Sample records for cyclic accelerators

  1. Method of barrier voltages in cyclic accelerators

    NASA Astrophysics Data System (ADS)

    Meshkov, I. N.

    2014-03-01

    Principle of operation of barrier RF voltage systems that are used for stacking and acceleration of charged particles in proton synchrotrons and storage rings is presented. The description is based on two sample models of such systems: with rectangular and quasi-sinusoidal barriers. Two different methods are used for description of particle dynamics in synchrotrons with barrier RF voltage. The first method is "stepwise" analysis of particle motion in the "momentum-phase" space. This method allows to give a clear and simple description of physical principles of the method and to obtain its main properties in analytical form. However, this method is not always efficient. Therefore, a method of analysis of phase motion of particles in barrier systems based on solution of differential equations of phase motion is presented in the paper and is widely used in practice. This method allows both analytical calculations and numeric simulation, which is illustrated with the aid of supplied examples.

  2. Bright cyclic light accelerates photoreceptor cell degeneration in tubby mice.

    PubMed

    Kong, Li; Li, Feng; Soleman, Charles E; Li, Sheng; Elias, Rajesh V; Zhou, Xiaohong; Lewis, David A; McGinnis, James F; Cao, Wei

    2006-03-01

    Photoreceptor cell death is an irreversible, pathologic event in many blinding retinal diseases including retinitis pigmentosa, age-related macular disease, and retinal detachment. Light exposure can exacerbate a variety of human retinal diseases by increasing the rate of photoreceptor cell death. In the present study, we characterize the kinetics of photoreceptor cell death in Tubby (homozygous tub/tub, which have inherited, progressive retinal degeneration) mice born and raised in a bright cyclic light environment. Our data show that raising tub/tub mice in a bright cyclic light environment induces rapid loss of photoreceptors. This effect can be slowed, but not prevented, by raising animals in constant darkness, which suggests the involvement of phototransduction in the accelerated death of photoreceptors in this animal. We further demonstrated that the activities of cytosolic cytochrome c and caspases-3 and -9 were significantly increased in the retinas of tub/tub mice. Raising animals in darkness significantly reduced the increased activities of caspases-3 and -9, as well as cytosolic cytochrome c. We also observed that rhodopsin, a phototransduction protein, is not restricted to the rod outer segment, but is distributed throughout the rod cell, including the inner segments, cell bodies, and synapses. In addition, the light-dependent translocation and compartmentalization of arrestin and transducin are affected by the tubby mutation. Our results support the interpretation that problems in protein trafficking in the photoreceptors of the tub/tub mouse may contribute to retinal degeneration. PMID:16216520

  3. Study of decoupling control for airborne hydraulic pump in the cyclic stress accelerated life test

    Microsoft Academic Search

    Mingxia Wang; Zhaoqin Peng; Yongling Fu; Xin Wang

    2009-01-01

    Based on the characteristics of stress change for the cyclic stress accelerated life testing (ALT) for the airborne hydraulic and ensured the accuracy acceleration model is established based on the pressure stress; the coupling relationship between the pressure subsystem and the rotation speed subsystem is analyzed. The coupling relationship will have cause a problem on the rotation speed with the

  4. Exposure to stallion accelerates the onset of mares' cyclicity.

    PubMed

    Wespi, B; Sieme, H; Wedekind, C; Burger, D

    2014-07-15

    Horses (Equus caballus) belong to the group of seasonally polyestrous mammals. Estrous cycles typically start with increasing daylight length after winter, but mares can differ greatly in the timing of onset of regular estrus cycles. Here, we test whether spatial proximity to a stallion also plays a role. Twenty-two anestrous mares were either exposed to one of two stallions (without direct physical contact) or not exposed (controls) under experimental conditions during two consecutive springs (February to April). Ovarian activity was monitored via transrectal ultrasound and stallion's direct contact time with each mare was determined three times per week for one hour each. We found that mares exposed to a stallion ovulated earlier and more often during the observational period than mares that were not exposed to stallions. Neither stallion identity nor direct contact time, mare age, body condition, size of her largest follicle at the onset of the experiment, or parasite burden significantly affected the onset of cyclicity. In conclusion, the timing of estrous cycles and cycle frequency, i.e., crucial aspects of female reproductive strategy, strongly depend on how the mares perceive their social environment. Exposing mares to the proximity of a stallion can therefore be an alternative to, for example, light programs or elaborated hormonal therapies to start the breeding season earlier and increase the number of estrous cycles in horses. PMID:24815602

  5. Accelerated kinetics and mechanism of growth of boride layers on titanium under isothermal and cyclic diffusion

    NASA Astrophysics Data System (ADS)

    Sarma, Biplab

    2011-12-01

    The tendency of titanium (Ti) and its alloys to wear, gall and seize during high contact stresses between sliding surfaces severely limits their applications in bearings, gears etc. One way to mitigate these problems is to modify their surfaces by applying hard and wear resistant surface coatings. Boriding, which involves solid state diffusion of boron (B) into Ti, thereby forming hard surface layers consisting of TiB2 and TiB compounds has been shown to produce extremely high wear resistant surfaces in Ti and its alloys. The growth kinetics of these layers are, however, limited by the low diffusivities of B in the high melting TiB2 and TiB compounds. On the basis of the fact that HCP metals such as Ti show enhanced (anomalous) self-diffusion near the phase transition temperature, the first hypothesis of this work has been that the diffusivity enhancement should cause rapid ingress of B atoms, thereby accelerating the growth of the hard boride layers. Isothermal boriding experiments were performed close to phase transition temperature (890, 910, and 915°C) for time periods ranging from 3 to 24 hours. It was found that indeed a much deeper growth of TiB into the Ti substrate (˜75 mum) occurred at temperatures very close to the transition temperature (910°C), compared to that obtained at 1050°C. A diffusion model based on error-function solutions of Fick's second law was developed to quantitatively illustrate the combined effects of the normal B diffusion in the TiB phase and the anomalous B diffusion in Ti phase in accelerating TiB layer growth. Furthermore, isothermal boriding experiments close to transition temperature (900°C) for a period of 71 hours resulted in coating thickness well above 100 mum, while at 1050°C, the layer growth saturated after about 24 hours of treatment time. In the second part of this work, a novel approach named "cyclic-phase-changediffusion, (CPCD)," to create deeper TiB2 and TiB coating layers on CP-Ti by cyclic thermal processing, has been investigated. It was found that thermal cyclic B diffusion in Ti across the alpha(alpha)-beta(beta) phase transition temperature led to highly hardened surface layers enriched with TiB whiskers that grow to depths exceeding 120 mum. By solving the transient heat transport problem for cyclic changes in surface temperatures, it was found that there is a "heat-packet" that travels back and forth from the surface to the interior of the material. This heat-packet appears to transport B dissolved in beta-Ti into interior causing increased coating depths.

  6. A cyclic peptide accelerates the loading of peptide antigens in major histocompatibility complex class II molecules.

    PubMed

    Afridi, Saifullah; Shaheen, Farzana; Roetzschke, Olaf; Shah, Zafar Ali; Abbas, Syed Comail; Siraj, Rizwana; Makhmoor, Talat

    2015-01-16

    Major histocompatibility complex (MHC)-loading enhancers (MLE) have recently attracted attention because of their ability to enhance the efficacy of peptide immunotherapeutics. As small molecular weight compounds, they influence the loading of peptides in MHC molecules by converting them from a non-receptive to a receptive state. Herein, we report a 14-mer cyclic peptide 1 (CP-1) as a new class of MLE-peptide. This peptide was used to investigate its loading on human leukocyte antigen (HLA)-DR molecules. It was found that CP-1 strongly accelerates peptide-loading on both soluble and cell surface HLA-DR molecules in a dose-dependent manner. The effect was evident for all subsets of HLA-DR tested, including HLA-DRB1*1501, indicating that it acts independently of P1-pocket size, which is the canonical MLE-binding site. Importantly, increased peptide-loading by CP-1 was correlated with improved CD4(+) T cell responses in vitro, while propidium iodide staining indicated low peptide-induced cytotoxicity. Thus, this study revealed a new class of peptide-based enhancers that catalyze peptide-loading by allosteric interactions with MHC molecules. Because of its low cellular cytotoxicity and high MLE activity, it may be useful in stimulating antigen-specific T cell responses for therapeutic purposes. PMID:25522880

  7. Accelerating FPGA-based emulation of quasi-cyclic LDPC codes with vector processing

    Microsoft Academic Search

    Xiaoheng Chen; Jingyu Kang; Shu Lin; Venkatesh Akella

    2009-01-01

    FPGAs are widely used for evaluating the error-floor performance of LDPC (low-density parity check) codes. We propose a scalable vector decoder for FPGA-based implementation of quasi-cyclic (QC) LDPC codes that takes advantage of the high bandwidth of the embedded memory blocks (called Block RAMs in a Xilinx FPGA) by packing multiple messages into the same word. We describe a vectorized

  8. Corrosion behaviour of weathering steel in diluted Qinghai salt lake water in a laboratory accelerated test that involved cyclic wet\\/dry conditions

    Microsoft Academic Search

    J. Wang; Z. Y. Wang; W. Ke

    2010-01-01

    The corrosion behaviour of CortenA weathering steel has been investigated using a laboratory accelerated test that involved cyclic wet\\/dry conditions in Qinghai salt lake water diluted 30 times. The characteristics of the rust layers on tested samples were observed by SEM and EPMA, analyzed by IRS and XRD, and studied by polarization and EIS measurements. The weight loss was almost

  9. Characteristics of Accelerated Fatigue Tests by Cyclic Flexion of SMT PC boards

    Microsoft Academic Search

    Zdzislaw Drozd; Marcin Szwech; Rafal Wrona

    2006-01-01

    The critical problem by implementation the EU RoHS directive is assurance of existing level of electronic products reliability. For accelerated reliability testing of soldered joints was developed the test stand for mechanical cycling. The test samples of printed circuits with soldered components are bent with constant radius at all length of the printed circuit. Some information about mechanical testing of

  10. Accelerators

    NSDL National Science Digital Library

    Lawrence Berkeley National Laboratory. Particle Data Group

    2002-01-01

    What is the purpose of particle accelerators? On this web page, part of a particle physics tutorial, students read that accelerators solve two problems. The accelerators provide an increase in momentum to produce particles of small wavelength, and the fast-moving particles can create new particles when smashed together. A photograph of the inside of a particle accelerator is provided. Copyright 2005 Eisenhower National Clearinghouse

  11. Acceleration

    Microsoft Academic Search

    Edward Geoghegan

    1897-01-01

    IN NATURE, NO. 1415, p. 125, Prof. Lodge asserts that the subject of acceleration is at the root of the perennial debate between engineers and teachers of mechanics; and he urges clearness of idea and accuracy of speech on all who deal with the junior student. Towards this end I would suggest that the too common phrase ``acceleration of velocity''

  12. Daily Exposure to Di(2-ethylhexyl) Phthalate Alters Estrous Cyclicity and Accelerates Primordial Follicle Recruitment Potentially Via Dysregulation of the Phosphatidylinositol 3-Kinase Signaling Pathway in Adult Mice1

    PubMed Central

    Hannon, Patrick R.; Peretz, Jackye; Flaws, Jodi A.

    2014-01-01

    ABSTRACT Humans are exposed daily to di(2-ethylhexyl) phthalate (DEHP), a plasticizer found in many consumer, medical, and building products containing polyvinyl chloride. Large doses of DEHP disrupt normal ovarian function; however, the effects of DEHP at environmentally relevant levels, the effects of DEHP on folliculogenesis, and the mechanisms by which DEHP disrupts ovarian function are unclear. The present study tested the hypothesis that relatively low levels of DEHP disrupt estrous cyclicity as well as accelerate primordial follicle recruitment by dysregulating phosphatidylinositol 3-kinase (PI3K) signaling. Adult CD-1 mice were orally dosed with DEHP (20 ?g/kg/day–750 mg/kg/day) daily for 10 and 30 days. Following dosing, the effects on estrous cyclicity were examined, and follicle numbers were histologically quantified. Further, the ovarian mRNA and protein levels of PI3K signaling factors that are associated with early folliculogenesis were quantified. The data indicate that 10- and 30-day exposure to DEHP prolonged the duration of estrus and accelerated primordial follicle recruitment. Specifically, DEHP exposure decreased the percentage of primordial follicles and increased the percentage of primary follicles counted following 10-day exposure and increased the percentage of primary follicles counted following 30-day exposure. DEHP exposure, at doses that accelerate folliculogenesis, increased the levels of 3-phosphoinositide-dependent protein kinase-1, mammalian target of rapamycin complex 1, and protein kinase B and decreased the levels of phosphatase and tensin homolog, potentially driving PI3K signaling. Collectively, relatively low levels of DEHP disrupt estrous cyclicity and accelerate primordial follicle recruitment potentially via a mechanism involving dysregulation of PI3K signaling. PMID:24804967

  13. Cyclic Voltammetry.

    ERIC Educational Resources Information Center

    Evans, Dennis H.; And Others

    1983-01-01

    Cyclic voltammetry is a simple experiment that has become popular in chemical research because it can provide useful information about redox reactions in a form which is easily obtained and interpreted. Discusses principles of the method and illustrates its use in the study of four electrode reactions. (Author/JN)

  14. Cyclic vomiting syndrome plus.

    PubMed

    Boles, Richard G; Powers, Amy L R; Adams, Kathleen

    2006-03-01

    Cyclic vomiting syndrome, which is characterized by severe discrete episodes of nausea, vomiting, and lethargy, is a fairly common, disabling, predominately childhood condition. Approximately 25% of cases have coexisting neuromuscular disease manifestations (cyclic vomiting syndrome plus). To determine whether patients with cyclic vomiting syndrome and neuromuscular disease represent a distinct subentity within cyclic vomiting syndrome, a clinical interview was conducted regarding 80 randomly ascertained sufferers of cyclic vomiting syndrome from a disease association database. Cyclic vomiting syndrome plus and "cyclic vomiting syndrome minus," herein defined as the presence of at least two and zero neuromuscular disease manifestations, were present in 23 and 44 subjects, respectively. Neuromuscular disease manifestations, including cognitive disorders, skeletal myopathy, cranial nerve dysfunction, and seizure disorders, were found to statistically cluster together among the same subjects. In addition, subjects with cyclic vomiting syndrome with neuromuscular disease had an earlier age at onset for vomiting episodes and a three- to eightfold statistically increased prevalence for certain dysautonomia-related (migraine, chronic fatigue, neurovascular dystrophy) and constitutional (growth retardation and birth defects) disorders. However, subjects with cyclic vomiting syndrome with and without neuromuscular disease were equally likely to have a sibling affected with neuromuscular disease manifestations. We conclude that cyclic vomiting syndrome plus, although likely not genetically distinct from cyclic vomiting syndrome minus, represents a distinct phenotypic entity that predicts an earlier onset of disease and increased comorbidity with a distinct list of medical conditions, possibly owing to a higher degree of mitochondrial dysfunction. PMID:16901417

  15. Cyclic phosphonium ionic liquids

    PubMed Central

    Mukhlall, Joshua A; Romeo, Alicia R; Gohdo, Masao; Ramati, Sharon; Berman, Marc; Suarez, Sophia N

    2014-01-01

    Summary Ionic liquids (ILs) incorporating cyclic phosphonium cations are a novel category of materials. We report here on the synthesis and characterization of four new cyclic phosphonium bis(trifluoromethylsulfonyl)amide ILs with aliphatic and aromatic pendant groups. In addition to the syntheses of these novel materials, we report on a comparison of their properties with their ammonium congeners. These exemplars are slightly less conductive and have slightly smaller self-diffusion coefficients than their cyclic ammonium congeners. PMID:24605146

  16. Finite element forced vibration analysis of rotating cyclic structures

    NASA Technical Reports Server (NTRS)

    Elchuri, V.; Smith, G. C. C.

    1981-01-01

    A capability was added to the general purpose finite element program NASTRAN Level 17.7 to conduct forced vibration analysis of tuned cyclic structures rotating about their axes of symmetry. The effects of Coriolis and centripetal accelerations together with those due to linear acceleration of the axis of rotation were included. The theoretical development of this capability is presented.

  17. Affordable Cyclic Voltammetry

    ERIC Educational Resources Information Center

    Stewart, Greg; Kuntzleman, Thomas S.; Amend, John R.; Collins, Michael J.

    2009-01-01

    Cyclic voltammetry is an important component of the undergraduate chemical curriculum. Unfortunately, undergraduate students rarely have the opportunity to conduct experiments in cyclic voltammetry owing to the high cost of potentiostats, which are required to control these experiments. By using MicroLab data acquisition interfaces in conjunction…

  18. No Arithmetic Cyclic Quadrilaterals

    ERIC Educational Resources Information Center

    Beauregard, Raymond A.

    2006-01-01

    A quadrilateral is arithmetic if its area is an integer and its sides are integers in an arithmetic progression, and it is cyclic if it can be inscribed in a circle. The author shows that no quadrilateral is both arithmetic and cyclic.

  19. Cyclic Shape Invariant Potentials

    E-print Network

    Sukhatme, U P; Khare, A

    1998-01-01

    We formulate and study the set of coupled nonlinear differential equations which define a series of shape invariant potentials which repeats after a cycle of $p$ iterations. These cyclic shape invariant potentials enlarge the limited reservoir of known analytically solvable quantum mechanical eigenvalue problems. At large values of $x$, cyclic superpotentials are found to have a linear harmonic oscillator behavior with superposed oscillations consisting of several systematically varying frequencies. At the origin, cyclic superpotentials vanish when the period $p$ is odd, but diverge for $p$ even. The eigenvalue spectrum consists of $p$ infinite sets of equally spaced energy levels, shifted with respect to each other by arbitrary energies spacings $\\omega_k$ can be identified with the periodic points generatedby the logistic map $z_{k+1}=r z_k (1 - z_k)$. Increasing the value of $r$ and following the bifurcation route to chaos corresponds to studying cyclic shape invariant potentials as the period $p$ takes va...

  20. Switched matrix accelerator

    SciTech Connect

    Whittum, David H.; Tantawi, Sami G.

    2001-01-01

    We describe a new concept for a microwave circuit functioning as a charged-particle accelerator at mm wavelengths, permitting an accelerating gradient higher than conventional passive circuits can withstand consistent with cyclic fatigue. The device provides acceleration for multiple bunches in parallel channels, and permits a short exposure time for the conducting surface of the accelerating cavities. Our analysis includes scalings based on a smooth transmission line model and a complementary treatment with a coupled-cavity simulation. We also provide an electromagnetic design for the accelerating structure, arriving at rough dimensions for a seven-cell accelerator matched to standard waveguide and suitable for bench tests at low power in air at 91.392 GHz. A critical element in the concept is a fast mm-wave switch suitable for operation at high power, and we present the considerations for implementation in an H-plane tee. We discuss the use of diamond as the photoconductor switch medium.

  1. Random cyclic matrices

    E-print Network

    Sudhir R. Jain; Shashi C. L. Srivastava

    2013-02-12

    We present a Gaussian ensemble of random cyclic matrices on the real field and study their spectral fluctuations. These cyclic matrices are shown to be pseudo-symmetric with respect to generalized parity. We calculate the joint probability distribution function of eigenvalues and the spacing distributions analytically and numerically. For small spacings, the level spacing distribution exhibits either a Gaussian or a linear form. Furthermore, for the general case of two arbitrary complex eigenvalues, leaving out the spacings among real eigenvalues, and, among complex conjugate pairs, we find that the spacing distribution agrees completely with the Wigner distribution for Poisson process on a plane. The cyclic matrices occur in a wide variety of physical situations, including disordered linear atomic chains and Ising model in two dimensions. These exact results are also relevant to two-dimensional statistical mechanics and $\

  2. Cyclic membrane separation process

    DOEpatents

    Nemser, Stuart M.

    2005-05-03

    A cyclic process for controlling environmental emissions of volatile organic compounds (VOC) from vapor recovery in storage and dispensing operations of liquids maintains a vacuum in the storage tank ullage. In the first part of a two-part cyclic process ullage vapor is discharged through a vapor recovery system in which VOC are stripped from vented gas with a selectively gas permeable membrane. In the second part, the membrane is inoperative while gas pressure rises in the ullage. In one aspect of this invention, a vacuum is drawn in the membrane separation unit thus reducing overall VOC emissions.

  3. Cyclic membrane separation process

    DOEpatents

    Bowser, John

    2004-04-13

    A cyclic process for controlling environmental emissions of volatile organic compounds (VOC) from vapor recovery in storage and dispensing operations of liquids maintains a vacuum in the storage tank ullage. In one of a two-part cyclic process ullage vapor is discharged through a vapor recovery system in which VOC are stripped from vented gas with a selectively gas permeable membrane. In the other part, the membrane is inoperative while gas pressure rises in the ullage. Ambient air is charged to the membrane separation unit during the latter part of the cycle.

  4. Forced vibration analysis of rotating cyclic structures in NASTRAN

    NASA Technical Reports Server (NTRS)

    Elchuri, V.; Gallo, A. M.; Skalski, S. C.

    1981-01-01

    A new capability was added to the general purpose finite element program NASTRAN Level 17.7 to conduct forced vibration analysis of tuned cyclic structures rotating about their axis of symmetry. The effects of Coriolis and centripetal accelerations together with those due to linear acceleration of the axis of rotation were included. The theoretical, user's, programmer's and demonstration manuals for this new capability are presented.

  5. Cyclic Voltammetry Experiment.

    ERIC Educational Resources Information Center

    Van Benschoten, James J.; And Others

    1983-01-01

    Describes a three-part experiment designed to introduce cyclic voltammetry to graduate/undergraduate students. Part 1 demonstrates formal reduction potential, redox electron transfer, diffusion coefficient, and electrochemical reversibility. Part 2 investigates electrochemical behavior of acetaminophen. Part 3 examines such experimental variables…

  6. Turnaround in Cyclic Cosmology

    SciTech Connect

    Baum, Lauris; Frampton, Paul H. [University of North Carolina, Chapel Hill, North Carolina 27599-3255 (United States)

    2007-02-16

    It is speculated how dark energy in a brane world can help reconcile an infinitely cyclic cosmology with the second law of thermodynamics. A cyclic model is described, in which dark energy with w<-1 equation of state leads to a turnaround at a time, extremely shortly before the would-be big rip, at which both volume and entropy of our Universe decrease by a gigantic factor, while very many independent similarly small contracting universes are spawned. The entropy of our model decreases almost to zero at turnaround but increases for the remainder of the cycle by a vanishingly small amount during contraction, empty of matter, then by a large factor during inflationary expansion.

  7. Turnaround in cyclic cosmology.

    PubMed

    Baum, Lauris; Frampton, Paul H

    2007-02-16

    It is speculated how dark energy in a brane world can help reconcile an infinitely cyclic cosmology with the second law of thermodynamics. A cyclic model is described, in which dark energy with w<-1 equation of state leads to a turnaround at a time, extremely shortly before the would-be big rip, at which both volume and entropy of our Universe decrease by a gigantic factor, while very many independent similarly small contracting universes are spawned. The entropy of our model decreases almost to zero at turnaround but increases for the remainder of the cycle by a vanishingly small amount during contraction, empty of matter, then by a large factor during inflationary expansion. PMID:17359014

  8. On Cyclic Harmonic Oscillators

    E-print Network

    Konishi, K; Konishi, Kenichi; Paffuti, Giampiero

    2004-01-01

    It is proven that the energy of a quantum mechanical harmonic oscillator with a generically time-dependent but cyclic frequency, $\\omega_{0}(t_{0})= \\omega_{0}(0)$, cannot decrease on the average if the system is originally in a stationary state, after the system goes through a full cycle. The energy exchange always takes place in the direction from the macroscopic system (environment) to the quantum microscopic system.

  9. Interacting New Agegraphic Dark Energy in a Cyclic Universe

    E-print Network

    Kh. Saaidi; H. Sheikhahmadi; A. H. Mohammadi

    2014-01-16

    The main goal of this work is investigation of NADE in the cyclic universe scenario. Since, cyclic universe is explained by a phantom phase ($\\omega<-1$), it is shown when there is no interaction between matter and dark energy, ADE and NADE do not produce a phantom phase, then can not describe cyclic universe. Therefore, we study interacting models of ADE and NADE in the modified Friedmann equation. We find out that, in the high energy regime, which it is a necessary part of cyclic universe evolution, only NADE can describe this phantom phase era for cyclic universe. Considering deceleration parameter tells us that the universe has a deceleration phase after an acceleration phase, and NADE is able to produce a cyclic universe. Also it is found valuable to study generalized second law of thermodynamics. Since the loop quantum correction is taken account in high energy regime, it may not be suitable to use standard treatment of thermodynamics, so we turn our attention to the result of \\citep{29}, which the authors have studied thermodynamics in loop quantum gravity, and we show that which condition can satisfy generalized second law of thermodynamics.

  10. Analysis of Longitudinal Accelerator Instabilities

    Microsoft Academic Search

    Robert L. Pease

    1965-01-01

    A sufficient stability condition for uniform coasting beams in cyclic particle accelerators is derived from Neil and Sessler's dispersion equation. Specific conditions are worked out for various injection patterns. The instability threshold depends fairly strongly upon the particle density distribution across the tank, and upon whether operation is below or above transition energy. For the latter case, the optimum distribution

  11. Trichloroacetylation of some cyclic enamines.

    PubMed

    Senöz, Hülya; Tuno?lu, Nazan

    2003-04-01

    The pyrrolidine and morpholine enamines of cyclic ketones such as cyclohexanone and cyclopentanone were successfully diacetylated at alpha- and alpha'-positions with trichloroacetyl chloride using zinc catalyst. Morpholine enamines of the cyclic ketones gave acetylated morpholine in good yields besides the corresponding diacetylated cyclic enamines. When the same reactions were performed by using triethylamine without using zinc, monoacetylation products of the same enamines were synthesized. PMID:12673003

  12. On Cyclic Harmonic Oscillators

    Microsoft Academic Search

    Kenichi Konishi; Giampiero Paffuti

    2004-01-01

    It is proven that the energy of a quantum mechanical harmonic oscillator with\\u000aa generically time-dependent but cyclic frequency, $\\\\omega_{0}(t_{0})=\\u000a\\\\omega_{0}(0)$, cannot decrease on the average if the system is originally in a\\u000astationary state, after the system goes through a full cycle. The energy\\u000aexchange always takes place in the direction from the macroscopic system\\u000a(environment) to the quantum

  13. Iontophoresis of cyclic AMP.

    PubMed Central

    Cohen, M H; Drage, D J; Robertson, A

    1975-01-01

    The design, calibration, and operation of a source of controlled amounts of cyclic AMP (c-AMP) are described. Typically, 1.5 s pulses containing 10(10)-10(-12) molecules of c-AMP can be delivered to a region about 10 mum in diameter on an agar plate. The resulting concentration profiles are given as functions of distance and time. The diffusion coefficient of c-AMP in agar was measured to be 0.97 times 10(-5) cm2-s-1 at 21 degrees C. PMID:167878

  14. Epistemology in Cyclic Time

    E-print Network

    Moninder Singh Modgil

    2005-01-30

    Consider the scenario, in which human civilization undergoes periodic eras of progression and regression, and consequently, changes in cosmological knowledge are cyclic. There exist solutions of general theory of relativity, such as the G\\"{o}del universe, in which the cosmos is rotating. If the real universe is indeed rotating, than this would be a reversion to rotating universe models, used in ancient cosmological models. We argue that such reversions in physical models would be inevitable in a space-time in which time is having $S^1$ (circular) topology.

  15. Surface and interface properties of carbon fiber composites under cyclical aging

    Microsoft Academic Search

    Xinying Lv; Rongguo Wang; Wenbo Liu; Long Jiang

    2011-01-01

    Carbon fiber–reinforced BMI composites have been subjected to combination accelerated aging comprising a hygrothermal process, a thermal-oxidative process, and a freezing process in order to simulate their responses under complicated service environments. This cyclical condition, including the freezing process, has not been investigated by other researchers so far. The effects of this combination accelerated aging on the mechanical properties have

  16. Cyclic generalized projection MRI.

    PubMed

    Sarty, Gordon E

    2015-04-01

    Progress in the development of portable MRI hinges on the ability to use lightweight magnets that have non-uniform magnetic fields. An image encoding method and mathematical procedure for recovering the image from the NMR signal from non-uniform magnets with closed isomagnetic contours is given. Individual frequencies in an NMR signal from an object in a non-uniform magnetic field give rise to integrals of the object along contours of constant magnetic field: generalized projections. With closed isomagnetic field contours a simple, cyclic, direct reconstruction of the image from the generalized projections is possible when the magnet and RF transmit coil are held fixed relative to the imaged object while the RF receive coil moves. Numerical simulations, using the Shepp and Logan mathematical phantom, were completed to show that the mathematical method works and to illustrate numerical limitations. The method is numerically verified and exact reconstruction demonstrated for discrete mathematical image phantoms. Correct knowledge of the RF receive field is necessary or severe image distortions will result. The cyclic mathematical reconstruction method presented here will be useful for portable MRI schemes that use non-uniform magnets with closed isomagnetic contours along with mechanically or electronically moving the RF receive coils. PMID:25532468

  17. The cyclic universe

    E-print Network

    Ding-Yu Chung

    2001-05-21

    The cyclic universe model is a modification of the ekpyrotic universe and the pyrotechnic universe models. The cyclic universe goes through the six transitions: the triplet universe, the inflation, the big bang, the quintessence, the big crush, and the deflation transitions. The universe starts with eleven dimensional space-time with two boundary 9-branes separated by a finite gap spanning an intervening bulk volume. The triplet transition starts when the bulk 9-brane is generated from the hidden boundary 9-brane, and collides with the pre-observable 9-brane. The collision starts the inflation transition. The collision is the brane dimensional interference mixing between the pre-observable 9-brane and the bulk 9-brane. The results are the mixed branes (combined brane dimensions), the internal space (cancelled brane dimensions), the bulk space, 3-brane vacuum, and cosmic radiation. Cosmic radiation generated during the inflation leads to the big bang. Meanwhile, the hidden brane undergoes stepwise fractionalization, changing in stepwise manner from 9-brane to 3-brane. The observable universe expands in a constant rate until the quintessence transition. Afterward, there are the big crush transition (the reverse of the big bang) and the deflation (the reverse of the inflation). The cosmic cycle of the fractionalization and condensation starts over again. The masses of all elementary particles and hadrons can be calculated.

  18. A theoretical comparison of batchmode, online, cyclic, and almost cyclic learning

    E-print Network

    Heskes, Tom

    A theoretical comparison of batch­mode, on­line, cyclic, and almost cyclic learning Tom Heskes: batch­mode learning, on­line learning, cyclic learning, and almost cyclic learning. Incremental learning for Neural Networks #12; Batch­mode, on­line, cyclic, and almost cyclic learning 1 1 Introduction In most

  19. The effects of aging on the cyclic stress-strain behavior and hysteresis loop evolution of lead free solders

    Microsoft Academic Search

    Muhannad Mustafa; Zijie Cai; Jeffrey C. Suhling; Pradeep Lall

    2011-01-01

    Solder joints in electronic assemblies are typically subjected to thermal cycling, either in actual application or in accelerated life testing used for qualification. Mismatches in the thermal expansion coefficients of the assembly materials leads to the solder joints being subjected to cyclic (positive\\/negative) mechanical strains and stresses. This cyclic loading leads to thermomechanical fatigue damage that involves damage accumulation, crack

  20. Cyclic Bonds in Branched Polymers

    E-print Network

    Kazumi Suematsu

    2015-02-19

    In the gelation theory it has been implicitly assumed that (I) a cyclic bond is a finite bond that returns to itself; (II) cyclic bonds distribute at random in network structures. In this paper these two assumptions are reexamined from a new point of view. The physical soundness of the assumptions are assessed through comparison with experimental observations.

  1. Release of prostaglandins from the isolated frog ventricle and associated changes in endogenous cyclic nucleotide levels.

    PubMed Central

    Flitney, F W; Singh, J

    1980-01-01

    1. A study has been made of the decline in contractility and some associated metabolic changes which occur in the isolated frog ventricle during the development of hypodynamic depression. 2. The release of two identified prostaglandins (PG), E1 and E2, together with several as yet unknown prostaglandin-related substances (PRS), accompanies the development of hypodynamic depression. There is a close correlation between the extent to which the isometric twitch is depressed and the quantity of prostaglandin released into the superfusate. 3. Fractionation of extracts of 'used' superfusates, using preparative-scale thin-layer chromatography, revealed the presence of six major components, four of which (PGE1 and PGE2 and two unidentified components) were found to be cardioactive and potentiated contraction when tested subsequently on hypodynamic preparations. 4. Two agents which influence prostaglandin biosynthesis, arachidonic acid and indomethacin, are found to affect both the rate at which the hypodynamic state develops and the extent to which the 'steady-state' twitch tension is depressed, in a dose-dependent manner. Indomethacin, a PG-synthetase inhibitor, accelerates the decay and depresses the final 'steady-state' tension attained, whereas arachidonic acid, the principal precursor for prostaglandin biosynthesis, has the converse effects. 5. Measurements of endogenous 3'5'-cyclic nucleotide levels reveal a time-dependent decrease in intracellular adenosine 3'5'-cyclic monophosphate (3'5'-cyclic AMP) and a concomitant increase in guanosine 3'5' cyclic monophosphate (3'5'-cyclic GMP). The decline in isometric twitch tension is paralleled almost exactly by an equivalent reduction in the ratio 3'5'-cyclic AMP: 3'5'-cyclic GMP. 6. Superfusion of isolated ventricles with Ringer solution containing exogenous, lipid-soluble derivatives of 3'5'-cyclic AMP and 3'5'-cyclic GMP affects both the rate of decline of the isometric twitch and the steady-state tension ultimately reached: thus, 8-bromo-3'5'-cyclic GMP accelerates the decline in contractility and depresses the steady-state level, whereas dibutyryl 3'5'-cyclic AMP delays the development of hypodynamic depression, and elevates the final twitch tension. The effects of both 3'5' cyclic nucleotide derivatives are dose-dependent. 7. The possible involvement of prostaglandins and 3'5'-cyclic nucleotides as causal agents in the mechanism of hypodynamic depression is discussed. The biochemical basis for the implied antangonistic effects of 3'5'-cyclic AMP and 3'5'-cyclic GMP in regulating ventricular contractility is considered in the following paper (Flitney & Singh, 1980). PMID:6255139

  2. The endogenous cyclic AMP antagonist, cyclic PIP: its ubiquity, hormone-stimulated synthesis and identification as prostaglandylinositol cyclic phosphate

    Microsoft Academic Search

    H. K. Wasner; U. Salge; M. Gebel

    1993-01-01

    This report shows that the cyclic AMP antagonist cyclic PIP is present in all organs and tissues of the rat so far examined: brain, heart, lung, intestine, kidney, liver, spleen, skeletal muscle and fat. The synthesis of cyclic PIP is stimulated by insulin or noradrenaline (a-adrenergic action) in a dose-dependent fashion. Increasing cyclic PIP synthesis with increasing insulin concentrations matches

  3. Cyclic AMP in prokaryotes.

    PubMed Central

    Botsford, J L; Harman, J G

    1992-01-01

    Cyclic AMP (cAMP) is found in a variety of prokaryotes including both eubacteria and archaebacteria. cAMP plays a role in regulating gene expression, not only for the classic inducible catabolic operons, but also for other categories. In the enteric coliforms, the effects of cAMP on gene expression are mediated through its interaction with and allosteric modification of a cAMP-binding protein (CRP). The CRP-cAMP complex subsequently binds specific DNA sequences and either activates or inhibits transcription depending upon the positioning of the complex relative to the promoter. Enteric coliforms have provided a model to explore the mechanisms involved in controlling adenylate cyclase activity, in regulating adenylate cyclase synthesis, and in performing detailed examinations of CRP-cAMP complex-regulated gene expression. This review summarizes recent work focused on elucidating the molecular mechanisms of CRP-cAMP complex-mediated processes. For other bacteria, less detail is known. cAMP has been implicated in regulating antibiotic production, phototrophic growth, and pathogenesis. A role for cAMP has been suggested in nitrogen fixation. Often the only data that support cAMP involvement in these processes includes cAMP measurement, detection of the enzymes involved in cAMP metabolism, or observed effects of high concentrations of the nucleotide on cell growth. PMID:1315922

  4. Small connections are cyclic Andrea Pulita

    E-print Network

    Pulita, Andrea

    |. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 1. Katz's simple algorithm for cyclic vectors Let (B, d) be a commutative ring B with unit) differential module over the complex numbers are given by means of a cyclic basis. In the p-adic setting in norm. Contents 1 Katz's simple algorithm for cyclic vectors 1 1.1 Three cyclic vector theorems

  5. Cyclic Nucleotide-Gated Channels

    Microsoft Academic Search

    Martin Biel; Stylianos Michalakis

    Cyclic nucleotide-gated (CNG) channels are ion channels which are activated by the binding of cGMP or cAMP. The channels are\\u000a important cellular switches which transduce changes in intracellular concentrations of cyclic nucleotides into changes of\\u000a the membrane potential and the Ca2+ concentration. CNG channels play a central role in the signal transduction pathways of vision and olfaction. Structurally,\\u000a the channels

  6. Nonsurgical treatment of cyclic esotropia.

    PubMed

    Voide, Nathalie; Presset, Claudine; Klainguti, Georges; Kaeser, Pierre-François

    2015-04-01

    Cyclic esotropia is characterized by a 24-hour period of straight eye position followed by 24 hours of large-angle esotropia. Possible mechanisms include notably progressive loss of compensation of a latent strabismus. The classic treatment is surgical correction of the angle measured on the days with manifest deviation. We report the first case of cyclic esotropia successfully treated by prismatic correction of the latent strabismus present on "straight" days. PMID:25828819

  7. Cyclic Polytopes and Oriented Matroids

    Microsoft Academic Search

    Raul Cordovil; Pierre Duchet

    2000-01-01

    Consider the moment curve in the real euclidean space Rddefined parametrically by the map ?: R?Rd,t???(t) = (t, t2,? , td). The cyclic d -polytopeCd (t1,? , tn) is the convex hull ofn&d different points on this curve. The matroidal analogs are the alternating oriented uniform matroids. A polytope (resp. matroid polytope) is called cyclic if its face lattice is

  8. Stable polygons of cyclic pursuit

    Microsoft Academic Search

    Tom Richardson

    2001-01-01

    In a companion paper [5] we resolved the question of whether cyclic pursuits can exhibit ‘non-mutual’ captures. Although,\\u000a as we showed, non-mutual captures can occur, the set of initial conditions which lead to them has Lebesgue measure zero. Thus,\\u000a generically, cyclic pursuits collapse into a mutual capture. In this paper we consider whether the pursuit configuration can\\u000a asymptotically approach a

  9. Post-Cyclic Undrained Behavior of Compacted Composite Clay Subjected to Various Cyclic Loading Paths

    Microsoft Academic Search

    H. R. Tavakoli; A. Shafiee; M. K. Jafari

    Using a sequential procedure of undrained cyclic and post cyclic tests, the strength and stiffness degradation characteristics\\u000a of compacted composite clays are studied immediately after various cyclic loading paths by triaxial and hollow cylinder tests.\\u000a The effects of cyclic loading paths, sand contents, cyclic loading amplitude and confining pressure on the post-cyclic mechanical\\u000a behavior of the composite clays are evaluated.

  10. Response of the ligamentous lumbar spine to cyclic bending loads.

    PubMed

    Goel, V K; Voo, L M; Weinstein, J N; Liu, Y K; Okuma, T; Njus, G O

    1988-03-01

    The effect of a "pure" cyclic flexion bending moment on the three-dimensional load-displacement behavior of fresh ligamentous lumbar spine was investigated. The load-displacement behavior, for 11 L1-sacrum specimens, pre- and post-cyclic fatigue bending tests were quantified using a Selspot II system. A special fixture was designed to mount the specimen within the MTS system to administer "pure" cyclic flexion bending, under displacement control, for 5 hours. The testing was accomplished in a 100% humidity chamber at 0.5 Hz. The maximum cyclic bending moment, based on the literature dealing with loads experienced by the spine during activities involving lifting, was set at 3.0 Nm. An increase in motion of the order of 10% in the extension loading mode was observed. The increase in motion in other loading modes was not significant. In the extension loading mode, the increase in the anteroposterior displacement (retrodisplacement) in general was higher than the corresponding rotation component. The results suggest that the bending moment of low magnitude, usually experienced by the spine during activities of daily living, alone may not trigger the mechanical failure processes in the disc. The presence of high axial compressive loads on the disc seems to be the main contributing factor in this process. The presence of bending moments and axial twist along with axial compressive load may accelerate the unstable processes leading to low back pain. PMID:3388115

  11. Cyclic vomiting syndrome in adults.

    PubMed

    Abell, T L; Adams, K A; Boles, R G; Bousvaros, A; Chong, S K F; Fleisher, D R; Hasler, W L; Hyman, P E; Issenman, R M; Li, B U K; Linder, S L; Mayer, E A; McCallum, R W; Olden, K; Parkman, H P; Rudolph, C D; Taché, Y; Tarbell, S; Vakil, N

    2008-04-01

    Cyclic vomiting syndrome (CVS) was initially described in children but can occur in all age groups. Cyclic vomiting syndrome is increasingly recognized in adults. However, the lack of awareness of CVS in adults has led to small numbers of diagnosed patients and a paucity of published data on the causes, diagnosis and management of CVS in adults. This article is a state-of-knowledge overview on CVS in adults and is intended to provide a framework for management and further investigations into CVS in adults. PMID:18371009

  12. Video looping of human cyclic motion 

    E-print Network

    Choi, Hye Mee

    2004-09-30

    In this thesis, a system called Video Looping is developed to analyze human cyclic motions. Video Looping allows users to extract human cyclic motion from a given video sequence. This system analyzes similarities from a large amount of live footage...

  13. Video looping of human cyclic motion

    E-print Network

    Choi, Hye Mee

    2004-09-30

    In this thesis, a system called Video Looping is developed to analyze human cyclic motions. Video Looping allows users to extract human cyclic motion from a given video sequence. This system analyzes similarities from a large amount of live footage...

  14. Cyclical magnetic field flow fractionation

    NASA Astrophysics Data System (ADS)

    Tasci, T. O.; Johnson, W. P.; Gale, B. K.

    2012-04-01

    In this study, a new magnetic field flow fractionation (FFF) system was designed and modeled by using finite element simulations. Other than current magnetic FFF systems, which use static magnetic fields, our system uses cyclical magnetic fields. Results of the simulations show that our cyclical magnetic FFF system can be used effectively for the separation of magnetic nanoparticles. Cyclical magnetic FFF system is composed of a microfluidic channel (length = 5 cm, height = 30 ?m) and 2 coils. Square wave currents of 1 Hz (with 90 deg of phase difference) were applied to the coils. By using Comsol Multiphysics 3.5a, magnetic field profile and corresponding magnetic force exerted on the magnetite nanoparticles were calculated. The magnetic force data were exported from Comsol to Matlab. In Matlab, a parabolic flow profile with maximum flow speed of 0.4 mL/h was defined. Particle trajectories were obtained by the calculation of the particle speeds resulted from both magnetic and hydrodynamic forces. Particle trajectories of the particles with sizes ranging from 10 to 50 nm were simulated and elution times of the particles were calculated. Results show that there is a significant difference between the elution times of the particles so that baseline separation of the particles can be obtained. In this work, it is shown that by the application of cyclical magnetic fields, the separation of magnetic nanoparticles can be done efficiently.

