by its Weyl subgroup results in a geometry possessing many of the properties of relativistic phase space, including both a natural symplectic form and non-degenerate Killing metric. We show that the general solution posesses orthogonal Lagrangian submanifolds, with the induced metric and the spin connection on the submanifolds necessarily Lorentzian, despite the Euclidean starting point. Using an orthonormal frame adapted to the phase space properties, we also find two new tensor fields not present in Riemannian geometry. The first is a combination of the Weyl vector with the scale factor on the metric, and determines the timelike directions on the submanifolds. The second comes from the components of the spin connection, symmetric with respect to the new metric. Though this field comes from the spin connection, it transforms homogeneously. Finally, we show that in the absence of Cartan curvature and sources, the configuration space has geometric terms equivalent to a perfect fluid and a cosmological constant.

  13. Iterative derivation of effective potentials to sample the conformational space of proteins at atomistic scale

    NASA Astrophysics Data System (ADS)

    Capelli, Riccardo; Paissoni, Cristina; Sormanni, Pietro; Tiana, Guido

    2014-05-01

    The current capacity of computers makes it possible to perform simulations of small systems with portable, explicit-solvent potentials achieving high degree of accuracy. However, simplified models must be employed to exploit the behavior of large systems or to perform systematic scans of smaller systems. While powerful algorithms are available to facilitate the sampling of the conformational space, successful applications of such models are hindered by the availability of simple enough potentials able to satisfactorily reproduce known properties of the system. We develop an interatomic potential to account for a number of properties of proteins in a computationally economic way. The potential is defined within an all-atom, implicit solvent model by contact functions between the different atom types. The associated numerical values can be optimized by an iterative Monte Carlo scheme on any available experimental data, provided that they are expressible as thermal averages of some conformational properties. We test this model on three different proteins, for which we also perform a scan of all possible point mutations with explicit conformational sampling. The resulting models, optimized solely on a subset of native distances, not only reproduce the native conformations within a few Angstroms from the experimental ones, but show the cooperative transition between native and denatured state and correctly predict the measured free-energy changes associated with point mutations. Moreover, differently from other structure-based models, our method leaves a residual degree of frustration, which is known to be present in protein molecules.

  14. Distal substitutions drive divergent DNA specificity among paralogous transcription factors through subdivision of conformational space.

    PubMed

    Hudson, William H; Kossmann, Bradley R; de Vera, Ian Mitchelle S; Chuo, Shih-Wei; Weikum, Emily R; Eick, Geeta N; Thornton, Joseph W; Ivanov, Ivaylo N; Kojetin, Douglas J; Ortlund, Eric A

    2016-01-12

    Many genomes contain families of paralogs--proteins with divergent function that evolved from a common ancestral gene after a duplication event. To understand how paralogous transcription factors evolve divergent DNA specificities, we examined how the glucocorticoid receptor and its paralogs evolved to bind activating response elements [(+)GREs] and negative glucocorticoid response elements (nGREs). We show that binding to nGREs is a property of the glucocorticoid receptor (GR) DNA-binding domain (DBD) not shared by other members of the steroid receptor family. Using phylogenetic, structural, biochemical, and molecular dynamics techniques, we show that the ancestral DBD from which GR and its paralogs evolved was capable of binding both nGRE and (+)GRE sequences because of the ancestral DBD's ability to assume multiple DNA-bound conformations. Subsequent amino acid substitutions in duplicated daughter genes selectively restricted protein conformational space, causing this dual DNA-binding specificity to be selectively enhanced in the GR lineage and lost in all others. Key substitutions that determined the receptors' response element-binding specificity were far from the proteins' DNA-binding interface and interacted epistatically to change the DBD's function through DNA-induced allosteric mechanisms. These amino acid substitutions subdivided both the conformational and functional space of the ancestral DBD among the present-day receptors, allowing a paralogous family of transcription factors to control disparate transcriptional programs despite high sequence identity. PMID:26715749

  15. Auxiliary Conformally Invariant Higher-Spin Field in de Sitter Space

    NASA Astrophysics Data System (ADS)

    Elmizadeh, M.; Tanhayi, M. R.

    2016-03-01

    We employ de Sitter isometry to study a mixed symmetric rank-3 tensor field in de Sitter space by finding the field equation, solution and two-point function which are conformally invariant. It is proved that such a tensor field plays a key role in conformal theory of linear gravity (Binegar et al., Phys. Rev. D 27, 2249, 1983) . In de Sitter space from the group theoretical point of view this kind of tensor could associate with two unitary irreducible representations (UIR) of the de Sitter group (Takook et al., J.Math. Phys. 51, 032503, 2010), which one representation has a flat limit, namely, in zero curvature coincides to the UIR of Poincaré group, however, the second one which is named as auxiliary field, becomes significant in the study of conformal gravity in de Sitter background. We show that the rank-3 tensor solution can be written in terms of a massless minimally coupled scalar field and also the related two-point function is a function of a massless minimally coupled scalar two-point function.

  16. Aviation or space policy: New challenges for the insurance sector to private human access to space

    NASA Astrophysics Data System (ADS)

    van Oijhuizen Galhego Rosa, Ana Cristina

    2013-12-01

    The phenomenon of private human access to space has introduced a new set of problems in the insurance sector. Orbital and suborbital space transportation will surely be unique commercial services for this new market. Discussions are under way regarding space insurance, in order to establish whether this new market ought to be regulated by aviation or space law. Alongside new definitions, infrastructures, legal frameworks and liability insurances, the insurance sector has also been introducing a new approach. In this paper, I aim to analyse some of the possibilities of new premiums, capacities, and policies (under aviation or space insurance rules), as well as the new insurance products related to vehicles, passengers and third party liability. This paper claims that a change toward new insurance regimes is crucial, due to the current stage in development of space tourism and the urgency to adapt insurance rules to support future development in this area.

  17. Innovative Airbreathing Propulsion Concepts for Access to Space

    NASA Technical Reports Server (NTRS)

    Whitlow, Jr., Woodrow; Blech, Richard A.; Blankson, Isaiah M.

    2001-01-01

    This paper will present technologies and concepts for novel aeropropulsion systems. These technologies will enhance the safety of operations, reduce life cycle costs, and contribute to reduced costs of air travel and access to space. One of the goals of the NASA program is to reduce the carbon-dioxide emissions of aircraft engines. Engine concepts that use highly efficient fuel cell/electric drive technologies in hydrogen-fueled engines will be presented in the proposed paper. Carbon-dioxide emissions will be eliminated by replacing hydrocarbon fuel with hydrogen, and reduce NOx emissions through better combustion process control. A revolutionary exoskeletal engine concept, in which the engine drum is rotated, will be shown. This concept has the potential to allow a propulsion system that can be used for subsonic through hypersonic flight. Dual fan concepts that have ultra-high bypass ratios, low noise, and low drag will be presented. Flow-controlled turbofans and control-configured turbofans also will be discussed. To increase efficiency, a system of microengines distributed along lifting surfaces and on the fuselage is being investigated. This concept will be presented in the paper. Small propulsion systems for affordable, safe personal transportation vehicles will be discussed. These low-oil/oilless systems use technologies that enable significant cost and weight reductions. Pulse detonation engine-based hybrid-cycle and combined-cycle propulsion systems for aviation and space access will be presented.

  18. Sharing Ideas: Making Earth and Space Science Accessible

    NASA Astrophysics Data System (ADS)

    Runyon, C. J.; Guimond, K.; Atkinson, C.

    2005-12-01

    There are nearly six million K-12 students with some form of disability in the U.S. and the majority of them are required to achieve the same academic levels as their non-impaired peers. Historically, students with disabilities have experienced difficulties in fully accessing and participating in middle school and high school science programs. With the passage of the No Child Left Behind (NCLB) Act and increasing focus on reading and math performance, many students with exceptional needs are now being taught science by mainstream science teachers, who have little to no training on how to work with students with exceptional needs. For the past 5 years, SERCH has engaged in organizing and hosting a series of Exceptional Space Science Materials for Exceptional Students Workshops (ENWS) focused on educating students with special needs about the space sciences. Each workshop has focused on a different aspect of formal and informal education and working with the various special needs. In all of these workshops, participants experience what a person or student with special needs might encounter when working through educational activities or exhibits by experiencing it first-hand. In addition to making many of NASA's education materials accessible for all learners, a top-ten list of "best practices" has been compiled by the professional educators as a result of our working together for five years and their formal and informal educational experiences.

  19. Conformally covariant quantization of the Maxwell field in de Sitter space

    NASA Astrophysics Data System (ADS)

    Faci, S.; Huguet, E.; Queva, J.; Renaud, J.

    2009-12-01

    In this article, we quantize the Maxwell (“massless spin one”) de Sitter field in a conformally invariant gauge. This quantization is invariant under the SO0(2,4) group and consequently under the de Sitter group. We obtain a new de Sitter-invariant two-point function which is very simple. Our method relies on the one hand on a geometrical point of view which uses the realization of Minkowski, de Sitter and anti-de Sitter spaces as intersections of the null cone in R6 and a moving plane, and on the other hand on a canonical quantization scheme of the Gupta-Bleuler type.

  20. Why Atens Enjoy Enhanced Accessibility For Human Space Flight

    NASA Technical Reports Server (NTRS)

    Barbee, Brent; Adamo, Daniel

    2011-01-01

    In the context of human space flight (HSF), the concept of near-Earth object (NEO) accessibility is highly subjective. Whether or not a particular NEO is accessible critically depends on mass, performance, and reliability of interplanetary HSF systems yet to be designed. Such systems would certainly include propulsion and crew life support with adequate shielding from both solar flares and galactic cosmic radiation. Equally critical architecture options are relevant to NEO accessibility. These options are also far from being determined and include the number of launches supporting an HSF mission, together with whether or not consumables are to be pre-emplaced at the destination. Until the unknowns of HSF to NEOs come into clearer focus, the notion of relative accessibility is of great utility. Imagine a group of NEOs, each with nearly equal HSF merit determined from their individual characteristics relating to crew safety, scientific return, resource utilization, and planetary defense. The more accessible members of this group are more likely to be explored first. A highly accessible NEO could conceivably be deferred in favor of a less accessible HSF destination because the latter is more accessible during a programmatically desirable launch compliant mission trajectory solutions detected in association with a specific NEO. The known NEO population is then surveyed to illustrate in which regions of heliocentric semi-major axis, eccentricity, and inclination (a, e, i) space NEOs with large n values are mapped. The (a, e, i) mapping is also formatted such that membership in each of four NEO orbit classifications, as defined below, is evident. Amors have orbits everywhere superior to (outside of) Earth's. An Amor is therefore defined to have perihelion between 1.017 astronomical units (AU) and the maximum NEO value of 1.3 AU. As of 0 hrs Universal Time on 1 January 2011 (UT epoch 2011.0), Amors numbered 2855 in the Jet Propulsion Laboratory (JPL) Small-Body Database

  1. Enabling Dedicated, Affordable Space Access Through Aggressive Technology Maturation

    NASA Technical Reports Server (NTRS)

    Jones, Jonathan; Kibbey, Tim; Lampton, Pat; Brown, Thomas

    2014-01-01

    A recent explosion in nano-sat, small-sat, and university class payloads has been driven by low cost electronics and sensors, wide component availability, as well as low cost, miniature computational capability and open source code. Increasing numbers of these very small spacecraft are being launched as secondary payloads, dramatically decreasing costs, and allowing greater access to operations and experimentation using actual space flight systems. While manifesting as a secondary payload provides inexpensive rides to orbit, these arrangements also have certain limitations. Small, secondary payloads are typically included with very limited payload accommodations, supported on a non interference basis (to the prime payload), and are delivered to orbital conditions driven by the primary launch customer. Integration of propulsion systems or other hazardous capabilities will further complicate secondary launch arrangements, and accommodation requirements. The National Aeronautics and Space Administration's Marshall Space Flight Center has begun work on the development of small, low cost launch system concepts that could provide dedicated, affordable launch alternatives to small, risk tolerant university type payloads and spacecraft. These efforts include development of small propulsion systems and highly optimized structural efficiency, utilizing modern advanced manufacturing techniques. This paper outlines the plans and accomplishments of these efforts and investigates opportunities for truly revolutionary reductions in launch and operations costs. Both evolution of existing sounding rocket systems to orbital delivery, and the development of clean sheet, optimized small launch systems are addressed. A launch vehicle at the scale and price point which allows developers to take reasonable risks with new propulsion and avionics hardware solutions does not exist today. Establishing this service provides a ride through the proverbial "valley of death" that lies between

  2. 46 CFR 154.340 - Access to tanks and spaces in the cargo area.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... Equipment Ship Arrangements § 154.340 Access to tanks and spaces in the cargo area. (a) Each cargo tank must.... by 23.6 in.). (b) Each access into and through a void space or other gas-dangerous space in the cargo area, except spaces described in paragraph (e) of the definition for “gas-dangerous space” in §...

  3. 46 CFR 154.340 - Access to tanks and spaces in the cargo area.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... Equipment Ship Arrangements § 154.340 Access to tanks and spaces in the cargo area. (a) Each cargo tank must.... by 23.6 in.). (b) Each access into and through a void space or other gas-dangerous space in the cargo area, except spaces described in paragraph (e) of the definition for “gas-dangerous space” in §...

  4. 46 CFR 154.340 - Access to tanks and spaces in the cargo area.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... Equipment Ship Arrangements § 154.340 Access to tanks and spaces in the cargo area. (a) Each cargo tank must.... by 23.6 in.). (b) Each access into and through a void space or other gas-dangerous space in the cargo area, except spaces described in paragraph (e) of the definition for “gas-dangerous space” in §...

  5. 46 CFR 154.340 - Access to tanks and spaces in the cargo area.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... Equipment Ship Arrangements § 154.340 Access to tanks and spaces in the cargo area. (a) Each cargo tank must.... by 23.6 in.). (b) Each access into and through a void space or other gas-dangerous space in the cargo area, except spaces described in paragraph (e) of the definition for “gas-dangerous space” in §...

  6. Improved small satellite access of the space network

    NASA Technical Reports Server (NTRS)

    Horan, Stephen; Osborne, William P.; Minnix, Timothy

    1994-01-01

    This report contains the results of a study performed under the sponsorship of the National Aeronautics and Space Administration (NASA) made as a grant to the Center for Space Telemetering and Telecommunication Systems at New Mexico State University. The purpose of this phase of the grant is to increase user access to the Space Network (SN) run by NASA for supplying space-to-ground communications for satellites and associated control centers. The identified need is to bring more users into the community of those accessing the SN, especially those in the small satellite class of users. The initial phase of the study concerned the potential for modifications to the standard transponder used in the SN. The results of that investigation are summarized in Section 4. As the hardware modifications were being investigated, a second option was developed, namely to consider changes to the operational mode for the small satellites. This operational concept was to use a single, fixed-pointing antenna in a spin-stabilized satellite and let the antenna pattern sweep past the Tracking and Data Relay Satellites (TDRS) in the SN. The question to be answered by this phase of the study was twofold: could enough contact time per day be made available using this simple operating mode and could the data rate be high enough to allow for sufficient data throughput to satisfy the user community using existing components. Section 2 outlines the methodology and simulation results to answer these questions. Section 3 contains a summary of an operational simulation of a simple satellite payload using these contact scenarios. The simulation is not all inclusive but shows how a payload simulation could be configured to utilize variable contact times. The answer to both of the questions desired to be answered is affirmative. By carefully choosing the correct system transmission power and antenna pattern, the system will allow support to the 50th percentile of expected systems. It is recommended

  7. Efficient solid rocket propulsion for access to space

    NASA Astrophysics Data System (ADS)

    Maggi, Filippo; Bandera, Alessio; Galfetti, Luciano; De Luca, Luigi T.; Jackson, Thomas L.

    2010-06-01

    Space launch activity is expected to grow in the next few years in order to follow the current trend of space exploitation for business purpose. Granting high specific thrust and volumetric specific impulse, and counting on decades of intense development, solid rocket propulsion is a good candidate for commercial access to space, even with common propellant formulations. Yet, some drawbacks such as low theoretical specific impulse, losses as well as safety issues, suggest more efficient propulsion systems, digging into the enhancement of consolidated techniques. Focusing the attention on delivered specific impulse, a consistent fraction of losses can be ascribed to the multiphase medium inside the nozzle which, in turn, is related to agglomeration; a reduction of agglomerate size is likely. The present paper proposes a model based on heterogeneity characterization capable of describing the agglomeration trend for a standard aluminized solid propellant formulation. Material microstructure is characterized through the use of two statistical descriptors (pair correlation function and near-contact particles) looking at the mean metal pocket size inside the bulk. Given the real formulation and density of a propellant, a packing code generates the material representative which is then statistically analyzed. Agglomerate predictions are successfully contrasted to experimental data at 5 bar for four different formulations.

  8. Improved ligand binding energies derived from molecular dynamics: replicate sampling enhances the search of conformational space.

    PubMed

    Adler, Marc; Beroza, Paul

    2013-08-26

    Does a single molecular trajectory provide an adequate sample conformational space? Our calculations indicate that for Molecular Mechanics--Poisson-Boltzmann Surface Area (MM-PBSA) measurement of protein ligand binding, a single molecular dynamics trajectory does not provide a representative sampling of phase space. For a single trajectory, the binding energy obtained by averaging over a number of molecular dynamics frames in an equilibrated system will converge after an adequate simulation time. A separate trajectory with nearly identical starting coordinates (1% randomly perturbed by 0.001 Å), however, can lead to a significantly different calculated binding energy. Thus, even though the calculated energy converges for a single molecular dynamics run, the variation across separate runs implies that a single run inadequately samples the system. The divergence in the trajectories is reflected in the individual energy components, such as the van der Waals and the electrostatics terms. These results indicate that the trajectories sample different conformations that are not in rapid exchange. Extending the length of the dynamics simulation does not resolve the energy differences observed between different trajectories. By averaging over multiple simulations, each with a nearly equivalent starting structure, we find the standard deviation in the calculated binding energy to be ∼1.3 kcal/mol. The work presented here indicates that combining MM-PBSA with multiple samples of the initial starting coordinates will produce more precise and accurate estimates of protein/ligand affinity. PMID:23845109

  9. TPS Sizing for Access-to-Space Vehicles

    NASA Technical Reports Server (NTRS)

    Henline, William; Olynick, David; Palmer, Grant; Chen, Y.-K.

    1996-01-01

    A study was carried out to identify, develop, and benchmark simulation techniques needed for optimum thermal protection system (TPS) material selection and sizing for reusable launch vehicles. Fully viscous, chemically reacting, Navier-Stokes flow solutions over the Langley wing-body single stage to orbit (SSTO) configuration were generated and coupled with an in-depth conduction code. Results from the study provide detailed TPS heat shield materials selection and thickness sizing for the wing-body SSTO. These results are the first ever achieved through the use of a complete, trajectory based hypersonic, Navier-Stokes solution database. TPS designs were obtained for both laminar and turbulent entry trajectories using the Access-to-Space baseline materials such as tailorable advanced blanket insulation. The TPS design effects (materials selection and thickness) of coupling material characteristics to the aerothermal environment are illustrated. Finally, a sample validation case using the shuttle flight database is included.

  10. Space Access for Small Satellites on the K-1

    NASA Astrophysics Data System (ADS)

    Faktor, L.

    Affordable access to space remains a major obstacle to realizing the increasing potential of small satellites systems. On a per kilogram basis, small launch vehicles are simply too expensive for the budgets of many small satellite programs. Opportunities for rideshare with larger payloads on larger launch vehicles are still rare, given the complications associated with coordinating delivery schedules and deployment orbits. Existing contractual mechanisms are also often inadequate to facilitate the launch of multiple payload customers on the same flight. Kistler Aerospace Corporation is committed to lowering the price and enhancing the availability of space access for small satellite programs through the fully-reusable K-1 launch vehicle. Kistler has been working with a number of entities, including Astrium Ltd., AeroAstro, and NASA, to develop innovative approaches to small satellite missions. The K-1 has been selected by NASA as a Flight Demonstration Vehicle for the Space Launch Initiative. NASA has purchased the flight results during the first four K-1 launches on the performance of 13 advanced launch vehicle technologies embedded in the K-1 vehicle. On K-1 flights #2-#4, opportunities exist for small satellites to rideshare to low-earth orbit for a low-launch price. Kistler's flight demonstration contract with NASA also includes options to fly Add-on Technology Experiment flights. Opportunities exist for rideshare payloads on these flights as well. Both commercial and government customers may take advantage of the rideshare pricing. Kistler is investigating the feasibility of flying dedicated, multiple small payload missions. Such a mission would launch multiple small payloads from a single customer or small payloads from different customers. The orbit would be selected to be compatible with the requirements of as many small payload customers as possible, and make use of reusable hardware, standard interfaces (such as the existing MPAS) and verification plans

  11. 41 CFR 105-8.152 - Program accessibility: Assignment of space.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 41 Public Contracts and Property Management 3 2011-01-01 2011-01-01 false Program accessibility: Assignment of space. 105-8.152 Section 105-8.152 Public Contracts and Property Management Federal Property...-8.152 Program accessibility: Assignment of space. (a) When GSA assigns or reassigns space to...

  12. 46 CFR 153.217 - Access to enclosed spaces and dedicated ballast tanks.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... tanks. An access opening to an enclosed space or a dedicated ballast tank must meet the requirements for a cargo tank access in § 153.254 (b), (c), and (d) if: (a) The enclosed space or dedicated ballast... within the enclosed space or dedicated ballast tank....

  13. 46 CFR 153.217 - Access to enclosed spaces and dedicated ballast tanks.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... tanks. An access opening to an enclosed space or a dedicated ballast tank must meet the requirements for a cargo tank access in § 153.254 (b), (c), and (d) if: (a) The enclosed space or dedicated ballast... within the enclosed space or dedicated ballast tank....

  14. 46 CFR 153.217 - Access to enclosed spaces and dedicated ballast tanks.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... tanks. An access opening to an enclosed space or a dedicated ballast tank must meet the requirements for a cargo tank access in § 153.254 (b), (c), and (d) if: (a) The enclosed space or dedicated ballast... within the enclosed space or dedicated ballast tank....

  15. 46 CFR 153.217 - Access to enclosed spaces and dedicated ballast tanks.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... tanks. An access opening to an enclosed space or a dedicated ballast tank must meet the requirements for a cargo tank access in § 153.254 (b), (c), and (d) if: (a) The enclosed space or dedicated ballast... within the enclosed space or dedicated ballast tank....

  16. Developing hybrid near-space technologies for affordable access to suborbital space

    NASA Astrophysics Data System (ADS)

    Badders, Brian David

    High power rockets and high altitude balloons are two near-space technologies that could be combined in order to provide access to the mesosphere and, eventually, suborbital space. This "rockoon" technology has been used by several large budget space programs before being abandoned in favor of even more expensive, albeit more accurate, ground launch systems. With the increased development of nano-satellites and atmospheric sensors, combined with rising interest in global atmospheric data, there is an increase in desire for affordable access to extreme altitudes that does not necessarily require the precision of ground launches. Development of hybrid near-space technologies for access to over 200k ft. on a small budget brings many challenges within engineering, systems integration, cost analysis, market analysis, and business planning. This research includes the design and simulation testing of all the systems needed for a safe and reusable launch system, the cost analysis for initial production, the development of a business plan, and the development of a marketing plan. This project has both engineering and scientific significance in that it can prove the space readiness of new technologies, raise their technology readiness levels (TRLs), expedite the development process, and also provide new data to the scientific community. It also has the ability to stimulate university involvement in the aerospace industry and help to inspire the next generation of workers in the space sector. Previous development of high altitude balloon/high power rocket hybrid systems have been undertaken by government funded military programs or large aerospace corporations with varying degrees of success. However, there has yet to be a successful flight with this type of system which provides access to the upper mesosphere in a university setting. This project will aim to design and analyze a viable system while testing the engineering process under challenging budgetary constraints. The

  17. Truncated conformal space approach for 2D Landau–Ginzburg theories

    DOE PAGESBeta

    Coser, A.; Beria, M.; Brandino, G. P.; Konik, R. M.; Mussardo, G.

    2014-12-10

    In this study, We examine the spectrum of Landau–Ginzburg theories in 1 + 1 dimensions using the truncated conformal space approach employing a compactified boson. We study these theories both in their broken and unbroken phases. We first demonstrate that we can reproduce the expected spectrum of a Φ² theory (i.e. a free massive boson) in this framework. We then turn to Φ⁴ in its unbroken phase and compare our numerical results with the predictions of two-loop perturbation theory, finding excellent agreement. We then analyze the broken phase of Φ⁴ where kink excitations together with their bound states are present.more » We confirm the semiclassical predictions for this model on the number of stable kink-antikink bound states. We also test the semiclassics in the double well phase of Φ⁶ Landau-Ginzburg theory, again finding agreement.« less

  18. Truncated conformal space approach for 2D Landau–Ginzburg theories

    SciTech Connect

    Coser, A.; Beria, M.; Brandino, G. P.; Konik, R. M.; Mussardo, G.

    2014-12-10

    In this study, We examine the spectrum of Landau–Ginzburg theories in 1 + 1 dimensions using the truncated conformal space approach employing a compactified boson. We study these theories both in their broken and unbroken phases. We first demonstrate that we can reproduce the expected spectrum of a Φ² theory (i.e. a free massive boson) in this framework. We then turn to Φ⁴ in its unbroken phase and compare our numerical results with the predictions of two-loop perturbation theory, finding excellent agreement. We then analyze the broken phase of Φ⁴ where kink excitations together with their bound states are present. We confirm the semiclassical predictions for this model on the number of stable kink-antikink bound states. We also test the semiclassics in the double well phase of Φ⁶ Landau-Ginzburg theory, again finding agreement.

  19. New Specimen Access Device for the Large Space Simulator

    NASA Astrophysics Data System (ADS)

    Lazzarini, P.; Ratti, F.

    2004-08-01

    The Large Space Simulator (LSS) is used to simulate in- orbit environmental conditions for spacecraft (S/C) testing. The LSS is intended to be a flexible facility: it can accommodate test articles that can differ significantly in shape and weight and carry various instruments. To improve the accessibility to the S/C inside the LSS chamber a new Specimen Access Device (SAD) has been procured. The SAD provides immediate and easy access to the S/C, thus reducing the amount of time necessary for the installations of set-ups in the LSS. The SAD has been designed as bridge crane carrying a basket to move the operator into the LSS. Such a crane moves on parallel rails on the top floor of the LSS building. The SAD is composed by three subsystems: the main bridge, the trolley that moves along the main bridge and the telescopic mast. A trade off analysis has been carried out for what concerns the telescopic mast design. The choice between friction pads vs rollers, to couple the different sections of the mast, has been evaluated. The resulting design makes use of a four sections square mast, with rollers driven deployment. This design has been chosen for the higher stiffness of the mast, due to the limited number of sections, and because it reduces radically the risk of contamination related to a solution based on sliding bushings. Analyses have been performed to assess the mechanical behaviour both in static and in dynamic conditions. In particular the telescopic mast has been studied in detail to optimise its stiffness and to check the safety margins in the various operational conditions. To increase the safety of the operations an anticollision system has been implemented by positioning on the basket two kind of sensors, ultrasonic and contact ones. All the translations are regulated by inverters with acceleration and deceleration ramps controlled by a Programmable Logic Controller (PLC). An absolute encoder is installed on each motor to provide the actual position of the

  20. ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS: Conformal Invariance and Noether Symmetry, Lie Symmetry of Birkhoffian Systems in Event Space

    NASA Astrophysics Data System (ADS)

    Zhang, Yi

    2010-01-01

    This paper focuses on studying a conformal invariance and a Noether symmetry, a Lie symmetry for a Birkhoffian system in event space. The definitions of the conformal invariance of the system are given. By investigation on the relations between the conformal invariance and the Noether symmetry, the conformal invariance and the Lie symmetry, the expressions of conformal factors of the system under these circumstances are obtained. The Noether conserved quantities and the Hojman conserved quantities directly derived from the conformal invariance are given. Two examples are given to illustrate the application of the results.

  1. Second order superintegrable systems in conformally flat spaces. IV. The classical 3D Staeckel transform and 3D classification theory

    SciTech Connect

    Kalnins, E.G.; Kress, J.M.; Miller, W. Jr.

    2006-04-15

    This article is one of a series that lays the groundwork for a structure and classification theory of second order superintegrable systems, both classical and quantum, in conformally flat spaces. In the first part of the article we study the Staeckel transform (or coupling constant metamorphosis) as an invertible mapping between classical superintegrable systems on different three-dimensional spaces. We show first that all superintegrable systems with nondegenerate potentials are multiseparable and then that each such system on any conformally flat space is Staeckel equivalent to a system on a constant curvature space. In the second part of the article we classify all the superintegrable systems that admit separation in generic coordinates. We find that there are eight families of these systems.

  2. 41 CFR 105-8.152 - Program accessibility: Assignment of space.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...: Assignment of space. 105-8.152 Section 105-8.152 Public Contracts and Property Management Federal Property...-8.152 Program accessibility: Assignment of space. (a) When GSA assigns or reassigns space to an.... (b) Prior to the assignment or reassignment of space to an agency, GSA shall inform the agency of...

  3. Marshall Space Flight Center's role in EASE/ACCESS mission management

    NASA Technical Reports Server (NTRS)

    Hawkins, Gerald W.

    1987-01-01

    The Marshall Space Flight Center (MSFC) Spacelab Payload Project Office was responsible for the mission management and development of several successful payloads. Two recent space construction experiments, the Experimental Assembly of Structures in Extravehicular Activity (EASE) and the Assembly Concept for Construction of Erectable Space Structures (ACCESS), were combined into a payload managed by the center. The Ease/ACCESS was flown aboard the Space Shuttle Mission 61-B. The EASE/ACCESS experiments were the first structures assembled in space, and the method used to manage this successful effort will be useful for future space construction missions. The MSFC mission management responsibilities for the EASE/ACCESS mission are addressed and how the lessons learned from the mission can be applied to future space construction projects are discussed.

  4. Proposed preliminary criteria for space shuttle access equipment at the operational site

    NASA Technical Reports Server (NTRS)

    Beck, P. E.

    1971-01-01

    A comparison was made between the methods of access utilized, or proposed, by the military, commercial airlines, and the space shuttle Phase B contractors. The methodology was subjected to consideration for space shuttle use and similarity to current space shuttle access concepts. The Phase B contractor concepts were in turn examined for degree of use of the state-of-the-art and progressive extension of new cost-effective ideas. This comparison disclosed a need for better definition of the criteria/requirements for space shuttle access equipment. Preliminary criteria, needed prior to initiation of the detail design (Phase C/D effort) of ground hardware for the operational site, are presented.

  5. Protein structure determination by conformational space annealing using NMR geometric restraints.

    PubMed

    Joo, Keehyoung; Joung, InSuk; Lee, Jinhyuk; Lee, Jinwoo; Lee, Weontae; Brooks, Bernard; Lee, Sung Jong; Lee, Jooyoung

    2015-12-01

    We have carried out numerical experiments to investigate the applicability of the global optimization method of conformational space annealing (CSA) to the enhanced NMR protein structure determination over existing PDB structures. The NMR protein structure determination is driven by the optimization of collective multiple restraints arising from experimental data and the basic stereochemical properties of a protein-like molecule. By rigorous and straightforward application of CSA to the identical NMR experimental data used to generate existing PDB structures, we redetermined 56 recent PDB protein structures starting from fully randomized structures. The quality of CSA-generated structures and existing PDB structures were assessed by multiobjective functions in terms of their consistencies with experimental data and the requirements of protein-like stereochemistry. In 54 out of 56 cases, CSA-generated structures were better than existing PDB structures in the Pareto-dominant manner, while in the remaining two cases, it was a tie with mixed results. As a whole, all structural features tested improved in a statistically meaningful manner. The most improved feature was the Ramachandran favored portion of backbone torsion angles with about 8.6% improvement from 88.9% to 97.5% (P-value <10(-17)). We show that by straightforward application of CSA to the efficient global optimization of an energy function, NMR structures will be of better quality than existing PDB structures. PMID:26454251

  6. Grooming the Shuttle for cost-effective access to space

    NASA Technical Reports Server (NTRS)

    Moore, J. W.

    1985-01-01

    An assessment is made of the performance of the Space Shuttle-based Space Transportation System (STS) from the initial flights in 1981 to the present, which has involved the launching of 12 satellites and the retrieval of two. It is expected that the STS will soon be able to schedule 24 routine missions/year, upon the achievement of full operational status for the full fleet of four Space Shuttles and the completion of support facilities at both the Kennedy Space Center and Vandenberg Air Force Base. The prospects for space industrialization efforts based on STS are noted.

  7. AGU to Launch a New Open-Access Journal Spanning the Earth and Space Sciences

    NASA Astrophysics Data System (ADS)

    Hanson, Brooks

    2014-02-01

    AGU is pleased to announce a new, fully open-access journal, Earth and Space Science (ESS), that will reflect the expansive range of science represented by AGU's members. ESS will publish research papers spanning all of the Earth, planetary, and space sciences, including related fields in environmental science, geoengineering, space engineering, and biogeochemistry.

  8. Gd(3+) Spin Labels Report the Conformation and Solvent Accessibility of Solution and Vesicle-Bound Melittin.

    PubMed

    Manukovsky, Nurit; Frydman, Veronica; Goldfarb, Daniella

    2015-10-29

    Although Gd(3+)-based spin labels have been shown to be an alternative to nitroxides for double electron-electron resonance (DEER) distance measurements at high fields, their ability to provide solvent accessibility information, as nitroxides do, has not been explored. In addition, the effect of the label type on the measured distance distribution has not been sufficiently characterized. In this work, we extended the applicability of Gd(3+) spin labels to solvent accessibility measurements on a peptide in model membranes, namely, large unilamellar vesicles (LUVs) using W-band (2)H Mims electron-nuclear double resonance (ENDOR) and electron spin echo envelope modulation (ESEEM) techniques and Gd(3+)-ADO3A-labeled melittin. In addition, we carried out Gd(3+)-Gd(3+) DEER distance measurements to probe the peptide conformation in solution and when bound to LUVs. A comparison with earlier results reported for the same system with nitroxide labels shows that, although in both cases the peptide binds parallel to the membrane surface, the Gd(3+)-ADO3A label tends to protrude from the membrane into the solvent, whereas the nitroxide does the opposite. This can be explained on the basis of the hydrophilicity of the Gd(3+)-ADO3A labels in contrast with the hydrophobicity of nitroxides. The distance distributions obtained from different labels are accordingly different, with the Gd(3+)-ADO3A yielding consistently broader distributions. These discrepancies are most pronounced when the peptide termini are labeled, which implies that such labeling positions may be inadvisible. PMID:26001213

  9. Crystal Structure of Inhibitor-Bound P450BM-3 Reveals Open Conformation of Substrate Access Channel

    SciTech Connect

    Haines, Donovan C.; Chen, Baozhi; Tomchick, Diana R.; Bondlela, Muralidhar; Hegde, Amita; Machius, Mischa; Peterson, Julian A.

    2008-08-19

    P450BM-3 is an extensively studied P450 cytochrome that is naturally fused to a cytochrome P450 reductase domain. Crystal structures of the heme domain of this enzyme have previously generated many insights into features of P450 structure, substrate binding specificity, and conformational changes that occur on substrate binding. Although many P450s are inhibited by imidazole, this compound does not effectively inhibit P450BM-3. {omega}-Imidazolyl fatty acids have previously been found to be weak inhibitors of the enzyme and show some unusual cooperativity with the substrate lauric acid. We set out to improve the properties of these inhibitors by attaching the {omega}-imidazolyl fatty acid to the nitrogen of an amino acid group, a tactic that we used previously to increase the potency of substrates. The resulting inhibitors were significantly more potent than their parent compounds lacking the amino acid group. A crystal structure of one of the new inhibitors bound to the heme domain of P450BM-3 reveals that the mode of interaction of the amino acid group with the enzyme is different from that previously observed for acyl amino acid substrates. Further, required movements of residues in the active site to accommodate the imidazole group provide an explanation for the low affinity of imidazole itself. Finally, the previously observed cooperativity with lauric acid is explained by a surprisingly open substrate-access channel lined with hydrophobic residues that could potentially accommodate lauric acid in addition to the inhibitor itself.

  10. Adjustment of local conformational flexibility and accessible surface area alterations of Serine128 and Valine183 in mnemiopsin

    NASA Astrophysics Data System (ADS)

    Hakiminia, Forough; Molakarimi, Maryam; Khalifeh, Khosrow; Jahani, Zohreh; Sajedi, Reza H.; Ranjbar, Bijan

    2016-08-01

    We used a combination of experimental and bioinformatic studies to elucidate the importance of Serine128 and Valine183 on the activity and thermal stability of mnemiopsin 1 by substitution of S128 and V183 with glycine and threonine, respectively (S128G and V183T mutants). Luminescence emissions of S128G and V183T were reduced to 71.6% and 46.6% with respect to the original activity of the wild type protein. According to circular dichroism (CD) measurements, compactness of mutants decreased in comparison with wild type (WT) protein. Differential scanning calorimetry (DSC) indicated that Tm values of thermal unfolding are not changed significantly upon mutation. Herein, we suggest that the protein variants unfold through molecular association and intermediate states. Bioinformatic studies revealed that local fluctuation of residues in S128G increased with respect to WT protein. However, S128G mutation leads to increment of the accessible surface area of lysine188. Therefore, this change is thermodynamically favorable. Finally, both experimental and theoretical studies showed a delicate balance between all structural alterations, determining total conformational stability of the protein.

  11. Anti-de Sitter-Space/Conformal-Field-Theory Casimir Energy for Rotating Black Holes

    SciTech Connect

    Gibbons, G.W.; Perry, M.J.; Pope, C.N.

    2005-12-02

    We show that, if one chooses the Einstein static universe as the metric on the conformal boundary of Kerr-anti-de Sitter spacetime, then the Casimir energy of the boundary conformal field theory can easily be determined. The result is independent of the rotation parameters, and the total boundary energy then straightforwardly obeys the first law of thermodynamics. Other choices for the metric on the conformal boundary will give different, more complicated, results. As an application, we calculate the Casimir energy for free self-dual tensor multiplets in six dimensions and compare it with that of the seven-dimensional supergravity dual. They differ by a factor of 5/4.

  12. Assessing equitable access to urban green space: the role of engineered water infrastructure.

    PubMed

    Wendel, Heather E Wright; Downs, Joni A; Mihelcic, James R

    2011-08-15

    Urban green space and water features provide numerous social, environmental, and economic benefits, yet disparities often exist in their distribution and accessibility. This study examines the link between issues of environmental justice and urban water management to evaluate potential improvements in green space and surface water access through the revitalization of existing engineered water infrastructures, namely stormwater ponds. First, relative access to green space and water features were compared for residents of Tampa, Florida, and an inner-city community of Tampa (East Tampa). Although disparities were not found in overall accessibility between Tampa and East Tampa, inequalities were apparent when quality, diversity, and size of green spaces were considered. East Tampa residents had significantly less access to larger, more desirable spaces and water features. Second, this research explored approaches for improving accessibility to green space and natural water using three integrated stormwater management development scenarios. These scenarios highlighted the ability of enhanced water infrastructures to increase access equality at a variety of spatial scales. Ultimately, the "greening" of gray urban water infrastructures is advocated as a way to address environmental justice issues while also reconnecting residents with issues of urban water management. PMID:21728276

  13. Attached shuttle payload carriers: Versatile and affordable access to space

    NASA Technical Reports Server (NTRS)

    1990-01-01

    The shuttle has been primarily designed to be a versatile vehicle for placing a variety of scientific and technological equipment in space including very large payloads; however, since many large payloads do not fill the shuttle bay, the space and weight margins remaining after the major payloads are accommodated often can be made available to small payloads. The Goddard Space Flight Center (GSFC) has designed standardized mounting structures and other support systems, collectively called attached shuttle payload (ASP) carriers, to make this additional space available to researchers at a relatively modest cost. Other carrier systems for ASP's are operated by other NASA centers. A major feature of the ASP carriers is their ease of use in the world of the Space Shuttle. ASP carriers attempt to minimized the payload interaction with Space Transportation System (STS) operations whenever possible. Where this is not possible, the STS services used are not extensive. As a result, the interfaces between the carriers and the STS are simplified. With this near autonomy, the requirements for supporting documentation are considerably lessened and payload costs correspondingly reduced. The ASP carrier systems and their capabilities are discussed in detail. The range of available capabilities assures that an experimenter can select the simplest, most cost-effective carrier that is compatible with his or her experimental objectives. Examples of payloads which use ASP basic hardware in nonstandard ways are also described.

  14. Secure Payload Access to the International Space Station

    NASA Technical Reports Server (NTRS)

    Pitts, R. Lee; Reid, Chris

    2002-01-01

    The ISS finally reached an operational state and exists for local and remote users. Onboard payload systems are managed by the Huntsville Operations Support Center (HOSC). Users access HOSC systems by internet protocols in support of daily operations, preflight simulation, and test. In support of this diverse user community, a modem security architecture has been implemented. The architecture has evolved over time from an isolated but open system to a system which supports local and remote access to the ISS over broad geographic regions. This has been accomplished through the use of an evolved security strategy, PKI, and custom design. Through this paper, descriptions of the migration process and the lessons learned are presented. This will include product decision criteria, rationale, and the use of commodity products in the end architecture. This paper will also stress the need for interoperability of various products and the effects of seemingly insignificant details.

  15. Analyzing green/open space accessibility by using GIS: case study of northern Cyprus cities

    NASA Astrophysics Data System (ADS)

    Kara, Can; Akçit, Nuhcan

    2015-06-01

    It is well known that green spaces are vital for increasing the quality of life within the urban environment. World Health Organization states that it should be 9 square meters per person at least. European Environment Agency defines that 5000 square meters of green space should be accessible within 300 meters distance from households. Green structure in Northern Cyprus is not sufficient and effective in this manner. In Northern Cyprus, they have neglected the urban planning process and they have started to lose significance and importance. The present work analyzes the accessibility of green spaces in Northern Cyprus cities. Kioneli, Famagusta, Kyrenia and the northern part of Nicosia are analyzed in this manner. To do that, green space structure is analyzed by using digital data. Additionally, accessibility of the green space is measured by using 300-meter buffers for each city. Euclidean distance is used from each building and accessibility maps are generated. Kyrenia and Famagusta have shortage in green space per capita. The amount of green space in these cities is less than 4 square meters. The factors affecting the accessibility and utilization of public spaces are discussed to present better solutions to urban planning.

  16. Transformational Technologies to Expedite Space Access and Development

    SciTech Connect

    Rather, John D. G.

    2010-01-28

    Throughout history the emergence of new technologies has enabled unforeseen breakthrough capabilities that rapidly transformed the world. Some global examples from the twentieth century include AC electric power, nuclear energy, and turbojet engines. At the systems level, success of both Apollo and the Space Shuttle programs depended upon taming hydrogen propulsion and developing high-temperature atmospheric reentry materials. Human space development now is stymied because of a great need for breakthrough technologies and strategies. It is believed that new capabilities exist within the present states-of-the-art of superconducting technology that can be implemented to transform the future of human space development. This paper is an overview of three other papers presented within this forum, which summarizes the principles and consequences of StarTram, showing how the resulting breakthrough advantages can lead directly to safe space tourism and massive development of the moon, Mars and the outer solar system. StarTram can implement cost-effective solar power from space, simple utilization of asteroid material to protect humans from ionizing radiation, and effective defense of the Earth from devastating cosmic impacts. Synergistically, StarTram technologies will revolutionize ground transportation on the Earth, leading to enormous reduction in energy consumption and creation of millions of jobs. High energy lasers will also be discussed because of their importance to power beaming applications.

  17. Transformational Technologies to Expedite Space Access and Development

    NASA Astrophysics Data System (ADS)

    Rather, John D. G.

    2010-01-01

    Throughout history the emergence of new technologies has enabled unforeseen breakthrough capabilities that rapidly transformed the world. Some global examples from the twentieth century include AC electric power, nuclear energy, and turbojet engines. At the systems level, success of both Apollo and the Space Shuttle programs depended upon taming hydrogen propulsion and developing high-temperature atmospheric reentry materials. Human space development now is stymied because of a great need for breakthrough technologies and strategies. It is believed that new capabilities exist within the present states-of-the-art of superconducting technology that can be implemented to transform the future of human space development. This paper is an overview of three other papers presented within this forum, which summarizes the principles and consequences of StarTram, showing how the resulting breakthrough advantages can lead directly to safe space tourism and massive development of the moon, Mars and the outer solar system. StarTram can implement cost-effective solar power from space, simple utilization of asteroid material to protect humans from ionizing radiation, and effective defense of the Earth from devastating cosmic impacts. Synergistically, StarTram technologies will revolutionize ground transportation on the Earth, leading to enormous reduction in energy consumption and creation of millions of jobs. High energy lasers will also be discussed because of their importance to power beaming applications.

  18. Update on NASA Space Shuttle Earth Observations Photography on the laser videodisc for rapid image access

    NASA Technical Reports Server (NTRS)

    Lulla, Kamlesh

    1994-01-01

    There have been many significant improvements in the public access to the Space Shuttle Earth Observations Photography Database. New information is provided for the user community on the recently released videodisc of this database. Topics covered included the following: earlier attempts; our first laser videodisc in 1992; the new laser videodisc in 1994; and electronic database access.

  19. [Analysis on accessibility of urban park green space: the case study of Shenyang Tiexi District].

    PubMed

    Lu, Ning; Li, Jun-Ying; Yan, Hong-Wei; Shi, Tuo; Li, Ying

    2014-10-01

    The accessibility of urban park green space is an important indicator to reflect how much the natural service supplied by parks could be enjoyed by citizens conveniently and fairly. This paper took Shenyang Tiexi District as an example to evaluate the accessibility of urban park green space based on QuickBird imagery and GIS software, with four modes of transportation, walking, non-motor vehicle, motor vehicle and public transport being considered. The research compared and analyzed the distribution of the accessible area and the accessible people of park green space. The result demonstrated that park green space in Shenyang Tiexi District was not enough and the distribution was not even. To be precise, the accessibility in southwest part and central part was relatively good, that in marginal sites was worse, and that in east part and north part was the worst. Furthermore, the accessibility based on different modes of transportation varied a lot. The accessibility of motor vehicle was the best, followed by non-motor vehicle and public transport, and walking was the worst. Most of the regions could be reached within 30 minutes by walking, 15 minutes by non-motor vehicle and public transport, and 10 minutes by motor vehicle. This paper had a realistic significance in terms of further, systematic research on the green space spatial pattern optimization. PMID:25796905

  20. Evaluation Method for Accessibility to Hollow Space of Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Fan, Jing; Yudasaka, Masako; Miyawaki, Jin; Iijima, Sumio

    2004-03-01

    For application of single-wall carbon nanotubes (SWNTs) and nanohorns (SWNHs) to material-storage media, holes are opened usually by oxidation through which materials enter inside the hollow space of tubes. The holes are known to pass only molecules with diameters smaller than those of the holes, thus molecular-size selective storage of gases inside tubes becomes possible [1]. To enhance utilities of inner hollow space of carbon nanoutbes, controlled opening of holes is important. It is especially so for SWNHs, because holes with various diameters are potentially available due to the various types of defects on the tube walls. We studied the methods of hole-opening for SWNHs, and, at the same time, developed simple methods for evaluating the sizes of holes and the volumes of inner hollow-spaces. [1] Murata et al. J. Phys.Chem.

  1. The New Millennium Program architecture and access to space

    NASA Technical Reports Server (NTRS)

    Herrell, Linda M.

    2005-01-01

    This paper identifies the trade space but focuses on two alternate approaches: using less-expensive spacecraft and partnering with other missions. Less-expensive spacecraft can provide a platform for flying NMP subsystem technologies, and partnering with other missions can be a cost-effective approach for NMP system-level technology validations.

  2. Enabling Dedicated, Affordable Space Access Through Aggressive Technology Maturation

    NASA Technical Reports Server (NTRS)

    Jones, Jonathan E.; Kibbey, Timothy P.; Cobb, C. Brent; Harris, Lawanna L.

    2014-01-01

    A launch vehicle at the scale and price point which allows developers to take reasonable risks with high payoff propulsion and avionics hardware solutions does not exist today. Establishing this service provides a ride through the proverbial technology "valley of death" that lies between demonstration in laboratory and flight environments. NASA's NanoLaunch effort will provide the framework to mature both earth-to-orbit and on-orbit propulsion and avionics technologies while also providing affordable, dedicated access to low earth orbit for cubesat class payloads.

  3. SLAC All Access: Fermi Gamma-ray Space Telescope

    ScienceCinema

    Romani, Roger

    2014-06-24

    Three hundred and fifty miles overhead, the Fermi Gamma-ray Space Telescope silently glides through space. From this serene vantage point, the satellite's instruments watch the fiercest processes in the universe unfold. Pulsars spin up to 700 times a second, sweeping powerful beams of gamma-ray light through the cosmos. The hyperactive cores of distant galaxies spew bright jets of plasma. Far beyond, something mysterious explodes with unfathomable power, sending energy waves crashing through the universe. Stanford professor and KIPAC member Roger W. Romani talks about this orbiting telescope, the most advanced ever to view the sky in gamma rays, a form of light at the highest end of the energy spectrum that's created in the hottest regions of the universe.

  4. SLAC All Access: Fermi Gamma-ray Space Telescope

    SciTech Connect

    Romani, Roger

    2013-05-31

    Three hundred and fifty miles overhead, the Fermi Gamma-ray Space Telescope silently glides through space. From this serene vantage point, the satellite's instruments watch the fiercest processes in the universe unfold. Pulsars spin up to 700 times a second, sweeping powerful beams of gamma-ray light through the cosmos. The hyperactive cores of distant galaxies spew bright jets of plasma. Far beyond, something mysterious explodes with unfathomable power, sending energy waves crashing through the universe. Stanford professor and KIPAC member Roger W. Romani talks about this orbiting telescope, the most advanced ever to view the sky in gamma rays, a form of light at the highest end of the energy spectrum that's created in the hottest regions of the universe.

  5. Concept for Multiple-Access Free-Space Laser Communications

    NASA Technical Reports Server (NTRS)

    Wilson, Keith

    2004-01-01

    A design concept for a proposed airborne or spaceborne free-space optical-communication terminal provides for simultaneous reception of signals from multiple other opticalcommunication terminals aboard aircraft or spacecraft that carry scientific instruments and fly at lower altitudes. The concept reflects the need for rapid acquisition and tracking of the signals coming from the lower-altitude terminals as they move across the field of view.

  6. Orbiter processing facility: Access platforms Kennedy Space Center, Florida, from challenge to achievement

    NASA Technical Reports Server (NTRS)

    Haratunian, M.

    1985-01-01

    A system of access platforms and equipment within the space shuttle orbiter processing facility at Kennedy Space Center is described. The design challenges of the platforms, including clearance envelopes, load criteria, and movement, are discussed. Various applications of moveable platforms are considered.

  7. Community Coordinated Modeling Center (CCMC): Providing Access to Space Weather Models and Research Support Tools

    NASA Astrophysics Data System (ADS)

    Chulaki, A.; Bakshi, S. S.; Berrios, D.; Hesse, M.; Kuznetsova, M. M.; Lee, H.; MacNeice, P. J.; Mendoza, A. M.; Mullinix, R.; Patel, K. D.; Pulkkinen, A.; Rastaetter, L.; Shim, J.; Taktakishvili, A.; Zheng, Y.

    2011-12-01

    The Community Coordinated Modeling Center at NASA, Goddard Space flight Center, provides access to state-of-the-art space weather models to the research community. The majority of the models residing at the CCMC are comprehensive computationally intensive physics-based models. The CCMC also provides free services and tools to assist the research community in analyzing the results from the space weather model simulations. We present an overview of the available tools and services at the CCMC: the Runs-On-Request system, the online visualization, the Kameleon access and interpolation library and the Metrics Challenge tools suite.

  8. REUSABLE PROPULSION ARCHITECTURE FOR SUSTAINABLE LOW-COST ACCESS TO SPACE

    NASA Technical Reports Server (NTRS)

    Bonometti, J. A.; Dankanich, J. W.; Frame, K. L.

    2005-01-01

    The primary obstacle to any space-based mission is, and has always been, the cost of access to space. Even with impressive efforts toward reusability, no system has come close to lowering the cost a significant amount. It is postulated here, that architectural innovation is necessary to make reusability feasible, not incremental subsystem changes. This paper shows two architectural approaches of reusability that merit further study investments. Both #inherently# have performance increases and cost advantages to make affordable access to space a near term reality. A rocket launched from a subsonic aircraft (specifically the Crossbow methodology) and a momentum exchange tether, reboosted by electrodynamics, offer possibilities of substantial reductions in the total transportation architecture mass - making access-to-space cost-effective. They also offer intangible benefits that reduce risk or offer large growth potential. The cost analysis indicates that approximately a 50% savings is obtained using today#s aerospace materials and practices.