  15. Cyclic pursuit in a plane

    Microsoft Academic Search

    F. Behroozi; R. Gagnon

    1979-01-01

    The motion of an arbitrary set of points (or bugs) in a plane chasing one another in cyclic pursuit is studied. It is shown that for regular center-symmetric configurations, analytic solutions are easily obtained by going to an appropriate rotating frame of reference. A few cases of nonsymmetric configurations are discussed. In particular, it is shown that for three bugs

  16. On the cyclic to acyclic scheme transformation and solving cyclic queries

    Microsoft Academic Search

    Z. Meral Ozsoyoglu; Elarbi Choukhmane

    1984-01-01

    Relational database schemes can be partitioned into acyclic (tree) schemes and cyclic schemes. This partitioning also classifies the natural join queries into tree queries and cyclic queries. The problems of determining the minimum number of joins needed (i) to transform a cyclic scheme into an acyclic one, and (ii) to solve a cyclic query are shown [GS1 82, GS2 82

  17. Settlements under consecutive series of cyclic loading

    Microsoft Academic Search

    Hüseyin Y?ld?r?m; Hayreddin Er?an

    2007-01-01

    In this study, consolidation settlements of soft clay caused by cyclic loading and the affecting factors such as number of cycles and stress level were experimentally investigated. A group of samples prepared in slurry consolidometer in the laboratory were tested using cyclic simple shear testing device. Normally consolidated samples were subjected to five consecutive series of cyclic loading and drainage

  18. Cyclic Testing of Concrete-Filled Circular Steel Bridge Piers having Encased Fixed-Based Detail

    E-print Network

    Bruneau, Michel

    column; 4 construction of the bridge may be accelerated if the steel shell alone can provide resistance in North America, nearly all new highway bridge substruc- tures are constructed of reinforced concreteCyclic Testing of Concrete-Filled Circular Steel Bridge Piers having Encased Fixed-Based Detail

  19. k -cyclic Orientations of Graphs

    Microsoft Academic Search

    Yasuaki Kobayashi; Yuichiro Miyamoto; Hisao Tamaki

    \\u000a An orientation of an undirected graph G is a directed graph D on V(G) with exactly one of directed edges (u, v) and (v, u) for each pair of vertices u and v adjacent in G. For integer k???3, we say a directed graph D is k-cyclic if every edge of D belongs to a directed cycle in D of

  20. Supramolecular nesting of cyclic polymers.

    PubMed

    Kondratuk, Dmitry V; Perdigão, Luís M A; Esmail, Ayad M S; O'Shea, James N; Beton, Peter H; Anderson, Harry L

    2015-04-01

    Advances in template-directed synthesis make it possible to create artificial molecules with protein-like dimensions, directly from simple components. These synthetic macromolecules have a proclivity for self-organization that is reminiscent of biopolymers. Here, we report the synthesis of monodisperse cyclic porphyrin polymers, with diameters of up to 21 nm (750 C–C bonds). The ratio of the intrinsic viscosities for cyclic and linear topologies is 0.72, indicating that these polymers behave as almost ideal flexible chains in solution. When deposited on gold surfaces, the cyclic polymers display a new mode of two-dimensional supramolecular organization, combining encapsulation and nesting; one nanoring adopts a near-circular conformation, thus allowing a second nanoring to be captured within its perimeter, in a tightly folded conformation. Scanning tunnelling microscopy reveals that nesting occurs in combination with stacking when nanorings are deposited under vacuum, whereas when they are deposited directly from solution under ambient conditions there is stacking or nesting, but not a combination of both. PMID:25970878

  1. Cyclic game dynamics driven by iterated reasoning.

    PubMed

    Frey, Seth; Goldstone, Robert L

    2013-01-01

    Recent theories from complexity science argue that complex dynamics are ubiquitous in social and economic systems. These claims emerge from the analysis of individually simple agents whose collective behavior is surprisingly complicated. However, economists have argued that iterated reasoning--what you think I think you think--will suppress complex dynamics by stabilizing or accelerating convergence to Nash equilibrium. We report stable and efficient periodic behavior in human groups playing the Mod Game, a multi-player game similar to Rock-Paper-Scissors. The game rewards subjects for thinking exactly one step ahead of others in their group. Groups that play this game exhibit cycles that are inconsistent with any fixed-point solution concept. These cycles are driven by a "hopping" behavior that is consistent with other accounts of iterated reasoning: agents are constrained to about two steps of iterated reasoning and learn an additional one-half step with each session. If higher-order reasoning can be complicit in complex emergent dynamics, then cyclic and chaotic patterns may be endogenous features of real-world social and economic systems. PMID:23441191

  2. Cyclic modular beta-sheets.

    PubMed

    Woods, R Jeremy; Brower, Justin O; Castellanos, Elena; Hashemzadeh, Mehrnoosh; Khakshoor, Omid; Russu, Wade A; Nowick, James S

    2007-03-01

    The development of peptide beta-hairpins is problematic, because folding depends on the amino acid sequence and changes to the sequence can significantly decrease folding. Robust beta-hairpins that can tolerate such changes are attractive tools for studying interactions involving protein beta-sheets and developing inhibitors of these interactions. This paper introduces a new class of peptide models of protein beta-sheets that addresses the problem of separating folding from the sequence. These model beta-sheets are macrocyclic peptides that fold in water to present a pentapeptide beta-strand along one edge; the other edge contains the tripeptide beta-strand mimic Hao [JACS 2000, 122, 7654] and two additional amino acids. The pentapeptide and Hao-containing peptide strands are connected by two delta-linked ornithine (deltaOrn) turns [JACS 2003, 125, 876]. Each deltaOrn turn contains a free alpha-amino group that permits the linking of individual modules to form divalent beta-sheets. These "cyclic modular beta-sheets" are synthesized by standard solid-phase peptide synthesis of a linear precursor followed by solution-phase cyclization. Eight cyclic modular beta-sheets 1a-1h containing sequences based on beta-amyloid and macrophage inflammatory protein 2 were synthesized and characterized by 1H NMR. Linked cyclic modular beta-sheet 2, which contains two modules of 1b, was also synthesized and characterized. 1H NMR studies show downfield alpha-proton chemical shifts, deltaOrn delta-proton magnetic anisotropy, and NOE cross-peaks that establish all compounds but 1c and 1g to be moderately or well folded into a conformation that resembles a beta-sheet. Pulsed-field gradient NMR diffusion experiments show little or no self-association at low (cyclic modular beta-sheets 1a, 1b, and 1f each have a phenylalanine directly across from Hao, suggesting that cyclic modular beta-sheets containing aromatic residues across from Hao are better folded. PMID:17295482

  3. Advances in targeting cyclic nucleotide phosphodiesterases

    PubMed Central

    Maurice, Donald H.; Ke, Hengming; Ahmad, Faiyaz; Wang, Yousheng; Chung, Jay; Manganiello, Vincent C.

    2014-01-01

    Cyclic nucleotide phosphodiesterases (PDEs) catalyse the hydrolysis of cyclic AMP and cyclic GMP, thereby regulating the intracellular concentrations of these cyclic nucleotides, their signalling pathways and, consequently, myriad biological responses in health and disease. Currently, a small number of PDE inhibitors are used clinically for treating the pathophysiological dysregulation of cyclic nucleotide signalling in several disorders, including erectile dysfunction, pulmonary hypertension, acute refractory cardiac failure, intermittent claudication and chronic obstructive pulmonary disease. However, pharmaceutical interest in PDEs has been reignited by the increasing understanding of the roles of individual PDEs in regulating the subcellular compartmentalization of specific cyclic nucleotide signalling pathways, by the structure-based design of novel specific inhibitors and by the development of more sophisticated strategies to target individual PDE variants. PMID:24687066

  4. Cyclic Imide Dioxime: Formation and Hydrolytic Stability

    SciTech Connect

    Kang, S.O. [University of Kansas; Vukovic, Sinisa [ORNL; Custelcean, Radu [ORNL; Hay, Benjamin [ORNL

    2012-01-01

    Poly(acrylamidoximes) play an important role in the uranium extraction from seawater. The present work reports solution studies of simple analogs to address the formation and stability of two binding sites present in these polymers, open-chain amidoximes and cyclic imide dioximes, including: 1) conditions that maximize the formation of the cyclic form, 2) existence of a base-induced conversion from open-chain to cyclic form, and 3) degradation under acid and base conditions.

  5. Non-mutual captures in cyclic pursuit

    Microsoft Academic Search

    T. J. Richardson

    2001-01-01

    In cyclic pursuit n bugs chase each other in cyclic order, each moving at unit speed. Mathematical problems and puzzles of pursuit, and cyclic\\u000a pursuit in particular, have attracted interest for many years. In 1971 Klamkin and Newman [17] showed that if n=3 and the initial positions of the bugs are not collinear, then all three bugs capture their prey

  6. Pressure solution creep under cyclic loading

    Microsoft Academic Search

    Vladimir Traskine; Zoya Skvortsova; Alexey Muralev; Dmitry Zubov

    2009-01-01

    Pressure solution creep was studied on sodium chloride, calcium carbonate and ammonium nitrate in respective saturated aqueous\\u000a solutions under static loading and cyclic unloading. Ball indentation and powder compaction curves show that each transition\\u000a from static to cyclic regime produces an increase—sometimes manifold—in creep rate which lasts over the whole time of cyclic\\u000a impact. After returning to static regime, the

  7. On numerically pluricanonical cyclic coverings

    NASA Astrophysics Data System (ADS)

    Kulikov, V. S.; Kharlamov, V. M.

    2014-10-01

    We investigate some properties of cyclic coverings f\\colon Y\\to X (where X is a complex surface of general type) branched along smooth curves B\\subset X that are numerically equivalent to a multiple of the canonical class of X. Our main results concern coverings of surfaces of general type with p_g=0 and Miyaoka-Yau surfaces. In particular, such coverings provide new examples of multi-component moduli spaces of surfaces with given Chern numbers and new examples of surfaces that are not deformation equivalent to their complex conjugates.

  8. Acceleration of heavy ions to very high energies

    SciTech Connect

    Barton, M.Q.

    1982-01-01

    The current interest of physicists in the collisions of heavy ions closes an interesting circle in the technology of accelerator building. The first cyclic accelerator, built by R. Wideroe, was a linear accelerator designed to accelerate potassium ions. Subsequent to Wideroe's achievement, much of the art of accelerator construction has been devoted to creating energetic beams of electrons and protons. Now we find ourselves returning to the heavy ions, and Wideroe's linear accelerator structure still plays an important role in many acceleration schemes. Fortunately, while the particle physics community has concentrated on the electron and proton machines, the nuclear physicists have kept alive the interest in heavy ions. Now a host of electrostatic machines, cyclotrons, and heavy ion linear accelerators provide beams of all species of ions at energies from about 100 MeV per nucleon for light isotopes to 10 MeV per nucleon for the heaviest isotopes in support of vigorous physics programs.

  9. Strain accumulation in sand due to cyclic loading: Drained cyclic tests with triaxial extension

    Microsoft Academic Search

    T. Wichtmann; A. Niemunis; Th. Triantafyllidis

    2007-01-01

    This paper presents results of numerous drained cyclic tests with triaxial extension. The influence of the strain amplitude, the average stress and the number of load cycles on the accumulation rate was studied. A simple cyclic flow rule was observed. Most findings confirm a previous study with cyclic triaxial compression tests. The test results serve as the basis of an

  10. Extraction, purification, identification and metabolism of 3',5'-cyclic UMP, 3',5'-cyclic IMP and 3',5'-cyclic dTMP from rat tissues.

    PubMed Central

    Newton, R P; Kingston, E E; Hakeem, N A; Salih, S G; Beynon, J H; Moyse, C D

    1986-01-01

    The large-scale extraction and partial purification of endogenous 3',5'-cyclic UMP, 3',5'-cyclic IMP and 3',5'-cyclic dTMP are described. Rat liver, kidney, heart, spleen and lung tissues were subjected to a sequential purification procedure involving freeze-clamping, perchlorate extraction, alumina and Sephadex ion-exchange chromatography and preparative electrophoresis. The samples thus obtained co-chromatographed with authentic cyclic UMP, cyclic IMP and cyclic dTMP on t.l.c. and h.p.l.c. and the u.v. spectra of the extracted samples were identical with those of the standards. Fast atom bombardment of the three cyclic nucleotide standards yielded mass spectra containing a molecular protonated ion in each case; mass-analysed ion kinetic-energy spectrometry ('m.i.k.e.s') of these ions produced a spectrum unique to the parent cyclic nucleotide. The extracted putative cyclic UMP, cyclic IMP and cyclic dTMP each produced a m.i.k.e.s. identical with that obtained with the corresponding cyclic nucleotide standard. Rat liver, heart, kidney, brain, intestine, spleen, testis and lung protein preparations were each found capable of the synthesis of cyclic UMP, cyclic IMP and cyclic dTMP from the corresponding nucleoside triphosphate, of the hydrolysis of these cyclic nucleotides and of their binding, with the exception that cyclic dTMP was not synthesized by the kidney preparation. PMID:3019316

  11. PRESENTING DEGENERATE RINGELHALL ALGEBRAS OF CYCLIC QUIVERS

    E-print Network

    Du, Jie

    ). This is achieved by establishing an isomorphism between H0(n) and the generic extension monoid algebra ZM(n) of (nPRESENTING DEGENERATE RINGEL­HALL ALGEBRAS OF CYCLIC QUIVERS BANGMING DENG, JIE DU AND ALEXANDRE­Hall algebra Hq(n) of a cyclic quiver (n), we give a presentation for the degenerate algebra H0(n

  12. Enantioselective Conjugate Allylation of Cyclic Enones

    PubMed Central

    Taber, Douglass F.; Gerstenhaber, David A.; Berry, James F.

    2011-01-01

    Enantioselective organocatalytic 1,2-allylation of a cyclic enone followed by anionic oxy-Cope rearrangement delivered the ketone as a mixture of diastereomers. This appears to be a general method for the net enantioselective conjugate allylation of cyclic enones. PMID:21830779

  13. Modular and p-adic Cyclic Codes

    Microsoft Academic Search

    A. Robert Calderbank; Neil J. A. Sloane

    1995-01-01

    This paper presents some basic theorems giving the structure of cyclic codes of length n over the ring of integers modulo pa and over the p-adic numbers, where p is a prime not dividing n. An especially interesting example is the 2-adic cyclic code of length 7 with generator polynomial X3 + ?X2 + (? ? 1)X ? 1, where

  14. Discrete wavelet transform based on cyclic convolutions

    Microsoft Academic Search

    Hideo Murakami

    2004-01-01

    A filterbank in which cyclic convolutions are used in place of linear convolutions will be referred to as a cyclic convolution filterbank (CCFB). A dyadic tree-structured CCFB can be used to perform a discrete wavelet transform suitable for coding based on symmetric extension methods. This paper derives two types of efficient implementation techniques for the tree-structured CCFB: one using complex

  15. Enantioselective Construction of Cyclic Quaternary Centers: (-)-Mesembrine

    E-print Network

    Taber, Douglass

    Enantioselective Construction of Cyclic Quaternary Centers: (-)-Mesembrine Douglass F. Taber, (-)-mesembrine 1. Amide 2 should be a useful chiron for the enantioselective construction of cyclic quaternary of mesembrine2,3 and its analogues is the enantioselective construction of the chiral quaternary center.4 We

  16. Wakefield accelerators

    SciTech Connect

    Simpson, J.D.

    1990-01-01

    The search for new methods to accelerate particle beams to high energy using high gradients has resulted in a number of candidate schemes. One of these, wakefield acceleration, has been the subject of considerable R D in recent years. This effort has resulted in successful proof of principle experiments and in increased understanding of many of the practical aspects of the technique. Some wakefield basics plus the status of existing and proposed experimental work is discussed, along with speculations on the future of wake field acceleration. 10 refs., 6 figs.

  17. 40 CFR 721.3440 - Haloalkyl substituted cyclic ethers.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... false Haloalkyl substituted cyclic ethers. 721.3440 Section 721.3440 ...3440 Haloalkyl substituted cyclic ethers. (a) Chemical substance and significant...substances haloalkyl substituted cyclic ethers (PMN P-85-368 and...

  18. 40 CFR 721.3440 - Haloalkyl substituted cyclic ethers.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... false Haloalkyl substituted cyclic ethers. 721.3440 Section 721.3440 ...3440 Haloalkyl substituted cyclic ethers. (a) Chemical substance and significant...substances haloalkyl substituted cyclic ethers (PMN P-85-368 and...

  19. 40 CFR 721.3440 - Haloalkyl substituted cyclic ethers.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... false Haloalkyl substituted cyclic ethers. 721.3440 Section 721.3440 ...3440 Haloalkyl substituted cyclic ethers. (a) Chemical substance and significant...substances haloalkyl substituted cyclic ethers (PMN P-85-368 and...

  20. 40 CFR 721.3440 - Haloalkyl substituted cyclic ethers.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... false Haloalkyl substituted cyclic ethers. 721.3440 Section 721.3440 ...3440 Haloalkyl substituted cyclic ethers. (a) Chemical substance and significant...substances haloalkyl substituted cyclic ethers (PMN P-85-368 and...

  1. 40 CFR 721.3440 - Haloalkyl substituted cyclic ethers.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... false Haloalkyl substituted cyclic ethers. 721.3440 Section 721.3440 ...3440 Haloalkyl substituted cyclic ethers. (a) Chemical substance and significant...substances haloalkyl substituted cyclic ethers (PMN P-85-368 and...

  2. Toward structure prediction of cyclic peptides.

    PubMed

    Yu, Hongtao; Lin, Yu-Shan

    2015-02-14

    Cyclic peptides are a promising class of molecules that can be used to target specific protein-protein interactions. A computational method to accurately predict their structures would substantially advance the development of cyclic peptides as modulators of protein-protein interactions. Here, we develop a computational method that integrates bias-exchange metadynamics simulations, a Boltzmann reweighting scheme, dihedral principal component analysis and a modified density peak-based cluster analysis to provide a converged structural description for cyclic peptides. Using this method, we evaluate the performance of a number of popular protein force fields on a model cyclic peptide. All the tested force fields seem to over-stabilize the ?-helix and PPII/? regions in the Ramachandran plot, commonly populated by linear peptides and proteins. Our findings suggest that re-parameterization of a force field that well describes the full Ramachandran plot is necessary to accurately model cyclic peptides. PMID:25566700

  3. Nonlinear, nonbinary cyclic group codes

    NASA Technical Reports Server (NTRS)

    Solomon, G.

    1992-01-01

    New cyclic group codes of length 2(exp m) - 1 over (m - j)-bit symbols are introduced. These codes can be systematically encoded and decoded algebraically. The code rates are very close to Reed-Solomon (RS) codes and are much better than Bose-Chaudhuri-Hocquenghem (BCH) codes (a former alternative). The binary (m - j)-tuples are identified with a subgroup of the binary m-tuples which represents the field GF(2 exp m). Encoding is systematic and involves a two-stage procedure consisting of the usual linear feedback register (using the division or check polynomial) and a small table lookup. For low rates, a second shift-register encoding operation may be invoked. Decoding uses the RS error-correcting procedures for the m-tuple codes for m = 4, 5, and 6.

  4. Cyclic strength of hard metals

    SciTech Connect

    Sereda, N.N.; Gerikhanov, A.K.; Koval'chenko, M.S.; Pedanov, L.G.; Tsyban', V.A.

    1986-02-01

    The authors study the strength of hard-metal specimens and structural elements under conditions of cyclic loading since many elements of processing plants, equipment, and machines are made of hard metals. Fatigue tests were conducted on KTS-1N, KTSL-1, and KTNKh-70 materials, which are titanium carbide hard metals cemented with nickel-molybdenum, nickelcobalt-chromium, and nickel-chromium alloys, respectively. As a basis of comparison, the standard VK-15 (WC+15% Co) alloy was used. Some key physicomechanical characteristics of the materials investigated are presented. On time bases not exceeding 10/sup 6/ cycles, titanium carbide hard metals are comparable in fatigue resistance to the standard tungstencontaining hard metals.

  5. Acceleration switch

    DOEpatents

    Abbin, Jr., Joseph P. (Albuquerque, NM); Devaney, Howard F. (Cedar Crest, NM); Hake, Lewis W. (Albuquerque, NM)

    1982-08-17

    The disclosure relates to an improved integrating acceleration switch of the type having a mass suspended within a fluid filled chamber, with the motion of the mass initially opposed by a spring and subsequently not so opposed.

  6. Accelerator-induced transients in Accelerator Driven Subcritical Reactors

    NASA Astrophysics Data System (ADS)

    Ahmad, Ali; Lindley, Benjamin A.; Parks, Geoffrey T.

    2012-12-01

    Achieving higher particles energies and beam powers have long been the main focus of research in accelerator technology. Since Accelerator Driven Subcritical Reactors (ADSRs) have become the subject of increasing interest, accelerator reliability and modes of operation have become important matters that require further research and development in order to accommodate the engineering and economic needs of ADSRs. This paper focuses on neutronic and thermo-mechanical analyses of accelerator-induced transients in an ADSR. Such transients fall into three main categories: beam interruptions (trips), pulsed-beam operation, and beam overpower. The concept of a multiple-target ADSR is shown to increase system reliability and to mitigate the negative effects of beam interruptions, such as thermal cyclic fatigue in the fuel cladding and the huge financial cost of total power loss. This work also demonstrates the effectiveness of the temperature-to-reactivity feedback mechanisms in ADSRs. A comparison of shutdown mechanisms using control rods and beam cut-off highlights the intrinsic safety features of ADSRs. It is evident that the presence of control rods is crucial in an industrial-scale ADSR. This paper also proposes a method to monitor core reactivity online using the repetitive pattern of beam current fluctuations in a pulsed-beam operation mode. Results were produced using PTS-ADS, a computer code developed specifically to study the dynamic neutronic and thermal responses to beam transients in subcritical reactor systems.

  7. Processable cyclic peptide nanotubes with tunable interiors.

    PubMed

    Hourani, Rami; Zhang, Chen; van der Weegen, Rob; Ruiz, Luis; Li, Changyi; Keten, Sinan; Helms, Brett A; Xu, Ting

    2011-10-01

    A facile route to generate cyclic peptide nanotubes with tunable interiors is presented. By incorporating 3-amino-2-methylbenzoic acid in the D,L-alternating primary sequence of a cyclic peptide, a functional group can be presented in the interior of the nanotubes without compromising the formation of high aspect ratio nanotubes. The new design of such a cyclic peptide also enables one to modulate the nanotube growth process to be compatible with the polymer processing window without compromising the formation of high aspect ratio nanotubes, thus opening a viable approach toward molecularly defined porous membranes. PMID:21894889

  8. Acceleration Studies

    NASA Technical Reports Server (NTRS)

    Rogers, Melissa J. B.

    1993-01-01

    Work to support the NASA MSFC Acceleration Characterization and Analysis Project (ACAP) was performed. Four tasks (analysis development, analysis research, analysis documentation, and acceleration analysis) were addressed by parallel projects. Work concentrated on preparation for and implementation of near real-time SAMS data analysis during the USMP-1 mission. User support documents and case specific software documentation and tutorials were developed. Information and results were presented to microgravity users. ACAP computer facilities need to be fully implemented and networked, data resources must be cataloged and accessible, future microgravity missions must be coordinated, and continued Orbiter characterization is necessary.

  9. Cyclic Group 15 Radical Cations.

    PubMed

    Brückner, Angelika; Hinz, Alexander; Priebe, Jacqueline B; Schulz, Axel; Villinger, Alexander

    2015-06-15

    Singlet cyclo-1,3-dipnicta-2,4-diazane-1,3-diyls of the type [E(?-NTer)2 E] (2, E=P, As, Ter=2,6-dimesitylphenyl) can undergo a one-electron-oxidation utilizing silver salts of weakly coordinating anions such as [AgLn ][B(C6 F5 )4 ] (L=donor solvents) to afford the novel cyclic radical cations, [E(?-NTer)2 E](+.) (3(+.) ). When smaller and more basic anions were employed in the reaction, the anions were found to form covalent bonds to the radical centers yielding dipnictadiazanes, [FP(?-NTer)2 PF] (5) and [(CF3 CO2 )P(?-NTer)2 P(CF3 CO2 )] (6). A two-electron oxidation process, resulting in the formation of dications of the type [E(?-NTer)2 E](2+) , could not be observed. Computational and EPR data revealed that the spin density is almost completely localized at the two heavier pnictogen centers E of the former 1,3-dipnictadiazane-1,3-diyls. The bonding situation in the radical cations features a rare example of a transannular one-electron ? bond without having a ? bond. PMID:25960190

  10. Anelastic relaxation controlled cyclic creep and cyclic stress rupture behavior of an oxide dispersion strengthened alloy

    Microsoft Academic Search

    D. E. Matejczyk; Y. Zhuang; J. K. Tien

    1983-01-01

    Cyclic creep deceleration relative to static creep was observed in oxide dispersion strengthened alloy Inconel MA 754 at 760\\u000a °C and cyclic stresses of 221 MPa-41 MPa, 231 MPa-41 MPa, and 241 MPa-41 MPa. Tests were run over the range of frequency from\\u000a 0.05 cycles per hour to six cycles per hour. The maximum cyclic deceleration, which was manifested as

  11. Anelastic relaxation controlled cyclic creep and cyclic stress rupture behavior of an oxide dispersion strengthened alloy

    Microsoft Academic Search

    D. E. Matejczyk; Y. Zhuang; J. K. Tien

    1983-01-01

    Cyclic creep deceleration relative to static creep was observed in oxide dispersion strengthened alloy Inconel MA 754 at 760 °C and cyclic stresses of 221 MPa-41 MPa, 231 MPa-41 MPa, and 241 MPa-41 MPa. Tests were run over the range of frequency from 0.05 cycles per hour to six cycles per hour. The maximum cyclic deceleration, which was manifested as

  12. Renormalization of the cyclic Wilson loop

    NASA Astrophysics Data System (ADS)

    Berwein, Matthias; Brambilla, Nora; Ghiglieri, Jacopo; Vairo, Antonio

    2013-03-01

    In finite-temperature field theory, the cyclic Wilson loop is defined as a rectangular Wilson loop spanning the whole compactified time direction. In a generic non-abelian gauge theory, we calculate the perturbative expansion of the cyclic Wilson loop up to order g 4. At this order and after charge renormalization, the cyclic Wilson loop is known to be ultraviolet divergent. We show that the divergence is not associated with cusps in the contour but is instead due to the contour intersecting itself because of the periodic boundary conditions. One consequence of this is that the cyclic Wilson loop mixes under renormalization with the correlator of two Polyakov loops. The resulting renormalization equation is tested up to order g 6 and used to resum the leading logarithms associated with the intersection divergence. Implications for lattice studies of this operator, which may be relevant for the phenomenology of quarkonium at finite temperature, are discussed.

  13. Cyclical dynamics of airline industry earnings

    E-print Network

    Pierson, Kawika

    Aggregate airline industry earnings have exhibited large-amplitude cyclical behavior since deregulation in 1978. To explore the causes of these cycles we develop a behavioral dynamic model of the airline industry with ...

  14. Ants, Crickets and Frogs in Cyclic Pursuit

    E-print Network

    Efrat, Alon

    Ants, Crickets and Frogs in Cyclic Pursuit A.M. Bruckstein 1 , N. Cohen 2 , A. Efrat 1 Abstract. We and with preassigned, varying speeds. We also consider two discrete analogs, in which crickets or frogs are engaged

  15. Braided cyclic cocycles and nonassociative geometry

    NASA Astrophysics Data System (ADS)

    Akrami, S. E.; Majid, S.

    2004-10-01

    We use monoidal category methods to study the noncommutative geometry of nonassociative algebras obtained by a Drinfeld-type cochain twist. These are the so-called quasialgebras and include the octonions as braided-commutative but nonassociative coordinate rings, as well as quasialgebra versions Cq(G) of the standard q-deformation quantum groups. We introduce the notion of ribbon algebras in the category, which are algebras equipped with a suitable generalized automorphism ?, and obtain the required generalization of cyclic cohomology. We show that this braided cyclic cohomology is invariant under a cochain twist. We also extend to our generalization the relation between cyclic cohomology and differential calculus on the ribbon quasialgebra. The paper includes differential calculus and cyclic cocycles on the octonions as a finite nonassociative geometry, as well as the algebraic noncommutative torus as an associative example.

  16. A study of cyclic pressuremeter testing for offshore applications 

    E-print Network

    Riner, Kenneth Byard

    1984-01-01

    Data Corrections Cyclic Pressuremeter Data 39 44 45 CHAPTER VI. ANALYSIS OF RESULTS 47 Introduction . ~ ~ . ~ ~ ~ . ~ ~ ~ ~ ~ ~ ~ Discussion of Cyclic Loads Shear Modulus Degradation Deformation Model and Shear Modulus Model Factors... Influencing the Degradation Parameter Backbone Pressuremeter Curves Cyclic Shear Modulus Prediction Model Recommendations 47 47 48 60 65 71 77 81 vii TABLE OF CONTENTS (Continued) Page CHAPTER VII. POTENTIAL APPLICATIONS Application of Cyclic...

  17. Undrained behavior of natural marine clay under cyclic loading

    Microsoft Academic Search

    Ling-Ling Li; Han-Bo Dan; Li-Zhong Wang

    2011-01-01

    To study the undrained behavior of natural marine clay under cyclic loading, two kinds of stress-controlled cyclic triaxial tests were conducted on natural K0-consolidated Wenzhou clay. In the Series I tests, samples were cyclically sheared until failure, and the accumulative behavior was studied; based on the results, a suitable cyclic failure criterion is suggested for natural clays. The effect of

  18. Cyclic Behavior of High Density Polyethylene (HDPE)

    NASA Astrophysics Data System (ADS)

    Dusunceli, Necmi; Aydemir, Bulent; Terzi, Niyazi U.

    2010-06-01

    This article presents the mechanical behavior of high density polyethylene (HDPE). Samples were prepared by extracting extruded HDPE pipe. Cyclic and strain rate jump behavior of HDPE were studied under uniaxial tensile loading conditions. The strain jump tests indicated that mechanical behavior of HDPE has deformation memory. Further, it was found that increasing cycle number on cyclic loading test increased strain accumulation amount and HDPE exhibited ratcheting behavior at on loading-unloading-reloading at constant stress level.

  19. Cyclic dynamics of eastern Canadian ermine populations

    Microsoft Academic Search

    Donald R. Johnson; Bradley J. Swanson; Judith L. Eger

    2000-01-01

    Based on partial autocorrelation analysis, 20 ermine (Mustela erminea) populations in Manitoba, Ontario, and Quebec demonstrated cyclic dynamics characterized by a latitudinal gradient of decreasing first-order feedback and increasing negativity of second-order feedback. Most of these populations exhibited three cyclic peaks and a 10-year interval of noncyclic dynamics during the sampling period (1915-1940). Changes in ermine density probably reflected those

  20. Cyclic fatty acid yields from linseed oil

    Microsoft Academic Search

    R. A. Eisenhauer; R. E. Beal; E. L. Griffin

    1963-01-01

    Increased yields of saturated cyclic fatty acids which are fluid at ?50C have been obtained from linseed oil. Depending on\\u000a reaction conditions, yields varied from 20–42 g of cyclic acids per 100 g of linseed oil. Solvent ratios of 6, 3, and 1.5?1;\\u000a catalyst concentrations of 10, 30, 60, and 100%; and reaction temps of 225, 275, 295, and 325C

  1. Constitutive model for cyclic deformation of perfluoroelastomers

    NASA Astrophysics Data System (ADS)

    Drozdov, A. D.

    2009-08-01

    Observations are reported in uniaxial cyclic tensile tests with a strain-controlled program on perfluoroelastomer Hyflon MFA. A constitutive model is developed for its viscoplastic response and damage at three-dimensional deformations with finite strains. Adjustable parameters in the stress-strain relations are found by fitting the experimental data. Numerical simulation demonstrates that the constitutive equations adequately describe the mechanical response of perfluoroelastomer in cyclic tests with complicated deformation programs.

  2. Fixed point theory for cyclic ? -contractions

    Microsoft Academic Search

    M?d?lina P?curar; Ioan A. Rus

    2010-01-01

    Following [W.A. Kirk, P.S. Srinivasan, P. Veeramany, Fixed points for mappings satisfying cyclical contractive conditions, Fixed Point Theory 4 (1) (2003) 79–89], we present a fixed point theorem for cyclic ?-contractions and following [I.A. Rus, The theory of a metrical fixed point theorem: Theoretical and applicative relevances, Fixed Point Theory 9 (2) (2008) 541–559] we construct a theory of this

  3. Automated Cyclic Entailment Proofs in Separation Logic

    Microsoft Academic Search

    James Brotherston; Dino Distefano; Rasmus Lerchedahl Petersen

    \\u000a We present a general automated proof procedure, based upon cyclic proof, for inductive entailments in separation logic. Our procedure has been implemented via a deep embedding of cyclic proofs\\u000a in the HOL Light theorem prover. Experiments show that our mechanism is able to prove a number of non-trivial entailments\\u000a involving inductive predicates.

  4. Accelerated Achievement

    ERIC Educational Resources Information Center

    Ford, William J.

    2010-01-01

    This article focuses on the accelerated associate degree program at Ivy Tech Community College (Indiana) in which low-income students will receive an associate degree in one year. The three-year pilot program is funded by a $2.3 million grant from the Lumina Foundation for Education in Indianapolis and a $270,000 grant from the Indiana Commission…

  5. Electrothermal accelerators

    Microsoft Academic Search

    M. D. Driga; M. W. Ingram; W. F. Weldon

    1989-01-01

    In electrothermal (ET) guns, the projectile acceleration is governed by gas dynamics as in explosively-driven guns. In a conventional gun, however, both the energy for heating and the material to be heated are contained in the solid propellant. Electrothermal launchers allow an external electric power supply to be used to provide the necessary energy; hence, lower atomic weight propellants may

  6. Plasma accelerator

    DOEpatents

    Wang, Zhehui (Los Alamos, NM); Barnes, Cris W. (Santa Fe, NM)

    2002-01-01

    There has been invented an apparatus for acceleration of a plasma having coaxially positioned, constant diameter, cylindrical electrodes which are modified to converge (for a positive polarity inner electrode and a negatively charged outer electrode) at the plasma output end of the annulus between the electrodes to achieve improved particle flux per unit of power.

  7. Particle acceleration

    NASA Technical Reports Server (NTRS)

    Vlahos, L.; Machado, M. E.; Ramaty, R.; Murphy, R. J.; Alissandrakis, C.; Bai, T.; Batchelor, D.; Benz, A. O.; Chupp, E.; Ellison, D.

    1986-01-01

    Data is compiled from Solar Maximum Mission and Hinothori satellites, particle detectors in several satellites, ground based instruments, and balloon flights in order to answer fundamental questions relating to: (1) the requirements for the coronal magnetic field structure in the vicinity of the energization source; (2) the height (above the photosphere) of the energization source; (3) the time of energization; (4) transistion between coronal heating and flares; (5) evidence for purely thermal, purely nonthermal and hybrid type flares; (6) the time characteristics of the energization source; (7) whether every flare accelerates protons; (8) the location of the interaction site of the ions and relativistic electrons; (9) the energy spectra for ions and relativistic electrons; (10) the relationship between particles at the Sun and interplanetary space; (11) evidence for more than one acceleration mechanism; (12) whether there is single mechanism that will accelerate particles to all energies and also heat the plasma; and (13) how fast the existing mechanisms accelerate electrons up to several MeV and ions to 1 GeV.

  8. Antimicrobial Cyclic Peptides for Plant Disease Control

    PubMed Central

    Lee, Dong Wan; Kim, Beom Seok

    2015-01-01

    Antimicrobial cyclic peptides derived from microbes bind stably with target sites, have a tolerance to hydrolysis by proteases, and a favorable degradability under field conditions, which make them an attractive proposition for use as agricultural fungicides. Antimicrobial cyclic peptides are classified according to the types of bonds within the ring structure; homodetic, heterodetic, and complex cyclic peptides, which in turn reflect diverse physicochemical features. Most antimicrobial cyclic peptides affect the integrity of the cell envelope. This is achieved through direct interaction with the cell membrane or disturbance of the cell wall and membrane component biosynthesis such as chitin, glucan, and sphingolipid. These are specific and selective targets providing reliable activity and safety for non-target organisms. Synthetic cyclic peptides produced through combinatorial chemistry offer an alternative approach to develop antimicrobials for agricultural uses. Those synthesized so far have been studied for antibacterial activity, however, the recent advancements in powerful technologies now promise to provide novel antimicrobial cyclic peptides that are yet to be discovered from natural resources. PMID:25774105

  9. Cyclic nucleotides of cone-dominant retinas. Reduction of cyclic AMP levels by light and by cone degeneration.

    PubMed

    Farber, D B; Souza, D W; Chase, D G; Lolley, R N

    1981-01-01

    Dark-adapted retinas or whole eyes of 13-line ground squirrels (Citellus tridecemlineatus) and western fence lizards (Sceloporus occidentalis) contain higher levels of cyclic AMP than of cyclic GMP. In these cone-dominant retinas, light reduces cyclic AMP content selectively. Freezing of dark- or light-adapted retinas or eyes also reduces cyclic AMP content, with only minimal changes in cyclic GMP levels. In addition, exposure of frozen retinas of dark-adapted ground squirrel to light results in a significant decrease in cyclic AMP content. The destruction of cone visual cells of ground squirrel retina by iodoacetic acid injection decreases the cyclic nucleotide content of the dark-adapted retina. Considering the relative loss of cyclic nucleotides from cone degeneration, we estimate that the content of cyclic AMP in visual cells of ground squirrel retina is about four times greater than that of cyclic GMP. PMID:6256308

  10. Urine cyclic nucleotide concentrations in cancer and other conditions; cyclic GMP: a potential marker for cancer treatment

    Microsoft Academic Search

    G A Turner; R D Ellis; D Guthrie; A L Latner; J M Monaghan; W M Ross; A W Skillen; R G Wilson

    1982-01-01

    Cyclic guanosine 3',5' monophosphate (cyclic GMP) and cyclic adenosine 3',5' monophosphate (cyclic AMP) have been determined in random urine specimens from 95 healthy individuals, 60 patients with non-cancerous conditions, 52 patients with benign tumours, and 74 patients with malignant tumours. Concentrations of cyclic GMP have also been determined in a number of other groups, including some undergoing cancer treatment. Ninety-three

  11. The envelope-based cyclic periodogram

    NASA Astrophysics Data System (ADS)

    Borghesani, P.

    2015-06-01

    Cyclostationary analysis has proven effective in identifying signal components for diagnostic purposes. A key descriptor in this framework is the cyclic power spectrum, traditionally estimated by the averaged cyclic periodogram and the smoothed cyclic periodogram. A lengthy debate about the best estimator finally found a solution in a cornerstone work by Antoni, who proposed a unified form for the two families, thus allowing a detailed statistical study of their properties. Since then, the focus of cyclostationary research has shifted towards algorithms, in terms of computational efficiency and simplicity of implementation. Traditional algorithms have proven computationally inefficient and the sophisticated "cyclostationary" definition of these estimators slowed their spread in the industry. The only attempt to increase the computational efficiency of cyclostationary estimators is represented by the cyclic modulation spectrum. This indicator exploits the relationship between cyclostationarity and envelope analysis. The link with envelope analysis allows a leap in computational efficiency and provides a "way in" for the understanding by industrial engineers. However, the new estimator lies outside the unified form described above and an unbiased version of the indicator has not been proposed. This paper will therefore extend the analysis of envelope-based estimators of the cyclic spectrum, proposing a new approach to include them in the unified form of cyclostationary estimators. This will enable the definition of a new envelope-based algorithm and the detailed analysis of the properties of the cyclic modulation spectrum. The computational efficiency of envelope-based algorithms will be also discussed quantitatively for the first time in comparison with the averaged cyclic periodogram. Finally, the algorithms will be validated with numerical and experimental examples.

  12. Measuring Cyclic Error in Laser Heterodyne Interferometers

    NASA Technical Reports Server (NTRS)

    Ryan, Daniel; Abramovici, Alexander; Zhao, Feng; Dekens, Frank; An, Xin; Azizi, Alireza; Chapsky, Jacob; Halverson, Peter

    2010-01-01

    An improved method and apparatus have been devised for measuring cyclic errors in the readouts of laser heterodyne interferometers that are configured and operated as displacement gauges. The cyclic errors arise as a consequence of mixing of spurious optical and electrical signals in beam launchers that are subsystems of such interferometers. The conventional approach to measurement of cyclic error involves phase measurements and yields values precise to within about 10 pm over air optical paths at laser wavelengths in the visible and near infrared. The present approach, which involves amplitude measurements instead of phase measurements, yields values precise to about .0.1 microns . about 100 times the precision of the conventional approach. In a displacement gauge of the type of interest here, the laser heterodyne interferometer is used to measure any change in distance along an optical axis between two corner-cube retroreflectors. One of the corner-cube retroreflectors is mounted on a piezoelectric transducer (see figure), which is used to introduce a low-frequency periodic displacement that can be measured by the gauges. The transducer is excited at a frequency of 9 Hz by a triangular waveform to generate a 9-Hz triangular-wave displacement having an amplitude of 25 microns. The displacement gives rise to both amplitude and phase modulation of the heterodyne signals in the gauges. The modulation includes cyclic error components, and the magnitude of the cyclic-error component of the phase modulation is what one needs to measure in order to determine the magnitude of the cyclic displacement error. The precision attainable in the conventional (phase measurement) approach to measuring cyclic error is limited because the phase measurements are af-

  13. CyclicRainbow A Multivariate Signature Scheme with a Partially Cyclic Public Key based on Rainbow

    E-print Network

    CyclicRainbow ­ A Multivariate Signature Scheme with a Partially Cyclic Public Key based on Rainbow key size of the UOV scheme by a large factor. In this paper we extend this idea to the Rainbow of the public key by up to 62 %. Keywords: Multivariate Cryptography, Rainbow Signature Scheme, keysize

  14. CyclicRainbow -A Multivariate Signature Scheme with a Partially Cyclic Public Key based on Rainbow

    E-print Network

    CyclicRainbow - A Multivariate Signature Scheme with a Partially Cyclic Public Key based on Rainbow key size of the UOV scheme by a large factor. In this paper we extend this idea to the Rainbow of the public key by up to 62 %. Keywords: Multivariate Cryptography, Rainbow Signature Scheme, keysize

  15. BICEP's acceleration

    E-print Network

    Carlo R. Contaldi

    2014-07-24

    The recent BICEP2 detection of, what is claimed to be primordial $B$-modes, opens up the possibility of constraining not only the energy scale of inflation but also the detailed acceleration history that occurred during inflation. In turn this can be used to determine the shape of the inflaton potential $V(\\phi)$ for the first time - if a single, scalar inflaton is assumed to be driving the acceleration. We carry out a Monte Carlo exploration of inflationary trajectories given the current data. Using this method we obtain a posterior distribution of possible acceleration profiles $\\epsilon(N)$ as a function of $e$-fold $N$ and derived posterior distributions of the primordial power spectrum $P(k)$ and potential $V(\\phi)$. We find that the BICEP2 result, in combination with Planck measurements of total intensity Cosmic Microwave Background (CMB) anisotropies, induces a significant feature in the scalar primordial spectrum at scales $k\\sim 10^{-3}$ Mpc$^{-1}$. This is in agreement with a previous detection of a suppression in the scalar power.

  16. Aircraft control by propeller cyclic blades

    NASA Technical Reports Server (NTRS)

    Deyoung, J.

    1979-01-01

    A theory is developed for aircraft control obtained from the propeller forces and moments generated by blade angle variation during a blade revolution. The propeller blade is pitched harmonically one cycle per propeller revolution which results in vehicle control forces and moments, termed cyclic-control. Using a power series respresentation of an arbitrary function of cyclic-blade angle, cyclic-control theory is developed which leads to exact solutions in terms of derivatives of steady-state thrust and power with respect to blade angle. An alternative solution, when the cyclic-blade angle function is limited to a sinusoidal cycle, is in terms of Bessel functions. An estimate of non-steady azimuth angle change or lag is presented. Cyclic-control analysis applied to the counter-rotating propeller shows that control forces or moments can be uniquely isolated from each other. Thus the dual rotor, in hovering mode, has propulsion without rotor tilt or moments, or, when in propeller mode at the tail of an air ship or submarine, vehicle control with no vehicle movement. Control isolation is also attainable from three or more propellers in-line.

  17. Cyclic depsipeptides as potential cancer therapeutics.

    PubMed

    Kitagaki, Jirouta; Shi, Genbin; Miyauchi, Shizuka; Murakami, Shinya; Yang, Yili

    2015-03-01

    Cyclic depsipeptides are polypeptides in which one or more amino acid is replaced by a hydroxy acid, resulting in the formation of at least one ester bond in the core ring structure. Many natural cyclic depsipeptides possessing intriguing structural and biological properties, including antitumor, antifungal, antiviral, antibacterial, anthelmintic, and anti-inflammatory activities, have been identified from fungi, plants, and marine organisms. In particular, the potent effects of cyclic depsipeptides on tumor cells have led to a number of clinical trials evaluating their potential as chemotherapeutic agents. Although many of the trials have not achieved the desired results, romidepsin (FK228), a bicyclic depsipeptide that inhibits histone deacetylase, has been shown to have clinical efficacy in patients with refractory cutaneous T-cell lymphoma and has received Food and Drug Administration approval for use in treatment. In this review, we discuss antitumor cyclic depsipeptides that have undergone clinical trials and focus on their structural features, mechanisms, potential applications in chemotherapy, and pharmacokinetic and toxicity data. The results of this study indicate that cyclic depsipeptides could be a rich source of new cancer therapeutics. PMID:25419631

  18. Accelerators and the Accelerator Community

    SciTech Connect

    Malamud, Ernest; Sessler, Andrew

    2008-06-01

    In this paper, standing back--looking from afar--and adopting a historical perspective, the field of accelerator science is examined. How it grew, what are the forces that made it what it is, where it is now, and what it is likely to be in the future are the subjects explored. Clearly, a great deal of personal opinion is invoked in this process.

  19. The nature of solar cyclicity. I

    NASA Astrophysics Data System (ADS)

    Romanchuk, P. R.

    1981-02-01

    The report contains a critical survey of work devoted to the study of the nature of solar cyclicity. The inconsistency of the representation of cyclic curves using a frequency spectrum is indicated. The useful contribution of the ideas of Wolf, Newcomb, and Waldmeier to the solution of the problem is noted. Data are cited in favor of the theory of the tidal nature of solar cyclicity developed by the author, which also takes into account the ideas of the above-mentioned authors: the continuous paired and single tidal actions of the planets and the resonance character of this action, thanks to which the approximately 10-year period of action of Jupiter and Saturn is transformed into the 11-year activity cycle.

  20. Cyclic and low temperature effects on microcircuits

    NASA Technical Reports Server (NTRS)

    Weissflug, V. A.; Sisul, E. V.

    1977-01-01

    Cyclic temperature and low temperature operating life tests, and pre-/post-life device evaluations were used to determine the degrading effects of thermal environments on microcircuit reliability. Low power transistor-transistor-logic gates and linear devices were included in each test group. Device metallization systems included aluminum metallization/aluminum wire, aluminum metallization/gold wire, and gold metallization/gold wire. Fewer than 2% electrical failures were observed during the cyclic and low temperature life tests and the post-life evaluations revealed approximately 2% bond pull failures. Reconstruction of aluminum die metallization was observed in all devices and the severity of the reconstruction appeared to be directly related to the magnitude of the temperature excursion. All types of bonds except the gold/gold bonds were weakened by exposure to repeated cyclic temperature stress.

  1. Cyclic fatty acids from linolenic acid

    Microsoft Academic Search

    R. A. Eisenhauer; R. E. Beal; E. L. Griffin

    1964-01-01

    Linolenic acid of 95% purity was heated with excess alkali in ethylene glycol to produce cyclic fatty acids. Reaction variables,\\u000a which are associated with the cyclization reaction and which were investigated, included solvent-to-fatty-acid ratio, catalyst\\u000a concentration, and reaction temperature, headspace gas (N2 or C2H4), and head-space gas pressure.\\u000a \\u000a Yields of cyclic acids were improved by increasing solvent ratio (1.5–6 wt

  2. Accelerator system and method of accelerating particles

    NASA Technical Reports Server (NTRS)

    Wirz, Richard E. (Inventor)

    2010-01-01

    An accelerator system and method that utilize dust as the primary mass flux for generating thrust are provided. The accelerator system can include an accelerator capable of operating in a self-neutralizing mode and having a discharge chamber and at least one ionizer capable of charging dust particles. The system can also include a dust particle feeder that is capable of introducing the dust particles into the accelerator. By applying a pulsed positive and negative charge voltage to the accelerator, the charged dust particles can be accelerated thereby generating thrust and neutralizing the accelerator system.

  3. Transverse and cyclic thermal loading of the fiber reinforced metal-matrix composite SCS6/Ti-15-3

    SciTech Connect

    Jansson, S.; Dal Bello, D.J.; Leckie, F.A. (Univ. of California, Santa Barbara, CA (United States). Dept. of Mechanical and Environmental Engineering)

    1994-12-01

    The transverse properties of a SiC fiber reinforced Ti alloy matrix composite subjected to transverse mechanical of cyclic thermal loading have been investigated. Fibers and matrix have a mismatch in the coefficients of thermal expansion that induces thermal stresses in addition to those caused by mechanical loading. When fluctuations occur in the operating temperature the thermal stresses change and this could cause an incremental accumulation of plastic strain or increase in creep rate. The composite under consideration has a modes mismatch and it was found that the strain accumulation is caused by creep deformation in the matrix at the high temperature portion of the thermal cycles. In the early stages of the deformation for low transverse loading the interface is in compressive contact and the creep rate is accelerated by the cyclic thermal stresses. After debonding has occurred the cyclic thermal stress component is diminished and the creep rate is given by a matrix with holes.

  4. 21 CFR 862.1230 - Cyclic AMP test system.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...DEVICES Clinical Chemistry Test Systems § 862.1230 Cyclic AMP test system. (a) Identification. A cyclic AMP test system is a device intended to measure...the diagnosis and treatment of endocrine disorders, including...

  5. 21 CFR 862.1230 - Cyclic AMP test system.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...DEVICES Clinical Chemistry Test Systems § 862.1230 Cyclic AMP test system. (a) Identification. A cyclic AMP test system is a device intended to measure...the diagnosis and treatment of endocrine disorders, including...

  6. 21 CFR 862.1230 - Cyclic AMP test system.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...DEVICES Clinical Chemistry Test Systems § 862.1230 Cyclic AMP test system. (a) Identification. A cyclic AMP test system is a device intended to measure...the diagnosis and treatment of endocrine disorders, including...

  7. 21 CFR 862.1230 - Cyclic AMP test system.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...DEVICES Clinical Chemistry Test Systems § 862.1230 Cyclic AMP test system. (a) Identification. A cyclic AMP test system is a device intended to measure...the diagnosis and treatment of endocrine disorders, including...

  8. 21 CFR 862.1230 - Cyclic AMP test system.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...DEVICES Clinical Chemistry Test Systems § 862.1230 Cyclic AMP test system. (a) Identification. A cyclic AMP test system is a device intended to measure...the diagnosis and treatment of endocrine disorders, including...

  9. CYCLIC REPRESENTATIONS OF THE QUANTUM MATRIX ALGEBRAS

    E-print Network

    Jakobsen, Hans Plesner

    ­called Dipper­Donkin quantum matrix algebra as well as of two other natural quantized matrix algebras. The cyclic representations of the quantum enveloping algebra U q (g) at a root of unity have been studied of functions on the quantized SL(n), roughly speaking by setting the quantum determinant equal to 1. Thus

  10. Sequential steam; An engineered cyclic steaming method

    SciTech Connect

    Jones, J. (Santa Fe Energy Resources Inc., Bakersfield, CA (US)); Cawthon, J. (Groundwater Resources Inc. (US))

    1990-07-01

    Cyclic steam injection has been the most widely used EOR method in areas of the Potter sand in the Midway-Sunset field, Kern County, CA. This paper discusses the field pilot and the statistical and theoretical studies leading to the design of a sequential steaming process,plus the implementation of this process on three leases.

  11. Symmetrization of cyclic sigma-telluranes

    SciTech Connect

    Sadekov, I.D.; Rivkin, B.B.; Maslakov, A.G.; Minkin, V.I.

    1987-09-01

    The authors examine reactions involving cyclic sigma-telluranes. Refluxing 5,5-dichlorodibenzotellurophene with tellurium tetrachloride in o-dichlorobenzene results in symmetrization and the formation of 2,2'-bis(trichlorotelluro)diphenyl in high yield. The other compounds formed and described are polymeric ditelluride, dibenzotellurophene, and dimethyltellurium dibromide.

  12. Sequential Steam: An Engineered Cyclic Steaming Method

    Microsoft Academic Search

    Jeff Jones; Gary Cawthon

    1990-01-01

    Cyclic steam injection has been the most widely used EOR method in areas of the Potter sand in the Midway-Sunset field, Kern County, CA. This paper discusses the field pilot and the statistical and theoretical studies leading to the design of a sequential steaming process,plus the implementation of this process on three leases.

  13. Cyclic Cratonic Carbonates and Phanerozoic Calcite Seas.

    ERIC Educational Resources Information Center

    Wilkinson, Bruce H.

    1982-01-01

    Discusses causes of cyclicity in cratonic carbonate sequences and evidence for and potential significance of postulated primary calcite sediment components in past Paleozoic seas, outlining problems, focusing on models explaining existing data, and identifying background. Future sedimentary geologists will need to address these and related areas…

  14. Original article Feed restriction in cyclic gilts

    E-print Network

    Paris-Sud XI, Université de

    Original article Feed restriction in cyclic gilts: Gonadotrophin-independent effects on follicular in metabolic hormones, induced by feed restriction, can alter follicle distribution in swine ovaries through larger than 2 mm and increa- sed the number of follicles smaller than 1 mm. The feed restriction did

  15. Cyclic energy harvesting from pyroelectric materials

    Microsoft Academic Search

    Poorna Mane; Jingsi Xie; Kam Leang; Karla Mossi

    2011-01-01

    A method of continuously harvesting energy from pyroelectric materials is demonstrated using an innovative cy- clic heating scheme. In traditional pyroelectric energy harvest- ing methods, static heating sources are used, and most of the available energy has to be harvested at once. A cyclic heating system is developed such that the temperature varies between hot and cold regions. Although the

  16. Damage description of metals under cyclic loading

    NASA Astrophysics Data System (ADS)

    Zhao, Jun; Zhang, Xing

    1993-04-01

    Through a newly formed mathematical description of the stiffness reduction of metals subjected to cyclic loads, and the principle of material frame-indifference of continuum mechanics, this paper evaluates the sufficient and necessary conditions of the single-variabled damage model for metals. The rational basis and the availability criterion of this model, which is usually applied by assumptions, are formulated.

  17. Damage description of metals under cyclic loading

    Microsoft Academic Search

    Jun Zhao; Xing Zhang

    1993-01-01

    Through a newly formed mathematical description of the stiffness reduction of metals subjected to cyclic loads, and the principle of material frame-indifference of continuum mechanics, this paper evaluates the sufficient and necessary conditions of the single-variabled damage model for metals. The rational basis and the availability criterion of this model, which is usually applied by assumptions, are formulated.

  18. AVOIDING ARITHMETIC PROGRESSIONS IN CYCLIC GROUPS

    E-print Network

    Halbeisen, Lorenz

    AVOIDING ARITHMETIC PROGRESSIONS IN CYCLIC GROUPS Lorenz & Stephanie Halbeisen Keywords: arithmetic-constant arithmetic progressions in one colour, i.e., for every length ` there are positive integers a and d such that all the numbers a; a + d; a + 2d; : : : ; a + `d have the same colour. Such arithmetic progressions

  19. AVOIDING ARITHMETIC PROGRESSIONS IN CYCLIC GROUPS

    E-print Network

    Halbeisen, Lorenz

    AVOIDING ARITHMETIC PROGRESSIONS IN CYCLIC GROUPS Lorenz & Stephanie Halbeisen Keywords: arithmetic the maximum cardinality of a subset of Zn which does not contain any non-constant arithmetic progression the numbers a, a + d, a + 2d, . . . , a + d have the same colour. Such arithmetic progressions are called

  20. Excision in Cyclic Homology Theories Michael Puschnigg

    E-print Network

    , we construct a fundamental diagram of chain complexes CdC *(I) ! dCC *(A fundamental diagram of Ind-complexes of Fr'echet spaces which implies the excision theorem for cyclic * *and of the fundamental diagram in more detail. Let ss : T A ! A be the canonical epimorphism of the tensor algebra over

  1. A Cyclic Nucleotide Modulated Prokaryotic K+ Channel

    PubMed Central

    Nimigean, Crina M.; Shane, Tania; Miller, Christopher

    2004-01-01

    A search of prokaryotic genomes uncovered a gene from Mesorhizobium loti homologous to eukaryotic K+ channels of the S4 superfamily that also carry a cyclic nucleotide binding domain at the COOH terminus. The gene was cloned from genomic DNA, and the protein, denoted MloK1, was overexpressed in Escherichia coli and purified. Gel filtration analysis revealed a heterogeneous distribution of protein sizes which, upon inclusion of cyclic nucleotide, coalesces into a homogeneous population, eluting at the size expected for a homotetramer. As followed by a radioactive 86Rb+ flux assay, the putative channel protein catalyzes ionic flux with a selectivity expected for a K+ channel. Ion transport is stimulated by cAMP and cGMP at submicromolar concentrations. Since this bacterial homologue does not have the “C-linker” sequence found in all eukaryotic S4-type cyclic nucleotide-modulated ion channels, these results show that this four-helix structure is not a general requirement for transducing the cyclic nucleotide-binding signal to channel opening. PMID:15337819

  2. Crack propagation in ceramics under cyclic loads

    Microsoft Academic Search

    L. Ewart; S. Suresh

    1987-01-01

    Stable crack growth is observed in notched plates of polycrystalline alumina subject to fully compressive far-field cyclic loads at room temperature in a moist air environment andin vacuo. The fatigue cracks propagate at a progressively decreasing velocity along the plane of the notch and in a direction macroscopically normal to the compression axis. The principal failure events leading to this

  3. Inflammation-related changes in cyclic AMP and cyclic GMP in bovine mastitis

    Microsoft Academic Search

    F. Atroshi; J. Parantainen; S. Sankari; T. Österman

    1989-01-01

    Cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) cocentrations in milk and plasma samples from healthy and mastitic cows were determined by radioi-immunoassay and compared with prostaglandins (PGE2, PGF2a and thromboxane B2 [TXB2]), phospholipids and other relevant parameters in milk and blood. The concentrations of cAMP were about five times higher in plasma (pp<0.01) than that in plasma in

  4. Probabilistic Models for Cyclic Straining of Saturated Clean Sands

    Microsoft Academic Search

    K. Onder Cetin; H. Tolga Bilge; Jiaer Wu; Annie M. Kammerer; Raymond B. Seed

    2009-01-01

    A maximum likelihood framework for the probabilistic assessment of post-cyclic straining of saturated clean sands is described. Databases consisting of cyclic laboratory test results including maximum shear and post-cyclic volumetric strains in conjunction with relative density, number of stress (strain) cycles and \\

  5. Technical Report No. 494 Using Cyclic Genetic Algorithms

    E-print Network

    Portland State University

    Technical Report No. 494 Using Cyclic Genetic Algorithms to Recon gure Hardware Controllers Indiana University Bloomington, Indiana 47405-4101 #12;Using Cyclic Genetic Algorithms to Recon gure for a small hexapod robot are generated by a cyclic genetic algorithm. From these automata a Xilinx net list

  6. NBER WORKING PAPER SERIES THE CHANGING CYCLICAL BEHAVIOR

    E-print Network

    NBER WORKING PAPER SERIES THE CHANGING CYCLICAL BEHAVIOR OF WAGES AND PRICES: 1890--1976 Jeffrey Research. #12;NBER Working Paper 304 December 1978 Summary The Changing Cyclical Behavior of Wages about .lX. The analysis makes use of two methods to study the changing cyclical behavior of inflation

  7. DETECTION AND DECOMPOSITION: TREATMENT-INDUCED CYCLIC GENE EXPRESSION

    E-print Network

    Qin, Wensheng

    DETECTION AND DECOMPOSITION: TREATMENT-INDUCED CYCLIC GENE EXPRESSION DISRUPTION IN HIGH of a day. How- ever, treatment-induced disruption of regular cyclic gene expression patterns presents to distinguish the cyclic patterns from the rest gene expression patterns, and discussed potential future

  8. A model for anelastic relaxation controlled cyclic creep

    Microsoft Academic Search

    V. C. Nardone; D. E. Matejczyk; J. K. Tien

    1985-01-01

    In the paper we derive an expression for the cyclic minimum strain rate of cyclic creep in systems where anelastic relaxation is a controlling mechanism. The cyclic creep behavior is modeled by assuming that the anelastic strain recovered during the off-load periods must first be stored during the on-load periods before nonrecoverable creep results. To perform the derivation, the time

  9. Stiffness degradation of natural fine grained soils during cyclic loading

    Microsoft Academic Search

    D. V. Okur; A. Ansal

    2007-01-01

    Cyclic behavior of natural fine grained soils under a broad range of strains were investigated considering the effects of plasticity index and changes in confining pressures based on cyclic triaxial tests. A total of 98 stress controlled cyclic triaxial tests were conducted on normally consolidated and slightly overconsolidated samples. The investigation was divided into two parts. The first part consists

  10. FERMI ACCELERATION. DMITRY DOLGOPYAT

    E-print Network

    Dolgopyat, Dmitry

    FERMI ACCELERATION. DMITRY DOLGOPYAT Abstract. Fermi acceleration is a mechanism, first suggested, on average, be accelerated. Since then Fermi acceleration has been used to explain a number of natural phenomena and sev- eral simple mathematical models demonstrating Fermi acceleration have been proposed. We

  11. Progress on plasma accelerators

    SciTech Connect

    Chen, P.

    1986-05-01

    Several plasma accelerator concepts are reviewed, with emphasis on the Plasma Beat Wave Accelerator (PBWA) and the Plasma Wake Field Accelerator (PWFA). Various accelerator physics issues regarding these schemes are discussed, and numerical examples on laboratory scale experiments are given. The efficiency of plasma accelerators is then revealed with suggestions on improvements. Sources that cause emittance growth are discussed briefly.

  12. Rhenium-Catalyzed [4 + 1] Annulation of Azobenzenes and Aldehydes via Isolable Cyclic Rhenium(I) Complexes.

    PubMed

    Geng, Xiaoyu; Wang, Congyang

    2015-05-15

    The first Re-catalyzed [4 + 1] annulation of azobenzenes with aldehydes was developed to furnish 2H-indazoles via isolable and characterized cyclic Re(I)-complexes. For the first time, the acetate-acceleration effect is showcased in Re-catalyzed C-H activation reactions. Remarkably, mechanistic studies revealed an irreversible aldehyde-insertion step, which is in sharp contrast to those of previous Rh- and Co-systems. PMID:25945598

  13. Low cycle fatigue and cyclic stress ratcheting failure behavior of carbon steel 45 under uniaxial cyclic loading

    Microsoft Academic Search

    Xianjie Yang

    2005-01-01

    In this paper, the cyclic strain low cycle fatigue and cyclic stress ratcheting failure of carbon steel 45 with quenched and tempered treatment were experimentally investigated. The tests for cyclic strain low cycle fatigue with or without mean strains were carried out to investigate the effect of mean strain on low cycle fatigue (LCF) behavior. The effects of mean stress

  14. Nonlocality of Accelerated Systems

    E-print Network

    Bahram Mashhoon

    2003-05-11

    The conceptual basis for the nonlocality of accelerated systems is presented. The nonlocal theory of accelerated observers and its consequences are briefly described. Nonlocal field equations are developed for the case of the electrodynamics of linearly accelerated systems.

  15. Ion Induction Accelerators

    Microsoft Academic Search

    John J. Barnard; Kazuhiko Horioka

    2011-01-01

    \\u000a The description of beams in RF and induction accelerators share many common features. Likewise, there is considerable commonality\\u000a between electron induction accelerators (see Chap. 7) and ion induction accelerators. However, in contrast to electron induction\\u000a accelerators, there are fewer ion induction accelerators that have been operated as application-driven user facilities. Ion\\u000a induction accelerators are envisioned for applications (see Chap. 10)

  16. Cyclic nucleotide signalling in kidney fibrosis.

    PubMed

    Schinner, Elisabeth; Wetzl, Veronika; Schlossmann, Jens

    2015-01-01

    Kidney fibrosis is an important factor for the progression of kidney diseases, e.g., diabetes mellitus induced kidney failure, glomerulosclerosis and nephritis resulting in chronic kidney disease or end-stage renal disease. Cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) were implicated to suppress several of the above mentioned renal diseases. In this review article, identified effects and mechanisms of cGMP and cAMP regarding renal fibrosis are summarized. These mechanisms include several signalling pathways of nitric oxide/ANP/guanylyl cyclases/cGMP-dependent protein kinase and cAMP/Epac/adenylyl cyclases/cAMP-dependent protein kinase. Furthermore, diverse possible drugs activating these pathways are discussed. From these diverse mechanisms it is expected that new pharmacological treatments will evolve for the therapy or even prevention of kidney failure. PMID:25622251

  17. A cyclic symmetry principle in physics

    NASA Astrophysics Data System (ADS)

    Green, H. S.

    Many areas of modern physics are illuminated by the application of a symmetry principle, requiring the invariance of the relevant laws of physics under a group of transformations. This paper examines the implications and some of the applications of the principle of cyclic symmetry, especially in the areas of statistical mechanics and quantum mechanics, including quantized field theory. This principle requires invariance under the transformations of a finite group, which may be a Sylow pi-group, a group of Lie type, or a symmetric group. The utility of the principle of cyclic invariance is demonstrated in finding solutions of the Yang-Baxter equation that include and generalize known solutions. It is shown that the Sylow pi-groups have other uses, in providing a basis for a type of generalized quantum statistics, and in parametrizing a new generalization of Lie groups, with associated algebras that include quantized algebras.

  18. Combustion oscillation control by cyclic fuel injection

    SciTech Connect

    Richards, G.A.; Yip, M.J. [USDOE Morgantown Energy Technology Center, WV (United States); Robey, E. [EG& G Technical Services of West Virginia, Morgantown Energy Technology Center, WV (United States); Cowell, L.; Rawlins, D. [Solar Turbines, Inc., San Diedgo, CA (United States)

    1995-04-01

    A number of recent articles have demonstrated the use of active control to mitigate the effects of combustion instability in afterburner and dump combustor applications. In these applications, cyclic injection of small quantities of control fuel has been proposed to counteract the periodic heat release that contributes to undesired pressure oscillations. This same technique may also be useful to mitigate oscillations in gas turbine combustors, especially in test rig combustors characterized by acoustic modes that do not exist in the final engine configuration. To address this issue, the present paper reports on active control of a subscale, atmospheric pressure nozzle/combustor arrangement. The fuel is natural gas. Cyclic injection of 14% control fuel in a premix fuel nozzle is shown to reduce oscillating pressure amplitude by a factor of 0.30 (i.e., {approximately}10 dB) at 300 Hz. Measurement of the oscillating heat release is also reported.

  19. Bouncing and cyclic string gas cosmologies

    SciTech Connect

    Greene, Brian; Marnerides, Stefanos [Institute for Strings, Cosmology and Astroparticle Physics and Department of Physics, Columbia University, New York, New York 10027 (United States); Kabat, Daniel [Institute for Strings, Cosmology and Astroparticle Physics and Department of Physics, Columbia University, New York, New York 10027 (United States); Department of Physics and Astronomy, Lehman College, City University of New York, Bronx, New York 10468 (United States)

    2009-09-15

    We show that, in the presence of a string gas, simple higher-derivative modifications to the effective action for gravity can lead to bouncing and cyclic cosmological models. The modifications bound the expansion rate and avoid singularities at finite times. In these models the scale factors can have long loitering phases that solve the horizon problem. Adding a potential for the dilaton gives a simple realization of the pre-big bang scenario. Entropy production in the cyclic phase drives an eventual transition to a radiation-dominated Universe. As a test of the Brandenberger-Vafa scenario, we comment on the probability of decompactifying three spatial dimensions in this class of models.

  20. Cyclic debonding of adhesively bonded composites

    NASA Technical Reports Server (NTRS)

    Mall, S.; Johnson, W. S.; Everett, R. A., Jr.

    1982-01-01

    The fatigue behavior of a simple composite to composite bonded joint was analyzed. The cracked lap shear specimen subjected to constant amplitude cyclic loading was studied. Two specimen geometries were tested for each bonded system: (1) a strap adherend of 16 plies bonded to a lap adherend of 8 plies; and (2) a strap adherend of 8 plies bonded to a lap adherend of 16 plies. In all specimens the fatigue failure was in the form of cyclic debonding with some 0 deg fiber pull off from the strap adherend. The debond always grew in the region of adhesive that had the highest mode (peel) loading and that region was close to the adhesive strap interface.

  1. Surface and interface properties of carbon fiber composites under cyclical aging

    NASA Astrophysics Data System (ADS)

    Lv, Xinying; Wang, Rongguo; Liu, Wenbo; Jiang, Long

    2011-10-01

    Carbon fiber-reinforced BMI composites have been subjected to combination accelerated aging comprising a hygrothermal process, a thermal-oxidative process, and a freezing process in order to simulate their responses under complicated service environments. This cyclical condition, including the freezing process, has not been investigated by other researchers so far. The effects of this combination accelerated aging on the mechanical properties have been characterized by FTIR, SEM/EDXA, XRD, and moisture-uptake determination. The results indicated that combination accelerated aging had great effects on the mechanical properties of the composite, the network structure of the BMI matrix, and the moisture uptake by the composite. After a third cycle of accelerated aging, moisture reached the center layer of the composite and as a result led to an obvious decrease in ILSS due to deterioration of the carbon fiber-BMI interface. Sufficient moisture absorption on the composite surface made the network structure of the BMI matrix more open, which facilitated stress relaxation and the creation of micro-cracks, with a consequent obvious decrease in flexural strength. With increasing number of combined-action accelerated aging cycles, ever more moisture was absorbed during each hygrothermal process due to the plasticizing effect of water, and micro-cracks propagated as a result of internal stresses caused by the hygrothermal process, the thermal-oxidative process, and the freezing process of each cycle. XRD analysis indicated that moisture penetrated through the amorphous region of the BMI matrix.

  2. Cyclic nucleotide signaling in polycystic kidney disease.

    PubMed

    Wang, Xiaofang; Ward, Christopher J; Harris, Peter C; Torres, Vicente E

    2010-01-01

    Increased levels of 3'-5'-cyclic adenosine monophosphate (cAMP) stimulate cell proliferation and fluid secretion in polycystic kidney disease. Levels of this molecule are more sensitive to inhibition of phosphodiesterases (PDEs), whose activity far exceeds the rate of cAMP synthesis by adenylyl cyclase. Several PDEs exist, and here we measured the activity and expression of PDE families, their isoforms, and the expression of downstream effectors of cAMP signaling in the kidneys of rodents with polycystic kidney disease. We found a higher overall PDE activity in kidneys from mice as compared with rats, as well as a higher contribution of PDE1, relative to PDE4 and PDE3, to total PDE activity of kidney lysates and lower PDE1, PDE3, and PDE4 activities in the kidneys of cystic as compared with wild-type mice. There were reduced amounts of several PDE1, PDE3, and PDE4 proteins, possibly due to increased protein degradation despite an upregulation of their mRNA. Increased levels of cGMP were found in the kidneys of cystic animals, suggesting in vivo downregulation of PDE1 activity. We found an additive stimulatory effect of cAMP and cGMP on cystogenesis in vitro. Cyclic AMP-dependent protein kinase subunits Ialpha and IIbeta, PKare, the transcription factor CREB-1 mRNA, and CREM, ATF-1, and ICER proteins were upregulated in the kidneys of cystic as compared with wild-type animals. Our study suggests that alterations in cyclic nucleotide catabolism may render cystic epithelium particularly susceptible to factors acting on Gs-coupled receptors. This may account, in part, for increased cyclic nucleotide signaling in polycystic kidney disease and contribute substantially to disease progression. PMID:19924104

  3. Mortality Factors in a Cyclic Vole Population

    Microsoft Academic Search

    Kai Norrdahl; Erkki Korpimaki

    1995-01-01

    The causes of cyclic fluctuations in microtine rodent populations are still a bone of contention. In particular, the actual causes of mortality in the different phases of the 3-4-year vole are an enigma. We present results from studies of radio-collared voles (Microtus agrestis, M. rossiaemeridionalis and Clethrionomys glareolus), which show that small mustelid predation was the major mortality factor of

  4. a Theorem on Cyclic Harmonic Oscillators

    Microsoft Academic Search

    Kenichi Konishi; Giampiero Paffuti

    2006-01-01

    It is proven that the energy of a quantum mechanical harmonic oscillator with a generically time-dependent but cyclic frequency, omega(t0) = omega(0), cannot decrease on an average if the system is originally in a stationary state, after the system goes through a full cycle. The energy exchange always takes place in the direction from the macroscopic system (environment) to the

  5. a Theorem on Cyclic Harmonic Oscillators

    NASA Astrophysics Data System (ADS)

    Konishi, Kenichi; Paffuti, Giampiero

    It is proven that the energy of a quantum mechanical harmonic oscillator with a generically time-dependent but cyclic frequency, ?(t0) = ?(0), cannot decrease on an average if the system is originally in a stationary state, after the system goes through a full cycle. The energy exchange always takes place in the direction from the macroscopic system (environment) to the quantum microscopic system.

  6. Precoder for DMT with insufficient cyclic prefix

    Microsoft Academic Search

    Kok-Wui Cheong; J. M. Cioffi

    1998-01-01

    Multi-carrier modulation is a modulation technique that enables higher transmission rate than traditional techniques, such as single-carrier quadrature amplitude modulation (QAM) systems. One implementation of multi-carrier modulation technique is discrete multi-tone (DMT). DMT used in asymmetric digital subscriber lines (ADSL) and very high speed DSL (VDSL) systems has a fixed cyclic prefix length. When the impulse response of the channel

  7. Cyclical Staff Scheduling Using Constraint Logic Programming

    Microsoft Academic Search

    Peter Chan; Georges Weil

    2000-01-01

    In organizations where duty is around the clock, seven days a week and every week of the year, timetabling is a very difficult\\u000a task, juggling between the workload and the constraints to be respected. Our work concerns cyclical timetabling. This is not\\u000a just duplicating a fixed sequence of assignments, but has to consider fixed annual leave, and various regulations on

  8. Constitutive model for cyclic deformation of perfluoroelastomers

    Microsoft Academic Search

    A. D. Drozdov

    2009-01-01

    Observations are reported in uniaxial cyclic tensile tests with a strain-controlled program on perfluoroelastomer Hyflon MFA. A constitutive model is developed for its viscoplastic response and damage at three-dimensional deformations with finite strains. Adjustable parameters in the stress-strain relations are found by fitting the experimental data. Numerical simulation demonstrates that the constitutive equations adequately describe the mechanical response of perfluoroelastomer

  9. Cyclic steaming in heavy oil diatomite

    SciTech Connect

    Kumar, M.; Beatty, F.D.

    1995-12-31

    Chevron currently uses cyclic steaming as a recovery method to produce economically its heavy oil diatomite resource in the Cymric field, San Joaquin Valley, California. A highly instrumented, cyclically steaming well from this field was simulated in this study to delineate important production mechanisms, to optimize operations, and to improve reservoir management. The model was constrained, as much as possible, by the available measured data. Results show that fluid flow from the well to the reservoir is primarily through the hydraulic fracture induced by the injected steam. Parameters with unique importance to modeling cyclic steaming in diatomites are: (1) induced fracture dimension (length and height), (2) matrix permeability, (3) oil/water capillary pressure, (4) grid size perpendicular to fracture face, and (5) producing bottomhole pressures. Additionally, parameters important for conventional steam injection processes, such as relative permeabilities and injected steam volume, quality, and rate, are important for diatomites also. Oil production rates and steam/oil ratios calculated by this model compare reasonably with field data.

  10. Cyclic energy harvesting from pyroelectric materials.

    PubMed

    Mane, Poorna; Xie, Jingsi; Leang, Kam K; Mossi, Karla

    2011-01-01

    A method of continuously harvesting energy from pyroelectric materials is demonstrated using an innovative cyclic heating scheme. In traditional pyroelectric energy harvesting methods, static heating sources are used, and most of the available energy has to be harvested at once. A cyclic heating system is developed such that the temperature varies between hot and cold regions. Although the energy harvested during each period of the heating cycle is small, the accumulated total energy over time may exceed traditional methods. Three materials are studied: a commonly available soft lead zirconate titanate (PZT), a pre-stressed PZT composite, and single-crystal PMN-30PT. Radiation heating and natural cooling are used such that, at smaller cyclic frequencies, the temporal rate of change in temperature is large enough to produce high power densities. The maximum power density of 8.64 ?W/cm3 is generated with a PMN-30PT single crystal at an angular velocity of 0.64 rad/s with a rate of 8.5°C/s. The pre-stressed PZT composite generated a power density of 6.31 ?W/cm(3), which is 40% larger than the density of 4.48 ?W/cm3 obtained from standard PZT. PMID:21244970

  11. Cyclic degassing of Erebus volcano, Antarctica

    NASA Astrophysics Data System (ADS)

    Ilanko, Tehnuka; Oppenheimer, Clive; Burgisser, Alain; Kyle, Philip

    2015-06-01

    Field observations have previously identified rapid cyclic changes in the behaviour of the lava lake of Erebus volcano. In order to understand more fully the nature and origins of these cycles, we present here a wavelet-based frequency analysis of time series measurements of gas emissions from the lava lake, obtained by open-path Fourier transform infrared spectroscopy. This reveals (i) a cyclic change in total gas column amount, a likely proxy for gas flux, with a period of about 10 min, and (ii) a similarly phased cyclic change in proportions of volcanic gases, which can be explained in terms of chemical equilibria and pressure-dependent solubilities. Notably, the wavelet analysis shows a persistent periodicity in the CO2/CO ratio and strong periodicity in H2O and SO2 degassing. The `peaks' of the cycles, defined by maxima in H2O and SO2 column amounts, coincide with high CO2/CO ratios and proportionally smaller increases in column amounts of CO2, CO, and OCS. We interpret the cycles to arise from recharge of the lake by intermittent pulses of magma from shallow depths, which degas H2O at low pressure, combined with a background gas flux that is decoupled from this very shallow magma degassing.

  12. Microwave evaluation of accelerated chloride ingress in mortar

    NASA Astrophysics Data System (ADS)

    Hu, C.; Case, T.; Castle, M.; Zoughi, R.; Kurtis, K.

    2001-04-01

    Corrosion of steel in reinforced concrete structures can be induced by the presence of chloride ions near the steel/concrete interface. To show the potential of microwave nondestructive testing techniques for evaluating chloride ingress, 8?×8?×8? mortar specimens with different mixture designs were prepared. To accelerate chloride ingress, they were exposed to cyclical wet/dry conditions, where the wet condition included exposure to salt bath. A complete discussion of the results will be presented in this paper.

  13. Factors Affecting Al Depletion During Cyclic Oxidation of Fe-Base Alumina-Forming Alloys

    SciTech Connect

    Pint, Bruce A [ORNL; Walker, Larry R [ORNL; Wright, Ian G [ORNL

    2009-01-01

    In order to develop an improved oxidation-limited lifetime model, experiments are being conducted to assess the critical factors that affect the rate of Al loss from Fe-base alumina-forming alloys during cyclic oxidation. Both wrought and dispersion strengthened ferritic and intermetallic Fe-Al {+-} Cr alloys are being investigated at exposure temperatures from 1100-1300 C. Higher temperatures, thinner specimens and cycle frequency are used to accelerate degradation during oxidation. However, the effects of these experimental choices often have not been critically assessed in prior work. Electron probe microanalysis has been used to measure the residual Al content under various conditions and at various stages of life. For 0.5-2 mm thick specimens, lifetime repeatedly showed a linear relationship to thickness. Increasing the oxidation temperature appears to be the most viable strategy to accelerate the evaluation of oxidation resistance for comparing and developing alloys.

  14. Covariant Uniform Acceleration

    E-print Network

    Yaakov Friedman; Tzvi Scarr

    2013-04-29

    We show that standard Relativistic Dynamics Equation F=dp/d\\tau is only partially covariant. To achieve full Lorentz covariance, we replace the four-force F by a rank 2 antisymmetric tensor acting on the four-velocity. By taking this tensor to be constant, we obtain a covariant definition of uniformly accelerated motion. We compute explicit solutions for uniformly accelerated motion which are divided into four types: null, linear, rotational, and general. For null acceleration, the worldline is cubic in the time. Linear acceleration covariantly extends 1D hyperbolic motion, while rotational acceleration covariantly extends pure rotational motion. We use Generalized Fermi-Walker transport to construct a uniformly accelerated family of inertial frames which are instantaneously comoving to a uniformly accelerated observer. We explain the connection between our approach and that of Mashhoon. We show that our solutions of uniformly accelerated motion have constant acceleration in the comoving frame. Assuming the Weak Hypothesis of Locality, we obtain local spacetime transformations from a uniformly accelerated frame K' to an inertial frame K. The spacetime transformations between two uniformly accelerated frames with the same acceleration are Lorentz. We compute the metric at an arbitrary point of a uniformly accelerated frame. We obtain velocity and acceleration transformations from a uniformly accelerated system K' to an inertial frame K. We derive the general formula for the time dilation between accelerated clocks. We obtain a formula for the angular velocity of a uniformly accelerated object. Every rest point of K' is uniformly accelerated, and its acceleration is a function of the observer's acceleration and its position. We obtain an interpretation of the Lorentz-Abraham-Dirac equation as an acceleration transformation from K' to K.

  15. I. ACCELERATION A. Introduction

    E-print Network

    McDonald, Kirk

    I. ACCELERATION A. Introduction Following cooling and initial bunch compression, the beams must be rapidly accelerated. The acceleration needed for a Higgs collider is probably the most conventional part undertaken. A sequence of linacs would work, but would be expensive. Some form of circulating acceleration

  16. Future accelerator technology

    SciTech Connect

    Sessler, A.M.

    1986-05-01

    A general discussion is presented of the acceleration of particles. Upon this foundation is built a categorization scheme into which all accelerators can be placed. Special attention is devoted to accelerators which employ a wake-field mechanism and a restricting theorem is examined. It is shown how the theorem may be circumvented. Comments are made on various acceleration schemes.

  17. Cyclic AMP Receptor Protein-Aequorin Molecular Switch for Cyclic AMP

    PubMed Central

    Scott, Daniel; Hamorsky, Krystal Teasley; Ensor, C. Mark; Anderson, Kimberly W.; Daunert, Sylvia

    2011-01-01

    Molecular switches are designer molecules that combine the functionality of two individual proteins into one, capable of manifesting an “on/off” signal in response to a stimulus. These switches have unique properties and functionalities and thus, can be employed as nanosensors in a variety of applications. To that end, we have developed a bioluminescent molecular switch for cyclic AMP. Bioluminescence offers many advantages over fluorescence and other detection methods including the fact that there is essentially zero background signal in physiological fluids, allowing for more sensitive detection and monitoring. The switch was created by combining the properties of the cyclic AMP receptor protein (CRP), a transcriptional regulatory protein from E. coli that binds selectively to cAMP with those of aequorin, a bioluminescent photoprotein native of the jellyfish Aequorea victoria. Genetic manipulation to split the genetic coding sequence of aequorin in two and genetically attach the fragments to the N and C termini of CRP, resulted in a hybrid protein molecular switch. The conformational change experienced by CRP upon the binding of cyclic AMP is suspected to result in the observed loss of bioluminescent signal from aequorin. The “on/off” bioluminescence can be modulated by cyclic AMP over a range of several orders of magnitude in a linear fashion in addition to the capacity to detect changes in cellular cyclic AMP of intact cells exposed to different external stimuli without the need to lyse the cells. We envision that the molecular switch could find applications in vitro as well as in vivo cyclic AMP detection and/or imaging. PMID:21329338

  18. Interactions of cyclic and non-cyclic naphthalene diimide derivatives with different nucleic acids.

    PubMed

    Czerwinska, Izabella; Sato, Shinobu; Juskowiak, Bernard; Takenaka, Shigeori

    2014-05-01

    Recently, strategy based on stabilization of G-quadruplex telomeric DNA by small organic molecule has been realized by naphthalene diimide derivatives (NDIs). At the same time NDIs bind to DNA duplex as threading intercalators. Here we present cyclic derivative of naphthalene diimide (ligand 1) as DNA-binding ligand with ability to recognition of different structures of telomeric G-quadruplexes and ability to bis-intercalate to double-stranded helixes. The results have been compared to non-cyclic derivative (ligand 2) and revealed that preferential binding of ligands to nucleic acids strongly depends on their topology and structural features of ligands. PMID:24726302

  19. Acceleration without Horizons

    E-print Network

    Alaric Doria; Gerardo Munoz

    2015-02-18

    We derive the metric of an accelerating observer moving with non-constant proper acceleration in flat spacetime. With the exception of a limiting case representing a Rindler observer, there are no horizons. In our solution, observers can accelerate to any desired terminal speed $v_{\\infty} accelerating observer is completely determined by the distance of closest approach and terminal velocity or, equivalently, by an acceleration parameter and terminal velocity.

  20. Inter-rater reliability of cyclic and non-cyclic task assessment using the hand activity level in appliance manufacturing

    PubMed Central

    Paulsen, Robert; Schwatka, Natalie; Gober, Jennifer; Gilkey, David; Anton, Dan; Gerr, Fred; Rosecrance, John

    2015-01-01

    This study evaluated the inter-rater reliability of the American Conference of Governmental Industrial Hygienists (ACGIH®) hand activity level (HAL), an observational ergonomic assessment method used to estimate physical exposure to repetitive exertions during task performance. Video recordings of 858 cyclic and non-cyclic appliance manufacturing tasks were assessed by sixteen pairs of raters using the HAL visual-analog scale. A weighted Pearson Product Moment-Correlation Coefficient was used to evaluate the agreement between the HAL scores recorded by each rater pair, and the mean weighted correlation coefficients for cyclic and non-cyclic tasks were calculated. Results indicated that the HAL is a reliable exposure assessment method for cyclic (r?-barw = 0.69) and non-cyclic work tasks (r?-barw = 0.68). When the two reliability scores were compared using a two-sample Student's t-test, no significant difference in reliability (p = 0.63) between these work task categories was found. This study demonstrated that the HAL may be a useful measure of exposure to repetitive exertions during cyclic and non-cyclic tasks. Relevance to industry Exposure to hazardous levels of repetitive action during non-cyclic task completion has traditionally been difficult to assess using simple observational techniques. The present study suggests that ergonomists could use the HAL to reliably and easily evaluate exposures associated with some non-cyclic work tasks.

  1. The role of peel stresses in cyclic debonding

    NASA Technical Reports Server (NTRS)

    Everett, R. A., Jr.

    1982-01-01

    When an adhesively bonded joint is undergoing cyclic loading, one of the possible damage modes that occurs is called cyclic debonding - progressive separation of the adherends by failure of the adhesive bond under cyclic loading. In most practical structures, both peel and shear stresses exist in the adhesive bonding during cyclic loading. The results of an experimental and analytical study to determine the role of peel stresses on cyclic debonding in a mixed mode specimen are presented. Experimentally, this was done by controlling the forces that create the peel stresses by applying a clamping force to oppose the peel stresses. Cracked lap shear joints were chosen for this study. A finite element analysis was developed to assess the effect of the clamping force on the strain energy release rates due to shear and peel stresses. The results imply that the peel stress is the principal stress causing cyclic debonding.