  9. Space Vision: Making Astronomy Accessible to Visually Impaired Students

    NASA Astrophysics Data System (ADS)

    Ries, J. G.; Baguio, M. R.; Jurgens, T. D.; Pruett, K. M.

    2004-05-01

    Astronomy, with good reason, is thought of as a visual science. Spectacular images of deep space objects or other worlds of our solar system inspire public interest in Astronomy. People encounter news about the universe during their daily life. Developing concepts about celestial objects presents an extra challenge of abstraction for people with visual impairments. The Texas Space Grant Consortium with educators at the Texas School for the Blind and Visually Impaired have developed a 2 day workshop to be held in April 2004 to help students with visual impairments understand these concepts. Hands-on activities and experiments will emphasize non-visual senses. For example, students will learn about: - Constellations as historical ways of finding one's way across the sky. - The size and structure of the Solar System by building a scale model on a running track. They will also: - Plan a planetary exploration mission. - Explore wave phenomenon using heat and sound waves. In preparation for the workshop we worked with teens involved in the countywide 4-H Teens Leading with Character (TLC) program to create the tactile materials necessary for the activities. The teens attended solar system education training so they would have the skills necessary to make the tactile displays to be used during the workshop. The results and evaluation of the workshop will be presented at the meeting. Touch the Universe: A NASA Braille Book of Astronomy inspired this workshop, and it is supported by HST Grant HST-ED-90255.01-A.

  10. SINP space physics data storage and access system

    NASA Astrophysics Data System (ADS)

    Barinova, Vera; Kalegaev, Vladimir; Parunakian, David

    In this paper we present the system for automated data retrieval and processing developed in the the Skobeltsyn Institute of Nuclear Physics. Telemetry data files containing scientific information (e.g. charged particle fluxes) are auto-matically parsed and stored in our Oracle database immediately upon arrival. Parsed telemetry files, metadata, instrument technical information and orbital parameters are also stored. Most of the data can be accessed via our public FTP server. Users can preview the data available for time intervals and channels of interest using the web interface provided. The preview plot building software has also been developed in-house. This system has been successfully used in 2009 with the following spacecraft and instru-ments: Electron-M-Pesca at Coronas-Photon (Electrons 200KeV -4 MeV+; Protons : 4 MeV -80MeV+ ;α : 5 -24 MeV/nucleon; CNO : 6 -15MeV/nucleon), DUFIK at Tatiana-2 (electrons, infrared 600nm ¡ ¡ 700nm and ultraviolet 300nm ¡ ¡ 400nm), MSGI and SKL at Meteor-M (10 spectral channels: 0,5-12,5 µm ). The data collections are available at http://smdc.sinp.msu.ru for visual preview and download.

  11. A global conformal extension theorem for perfect fluid Bianchi space-times

    SciTech Connect

    Luebbe, Christian Tod, Paul

    2008-12-15

    A global extension theorem is established for isotropic singularities in polytropic perfect fluid Bianchi space-times. When an extension is possible, the limiting behaviour of the physical space-time near the singularity is analysed.

  12. Accessibility

    MedlinePlus

    ... www.nlm.nih.gov/medlineplus/accessibility.html MedlinePlus Accessibility To use the sharing features on this page, ... Subscribe to RSS Follow us Disclaimers Copyright Privacy Accessibility Quality Guidelines Viewers & Players MedlinePlus Connect for EHRs ...

  13. Considerations on private human access to space from an institutional point of view

    NASA Astrophysics Data System (ADS)

    Hufenbach, Bernhard

    2013-12-01

    Private human access to space as discussed in this article addresses two market segments: suborbital flight and crew flights to Low Earth Orbit. The role of entrepreneurs, the technical complexity, the customers, the market conditions as well as the time to market in these two segments differ significantly. Space agencies take currently a very different approach towards private human access to space in both segments. Analysing the outcome of broader inter-agency deliberations on the future of human spaceflight and exploration, performed e.g. in the framework of the International Space Exploration Coordination Group, enables to derive some common general views on this topic. Various documents developed by inter-agency working groups recognise the general strategic importance for enabling private human access to space for ensuring a sustainable future of human spaceflight, although the specific definition of private human access and approaches vary. ESA has performed some reflections on this subject throughout the last 5 years. While it gained through these reflections a good understanding on the opportunities and implications resulting from the development of capabilities and markets for Private Human Access, limited concrete activities have been initiated in relation to this topic as of today.

  14. Sampling the conformational space of the catalytic subunit of human γ-secretase.

    PubMed

    Bai, Xiao-chen; Rajendra, Eeson; Yang, Guanghui; Shi, Yigong; Scheres, Sjors H W

    2015-01-01

    Human γ-secretase is an intra-membrane protease that cleaves many different substrates. Aberrant cleavage of Notch is implicated in cancer, while abnormalities in cutting amyloid precursor protein lead to Alzheimer's disease. Our previous cryo-EM structure of γ-secretase revealed considerable disorder in its catalytic subunit presenilin. Here, we describe an image classification procedure that characterizes molecular plasticity at the secondary structure level, and apply this method to identify three distinct conformations in our previous sample. In one of these conformations, an additional transmembrane helix is visible that cannot be attributed to the known components of γ-secretase. In addition, we present a γ-secretase structure in complex with the dipeptidic inhibitor N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester (DAPT). Our results reveal how conformational mobility in the second and sixth transmembrane helices of presenilin is greatly reduced upon binding of DAPT or the additional helix, and form the basis for a new model of how substrate enters the transmembrane domain. PMID:26623517

  15. Sampling the conformational space of the catalytic subunit of human γ-secretase

    PubMed Central

    Bai, Xiao-chen; Rajendra, Eeson; Yang, Guanghui; Shi, Yigong; Scheres, Sjors HW

    2015-01-01

    Human γ-secretase is an intra-membrane protease that cleaves many different substrates. Aberrant cleavage of Notch is implicated in cancer, while abnormalities in cutting amyloid precursor protein lead to Alzheimer's disease. Our previous cryo-EM structure of γ-secretase revealed considerable disorder in its catalytic subunit presenilin. Here, we describe an image classification procedure that characterizes molecular plasticity at the secondary structure level, and apply this method to identify three distinct conformations in our previous sample. In one of these conformations, an additional transmembrane helix is visible that cannot be attributed to the known components of γ-secretase. In addition, we present a γ-secretase structure in complex with the dipeptidic inhibitor N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester (DAPT). Our results reveal how conformational mobility in the second and sixth transmembrane helices of presenilin is greatly reduced upon binding of DAPT or the additional helix, and form the basis for a new model of how substrate enters the transmembrane domain. DOI: http://dx.doi.org/10.7554/eLife.11182.001 PMID:26623517

  16. Conformational Space and Stability of ETD Charge Reduction Products of Ubiquitin

    NASA Astrophysics Data System (ADS)

    Lermyte, Frederik; Łącki, Mateusz Krzysztof; Valkenborg, Dirk; Gambin, Anna; Sobott, Frank

    2016-08-01

    Owing to its versatility, electron transfer dissociation (ETD) has become one of the most commonly utilized fragmentation techniques in both native and non-native top-down mass spectrometry. However, several competing reactions—primarily different forms of charge reduction—occur under ETD conditions, as evidenced by the distorted isotope patterns usually observed. In this work, we analyze these isotope patterns to compare the stability of nondissociative electron transfer (ETnoD) products, specifically noncovalent c/z fragment complexes, across a range of ubiquitin conformational states. Using ion mobility, we find that more extended states are more prone to fragment release. We obtain evidence that for a given charge state, populations of ubiquitin ions formed either directly by electrospray ionization or through collapse of more extended states upon charge reduction, span a similar range of collision cross-sections. Products of gas-phase collapse are, however, less stabilized towards unfolding than the native conformation, indicating that the ions retain a memory of previous conformational states. Furthermore, this collapse of charge-reduced ions is promoted if the ions are `preheated' using collisional activation, with possible implications for the kinetics of gas-phase compaction.

  17. Man-made space debris - Does it restrict free access to space

    NASA Technical Reports Server (NTRS)

    Wolfe, M.; Chobotov, V.; Kessler, D.; Reynolds, R.

    1981-01-01

    Consideration is given to the hazards posed by existing and future man-made space debris to spacecraft operations. The components of the hazard are identified as those fragments resulting from spacecraft explosions and spent stages which can be tracked, those fragments which are too small to be tracked at their present distances, and future debris, which, if present trends in spacecraft design and operation continue, may lead to an unacceptably high probability of collision with operational spacecraft within a decade. It is argued that a coordinated effort must be undertaken by all space users to evaluate means of space debris control in order to allow for the future unrestricted use of near-earth space. A plan for immediate action to forestall the space debris problem by activities in the areas of education, debris monitoring and collection technology, space vehicle design, space operational procedures and practices and space policies and treaties is proposed.

  18. The space of access to primary mental health care: a qualitative case study.

    PubMed

    Kovandžić, Marija; Funnell, Emma; Hammond, Jonathan; Ahmed, Abdi; Edwards, Suzanne; Clarke, Pam; Hibbert, Derek; Bristow, Katie; Dowrick, Christopher

    2012-05-01

    Guided by theoretical perspectives of relational social science, this paper draws on reanalyses of multiple qualitative datasets related to a multi-ethnic, economically disadvantaged area in Liverpool, UK, with the aim to advance general understanding of access to primary mental health care while using local Somali minority as an instrumental focus. The findings generate a novel concept: the space of access. The shape and dynamics of the space of access are determined by at least four fields of tensions: understandings of area and community; cognitive mapping of mental well-being, illness and care; positioning of primary care services; and dynamics of resources beyond the 'medical zone' of care. The conclusions indicate a need for de-centring and re-connecting the role of medical professionals within primary care which itself needs to be transformed by endorsement of multiple avenues of access to diverse support and intrepid communication among all involved actors. PMID:22386985

  19. Access to space weather model data provided by the Community Coordinated Modeling Center

    NASA Astrophysics Data System (ADS)

    Chulaki, A.; Berrios, D.; Hesse, M.; Kuznetsova, M. M.; MacNeice, P. J.; Maddox, M.; Rastaetter, L.; Taktakishvili, A.

    2009-12-01

    The Community Coordinated Modeling Center (CCMC), located at NASA Goddard Space Flight Center, provides access to state-of-the-art space weather models to the research community. The majority of the models residing at the CCMC are comprehensive, computationally intensive physics-based models. The CCMC provides access to output of performed model runs through a searchable and sortable online database and offers services and tools to assist the research community in analyzing results from space weather model simulations. Virtual Observatories can provide access to model output for corresponding events using the CCMC run database and interface. CCMC is planning to expand its database of run information to improve the service to users as well as its connection with VOs.

  20. Free-space optical mesh-connected bus networks using wavelength-division multiple access.

    PubMed

    Li, Y; Lohmann, A W; Rao, S B

    1993-11-10

    A novel optical free-space mesh-connected bus interconnect network architecture is proposed. A mesh-connected bus [IEEE Trans. Comput. C-30, 264-273 (1981)] is known to have the capability of interconnecting, with a three-stage switching, N nodes with a power distribution loss proportional to √N and is therefore advantageous for networking a large number, say over 1000, of communicating ports. Based on conventional space-invariant optical components in a compact and efficient geometry, the proposed optical mesh-connected bus system concept can be used to build either free-space optical interconnect links for parallel processing applications or central switching systems for local or global lightwave communication networks. The proposed architecture lends itself to networking under both the wavelength-division multiple access and other multiple-access environments. In this paper, based on the wavelength-division multiple-access environment, various optical system implementation and performance issues are discused and parameters are analyzed. It was found that by use of a reasonably compact three-dimensional free-space volume, more than 100,000 dispersion-limited communication nodes at a uniform channel spacing of 0.75 nm can be linked with a moderate power distribution loss of 28 dB. Some preliminary optical wavelength-division multiple-access mesh-connected bus experiments based on a 27 × 27 panchromatic optical source array were performed to confirm the operational principle of the proposed concept. PMID:20856480

  1. Beyond traffic depiction: conformally integrating the conflict space to support Level 3 situation awareness

    NASA Astrophysics Data System (ADS)

    Tadema, Jochum; Theunissen, Erik; Kirk, Kevin M.

    2010-04-01

    The research described in this paper explores the addition of conformally integrated traffic probes into an egocentric Synthetic Vision (SV) Primary Flight Display (PFD). The underlying thought is that, although the traffic that is predicted to cause a future loss of separation may not lie within the field of view of the display, the location where the loss of separation is predicted to occur always will. Hence, rather than focusing on the depiction of traffic, which contributes to level 2 Situation Awareness (SA), the concept pursues spatially integrated depiction of the airspace where a loss of separation is predicted. This provides readily actionable conflict information, relieving pilots from the traffic position and conflict estimation task and contributing to level 3 SA. The paper describes the integration of the data from the traffic probe into an SV PFD. The advantages of the concept will be illustrated using several traffic conflict scenarios, including an overtaking scenario involving unmanned aircraft. Given that unmanned aircraft may be markedly slower than manned aircraft which operate within the same airspace, a spatially integrated depiction of airspace where a future loss of separation is predicted, can help to preserve safety in classes of airspace that accommodate both manned and unmanned aircraft. Additionally, examples are provided illustrating how traffic probes can support pilots in monitoring the conformance of traffic to the priority rules of 14 CFR 91.113.

  2. A suite of methods for representing activity space in a healthcare accessibility study

    PubMed Central

    Sherman, Jill E; Spencer, John; Preisser, John S; Gesler, Wilbert M; Arcury, Thomas A

    2005-01-01

    Background "Activity space" has been used to examine how people's habitual movements interact with their environment, and can be used to examine accessibility to healthcare opportunities. Traditionally, the standard deviational ellipse (SDE), a Euclidean measure, has been used to represent activity space. We describe the construction and application of the SDE at one and two standard deviations, and three additional network-based measures of activity space using common tools in GIS: the road network buffer (RNB), the 30-minute standard travel time polygon (STT), and the relative travel time polygon (RTT). We compare the theoretical and methodological assumptions of each measure, and evaluate the measures by examining access to primary care services, using data from western North Carolina. Results Individual accessibility is defined as the availability of healthcare opportunities within that individual's activity space. Access is influenced by the shape and area of an individual's activity space, the spatial distribution of opportunities, and by the spatial structures that constrain and direct movement through space; the shape and area of the activity space is partly a product of how it is conceptualized and measured. Network-derived measures improve upon the SDE by incorporating the spatial structures (roads) that channel movement. The area of the STT is primarily influenced by the location of a respondent's residence within the road network hierarchy, with residents living near primary roads having the largest activity spaces. The RNB was most descriptive of actual opportunities and can be used to examine bypassing. The area of the RTT had the strongest correlation with a healthcare destination being located inside the activity space. Conclusion The availability of geospatial technologies and data create multiple options for representing and operationalizing the construct of activity space. Each approach has its strengths and limitations, and presents a different

  3. A note on classification of teleparallel conformal symmetries in non-static plane symmetric space-times in the teleparallel theory of gravitation using diagonal tetrads

    NASA Astrophysics Data System (ADS)

    Shabbir, Ghulam; Khan, Alamgeer; Amer Qureshi, M.; Kara, A. H.

    2016-02-01

    In this paper, we explore teleparallel conformal vector fields in non-static plane symmetric space-times in the teleparallel theory of gravitation using the direct integration technique and diagonal tetrads. This study will also cover the static plane symmetric space-times as well. In the teleparallel theory curvature of the non-static plane symmetric space-times is zero and the presence of torsion allows more symmetries. In this study after solving the integrabilty conditions it turns out that the dimension of teleparallel conformal vector fields are 5, 6, 7 or 8.

  4. Astronaut Ross Approaches Assembly Concept for Construction of Erectable Space Structure (ACCESS)

    NASA Technical Reports Server (NTRS)

    1999-01-01

    The crew assigned to the STS-61B mission included Bryan D. O'Conner, pilot; Brewster H. Shaw, commander; Charles D. Walker, payload specialist; mission specialists Jerry L. Ross, Mary L. Cleave, and Sherwood C. Spring; and Rodolpho Neri Vela, payload specialist. Launched aboard the Space Shuttle Atlantis November 28, 1985 at 7:29:00 pm (EST), the STS-61B mission's primary payload included three communications satellites: MORELOS-B (Mexico); AUSSAT-2 (Australia); and SATCOM KU-2 (RCA Americom). Two experiments were conducted to test assembling erectable structures in space: EASE (Experimental Assembly of Structures in Extravehicular Activity), and ACCESS (Assembly Concept for Construction of Erectable Space Structure). In a joint venture between NASA/Langley Research Center in Hampton, Virginia, and the Marshall Space Flight Center (MSFC), EASE and ACCESS were developed and demonstrated at MSFC's Neutral Buoyancy Simulator (NBS). In this STS-61B onboard photo, astronaut Ross, perched on the Manipulator Foot Restraint (MFR) approaches the erected ACCESS. The primary objective of these experiments was to test the structural assembly concepts for suitability as the framework for larger space structures and to identify ways to improve the productivity of space construction.

  5. Ross Works on the Assembly Concept for Construction of Erectable Space Structure (ACCESS) During

    NASA Technical Reports Server (NTRS)

    1985-01-01

    The crew assigned to the STS-61B mission included Bryan D. O'Conner, pilot; Brewster H. Shaw, commander; Charles D. Walker, payload specialist; mission specialists Jerry L. Ross, Mary L. Cleave, and Sherwood C. Spring; and Rodolpho Neri Vela, payload specialist. Launched aboard the Space Shuttle Atlantis November 28, 1985 at 7:29:00 pm (EST), the STS-61B mission's primary payload included three communications satellites: MORELOS-B (Mexico); AUSSAT-2 (Australia); and SATCOM KU-2 (RCA Americom). Two experiments were conducted to test assembling erectable structures in space: EASE (Experimental Assembly of Structures in Extravehicular Activity), and ACCESS (Assembly Concept for Construction of Erectable Space Structure). In a joint venture between NASA/Langley Research Center in Hampton, Virginia, and the Marshall Space Flight Center (MSFC), EASE and ACCESS were developed and demonstrated at MSFC's Neutral Buoyancy Simulator (NBS). In this STS-61B onboard photo, astronaut Ross works on ACCESS high above the orbiter. The primary objective of these experiments was to test the structural assembly concepts for suitability as the framework for larger space structures and to identify ways to improve the productivity of space construction.

  6. Theoretical predictor for candidate structure assignment from IMS data of biomolecule-related conformational space

    PubMed Central

    Schenk, Emily R.; Nau, Frederic

    2016-01-01

    The ability to correlate experimental ion mobility data with candidate structures from theoretical modeling provides a powerful analytical and structural tool for the characterization of biomolecules. In the present paper, a theoretical workflow is described to generate and assign candidate structures for experimental trapped ion mobility and H/D exchange (HDX-TIMS-MS) data following molecular dynamics simulations and statistical filtering. The applicability of the theoretical predictor is illustrated for a peptide and protein example with multiple conformations and kinetic intermediates. The described methodology yields a low computational cost and a simple workflow by incorporating statistical filtering and molecular dynamics simulations. The workflow can be adapted to different IMS scenarios and CCS calculators for a more accurate description of the IMS experimental conditions. For the case of the HDX-TIMS-MS experiments, molecular dynamics in the “TIMS box” accounts for a better sampling of the molecular intermediates and local energy minima. PMID:27330407

  7. 41 CFR 105-8.152 - Program accessibility: Assignment of space.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 41 Public Contracts and Property Management 3 2010-07-01 2010-07-01 false Program accessibility: Assignment of space. 105-8.152 Section 105-8.152 Public Contracts and Property Management Federal Property Management Regulations System (Continued) GENERAL SERVICES ADMINISTRATION 8-ENFORCEMENT OF NONDISCRIMINATION ON THE BASIS OF HANDICAP...

  8. Nanotube structures, methods of making nanotube structures, and methods of accessing intracellular space

    DOEpatents

    VanDersarl, Jules J.; Xu, Alexander M.; Melosh, Nicholas A.; Tayebi, Noureddine

    2016-02-23

    In accordance with the purpose(s) of the present disclosure, as embodied and broadly described herein, embodiments of the present disclosure, in one aspect, relate to methods of making a structure including nanotubes, a structure including nanotubes, methods of delivering a fluid to a cell, methods of removing a fluid to a cell, methods of accessing intracellular space, and the like.

  9. Spaces for Change: Gender and Technology Access in Collaborative Software Design.

    ERIC Educational Resources Information Center

    Ching, Cynthia Carter; Kafai, Yasmin B.; Marshall, Sue K.

    2000-01-01

    Examines a three-month software design activity in which mixed teams of girls and boys designed and implemented multimedia astronomy resources for younger students. Finds that the configuration of social, physical, and cognitive spaces in the project environment contributed to a positive change in girls' level of access. Discusses implications for…

  10. 46 CFR 154.340 - Access to tanks and spaces in the cargo area.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 5 2012-10-01 2012-10-01 false Access to tanks and spaces in the cargo area. 154.340 Section 154.340 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CERTAIN BULK DANGEROUS CARGOES SAFETY STANDARDS FOR SELF-PROPELLED VESSELS CARRYING BULK LIQUEFIED GASES Design, Construction and Equipment Ship Arrangements §...

  11. 46 CFR 153.217 - Access to enclosed spaces and dedicated ballast tanks.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 5 2012-10-01 2012-10-01 false Access to enclosed spaces and dedicated ballast tanks. 153.217 Section 153.217 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CERTAIN BULK DANGEROUS CARGOES SHIPS CARRYING BULK LIQUID, LIQUEFIED GAS, OR COMPRESSED GAS HAZARDOUS MATERIALS Design and Equipment General Vessel...

  12. High data rate modem simulation for the space station multiple-access communications system

    NASA Technical Reports Server (NTRS)

    Horan, Stephen

    1987-01-01

    The communications system for the space station will require a space based multiple access component to provide communications between the space based program elements and the station. A study was undertaken to investigate two of the concerns of this multiple access system, namely, the issues related to the frequency spectrum utilization and the possibilities for higher order (than QPSK) modulation schemes for use in possible modulators and demodulators (modems). As a result of the investigation, many key questions about the frequency spectrum utilization were raised. At this point, frequency spectrum utilization is seen as an area requiring further work. Simulations were conducted using a computer aided communications system design package to provide a straw man modem structure to be used for both QPSK and 8-PSK channels.

  13. Making Astronomy and Space Science Accessible to the Blind and Visually Impaired

    NASA Astrophysics Data System (ADS)

    Beck-Winchatz, B.; Hoette, V.; Grice, N.

    2003-12-01

    One of the biggest obstacles blind and visually impaired people face in science is the ubiquity of important graphical information, which is generally not made available in alternate formats accessible to them. Funded by NASA's Initiative to Develop Education through Astronomy and Space Science (IDEAS), we have recently formed a team of scientists and educators from universities, the SOFIA NASA mission, a science museum, an observatory, and schools for the blind. Our goal is to develop and test Braille/tactile space science activities that actively engage students from elementary grades through introductory college-level in space science. We will discuss effective strategies and low-cost technologies that can be used to make graphical information accessible. We will also demonstrate examples, such a thermal expansion graphics created from telescope images of the Moon and other celestial objects, a tactile planisphere, three-dimensional models of near-Earth asteroids and tactile diagrams of their orbits, and an infrared detector activity.

  14. Curvatures with uncertainties derived in conformal space to characterize tendon microstructure.

    PubMed

    Harvey, Ann K; Szilagyi, Tunde; Brady, Michael; Thompson, Mark S; Joshi, Niranjan

    2010-01-01

    There is a growing demand for non-invasive methods to diagnose tendon injuries and monitor the healing processes of their repair. To date there is limited knowledge on their structure and function and the interlink between these. One of the potential targets in this investigation is the extracellular matrix (ECM) that captures its structural changes. Recently we reported on the assessment tendon damage on a macroscopic level from high field MR signals. In this paper, we present a methodology that enables structural description on a microscopic level. We derived curvature values from the conformal monogenic signal, which however can become unreliable in the presence of noise. To account for this we use non parametric noise properties and a 1D feature based uncertainty measure in an iterative framework using Hidden Markov Measure Field (HMMF). The proposed method reveals that curvature values derived from normal tendon tissue microscopy images are higher and more homogenous than curvature values derived from the damaged tendon images. PMID:21096485

  15. Test of the Anti-de Sitter-Space/Conformal-Field-Theory Correspondence Using High-Spin Operators

    SciTech Connect

    Benna, M. K.; Benvenuti, S.; Klebanov, I. R.; Scardicchio, A.

    2007-03-30

    In two remarkable recent papers the planar perturbative expansion was proposed for the universal function of the coupling appearing in the dimensions of high-spin operators of the N=4 super Yang-Mills theory. We study numerically the integral equation derived by Beisert, Eden, and Staudacher, which resums the perturbative series. In a confirmation of the anti-de Sitter-space/conformal-field-theory (AdS/CFT) correspondence, we find a smooth function whose two leading terms at strong coupling match the results obtained for the semiclassical folded string spinning in AdS{sub 5}. We also make a numerical prediction for the third term in the strong coupling series.

  16. Multiple Simulated Annealing-Molecular Dynamics (MSA-MD) for Conformational Space Search of Peptide and Miniprotein

    PubMed Central

    Hao, Ge-Fei; Xu, Wei-Fang; Yang, Sheng-Gang; Yang, Guang-Fu

    2015-01-01

    Protein and peptide structure predictions are of paramount importance for understanding their functions, as well as the interactions with other molecules. However, the use of molecular simulation techniques to directly predict the peptide structure from the primary amino acid sequence is always hindered by the rough topology of the conformational space and the limited simulation time scale. We developed here a new strategy, named Multiple Simulated Annealing-Molecular Dynamics (MSA-MD) to identify the native states of a peptide and miniprotein. A cluster of near native structures could be obtained by using the MSA-MD method, which turned out to be significantly more efficient in reaching the native structure compared to continuous MD and conventional SA-MD simulation. PMID:26492886

  17. The Road from the NASA Access to Space Study to a Reusable Launch Vehicle

    NASA Technical Reports Server (NTRS)

    Powell, Richard W.; Cook, Stephen A.; Lockwood, Mary Kae

    1998-01-01

    NASA is cooperating with the aerospace industry to develop a space transportation system that provides reliable access-to-space at a much lower cost than is possible with today's launch vehicles. While this quest has been on-going for many years it received a major impetus when the U.S. Congress mandated as part of the 1993 NASA appropriations bill that: "In view of budget difficulties, present and future..., the National Aeronautics and Space Administration shall ... recommend improvements in space transportation." NASA, working with other organizations, including the Department of Transportation, and the Department of Defense identified three major transportation architecture options that were to be evaluated in the areas of reliability, operability and cost. These architectural options were: (1) retain and upgrade the Space Shuttle and the current expendable launch vehicles; (2) develop new expendable launch vehicles using conventional technologies and transition to these new vehicles beginning in 2005; and (3) develop new reusable vehicles using advanced technology, and transition to these vehicles beginning in 2008. The launch needs mission model was based on 1993 projections of civil, defense, and commercial payload requirements. This "Access to Space" study concluded that the option that provided the greatest potential for meeting the cost, operability, and reliability goals was a rocket-powered single-stage-to-orbit fully reusable launch vehicle (RLV) fleet designed with advanced technologies.

  18. URSA MAIOR: a One Liter Nanosatellite Bus for Low Cost Access to Space

    NASA Astrophysics Data System (ADS)

    Santoni, F.

    One of the main limitations in the access to space for developing countries is the economical effort typically required by space missions. Secondly, space activity is a field of very high technology, requiring technical skills, education and practice, at a level which is seldom reached by developing countries. Interventions aimed to facilitate access to space for developing countries should be focussed primarily on the missions allowing access to space at reasonable cost. Moreover, perhaps more importantly, they should emphasize conducting the mission design, construction, ground testing and operation in orbit as an open activity, accessible to developing countries personnel, in order to set up an education process, which is not just selling a product ready satellite. Universities could have a very important role in this activity. Many Universities around the world have designed, built and launched small satellites. Università di Roma "La Sapienza" set up a program for the construction of small satellites in an academic environment, involving directly the students in the design, construction, ground testing and operation in orbit. The first satellite built in the framework of this program, UNISAT, was successfully launched in September 2000. The second, UNISAT-2, initially scheduled for launch in 2001, has been delayed by the launch provider to late 2002. These two satellites, based on a modular design, emphasizing ease of construction and assembly, weight roughly 10 kg. The realization of these satellites was made possible within the regular financing given to university research programs, keeping down cost by the use of commercial off the shelf components instead of space rated ones. The microsatellite experience at Università di Roma "La Sapienza", is going further with the development of a new nanosatellite bus, URSA MAIOR (Università di Roma "la SApienza" Micro Autonomous Imager in ORbit), aiming at cutting down cost and possibly improving performance. The

  19. Random Access Frames (RAF): Alternative to Rack and Standoff for Deep Space Habitat Outfitting

    NASA Technical Reports Server (NTRS)

    Howe, A. Scott; Polit-Casillas, Raul

    2014-01-01

    A modular Random Access Frame (RAF) system is proposed as an alternative to the International Standard Payload Rack (ISPR) for internal module layout and outfitting in a Deep Space Habitat (DSH). The ISPR approach was designed to allow for efficient interchangeability of payload and experiments for the International Space Station (ISS) when frequent resupply missions were available (particularly the now-retired Space Shuttle). Though the standard interface approach to the ISPR system allowed integration of subsystems and hardware from a variety of sources and manufacturers, the heavy rack and standoff approach may not be appropriate when resupply or swap-out capabilities are not available, such as on deep space, long-duration missions. The lightweight RAF concept can allow a more dense packing of stowage and equipment, and may be easily broken down for repurposing or reuse. Several example layouts and workstations are presented.

  20. Conformationally Constrained Histidines in the Design of Peptidomimetics: Strategies for the χ-Space Control

    PubMed Central

    Stefanucci, Azzurra; Pinnen, Francesco; Feliciani, Federica; Cacciatore, Ivana; Lucente, Gino; Mollica, Adriano

    2011-01-01

    A successful design of peptidomimetics must come to terms with χ-space control. The incorporation of χ-space constrained amino acids into bioactive peptides renders the χ1 and χ2 torsional angles of pharmacophore amino acids critical for activity and selectivity as with other relevant structural features of the template. This review describes histidine analogues characterized by replacement of native α and/or β-hydrogen atoms with alkyl substituents as well as analogues with α, β-didehydro unsaturation or Cα-Cβ cyclopropane insertion (ACC derivatives). Attention is also dedicated to the relevant field of β-aminoacid chemistry by describing the synthesis of β2- and β3-models (β-hHis). Structural modifications leading to cyclic imino derivatives such as spinacine, aza-histidine and analogues with shortening or elongation of the native side chain (nor-histidine and homo-histidine, respectively) are also described. Examples of the use of the described analogues to replace native histidine in bioactive peptides are also given. PMID:21686155

  1. ACCESS (Assembly Concept for Construction of Erectable Space Structure) - A Shuttle flight experiment

    NASA Technical Reports Server (NTRS)

    Heard, W. L., Jr.

    1985-01-01

    ACCESS is a planned Shuttle flight experiment to assess the potential of an on-orbit construction concept designed for efficient manual assembly of a space truss. The experiment, which is scheduled for launch November 27, 1985, on the Space Transportation System (STS) flight 61-B, uses two astronauts secured in fixed foot restraints located in the Shuttle cargo bay to assemble a 45-foot long aluminum truss beam from 93 tubular struts and 33 nodal joints. Neutral buoyancy simulations of the flight experiment indicate the truss can be assembled in less than thirty minutes. Structural assembly, structural repair, flexible cable attachment and manual manipulation of the truss is also planned for the experiment using an astronaut secured in the Manipulator Foot Restraint attached to the Remote Manipulator System arm. Flight assembly data will be generated for correlation of the neutral buoyancy ground test data. This paper describes the ACCESS flight experiment and presents results of the neutral buoyancy development and training tests.

  2. Mapping the Conformation Space of Wildtype and Mutant H-Ras with a Memetic, Cellular, and Multiscale Evolutionary Algorithm

    PubMed Central

    Clausen, Rudy; Ma, Buyong; Nussinov, Ruth; Shehu, Amarda

    2015-01-01

    An important goal in molecular biology is to understand functional changes upon single-point mutations in proteins. Doing so through a detailed characterization of structure spaces and underlying energy landscapes is desirable but continues to challenge methods based on Molecular Dynamics. In this paper we propose a novel algorithm, SIfTER, which is based instead on stochastic optimization to circumvent the computational challenge of exploring the breadth of a protein’s structure space. SIfTER is a data-driven evolutionary algorithm, leveraging experimentally-available structures of wildtype and variant sequences of a protein to define a reduced search space from where to efficiently draw samples corresponding to novel structures not directly observed in the wet laboratory. The main advantage of SIfTER is its ability to rapidly generate conformational ensembles, thus allowing mapping and juxtaposing landscapes of variant sequences and relating observed differences to functional changes. We apply SIfTER to variant sequences of the H-Ras catalytic domain, due to the prominent role of the Ras protein in signaling pathways that control cell proliferation, its well-studied conformational switching, and abundance of documented mutations in several human tumors. Many Ras mutations are oncogenic, but detailed energy landscapes have not been reported until now. Analysis of SIfTER-computed energy landscapes for the wildtype and two oncogenic variants, G12V and Q61L, suggests that these mutations cause constitutive activation through two different mechanisms. G12V directly affects binding specificity while leaving the energy landscape largely unchanged, whereas Q61L has pronounced, starker effects on the landscape. An implementation of SIfTER is made available at http://www.cs.gmu.edu/~ashehu/?q=OurTools. We believe SIfTER is useful to the community to answer the question of how sequence mutations affect the function of a protein, when there is an abundance of experimental

  3. Advanced cosmic-ray composition experiment for the space station (ACCESS)

    SciTech Connect

    Israel, Martin H.; Streitmatter, Robert E.; Swordy, Simon P.

    1999-01-22

    ACCESS is a large electronic cosmic-ray detector, designed for one of the zenith-pointing external attach points on the International Space Station. ACCESS addresses the fundamental astrophysical question: How do cosmic rays gain their enormous energies? It does this by combining two kinds of measurements. By determining the energy spectra of individual elements with atomic number (Z) in the interval 1{<=}Z{<=}28 up to an energy of 10{sup 15} eV, ACCESS will probe a region of the spectra where theories of supernova acceleration predict changes in the cosmic-ray element composition. By measuring individual element abundances at more moderate energies of every element in the entire periodic table, ACCESS will distinguish between competing theories of how the cosmic-ray nuclei are initially injected into the accelerator that gives them their high energies. ACCESS will identify the atomic number of incident cosmic-ray nuclei using silicon solid-state detectors Cherenkov detectors, and scintillators. It will measure the energy of heavy nuclei (Z{>=}4) with transition radiation detectors, and the energy of light nuclei (Z{<=}8) with an ionization calorimeter.

  4. Rocket-Based Combined-Cycle Propulsion Technology for Access-to-Space Applications

    NASA Technical Reports Server (NTRS)

    Hueter, Uwe

    1999-01-01

    NASA's Office of Aero-Space Technology (OAST) established three major goals, referred to as, "The Three Pillars for Success". The Advanced Space Transportation Program Office (ASTP) at the NASA's Marshall Space Flight Center (MSFC) in Huntsville, Ala. focuses on future space transportation technologies under the "Access to Space" pillar. One of the main activities over the past three years has been on advancing the hydrogen fueled rocket-based combined cycle (RBCC) technologies. The RBCC effort that was completed early this year was the initial step leading to flight demonstrations of the technology for space launch vehicle propulsion. Aerojet and Boeing-Rocketdyne designed, built and ground tested their RBCC engine concepts. In addition, ASTROX, Georgia Institute of Technology, McKinney Associates, Pennsylvania State University (PSU), and University of Alabama in Huntsville conducted supporting activities. The RBCC activity included ground testing of components (e.g., injectors, thrusters, ejectors and inlets) and integrated flowpaths. Inlet testing was performed at the Lewis Research Center's 1 x 1 wind tunnel. All direct connect and free-jet engine testing were conducted at the GASL facilities on Long Island, New York. Testing spanned the Mach range from sea level static to Mach 8. Testing of the rocket-only mode, simulating the final phase of the ascent mission profile, was also performed. The originally planned work on these contracts was completed in 1999. Follow-on activities have been initiated for both hydrogen and hydrocarbon fueled RBCC concepts. Studies to better understand system level issues with the integration of RBCC propulsion with earth-to-orbit vehicles have also been conducted. This paper describes the status, progress and future plans of the RBCC activities funded by NASA/MSFC with a major focus on the benefits of utilizing air-breathing combined-cycle propulsion in access-to-space applications.

  5. Exploring the Unknown: Selected Documents in the History of the U.S. Civil Space Program. Volume 4; Accessing Space

    NASA Technical Reports Server (NTRS)

    Logsdon, John M. (Editor); Williamson, Ray A. (Editor); Launius, Roger D. (Editor); Acker, Russell J. (Editor); Garber, Stephen J. (Editor); Friedman, Jonathan L. (Editor)

    1999-01-01

    The documents selected for inclusion in this volume are presented in four major chapters, each covering a particular aspect of access to space and the manner in which it has developed over time. These chapters focus on the evolution toward the giant Saturn V rocket, the development of the Space Shuttle, space transportation commercialization, and future space transportation possibilities. Each chapter in this volume is introduced by an overview essay, prepared by individuals who are particularly well qualified to write on the topic. In the main, these essays are intended to introduce and complement the documents in the chapter and to place them, for the most part, in a chronological and substantive context. Each essay contains references to the documents in the chapter it introduces, and many also contain references to documents in other chapters of the collection. These introductory essays are the responsibility of their individual authors, and the views and conclusions contained therein do not necessarily represent the opinions of either George Washington University or NASA.

  6. URSA MAIOR: a One Liter Nanosatellite Bus for Low Cost Access to Space

    NASA Astrophysics Data System (ADS)

    Santoni, F.

    One of the main limitations in the access to space for developing countries is the economical effort typically required by space missions. Secondly, space activity is a field of very high technology, requiring technical skills, education and practice, at a level which is seldom reached by developing countries. Interventions aimed to facilitate access to space for developing countries should be focussed primarily on the missions allowing access to space at reasonable cost. Moreover, perhaps more importantly, they should emphasize conducting the mission design, construction, ground testing and operation in orbit as an open activity, accessible to developing countries personnel, in order to set up an education process, which is not just selling a product ready satellite. Universities could have a very important role in this activity. Many Universities around the world have designed, built and launched small satellites. Università di Roma "La Sapienza" set up a program for the construction of small satellites in an academic environment, involving directly the students in the design, construction, ground testing and operation in orbit. The first satellite built in the framework of this program, UNISAT, was successfully launched in September 2000. The second, UNISAT-2, initially scheduled for launch in 2001, has been delayed by the launch provider to late 2002. These two satellites, based on a modular design, emphasizing ease of construction and assembly, weight roughly 10 kg. The realization of these satellites was made possible within the regular financing given to university research programs, keeping down cost by the use of commercial off the shelf components instead of space rated ones. The microsatellite experience at Università di Roma "La Sapienza", is going further with the development of a new nanosatellite bus, URSA MAIOR (Università di Roma "la SApienza" Micro Autonomous Imager in ORbit), aiming at cutting down cost and possibly improving performance. The

  7. A novel intramolecular through-space interaction between F and CN: a strategy for the conformational control of an acyclic system.

    PubMed

    Nishide, K; Hagimoto, Y; Hasegawa, H; Shiro, M; Node, M

    2001-11-21

    X-Ray crystallographic analyses of fluorocyanides anti-1 and 2 revealed a novel intramolecular through-space interaction between F and CN in an acyclic system, which was applied to a stereoselective protonation of acyclic fluorocyanides 2 having flexible conformation. PMID:12240092

  8. A new open-source Python-based Space Weather data access, visualization, and analysis toolkit

    NASA Astrophysics Data System (ADS)

    de Larquier, S.; Ribeiro, A.; Frissell, N. A.; Spaleta, J.; Kunduri, B.; Thomas, E. G.; Ruohoniemi, J.; Baker, J. B.

    2013-12-01

    Space weather research relies heavily on combining and comparing data from multiple observational platforms. Current frameworks exist to aggregate some of the data sources, most based on file downloads via web or ftp interfaces. Empirical models are mostly fortran based and lack interfaces with more useful scripting languages. In an effort to improve data and model access, the SuperDARN community has been developing a Python-based Space Science Data Visualization Toolkit (DaViTpy). At the center of this development was a redesign of how our data (from 30 years of SuperDARN radars) was made available. Several access solutions are now wrapped into one convenient Python interface which probes local directories, a new remote NoSQL database, and an FTP server to retrieve the requested data based on availability. Motivated by the efficiency of this interface and the inherent need for data from multiple instruments, we implemented similar modules for other space science datasets (POES, OMNI, Kp, AE...), and also included fundamental empirical models with Python interfaces to enhance data analysis (IRI, HWM, MSIS...). All these modules and more are gathered in a single convenient toolkit, which is collaboratively developed and distributed using Github and continues to grow. While still in its early stages, we expect this toolkit will facilitate multi-instrument space weather research and improve scientific productivity.

  9. Interoperative fundus image and report sharing in compliance with integrating the healthcare enterprise conformance and web access to digital imaging and communication in medicine persistent object protocol

    PubMed Central

    Wu, Hui-Qun; Lv, Zheng-Min; Geng, Xing-Yun; Jiang, Kui; Tang, Le-Min; Zhou, Guo-Min; Dong, Jian-Cheng

    2013-01-01

    AIM To address issues in interoperability between different fundus image systems, we proposed a web eye-picture archiving and communication system (PACS) framework in conformance with digital imaging and communication in medicine (DICOM) and health level 7 (HL7) protocol to realize fundus images and reports sharing and communication through internet. METHODS Firstly, a telemedicine-based eye care work flow was established based on integrating the healthcare enterprise (IHE) Eye Care technical framework. Then, a browser/server architecture eye-PACS system was established in conformance with the web access to DICOM persistent object (WADO) protocol, which contains three tiers. RESULTS In any client system installed with web browser, clinicians could log in the eye-PACS to observe fundus images and reports. Multipurpose internet mail extensions (MIME) type of a structured report is saved as pdf/html with reference link to relevant fundus image using the WADO syntax could provide enough information for clinicians. Some functions provided by open-source Oviyam could be used to query, zoom, move, measure, view DICOM fundus images. CONCLUSION Such web eye-PACS in compliance to WADO protocol could be used to store and communicate fundus images and reports, therefore is of great significance for teleophthalmology. PMID:24392341

  10. Accessing space: A catalogue of process, equipment and resources for commercial users

    NASA Technical Reports Server (NTRS)

    1988-01-01

    This catalogue, produced by NASA's Office of Commercial Programs, provides a broad source of information for the commercial developer interested in the areas of microgravity research and remote sensing. Methods for accessing space for research are reviewed including the shuttle, expendable launch vehicles, suborbital sounding rockets, experimental aircraft, and drop towers and other ground-based facilities. Procedures for using these vehicles and facilities are described along with funding options to pay for their use. Experiment apparatus and carriers for microgravity research are also described. A separate directory of resources and services is also included which contains a listing of transportation products and services, a listing of businesses and industries which provide space-related services and products, and a listing of the NASA and CCDS (Center for the Commercial Development of Space) points of contact.

  11. The Ares I Crew Launch Vehicle: Human Space Access for the Moon and Beyond

    NASA Technical Reports Server (NTRS)

    Cook, Stephen A.

    2008-01-01

    The National Aeronautics and Space Administration (NASA)'s Constellation Program is depending on the Ares Projects to deliver the crew launch capabilities needed to send human explorers to the Moon and beyond. The Ares Projects continue to make progress toward design, component testing, and early flight testing of the Ares I crew launch vehicle (Figure 1), the United States first new human-rated launch vehicle in over 25 years. Ares I will provide the core space launch capabilities the United States needs to continue providing crew and cargo access to the International Space Station (ISS), maintaining the U.S. pioneering tradition as a spacefaring nation, and enabling cooperative international ventures to the Moon and beyond. This paper will discuss programmatic, design, fabrication, and testing progress toward building this new launch vehicle.

  12. 41 CFR 102-79.65 - May Executive agencies outlease space on major public access levels, courtyards and rooftops of...

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 41 Public Contracts and Property Management 3 2011-01-01 2011-01-01 false May Executive agencies outlease space on major public access levels, courtyards and rooftops of public buildings? 102-79.65... Utilization of Space Outleasing § 102-79.65 May Executive agencies outlease space on major public...

  13. Ab initio materials design using conformational space annealing and its application to searching for direct band gap silicon crystals

    NASA Astrophysics Data System (ADS)

    Lee, In-Ho; Oh, Young Jun; Kim, Sunghyun; Lee, Jooyoung; Chang, K. J.

    2016-06-01

    Lately, the so-called inverse method of materials design has drawn much attention, where specific material properties are initially assigned and target materials are subsequently searched for. Although this method has been successful for some problems, the success of designing complex crystal structures containing many atoms is often limited by the efficiency of the search method utilized. Here we combine the global optimization method of conformational space annealing (CSA) with first-principles quantum calculations and report a new scheme named AMADEUS (Ab initio MAterials DEsign Using cSa). We demonstrate the utility of AMADEUS through the discovery of direct band gap Si crystals. The newly-designed direct gap Si allotropes show excellent optical properties and the spectroscopic limited maximum efficiencies comparable to those of best-known non-silicon photovoltaic materials. Our scheme not only provides a new perspective for the inverse problem of materials design but also may serve as a new tool for the computational design of a wide range of materials.

  14. Exchange Coupling Mediated Through-Bonds and Through-Space in Conformationally-Constrained Polyradical Scaffolds: Calix[4]arene Nitroxide Tetraradicals And Diradical

    PubMed Central

    Rajca, Andrzej; Mukherjee, Sumit; Pink, Maren; Rajca, Suchada

    2008-01-01

    Calix[4]arenes constrained to 1,3-alternate conformation and functionalized at the upper rim with four and two tert-butylnitroxides have been synthesized, and characterized by X-ray crystallography, magnetic resonance (EPR and 1H NMR) spectroscopy, and magnetic studies. The 1,3-alternate nitroxide tetraradical and diradical provide unique polyradical scaffolds for dissection of the through-bond and through-space intramolecular exchange couplings. In addition, detailed magnetic studies of the previously reported calix[4]arene nitroxide tetraradical, which possesses cone conformation in solution, reveal conformational dependence of exchange coupling. Through-bond coupling between the adjacent nitroxide radicals is mediated by the nitroxide-m-phenylene-CH2-m-phenylene-nitroxide coupling pathway, and through-space coupling is found between the diagonal nitroxide radicals at the conformationally-constrained N···N distance of 5–6 Å. Magnetic studies of the calix[4]arene polyradical scaffolds in frozen solutions show that the through-bond exchange coupling in the 1,3-alternate calix[4]arene tetraradical is antiferromagnetic, while that in cone calix[4]arene tetraradical is ferromagnetic. The through-space exchange couplings are antiferromagnetic in both cone and 1,3-alternate calix[4]arene tetraradical, as well as in the 1,3-alternate calix[4]arene diradical. The exchange coupling constants (|J/k|) are of the order of 1 Kelvin. PMID:17031963

  15. Ethernet access network based on free-space optic deployment technology

    NASA Astrophysics Data System (ADS)

    Gebhart, Michael; Leitgeb, Erich; Birnbacher, Ulla; Schrotter, Peter

    2004-06-01

    The satisfaction of all communication needs from single households and business companies over a single access infrastructure is probably the most challenging topic in communications technology today. But even though the so-called "Last Mile Access Bottleneck" is well known since more than ten years and many distribution technologies have been tried out, the optimal solution has not yet been found and paying commercial access networks offering all service classes are still rare today. Conventional services like telephone, radio and TV, as well as new and emerging services like email, web browsing, online-gaming, video conferences, business data transfer or external data storage can all be transmitted over the well known and cost effective Ethernet networking protocol standard. Key requirements for the deployment technology driven by the different services are high data rates to the single customer, security, moderate deployment costs and good scalability to number and density of users, quick and flexible deployment without legal impediments and high availability, referring to the properties of optical and wireless communication. We demonstrate all elements of an Ethernet Access Network based on Free Space Optic distribution technology. Main physical parts are Central Office, Distribution Network and Customer Equipment. Transmission of different services, as well as configuration, service upgrades and remote control of the network are handled by networking features over one FSO connection. All parts of the network are proven, the latest commercially available technology. The set up is flexible and can be adapted to any more specific need if required.

  16. An Indoor Space Partition Method and its Fingerprint Positioning Optimization Considering Pedestrian Accessibility

    NASA Astrophysics Data System (ADS)

    Xu, Yue; Shi, Yong; Zheng, Xingyu; Long, Yi

    2016-06-01

    Fingerprint positioning method is generally the first choice in indoor navigation system due to its high accuracy and low cost. The accuracy depends on partition density to the indoor space. The accuracy will be higher with higher grid resolution. But the high grid resolution leads to significantly increasing work of the fingerprint data collection, processing and maintenance. This also might decrease the performance, portability and robustness of the navigation system. Meanwhile, traditional fingerprint positioning method use equational grid to partition the indoor space. While used for pedestrian navigation, sometimes a person can be located at the area where he or she cannot access. This paper studied these two issues, proposed a new indoor space partition method considering pedestrian accessibility, which can increase the accuracy of pedestrian position, and decrease the volume of the fingerprint data. Based on this proposed partition method, an optimized algorithm for fingerprint position was also designed. A across linker structure was used for fingerprint point index and matching. Experiment based on the proposed method and algorithm showed that the workload of fingerprint collection and maintenance were effectively decreased, and poisoning efficiency and accuracy was effectively increased

  17. The Road from the NASA Access-to-Space Study to a Reusable Launch Vehicle

    NASA Technical Reports Server (NTRS)

    Powell, Richard W.; Lockwood, Mary Kae; Cook, Stephen A.

    1998-01-01

    NASA has established a goal of providing low-cost reliable access to space. While this goal has been around for many years, it received a major impetus when the U.S Congress mandated the Access-to-Space study in 1993. This study concluded that a rocket powered single-stage-to-orbit vehicle offered the best opportunity for low-cost reliable space transportation by the first decade of the new millennium. This required a focused technology development program before such a vehicle could be built. NASA recognized that no commercial entity would commit to the development of a single-stage-to-orbit vehicle without the U.S. Government's participation. To this end, NASA entered into a cooperative agreement with industry to mature the required technologies. This effort includes the development of an experimental subscale-vehicle known as the X-33, an extensive ground-based program to provide the required additional technology development, and conceptual through preliminary design of an operational reusable launch vehicle. Following this effort, a decision will be made whether or not to proceed with the detailed design and fabrication of an operational vehicle.

  18. The Road from the NASA Access-to-Space Study to a Reusable Launch Vehicle

    NASA Technical Reports Server (NTRS)

    Powell, Richard W.; Lockwood, Mary Kae; Cook, Stephen A.

    1998-01-01

    NASA has established a goal of providing low-cost reliable access to space. While this goal has been around for many years, it received a major impetus when the U.S. Congress mandated the Access-to-Space study in 1993. This study concluded that a rocket powered single-state-to-orbit vehicle offered the best opportunity for low-cost reliable space transportation by the first decade of the new millennium. This required a focused technology development program before such a vehicle could be built. NASA recognized that no commercial entity would commit to the development of a single-stage-to-orbit vehicle without the U.S. Government's participation. To this end, NASA entered into a cooperative agreement with industry to mature the required technologies. This effort includes the development of an experimental subscale-vehicle known as the X-33, an extensive ground-based program to provide the required additional technology development, and conceptual through preliminary design of an operational reusable launch vehicle. Following this effort, a decision will be made whether or not to proceed with the detailed design and fabrication of an operational vehicle.

  19. Virtual Mission Operations of Remote Sensors With Rapid Access To and From Space

    NASA Technical Reports Server (NTRS)

    Ivancic, William D.; Stewart, Dave; Walke, Jon; Dikeman, Larry; Sage, Steven; Miller, Eric; Northam, James; Jackson, Chris; Taylor, John; Lynch, Scott; Heberle, Jay

    2010-01-01

    This paper describes network-centric operations, where a virtual mission operations center autonomously receives sensor triggers, and schedules space and ground assets using Internet-based technologies and service-oriented architectures. For proof-of-concept purposes, sensor triggers are received from the United States Geological Survey (USGS) to determine targets for space-based sensors. The Surrey Satellite Technology Limited (SSTL) Disaster Monitoring Constellation satellite, the United Kingdom Disaster Monitoring Constellation (UK-DMC), is used as the space-based sensor. The UK-DMC s availability is determined via machine-to-machine communications using SSTL s mission planning system. Access to/from the UK-DMC for tasking and sensor data is via SSTL s and Universal Space Network s (USN) ground assets. The availability and scheduling of USN s assets can also be performed autonomously via machine-to-machine communications. All communication, both on the ground and between ground and space, uses open Internet standards.