  2. A cyclic model for superelastic shape memory alloys

    NASA Astrophysics Data System (ADS)

    Saint-Sulpice, Luc; Chirani, Shabnam Arbab; Calloch, Sylvain

    2007-04-01

    This study concerns the superelasticity of Shape Memory Alloys (SMA) under cyclic loading. A particular attention is paid to the evolution of residual strain with number of cycles (like ratcheting in cyclic plasticity of classical metals). To study the phenomenology of the cyclic behavior and to identify the origin of the developed residual strain a series of cyclic uniaxial tensile tests on copper based alloys wires has been realized. A macroscopic model describing the cyclic behavior of superelastic SMA has been proposed. The originalities of the model are, on the one hand, the definition of a particular elasticity domain when the material is in a two phased state and, on the other hand, an ad hoc kinetic of transformation strain taking into account a residual strain evolution. The proposed model has been identified using our experimental data base and has been used to simulate various cyclic multiaxial loadings.

  3. Modelling water molecules inside cyclic peptide nanotubes

    NASA Astrophysics Data System (ADS)

    Tiangtrong, Prangsai; Thamwattana, Ngamta; Baowan, Duangkamon

    2015-03-01

    Cyclic peptide nanotubes occur during the self-assembly process of cyclic peptides. Due to the ease of synthesis and ability to control the properties of outer surface and inner diameter by manipulating the functional side chains and the number of amino acids, cyclic peptide nanotubes have attracted much interest from many research areas. A potential application of peptide nanotubes is their use as artificial transmembrane channels for transporting ions, biomolecules and waters into cells. Here, we use the Lennard-Jones potential and a continuum approach to study the interaction of a water molecule in a cyclo[(-uc(D)-Ala-uc(L)-Ala)_4 -] peptide nanotube. Assuming that each unit of a nanotube comprises an inner and an outer tube and that a water molecule is made up of a sphere of two hydrogen atoms uniformly distributed over its surface and a single oxygen atom at the centre, we determine analytically the interaction energy of the water molecule and the peptide nanotube. Using this energy, we find that, independent of the number of peptide units, the water molecule will be accepted inside the nanotube. Once inside the nanotube, we show that a water molecule prefers to be off-axis, closer to the surface of the inner nanotube. Furthermore, our study of two water molecules inside the peptide nanotube supports the finding that water molecules form an array of a 1-2-1-2 file inside peptide nanotubes. The theoretical study presented here can facilitate thorough understanding of the behaviour of water molecules inside peptide nanotubes for applications, such as artificial transmembrane channels.

  4. Cyclical konzo epidemics and climate variability.

    PubMed

    Oluwole, Olusegun Steven A

    2015-03-01

    Konzo epidemics have occurred during droughts in the Democratic Republic of Congo (DR Congo) for >70 years, but also in Mozambique, Tanzania, and the Central African Republic. The illness is attributed to exposure to cyanide from cassava foods, on which the population depends almost exclusively during droughts. Production of cassava, a drought-resistant crop, has been shown to correlate with cyclical changes in precipitation in konzo-affected countries. Here we review the epidemiology of konzo as well as models of its pathogenesis. A spectral analysis of precipitation and konzo is performed to determine whether konzo epidemics are cyclical and whether there is spectral coherence. Time series of environmental temperature, precipitation, and konzo show cyclical changes. Periodicities of dominant frequencies in the spectra of precipitation and konzo range from 3 to 6 years in DR Congo. There is coherence of the spectra of precipitation and konzo. The magnitude squared coherence of 0.9 indicates a strong relationship between variability of climate and konzo epidemics. Thus, it appears that low precipitation phases of climate variability reduce the yield of food crops except cassava, upon which the population depends for supply of calories during droughts. Presence of very high concentrations of thiocyanate (SCN(-) ), the major metabolite of cyanide, in the bodily fluids of konzo subjects is a consequence of dietary exposure to cyanide, which follows intake of poorly processed cassava roots. Because cyanogens and minor metabolites of cyanide have not induced konzo-like illnesses, SCN(-) remains the most likely neurotoxicant of konzo. Public health control of konzo will require food and water programs during droughts. [Correction added on 26 February 2015, after first online publication: abstract reformatted per journal style] PMID:25523348

  5. Interpretation of tandem mass spectra obtained from cyclic nonribosomal peptides.

    PubMed

    Liu, Wei-Ting; Ng, Julio; Meluzzi, Dario; Bandeira, Nuno; Gutierrez, Marcelino; Simmons, Thomas L; Schultz, Andrew W; Linington, Roger G; Moore, Bradley S; Gerwick, William H; Pevzner, Pavel A; Dorrestein, Pieter C

    2009-06-01

    Natural and non-natural cyclic peptides are a crucial component in drug discovery programs because of their considerable pharmaceutical properties. Cyclosporin, microcystins, and nodularins are all notable pharmacologically important cyclic peptides. Because these biologically active peptides are often biosynthesized nonribosomally, they often contain nonstandard amino acids, thus increasing the complexity of the resulting tandem mass spectrometry data. In addition, because of the cyclic nature, the fragmentation patterns of many of these peptides showed much higher complexity when compared to related counterparts. Therefore, at the present time it is still difficult to annotate cyclic peptides MS/MS spectra. In this current work, an annotation program was developed for the annotation and characterization of tandem mass spectra obtained from cyclic peptides. This program, which we call MS-CPA is available as a web tool (http://lol.ucsd.edu/ms-cpa_v1/Input.py). Using this program, we have successfully annotated the sequence of representative cyclic peptides, such as seglitide, tyrothricin, desmethoxymajusculamide C, dudawalamide A, and cyclomarins, in a rapid manner and also were able to provide the first-pass structure evidence of a newly discovered natural product based on predicted sequence. This compound is not available in sufficient quantities for structural elucidation by other means such as NMR. In addition to the development of this cyclic annotation program, it was observed that some cyclic peptides fragmented in unexpected ways resulting in the scrambling of sequences. In summary, MS-CPA not only provides a platform for rapid confirmation and annotation of tandem mass spectrometry data obtained with cyclic peptides but also enables quantitative analysis of the ion intensities. This program facilitates cyclic peptide analysis, sequencing, and also acts as a useful tool to investigate the uncommon fragmentation phenomena of cyclic peptides and aids the characterization of newly discovered cyclic peptides encountered in drug discovery programs. PMID:19413302

  6. Calabi-Yau Deformations and Negative Cyclic Homology

    E-print Network

    Bergh, Michel Van den

    2012-01-01

    In this paper we relate the deformation theory of Ginzburg Calabi-Yau algebras to negative cyclic homology. We do this by exhibiting a DG-Lie algebra that controls this deformation theory and whose homology is negative cyclic homology. We show that the bracket induced on negative cyclic homology coincides with Menichi's string topology bracket. In the commutative we show that our DG-Lie algebra is homotopy equivalent to $(T^{poly}[[u

  7. Excision in Hochschild and cyclic homology without continuous linear sections

    E-print Network

    Meyer, Ralf

    2009-01-01

    We prove that continuous Hochschild and cyclic homology satisfy excision for extensions of nuclear H-unital Frechet algebras and use this to compute them for the algebra of Whitney functions on an arbitrary closed subset of a smooth manifold. Using a similar excision result for periodic cyclic homology, we also compute the periodic cyclic homology of algebras of smooth functions and Whitney functions on closed subsets of smooth manifolds.

  8. Cyclic stress–strain behavior of polycrystalline nickel

    Microsoft Academic Search

    Y. El-Madhoun; A. Mohamed; M. N. Bassim

    2004-01-01

    The influence of strain amplitude and fatigue cycles on cyclic deformation of polycrystalline specimens of commercially 99.53% purity nickel was investigated using fully reversed strain-controlled fatigue tests. The fatigue tests were performed under constant strain amplitude, in air and at room temperature, at a constant strain rate of 0.0001s?1. The objective was to study cyclic deformation behavior and characterize cyclic

  9. A model for anelastic relaxation controlled cyclic creep

    Microsoft Academic Search

    V. C. Nardone; D. E. Matejczyk; J. K. Tien

    1985-01-01

    In the paper we derive an expression for the cyclic minimum strain rate of cyclic creep in systems where anelastic relaxation\\u000a is a controlling mechanism. The cyclic creep behavior is modeled by assuming that the anelastic strain recovered during the\\u000a off-load periods must first be stored during the on-load periods before nonrecoverable creep results. To perform the derivation,\\u000a the time

  10. Intercalation of cyclic ketones into vanadyl phosphate

    NASA Astrophysics Data System (ADS)

    Zima, Vít?zslav; Melánová, Klára; Beneš, Ludvík; Trchová, Miroslava; Dybal, Ji?í

    2005-01-01

    Intercalation compounds of vanadyl phosphate with cyclic ketones (cyclopentanone, cyclohexanone, 4-methylcyclohexanone, and 1,4-cyclohexanedione) were prepared from corresponding propanol or ethanol intercalates by a molecular exchange. The intercalates prepared were characterized using powder X-ray diffraction and thermogravimetric analysis. The intercalates are stable in dry environment and decompose slowly in humid air. Infrared and Raman spectra indicate that carbonyl oxygens of the guest molecules are coordinated to the vanadium atoms of the host layers. The local structure and interactions in the cyclopentanone intercalate have been suggested on the basis of quantum chemical calculations.

  11. A Cyclic Universe Approach to Fine Tuning

    E-print Network

    Alexander, Stephon; Gleiser, Marcelo

    2015-01-01

    We present a closed bouncing universe model where the value of coupling constants is set by the dynamics of a ghost-like dilatonic scalar field. We show that adding a periodic potential for the scalar field leads to a cyclic Friedmann universe where the values of the couplings vary randomly from one cycle to the next. While the shuffling of values for the couplings happens during the bounce, within each cycle their time-dependence remains safely within present observational bounds for physically-motivated values of the model parameters. Our model presents an alternative to solutions of the fine tuning problem based on string landscape scenarios.

  12. CyBase: a database of cyclic protein sequences and structures, with applications in protein discovery and engineering.

    PubMed

    Wang, Conan K L; Kaas, Quentin; Chiche, Laurent; Craik, David J

    2008-01-01

    CyBase was originally developed as a database for backbone-cyclized proteins, providing search and display capabilities for sequence, structure and function data. Cyclic proteins are interesting because, compared to conventional proteins, they have increased stability and enhanced binding affinity and therefore can potentially be developed as protein drugs. The new CyBase release features a redesigned interface and internal architecture to improve user-interactivity, collates double the amount of data compared to the initial release, and hosts a novel suite of tools that are useful for the visualization, characterization and engineering of cyclic proteins. These tools comprise sequence/structure 2D representations, a summary of grafting and mutation studies of synthetic analogues, a study of N- to C-terminal distances in known protein structures and a structural modelling tool to predict the best linker length to cyclize a protein. These updates are useful because they have the potential to help accelerate the discovery of naturally occurring cyclic proteins and the engineering of cyclic protein drugs. The new release of CyBase is available at http://research1t.imb.uq.edu.au/cybase. PMID:17986451

  13. TURBULENT SHEAR ACCELERATION

    SciTech Connect

    Ohira, Yutaka, E-mail: ohira@phys.aoyama.ac.jp [Department of Physics and Mathematics, Aoyama Gakuin University, 5-10-1 Fuchinobe, Sagamihara 252-5258 (Japan)

    2013-04-10

    We consider particle acceleration by large-scale incompressible turbulence with a length scale larger than the particle mean free path. We derive an ensemble-averaged transport equation of energetic charged particles from an extended transport equation that contains the shear acceleration. The ensemble-averaged transport equation describes particle acceleration by incompressible turbulence (turbulent shear acceleration). We find that for Kolmogorov turbulence, the turbulent shear acceleration becomes important on small scales. Moreover, using Monte Carlo simulations, we confirm that the ensemble-averaged transport equation describes the turbulent shear acceleration.

  14. Superplastic deformation induced by cyclic hydrogen charging

    SciTech Connect

    Choe, Heeman; Schuh, Christopher A.; Dunand, David C. [School of Advanced Materials Engineering, Kookmin University, Chungneung-dong, Songbuk-ku, Seoul 136-702 (Korea, Republic of); Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208 (United States)

    2008-05-15

    Deformation under the combined action of external stress and cyclic hydrogen charging/discharging is studied in a model material, titanium. Cyclic charging with hydrogen is carried out at 860 deg. C, which repeatedly triggers the transformation between hydrogen-lean {alpha}-Ti and hydrogen-rich {beta}-Ti. Due to bias from the externally applied tensile stress, the internal mismatch strains produced by this isothermal {alpha}-{beta} transformation accumulate preferentially along the loading axis. These strain increments are linearly proportional to the applied stress, i.e., flow is ideally Newtonian, at small stress levels (below {approx}2 MPa). Therefore, after multiple chemical cycles, a tensile engineering strain of 100% is achieved without fracture, with an average strain rate of 10{sup -5} s{sup -1}, which demonstrates for the first time that superplastic elongations can be achieved by chemical cycling. The effect of hydrogen partial pressure, cycle time, and external stress on the value of the superplastic strain increments is experimentally measured and discussed in light of a diffusional phase transformation model. Special attention is paid to understanding the two contributions to the internal mismatch strains from the phase transformation and lattice swelling.

  15. Effects of Cyclic Hydraulic Pressure on Osteocytes

    PubMed Central

    Liu, Chao; Zhao, Yan; Cheung, Wing-Yee; Gandhi, Ronak; Wang, Liyun; You, Lidan

    2010-01-01

    Bone is able to adapt its composition and structure in order to suit its mechanical environment. Osteocytes, bone cells embedded in the calcified matrix, are believed to be the mechanosensors and responsible for orchestrating the bone remodeling process. Recent in vitro studies have shown that osteocytes are able to sense and respond to substrate strain and fluid shear. However the capacity of osteocytes to sense cyclic hydraulic pressure (CHP) associated with physiological mechanical loading is not well understood. In this study, we subjected osteocyte-like MLO-Y4 cells to controlled CHP of 68 kPa at 0.5 Hz, and investigated the effects of CHP on intracellular calcium concentration, cytoskeleton organization, mRNA expression of genes related to bone remodeling, and osteocyte apoptosis. We found that osteocytes were able to sense CHP and respond by increased intracellular calcium concentration, altered microtubule organization, a time-dependent increase in COX-2 mRNA level and RANKL/OPG mRNA ratio, and decreased apoptosis. These findings support the hypothesis that loading induced cyclic hydraulic pressure in bone serves as a mechanical stimulus to osteocytes and may play a role in regulating bone remodeling in vivo. PMID:20149907

  16. Cyclic Vomiting Presentations Following Marijuana Liberalization in Colorado

    PubMed Central

    Kim, Howard S.; Anderson, John D.; Saghafi, Omeed; Heard, Kennon J.; Monte, Andrew A.

    2015-01-01

    Objectives Case reports have described a syndrome of cyclic vomiting associated with chronic marijuana use, termed cannabinoid hyperemesis syndrome. The primary objective was to determine the prevalence of patients presenting with cyclic vomiting before and after the liberalization of medical marijuana in Colorado in 2009. The secondary objective was to describe the odds of marijuana use among cyclic vomiting visits in these same time periods. Methods This was a cross-sectional study of cyclic vomiting visits to the emergency department (ED) before and after marijuana liberalization. ED visits with International Classification of Diseases, ninth revision, coding for cyclic vomiting or that met diagnostic criteria for cyclic vomiting by the Rome III criteria were included. Results The authors reviewed 2,574 visits and identified 36 patients diagnosed with cyclic vomiting over 128 visits. The prevalence of cyclic vomiting visits increased from 41 per 113,262 ED visits to 87 per 125,095 ED visits after marijuana liberalization, corresponding to a prevalence ratio of 1.92 (95% confidence interval [CI] = 1.33 to 2.79). Patients with cyclic vomiting in the postliberalization period were more likely to have marijuana use documented than patients in the preliberalization period (odds ratio = 3.59, 95% CI = 1.44 to 9.00). Conclusions The prevalence of cyclic vomiting presentations nearly doubled after the liberalization of medical marijuana. Patients presenting with cyclic vomiting in the postliberalization period were more likely to endorse marijuana use, although it is unclear whether this was secondary to increased marijuana use, more accurate marijuana reporting, or both. PMID:25903855

  17. Timescale Correlation between Marine Atmospheric Exposure and Accelerated Corrosion Testing

    NASA Technical Reports Server (NTRS)

    Montgomery, Eliza L.; Calle, Luz Marina; Curran, Jerone C.; Kolody, Mark R.

    2011-01-01

    Evaluation of metal-based structures has long relied on atmospheric exposure test sites to determine corrosion resistance in marine environments. Traditional accelerated corrosion testing relies on mimicking the exposure conditions, often incorporating salt spray and ultraviolet (UV) radiation, and exposing the metal to continuous or cyclic conditions of the corrosive environment. Their success for correlation to atmospheric exposure is often a concern when determining the timescale to which the accelerated tests can be related. Accelerated laboratory testing, which often focuses on the electrochemical reactions that occur during corrosion conditions, has yet to be universally accepted as a useful tool in predicting the long term service life of a metal despite its ability to rapidly induce corrosion. Although visual and mass loss methods of evaluating corrosion are the standard and their use is imperative, a method that correlates timescales from atmospheric exposure to accelerated testing would be very valuable. This work uses surface chemistry to interpret the chemical changes occurring on low carbon steel during atmospheric and accelerated corrosion conditions with the objective of finding a correlation between its accelerated and long-term corrosion performance. The current results of correlating data from marine atmospheric exposure conditions at the Kennedy Space Center beachside corrosion test site, alternating seawater spray, and immersion in typical electrochemical laboratory conditions, will be presented. Key words: atmospheric exposure, accelerated corrosion testing, alternating seawater spray, marine, correlation, seawater, carbon steel, long-term corrosion performance prediction, X-ray photoelectron spectroscopy.

  18. Linear Accelerator (LINAC)

    MedlinePLUS

    ... equipment? How is safety ensured? What is this equipment used for? A linear accelerator (LINAC) is the ... pg=stereotactic) . top of page How does the equipment work? View larger with caption The linear accelerator ...

  19. Accelerator Technology Division

    NASA Astrophysics Data System (ADS)

    1992-04-01

    In fiscal year (FY) 1991, the Accelerator Technology (AT) division continued fulfilling its mission to pursue accelerator science and technology and to develop new accelerator concepts for application to research, defense, energy, industry, and other areas of national interest. This report discusses the following programs: The Ground Test Accelerator Program; APLE Free-Electron Laser Program; Accelerator Transmutation of Waste; JAERI, OMEGA Project, and Intense Neutron Source for Materials Testing; Advanced Free-Electron Laser Initiative; Superconducting Super Collider; The High-Power Microwave Program; (Phi) Factory Collaboration; Neutral Particle Beam Power System Highlights; Accelerator Physics and Special Projects; Magnetic Optics and Beam Diagnostics; Accelerator Design and Engineering; Radio-Frequency Technology; Free-Electron Laser Technology; Accelerator Controls and Automation; Very High-Power Microwave Sources and Effects; and GTA Installation, Commissioning, and Operations.

  20. Acceleration of Gravity 1

    NSDL National Science Digital Library

    Michael Horton

    2009-05-30

    This lab is a Level 2 inquiry activity that should be taught after students understand acceleration but before they learn the equations for calculating the acceleration of a body dropped from a certain height. After this activity, students should understa

  1. Improved plasma accelerator

    NASA Technical Reports Server (NTRS)

    Cheng, D. Y.

    1971-01-01

    Converging, coaxial accelerator electrode configuration operates in vacuum as plasma gun. Plasma forms by periodic injections of high pressure gas that is ionized by electrical discharges. Deflagration mode of discharge provides acceleration, and converging contours of plasma gun provide focusing.

  2. Accelerating Particles with Plasma

    SciTech Connect

    Litos, Michael; Hogan, Mark

    2014-11-05

    Researchers at SLAC explain how they use plasma wakefields to accelerate bunches of electrons to very high energies over only a short distance. Their experiments offer a possible path for the future of particle accelerators.

  3. Oxidations of cyclic {beta}-diketones catalyzed by methylrhenium trioxide

    SciTech Connect

    Abu-Omar, M.M.; Espenson, J.H. [Ames Lab., IA (United States)] [Ames Lab., IA (United States); [Iowa State Univ., Ames, IA (United States)

    1996-08-06

    Methylrhenium trioxide (CH{sub 3}ReO{sub 3} or MTO) catalyzes the oxidation of {beta}-diketones by hydrogen peroxide. The kinetics of the initial oxidation step have been investigated in CH{sub 3}CN/H{sub 2}O (1:1 v/v) at 25{degree}C for a group of cyclic {beta}-diketones. The initial oxidation step features the enol form, the majority species, as the reactant. Its rate responds to substituents in the `normal` manner: electron-donating groups accelerate the reaction. We suggest that the double bond of the enol attacks a peroxo oxygen of a peroxorhenium complex A = CH{sub 3}Re(O){sub 2}(O{sub 2}) or B = CH{sub 3}Re(O)(O{sub 2}){sub 2}(H{sub 2}O). This reaction affords a 2-hydroxy-1,3-dicarbonyl intermediate, which in some instances was detected by {sup 1}H NMR. This hydroxy intermediate is susceptible to cleavage via a Baeyer-Villiger oxidation to yield carboxylic acids as final products. In contrast to the first reaction, this step may feature the peroxorhenium complexes A and B as nucleophiles rather than their customary electrophilic behavior; perhaps the trend is reversed by substrate binding to rhenium. Time profiles for the different stages of the reaction were also determined. The mechanistic aspects of these multistep catalytic oxidations are discussed in terms of the electronic nature of the activated rhenium-bound peroxo ligands. 38 refs., 3 figs., 3 tabs.

  4. Swimming in Spacetime: Motion by Cyclic Changes in Body Shape

    E-print Network

    Wisdom, Jack

    Swimming in Spacetime: Motion by Cyclic Changes in Body Shape Jack Wisdom Cyclic changes in the shape of a quasi-rigid body on a curved manifold can lead to net translation and/or rotation of the body changes in the shape of a body, without any external forces. The motion of a swimmer at low Reynolds

  5. Cyclic and Tangential Polygons 1: Extending a Familiar Concept

    ERIC Educational Resources Information Center

    Lopez-Real, Francis

    2002-01-01

    This article "opens up" the study of the relationship between quadrilaterals and circles to two sets of quadrilaterals--those that can be drawn either inside (cyclic) or outside (tangential) a circle (or both). Of course, "all" triangles are both cyclic and tangential. Or, to use the traditional Euclidean language for triangles, a unique…

  6. Spherical Cyclic Motions in Euclidean Space E3

    E-print Network

    Mehdi Jafari; Yusuf Yayli

    2015-05-20

    By considering a spatial curve in a Euclidean space, we use its components, together with attaining a cyclic matrix, to show that this matrix is homothetic too and is in correspondence with a homothetic motion. Furthermore, if the curve lies on a unit sphere, then the motion is a spherical cyclic motion.

  7. MICROWAVE-ASSISTED PREPARATION OF CYCLIC UREAS FROM DIAMINES

    EPA Science Inventory

    Rajender S. Varma* and Yong-Jin Kim Cyclic ureas are useful intermediates for a variety of pharmaceuticals and pesticides. One of the attractive approaches for the synthesis of cyclic ureas uses condensation of diamines with urea as a carbonyl source under dynamic evacuation. ...

  8. Introduction Mammalian mastication is a rhythmic, cyclic activity, the

    E-print Network

    mammalian mastication provides insight into force modulation in rhythmic, cyclic behaviors. This study uses1046 Introduction Mammalian mastication is a rhythmic, cyclic activity, the rhythmic components during rhythmic mastication in mammals: (1) that bite force is modulated by varying the duration of force

  9. The cyclic prefix of OFDM\\/DMT - an analysis

    Microsoft Academic Search

    Werner Henkel; Georg Taubock; Per Odling; Per Ola Borjesson; Niklas Petersson

    2002-01-01

    We address the impact of a too short cyclic prefix on multicarrier systems such as orthogonal frequency division multiplexing (OFDM) and discrete multitone (DMT). The main result is that the intersymbol interference (ISI) and intercarrier interference (ICI) may be spectrally concentrated and analytical expressions showing this are given. A practical implication is, e.g., that the cyclic prefix in some xDSL

  10. An alternative model of pro-cyclical absenteeism

    Microsoft Academic Search

    Kim Kaivanto

    1997-01-01

    Current economic models of absenteeism derive pro-cyclical properties from cyclical variations in the costs and consequences of absence. Through an extension of the household production model, this paper proposes a complementary approach based on variations in forgone earnings associated with work-commodity itself.

  11. Variation potential influence on photosynthetic cyclic electron flow in pea

    PubMed Central

    Sukhov, Vladimir; Surova, Lyubov; Sherstneva, Oksana; Katicheva, Lyubov; Vodeneev, Vladimir

    2015-01-01

    Cyclic electron flow is an important component of the total photosynthetic electron flow and participates in adaptation to the action of stressors. Local leaf stimulation induces electrical signals, including variation potential (VP), which inactivate photosynthesis; however, their influence on cyclic electron flow has not been investigated. The aim of this study was to investigate VP's influence on cyclic electron flow in pea (Pisum sativum L.). VP was induced in pea seedling leaves by local heating and measured in an adjacent, undamaged leaf by extracellular electrodes. CO2 assimilation was measured using a portable gas exchange measuring system. Photosystem I and II parameters were investigated using a measuring system for simultaneous assessment of P700 oxidation and chlorophyll fluorescence. Heating-induced VP reduced CO2 assimilation and electron flow through photosystem II. In response, cyclic electron flow rapidly decreased and subsequently slowly increased. Slow increases in cyclic flow were caused by decreased electron flow through photosystem II, which was mainly connected with VP-induced photosynthetic dark stage inactivation. However, direct influence by VP on photosystem I also participated in activation of cyclic electron flow. Thus, VP, induced by local leaf-heating, activated cyclic electron flow in undamaged leaves. This response was similar to photosynthetic changes observed under the direct action of stressors. Possible mechanisms of VP's influence on cyclic flow were discussed. PMID:25610447

  12. Cyclic neutropenia in mammals Jorge M. Pacheco,1

    E-print Network

    Traulsen, Arne

    species. The fact that it correctly accounts simultaneously for the cycling periods in dogs and humansCyclic neutropenia in mammals Jorge M. Pacheco,1 Arne Traulsen,2 Tibor Antal,3 and David Dingli4 * Cyclic neutropenia (CN) has been well documented in humans and the gray collie. A recent model

  13. Nitric Oxide/Cyclic Guanosine Monophosphate Signaling in the Central

    E-print Network

    Ganter, Geoffrey

    Nitric Oxide/Cyclic Guanosine Monophosphate Signaling in the Central Complex of the Grasshopper oxide/cyclic guanosine monophosphate (cGMP) signaling pathway. The nitric oxide-donor sodium inhibited singing. To identify pu- tative sources of nitric oxide, brains of Ch. biguttulus were subjected

  14. Cyclic deformation behavior of steels and light-metal alloys

    Microsoft Academic Search

    Frank Walther; Dietmar Eifler

    2007-01-01

    The detailed knowledge of the cyclic deformation behavior of metallic materials is an essential condition for the comprehensive understanding of fatigue mechanisms and a reliable lifetime calculation of cyclically loaded specimens and components. Various steels and light-metal alloys were investigated under stress and strain control on servohydraulic testing systems. In addition to mechanical stress–strain hysteresis measurements, the changes of the

  15. Mathematical Modeling of Stress Fiber Reorganization Induced by Cyclic Stretch 

    E-print Network

    Hsu, Hui-Ju

    2010-01-14

    patterns of strain. There is much evidence that cyclic uniaxial strain results in a perpendicular orientation of ECs and their stress fibers, while no such alignment occurs in response to cyclic equaibiaxial stretch. It is unclear how cells and their stress...

  16. Blind Block Synchronization Algorithms in Cyclic Prefix Systems

    E-print Network

    Vaidyanathan, P. P.

    reported algorithms in presence of noise. 1 I. INTRODUCTION Blind channel identification in cyclic prefixBlind Block Synchronization Algorithms in Cyclic Prefix Systems Borching Su Department synchronization problem is especially important in many blind channel estimation algorithms in the literature

  17. High-Temperature Cyclic Oxidation Data, Volume 1

    NASA Technical Reports Server (NTRS)

    Barrett, C. A.; Garlick, R. G.; Lowell, C. E.

    1984-01-01

    This first in a series of cyclic oxidation handbooks contains specific-weight-change-versus-time data and X-ray diffraction results derived from high-temperature cyclic tests on high-temperature, high-strength nickel-base gamma/gamma' and cobalt-base turbine alloys. Each page of data summarizes a complete test on a given alloy sample.

  18. Synthesis of Cyclic Guanidines via Pd-Catalyzed Alkene Carboamination

    PubMed Central

    Zavesky, Blane P.; Babij, Nicholas R.; Fritz, Jonathan A.

    2013-01-01

    A new approach to the synthesis of substituted 5-membered cyclic guanidines is described. Palladium-catalyzed alkene carboamination reactions between acyclic N-allyl guanidines and aryl or alkenyl halides provide these products in good yield. This method allows access to a number of different cyclic guanidine derivatives in only two steps from readily available allylic amines. PMID:24147839

  19. Mechanical degradation of coating systems in high temperature cyclic oxidation

    Microsoft Academic Search

    R. C. Pennefather; D. H. Boone

    1996-01-01

    Cyclic oxidation tests were performed on a large variety of commercially available overlay coatings. The results of cyclic oxidation tests confirmed that the composition of the coating as well as the processing method of the coating can affect the life of the system. Coating life was determined by the time to coating penetration and initiation of substrate attack. As this

  20. Force, mass and acceleration

    Microsoft Academic Search

    Phil Dalrymple; Richard Griffiths

    2005-01-01

    Force, mass and acceleration are everyday words but often used inaccurately. Force is a physical influence, which when applied to an object causes it to accelerate in the direction from which it was applied. Mass is the amount of matter in an object and is expressed in kilograms. Acceleration is the rate of change of velocity of an object in

  1. Multistage induction mass accelerator

    Microsoft Academic Search

    T. J. Burgess; M. Cowan

    1984-01-01

    The present investigation has the objective to discuss considerations which define the design and performance of a multistage, coaxial induction mass accelerator operating at high magnetic energy density. A review is presented of the magnetohydrodynamic computational model required to design, in detail, a high energy density, coaxial, magnetic induction mass accelerator. Attention is given to the derivation of the accelerator

  2. Direction of Acceleration

    NSDL National Science Digital Library

    Mary Spaulding, Clearbrook-Gonvick Public School, Clearbrook Minnesota, based on an original activity from Physics Principles and Problems (1995) page 75.

    In this short lab, students observe the movement of an air bubble in a small level, attached to a toy truck, as it is moved from a stop, to a steady speed and back to a stop. This gives a visual to the concepts positive acceleration, zero acceleration and negative acceleration.

  3. Acceleration: It's Elementary

    ERIC Educational Resources Information Center

    Willis, Mariam

    2012-01-01

    Acceleration is one tool for providing high-ability students the opportunity to learn something new every day. Some people talk about acceleration as taking a student out of step. In actuality, what one is doing is putting a student in step with the right curriculum. Whole-grade acceleration, also called grade-skipping, usually happens between…

  4. Acceleration-Induced Nonlocality

    E-print Network

    Bahram Mashhoon

    2003-01-17

    The standard relativistic theory of accelerated reference frames in Minkowski spacetime is described. The measurements of accelerated observers are considered and the limitations of the standard theory, based on the hypothesis of locality, are pointed out. The physical principles of the nonlocal theory of accelerated observers are presented. The implications of the nonlocal theory are briefly discussed.

  5. Angular Acceleration without Torque?

    ERIC Educational Resources Information Center

    Kaufman, Richard D.

    2012-01-01

    Hardly. Just as Robert Johns qualitatively describes angular acceleration by an internal force in his article "Acceleration Without Force?" here we will extend the discussion to consider angular acceleration by an internal torque. As we will see, this internal torque is due to an internal force acting at a distance from an instantaneous center.

  6. Compensation for the Variable Cyclic Error in Homodyne Laser Interferometers

    PubMed Central

    Hu, Pengcheng; Zhu, Jinghao; Guo, Xuanbiao; Tan, Jiubin

    2015-01-01

    This paper presents a real-time method to compensate for the variable cyclic error in a homodyne laser interferometer. The parameters describing the quadrature signals of the interferometer are estimated using simple peak value detectors. The cyclic error in the homodyne laser interferometer was then corrected through simple arithmetic calculations of the quadrature signals. A field programmable gate array was utilized for the real-time compensation of the cyclic error in a homodyne laser interferometer. The simulation and experimental results indicated that the proposed method could provide a cyclic error that was fixed without compensation down to a value under 0.6 nm in a homodyne laser interferometer. The proposed method could also reduce the time-varying cyclic error to a value under 0.6 nm in a homodyne laser interferometer, in contrast to the equivalent value of 13.3 nm for a conventional elliptical fitting method. PMID:25647739

  7. Statistical cyclicity of the supercontinent cycle

    NASA Astrophysics Data System (ADS)

    Rolf, T.; Coltice, N.; Tackley, P. J.

    2014-04-01

    Supercontinents like Pangea impose a first-order control on Earth's evolution as they modulate global heat loss, sea level, climate, and biodiversity. In a traditional view, supercontinents form and break up in a regular, perhaps periodic, manner in a cycle lasting several 100 Myr as reflected in the assembly times of Earth's major continental aggregations: Columbia, Rodinia, and Pangea. However, modern views of the supercontinent cycle propose a more irregular evolution on the basis of an improved understanding of the Precambrian geologic record. Here we use fully dynamic spherical mantle convection models featuring plate-like behavior and continental drift to investigate supercontinent formation and breakup. We further dismiss the concept of regularity but suggest a statistical cyclicity in which the supercontinent cycle may have a characteristic period imposed by mantle and lithosphere properties, but this is hidden in immense fluctuations between different cycles that arise from the chaotic nature of mantle flow.

  8. Quasi-Cyclic Asymptotically Regular LDPC Codes

    E-print Network

    Mitchell, David G M; Lentmaier, Michael; Costello, Daniel J

    2010-01-01

    Families of "asymptotically regular" LDPC block code ensembles can be formed by terminating (J,K)-regular protograph-based LDPC convolutional codes. By varying the termination length, we obtain a large selection of LDPC block code ensembles with varying code rates, minimum distance that grows linearly with block length, and capacity approaching iterative decoding thresholds, despite the fact that the terminated ensembles are almost regular. In this paper, we investigate the properties of the quasi-cyclic (QC) members of such an ensemble. We show that an upper bound on the minimum Hamming distance of members of the QC sub-ensemble can be improved by careful choice of the component protographs used in the code construction. Further, we show that the upper bound on the minimum distance can be improved by using arrays of circulants in a graph cover of the protograph.

  9. Cyclic steps incised on experimental bedrock

    NASA Astrophysics Data System (ADS)

    Yokokawa, M.; Kyogoku, A.; Kotera, A.; Izumi, N.

    2013-12-01

    In rivers flowing in mountain areas, a series of steps are often observed on bedrock. They are thought to be cyclic steps formed due to erosion of bedrock, which should be driven by abrasion due to bedload sediment transport. We demonstrated a series of flume experiments of the formation of cyclic steps on bedrock by abrasion due to bedload transportation using weak mortar as the model bedrock. We also compared the shapes of the steps reproduced in the experiments with those obtained in the analysis. The experiments were conducted using a 1.5 m long, 2 cm wide, and 20 cm deep flume made of glass in Osaka Institute of Technology. The flume has 10-cm-high weirs at both ends, so that there is a 10-cm-deep reservoir. We put mortar into the reservoir and hardened it. In order to make a highly erodible mortar, we casted the mortar with extremely low amount of cement. The ratio of cement, sand (0.2 mm in diameter), and water is x:150:50 (x ranges 1-3). The flume is tilted by 10 degrees. The water and colored sand is supplied from a head tank to the upstream end of the flume, flows on 'model bedrock' in the flume, and was dropped from the downstream end. We observed morphological changes of the surface of the bedrock by photos. We also used a laser displacement sensor to measure the surface topography of the 'model bedrock' before and after each run. The configuration of steps largely depends on the hardness of model bedrocks. In the case of the softest model bedrock (cement-sand-water ratio is 1:150:50) with small amount of sand, long-drawn potholes tend to be formed. Clear cyclic steps are formed on harder model bedrocks with large cement-sand-water ratios such as 2:150:50 and 3:150:50. When a series of steps are formed on the bed, typical wavelength and wave height are approximately 20 cm, and 2 - 3 cm, respectively. The general shape of a step is characterized by a relatively long downward-inclined slope just upstream of a short upward-inclined slope. The feature of the step shape has been predicted by the mathematical model (Izumi et al., 2012). Among three cases of sediment supply: 1 g/sec, 3 g/sec, and 6 g/sec with fixed water discharge (52 g/sec), the erosion rate was maximized in the cases of the sediment supply of 3 g/sec both in the cement-sand-water ratios of 2:150:50 and 3:150:50. The erosion rate is higher in the case of the moderate amount of sediment supply rather than in the case of the largest amount of sediment supply in which the alluvial cover effect inhibited erosion. This result is consistent with that observed in previous studies (Sklar & Dietrich, 2004; Johnson & Whipple, 2010). References Izumi, N., Yokokawa, M. & Parker G. 2012. Cyclic step morphology formed on bedrock. Annual Journal of Hydraulic Engineering 68(4) : I_955-I_960. Johnson, J.P.L. & Whipple, K.X. 2010. Evaluating the controls of shear stress, sediment supply, alluvial cover, and channel morphology on experimental bedrock incision rate. Journal of Geophysical Research 115, F02018, doi:10.1029/2009JF001335. Sklar, L.S. & Dietrich, W.E. 2004. A mechanistic model for river incision into bedrock by sultating bedload. Water Resources Re-search 40, W06301, doi:10.1029/2003WR002496.

  10. Cyclic phosphatidic acid relieves osteoarthritis symptoms

    PubMed Central

    2014-01-01

    Background Cyclic phosphatidic acid (cPA) is a naturally occurring phospholipid mediator with a unique cyclic phosphate ring at the sn-2 and sn-3 positions of its glycerol backbone. Natural cPA and its chemically stabilized cPA derivative, 2-carba-cPA (2ccPA), inhibit chronic and acute inflammation, and 2ccPA attenuates neuropathic pain. Osteoarthritis (OA) is a degenerative disease frequently associated with symptoms such as inflammation and joint pain. Because 2ccPA has obvious antinociceptive activity, we hypothesized that 2ccPA might relieve the pain caused by OA. We aimed to characterize the effects of 2ccPA on the pathogenesis of OA induced by total meniscectomy in the rabbit knee joint. Results Intra-articular injection of 2ccPA (twice a week for 42 days) significantly reduced pain and articular swelling. Histopathology showed that 2ccPA suppressed cartilage degeneration in OA. We also examined the effects of 2ccPA on the inflammatory and catabolic responses of human OA synoviocytes and chondrosarcoma SW1353 cells in vitro. 2ccPA stimulated synthesis of hyaluronic acid and suppressed production of the metalloproteinases MMP-1, -3, and -13. However, it had no effect on the production of interleukin (IL)-6, an inflammatory cytokine. The suppressive effect of 2ccPA on MMP-1 and -3 production in synoviocytes and on MMP-13 production in SW1353 cells was not mediated by the lysophosphatidic acid receptor, LPA1 receptor (LPA1R). Conclusions Our results suggest that 2ccPA significantly reduces the pain response to OA by inducing hyaluronic acid production and suppressing MMP-1, -3, and -13 production in synoviocytes and chondrocytes. PMID:25123228

  11. Globally synchronized oscillations in complex cyclic games.

    PubMed

    Rulquin, Charlotte; Arenzon, Jeferson J

    2014-03-01

    The rock-paper-scissors game and its generalizations with S>3 species are well-studied models for cyclically interacting populations. Four is, however, the minimum number of species that, by allowing other interactions beyond the single, cyclic loop, breaks both the full intransitivity of the food graph and the one-predator, one-prey symmetry. Lütz et al. [J. Theor. Biol. 317, 286 (2013)] have shown the existence, on a square lattice, of two distinct phases, with either four or three coexisting species. In both phases, each agent is eventually replaced by one of its predators, but these strategy oscillations remain localized as long as the interactions are short ranged. Distant regions may be either out of phase or cycling through different food-web subloops (if any). Here we show that upon replacing a minimum fraction Q of the short-range interactions by long-range ones, there is a Hopf bifurcation, and global oscillations become stable. Surprisingly, to build such long-distance, global synchronization, the four-species coexistence phase requires fewer long-range interactions than the three-species phase, while one would naively expect the opposite to be true. Moreover, deviations from highly homogeneous conditions (?=0 or 1) increase Qc, and the more heterogeneous is the food web, the harder the synchronization is. By further increasing Q, while the three-species phase remains stable, the four-species one has a transition to an absorbing, single-species state. The existence of a phase with global oscillations for S>3, when the interaction graph has multiple subloops and several possible local cycles, leads to the conjecture that global oscillations are a general characteristic, even for large, realistic food webs. PMID:24730816

  12. Ali Fatemi-University of Toledo All Rights Reserved Chapter 5-Cyclic Deformation & e-N Approach 1 CYCLIC DEFORMATION &

    E-print Network

    Fatemi, Ali

    Ali Fatemi-University of Toledo All Rights Reserved Chapter 5-Cyclic Deformation & e-N Approach 1 INFLUENCING STRAIN-LIFE BEHAVIOR #12;Ali Fatemi-University of Toledo All Rights Reserved Chapter 5-Cyclic Deformation & e-N Approach 2 MONOTONIC TENSION TEST AND STRESS-STRAIN BEHAVIOR #12;Ali Fatemi

  13. Compact Plasma Accelerator

    NASA Technical Reports Server (NTRS)

    Foster, John E.

    2004-01-01

    A plasma accelerator has been conceived for both material-processing and spacecraft-propulsion applications. This accelerator generates and accelerates ions within a very small volume. Because of its compactness, this accelerator could be nearly ideal for primary or station-keeping propulsion for spacecraft having masses between 1 and 20 kg. Because this accelerator is designed to generate beams of ions having energies between 50 and 200 eV, it could also be used for surface modification or activation of thin films.

  14. Entanglement of Accelerating Particles

    E-print Network

    W. L. Ku; M. -C. Chu

    2007-09-03

    We study how the entanglement of a maximally entangled pair of particles is affected when one or both of the pair are uniformly accelerated, while the detector remains in an inertial frame. We find that the entanglement is unchanged if all degrees of freedom are considered. However, particle pairs are produced, and the entanglements of different bipartite systems may change with the acceleration. In particular, the entanglement between accelerating fermions is transferred preferentially to the produced antiparticles when the acceleration is large, and the entanglement transfer is complete when the acceleration approaches infinity. However, for scalar particles, no entanglement transfer to the antiparticles is observed.

  15. Accelerations in Flight

    NASA Technical Reports Server (NTRS)

    Doolittle, J H

    1925-01-01

    This work on accelerometry was done at McCook Field for the purpose of continuing the work done by other investigators and obtaining the accelerations which occur when a high-speed pursuit airplane is subjected to the more common maneuvers. The accelerations obtained in suddenly pulling out of a dive with well-balanced elevators are shown to be within 3 or 4 per cent of the theoretically possible accelerations. The maximum acceleration which a pilot can withstand depends upon the length of time the acceleration is continued. It is shown that he experiences no difficulty under the instantaneous accelerations as high as 7.8 G., but when under accelerations in excess of 4.5 G., continued for several seconds, he quickly loses his faculties.

  16. High brightness electron accelerator

    DOEpatents

    Sheffield, Richard L. (Los Alamos, NM); Carlsten, Bruce E. (Los Alamos, NM); Young, Lloyd M. (Los Alamos, NM)

    1994-01-01

    A compact high brightness linear accelerator is provided for use, e.g., in a free electron laser. The accelerator has a first plurality of acclerating cavities having end walls with four coupling slots for accelerating electrons to high velocities in the absence of quadrupole fields. A second plurality of cavities receives the high velocity electrons for further acceleration, where each of the second cavities has end walls with two coupling slots for acceleration in the absence of dipole fields. The accelerator also includes a first cavity with an extended length to provide for phase matching the electron beam along the accelerating cavities. A solenoid is provided about the photocathode that emits the electons, where the solenoid is configured to provide a substantially uniform magnetic field over the photocathode surface to minimize emittance of the electons as the electrons enter the first cavity.