  20. Space environment data storage and access: lessons learned and recommendations for the future

    NASA Astrophysics Data System (ADS)

    Evans, Hugh; Heynderickx, Daniel

    2012-07-01

    With the ever increasing volume of space environment data available at present and planned for the near future, the demands on data storage and access methods are increasing as well. In addition, continued access to historical, archived data remains crucial. On the basis of many years of experience, the authors identify the following issues as important for continued and efficient handling of datasets now and in the future: The huge data volumes currently or very soon avaiable from a number of space missions will limi direct Internet download access to even relatively short epoch ranges of data. Therefore, data providers should establish or extend standardised data (post-) processing services so that only data query results should be downloaded. Although a single standardised data format will in all likelihood remain utopia, data providers should at least include extensive metadata with their data products, according to established standards and practices (e.g. ISTP, SPASE). Standardisation of (sets of) metadata greatly facilitates data mining and querying. The use of SQL database storage should be considered instead of, or in parallel with, classic storage of data files. The use of SQL does away with having to handle file parsing and processing, while at the same time standard access protocols can be used to (remotely) connect to such data repositories. Many data holdings are still lacking in extensive descriptions of data provenance (e.g. instrument description), content and format. Unfortunately, detailed data information is usually rejected by scientific and technical journals. Re-processing of historical archived datasets into modern formats, making them easily available and usable, is urgently required, as knowledge is being lost. A global data directory has still not been achieved; policy makers should enforce stricter rules for "broadcasting" dataset information.

  1. ESPAS: the European e-science platform to access near-Earth space data (Invited)

    NASA Astrophysics Data System (ADS)

    Belehaki, A.; Hapgood, M. A.; Ritschel, B.; Manola, N.

    2013-12-01

    The aim of ESPAS platform is to integrate heterogeneous data from the earth's thermosphere, ionosphere, plasmasphere and magnetosphere. ESPAS supports the systematic exploration of multipoint measurements from the near-Earth space through homogenised access to multi-instrument data. It provides access to more than 40 datasets: Cluster, EISCAT, GIRO, DIAS, SWACI, CHAMP, SuperDARN, FPI, magnetometers INGV, SGO, DTU, IMAGE, TGO, IMAGE/RPI, ACE, SOHO, PROBA2, NOAA/POES, etc. The concept of extensibility to new data sets is an important element in the ESPAS architecture. Within the first year of the project, the main components of the system have been developed, namely, the data model, the XML schemas for metadata exchange format, the ontology, the wrapper installed at the data nodes so that the main platform harvest the metadata, the main platform built on the D-NET framework and the GUI with its designed workflows. The first working prototype supports the search for datasets among a selected number of databases (i.e., EDAM, DIAS, Cluster, SWACI data). The next immediate step would be the implementation of search for characteristics within the datasets. For the second release we are planning to deploy tools for conjunctions between ground-space and space-space and for coincidences. For the final phase of the project the ESPAS infrastructure will be extensively tested through the application of several use cases, designed to serve the needs of the wide interdisciplinary users and producers communities, such as the ionospheric, thermospheric, magnetospheric, space weather and space climate communities, the geophysics community, the space communications engineering, HF users, satellite operators, navigation and surveillance systems, and space agencies. The final ESPAS platform is expected to be delivered in 2015. The abstract is submitted on behalf of the ESPAS-FP7EU team (http://www.espas-fp7.eu): Mike Hapgood, Anna Belehaki, Spiros Ventouras, Natalia Manola, Antonis

  2. DisVis: quantifying and visualizing accessible interaction space of distance-restrained biomolecular complexes

    PubMed Central

    van Zundert, G.C.P.; Bonvin, A.M.J.J.

    2015-01-01

    Summary: We present DisVis, a Python package and command line tool to calculate the reduced accessible interaction space of distance-restrained binary protein complexes, allowing for direct visualization and quantification of the information content of the distance restraints. The approach is general and can also be used as a knowledge-based distance energy term in FFT-based docking directly during the sampling stage. Availability and implementation: The source code with documentation is freely available from https://github.com/haddocking/disvis. Contact: a.m.j.j.bonvin@uu.nl Supplementary information: Supplementary data are available at Bioinformatics online. PMID:26026169

  3. Exploration of the full conformational space of N-acetyl-L-glutamate-N-methylamide . An ab initio and DFT study

    NASA Astrophysics Data System (ADS)

    Masman, M. F.; Zamora, M. A.; Rodríguez, A. M.; Fidanza, N. G.; Peruchena, N. M.; Enriz, R. D.; Csizmadia, I. G.

    2002-09-01

    A conformational and electronic study on N-acetyl-L-glutamate-N-methylamide was carried out. Theoretical computational analysis revealed 21 different conformations at the RB3LYP/6-31G(d) level of theory. Ab initio calculations at two levels of theory (RHF/3-21G and RHF/6-31G(d)) were also performed. All side-chain conformations were explored for this compound. N-acetyl-L-glutamate-N-methylamide displayed a different conformational behaviour in comparison with other amino acids possessing shorter side-chains. These results can be attributed, at least in part, to the side-chain-backbone interactions, which are stabilizing the low-energy conformations in this molecule.

  4. Express Payload Project - A new method for rapid access to Space Station Freedom

    NASA Technical Reports Server (NTRS)

    Uhran, Mark L.; Timm, Marc G.

    1993-01-01

    The deployment and permanent operation of Space Station Freedom will enable researchers to enter a new era in the 21st century, in which continuous on-orbit experimentation and observation become routine. In support of this objective, the Space Station Freedom Program Office has initiated the Express Payload Project. The fundamental project goal is to reduce the marginal cost associated with small payload development, integration, and operation. This is to be accomplished by developing small payload accommodations hardware and a new streamlined small payload integration process. Standardization of small payload interfaces, certification of small payload containers, and increased payload developer responsibility for mission success are key aspects of the Express Payload Project. As the project progresses, the principles will be applied to both pressurized payloads flown inside the station laboratories and unpressurized payloads attached to the station external structures. The increased access to space afforded by Space Station Freedom and the Express Payload Project has the potential to significantly expand the scope, magnitude, and success of future research in the microgravity environment.

  5. A rapid prototyping/artificial intelligence approach to space station-era information management and access

    NASA Technical Reports Server (NTRS)

    Carnahan, Richard S., Jr.; Corey, Stephen M.; Snow, John B.

    1989-01-01

    Applications of rapid prototyping and Artificial Intelligence techniques to problems associated with Space Station-era information management systems are described. In particular, the work is centered on issues related to: (1) intelligent man-machine interfaces applied to scientific data user support, and (2) the requirement that intelligent information management systems (IIMS) be able to efficiently process metadata updates concerning types of data handled. The advanced IIMS represents functional capabilities driven almost entirely by the needs of potential users. Space Station-era scientific data projected to be generated is likely to be significantly greater than data currently processed and analyzed. Information about scientific data must be presented clearly, concisely, and with support features to allow users at all levels of expertise efficient and cost-effective data access. Additionally, mechanisms for allowing more efficient IIMS metadata update processes must be addressed. The work reported covers the following IIMS design aspects: IIMS data and metadata modeling, including the automatic updating of IIMS-contained metadata, IIMS user-system interface considerations, including significant problems associated with remote access, user profiles, and on-line tutorial capabilities, and development of an IIMS query and browse facility, including the capability to deal with spatial information. A working prototype has been developed and is being enhanced.

  6. Numerical Methodology For Full-Body TPS Sizing And Optimization For Access-To-Space Vehicles

    NASA Technical Reports Server (NTRS)

    Milos, Frank S.; Henline, William D.; Rasky, Daniel J. (Technical Monitor)

    1995-01-01

    This paper presents details of the methodology and numerical procedures developed at NASA Ames for full-body TEXAS sizing and optimization for Access to Space vehicle concepts. The core of the procedures is a robust implicit solver for one dimensional transient heat conduction in reusable multilayer TEXAS stackups. The solver includes an arbitrary number of material layers, contact resistances between materials, temperature and pressure dependent material and surface properties, numerous boundary-condition options, and self-adaptive time stepping. The solver is coupled with the Access-to-Space material database of 23 candidate TPS and structural materials and a thermal-environment database obtained from trajectory-based fullbody Navier-Stokes computations of the external flowfield. The thermal environment and material response are coupled through the use of T-type heat transfer coefficients. TIPS sizing and weight optimization are performed at every surface point on the vehicle based on sizing constraints which include material temperature limits, maximum backwall temperature, and cumulative interior heat flux. Typical results are presented for a lifting body concept with 10000 surface points, which required 35 minutes to compute on an SGI Indigo 2.

  7. Virtual Observatories for Space Physics Observations and Simulations: New Routes to Efficient Access and Visualization

    NASA Technical Reports Server (NTRS)

    Roberts, Aaron

    2005-01-01

    New tools for data access and visualization promise to make the analysis of space plasma data both more efficient and more powerful, especially for answering questions about the global structure and dynamics of the Sun-Earth system. We will show how new existing tools (particularly the Virtual Space Physics Observatory-VSPO-and the Visual System for Browsing, Analysis and Retrieval of Data-ViSBARD; look for the acronyms in Google) already provide rapid access to such information as spacecraft orbits, browse plots, and detailed data, as well as visualizations that can quickly unite our view of multispacecraft observations. We will show movies illustrating multispacecraft observations of the solar wind and magnetosphere during a magnetic storm, and of simulations of 3 0-spacecraft observations derived from MHD simulations of the magnetosphere sampled along likely trajectories of the spacecraft for the MagCon mission. An important issue remaining to be solved is how best to integrate simulation data and services into the Virtual Observatory environment, and this talk will hopefully stimulate further discussion along these lines.

  8. Analysis of Potential Alternatives to Reduce NASA's Cost of Human Access to Space

    NASA Technical Reports Server (NTRS)

    1998-01-01

    The purpose of this report is to analyze NASA's potential options for significantly reducing the cost of human access to space. The opinions expressed in this report are based on Hawthorne, Krauss & Associates' ("HKA") interaction with NASA and several of its key contractors over the past nine months. This report is not intended to be an exhaustive quantitative analysis of the various options available to NASA. Instead, its purpose is to outline key decision-related issues that the agency should consider prior to making a decision as to which option to pursue. This report attempts to bring a private-sector perspective to bear on the issue of reducing the cost of human access to space. HKA believes that the key to the NASA's success in reducing those costs over the long-term is the involvement of the private-sector incentives and disciplines--which is achieved only through the assumption of risk by the private sector, not through a traditional contractor relationship--is essential to achieve significant long-term cost reductions.

  9. Conformal triality of the Kepler problem

    NASA Astrophysics Data System (ADS)

    Cariglia, Marco

    2016-08-01

    We show that the Kepler problem is projectively equivalent to null geodesic motion on the conformal compactification of Minkowski-4 space. This space realises the conformal triality of Minkowski, dS and AdS spaces.

  10. ACCESS - A Science and Engineering Assessment of Space Coronagraph Concepts for the Direct Imaging and Spectroscopy of Exoplanetary Systems

    NASA Technical Reports Server (NTRS)

    Trauger, John

    2008-01-01

    Topics include and overview, science objectives, study objectives, coronagraph types, metrics, ACCESS observatory, laboratory validations, and summary. Individual slides examine ACCESS engineering approach, ACCESS gamut of coronagraph types, coronagraph metrics, ACCESS Discovery Space, coronagraph optical layout, wavefront control on the "level playing field", deformable mirror development for HCIT, laboratory testbed demonstrations, high contract imaging with the HCIT, laboratory coronagraph contrast and stability, model validation and performance predictions, HCIT coronagraph optical layout, Lyot coronagraph on the HCIT, pupil mapping (PIAA), shaped pupils, and vortex phase mask experiments on the HCIT.

  11. Socializing in an Open Drug Scene: The relationship Between Access to Private Space and Drug-Related Street Disorder

    PubMed Central

    DeBeck, Kora; Wood, Evan; Qi, Jiezhi; Fu, Eric; McArthur, Doug; Montaner, Julio; Kerr, Thomas

    2011-01-01

    Background Limited attention has been given to the potential role that the structure of housing available to people who are entrenched in street-based drug scenes may play in influencing the amount of time injection drug users (IDU) spend on public streets. We sought to examine the relationship between time spent socializing in Vancouver's drug scene and access to private space. Methods Using multivariate logistic regression we evaluated factors associated with socializing (three+ hours each day) in Vancouver's open drug scene among a prospective cohort of IDU. We also assessed attitudes towards relocating socializing activities if greater access to private indoor space was provided. Results Among our sample of 1114 IDU, 43% fit our criteria for socializing in the open drug scene. In multivariate analysis, having limited access to private space was independently associated with socializing (adjusted odds ratio: 1.80, 95% confidence interval: 1.28 – 2.55). In further analysis, 65% of ‘socializers’ reported positive attitudes towards relocating socializing if they had greater access to private space. Conclusion These findings suggest that providing IDU with greater access to private indoor space may reduce one component of drug-related street disorder. Low-threshold supportive housing based on the ‘housing first’ model that include safeguards to manage behaviors associated with illicit drug use appear to offer important opportunities to create the types of private spaces that could support a reduction in street disorder. PMID:21764528

  12. Accessing Solar Irradiance Data via LISIRD, the Laboratory for Atmospheric and Space Physics Interactive Solar Irradiance Datacenter

    NASA Astrophysics Data System (ADS)

    Pankratz, C. K.; Wilson, A.; Snow, M. A.; Lindholm, D. M.; Woods, T. N.; Traver, T.; Woodraska, D.

    2015-12-01

    The LASP Interactive Solar Irradiance Datacenter, LISIRD, http://lasp.colorado.edu/lisird, allows the science community and the public to explore and access solar irradiance and related data sets using convenient, interactive or scriptable, standards-based interfaces. LISIRD's interactive plotting allows users to investigate and download irradiance data sets from a variety of sources, including space missions, ground observatories, and modeling efforts. LISIRD's programmatic interfaces allow software-level data retrievals and facilitate automation. This presentation will describe the current state of LISIRD, provide details of the data sets it serves, outline data access methods, identify key technologies in-use, and address other related aspects of serving spectral and other time series data. We continue to improve LISIRD by integrating new data sets, and also by advancing its data management and presentation capabilities to meet evolving best practices and community needs. LISIRD is hosted and operated by the Laboratory for Atmospheric and Space Physics, LASP, which has been a leader in Atmospheric and Heliophysics science for over 60 years. LASP makes a variety of space-based measurements of solar irradiance, which provide crucial input for research and modeling in solar-terrestrial interactions, space physics, planetary, atmospheric, and climate sciences. These data sets consist of fundamental measurements, composite data sets, solar indices, space weather products, and models. Current data sets available through LISIRD originate from the SORCE, SDO (EVE), UARS (SOLSTICE), TIMED (SEE), and SME space missions, as well as several other space and ground-based projects. LISIRD leverages several technologies to provide flexible and standards-based access to the data holdings available through LISIRD. This includes internet-accessible interfaces that permit data access in a variety of formats, data subsetting, as well as program-level access from data analysis

  13. Creating Assemblies in Media Space: Recent Developments in Enhancing Access to Workspaces

    NASA Astrophysics Data System (ADS)

    Luff, Paul; Kuzuoka, Hideaki; Heath, Christian; Yamazaki, Keiichi; Yamashita, Jun

    In this chapter, we discuss a programme of social and technical research that we have undertaken over the last few years concerned with the design, assessment and development of systems to support real-time, distributed work; work that relies upon a participants' ability to access a range of tangible and digital resources. The programme of work has been informed by findings from a range of studies of work and collaboration in environments that include architectural practices, control centres, surgeries, hospitals, news rooms, and the like. These studies have a framework of considerations, criteria, and insights into the organization of everyday work and interaction that have enabled us to identify some of the limitations of con¬ventional media spaces, including systems which we have helped develop, and to pose a set of requirements and challenges, which we believe are fundamental to the creation of a media space that could support the flexible and contingent demands of seemingly simple forms of collaborative work. These studies, coupled with the development and assessment of a series of experimental systems, have enabled us to identify three key issues that we believe have to be addressed and resolved (in one way or another) if media space research is going to achieve its early potential.

  14. Active pore space utilization in nanoporous carbon-based supercapacitors: Effects of conductivity and pore accessibility

    NASA Astrophysics Data System (ADS)

    Seredych, Mykola; Koscinski, Mikolaj; Sliwinska-Bartkowiak, Malgorzata; Bandosz, Teresa J.

    2012-12-01

    Composites of commercial graphene and nanoporous sodium-salt-polymer-derived carbons were prepared with 5 or 20 weight% graphene. The materials were characterized using the adsorption of nitrogen, SEM/EDX, thermal analysis, Raman spectroscopy and potentiometric titration. The samples' conductivity was also measured. The performance of the carbon composites in energy storage was linked to their porosity and electronic conductivity. The small pores (<0.7) were found as very active for double layer capacitance. It was demonstrated that when double layer capacitance is a predominant mechanism of charge storage, the degree of the pore space utilization for that storage can be increased by increasing the conductivity of the carbons. That active pore space utilization is defined as gravimetric capacitance per unit pore volume in pores smaller than 0.7 nm. Its magnitude is affected by conductivity of the carbon materials. The functional groups, besides pseudocapacitive contribution, increased the wettability and thus the degree of the pore space utilization. Graphene phase, owing to its conductivity, also took part in an insitu increase of the small pore accessibility and thus the capacitance of the composites via enhancing an electron transfer to small pores and thus imposing the reduction of groups blocking the pores for electrolyte ions.

  15. Sounding Rockets within Swedish National Balloon and Rocket Programme- Providing Access to Space from Esrange

    NASA Astrophysics Data System (ADS)

    Sjolander, K.; Karlsson, T.; Lockowandt, C.

    2015-09-01

    Initiated in 2012 by the Swedish National Space Board (SNSB), a new programme dedicated for Swedish scientists to gain access to space using balloons and sounding rockets was started. This programme promotes the possibility to ensure continuity in both the science and the technology used. The sounding rocket part of this national programme started with three possible missions. SPIDER (Small Payloads for Investigation of Disturbances in Electrojet by Rockets) from the Space and Plasma physics department of KTH, 0-STATES (Oxygen Species and Thermospheric Airglow in The Earth's Sky) from the Department of Meteorology Stockholm University (MISU) and LEEWAVES (Local Excitation and Effects of Waves on Atmospheric VErtical Structure) that is collaboration between KTH and MISU. These three missions were planned for launches in 2015 and 2016. SSc has been contracted on a launch ticket basis to provide the launch and service to the scientific instrumentation. This paper presents the SPIDER, 0-STATES and LEEWAVES missions focussing on a mission related technical solutions perspective.

  16. Assay for transposase-accessible chromatin and circularized chromosome conformation capture, two methods to explore the regulatory landscapes of genes in zebrafish.

    PubMed

    Fernández-Miñán, A; Bessa, J; Tena, J J; Gómez-Skarmeta, J L

    2016-01-01

    Accurate transcriptional control of genes is fundamental for the correct functioning of organs and developmental processes. This control depends on the interplay between the promoter of genes and other noncoding sequences, whose interaction is mediated by 3D chromatin arrangements. Thus, the detailed description of transcriptional regulatory landscapes is essential to understand the mechanisms of transcriptional regulation. However, to achieve that, two important challenges have to be faced: (1) the identification of the noncoding sequences that contribute to gene transcription and (2) the association of these sequences to the respective genes they control. In this chapter, we describe two protocols that allow overcoming these important challenges: the assay for transposase-accessible chromatin using sequencing (ATAC-seq) and circularized chromosome conformation capture (4C-seq). ATAC-seq is a very efficient technique that, using a very low number of cells as starting material, allows the identification of active chromatin regions genome wide, whereas 4C-seq detects the subset of sequences that interact specifically with the promoter of a given gene. When combined, both techniques provide a comprehensive snapshot of the regulatory landscapes of developmental genes. The protocols we present here have been optimized for teleost fish samples, zebrafish and medaka, allowing the in-depth study of transcriptional regulation in these two emerging animal models. Given the amenability and easy genetic manipulation of these two experimental systems, we anticipate that they will be important in revealing general principles of the vertebrate regulatory genome. PMID:27443938

  17. Based on asynchronous communication protocol of geographic space information service access mechanism research

    NASA Astrophysics Data System (ADS)

    Chen, G.; Zhao, J.; Gu, M.; Li, D.

    2014-04-01

    At present, the traditional way of accessing to classified network in geographic spatial information services is using network gatekeeper and firewall etc. to ensure public and classified network communications links. However, the physical isolation between classified network and public network is crossed, which is bound to cause classified network potential security hazard. In Yunnan province space Land dynamic monitoring integration project, it proposed the point to point text message communication protocol and asynchronous transmission mechanism. Using geo-spatial information encryption processing and data compression processing method, it reduced the risk of data sensitivity and monitored, namely to ensure data security, which realized geographic spatial information services data communication effectively between classified network and public network in the rigid field conditions.

  18. Transcriptome Tomography for Brain Analysis in the Web-Accessible Anatomical Space

    PubMed Central

    Okamura-Oho, Yuko; Shimokawa, Kazuro; Takemoto, Satoko; Hirakiyama, Asami; Nakamura, Sakiko; Tsujimura, Yuki; Nishimura, Masaomi; Kasukawa, Takeya; Masumoto, Koh-hei; Nikaido, Itoshi; Shigeyoshi, Yasufumi; Ueda, Hiroki R.; Song, Gang; Gee, James; Himeno, Ryutaro; Yokota, Hideo

    2012-01-01

    Increased information on the encoded mammalian genome is expected to facilitate an integrated understanding of complex anatomical structure and function based on the knowledge of gene products. Determination of gene expression-anatomy associations is crucial for this understanding. To elicit the association in the three-dimensional (3D) space, we introduce a novel technique for comprehensive mapping of endogenous gene expression into a web-accessible standard space: Transcriptome Tomography. The technique is based on conjugation of sequential tissue-block sectioning, all fractions of which are used for molecular measurements of gene expression densities, and the block- face imaging, which are used for 3D reconstruction of the fractions. To generate a 3D map, tissues are serially sectioned in each of three orthogonal planes and the expression density data are mapped using a tomographic technique. This rapid and unbiased mapping technique using a relatively small number of original data points allows researchers to create their own expression maps in the broad anatomical context of the space. In the first instance we generated a dataset of 36,000 maps, reconstructed from data of 61 fractions measured with microarray, covering the whole mouse brain (ViBrism: http://vibrism.riken.jp/3dviewer/ex/index.html) in one month. After computational estimation of the mapping accuracy we validated the dataset against existing data with respect to the expression location and density. To demonstrate the relevance of the framework, we showed disease related expression of Huntington’s disease gene and Bdnf. Our tomographic approach is applicable to analysis of any biological molecules derived from frozen tissues, organs and whole embryos, and the maps are spatially isotropic and well suited to the analysis in the standard space (e.g. Waxholm Space for brain-atlas databases). This will facilitate research creating and using open-standards for a molecular-based understanding of

  19. The University of Arizona Nanosat Program: Making Space accessible to scientific and commercial packages.

    NASA Astrophysics Data System (ADS)

    Fink, U.; Fevig, R. A.

    2003-05-01

    For the last couple of years we have been engaged in building nanosatellites within a student-mentor framework. The satellites are 10x10x10cm cubes, have a maximum mass of 1 kg, and power of a few watts. The standardized "cube-sat" form factor was suggested by Bob Twiggs of Stanford University so that a common launch platform could be utilized and more Universities could participate. We have now built four "cube-sats': a launchable Engineering model, Rincon 1 & 2, (funded by Rincon corporation), and Alcatel funded by Alcatel Espace. The costs for the four satellites are \\250,000. Launch costs using a Russian SS-18 are typically \\10,000 per kg. The payload for Rincon 1 & 2 is a sophisticated telecommunications board using only 10 mw of transmitting power. The Alcatel payload consists of three communications IC's whose radiation exposure and annealing properties will be studied over a period of years. Future nanosatellites will have considerable value in providing low cost access to space for experiments in nanotechnology, space electronics, micropropulsion, radiation experiments, astrobionics and climate change studies. For the latter area we are considering experiments to monitor the solar constant, the solar UV spectrum, the chromospheric activity through the Mg II index, the Earth's Albedo, etc. For this purpose we are developing a slightly larger satellite, 20x20x20cm and 10 kg. We have built a C-MOS camera with a 1 ms exposure time for attitude determination, and we are working with Honeywell Industries to develop micro-reaction wheels for attitude control. We are also working on micro-propulsion units with the Air Force and several aerospace companies. Preliminary calculations show that we can develop delta-V's of 5km/s which will allow us to visit 5% (about 100) of the NEA population or possibly some comets. We firmly believe a vigorous nanosatellite program will allow useful space experiments for costs of millions of Dollars instead of the present tens of

  20. Group space allowance has little effect on sow health, productivity, or welfare in a free-access stall system

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Free-access stalls allow sows to choose the protection of a stall or use of a shared group space. This study investigated the effect of group space width: 0.91 (SS), 2.13 (IS), and 3.05 (LS) m on the health, production, behavior, and welfare of gestating sows. At gestational day (GD) 35.4 ± 2.3, 21 ...

  1. A prototype computerized synthesis methodology for generic space access vehicle (SAV) conceptual design

    NASA Astrophysics Data System (ADS)

    Huang, Xiao

    2006-04-01

    Today's and especially tomorrow's competitive launch vehicle design environment requires the development of a dedicated generic Space Access Vehicle (SAV) design methodology. A total of 115 industrial, research, and academic aircraft, helicopter, missile, and launch vehicle design synthesis methodologies have been evaluated. As the survey indicates, each synthesis methodology tends to focus on a specific flight vehicle configuration, thus precluding the key capability to systematically compare flight vehicle design alternatives. The aim of the research investigation is to provide decision-making bodies and the practicing engineer a design process and tool box for robust modeling and simulation of flight vehicles where the ultimate performance characteristics may hinge on numerical subtleties. This will enable the designer of a SAV for the first time to consistently compare different classes of SAV configurations on an impartial basis. This dissertation presents the development steps required towards a generic (configuration independent) hands-on flight vehicle conceptual design synthesis methodology. This process is developed such that it can be applied to any flight vehicle class if desired. In the present context, the methodology has been put into operation for the conceptual design of a tourist Space Access Vehicle. The case study illustrates elements of the design methodology & algorithm for the class of Horizontal Takeoff and Horizontal Landing (HTHL) SAVs. The HTHL SAV design application clearly outlines how the conceptual design process can be centrally organized, executed and documented with focus on design transparency, physical understanding and the capability to reproduce results. This approach offers the project lead and creative design team a management process and tool which iteratively refines the individual design logic chosen, leading to mature design methods and algorithms. As illustrated, the HTHL SAV hands-on design methodology offers growth

  2. Joint Estimation of 2D-DOA and Frequency Based on Space-Time Matrix and Conformal Array

    PubMed Central

    Wan, Liang-Tian; Liu, Lu-Tao; Si, Wei-Jian; Tian, Zuo-Xi

    2013-01-01

    Each element in the conformal array has a different pattern, which leads to the performance deterioration of the conventional high resolution direction-of-arrival (DOA) algorithms. In this paper, a joint frequency and two-dimension DOA (2D-DOA) estimation algorithm for conformal array are proposed. The delay correlation function is used to suppress noise. Both spatial and time sampling are utilized to construct the spatial-time matrix. The frequency and 2D-DOA estimation are accomplished based on parallel factor (PARAFAC) analysis without spectral peak searching and parameter pairing. The proposed algorithm needs only four guiding elements with precise positions to estimate frequency and 2D-DOA. Other instrumental elements can be arranged flexibly on the surface of the carrier. Simulation results demonstrate the effectiveness of the proposed algorithm. PMID:24453856

  3. Quantizing Open Spin Chains with Variable Length and Giant Gravitons in the Anti-de Sitter-Space/Conformal Field-Theory Correspondence

    SciTech Connect

    Berenstein, David; Correa, Diego H.; Vazquez, Samuel E.

    2005-11-04

    We study an XXX open spin chain with variable number of sites, where the variability is introduced only at the boundaries. This model arises naturally in the study of giant gravitons in the anti-de Sitter-space/conformal field-theory correspondence. We show how to quantize the spin chain by mapping its states to a bosonic lattice of finite length with sources and sinks of particles at the boundaries. Using coherent states, we show how the Hamiltonian for the bosonic lattice gives the correct description of semiclassical open strings ending on giant gravitons.

  4. Galilean conformal and superconformal symmetries

    SciTech Connect

    Lukierski, J.

    2012-10-15

    Firstly we discuss briefly three different algebras named as nonrelativistic (NR) conformal: Schroedinger, Galilean conformal, and infinite algebra of local NR conformal isometries. Further we shall consider in some detail Galilean conformal algebra (GCA) obtained in the limit c{yields}{infinity} from relativistic conformal algebraO(d+1, 2) (d-number of space dimensions). Two different contraction limits providing GCA and some recently considered realizations will be briefly discussed. Finally by considering NR contraction of D = 4 superconformal algebra the Galilei conformal superalgebra (GCSA) is obtained, in the formulation using complexWeyl supercharges.

  5. 41 CFR 102-79.65 - May Executive agencies outlease space on major public access levels, courtyards and rooftops of...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 41 Public Contracts and Property Management 3 2010-07-01 2010-07-01 false May Executive agencies outlease space on major public access levels, courtyards and rooftops of public buildings? 102-79.65 Section 102-79.65 Public Contracts and Property Management Federal Property Management Regulations System (Continued) FEDERAL MANAGEMENT...

  6. 41 CFR 102-79.65 - May Executive agencies outlease space on major public access levels, courtyards and rooftops of...

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 41 Public Contracts and Property Management 3 2012-01-01 2012-01-01 false May Executive agencies outlease space on major public access levels, courtyards and rooftops of public buildings? 102-79.65 Section 102-79.65 Public Contracts and Property Management Federal Property Management Regulations System (Continued) FEDERAL MANAGEMENT...

  7. 41 CFR 102-79.65 - May Executive agencies outlease space on major public access levels, courtyards and rooftops of...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 41 Public Contracts and Property Management 3 2013-07-01 2013-07-01 false May Executive agencies outlease space on major public access levels, courtyards and rooftops of public buildings? 102-79.65 Section 102-79.65 Public Contracts and Property Management Federal Property Management Regulations System (Continued) FEDERAL MANAGEMENT...

  8. 41 CFR 102-79.65 - May Executive agencies outlease space on major public access levels, courtyards and rooftops of...

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 41 Public Contracts and Property Management 3 2014-01-01 2014-01-01 false May Executive agencies outlease space on major public access levels, courtyards and rooftops of public buildings? 102-79.65 Section 102-79.65 Public Contracts and Property Management Federal Property Management Regulations System (Continued) FEDERAL MANAGEMENT...

  9. Building a Virtual Space Physics Observatory for Easy Access to and Novel Visualization of Distributed Data

    NASA Astrophysics Data System (ADS)

    Rezapkin, V.; Roberts, D. A.; Coleman, J.; Boller, R.

    2003-12-01

    Progress in space physics has become strongly dependent on the simultaneous analysis of data from multiple spacecraft, each with many instruments. Historically, these data have been stored by different investigators in a variety of formats and with widely varying metadata describing the datasets. We are working on many fronts to integrate this ``data universe" such that a researcher will ultimately be able to obtain data using a uniform terminology through a variety of interfaces, obtaining either specifically formatted files or a direct stream into an application. Our main accomplishments to date include a general data dictionary (working with the SPASE group), a well-developed front-end visualization tool, and the beginnings of a simpler interface and ``middleware" to access the data directly from various repositories. We are working with as many other groups as we can to assure that the resulting system is made useful through the incorporation and coordination of many applications and ideas. This talk will give an overview of our status and plans.

  10. Mitochondrial 3β-Hydroxysteroid Dehydrogenase Enzyme Activity Requires Reversible pH-dependent Conformational Change at the Intermembrane Space*

    PubMed Central

    Prasad, Manoj; Thomas, James L.; Whittal, Randy M.; Bose, Himangshu S.

    2012-01-01

    The inner mitochondrial membrane protein 3β-hydroxysteroid dehydrogenase 2 (3βHSD2) synthesizes progesterone and androstenedione through its dehydrogenase and isomerase activities. This bifunctionality requires 3βHSD2 to undergo a conformational change. Given its proximity to the proton pump, we hypothesized that pH influences 3βHSD2 conformation and thus activity. Circular dichroism (CD) showed that between pH 7.4 and 4.5, 3βHSD2 retained its primarily α-helical character with a decrease in α-helical content at lower pH values, whereas the β-sheet content remained unchanged throughout. Titrating the pH back to 7.4 restored the original conformation within 25 min. Metabolic conversion assays indicated peak 3βHSD2 activity at pH 4.5 with ∼2-fold more progesterone synthesized at pH 4.5 than at pH 3.5 and 7.4. Increasing the 3βHSD2 concentration from 1 to 40 μg resulted in a 7-fold increase in progesterone at pH 4.5, but no change at pH 7.4. Incubation with guanidinum hydrochloride (GdmHCl) showed a three-step cooperative unfolding of 3βHSD2 from pH 7.4 to 4.5, possibly due to the native state unfolding to the intermediate ion core state. With further decreases in pH, increasing concentrations of GdmHCl led to rapid two-step unfolding that may represent complete loss of structure. Between pH 4 and 5, the two intermediate states appeared stable. Stopped-flow kinetics showed slower unfolding at around pH 4, where the protein is in a pseudostable state. Based on our data, we conclude that at pH 4–5, 3βHSD2 takes on a molten globule conformation that promotes the dual functionality of the enzyme. PMID:22262841

  11. Simultaneous escaping of explicit and hidden free energy barriers: application of the orthogonal space random walk strategy in generalized ensemble based conformational sampling.

    PubMed

    Zheng, Lianqing; Chen, Mengen; Yang, Wei

    2009-06-21

    To overcome the pseudoergodicity problem, conformational sampling can be accelerated via generalized ensemble methods, e.g., through the realization of random walks along prechosen collective variables, such as spatial order parameters, energy scaling parameters, or even system temperatures or pressures, etc. As usually observed, in generalized ensemble simulations, hidden barriers are likely to exist in the space perpendicular to the collective variable direction and these residual free energy barriers could greatly abolish the sampling efficiency. This sampling issue is particularly severe when the collective variable is defined in a low-dimension subset of the target system; then the "Hamiltonian lagging" problem, which reveals the fact that necessary structural relaxation falls behind the move of the collective variable, may be likely to occur. To overcome this problem in equilibrium conformational sampling, we adopted the orthogonal space random walk (OSRW) strategy, which was originally developed in the context of free energy simulation [L. Zheng, M. Chen, and W. Yang, Proc. Natl. Acad. Sci. U.S.A. 105, 20227 (2008)]. Thereby, generalized ensemble simulations can simultaneously escape both the explicit barriers along the collective variable direction and the hidden barriers that are strongly coupled with the collective variable move. As demonstrated in our model studies, the present OSRW based generalized ensemble treatments show improved sampling capability over the corresponding classical generalized ensemble treatments. PMID:19548709

  12. Probing RNA Native Conformational Ensembles with Structural Constraints.

    PubMed

    Fonseca, Rasmus; van den Bedem, Henry; Bernauer, Julie

    2016-05-01

    Noncoding ribonucleic acids (RNA) play a critical role in a wide variety of cellular processes, ranging from regulating gene expression to post-translational modification and protein synthesis. Their activity is modulated by highly dynamic exchanges between three-dimensional conformational substates, which are difficult to characterize experimentally and computationally. Here, we present an innovative, entirely kinematic computational procedure to efficiently explore the native ensemble of RNA molecules. Our procedure projects degrees of freedom onto a subspace of conformation space defined by distance constraints in the tertiary structure. The dimensionality reduction enables efficient exploration of conformational space. We show that the conformational distributions obtained with our method broadly sample the conformational landscape observed in NMR experiments. Compared to normal mode analysis-based exploration, our procedure diffuses faster through the experimental ensemble while also accessing conformational substates to greater precision. Our results suggest that conformational sampling with a highly reduced but fully atomistic representation of noncoding RNA expresses key features of their dynamic nature. PMID:27028235

  13. Conformal superalgebras via tractor calculus

    NASA Astrophysics Data System (ADS)

    Lischewski, Andree

    2015-01-01

    We use the manifestly conformally invariant description of a Lorentzian conformal structure in terms of a parabolic Cartan geometry in order to introduce a superalgebra structure on the space of twistor spinors and normal conformal vector fields formulated in purely algebraic terms on parallel sections in tractor bundles. Via a fixed metric in the conformal class, one reproduces a conformal superalgebra structure that has been considered in the literature before. The tractor approach, however, makes clear that the failure of this object to be a Lie superalgebra in certain cases is due to purely algebraic identities on the spinor module and to special properties of the conformal holonomy representation. Moreover, it naturally generalizes to higher signatures. This yields new formulas for constructing new twistor spinors and higher order normal conformal Killing forms out of existing ones, generalizing the well-known spinorial Lie derivative. Moreover, we derive restrictions on the possible dimension of the space of twistor spinors in any metric signature.

  14. Conformational sampling techniques.

    PubMed

    Hatfield, Marcus P D; Lovas, Sándor

    2014-01-01

    The potential energy hyper-surface of a protein relates the potential energy of the protein to its conformational space. This surface is useful in determining the native conformation of a protein or in examining a statistical-mechanical ensemble of structures (canonical ensemble). In determining the potential energy hyper-surface of a protein three aspects must be considered; reducing the degrees of freedom, a method to determine the energy of each conformation and a method to sample the conformational space. For reducing the degrees of freedom the choice of solvent, coarse graining, constraining degrees of freedom and periodic boundary conditions are discussed. The use of quantum mechanics versus molecular mechanics and the choice of force fields are also discussed, as well as the sampling of the conformational space through deterministic and heuristic approaches. Deterministic methods include knowledge-based statistical methods, rotamer libraries, homology modeling, the build-up method, self-consistent electrostatic field, deformation methods, tree-based elimination and eigenvector following routines. The heuristic methods include Monte Carlo chain growing, energy minimizations, metropolis monte carlo and molecular dynamics. In addition, various methods to enhance the conformational search including the deformation or smoothing of the surface, scaling of system parameters, and multi copy searching are also discussed. PMID:23947647

  15. Interplanetary space science data base and access/display tool on the NSSDC heliospheric CD-ROM

    NASA Technical Reports Server (NTRS)

    Papitashvili, N. E.; King, J. H.

    1995-01-01

    The National Space Science Data Center (NSSDC) has accumulated a rich archive of heliospheric, magnetospheric, and ionospheric data, as well as data from most other NASA-involved science disciplines. To facilitate access to and use of these data, NSSDC has begun to put selected data onto CD-ROM's. This paper describes one such CD-ROM, and the access and display software developed at NSSDC to support its use. The data on the CD-ROM consist primarily of hourly solar wind magnetic field and plasma data from many near-Earth spacecraft (OMNI) and deep space spacecraft (Voyagers, Pioneers, Helios, Pioneer Venus Orbiter). In addition, 5-minute resolution IMP-8 and ISEE-3 magnetic field and plasma data are also included. Data are stored in both ASCII and CDF formats.

  16. A Science Information Infrastructure for Access to Earth and Space Science Data through the Nation's Science Museums

    NASA Technical Reports Server (NTRS)

    Murray, S.

    1999-01-01

    In this project, we worked with the University of California at Berkeley/Center for Extreme Ultraviolet Astrophysics and five science museums (the National Air and Space Museum, the Science Museum of Virginia, the Lawrence Hall of Science, the Exploratorium., and the New York Hall of Science) to formulate plans for computer-based laboratories located at these museums. These Science Learning Laboratories would be networked and provided with real Earth and space science observations, as well as appropriate lesson plans, that would allow the general public to directly access and manipulate the actual remote sensing data, much as a scientist would.

  17. Assemblies of Conformal Tanks

    NASA Technical Reports Server (NTRS)

    DeLay, Tom

    2009-01-01

    Assemblies of tanks having shapes that conform to each other and/or conform to other proximate objects have been investigated for use in storing fuels and oxidizers in small available spaces in upper stages of spacecraft. Such assemblies might also prove useful in aircraft, automobiles, boats, and other terrestrial vehicles in which space available for tanks is limited. The basic concept of using conformal tanks to maximize the utilization of limited space is not new in itself: for example, conformal tanks are used in some automobiles to store windshield -washer liquid and coolant that overflows from radiators. The novelty of the present development lies in the concept of an assembly of smaller conformal tanks, as distinguished from a single larger conformal tank. In an assembly of smaller tanks, it would be possible to store different liquids in different tanks. Even if the same liquid were stored in all the tanks, the assembly would offer an advantage by reducing the mechanical disturbance caused by sloshing of fuel in a single larger tank: indeed, the requirement to reduce sloshing is critical in some applications. The figure shows a prototype assembly of conformal tanks. Each tank was fabricated by (1) copper plating a wax tank mandrel to form a liner and (2) wrapping and curing layers of graphite/epoxy composite to form a shell supporting the liner. In this case, the conformal tank surfaces are flat ones where they come in contact with the adjacent tanks. A band of fibers around the outside binds the tanks together tightly in the assembly, which has a quasi-toroidal shape. For proper functioning, it would be necessary to maintain equal pressure in all the tanks.

  18. Internet access to the web resources of a geographically distributed system of near-and deep-space monitoring

    NASA Astrophysics Data System (ADS)

    Chernenkov, V. N.; Vitkovskij, V. V.; Kalinina, N. A.

    2007-12-01

    The state and speed characteristics of Web access to the first five nodes of the projected geographically distributed system of scientific monitoring of near and deep space are analyzed. The possibility of developing an architecture involving user query redirection to a caching server is studied. This will make it possible to relieve hardware communication links substantially and speed up HTTP connection time, especially for nodes linked via heavily congested Internet links.

  19. Vacuum Averages of the Energy-Momentum Tensor of a Scalar Field in Homogeneous Spaces with a Conformal Metric

    NASA Astrophysics Data System (ADS)

    Breev, A. I.; Kozlov, A. V.

    2016-01-01

    Within the framework of the method of orbits, expressions have been obtained for the vacuum averages of the energy-momentum tensor of a scalar field with an arbitrary coupling constant in a spacetime with a nonstationary metric of Robertson-Walker type, where space is a homogeneous Riemannian manifold. It is shown that the vacuum averages of the energy-momentum tensor are determined by the complete set of solutions of the reduced equation with a smaller number of independent variables and with algebraic characteristics of homogeneous space.

  20. Di-Jet Conical Correlations Associated with Heavy Quark Jets in anti-de Sitter Space/Conformal Field Theory Correspondence

    SciTech Connect

    Noronha, Jorge; Gyulassy, Miklos; Torrieri, Giorgio

    2009-03-13

    We show that far zone Mach and diffusion wake 'holograms' produced by supersonic strings in anti-de Sitter space/conformal field theory (AdS/CFT) correspondence do not lead to observable conical angular correlations in the strict N{sub c}{yields}{infinity} supergravity limit if Cooper-Frye hadronization is assumed. However, a special nonequilibrium 'neck' zone near the jet is shown to produce an apparent sonic boom azimuthal angle distribution that is roughly independent of the heavy quark's velocity. Our results indicate that a measurement of the dependence of the away-side correlations on the velocity of associated identified heavy quark jets at the BNL Relativistic Heavy Ion Collider and CERN LHC will provide a direct test of the nonperturbative dynamics involved in the coupling between jets and the strongly coupled quark-gluon plasma implied by AdS/CFT correspondence.

  1. Di-jet conical correlations associated with heavy quark jets in anti-de sitter space/conformal field theory correspondence.

    PubMed

    Noronha, Jorge; Gyulassy, Miklos; Torrieri, Giorgio

    2009-03-13

    We show that far zone Mach and diffusion wake "holograms" produced by supersonic strings in anti-de Sitter space/conformal field theory (AdS/CFT) correspondence do not lead to observable conical angular correlations in the strict N_{c}-->infinity supergravity limit if Cooper-Frye hadronization is assumed. However, a special nonequilibrium "neck" zone near the jet is shown to produce an apparent sonic boom azimuthal angle distribution that is roughly independent of the heavy quark's velocity. Our results indicate that a measurement of the dependence of the away-side correlations on the velocity of associated identified heavy quark jets at the BNL Relativistic Heavy Ion Collider and CERN LHC will provide a direct test of the nonperturbative dynamics involved in the coupling between jets and the strongly coupled quark-gluon plasma implied by AdS/CFT correspondence. PMID:19392107

  2. Perception of available space during chimpanzee introductions: Number of accessible areas is more important than enclosure size.

    PubMed

    Herrelko, Elizabeth S; Buchanan-Smith, Hannah M; Vick, Sarah-Jane

    2015-01-01

    Restricting animals to different areas of their enclosure, for both brief and extended durations, is a key element of animal management practices. With such restrictions, available space decreases and the choices the animals can make are more limited, particularly in relation to social dynamics. When unfamiliar individuals are introduced to each other, group dynamics can be unpredictable and understanding space usage is important to facilitate successful introductions. We studied the behavioral, welfare-related responses of two groups of zoo-housed chimpanzees (n = 22) as they were introduced to each other and experienced a variety of enclosure restrictions and group composition changes. Our analysis of available space while controlling for chimpanzee density, found that arousal-related scratching and yawning decreased as the number of enclosure areas (separate rooms) available increased, whereas only yawning decreased as the amount of available space (m(2)) increased. Allogrooming, rubbing, and regurgitation/reingestion rates remained constant as both the number of enclosure areas and amount of space changed. Enclosure space is important to zoo-housed chimpanzees, but during introductions, a decrease in arousal-related scratching indicates that the number of accessible areas is more important than the total amount of space available, suggesting that it is important to provide modular enclosures that provide choice and flexible usage, to minimize the welfare impact of short- and long-term husbandry needs. PMID:26235989

  3. The Blueprint for Change: A National Strategy to Enhance Access to Earth and Space Science Education Resources

    NASA Astrophysics Data System (ADS)

    Geary, E. E.; Barstow, D.

    2001-12-01

    Enhancing access to high quality science education resources for teachers, students, and the general public is a high priority for the earth and space science education communities. However, to significantly increase access to these resources and promote their effective use will require a coordinated effort between content developers, publishers, professional developers, policy makers, and users in both formal and informal education settings. Federal agencies, academic institutions, professional societies, informal science centers, the Digital Library for Earth System Education, and other National SMETE Digital Library Projects are anticipated to play key roles in this effort. As a first step to developing a coordinated, national strategy for developing and delivering high quality earth and space science education resources to students, teachers, and the general public, 65 science educators, scientists, teachers, administrators, policy makers, and business leaders met this June in Snowmass, Colorado to create "Earth and Space Science Education 2010: A Blueprint for Change". The Blueprint is a strategy document that will be used to guide Earth and space science education reform efforts in grades K-12 during the next decade. The Blueprint contains specific goals, recommendations, and strategies for coordinating action in the areas of: Teacher Preparation and Professional Development, Curriculum and Materials, Equity and Diversity, Assessment and Evaluation, Public Policy and Systemic Reform, Public and Informal Education, Partnerships and Collaborations, and Technology. If you develop, disseminate, or use exemplary earth and space science education resources, we invite you to review the Blueprint for Change, share it with your colleagues and local science educators, and join as we work to revolutionize earth and space science education in grades K-12.

  4. Killing Initial Data on spacelike conformal boundaries

    NASA Astrophysics Data System (ADS)

    Paetz, Tim-Torben

    2016-08-01

    We analyze Killing Initial Data on Cauchy surfaces in conformally rescaled vacuum space-times satisfying Friedrich's conformal field equations. As an application, we derive the KID equations on a spacelike ℐ-.

  5. Remote Access to Earth Science Data by Content, Space and Time

    NASA Technical Reports Server (NTRS)

    Dobinson, E.; Raskin, G.

    1998-01-01

    This demo presents the combination on an http-based client/server application that facilitates internet access to Earth science data coupled with a Java applet GUI that allows the user to graphically select data based on spatial and temporal coverage plots and scientific parameters.

  6. The scientific potential of increased access to the Deep Space Network

    NASA Astrophysics Data System (ADS)

    Margot, J. L.

    2014-12-01

    Steven J. Ostro devoted most of his career to asteroid radar astronomyand encouraged young scientists at a variety of institutions toobserve with the Goldstone Solar System Radar. I will review thisimpressive legacy with results from observations of asteroids,terrestrial planets, and Galilean satellites. Ostro's vision providesa glimpse of the potential of making the DSN accessible to a broadercommunity.

  7. Conformal Visualization for Partially-Immersive Platforms

    PubMed Central

    Petkov, Kaloian; Papadopoulos, Charilaos; Zhang, Min; Kaufman, Arie E.; Gu, Xianfeng

    2010-01-01

    Current immersive VR systems such as the CAVE provide an effective platform for the immersive exploration of large 3D data. A major limitation is that in most cases at least one display surface is missing due to space, access or cost constraints. This partially-immersive visualization results in a substantial loss of visual information that may be acceptable for some applications, however it becomes a major obstacle for critical tasks, such as the analysis of medical data. We propose a conformal deformation rendering pipeline for the visualization of datasets on partially-immersive platforms. The angle-preserving conformal mapping approach is used to map the 360°3D view volume to arbitrary display configurations. It has the desirable property of preserving shapes under distortion, which is important for identifying features, especially in medical data. The conformal mapping is used for rasterization, realtime raytracing and volume rendering of the datasets. Since the technique is applied during the rendering, we can construct stereoscopic images from the data, which is usually not true for image-based distortion approaches. We demonstrate the stereo conformal mapping rendering pipeline in the partially-immersive 5-wall Immersive Cabin (IC) for virtual colonoscopy and architectural review. PMID:26279083

  8. NASA Hypersonic X-Plane Flight Development of Technologies and Capabilities for the 21st Century Access to Space

    NASA Technical Reports Server (NTRS)

    Hicks, John W.; Trippensee, Gary

    1997-01-01

    A new family of NASA experimental aircraft (X-planes) is being developed to uniquely, yet synergistically tackle a wide class of technologies to advance low-cost, efficient access to space for a range of payload classes. This family includes two non-air-breathing rocket-powered concepts, the X-33 and the X-34 aircraft, and two air-breathing vehicle concepts, the scramjet-powered Hyper-X and the rocket-based combined cycle flight vehicle. This report describes the NASA vision for reliable, reusable, fly-to-orbit spacecraft in relation to the current space shuttle capability. These hypersonic X-plane programs, their objectives, and their status are discussed. The respective technology sets and flight program approaches are compared and contrasted. Additionally, the synergy between these programs to advance the entire technology front in a uniform way is discussed. NASA's view of the value of in-flight hypersonic experimentation and technology development to act as the ultimate crucible for proving and accelerating technology readiness is provided. Finally, an opinion on end technology products and space access capabilities for the 21st century is offered.

  9. Accessing space: A catalogue of process, equipment and resources for commercial users, 1990

    NASA Technical Reports Server (NTRS)

    1990-01-01

    A catalogue is presented which is intended for commercial developers who are considering, or who have in progress, a project involving the microgravity environment of space or remote sensing of the Earth. An orientation is given to commercial space activities along with a current inventory of equipment, apparatus, carriers, vehicles, resources, and services available from NASA, other government agencies and U.S. industry. The information describes the array of resources that commercial users should consider when planning ground or space based developments. Many items listed have flown in space or been tested in labs and aboard aircraft and can be reused, revitalized, or adapted to suit specific requirements. New commercial ventures are encouraged to exploit existing inventory and expertise to the greatest extent possible.

  10. Small Satellites for Atmospheric and near earth Space sciences - the Indian perspectives of a low cost access to Space

    NASA Astrophysics Data System (ADS)

    Sridharan, R.

    Small satellites of 100-400 kg class are expected to play bigger roles in the years to come. With the advancement of technology in terms of miniaturization and also reliability, it has become possible to configure small satellites which otherwise would have demanded larger platforms, both in terms of weight and power. The atmospheric and near Earth space processes are truly multi-dimensional and are extremely complex with large temporal and spatial variability and also respond closely to the processes in the Sun. As a consequence, no single satellite mission would be able to provide the complete information thus warranting multiple missions. With the successful demonstration of multiple satellites launching capability, the spare capacity of the launch vehicles could be effectively and judiciously used for launching dedicated small scientific satellites as co passengers with negligible cost factor. This is viewed as an opening up of an otherwise difficult opportunity involving dedicated launches. With the prospect of multiple satellites for science missions becoming a reality the overall mission with an active life of 2-3 years could be realized with judicious choice of components. This is expected to bring in a larger user community in the country. The first step in this direction is the configuration of a modular micro and small satellite bus. The upcoming missions of TWSAT (Third world satellite), Youth Sat (active participation of the student community), SARAL (Satellite for ARGOs and Altimetry), SENSE/E and SENSE/P (Satellite for Earth's Near Space environment), ISTAG (Indian Satellite for Aerosols and Gases), are utilizing the above concepts. ISRO has also come out with AO's for Astronomy and Astrophysics payloads, as most of the stringent requirements of various experiments could be met with the small satellite platforms themselves. A brief outline of the upcoming and proposed activities would be presented and discussed in the talk.

  11. A packetised remote visual access data system for space station interactive payload operations.

    PubMed

    Carvell, R P

    1987-09-01

    Potential users of the pressurised Columbus elements, (the Attached Pressurised Module and the Man-Tended Free Flyer), were consulted in order to establish the requirements necessary to achieve effective and efficient remote interactive payload operations. These are briefly described and clearly indicate that the key to such operations is a versatile remote visual access (video) system which is well-tuned to the requirements of the users in both the on-board and ground segments. A packetised remote visual access data system is proposed which accommodates these requirements and offers a very flexible operational environment. It incorporates a scheme for optimising users' remote visual access to their experiments. Methods of implementing the necessary multiplexing and compression aspects of the system are discussed. A scheme for centralized on-board monitoring, which is complicated by the wide range of video sources required by the users, is outlined and aspects of the ground segment, in particular the problem is link delays, are considered. PMID:11542957

  12. Changing Chromatin Fiber Conformation by Nucleosome Repositioning

    PubMed Central

    Müller, Oliver; Kepper, Nick; Schöpflin, Robert; Ettig, Ramona; Rippe, Karsten; Wedemann, Gero

    2014-01-01

    Chromatin conformation is dynamic and heterogeneous with respect to nucleosome positions, which can be changed by chromatin remodeling complexes in the cell. These molecular machines hydrolyze ATP to translocate or evict nucleosomes, and establish loci with regularly and more irregularly spaced nucleosomes as well as nucleosome-depleted regions. The impact of nucleosome repositioning on the three-dimensional chromatin structure is only poorly understood. Here, we address this issue by using a coarse-grained computer model of arrays of 101 nucleosomes considering several chromatin fiber models with and without linker histones, respectively. We investigated the folding of the chain in dependence of the position of the central nucleosome by changing the length of the adjacent linker DNA in basepair steps. We found in our simulations that these translocations had a strong effect on the shape and properties of chromatin fibers: i), Fiber curvature and flexibility at the center were largely increased and long-range contacts between distant nucleosomes on the chain were promoted. ii), The highest destabilization of the fiber conformation occurred for a nucleosome shifted by two basepairs from regular spacing, whereas effects of linker DNA changes of ∼10 bp in phase with the helical twist of DNA were minimal. iii), A fiber conformation can stabilize a regular spacing of nucleosomes inasmuch as favorable stacking interactions between nucleosomes are facilitated. This can oppose nucleosome translocations and increase the energetic costs for chromatin remodeling. Our computational modeling framework makes it possible to describe the conformational heterogeneity of chromatin in terms of nucleosome positions, and thus advances theoretical models toward a better understanding of how genome compaction and access are regulated within the cell. PMID:25418099

  13. Maglev Launch: Ultra-low Cost, Ultra-high Volume Access to Space for Cargo and Humans

    NASA Astrophysics Data System (ADS)

    Powell, James; Maise, George; Rather, John

    2010-01-01

    Despite decades of efforts to reduce rocket launch costs, improvements are marginal. Launch cost to LEO for cargo is ~$10,000 per kg of payload, and to higher orbit and beyond much greater. Human access to the ISS costs $20 million for a single passenger. Unless launch costs are greatly reduced, large scale commercial use and human exploration of the solar system will not occur. A new approach for ultra low cost access to space-Maglev Launch-magnetically accelerates levitated spacecraft to orbital speeds, 8 km/sec or more, in evacuated tunnels on the surface, using Maglev technology like that operating in Japan for high speed passenger transport. The cost of electric energy to reach orbital speed is less than $1 per kilogram of payload. Two Maglev launch systems are described, the Gen-1System for unmanned cargo craft to orbit and Gen-2, for large-scale access of human to space. Magnetically levitated and propelled Gen-1 cargo craft accelerate in a 100 kilometer long evacuated tunnel, entering the atmosphere at the tunnel exit, which is located in high altitude terrain (~5000 meters) through an electrically powered ``MHD Window'' that prevents outside air from flowing into the tunnel. The Gen-1 cargo craft then coasts upwards to space where a small rocket burn, ~0.5 km/sec establishes, the final orbit. The Gen-1 reference design launches a 40 ton, 2 meter diameter spacecraft with 35 tons of payload. At 12 launches per day, a single Gen-1 facility could launch 150,000 tons annually. Using present costs for tunneling, superconductors, cryogenic equipment, materials, etc., the projected construction cost for the Gen-1 facility is 20 billion dollars. Amortization cost, plus Spacecraft and O&M costs, total $43 per kg of payload. For polar orbit launches, sites exist in Alaska, Russia, and China. For equatorial orbit launches, sites exist in the Andes and Africa. With funding, the Gen-1 system could operate by 2020 AD. The Gen-2 system requires more advanced technology

  14. The place of receptionists in access to primary care: Challenges in the space between community and consultation.

    PubMed

    Neuwelt, Pat M; Kearns, Robin A; Browne, Annette J

    2015-05-01

    At the point of entry to the health care system sit general practice receptionists (GPRs), a seldom studied employment group. The place of the receptionist involves both a location within the internal geography of the clinic and a position within the primary care team. Receptionists literally 'receive' those who phone or enter the clinic, and are a critical influence in their transformation from a 'person' to a 'patient'. This process occurs in a particular space: the 'waiting room'. We explore the waiting room and its dynamics in terms of 'acceptability', an under-examined aspect of access to primary care. We ask 'How do GPRs see their role with regard to patients with complex health and social needs, in light of the spatio-temporal constraints of their working environments?' We engaged receptionists as participants to explore perceptions of their roles and their workspaces, deriving narrative data from three focus groups involving 14 GPRs from 11 practices in the Northland region of New Zealand. The study employed an adapted form of grounded theory. Our findings indicate that GPRs are on the edge of the practice team, yet carry a complex role at the frontline, in the waiting space. They are de facto managers of this space; however, they have limited agency within general practice settings, due to the constraints imposed upon them by physical and organisational structures. The agency of GPRs is most evident in their ability to shape the social dynamics of the waiting space, and to frame the health care experience as positive for people whose usual experience is marginalisation. We conclude that, if well supported, receptionists have the potential to positively influence health care acceptability, and patients' access to care. PMID:25455478

  15. GeneLab: NASA's Open Access, Collaborative Platform for Systems Biology and Space Medicine

    NASA Technical Reports Server (NTRS)

    Berrios, Daniel C.; Thompson, Terri G.; Fogle, Homer W.; Rask, Jon C.; Coughlan, Joseph C.

    2015-01-01

    NASA is investing in GeneLab1 (http:genelab.nasa.gov), a multi-year effort to maximize utilization of the limited resources to conduct biological and medical research in space, principally aboard the International Space Station (ISS). High-throughput genomic, transcriptomic, proteomic or other omics analyses from experiments conducted on the ISS will be stored in the GeneLab Data Systems (GLDS), an open-science information system that will also include a biocomputation platform with collaborative science capabilities, to enable the discovery and validation of molecular networks.

  16. Charged conformal Killing spinors

    SciTech Connect

    Lischewski, Andree

    2015-01-15

    We study the twistor equation on pseudo-Riemannian Spin{sup c}-manifolds whose solutions we call charged conformal Killing spinors (CCKSs). We derive several integrability conditions for the existence of CCKS and study their relations to spinor bilinears. A construction principle for Lorentzian manifolds admitting CCKS with nontrivial charge starting from CR-geometry is presented. We obtain a partial classification result in the Lorentzian case under the additional assumption that the associated Dirac current is normal conformal and complete the classification of manifolds admitting CCKS in all dimensions and signatures ≤5 which has recently been initiated in the study of supersymmetric field theories on curved space.

  17. Bias and Evolution of the Mutationally Accessible Phenotypic Space in a Developmental System

    PubMed Central

    Braendle, Christian; Baer, Charles F.; Félix, Marie-Anne

    2010-01-01

    Genetic and developmental architecture may bias the mutationally available phenotypic spectrum. Although such asymmetries in the introduction of variation may influence possible evolutionary trajectories, we lack quantitative characterization of biases in mutationally inducible phenotypic variation, their genotype-dependence, and their underlying molecular and developmental causes. Here we quantify the mutationally accessible phenotypic spectrum of the vulval developmental system using mutation accumulation (MA) lines derived from four wild isolates of the nematodes Caenorhabditis elegans and C. briggsae. The results confirm that on average, spontaneous mutations degrade developmental precision, with MA lines showing a low, yet consistently increased, proportion of developmental defects and variants. This result indicates strong purifying selection acting to maintain an invariant vulval phenotype. Both developmental system and genotype significantly bias the spectrum of mutationally inducible phenotypic variants. First, irrespective of genotype, there is a developmental bias, such that certain phenotypic variants are commonly induced by MA, while others are very rarely or never induced. Second, we found that both the degree and spectrum of mutationally accessible phenotypic variation are genotype-dependent. Overall, C. briggsae MA lines exhibited a two-fold higher decline in precision than the C. elegans MA lines. Moreover, the propensity to generate specific developmental variants depended on the genetic background. We show that such genotype-specific developmental biases are likely due to cryptic quantitative variation in activities of underlying molecular cascades. This analysis allowed us to identify the mutationally most sensitive elements of the vulval developmental system, which may indicate axes of potential evolutionary variation. Consistent with this scenario, we found that evolutionary trends in the vulval system concern the phenotypic characters that

  18. A Characterization of Endurance in 64 Mbit Ferroelectric Random Access Memory by Analyzing the Space Charge Concentration

    NASA Astrophysics Data System (ADS)

    Lee, Eun Sun; Jung, Dong Jin; Kang, Young Min; Kim, Hyun Ho; Hong, Young Ki; Park, Jung Hoon; Kuk Kang, Seung; Kim, Jae Hyun; San Kim, Hee; Jung, Won Woong; Ahn, Woo Song; Jung, Ju Young; Kang, Jin Young; Choi, Do Yeon; Goh, Han Kyung; Kim, Song Yi; Lee, Sang Young; Jeong, Hong Sik

    2008-04-01

    Space charge concentration due to fatigue cycles was examined with an adequate modeling in order to expect read/write endurance of a 64 Mbit one-transistor and one-capacitor (1T1C) ferroelectric random access memory (FRAM). For monitoring the change in space charge concentration according to fatigue cycles, we assumed that our ferroelectric capacitor is governed by a partially depleted Schottky conduction model. With this, the space charge concentration at the each decade of the fatigue cycles was calculated by measuring the current-voltage characteristics. The space charge concentration at the initial stage was evaluated into 1.95 ×1020 and 2.16 ×1020/cm3 after the 1011 cycles. The concentration of 2.29 ×1020/cm3 was expected at the fatigue cycles of 1016 through a linear regression of the concentration plot against fatigue cycles. Accordingly, it could be said that our ferroelectric capacitor has few problems of endurance up to the 1016 cycles considering the concentration of ˜1020 and the film thickness of 80 nm. Other empirical data obtained in the capacitor level after full integration are supporting this expectation as well.

  19. Group space allowance has little effect on sow health, productivity, or welfare in a free-access stall system.

    PubMed

    Mack, L A; Lay, D C; Eicher, S D; Johnson, A K; Richert, B T; Pajor, E A

    2014-06-01

    Free-access stalls allow sows to choose the protection of a stall or use of a shared group space. This study investigated the effect of group space width, 0.91 (SS), 2.13 (IS), and 3.05 (LS) m, on the health, production, behavior, and welfare of gestating sows. Nine replications of 21 (N = 189) gestating sows were used. At gestational d 35.4 ± 2.3, the pregnant sows were distributed into 3 pens of 7 sows, where they remained until 104.6 ± 3.5 d. Each treatment pen had 7 free-access stalls and a group space that together provided 1.93 (SS), 2.68 (IS), or 3.24 (LS) m(2)/sow. Baseline measurements were obtained before mixing. Back fat depth, BW, BCS, and lameness were measured monthly, and skin lesions were scored weekly. Blood was collected monthly for hematological, immunological, and cortisol analyses. Sow behavior was video recorded continuously during the initial 4 d of treatment and 24 h every other week thereafter. Behavior was analyzed for location, posture, pen investigation, social contact, and aggression. Skin response to the mitogen concanavalin A (Con A) was tested at mean gestational d 106. Litter characteristics including size and weight were collected at birth and weaning. The data were analyzed using a mixed model. Multiple comparisons were adjusted with the Tukey-Kramer and Bejamini-Hochberg methods. Group space allowance had no effect on any measure of sow health, physiology, or production (P ≥ 0.10). Sows in the SS, IS, and LS pens spent 77.88% ± 3.88%, 66.02% ± 3.87%, and 63.64% ± 3.91%, respectively, of their time in the free-access stalls (P = 0.12). However, SS sows used the group space less than IS and LS sows (P = 0.01). Overall, pen investigatory behavior was not affected by group space allowance (P = 0.91). Sows in the LS pens spent more time in a social group than SS sows (P = 0.02), whereas sows in IS pens were intermediate to, but not different from, the other treatments (P ≥ 0.10). The size of the social groups was also

  20. A monograph of the National Space Transportation System Office (NSTSO) integration activities conducted at the NASA Lyndon B. Johnson Space Center for the EASE/ACCESS payload flown on STS 61-B

    NASA Technical Reports Server (NTRS)

    Chassay, Charles

    1987-01-01

    The integration process of activities conducted at the NASA Lyndon B. Johnson Space Center (JSC) for the Experimental Assembly of Structures in Extravehicular activity (EASE)/Assembly Concept for Construction of Erectable Space Structures (ACCESS) payload is provided as a subset to the standard payload integration process used by the NASA Space Transportation System (STS) to fly payloads on the Space Shuttle. The EASE/ACCESS payload integration activities are chronologically reviewed beginning with the initiation of the flight manifesting and integration process. The development and documentation of the EASE/ACCESS integration requirements are also discussed along with the implementation of the mission integration activities and the engineering assessments supporting the flight integration process. In addition, the STS management support organizations, the payload safety process leading to the STS 61-B flight certification, and the overall EASE/ACCESS integration schedule are presented.

  1. Influence of Crystal Packing on Global Protein Conformation

    NASA Astrophysics Data System (ADS)

    Ahlstrom, Logan; Miyashita, Osamu

    2011-10-01

    X-ray crystallography is the most robust method for solving protein structure. However, packing forces in the crystal lattice select just a snapshot of a protein's conformational ensemble, whereas proteins are flexible and can adopt different conformations. Here we compare molecular dynamics (MD) simulations in solution and the crystal lattice to add dynamical insight to the static X-ray images of proteins. As a model system, we consider the λ Cro dimer, whose solved X-ray structures range from a ``closed'' to an ``open'' global conformation. Free energy profiles depicting the conformational space sampled by the dimer in solution show some reported structures correspond to stable states. Yet other conformations, while accessible, lie higher in energy, indicating the effect of crystal packing. Subsequent crystal MD simulations estimated the strength of packing interfaces in the lattice, showing the influence of crystal form and mutation in stabilizing different dimer conformations. Our quantitative results will aid analysis of X-ray data in establishing protein structure-function relationships.

  2. United States Human Access to Space, Exploration of the Moon and Preparation for Mars Exploration

    NASA Technical Reports Server (NTRS)

    Rhatigan, Jennifer L.

    2009-01-01

    In the past, men like Leonardo da Vinci and Jules Verne imagined the future and envisioned fantastic inventions such as winged flying machines, submarines, and parachutes, and posited human adventures like transoceanic flight and journeys to the Moon. Today, many of their ideas are reality and form the basis for our modern world. While individual visionaries like da Vinci and Verne are remembered for the accuracy of their predictions, today entire nations are involved in the process of envisioning and defining the future development of mankind, both on and beyond the Earth itself. Recently, Russian, European, and Chinese teams have all announced plans for developing their own next generation human space vehicles. The Chinese have announced their intention to conduct human lunar exploration, and have flown three crewed space missions since 2003, including a flight with three crew members to test their extravehicular (spacewalking) capabilities in September 2008. Very soon, the prestige, economic development, scientific discovery, and strategic security advantage historically associated with leadership in space exploration and exploitation may no longer be the undisputed province of the United States. Much like the sponsors of the seafaring explorers of da Vinci's age, we are motivated by the opportunity to obtain new knowledge and new resources for the growth and development of our own civilization. NASA's new Constellation Program, established in 2005, is tasked with maintaining the United States leadership in space, exploring the Moon, creating a sustained human lunar presence, and eventually extending human operations to Mars and beyond. Through 2008, the Constellation Program developed a full set of detailed program requirements and is now completing the preliminary design phase for the new Orion Crew Exploration Vehicle (CEV), the Ares I Crew Launch Vehicle, and the associated infrastructure necessary for humans to explore the Moon. Component testing is well

  3. Human factors in space station architecture 2. EVA access facility: A comparative analysis of 4 concepts for on-orbit space suit servicing

    NASA Technical Reports Server (NTRS)

    Cohen, Marc M.; Bussolari, Steven

    1987-01-01

    Four concepts for on-orbit spacesuit donning, doffing, servicing, check-out, egress and ingress are presented. These are: the Space Transportation System (STS) Type (shuttle system enlarged), the Transit Airlock (Shuttle Airlock with suit servicing removed from the pump-down chamber), the Suitport (a rear-entry suit mates to a port in the airlock wall), and the Crewlock (a small, individual, conformal airlock). Each of these four concepts is compared through a series of seven steps representing a typical Extra Vehicular Activity (EVA) mission: (1) Predonning suit preparation; (2) Portable Life Support System (PLSS) preparation; (3) Suit Donning and Final Check; (4) Egress/Ingress; (5) Mid-EVA rest period; (6) Post-EVA Securing; (7) Non-Routine Maintenance. The different characteristics of each concept are articulated through this step-by-step approach. Recommendations concerning an approach for further evaluations of airlock geometry, anthropometrics, ergonomics, and functional efficiency are made. The key recommendation is that before any particular airlock can be designed, the full range of spacesuit servicing functions must be considered, including timelines that are most supportive of EVA human productivity.

  4. Orion: Design of a system for assured low-cost human access to space

    NASA Technical Reports Server (NTRS)

    Elvander, Josh; Heifetz, Andy; Hunt, Teresa; Zhu, Martin

    1994-01-01

    In recent years, Congress and the American people have begun to seriously question the role and importance of future manned spaceflight. This is mainly due to two factors: a decline in technical competition caused by the collapse of communism, and the high costs associated with the Space Shuttle transportation system. With these factors in mind, the ORION system was designed to enable manned spaceflight at a low cost, while maintaining the ability to carry out diverse missions, each with a high degree of flexibility. It is capable of performing satellite servicing missions, supporting a space station via crew rotation and resupply, and delivering satellites into geosynchronous orbit. The components of the system are a primary launch module, an upper stage, and a manned spacecraft capable of dynamic reentry. For satellite servicing and space station resupply missions, the ORION system utilizes three primary modules, an upper stage, and the spacecraft, which is delivered to low earth orbit and used to rendezvous, transfer materials, and make repairs. For launching a geosynchronous satellite, one primary module and an upper stage are used to deliver the satellite, along with an apogee kick motor, into orbit. The system is designed with reusability and modularity in mind in an attempt to lower cost.

  5. Rocketdyne Development of RBCC Engine for Low Cost Access to Space

    NASA Technical Reports Server (NTRS)

    Ortwerth, P.; Ratekin, G.; Goldman, A.; Emanuel, M.; Ketchum, A.; Horn, M.

    1997-01-01

    Rocketdyne is pursuing the conceptual design and development of a Rocket Based Combined Cycle (RBCC) engine for booster and SSTO, advanced reusable space transportation ARTT systems under contract with NASA Marshall Space Flight Center. The Rocketdyne concept is fixed geometry integrated Rocket, Ram Scramjet which is Hydrogen fueled and uses Hydrogen regenerative cooling. Vision vehicle integration studies have determined that scramjet operation to Mach 12 has high payoff for low cost reusable space transportation. Rocketdyne is internally developing versions of the concept for other applications in high speed aircraft and missiles with Hydrocarbon fuel systems. Subscale engine ground testing is underway for all modes of operation from takeoff to Mach 8. High altitude Rocket only mode tests will be completed as part of the ground test program to validate high expansion ratio performance. A unique feature of the ground test series is the inclusion of dynamic trajectory simulation with real time Mach number, altitude, engine throttling, and RBCC mode changes in a specially modified freejet test facility at GASL. Preliminary cold flow Air Augmented Rocket mode test results and Short Combustor tests have met program goals and have been used to integrate all modes of operation in a single combustor design with a fixed geometry inlet for design confirmation tests. A water cooled subscale engine is being fabricated and installed for test beginning the last quarter of 1997.

  6. Towards conformal loop quantum gravity

    NASA Astrophysics Data System (ADS)

    H-T Wang, Charles

    2006-03-01

    A discussion is given of recent developments in canonical gravity that assimilates the conformal analysis of gravitational degrees of freedom. The work is motivated by the problem of time in quantum gravity and is carried out at the metric and the triad levels. At the metric level, it is shown that by extending the Arnowitt-Deser-Misner (ADM) phase space of general relativity (GR), a conformal form of geometrodynamics can be constructed. In addition to the Hamiltonian and Diffeomorphism constraints, an extra first class constraint is introduced to generate conformal transformations. This phase space consists of York's mean extrinsic curvature time, conformal three-metric and their momenta. At the triad level, the phase space of GR is further enlarged by incorporating spin-gauge as well as conformal symmetries. This leads to a canonical formulation of GR using a new set of real spin connection variables. The resulting gravitational constraints are first class, consisting of the Hamiltonian constraint and the canonical generators for spin-gauge and conformorphism transformations. The formulation has a remarkable feature of being parameter-free. Indeed, it is shown that a conformal parameter of the Barbero-Immirzi type can be absorbed by the conformal symmetry of the extended phase space. This gives rise to an alternative approach to loop quantum gravity that addresses both the conceptual problem of time and the technical problem of functional calculus in quantum gravity.

  7. Feasibility of ultrasound-guided epidural access at the lumbo-sacral space in dogs.

    PubMed

    Liotta, Annalisa; Busoni, Valeria; Carrozzo, Maria Valentina; Sandersen, Charlotte; Gabriel, Annick; Bolen, Géraldine

    2015-01-01

    Epidural injections are commonly performed blindly in veterinary medicine. The aims of this study were to describe the lumbosacral ultrasonographic anatomy and to assess the feasibility of an ultrasound-guided epidural injection technique in dogs. A cross sectional anatomic atlas of the lumbosacral region and ex vivo ultrasound images were obtained in two cadavers to describe the ultrasound anatomy and to identify the landmarks. Sixteen normal weight canine cadavers were used to establish two variations of the technique for direct ultrasound-guided injection, using spinal needles or epidural catheters. The technique was finally performed in two normal weight cadavers, in two overweight cadavers and in five live dogs with radiographic abnormalities resulting of the lumbosacral spine. Contrast medium was injected and CT was used to assess the success of the injection. The anatomic landmarks to carry out the procedure were the seventh lumbar vertebra, the iliac wings, and the first sacral vertebra. The target for directing the needle was the trapezoid-shaped echogenic zone between the contiguous articular facets of the lumbosacral vertebral canal visualized in a parasagittal plane. The spinal needle or epidural catheter was inserted in a 45° craniodorsal-caudoventral direction through the subcutaneous tissue and the interarcuate ligament until reaching the epidural space. CT examination confirmed the presence of contrast medium in the epidural space in 25/25 dogs, although a variable contamination of the subarachnoid space was also noted. Findings indicated that this ultrasound-guided epidural injection technique is feasible for normal weight and overweight dogs, with and without radiographic abnormalities of the spine. PMID:25187175

  8. Ablation modeling of electro-magnetically launched projectile for access to space

    NASA Astrophysics Data System (ADS)

    Gosse, Ryan C.

    It has been proposed to study and identify the technical issues involved in the launch to space of micro-satellite payloads using an airborne electromagnetic launcher (AEML). A computational fluid dynamics (CFD) computer code was developed to help characterize the aerothermal issues involved with the flight of the projectile as it exits the Earth's atmosphere. Conceptual geometries were chosen to evaluate the feasibility of launching to orbit from an aircraft. Due to expected high heating fluxes, carboncarbon material was selected for the thermal protection system (TPS). Results of the conceptual study are presented and used to evaluate the practicality of the AEML concept.

  9. REUSABLE PROPULSION ARCHITECTURE FOR SUSTAINABLE LOW-COST ACCESS TO SPACE

    NASA Technical Reports Server (NTRS)

    Bonometti, Joseph; Frame, Kyle L.; Dankanich, John W.

    2005-01-01

    Two transportation architecture changes are presented at either end of a conventional two-stage rocket flight: 1) Air launch using a large, conventional, pod hauler design (i.e., Crossbow)ans 2) Momentum exchange tether (i.e., an in-space asset like MXER). Air launch has ana analytically justified cost reduction of approx. 10%, but its intangible benefits suggest real-world operations cost reductions much higher: 1) Inherent launch safety; 2) Mission Risk Reduction; 3) Favorable payload/rocket limitations; and 4) Leveraging the aircraft for other uses (military transport, commercial cargo, public outreach activities, etc.)

  10. The alloantigenic sites of alpha3alpha4alpha5(IV) collagen: pathogenic X-linked alport alloantibodies target two accessible conformational epitopes in the alpha5NC1 domain.

    PubMed

    Kang, Jeong Suk; Kashtan, Clifford E; Turner, A Neil; Heidet, Laurence; Hudson, Billy G; Borza, Dorin-Bogdan

    2007-04-01

    Anti-glomerular basement membrane (GBM) antibody nephritis is caused by an autoimmune or alloimmune reaction to the NC1 domains of alpha3alpha4alpha5(IV) collagen. Some patients with X-linked Alport syndrome (XLAS) develop post-transplant nephritis mediated by pathogenic anti-GBM alloantibodies to collagen IV chains present in the renal allograft but absent from the tissues of the patient. In this work, the epitopes targeted by alloantibodies from these patients were identified and characterized. All XLAS alloantibodies recognized conformational epitopes in the NC1 domain of alpha5(IV) collagen, which were mapped using chimeric alpha1/alpha5 NC1 domains expressed in mammalian cells. Allograft-eluted alloantibodies mainly targeted two conformational alloepitopes mapping to alpha5NC1 residues 1-45 and 114-168. These regions also encompassed the major epitopes of circulating XLAS alloantibodies, which in some patients additionally targeted alpha5NC1 residues 169-229. Both kidney-eluted and circulating alloantibodies to alpha5NC1 distinctively targeted epitopes accessible in the alpha3alpha4alpha5NC1 hexamers of human GBM, unlike anti-GBM autoantibodies, which targeted sequestered alpha3NC1 epitopes. The results identify two immunodominant alpha5NC1 epitopes as major alloantigenic sites of alpha3alpha4alpha5(IV) collagen specifically implicated in the pathogenesis of post-transplant nephritis in XLAS patients. The contrast between the accessibility of these alloepitopes and the crypticity of autoepitopes indicates that distinct molecular forms of antigen may initiate the immunopathogenic processes in the two forms of anti-GBM disease. PMID:17293596

  11. Rockot-an available launch system for affordable access to space

    NASA Astrophysics Data System (ADS)

    de Vries, U.; Kinnersley, M.; Freeborn, P.

    2000-01-01

    The Rockot launcher will perform its fifth launch, the first commercial launch, in Spring 2000 from the Plesetsk Cosmodrome in Northern Russia carrying two American satellites into a LEO orbit. In preparation for that a launch pad verification flight will be carried out in November this year to prove the functionality of the adapted facilities at the Plesetsk launch site and by placing a Russian satellite into a highly inclined orbit. The results of the launches will be described in detail in the paper as well as the installations at the launch site. Eurockot, the German-Russian joint-venture company marketing and managing the Rockot launch vehicle is meanwhile an integral part of the space launch community. Eurockot was formed by DaimlerChrysler Aerospace and Khrunichev State Research and Production Space Center. A brief overview of its activities, the commercial program and the performance/services offered by Eurockot is presented. Rockot can launch satellites weighing up to 1850 kg into polar or other low earth orbits (LEO). The Rockot launch vehicle is based on the former Russian SS-19 strategic missile. The first and second stages are inherited from the SS-19, the third stage Breeze which has already been developed has multiple ignition capability. The Breeze upper stage is under production at Khrunichev in Moscow. The Rockot launch system is flight proven and is operated from the Plesetsk as well as from the Baikonur launch site. .

  12. The DEMETER micro satellite launch campaign: A cheap access to space

    NASA Astrophysics Data System (ADS)

    Dubourg, Vincent; Kainov, Vladimir; Thoby, Michel; Silkin, Olexyi; Solovey, Vladislav

    The CNES micro satellite DEMETER has been successfully launched on June 29th 2004 by a DNEPR launcher, from the Baïkonur Cosmodrome. DEMETER was the main payload among eight co-passengers. Initiated by CNES in 1998, DEMETER is the first model of the MYRIADE micro satellites line of products; its objectives are both scientific and technological; the satellite has now been flying for science for almost one year. The space head module of the launcher has been developed by the Ukrainian company Yuzhnoye, and a complete fit check test campaign has been performed in December 2003 to confirm the compatibility of the payloads with their launcher interfaces. The launch campaign took place at Baïkonur Cosmodrome from the end of May to the end of June 2004, implying a close partnership between the CNES satellite team and the Russian and Ukrainian launcher authorities: DEMETER has been a pioneer not only for the concept itself, but also for being the first satellite of this range (three axis stabilized, including an hydrazine propulsion system and developed by a national space agency) to be launched on a former intercontinental ballistic missile SS18. The launch service was managed by ISC Kosmotras, and it was the first sun synchronous orbit launch for DNEPR. The present paper deals with the details of DEMETER satellite and its launch, and preliminary results.

  13. Impaired access to semantic memory for the cognition of geographic space in Alzheimer's disease.

    PubMed

    Mazzei, Debora; Brugnolo, Andrea; Dessi, Barbara; Girtler, Nicola; Famà, Francesco; Rizza, Elisa; Nobili, Flavio; Rodriguez, Guido

    2010-01-01

    This study explores the possibility to capitalize from a widely used semantic fluency test, in order to investigate aspects of topographical space representation, still poorly studied in neurodegenerative diseases. Twenty-six patients with mild Alzheimer's disease (AD) and 13 healthy control (CTR) subjects underwent neuropsychological assessment at baseline (T0) and about 2 years later (T1). The cities named during category verbal fluency test ("names of cities") were marked on a map, and the polygon perimeter obtained by joining the external points was computed. Mini-mental state examination (MMSE) score, number of cities named and perimeter length were compared between T0 and T1, both within-group and between groups. MMSE score and number of cities significantly differed between AD and CTR both at T0 and at T1; perimeter length differed significantly only at T1. Between T0 and T1, all the three parameters significantly decreased in AD, while they were substantially unchanged in CTR. Besides a reduction of semantic verbal fluency, there seems to be a 'restriction' of mental geographic space representation already in mild AD. These findings should be confirmed and exploited by further ad hoc investigations. PMID:19427044

  14. A strand-passage conformation of DNA gyrase is required to allow the bacterial toxin, CcdB, to access its binding site.

    PubMed

    Smith, Andrew B; Maxwell, Anthony

    2006-01-01

    DNA gyrase is the only topoisomerase able to introduce negative supercoils into DNA. Absent in humans, gyrase is a successful target for antibacterial drugs. However, increasing drug resistance is a serious problem and new agents are urgently needed. The naturally-produced Escherichia coli toxin CcdB has been shown to target gyrase by what is predicted to be a novel mechanism. CcdB has been previously shown to stabilize the gyrase 'cleavage complex', but it has not been shown to inhibit the catalytic reactions of gyrase. We present data showing that CcdB does indeed inhibit the catalytic reactions of gyrase by stabilization of the cleavage complex and that the GyrA C-terminal DNA-wrapping domain and the GyrB N-terminal ATPase domain are dispensable for CcdB's action. We further investigate the role of specific GyrA residues in the action of CcdB by site-directed mutagenesis; these data corroborate a model for CcdB action based on a recent crystal structure of a CcdB-GyrA fragment complex. From this work, we are now able to present a model for CcdB action that explains all previous observations relating to CcdB-gyrase interaction. CcdB action requires a conformation of gyrase that is only revealed when DNA strand passage is taking place. PMID:16963775

  15. Photosynthetic flagellates as model systems for accessing the impact of space conditions on plants

    NASA Astrophysics Data System (ADS)

    Lebert, Michael; Richter, Peter; Häder, Donat

    Plants are an integral part of the exploration attempts for the planned missions to Mars and Moon. Photosynthetic, motile flagellates like Euglena gracilis can serve as model systems for the better understanding of the impact of microgravity and cosmic radiation on plants. Recent parabolic flights indicate that photosynthesis is impaired by microgravity. While oxygen production decreased during the short-term microgravity phases, other photosynthetic parameters remained constant or increased (photosynthetic yield and Ft as indicated by Pulse Amplitude Modulated Fluorescence measurements (PAM)). Ground-based long-term measurements in static bioreactors indicate a strong circadian rhythm of the related PAM-accessible parameters including oxygen production. Besides the problem of scientific analysis of these findings, practical implications with respect to life support systems or controlled environmental systems (CES) are significant. In two FOTON missions a CES system (AQUACELLS and its successor OMEGAHAB) was flown. The detailed analysis is still ongoing. In the paper oxygen production rates are compared to reference experiments on ground. In addition, the results of an upcoming parabolic flight campaign centred around fast PAM kinetics for a closer understanding of the impaired photosynthetic parameters will be presented.

  16. I(sup STAR), NASA's Next Step in Air-Breathing Propulsion for Space Access

    NASA Technical Reports Server (NTRS)

    Hutt, John J.; McArthur, Craig; Cook, Stephen (Technical Monitor)

    2001-01-01

    The United States' National Aeronautics and Space Administration (NASA) has established a strategic plan for future activities in space. A primary goal of this plan is to make drastic improvements in the cost and safety of earth to low-earth-orbit transportation. One approach to achieving this goal is through the development of highly reusable, highly reliable space transportation systems analogous to the commercial airline system. In the year 2000, NASA selected the Rocket Based Combined Cycle (RBCC) engine as the next logical step towards this goal. NASA will develop a complete flight-weight, pump-fed engine system under the Integrated System Test of an Airbreathing Rocket (I(sup STAR)) Project. The objective of this project is develop a reusable engine capable of self-powering a vehicle through the air-augmented rocket, ramjet and scramjet modes required in all RBCC based operational vehicle concepts. The project is currently approved and funded to develop the engine through ground test demonstration. Plans are in place to proceed with flight demonstration pending funding approval. The project is in formulation phase and the Preliminary Requirements Review has been completed. The engine system and vehicle have been selected at the conceptual level. The I(sup STAR) engine concept is based on an air-breathing flowpath downselected from three configurations evaluated in NASA's Advanced Reusable Technology contract. The selected flowpath features rocket thrust chambers integrated into struts separating modular flowpath ducts, a variable geometry inlet, and a thermally choked throat. The engine will be approximately 220 inches long and 79 inches wide and fueled with a hydrocarbon fuel using liquid oxygen as the primary oxidizer candidate. The primary concept for the pump turbine drive is pressure-fed catalyzed hydrogen peroxide. In order to control costs, the flight demonstration vehicle will be launched from a B-52 aircraft. The vehicle concept is based on the Air

  17. Community Access to the C/NOFS Satellite Data -- Facilitating New Opportunities for Space Weather Research

    NASA Astrophysics Data System (ADS)

    Martin, S.; de La Beaujardiere, O.; Hunton, D.; Wilson, G.; Roddy, P.; Coley, R.; Heelis, R.; Earle, G.; Straus, P.; Bernhardt, P.; Bromund, K.; Candey, R.; Pfaff, R.; Rowland, D.; Holzworth, R.; Kessel, M.

    2008-12-01

    The Air Force Communication/Navigation Outage Forecasting System (C/NOFS) satellite was launched on April 17, 2008 into a low latitude orbit (401 by 867 km, 13 deg inclination) and is designed to understand, model, and forecast the presence of ionospheric irregularities that cause scintillations and other radiowave disruptions. Its instruments include those that sample the plasma density and temperature, DC/AC electric fields, DC magnetic fields, ion drift velocity, neutral density, and GPS occultations. A radiowave tomography experiment and a lightning detector are also included on the satellite. C/NOFS provides a tremendous opportunity to merge space-based and ground-based observations and research, while engendering comparisons with, and data input to, the latest ionospheric models and theoretical calculations and simulations. To help coordinate this research and exchange of data products, the C/NOFS satellite data will be made available to the community through the Coordinated Data Analysis web site (http://cdaweb.gsfc.nasa.gov/) that resides at the NASA/Goddard Space Flight Center. The data will be distributed via FTP, OPENDAP (data streaming), HTTP, and web services with output in CDF, ASCII listings, PDF, and PS formats. This activity is sponsored by the NASA/Living With a Star program. This data distribution web site is in addition to the main Air Force Research Laboratory web site for the C/NOFS program that is located at http://www.kirtland.af.mil/library/factsheets/factsheet.asp?id=12776 and includes links to the C/NOFS instrument web sites, ground-based research, and satellite updates. A description of the C/NOFS satellite instruments and their standard data products available to the community via the CDA web site will be provided.

  18. Space Science IS Accessible to Students with Exceptional Needs: Results from Exceptional Needs Workshops

    NASA Astrophysics Data System (ADS)

    Runyon, C. J.; Merritt, M.; Guimond, K.

    2003-12-01

    The majority of students with disabilities in the US are required to achieve the same academic levels as their non-impaired peers. Unfortunately, there are few specialized materials to help these exceptional students. To assist students in meeting their goals, SERCH, a NASA Office of Space Science Broker/Facilitator, has been working with NASA education product developers and educators from informal and formal settings to identify what kinds of materials they need and what mediums will work best. As a result of both direct classrooms observations and hands-on workshops we have begun generating adaptive lessons plans that meet the national standards for Science, Technology, Engineering and Mathematics. During the workshops, participants simulate various disabilities (e.g., hearing, vision, orthopedic impairments, learning difficulties) while working through Space Science activities and discuss necessary adaptations/modifications in real-time. For example, we modified the Solar System Distance activity first designed by ASU to include the use of larger beads or pom-poms instead of the suggested small plastic beads. This simple adaptation permits students with orthopedic impairments to more readily take part in the lesson and to actively "observe" the distance between the planets. Examples of this activity and more will be illustrated. In addition to making modifications and suggestions for adaptations, workshop participants shared many simple recommendations that can help ALL learners participate more readily in classroom activities and discussions. Among these are: (1) Use simple, sans-serif fonts and high contrast presentation media (e.g., white text on black is most effective); (2) Repetition and use of multiple presentation modes is very helpful. (3) Actively involve the learner, and (4) Keep things simple to begin with, then work toward the more complex - think of the audience, the ultimate user.

  19. Transvenous Access to the Pericardial Space: A Novel Approach to Epicardial Lead Implantation for Cardiac Resynchronization Therapy

    PubMed Central

    MICKELSEN, STEVEN R.; ASHIKAGA, HIROSHI; DESILVA, RANIL; RAVAL, AMISH N.; MCVEIGH, ELLIOT; KUSUMOTO, FRED

    2007-01-01

    Background: Percutaneous access to the pericardial space (PS) may be useful for a number of therapeutic modalities including implantation of epicardial pacing leads. We have developed a catheter-based transvenous method to access the PS for implanting chronic medical devices. Methods: In eight pigs, a transseptal Mullins sheath and Brockenbrough needle were introduced into the right atrium (RA) from the jugular vein under fluoroscopic guidance. The PS was entered through a controlled puncture of the terminal anterior superior vena cava (SVC) (n = 7) or right atrial appendage (n = 1). A guidewire was advanced through the transseptal sheath, which was then removed leaving the wire in PS. The guidewire was used to direct both passive and active fixation pacing leads into the PS. Pacing was attempted and lead position was confirmed by cine fluoroscopy. Animals were sacrificed acutely and at 2 and 6 weeks. Results: All animals survived the procedure. Pericardial effusion (PE) during the procedure was hemodynamically significant in four of the eight animals. At necropsy, lead exit sites appeared to heal without complication at 2 and 6 weeks. Volume of pericardial fluid was 10.8 ± 6.2 mL and appeared normal in four of the six chronic animals. Moderate fibrinous deposition was observed in two animals, which had exhibited significant over-procedural PE. Conclusions: Access to the PS via a transvenous approach is feasible. Pacing leads can be negotiated into this region. The puncture site heals with the lead in place. Further development should focus on eliminating PE and performing this technique in appropriate heart failure models. PMID:16221257

  20. The Fab Conformations in the Solution Structure of Human Immunoglobulin G4 (IgG4) Restrict Access to Its Fc Region

    PubMed Central

    Rayner, Lucy E.; Hui, Gar Kay; Gor, Jayesh; Heenan, Richard K.; Dalby, Paul A.; Perkins, Stephen J.

    2014-01-01

    Human IgG4 antibody shows therapeutically useful properties compared with the IgG1, IgG2, and IgG3 subclasses. Thus IgG4 does not activate complement and shows conformational variability. These properties are attributable to its hinge region, which is the shortest of the four IgG subclasses. Using high throughput scattering methods, we studied the solution structure of wild-type IgG4(Ser222) and a hinge mutant IgG4(Pro222) in different buffers and temperatures where the proline substitution suppresses the formation of half-antibody. Analytical ultracentrifugation showed that both IgG4 forms were principally monomeric with sedimentation coefficients s20,w0 of 6.6–6.8 S. A monomer-dimer equilibrium was observed in heavy water buffer at low temperature. Scattering showed that the x-ray radius of gyration Rg was unchanged with concentration in 50–250 mm NaCl buffers, whereas the neutron Rg values showed a concentration-dependent increase as the temperature decreased in heavy water buffers. The distance distribution curves (P(r)) revealed two peaks, M1 and M2, that shifted below 2 mg/ml to indicate concentration-dependent IgG4 structures in addition to IgG4 dimer formation at high concentration in heavy water. Constrained x-ray and neutron scattering modeling revealed asymmetric solution structures for IgG4(Ser222) with extended hinge structures. The IgG4(Pro222) structure was similar. Both IgG4 structures showed that their Fab regions were positioned close enough to the Fc region to restrict C1q binding. Our new molecular models for IgG4 explain its inability to activate complement and clarify aspects of its stability and function for therapeutic applications. PMID:24876381

  1. The History and Promise of Combined Cycle Engines for Access to Space Applications

    NASA Technical Reports Server (NTRS)

    Clark, Casie

    2010-01-01

    For the summer of 2010, I have been working in the Aerodynamics and Propulsion Branch at NASA Dryden Flight Research Center studying combined-cycle engines, a high speed propulsion concept. Combined cycle engines integrate multiple propulsion systems into a single engine capable of running in multiple modes. These different modes allow the engine to be extremely versatile and efficient in varied flight conditions. The two most common types of combined cycle engines are Rocket-Based Combined Cycle (RBCC) and Turbine Based Combined Cycle (TBCC). The RBCC essentially combines a rocket and ramjet engine, while the TBCC integrates a turbojet and ramjet1. These two engines are able to switch between different propulsion modes to achieve maximum performance. Extensive conceptual and ground test studies of RBCC engines have been undertaken; however, an RBCC engine has never, to my knowledge, been demonstrated in flight. RBCC engines are of particular interest because they could potentially power a reusable launch vehicle (RLV) into space. The TBCC has been flight tested and shown to be effective at reaching supersonic speeds, most notably in the SR-71 Blackbird2.

  2. Projectors, shadows, and conformal blocks

    NASA Astrophysics Data System (ADS)

    Simmons-Duffin, David

    2014-04-01

    We introduce a method for computing conformal blocks of operators in arbitrary Lorentz representations in any spacetime dimension, making it possible to apply bootstrap techniques to operators with spin. The key idea is to implement the "shadow formalism" of Ferrara, Gatto, Grillo, and Parisi in a setting where conformal invariance is manifest. Conformal blocks in d-dimensions can be expressed as integrals over the projective null-cone in the "embedding space" d+1,1. Taking care with their analytic structure, these integrals can be evaluated in great generality, reducing the computation of conformal blocks to a bookkeeping exercise. To facilitate calculations in four-dimensional CFTs, we introduce techniques for writing down conformally-invariant correlators using auxiliary twistor variables, and demonstrate their use in some simple examples.

  3. The Near-Earth Object Human Space Flight Accessible Targets Study (NHATS) List of Near-Earth Asteroids: Identifying Potential Targets for Future Exploration

    NASA Astrophysics Data System (ADS)

    Abell, Paul; Barbee, B. W.; Mink, R. G.; Adamo, D. R.; Alberding, C. M.; Mazanek, D. D.; Johnson, L. N.; Yeomans, D. K.; Chodas, P. W.; Chamberlin, A. B.; Benner, L. A. M.; Drake, B. G.; Friedensen, V. P.

    2012-10-01

    Introduction: Much attention has recently been focused on human exploration of near-Earth asteroids (NEAs). Detailed planning for deep space exploration and identification of potential NEA targets for human space flight requires selecting objects from the growing list of known NEAs. NASA therefore initiated the Near-Earth Object Human Space Flight Accessible Target Study (NHATS), which uses dynamical trajectory performance constraints to identify potentially accessible NEAs. Accessibility Criteria: Future NASA human space flight capability is being defined while the Orion Multi-Purpose Crew Vehicle and Space Launch System are under development. Velocity change and mission duration are two of the most critical factors in any human spaceflight endeavor, so the most accessible NEAs tend to be those with orbits similar to Earth’s. To be classified as NHATS-compliant, a NEA must offer at least one round-trip trajectory solution satisfying purposely inclusive constraints, including total mission change in velocity ≤ 12 km/s, mission duration ≤ 450 days (with at least 8 days at the NEA), Earth departure between Jan 1, 2015 and Dec 31, 2040, Earth departure C3 ≤ 60 km2/s2, and Earth return atmospheric entry speed ≤ 12 km/s. Monitoring and Updates: The NHATS list of potentially accessible targets is continuously updated as NEAs are discovered and orbit solutions for known NEAs are improved. The current list of accessible NEAs identified as potentially viable for future human exploration under the NHATS criteria is available to the international community via a website maintained by NASA’s NEO Program Office (http://neo.jpl.nasa.gov/nhats/). This website also lists predicted optical and radar observing opportunities for each NHATS-compliant NEA to facilitate acquisition of follow-up observations. Conclusions: This list of NEAs will be useful for analyzing robotic mission opportunities, identifying optimal round trip human space flight trajectories, and

  4. Methodology and Results of the Near-Earth Object (NEO) Human Space Flight (HSF) Accessible Targets Study (NHATS)

    NASA Technical Reports Server (NTRS)

    Barbee, Brent; Mink, Ronald; Adamo, Daniel

    2011-01-01

    Near-Earth Asteroids (NEAs) have been identified by the current administration as potential destinations for human explorers during the mid-2020s. While the close proximity of these objects' orbits to Earth's orbit creates a risk of highly damaging or catastrophic impacts, it also makes some of these objects particularly accessible to spacecraft departing Earth, and this presents unique opportunities for solar system science and humanity's first ventures beyond cislunar space. Planning such ambitious missions first requires the selection of potentially accessible targets from the growing population of nearly 7,800 NEAs. To accomplish this, NASA is conducting the Near-Earth Object (NEO) Human Space Flight (HSF) Accessible Targets Study (NHATS). Phase I of the NHATS was executed during September of 2010, and Phase II was completed by early March of 2011. The study is ongoing because previously undetected NEAs are being discovered constantly, which has motivated an effort to automate the analysis algorithms in order to provide continuous monitoring of NEA accessibility. The NHATS analysis process consists of a trajectory filter and a minimum maximum estimated size criterion. The trajectory filter employs the method of embedded trajectory grids to compute all possible ballistic round-trip mission trajectories to every NEA in the Jet Propulsion Laboratory (JPL) Small-Body Database (SBDB) and stores all solutions that satisfy the trajectory filter criteria. An NEA must offer at least one qualifying trajectory solution to pass the trajectory filter. The Phase II NHATS filter criteria were purposely chosen to be highly inclusive, requiring Earth departure date between January 1st, 2015 and December 31st, 2040, total round-trip flight time <= 450 days, stay time at the NEA >= 8 days, Earth departure C(sub 3) energy <= 60 km(exp 2)/s(exp 2), total mission delta-v <= 12 km/s (including an Earth departure maneuver from a 400 km altitude circular parking orbit), and a maximum

  5. Interactive visibility retargeting in VR using conformal visualization.

    PubMed

    Petkov, Kaloian; Papadopoulos, Charilaos; Zhang, Min; Kaufman, Arie E; Gu, Xianfeng David

    2012-07-01

    In Virtual Reality, immersive systems such as the CAVE provide an important tool for the collaborative exploration of large 3D data. Unlike head-mounted displays, these systems are often only partially immersive due to space, access, or cost constraints. The resulting loss of visual information becomes a major obstacle for critical tasks that need to utilize the users' entire field of vision. We have developed a conformal visualization technique that establishes a conformal mapping between the full 360° field of view and the display geometry of a given visualization system. The mapping is provably angle-preserving and has the desirable property of preserving shapes locally, which is important for identifying shape-based features in the visual data. We apply the conformal visualization to both forward and backward rendering pipelines in a variety of retargeting scenarios, including CAVEs and angled arrangements of flat panel displays. In contrast to image-based retargeting approaches, our technique constructs accurate stereoscopic images that are free of resampling artifacts. Our user study shows that on the visual polyp detection task in Immersive Virtual Colonoscopy, conformal visualization leads to improved sensitivity at comparable examination times against the traditional rendering approach. We also develop a novel user interface based on the interactive recreation of the conformal mapping and the real-time regeneration of the view direction correspondence. PMID:22105016

  6. Eikonalization of conformal blocks

    SciTech Connect

    Fitzpatrick, A. Liam; Kaplan, Jared; Walters, Matthew T.; Wang, Junpu

    2015-09-03

    Classical field configurations such as the Coulomb potential and Schwarzschild solution are built from the t-channel exchange of many light degrees of freedom. We study the CFT analog of this phenomenon, which we term the 'eikonalization' of conformal blocks. We show that when an operator T appears in the OPE Ο(x)Ο(0), then the large spin Fock space states [TT···T] also appear in this OPE with a computable coefficient. The sum over the exchange of these Fock space states in an correlator build the classical 'T field' in the dual AdS description. In some limits the sum of all Fock space exchanges can be represented as the exponential of a single T exchange in the 4-pt correlator of O. Our results should be useful for systematizing 1/ℓ perturbation theory in general CFTs and simplifying the computation of large spin OPE coefficients. As examples we obtain the leading log ℓ dependence of Fock space conformal block coefficients, and we directly compute the OPE coefficients of the simplest ‘triple-trace’ operators.

  7. Access to space

    NASA Technical Reports Server (NTRS)

    1994-01-01

    The goal of this conceptual design was to devise a reusable, commercially viable, single-stage-to-orbit vehicle. The vehicle has the ability to deliver a 9100 kg (20,000 lb) payload to a low earth orbit of 433 km to 933 km (250 n.mi. - 450 n.mi.). The SSTO vehicle is 51 meters in length and has a gross takeoff mass of 680,400 kg (1,500,000 lb). The vehicle incorporates three RD-701 engines for the main propulsion system and two RL-10 engines for the orbital maneuvering system. The vehicle is designed for a three day stay on orbit with two crew members.

  8. SCit: web tools for protein side chain conformation analysis.

    PubMed

    Gautier, R; Camproux, A-C; Tufféry, P

    2004-07-01

    SCit is a web server providing services for protein side chain conformation analysis and side chain positioning. Specific services use the dependence of the side chain conformations on the local backbone conformation, which is described using a structural alphabet that describes the conformation of fragments of four-residue length in a limited library of structural prototypes. Based on this concept, SCit uses sets of rotameric conformations dependent on the local backbone conformation of each protein for side chain positioning and the identification of side chains with unlikely conformations. The SCit web server is accessible at http://bioserv.rpbs.jussieu.fr/SCit. PMID:15215438

  9. Eikonalization of conformal blocks

    DOE PAGESBeta

    Fitzpatrick, A. Liam; Kaplan, Jared; Walters, Matthew T.; Wang, Junpu

    2015-09-03

    Classical field configurations such as the Coulomb potential and Schwarzschild solution are built from the t-channel exchange of many light degrees of freedom. We study the CFT analog of this phenomenon, which we term the 'eikonalization' of conformal blocks. We show that when an operator T appears in the OPE Ο(x)Ο(0), then the large spin Fock space states [TT···T]ℓ also appear in this OPE with a computable coefficient. The sum over the exchange of these Fock space states in an correlator build the classical 'T field' in the dual AdS description. In some limits the sum of all Fock spacemore » exchanges can be represented as the exponential of a single T exchange in the 4-pt correlator of O. Our results should be useful for systematizing 1/ℓ perturbation theory in general CFTs and simplifying the computation of large spin OPE coefficients. As examples we obtain the leading log ℓ dependence of Fock space conformal block coefficients, and we directly compute the OPE coefficients of the simplest ‘triple-trace’ operators.« less

  10. Chip-interleaved optical code division multiple access relying on a photon-counting iterative successive interference canceller for free-space optical channels.