  17. Phorbol esters modulate cyclic AMP accumulation in porcine thyroid cells

    SciTech Connect

    Emoto, T.; Kasai, K.; Hiraiwa, M.; Shimoda, S.

    1988-01-01

    In cultured porcine thyroid cells, during 60 min incubation phorbol 12-myristate 13-acetate (PMA) had no effect on basal cyclic AMP accumulation and slightly stimulated cyclic AMP accumulation evoked by thyroid stimulating hormone (TSH) or forskolin. Cholera toxin-induced cyclic AMP accumulation was significantly stimulated by PMA. On the other hand, cyclic AMP accumulation evoked by prostaglandin E/sub 1/ or E/sub 2/ (PGE/sub 1/ and PGE/sub 2/) was markedly depressed by simultaneous addition of PMA. These opposing effects of PMA on cyclic AMP accumulation evoked by PGE and cholera toxin were observed in a dose-related fashion, with half-maximal effect of around 10/sup -9/ M in either case. The almost same effects of PMA on cyclic AMP accumulation in basal and stimulated conditions were also observed in freshly prepared thyroid cells. The present study was performed in the presence of phosphodiesterase inhibitor, 3-iso-butyl-1-methylxanthine (IBMX), indicating that PMA affected adenylate cyclase activity. Therefore, it is suggested that PMA may modulate the production of cyclic AMP in response to different stimuli, possibly by affecting several sites in the adenylate cyclase complex in thyroid cells.

  18. A cyclic model of the universe.

    PubMed

    Steinhardt, Paul J; Turok, Neil

    2002-05-24

    We propose a cosmological model in which the universe undergoes an endless sequence of cosmic epochs that begin with a "bang" and end in a "crunch." Temperature and density at the transition remain finite. Instead of having an inflationary epoch, each cycle includes a period of slow accelerated expansion (as recently observed) followed by contraction that produces the homogeneity, flatness, and energy needed to begin the next cycle. PMID:11976408

  19. On quantum codes obtained from cyclic codes over A2

    NASA Astrophysics Data System (ADS)

    Dertli, Abdullah; Cengellenmis, Yasemin; Eren, Senol

    2015-05-01

    In this paper, quantum codes from cyclic codes over A2 = F2 + uF2 + vF2 + uvF2, u2 = u, v2 = v, uv = vu, for arbitrary length n have been constructed. It is shown that if C is self orthogonal over A2, then so is ?(C), where ? is a Gray map. A necessary and sufficient condition for cyclic codes over A2 that contains its dual has also been given. Finally, the parameters of quantum error correcting codes are obtained from cyclic codes over A2.

  20. Accurate simulations of planar topological codes cannot use cyclic boundaries

    NASA Astrophysics Data System (ADS)

    Fowler, Austin G.

    2013-06-01

    Cyclic boundaries are used in many branches of physics and mathematics, typically to assist the approximation of a large space. We show that when determining the performance of planar, fault-tolerant, topological quantum error correction, using cyclic boundaries leads to a significant underestimate of the logical error rate. We present cyclic and noncyclic surface code simulations exhibiting this discrepancy and analytic formulas precisely reproducing the observed behavior in the limit of low physical error. These asymptotic formulas are then used to prove that the underestimate is exponentially large in the code distance d at any fixed physical error rate p below the threshold error rate pth.

  1. Maternal inheritance in cyclic vomiting syndrome.

    PubMed

    Boles, Richard G; Adams, Kathleen; Li, B U K

    2005-02-15

    Cyclic vomiting syndrome (CVS), characterized by severe discrete episodes of nausea, vomiting, and lethargy, is a fairly common, disabling, predominately-childhood condition most often associated with migraine and dysautonomic features. Our group recently reported that children with CVS and additional neuromuscular disease manifestations demonstrate strong maternal inheritance of multiple disease manifestations and abnormal urine organic acids, suggesting the presence of predisposing mitochondrial DNA (mtDNA) sequence variants. In order to determine if maternal inheritance is present in CVS in general, a clinical interview was administered regarding 80 unrelated individuals with CVS ascertained randomly from the database of the Cyclic Vomiting Syndrome Association (CVSA). Disease manifestations consistent with potential mitochondrial dysfunction were far more common in matrilineal (sharing the same mtDNA sequence) versus in non-matrilineal relatives, including mothers versus fathers (P = 3 x 10(-9)) and maternal versus paternal grandmothers (P = 2 x 10(-6)). Maternal inheritance is suggested in 52% of the 23 subjects with two or more neuromuscular abnormalities ("CVS+") and in 54% of the 44 subjects without any neuromuscular abnormalities ("CVS-"). In both the CVS+ and CVS- sub-groups, subjects, and affected matrilineal relatives of all ages suffer at a far higher incidence from several dysautonomic-related conditions, including migraine and irritable bowel, as well as depression and hypothyroidism, while neuromuscular and cognitive disorders such as hypotonia and ADHD are common only in affected children. We conclude that mtDNA sequences predispose towards the development of protean disease manifestations in CVS patients ascertained through a disease-specific association, as well as among their matrilineal relatives, whether or not neuromuscular disease is present in the proband. Since CVS was absent in all but one matrilineal relative of our probands, CVS is apparently a rare clinical presentation in individuals carrying the predisposing mtDNA sequences. The four conditions reported most frequently among the matrilineal relatives of our cases, migraine, depression, irritable bowel, and hypothyroidism, are known to segregate together in families, and our findings suggest that a common predisposing genetic factor is likely present on the mtDNA. PMID:15643622

  2. Leaky Fermi accelerators

    NASA Astrophysics Data System (ADS)

    Shah, Kushal; Gelfreich, Vassili; Rom-Kedar, Vered; Turaev, Dmitry

    2015-06-01

    A Fermi accelerator is a billiard with oscillating walls. A leaky accelerator interacts with an environment of an ideal gas at equilibrium by exchange of particles through a small hole on its boundary. Such interaction may heat the gas: we estimate the net energy flow through the hole under the assumption that the particles inside the billiard do not collide with each other and remain in the accelerator for a sufficiently long time. The heat production is found to depend strongly on the type of Fermi accelerator. An ergodic accelerator, i.e., one that has a single ergodic component, produces a weaker energy flow than a multicomponent accelerator. Specifically, in the ergodic case the energy gain is independent of the hole size, whereas in the multicomponent case the energy flow may be significantly increased by shrinking the hole size.

  3. Precipitation in solution-treated Al-4wt%Cu under cyclic strain

    SciTech Connect

    Farrow, Adam M [Los Alamos National Laboratory; Laird, Campbell [U PENN

    2010-09-15

    Solution-treated Al-4wt%Cu was strain-cycled at ambient temperature and above and the precipitation behavior investigated by TEM. In the temperature range 100 C to 200 C precipitation of {Theta}'' appears to have been suppressed and precipitation of {Theta}' promoted via cyclic strain. Anomalously rapid growth of precipitates appears to have been facilitated by a vacancy supersaturation generated by dislocation motion, with a diminishing effect observed at higher temperatures due to the faster recovery of non-equilibrium vacancy concentrations. {Theta}' precipitates generated under cyclic strain are considerably smaller and more finely dispersed than those typically produced via quench-aging due to their heterogeneous nucleation on dislocations, and possess a low aspect ratio and rounded edges of the broad faces due to the introduction of ledges into the growing precipitates by dislocation cutting. Frequency effects indicate that dislocation motion, rather than the extremely small precipitate size, is responsible for the observed reduction in aspect ratio. Accelerated formation of grain boundary precipitates appears partially responsible for rapid intergranular fatigue failure following cycling at elevated temperatures, producing fatigue striations and ductile dimples coexistent on the fracture surface.

  4. Cyclic and radial variation of the Doppler power from porcine whole blood.

    PubMed

    Paeng, Dong-Guk; Shung, K Kirk

    2003-06-01

    The Doppler power from porcine blood was observed in a mock flow loop to have cyclic and radial variation during a pulsatile cycle. It was found to decrease with shear rate under steady flow, except near the center of the tube at which other mechanisms such as the effects of radial distribution on the rouleaux might be involved. Under pulsatile flow, the timing of the peak of the Doppler power measured at the center of the tube became closer to the peak systole from 20 to 60 beats/minute (BPM), and the power and velocity peaks coincided at 60 BPM. The overall radial variation of the Doppler power during a whole pulsatile cycle was prominent due to the increase of shear rate from the center to 4.5 mm radial position within a tube of 6.35 mm radius. The cyclic variation of the Doppler power varied with the radial position, being relatively large at the center, reaching a minimum at an intermediate radial position, and increasing again near the wall. The peak of the Doppler power occurred at early systole near the tube wall and lagged the flow closer to the center. The "black hole" phenomenon was observed only over portions of the flow cycle. All these complex variations of the Doppler power across the tube over a cycle are thought to be the result of red cell aggregation, which can be affected by shear rate and acceleration. PMID:12839173

  5. Spin, Acceleration and Gravity

    E-print Network

    Donato Bini; Christian Cherubini; Bahram Mashhoon

    2004-06-14

    The massless field perturbations of the accelerating Minkowski and Schwarzschild spacetimes are studied. The results are extended to the propagation of the Proca field in Rindler spacetime. We examine critically the possibility of existence of a general spin-acceleration coupling in complete analogy with the well-known spin-rotation coupling. We argue that such a direct coupling between spin and linear acceleration does not exist.

  6. Optically pulsed electron accelerator

    DOEpatents

    Fraser, J.S.; Sheffield, R.L.

    1985-05-20

    An optically pulsed electron accelerator can be used as an injector for a free electron laser and comprises a pulsed light source, such as a laser, for providing discrete incident light pulses. A photoemissive electron source emits electron bursts having the same duration as the incident light pulses when impinged upon by same. The photoemissive electron source is located on an inside wall of a radiofrequency-powered accelerator cell which accelerates the electron burst emitted by the photoemissive electron source.

  7. A new multicomponent reaction: unexpected formation of derivatizable cyclic ?-alkoxy isothioureas.

    PubMed

    Brockmeyer, Fabian; Morosow, Valentin; Martens, Jürgen

    2015-03-21

    An unexpected formation of cyclic ?-alkoxy isothioureas has been achieved. As is known, the heterocyclic imines 2,5-dihydro-1,3-thiazoles are convertible to bisamides with the aid of a carboxylic acid and an isocyanide (Ugi reaction). Herein, it is shown that 2,5-dihydro-1,3-thiazole S-monoxides-the respective ?-sulfinyl imines-are characterized by an altered reaction behavior. In a hitherto unknown multicomponent reaction the ?-sulfinyl imines react with an isocyanide under acidic conditions in an alcoholic solution to the respective ?-alkoxy isothioureas in good yields. In addition to the investigations on this unexpected synthesis the regioselectivity of the acylation of the synthesized compounds is described. A rearrangement, which is accelerated by EDC and HOBt, between both possible regioisomers was found. PMID:25655707

  8. Mechanistic understanding of surface plasmon assisted catalysis on a single particle: cyclic redox of 4-aminothiophenol

    PubMed Central

    Xu, Ping; Kang, Leilei; Mack, Nathan H.; Schanze, Kirk S.; Han, Xijiang; Wang, Hsing-Lin

    2013-01-01

    Surface plasmon assisted catalysis (SPAC) reactions of 4-aminothiophenol (4ATP) to and back from 4,4?-dimercaptoazobenzene (DMAB) have been investigated by single particle surface enhanced Raman spectroscopy, using a self-designed gas flow cell to control the reductive/oxidative environment over the reactions. Conversion of 4ATP into DMAB is induced by energy transfer (plasmonic heating) from surface plasmon resonance to 4ATP, where O2 (as an electron acceptor) is essential and H2O (as a base) can accelerate the reaction. In contrast, hot electron (from surface plasmon decay) induction drives the reverse reaction of DMAB to 4ATP, where H2O (or H2) acts as the hydrogen source. More interestingly, the cyclic redox between 4ATP and DMAB by SPAC approach has been demonstrated. This SPAC methodology presents a unique platform for studying chemical reactions that are not possible under standard synthetic conditions. PMID:24141289

  9. Particle acceleration in flares

    NASA Technical Reports Server (NTRS)

    Benz, Arnold O.; Kosugi, Takeo; Aschwanden, Markus J.; Benka, Steve G.; Chupp, Edward L.; Enome, Shinzo; Garcia, Howard; Holman, Gordon D.; Kurt, Victoria G.; Sakao, Taro

    1994-01-01

    Particle acceleration is intrinsic to the primary energy release in the impulsive phase of solar flares, and we cannot understand flares without understanding acceleration. New observations in soft and hard X-rays, gamma-rays and coherent radio emissions are presented, suggesting flare fragmentation in time and space. X-ray and radio measurements exhibit at least five different time scales in flares. In addition, some new observations of delayed acceleration signatures are also presented. The theory of acceleration by parallel electric fields is used to model the spectral shape and evolution of hard X-rays. The possibility of the appearance of double layers is further investigated.

  10. Accelerator Control Middle Layer

    SciTech Connect

    Corbett, J.

    2004-09-15

    This paper reviews an efficient implementation of the software ''middle layer'' that resides between high-level accelerator control applications and the low-level accelerator control system. The middle layer software is written in MATLAB and includes links to the EPICS Channel Access Library. Functionally, the middle layer syntax closely parallels the Family/Index naming scheme used in many accelerator simulation codes and uses the same convention to communicate with both the online machine and the accelerator model. Hence, machine control, machine simulation and data analysis tools are integrated into a single, easy-to-use software package.

  11. Accelerators and Nobel Laureates

    NSDL National Science Digital Library

    Kullander, Sven

    This online article written by Sven Kullander at the Nobel e-Museum discusses the importance of particle accelerators to physics in a historical context. After studying their basic operatation, users can then learn about the many accelerator inventions and their assistance in various discoveries such as x-rays and electrons. The website provides links to descriptions of the many Nobel Prize winners who have utilized accelerators in their important work. Users can view images of the large accelerators from all over the world including the United Kingdom, Sweden, and the United State.

  12. Charged particle accelerator grating

    DOEpatents

    Palmer, Robert B. (Shoreham, NY)

    1986-01-01

    A readily disposable and replaceable accelerator grating for a relativistic particle accelerator. The grating is formed for a plurality of liquid droplets that are directed in precisely positioned jet streams to periodically dispose rows of droplets along the borders of a predetermined particle beam path. A plurality of lasers are used to direct laser beams into the droplets, at predetermined angles, thereby to excite the droplets to support electromagnetic accelerating resonances on their surfaces. Those resonances operate to accelerate and focus particles moving along the beam path. As the droplets are distorted or destroyed by the incoming radiation, they are replaced at a predetermined frequency by other droplets supplied through the jet streams.

  13. Accelerator-based BNCT.

    PubMed

    Kreiner, A J; Baldo, M; Bergueiro, J R; Cartelli, D; Castell, W; Thatar Vento, V; Gomez Asoia, J; Mercuri, D; Padulo, J; Suarez Sandin, J C; Erhardt, J; Kesque, J M; Valda, A A; Debray, M E; Somacal, H R; Igarzabal, M; Minsky, D M; Herrera, M S; Capoulat, M E; Gonzalez, S J; del Grosso, M F; Gagetti, L; Suarez Anzorena, M; Gun, M; Carranza, O

    2014-06-01

    The activity in accelerator development for accelerator-based BNCT (AB-BNCT) both worldwide and in Argentina is described. Projects in Russia, UK, Italy, Japan, Israel, and Argentina to develop AB-BNCT around different types of accelerators are briefly presented. In particular, the present status and recent progress of the Argentine project will be reviewed. The topics will cover: intense ion sources, accelerator tubes, transport of intense beams, beam diagnostics, the (9)Be(d,n) reaction as a possible neutron source, Beam Shaping Assemblies (BSA), a treatment room, and treatment planning in realistic cases. PMID:24365468

  14. Cyclic peptides as proteases: a reevaluation.

    PubMed Central

    Corey, D R; Phillips, M A

    1994-01-01

    A recent report [Atassi, M. Z. and Manshouri, T. (1993) Proc. Natl. Acad. Sci. USA 90, 8282-8286] described the design and synthesis of two 29-amino acid cyclic peptides that were reported to hydrolyze both ester and amide bonds with chymotrypsin-like or trypsin-like specificity. We have synthesized the trypsin-mimic peptide (TrPepz) and detect no activity toward either ester or peptide substrates. The same result was independently obtained by Wells et al. [Wells, J. A., Fairbrother, W. J., Otlewski, J., Laskowski, M., Jr., & Burnier, J. (1994) Proc. Natl. Acad. Sci. USA 91, 4110-4114.] Additionally, we found that Atassi and Manshouri failed to obtain accurate kinetic constants for trypsin- and chymotrypsin-catalyzed ester hydrolysis because the high concentrations of trypsin and chymotrypsin that they report using would have prevented evaluation of initial rates. These findings are incompatible with the claims, reported by Atassi and Manshouri, that TrPepz has trypsin-like activity. PMID:8183879

  15. A low-power arcjet cyclic lifetest

    NASA Technical Reports Server (NTRS)

    Curran, Francis M.; Hardy, Terry L.; Haag, Thomas W.

    1987-01-01

    A cyclic lifetest of a low power dc arcjet thruster using a hydrogen/nitrogen propellant mixture simulating hydrazine is currently in progress. Over 300 hr of operation have been accumulated to date in 2 hr duty cycles at a power level of about 1.15 kW, approximating that available on commercial communications satellites. A burn-in period was carried out before consistent operation was attained. After this period, the arcjet operated in a very stable fashion from cycle to cycle. At the beginning of each cycle, there was a brief starting transient followed by a rapid rise to a steady-state voltage. The steady-state voltage increased by about 5 V over the first 95 cycles. After this, it increased by only 1 V through the remainder of the test. Thrust measurements taken before the life test and again after the completion of the 144th cycle showed that both thrust, specific impulse, and arc voltage had increased over this period of operation. No life limiting mechanisms were observed during the course of the testing.

  16. Cyclic dynamics in simulated plant populations.

    PubMed Central

    Bauer, Silke; Berger, Uta; Hildenbrandt, Hanno; Grimm, Volker

    2002-01-01

    Despite the general interest in nonlinear dynamics in animal populations, plant populations are supposed to show a stable equilibrium that is attributed to fundamental differences compared with animals. Some studies find more complex dynamics, but empirical studies usually are too short and most modelling studies ignore important spatial aspects of local competition and establishment. Therefore, we used a spatially explicit individual-based model of a hypothetical, non-clonal perennial to explore which mechanisms might generate complex dynamics, i.e. cycles. The model is based on the field-of-neighbourhood approach that describes local competition and establishment in a phenomenological manner. We found cyclic population dynamics for a wide spectrum of model variants, provided that mortality is determined by local competition and recruitment is virtually completely suppressed within the zone of influence of established plants. This destabilizing effect of local processes within plant populations might have wide-ranging implications for the understanding of plant community dynamics and coexistence. PMID:12495487

  17. Gadolinium-binding cyclic hexapeptoids: synthesis and relaxometric properties.

    PubMed

    De Cola, Chiara; Fiorillo, Gaetano; Meli, Alessandra; Aime, Silvio; Gianolio, Eliana; Izzo, Irene; De Riccardis, Francesco

    2014-01-21

    Two new cyclic hexapeptoids incorporating N-carboxyethylglycine and N-methoxyethylglycine residues are able to efficiently bind Gd(3+). Their thermodynamic stabilities and relaxivities have been assessed by (1)H-relaxometric investigations. PMID:24287618

  18. Thermoacoustic theory for cyclic flow regenerators. I - Fundamentals

    NASA Astrophysics Data System (ADS)

    Xiao, J. H.

    A thermoacoustic theory is presented for analysis of gas oscillations and time-averaged energy fluxes and energy transformations in cyclic flow regenerators. The fluctuations of pressure and velocity of the gaseous medium are transmitted along the longitudinal direction of cyclic flow regenerators in the form of acoustic wave motion. The working of cyclic flow regenerators relies on thermoacoustic effects, i.e., time-averaged energy effects caused by the thermal interaction of the oscillatory gaseous fluid medium and the porous solid-matrix medium. Regenerators used in regenerative heat engines are active components in which heat energy is transformed into acoustic energy to produce acoustic power (in prime movers) or acoustic energy is consumed and transformed into heat energy to pump heat (in refrigerators). The wave equations and energy-temperature equations to describe cyclic flow regenerators have been deduced, and a set of parameters to evaluate the regenerator performance and effectiveness is proposed.

  19. Cyclic deformation, fracture, and nondestructive evaluation of advanced materials

    SciTech Connect

    Mitchell, M.R.; Buck, O.

    1992-01-01

    Papers are presented on cyclic fatigue of alumnia, fatigue crack growth in ceramics and ceramic-matrix composites, fatigue test methodology and results for ceramic matrix composites at room and elevated temperatures, and modeling crack growth resistance in ceramics and ceramic-matrix composites. Attention is also given to thermomechanical cyclic deformation of metal-matrix composites, the effect of tensile mean stress on the fatigue behavior of single-crystal and directionally solidified superalloys, the influence of constituent properties on the compression behavior of aluminates with discontinuities, and cyclic creep effects in single-overlap bonded joints under constant-amplitude testing. Other papers discuss an ultrasonic wave technique to assess cyclic-load fatigue damage in silicon-carbide whisker-reinforced 2124 aluminum alloy composites, nondestructive characterization for metal-matrix composite fabrication, NDE of a ceramic matrix composite material, and split spectrum processing of backscattered Rayleigh wave signals to improve detectability of fatigue microcracks.

  20. Cyclic AMP Signaling: A Molecular Determinant of Peripheral Nerve Regeneration

    PubMed Central

    Knott, Eric P.; Assi, Mazen; Pearse, Damien D.

    2014-01-01

    Disruption of axonal integrity during injury to the peripheral nerve system (PNS) sets into motion a cascade of responses that includes inflammation, Schwann cell mobilization, and the degeneration of the nerve fibers distal to the injury site. Yet, the injured PNS differentiates itself from the injured central nervous system (CNS) in its remarkable capacity for self-recovery, which, depending upon the length and type of nerve injury, involves a series of molecular events in both the injured neuron and associated Schwann cells that leads to axon regeneration, remyelination repair, and functional restitution. Herein we discuss the essential function of the second messenger, cyclic adenosine monophosphate (cyclic AMP), in the PNS repair process, highlighting the important role the conditioning lesion paradigm has played in understanding the mechanism(s) by which cyclic AMP exerts its proregenerative action. Furthermore, we review the studies that have therapeutically targeted cyclic AMP to enhance endogenous nerve repair. PMID:25177696

  1. Cyclical Cohabitation Among Unmarried Parents in Fragile Families

    PubMed Central

    Nepomnyaschy, Lenna; Teitler, Julien

    2013-01-01

    Building on past research suggesting that cohabitation is an ambiguous family form, the authors examined an understudied residential pattern among unmarried parents: cyclical cohabitation, in which parents have multiple cohabitation spells with each other. Using 9 years of panel data from the Fragile Families and Child Wellbeing Study (N = 2,084), they found that 10% of all parents with nonmarital births, and nearly a quarter of those living together when the child is 9 years old, are cyclical cohabitors. Cyclically cohabiting mothers reported more material hardships than mothers in most other relationship patterns but also reported more father involvement with children. On all measures of child well-being, except grade retention, children of cyclically cohabiting parents fared no worse than children of stably cohabiting biological parents and did not differ significantly from any other group. PMID:25067855

  2. Acceleration Worksheet 8/24/2011 ACCELERATION WORKSHEET

    E-print Network

    Davis, H. Floyd

    Acceleration Worksheet 8/24/2011 ACCELERATION WORKSHEET College of Arts and Sciences Name _____________ TO _____________ month/year month/year II. I meet the requirements for acceleration under [fill out either a) or b;Acceleration Worksheet 8/24/2011 Acceleration 2011-2012 Courses of Study The faculty of the college desires

  3. Unified constitutive modeling for proportional and nonproportional cyclic plasticity responses

    NASA Astrophysics Data System (ADS)

    Krishna, Shree

    Several features of cyclic plasticity, e.g. cyclic hardening/softening, ratcheting, relaxation, and their dependence on strain range, nonproportionality of loading, time, and temperature determine the stress-strain responses of materials under cyclic loading. Numerous efforts have been made in the past decades to characterize and model these responses. Many of these responses can be simulated reasonably by the existing constitutive models, but the same models would fail in simulating the structural responses, local stress-strain or global deformation. One of the reasons for this deficiency is that the constitutive models are not robust enough to simulate the cyclic plasticity responses when they interact with each other. This deficiency can be understood better or resolved by developing and validating constitutive models against a broad set of experimental responses and two or more of the responses interacting with each other. This dissertation develops a unified constitutive model by studying the cyclic plasticity features in an integrated manner and validating the model by simulating a broad set of proportional and nonproportional cyclic plasticity responses. The study demonstrates the drawbacks of the existing nonlinear kinematic hardening model originally developed by Chaboche and then develop and incorporate novel ideas into the model for improving its cyclic response simulations. The Chaboche model is modified by incorporating strain-range dependent cyclic hardening/softening through the kinematic hardening rule parameters, in addition to the conventional method of using only the isotropic hardening parameters. The nonproportional loading memory parameters of Tanaka and of Benallal and Marquis are incorporated to study the influence of nonproportionality. The model is assessed by simulating hysteresis loop shape, cyclic hardening-softening, cross-effect, cyclic relaxation, subsequent cyclic softening, and finally a series of ratcheting responses under uniaxial and biaxial loading responses. Next, it is demonstrated that the hysteresis loop shape and width can be improved by incorporation of time dependence (visco-effect) and a novel modeling scheme of backstress shift. Overall, this dissertation demonstrates a methodical and systematic development of a constitutive model for simulating a broad set of low-cycle fatigue responses.

  4. Detection of nonstationarities in geological time series: Wavelet transform of chaotic and cyclic sequences

    Microsoft Academic Search

    Andreas Prokoph; Franz Barthelmes

    1996-01-01

    Wavelet analysis is used to detect and localize unconformities, events, or chaotic and periodic-cyclic sequences in marine sedimentary successions. Computer modeling using a single nonlinear algorithm provides a quantitative approach to a better understanding of chaotic, cyclic and monotonous sedimentation, and the preservation of unconformities. To model cyclic and chaotic sequences, we consider nonlinear and cyclic fluctuations in the rate

  5. Strain and pore pressure behavior of fine grained soils subjected to cyclic shear loading

    Microsoft Academic Search

    R. Dyvik

    1981-01-01

    The behavior of fine grained soils subjected to cyclic loading is investigated. Consolidated, constant volume, static (monotonic) and cyclic laboratory shear tests were performed using the Norwegian Geotechnical Institute direct simple shear device, which was modified for cyclic loading capabilities. All cyclic tests were performed with stress controlled square wave loading and most with complete and symmetric stress reversal. Pore

  6. Cyclic plastic deformation of tantalum and niobium at very high numbers of cycles

    Microsoft Academic Search

    M Papakyriacou; H Mayer; H Plenk; S Stanzl-Tschegg

    2002-01-01

    Niobium and tantalum in the annealed and cold-worked condition have been cycled at ultrasonic frequency at 90% of the fatigue limit at 2×108 cycles. Tantalum showed first cyclic softening followed by cyclic hardening after 105 cycles. Niobium showed cyclic softening only. Cyclic stress–strain behaviour of cold worked and annealed material showed similar trends.

  7. Cyclic-Oxidation Resistance of Protective Silicide Layers on Titanium

    Microsoft Academic Search

    D. Vojt?ch; T. Kubatík; K. Jurek; J. Maixner

    2005-01-01

    Titanium was powder siliconized and gas nitrided, in order to improve its cyclic-oxidation resistance. Siliconizing was performed in a pure-silicon powder at temperatures in the range of 800–1100° C for 3–48 h. Gas nitriding was carried out in pure N2 at 1100° C\\/12 h. Cyclic-oxidation experiments with the siliconized and nitrided samples were conducted in air at 850 and 950° C for up to 560 h.

  8. Phantom energy accretion onto black holes in a cyclic universe

    SciTech Connect

    Sun Chengyi [Institute of Modern Physics, Northwest University Xian, 710069 (China)

    2008-09-15

    Black holes pose a serious problem in cyclic or oscillating cosmology. It is speculated that, in the cyclic universe with phantom turnarounds, black holes will be torn apart by phantom energy prior to turnaround before they can create any problems. In this paper, using the mechanism of phantom accretion onto black holes, we find that black holes do not disappear before phantom turnaround. But the remanent black holes will not cause any problems due to Hawking evaporation.

  9. A rare cyclic recurrent hematuria case; bladder endometriosis

    PubMed Central

    Akp?nar, Süha; Çelebio?lu, Emre

    2015-01-01

    Endometriosis is a benign gynecological disease that is characterized by the presence of functional endometrial tissue outside the uterus. Although the ovaries and uterine ligaments are the most common locations, urinary tract involvement especially the bladder endometriosis is a rare entity in women of reproductive age with clinical symptoms of cyclical urgency, hematuria and suprapubic pain. We herein present magnetic resonance imaging (MRI) findings of spontaneous bladder endometriosis case with cyclical hematuria symptoms. PMID:26029655

  10. Cyclic Diguanylate Regulates Vibrio cholerae Virulence Gene Expression

    Microsoft Academic Search

    Anna D. Tischler; Andrew Camilli

    2005-01-01

    The cyclic dinucleotide second messenger cyclic diguanylate (c-diGMP) has been implicated in regulation of cell surface properties in several bacterial species, including Vibrio cholerae. Expression of genes required for V. cholerae biofilm formation is activated by an increased intracellular c-diGMP concentration. The response regulator VieA, which contains a domain responsible for degradation of c-diGMP, is required to maintain a low

  11. Channel equalization for DMT with insufficient cyclic prefix

    Microsoft Academic Search

    Jie Zhu; Wee Ser; Arye Nehorai

    2000-01-01

    In discrete multi-tone (DMT) systems a cyclic prefix is added to the front of each modulated symbol-frame in order to partition the whole channel into many narrow independent sub-channels. When the length of the cyclic prefix is shorter than the channel length, inter-carrier interference (ICI) and inter-symbol interference (ISI) will occur in the output signal. This paper presents a decision

  12. Isocyanide-based multicomponent reactions towards cyclic constrained peptidomimetics

    PubMed Central

    Koopmanschap, Gijs; Ruijter, Eelco

    2014-01-01

    Summary In the recent past, the design and synthesis of peptide mimics (peptidomimetics) has received much attention. This because they have shown in many cases enhanced pharmacological properties over their natural peptide analogues. In particular, the incorporation of cyclic constructs into peptides is of high interest as they reduce the flexibility of the peptide enhancing often affinity for a certain receptor. Moreover, these cyclic mimics force the molecule into a well-defined secondary structure. Constraint structural and conformational features are often found in biological active peptides. For the synthesis of cyclic constrained peptidomimetics usually a sequence of multiple reactions has been applied, which makes it difficult to easily introduce structural diversity necessary for fine tuning the biological activity. A promising approach to tackle this problem is the use of multicomponent reactions (MCRs), because they can introduce both structural diversity and molecular complexity in only one step. Among the MCRs, the isocyanide-based multicomponent reactions (IMCRs) are most relevant for the synthesis of peptidomimetics because they provide peptide-like products. However, these IMCRs usually give linear products and in order to obtain cyclic constrained peptidomimetics, the acyclic products have to be cyclized via additional cyclization strategies. This is possible via incorporation of bifunctional substrates into the initial IMCR. Examples of such bifunctional groups are N-protected amino acids, convertible isocyanides or MCR-components that bear an additional alkene, alkyne or azide moiety and can be cyclized via either a deprotection–cyclization strategy, a ring-closing metathesis, a 1,3-dipolar cycloaddition or even via a sequence of multiple multicomponent reactions. The sequential IMCR-cyclization reactions can afford small cyclic peptide mimics (ranging from four- to seven-membered rings), medium-sized cyclic constructs or peptidic macrocycles (>12 membered rings). This review describes the developments since 2002 of IMCRs-cyclization strategies towards a wide variety of small cyclic mimics, medium sized cyclic constructs and macrocyclic peptidomimetics. PMID:24605172

  13. Numerical modeling of centrifuge cyclic lateral pile load experiments

    Microsoft Academic Search

    Nikos Gerolymos; Sandra Escoffier; George Gazetas; Jacques Garnier

    2009-01-01

    To gain insight into the inelastic behavior of piles, the response of a vertical pile embedded in dry sand and subjected to\\u000a cyclic lateral loading was studied experimentally in centrifuge tests conducted in Laboratoire Central des Ponts et Chaussées.\\u000a Three types of cyclic loading were applied, two asymmetric and one symmetric with respect to the unloaded pile. An approximately\\u000a square-root

  14. Similarity analysis, synthesis, and bioassay of antibacterial cyclic peptidomimetics

    PubMed Central

    Berhanu, Workalemahu M; Ibrahim, Mohamed A; Pillai, Girinath G; Oliferenko, Alexander A; Khelashvili, Levan; Jabeen, Farukh; Mirza, Bushra; Ansari, Farzana Latif; ul-Haq, Ihsan; El-Feky, Said A

    2012-01-01

    Summary The chemical similarity of antibacterial cyclic peptides and peptidomimetics was studied in order to identify new promising cyclic scaffolds. A large descriptor space coupled with cluster analysis was employed to digitize known antibacterial structures and to gauge the potential of new peptidomimetic macrocycles, which were conveniently synthesized by acylbenzotriazole methodology. Some of the synthesized compounds were tested against an array of microorganisms and showed antibacterial activity against Bordetella bronchistepica, Micrococcus luteus, and Salmonella typhimurium. PMID:23019443

  15. Similarity analysis, synthesis, and bioassay of antibacterial cyclic peptidomimetics.

    PubMed

    Berhanu, Workalemahu M; Ibrahim, Mohamed A; Pillai, Girinath G; Oliferenko, Alexander A; Khelashvili, Levan; Jabeen, Farukh; Mirza, Bushra; Ansari, Farzana Latif; Ul-Haq, Ihsan; El-Feky, Said A; Katritzky, Alan R

    2012-01-01

    The chemical similarity of antibacterial cyclic peptides and peptidomimetics was studied in order to identify new promising cyclic scaffolds. A large descriptor space coupled with cluster analysis was employed to digitize known antibacterial structures and to gauge the potential of new peptidomimetic macrocycles, which were conveniently synthesized by acylbenzotriazole methodology. Some of the synthesized compounds were tested against an array of microorganisms and showed antibacterial activity against Bordetella bronchistepica, Micrococcus luteus, and Salmonella typhimurium. PMID:23019443

  16. Crack growth in transforming ceramics under cyclic tensile loads

    Microsoft Academic Search

    L. A. Sylva; S. Suresh

    1989-01-01

    The mechanisms of stable growth of short fatigue cracks (crack length up to 1 mm) at room temperature in magnesia-partially stabilized zirconia subjected to cyclic tensile loads were investigated. Single edge-notched specimens were fractured in the four-point bend configuration under cyclic and quasi-static tensile loads. At a load ratio of 0.1, the threshold stress intensity factor range, ?K, for fracture

  17. Cyclic peptides and depsipeptides from cyanobacteria: A review

    Microsoft Academic Search

    R E Moore

    1996-01-01

    An elaborate array of structurally-novel and biologically-active cyclic peptides and depsipeptides are found in blue-green algae (cyanobacteria). Several of these compounds possess structures that are similar to those of natural products from marine invertebrates. Most of these cyclic peptides and depsipeptides, such as the microcystins and the lyngbyatoxins, will probably only be useful as biochemical research tools. A few, however,

  18. Cyclic q-ary images of codes and burst correction

    Microsoft Academic Search

    W. Wafo; J. Wolfmann

    1994-01-01

    In the case where the cyclic code C is determined by a constancy-clique code described in Jensen's (see IEEE Trans. Inform. Theory, vol.38, p.950-959, 1992) theorem, we are able to find a lower bound for the minimum weight of C. By using the previous proposition we deduce lower bounds for the burst correction capacity of cyclic codes with composite lengths

  19. Inhibition of Ras-Effector Interaction by Cyclic Peptides

    PubMed Central

    Wu, Xianghong; Upadhyaya, Punit; Villalona-Calero, Miguel A.; Briesewitz, Roger; Pei, Dehua

    2013-01-01

    A combinatorial library of 6 × 106 cyclic peptides was synthesized in the one bead-two compound format, with each bead displaying a unique cyclic peptide on its surface and a linear peptide encoding tag in its interior. Screening of the library against K-Ras identified compounds that bound K-Ras with submicromolar affinity and disrupted its interaction with effector proteins. PMID:23585920

  20. Microgravity changes in heart structure and cyclic-AMP metabolism

    NASA Technical Reports Server (NTRS)

    Philpott, D. E.; Fine, A.; Kato, K.; Egnor, R.; Cheng, L.

    1985-01-01

    The effects of microgravity on cardiac ultrastructure and cyclic AMP metabolism in tissues of rats flown on Spacelab 3 are reported. Light and electron microscope studies of cell structure, measurements of low and high Km phosphodiesterase activity, cyclic AMP-dependent protein kinase activity, and regulatory subunit compartmentation show significant deviations in flight animals when compared to ground controls. The results indicate that some changes have occurred in cellular responses associated with catecholamine receptor interactions and intracellular signal processing.

  1. Dynamic Properties of Linear and Cyclic Alkane Melts

    NASA Astrophysics Data System (ADS)

    Ozisik, Rahmi; Mattice, Wayne L.; von Meerwall, Ernst D.

    2000-03-01

    The diffusion coefficients, D, of linear and cyclic alkanes in the melt were calculated by a Monte Carlo simulation on the second nearest neighbor diamond (2nnd) lattice. The results of the 2nnd simulations were compared to pulsed-gradient spin-echo nuclear magnetic resonance (PGSE NMR) experiments for the linear alkanes. The 2nnd lattice simulations were able to represent the bulk dynamic properties of linear alkane chains. D was influenced by two kinds of factors: local and global. Local factors are those that change the interactions of the individual beads, such as the occupancy of the neighboring shells, and global factors are those that change the interactions of the chains, such as the density and entanglement effects. In this study, the D of the cyclic chains was found to be lower than that of the linear chains at the same molecular weight below M_e. This crossover is attributed to the interplay between the local factors, which dominate the dynamics of the cyclic chains below M_e, and the entanglement effects above M_e. The cyclic alkane chain is smaller than a linear chain at all times. Below M_e, the high local density slows down the dynamics of the cyclic chains compared to the linear chains, and above M_e, the cyclic chains have higher D, because they are not affected by the entanglement effects observed by the linear chains.

  2. Effects of thin anodic films on cyclic deformation of tungsten

    SciTech Connect

    Bowman, K.J.

    1987-01-01

    The dynamics of edge and screw dislocation motion as a function of temperature play a decisive role in the mechanical response of bcc metals. Cyclic deformation over a range of plastic-strain levels was used to investigate many aspects of the cyclic stress-strain response of tungsten single crystals at room temperature. The results of this investigation fully support a two-dislocation model of deformation for bcc metals at low homologous temperatures (T less than or equal to 0.15T/sub m/). The occurrence of stress asymmetry and cyclic stress-strain behavior which fits a two-dislocation model are demonstrated in crystals of several orientations. The results indicate that the nearly isotropic elastic response of tungsten produces the nearly ideal stress asymmetry expected for bcc crystals. Thin anodic films (approx. 80 nm) were utilized to determine the effects of surface modification on the cyclic stress-strain behavior of tungsten. At cyclic microstrains, the anodization of tungsten produces a large reversible hardening effect. At cyclic macrostrains the anodization of tungsten produces a smaller, less reversible softening effect. These two effects are explained in terms of dislocation multiplication and annihilation processes

  3. Are Submarine Cyclic Steps Present on the Surface of Mars?

    NASA Astrophysics Data System (ADS)

    Kostic, Svetlana; Covault, Jacob A.; Smith, Isaac

    2015-04-01

    Cyclic steps emplaced by turbidity currents are common features on the ocean floor of Earth. Recent observations and modeling studies have indicated that cyclic steps exist on Mars as well. The spiral troughs of Mars North Polar Layered Deposits have been interpreted as cyclic steps. Their formation and evolution can be tied to atmospheric processes, including Coriolis steered katabatic winds and asymmetric ice accumulation that is caused by katabatic jumps. The objective of this research is to evaluate whether cyclic steps emplaced by turbidity currents are present on the surface of Mars. The presence of deep-sea cyclic steps on the surface of Mars might favor the existence of a Martian ocean, analogous to Earth. We have started our search by looking at surface data collected by Mars Orbiter Laser Altimeter (MOLA) topography with the Context Imager (CTX), High Resolution Imaging Science Experiment (HiRISE), and Mars Orbiter Camera (MOC) images and literature on Martian bedforms. Preliminary results of our search highlight potential remnants of cyclic steps on several fluvial delta deposits spreading along a proposed shoreline of the shallow primordial ocean.

  4. Determination of nonlinear energy toughness values for cyclic loading applications

    NASA Technical Reports Server (NTRS)

    Poulose, P. K.; Jones, D. L.; Liebowitz, H.

    1976-01-01

    For several years the nonlinear energy method proposed by Liebowitz and Eftis has been examined as a failure criterion for static testing of center-cracked and compact tension specimens. Since the method appears to be valid under conditions of crack-tip plasticity, subcritical crack growth and load relaxation, tests have been conducted to ascertain the merit of this method as a failure criterion under cyclic loading conditions. The nonlinear energy toughness for cyclic loading is obtained from an envelope of the cyclic load-displacement record, which naturally imposes some restrictions on the loading program. The cyclic toughness parameter has been evaluated for thin center-cracked sheets of 2024-T3 and 7075-T6 aluminum alloys. Both alloys exhibited a significant reduction of the cyclic toughness parameter with increasing cyclic life in a manner similar to the classical S-N diagram. It is suggested that this method may serve the design process by allowing the establishment of a fracture toughness parameter capable of including the effects of the entire loading history of a structure into the fracture toughness requirements.

  5. Cyclic imino ethers in practical step-growth polymerizations

    SciTech Connect

    Culbertson, B.M. [Ohio State Univ., Columbus, OH (United States)

    1993-12-31

    Dicarboxylic acids, glycols, diamines, epoxy resins, phenolics, etc., have significant uses in a variety of thermoplastics and thermosets. Cyclic imino ethers may be used to react with the functionalities on the aforesaid starting compounds, providing practical paths to a host of improved performance materials. For example, the dicarboxylic acid-cyclic imino ether reaction may be employed to produce super tough, poly(amide-ester) thermosets. Or, phenolics may be chain extended and/or crosslinked with cyclic imino ethers to produce poly(amide-ether) thermosets with highly attractive thermal, physical and mechanical properties, with a wide variety of composite applications. In the recycling area, it is also very practical to use cyclic imino ethers to chain extend, i.e., enhance the molecules weight, of recovered polyesters or polyamides to enhance performance of the recovered materials. The use of monomers and polymers containing two or more cyclic imino ether moieties for production of new materials will be discussed. The phenolic hydroxyl-cyclic imino ether reaction will receive the main focus as a practical route to new poly(amide-ether) thermosets, based on the authors experience in using this chemistry to design matrix resins for high performance composities.

  6. The Role of Cyclic Nucleotide Signaling Pathways in Cancer: Targets for Prevention and Treatment

    PubMed Central

    Fajardo, Alexandra M.; Piazza, Gary A.; Tinsley, Heather N.