    PubMed

    Zhou, Xiaolin; Zheng, Xiaowei; Zhang, Rong; Hanzo, Lajos

    2013-07-01

    In this paper, we design a novel Poisson photon-counting based iterative successive interference cancellation (SIC) scheme for transmission over free-space optical (FSO) channels in the presence of both multiple access interference (MAI) as well as Gamma-Gamma atmospheric turbulence fading, shot-noise and background light. Our simulation results demonstrate that the proposed scheme exhibits a strong MAI suppression capability. Importantly, an order of magnitude of BER improvements may be achieved compared to the conventional chip-level optical code-division multiple-access (OCDMA) photon-counting detector. PMID:23842379

  11. Application of time series analysis on molecular dynamics simulations of proteins: A study of different conformational spaces by principal component analysis

    NASA Astrophysics Data System (ADS)

    Alakent, Burak; Doruker, Pemra; Camurdan, Mehmet C.

    2004-09-01

    Time series analysis is applied on the collective coordinates obtained from principal component analysis of independent molecular dynamics simulations of α-amylase inhibitor tendamistat and immunity protein of colicin E7 based on the Cα coordinates history. Even though the principal component directions obtained for each run are considerably different, the dynamics information obtained from these runs are surprisingly similar in terms of time series models and parameters. There are two main differences in the dynamics of the two proteins: the higher density of low frequencies and the larger step sizes for the interminima motions of colicin E7 than those of α-amylase inhibitor, which may be attributed to the higher number of residues of colicin E7 and/or the structural differences of the two proteins. The cumulative density function of the low frequencies in each run conforms to the expectations from the normal mode analysis. When different runs of α-amylase inhibitor are projected on the same set of eigenvectors, it is found that principal components obtained from a certain conformational region of a protein has a moderate explanation power in other conformational regions and the local minima are similar to a certain extent, while the height of the energy barriers in between the minima significantly change. As a final remark, time series analysis tools are further exploited in this study with the motive of explaining the equilibrium fluctuations of proteins.

  12. Structure of the antiviral stavudine using quantum chemical methods: Complete conformational space analysis, 3D potential energy surfaces and solid state simulations

    NASA Astrophysics Data System (ADS)

    Alcolea Palafox, M.; Iza, N.

    2012-11-01

    The molecular structure and energy of the anti-HIV, 2',3'-didehydro-3'-deoxythymidine (D4T, stavudine or Zerit) nucleoside analogue was determined by using MP2, B3LYP and B971 quantum chemical methods. The global minimum was determined through 3D potential energy surfaces (PES). These surfaces were built by rotation of the exocyclic χ, γ and β torsional angles, in steps of 20°, and full optimization of the remaining parameters. As consequence 5832 geometries were final optimized. The search located 25 local minimum, 4 of which are by MP2 within a 2 kcal/mol electronic energy range of the global minimum. The whole conformational parameters as well as P, νmax were analyzed in all the stable conformers. The global minimum by MP2 corresponds to the calculated values of the exocyclic torsional angles: χ = -103.6°, β = 63.8° and γ = 60.6°. The results obtained are in accordance to those found in thymidine and in related anti-HIV nucleoside analogues. The effect of hydration on the two most stable conformers is analyzed by continuous and discrete models up to 20 water molecules. The solid state was also simulated. The dimer forms found in the crystal unit cell were accurately determined and they are in accordance to the X-ray data.

  13. Attitudinal Conformity and Anonymity

    ERIC Educational Resources Information Center

    Tyson, Herbert; Kaplowitz, Stan

    1977-01-01

    Tested college students for conformity when conditions contributing to conformity were absent. Found that social pressures (responding in public, being surveyed by fellow group members) are necessary to produce conformity. (RL)

  14. Conformal mechanics

    SciTech Connect

    Gonera, Joanna

    2013-08-15

    The SL(2,R) invariant Hamiltonian systems are discussed within the framework of the orbit method. It is shown that both the dynamics and the symmetry transformations are globally well-defined on phase space. The flexibility in the choice of the time variable and the Hamiltonian function described in the paper by de Alfaro et al. [Nuovo Cimento 34A (1976) 569] is related to the nontrivial global structure of 1+0-dimensional space–time. The operational definition of time is discussed.

  15. System performances of optical space code-division multiple-access-based fiber-optic two-dimensional parallel data link.

    PubMed

    Nakamura, M; Kitayama, K

    1998-05-10

    Optical space code-division multiple access is a scheme to multiplex and link data between two-dimensional processors such as smart pixels and spatial light modulators or arrays of optical sources like vertical-cavity surface-emitting lasers. We examine the multiplexing characteristics of optical space code-division multiple access by using optical orthogonal signature patterns. The probability density function of interference noise in interfering optical orthogonal signature patterns is calculated. The bit-error rate is derived from the result and plotted as a function of receiver threshold, code length, code weight, and number of users. Furthermore, we propose a prethresholding method to suppress the interference noise, and we experimentally verify that the method works effectively in improving system performance. PMID:18273237

  16. Protein Allostery and Conformational Dynamics.

    PubMed

    Guo, Jingjing; Zhou, Huan-Xiang

    2016-06-01

    The functions of many proteins are regulated through allostery, whereby effector binding at a distal site changes the functional activity (e.g., substrate binding affinity or catalytic efficiency) at the active site. Most allosteric studies have focused on thermodynamic properties, in particular, substrate binding affinity. Changes in substrate binding affinity by allosteric effectors have generally been thought to be mediated by conformational transitions of the proteins or, alternatively, by changes in the broadness of the free energy basin of the protein conformational state without shifting the basin minimum position. When effector binding changes the free energy landscape of a protein in conformational space, the change affects not only thermodynamic properties but also dynamic properties, including the amplitudes of motions on different time scales and rates of conformational transitions. Here we assess the roles of conformational dynamics in allosteric regulation. Two cases are highlighted where NMR spectroscopy and molecular dynamics simulation have been used as complementary approaches to identify residues possibly involved in allosteric communication. Perspectives on contentious issues, for example, the relationship between picosecond-nanosecond local and microsecond-millisecond conformational exchange dynamics, are presented. PMID:26876046

  17. A closed-cycle dilution refrigerator with free-space and fiber optical access for quantum optomechanics experiments at 25mK

    NASA Astrophysics Data System (ADS)

    Groeblacher, Simon; Wieczorek, Witlef; Christ, Peter; Buehler, Matthias; Wernicke, Doreen; Hoehne, Jens; Aspelmeyer, Markus

    2011-03-01

    We report on the operation of a closed-cycle dilution refrigerator for quantum optomechanics experiments at 25mK. The dilution fridge is accessible both via free-space as well as fiber coupling, allowing us to perform a variety of optical experiments at low temperatures. It is designed to vibrationally isolate the experiment allowing for stable operation of a high-finesse optical cavity. This enables us to perform cavity-optomechanics experiments at ultra-low temperatures.

  18. Spontaneous breaking of conformal invariance, solitons, and gravitational waves in theories of conformally invariant gravitation

    NASA Astrophysics Data System (ADS)

    Bouchami, Jihène; Paranjape, M. B.

    2008-08-01

    We study conformal gravity as an alternative theory of gravitation. For conformal gravity to be phenomenologically viable requires that the conformal symmetry is not manifest at the energy scales of the other known physical forces. Hence we are required to find a mechanism for the spontaneous breaking of conformal invariance. In this paper we study the possibility that conformal invariance is spontaneously broken due to interactions with conformally coupled matter fields. The vacuum of the theory admits conformally noninvariant solutions corresponding to maximally symmetric space-times and variants thereof. These are either de Sitter space-time or anti-de Sitter space-time in the full four space-time dimensions and we find new solutions corresponding to maximal symmetry restricted to a lower dimensional subspace. We also consider normalizable, linearized gravitational perturbations around the anti-de Sitter background. We show to second order, that these gravitational fluctuations carry zero energy momentum. Finally we also show the possibility of domain wall solitons interpolating between the ground states of spontaneously broken conformal symmetry that we have found. These solitons necessarily require the vanishing of the scalar field. This offers a way of eschewing the recent suggestion and its consequences [E. Flanagan, Phys. Rev. D 74, 023002 (2006).PRVDAQ0556-282110.1103/PhysRevD.74.023002] that the conformal symmetry could be quarantined to a sterile sector of the theory by choosing an appropriate field redefinition.

  19. Insights into How Cyclic Peptides Switch Conformations.

    PubMed

    McHugh, Sean M; Rogers, Julia R; Yu, Hongtao; Lin, Yu-Shan

    2016-05-10

    Cyclic peptides have recently emerged as promising modulators of protein-protein interactions. However, it is currently highly difficult to predict the structures of cyclic peptides owing to their rugged conformational free energy landscape, which prevents sampling of all thermodynamically relevant conformations. In this article, we first investigate how a relatively flexible cyclic hexapeptide switches conformations. It is found that, although the circular geometry of small cyclic peptides of size 6-8 may require rare, coherent dihedral changes to sample a new conformation, the changes are rather local, involving simultaneous changes of ϕi and ψi or ψi and ϕi+1. The understanding of how these cyclic peptides switch conformations enables the use of metadynamics simulations with reaction coordinates specifically targeting such coupled two-dihedral changes to effectively sample cyclic peptide conformational space. PMID:27031286

  20. Conformal gravity and time

    NASA Astrophysics Data System (ADS)

    Hazboun, Jeffrey Shafiq

    2014-10-01

    Cartan geometry provides a rich formalism from which to look at various geometrically motivated extensions to general relativity. In this manuscript, we start by motivating reasons to extend the theory of general relativity. We then introduce the reader to our technique, called the quotient manifold method, for extending the geometry of spacetime. We will specifically look at the class of theories formed from the various quotients of the conformal group. Starting with the conformal symmetries of Euclidean space, we construct a manifold where time manifests as a part of the geometry. Though there is no matter present in the geome- try studied here, geometric terms analogous to dark energy and dark matter appear when we write down the Einstein tensor. Specifically, the quotient of the conformal group of Euclidean four-space by its Weyl subgroup results in a geometry possessing many of the properties of relativistic phase space, including both a natural symplectic form and nondegenerate Killing metric. We show the general solution possesses orthogonal Lagrangian submanifolds, with the induced metric and the spin connection on the submanifolds necessarily Lorentzian, despite the Euclidean starting point. By examining the structure equations of the biconformal space in an orthonormal frame adapted to its phase space properties, we also find two new tensor fields exist in this geometry, not present in Riemannian geometry. The first is a combination of the Weyl vector with the scale factor on the metric, and determines the time-like directions on the submanifolds. The second comes from the components of the spin connection, symmetric with respect to the new metric. Though this field comes from the spin connection, it transforms ho- mogeneously. Finally, we show in the absence of Cartan curvature or sources, the configuration space has geometric terms equivalent to a perfect fluid and a cosmological constant. We complete the analysis of this homogeneous space by

  1. Bridging the Digital Divide between Discrete and Continuous Space-Time Array Data to Enhance Accessibility to and Usability of NASA Earth Sciences Data for the Hydrological Community

    NASA Astrophysics Data System (ADS)

    Teng, W. L.; Maidment, D. R.; Vollmer, B.; Peters-Lidard, C. D.; Rui, H.; Strub, R.; Whiteaker, T.; Mocko, D. M.; Kirschbaum, D. B.

    2012-12-01

    A longstanding and significant "Digital Divide" in data representation exists between hydrology and climatology and meteorology. Typically, in hydrology, earth surface features are expressed as discrete spatial objects such as watersheds, river reaches, and point observation sites; and time varying data are contained in time series associated with these spatial objects. Long time histories of data may be associated with a single point or feature in space. In meteorology and climatology, remotely sensed observations and weather and climate model information are expressed as continuous spatial fields, with data sequenced in time from one data file to the next. Hydrology tends to be narrow in space and deep in time, while meteorology and climatology are broad in space and narrow in time. This Divide has been an obstacle, specifically, between the hydrological community, as represented by the Consortium of Universities for the Advancement of Hydrologic Science, Inc. (CUAHSI) and relevant data sets at the NASA Goddard Earth Sciences Data and Information Services Center (GES DISC). CUAHSI has developed the Hydrologic Information System (HIS), which is built on international geospatial standards, with one of its aims to bridge the Divide. The opportunity costs of the Divide are high. It has largely prevented the routine access and use of NASA Earth sciences data by the hydrological and, more generally, geospatial community. This presentation describes a recently-begun NASA ACCESS project that addresses the Digital Divide problem. Progress to date is summarized; technical details are provided in a related presentation (Rui et al., Data Reorganization for Optimal Time Series Data Access, Analysis, and Visualization, IN016). Building on prior prototype efforts with EPA BASINS (Better Assessment Science Integrating point and Nonpoint Sources) and CUAHSI HIS, this project focuses on the following approaches to the problems of data discovery, access, and use: (1) Link HIS and

  2. On the automorphism group of the conformal superalgebra

    PubMed Central

    Sternberg, Shlomo

    1986-01-01

    There is no automorphism of the conformal superalgebra that induces PT (parity and time reversal) on space time. Those conformal transformations that induce PT must change the sign of the odd brackets. In particular, in any implementation of conformal supersymmetry, CP can preserve but CPT must (at best) reverse the sign of the odd brackets (C, charge conjugation). PMID:16593646

  3. Partition coefficient and molecular flexibility: the concept of lipophilicity space.

    PubMed

    Vistoli, Giulio; Pedretti, Alessandro; Testa, Bernard

    2009-08-01

    The rationale of this study was to investigate molecular flexibility and its influence on physicochemical properties with a view to uncovering additional information on the fuzzy concept of dynamic molecular structure. Indeed, it is now known that computed molecular interaction fields (MIFs) such as molecular electrostatic potentials (MEPs) and lipophilicity potentials (MLPs) are conformation-dependent, as are dipole moments. A database of 125 compounds was used whose conformational space was explored, while conformation-dependent parameters were computed for each non-redundant conformer found in the conformational space of the compounds. These parameters were the virtual log P (log P(MLP), calculated by a MLP approach), the apolar surface area (ASA), polar surface area (PSA), and solvent-accessible surface (SAS). For each compound, the range taken by each parameter (its property space) was divided by the number of rotors taken as an index of flexibility, yielding a parameter termed 'molecular sensitivity'. This parameter was poorly correlated with others (i.e., it contains novel information) and showed the compounds to fall into two broad classes. 'Sensitive' molecules are those whose computed property ranges are markedly sensitive to conformational effects, whereas 'insensitive' (in fact, less sensitive) molecules have property ranges which are comparatively less affected by conformational fluctuations. A pharmacokinetic application is presented. PMID:19697333

  4. Fake conformal symmetry in conformal cosmological models

    NASA Astrophysics Data System (ADS)

    Jackiw, R.; Pi, So-Young

    2015-03-01

    We examine the local conformal invariance (Weyl invariance) in tensor-scalar theories used in recently proposed conformal cosmological models. We show that the Noether currents associated with Weyl invariance in these theories vanish. We assert that the corresponding Weyl symmetry does not have any dynamical role.

  5. Logarithmic conformal field theory: beyond an introduction

    NASA Astrophysics Data System (ADS)

    Creutzig, Thomas; Ridout, David

    2013-12-01

    This article aims to review a selection of central topics and examples in logarithmic conformal field theory. It begins with the remarkable observation of Cardy that the horizontal crossing probability of critical percolation may be computed analytically within the formalism of boundary conformal field theory. Cardy’s derivation relies on certain implicit assumptions which are shown to lead inexorably to indecomposable modules and logarithmic singularities in correlators. For this, a short introduction to the fusion algorithm of Nahm, Gaberdiel and Kausch is provided. While the percolation logarithmic conformal field theory is still not completely understood, there are several examples for which the formalism familiar from rational conformal field theory, including bulk partition functions, correlation functions, modular transformations, fusion rules and the Verlinde formula, has been successfully generalized. This is illustrated for three examples: the singlet model \\mathfrak {M} (1,2), related to the triplet model \\mathfrak {W} (1,2), symplectic fermions and the fermionic bc ghost system; the fractional level Wess-Zumino-Witten model based on \\widehat{\\mathfrak {sl}} \\left( 2 \\right) at k=-\\frac{1}{2}, related to the bosonic βγ ghost system; and the Wess-Zumino-Witten model for the Lie supergroup \\mathsf {GL} \\left( 1 {\\mid} 1 \\right), related to \\mathsf {SL} \\left( 2 {\\mid} 1 \\right) at k=-\\frac{1}{2} and 1, the Bershadsky-Polyakov algebra W_3^{(2)} and the Feigin-Semikhatov algebras W_n^{(2)}. These examples have been chosen because they represent the most accessible, and most useful, members of the three best-understood families of logarithmic conformal field theories. The logarithmic minimal models \\mathfrak {W} (q,p), the fractional level Wess-Zumino-Witten models, and the Wess-Zumino-Witten models on Lie supergroups (excluding \\mathsf {OSP} \\left( 1 {\\mid} 2n \\right)). In this review, the emphasis lies on the representation theory

  6. James Webb Space Telescope (JWST) Integrated Science Instruments Module (ISIM) Electronics Compartment (IEC) Conformal Shields Composite Bond Structure Qualification Test Method

    NASA Technical Reports Server (NTRS)

    Yew, Calinda; Stephens, Matt

    2015-01-01

    The JWST IEC conformal shields are mounted onto a composite frame structure that must undergo qualification testing to satisfy mission assurance requirements. The composite frame segments are bonded together at the joints using epoxy, EA 9394. The development of a test method to verify the integrity of the bonded structure at its operating environment introduces challenges in terms of requirements definition and the attainment of success criteria. Even though protoflight thermal requirements were not achieved, the first attempt in exposing the structure to cryogenic operating conditions in a thermal vacuum environment resulted in approximately 1 bonded joints failure during mechanical pull tests performed at 1.25 times the flight loads. Failure analysis concluded that the failure mode was due to adhesive cracks that formed and propagated along stress concentrated fillets as a result of poor bond squeeze-out control during fabrication. Bond repairs were made and the structures successfully re-tested with an improved LN2 immersion test method to achieve protoflight thermal requirements.

  7. SPRAY FOAM IN ACCESSIBLE SPACES:BEST PRACTICES AND CASE STUDIES FOR RETROFIT IN MIXED-HUMID CLIMATE

    SciTech Connect

    Christian, Jeffrey E; Gant, Kathy

    2013-12-01

    Heating and cooling the house is one of the homeowners major expenses. Reducing these costs, saving energy, and creating a healthier, more comfortable indoor environment are good reasons to consider improving the building thermal envelope. Improvements usually consider increasing the amount of insulation, reducing the infiltration of outside air, and controlling moisture in existing buildings. This report describes the use of spray foam materials to insulate, seal, and control moisture. This discussion is limited to treating areas that are accessible. What is accessible, however, can vary depending on the type of renovation. If the building has been gutted or exterior surfaces removed, there are more options. This report will look at areas to consider for spray foam application and discuss the types of spray foams available and their uses. A number of case studies are presented to show the effectiveness of this retrofit in existing houses based on performance data.

  8. New Interface for Accessing Archived European Space Agency Planetary Science Data, Such as the New Venus Express Atmospheric Drag Experiment Data Set

    NASA Astrophysics Data System (ADS)

    Grotheer, E.; Barbarisi, I.; Rios, C.; Macfarlane, A. J.; Docasal, R.; Arviset, C.; Besse, S.; Heather, D.; Gonzalez, J.; De Marchi, G.; Martinez, S.; Lim, T.; Fraga, D.

    2015-12-01

    All Venus Express (VEX) instruments delivered their data products according to the Planetary Data System version 3 (PDS3) standard, and the atmospheric drag experiment (ADE) data was no exception. The European Space Agency's (ESA) Planetary Science Archive (PSA), which can be accessed at www.rssd.esa.int/PSA, is being upgraded to make PDS4 data available from newer missions such as ExoMars and BepiColombo. Thus, the PSA development team has been working to ensure that the legacy PDS3 data will be accessible via the new interface as well. We will preview some of the new methods of accessing legacy VEX data via the new interface, with a focus being placed on the ADE data set. We will show how the ADE data can be accessed using Geographic Information Systems (GIS) and our plans for making this and other data sets compatible with the Virtual European Solar and Planetary Access (VESPA) project for creating a virtual observatory. From February 2010 through March 2014, ESA's Venus Express mission conducted 11 ADE campaigns. During these observation campaigns, VEX's pericenter was in the range of 165 to 190 km, while the spacecraft was near Venus' North pole, and the entire spacecraft was used to make in situ measurements of the atmospheric density. This was done by rotating the solar panels in a manner that somewhat resembles a windmill. Also, VEX 's attitude and orbit control system was tasked with maintaining the spacecraft in a 3-axis stabilized mode during these pericenter passes. The torques that the reaction wheels had to exert to maintain this attitude were then analyzed to yield density readings.

  9. Four-Channel, 8 x 8 Bit, Two-Dimensional Parallel Transmission by use of Space-Code-Division Multiple-Access Encoder and Decoder Modules.

    PubMed

    Nakamura, M; Kitayama, K; Igasaki, Y; Kaneda, K

    1998-07-10

    We experimentally demonstrate four-channel multiplexing of 64-bit (8 x 8) two-dimensional (2-D) parallel data links on the basis of optical space-code-division multiple access (CDMA) by using new modules of optical spatial encoders and a decoder with a new high-contrast 9-m-long image fiber with 3 x 10(4) cores. Each 8 x 8 bit plane (64-bit parallel data) is optically encoded with an 8 x 8, 2-D optical orthogonal signature pattern. The encoded bit planes are spatially multiplexed and transmitted through an image fiber. A receiver can recover the intended input bit plane by means of an optical decoding process. This result should encourage the application of optical space-CDMA to future high-throughput 2-D parallel data links connecting massively parallel processors. PMID:18285889

  10. Space.

    ERIC Educational Resources Information Center

    Web Feet K-8, 2001

    2001-01-01

    This annotated subject guide to Web sites and additional resources focuses on space and astronomy. Specifies age levels for resources that include Web sites, CD-ROMS and software, videos, books, audios, and magazines; offers professional resources; and presents a relevant class activity. (LRW)

  11. 10. Exploring the Conformal Constraint Equations

    NASA Astrophysics Data System (ADS)

    Butscher, Adrian

    One method of studying the asymptotic structure of spacetime is to apply Penrose's conformal rescaling technique. In this setting, the rescaled Einstein equations for the metric and the conformal factor in the unphysical spacetime degenerate where the conformal factor vanishes, namely at the boundary representing null infinity. This problem can be avoided by means of a technique of H. Friedrich, which replaces the Einstein equations in the unphysical spacetime by an equivalent system of equations which is regular at the boundary. The initial value problem for these equations produces a system of constraint equations known as the conformal constraint equations. This work describes some of the properties of the conformal constraint equations and develops a perturbative method of generating solutions near Euclidean space under certain simplifying assumptions.

  12. 14 CFR 21.130 - Statement of conformity.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Statement of conformity. 21.130 Section 21.130 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT CERTIFICATION PROCEDURES FOR PRODUCTS AND PARTS Production Under Type Certificate Only § 21.130 Statement of conformity. Each holder or licensee of...

  13. Conformal, macroscopic crystalline nanoparticle sheets assembled with DNA.

    PubMed

    Ku, Jessie C; Ross, Michael B; Schatz, George C; Mirkin, Chad A

    2015-05-27

    A novel method for preparing conformal silica-embedded crystalline nanoparticle sheets via DNA programmable assembly provides independent control over nanoparticle size, nanoparticle spacing, and film thickness. The conformal materials retain the nanoparticle crystallinity and spacing after being transferred to flat or highly curved substrates even after being subjected to various mechanical, physical, and chemical stimuli. PMID:25864411

  14. Programmable Ultra Lightweight System Adaptable Radio (PULSAR) Low Cost Telemetry - Access from Space Advanced Technologies or Down the Middle

    NASA Technical Reports Server (NTRS)

    Sims. Herb; Varnavas, Kosta; Eberly, Eric

    2013-01-01

    Software Defined Radio (SDR) technology has been proven in the commercial sector since the early 1990's. Today's rapid advancement in mobile telephone reliability and power management capabilities exemplifies the effectiveness of the SDR technology for the modern communications market. In contrast, presently qualified satellite transponder applications were developed during the early 1960's space program. Programmable Ultra Lightweight System Adaptable Radio (PULSAR, NASA-MSFC SDR) technology revolutionizes satellite transponder technology by increasing data through-put capability by, at least, an order of magnitude. PULSAR leverages existing Marshall Space Flight Center SDR designs and commercially enhanced capabilities to provide a path to a radiation tolerant SDR transponder. These innovations will (1) reduce the cost of NASA Low Earth Orbit (LEO) and Deep Space transponders, (2) decrease power requirements, and (3) a commensurate volume reduction. Also, PULSAR increases flexibility to implement multiple transponder types by utilizing the same hardware with altered logic - no analog hardware change is required - all of which can be accomplished in orbit. This provides high capability, low cost, transponders to programs of all sizes. The final project outcome would be the introduction of a Technology Readiness Level (TRL) 7 low-cost CubeSat to SmallSat telemetry system into the NASA Portfolio.

  15. Scalar scattering via conformal higher spin exchange

    NASA Astrophysics Data System (ADS)

    Joung, Euihun; Nakach, Simon; Tseytlin, Arkady A.

    2016-02-01

    Theories containing infinite number of higher spin fields require a particular definition of summation over spins consistent with their underlying symmetries. We consider a model of massless scalars interacting (via bilinear conserved currents) with conformal higher spin fields in flat space. We compute the tree-level four-scalar scattering amplitude using a natural prescription for summation over an infinite set of conformal higher spin exchanges and find that it vanishes. Independently, we show that the vanishing of the scalar scattering amplitude is, in fact, implied by the global conformal higher spin symmetry of this model. We also discuss one-loop corrections to the four-scalar scattering amplitude.

  16. Invariant classification of second-order conformally flat superintegrable systems

    NASA Astrophysics Data System (ADS)

    Capel, J. J.; Kress, J. M.

    2014-12-01

    In this paper we continue the work of Kalnins et al in classifying all second-order conformally-superintegrable (Laplace-type) systems over conformally flat spaces, using tools from algebraic geometry and classical invariant theory. The results obtained show, through Stäckel equivalence, that the list of known nondegenerate superintegrable systems over three-dimensional conformally flat spaces is complete. In particular, a seven-dimensional manifold is determined such that each point corresponds to a conformal class of superintegrable systems. This manifold is foliated by the nonlinear action of the conformal group in three dimensions. Two systems lie in the same conformal class if and only if they lie in the same leaf of the foliation. This foliation is explicitly described using algebraic varieties formed from representations of the conformal group. The proof of these results rely heavily on Gröbner basis calculations using the computer algebra software packages Maple and Singular.

  17. Thermodynamics of a conformational change using a random walk in energy-reaction coordinate space: Application to methane dimer hydrophobic interactions

    NASA Astrophysics Data System (ADS)

    Morozov, A. N.; Lin, S. H.

    2009-02-01

    A random walk sampling algorithm allows the extraction of the density of states distribution in energy-reaction coordinate space. As a result, the temperature dependences of thermodynamic quantities such as relative energy, entropy, and heat capacity can be calculated using first-principles statistical mechanics. The strategies for optimal convergence of the algorithm and control of its accuracy are proposed. We show that the saturation of the error [Q. Yan and J. J. de Pablo, Phys. Rev. Lett. 90, 035701 (2003); E. Belardinelli and V. D. Pereyra, J. Chem. Phys. 127, 184105 (2007)] is due to the use of histogram flatness as a criterion of convergence. An application of the algorithm to methane dimer hydrophobic interactions is presented. We obtained a quantitatively accurate energy-entropy decomposition of the methane dimer cavity potential. The presented results confirm the previous results, and they provide new information regarding the thermodynamics of hydrophobic interactions. We show that the finite-difference approximation, which is widely used in molecular dynamic simulations for the energy-entropy decomposition of a free energy potential, can lead to a significant error.

  18. High Speed, Low Cost Telemetry Access from Space Development Update on Programmable Ultra Lightweight System Adaptable Radio (PULSAR)

    NASA Technical Reports Server (NTRS)

    Simms, William Herbert, III; Varnavas, Kosta; Eberly, Eric

    2014-01-01

    Software Defined Radio (SDR) technology has been proven in the commercial sector since the early 1990's. Today's rapid advancement in mobile telephone reliability and power management capabilities exemplifies the effectiveness of the SDR technology for the modern communications market. In contrast, the foundations of transponder technology presently qualified for satellite applications were developed during the early space program of the 1960's. Conventional transponders are built to a specific platform and must be redesigned for every new bus while the SDR is adaptive in nature and can fit numerous applications with no hardware modifications. A SDR uses a minimum amount of analog / Radio Frequency (RF) components to up/down-convert the RF signal to/from a digital format. Once the signal is digitized, all processing is performed using hardware or software logic. Typical SDR digital processes include; filtering, modulation, up/down converting and demodulation. NASA Marshall Space Flight Center (MSFC) Programmable Ultra Lightweight System Adaptable Radio (PULSAR) leverages existing MSFC SDR designs and commercial sector enhanced capabilities to provide a path to a radiation tolerant SDR transponder. These innovations (1) reduce the cost of NASA Low Earth Orbit (LEO) and Deep Space standard transponders, (2) decrease power requirements, and (3) commensurately reduce volume. A second pay-off is the increased SDR flexibility by allowing the same hardware to implement multiple transponder types simply by altering hardware logic - no change of hardware is required - all of which will ultimately be accomplished in orbit. Development of SDR technology for space applications will provide a highly capable, low cost transponder to programs of all sizes. The MSFC PULSAR Project results in a Technology Readiness Level (TRL) 7 low-cost telemetry system available to Smallsat and CubeSat missions, as well as other platforms. This paper documents the continued development and

  19. The Near-Earth Object Human Space Flight Accessible Targets Study (NHATS) List of Near-Earth Asteroids: Identifying Potential Targets for Future Exploration

    NASA Technical Reports Server (NTRS)

    Abell, Paul A.; Barbee, B. W.; Mink, R. G.; Alberding, C. M.; Adamo, D. R.; Mazanek, D. D.; Johnson, L. N.; Yeomans, D. K.; Chodas, P. W.; Chamberlin, A. B.; Benner, L. A. M.; Drake, B. G.; Friedensen, V. P.

    2012-01-01

    Over the past several years, much attention has been focused on the human exploration of near-Earth asteroids (NEAs). Two independent NASA studies examined the feasibility of sending piloted missions to NEAs [1, 2], and in 2009, the Augustine Commission identified NEAs as high profile destinations for human exploration missions beyond the Earth-Moon system [3]. More recently the current U.S. presidential administration directed NASA to include NEAs as destinations for future human exploration with the goal of sending astronauts to a NEA in the mid to late 2020s. This directive became part of the official National Space Policy of the United States of America as of June 28, 2010 [4]. Detailed planning for such deep space exploration missions and identifying potential NEAs as targets for human spaceflight requires selecting objects from the ever growing list of newly discovered NEAs. Hence NASA developed and implemented the Near-Earth Object (NEO) Human Space Flight (HSF) Accessible Target Study (NHATS), which identifies potential candidate objects on the basis of defined dynamical trajectory performance constraints.

  20. Conformational analysis of small molecules: NMR and quantum mechanics calculations.

    PubMed

    Tormena, Cláudio F

    2016-08-01

    This review deals with conformational analysis in small organic molecules, and describes the stereoelectronic interactions responsible for conformational stability. Conformational analysis is usually performed using NMR spectroscopy through measurement of coupling constants at room or low temperature in different solvents to determine the populations of conformers in solution. Quantum mechanical calculations are used to address the interactions responsible for conformer stability. The conformational analysis of a large number of small molecules is described, using coupling constant measurements in different solvents and at low temperature, as well as recent applications of through-space and through-hydrogen bond coupling constants JFH as tools for the conformational analysis of fluorinated molecules. Besides NMR parameters, stereoelectronic interactions such as conjugative, hyperconjugative, steric and intramolecular hydrogen bond interactions involved in conformational preferences are discussed. PMID:27573182

  1. Galilean conformal electrodynamics

    NASA Astrophysics Data System (ADS)

    Bagchi, Arjun; Basu, Rudranil; Mehra, Aditya

    2014-11-01

    Maxwell's Electrodynamics admits two distinct Galilean limits called the Electric and Magnetic limits. We show that the equations of motion in both these limits are invariant under the Galilean Conformal Algebra in D = 4, thereby exhibiting non-relativistic conformal symmetries. Remarkably, the symmetries are infinite dimensional and thus Galilean Electrodynamics give us the first example of an infinitely extended Galilean Conformal Field Theory in D > 2. We examine details of the theory by looking at purely non-relativistic conformal methods and also use input from the limit of the relativistic theory.

  2. Earth Science Data Archive and Access at the NASA/Goddard Space Flight Center Distributed Active Archive Center (DAAC)

    NASA Technical Reports Server (NTRS)

    Leptoukh, Gregory

    1999-01-01

    The Goddard Distributed Active Archive Center (DAAC), as an integral part of the Earth Observing System Data and Information System (EOSDIS), is the official source of data for several important earth remote sensing missions. These include the Sea-viewing Wide-Field-of-view Sensor (SeaWiFS) launched in August 1997, the Tropical Rainfall Measuring Mission (TRMM) launched in November 1997, and the Moderate Resolution Imaging Spectroradiometer (MODIS) scheduled for launch in mid 1999 as part of the EOS AM-1 instrumentation package. The data generated from these missions supports a host of users in the hydrological, land biosphere and oceanographic research and applications communities. The volume and nature of the data present unique challenges to an Earth science data archive and distribution system such as the DAAC. The DAAC system receives, archives and distributes a large number of standard data products on a daily basis, including data files that have been reprocessed with updated calibration data or improved analytical algorithms. A World Wide Web interface is provided allowing interactive data selection and automatic data subscriptions as distribution options. The DAAC also creates customized and value-added data products, which allow additional user flexibility and reduced data volume. Another significant part of our overall mission is to provide ancillary data support services and archive support for worldwide field campaigns designed to validate the results from the various satellite-derived measurements. In addition to direct data services, accompanying documentation, WWW links to related resources, support for EOSDIS data formats, and informed response to inquiries are routinely provided to users. The current GDAAC WWW search and order system is being restructured to provide users with a simplified, hierarchical access to data. Data Browsers have been developed for several data sets to aid users in ordering data. These Browsers allow users to specify

  3. Conformational Restriction of Peptides Using Dithiol Bis-Alkylation.

    PubMed

    Peraro, L; Siegert, T R; Kritzer, J A

    2016-01-01

    Macrocyclic peptides are highly promising as inhibitors of protein-protein interactions. While many bond-forming reactions can be used to make cyclic peptides, most have limitations that make this chemical space challenging to access. Recently, a variety of cysteine alkylation reactions have been used in rational design and library approaches for cyclic peptide discovery and development. We and others have found that this chemistry is versatile and robust enough to produce a large variety of conformationally constrained cyclic peptides. In this chapter, we describe applications, methods, mechanistic insights, and troubleshooting for dithiol bis-alkylation reactions for the production of cyclic peptides. This method for efficient solution-phase macrocyclization is highly useful for the rapid production and screening of loop-based inhibitors of protein-protein interactions. PMID:27586339

  4. [Food environment and space accessibility evaluation to perform physical activity in 3 socially contrasting neighbourhoods of Buenos Aires city].

    PubMed

    Garipe, Leila Yasmin; Gónzalez, Verónica; Biasizzo, Antonella; Soriano, Jennifer Laila; Perman, Gaston; Giunta, Diego

    2014-01-01

    Due to the environmental influences on health, the goal of this study was to describe and compare the built environment in 3 socially contrasting neighbourhoods of Buenos Aires city.In 2011 a cross-sectional study was conducted in 3 socially contrasting neighbourhoods of Buenos Aires city: Recoleta (upper class), Almagro (middle class) and Constitución (lower class). Grocery stores and food stands were surveyed as well as all suitable spaces to perform physical activity. An analysis was conducted to assess the density of every food outlet per Km2 of each neighbourhood's area and per 10000 inhabitants. 2778 food stores and 149 outdoor physical activity facilities were surveyed. A higher density was observed in Constitución for fast food restaurants (Recoleta 3.6; Almagro 2.4; Constitución 6.7) and food stands (Recoleta 4.2; Almagro 1.2; Constitución 25.7) and a lower density for outdoor physical activity facilities. Population density and area density proved to be analogous. Statistically relevant differences were observed regarding the dimension of each food outlet: grocery stores, fruit stands, pubs, restaurants and food stands, as well as in the number of food stores and outdoor physical activity facilities. The information gathered in this study could be highly useful for public health policies on healthy lifestyles, and could eventually redefine the built environment in order to improve the city's equality regarding outdoor physical activity facilities and food stores. PMID:25647550

  5. NASA Affordable Vehicle Avionics (AVA): Common Modular Avionics System for Nano-Launchers Offering Affordable Access to Space

    NASA Technical Reports Server (NTRS)

    Cockrell, James

    2015-01-01

    Small satellites are becoming ever more capable of performing valuable missions for both government and commercial customers. However, currently these satellites can only be launched affordably as secondary payloads. This makes it difficult for the small satellite mission to launch when needed, to the desired orbit, and with acceptable risk. NASA Ames Research Center has developed and tested a prototype low-cost avionics package for space launch vehicles that provides complete GNC functionality in a package smaller than a tissue box with a mass less than 0.84 kg. AVA takes advantage of commercially available, low-cost, mass-produced, miniaturized sensors, filtering their more noisy inertial data with realtime GPS data. The goal of the Advanced Vehicle Avionics project is to produce and flight-verify a common suite of avionics and software that deliver affordable, capable GNC and telemetry avionics with application to multiple nano-launch vehicles at 1 the cost of current state-of-the-art avionics.

  6. False security or greater social inclusion? Exploring perceptions of CCTV use in public and private spaces accessed by the homeless.

    PubMed

    Huey, Laura

    2010-03-01

    It has been well documented that owing to the vulnerability inherent in their situation and status, the homeless experience high rates of harassment and criminal victimization. And yet, the question of whether CCTV surveillance of public and private spaces - so frequently viewed by the middle classes as a positive source of potential security - might also be viewed by the homeless in similar ways. Within the present paper, I address this issue by considering the possibility that CCTV might be seen by some homeless men and women as offering: a) a measure of enhanced security for those living in the streets and in shelters, and; b) to the extent that security is conceived of as a social good, the receipt of which marks one as a citizen of the state, a means by which they can be reconstituted as something more than 'lesser citizens'. To test these ideas, I rely on data from interviews conducted with homeless service users, service providers for the homeless, and police personnel in three cities. What is revealed is a mixed set of beliefs as to the relative security and meaning of CCTV. PMID:20377597

  7. Logarithmic conformal field theory

    NASA Astrophysics Data System (ADS)

    Gainutdinov, Azat; Ridout, David; Runkel, Ingo

    2013-12-01

    Conformal field theory (CFT) has proven to be one of the richest and deepest subjects of modern theoretical and mathematical physics research, especially as regards statistical mechanics and string theory. It has also stimulated an enormous amount of activity in mathematics, shaping and building bridges between seemingly disparate fields through the study of vertex operator algebras, a (partial) axiomatisation of a chiral CFT. One can add to this that the successes of CFT, particularly when applied to statistical lattice models, have also served as an inspiration for mathematicians to develop entirely new fields: the Schramm-Loewner evolution and Smirnov's discrete complex analysis being notable examples. When the energy operator fails to be diagonalisable on the quantum state space, the CFT is said to be logarithmic. Consequently, a logarithmic CFT is one whose quantum space of states is constructed from a collection of representations which includes reducible but indecomposable ones. This qualifier arises because of the consequence that certain correlation functions will possess logarithmic singularities, something that contrasts with the familiar case of power law singularities. While such logarithmic singularities and reducible representations were noted by Rozansky and Saleur in their study of the U (1|1) Wess-Zumino-Witten model in 1992, the link between the non-diagonalisability of the energy operator and logarithmic singularities in correlators is usually ascribed to Gurarie's 1993 article (his paper also contains the first usage of the term 'logarithmic conformal field theory'). The class of CFTs that were under control at this time was quite small. In particular, an enormous amount of work from the statistical mechanics and string theory communities had produced a fairly detailed understanding of the (so-called) rational CFTs. However, physicists from both camps were well aware that applications from many diverse fields required significantly more

  8. Conformations of Substituted Ethanes.

    ERIC Educational Resources Information Center

    Kingsbury, Charles A.

    1979-01-01

    Reviews state-of-the-art of conformational analysis and factors which affect it. Emphasizes sp-3 hybridized acrylic molecules. Provides examples on the importance of certain factors in determining conformation. Purpose, is to provide examples for examination questions. (Author/SA)

  9. Conformational Isomerism Can Limit Antibody Catalysis

    SciTech Connect

    Debler, E.W.; Muller, R.; Hilvert, D.; Wilson, I.A.

    2009-05-14

    Ligand binding to enzymes and antibodies is often accompanied by protein conformational changes. Although such structural adjustments may be conducive to enzyme catalysis, much less is known about their effect on reactions promoted by engineered catalytic antibodies. Crystallographic and pre-steady state kinetic analyses of antibody 34E4, which efficiently promotes the conversion of benzisoxazoles to salicylonitriles, show that the resting catalyst adopts two interconverting active-site conformations, only one of which is competent to bind substrate. In the predominant isomer, the indole side chain of Trp{sup L91} occupies the binding site and blocks ligand access. Slow conformational isomerization of this residue, on the same time scale as catalytic turnover, creates a deep and narrow binding site that can accommodate substrate and promote proton transfer using Glu{sup H50} as a carboxylate base. Although 34E4 is among the best catalysts for the deprotonation of benzisoxazoles, its efficiency appears to be significantly limited by this conformational plasticity of its active site. Future efforts to improve this antibody might profitably focus on stabilizing the active conformation of the catalyst. Analogous strategies may also be relevant to other engineered proteins that are limited by an unfavorable conformational pre-equilibrium.

  10. Conformational properties of oxazoline-amino acids

    NASA Astrophysics Data System (ADS)

    Staś, Monika; Broda, Małgorzata A.; Siodłak, Dawid

    2016-04-01

    Oxazoline-amino acids (Xaa-Ozn) occur in natural peptides of potentially important bioactivity. The conformations of the model compounds: Ac-(S)-Ala-Ozn(4R-Me), Ac-(S)-Ala-Ozn(4S-Me), and (gauche+, gauche-, anti) Ac-(S)-Val-Ozn(4R-Me) were studied at meta-hybrid M06-2X/6-311++G(d,p) method including solvent effect. Boc-L-Ala-L-Ozn-4-COOMe and Boc-L-Val-L-Ozn-4-COOMe were synthesized and studied by FT-IR and NMR-NOE methods. The conformations in crystal state were gathered from the Cambridge Structural Data Base. The main conformational feature of the oxazoline amino acids is the conformation β2 (ϕ,ψ ∼ -161°, -6°), which predominates in weakly polar environment and still is accessible in polar surrounding. The changes of the conformational preferences towards the conformations αR (ϕ,ψ ∼ -70°, -15°) and then β (ϕ,ψ ∼ -57°, -155°) are observed with increase of the environment polarity.

  11. ConfGen: a conformational search method for efficient generation of bioactive conformers.

    PubMed

    Watts, K Shawn; Dalal, Pranav; Murphy, Robert B; Sherman, Woody; Friesner, Rich A; Shelley, John C

    2010-04-26

    We describe the methodology, parametrization, and application of a conformational search method, called ConfGen, designed to efficiently generate bioactive conformers. We define efficiency as the ability to generate a bioactive conformation within a small total number of conformations using a reasonable amount of computer time. The method combines physics-based force field calculations with empirically derived heuristics designed to achieve efficient searching and prioritization of the ligand's conformational space. While many parameter settings are supported, four modes spanning a range of speed and quality trades-offs are defined and characterized. The validation set used to test the method is composed of ligands from 667 crystal structures covering a broad array of target and ligand classes. With the fastest mode, ConfGen uses an average of 0.5 s per ligand and generates only 14.3 conformers per ligand, at least one of which lies within 2.0 A root-mean-squared deviation of the crystal structure for 96% of the ligands. The most computationally intensive mode raises this recovery rate to 99%, while taking 8 s per ligand. Combining multiple search modes to "fill-in" holes in the conformation space or energy minimizing using an all-atom force field each lead to improvements in the recovery rates at higher resolutions. Overall, ConfGen is at least as good as competing programs at high resolution and demonstrates higher efficiency at resolutions sufficient for many downstream applications, such as pharmacophore modeling. PMID:20373803

  12. Quantifying macromolecular conformational transition pathways

    NASA Astrophysics Data System (ADS)

    Seyler, Sean; Kumar, Avishek; Thorpe, Michael; Beckstein, Oliver

    2015-03-01

    Diverse classes of proteins function through large-scale conformational changes that are challenging for computer simulations. A range of fast path-sampling techniques have been used to generate transitions, but it has been difficult to compare paths from (and assess the relative strengths of) different methods. We introduce a comprehensive method (pathway similarity analysis, PSA) for quantitatively characterizing and comparing macromolecular pathways. The Hausdorff and Fréchet metrics (known from computational geometry) are used to quantify the degree of similarity between polygonal curves in configuration space. A strength of PSA is its use of the full information available from the 3 N-dimensional configuration space trajectory without requiring additional specific knowledge about the system. We compare a sample of eleven different methods for the closed-to-open transitions of the apo enzyme adenylate kinase (AdK) and also apply PSA to an ensemble of 400 AdK trajectories produced by dynamic importance sampling MD and the Geometrical Pathways algorithm. We discuss the method's potential to enhance our understanding of transition path sampling methods, validate them, and help guide future research toward deeper physical insights into conformational transitions.

  13. FAST Conformational Searches by Balancing Exploration/Exploitation Trade-Offs.

    PubMed

    Zimmerman, Maxwell I; Bowman, Gregory R

    2015-12-01

    Molecular dynamics simulations are a powerful means of understanding conformational changes. However, it is still difficult to simulate biologically relevant time scales without the use of specialized supercomputers. Here, we introduce a goal-oriented sampling method, called fluctuation amplification of specific traits (FAST), for extending the capabilities of commodity hardware. This algorithm rapidly searches conformational space for structures with desired properties by balancing trade-offs between focused searches around promising solutions (exploitation) and trying novel solutions (exploration). FAST was inspired by the hypothesis that many physical properties have an overall gradient in conformational space, akin to the energetic gradients that are known to guide proteins to their folded states. For example, we expect that transitioning from a conformation with a small solvent-accessible surface area to one with a large surface area will require passing through a series of conformations with steadily increasing surface areas. We demonstrate that such gradients are common through retrospective analysis of existing Markov state models (MSMs). Then we design the FAST algorithm to exploit these gradients to find structures with desired properties by (1) recognizing and amplifying structural fluctuations along gradients that optimize a selected physical property whenever possible, (2) overcoming barriers that interrupt these overall gradients, and (3) rerouting to discover alternative paths when faced with insurmountable barriers. To test FAST, we compare its performance to other methods for three common types of problems: (1) identifying unexpected binding pockets, (2) discovering the preferred paths between specific structures, and (3) folding proteins. Our conservative estimate is that FAST outperforms conventional simulations and an adaptive sampling algorithm by at least an order of magnitude. Furthermore, FAST yields both the proper thermodynamics and

  14. [Conformers of carnosine].

    PubMed

    Kliuev, S A

    2006-01-01

    The geometric and energetic parameters of most stable conformations of carnosine were calculated by the semiempirical guantum-chemical method PM3. The carnosine-water-zinc (II) clusters were simulated. PMID:16909845

  15. Quantum massive conformal gravity

    NASA Astrophysics Data System (ADS)

    Faria, F. F.

    2016-04-01

    We first find the linear approximation of the second plus fourth order derivative massive conformal gravity action. Then we reduce the linearized action to separated second order derivative terms, which allows us to quantize the theory by using the standard first order canonical quantization method. It is shown that quantum massive conformal gravity is renormalizable but has ghost states. A possible decoupling of these ghost states at high energies is discussed.

  16. Performance of asynchronous fiber-optic code division multiple access system based on three-dimensional wavelength/time/space codes and its link analysis.

    PubMed

    Singh, Jaswinder

    2010-03-10

    A novel family of three-dimensional (3-D) wavelength/time/space codes for asynchronous optical code-division-multiple-access (CDMA) systems with "zero" off-peak autocorrelation and "unity" cross correlation is reported. Antipodal signaling and differential detection is employed in the system. A maximum of [(W x T+1) x W] codes are generated for unity cross correlation, where W and T are the number of wavelengths and time chips used in the code and are prime. The conditions for violation of the cross-correlation constraint are discussed. The expressions for number of generated codes are determined for various code dimensions. It is found that the maximum number of codes are generated for S < or = min(W,T), where W and T are prime and S is the number of space channels. The performance of these codes is compared to the earlier reported two-dimensional (2-D)/3-D codes for asynchronous systems. The codes have a code-set-size to code-size ratio greater than W/S. For instance, with a code size of 2065 (59 x 7 x 5), a total of 12,213 users can be supported, and 130 simultaneous users at a bit-error rate (BER) of 10(-9). An arrayed-waveguide-grating-based reconfigurable encoder/decoder design for 2-D implementation for the 3-D codes is presented so that the need for multiple star couplers and fiber ribbons is eliminated. The hardware requirements of the coders used for various modulation/detection schemes are given. The effect of insertion loss in the coders is shown to be significantly reduced with loss compensation by using an amplifier after encoding. An optical CDMA system for four users is simulated and the results presented show the improvement in performance with the use of loss compensation. PMID:20220892

  17. Experimental Evaluation of Time Diversity Effect in Hybrid ARQ Considering Space and Path Diversity for Downlink OFDM-Based Broadband Radio Access

    NASA Astrophysics Data System (ADS)

    Miki, Nobuhiko; Atarashi, Hiroyuki; Higuchi, Kenichi; Sawahashi, Mamoru; Nakagawa, Masao

    This paper presents experimental evaluations of the effect of time diversity obtained by hybrid automatic repeat request (HARQ) with soft combining in space and path diversity schemes on orthogonal frequency division multiplexing (OFDM)-based packet radio access in a downlink broadband multipath fading channel. The effect of HARQ is analyzed through laboratory experiments employing fading simulators and field experiments conducted in downtown Yokosuka near Tokyo. After confirming the validity of experimental results based on numerical analysis of the time diversity gain in HARQ, we show by the experimental results that, for a fixed modulation and channel coding scheme (MCS), time diversity obtained by HARQ is effective in reducing the required received signal-to-interference plus noise power ratio (SINR) according to an increase in the number of transmissions, K, up to 10, even when the diversity effects are obtained through two-branch antenna diversity reception and path diversity using a number of multipaths greater than 12 observed in a real fading channel. Meanwhile, in combined use with the adaptive modulation and channel coding (AMC) scheme associated with space and path diversity, we clarify that the gain obtained by time diversity is almost saturated at the maximum number of transmissions in HARQ, K' = 4 in Chase combining and K' = 2 in Incremental redundancy, since the improvement in the residual packet error rate (PER) obtained through time diversity becomes small owing to the low PER in the initial packet transmission arising from appropriately selecting the optimum MCS in AMC. However, the experimental results elucidate that the time diversity in HARQ with soft combining associated with antenna diversity reception is effective in improving the throughput even in a broadband multipath channel with sufficient path diversity.

  18. Conformation analysis of intermediates of analogues of Tamoxifen

    NASA Astrophysics Data System (ADS)

    Kapiller-Dezsőfi, Rita; Németh, Gábor; Lax, Györgyi; Simig, Gyula; Sohár, Pál

    1998-01-01

    The configuration and the conformation of two trifluoromethyl-triaryl-ethane diastereomer pairs and of some sole isomers were determined using the through-space spin-spin coupling between fluorine atoms and the hydrogen of the hydroxyl group. The molecule-mechanical calculations support the results of the conformation-analysis based on the NMR data.

  19. NLO conformal symmetry in the Regge limit of QCD

    SciTech Connect

    Coriano, C.; White, A.R.; Wuesthoff, M.