    2014-01-01

    For more than four decades, the cyclic nucleotides cyclic AMP (cAMP) and cyclic GMP (cGMP) have been recognized as important signaling molecules within cells. Under normal physiological conditions, cyclic nucleotides regulate a myriad of biological processes such as cell growth and adhesion, energy homeostasis, neuronal signaling, and muscle relaxation. In addition, altered cyclic nucleotide signaling has been observed in a number of pathophysiological conditions, including cancer. While the distinct molecular alterations responsible for these effects vary depending on the specific cancer type, several studies have demonstrated that activation of cyclic nucleotide signaling through one of three mechanisms—induction of cyclic nucleotide synthesis, inhibition of cyclic nucleotide degradation, or activation of cyclic nucleotide receptors—is sufficient to inhibit proliferation and activate apoptosis in many types of cancer cells. These findings suggest that targeting cyclic nucleotide signaling can provide a strategy for the discovery of novel agents for the prevention and/or treatment of selected cancers. PMID:24577242

  7. A 15,000-hour cyclic endurance test of an 8-centimeter-diameter electron bombardment mercury ion thruster

    NASA Technical Reports Server (NTRS)

    Nakanishi, S.

    1976-01-01

    A laboratory model 8 cm thruster with improvements to minimize ion chamber erosion and peeling of sputtered metal was subjected to a cyclic endurance test for 15,040 hours and 460 restarts. A charted history of several thruster operating variables and off-normal events are shown in 600-hour segments at three points in the test. The transient behavior of these variables during a typical start-stop cycle is presented. Finding of the post-test inspection confirmed most of the expected results. Charge exchange ions caused normal accelerator grid erosion. The workability of the various design features was substantiated, and attainable improvements in propellant utilization efficiency should significantly reduce accelerator erosion.

  8. Semiconductor acceleration sensor

    NASA Astrophysics Data System (ADS)

    Ueyanagi, Katsumichi; Kobayashi, Mitsuo; Goto, Tomoaki

    1996-09-01

    This paper reports a practical semiconductor acceleration sensor especially suited for automotive air bag systems. The acceleration sensor includes four beams arranged in a swastika structure. Two piezoresistors are formed on each beam. These eight piezoresistors constitute a Wheatstone bridge. The swastika structure of the sensing elements, an upper glass plate and a lower glass plate exhibit the squeeze film effect which enhances air dumping, by which the constituent silicon is prevented from breakdown. The present acceleration sensor has the following features. The acceleration force component perpendicular to the sensing direction can be cancelled. The cross-axis sensitivity is less than 3 percent. And, the erroneous offset caused by the differences between the thermal expansion coefficients of the constituent materials can be canceled. The high aspect ratio configuration realized by plasma etching facilitates reducing the dimensions and improving the sensitivity of the acceleration sensor. The present acceleration sensor is 3.9 mm by 3.9 mm in area and 1.2 mm in thickness. The present acceleration sensor can measure from -50 to +50 G with sensitivity of 0.275 mV/G and with non-linearity of less than 1 percent. The acceleration sensor withstands shock of 3000 G.

  9. Accelerating Research with

    E-print Network

    Bernstein, Phil

    -for- use basis. Software and data are hosted on remote computers "in the cloud," and users connect throughAccelerating Academic Research with Cloud Computing Published: September 2014 For the latest information, please see www.microsoft.com/education #12;Accelerating Academic Research with Cloud Computing

  10. Electromagnetic mass accelerators

    Microsoft Academic Search

    Pavel V. Kasyanenko; Vasily A. Efremov; Sergey A. Kharitonov

    2010-01-01

    The powerful power supplies system (up to 3 - 4 GW in impulse) was developed for the electromagnetic mass accelerator. Unique blocks of repeated switching rated on high currents (up to 1.2MA and voltage up to 5KV) are considered. In this paper various designs of the mass accelerator system and its power supplies are described.

  11. Exploring acceleration through vectors

    NSDL National Science Digital Library

    This in class worksheet is designed to get students to think about and manipulate different accelerations in their head. Students work together with written descriptions of velocity and acceleration and draw the vectors in part one, and then turn that around in part two where they write descriptions of a car's motion based on the vector pictures they are given.

  12. J-PARC Accelerator

    SciTech Connect

    Yamazaki, Yoshishige [J-PARC Center High Energy Accelerator Research Organization (KEK) and Japan Atomic Energy Organization (JAEA) Shirakata-Shirane, Tokai-Mura, Naka-Gun, Ibaraki-Ken (Japan)

    2008-02-21

    The Japan Proton Accelerator Research Complex (J-PARC) is under construction in Tokai site. The linac beam commissioning started last fall, while the beam commissioning of the 3-GeV Rapid-Cycling Synchrotron (RCS) will start this fall. The status of the J-PARC accelerator is reported with emphasis on the technical development accomplished for the J-PARC.

  13. Particle Acceleration in Jets

    NASA Technical Reports Server (NTRS)

    Nishikawa, Ken-Ichi

    2005-01-01

    Nonthermal radiation observed from astrophysical systems containing relativistic jets and shocks, e.g., active galactic nuclei (AGNs), gamma ray burst (GRBs), and Galactic microquasar systems usually have power-law emission spectra. Fermi acceleration is the mechanism usually assumed for the acceleration of particles in astrophysical environments.

  14. Accelerators (3/5)

    ScienceCinema

    None

    2011-10-06

    1a) Introduction and motivation 1b) History and accelerator types 2) Transverse beam dynamics 3a) Longitudinal beam dynamics 3b) Figure of merit of a synchrotron/collider 3c) Beam control 4) Main limiting factors 5) Technical challenges Prerequisite knowledge: Previous knowledge of accelerators is not required.

  15. Acceleration of Gravity 2

    NSDL National Science Digital Library

    Michael Horton

    2009-05-30

    This lab is between a Level 2 and Level 3 inquiry activity in that it should be assigned after students understand acceleration but before they learn about the acceleration gravity. Because there are many sources of error when using a pendulum, students c

  16. Accelerators (4/5)

    ScienceCinema

    None

    2011-10-06

    1a) Introduction and motivation 1b) History and accelerator types 2) Transverse beam dynamics 3a) Longitudinal beam dynamics 3b) Figure of merit of a synchrotron/collider 3c) Beam control 4) Main limiting factors 5) Technical challenges Prerequisite knowledge: Previous knowledge of accelerators is not required.

  17. ACCELERATOR RESEARCH STUDIES

    SciTech Connect

    P.G. O'Shea, M. Reiser, V. L. Granatstein, W. Lawson, I. Haber, R. Kishek

    2004-01-23

    ACCELERATOR RESEARCH STUDIES Task A: Study of the Physics of Space-Charge Dominated Beams for Advanced Accelerator Applications Task B: Studies of High-Power Gyroklystrons and Application to Linear Colliders Task C: Theory and Simulation of the Physics Space-Charge Dominated Beams Annual Report for the Period June 1, 2003 to May 31, 2004

  18. Diagnostics for induction accelerators

    SciTech Connect

    Fessenden, T.J.

    1996-04-01

    The induction accelerator was conceived by N. C. Christofilos and first realized as the Astron accelerator that operated at LLNL from the early 1960`s to the end of 1975. This accelerator generated electron beams at energies near 6 MeV with typical currents of 600 Amperes in 400 ns pulses. The Advanced Test Accelerator (ATA) built at Livermore`s Site 300 produced 10,000 Ampere beams with pulse widths of 70 ns at energies approaching 50 MeV. Several other electron and ion induction accelerators have been fabricated at LLNL and LBNL. This paper reviews the principal diagnostics developed through efforts by scientists at both laboratories for measuring the current, position, energy, and emittance of beams generated by these high current, short pulse accelerators. Many of these diagnostics are closely related to those developed for other accelerators. However, the very fast and intense current pulses often require special diagnostic techniques and considerations. The physics and design of the more unique diagnostics developed for electron induction accelerators are presented and discussed in detail.

  19. Angular velocities, angular accelerations, and coriolis accelerations

    NASA Technical Reports Server (NTRS)

    Graybiel, A.

    1975-01-01

    Weightlessness, rotating environment, and mathematical analysis of Coriolis acceleration is described for man's biological effective force environments. Effects on the vestibular system are summarized, including the end organs, functional neurology, and input-output relations. Ground-based studies in preparation for space missions are examined, including functional tests, provocative tests, adaptive capacity tests, simulation studies, and antimotion sickness.

  20. Cyclical Regolith Processes on Hydrous Asteroids

    NASA Astrophysics Data System (ADS)

    Zolensky, M. E.

    1995-09-01

    Carbonaceous chondrites experienced and recorded a very wide range of chemical and physical processing in both nebular and asteroidal settings. Among the features arising from asteroidal processes are the following: (1) most of these meteorites are breccias; (2) some CV3s and CMs contain flattened chondrules and exhibit foliation; (3) veins are found in some CIs, CMs, CV3 dark inclusions; (4) CR2s, all CIs, some CR2s and CMs display weak alignment of matrix phyllosilicates, and (5) shearing (mylonitization) around lithic fragments. While these features have generally been assumed to have involved impact deformation in asteroidal regoliths, a process sometimes referred to as regolith or impact gardening, we suggest here that all of these particular features would have arisen naturally from cycles of wet-dry and freeze-thaw environmental conditions in asteroid regoliths. All of the extensively (Y82042, ALH 83100, Cold Bokkeveld, Y891198, EET 90047) and completely (ALH 88045, EET 83334, Kaidun CM1 lithology) altered CMs contain rounded to elliptical aggregates of phyllosilicates, carbonates, spinels (chromite and magnetite), Fe-Ni sulfides, and embayed olivines and pyroxenes, which we interpret as relict chondrules [1]; these sometimes define a definite foliation direction generally ascribed to impact shock [2&3]. We examined all available relict olivines from CMs showing the most pronounced chondrule flattening and foliation, and found only a few planar fractures in a single olivine grain in one sample (EET 90047), and no sign of shock effects in the others. We therefore suggest that static burial pressure was agent responsible for chondrule flattening in this case, and believe that the processes involved in burial compaction deserve more attention than they have hitherto received in the asteroid literature. It is probable that even in the wettest regions of an asteroid dry periods were experienced during the periodic breaching of an icy surficial rind [4], which could have occurred during impacts or "volcanic" venting of gas and heat from the interior (this assumes internal heating). Thus, there should have been multiple wet-dry cycles involved in the genesis of these materials. It is well-known to soil scientists that conditions of radically alternating humidity can have important morphologic and petrologic consequences. Grains and lithic clasts can become rotated, crushed and drawn out into linear features (shearing). Porosity (including contraction and shearing cracks) and other bulk physical properties will vary in dramatic manner. These effects would be most pronounced for the CI and CR chondrites, as well as the Kaidun CM1 lithology, where the swelling clay saponite is found in abundance. Easily altered materials will be dissolved while more resistant materials will be pulverized and mixed into matrix [5]. Another important process to be considered is periodic growth and melting of ice crystals in the regolith [6]. The positive molal volume change during crystallization of water will induce oriented microfabrics to develop in the regolith, normal to the direction of ice crystal growth. Thus, platy grains (such as phyllosilicates) will develop a pronounced compaction and preferred alignment. Since the orientation of the growing ice mass will vary for each succeeding generation of growth, the eventual result will be to impart a particular, invasive, regolith fabric consisting of anastomosing strings of phyllosilicates with roughly aligned basal directions for each string. Such textures are common in the wettest chondrites: CIs and CMs. Growth and collapse of these asteroidal icicles will also impart cyclical changes in bulk regolith porosity, induce rotation and movement of crystals and lithic fragments through frost heaving, and consequent shearing. This process could also account, to some degree, for the flattened chondrules. We therefore suggest that cyclical, indigenous environmental processes, rather than impact gardening, could be responsible for many (most?) of the late stage petrologic characteri

  1. Symmetry Restoration By Acceleration

    E-print Network

    P. Castorina; M. Finocchiaro

    2012-07-16

    The restoration of spontaneous symmetry breaking for a scalar field theory for an accelerated observer is discussed by the one-loop effective potential calculation and by considering the effective potential for composite operators. Above a critical acceleration, corresponding to the critical restoration temperature,T_c, for a Minkowski observer by Unruh relation, i.e. a_c/2\\pi=T_c, the symmetry is restored. This result confirms other recent calculations in effective field theories that symmetry restoration can occur for an observer with an acceleration larger than some critical value. From the physical point of view, a constant acceleration is locally equivalent to a gravitational field and the critical acceleration to restore the spontaneous symmetry breaking corresponds to a huge gravitational effect which, therefore, prevents boson condensation.

  2. Collinear wake field acceleration

    SciTech Connect

    Bane, K.L.F.; Chen, P.; Wilson, P.B.

    1985-04-01

    In the Voss-Weiland scheme of wake field acceleration a high current, ring-shaped driving bunch is used to accelerate a low current beam following along on axis. In such a structure, the transformer ratio, i.e., the ratio of maximum voltage that can be gained by the on-axis beam and the voltage lost by the driving beam, can be large. In contrast, it has been observed that for an arrangement in which driving and driven bunches follow the same path, and where the current distribution of both bunches is gaussian, the transformer ratio is not normally greater than two. This paper explores some of the possibilities and limitations of a collinear acceleration scheme. In addition to its application to wake field acceleration in structures, this study is also of interest for the understanding of the plasma wake field accelerator. 11 refs., 4 figs.

  3. Cyclic Peptidomimetics and Pseudopeptides from Multicomponent Reactions

    NASA Astrophysics Data System (ADS)

    Wessjohann, Ludger A.; Rhoden, Cristiano R. B.; Rivera, Daniel G.; Vercillo, Otilie Eichler

    Multicomponent reactions (MCRs) that provide in the final product amides are suitable to produce peptides and peptide-like moieties. The Passerini and Staudinger reactions provide one amide bond, and the Ugi-four-component reaction generates two amides from three or even four (or more) components, respectively. The Ugi-reaction thus is most important to produce peptides and peptoids while the Passerini reaction is useful to generate depsipeptoid moieties. In order to produce cyclic peptides and pseudopeptides, the linear peptidic MCR products have to be cyclized, usually with the help of bifunctional or activatable building blocks. Orthogonal but cyclizable secondary functionalities that need no protection in isonitrile MCRs commonly include alkenes (for ring closing metathesis), azide/alkyne (for Huisgen click reactions) or dienes and enoates (Diels-Alder) etc. If MCR-reactive groups are to be used also for the cyclisation, monoprotected bifunctional building blocks are used and deprotected after the MCR, e.g. for Ugi reactions as Ugi-Deprotection-Cyclisation (UDC). Alternatively one of the former building blocks or functional groups generated by the MCR can be activated. Most commonly these are activated amides (from so-called convertible isonitriles) which can be used e.g. for Ugi-Activation-Cyclisation (UAC) protocols, or most recently for a simultaneous use of both strategies Ugi-Deprotection/Activation-Cyclisation (UDAC). These methods mostly lead to small, medicinally relevant peptide turn mimics. In an opposing strategy, the MCR is rather used as ring-closing reaction, thereby introducing a (di-)peptide moiety. Most recently these processes have been combined to use MCRs for both, linear precursor synthesis and cyclisation. These multiple MCR approaches allow the most efficient and versatile one pot synthesis of macrocyclic pseudopeptides known to date.

  4. A Material Model for the Cyclic Behavior of Nitinol

    NASA Astrophysics Data System (ADS)

    Rebelo, Nuno; Zipse, Achim; Schlun, Martin; Dreher, Gael

    2011-07-01

    The uniaxial behavior of Nitinol in different forms and at different temperatures has been well documented in the literature. Mathematical models for the three-dimensional behavior of this class of materials, covering superelasticity, plasticity, and shape memory effects have been previously developed. Phenomenological models embedded in FEA analysis are part of common practice today in the development of devices made out of Nitinol. In vivo loading of medical devices has cyclic characteristics. There have been some indications in the literature that cyclic loading of Nitinol modifies substantially its behavior. A consortium of several stent manufacturers, Safe Technology and Dassault Systèmes Simulia Corp., dedicated to the development of fatigue laws suitable for life prediction of Nitinol devices, has conducted an extensive experimental study of the modifications in uniaxial behavior of both Nitinol wire and tubing due to cyclic loading. The Abaqus Nitinol material model has been extended to capture some of the phenomena observed and is described in this article. Namely, a preload beyond 6% strain alters the transformation plateaus; if the cyclic load amplitude is large enough, permanent deformations (residual martensite) are observed; the lower plateau increases; and the upper plateau changes. The modifications to the upper plateau are very interesting in the sense that it appears broken: its start stress gets lowered creating a new plateau up to the highest level of cyclic strain, followed by resuming the original plateau until full transformation. Since quite often the geometry of a device at the point at which it is subjected to cyclic loading is very much dependent on the manufacturing, deployment, and preloading sequence, it is important that analyses be conducted with the original material behavior up to that point, and then with the cyclic behavior thereafter.

  5. Large electrostatic accelerators

    SciTech Connect

    Jones, C.M.

    1984-01-01

    The increasing importance of energetic heavy ion beams in the study of atomic physics, nuclear physics, and materials science has partially or wholly motivated the construction of a new generation of large electrostatic accelerators designed to operate at terminal potentials of 20 MV or above. In this paper, the author briefly discusses the status of these new accelerators and also discusses several recent technological advances which may be expected to further improve their performance. The paper is divided into four parts: (1) a discussion of the motivation for the construction of large electrostatic accelerators, (2) a description and discussion of several large electrostatic accelerators which have been recently completed or are under construction, (3) a description of several recent innovations which may be expected to improve the performance of large electrostatic accelerators in the future, and (4) a description of an innovative new large electrostatic accelerator whose construction is scheduled to begin next year. Due to time and space constraints, discussion is restricted to consideration of only tandem accelerators.

  6. Amps particle accelerator definition study

    NASA Technical Reports Server (NTRS)

    Sellen, J. M., Jr.

    1975-01-01

    The Particle Accelerator System of the AMPS (Atmospheric, Magnetospheric, and Plasmas in Space) payload is a series of charged particle accelerators to be flown with the Space Transportation System Shuttle on Spacelab missions. In the configuration presented, the total particle accelerator system consists of an energetic electron beam, an energetic ion accelerator, and both low voltage and high voltage plasma acceleration devices. The Orbiter is illustrated with such a particle accelerator system.

  7. 8-Bromo-cyclic inosine diphosphoribose: towards a selective cyclic ADP-ribose agonist

    PubMed Central

    Kirchberger, Tanja; Moreau, Christelle; Wagner, Gerd K.; Fliegert, Ralf; Siebrands, Cornelia C.; Nebel, Merle; Schmid, Frederike; Harneit, Angelika; Odoardi, Francesca; Flügel, Alexander; Potter, Barry V. L.; Guse, Andreas H.

    2009-01-01

    cADPR (cyclic ADP-ribose) is a universal Ca2+ mobilizing second messenger. In T-cells cADPR is involved in sustained Ca2+ release and also in Ca2+ entry. Potential mechanisms for the latter include either capacitative Ca2+ entry, secondary to store depletion by cADPR, or direct activation of the non-selective cation channel TRPM2 (transient receptor potential cation channel, subfamily melastatin, member 2). Here we characterize the molecular target of the newly-described membrane-permeant cADPR agonist 8-Br-N1-cIDPR (8-bromo-cyclic IDP-ribose). 8-Br-N1-cIDPR evoked Ca2+ signalling in the human T-lymphoma cell line Jurkat and in primary rat T-lymphocytes. Ca2+ signalling induced by 8-Br-N1-cIDPR consisted of Ca2+ release and Ca2+ entry. Whereas Ca2+ release was sensitive to both the RyR (ryanodine receptor) blocker RuRed (Ruthenium Red) and the cADPR antagonist 8-Br-cADPR (8-bromo-cyclic ADP-ribose), Ca2+ entry was inhibited by the Ca2+ entry blockers Gd3+ (gadolinium ion) and SKF-96365, as well as by 8-Br-cADPR. To unravel a potential role for TRPM2 in sustained Ca2+ entry evoked by 8-Br-N1-cIDPR, TRPM2 was overexpressed in HEK (human embryonic kidney)-293 cells. However, though activation by H2O2 was enhanced dramatically in those cells, Ca2+ signalling induced by 8-Br-N1-cIDPR was almost unaffected. Similarly, direct analysis of TRPM2 currents did not reveal activation or co-activation of TRPM2 by 8-Br-N1-cIDPR. In summary, the sensitivity to the Ca2+ entry blockers Gd3+ and SKF-96365 is in favour of the concept of capacitative Ca2+ entry, secondary to store depletion by 8-Br-N1-cIDPR. Taken together, 8-Br-N1-cIDPR appears to be the first cADPR agonist affecting Ca2+ release and secondary Ca2+ entry, but without effect on TRPM2. PMID:19492987

  8. Ion beam accelerator system

    NASA Technical Reports Server (NTRS)

    Aston, Graeme (Inventor)

    1984-01-01

    A system is described that combines geometrical and electrostatic focusing to provide high ion extraction efficiency and good focusing of an accelerated ion beam. The apparatus includes a pair of curved extraction grids (16, 18) with multiple pairs of aligned holes positioned to direct a group of beamlets (20) along converging paths. The extraction grids are closely spaced and maintained at a moderate potential to efficiently extract beamlets of ions and allow them to combine into a single beam (14). An accelerator electrode device (22) downstream from the extraction grids, is at a much lower potential than the grids to accelerate the combined beam.

  9. The MESA accelerator

    SciTech Connect

    Aulenbacher, Kurt [Institut für Kernphysik, Johannnes-Gutenberg-Universität Mainz (Germany)

    2013-11-07

    The MESA accelerator will operate for particle and nuclear physics experiments in two different modes. A first option is conventional c.w. acceleration yielding 150-200MeV spin-polarized external beam. Second, MESA will be operated as a superconducting multi-turn energy recovery linac (ERL), opening the opportunity to perform experiments with a windowless target with beam current of up to 10 mA. The perspectives for innovative experiments with such a machine are discussed together with a sketch of the accelerator physics issues that have to be solved.

  10. Cyclic peptides. X. Bitter taste and chymotryptic hydrolysis of cyclic depsidipeptides containing a tryptophan residue.

    PubMed

    Miyazaki, K; Yasutake, A; Nishino, N; Aoyagi, H; Kato, T; Izumiya, N

    1981-01-01

    Four stereoisomers (I-LL, I-LD, I-DL and I-DD) of a cyclic depsidipeptide (I) containing a tryptophan and a 2-hydroxy-4-methylpentanoic acid residue were synthesized, and their taste and chymotryptic susceptibility were examined. Compound I-LL is a depsipeptide analog of a bitter principle BP-II, cyclo(-L-Trp-L-Leu-), obtained from casein hydrolyzate. All of the four stereoisomers of I are strongly bitter to taste. Another depsipeptide analog, L-aspartyl-L-2-hydroxy-3-phenylpropanoic acid methyl ester, of the sweet H-L-Asp-L-Phe-OMe showed bitter taste instead of sweet. Chymotrypsin hydrolyzed I-LL and I-LD in moderate rates, and I-DL and I-DD very slowly. PMID:7228487

  11. Cyclic peptides. VIII. Synthesis and tryptic hydrolysis of cyclic depsidipeptides containing a lysine residue.

    PubMed

    Yasutake, A; Miyazaki, K; Aoyagi, H; Kato, T; Izumiya, N

    1980-07-01

    Four stereoisomers of a cyclic depsidipeptide containing a lysine and a 2-hydroxy-3-phenylpropanoic acid (Hpp) residue have been synthesized and their susceptibility toward trypsin examined. Trypsin hydrolyzed cyclo(-L-Lys-L-Hpp-) (I-LL) and cyclo(-L-Lys-D-Hpp-) (I-LD) rapidly and cyclo(-D-Lys-L-Hpp-) (I-DL) and cyclo(-D-Lys-D-Hpp-) (I-DD) very slowly. Proteolytic coefficients of these substrates and a reference compound are shown as follows: I-LL, 112; I-LD, 34; I-DL, 0.34; I-DD, 0.11, and Ac-L-Lys-OEt, 44. Possible mode of actin of trypsin on these substrates was discussed. PMID:6777325

  12. Effect of cyclic tension on lacerated flexor tendons in vitro.

    PubMed

    Tanaka, H; Manske, P R; Pruitt, D L; Larson, B J

    1995-05-01

    The effect of tension on tendon healing was evaluated in vitro using cyclic tension and no tension groups of chicken flexor digitorum profundus tendons and histologic and immunohistologic techniques. A Vitrodyne force-loading machine was used for application of cyclic tension on partially lacerated chicken flexor tendons in culture media. Laceration sites under cyclic tension after 14 days were covered by newly proliferated fibroblasts, aligned in the direction of tension. This new growth was much thicker than that seen in the no tension group at the same time interval. Procollagen synthetic activity began at 3 days of culture in both groups. At 21 days, newly formed fibroblasts in the cyclic tension group were stained positive more strongly at the surface layer than in the deeper layers. In the no tension group, the staining was primarily in the surface layer. Cyclic tension stimulated the intrinsic response of lacerated flexor tendons significantly more than no tension did by enhancing proliferation and migration of fibroblasts, as well as stimulating collagen synthesis. PMID:7642929

  13. Sequences and cyclicities in the upper Rotliegende of the Netherlands

    SciTech Connect

    Kouwe, W. (InterGeos, Leiderdorp (Netherlands))

    1993-09-01

    A regional study of released well and core data from the Netherlands on- and offshore territory, performed by InterGeos, has revealed the preservation of supersequences, sequences, and short-term cyclicities in upper Rotliegende deposits. These have always been interpreted as formed in an inland basin, disconnected from marine influence. Sequences and cyclicities are reflected in vertical sections by correlatable alternations of lithofacies, which can be observed in cores and wireline logs. The lithofacies shifts, which often show a marked periodicity, are interpreted as caused by climatic fluctuations. This implies that sequence stratigraphic methods can be used also in the southern Permian basin, even though direct marine influence is dubious. Supersequences, sequences, and cyclicities each have specific applications in Rotliegende exploration. Supersequences serve best for rough regional correlation and prediction of sand and clay. Sequences are suited for detailed regional or field correlation and studies of the detailed distribution of (un) favorable lithofacies, e.g., within a field. the correlation of sequences has revealed that existing lithostratigraphy is diachronous in character. Short-term cycles can be used to make estimates of net sedimentation rates and sequence durations, because the periods of these Milankovitch cycles are known. Short-term cyclicities are preserved better in the desert red beds of the rotliegende than in coastal plain deposits such as the Carboniferous, where they are overprinted heavily by longer term cyclicities.

  14. Viscoplastic response of tooth enamel under cyclic microindentation.

    PubMed

    Jia, Yunfei; Xuan, Fu-Zhen; Yang, Fuqian

    2015-10-01

    Cyclic microindentations were performed on the occlusal surface and axial section of tooth enamel, using the Berkovich indenter. Under the action of a cyclic indentation load, the indenter continuously penetrated into the tooth enamel and reached a quasi-steady state at which the penetration depth per cycle was a constant. At the quasi-steady state, both the amplitude of the indentation depth and the penetration depth per cycle for the cyclic indentation of the axial section are larger than those for the indentation of the occlusal section under the same loading condition. The energy dissipation per cycle consists of two contributions; one is the plastic energy dissipated per cycle due to the propagation of the plastic zone underneath the indentation and the other is the energy dissipation due to the viscous flow during the cyclic indentation. Both the penetration depth and the plastic energy dissipated per cycle at the quasi-steady state are independent of the maximum applied load and increase with increasing the amplitude of the cyclic indentation load. PMID:26117776

  15. Strain estimates for small-ring cyclic allenes and butatrienes.

    PubMed

    Daoust, Kimberly J; Hernandez, Susanna M; Konrad, Kaleen M; Mackie, Iain D; Winstanley, James; Johnson, Richard P

    2006-07-21

    Isodesmic and homodesmic equations at the B3LYP/6-311+G(d,p)+ZPVE level of theory have been used to estimate strain for the homologous series of cyclic allenes and cyclic butatrienes. A simple fragment deformation approach also has been applied and appears to work better for the larger rings. For the cyclic allene series, estimates for allene functional group strain (kcal/mol) include: 1,2-cyclobutadiene, 65; 1,2-cyclopentadiene, 51; 1,2-cyclohexadiene, 32; 1,2-cycloheptadiene, 14; 1,2-cyclooctadiene, 5; 1,2-cyclononadiene, 2; 1,2,4-cyclohexatriene, 34; and bicyclo[3.2.1]octa-2,3-diene, 39. For cyclic butatrienes, functional group strain estimates include: 1,2,3-cyclobutatriene, >100; 1,2,3-cyclopentatriene, 80; 1,2,3-cyclohexatriene, 50; 1,2,3-cycloheptatriene, 26; 1,2,3-cyclooctatriene, 17; and 1,2,3-cyclononatriene, 4. Barriers to interconversion of enantiomers in cyclic allenes are reduced with increasing strain. Newly predicted values include: 1,2-cyclopentadiene <1 kcal/mol and bicyclo[3.2.1]octa-2,3-diene, 7.4 kcal/mol. Estimated levels of strain parallel the known reactivity of these substances. PMID:16839152

  16. Analysis of cyclic combustion of the coal-water suspension

    NASA Astrophysics Data System (ADS)

    Kijo-Kleczkowska, Agnieszka

    2011-04-01

    Combustion technology of the coal-water suspension creates a number of new possibilities to organize the combustion process fulfilling contemporary requirements, e.g. in the environment protection. Therefore the in-depth analysis is necessary to examine the technical application of coal as a fuel in the form of suspension. The research undertakes the complex investigations of the continuous coal-water suspension as well as cyclic combustion. The cyclic nature of fuel combustion results from the movement of the loose material in the flow contour of the circulating fluidized bed (CFB): combustion chamber, cyclone and downcomer. The experimental results proved that the cyclic change of oxygen concentration around fuel, led to the vital change of both combustion mechanisms and combustion kinetics. The mathematical model of the process of fuel combustion has been presented. Its original concept is based on the allowance for cyclic changes of concentrations of oxygen around the fuel. It enables the prognosis for change of the surface and the centre temperatures as well as mass loss of the fuel during combustion in air, in the fluidized bed and during the cyclic combustion.

  17. Cyclic material properties tests supporting elastic-plastic analysis development

    SciTech Connect

    Hodge, S.C.; Minicucci, J.M. [Electric Boat Corp., Groton, CT (United States)

    1996-11-01

    Correlation studies have shown that hardening models currently available in the ABAQUS finite element code (isotropic, kinematic) do not accurately capture the inelastic strain reversals that occur due to structural rebounding from a rapidly applied transient dynamic load. The purpose of the Cyclic Material properties Test program was to obtain response data for the first several cycles of inelastic strain reversal from a cyclic properties test. This data is needed to develop elastic-plastic analysis methods that can accurately predict strains and permanent sets in structures due to rapidly applied transient dynamic loading. Test specimens were cycled at inelastic strain levels typical of rapidly applied transient dynamic analyses (0.5% to 4.0%). In addition to the inelastic response data, cyclic material properties for high yield strength (80 ksi) steel were determined including a cyclic stress-strain curve for a stabilized specimen. Two test methods, the Incremental Step method and the Companion specimen Method, were sued to determine cyclic properties. The incrementally decreasing strain amplitudes in the first loading block of the Incremental Step method test is representative of the response of structures subjected to rapidly applied transient dynamic loads. The inelastic strain history data generated by this test program will be used to support development of a material model that can accurately predict inelastic material behavior including inelastic strain reversals. Additionally, this data can be used to verify material model enhancements to elastic-plastic finite element analysis codes.

  18. Numerical modeling of centrifuge cyclic lateral pile load experiments

    NASA Astrophysics Data System (ADS)

    Gerolymos, Nikos; Escoffier, Sandra; Gazetas, George; Garnier, Jacques

    2009-03-01

    To gain insight into the inelastic behavior of piles, the response of a vertical pile embedded in dry sand and subjected to cyclic lateral loading was studied experimentally in centrifuge tests conducted in Laboratoire Central des Ponts et Chaussées. Three types of cyclic loading were applied, two asymmetric and one symmetric with respect to the unloaded pile. An approximately square-root variation of soil stiffness with depth was obtained from indirect in-flight density measurements, laboratory tests on reconstituted samples, and well-established empirical correlations. The tests were simulated using a cyclic nonlinear Winkler spring model, which describes the full range of inelastic phenomena, including separation and re-attachment of the pile from and to the soil. The model consists of three mathematical expressions capable of reproducing a wide variety of monotonic and cyclic experimental p-y curves. The physical meaning of key model parameters is graphically explained and related to soil behavior. Comparisons with the centrifuge test results demonstrate the general validity of the model and its ability to capture several features of pile-soil interaction, including: soil plastification at an early stage of loading, “pinching” behavior due to the formation of a relaxation zone around the upper part of the pile, and stiffness and strength changes due to cyclic loading. A comparison of the p-y curves derived from the test results and the proposed model, as well as those from the classical curves of Reese et al. (1974) for sand, is also presented.

  19. Low severity coal liquefaction promoted by cyclic olefins

    SciTech Connect

    Curtis, C.W.

    1992-01-01

    Low severity coal liquefaction promoted by cyclic olefins offers a means of liquefying coal at low severity conditions. Lower temperature, 350[degrees]C, and lower hydrogen pressure, 500 psi, have been used to perform liquefaction reactions. The presence of the cyclic olefin, hexahydroanthracene, made a substantial difference in the conversion of Illinois No. 6 coal at these low severity conditions. The Researchperformed this quarter was a parametric evaluation of the effect of different parameters on the coal conversion and product distribution from coal. The effect of the parameters on product distribution from hexahydroanthracene was also determined. The work planned for next quarter includes combining the most effective parametric conditions for the low severity reactions and determining their effect. The second part ofthe research performed this quarter involved performing Fourier transform infrared (FTIR) spectroscopy using cyclic olefins. The objective of this study was to determine the feasibility of using FTIR and a heated cell to determine the reaction pathway that occurs in the hydrogen donation reactions from cyclic olefins. The progress made to date includes evaluating the FTIR spectra of cyclic olefins and their expected reaction products. This work is included in this progress report.

  20. Cyclic electron flow around photosystem I is essential for photosynthesis.

    PubMed

    Munekage, Yuri; Hashimoto, Mihoko; Miyake, Chikahiro; Tomizawa, Ken-ichi; Endo, Tsuyoshi; Tasaka, Masao; Shikanai, Toshiharu

    2004-06-01

    Photosynthesis provides at least two routes through which light energy can be used to generate a proton gradient across the thylakoid membrane of chloroplasts, which is subsequently used to synthesize ATP. In the first route, electrons released from water in photosystem II (PSII) are eventually transferred to NADP+ by way of photosystem I (PSI). This linear electron flow is driven by two photochemical reactions that function in series. The cytochrome b6f complex mediates electron transport between the two photosystems and generates the proton gradient (DeltapH). In the second route, driven solely by PSI, electrons can be recycled from either reduced ferredoxin or NADPH to plastoquinone, and subsequently to the cytochrome b6f complex. Such cyclic flow generates DeltapH and thus ATP without the accumulation of reduced species. Whereas linear flow from water to NADP+ is commonly used to explain the function of the light-dependent reactions of photosynthesis, the role of cyclic flow is less clear. In higher plants cyclic flow consists of two partially redundant pathways. Here we have constructed mutants in Arabidopsis thaliana in which both PSI cyclic pathways are impaired, and present evidence that cyclic flow is essential for efficient photosynthesis. PMID:15175756

  1. Cyclic Adenosine 3?:5?-Monophosphate in Moss Protonema

    PubMed Central

    Handa, Avtar Krishan; Johri, Man Mohan

    1977-01-01

    From the protonema of the moss Funaria hygrometrica (L.) Sibth, a factor indistinguishable from cyclic adenosine 3?:5?-monophosphate (cAMP) has been isolated. The factor stimulated the activity of protein kinase from rabbit skeletal muscle and co-chromatographed with authentic cAMP in two solvent systems. Its ability to stimulate protein kinase activity was completely abolished by 3?:5?-cyclic nucleotide phosphodiesterase, the rate of inactivation being similar to that of authentic cAMP. Based on these properties, this factor is identified as 3?,5?-cAMP. Cyclic AMP could be readily removed from the cells and washing the cells with water reduced the endogenous level of cAMP by 2- to 3-fold. A comparison of cAMP levels by protein kinase and Gilman assays was made. The intracellular levels determined by protein kinase assay were about 7-fold lower than the values obtained by Gilman assay. This discrepancy was due to the presence of unidentified compounds which were completely degraded by 3?:5?-cyclic nucleotide phosphodiesterase. Although these displaced labeled cAMP in the Gilman assay, they did not stimulate the protein kinase activity. The protonema may contain cyclic nucleotides other than cAMP; these will not be detected in the protein kinase assay due to the specificity of this reaction. The crude extracts were found to be unsuitable for assaying cAMP by either method. PMID:16659878

  2. Accelerator on a Chip

    SciTech Connect

    England, Joel

    2014-06-30

    SLAC's Joel England explains how the same fabrication techniques used for silicon computer microchips allowed their team to create the new laser-driven particle accelerator chips. (SLAC Multimedia Communications)

  3. Accelerator on a Chip

    ScienceCinema

    England, Joel

    2014-07-16

    SLAC's Joel England explains how the same fabrication techniques used for silicon computer microchips allowed their team to create the new laser-driven particle accelerator chips. (SLAC Multimedia Communications)

  4. Acceleration of Logarithmic Convergence

    NASA Technical Reports Server (NTRS)

    Gaskin, J. G.; Ford, W. F.

    1998-01-01

    In this paper, we shall give a characterization of all monotonically decreasing sequence of positive terms, whose sum converge and then introduce a Transformation which can be used to accelerate the convergence of a large class of logarithmically convergent series.

  5. Charged particle accelerator grating

    DOEpatents

    Palmer, R.B.

    1985-09-09

    A readily disposable and replaceable accelerator grating for a relativistic particle accelerator is described. The grating is formed for a plurality of liquid droplets that are directed in precisely positioned jet streams to periodically dispose rows of droplets along the borders of a predetermined particle beam path. A plurality of lasers are used to direct laser beams onto the droplets, at predetermined angles, thereby to excite the droplets to support electromagnetic accelerating resonances on their surfaces. Those resonances operate to accelerate and focus particles moving along the beam path. As the droplets are distorted or destroyed by the incoming radiation, they are replaced at a predetermined frequency by other droplets supplied through the jet streams.

  6. Vibration control in accelerators

    SciTech Connect

    Montag, C.

    2011-01-01

    In the vast majority of accelerator applications, ground vibration amplitudes are well below tolerable magnet jitter amplitudes. In these cases, it is necessary and sufficient to design a rigid magnet support structure that does not amplify ground vibration. Since accelerator beam lines are typically installed at an elevation of 1-2m above ground level, special care has to be taken in order to avoid designing a support structure that acts like an inverted pendulum with a low resonance frequency, resulting in untolerable lateral vibration amplitudes of the accelerator components when excited by either ambient ground motion or vibration sources within the accelerator itself, such as cooling water pumps or helium flow in superconducting magnets. In cases where ground motion amplitudes already exceed the required jiter tolerances, for instance in future linear colliders, passive vibration damping or active stabilization may be considered.

  7. Motion with Constant Acceleration

    NSDL National Science Digital Library

    Dr. Russell Herman

    The purpose of this experiment is to track the motion for an air cart on a sloped track to fall a distance x with constant acceleration a = g sinq. You will verify that the distance and velocity along the incline are given by the parabola x = xo + vo t +1/2at2 and the line v = vo +at. Finally, you will determine the acceleration due to gravity.

  8. An active particle accelerator

    SciTech Connect

    Goldman, T.

    1991-01-01

    Although a static charge is difficult to maintain on macroscopic particles, it is straightforward to construct a small object with a regularly oscillating electric dipole moment. For objects of a given size, one may then construct an accelerator by appropriately matching the frequency and separations of an external array of electrodes to this size. Physically feasible size ranges, an accelerator design, and possible applications of such systems are discussed. 8 refs., 9 figs.

  9. CEBAF accelerator achievements

    SciTech Connect

    Y.C. Chao, M. Drury, C. Hovater, A. Hutton, G.A. Krafft, M. Poelker, C. Reece, M. Tiefenback

    2011-06-01

    In the past decade, nuclear physics users of Jefferson Lab's Continuous Electron Beam Accelerator Facility (CEBAF) have benefited from accelerator physics advances and machine improvements. As of early 2011, CEBAF operates routinely at 6 GeV, with a 12 GeV upgrade underway. This article reports highlights of CEBAF's scientific and technological evolution in the areas of cryomodule refurbishment, RF control, polarized source development, beam transport for parity experiments, magnets and hysteresis handling, beam breakup, and helium refrigerator operational optimization.

  10. Breakthrough: Fermilab Accelerator Technology

    ScienceCinema

    None

    2014-08-12

    There are more than 30,000 particle accelerators in operation around the world. At Fermilab, scientists are collaborating with other laboratories and industry to optimize the manufacturing processes for a new type of powerful accelerator that uses superconducting niobium cavities. Experimenting with unique polishing materials, a Fermilab team has now developed an efficient and environmentally friendly way of creating cavities that can propel particles with more than 30 million volts per meter.

  11. UHECR acceleration in dark matter filaments of cosmological structure formation

    SciTech Connect

    Malkov, M.A.; Diamond, P.H. [CASS and Department of Physics, University of California, San Diego, La Jolla, CA 92093-0424 (United States); Sagdeev, R.Z., E-mail: mmalkov@ucsd.edu, E-mail: rzs@umd.edu, E-mail: phd@physics.ucsd.edu [University of Maryland, College Park, MD 20742-3280 (United States)

    2011-04-01

    A mechanism for proton acceleration to ? 10{sup 21} eV is suggested. It may operate in accretion flows onto thin dark matter filaments of cosmic structure formation. The flow compresses the ambient magnetic field to strongly increase and align it with the filament. Particles begin the acceleration by E × B drift with the accretion flow. The energy gain in the drift regime is limited by the conservation of the adiabatic invariant p{sub p}erpendicular{sup 2}/B(r). Upon approaching the filament, the drift turns into the gyro-motion around the filament so that the particle moves parallel to the azimuthal electric field. In this 'betatron' regime the acceleration speeds up to rapidly reach the electrodynamic limit cp{sub max} = eBR for an accelerator with magnetic field B and the orbit radius R (Larmor radius). The periodic orbit becomes unstable and the particle slings out of the filament to the region of a weak (uncompressed) magnetic field, which terminates the acceleration. To escape the filament, accelerated particles must have gyro-radii comparable with the filament radius. Therefore, the mechanism requires pre-acceleration that is likely to occur in large scale shocks upstream or nearby the filament accretion flow. Previous studies identify such shocks as efficient proton accelerators, with a firm upper limit ? 10{sup 19.5} eV placed by the catastrophic photo-pion losses. The present mechanism combines explosive energy gain in its final (betatron) phase with prompt particle release from the region of strong magnetic field. It is this combination that allows protons to overcome both the photo-pion and the synchrotron-Compton losses and therefore attain energy ? 10{sup 21} eV. A customary requirement on accelerator power to reach a given E{sub max}, which is placed by the accelerator energy dissipation ?E{sub max}{sup 2}/Z{sub 0} due to the finite vacuum impedance Z{sub 0}, is circumvented by the cyclic operation of the accelerator.

  12. Cyclic peptide marine metabolites and CuII.

    PubMed

    Comba, Peter; Dovalil, Nina; Gahan, Lawrence R; Hanson, Graeme R; Westphal, Michael

    2014-02-01

    Cyclic pseudo-peptides derived from marine metabolites of the genus Lissoclinum bistratum and Lissoclinum patella have attracted scientific interest in the last two decades. Their structural properties and solution dynamics have been analyzed in detail, elaborate synthetic procedures for the natural products and synthetic derivatives developed, the biosynthetic pathways studied and it now is possible to produce them biosynthetically. Initially, these macrocyclic ligands were studied due to their medicinal and pharmaceutical potential - some of the isolated cyclic pseudo-peptides show high cytotoxic and antiviral activity. A major focus in the last decade has been on their Cu(II) coordination chemistry, as a number of studies have indicated that dinuclear Cu(II) complexes of cyclic peptides may be involved in the ascidians' metabolism, and this is the focus of the present review. PMID:24202205

  13. Low Severity Coal Liquefaction Promoted by Cyclic Olefins

    SciTech Connect

    Christine W. Curtis

    1998-04-09

    The development of the donor solvent technology for coal liquefaction has drawn a good deal of attention over the last three decades. The search for better hydrogen donors led investigators to a class of compounds known as cyclic olefins. Cyclic olefins are analogues of the conventional hydroaromatic donor species but do not contain aromatic rings. The cyclic olefins are highly reactive compounds which readily release their hydrogen at temperatures of 200 C or higher. Considerable effort has been o expended toward understanding the process of hydrogen donation. Most of this work was conducted in bomb reactors, with product analysis being carried out after the reaction was complete. Efforts directed towards fundamental studies of these reactions in situ are rare. The current work employs a high temperature and high pressure infrared cell to monitor in situ the concentrations of reactants and products during hydrogen release from hydrogen donor compounds.

  14. On the connection between multigrid and cyclic reduction

    NASA Technical Reports Server (NTRS)

    Merriam, M. L.

    1984-01-01

    A technique is shown whereby it is possible to relate a particular multigrid process to cyclic reduction using purely mathematical arguments. This technique suggest methods for solving Poisson's equation in 1-, 2-, or 3-dimensions with Dirichlet or Neumann boundary conditions. In one dimension the method is exact and, in fact, reduces to cyclic reduction. This provides a valuable reference point for understanding multigrid techniques. The particular multigrid process analyzed is referred to here as Approximate Cyclic Reduction (ACR) and is one of a class known as Multigrid Reduction methods in the literature. It involves one approximation with a known error term. It is possible to relate the error term in this approximation with certain eigenvector components of the error. These are sharply reduced in amplitude by classical relaxation techniques. The approximation can thus be made a very good one.

  15. The SU(3) Algebra in a Cyclic Basis

    E-print Network

    P. F. Harrison; R. Krishnan; W. G. Scott

    2014-07-31

    With the couplings between the eight gluons constrained by the structure constants of the su(3) algebra in QCD, one would expect that there should exist a special basis (or set of bases) for the algebra wherein, unlike in a Cartan-Weyl basis, {\\em all} gluons interact identically (cyclically) with each other, explicitly on an equal footing. We report here particular such bases, which we have found in a computer search, and we indicate associated $3 \\times 3$ representations. We conjecture that essentially all cyclic bases for su(3) may be obtained from these making appropriate circulant transformations,and that cyclic bases may also exist for other su(n), n>3.

  16. Cyclic AMP system in muscle tissue during prolonged hypokinesia

    NASA Technical Reports Server (NTRS)

    Antipenko, Y. A.; Bubeyev, Y. A.; Korovkin, B. F.; Mikhaleva, N. P.

    1980-01-01

    Components of the cyclic Adenosine-cyclic-35-monophosphate (AMP) system in the muscle tissue of white rats were studied during 70-75 days of hypokinesia, created by placing the animals in small booths which restricted their movements, and during the readaptation period. In the initial period, cyclic AMP levels and the activities of phosphodiesterase and adenylate cyclase in muscle tissue were increased. The values for these indices were roughly equal for controls and experimental animals during the adaptation period, but on the 70th day of the experiment cAMP levels dropped, phosphodiesterase activity increased, and the stimulative effect of epinephrine on the activity of adenylate cyclase decreased. The indices under study normalized during the readaptation period.

  17. Cyclic nucleotide regulation of teleost rod photoreceptor inner segment length

    PubMed Central

    1993-01-01

    Retinal rod photoreceptors of teleost fish elongate in the light and shorten in the dark. Rod cell elongation and shortening are both mediated by actin-dependent mechanisms that occur in the inner segment myoid and ellipsoid. The intracellular signaling pathways by which light and dark regulate the actin cytoskeleton in the inner segment are unknown. To investigate the intracellular signals that regulate teleost rod motility, we have been using mechanically isolated rod inner/outer segments (RIS-ROS) obtained from the retinas of green sunfish, Lepomis cyanellus. In culture, RIS-ROS retain the ability to elongate in response to light; myoids elongate 15-20 microns in length during 45 min of light culture. A pharmacological approach was taken to investigate the role of cyclic nucleotides, cyclic nucleotide-dependent kinases, and protein phosphatases in the regulation of RIS-ROS motility. Millimolar concentrations of cAMP and cGMP analogues were both found to inhibit light-induced myoid elongation and two cyclic nucleotide analogues, SpCAMPS and 8BrcGMP, promoted myoid shortening after RIS-ROS had elongated in response to light. The cyclic nucleotide- dependent kinase inhibitor, H8, mimicked light by promoting myoid elongation in the dark. The effects of H8 were dose dependent, with maximal elongation occurring at concentrations of approximately 100 microM. Similar to the effects of cyclic nucleotide analogues, the phosphatase inhibitor, okadaic acid (0.1-10 microM), inhibited light- induced elongation and promoted shortening. The results presented here suggest that RIS-ROS motility is regulated by protein phosphorylation: phosphorylation in the dark by cyclic nucleotide-dependent protein kinases promotes rod shortening, while dephosphorylation in the light promotes rod elongation. PMID:7690838

  18. Cyclic nucleotide regulation of teleost rod photoreceptor inner segment length.

    PubMed

    Liepe, B A; Burnside, B

    1993-07-01

    Retinal rod photoreceptors of teleost fish elongate in the light and shorten in the dark. Rod cell elongation and shortening are both mediated by actin-dependent mechanisms that occur in the inner segment myoid and ellipsoid. The intracellular signaling pathways by which light and dark regulate the actin cytoskeleton in the inner segment are unknown. To investigate the intracellular signals that regulate teleost rod motility, we have been using mechanically isolated rod inner/outer segments (RIS-ROS) obtained from the retinas of green sunfish, Lepomis cyanellus. In culture, RIS-ROS retain the ability to elongate in response to light; myoids elongate 15-20 microns in length during 45 min of light culture. A pharmacological approach was taken to investigate the role of cyclic nucleotides, cyclic nucleotide-dependent kinases, and protein phosphatases in the regulation of RIS-ROS motility. Millimolar concentrations of cAMP and cGMP analogues were both found to inhibit light-induced myoid elongation and two cyclic nucleotide analogues, SpCAMPS and 8BrcGMP, promoted myoid shortening after RIS-ROS had elongated in response to light. The cyclic nucleotide-dependent kinase inhibitor, H8, mimicked light by promoting myoid elongation in the dark. The effects of H8 were dose dependent, with maximal elongation occurring at concentrations of approximately 100 microM. Similar to the effects of cyclic nucleotide analogues, the phosphatase inhibitor, okadaic acid (0.1-10 microM), inhibited light-induced elongation and promoted shortening. The results presented here suggest that RIS-ROS motility is regulated by protein phosphorylation: phosphorylation in the dark by cyclic nucleotide-dependent protein kinases promotes rod shortening, while dephosphorylation in the light promotes rod elongation. PMID:7690838

  19. Physically Based Rendering Intersection Acceleration

    E-print Network

    Kazhdan, Michael

    Physically Based Rendering (600.657) Intersection Acceleration #12;Intersection Testing Accelerated partitions: Group objects into clusters Cluster volumes may overlap #12;Uniform (Voxel) Grid Acceleration Acceleration · Trace rays through grid cells ­ Fast ­ Incremental A B C D E F Only check primitives

  20. Plasma-based accelerator structures

    SciTech Connect

    Schroeder, Carl B.

    1999-12-01

    Plasma-based accelerators have the ability to sustain extremely large accelerating gradients, with possible high-energy physics applications. This dissertation further develops the theory of plasma-based accelerators by addressing three topics: the performance of a hollow plasma channel as an accelerating structure, the generation of ultrashort electron bunches, and the propagation of laser pulses is underdense plasmas.

  1. Period measurement by accelerating observers

    E-print Network

    Bernhard Rothenstein; Stefan Popescu

    2006-07-04

    We consider the problem of the period measurement in the case of the following scenarios: stationary source of successive light signals and accelerating receiver, stationary receiver and accelerating source of successive light signals and stationary machine gun that fires successive bullets received by an accelerating receiver. The accelerated motion is the hyperbolic one.

  2. Solar Flares and particle acceleration

    E-print Network

    Solar Flares and particle acceleration Eduard Kontar School of Physics and Astronomy University and accelerated particles #12;Solar flares and accelerated particles From Emslie et al., 2004, 2005 Free magnetic Spectroscopic Imager RHESSI is designed to investigate particle acceleration and energy release in solar flares

  3. BCYCLIC: A PARALLEL BLOCK TRIDIAGONAL MATRIX CYCLIC SOLVER

    SciTech Connect

    Hirshman, Steven Paul [ORNL; Lynch, Vickie E [ORNL; Perumalla, Kalyan S [ORNL; Sanchez, Raul [ORNL

    2010-01-01

    A block tri-diagonal matrix is factored with minimal fill-in using a cyclic reduction algorithm that is easily parallelized. Storage of the factored blocks allows the application of the inverse to multiple right-hand sides which may not be known at factorization time. Scalability with the number of block rows is achieved with cyclic reduction, while scalability with the block size is achieved using multithreaded routines (OPENMP, GotoBLAS) for block matrix manipulation. This dual scalability is a noteworthy feature of this new solver, as well as its ability to handle arbitrary block row and processor numbers. Comparisons with other parallel block solvers are presented.

  4. Cyclic explosive activity of the Iceland plume in the quaternary

    NASA Astrophysics Data System (ADS)

    Eroshenko, D. V.; Kharin, G. S.

    2014-02-01

    Data on the volcanic ash layers in 70 DSDP and ODP Sites and 100 cores obtained during cruises of the R/V Akademik Kurchatov and Mikhail Lomonosov were used for compiling tephrostratigraphic scale and schematic distribution maps of the pyroclastic material in the Quaternary sediments of the North Atlantic and Norwegian-Greenland Basin. It is revealed that the distribution of pyroclastic material through this region is characterized by cyclic and spatially irregular patterns. Based on their petrochemical and geochemical properties, these ashes are compared with the volcanics of Iceland and the Jan Mayen islands. The relations between the extreme climatic and cyclic explosive events are discussed.

  5. Bounce and cyclic cosmology in extended nonlinear massive gravity

    SciTech Connect

    Cai, Yi-Fu [Department of Physics, Arizona State University, 650 E. Tyler Mall, Tempe, AZ 85287 (United States); Gao, Caixia [Department of Physics and Astronomy, University of Mississippi, 123 Lewis Hall, University, MS 38677 (United States); Saridakis, Emmanuel N., E-mail: ycai21@asu.edu, E-mail: cgao1@go.olemiss.edu, E-mail: Emmanuel_Saridakis@baylor.edu [Physics Division, National Technical University of Athens, 15780 Zografou Campus, Athens (Greece)

    2012-10-01

    We investigate non-singular bounce and cyclic cosmological evolutions in a universe governed by the extended nonlinear massive gravity, in which the graviton mass is promoted to a scalar-field potential. The extra freedom of the theory can lead to certain energy conditions violations and drive cyclicity with two different mechanisms: either with a suitably chosen scalar-field potential under a given Stückelberg-scalar function, or with a suitably chosen Stückelberg-scalar function under a given scalar-field potential. Our analysis shows that extended nonlinear massive gravity can alter significantly the evolution of the universe at both early and late times.

  6. Cyclolinopeptides B - E, new cyclic peptides from Linum usitatissimum

    Microsoft Academic Search

    Hiroshi Morita; Akira Shishido; Teruki Matsumoto; Hideji Itokawa; Koichi Takeya

    1999-01-01

    New cyclic nona and octapeptides, cyclolinopeptides B - E were isolated from the seeds of Linum usitatissimum and their structures were elucidated as cyclo (-Pro-Pro-Phe-Phe-Val-Ile-Met-Leu-Ile-), cyclo (-Pro-Pro-Phe-Phe-Val-Ile-Mso-Leu-Ile-), cyclo (-Pro-Phe-Phe-Trp-Ile-Mso-Leu-Leu-), and cyclo (-Pro-Leu-Phe-Ile-Mso-Leu-Val-Phe-), respectively, by extensive 2D NMR methods and chemical degradations. Cyclolinopeptides B and E showed immunosuppressive activity.New cyclic nona and octapeptides, cyclolinopeptides B - E were isolated from the

  7. Thermal cyclic durability testing of ceramic materials for turbine engines

    NASA Technical Reports Server (NTRS)

    Lindberg, L. J.

    1986-01-01

    The thermal cyclic durability of commercial ceramic materials for turbine engines was under evaluation since 1978. Ceramic materials are exposed to cyclic diesel-fired burner exhaust at either 1204 or 1371 C (2200 or 2500 F) for up to 3500 hours. The test conditions are selected to simulate the environment experienced by the hot flow path components in an automotive gas turbine engine. The silicon nitride and silicon carbide materials tested are the same ceramic materials currently used on the AGT100 and AGT101 ceramic turbine engine program.

  8. Photon acceleration in laser wakefield accelerators

    NASA Astrophysics Data System (ADS)

    Trines, R. M. G. M.

    2007-07-01

    If the index of a refraction of a dispersive medium, such as a plasma, changes in time, it can be used to change the frequency of light propagating through the medium. This effect is called photon acceleration. It has been predicted in both theory and simulations, and also been demonstrated experimentally for the case of moving ionization fronts in gases (the so-called ionization blueshift) as well as for laser-driven wakefields. Here, we present studies of photon acceleration in laser-driven plasma wakefields. The unique spectral characteristics of this process will be discussed, to distinguish it from e.g. photon acceleration by ionization fronts, frequency domain interferometry or self-phase modulation. The dynamics of the photons in laser-wakefield interaction are studied through both regular particle-in-cell and wave-kinetic simulations. The latter approach provides a powerful, versatile, and easy-to-use method to track the propagation of individual spectral components, providing new insight into the physics of laser-plasma interaction. Theory, simulations and experimental results will be brought together to provide a full understanding of the dynamics of a laser pulse in its own wakefield. Even though the wave-kinetic approach mentioned above has mainly been developed for the description of laser-plasma interaction, it can be applied to a much wider range of fast wave-slow wave interaction processes: Langmuir waves-ion acoustic waves, drift waves-zonal flow, Rossby waves-zonal flow, or even photons-gravitational waves. Several recent results in these areas will be shown, often with surprising results.

  9. Fermi acceleration in astrophysical jets

    E-print Network

    Frank M. Rieger; Valenti Bosch-Ramon; Peter Duffy

    2006-10-05

    We consider the acceleration of energetic particles by Fermi processes (i.e., diffusive shock acceleration, second order Fermi acceleration, and gradual shear acceleration) in relativistic astrophysical jets, with particular attention given to recent progress in the field of viscous shear acceleration. We analyze the associated acceleration timescales and the resulting particle distributions, and discuss the relevance of these processes for the acceleration of charged particles in the jets of AGNs, GRBs and microquasars, showing that multi-component powerlaw-type particle distributions are likely to occur.

  10. Issues regarding acceleration in crystals

    SciTech Connect

    Chen, P. [Stanford Linear Accelerator Center, Menlo Park, CA (United States); Cline, D.B.; Gabella, W.E. [California Univ., Los Angeles, CA (United States). Dept. of Physics

    1992-12-01

    Both self-acceleration and laser-acoustic acceleration in crystals are considered. The conduction electrons in the crystal are treated as a plasma and are the medium through which the acceleration takes place. Self-acceleration is the possible acceleration of part of a bunch due to plasma oscillations driven by the leading part. Laser- acoustic acceleration uses a laser in quasi-resonance with an acoustic wave to pump up the plasma oscillation to accelerate a beam. Self-driven schemes though experimentally simple seem problematic because single bunch densities must be large.

  11. Laser acceleration with open waveguides

    SciTech Connect

    Xie, Ming

    1999-03-01

    A unified framework based on solid-state open waveguides is developed to overcome all three major limitations on acceleration distance and hence on the feasibility of two classes of laser acceleration. The three limitations are due to laser diffraction, acceleration phase slippage, and damage of waveguide structure by high power laser. The two classes of laser acceleration are direct-field acceleration and ponderomotive-driven acceleration. Thus the solutions provided here encompass all mainstream approaches for laser acceleration, either in vacuum, gases or plasmas.

  12. Studies of accelerated compact toruses

    SciTech Connect

    Hartman, C.W.; Eddleman, J.; Hammer, J.H.

    1983-01-04

    In an earlier publication we considered acceleration of plasma rings (Compact Torus). Several possible accelerator configurations were suggested and the possibility of focusing the accelerated rings was discussed. In this paper we consider one scheme, acceleration of a ring between coaxial electrodes by a B/sub theta/ field as in a coaxial rail-gun. If the electrodes are conical, a ring accelerated towards the apex of the cone undergoes self-similar compression (focusing) during acceleration. Because the allowable acceleration force, F/sub a/ = kappaU/sub m//R where (kappa < 1), increases as R/sup -2/, the accelerating distance for conical electrodes is considerably shortened over that required for coaxial electrodes. In either case, however, since the accelerating flux can expand as the ring moves, most of the accelerating field energy can be converted into kinetic energy of the ring leading to high efficiency.

  13. Microelectromechanical acceleration-sensing apparatus

    DOEpatents

    Lee, Robb M. (Albuquerque, NM); Shul, Randy J. (Albuquerque, NM); Polosky, Marc A. (Albuquerque, NM); Hoke, Darren A. (Albuquerque, NM); Vernon, George E. (Rio Rancho, NM)

    2006-12-12

    An acceleration-sensing apparatus is disclosed which includes a moveable shuttle (i.e. a suspended mass) and a latch for capturing and holding the shuttle when an acceleration event is sensed above a predetermined threshold level. The acceleration-sensing apparatus provides a switch closure upon sensing the acceleration event and remains latched in place thereafter. Examples of the acceleration-sensing apparatus are provided which are responsive to an acceleration component in a single direction (i.e. a single-sided device) or to two oppositely-directed acceleration components (i.e. a dual-sided device). A two-stage acceleration-sensing apparatus is also disclosed which can sense two acceleration events separated in time. The acceleration-sensing apparatus of the present invention has applications, for example, in an automotive airbag deployment system.

  14. Sandia LSI accelerated aging and data acquisition techniques

    SciTech Connect

    Walker, J.E.

    1980-04-01

    The purpose of the Microelectronic Evaluation Laboratory at Sandia is to develop a program for evaluating CMOS LSI (complementary metal oxide silicon - large scale integrated) technology devices which are being used for the first time in a weapon system. These evaluations are based on accelerated aging studies and electrical tests to determine the reliability and life of the devices. In accelerated aging, specific, controlled stresses are applied to the device to accelerate time-to-failure. Data are used tin mathematical models to estimate life in acutal use. The stresses used for this technology are temperature and voltage. The devices are stored at temperatures with or without voltage applied (steady-state or cyclical) and periodically tested until at least 50% failures are encountered. Since most current technologies use epoxy-die-attachment, aging temperatures must be under 200/sup 0/C. This delays device failure, and a 16% failure level is used when this extrapolation is considered valid. Statistical analysis is performed on the resultant data to predict reliability with time. The equipment and procedures used for accelerated aging tests are described in detail. The data acquisition system and its use are discussed. All devices, after functional failure has occurred, are given to the failure analysis group for failure evaluations. In order to improve reliability predictions, failure analysis is most concerned with the separation of freak and main life mechanisms. Through these evaluations, higher reliability and longer device life have become a milestone of the future. (LCL)

  15. Dielectric laser accelerators

    NASA Astrophysics Data System (ADS)

    England, R. Joel; Noble, Robert J.; Bane, Karl; Dowell, David H.; Ng, Cho-Kuen; Spencer, James E.; Tantawi, Sami; Wu, Ziran; Byer, Robert L.; Peralta, Edgar; Soong, Ken; Chang, Chia-Ming; Montazeri, Behnam; Wolf, Stephen J.; Cowan, Benjamin; Dawson, Jay; Gai, Wei; Hommelhoff, Peter; Huang, Yen-Chieh; Jing, Chunguang; McGuinness, Christopher; Palmer, Robert B.; Naranjo, Brian; Rosenzweig, James; Travish, Gil; Mizrahi, Amit; Schachter, Levi; Sears, Christopher; Werner, Gregory R.; Yoder, Rodney B.

    2014-10-01

    The use of infrared lasers to power optical-scale lithographically fabricated particle accelerators is a developing area of research that has garnered increasing interest in recent years. The physics and technology of this approach is reviewed, which is referred to as dielectric laser acceleration (DLA). In the DLA scheme operating at typical laser pulse lengths of 0.1 to 1 ps, the laser damage fluences for robust dielectric materials correspond to peak surface electric fields in the GV /m regime. The corresponding accelerating field enhancement represents a potential reduction in active length of the accelerator between 1 and 2 orders of magnitude. Power sources for DLA-based accelerators (lasers) are less costly than microwave sources (klystrons) for equivalent average power levels due to wider availability and private sector investment. Because of the high laser-to-particle coupling efficiency, required pulse energies are consistent with tabletop microJoule class lasers. Combined with the very high (MHz) repetition rates these lasers can provide, the DLA approach appears promising for a variety of applications, including future high-energy physics colliders, compact light sources, and portable medical scanners and radiative therapy machines.

  16. Advanced accelerator theory development

    SciTech Connect

    Sampayan, S.E.; Houck, T.L.; Poole, B.; Tishchenko, N.; Vitello, P.A.; Wang, I.

    1998-02-09

    A new accelerator technology, the dielectric wall accelerator (DWA), is potentially an ultra compact accelerator/pulsed power driver. This new accelerator relies on three new components: the ultra-high gradient insulator, the asymmetric Blumlein and low jitter switches. In this report, we focused our attention on the first two components of the DWA system the insulators and the asymmetric Blumlein. First, we sought to develop the necessary design tools to model and scale the behavior of the high gradient insulator. To perform this task we concentrated on modeling the discharge processes (i.e., initiation and creation of the surface discharge). In addition, because these high gradient structures exhibit favorable microwave properties in certain accelerator configurations, we performed experiments and calculations to determine the relevant electromagnetic properties. Second, we performed circuit modeling to understand energy coupling to dynamic loads by the asymmetric Blumlein. Further, we have experimentally observed a non-linear coupling effect in certain asymmetric Blumlein configurations. That is, as these structures are stacked into a complete module, the output voltage does not sum linearly and a lower than expected output voltage results. Although we solved this effect experimentally, we performed calculations to understand this effect more fully to allow better optimization of this DWA pulse-forming line system.

  17. Acoustic particle acceleration sensors

    SciTech Connect

    Franklin, J.B. [Franklin Scientific Services (work performed while Mr. Franklin was employed by Defence Research Establishment Atlantic); Barry, P.J. [Defence Research Establishment Atlantic, P.O. Box 1012, Dartmouth, B2Y 3Z7 (CANADA)

    1996-04-01

    A crossed dipole array provides a directional receiving capability in a relatively small sensor package and is therefore very attractive for many applications in acoustics. Particle velocity measurements on two axes perpendicular to each other are required to provide the dipole signals. These can be obtained directly using particle velocity sensors or via simple transfer functions using acceleration and displacement sensors. Also, the derivative of the acoustic pressure with respect to space provides a signal proportional to the particle acceleration and gives rise to the pressure gradient sensor. Each of these sensors has strengths and drawbacks depending on the frequency regime of interest, the noise background, and whether a point or a line configuration of dipole sensors is desired. In this paper, the performance of acceleration sensors is addressed using a sensor concept developed at DREA. These sensors exploit bending stresses in a cantilever beam of piezoelectric material to obtain wide bandwidth and high sensitivity. Models which predict the acceleration sensitivity, pressure sensitivity, and natural frequency for this type of sensor are described. Experimental results obtained using several different versions of these sensors are presented and compared with theory. The predicted performance of acceleration sensors are compared with that of pressure gradient arrays and particle velocity sensors. {copyright} {ital 1996 American Institute of Physics.}

  18. Correlation between Experimental Cyclic Fatigue Resistance and Numerical Stress Analysis for Nickel-Titanium Rotary Files

    Microsoft Academic Search

    Min-Ho Lee; Antheunis Versluis; Byung-Min Kim; Chan-Joo Lee; Bock Hur; Hyeon-Cheol Kim

    2011-01-01

    IntroductionThe aim of this investigation was to study cyclic fatigue resistance of various nickel-titanium (NiTi) rotary files under various root canal curvatures by correlating cyclic fatigue fracture tests with finite-element analysis (FEA).

  19. Finite Element Analyses of a Cyclically Loaded Linear Viscoelastic Biodegradable Stent 

    E-print Network

    Murphy, Jason Kyle

    2014-12-03

    cyclic pressure equivalent to an ideal resting blood pressure. The degradation considered is defined as strain-induced. Loading is applied under two cases. A linearly ramped loading is first studied, followed by a creep-cyclic study. Circumferential...

  20. 40 CFR 721.10570 - Cyclic amine reaction product with acetophenone and formaldehyde acid salt (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...New Uses for Specific Chemical Substances § 721.10570 Cyclic amine reaction product with acetophenone...generic). (a) Chemical substance and significant...reporting. (1) The chemical substance identified generically as cyclic amine reaction product with...

  1. Cyclic exchange neighborhood search technique for the K-means clustering problem

    E-print Network

    Thirathon, Nattavude, 1980-

    2004-01-01

    Cyclic Exchange is an application of the cyclic transfers neighborhood search technique for the k-means clustering problem. Neighbors of a feasible solution are obtained by moving points between clusters in a cycle. This ...

  2. Cyclic nucleotide responses and radiation-induced mitotic delay in Physarum polycephalum

    SciTech Connect

    Daniel, J.W.; Oleinick, N.L.

    1984-02-01

    The response of the plasmodial levels of cyclic AMP and cyclic GMP in Physarum polycephalum to several putative phosphodiesterase inhibitors and to ionizing radiation has been measured. Isobutylmethylxanthine (2 mM) induces a rapid transient threefold elevation of cyclic AMP alone, with maximum response in about 10 min and return to the base line in about 30 min. Theophylline (2 mM) induces a rapid, sustained twofold elevation of cyclic GMP only. Caffeine (2mM) and Ro-20-1724 (18 ..mu..M) both elicit a rapid transient rise in cyclic AMP, resembling the isobutylmethylxanthine response, and a slow transient elevation of the cyclic GMP level. Of particular interest is the rapid threefold transient elevation of the cyclic AMP, but not of the cyclic GMP, level by ..gamma.. radiation.

  3. Perturbations for transient acceleration

    SciTech Connect

    Vargas, Cristofher Zuñiga; Zimdahl, Winfried [Universidade Federal do Espírito Santo, Departamento de Física, Av. Fernando Ferrari, 514, Campus de Goiabeiras, CEP 29075-910, Vitória, Espírito Santo (Brazil); Hipólito-Ricaldi, Wiliam S., E-mail: win_unac@hotmail.com, E-mail: hipolito@ceunes.ufes.br, E-mail: winfried.zimdahl@pq.cnpq.br [Universidade Federal do Espírito Santo, Departamento de Ciências Naturais, Grupo de Física Teórica, Rodovia BR 101 Norte, km 60, Campus de São Mateus, CEP 29932-540, São Mateus, Espírito Santo (Brazil)

    2012-04-01

    According to the standard ?CDM model, the accelerated expansion of the Universe will go on forever. Motivated by recent observational results, we explore the possibility of a finite phase of acceleration which asymptotically approaches another period of decelerated expansion. Extending an earlier study on a corresponding homogeneous and isotropic dynamics, in which interactions between dark matter and dark energy are crucial, the present paper also investigates the dynamics of the matter perturbations both on the Newtonian and General Relativistic (GR) levels and quantifies the potential relevance of perturbations of the dark-energy component. In the background, the model is tested against the Supernova type Ia (SNIa) data of the Constitution set and on the perturbative level against growth rate data, among them those of the WiggleZ survey, and the data of the 2dFGRS project. Our results indicate that a transient phase of accelerated expansion is not excluded by current observations.

  4. Medical uses of accelerators

    SciTech Connect

    Bradbury, J.N.

    1981-01-01

    A variety of particle accelerators have either potential or already demonstrated uses in connection with medically-related research, diagnosis, and treatment. For cancer radiotherapy, nuclear particles including protons, neutrons, heavy ions, and negative pi mesons have advantages compared to conventional radiations in terms of dose localization and/or biological effectiveness. Clinical evaluations of these particles are underway at a number of institutions. Accelerator-produced radionuclides are in widespread use for research and routine diagnostic purposes. Elemental analysis techniques with charged particles and neutrons are being applied to bone, blood, and other tissues. Finally, low-dose medical imaging can be accomplished with accelerated protons and heavy ions. The status and future of these programs are discussed.

  5. Adenosine 3':5'-cyclic monophosphate in higher plants: Isolation and characterization of adenosine 3':5'-cyclic monophosphate from Kalanchoe and Agave.

    PubMed Central

    Ashton, A R; Polya, G M

    1977-01-01

    1.3':5'-Cyclic AMP was extensively purified from Kalanchoe daigremontiana and Agave americana by neutral alumina and anion- and cation-exchange column chromatography. Inclusion of 3':5'-cyclic [8-3H]AMP from the point of tissue extraction permitted calculation of yields. The purification procedure removed contaminating material that was shown to interfere with the 3':5'-cyclic AMP estimation and characterization procedures. 2. The partially purified 3':5'-cyclic AMP was quantified by means of a radiochemical saturation assay using an ox heart 3':5'-cyclic AMP-binding protein and by an assay involving activation of a mammalian protein kinase. 3. The plant 3':5'-cyclic AMP co-migrated with 3':5'-cyclic [8-3H]AMP on cellulose chromatography, poly(ethyleneimine)-cellulose chromatography and silica-gel t.l.c. developed with several solvent systems. 4. The plant 3':5'-cyclic AMP was degraded by ox heart 3':5'-cyclic nucleotide phosphodiesterase at the same rates as authentic 3':5'-cyclic AMP. 1-Methyl-3-isobutylxanthine (1 mM), a specific inhibitor of the 3':5'-cyclic nucleotide phosphodieterase, completely inhibited such degradation. 5. The concentrations of 3':5'-cyclic AMP satisfying the above criteria in Kalanchoe and Agave were 2-6 and 1 pmol/g fresh wt. respectively. Possible bacterial contribution to these analyses was estimated to be less than 0.002pmol/g fresh wt. Evidence for the occurrence of 3':5'-cyclic AMP in plants is discussed. PMID:196595

  6. CYCLICITY OF LUSZTIG'S STRATIFICATION OF GRASSMANNIANS AND POISSON GEOMETRY

    E-print Network

    Caenepeel, Stefaan

    CYCLICITY OF LUSZTIG'S STRATIFICATION OF GRASSMANNIANS AND POISSON GEOMETRY M. Yakimov Department variety G/P. He also constructed an algebro-geometric stratification of G/P and conjectured that intersecting this stratification with (G/P)0 is pro- ducing a cell decomposition of (G/P)0. This was latter

  7. CYCLICITY OF LUSZTIG'S STRATIFICATION OF GRASSMANNIANS AND POISSON GEOMETRY

    E-print Network

    Yakimov, Milen

    CYCLICITY OF LUSZTIG'S STRATIFICATION OF GRASSMANNIANS AND POISSON GEOMETRY MILEN YAKIMOV Abstract-geometric stratification of G/P and conjectured that in- tersecting this stratification with (G/P)0 is producing a cell and the Lusztig stratification of a flag variety were studied in recent years from many different combinatorial

  8. CYCLICITY OF LUSZTIG'S STRATIFICATION OF GRASSMANNIANS AND POISSON GEOMETRY

    E-print Network

    Yakimov, Milen

    CYCLICITY OF LUSZTIG'S STRATIFICATION OF GRASSMANNIANS AND POISSON GEOMETRY MILEN YAKIMOV Abstract­geometric stratification of G/P and conjectured that in­ tersecting this stratification with (G/P ) #0 is producing a cell and the Lusztig stratification of a flag variety were studied in recent years from many di#erent combinatorial

  9. Twisted Conjugacy for Virtually Cyclic Groups and Crystallographic Groups

    Microsoft Academic Search

    Daciberg Gonçalves; Peter Wong

    \\u000a A group is said to have the property R\\u000a ? if every automorphism has an infinite number of twisted conjugacy classes. In this paper, we classify all virtually cyclic\\u000a groups with the R\\u000a ? property. Furthermore, we determine which of the 17 crystallographic groups of rank 2 have this property.

  10. On the densest MIMO lattices from cyclic division algebras

    Microsoft Academic Search

    Roope Vehkalahti; Camilla Hollanti; Jyrki T. Lahtonen; Kalle Ranto

    2009-01-01

    It is shown why the discriminant of a maximal order within a cyclic division algebra must be minimized in order to get the densest possible matrix lattices with a prescribed nonvanishing minimum determinant. Using results from class field theory, a lower bound to the minimum discriminant of a maximal order with a given center and index (= the number of

  11. Representing cyclic human motion using functional analysis* Dirk Ormoneit a

    E-print Network

    Kjellström, Hedvig

    for Bayesian tracking of 3D human motion. q 2005 Elsevier B.V. All rights reserved. Keywords: Human motion represents cyclic human motion using PCA. To illustrate the methods we learn a probabilistic model for human' [12]) prior to statistical analysis. For example, in the case of repetitive human motion

  12. Methods and systems for the formation of cyclic carbonates

    DOEpatents

    Hatton, Trevor Alan; Jamison, Timothy F; Kozak, Jennifer Aiden; Simeon, Fritz; Wu, Jie

    2014-12-30

    Described herein are inventive methods for synthesis of cyclic carbonates from CO.sub.2 and epoxide. In some embodiments, the methods are carried out in the presence of a catalyst comprising an electrophilic halogen. In some embodiments, the methods are carried out in a flow reactor.

  13. An adaptive maximally decimated channelized UWB receiver with cyclic prefix

    Microsoft Academic Search

    Lei Feng; Won Namgoong

    2005-01-01

    The frequency channelized receiver based on hybrid filter bank is a promising receiver structure for ultra-wideband (UWB) radio because of its relaxed circuit requirements and robustness to narrowband interference. Maximally decimated channelizer requires the fewest number of ADCs, but it suffers from poor convergence speed, making it ill-suited for UWB systems. By applying cyclic prefix (CP) to the transmitted data,

  14. Fast joint detection with cyclic reduction exploiting displacement structures

    Microsoft Academic Search

    Weidong Yang; Sang-Youb Kim; Guanghan Xu; Adnan Kavak

    2000-01-01

    Joint detection with the minimum-mean square error (MMSE) criterion has been explored in previous works. Yang, Liu, Xu and Kim (see Asilomar Conference on Signals, Systems and Computers, Asilomar, CA, 1999) discussed joint detection with cyclic reduction, which has been proved to be faster than the popular Cholesky decomposition based algorithm under many scenarios. In this paper, a faster version

  15. Antifungal cyclic peptides from the marine sponge Microscleroderma herdmani

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Screening natural product extracts from National Cancer Institute Open Repository for antifungal discovery afforded hits for bioassay-guided fractionation. Upon LC-MS analysis of column fractions with antifungal activities to generate information on chemical structure, two new cyclic hexapeptides, m...

  16. Cyclic AMP Modulation of Axonal Regeneration Following Spinal Cord Injury

    Microsoft Academic Search

    Sari S. Hannila; Marie T. Filbin

    Central nervous system (CNS) myelin contains several proteins that contribute to regenerative failure after spinal cord injury, and elevation of intracellular cyclic adenosine monophosphate (cAMP) has proven to be one of the most effective means of overcoming myelin inhibition. In this chapter, we describe how increasing cAMP promotes axonal regeneration in the CNS and how this finding has advanced the

  17. Quantum diffusion on a cyclic one dimensional lattice

    E-print Network

    A. C. de la Torre; H. O. Martin; D. Goyeneche

    2003-04-09

    The quantum diffusion of a particle in an initially localized state on a cyclic lattice with N sites is studied. Diffusion and reconstruction time are calculated. Strong differences are found for even or odd number of sites and the limit N->infinit is studied. The predictions of the model could be tested with micro - and nanotechnology devices.

  18. Cyclic Properties of Superelastic Shape Memory Alloy Wires and Bars

    Microsoft Academic Search

    Reginald DesRoches; Jason McCormick; Michael Delemont

    2004-01-01

    This study evaluates the properties of superelastic Ni-Ti shape memory alloys under cyclic loading to assess their potential for applications in seismic resistant design and retrofit. Shape memory alloy wire and bars are tested to evaluate the effect of bar size and loading history on the strength, equivalent damping, and recentering properties of the shape memory alloys in superelastic form.

  19. Efficient DMT\\/OFDM Transmission With Insufficient Cyclic Prefix

    Microsoft Academic Search

    Cheol-Jin Park; Gi-Hong Im

    2004-01-01

    In this letter, we describe a new method to eliminate intersymbol interference (ISI) and interchannel interference (ICI) for discrete multitone\\/orthogonal frequency division multiplexing (DMT\\/OFDM) systems with insufficient cyclic prefix (CP). The proposed structure prevents ICI with a preprocessing method that utilizes redundancy in the frequency domain at the transmitter and removes ISI with a simple cancellation method at the receiver.

  20. COMMUNICATIONS Near-infrared femtosecond photoionization/dissociation of cyclic

    E-print Network

    Levis, Robert J.

    of free space, and c is the speed of light. A laser pulse of 1015 W cm 2 , corresponding to an electricCOMMUNICATIONS Near-infrared femtosecond photoionization/dissociation of cyclic aromatic ions for all of the molecules studied. Measurements of the ion intensity as a function of laser fluence

  1. Cyclic RGD peptides ameliorate ischemic acute renal failure in rats

    Microsoft Academic Search

    Eisei Noiri; James Gailit; Dipak Sheth; Harold Magazine; Marion Gurrath; Gerhard Muller; Horst Kessler; Michael S Goligorsky

    1994-01-01

    Cyclic RGD peptides ameliorate ischemic acute renal failure in rats. Renal tubular obstruction is an important contributor to the pathophysiology of acute renal failure. Based on the previous findings of the role played by arginine-glycine-aspartic acid (RGD) recognizing integrins in tubular obstruction, this study examined the effect of RGD peptides on the course of ischemic acute renal failure in rats.

  2. Finite generation and continuity of topological Hochschild and cyclic homology

    E-print Network

    Ferrari, Patrik L.

    of Artin­Rees properties and homology theories 6 1.1 Pro abelian groups and Artin­Rees properties n(A; p) denotes, as is now usual, the homotopy groups of the fixed point spectrum for the action of the cyclic group Cpr-1 on the topological Hochschild homology spectrum THH(A). It is known that TRr n(A; p

  3. Energy dissipation in shape memory alloy wires under cyclic bending

    Microsoft Academic Search

    Kim-Ho Ip

    2000-01-01

    An analytical formula is developed to predict the energy dissipation in nickel-titanium (Ni-Ti) shape memory alloy (SMA) wires under cyclic bending. Such a formula is derived based on the classical beam theory together with an idealized material curve for SMAs. To demonstrate its accuracy, the formula is first applied to an elastoplastic wire. The results are in agreement with those

  4. Liquefaction and cyclic mobility model for saturated granular media

    Microsoft Academic Search

    S. López-Querol; R. Blázquez

    2006-01-01

    A new constitutive law for the behaviour of undrained sand subjected to dynamic loading is presented. The proposed model works for small and large strain ranges and incorporates contractive and dilative properties of the sand into the unified numerical scheme. These features allow to correctly predict liquefaction and cyclic mobility phenomena for different initial relative densities of the soil. The

  5. Effect of cyclic shearing on shear localisation in granular bodies

    Microsoft Academic Search

    J. Tejchman; E. Bauer

    2004-01-01

    Cyclic shearing of an infinite narrow layer of dry and cohesionless sand between two very rough boundaries under constant vertical pressure is numerically modelled with the finite element method using a polar hypoplastic constitutive relation. The constitutive relation was obtained through an extension of a non-polar model by polar quantities, viz. particle rotations, curvatures, couple stresses using the mean grain

  6. Storing static and cyclic patterns in an Hopfield neural network

    Microsoft Academic Search

    Colin Molter; Utku Salihoglu; Hugues Bersini

    2005-01-01

    While perceiving recurrent neural networks as brain-like information storing and retrieving machines, it is fundamental to explore at best these storing, indexing and retrieving capacities. This paper reviews an efficient Hebb ian learning rule used to store both static and cyclic patterns in the dynamical attractors of an Hopfield neural network. A key improvement will be presented which consists in

  7. Crack Growth in Ferroelectric Ceramics Driven by Cyclic Polarization Switching

    Microsoft Academic Search

    C. S. Lynch; L. Chen; Z. Suo; R. M. Mcmeeking; W. Yang

    1995-01-01

    Ferroelectric ceramics are susceptible to stable crack growth under cyclic electric field of high magnitude. The stresses originate from mismatch strains induced by the electric field around inhomogeneities, such as processing flaws, terminated electrodes and the cracks themselves. The phenomenon is studied using a lead lanthanum zirconate-titanate ceramic. A flaw is indented on the surface of a ceramic sample. Subject

  8. High temperature cyclic oxidation data. Part 1: Turbine alloys

    NASA Technical Reports Server (NTRS)

    Barrett, Charles A.; Garlick, Ralph G.; Lowell, Carl E.

    1989-01-01

    Specific-weight-change-versus-time data and x ray diffraction results are presented derived from high temperature cyclic tests on high temperature, high strength nickel-base gamma/gamma prime and cobalt-base turbine alloys. Each page of data summarizes a complete test on a given alloy sample.

  9. Counting Subgroups in a Direct Product of Finite Cyclic Groups

    ERIC Educational Resources Information Center

    Petrillo, Joseph

    2011-01-01

    We calculate the number of subgroups in a direct product of finite cyclic groups by applying the fundamental theorem of finite abelian groups and a well-known structure theorem due to Goursat. We also suggest ways in which the results can be generalized to a direct product of arbitrary finite groups.

  10. A genus six cyclic tetragonal reduction of the Benney equations

    E-print Network

    Matthew England; John Gibbons

    2009-03-30

    A reduction of Benney's equations is constructed corresponding to Schwartz-Christoffel maps associated with a family of genus six cyclic tetragonal curves. The mapping function, a second kind Abelian integral on the associated Riemann surface, is constructed explicitly as a rational expression in derivatives of the Kleinian sigma-function of the curve.

  11. Gravity Dual for Cyclic Renormalization Group Flow without Conformal Invariance

    E-print Network

    Yu Nakayama

    2011-07-21

    We construct a gravity dual for scale invariant but non-conformal field theories with a cyclic renormalization group flow. A slight modification of our construction gives a gravity dual of discretely scale invariant field theories. The underlying gravitational theory breaks the null energy condition.

  12. Modeling Tracer Transport in an Osteon under Cyclic Loading

    Microsoft Academic Search

    Liyun Wang; Stephen C. Cowin; Sheldon Weinbaum; Susannah P. Fritton

    2000-01-01

    A mathematical model is developed to explain the fundamental conundrum as to how during cyclic mechanical loading there can be net solute (e.g., nutrient, tracer) transport in bone via the lacunar-canalicular porosity when there is no net fluid movement in the canaliculi over a loading cycle. Our hypothesis is that the fluid space in an osteocytic lacuna facilitates a nearly

  13. Cyclic Genetic Algorithm with Conditional Branching PredatorPrey Scenario

    E-print Network

    Parker, Gary B.