    1996-09-18

    The authors show that a scale invariant approximation to the next-to-leading order BFKL kernel, constructed via transverse momentum diagrams, has a simple conformally invariant representation in impact parameter space. That a conformally invariant representation exists is shown first by relating the kernel directly to Feynman diagrams contributing to two photon diffractive dissociation.

  20. Conformal Invariance of the 3D Self-Avoiding Walk

    NASA Astrophysics Data System (ADS)

    Kennedy, Tom

    2013-10-01

    We show that if the three-dimensional self-avoiding walk (SAW) is conformally invariant, then one can compute the hitting densities for the SAW in a half-space and in a sphere. We test these predictions by Monte Carlo simulations and find excellent agreement, thus providing evidence that the SAW is conformally invariant in three dimensions.

  1. Protein Conformational Populations and Functionally Relevant Sub-states

    SciTech Connect

    Agarwal, Pratul K; Burger, Virginia; Savol, Andrej; Ramanathan, Arvind; Chennubhotla, Chakra

    2013-01-01

    Functioning proteins do not remain fixed in a unique structure, but instead they sample a range of conformations facilitated by motions within the protein. Even in the native state, a protein exists as a collection of interconverting conformations driven by thermodynamic fluctuations. Motions on the fast time scale allow a protein to sample conformations in the nearby area of its conformational landscape, while motions on slower time scales give it access to conformations in distal areas of the landscape. Emerging evidence indicates that protein landscapes contain conformational substates with dynamic and structural features that support the designated function of the protein. Nuclear magnetic resonance (NMR) experiments provide information about conformational ensembles of proteins. X-ray crystallography allows researchers to identify the most populated states along the landscape, and computational simulations give atom-level information about the conformational substates of different proteins. This ability to characterize and obtain quantitative information about the conformational substates and the populations of proteins within them is allowing researchers to better understand the relationship between protein structure and dynamics and the mechanisms of protein function. In this Account, we discuss recent developments and challenges in the characterization of functionally relevant conformational populations and substates of proteins. In some enzymes, the sampling of functionally relevant conformational substates is connected to promoting the overall mechanism of catalysis. For example, the conformational landscape of the enzyme dihydrofolate reductase has multiple substates, which facilitate the binding and the release of the cofactor and substrate and catalyze the hydride transfer. For the enzyme cyclophilin A, computational simulations reveal that the long time scale conformational fluctuations enable the enzyme to access conformational substates that allow

  2. A disulfide-stabilized conformer of methionine synthase reveals an unexpected role for the histidine ligand of the cobalamin cofactor

    PubMed Central

    Datta, Supratim; Koutmos, Markos; Pattridge, Katherine A.; Ludwig, Martha L.; Matthews, Rowena G.

    2008-01-01

    B12-dependent methionine synthase (MetH) from Escherichia coli is a large modular protein that is alternately methylated by methyltetrahydrofolate to form methylcobalamin and demethylated by homocysteine to form cob(I)alamin. Major domain rearrangements are required to allow cobalamin to react with three different substrates: homocysteine, methyltetrahydrofolate, and S-adenosyl-l-methionine (AdoMet). These same rearrangements appear to preclude crystallization of the wild-type enzyme. Disulfide cross-linking was used to lock a C-terminal fragment of the enzyme into a unique conformation. Cysteine point mutations were introduced at Ile-690 and Gly-743. These cysteine residues span the cap and the cobalamin-binding module and form a cross-link that reduces the conformational space accessed by the enzyme, facilitating protein crystallization. Here, we describe an x-ray structure of the mutant fragment in the reactivation conformation; this conformation enables the transfer of a methyl group from AdoMet to the cobalamin cofactor. In the structure, the axial ligand to the cobalamin, His-759, dissociates from the cobalamin and forms intermodular contacts with residues in the AdoMet-binding module. This unanticipated intermodular interaction is expected to play a major role in controlling the distribution of conformers required for the catalytic and the reactivation cycles of the enzyme. PMID:18332423

  3. A disulfide-stabilized conformer of methionine synthase reveals an unexpected role for the histidine ligand of the cobalamin cofactor

    SciTech Connect

    Datta, Supratim; Koutmos, Markos; Pattridge, Katherine A.; Ludwig, Martha L.; Matthews, Rowena G.

    2008-07-08

    B{sub 12}-dependent methionine synthase (MetH) from Escherichia coli is a large modular protein that is alternately methylated by methyltetrahydrofolate to form methylcobalamin and demethylated by homocysteine to form cob(I)alamin. Major domain rearrangements are required to allow cobalamin to react with three different substrates: homocysteine, methyltetrahydrofolate, and S-adenosyl-l-methionine (AdoMet). These same rearrangements appear to preclude crystallization of the wild-type enzyme. Disulfide cross-linking was used to lock a C-terminal fragment of the enzyme into a unique conformation. Cysteine point mutations were introduced at Ile-690 and Gly-743. These cysteine residues span the cap and the cobalamin-binding module and form a cross-link that reduces the conformational space accessed by the enzyme, facilitating protein crystallization. Here, we describe an x-ray structure of the mutant fragment in the reactivation conformation; this conformation enables the transfer of a methyl group from AdoMet to the cobalamin cofactor. In the structure, the axial ligand to the cobalamin, His-759, dissociates from the cobalamin and forms intermodular contacts with residues in the AdoMet-binding module. This unanticipated intermodular interaction is expected to play a major role in controlling the distribution of conformers required for the catalytic and the reactivation cycles of the enzyme.

  4. Fluorine in fragrances: exploring the difluoromethylene (CF2) group as a conformational constraint in macrocyclic musk lactones.

    PubMed

    Corr, Michael J; Cormanich, Rodrigo A; von Hahmann, Cortney N; Bühl, Michael; Cordes, David B; Slawin, Alexandra M Z; O'Hagan, David

    2016-01-01

    The CF2 group is incorporated into specific positions within the lactone ring of the natural musk lactone, (12R)-(+)-12-methyl-13-tridecanolide, a constituent of Angelica root oil, Angelica archangelica L. The approach is taken as it was anticipated that CF2 groups would dictate corner locations in the macrocycle and limit the conformational space available to the lactone. Three fluorine containing lactones are prepared by organic synthesis. One (8) has CF2 groups located at the C-6 and C-9 positions, another (9) with CF2 groups at the C-5 and C-9 positions, and a third (10) with a CF2 group at C-8. Two of the fluorine containing lactones (8 and 10) were sufficiently crystalline to obtain X-ray crystal structures which revealed that the CF2 groups do adopt corner locations. All three lactones were subject to computational analysis at the B3LYP-D3/6-311+G** level to assess the relative energies of different conformers. In all cases, the global minima and most of the lowest energy minima have squared/rectangular geometries and located the CF2 groups at the corners. The lowest energy structures for 8 and 10 closely approximated the observed X-ray structures, suggesting good convergence of theory and experiment in determining relevant low energy conformations. All three compounds retained a pleasant odour suggesting the rings retained sufficient conformational flexibility to access relevant olfactory conformations. PMID:26584449

  5. CONSTRUCTING SURROGATE MODELS OF COMPLEX SYSTEMS WITH ENHANCED SPARSITY: QUANTIFYING THE INFLUENCE OF CONFORMATIONAL UNCERTAINTY IN BIOMOLECULAR SOLVATION*

    PubMed Central

    Lei, H.; Yang, X.; Zheng, B.; Lin, G.; Baker, N. A.

    2015-01-01

    Biomolecules exhibit conformational fluctuations near equilibrium states, inducing uncertainty in various biological properties in a dynamic way. We have developed a general method to quantify the uncertainty of target properties induced by conformational fluctuations. Using a generalized polynomial chaos (gPC) expansion, we construct a surrogate model of the target property with respect to varying conformational states. To alleviate the high-dimensionality of the corresponding stochastic space, we propose a method to increase the sparsity of the gPC expansion by defining a set of conformational “active space” random variables. With the increased sparsity, we employ the compressive sensing method to accurately construct the surrogate model. We demonstrate the performance of the surrogate model by evaluating fluctuation-induced uncertainty in solvent-accessible surface area for the bovine trypsin inhibitor protein system and show that the new approach offers more accurate statistical information than standard Monte Carlo approaches. Furthermore, the constructed surrogate model also enables us to directly evaluate the target property under various conformational states, yielding a more accurate response surface than standard sparse grid collocation methods. In particular, the new method provides higher accuracy in high-dimensional systems, such as biomolecules, where sparse grid performance is limited by the accuracy of the computed quantity of interest. Our new framework is generalizable and can be used to investigate the uncertainty of a wide variety of target properties in biomolecular systems. PMID:26766929

  6. Logarithmic conformal field theory

    NASA Astrophysics Data System (ADS)

    Gainutdinov, Azat; Ridout, David; Runkel, Ingo

    2013-12-01

    Conformal field theory (CFT) has proven to be one of the richest and deepest subjects of modern theoretical and mathematical physics research, especially as regards statistical mechanics and string theory. It has also stimulated an enormous amount of activity in mathematics, shaping and building bridges between seemingly disparate fields through the study of vertex operator algebras, a (partial) axiomatisation of a chiral CFT. One can add to this that the successes of CFT, particularly when applied to statistical lattice models, have also served as an inspiration for mathematicians to develop entirely new fields: the Schramm-Loewner evolution and Smirnov's discrete complex analysis being notable examples. When the energy operator fails to be diagonalisable on the quantum state space, the CFT is said to be logarithmic. Consequently, a logarithmic CFT is one whose quantum space of states is constructed from a collection of representations which includes reducible but indecomposable ones. This qualifier arises because of the consequence that certain correlation functions will possess logarithmic singularities, something that contrasts with the familiar case of power law singularities. While such logarithmic singularities and reducible representations were noted by Rozansky and Saleur in their study of the U (1|1) Wess-Zumino-Witten model in 1992, the link between the non-diagonalisability of the energy operator and logarithmic singularities in correlators is usually ascribed to Gurarie's 1993 article (his paper also contains the first usage of the term 'logarithmic conformal field theory'). The class of CFTs that were under control at this time was quite small. In particular, an enormous amount of work from the statistical mechanics and string theory communities had produced a fairly detailed understanding of the (so-called) rational CFTs. However, physicists from both camps were well aware that applications from many diverse fields required significantly more

  7. ACCESS Pointing Control System

    NASA Technical Reports Server (NTRS)

    Brugarolas, Paul; Alexander, James; Trauger, John; Moody, Dwight; Egerman, Robert; Vallone, Phillip; Elias, Jason; Hejal, Reem; Camelo, Vanessa; Bronowicki, Allen; O'Connor, David; Partrick, Richard; Orzechowski, Pawel; Spitter, Connie; Lillie, Chuck

    2010-01-01

    ACCESS (Actively-Corrected Coronograph for Exoplanet System Studies) was one of four medium-class exoplanet concepts selected for the NASA Astrophysics Strategic Mission Concept Study (ASMCS) program in 2008/2009. The ACCESS study evaluated four major coronograph concepts under a common space observatory. This paper describes the high precision pointing control system (PCS) baselined for this observatory.

  8. Sampling Long Timescale Protein Motions: OSRW Simulation of Active Site Loop Conformational Free Energies in Formyl-CoA:Oxalate CoA Transferase

    PubMed Central

    Lee, Sangbae; Chen, Mengen; Yang, Wei; Richards, Nigel G. J.

    2010-01-01

    X-ray crystallographic snapshots have shown that conformational changes of a tetraglycine loop in the active site of formyl-CoA: oxalate CoA transferase (FRC) play an important role in the catalytic cycle of the enzyme. Orthogonal space random walk (OSRW) simulations have been applied to obtain quantitative computational estimates of the relative free energy of the “open” and “closed” conformations of this loop together with the energetic barrier for interconversion of these states in wild type FRC. These OSRW calculations not only show that the two conformations have similar free energies but also predict a barrier that is consistent with the observed turnover number of the enzyme. In an effort to quantitate the importance of specific residues in the tetraglycine loop, OSRW simulations have also been performed on the G258A, G259A, G260A and G261A FRC variants both to examine the energetic effects of replacing each glycine residue and to correlate the computed energies with kinetic and structural observations. In enzymes with substantially reduced catalytic efficiency (kcat/KM), the OSRW simulations reveal the adoption of additional low energy loop conformations. In the case of the G260A FRC variant, the new conformation identified by simulation is similar to that observed in the X-ray crystal structure of the protein. These results provide further evidence for the power of the OSRW method in sampling conformational space, and hence in providing quantitative free energy estimates for the conformations adopted by functionally important active site loops. In addition, these simulations model the motions of side chains that are correlated with changes in loop conformation thereby permitting access to long time-scale motions through the use of nanosecond simulations. PMID:20446682

  9. Bianchi type-I models with conformally invariant scalar field

    SciTech Connect

    Accioly, A.J.; Vaidya, A.N.; Som, M.M.

    1983-05-15

    The solutions of the Einstein equations with the trace-free energy-momentum tensor of conformally invariant scalar field as source are obtained in a spatially homogeneous anisotropic space-time. Some interesting features of the solutions are discussed.

  10. Picosecond conformational transition and equilibration of a cyclic peptide

    NASA Astrophysics Data System (ADS)

    Bredenbeck, Jens; Helbing, Jan; Sieg, Arne; Schrader, Tobias; Zinth, Wolfgang; Renner, Christian; Behrendt, Raymond; Moroder, Luis; Wachtveitl, Josef; Hamm, Peter

    2003-05-01

    Ultrafast IR spectroscopy is used to monitor the nonequilibrium backbone dynamics of a cyclic peptide in the amide I vibrational range with picosecond time resolution. A conformational change is induced by means of a photoswitch integrated into the peptide backbone. Although the main conformational change of the backbone is completed after only 20 ps, the subsequent equilibration in the new region of conformational space continues for times >16 ns. Relaxation and equilibration processes of the peptide backbone occur on a discrete hierarchy of time scales. Albeit possessing only a few conformational degrees of freedom compared with a protein, the peptide behaves highly nontrivially and provides insights into the complexity of fast protein folding.

  11. Isoperimetric inequality on conformally hyperbolic manifolds

    SciTech Connect

    Kesel'man, V M

    2003-04-30

    It is shown that on an arbitrary non-compact Riemannian manifold of conformally hyperbolic type the isoperimetric inequality can be taken by a conformal change of the metric to the same canonical linear form as in the case of the standard hyperbolic Lobachevskii space. Both the absolute isoperimetric inequality and the relative one (for manifolds with boundary) are obtained. This work develops the results and methods of a joint paper with Zorich, in which the absolute isoperimetric inequality was obtained under a certain additional condition; the resulting statements are definitive in a certain sense.

  12. Conformal Collineations in String Cosmology

    NASA Astrophysics Data System (ADS)

    Baysal, Hüsnü; Camci, U.ğur; Tarhan, İsmail; Yilmaz, İhsan; Yavuz, İlhami; Dolgov, A.

    In this paper, we study the consequences of the existence of conformal collineations (CC) for string cloud in the context of general relativity. Especially, we interest in special conformal collineation (SCC), generated by a special affine conformal collineation (SACC) in the string cloud. Some results on the restrictions imposed by a conformal collineation symmetry in the string cloud are obtained.

  13. Conformational kinetics reveals affinities of protein conformational states

    PubMed Central

    Daniels, Kyle G.; Suo, Yang; Oas, Terrence G.

    2015-01-01

    Most biological reactions rely on interplay between binding and changes in both macromolecular structure and dynamics. Practical understanding of this interplay requires detection of critical intermediates and determination of their binding and conformational characteristics. However, many of these species are only transiently present and they have often been overlooked in mechanistic studies of reactions that couple binding to conformational change. We monitored the kinetics of ligand-induced conformational changes in a small protein using six different ligands. We analyzed the kinetic data to simultaneously determine both binding affinities for the conformational states and the rate constants of conformational change. The approach we used is sufficiently robust to determine the affinities of three conformational states and detect even modest differences in the protein’s affinities for relatively similar ligands. Ligand binding favors higher-affinity conformational states by increasing forward conformational rate constants and/or decreasing reverse conformational rate constants. The amounts by which forward rate constants increase and reverse rate constants decrease are proportional to the ratio of affinities of the conformational states. We also show that both the affinity ratio and another parameter, which quantifies the changes in conformational rate constants upon ligand binding, are strong determinants of the mechanism (conformational selection and/or induced fit) of molecular recognition. Our results highlight the utility of analyzing the kinetics of conformational changes to determine affinities that cannot be determined from equilibrium experiments. Most importantly, they demonstrate an inextricable link between conformational dynamics and the binding affinities of conformational states. PMID:26162682

  14. Conformational flexibility of mephenesin.

    PubMed

    Écija, Patricia; Evangelisti, Luca; Vallejo, Montserrat; Basterretxea, Francisco J; Lesarri, Alberto; Castaño, Fernando; Caminati, Walther; Cocinero, Emilio J

    2014-05-22

    The mephenesin molecule (3-(2-methylphenoxy)propane-1,2-diol) serves as a test bank to explore several structural and dynamical issues, such as conformational flexibility, the orientation of the carbon linear chain relative to the benzene plane, or the effect of substituent position on the rotational barrier of a methyl group. The molecule has been studied by rotational spectroscopy in the 4-18 GHz frequency range by Fourier-transform methods in a supersonic expansion. The experiment has been backed by a previous conformational search plus optimization of the lowest energy structures by ab initio and density functional quantum calculations. The three lowest-lying conformers that can interconvert to each other by simple bond rotations have been detected in the jet. Rotational parameters for all structures have been obtained, and methyl torsional barriers have been determined for the two lowest-lying rotamers. The lowest-lying structure of mephenesin is highly planar, with all carbon atoms lying nearly in the benzene ring plane, and is stabilized by the formation of cooperative intramolecular hydrogen bonding. An estimation of the relative abundance of the detected conformers indicates that the energetically most stable conformer will have an abundance near 80% at temperatures relevant for biological activity. PMID:24754523

  15. Conformers of Gaseous Serine.

    PubMed

    He, Kedan; Allen, Wesley D

    2016-08-01

    The myriad conformers of the neutral form of natural amino acid serine (Ser) have been investigated by systematic computations with reliable electronic wave function methods. A total of 85 unique conformers were located using the MP2/cc-pVTZ level of theory. The 12 lowest-energy conformers of serine fall within a 8 kJ mol(-1) window, and for these species, geometric structures, precise relative energies, equilibrium and vibrationally averaged rotational constants, anharmonic vibrational frequencies, infrared intensities, quartic and sextic centrifugal distortion constants, dipole moments, and (14)N nuclear quadrupole coupling constants were computed. The relative energies were refined through composite focal-point analyses employing basis sets as large as aug-cc-pV5Z and correlation treatments through CCSD(T). The rotational constants for seven conformers measured by Fourier-transform microwave spectroscopy are in good agreement with the vibrationally averaged rotational constants computed in this study. Our anharmonic vibrational frequencies are compared to the large number of experimental vibrational absorptions attributable to at least six conformers. PMID:27294314

  16. Enhancing Scientific Collaboration, Transparency, and Public Access: Utilizing the Second Life Platform to Convene a Scientific Conference in 3-D Virtual Space

    NASA Astrophysics Data System (ADS)

    McGee, B. W.

    2006-12-01

    Recent studies reveal a general mistrust of science as well as a distorted perception of the scientific method by the public at-large. Concurrently, the number of science undergraduate and graduate students is in decline. By taking advantage of emergent technologies not only for direct public outreach but also to enhance public accessibility to the science process, it may be possible to both begin a reversal of popular scientific misconceptions and to engage a new generation of scientists. The Second Life platform is a 3-D virtual world produced and operated by Linden Research, Inc., a privately owned company instituted to develop new forms of immersive entertainment. Free and downloadable to the public, Second Life offers an imbedded physics engine, streaming audio and video capability, and unlike other "multiplayer" software, the objects and inhabitants of Second Life are entirely designed and created by its users, providing an open-ended experience without the structure of a traditional video game. Already, educational institutions, virtual museums, and real-world businesses are utilizing Second Life for teleconferencing, pre-visualization, and distance education, as well as to conduct traditional business. However, the untapped potential of Second Life lies in its versatility, where the limitations of traditional scientific meeting venues do not exist, and attendees need not be restricted by prohibitive travel costs. It will be shown that the Second Life system enables scientific authors and presenters at a "virtual conference" to display figures and images at full resolution, employ audio-visual content typically not available to conference organizers, and to perform demonstrations or premier three-dimensional renderings of objects, processes, or information. An enhanced presentation like those possible with Second Life would be more engaging to non- scientists, and such an event would be accessible to the general users of Second Life, who could have an

  17. Crystal Structures of the FAK Kinase in Complex with TAE226 and Related bis-anilino Pyrimidine Inhibitors Reveal a Helical DFG Conformation

    SciTech Connect

    Lietha, D.; Eck, M

    2008-01-01

    Focal Adhesion Kinase (FAK) is a non-receptor tyrosine kinase required for cell migration, proliferation and survival. FAK overexpression has been documented in diverse human cancers and is associated with a poor clinical outcome. Recently, a novel bis-anilino pyrimidine inhibitor, TAE226, was reported to efficiently inhibit FAK signaling, arrest tumor growth and invasion and prolong the life of mice with glioma or ovarian tumor implants. Here we describe the crystal structures of the FAK kinase bound to TAE226 and three related bis-anilino pyrimidine compounds. TAE226 induces a conformation of the N-terminal portion of the kinase activation loop that is only observed in FAK, but is distinct from the conformation in both the active and inactive states of the kinase. This conformation appears to require a glycine immediately N-terminal to the 'DFG motif', which adopts a helical conformation stabilized by interactions with TAE226. The presence of a glycine residue in this position contributes to the specificity of TAE226 and related compounds for FAK. Our work highlights the fact that kinases can access conformational space that is not necessarily utilized for their native catalytic regulation, and that such conformations can explain and be exploited for inhibitor specificity.

  18. Extended conformal algebras

    NASA Astrophysics Data System (ADS)

    Bouwknegt, Peter

    1988-06-01

    We investigate extensions of the Virasoro algebra by a single primary field of integer or halfinteger conformal dimension Δ. We argue that for vanishing structure constant CΔΔΔ, the extended conformal algebra can only be associative for a generic c-value if Δ=1/2, 1, 3/2, 2 or 3. For the other Δ<=5 we compute the finite set of allowed c-values and identify the rational solutions. The case CΔΔΔ≠0 is also briefly discussed. I would like to thank Kareljan Schoutens for discussions and Sander Bais for a careful reading of the manuscript.

  19. Space Construction

    NASA Technical Reports Server (NTRS)

    Hagaman, Jane A. (Editor)

    1987-01-01

    The purpose was to present to the aerospace community an in-depth review of Experimental Assembly of Structures on EVA (EASE)/Assembly Concept for Construction of Erectable Space Structures (ACCESS) space flight experiments and to present the status of activities regarding future space flight experiments and accompanying technology developments that will demonstrate the capability of on-orbit construction required for the Space Station.

  20. Transgender Adults' Access to College Bathrooms and Housing and the Relationship to Suicidality.

    PubMed

    Seelman, Kristie L

    2016-10-01

    Transgender and gender non-conforming people frequently experience discrimination, harassment, and marginalization across college and university campuses (Bilodeau, 2007; Finger, 2010; Rankin et al., 2010; Seelman et al., 2012). The minority stress model (Meyer, 2007) posits that experiences of discrimination often negatively impact the psychological wellbeing of minority groups. However, few scholars have examined whether college institutional climate factors-such as being denied access to bathrooms or gender-appropriate campus housing-are significantly associated with detrimental psychological outcomes for transgender people. Using the National Transgender Discrimination Survey, this study analyzes whether being denied access to these spaces is associated with lifetime suicide attempts, after controlling for interpersonal victimization by students or teachers. Findings from sequential logistic regression (N = 2,316) indicate that denial of access to either space had a significant relationship to suicidality, even after controlling for interpersonal victimization. This article discusses implications for higher education professionals and researchers. PMID:26914181

  1. Atomistic simulations of the MS2 coat protein conformational transition

    NASA Astrophysics Data System (ADS)

    Perkett, Matthew; Pontiggia, Francesco; Hagan, Michael

    2012-02-01

    During the replication of many viruses, hundreds to thousands of proteins self-assemble to form a protective protein coat, called a capsid, around the viral nucleic acid. Often these proteins have identical amino acid sequences with slightly different, or quasi-equivalent, conformations, which join in precise spatial arrangements. Although the structure of completed capsids is known to atomic resolution, little is known about the assembly intermediates and how protein conformations are selected during assembly. In this talk, we will use all-atom simulations to investigate how protein-RNA interactions guide conformational transitions of capsid proteins from the single-stranded RNA bacteriophage MS2. Since conformational changes occur on timescales which are not accessible to all-atom simulations, we use enhanced sampling methods to sample probable transition pathways and corresponding free energy profiles. Specifically, we will present free energy profiles associated with the MS2 capsid protein conformation in the presence and absence of RNA.

  2. Dynamics and Conformational Energetics of a Peptide Hormone: Vasopressin

    NASA Astrophysics Data System (ADS)

    Hagler, A. T.; Osguthorpe, D. J.; Dauber-Osguthorpe, P.; Hempel, J. C.

    1985-03-01

    A theoretical methodology for use in conjunction with experiment was applied to the neurohypophyseal hormone lysine vasopressin for elucidation of its accessible molecular conformations and associated flexibility, conformational transitions, and dynamics. Molecular dynamics and energy minimization techniques make possible a description of the conformational properties of a peptide in terms of the precise positions of atoms, their fluctuations in time, and the interatomic forces acting on them. Analysis of the dynamic trajectory of lysine vasopressin shows the ability of a flexible peptide hormone to undergo spontaneous conformational transitions. The excursions of an individual phenylalanine residue exemplify the dynamic flexibility and multiple conformational states available to small peptide hormones and their component residues, even within constraints imposed by a cyclic hexapeptide ring.

  3. Conformal cloak for waves

    SciTech Connect

    Chen Huanyang; Leonhardt, Ulf; Tyc, Tomas

    2011-05-15

    Conformal invisibility devices are only supposed to work within the valid range of geometrical optics. Here, we show by numerical simulations and analytical arguments that for certain quantized frequencies, they are nearly perfect even in a regime that clearly violates geometrical optics. The quantization condition follows from the analogy between the Helmholtz equation and the stationary Schroedinger equation.

  4. Extended conformal field theories

    NASA Astrophysics Data System (ADS)

    Taormina, Anne

    1990-08-01

    Some extended conformal field theories are briefly reviewed. They illustrate how non minimal models of the Virasoro algebra (c≥1) can become minimal with respect to a larger algebra. The accent is put on N-extended superconformal algebras, which are relevant in superstring compactification.

  5. PERSONALITY AND CONFORMITY.

    ERIC Educational Resources Information Center

    BAROCAS, RALPH; GORLOW, LEON

    AN INVESTIGATION WAS MADE OF THE RELATIONSHIP BETWEEN PERSONALITY FACTORS AND CONFORMITY. THE SUBJECTS WERE 243 RANDOMLY SELECTED STUDENTS ENROLLED IN COLLEGE PSYCHOLOGY COURSES WHO WERE DIVIDED INTO GROUPS OF 97, 96, AND 50 SUBJECTS. A PERSONALITY FACTOR INVENTORY WAS OBTAINED FROM RESPONSES TO A LARGE LIST OF TRUE-FALSE PERSONALITY ITEM…

  6. Animal culture: chimpanzee conformity?

    PubMed

    van Schaik, Carel P

    2012-05-22

    Culture-like phenomena in wild animals have received much attention, but how good is the evidence and how similar are they to human culture? New data on chimpanzees suggest their culture may even have an element of conformity. PMID:22625856

  7. Conformal dome correction with counterrotating phase plates

    NASA Astrophysics Data System (ADS)

    Sparrold, Scott W.; Mills, James P.; Knapp, David J.; Ellis, Kenneth S.; Mitchell, Thomas A.; Manhart, Paul K.

    2000-07-01

    Windows and domes that are shaped to aerodynamic requirements can increase range and speed for the host platform. This class of optical systems is referred to as conformal optics. The solution discussed here is intended for conformal missile systems having gimbals that point the optical line of sight through different parts of the dome. A conformal dome induces large amounts of varying aberration, tens to hundreds of waves across gimbal angle, and therefore requires dynamic correction. Space is very constricted in missile sensors, and it is therefore highly desirable to limit the number of motors used for aberration correction. This paper describes the performance of a new class of optical systems that employ counterrotating phase prisms to correct conformal dome aberrations while gimbaling the optical system. The phase surfaces on the prisms are described by Zernike circular polynomials. Since the shear across the phase surfaces is rotational, the only aberrations that are generated are those without rotational symmetry, such as tilt, coma, or astigmatism. Using this approach, CODE VTM was used to analyze and design a compact, high-performance conformal optical system.

  8. Global attractors of complete conformal foliations

    SciTech Connect

    Zhukova, Nina I

    2012-03-31

    We prove that every complete conformal foliation (M,F) of codimension q{>=}3 is either Riemannian or a (Conf(S{sup q}), S{sup q})-foliation. We further prove that if (M,F) is not Riemannian, it has a global attractor which is either a nontrivial minimal set or a closed leaf or a union of two closed leaves. In this theorem we do not assume that the manifold M is compact. In particular, every proper conformal non-Riemannian foliation (M,F) has a global attractor which is either a closed leaf or a union of two closed leaves, and the space of all nonclosed leaves is a connected q-dimensional orbifold. We show that every countable group of conformal transformations of the sphere S{sup q} can be realized as the global holonomy group of a complete conformal foliation. Examples of complete conformal foliations with exceptional and exotic minimal sets as global attractors are constructed. Bibliography: 20 titles.

  9. Seed conformal blocks in 4D CFT

    NASA Astrophysics Data System (ADS)

    Echeverri, Alejandro Castedo; Elkhidir, Emtinan; Karateev, Denis; Serone, Marco

    2016-02-01

    We compute in closed analytical form the minimal set of "seed" conformal blocks associated to the exchange of generic mixed symmetry spinor/tensor operators in an arbitrary representation ( ℓ, overline{ℓ} ) of the Lorentz group in four dimensional conformal field theories. These blocks arise from 4-point functions involving two scalars, one (0, | ℓ - overline{7ell;} |) and one (| ℓ - overline{ℓ} |, 0) spinors or tensors. We directly solve the set of Casimir equations, that can elegantly be written in a compact form for any ( ℓ, overline{ℓ} ), by using an educated ansatz and reducing the problem to an algebraic linear system. Various details on the form of the ansatz have been deduced by using the so called shadow formalism. The complexity of the conformal blocks depends on the value of p = | ℓ - overline{ℓ} | and grows with p, in analogy to what happens to scalar conformal blocks in d even space-time dimensions as d increases. These results open the way to bootstrap 4-point functions involving arbitrary spinor/tensor operators in four dimensional conformal field theories.

  10. Conformational changes in biopolymers

    NASA Astrophysics Data System (ADS)

    Ivanov, Vassili

    2005-12-01

    Biopolymer conformational changes are involved in many biological processes. This thesis summarizes some theoretical and experimental approaches which I have taken at UCLA to explore conformational changes in biopolymers. The reversible thermal denaturation of the DNA double helix is, perhaps, the simplest example of biopolymer conformational change. I have developed a statistical mechanics model of DNA melting with reduced degrees of freedom, which allows base stacking interaction to be taken into account and treat base pairing and stacking separately. Unlike previous models, this model describes both the unpairing and unstacking parts of the experimental melting curves and explains the observed temperature dependence of the effective thermodynamic parameters used in models of the nearest neighbor type. I developed a basic kinetic model for irreversible thermal denaturation of F-actin, which incorporates depolymerization of F-actin from the ends and breaking of F-actin fiber in the middle. The model explains the cooperativity of F-actin thermal denaturation observed by D. Pavlov et al. in differential calorimetry measurements. CG-rich DNA sequences form left-handed Z-DNA at high ionic strength or upon binding of polyvalent ions and some proteins. I studied experimentally the B-to-Z transition of the (CG)6 dodecamer. Improvement of the locally linearized model used to interpret the data gives evidence for an intermediate state in the B-to-Z transition of DNA, contrary to previous research on this subject. In the past 15 years it has become possible to study the conformational changes of biomolecules using single-molecule techniques. In collaboration with other lab members I performed a single-molecule experiment, where we monitored the displacement of a micrometer-size bead tethered to a surface by a DNA probe undergoing the conformational change. This technique allows probing of conformational changes with subnanometer accuracy. We applied the method to detect

  11. The HAMP Signal Relay Domain Adopts Multiple Conformational States through Collective Piston and Tilt Motions

    PubMed Central

    Zhu, Lizhe; Bolhuis, Peter G.; Vreede, Jocelyne

    2013-01-01

    The HAMP domain is a linker region in prokaryotic sensor proteins and relays input signals to the transmitter domain and vice versa. Functional as a dimer, the structure of HAMP shows a parallel coiled-coil motif comprising four helices. To date, it is unclear how HAMP can relay signals from one domain to another, although several models exist. In this work, we use molecular simulation to test the hypothesis that HAMP adopts different conformations, one of which represents an active, signal-relaying configuration, and another an inactive, resting state. We first performed molecular dynamics simulation on the prototype HAMP domain Af1503 from Archaeoglobus fulgidus. We explored its conformational space by taking the structure of the A291F mutant disabling HAMP activity as a starting point. These simulations revealed additional conformational states that differ in the tilt angles between the helices as well as the relative piston shifts of the helices relative to each other. By enhancing the sampling in a metadynamics set up, we investigated three mechanistic models for HAMP signal transduction. Our results indicate that HAMP can access additional conformational states characterized by piston motion. Furthermore, the piston motion of the N-terminal helix of one monomer is directly correlated with the opposite piston motion of the C-terminal helix of the other monomer. The change in piston motion is accompanied by a change in tilt angle between the monomers, thus revealing that HAMP exhibits a collective motion, i.e. a combination of changes in tilt angles and a piston-like displacement. Our results provide insights into the conformational changes that underlie the signaling mechanism involving HAMP. PMID:23468603

  12. Cyclopeptides containing the DEKS motif as conformationally restricted collagen telopeptide analogues: synthesis and conformational analysis.

    PubMed

    Wodtke, Robert; Ruiz-Gómez, Gloria; Kuchar, Manuela; Pisabarro, M Teresa; Novotná, Pavlina; Urbanová, Marie; Steinbach, Jörg; Pietzsch, Jens; Löser, Reik

    2015-02-14

    The collagen telopeptides play an important role for lysyl oxidase-mediated crosslinking, a process which is deregulated during tumour progression. The DEKS motif which is located within the N-terminal telopeptide of the α1 chain of type I collagen has been suggested to adopt a βI-turn conformation upon docking to its triple-helical receptor domain, which seems to be critical for lysyl oxidase-catalysed deamination and subsequent crosslinking by Schiff-base formation. Herein, the design and synthesis of cyclic peptides which constrain the DEKS sequence in a β-turn conformation will be described. Lysine-side chain attachment to 2-chlorotrityl chloride-modified polystyrene resin followed by microwave-assisted solid-phase peptide synthesis and on-resin cyclisation allowed for an efficient access to head-to-tail cyclised DEKS-derived cyclic penta- and hexapeptides. An N(ε)-(4-fluorobenzoyl)lysine residue was included in the cyclopeptides to allow their potential radiolabelling with fluorine-18 for PET imaging of lysyl oxidase. Conformational analysis by (1)H NMR and chiroptical (electronic and vibrational CD) spectroscopy together with MD simulations demonstrated that the concomitant incorporation of a D-proline and an additional lysine for potential radiolabel attachment accounts for a reliable induction of the desired βI-turn structure in the DEKS motif in both DMSO and water as solvents. The stabilised conformation of the cyclohexapeptide is further reflected by its resistance to trypsin-mediated degradation. In addition, the deaminated analogue containing allysine in place of lysine has been synthesised via the corresponding ε-hydroxynorleucine containing cyclohexapeptide. Both ε-hydroxynorleucine and allysine containing cyclic hexapeptides have been subjected to conformational analysis in the same manner as the lysine-based parent structure. Thus, both a conformationally restricted lysyl oxidase substrate and product have been synthetically accessed, which

  13. Conformally invariant wave equations for massless particles

    NASA Astrophysics Data System (ADS)

    McLennan, James A.

    1984-07-01

    The invariance of wave equations for massless particles under conformal transformations of space-time is briefly summarized. Particular attention is given to a recent paper by Bracken and Jessup in which it is claimed that results obtained by the author are in error. Their paper contains several misleading statements based on a misreading of the author's paper, and in addition an argument of theirs, intended to show error, is itself invalid. Their claims of error on the author's part are therefore unfounded.

  14. Multiscale conformal pattern transfer

    PubMed Central

    Lodewijks, Kristof; Miljkovic, Vladimir; Massiot, Inès; Mekonnen, Addis; Verre, Ruggero; Olsson, Eva; Dmitriev, Alexandre

    2016-01-01

    We demonstrate a method for seamless transfer from a parent flat substrate of basically any lithographic top-down or bottom-up pattern onto essentially any kind of surface. The nano- or microscale patterns, spanning macroscopic surface areas, can be transferred with high conformity onto a large variety of surfaces when such patterns are produced on a thin carbon film, grown on top of a sacrificial layer. The latter allows lifting the patterns from the flat parent substrate onto a water-air interface to be picked up by the host surface of choice. We illustrate the power of this technique by functionalizing broad range of materials including glass, plastics, metals, rough semiconductors and polymers, highlighting the potential applications in in situ colorimetry of the chemistry of materials, anti-counterfeit technologies, biomolecular and biomedical studies, light-matter interactions at the nanoscale, conformal photovoltaics and flexible electronics. PMID:27329824

  15. Multiscale conformal pattern transfer

    NASA Astrophysics Data System (ADS)

    Lodewijks, Kristof; Miljkovic, Vladimir; Massiot, Inès; Mekonnen, Addis; Verre, Ruggero; Olsson, Eva; Dmitriev, Alexandre

    2016-06-01

    We demonstrate a method for seamless transfer from a parent flat substrate of basically any lithographic top-down or bottom-up pattern onto essentially any kind of surface. The nano- or microscale patterns, spanning macroscopic surface areas, can be transferred with high conformity onto a large variety of surfaces when such patterns are produced on a thin carbon film, grown on top of a sacrificial layer. The latter allows lifting the patterns from the flat parent substrate onto a water-air interface to be picked up by the host surface of choice. We illustrate the power of this technique by functionalizing broad range of materials including glass, plastics, metals, rough semiconductors and polymers, highlighting the potential applications in in situ colorimetry of the chemistry of materials, anti-counterfeit technologies, biomolecular and biomedical studies, light-matter interactions at the nanoscale, conformal photovoltaics and flexible electronics.

  16. Multiscale conformal pattern transfer.

    PubMed

    Lodewijks, Kristof; Miljkovic, Vladimir; Massiot, Inès; Mekonnen, Addis; Verre, Ruggero; Olsson, Eva; Dmitriev, Alexandre

    2016-01-01

    We demonstrate a method for seamless transfer from a parent flat substrate of basically any lithographic top-down or bottom-up pattern onto essentially any kind of surface. The nano- or microscale patterns, spanning macroscopic surface areas, can be transferred with high conformity onto a large variety of surfaces when such patterns are produced on a thin carbon film, grown on top of a sacrificial layer. The latter allows lifting the patterns from the flat parent substrate onto a water-air interface to be picked up by the host surface of choice. We illustrate the power of this technique by functionalizing broad range of materials including glass, plastics, metals, rough semiconductors and polymers, highlighting the potential applications in in situ colorimetry of the chemistry of materials, anti-counterfeit technologies, biomolecular and biomedical studies, light-matter interactions at the nanoscale, conformal photovoltaics and flexible electronics. PMID:27329824

  17. Conformal gripping device

    NASA Technical Reports Server (NTRS)

    Vranish, John M. (Inventor)

    2009-01-01

    The present invention relates to a conformal gripping device. In an embodiment of the present invention a conformal gripper device may be disclosed comprising a frame that includes an array of movable pins. The device may also include a roller locking and unlocking system within the frame. The system may comprise a pair of locking rollers for each row of gripper pins to facilitate locking and unlocking the array of gripper pins on a column-by-column basis. The system may also include a striker element that may force the locking rollers to roll along an angled roll surface to facilitate unlocking of the array of pins on a column-by-column basis. The system may further include an electromagnetic actuator or solenoid and permanent magnets to facilitate movement of the striker element and the locking rollers.

  18. Conformational flexibility of aspartame.

    PubMed

    Toniolo, Claudio; Temussi, Pierandrea

    2016-05-01

    L-Aspartyl-L-phenylalanine methyl ester, better known as aspartame, is not only one of the most used artificial sweeteners, but also a very interesting molecule with respect to the correlation between molecular structure and taste. The extreme conformational flexibility of this dipeptide posed a huge difficulty when researchers tried to use it as a lead compound to design new sweeteners. In particular, it was difficult to take advantage of its molecular model as a mold to infer the shape of the, then unknown, active site of the sweet taste receptor. Here, we follow the story of the 3D structural aspects of aspartame from early conformational studies to recent docking into homology models of the receptor. © 2016 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 106: 376-384, 2016. PMID:27038223

  19. Assessing the Impact of Backbone Length and Capping Agent on the Conformational Preferences of a Model Peptide: Conformation Specific IR and UV Spectroscopy of 2-AMINOISOBUTYRIC Acid

    NASA Astrophysics Data System (ADS)

    Gord, Joseph R.; Hewett, Daniel M.; Kubasik, Matthew A.; Zwier, Timothy S.

    2015-06-01

    2-Aminoisobutyric acid (Aib) is an achiral, α-amino acid having two equivalent methyl groups attached to C_α. Extended Aib oligomers are known to have a strong preference for the adoption of a 310-helical structure in the condensed phase. Here, we have taken a simplifying step and focused on the intrinsic folding propensities of Aib by looking at a series of capped Aib oligomers in the gas phase, free from the influence of solvent molecules and cooled in a supersonic expansion. Resonant two-photon ionization and IR-UV holeburning have been used to record single-conformation UV spectra using the Z-cap as the UV chromophore. Resonant ion-dip infrared (RIDIR) spectroscopy provides single-conformation IR spectra in the OH stretch and NH stretch regions. Data have been collected on a set of Z-(Aib)n-X oligomers with n = 1, 2, 4, 6 and X = -OH and -OMethyl. The impacts of these capping groups and differences in backbone length have been found to dramatically influence the conformational space accessed by the molecules studied here. Oligomers of n=4 have sufficient backbone length for a full turn of the 310-helix to be formed. Early interpretation of the data collected shows clear spectroscopic markers signaling the onset of 310-helix formation as well as evidence of structures incorporating C7 and C14 hydrogen bonded rings. Toniolo, C.; Bonora, G. M.; Barone, V.; Bavoso, A.; Benedetti, E.; Di Blasio, B.; Grimaldi, P.; Lelj, F.; Pavone, V.; Pedone, C., Conformation of Pleionomers of α-Aminoisobutyric Acid. Macromolecules 1985, 18, 895-902.

  20. The conformal bootstrap

    NASA Astrophysics Data System (ADS)

    Poland, David; Simmons-Duffin, David

    2016-06-01

    The conformal bootstrap was proposed in the 1970s as a strategy for calculating the properties of second-order phase transitions. After spectacular success elucidating two-dimensional systems, little progress was made on systems in higher dimensions until a recent renaissance beginning in 2008. We report on some of the main results and ideas from this renaissance, focusing on new determinations of critical exponents and correlation functions in the three-dimensional Ising and O(N) models.

  1. Conformal scalar field wormholes

    NASA Technical Reports Server (NTRS)

    Halliwell, Jonathan J.; Laflamme, Raymond

    1989-01-01

    The Euclidian Einstein equations with a cosmological constant and a conformally coupled scalar field are solved, taking the metric to be of the Robertson-Walker type. In the case Lambda = 0, solutions are found which represent a wormhole connecting two asymptotically flat Euclidian regions. In the case Lambda greater than 0, the solutions represent tunneling from a small Tolman-like universe to a large Robertson-Walker universe.

  2. Conformations of organophosphine oxides

    DOE PAGESBeta

    De Silva, Nuwan; Zahariev, Federico; Hay, Benjamin P.; Gordon, Mark S.; Windus, Theresa L.

    2015-07-17

    The conformations of a series of organophosphine oxides, OP(CH3)2R, where R = methyl, ethyl, isopropyl, tert-butyl, vinyl, and phenyl, are predicted using the MP2/cc-pVTZ level of theory. Comparison of potential energy surfaces for rotation about P–C bonds with crystal structure data reveals a strong correlation between predicted location and energetics of minima and histograms of dihedral angle distributions observed in the solid state. In addition, the most stable conformers are those that minimize the extent of steric repulsion between adjacent rotor substituents, and the torsional barriers tend to increase with the steric bulk of the rotating alkyl group. MM3 forcemore » field parameters were adjusted to fit the MP2 results, providing a fast and accurate model for predicting organophosphine oxides shapes—an essential part of understanding the chemistry of these compounds. As a result, the predictive power of the modified MM3 model was tested against MP2/cc-pVTZ conformations for triethylphosphine oxide, OP(CH2CH3)3, and triphenylphosphine oxide, OP(Ph)3.« less

  3. Conformations of organophosphine oxides

    SciTech Connect

    De Silva, Nuwan; Zahariev, Federico; Hay, Benjamin P.; Gordon, Mark S.; Windus, Theresa L.

    2015-07-17

    The conformations of a series of organophosphine oxides, OP(CH3)2R, where R = methyl, ethyl, isopropyl, tert-butyl, vinyl, and phenyl, are predicted using the MP2/cc-pVTZ level of theory. Comparison of potential energy surfaces for rotation about P–C bonds with crystal structure data reveals a strong correlation between predicted location and energetics of minima and histograms of dihedral angle distributions observed in the solid state. In addition, the most stable conformers are those that minimize the extent of steric repulsion between adjacent rotor substituents, and the torsional barriers tend to increase with the steric bulk of the rotating alkyl group. MM3 force field parameters were adjusted to fit the MP2 results, providing a fast and accurate model for predicting organophosphine oxides shapes—an essential part of understanding the chemistry of these compounds. As a result, the predictive power of the modified MM3 model was tested against MP2/cc-pVTZ conformations for triethylphosphine oxide, OP(CH2CH3)3, and triphenylphosphine oxide, OP(Ph)3.

  4. Hot conformal gauge theories

    NASA Astrophysics Data System (ADS)

    Mojaza, Matin; Pica, Claudio; Sannino, Francesco

    2010-12-01

    We compute the nonzero temperature free energy up to the order g6ln⁡(1/g) in the coupling constant for vectorlike SU(N) gauge theories featuring matter transforming according to different representations of the underlying gauge group. The number of matter fields, i.e. flavors, is arranged in such a way that the theory develops a perturbative stable infrared fixed point at zero temperature. Because of large distance conformality we trade the coupling constant with its fixed point value and define a reduced free energy which depends only on the number of flavors, colors, and matter representation. We show that the reduced free energy changes sign, at the second, fifth, and sixth order in the coupling, when decreasing the number of flavors from the upper end of the conformal window. If the change in sign is interpreted as a signal of an instability of the system then we infer a critical number of flavors. Surprisingly this number, if computed to the order g2, agrees with previous predictions for the lower boundary of the conformal window for nonsupersymmetric gauge theories. The higher order results tend to predict a higher number of critical flavors. These are universal properties, i.e. they are independent of the specific matter representation.

  5. A homology/ab initio hybrid algorithm for sampling near-native protein conformations.

    PubMed

    Dhingra, Priyanka; Jayaram, Bhyravabhotla

    2013-08-15

    One of the major challenges for protein tertiary structure prediction strategies is the quality of conformational sampling algorithms, which can effectively and readily search the protein fold space to generate near-native conformations. In an effort to advance the field by making the best use of available homology as well as fold recognition approaches along with ab initio folding methods, we have developed Bhageerath-H Strgen, a homology/ab initio hybrid algorithm for protein conformational sampling. The methodology is tested on the benchmark CASP9 dataset of 116 targets. In 93% of the cases, a structure with TM-score ≥ 0.5 is generated in the pool of decoys. Further, the performance of Bhageerath-H Strgen was seen to be efficient in comparison with different decoy generation methods. The algorithm is web enabled as Bhageerath-H Strgen web tool which is made freely accessible for protein decoy generation (http://www.scfbio-iitd.res.in/software/Bhageerath-HStrgen1.jsp). PMID:23728619

  6. 18 CFR 1307.6 - Accessibility.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... conformance with Sections 3-8 of the Uniform Federal Accessibility Standards (UFAS) (41 CFR Subpart 101-19.6... RESPECT TO HANDICAP § 1307.6 Accessibility. (a) General. No qualified handicapped person shall, because facilities are inaccessible to or unusable by handicapped persons, be denied the benefits of, be...

  7. 18 CFR 1307.6 - Accessibility.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... conformance with Sections 3-8 of the Uniform Federal Accessibility Standards (UFAS) (41 CFR subpart 101-19.6... 18 Conservation of Power and Water Resources 2 2011-04-01 2011-04-01 false Accessibility. 1307.6 Section 1307.6 Conservation of Power and Water Resources TENNESSEE VALLEY AUTHORITY NONDISCRIMINATION...

  8. Paving the Way for Small Satellite Access to Orbit: Cyclops' Deployment of SpinSat, the Largest Satellite Ever Deployed from the International Space Station

    NASA Technical Reports Server (NTRS)

    Hershey, Matthew P.; Newswander, Daniel R.; Smith, James P.; Lamb, Craig R.; Ballard, Perry G.

    2015-01-01

    The Space Station Integrated Kinetic Launcher for Orbital Payload Systems (SSIKLOPS), known as "Cyclops" to the International Space Station (ISS) community, successfully deployed the largest satellite ever (SpinSat) from the ISS on November 28, 2014. Cyclops, a collaboration between the NASA ISS Program, NASA Johnson Space Center Engineering, and Department of Defense Space Test Program (DoD STP) communities, is a dedicated 10-100 kg class ISS small satellite deployment system. This paper will showcase the successful deployment of SpinSat from the ISS. It will also outline the concept of operations, interfaces, requirements, and processes for satellites to utilize the Cyclops satellite deployment system.

  9. Pressure-induced conformational switch of an interfacial protein.

    PubMed

    Johnson, Quentin R; Lindsay, Richard J; Nellas, Ricky B; Shen, Tongye

    2016-06-01

    A special class of proteins adopts an inactive conformation in aqueous solution and activates at an interface (such as the surface of lipid droplet) by switching their conformations. Lipase, an essential enzyme for breaking down lipids, serves as a model system for studying such interfacial proteins. The underlying conformational switch of lipase induced by solvent condition is achieved through changing the status of the gated substrate-access channel. Interestingly, a lipase was also reported to exhibit pressure activation, which indicates it is drastically active at high hydrostatic pressure. To unravel the molecular mechanism of this unusual phenomenon, we examined the structural changes induced by high hydrostatic pressures (up to 1500 MPa) using molecular dynamics simulations. By monitoring the width of the access channel, we found that the protein undergoes a conformational transition and opens the access channel at high pressures (>100 MPa). Particularly, a disordered amphiphilic α5 region of the protein becomes ordered at high pressure. This positive correlation between the channel opening and α5 ordering is consistent with the early findings of the gating motion in the presence of a water-oil interface. Statistical analysis of the ensemble of conformations also reveals the essential collective motions of the protein and how these motions contribute to gating. Arguments are presented as to why heightened sensitivity to high-pressure perturbation can be a general feature of switchable interfacial proteins. Further mutations are also suggested to validate our observations. Proteins 2016; 84:820-827. © 2016 Wiley Periodicals, Inc. PMID:26967808

  10. 14 CFR 325.14 - Conformity with subpart A of part 302.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 4 2011-01-01 2011-01-01 false Conformity with subpart A of part 302. 325.14 Section 325.14 Aeronautics and Space OFFICE OF THE SECRETARY, DEPARTMENT OF TRANSPORTATION (AVIATION PROCEEDINGS) PROCEDURAL REGULATIONS ESSENTIAL AIR SERVICE PROCEDURES § 325.14 Conformity...

  11. 14 CFR 325.14 - Conformity with subpart A of part 302.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 4 2012-01-01 2012-01-01 false Conformity with subpart A of part 302. 325.14 Section 325.14 Aeronautics and Space OFFICE OF THE SECRETARY, DEPARTMENT OF TRANSPORTATION (AVIATION PROCEEDINGS) PROCEDURAL REGULATIONS ESSENTIAL AIR SERVICE PROCEDURES § 325.14 Conformity...

  12. 14 CFR 325.14 - Conformity with subpart A of part 302.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 4 2014-01-01 2014-01-01 false Conformity with subpart A of part 302. 325.14 Section 325.14 Aeronautics and Space OFFICE OF THE SECRETARY, DEPARTMENT OF TRANSPORTATION (AVIATION PROCEEDINGS) PROCEDURAL REGULATIONS ESSENTIAL AIR SERVICE PROCEDURES § 325.14 Conformity...

  13. 14 CFR 325.14 - Conformity with subpart A of part 302.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 4 2013-01-01 2013-01-01 false Conformity with subpart A of part 302. 325.14 Section 325.14 Aeronautics and Space OFFICE OF THE SECRETARY, DEPARTMENT OF TRANSPORTATION (AVIATION PROCEEDINGS) PROCEDURAL REGULATIONS ESSENTIAL AIR SERVICE PROCEDURES § 325.14 Conformity...

  14. 14 CFR 325.14 - Conformity with subpart A of part 302.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 4 2010-01-01 2010-01-01 false Conformity with subpart A of part 302. 325.14 Section 325.14 Aeronautics and Space OFFICE OF THE SECRETARY, DEPARTMENT OF TRANSPORTATION (AVIATION PROCEEDINGS) PROCEDURAL REGULATIONS ESSENTIAL AIR SERVICE PROCEDURES § 325.14 Conformity...

  15. Conformal anomaly actions for dilaton interactions

    NASA Astrophysics Data System (ADS)

    Delle Rose, Luigi; Marzo, Carlo; Serino, Mirko

    2014-11-01

    We discuss, in conformally invariant field theories such as QCD with massless fermions, a possible link between the perturbative signature of the conformal anomaly, in the form of anomaly poles of the 1-particle irreducible effective action, and its descrip- tion in terms of Wess-Zumino actions with a dilaton. The two descriptions are expected to capture the UV and IR behaviour of the conformal anomaly, in terms of fundamental and effective degrees of freedom respectively, with the dilaton effective state appearing in a nonlinear realization. As in the chiral case, conformal anomalies seem to be related to the appearance of these effective interactions in the 1PI action in all the gauge-invariant sectors of the Standard Model. We show that, as a consequence of the underlying anomalous symmetry, the infinite hierarchy of recurrence relations involving self-interactions of the dilaton is entirely determined only by the first four of them. This relation can be generalized to any even space-time dimension.

  16. OSI Conformance Testing for Bibliographic Applications.

    ERIC Educational Resources Information Center

    Arbez, Gilbert; Swain, Leigh

    1990-01-01

    Describes the development of Open Systems Interconnection (OSI) conformance testing sites, conformance testing tools, and conformance testing services. Discusses related topics such as interoperability testing, arbitration testing, and international harmonization of conformance testing. A glossary is included. (24 references) (SD)

  17. Simulating Massive Conformation Changes within Polypeptide Systems

    NASA Astrophysics Data System (ADS)

    Singh, Jaspinder Paul

    In this dissertation I employ all-atom structure based models with stable energy basins to several existing and novel polypeptide systems (postulated conformation changes of the mammalian prion protein and structurally dual proteins). The common themes are finding unfolding and refolding pathways between highly dissimilar protein structures as a means of understanding exactly how and why a protein may misfold. The modeling is based on the energy funnel landscape theory of protein conformation space. The principle of minimal frustration is considered as the model includes parameters which vary the roughness of the landscape and give rise to off-pathway misfoldings. The dual basin model is applied to the C-terminal (residues 166-226) of the mammalian prion protein. One basin represents the known alpha-helical (aH) structure while the other represents the same residues in a lefthanded beta-helical (LHBH) conformation. The LHBH structure has been proposed to help describe one class of in vitro grown fibrils, as well as possibly self-templating the conversion of normal cellular prion protein to the infectious form. Yet, it is unclear how the protein may make this global rearrangement. Our results demonstrate that the conformation changes are not strongly limited by large-scale geometry modification and that there may exist an overall preference for the LHBH conformation. Furthermore, our model presents novel intermediate trapping conformations with twisted LHBH structure. Polypeptides that display structural duality have primary structures that can give rise to different potential native conformations. We apply the structure-based all-atom model to a leucine zipper protein template with a stable aH structure that has been shown in experiment to switch to a β hairpin structure when exposed to a low-pH environment. We show that the model can be used to perform large-scale temperature-dependent conformational switching by simulating this switching behavior. We augmented

  18. Leaf growth is conformal.

    PubMed

    Alim, Karen; Armon, Shahaf; Shraiman, Boris I; Boudaoud, Arezki

    2016-01-01

    Growth pattern dynamics lie at the heart of morphogenesis. Here, we investigate the growth of plant leaves. We compute the conformal transformation that maps the contour of a leaf at a given stage onto the contour of the same leaf at a later stage. Based on the mapping we predict the local displacement field in the leaf blade and find it to agree with the experimentally measured displacement field to 92%. This approach is applicable to any two-dimensional system with locally isotropic growth, enabling the deduction of the whole growth field just from observation of the tissue contour. PMID:27597439

  19. Metamaterials with conformational nonlinearity

    NASA Astrophysics Data System (ADS)

    Lapine, Mikhail; Shadrivov, Ilya V.; Powell, David A.; Kivshar, Yuri S.

    2011-11-01

    Within a decade of fruitful development, metamaterials became a prominent area of research, bridging theoretical and applied electrodynamics, electrical engineering and material science. Being man-made structures, metamaterials offer a particularly useful playground to develop interdisciplinary concepts. Here we demonstrate a novel principle in metamaterial assembly which integrates electromagnetic, mechanical, and thermal responses within their elements. Through these mechanisms, the conformation of the meta-molecules changes, providing a dual mechanism for nonlinearity and offering nonlinear chirality. Our proposal opens a wide road towards further developments of nonlinear metamaterials and photonic structures, adding extra flexibility to their design and control.

  20. Conformation effects on the molecular orbitals of serine

    NASA Astrophysics Data System (ADS)

    Wang, Ke-Dong; Ma, Peng-Fei; Shan, Xu

    2011-03-01

    This paper calculates the five most stable conformers of serine with Hartree—Fock theory, density functional theory (B3LYP), Møller—Plesset perturbation theory (MP4(SDQ)) and electron propagation theory with the 6-311++G(2d,2p) basis set. The calculated vertical ionization energies for the valence molecular orbitals of each conformer are in agreement with the experimental data, indicating that a range of molecular conformations would coexist in an equilibrium sample. Information of the five outer valence molecular orbitals for each conformer is explored in coordinate and momentum spaces using dual space analysis to investigate the conformational processes, which are generated from the global minimum conformer Ser1 by rotation of C2-C3 (Ser4), C1-C2 (Ser5) and C1-O2 (Ser2 and Ser3). Orbitals 28a, 27a and 26a are identified as the fingerprint orbitals for all the conformational processes. Project supported by the Doctoral Research Fund of Henan Normal University, China (Grant No. 525449).

  1. Calculus on manifolds of conformal maps and CFT

    NASA Astrophysics Data System (ADS)

    Doyon, Benjamin

    2012-08-01

    In conformal field theory (CFT) on simply connected domains of the Riemann sphere, the natural conformal symmetries under self-maps are extended, in a certain way, to local symmetries under general conformal maps, and this is at the basis of the powerful techniques of CFT. Conformal maps of simply connected domains naturally have the structure of an infinite-dimensional groupoid, which generalizes the finite-dimensional group of self-maps. We put a topological structure on the space of conformal maps on simply connected domains, which makes it into a topological groupoid. Further, we (almost) extend this to a local manifold structure based on the infinite-dimensional Fréchet topological vector space of holomorphic functions on a given domain A. From this, we develop the notion of conformal A-differentiability at the identity. Our main conclusion is that quadratic differentials characterizing cotangent elements on the local manifold enjoy properties similar to those of the holomorphic stress-energy tensor of CFT; these properties underpin the local symmetries of CFT. Applying the general formalism to CFT correlation functions, we show that the stress-energy tensor is exactly such a quadratic differential. This is at the basis of constructing the stress-energy tensor in conformal loop ensembles. It also clarifies the relation between Cardy's boundary conditions for CFT on simply connected domains, and the expression of the stress-energy tensor in terms of metric variations.

  2. Conformally symmetric traversable wormholes

    SciTech Connect

    Boehmer, Christian G.; Harko, Tiberiu; Lobo, Francisco S. N.

    2007-10-15

    Exact solutions of traversable wormholes are found under the assumption of spherical symmetry and the existence of a nonstatic conformal symmetry, which presents a more systematic approach in searching for exact wormhole solutions. In this work, a wide variety of solutions are deduced by considering choices for the form function, a specific linear equation of state relating the energy density and the pressure anisotropy, and various phantom wormhole geometries are explored. A large class of solutions impose that the spatial distribution of the exotic matter is restricted to the throat neighborhood, with a cutoff of the stress-energy tensor at a finite junction interface, although asymptotically flat exact solutions are also found. Using the 'volume integral quantifier', it is found that the conformally symmetric phantom wormhole geometries may, in principle, be constructed by infinitesimally small amounts of averaged null energy condition violating matter. Considering the tidal acceleration traversability conditions for the phantom wormhole geometry, specific wormhole dimensions and the traversal velocity are also deduced.

  3. Spherically symmetric conformal gravity and ``gravitational bubbles''

    NASA Astrophysics Data System (ADS)

    Berezin, V. A.; Dokuchaev, V. I.; Eroshenko, Yu. N.

    2016-01-01

    The general structure of the spherically symmetric solutions in the Weyl conformal gravity is described. The corresponding Bach equations are derived for the special type of metrics, which can be considered as the representative of the general class. The complete set of the pure vacuum solutions is found. It consists of two classes. The first one contains the solutions with constant two-dimensional curvature scalar of our specific metrics, and the representatives are the famous Robertson-Walker metrics. One of them we called the ``gravitational bubbles'', which is compact and with zero Weyl tensor. Thus, we obtained the pure vacuum curved space-times (without any material sources, including the cosmological constant) what is absolutely impossible in General Relativity. Such a phenomenon makes it easier to create the universe from ``nothing''. The second class consists of the solutions with varying curvature scalar. We found its representative as the one-parameter family. It appears that it can be conformally covered by the thee-parameter Mannheim-Kazanas solution. We also investigated the general structure of the energy-momentum tensor in the spherical conformal gravity and constructed the vectorial equation that reveals clearly some features of non-vacuum solutions. Two of them are explicitly written, namely, the metrics à la Vaidya, and the electrovacuum space-time metrics.

  4. Web Accessibility and Accessibility Instruction

    ERIC Educational Resources Information Center

    Green, Ravonne A.; Huprich, Julia

    2009-01-01

    Section 508 of the Americans with Disabilities Act (ADA) mandates that programs and services be accessible to people with disabilities. While schools of library and information science (SLIS*) and university libraries should model accessible Web sites, this may not be the case. This article examines previous studies about the Web accessibility of…

  5. The pseudo-conformal universe: scale invariance from spontaneous breaking of conformal symmetry

    SciTech Connect

    Hinterbichler, Kurt; Khoury, Justin E-mail: jkhoury@sas.upenn.edu

    2012-04-01

    We present a novel theory of the very early universe which addresses the traditional horizon and flatness problems of big bang cosmology and predicts a scale invariant spectrum of perturbations. Unlike inflation, this scenario requires no exponential accelerated expansion of space-time. Instead, the early universe is described by a conformal field theory minimally coupled to gravity. The conformal fields develop a time-dependent expectation value which breaks the flat space so(4,2) conformal symmetry down to so(4,1), the symmetries of de Sitter, giving perturbations a scale invariant spectrum. The solution is an attractor, at least in the case of a single time-dependent field. Meanwhile, the metric background remains approximately flat but slowly contracts, which makes the universe increasingly flat, homogeneous and isotropic, akin to the smoothing mechanism of ekpyrotic cosmology. Our scenario is very general, requiring only a conformal field theory capable of developing the appropriate time-dependent expectation values, and encompasses existing incarnations of this idea, specifically the U(1) model of Rubakov and the Galileon Genesis scenario. Its essential features depend only on the symmetry breaking pattern and not on the details of the underlying lagrangian. It makes generic observational predictions that make it potentially distinguishable from standard inflation, in particular significant non-gaussianities and the absence of primordial gravitational waves.

  6. Recent Advances in Conformal Gravity

    NASA Astrophysics Data System (ADS)

    O'Brien, James; Chaykov, Spasen

    2016-03-01

    In recent years, significant advances have been made in alternative gravitational theories. Although MOND remains the leading candidate among the alternative models, Conformal Gravity has been studied by Mannheim and O'Brien to solve the rotation curve problem without the need for dark matter. Recently, Mannheim, O'Brien and Chaykov have begun solving other gravitational questions in Conformal Gravity. In this presentation, we highlight the new work of Conformal Gravity's application to random motions of clusters (the original Zwicky problem), gravitational bending of light, gravitational lensing and a very recent survey of dwarf galaxy rotation curves. We will show in each case that Conformal Gravity can provide an accurate explanation and prediction of the data without the need for dark matter. Coupled with the fact that Conformal Gravity is a fully re-normalizable metric theory of gravity, these results help to push Conformal Gravity onto a competitive stage against other alternative models.

  7. Conformal Gravity and Gravitational Waves

    NASA Astrophysics Data System (ADS)

    Fabbri, Luca; Paranjape, M. B.

    We consider monochromatic, plane gravitational waves in a conformally invariant theory of general relativity. We show that the simple, standard ansatz for the metric, usually that which is taken for the linearized theory of these waves, is reducible to the metric of Minkowski spacetime via a sequence of conformal and coordinate transformations. This implies that we have in fact, exact plane wave solutions. However they are simply coordinate/conformal artifacts. As a consequence, they carry no energy.

  8. Killing and conformal Killing tensors

    NASA Astrophysics Data System (ADS)

    Heil, Konstantin; Moroianu, Andrei; Semmelmann, Uwe

    2016-08-01

    We introduce an appropriate formalism in order to study conformal Killing (symmetric) tensors on Riemannian manifolds. We reprove in a simple way some known results in the field and obtain several new results, like the classification of conformal Killing 2-tensors on Riemannian products of compact manifolds, Weitzenböck formulas leading to non-existence results, and construct various examples of manifolds with conformal Killing tensors.

  9. Loop Virasoro Lie conformal algebra

    SciTech Connect

    Wu, Henan Chen, Qiufan; Yue, Xiaoqing

    2014-01-15

    The Lie conformal algebra of loop Virasoro algebra, denoted by CW, is introduced in this paper. Explicitly, CW is a Lie conformal algebra with C[∂]-basis (L{sub i} | i∈Z) and λ-brackets [L{sub i} {sub λ} L{sub j}] = (−∂−2λ)L{sub i+j}. Then conformal derivations of CW are determined. Finally, rank one conformal modules and Z-graded free intermediate series modules over CW are classified.

  10. Mapping L1 Ligase ribozyme conformational switch

    PubMed Central

    Giambaşu, George M.; Lee, Tai-Sung; Scott, William G.; York, Darrin M.

    2012-01-01

    L1 Ligase (L1L)molecular switch is an in vitro optimized synthetic allosteric ribozyme that catalyzes the regioselective formation of a 5’-to-3’ phosphodiester bond, a reaction for which there is no known naturally occurring RNA catalyst. L1L serves as a proof of principle that RNA can catalyze a critical reaction for prebiotic RNA self-replication according to the RNA World hypothesis. L1L crystal structure captures two distinct conformations that differ by a re-orientation of one of the stems by around 80 Å and are presumed to correspond to the active and inactive state, respectively. It is of great interest to understand the nature of these two states in solution, and the pathway for their interconversion. In this study, we use explicit solvent molecular simulation together with a novel enhanced sampling method that utilizes concepts from network theory to map out the conformational transition between active and inactive states of L1L. We find that the overall switching mechanism can be described as a 3-state/2-step process. The first step involves a large-amplitude swing that re-orients stem C. The second step involves the allosteric activation of the catalytic site through distant contacts with stem C. Using a conformational space network representation of the L1L switch transition, it is shown that the connection between the three states follows different topographical patterns: the stem C swing step passes through a narrow region of the conformational space network, whereas the allosteric activation step covers a much wider region and a more diverse set of pathways through the network. PMID:22771572

  11. Reflections on conformal spectra

    NASA Astrophysics Data System (ADS)

    Kim, Hyungrok; Kravchuk, Petr; Ooguri, Hirosi

    2016-04-01

    We use modular invariance and crossing symmetry of conformal field theory to reveal approximate reflection symmetries in the spectral decompositions of the partition function in two dimensions in the limit of large central charge and of the four-point function in any dimension in the limit of large scaling dimensions Δ0 of external operators. We use these symmetries to motivate universal upper bounds on the spectrum and the operator product expansion coefficients, which we then derive by independent techniques. Some of the bounds for four-point functions are valid for finite Δ0 as well as for large Δ0. We discuss a similar symmetry in a large spacetime dimension limit. Finally, we comment on the analogue of the Cardy formula and sparse light spectrum condition for the four-point function.

  12. Capturing Chromosome Conformation

    NASA Astrophysics Data System (ADS)

    Dekker, Job; Rippe, Karsten; Dekker, Martijn; Kleckner, Nancy

    2002-02-01

    We describe an approach to detect the frequency of interaction between any two genomic loci. Generation of a matrix of interaction frequencies between sites on the same or different chromosomes reveals their relative spatial disposition and provides information about the physical properties of the chromatin fiber. This methodology can be applied to the spatial organization of entire genomes in organisms from bacteria to human. Using the yeast Saccharomyces cerevisiae, we could confirm known qualitative features of chromosome organization within the nucleus and dynamic changes in that organization during meiosis. We also analyzed yeast chromosome III at the G1 stage of the cell cycle. We found that chromatin is highly flexible throughout. Furthermore, functionally distinct AT- and GC-rich domains were found to exhibit different conformations, and a population-average 3D model of chromosome III could be determined. Chromosome III emerges as a contorted ring.

  13. Accessibility Standards, Illustrated.

    ERIC Educational Resources Information Center

    Jones, Michael A.

    The book sets forth Illinois environmental accessibility standards for disabled persons based on observation and interview data. Photographs, drawings, and detailed floor plans are included in sections dealing with human data (including space requirements for maneuvering wheelchairs, color blindness, incontinence, and severe auditory or visual…

  14. SpaceCube Mini

    NASA Technical Reports Server (NTRS)

    Lin, Michael; Petrick, David; Geist, Alessandro; Flatley, Thomas

    2012-01-01

    This version of the SpaceCube will be a full-fledged, onboard space processing system capable of 2500+ MIPS, and featuring a number of plug-andplay gigabit and standard interfaces, all in a condensed 3x3x3 form factor [less than 10 watts and less than 3 lb (approximately equal to 1.4 kg)]. The main processing engine is the Xilinx SIRF radiation- hardened-by-design Virtex-5 FX-130T field-programmable gate array (FPGA). Even as the SpaceCube 2.0 version (currently under test) is being targeted as the platform of choice for a number of the upcoming Earth Science Decadal Survey missions, GSFC has been contacted by customers who wish to see a system that incorporates key features of the version 2.0 architecture in an even smaller form factor. In order to fulfill that need, the SpaceCube Mini is being designed, and will be a very compact and low-power system. A similar flight system with this combination of small size, low power, low cost, adaptability, and extremely high processing power does not otherwise exist, and the SpaceCube Mini will be of tremendous benefit to GSFC and its partners. The SpaceCube Mini will utilize space-grade components. The primary processing engine of the Mini is the Xilinx Virtex-5 SIRF FX-130T radiation-hardened-by-design FPGA for critical flight applications in high-radiation environments. The Mini can also be equipped with a commercial Xilinx Virtex-5 FPGA with integrated PowerPCs for a low-cost, high-power computing platform for use in the relatively radiation- benign LEOs (low-Earth orbits). In either case, this version of the Space-Cube will weigh less than 3 pounds (.1.4 kg), conform to the CubeSat form-factor (10x10x10 cm), and will be low power (less than 10 watts for typical applications). The SpaceCube Mini will have a radiation-hardened Aeroflex FPGA for configuring and scrubbing the Xilinx FPGA by utilizing the onboard FLASH memory to store the configuration files. The FLASH memory will also be used for storing algorithm and

  15. Multiple Conformational States of Proteins: A Molecular Dynamics Analysis of Myoglobin

    NASA Astrophysics Data System (ADS)

    Elber, R.; Karplus, M.

    1987-01-01

    A molecular dynamics simulation of myoglobin provides the first direct demonstration that the potential energy surface of a protein is characterized by a large number of thermally accessible minima in the neighborhood of the native structure (for example, approximately 2000 minima were sampled in a 300-picosecond trajectory). This is expected to have important consequences for the interpretation of the activity of transport proteins and enzymes. Different minima correspond to changes in the relative orientation of the helices coupled with side-chain rearrangements that preserve the close packing of the protein interior. The conformational space sampled by the simulation is similar to that found in the evolutionary development of the globins. Glasslike behavior is expected at low temperatures. The minima obtained from the trajectory do not satisfy certain criteria for ultrametricity.

  16. Replacement between conformity and counter-conformity in consumption decisions.

    PubMed

    Chou, Ting-Jui; Chang, En-Chung; Dai, Qi; Wong, Veronica

    2013-02-01

    This study assessed, in a Chinese context, how self-esteem interacts with perceived similarity and uniqueness to yield cognitive dissonance, and whether the dissonance leads to self-reported conformity or counter-conformity behavior. Participants were 408 respondents from 4 major Chinese cities (M age = 33.0 yr., SD = 4.3; 48% men). Self-perceptions of uniqueness, similarity, cognitive dissonance, self-esteem and need to behave in conformity or counter-conformity were measured. A theoretical model was assessed in four situations, relating the ratings of self-esteem and perceived similarity/uniqueness to the way other people at a wedding were dressed, and the resultant cognitive dissonance and conformity/ counter-conformity behavior. Regardless of high or low self-esteem, all participants reported cognitive dissonance when they were told that they were dressed extremely similarly to or extremely differently from the other people attending the wedding. However, the conforming/counter-conforming strategies used by participants to resolve the cognitive dissonance differed. When encountering dissonance induced by the perceived extreme uniqueness of dress, participants with low self-esteem tended to say they would dress next time so as to conform with the way others were dressed, while those with high self-esteem indicated they would continue their counter-conformity in attire. When encountering dissonance induced by the perceived extreme similarity to others, both those with high and low self-esteem tended to say they would dress in an unorthodox manner to surprise other people in the future. PMID:23654033

  17. Is Your Church Accessible? Houses of Worship: Physical Accessibility Checklist.

    ERIC Educational Resources Information Center

    Ensign, Arselia, Ed.

    1991-01-01

    This checklist is intended to help churches evaluate the accessibility of their facilities to those with physical disabilities. Categories covered are: basic accessibility, parking lots, walks, ramps, entrances/exits, doors and doorways, stairs and steps, floors, worship space, rest rooms, controls, water fountains, identification, warning…

  18. Conformational Entropy of Intrinsically Disordered Proteins from Amino Acid Triads

    PubMed Central

    Baruah, Anupaul; Rani, Pooja; Biswas, Parbati

    2015-01-01

    This work quantitatively characterizes intrinsic disorder in proteins in terms of sequence composition and backbone conformational entropy. Analysis of the normalized relative composition of the amino acid triads highlights a distinct boundary between globular and disordered proteins. The conformational entropy is calculated from the dihedral angles of the middle amino acid in the amino acid triad for the conformational ensemble of the globular, partially and completely disordered proteins relative to the non-redundant database. Both Monte Carlo (MC) and Molecular Dynamics (MD) simulations are used to characterize the conformational ensemble of the representative proteins of each group. The results show that the globular proteins span approximately half of the allowed conformational states in the Ramachandran space, while the amino acid triads in disordered proteins sample the entire range of the allowed dihedral angle space following Flory’s isolated-pair hypothesis. Therefore, only the sequence information in terms of the relative amino acid triad composition may be sufficient to predict protein disorder and the backbone conformational entropy, even in the absence of well-defined structure. The predicted entropies are found to agree with those calculated using mutual information expansion and the histogram method. PMID:26138206

  19. Classical Virasoro irregular conformal block

    NASA Astrophysics Data System (ADS)

    Rim, Chaiho; Zhang, Hong

    2015-07-01

    Virasoro irregular conformal block with arbitrary rank is obtained for the classical limit or equivalently Nekrasov-Shatashvili limit using the beta-deformed irregular matrix model (Penner-type matrix model for the irregular conformal block). The same result is derived using the generalized Mathieu equation which is equivalent to the loop equation of the irregular matrix model.

  20. Conformational preferences of 3,4-dihydroxyphenylacetic acid (DOPAC)

    NASA Astrophysics Data System (ADS)

    Lopes Jesus, A. J.; Jarmelo, S.; Fausto, R.; Reva, I.

    2015-04-01

    The conformational space of 3,4-dihydroxyphenylacetic acid (DOPAC), an important dopamine metabolite, has been investigated by quantum chemical methods (B3LYP and MP2, with the 6-311++G(d,p) basis set) and matrix-isolation infrared spectroscopy. Detailed analysis of the calculated potential energy surfaces of the molecule led to identification of thirteen unique conformers, all of them showing the acetic acid side chain out of the aromatic ring plane by 60-95°. According to the calculated Gibbs energies, the five lowest energy conformers make up 99.7% of the conformational mixture at 298.15 K, exhibiting individual populations falling between 16% and 24%. The main conformational trends of this molecule were interpreted on the grounds of a thorough analysis of the structural parameters and by the application of the Natural Bond Orbital theory. The role of the intramolecular interactions on the relative stability and structure of the conformers was also investigated. The infrared spectrum of DOPAC was registered after isolation of its monomers in argon and xenon matrices. Only one of DOPAC forms populated in the gas phase could be trapped in both matrix gases. This result is in agreement with the predicted low energy barriers for conformational isomerization and is also supported by annealing experiments. The spectra of matrix-isolated model compounds, phenylacetic acid and catechol, were studied under the same experimental conditions. These data were used as references and assisted in the interpretation of the results obtained for DOPAC.

  1. Open Access

    ERIC Educational Resources Information Center

    Suber, Peter

    2012-01-01

    The Internet lets us share perfect copies of our work with a worldwide audience at virtually no cost. We take advantage of this revolutionary opportunity when we make our work "open access": digital, online, free of charge, and free of most copyright and licensing restrictions. Open access is made possible by the Internet and copyright-holder…

  2. Access Denied

    ERIC Educational Resources Information Center

    Villano, Matt

    2008-01-01

    Building access control (BAC)--a catchall phrase to describe the systems that control access to facilities across campus--has traditionally been handled with remarkably low-tech solutions: (1) manual locks; (2) electronic locks; and (3) ID cards with magnetic strips. Recent improvements have included smart cards and keyless solutions that make use…

  3. Unitary Fermi Gas, ɛ Expansion, and Nonrelativistic Conformal Field Theories

    NASA Astrophysics Data System (ADS)

    Nishida, Yusuke; Son, Dam Thanh

    We review theoretical aspects of unitary Fermi gas (UFG), which has been realized in ultracold atom experiments. We first introduce the ɛ expansion technique based on a systematic expansion in terms of the dimensionality of space. We apply this technique to compute the thermodynamic quantities, the quasiparticle cum, and the criticl temperature of UFG. We then discuss consequences of the scale and conformal invariance of UFG. We prove a correspondence between primary operators in nonrelativistic conformal field theories and energy eigenstates in a harmonic potential. We use this correspondence to compute energies of fermions at unitarity in a harmonic potential. The scale and conformal invariance together with the general coordinate invariance constrains the properties of UFG. We show the vanishing bulk viscosities of UFG and derive the low-energy effective Lagrangian for the superfluid UFG. Finally we propose other systems exhibiting the nonrelativistic scaling and conformal symmetries that can be in principle realized in ultracold atom experiments.

  4. Gravitationally coupled magnetic monopole and conformal symmetry breaking

    NASA Astrophysics Data System (ADS)

    Edery, Ariel; Fabbri, Luca; Paranjape, M. B.

    We consider a Georgi-Glashow model conformally coupled to gravity. The conformally invariant action includes a triplet of scalar fields and SO(3) non-Abelian gauge fields. However, the usual mass term $\\mu^2 \\phi^2$ is forbidden by the symmetry and this role is now played by the conformal coupling of the Ricci scalar to the scalar fields. Spontaneous symmetry breaking occurs via gravitation. The spherically symmetric solutions correspond to localized solitons (magnetic monopoles) in asymptotically anti-de-Sitter (AdS) space-time and the metric outside the core of the monopole is found to be Schwarzschild-AdS. Though conformal symmetry excludes the Einstein-Hilbert term in the original action, it emerges in the effective action after spontaneous symmetry breaking and dominates the low-energy/long-distance regime outside the core of the monopole.

  5. Salt effects on peptide conformers: a dielectric study of tuftsin.

    PubMed Central

    Yang, L; Valdeavella, C V; Blatt, H D; Pettitt, B M

    1996-01-01

    Four 1-ns molecular dynamics computer simulations of tuftsin, Thr-Lys-Pro-Arg, are analyzed: (1) cis tuftsin in water, (2) trans tuftsin in water, (3) cis tuftsin in 1 M NaCl, and (4) trans tuftsin in 1 M NaCl. Independently of the salt concentration, the trans conformer has a higher dielectric constant than the cis conformer because the former exhibits a more widely distributed charge distribution in space. Independently of the peptide conformation, the presence of salt reduces the dielectric constants of both the peptide and the solvating water molecules because ions, on binding, restrict the motion of other atoms. In contrast to the dielectric constants, neither the peptide conformation nor the salt concentration shows a significant influence on the dielectric relaxation time of water molecules. PMID:8968573

  6. In silico Exploration of the Conformational Universe of GPCRs.

    PubMed

    Rodríguez-Espigares, Ismael; Kaczor, Agnieszka A; Selent, Jana

    2016-07-01

    The structural plasticity of G protein coupled receptors (GPCRs) leads to a conformational universe going from inactive to active receptor states with several intermediate states. Many of them have not been captured yet and their role for GPCR activation is not well understood. The study of this conformational space and the transition dynamics between different receptor populations is a major challenge in molecular biophysics. The rational design of effector molecules that target such receptor populations allows fine-tuning receptor signalling with higher specificity to produce drugs with safer therapeutic profiles. In this minireview, we outline highly conserved receptor regions which are considered determinant for the establishment of distinct receptor states. We then discuss in-silico approaches such as dimensionality reduction methods and Markov State Models to explore the GPCR conformational universe and exploit the obtained conformations through structure-based drug design. PMID:27492237

  7. Warped conformal field theory

    NASA Astrophysics Data System (ADS)

    Detournay, Stéphane; Hartman, Thomas; Hofman, Diego M.

    2012-12-01

    We study field theories in two spacetime dimensions invariant under a chiral scaling symmetry that acts only on right-movers. The local symmetries include one copy of the Virasoro algebra and a U(1) current algebra. This differs from the two-dimensional conformal group but in some respects is equally powerful in constraining the theory. In particular, the symmetries on a torus lead to modular covariance of the partition function, which is used to derive a universal formula for the asymptotic density of states. For an application we turn to the holographic description of black holes in quantum gravity, motivated by the fact that the symmetries in the near-horizon geometry of any extremal black hole are identical to those of a two-dimensional field theory with chiral scaling. We consider two examples: black holes in warped AdS3 in topologically massive gravity and in string theory. In both cases, the density of states in the two-dimensional field theory reproduces the Bekenstein-Hawking entropy of black holes in the gravity theory.

  8. Dynamics of protein conformations

    NASA Astrophysics Data System (ADS)

    Stepanova, Maria

    2010-10-01

    A novel theoretical methodology is introduced to identify dynamic structural domains and analyze local flexibility in proteins. The methodology employs a multiscale approach combining identification of essential collective coordinates based on the covariance analysis of molecular dynamics trajectories, construction of the Mori projection operator with these essential coordinates, and analysis of the corresponding generalized Langevin equations [M.Stepanova, Phys.Rev.E 76(2007)051918]. Because the approach employs a rigorous theory, the outcomes are physically transparent: the dynamic domains are associated with regions of relative rigidity in the protein, whereas off-domain regions are relatively soft. This also allows scoring the flexibility in the macromolecule with atomic-level resolution [N.Blinov, M.Berjanskii, D.S.Wishart, and M.Stepanova, Biochemistry, 48(2009)1488]. The applications include the domain coarse-graining and characterization of conformational stability in protein G and prion proteins. The results are compared with published NMR experiments. Potential applications for structural biology, bioinformatics, and drug design are discussed.

  9. Conformal gravity and “gravitational bubbles”

    NASA Astrophysics Data System (ADS)

    Berezin, V. A.; Dokuchaev, V. I.; Eroshenko, Yu. N.

    2016-01-01

    We describe the general structure of the spherically symmetric solutions in the Weyl conformal gravity. The corresponding Bach equations are derived for the special type of metrics, which can be considered as the representative of the general class. The complete set of the pure vacuum solutions, consisting of two classes, is found. The first one contains the solutions with constant two-dimensional curvature scalar, and the representatives are the famous Robertson-Walker metrics. We called one of them the “gravitational bubbles”, which is compact and with zero Weyl tensor. These “gravitational bubbles” are the pure vacuum curved space-times (without any material sources, including the cosmological constant), which are absolutely impossible in General Relativity. This phenomenon makes it easier to create the universe from “nothing”. The second class consists of the solutions with varying curvature scalar. We found its representative as the one-parameter family, which can be conformally covered by the thee-parameter Mannheim-Kazanas solution. We describe the general structure of the energy-momentum tensor in the spherical conformal gravity and construct the vectorial equation that reveals clearly some features of non-vacuum solutions.

  10. Routine Access to Millisecond Time Scale Events with Accelerated Molecular Dynamics

    PubMed Central

    2012-01-01

    In this work, we critically assess the ability of the all-atom enhanced sampling method accelerated molecular dynamics (aMD) to investigate conformational changes in proteins that typically occur on the millisecond time scale. We combine aMD with the inherent power of graphics processor units (GPUs) and apply the implementation to the bovine pancreatic trypsin inhibitor (BPTI). A 500 ns aMD simulation is compared to a previous millisecond unbiased brute force MD simulation carried out on BPTI, showing that the same conformational space is sampled by both approaches. To our knowledge, this represents the first implementation of aMD on GPUs and also the longest aMD simulation of a biomolecule run to date. Our implementation is available to the community in the latest release of the Amber software suite (v12), providing routine access to millisecond events sampled from dynamics simulations using off the shelf hardware. PMID:22984356

  11. HL-20 structural design comparison - Conformal shell versus cylindrical crew compartment

    NASA Astrophysics Data System (ADS)

    Bush, Lance B.; Wahls, Deborah M.; Robinson, James C.

    1993-04-01

    Extensive studies have been performed at NASA Langley Research Center (LaRC) on personnel launch systems (PLS) concepts. The primary mission of a PLS is the transport of Space Station crew members from Earth to the Space Station and return. The NASA LaRC PLS studies have led to the design of a lifting body configuration named the HL-20. In this study, two different HL-20 structural configurations are evaluated. The two configurations are deemed the conformal shell and the cylindrical crew compartment. The configurations are based on two different concerns for maintenance and operations. One configuration allows for access to subsystems while on-orbit from the interior, while the other allows for easy access to the subsystems during ground maintenance and operations. For each concept, the total structural weight required to sustain the applied loads is quantified through a structural evaluation. Structural weight for both configurations is compared along with the particular attributes of each. Analyses of both configurations indicate no appreciable weight or load relief advantage of one concept over the other. Maintainability and operability, therefore become the primary discriminator, leading to a choice of a crew compartment configuration.

  12. Conformal Ablative Thermal Protection System for Planetary and Human Exploration Missions:An Overview of the Technology Maturation Effort

    NASA Technical Reports Server (NTRS)

    Beck, Robin A S.; Arnold, James O.; Gasch, Matthew J.; Stackpoole, Margaret M.; Prabhu, Dinesh K.; Szalai, Christine E.; Wercinski, Paul F.; Venkatapathy, Ethiraj

    2013-01-01

    The Office of Chief Technologist, NASA identified the need for research and technology development in part from NASAs Strategic Goal 3.3 of the NASA Strategic Plan to develop and demonstrate the critical technologies that will make NASAs exploration, science, and discovery missions more affordable and more capable. Furthermore, the Game Changing Development Program is a primary avenue to achieve the Agencys 2011 strategic goal to Create the innovative new space technologies for our exploration, science, and economic future. The National Research Council (NRC) Space Technology Roadmaps and Priorities report highlights six challenges and they are: Mass to Surface, Surface Access, Precision Landing, Surface Hazard Detection and Avoidance, Safety and Mission Assurance, and Affordability. In order for NASA to meet these challenges, the report recommends immediate focus on Rigid and Flexible Thermal Protection Systems. Rigid TPS systems such as Avcoat or SLA are honeycomb based and PICA is in the form of tiles. The honeycomb systems are manufactured using techniques that require filling of each (38 cell) by hand, and in a limited amount of time all of the cells must be filled and the heatshield must be cured. The tile systems such as PICA pose a different challenge as the low strain-to-failure and manufacturing size limitations require large number of small tiles with gap-fillers between the tiles. Recent investments in flexible ablative systems have given rise to the potential for conformal ablative TPS. A conformal TPS over a rigid aeroshell has the potential to solve a number of challenges faced by traditional rigid TPS materials. The high strain-to-failure nature of the conformal ablative materials will allow integration of the TPS with the underlying aeroshell structure much easier and enable monolithic-like configuration and larger segments (or parts) to be used. By reducing the overall part count, the cost of installation (based on cost comparisons between blanket

  13. Solidifying Small Satellite Access to Orbit via the International Space Station (ISS): Cyclops' Deployment of the Lonestar SmallSat from the ISS

    NASA Technical Reports Server (NTRS)

    Hershey, Matthew P.; Newswander, Daniel R.; Evernden, Brent A.

    2016-01-01

    On January 29, 2016, the Space Station Integrated Kinetic Launcher for Orbital Payload Systems (SSIKLOPS), known as "Cyclops" to the International Space Station (ISS) community, deployed Lonestar from the ISS. The deployment of Lonestar, a collaboration between Texas A&M University and the University of Texas at Austin, continued to showcase the simplicity and reliability of the Cyclops deployment system. Cyclops, a NASA-developed, dedicated 10-100 kg class ISS SmallSat deployment system, utilizes the Japanese airlock and robotic systems to seamlessly insert SmallSats into orbit. This paper will illustrate Cyclops' successful deployment of Lonestar from the ISS as well as outline its concept of operations, interfaces, requirements, and processes.

  14. Conformal invariance, dark energy, and CMB non-gaussianity

    NASA Astrophysics Data System (ADS)

    Antoniadis, Ignatios; Mazur, Pawel O.; Mottola, Emil

    2012-09-01

    In addition to simple scale invariance, a universe dominated by dark energy naturally gives rise to correlation functions possessing full conformal invariance. This is due to the mathematical isomorphism between the conformal group of certain three dimensional slices of de Sitter space and the de Sitter isometry group SO(4,1). In the standard homogeneous, isotropic cosmological model in which primordial density perturbations are generated during a long vacuum energy dominated de Sitter phase, the embedding of flat spatial Bbb R3 sections in de Sitter space induces a conformal invariant perturbation spectrum and definite prediction for the shape of the non-Gaussian CMB bispectrum. In the case in which the density fluctuations are generated instead on the de Sitter horizon, conformal invariance of the Bbb S2 horizon embedding implies a different but also quite definite prediction for the angular correlations of CMB non-Gaussianity on the sky. Each of these forms for the bispectrum is intrinsic to the symmetries of de Sitter space, and in that sense, independent of specific model assumptions. Each is different from the predictions of single field slow roll inflation models, which rely on the breaking of de Sitter invariance. We propose a quantum origin for the CMB fluctuations in the scalar gravitational sector from the conformal anomaly that could give rise to these non-Gaussianities without a slow roll inflaton field, and argue that conformal invariance also leads to the expectation for the relation nS-1 = nT between the spectral indices of the scalar and tensor power spectrum. Confirmation of this prediction or detection of non-Gaussian correlations in the CMB of one of the bispectral shape functions predicted by conformal invariance can be used both to establish the physical origins of primordial density fluctuations, and distinguish between different dynamical models of cosmological vacuum dark energy.

  15. Conformal invariance, dark energy, and CMB non-gaussianity

    SciTech Connect

    Antoniadis, Ignatios; Mazur, Pawel O.; Mottola, Emil E-mail: mazur@physics.sc.edu

    2012-09-01

    In addition to simple scale invariance, a universe dominated by dark energy naturally gives rise to correlation functions possessing full conformal invariance. This is due to the mathematical isomorphism between the conformal group of certain three dimensional slices of de Sitter space and the de Sitter isometry group SO(4,1). In the standard homogeneous, isotropic cosmological model in which primordial density perturbations are generated during a long vacuum energy dominated de Sitter phase, the embedding of flat spatial R{sup 3} sections in de Sitter space induces a conformal invariant perturbation spectrum and definite prediction for the shape of the non-Gaussian CMB bispectrum. In the case in which the density fluctuations are generated instead on the de Sitter horizon, conformal invariance of the S{sup 2} horizon embedding implies a different but also quite definite prediction for the angular correlations of CMB non-Gaussianity on the sky. Each of these forms for the bispectrum is intrinsic to the symmetries of de Sitter space, and in that sense, independent of specific model assumptions. Each is different from the predictions of single field slow roll inflation models, which rely on the breaking of de Sitter invariance. We propose a quantum origin for the CMB fluctuations in the scalar gravitational sector from the conformal anomaly that could give rise to these non-Gaussianities without a slow roll inflaton field, and argue that conformal invariance also leads to the expectation for the relation n{sub S}−1 = n{sub T} between the spectral indices of the scalar and tensor power spectrum. Confirmation of this prediction or detection of non-Gaussian correlations in the CMB of one of the bispectral shape functions predicted by conformal invariance can be used both to establish the physical origins of primordial density fluctuations, and distinguish between different dynamical models of cosmological vacuum dark energy.

  16. Selective access and editing in a database

    NASA Technical Reports Server (NTRS)

    Maluf, David A. (Inventor); Gawdiak, Yuri O. (Inventor)

    2010-01-01

    Method and system for providing selective access to different portions of a database by different subgroups of database users. Where N users are involved, up to 2.sup.N-1 distinguishable access subgroups in a group space can be formed, where no two access subgroups have the same members. Two or more members of a given access subgroup can edit, substantially simultaneously, a document accessible to each member.

  17. CONFORMANCE IMPROVEMENT USING GELS

    SciTech Connect

    Randall S. Seright

    2002-02-28

    This technical progress report describes work performed from June 20 through December 19, 2001, for the project, ''Conformance Improvement Using Gels''. Interest has increased in some new polymeric products that purport to substantially reduce permeability to water while causing minimum permeability reduction to oil. In view of this interest, we are currently studying BJ's Aqua Con. Results from six corefloods revealed that the Aqua Con gelant consistently reduced permeability to water more than that to oil. However, the magnitude of the disproportionate permeability reduction varied significantly for the various experiments. Thus, as with most materials tested to date, the issue of reproducibility and control of the disproportionate permeability remains to be resolved. Concern exists about the ability of gels to resist washout after placement in fractures. We examined whether a width constriction in the middle of a fracture would cause different gel washout behavior upstream versus downstream of the constriction. Tests were performed using a formed Cr(III)-acetate-HPAM gel in a 48-in.-long fracture with three sections of equal length, but with widths of 0.08-, 0.02-, and 0.08-in., respectively. The pressure gradients during gel extrusion (i.e., placement) were similar in the two 0.08-in.-wide fracture sections, even though they were separated by a 0.02-in.-wide fracture section. The constriction associated with the middle fracture section may have inhibited gel washout during the first pulse of brine injection after gel placement. However, during subsequent phases of brine injection, the constriction did not inhibit washout in the upstream fracture section any more than in the downstream section.

  18. Conformational changes of adsorbed proteins

    NASA Astrophysics Data System (ADS)

    Allen, Scott

    2005-03-01

    The adsorption of bovine serum albumin (BSA) and pepsin to gold surfaces has been studied using surface plasmon resonance (SPR). Proteins are adsorbed from solution onto a gold surface and changes in the conformation of the adsorbed proteins are induced by changing the buffer solution. We selected pH and ionic strength values for the buffer solutions that are known from our circular dichroism measurements to cause conformational changes of the proteins in bulk solution. We find that for both BSA and pepsin the changes in conformation are impeded by the interaction of the protein with the gold surface.

  19. Vanishing theorems of conformal Killing forms and their applications to electrodynamics in the general relativity theory

    NASA Astrophysics Data System (ADS)

    Stepanov, Sergey E.; Jukl, Marek; Mikeš, Josef

    2014-03-01

    Conformal Killing forms are a natural generalization of conformal Killing vector fields. These forms have applications in physics related to hidden symmetries, conserved quantities, symmetry operators, or separation of variables. In this paper, we prove two vanishing theorems of conformal Killing forms on a space-like totally umbilical submanifold of a Lorentzian manifold. Finally, we show an application of these results to electrodynamics in the General Relativity Theory.

  20. Conformational Landscape of Nicotinoids: Solving the "conformational - Rity" of Anabasine

    NASA Astrophysics Data System (ADS)

    Lesarri, Alberto; Cocinero, Emilio J.; Evangelisti, Luca; Suenram, Richard D.; Caminati, Walther; Grabow, Jens-Uwe

    2010-06-01

    The conformational landscape of the alkaloid anabasine (neonicotine) has been investigated using rotational spectroscopy and ab initio calculations. The results allow a detailed comparison of the structural properties of the prototype piperidinic and pyrrolidinic nicotinoids (anabasine vs. nicotine). Anabasine adopts two most stable conformations in isolation conditions, for which we determined accurate rotational and nuclear quadrupole coupling parameters. The preferred conformations are characterized by an equatorial pyridine moiety and additional N-H equatorial stereochemistry at the piperidine ring (Eq-Eq). The two rings of anabasine are close to a bisecting arrangement, with the observed conformations differing in a ca. 180° rotation of the pyridine subunit, denoted either Syn or Anti. The preference of anabasine for the Eq-Eq-Syn conformation has been established by relative intensity measurements (Syn/Anti˜5(2)). The conformational preferences of free anabasine are directed by a N\\cdot\\cdot\\cdotH-C weak hydrogen bond interaction between the nitrogen lone pair at piperidine and the closest hydrogen bond in pyridine, with N\\cdot\\cdot\\cdotN distances ranging from 4.750 Å (Syn) to 4.233 Å (Anti). R. J. Lavrich, R. D. Suenram, D. F. Plusquellic and S. Davis, 58^th OSU Int. Symp. on Mol. Spectrosc., Columbus, OH, 2003, Comm. RH13.

  1. A Fast Conformal Mapping Algorithm with No FFT

    NASA Astrophysics Data System (ADS)

    Luchini, P.; Manzo, F.

    1992-08-01

    An algorithm is presented for the computation of a conformal mapping discretized on a non-uniformly spaced point set, useful for the numerical solution of many problems of fluid dynamics. Most existing iterative techniques, both those having a linear and those having a quadratic type of convergence, rely on the fast Fourier transform ( FFT) algorithm for calculating a convolution integral which represents the most time-consuming phase of the computation. The FFT, however, definitely cannot be applied to a non-uniform spacing. The algorithm presented in this paper has been made possible by the construction of a calculation method for convolution integrals which, despite not using an FFT, maintains a computation time of the same order as that of the FFT. The new technique is successfully applied to the problem of conformally mapping a closely spaced cascade of airfoils onto a circle, which requires an exceedingly large number of points if it is solved with uniform spacing.

  2. Null conformal Killing-Yano tensors and Birkhoff theorem

    NASA Astrophysics Data System (ADS)

    Ferrando, Joan Josep; Sáez, Juan Antonio

    2016-04-01

    We study the space-times admitting a null conformal Killing-Yano tensor whose divergence defines a Killing vector. We analyze the similarities and differences with the recently studied non null case (Ferrando and Sáez in Gen Relativ Gravit 47:1911, 2015). The results by Barnes concerning the Birkhoff theorem for the case of null orbits are analyzed and generalized.

  3. Investigation of the conformational flexibility of DGAT1 peptides using tryptophan fluorescence

    NASA Astrophysics Data System (ADS)

    Lopes, Jose L. S.; Araujo, Ana P. U.; Jameson, David M.

    2015-06-01

    The conformational behavior of synthetic peptides corresponding to the putative binding sites of the diacylglycerol acyltransferase 1 enzyme (a polytopic integral membrane protein) was investigated using steady-state and time-resolved fluorescence spectroscopies. Three small linear peptides with 13, 15 and 22 amino acid residues, containing one, two and three Trp residues, respectively, were studied in aqueous solution, in the absence and presence of model membranes. The high flexibility and unordered conformation of the peptides in solution were confirmed by the low Trp polarization values, the high accessibility to water-soluble quencher, and the fast rotational correlation times of the Trp residues. However, upon binding to the lipid systems, the Trp residues were incorporated within the acyl hydrophobic core and their lifetimes and rotational correlation times increased. Phasor plots were employed to analyze intensity decay of peptide-lipid binding and provided a trajectory, in phasor space, that lies along a line connecting the points of the free and bound peptide. This trajectory was analyzed to determine the association constant of the peptide to the model membrane.

  4. A molecular modeling approach to understand the structure and conformation relationship of (GlcpA)Xylan.

    PubMed

    Guo, Qingbin; Kang, Ji; Wu, Yan; Cui, Steve W; Hu, Xinzhong; Yada, Rickey Y

    2015-12-10

    The structure and conformation relationships of a heteropolysaccharide (GlcpA)Xylan in terms of various molecular weights, Xylp/GlcpA ratio and the distribution of GlcpA along xylan chain were investigated using computer modeling. The adiabatic contour maps of xylobiose, XylpXylp(GlcpA) and (GlcpA)XylpXylp(GlcpA) indicated that the insertion of the side group (GlcpA) influenced the accessible conformational space of xylobiose molecule. RIS-Metropolis Monte Carlo method indicated that insertion of GlcpA side chain induced a lowering effect of the calculated chain extension at low GlcpA:Xylp ratio (GlcpA:Xylp = 1:3). The chain, however, became extended when the ratio of GlcpA:Xylp above 2/3. It was also shown that the spatial extension of the polymer chains was dependent on the distribution of side chain: the random distribution demonstrated the most flexible structure compared to block and alternative distribution. The present studies provide a unique insight into the dependence of both side chain ratio and distribution on the stiffness and flexibility of various (GlcpA)Xylan molecules. PMID:26428114

  5. Lattice Simulations and Infrared Conformality

    DOE PAGESBeta

    Appelquist, Thomas; Fleming, George T.; Lin, Meifeng; Neil, Ethan T.; Schaich, David A

    2011-09-01

    We examine several recent lattice-simulation data sets, asking whether they are consistent with infrared conformality. We observe, in particular, that for an SU(3) gauge theory with 12 Dirac fermions in the fundamental representation, recent simulation data can be described assuming infrared conformality. Lattice simulations include a fermion mass m which is then extrapolated to zero, and we note that this data can be fit by a small-m expansion, allowing a controlled extrapolation. We also note that the conformal hypothesis does not work well for two theories that are known or expected to be confining and chirally broken, and that itmore » does work well for another theory expected to be infrared conformal.« less

  6. Conformation Distributions in Adsorbed Proteins.

    NASA Astrophysics Data System (ADS)

    Meuse, Curtis W.; Hubbard, Joseph B.; Vrettos, John S.; Smith, Jackson R.; Cicerone, Marcus T.

    2007-03-01

    While the structural basis of protein function is well understood in the biopharmaceutical and biotechnology industries, few methods for the characterization and comparison of protein conformation distributions are available. New methods capable of measuring the stability of protein conformations and the integrity of protein-protein, protein-ligand and protein-surface interactions both in solution and on surfaces are needed to help the development of protein-based products. We are developing infrared spectroscopy methods for the characterization and comparison of molecular conformation distributions in monolayers and in solutions. We have extracted an order parameter describing the orientational and conformational variations of protein functional groups around the average molecular values from a single polarized spectrum. We will discuss the development of these methods and compare them to amide hydrogen/deuterium exchange methods for albumin in solution and on different polymer surfaces to show that our order parameter is related to protein stability.

  7. Lattice Simulations and Infrared Conformality

    SciTech Connect

    Appelquist, Thomas; Fleming, George T.; Lin, Meifeng; Neil, Ethan T.; Schaich, David A

    2011-09-01

    We examine several recent lattice-simulation data sets, asking whether they are consistent with infrared conformality. We observe, in particular, that for an SU(3) gauge theory with 12 Dirac fermions in the fundamental representation, recent simulation data can be described assuming infrared conformality. Lattice simulations include a fermion mass m which is then extrapolated to zero, and we note that this data can be fit by a small-m expansion, allowing a controlled extrapolation. We also note that the conformal hypothesis does not work well for two theories that are known or expected to be confining and chirally broken, and that it does work well for another theory expected to be infrared conformal.

  8. CONFORMANCE IMPROVEMENT USING GELS

    SciTech Connect

    Randall S. Seright

    2004-03-01

    This technical progress report describes work performed from September 1, 2003, through February 29, 2004, for the project, ''Conformance Improvement Using Gels.'' We examined the properties of several ''partially formed'' gels that were formulated with a combination of high and low molecular weight HPAM polymers. After placement in 4-mm-wide fractures, these gels required about 25 psi/ft for brine to breach the gel (the best performance to date in fractures this wide). After this breach, stabilized residual resistance factors decreased significantly with increased flow rate. Also, residual resistance factors were up to 9 times greater for water than for oil. Nevertheless, permeability reduction factors were substantial for both water and oil flow. Gel with 2.5% chopped fiberglass effectively plugged 4-mm-wide fractures if a 0.5-mm-wide constriction was present. The ability to screen-out at a constriction appears crucial for particulate incorporation to be useful in plugging fractures. In addition to fiberglass, we examined incorporation of polypropylene fibers into gels. Once dispersed in brine or gelant, the polypropylene fibers exhibited the least gravity segregation of any particulate that we have tested to date. In fractures with widths of at least 2 mm, 24-hr-old gels (0.5% high molecular weight HPAM) with 0.5% fiber did not exhibit progressive plugging during placement and showed extrusion pressure gradients similar to those of gels without the fiber. The presence of the fiber roughly doubled the gel's resistance to first breach by brine flow. The breaching pressure gradients were not as large as for gels made with high and low molecular weight polymers (mentioned above). However, their material requirements and costs (i.e., polymer and/or particulate concentrations) were substantially lower than for those gels. A partially formed gel made with 0.5% HPAM did not enter a 0.052-mm-wide fracture when applying a pressure gradient of 65 psi/ft. This result

  9. CONFORMANCE IMPROVEMENT USING GELS

    SciTech Connect

    Randall S. Seright

    2004-09-30

    This report describes work performed during the third and final year of the project, ''Conformance Improvement Using Gels.'' Corefloods revealed throughput dependencies of permeability reduction by polymers and gels that were much more prolonged during oil flow than water flow. This behavior was explained using simple mobility ratio arguments. A model was developed that quantitatively fits the results and predicts ''clean up'' times for oil productivity when production wells are returned to service after application of a polymer or gel treatment. X-ray computed microtomography studies of gels in strongly water-wet Berea sandstone and strongly oil-wet porous polyethylene suggested that oil penetration through gel-filled pores occurs by a gel-dehydration mechanism, rather than gel-ripping or gel-displacement mechanisms. In contrast, analysis of data from the University of Kansas suggests that the gel-ripping or displacement mechanisms are more important in more permeable, strongly water-wet sandpacks. These findings help to explain why aqueous gels can reduce permeability to water more than to oil under different conditions. Since cement is the most commonly used material for water shutoff, we considered when gels are preferred over cements. Our analysis and experimental results indicated that cement cannot be expected to completely fill (top to bottom) a vertical fracture of any width, except near the wellbore. For vertical fractures with apertures less than 4 mm, the cement slurry will simply not penetrate very far into the fracture. For vertical fractures with apertures greater than 4 mm, the slurry may penetrate a substantial distance into the bottom part of the fracture. However, except near the wellbore, the upper part of the fracture will remain open due to gravity segregation. We compared various approaches to plugging fractures using gels, including (1) varying polymer content, (2) varying placement (extrusion) rate, (3) using partially formed gels, (4

  10. 14 CFR 420.53 - Control of public access.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 4 2011-01-01 2011-01-01 false Control of public access. 420.53 Section 420.53 Aeronautics and Space COMMERCIAL SPACE TRANSPORTATION, FEDERAL AVIATION ADMINISTRATION....53 Control of public access. (a) A licensee shall prevent unauthorized access to the launch site,...

  11. Exploring the conformational energy landscape of proteins

    SciTech Connect

    Nienhaus, G.U. |; Mueller, J.D.; McMahon, B.H.

    1997-04-01

    Proteins possess a complex energy landscape with a large number of local minima called conformational substates that are arranged in a hierarchical fashion. Here we discuss experiments aimed at the elucidation of the energy landscape in carbonmonoxy myoglobin (MbCO). In the highest tier of the hierarchy, a few taxonomic substates exist. Because of their small number, these substates are accessible to detailed structural investigations. Spectroscopic experiments are discussed that elucidate the role of protonations of amino acid side chains in creating the substates. The lower tiers of the hierarchy contain a large number of statistical substates. Substate interconversions are observed in the entire temperature range from below 1 K up to the denaturation temperature, indicating a wide spectrum of energy barriers that separate the substates.

  12. Exploring the Conformational Transitions of Biomolecular Systems Using a Simple Two-State Anisotropic Network Model

    PubMed Central

    Jo, Sunhwan; Bahar, Ivet; Roux, Benoît

    2014-01-01

    Biomolecular conformational transitions are essential to biological functions. Most experimental methods report on the long-lived functional states of biomolecules, but information about the transition pathways between these stable states is generally scarce. Such transitions involve short-lived conformational states that are difficult to detect experimentally. For this reason, computational methods are needed to produce plausible hypothetical transition pathways that can then be probed experimentally. Here we propose a simple and computationally efficient method, called ANMPathway, for constructing a physically reasonable pathway between two endpoints of a conformational transition. We adopt a coarse-grained representation of the protein and construct a two-state potential by combining two elastic network models (ENMs) representative of the experimental structures resolved for the endpoints. The two-state potential has a cusp hypersurface in the configuration space where the energies from both the ENMs are equal. We first search for the minimum energy structure on the cusp hypersurface and then treat it as the transition state. The continuous pathway is subsequently constructed by following the steepest descent energy minimization trajectories starting from the transition state on each side of the cusp hypersurface. Application to several systems of broad biological interest such as adenylate kinase, ATP-driven calcium pump SERCA, leucine transporter and glutamate transporter shows that ANMPathway yields results in good agreement with those from other similar methods and with data obtained from all-atom molecular dynamics simulations, in support of the utility of this simple and efficient approach. Notably the method provides experimentally testable predictions, including the formation of non-native contacts during the transition which we were able to detect in two of the systems we studied. An open-access web server has been created to deliver ANMPathway results

  13. CONFORMANCE IMPROVEMENT USING GELS

    SciTech Connect

    Randall S. Seright

    2003-09-01

    This report describes work performed during the second year of the project, ''Conformance Improvement Using Gels.'' The project has two objectives. The first objective is to identify gel compositions and conditions that substantially reduce flow through fractures that allow direct channeling between wells, while leaving secondary fractures open so that high fluid injection and production rates can be maintained. The second objective is to optimize treatments in fractured production wells, where the gel must reduce permeability to water much more than that to oil. Pore-level images from X-ray computed microtomography were re-examined for Berea sandstone and porous polyethylene. This analysis suggests that oil penetration through gel-filled pores occurs by a gel-dehydration mechanism, rather than a gel-ripping mechanism. This finding helps to explain why aqueous gels can reduce permeability to water more than to oil. We analyzed a Cr(III)-acetate-HPAM gel treatment in a production well in the Arbuckle formation. The availability of accurate pressure data before, during, and after the treatment was critical for the analysis. After the gel treatment, water productivity was fairly constant at about 20% of the pre-treatment value. However, oil productivity was stimulated by a factor of 18 immediately after the treatment. During the six months after the treatment, oil productivity gradually decreased to approach the pre-treatment value. To explain this behavior, we proposed that the fracture area open to oil flow was increased substantially by the gel treatment, followed by a gradual closing of the fractures during subsequent production. For a conventional Cr(III)-acetate-HPAM gel, the delay between gelant preparation and injection into a fracture impacts the placement, leakoff, and permeability reduction behavior. Formulations placed as partially formed gels showed relatively low pressure gradients during placement, and yet substantially reduced the flow capacity of

  14. Hemodialysis access - self care

    MedlinePlus

    Kidney failure - chronic-hemodialysis access; Renal failure - chronic-hemodialysis access; Chronic renal insufficiency - hemodialysis access; Chronic kidney failure - hemodialysis access; Chronic renal failure - hemodialysis access; dialysis - hemodialysis access

  15. To Conform or Not to Conform: Spontaneous Conformity Diminishes the Sensitivity to Monetary Outcomes

    PubMed Central

    2013-01-01

    When people have different opinions in a group, they often adjust their own attitudes and behaviors to match the group opinion, known as social conformity. The affiliation account of normative conformity states that people conform to norms in order to ‘fit in’, whereas the accuracy account of informative conformity posits that the motive to learn from others produces herding. Here, we test another possibility that following the crowd reduces the experienced negative emotion when the group decision turns out to be a bad one. Using event related potential (ERP) combined with a novel group gambling task, we found that participants were more likely to choose the option that was predominately chosen by other players in previous trials, although there was little explicit normative pressure at the decision stage and group choices were not informative. When individuals' choices were different from others, the feedback related negativity (FRN), an ERP component sensitive to losses and errors, was enhanced, suggesting that being independent is aversive. At the outcome stage, the losses minus wins FRN effect was significantly reduced following conformity choices than following independent choices. Analyses of the P300 revealed similar patterns both in the response and outcome period. Our study suggests that social conformity serves as an emotional buffer that protects individuals from experiencing strong negative emotion when the outcomes are bad. PMID:23691242

  16. Influence of rotational energy barriers to the conformational search of protein loops in molecular dynamics and ranking the conformations.

    PubMed

    Tappura, K

    2001-08-15

    An adjustable-barrier dihedral angle potential was added as an extension to a novel, previously presented soft-core potential to study its contribution to the efficacy of the search of the conformational space in molecular dynamics. As opposed to the conventional soft-core potential functions, the leading principle in the design of the new soft-core potential, as well as of its extension, the soft-core and adjustable-barrier dihedral angle (SCADA) potential (referred as the SCADA potential), was to maintain the main equilibrium properties of the original force field. This qualifies the methods for a variety of a priori modeling problems without need for additional restraints typically required with the conventional soft-core potentials. In the present study, the different potential energy functions are applied to the problem of predicting loop conformations in proteins. Comparison of the performance of the soft-core and SCADA potential showed that the main hurdles for the efficient sampling of the conformational space of (loops in) proteins are related to the high-energy barriers caused by the Lennard-Jones and Coulombic energy terms, and not to the rotational barriers, although the conformational search can be further enhanced by lowering the rotational barriers of the dihedral angles. Finally, different evaluation methods were studied and a few promising criteria found to distinguish the near-native loop conformations from the wrong ones. PMID:11455590

  17. Non-linear realizations of conformal symmetry and effective field theory for the pseudo-conformal universe

    SciTech Connect

    Hinterbichler, Kurt; Joyce, Austin; Khoury, Justin E-mail: joyceau@sas.upenn.edu

    2012-06-01

    The pseudo-conformal scenario is an alternative to inflation in which the early universe is described by an approximate conformal field theory on flat, Minkowski space. Some fields acquire a time-dependent expectation value, which breaks the flat space so(4,2) conformal algebra to its so(4,1) de Sitter subalgebra. As a result, weight-0 fields acquire a scale invariant spectrum of perturbations. The scenario is very general, and its essential features are determined by the symmetry breaking pattern, irrespective of the details of the underlying microphysics. In this paper, we apply the well-known coset technique to derive the most general effective lagrangian describing the Goldstone field and matter fields, consistent with the assumed symmetries. The resulting action captures the low energy dynamics of any pseudo-conformal realization, including the U(1)-invariant quartic model and the Galilean Genesis scenario. We also derive this lagrangian using an alternative method of curvature invariants, consisting of writing down geometric scalars in terms of the conformal mode. Using this general effective action, we compute the two-point function for the Goldstone and a fiducial weight-0 field, as well as some sample three-point functions involving these fields.

  18. 14 CFR 25.611 - Accessibility provisions.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Accessibility provisions. 25.611 Section 25... AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Design and Construction General § 25.611 Accessibility... required by § 25.1529. (b) EWIS must meet the accessibility requirements of § 25.1719....

  19. Hemodialysis access - self care

    MedlinePlus

    Kidney failure - chronic-hemodialysis access; Renal failure - chronic-hemodialysis access; Chronic renal insufficiency - hemodialysis access; Chronic kidney failure - hemodialysis access; Chronic renal failure - ...

  20. 14 CFR 23.611 - Accessibility provisions.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Accessibility provisions. 23.611 Section 23.611 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT... § 23.611 Accessibility provisions. For each part that requires maintenance, inspection, or...

  1. Twisted geometries, twistors, and conformal transformations

    NASA Astrophysics Data System (ADS)

    Lângvik, Miklos; Speziale, Simone

    2016-07-01

    The twisted geometries of spin network states are described by simple twistors, isomorphic to null twistors with a timelike direction singled out. The isomorphism depends on the Immirzi parameter γ and reduces to the identity for γ =∞ . Using this twistorial representation, we study the action of the conformal group SU(2,2) on the classical phase space of loop quantum gravity, described by twisted geometry. The generators of translations and conformal boosts do not preserve the geometric structure, whereas the dilatation generator does. It corresponds to a one-parameter family of embeddings of T*SL(2,C) in twistor space, and its action preserves the intrinsic geometry while changing the extrinsic one—that is the boosts among polyhedra. We discuss the implication of this action from a dynamical point of view and compare it with a discretization of the dilatation generator of the continuum phase space, given by the Lie derivative of the group character. At leading order in the continuum limit, the latter reproduces the same transformation of the extrinsic geometry, while also rescaling the areas and volumes and preserving the angles associated with the intrinsic geometry. Away from the continuum limit, its action has an interesting nonlinear structure but is in general incompatible with the closure constraint needed for the geometric interpretation. As a side result, we compute the precise relation between the extrinsic geometry used in twisted geometries and the one defined in the gauge-invariant parametrization by Dittrich and Ryan and show that the secondary simplicity constraints they posited coincide with those dynamically derived in the toy model of [Classical Quantum Gravity 32, 195015 (2015)].

  2. Conformal invariance, dynamical dark energy and the CMB

    SciTech Connect

    Mottola, Emil

    2010-01-01

    Einstein's General Relativity receives quantum corrections relevant at cosmological distance scales. These effects arise from conformal scalar degrees of freedom in the extended Effective Field Theory (EFT) of gravity required by the trace anomaly of the quantum stress tensor in curved space. Scalar degrees of freedom in cosmology arise naturally from the effective action of the trace anomaly in the Standard Model, without the ad hoc introduction of an inflaton field. In the EFT including the trace anomaly terms, {Lambda}{sub eff} becomes dynamical and potentially dependent upon both space and time. The fluctuations of these anomaly scalars may also influence the spectrum and statistics of the Cosmic Microwave Background (CMB). Under the hypothesis that scale invariance should be promoted to full conformal invariance, an hypothesis supported by the embedding of the conformal group of three dimensional flat sections in de Sitter space, the form of the CMB bi-spectrum can be fixed, and the tri-spectrum constrained. The angular spectra predicted by conformal invariance differ from those suggested by simple models of inflation.

  3. Gauge theory of a group of diffeomorphisms. II. The conformal and de Sitter groups

    NASA Astrophysics Data System (ADS)

    Lord, Eric A.

    1986-12-01

    The extension of Hehl's Poincaré gauge theory to more general groups that include space-time diffeomorphisms is worked out for two particular examples, one corresponding to the action of the conformal group on Minkowski space, and the other to the action of the de Sitter group on de Sitter space, and the effect of these groups on physical fields.

  4. Expanding Access

    ERIC Educational Resources Information Center

    Roach, Ronald

    2007-01-01

    There is no question that the United States lags behind most industrialized nations in consumer access to broadband Internet service. For many policy makers and activists, this shortfall marks the latest phase in the struggle to overcome the digital divide. To remedy this lack of broadband affordability and availability, one start-up firm--with…

  5. Access Denied

    ERIC Educational Resources Information Center

    Raths, David

    2012-01-01

    As faculty members add online and multimedia elements to their courses, colleges and universities across the country are realizing that there is a lot of work to be done to ensure that disabled students (and employees) have equal access to course material and university websites. Unfortunately, far too few schools consider the task a top priority.…

  6. Easy Access

    ERIC Educational Resources Information Center

    Gettelman, Alan

    2009-01-01

    School and university restrooms, locker and shower rooms have specific ADA accessibility requirements that serve the needs of staff, students and campus visitors who are disabled as a result of injury, illness or age. Taking good care of them is good for the reputation of a sensitive community institution, and fosters positive public relations.…

  7. The principle of conformational signaling.

    PubMed

    Tompa, Peter

    2016-07-25

    Signal transduction is the primary process by which cells respond to changes in their physical and chemical environments. Cellular response is initiated through a signaling protein (a receptor), which interacts with the "signal", most often a novel molecule outside or inside the cell. The mechanism of activation of the receptor is a conformational change and/or covalent modification, which then sets in motion a signaling pathway, i.e. a cascade of modification and binding events that relay and amplify the message to eventually alter the state of the cell. In reflection of this general perception, concepts such as the "second messenger" and the "phosphorylation cascade" dominate our views of signal transduction. The idea I advocate here is that the non-covalent change in protein conformation itself might serve as the initial or intermittent "signal" in the cascade, and it is often the primary event being recognized and interpreted by downstream receptor(s). This signaling principle is intertwined with many other cellular regulatory concepts, such as (pathway) allostery, conformational spread, induced folding/unfolding, conformational memory, the hierarchical assembly of complexes, and the action of regulatory chaperones and prions. By elaborating on many examples and also recent advances in experimental methodology, I show that conformational signaling, although thus far underappreciated, is a general and robust signaling principle that most of the time operates in close interplay with covalent signals in the cell. PMID:27242242

  8. Bootstrapping conformal field theories with the extremal functional method.

    PubMed

    El-Showk, Sheer; Paulos, Miguel F

    2013-12-13

    The existence of a positive linear functional acting on the space of (differences between) conformal blocks has been shown to rule out regions in the parameter space of conformal field theories (CFTs). We argue that at the boundary of the allowed region the extremal functional contains, in principle, enough information to determine the dimensions and operator product expansion (OPE) coefficients of an infinite number of operators appearing in the correlator under analysis. Based on this idea we develop the extremal functional method (EFM), a numerical procedure for deriving the spectrum and OPE coefficients of CFTs lying on the boundary (of solution space). We test the EFM by using it to rederive the low lying spectrum and OPE coefficients of the two-dimensional Ising model based solely on the dimension of a single scalar quasiprimary--no Virasoro algebra required. Our work serves as a benchmark for applications to more interesting, less known CFTs in the near future. PMID:24483643

  9. pH-Dependent conformational changes in tear lipocalin by site-directed tryptophan fluorescence.

    PubMed

    Gasymov, Oktay K; Abduragimov, Adil R; Glasgow, Ben J

    2010-01-26

    Tear lipocalin (TL), a major protein of human tears, binds a broad array of endogenous ligands. pH-dependent ligand binding in TL may have functional implications in tears. Previously, conformational selections of the AB and GH loops have been implicated in ligand binding by site-directed tryptophan fluorescence (SDTF). In this study, SDTF was applied to the AB and GH loops to investigate pH-driven conformational changes relevant to ligand binding. Both loops demonstrate significant but distinct conformational rearrangements over a wide pH range. In the low-pH transition, from 7.3 to 3.0, residues of the GH loop exhibit decreased solvent accessibilities. In acrylamide quenching experiments, the average quenching rate constant (k(q), accessibility parameter) of the residues in the GH loop is decreased approximately 38%, from 2.1 x 10(9) to 1.3 x 10(9) M(-1) s(-1). However, despite the significant changes in accessibilities for some residues in the AB loop, the average accessibility per residue remained unchanged (average k(q) = 1.2 M(-1) s(-1)). Accordingly, the low-pH transition induces conformational changes that reshuffle the accessibility profiles of the residues in the AB loop. A significant difference in the titration curves between the holo and apo forms of the W28 mutant suggests that the protonation states of the residues around position 28 modulate conformational switches of the AB loop relevant to ligand binding. PMID:20025287

  10. PH-dependent Conformational Changes in Tear Lipocalin by Site Directed Tryptophan Fluorescence

    PubMed Central

    Gasymov, Oktay K.; Abduragimov, Adil R.; Glasgow, Ben J.

    2010-01-01

    Tear lipocalin (TL), a major protein of human tears, binds a broad array of endogenous ligands. PH-dependent ligand binding in TL may have functional implications in tears. Previously, conformational selections of the loops AB and GH have been implicated in ligand binding by site-directed tryptophan fluorescence (SDTF). In this study, SDTF was applied on the loops AB and GH to investigate pH-driven conformational changes relevant to ligand binding. Both loops demonstrate significant but distinct conformational rearrangements over a wide pH range. In the low pH transition, from 7.3 to 3.0, residues of the loop GH show the decreased solvent accessibilities. In acrylamide quenching experiments, the average quenching rate constant (kq, accessibility parameter) of the residues in the loop GH is decreased about 38%, from 2.1×109 M−1s−1 to 1.3×109 M−1s−1. However, despite the significant changes in accessibilities for some residues in the loop AB, the average accessibility per residue remained unchanged (average kq= 1.2 M−1s−1). Accordingly, low pH transition induces conformational changes that reshuffle accessibility profiles of the residues in the loop AB. A significant difference in the titration curves between holo- and apo-forms of W28 mutant suggests that the protonation states of the residues around the position 28 modulate conformational switches of the loop AB relevant to ligand binding. PMID:20025287

  11. Annual Report Electrochemical Machining of Access Holes

    SciTech Connect

    Cooper, J F; Evans, M; Whipple, R

    2006-01-04

    We report the advances made in electrochemical machining of access holes through sheet metal during FY2005. The cutting tool underwent a major engineering re-design to accommodate an oblong cut with parallel sides (1.5'' spacing) on a surface of arbitrary curvature. The solid cathode was replaced by an array of separately movable steel pins, allowing the tool to conform to the surface shape of the work piece prior to beginning cutting. Preliminary cuts through a hardened steel drum (0.04 inch thickness) were successfully completed at a low current (50A) but the current efficiency of the cutting process was poor (<30%). Efficiency was improved to 75% and the cutting time reduced to 8 minutes in heated electrolyte at 100 A and 4.5 V. This work led to improvements in process simplicity and ease of operation: (1) continuous movement of the cathode towards the work piece was eliminated in favor of a fixed cathode; (2) the surfaces of the cutting pins do not require insulation; (3) a spider support for the tool provides for rapid positioning of the cutting tool; (4) negative electrolyte pressure minimized leakage into the drum following breakthrough. We found no reactivity of various HE's with alternative candidate ECM electrolytes.

  12. Molecular simulations for the conformational assessment of a porphyrin-fullerene dyad in different environments.

    PubMed

    Tappura, Kirsi; Cramariuc, Oana; Hukka, Terttu I; Rantala, Tapio T

    2005-09-01

    Conformational space of a porphyrin-fullerene dyad with the donor and acceptor connected by a relatively flexible linker is studied by molecular dynamics simulations in both non-polar and polar solvents, as well as in vacuum. The most probable conformations obtained from the vacuum MD simulations were optimized with semi-empirical (SE) and density functional theory (DFT) methods and the extent of the structural changes is assessed. The computational results indicate the co-existence of different conformers in both polar and nonpolar solvents showing agreement with experimental results. The most probable vacuum conformations at 300 K are similar to the ones at 0 K, while the structures most often observed in the solvents show less compact conformations. Optimization with SE and DFT calculations leads to structures, which represent relatively well the folded conformations in solvent, which validates the electronic structure calculations relevant to describing photoinduced electron-transfer in H2P-O34-C60. PMID:16240023

  13. New conformational search method using genetic algorithm and knot theory for proteins.

    PubMed

    Sakae, Y; Hiroyasu, T; Miki, M; Okamoto, Y

    2011-01-01

    We have proposed a parallel simulated annealing using genetic crossover as one of powerful conformational search methods, in order to find the global minimum energy structures for protein systems. The simulated annealing using genetic crossover method, which incorporates the attractive features of the simulated annealing and the genetic algorithm, is useful for finding a minimum potential energy conformation of protein systems. However, when we perform simulations by using this method, we often find obviously unnatural stable conformations, which have "knots" of a string of an amino-acid sequence. Therefore, we combined knot theory with our simulated annealing using genetic crossover method in order to avoid the knot conformations from the conformational search space. We applied this improved method to protein G, which has 56 amino acids. As the result, we could perform the simulations, which avoid knot conformations. PMID:21121049

  14. Conformational study of arbutin by quantum chemical calculations and multivariate analysis

    NASA Astrophysics Data System (ADS)

    Araujo-Andrade, Cuauhtémoc; Lopes, Susy; Fausto, Rui; Gómez-Zavaglia, Andrea

    2010-06-01

    A conformational study of the molecule of arbutin (4-hydroxyphenyl-β- D-glucopyranoside) has been undertaken. The molecule is composed by a glucopyranoside moiety bound to a phenol ring. It has eight conformationally relevant dihedral angles, five of them related with the orientation of the hydroxyl groups and the remaining three taking part in the skeleton of the molecule. A systematic search on the conformational space of arbutin was performed using molecular orbital methods, followed by the identification of structural similarities between the different conformers, using multivariate analyses. This approach allowed the grouping of conformers according to their structural affinity and the establishment of correlations between their structures and several properties. Intramolecular interactions involving OH groups were also investigated and correlations between spectroscopic, structural and thermodynamic properties established. The developed strategy might be useful to investigate the structure and structure/properties correlations in other conformationally flexible molecules.

  15. DBI realizations of the pseudo-conformal universe and Galilean Genesis scenarios

    SciTech Connect

    Hinterbichler, Kurt; Joyce, Austin; Khoury, Justin; Miller, Godfrey E.J. E-mail: joyceau@sas.upenn.edu E-mail: godfreym@sas.upenn.edu

    2012-12-01

    The pseudo-conformal universe is an alternative to inflation in which the early universe is described by a conformal field theory on approximately flat space-time. The fields develop time-dependent expectation values, spontaneously breaking the conformal symmetries to a de Sitter subalgebra, and fields of conformal weight zero acquire a scale invariant spectrum of perturbations. In this paper, we show that the pseudo-conformal scenario can be naturally realized within theories that would ordinarily be of interest for DBI inflation, such as the world-volume theory of a probe brane in an AdS bulk space-time. In this approach, the weight zero spectator field can be associated with a geometric flat direction in the bulk, and its scale invariance is protected by a shift symmetry.

  16. Conformers, infrared spectrum, UV-induced photochemistry, and near-IR-induced generation of two rare conformers of matrix-isolated phenylglycine

    SciTech Connect

    Borba, Ana Fausto, Rui; Gómez-Zavaglia, Andrea

    2014-10-21

    The conformational space of α-phenylglycine (PG) have been investigated theoretically at both the DFT/B3LYP/6-311++G(d,p) and MP2/6-311++G(d,p) levels of approximation. Seventeen different minima were found on the investigated potential energy surfaces, which are characterized by different dominant intramolecular interactions: type I conformers are stabilized by hydrogen bonds of the type N–H···O=C, type II by a strong O–H···N hydrogen bond, type III by weak N–H···O–H hydrogen bonds, and type IV by a C=O···H–C contact. The calculations indicate also that entropic effects are relevant in determining the equilibrium populations of the conformers of PG in the gas phase, in particular in the case of conformers of type II, where the strong intramolecular O–H···N hydrogen bond considerably diminishes entropy by reducing the conformational mobility of the molecule. In consonance with the relative energies of the conformers and barriers for conformational interconversion, only 3 conformers of PG were observed for the compound isolated in cryogenic Ar, Xe, and N{sub 2} matrices: the conformational ground state (ICa), and forms ICc and IITa. All other significantly populated conformers existing in the gas phase prior to deposition convert either to conformer ICa or to conformer ICc during matrix deposition. The experimental observation of ICc had never been achieved hitherto. Narrowband near-IR irradiation of the first overtone of νOH vibrational mode of ICa and ICc in nitrogen matrices (at 6910 and 6930 cm{sup −1}, respectively) led to selective generation of two additional conformers of high-energy, ITc and ITa, respectively, which were also observed experimentally for the first time. In addition, these experiments also provided the key information for the detailed vibrational characterization of the 3 conformers initially present in the matrices. On the other hand, UV irradiation (λ = 255 nm) of PG isolated in a xenon matrix revealed that

  17. Nonlocal gravity: Conformally flat spacetimes

    NASA Astrophysics Data System (ADS)

    Bini, Donato; Mashhoon, Bahram

    2016-04-01

    The field equations of the recent nonlocal generalization of Einstein’s theory of gravitation are presented in a form that is reminiscent of general relativity. The implications of the nonlocal field equations are studied in the case of conformally flat spacetimes. Even in this simple case, the field equations are intractable. Therefore, to gain insight into the nature of these equations, we investigate the structure of nonlocal gravity (NLG) in 2D spacetimes. While any smooth 2D spacetime is conformally flat and satisfies Einstein’s field equations, only a subset containing either a Killing vector or a homothetic Killing vector can satisfy the field equations of NLG.

  18. Conformational dynamics through an intermediate

    NASA Astrophysics Data System (ADS)

    Garai, Ashok; Zhang, Yaojun; Dudko, Olga K.

    2014-04-01

    The self-assembly of biological and synthetic nanostructures commonly proceeds via intermediate states. In living systems in particular, the intermediates have the capacity to tilt the balance between functional and potentially fatal behavior. This work develops a statistical mechanical treatment of conformational dynamics through an intermediate under a variable force. An analytical solution is derived for the key experimentally measurable quantity—the distribution of forces at which a conformational transition occurs. The solution reveals rich kinetics over a broad range of parameters and enables one to locate the intermediate and extract the activation barriers and rate constants.

  19. A sampling approach for protein backbone fragment conformations.

    PubMed

    Yu, J Y; Zhang, W

    2013-01-01

    In protein structure prediction, backbone fragment bias information can narrow down the conformational space of the whole polypeptide chain significantly. Unlike existing methods that use fragments as building blocks, the paper presents a probabilistic sampling approach for protein backbone torsion angles by modelling angular correlation of (phi, psi) with a directional statistics distribution. Given a protein sequence and secondary structure information, this method samples backbone fragments conformations by using a backtrack sampling algorithm for the hidden Markov model with multiple inputs and a single output. The proposed approach is applied to a fragment library, and some well-known structural motifs are sampled very well on the optimal path. Computational results show that the method can help to obtain native-like backbone fragments conformations. PMID:23777175

  20. Proper Time Dynamics in General Relativity and Conformal Unified Theory

    NASA Astrophysics Data System (ADS)

    Gyngazov, L. N.; Pawlowski, M.; Pervushin, V. N.; Smirichinski, V. I.

    1998-12-01

    The paper is devoted to the description a measurable time-interval ("proper time") in the Hamiltonian version of general relativity with the Dirac-ADM metric. To separate the dynamical parameter of evolution from the space metric we use the Lichnerowicz conformally invariant variables. In terms of these variables GR is equivalent to the conformally invariant Penrose-Chernikov-Tagirov theory of a scalar field the role of which is played by the scale factor multiplied by the Planck constant. Identification of this scalar field with the modulus of the Higgs field in the standard model of electroweak and strong interactions allows us to formulate an example of conformally invariant unified theory where the vacuum averaging of the scalar field is determined by cosmological integrals of motion of the evolution of the universe.

  1. Plan-graph Based Heuristics for Conformant Probabilistic Planning

    NASA Technical Reports Server (NTRS)

    Ramakrishnan, Salesh; Pollack, Martha E.; Smith, David E.

    2004-01-01

    In this paper, we introduce plan-graph based heuristics to solve a variation of the conformant probabilistic planning (CPP) problem. In many real-world problems, it is the case that the sensors are unreliable or take too many resources to provide knowledge about the environment. These domains are better modeled as conformant planning problems. POMDP based techniques are currently the most successful approach for solving CPP but have the limitation of state- space explosion. Recent advances in deterministic and conformant planning have shown that plan-graphs can be used to enhance the performance significantly. We show that this enhancement can also be translated to CPP. We describe our process for developing the plan-graph heuristics and estimating the probability of a partial plan. We compare the performance of our planner PVHPOP when used with different heuristics. We also perform a comparison with a POMDP solver to show over a order of magnitude improvement in performance.

  2. Correspondence between Asymptotically Flat Spacetimes and Nonrelativistic Conformal Field Theories

    SciTech Connect

    Bagchi, Arjun

    2010-10-22

    We find a surprising connection between asymptotically flat spacetimes and nonrelativistic conformal systems in one lower dimension. The Bondi-Metzner-Sachs (BMS) group is the group of asymptotic isometries of flat Minkowski space at null infinity. This is known to be infinite dimensional in three and four dimensions. We show that the BMS algebra in 3 dimensions is the same as the 2D Galilean conformal algebra (GCA) which is of relevance to nonrelativistic conformal symmetries. We further justify our proposal by looking at a Penrose limit on a radially infalling null ray inspired by nonrelativistic scaling and obtain a flat metric. The BMS{sub 4} algebra is also discussed and found to be the same as another class of GCA, called semi-GCA, in three dimensions. We propose a general BMS-GCA correspondence. Some consequences are discussed.

  3. Conformal Doping of FINFETs: a Fabrication and Metrology Challenge

    SciTech Connect

    Vandervorst, W.; Mody, J.; Zschaetzsch, G.; Koelling, S.; Everaert, J. L.; Rosseel, E.; Jurczak, M.; Hoffman, T.; Eyben, P.; Gilbert, M.; Poon, T.; Del Agua Borniquel, J.; Foad, M.; Duffy, R.; Pawlak, B. J.

    2008-11-03

    Whereas the introduction of 3D-dimensional devices such as FINFETs may be a solution for next generation technologies, they do represent significant challenges with respect to the doping strategies and the junction characterization. Aiming at a conformal doping, classical beam implants fail due to the differences in impact angle, ion incorporation efficiency and the effect of wafer rotation. Moreover shadowing represents an additional limitation for larger tilt angles when considering closely spaced FINs. Plasma immersion doping is an alternative approach which holds the promise of conformality but is also quite challenging and relies on secondary processes such as resputtering, deposition and in diffusion etc. Its implementation is compromised by concurrent artifacts, sputter erosion being the most important one. In support of these developments the measurement of the 3D-dopant distribution and the identification of conformality is essential requiring adequate metrology such as Scanning Spreading Resistance Microscopy, SIMS through FINs, resistors and the Tomographic Atomprobe.

  4. C-Graded vertex algebras and conformal flow

    SciTech Connect

    Laber, Rob; Mason, Geoffrey

    2014-01-15

    We consider C-graded vertex algebras, which are vertex algebras V with a C-grading such that V is an admissible V-module generated by “lowest weight vectors.” We show that such vertex algebras have a “good” representation theory in the sense that there is a Zhu algebra A(V) and a bijection between simple admissible V-modules and simple A(V)-modules. We also consider pseudo vertex operator algebras (PVOAs), which are C-graded vertex algebras with a conformal vector such that the homogeneous subspaces of V are generalized eigenspaces for L(0); essentially, these are VOAs that lack any semisimplicity or integrality assumptions on L(0). As a motivating example, we show that deformation of the conformal structure (conformal flow) of a strongly regular VOA (e.g., a lattice theory, or Wess-Zumino-Witten model) is a path in a space whose points are PVOAs.

  5. Conformational dynamics and thermodynamics of protein-ligand binding studied by NMR relaxation.

    PubMed

    Akke, Mikael

    2012-04-01

    Protein conformational dynamics can be critical for ligand binding in two ways that relate to kinetics and thermodynamics respectively. First, conformational transitions between different substates can control access to the binding site (kinetics). Secondly, differences between free and ligand-bound states in their conformational fluctuations contribute to the entropy of ligand binding (thermodynamics). In the present paper, I focus on the second topic, summarizing our recent results on the role of conformational entropy in ligand binding to Gal3C (the carbohydrate-recognition domain of galectin-3). NMR relaxation experiments provide a unique probe of conformational entropy by characterizing bond-vector fluctuations at atomic resolution. By monitoring differences between the free and ligand-bound states in their backbone and side chain order parameters, we have estimated the contributions from conformational entropy to the free energy of binding. Overall, the conformational entropy of Gal3C increases upon ligand binding, thereby contributing favourably to the binding affinity. Comparisons with the results from isothermal titration calorimetry indicate that the conformational entropy is comparable in magnitude to the enthalpy of binding. Furthermore, there are significant differences in the dynamic response to binding of different ligands, despite the fact that the protein structure is virtually identical in the different protein-ligand complexes. Thus both affinity and specificity of ligand binding to Gal3C appear to depend in part on subtle differences in the conformational fluctuations that reflect the complex interplay between structure, dynamics and ligand interactions. PMID:22435823

  6. Ligand induced conformational changes of the human serotonin transporter revealed by molecular dynamics simulations.

    PubMed

    Koldsø, Heidi; Autzen, Henriette Elisabeth; Grouleff, Julie; Schiøtt, Birgit

    2013-01-01

    The competitive inhibitor cocaine and the non-competitive inhibitor ibogaine induce different conformational states of the human serotonin transporter. It has been shown from accessibility experiments that cocaine mainly induces an outward-facing conformation, while the non-competitive inhibitor ibogaine, and its active metabolite noribogaine, have been proposed to induce an inward-facing conformation of the human serotonin transporter similar to what has been observed for the endogenous substrate, serotonin. The ligand induced conformational changes within the human serotonin transporter caused by these three different types of ligands, substrate, non-competitive and competitive inhibitors, are studied from multiple atomistic molecular dynamics simulations initiated from a homology model of the human serotonin transporter. The results reveal that diverse conformations of the human serotonin transporter are captured from the molecular dynamics simulations depending on the type of the ligand bound. The inward-facing conformation of the human serotonin transporter is reached with noribogaine bound, and this state resembles a previously identified inward-facing conformation of the human serotonin transporter obtained from molecular dynamics simulation with bound substrate, but also a recently published inward-facing conformation of a bacterial homolog, the leucine transporter from Aquifex Aoelicus. The differences observed in ligand induced behavior are found to originate from different interaction patterns between the ligands and the protein. Such atomic-level understanding of how an inhibitor can dictate the conformational response of a transporter by ligand binding may be of great importance for future drug design. PMID:23776432

  7. Ligand Induced Conformational Changes of the Human Serotonin Transporter Revealed by Molecular Dynamics Simulations

    PubMed Central

    Grouleff, Julie; Schiøtt, Birgit

    2013-01-01

    The competitive inhibitor cocaine and the non-competitive inhibitor ibogaine induce different conformational states of the human serotonin transporter. It has been shown from accessibility experiments that cocaine mainly induces an outward-facing conformation, while the non-competitive inhibitor ibogaine, and its active metabolite noribogaine, have been proposed to induce an inward-facing conformation of the human serotonin transporter similar to what has been observed for the endogenous substrate, serotonin. The ligand induced conformational changes within the human serotonin transporter caused by these three different types of ligands, substrate, non-competitive and competitive inhibitors, are studied from multiple atomistic molecular dynamics simulations initiated from a homology model of the human serotonin transporter. The results reveal that diverse conformations of the human serotonin transporter are captured from the molecular dynamics simulations depending on the type of the ligand bound. The inward-facing conformation of the human serotonin transporter is reached with noribogaine bound, and this state resembles a previously identified inward-facing conformation of the human serotonin transporter obtained from molecular dynamics simulation with bound substrate, but also a recently published inward-facing conformation of a bacterial homolog, the leucine transporter from Aquifex Aoelicus. The differences observed in ligand induced behavior are found to originate from different interaction patterns between the ligands and the protein. Such atomic-level understanding of how an inhibitor can dictate the conformational response of a transporter by ligand binding may be of great importance for future drug design. PMID:23776432

  8. Scale invariance, conformality, and generalized free fields

    NASA Astrophysics Data System (ADS)

    Dymarsky, Anatoly; Farnsworth, Kara; Komargodski, Zohar; Luty, Markus A.; Prilepina, Valentina

    2016-02-01

    This paper addresses the question of whether there are 4D Lorentz invariant unitary quantum field theories with scale invariance but not conformal invariance. An important loophole in the arguments of Luty-Polchinski-Rattazzi and Dymarsky-Komargodski-Schwimmer-Theisen is that trace of the energy-momentum tensor T could be a generalized free field. In this paper we rule out this possibility. The key ingredient is the observation that a unitary theory with scale but not conformal invariance necessarily has a non-vanishing anomaly for global scale transformations. We show that this anomaly cannot be reproduced if T is a generalized free field unless the theory also contains a dimension-2 scalar operator. In the special case where such an operator is present it can be used to redefine ("improve") the energy-momentum tensor, and we show that there is at least one energy-momentum tensor that is not a generalized free field. In addition, we emphasize that, in general, large momentum limits of correlation functions cannot be understood from the leading terms of the coordinate space OPE. This invalidates a recent argument by Farnsworth-Luty-Prilepina (FLP). Despite the invalidity of the general argument of FLP, some of the techniques turn out to be useful in the present context.

  9. Polymer conformations in internal (polyspherical) coordinates.

    PubMed

    Pesonen, Janne; Henriksson, Krister O E

    2010-07-15

    The small-amplitude conformational changes in macromolecules can be described by the changes in bond lengths and bond angles. The descriptors of large scale changes are torsions. We present a recursive algorithm, in which a bond vector is explicitly written in terms of these internal, or polyspherical coordinates, in a local frame defined by two other bond vectors and their cross product. Conformations of linear and branched molecules, as well as molecules containing rings can be described in this way. The orientation of the molecule is described by the orientation of a body frame. It is parametrized by the instantaneous rotation angle, and the two angles that parametrize the orientation of the instantaneous rotation axis. The reason not to use more conventional Euler angles is due to the fact that Euler angles are not well-defined in gimbal lock (i.e., when a body axis becomes aligned with its space fixed counter part). The position of the molecule is parametrized by its center of mass. Original and calculated positions are compared for several proteins, containing up to about 100,000 atoms. PMID:20082385

  10. Conformal coating value/risk assessment for Sandia satellite programs.

    SciTech Connect

    Russick, Edward Mark; Thayer, Gayle Echo

    2008-03-01

    Conformal coatings are used in space applications on printed circuit board (PCB) assemblies primarily as a protective barrier against environmental contaminants. Such coatings have been used at Sandia for decades in satellite applications including the GPS satellite program. Recently, the value of conformal coating has been questioned because it is time consuming (requiring a 5-6 week schedule allowance) and delays due to difficulty of repairs and rework performed afterward are troublesome. In an effort to find opportunities where assembly time can be reduced, a review of the literature as well as discussions with satellite engineers both within and external to Sandia regarding the value of conformal coating was performed. Several sources on the value of conformal coating, the functions it performs, and on whether coatings are necessary and should be used at all were found, though nearly all were based on anecdotal information. The first section of this report, titled 'Conformal Coating for Space Applications', summarizes the results of an initial risk-value assessment of the conformal coating process for Sandia satellite programs based on information gathered. In the process of collecting information to perform the assessment, it was necessary to obtain a comprehensive understanding of the entire satellite box assembly process. A production time-line was constructed and is presented in the second section of this report, titled 'Satellite Box Assembly', specifically to identify potential sources of time delays, manufacturing issues, and component failures related to the conformal coating process in relation to the box assembly. The time-line also allows for identification of production issues that were anecdotally attributed to the conformal coating but actually were associated with other production steps in the box assembly process. It was constructed largely in consultation with GPS program engineers with empirical knowledge of times required to complete the

  11. Accessible solitons of fractional dimension

    NASA Astrophysics Data System (ADS)

    Zhong, Wei-Ping; Belić, Milivoj; Zhang, Yiqi

    2016-05-01

    We demonstrate that accessible solitons described by an extended Schrödinger equation with the Laplacian of fractional dimension can exist in strongly nonlocal nonlinear media. The soliton solutions of the model are constructed by two special functions, the associated Legendre polynomials and the Laguerre polynomials in the fraction-dimensional space. Our results show that these fractional accessible solitons form a soliton family which includes crescent solitons, and asymmetric single-layer and multi-layer necklace solitons.

  12. Facilitated diffusion framework for transcription factor search with conformational changes

    NASA Astrophysics Data System (ADS)

    Cartailler, Jérôme; Reingruber, Jürgen

    2015-07-01

    Cellular responses often require the fast activation or repression of specific genes, which depends on transcription factors (TFs) that have to quickly find the promoters of these genes within a large genome. TFs search for their DNA promoter target by alternating between bulk diffusion and sliding along the DNA, a mechanism known as facilitated diffusion. We study a facilitated diffusion framework with switching between three search modes: a bulk mode and two sliding modes triggered by conformational changes between two protein conformations. In one conformation (search mode) the TF interacts unspecifically with the DNA backbone resulting in fast sliding. In the other conformation (recognition mode) it interacts specifically and strongly with DNA base pairs leading to slow displacement. From the bulk, a TF associates with the DNA at a random position that is correlated with the previous dissociation point, which implicitly is a function of the DNA structure. The target affinity depends on the conformation. We derive exact expressions for the mean first passage time (MFPT) to bind to the promoter and the conditional probability to bind before detaching when arriving at the promoter site. We systematically explore the parameter space and compare various search scenarios. We compare our results with experimental data for the dimeric Lac repressor search in E. coli bacteria. We find that a coiled DNA conformation is absolutely necessary for a fast MFPT. With frequent spontaneous conformational changes, a fast search time is achieved even when a TF becomes immobilized in the recognition state due to the specific bindings. We find a MFPT compatible with experimental data in presence of a specific TF-DNA interaction energy that has a Gaussian distribution with a large variance.

  13. Conformational distributions of unfolded polypeptides from novel NMR techniques

    NASA Astrophysics Data System (ADS)

    Meier, Sebastian; Blackledge, Martin; Grzesiek, Stephan

    2008-02-01

    How the information content of an unfolded polypeptide sequence directs a protein towards a well-formed three-dimensional structure during protein folding remains one of the fundamental questions in structural biology. Unfolded proteins have recently attracted further interest due to their surprising prevalence in the cellular milieu, where they fulfill not only central regulatory functions, but also are implicated in diseases involving protein aggregation. The understanding of both the protein folding transition and these often natively unfolded proteins hinges on a more detailed experimental characterization of the conformations and conformational transitions in the unfolded state. This description is intrinsically very difficult due to the very large size of the conformational space. In principle, solution NMR can monitor unfolded polypeptide conformations and their transitions at atomic resolution. However, traditional NMR parameters such as chemical shifts, J couplings, and nuclear Overhauser enhancements yield only rather limited and often qualitative descriptions. This situation has changed in recent years by the introduction of residual dipolar couplings and paramagnetic relaxation enhancements, which yield a high number of well-defined, quantitative parameters reporting on the averages of local conformations and long-range interactions even under strongly denaturing conditions. This information has been used to obtain plausible all-atom models of the unfolded state at increasing accuracy. Currently, the best working model is the coil model, which derives amino acid specific local conformations from the distribution of amino acid torsion angles in the nonsecondary structure conformations of the protein data bank. Deviations from the predictions of such models can often be interpreted as increased order resulting from long-range contacts within the unfolded ensemble.

  14. Conformal killing tensors and covariant Hamiltonian dynamics

    SciTech Connect

    Cariglia, M.; Gibbons, G. W.; Holten, J.-W. van; Horvathy, P. A.; Zhang, P.-M.

    2014-12-15

    A covariant algorithm for deriving the conserved quantities for natural Hamiltonian systems is combined with the non-relativistic framework of Eisenhart, and of Duval, in which the classical trajectories arise as geodesics in a higher dimensional space-time, realized by Brinkmann manifolds. Conserved quantities which are polynomial in the momenta can be built using time-dependent conformal Killing tensors with flux. The latter are associated with terms proportional to the Hamiltonian in the lower dimensional theory and with spectrum generating algebras for higher dimensional quantities of order 1 and 2 in the momenta. Illustrations of the general theory include the Runge-Lenz vector for planetary motion with a time-dependent gravitational constant G(t), motion in a time-dependent electromagnetic field of a certain form, quantum dots, the Hénon-Heiles and Holt systems, respectively, providing us with Killing tensors of rank that ranges from one to six.

  15. Hemodialysis access procedures

    MedlinePlus

    Kidney failure - chronic-dialysis access; Renal failure - chronic-dialysis access; Chronic renal insufficiency-dialysis access; Chronic kidney failure-dialysis access; Chronic renal failure-dialysis access

  16. Molecular mechanics conformational analysis of tylosin

    NASA Astrophysics Data System (ADS)

    Ivanov, Petko M.

    1998-01-01

    The conformations of the 16-membered macrolide antibiotic tylosin were studied with molecular mechanics (AMBER∗ force field) including modelling of the effect of the solvent on the conformational preferences (GB/SA). A Monte Carlo conformational search procedure was used for finding the most probable low-energy conformations. The present study provides complementary data to recently reported analysis of the conformations of tylosin based on NMR techniques. A search for the low-energy conformations of protynolide, a 16-membered lactone containing the same aglycone as tylosin, was also carried out, and the results were compared with the observed conformation in the crystal as well as with the most probable conformations of the macrocyclic ring of tylosin. The dependence of the results on force field was also studied by utilizing the MM3 force field. Some particular conformations were computed with the semiempirical molecular orbital methods AM1 and PM3.

  17. Defects in conformal field theory

    NASA Astrophysics Data System (ADS)

    Billò, Marco; Gonçalves, Vasco; Lauria, Edoardo; Meineri, Marco

    2016-04-01

    We discuss consequences of the breaking of conformal symmetry by a flat or spherical extended operator. We adapt the embedding formalism to the study of correlation functions of symmetric traceless tensors in the presence of the defect. Two-point functions of a bulk and a defect primary are fixed by conformal invariance up to a set of OPE coefficients, and we identify the allowed tensor structures. A correlator of two bulk primaries depends on two cross-ratios, and we study its conformal block decomposition in the case of external scalars. The Casimir equation in the defect channel reduces to a hypergeometric equation, while the bulk channel blocks are recursively determined in the light-cone limit. In the special case of a defect of codimension two, we map the Casimir equation in the bulk channel to the one of a four-point function without defect. Finally, we analyze the contact terms of the stress-tensor with the extended operator, and we deduce constraints on the CFT data. In two dimensions, we relate the displacement operator, which appears among the contact terms, to the reflection coefficient of a conformal interface, and we find unitarity bounds for the latter.

  18. Precision conformal optics technology program

    NASA Astrophysics Data System (ADS)

    Trotta, Patrick A.

    2001-09-01

    Conformal optics are defined as optics that deviate from conventional form to best satisfy the contour and shape needs of system platforms. Precision Conformal Optics Technology (PCOT), a comprehensive 48 month program funded by the Defense Advanced Research Program Agency (DARPA) and the U. S. Army Missile Research, Development, and Engineering Center (MRDEC), assessed the potential benefits achieved by use of conformal optics on a variety of U.S. weapon systems. Also addressed were all barriers impeding conformal optics use. The PCOT program was executed by a consortium of organizations ranging from major U.S. defense prime contractors, to small businesses, and academia. The diversity of organizations encouraged synergy across a broad array of skills and perspectives. Smooth team interaction was made possible by the 845 contractual structure of the program. Benefits identified by the PCOT consortium included major reductions in aerodynamic drag (by as much as 50%), reduced time-to-targets (by as much as 60%), and reduced weapon signatures. Impediments addressed included inadequacies in optical design tools, optical manufacturing methods and equipment, optical testing, and system integration. The PCOT program was successfully completed with a demonstration of a highly contoured missile dome, which reduced overall missile drag by 25%, and led to a predicted twofold increase in missile range.

  19. Temperature: Human Regulating, Ants Conforming

    ERIC Educational Resources Information Center

    Clopton, Joe R.

    2007-01-01

    Biological processes speed up as temperature rises. Procedures for demonstrating this with ants traveling on trails, and data gathered by students on the Argentine ant ("Linepithema humile") are presented. The concepts of temperature regulation and conformity are detailed with a focus on the processes rather than on terms that label the organisms.

  20. Parsimony in Protein Conformational Change

    PubMed Central

    Chapman, Brynmor K.; Davulcu, Omar; Skalicky, Jack J.; Brüschweiler, Rafael P.; Chapman, Michael S.

    2015-01-01

    Summary Protein conformational change is analyzed by finding the minimalist backbone torsion angle rotations that superpose crystal structures within experimental error. Of several approaches to enforcing parsimony during flexible least-squares superposition, an ℓ1-norm restraint provided greatest consistency with independent indications of flexibility from NMR relaxation dispersion and chemical shift perturbation in arginine kinase, and four previously studied systems. Crystallographic cross-validation shows that the dihedral parameterization describes conformational change more accurately than rigid-group approaches. The rotations that superpose the principal elements of structure constitute a small fraction of the raw (φ, ψ)-differences that also reflect local conformation and experimental error. Substantial long-range displacements can be mediated by modest dihedral rotations, accommodated even within α-helices and β-sheets without disruption of hydrogen bonding at the hinges. Consistency between ligand-associated and intrinsic motions (in the unliganded state) implies that induced changes tend to follow low-barrier paths between conformational sub-states that are in intrinsic dynamic equilibrium. PMID:26095029