    Cyclic Genetic Algorithm with Conditional Branching Predator­Prey Scenario Gary Parker Computer Science Connecticut College New London, 06320 parker@conncoll.edu Parashkevov Computer Science Connecticut) found to a successful method evolving single control programs legged robots. major limitation

  14. Endothelial cell alignment on cyclically-stretched silicone surfaces

    Microsoft Academic Search

    M. Moretti; A. Prina-Mello; A. J. Reid; V. Barron; P. J. Prendergast

    2004-01-01

    Endothelial cells at the interface between the bloodstream and the vessel wall are continuously subjected to mechanical stimulation in vivo, and it widely recognised that such stimulation plays an important role in cardiovascular physiology. Cell deformation is induced by mechanical forces such as cyclic stretch, fluid shear stress, and transmural pressure. Although much of the work in this field has

  15. Performance of Cemented Carbides in Cyclic Loading Conditions

    Microsoft Academic Search

    Heinrich KLAASEN; Jakob KÜBARSEPP; Feodor SERGEJEV; Rainer TRAKSMAA

    2006-01-01

    This article analyzes the fatigue behaviour of some cemented carbides based on tungsten and titanium carbide. It is shown that the performance of carbides in cyclic loading conditions is controlled by the fatigue sensitivity (slope of Wöhler curve) and plasticity of an alloy. The scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD) studies revealed that the fatigue damage is

  16. Mechanical and thermal fracture of plastics under cyclic strains

    Microsoft Academic Search

    S. B. Ratner; V. I. Korobov; S. G. Agamalyan

    1972-01-01

    It is shown on the basis of the theory of cyclic strain-induced heating of plastics that two forms of fatigue fracture are possible (thermal and mechanical), this being reflected in the fact that the appropriate Wöhler curves consist of two branches. The conditions under which a transition from one form of fracture to another takes place are analyzed, and the

  17. The Cyclic Theory of the Universe Paul J. Steinhardt

    E-print Network

    Millis, Andrew

    fluctuations. The theory is based on three underlying notions: (1) the big bang is not the beginning of space of the universe is a radical alternative to the standard big bang/inflationary scenario that offers a new approach a second brane. The cyclic model proposes that the big bang is a collision between branes that occurs

  18. Experimental study on stud shear connectors subjected to cyclic loading

    Microsoft Academic Search

    N. Gattesco; E. Giuriani

    1996-01-01

    Steel and concrete composite beams with deformable connections subjected to repeated loads may force the studs during unloading to a reverse shear load. In order to investigate the behavior of connectors in structures subjected to shear there is a need of a test that can simulate as confidently as possible the actual behavior of studs under reverse cyclic loading. For

  19. Cyclic methylsiloxanes as working fluids for space power cycles

    Microsoft Academic Search

    G. Angelino; C. Invernizzi

    1993-01-01

    The potential merits of cyclic polymethylsiloxanes, particularly those conventionally denominated D[sub 4] and D[sub 5], as working fluids for space power cycles are discussed. The attractive technical characteristics of these substances which are fully nontoxic, moderately flammable, and stable at high temperature are presented. Some experimental results on vapor pressure and on thermal stability are reported. A maximum operating temperature

  20. Parametric analysis of a passive cyclic control device for helicopters

    NASA Technical Reports Server (NTRS)

    Kumagai, H.

    1984-01-01

    A parametric study of a passive device which provides a cyclic longitudinal control moment for a helicopter rotor was performed. It utilizes a rotor blade tip which is structurally decoupled from the blade inboard section. This rotor configuration is generally called the Free-Tip Rotor. A two dimensional numerical model was used to review the Constant Lift Tip Rotor, a predecessor of the current configuration, and then the same model was applied to the Passive Cyclic Control Device. The Constant Lift Tip was proven to have the ability to suppress the vibratory lift loading on the tip around the azimuth and to eliminate a significant negative lift peak on the advancing tip. The Passive Cyclic Control Device showed a once-per-revolution lift oscillation with a large amplitude, while minimizing the higher harmonic terms of the lift oscillation. This once-per-revolution oscillation results in the cyclic moment to trim the rotor longitudinally. A rotor performance analysis was performed by a three dimensional numerical model. It indicated that the vortices shed from the junction between the tip and the inboard section has a strong influence on the tip, and it may severely limit the tip performance. It was also shown that the Free-Tip allows the inboard section to have a larger twist, which results in a better performance.

  1. Multiaxial cyclic ratcheting in coiled tubing -- Part 1: Theoretical modeling

    Microsoft Academic Search

    Radovan Rolovic; Steven M. Tipton

    2000-01-01

    Coiled tubing is a long, continuous string of steel tubing that is used in the oil well drilling and servicing industry. Bending strains imposed on coiled tubing as it is deployed and retrieved from a well are considerably into the plastic regime and can be as high as 3%. Progressive growth of tubing diameter occurs when tubing is cyclically bent-straightened

  2. Piezoelectric Energy Harvesting under High PreStressed Cyclic Vibrations

    Microsoft Academic Search

    Hyeoung Woo Kim; Shashank Priya; Kenji Uchino; Robert E. Newnham

    2005-01-01

    Cymbal transducers have been found as a promising structure for piezoelectric energy harvesting under high force (? 100 N) at cyclic conditions (? 100–200 Hz). The thicker steel cap enhances the endurance of the ceramic to sustain higher ac loads along with stress amplification. This study reports the performance of the cymbal transducer under ac force of 70 N with

  3. Cyclic Oxidation Testing and Modelling: A NASA Lewis Perspective

    NASA Technical Reports Server (NTRS)

    Smialek, J. L.; Nesbitt, J. A.; Barrett, C. A.; Lowell, C. E.

    2000-01-01

    The Materials Division of the NASA Lewis Research Center has been heavily involved in the cyclic oxidation of high temperature materials for 30 years. Cyclic furnace and burner rig apparati have been developed, refined, and replicated to provide a large scale facility capable of evaluating many materials by a standard technique. Material behavior is characterized by weight change data obtained throughout the test, which has been modelled in a step-wise process of scale growth and spallation. This model and a coupled diffusion model have successfully described cyclic behavior for a number of systems and have provided insights regarding life prediction and variations in the spalling process. Performance ranking and mechanistic studies are discussed primarily for superalloys and coating alloys. Similar cyclic oxidation studies have been performed on steels, intermetallic compounds, thermal barrier coatings, ceramics, and ceramic composites. The most common oxidation test was performed in air at temperatures ranging from 800 deg. to 1600 C, for times up to 10000 h, and for cycle durations of 0.1 to 1000 h. Less controlled, but important, test parameters are the cooling temperature and humidity level. Heating and cooling rates are not likely to affect scale spallation. Broad experience has usually allowed for considerable focus and simplification of these test parameters, while still revealing the principal aspects of material behavior and performance. Extensive testing has been performed to statistically model the compositional effects of experimental alloys and to construct a comprehensive database of complex commercial alloys.

  4. Improving the Biopharmaceutical Properties of Cyclic Opioid Peptide Prodrugs

    E-print Network

    Nofsinger, Rebecca Anne

    2008-05-05

    microsomes and human recombinant cytochrome P450-3A4 (hCYP3A4). The sites of metabolite formation were located on the Tyr1 and Phe4 amino acids. New cyclic prodrug analogs of CA-DADLE, CA-[Cha4,D-Leu5]-Enk and CA-[Cha4,D-Ala5]-Enk were designed, synthesized...

  5. Virtual Character Behavior Architecture using Cyclic Richard Zhao

    E-print Network

    Szafron, Duane

    Virtual Character Behavior Architecture using Cyclic Scheduling Richard Zhao Department@ualberta.ca ABSTRACT A story-based video game contains many characters. The majority are virtual characters controlled by artificial intelligence. In recent years, virtual character artificial intelligence has developed slower than

  6. Oil Recovery from Fracture Blocks by Cyclic Injection

    Microsoft Academic Search

    M. Felsenthal; H. H. Ferrell

    1969-01-01

    Results obtained from a number of laboratory tests confirm the previously proposed idea that a cyclic pressuring\\/depressuring process in fractured reservoirs may have considerable merit over conventional waterflooding. A new idea brought out by these tests is that conservation of reservoir gas and a supplementary gas injection appear to be necessary for the success of pressure pulsing in applicable reservoirs.

  7. Novel Cyclic Sugar Imines: Carbohydrate Mimics and Easily

    E-print Network

    Davis, Ben G.

    Novel Cyclic Sugar Imines: Carbohydrate Mimics and Easily Elaborated Scaffolds for Aza (e.g., DNJ) imines not only are potential carbohydrate- processing enzyme inhibitors that may for a nitrogen atom.1 The often potent inhibitory activity of many of these compounds toward carbohydrate

  8. Cyclic fatigue and wear in deepwater polyester mooring systems

    Microsoft Academic Search

    Ray R. Ayers; Saltuk B. Aksu

    2009-01-01

    Fatigue life of deepwater mooring lines is a very important issue in the design of mooring systems for offshore structures. Polyester ropes experience cyclic loading over the life of the mooring, and the remaining strength of those ropes is reduced over time as individual fibers comprising the rope are broken. Fatigue and wear testing of polyester fibers and polyester subropes

  9. EVOLVING HEXAPOD GAITS USING A CYCLIC GENETIC ALGORITHM

    E-print Network

    Parker, Gary B.

    as possible. In addition, learning reduces the human engineering required to develop the intricaciesEVOLVING HEXAPOD GAITS USING A CYCLIC GENETIC ALGORITHM GARY B. PARKER, DAVID W. BRAUN, AND INGO with the differences between and within robots would greatly reduce engineering calculations and increase robot

  10. Cyclic and Chaotic Behavior in Genetic Algorithms Alden H. Wright

    E-print Network

    Wright, Alden H.

    Cyclic and Chaotic Behavior in Genetic Algorithms Alden H. Wright Computer Science Department University of Montana Missoula, MT 59812 USA wright@cs.umt.edu Alexandru Agapie Laboratory of Computational and Wright, 1994] and [Vose, 1999] for examples.) They have developed an elegant theory of simple genetic

  11. Cyclic Feature Based Wideband Spectrum Sensing Using Compressive Sampling

    Microsoft Academic Search

    Zhi Tian

    2011-01-01

    To enable dynamic spectrum access in cognitive radio networks, fast and accurate spectrum sensing has to be performed over very wide bandwidth in noisy channel envi- ronments under energy constraints. The cyclic feature based sensing approach is robust to noise uncertainty, but requires very high sampling rates in the wideband regime and hence incurs high energy consumption and hardware costs.

  12. Cyclic Network Automata and Cohomological Department of Mathematics

    E-print Network

    Ghrist, Robert W.

    one to "program" pulses in the sensor network according to cohomology class. We give a realization theorem for such pulse waves. Keywords: Cyclic cellular automata, wireless sensor network, wavefront. 1 This paper considers a dynamic coverage problem for sensor networks that are sufficiently dense

  13. Cyclic prefixing or zero padding for wireless multicarrier transmissions?

    Microsoft Academic Search

    Bertrand Muquet; Zhengdao Wang; Georgios B. Giannakis; Marc de Courville; Pierre Duhamel

    2002-01-01

    Zero padding (ZP) of multicarrier transmissions has been proposed as an appealing alternative to the traditional cyclic prefix (CP) orthogonal frequency-division multiplexing (OFDM) to ensure symbol recovery regardless of the channel zero locations. In this paper, both systems are studied to delineate their relative merits in wireless systems where channel knowledge is not available at the transmitter. Two novel equalizers

  14. GALOIS EMBEDDING PROBLEMS WITH CYCLIC QUOTIENT OF ORDER p

    E-print Network

    over a field F containing a primitive pth root of unity. We consider Galois embedding of characteristicpnot_p containing a primitive pth root of unity ,p. Suppose that K = F ( pa) is a cyclic field as follows. Since the group ~p of pth roots of unity is contained in F , we may identify the center of E

  15. GALOIS EMBEDDING PROBLEMS WITH CYCLIC QUOTIENT OF ORDER p

    E-print Network

    # Abstract. Let K be a cyclic Galois extension of degree p over a field F containing a primitive pth root. Introduction Let p > 2 be a prime and F a field of characteristic not p containing a primitive pth root of this embedding problem may be computed as follows. Since the group µ p of pth roots of unity is contained in F

  16. GALOIS EMBEDDING PROBLEMS WITH CYCLIC QUOTIENT OF ORDER p

    E-print Network

    . Let K be a cyclic Galois extension of degree p over a field F containing a primitive pth root of unity. Introduction Let p > 2 be a prime and F a field of characteristic not p containing a primitive pth root may be computed as follows. Since the group µp of pth roots of unity is contained in F, we may

  17. Cyclical modulation of human ventricular repolarization by respiration

    PubMed Central

    Hanson, Ben; Gill, Jaswinder; Western, David; Gilbey, Michael P.; Bostock, Julian; Boyett, Mark R.; Zhang, Henggui; Coronel, Ruben; Taggart, Peter

    2012-01-01

    Background: Respiratory modulation of autonomic input to the sinus node results in cyclical modulation of heart rate, known as respiratory sinus arrhythmia (RSA). We hypothesized that the respiratory cycle may also exert cyclical modulation on ventricular repolarization, which may be separately measurable using local endocardial recordings. Methods and Results: The study included 16 subjects with normal ventricles undergoing routine clinical electrophysiological procedures for supraventricular arrhythmias. Unipolar electrograms were recorded from 10 right and 10 left ventricular endocardial sites. Breathing was voluntarily regulated at 5 fixed frequencies (6, 9, 12, 15, and 30 breaths per min) and heart rate was clamped by RV pacing. Activation-recovery intervals (ARI: a surrogate for APD) exhibited significant (p < 0.025) cyclical variation at the respiratory frequency in all subjects; ARI shortened with inspiration and lengthened with expiration. Peak-to-peak ARI variation ranged from 0–26 ms; the spatial pattern varied with subject. Arterial blood pressure also oscillated at the respiratory frequency (p < 0.025) and lagged behind respiration by between 1.5 s and 0.65 s from slowest to fastest breathing rates respectively. Systolic oscillation amplitude was significantly greater than diastolic (14 ± 5 vs. 8 ± 4 mm Hg ± SD, p < 0.001). Conclusions: Observations in humans with healthy ventricles using multiple left and right ventricular endocardial recordings showed that ARI action potential duration (APD) varied cyclically with respiration. PMID:23055983

  18. Evaluating cyclic liquefaction potential using the cone penetration test

    Microsoft Academic Search

    P. K. Robertson

    1998-01-01

    Soil liquefaction is a major concern for strctures constrcted with or on sandy soils. This paper describes the phenomena of soil liquefaction, reviews suitable definitions, and provides an update on methods to evaluate cyclic liquefaction using the cone penetrtion test (CPT). A method is described t.o estimate grain characteristics directly ûom the CPT and to incorporate this into one of

  19. AN ANALYSIS OF A PROLIFIC TORNADO PRODUCING CYCLIC SUPERCELL THUNDERSTORM

    E-print Network

    1 P3.1 AN ANALYSIS OF A PROLIFIC TORNADO PRODUCING CYCLIC SUPERCELL THUNDERSTORM IN NUCKOLLS COUNTY Adams, Clay, Nuckolls and Thayer Counties, Nebraska and Republic County, Kansas, spawning 11 tornadoes in Nebraska alone (Fig. 1and Table 1). Figure 1 Locations and tracks of 11 tornadoes associated

  20. MODELING CYCLIC WAVES OF CIRCULATING T CELLS IN AUTOIMMUNE DIABETES

    E-print Network

    Mahaffy, Joseph M.

    MODELING CYCLIC WAVES OF CIRCULATING T CELLS IN AUTOIMMUNE DIABETES JOSEPH M. MAHAFFY AND LEAH EDELSTEIN-KESHET Abstract. Type 1 diabetes (T1D) is an autoimmune disease in which immune cells, notably T diabetes result once a large enough fraction of these beta cells have been destroyed. Recent investigation

  1. Investigation of residual stress relaxation under cyclic load

    Microsoft Academic Search

    Wyman Z. Zhuang; Gary R. Halford

    2001-01-01

    Compressive residual stresses induced by mechanical surface treatment such as shot peening, autofretage, hole expansion, laser shock peening, and low-plasticity burnishing can be highly beneficial to fatigue resistance. Cyclic relaxation of compressive residual stress, however, reduces the benefit. An analytical model is proposed for estimation of residual stress relaxation. Parameters considered by the model include the magnitude and distribution of

  2. Degradation in Cemented Marine Clay Subjected to Cyclic Compressive Loading

    Microsoft Academic Search

    G. GERALD MOSES; S. NARASIMHA RAO

    2003-01-01

    The influence of cyclic loading on the strength and deformation behavior of cemented marine clay has been studied. This marine clay is of recent Pleistocene origin and deposited in a shallow water marine environment. Open pits were dug in sheeted enclosures and from these pits, undisturbed samples were taken for strength testing. A series of standard triaxial shear tests and

  3. Damage induced anisotropy of polycrystals under complex cyclic loadings

    Microsoft Academic Search

    T. B. Mounounga; A. Abdul-Latif; D. Razafindramary

    2011-01-01

    Motivated by a low-cyclic fatigue micromechanical model proposed recently [1], qualitative and quantitative studies are performed emphasizing the concept of damage induced anisotropy. In this model, the plastic strain and local damage variables are examined at the crystallographic slip system scale for FCC metallic polycrystals. Determined at the macroscopic scale, the elastic behavior is initially assumed to be compressible and

  4. Cyclic strengthening of polypropylene under strain-controlled loading

    Microsoft Academic Search

    A. D. Drozdov

    2011-01-01

    Experimental data are reported on isotactic polypropylene in uniaxial tensile cyclic tests with a strain-controlled program (oscillations between fixed minimum and maximum strains) at room temperature. The stress–strain diagrams demonstrate that (i) maximum and minimum stresses per cycle decay with number of cycles, (ii) the rate of decrease in minimum stress strongly exceeds that in maximum stress, (iii) secant elastic

  5. Analysis and optimization of cyclic methods in orbit computation

    NASA Technical Reports Server (NTRS)

    Pierce, S.

    1973-01-01

    The mathematical analysis and computation of the K=3, order 4; K=4, order 6; and K=5, order 7 cyclic methods and the K=5, order 6 Cowell method and some results of optimizing the 3 backpoint cyclic multistep methods for solving ordinary differential equations are presented. Cyclic methods have the advantage over traditional methods of having higher order for a given number of backpoints while at the same time having more free parameters. After considering several error sources the primary source for the cyclic methods has been isolated. The free parameters for three backpoint methods were used to minimize the effects of some of these error sources. They now yield more accuracy with the same computing time as Cowell's method on selected problems. This work is being extended to the five backpoint methods. The analysis and optimization are more difficult here since the matrices are larger and the dimension of the optimizing space is larger. Indications are that the primary error source can be reduced. This will still leave several parameters free to minimize other sources.

  6. Crack growth in Westerly granite during a cyclic loading test

    Microsoft Academic Search

    Youqing Chen; Kota Watanabe; Hiromu Kusuda; Eishi Kusaka; Mamoru Mabuchi

    2011-01-01

    To examine the fatigue process of granite, cylindrical Westerly granite specimens, 10mm in diameter and 20mm in length, were subjected to a cyclic loading test under uniaxial compression with a maximum of 140MPa at room temperature, and crack growth patterns within them were analyzed by microscopic observation and image analysis techniques. The fatigue process is divided into three characteristic stages;

  7. Cyclic stress-strain curve and springback simulation

    NASA Astrophysics Data System (ADS)

    Zhao, Kunmin

    The main objective of this dissertation is to generate cyclic stress-strain curves for sheet metals so that the springback can be simulated accurately. Material parameters are identified by an inverse method within a selected constitutive model (Chaboche model) that represents the hardening behavior of materials subjected to a cyclic loading. Three-point bending tests are conducted on sheet steels (mild steel and high strength steel) and sheet aluminum. Punch stroke, punch load, bending strain and bending angle are measured directly during the tests. Bending moments are then computed from these measured data. Bending moments are also calculated based on a constitutive model. Normal anisotropy and nonlinear isotropic/kinematic hardening are considered. Material parameters are identified by minimizing the normalized error between two bending moments. Micro genetic algorithm is used in the optimization procedure. Stress-strain curves are generated with the material parameters found in this way, which can be used with other plastic models. This dissertation contributes to the generation of cyclic stress-strain curves of sheet metals for more accurate simulation of forming process and especially for springback prediction when the process includes a cyclic loading.

  8. Behavior of Nonplastic Silty Soils under Cyclic Loading

    PubMed Central

    Ural, Nazile; Gunduz, Zeki

    2014-01-01

    The engineering behavior of nonplastic silts is more difficult to characterize than is the behavior of clay or sand. Especially, behavior of silty soils is important in view of the seismicity of several regions of alluvial deposits in the world, such as the United States, China, and Turkey. In several hazards substantial ground deformation, reduced bearing capacity, and liquefaction of silty soils have been attributed to excess pore pressure generation during dynamic loading. In this paper, an experimental study of the pore water pressure generation of silty soils was conducted by cyclic triaxial tests on samples of reconstituted soils by the slurry deposition method. In all tests silty samples which have different clay percentages were studied under different cyclic stress ratios. The results have showed that in soils having clay content equal to and less than 10%, the excess pore pressure ratio buildup was quicker with an increase in different cyclic stress ratios. When fine and clay content increases, excess pore water pressure decreases constant cyclic stress ratio in nonplastic silty soils. In addition, the applicability of the used criteria for the assessment of liquefaction susceptibility of fine grained soils is examined using laboratory test results. PMID:24672343

  9. Effects of cyclic hydraulic pressure on osteocytes , Yan Zhao b

    E-print Network

    You, Lidan

    Effects of cyclic hydraulic pressure on osteocytes Chao Liu a , Yan Zhao b , Wing-Yee Cheung b: Osteocyte Mechanotransduction Hydraulic pressure Calcium Apoptosis Bone is able to adapt its composition and structure in order to suit its mechanical environment. Osteocytes, bone cells embedded in the calcified

  10. High-temperature cyclic oxidation data. Part 2: Turbine alloys

    NASA Technical Reports Server (NTRS)

    Barrett, Charles A.; Garlick, Ralph G.

    1989-01-01

    Specific-weight-change-versus-time data and x ray diffraction results are presented derived from high temperature cyclic tests on high temperature, high strength nickel-base gamma/gamma prime and cobalt-base turbine alloys. Each page of data summarizes a complete test on a given alloy sample.

  11. The Bauschinger effect in cyclically deformed niobium single crystals

    Microsoft Academic Search

    M. Anglada; F. Guiu

    1988-01-01

    The Bauschinger effect has been studied in niobium single crystals cyclically deformed to saturation at small strain amplitudes and at different temperatures. The parameters used to characterize the Bauschinger effect have been measured from the saturation hysteresis loops. The fatigued work-hardened crystals have been modelled as a composite consisting of a hard deformable phase (the regions of high dislocation density)

  12. Selective hydrodeoxygenation of cyclic vicinal diols to cyclic alcohols over tungsten oxide-palladium catalysts.

    PubMed

    Amada, Yasushi; Ota, Nobuhiko; Tamura, Masazumi; Nakagawa, Yoshinao; Tomishige, Keiichi

    2014-08-01

    Hydrodeoxygenation of cyclic vicinal diols such as 1,4-anhydroerythritol was conducted over catalysts containing both a noble metal and a group 5-7 transition-metal oxide. The combination of Pd and WOx allowed the removal of one of the two OH groups selectively. 3-Hydroxytetrahydrofuran was obtained from 1,4-anhydroerythritol in 72 and 74% yield over WOx -Pd/C and WOx -Pd/ZrO2 , respectively. The WOx -Pd/ZrO2 catalyst was reusable without significant loss of activity if the catalyst was calcined as a method of regeneration. Characterization of WOx -Pd/C with temperature-programmed reduction, X-ray diffraction, and transmission electron microscopy/energy-dispersive X-ray spectroscopy suggested that Pd metal particles approximately 9 nm in size were formed on amorphous tungsten oxide particles. A reaction mechanism was proposed on the basis of kinetics, reaction results with tungsten oxides under an atmosphere of Ar, and density functional theory calculations. A tetravalent tungsten center (W(IV) ) was formed by reduction of WO3 with the Pd catalyst and H2 , and this center served as the reductant for partial hydrodeoxygenation. PMID:24974957

  13. Diffusive Shock Acceleration

    NASA Astrophysics Data System (ADS)

    Baring, Matthew

    2003-04-01

    The process of diffusive acceleration of charged particles in shocked plasmas is widely invoked in astrophysics to account for the ubiquitous presence of signatures of non-thermal relativistic electrons and ions in the universe. This statistical energization mechanism, manifested in turbulent media, was first posited by Enrico Fermi in 1949 to explain the observed cosmic ray population, which exhibits an almost power-law distribution in rigidity. The absence of a momentum scale is a key characteristic of diffusive shock acceleration, and astrophysical systems generally only impose scales at the injection (low energy) and loss (high energy) ends of the particle spectrum. The existence of structure in the cosmic ray spectrum (the "knee") at around 3000 TeV has promoted contentions that there are at least two origins for cosmic rays, a galactic one supplying those up to the knee, and perhaps an extragalactic one that can explain even the ultra-high energy cosmic rays (UHECRs) seen at 1-300 EeV. Accounting for the UHECRs with familiar astrophysical sites of acceleration has historically proven difficult due to the need to assume high magnetic fields in order to reduce the shortest diffusive acceleration timescale, the ion gyroperiod, to meaningful values. Yet active galaxies and gamma-ray bursts remain strong and interesting candidate sources for UHECRs, turning the theoretical focus to relativistic shocks. This review summarizes properties of diffusive shock acceleration that are salient to the issue of UHECR generation. These include spectral indices, anisotropies, acceleration efficencies and timescales, as functions of the shock speed and mean field orientation, and also the degree of field turbulence. Astrophysical sites for UHECR production are also critiqued.

  14. Morphodynamics of cyclic steps: a depth-resolved numerical model

    NASA Astrophysics Data System (ADS)

    Vellinga, Age; Cartigny, Matthieu; Eggenhuisen, Joris; Hansen, Ernst

    2015-04-01

    Although the majority of sediment transport is associated to high-discharge events, and such events are prone to Froude-supercritical flow conditions, there are only limited outcrop examples of supercritical-flow deposits. These low numbers of outcrop examples are often explained as being the result of poor preservation potential of upper-stage flow-regime deposits, due to reworking by subcritical flows in the waning stages of these high-discharge events. However, an alternative explanation for this might be that there is not enough knowledge on supercritical-flow deposits to recognise these deposits. This last argument is supported by the fact that numerical and physical experiments in recent years have strongly increased the number of recognised supercritical-flow deposits. Although large progress has been made in the study of the architecture of supercritical-flow deposits, using experimental data and depth-averaged models, scaling issues and measurement difficulties in experiments, and the limitations of depth-averaged models, are impeding further insights in the interaction between the flow and the bed development. Froude-supercritical flows can lead to the formation of bedforms such as antidunes, chutes-and-pools and cyclic steps, the last of which will be focussed of this study. Cyclic steps are described as a series of upstream migrating steps, each step is characterized by a lee-side of the bedform which is eroded by a Froude-supercritical flow and depositional stoss-side of the bedform associated with subcritical flow. The transition between the two flow-regimes is characterized by a hydraulic jump which is located roughly in the trough of a cyclic step bedform. The deposits of cyclic steps can be characterised by backset laminations terminating upstream against the erosional or transportational lee-side of the cyclic step, the backsets can also be eroded by the lee-side of the next upstream-migrating bedform on the downstream end. A novel approach is taken by using a fully depth-resolved computational fluid dynamics model, capable of rendering complex 3D geometries, allowing for a more detailed picture on morphodynamic interaction between flows and cyclic step bedforms than ever before. The study presented provides a quantification of physical parameters, such as Froude number, shear stresses and sediment concentrations. These physical parameters will characterise the facies associated to cyclic step deposits.

  15. Cyclic3?,5?-nucleotide phosphodiesterase isozymes in cell biology and pathophysiology of the kidney

    Microsoft Academic Search

    THOMAS P DOUSA

    1999-01-01

    Cyclic-3?,5?-nucleotide phosphodiesterase isozymes in cell biology and pathophysiology of the kidney. Investigations of recent years revealed that isozymes of cyclic-3?,5?-nucleotide phosphodiesterase (PDE) are a critically important component of the cyclic-3?,5?-adenosine monophosphate (cAMP) protein kinase A (PKA) signaling pathway. The superfamily of cyclic-3?,5?-phosphodiesterase (PDE) isozymes consists of at least nine gene families (types): PDE1 to PDE9. Some PDE families are very

  16. Continuum Damage Based Constitutive Equations for Copper under High Temperature Creep and Cyclic Plasticity

    Microsoft Academic Search

    F. P. E. Dunne; D. R. Hayhurst

    1992-01-01

    Viscoplastic constitutive equations without damage for cast copper have been developed for cyclic mechanical and cyclic thermal loading over the temperature range 20-500 degrees C (nominal composition: 99.99% Cu, 0.005% O2, B.S. 10355-1037). Model predictions have been compared with experimental cyclic plasticity tests. Good agreement has been achieved. Creep and cyclic plasticity damage evolution equations have been developed. The effect

  17. Laser driven ion acceleration

    NASA Astrophysics Data System (ADS)

    Mora, P.

    2007-07-01

    The different acceleration mechanisms of ion acceleration from a foil irradiated by a short-pulse laser are briefly discussed, i.e., the backward and forward ion acceleration from the front side, the forward ion acceleration from the rear side, and the shock acceleration inside the target itself. A particular attention is then given to the forward ion acceleration from the rear side, as it appears presently as the most efficient mechanism. Fast electrons are first created at the front side of a thin foil by the laser-plasma interaction, then propagate through the target and build a charge separation field at the rear side. The corresponding electric field ionizes atoms and accelerates ions. The paradigm for the plasma expansion is the self-similar quasi-neutral expansion of an isothermal semi-infinite plasma into a vacuum that is first presented together with the resultant energy spectrum. The analysis of the conditions of validity of the quasi-neutrality assumption enables to determine the structure of the ion front and the maximum ion velocity as a function of time. Various effects are then discussed which may modify the ion spectrum with respect to the simple model : (i) Electron cooling (finite plasma slab case) : the thermal electron energy is progressively converted into the kinetic energy of the ions. The ion spectrum now converges when time goes to infinity in contrast with the isothermal semi-infinite plasma case. (ii) Two-phase model : a refined model is presented, where the electron temperature first rises together with the laser pulse intensity, and then decreases adiabatically while the energy is transferred to the ions. (iii) Two-temperature electron distribution function : as expected, the high energy part of the spectrum is governed by the hot electron component (iv) Existence of a finite initial ion density gradient : a wave breaking of the ion flow occurs after a finite time, with the formation of an ion front. When electron cooling is taken into account, and when the initial ion density scale length lss is larger than a few percent of the total plasma slab width, the final maximum ion velocity decreases with lss. (v) Multispecies ions: optimisation of the target structure can lead to the acceleration of quasi-monoenergetic light ions (especially protons).

  18. A Smoother Acceleration

    NSDL National Science Digital Library

    Christine Chapman

    2009-03-01

    Some may argue that gifted children have many education options, but these options do not always help gifted students learn science. Unfortunately, gifted students often do not reach their full academic potential--they are frequently less motivated to succeed because they are not being academically challenged in regular classrooms (McCoach and Siegle 2003). To counter these problems, a strong option for educating gifted students is acceleration. This article describes the challenges that more and more gifted students face when accelerating, particularly when skipping an entire academic year. Strategies to lessen their intensity and duration and, ultimately, help gifted students to succeed are also included.

  19. Accelerated molecular dynamics methods

    SciTech Connect

    Perez, Danny [Los Alamos National Laboratory

    2011-01-04

    The molecular dynamics method, although extremely powerful for materials simulations, is limited to times scales of roughly one microsecond or less. On longer time scales, dynamical evolution typically consists of infrequent events, which are usually activated processes. This course is focused on understanding infrequent-event dynamics, on methods for characterizing infrequent-event mechanisms and rate constants, and on methods for simulating long time scales in infrequent-event systems, emphasizing the recently developed accelerated molecular dynamics methods (hyperdynamics, parallel replica dynamics, and temperature accelerated dynamics). Some familiarity with basic statistical mechanics and molecular dynamics methods will be assumed.

  20. HIGH GRADIENT INDUCTION ACCELERATOR

    SciTech Connect

    Caporaso, G J; Sampayan, S; Chen, Y; Blackfield, D; Harris, J; Hawkins, S; Holmes, C; Krogh, M; Nelson, S; Nunnally, W; Paul, A; Poole, B; Rhodes, M; Sanders, D; Selenes, K; Sullivan, J; Wang, L; Watson, J

    2007-06-21

    A new type of compact induction accelerator is under development at the Lawrence Livermore National Laboratory that promises to increase the average accelerating gradient by at least an order of magnitude over that of existing induction machines. The machine is based on the use of high gradient vacuum insulators, advanced dielectric materials and switches and is stimulated by the desire for compact flash x-ray radiography sources. Research describing an extreme variant of this technology aimed at proton therapy for cancer will be described. Progress in applying this technology to several applications will be reviewed.

  1. An accelerator technology legacy

    SciTech Connect

    Heighway, E.A.

    1994-11-01

    Accelerator technology has been a major beneficiary of the investment made over the last decade. It is the intention of this paper to provide the reader with a glimpse of the broad nature of those advances. Development has been on a broad front and this paper can highlight only a few of those. Two spin-off applications will be outlined -- a concept for a compact, active, beam probe for solar body exploration and the concept for an accelerator-driven transmutation system for energy production.

  2. Interfacing to accelerator instrumentation

    SciTech Connect

    Shea, T.J.

    1995-12-31

    As the sensory system for an accelerator, the beam instrumentation provides a tremendous amount of diagnostic information. Access to this information can vary from periodic spot checks by operators to high bandwidth data acquisition during studies. In this paper, example applications will illustrate the requirements on interfaces between the control system and the instrumentation hardware. A survey of the major accelerator facilities will identify the most popular interface standards. The impact of developments such as isochronous protocols and embedded digital signal processing will also be discussed.

  3. Photocathodes in accelerator applications

    SciTech Connect

    Fraser, J.S.; Sheffield, R.L.; Gray, E.R.; Giles, P.M.; Springer, R.W.; Loebs, V.A.

    1987-01-01

    Some electron accelerator applications require bursts of short pulses at high microscopic repetition rates and high peak brightness. A photocathode, illuminated by a mode-locked laser, is well suited to filling this need. The intrinsic brightness of a photoemitter beam is high; experiments are under way at Los Alamos to study the brightness of short bunches with high space charge after acceleration. A laser-illuminated Cs/sub 3/Sb photoemitter is located in the first rf cavity of an injector linac. Diagnostics include a pepper-pot emittance analyzer, a magnetic spectrometer, and a streak camera.

  4. Cyclic Mechanical Stress and Trabecular Meshwork Cell Contractility

    PubMed Central

    Ramos, Renata F.; Sumida, Grant M.; Stamer, W. Daniel

    2009-01-01

    Purpose Ocular pulse decreases outflow facility of perfused anterior segments. However, the mechanism by which conventional outflow tissues respond to cyclic intraocular pressure oscillations is unknown. The purpose of the present study was to examine responses of trabecular meshwork (TM) cells to cyclic biomechanical stress in the presence and absence of compounds known to affect cell contractility. Methods To model flow in the juxtacanalicular region of the TM and to measure changes in transendothelial flow, human TM cell monolayers on permeable filters were perfused at a constant flow rate until reaching a stable baseline pressure and then were exposed to cyclic stress with an average amplitude of 2.7 mm Hg peak to peak at a 1-Hz frequency for 2 hours in the presence or absence of compounds known to affect cell contractility (isoproterenol, Y27632, pilocarpine, and nifedipine). Pressure was recorded continuously. Immunocytochemistry staining was used to determine filamentous actin stress fiber content, whereas Western blot analysis was used to measure the extent of myosin light chain (p-MLC) phosphorylation and ratio of filamentous to globular actin. Results Human TM cells respond to cyclic pressure oscillations by increasing mean intrachamber pressure (decreasing hydraulic conductivity) (126.13% ± 2.4%; P < 0.05), a response blocked in the presence of Y27632, a rho-kinase inhibitor (101.35 ± 0.59; P = 0.234), but not isoproterenol, pilocarpine, or nifedipine. Although mechanical stress appeared to have no effect, Y27632 decreased phosphorylated myosin light chain, filamentous/globular actin ratio, and stress fiber formation in TM cells. Conclusions Human TM cells respond to cyclic mechanical stress by increasing intrachamber pressure. Pulse-mediated effects are blocked by Y27632, implicating a role for Rho-kinase-mediated signaling and cellular contractility in ocular pulse-associated changes in outflow facility. PMID:19339745

  5. Family of prokaryote cyclic nucleotide-modulated ion channels

    PubMed Central

    Brams, Marijke; Kusch, Jana; Spurny, Radovan; Benndorf, Klaus; Ulens, Chris

    2014-01-01

    Cyclic nucleotide-modulated ion channels are molecular pores that mediate the passage of ions across the cell membrane in response to cAMP or GMP. Structural insight into this class of ion channels currently comes from a related homolog, MloK1, that contains six transmembrane domains and a cytoplasmic cyclic nucleotide binding domain. However, unlike eukaryote hyperpolarization-activated cyclic nucleotide-modulated (HCN) and cyclic nucleotide-gated (CNG) channels, MloK1 lacks a C-linker region, which critically contributes to the molecular coupling between ligand binding and channel opening. In this study, we report the identification and characterization of five previously unidentified prokaryote homologs with high sequence similarity (24–32%) to eukaryote HCN and CNG channels and that contain a C-linker region. Biochemical characterization shows that two homologs, termed AmaK and SthK, can be expressed and purified as detergent-solubilized protein from Escherichia coli membranes. Expression of SthK channels in Xenopus laevis oocytes and functional characterization using the patch-clamp technique revealed that the channels are gated by cAMP, but not cGMP, are highly selective for K+ ions over Na+ ions, generate a large unitary conductance, and are only weakly voltage dependent. These properties resemble essential properties of various eukaryote HCN or CNG channels. Our results contribute to an understanding of the evolutionary origin of cyclic nucleotide-modulated ion channels and pave the way for future structural and functional studies. PMID:24821777

  6. Ion Trapping for Ion Mobility Spectrometry Measurements in a Cyclical Drift Tube

    E-print Network

    Clemmer, David E.

    Ion Trapping for Ion Mobility Spectrometry Measurements in a Cyclical Drift Tube Rebecca S. Glaskin in a cyclical drift tube, as a means of enhancing ion signals for scanning ion cyclotron mobility measurements of the cyclical drift tube and these pulses are accumulated prior to initiation of the mobility measurements

  7. Cyclic Material Properties Test to Determine Hardening/Softening Characteristics of HY-80 Steel

    SciTech Connect

    S.C. Hodge; J.M. Minicucci; T.F. Trimble

    2003-04-30

    The Cyclic Material Properties Test was structured to obtain and provide experimental data for determining cyclic hardening/softening characteristics of HY-80 steel. The inelastic strain history data generated by this test program and the resulting cyclic stress-strain curve will be used to enhance material models in the finite element codes used to perform nonlinear elastic-plastic analysis.

  8. DOI: 10.1002/chem.200802337 Cyclic PeptidePolymer Complexes and Their Self-Assembly

    E-print Network

    Zhao, Yue

    features, the processability of polymers can be exploited for the manipulation of peptide nanotubes-assembly process of cyclic peptides in different ways. In the study by Biesalski and Couet,[7] cyclic peptidesDOI: 10.1002/chem.200802337 Cyclic Peptide­Polymer Complexes and Their Self-Assembly Dominique

  9. Cyclic Brush Polymers by Combining Ring-Expansion Metathesis Polymerization and the "Grafting from" Technique

    E-print Network

    Tew, Gregory N.

    Cyclic Brush Polymers by Combining Ring-Expansion Metathesis Polymerization and the "Grafting from route to cyclic brush polymers was developed by combining ring-expansion metathesis polymerization (REMP-opening polymerization to produce the cyclic brush polymers. Brush polymers have received considerable attention

  10. Cyclic plastic response and fatigue life in superduplex 2507 stainless steel

    Microsoft Academic Search

    Jaroslav Polák; Martin Petrenec; Tomáš Kruml

    2010-01-01

    Superduplex 2507 type steel has been subjected to symmetric cyclic loading with constant strain rate and constant plastic strain amplitude or sinusoidal cyclic loading with constant stress amplitude at room temperature in a wide interval of stress and plastic strain amplitudes. Fatigue hardening\\/softening curves were recorded and compared for both types of loading. Cyclic stress–strain curves and fatigue life curves

  11. Properties of Tangential and Cyclic Polygons: An Application of Circulant Matrices

    ERIC Educational Resources Information Center

    Leung, Allen; Lopez-Real, Francis

    2003-01-01

    In this paper, the properties of tangential and cyclic polygons proposed by Lopez-Real are proved rigorously using the theory of circulant matrices. In particular, the concepts of slippable tangential polygons and conformable cyclic polygons are defined. It is shown that an n-sided tangential (or cyclic) polygon P[subscript n] with n even is…

  12. Prestrain and mean stress effects on cyclic plastic deformation responses of iron-based alloys

    Microsoft Academic Search

    Hai Ni

    2002-01-01

    It has recently been reported that sagging behavior in spring steels is a direct result of asymmetrical cyclic loading. Although previous work showed that cyclic creep and cyclic softening are the two main reasons for the sagging of mechanical springs, the mechanisms of sagging are still not well understood. In order understand sagging mechanisms in commercial spring materials, both symmetrical

  13. Cyclic evasion in the three bug problem Maxim Arnold and Vadim Zharnitsky

    E-print Network

    Zharnitsky, Vadim

    Cyclic evasion in the three bug problem Maxim Arnold and Vadim Zharnitsky April 10, 2014 Abstract. In this note we present a simple proof that 3 bugs involved in cyclic evasion, converge to an equilateral for the triangle. The problem of the cyclic pursuit or n-bug problem is a classical one, see e.g. an article

  14. A simple model for cyclic variations in a spark-ignition engine

    E-print Network

    Tennessee, University of

    A simple model for cyclic variations in a spark-ignition engine C.S. Dawy, C.E.A. Finneyz, J important characteristics of cyclic combustion variations in spark-ignited engines. A key model feature apparently conflicting observations of cyclic combus- tion variations in spark-ignition engines

  15. ORIGINAL ARTICLE Elevational gradient in the cyclicity of a forest-defoliating insect

    E-print Network

    Liebhold, Andrew

    unexplored. We quantified the cyclicity of gypsy moth populations along an elevational gradient by applying relationship between elevation and the cyclicity of gypsy moth populations and a positive relationship between cyclicity and the density of the gypsy moth's preferred host-tree species. The potential effects

  16. An investigation of the cyclic fatigue and fracture behavior of a niobium aluminide intermetallic

    Microsoft Academic Search

    D. G. Konitzer

    1997-01-01

    This paper presents the results of a study designed to improve our understanding of the cyclic fatigue and fracture characteristics of a niobium aluminide intermetallic. Specimens of the intermetallic were deformed to failure in uniaxial tension, fully-reversed total strain amplitude control and cyclic stress amplitude control. The alloy exhibited limited plasticity and life under strain amplitude-controlled fatigue. Cyclic stress controlled

  17. Cell alignment is induced by cyclic changes in cell length: studies of cells grown in cyclically stretched substrates

    Microsoft Academic Search

    C. Neidlinger-Wilke; E. S. Grood; J. H.-C. Wang; R. A. Brand; L. Claes

    2001-01-01

    Many types of cells, when grown on the surface of a cyclically stretched substrate, align away from the stretch direction. Although cell alignment has been described as an avoidance response to stretch, the specific deformation signal that causes a cell population to become aligned has not been identified. Planar surface deformation is characterized by three strains: two normal strains describe

  18. Stacked insulator induction accelerator gaps

    SciTech Connect

    Houck, T.I.; Westenskow, G.A.; Kim, J.S.; Eylon, S.; Henestroza, E.; Yu, S.S.; Vanecek, D.

    1997-05-01

    Stacked insulators, with alternating layers of insulating material and conducting film, have been shown to support high surface electrical field stresses. We have investigated the application of the stacked insulator technology to the design of induction accelerator modules for the Relativistic-Klystron Two-Beam Accelerator program. The rf properties of the accelerating gaps using stacked insulators, particularly the impedance at frequencies above the beam pipe cutoff frequency, are investigated. Low impedance is critical for Relativistic-Klystron Two-Beam Accelerator applications where a high current, bunched beam is trsnsported through many accelerating gaps. An induction accelerator module designs using a stacked insulator is presented.

  19. European particle accelerator conference

    SciTech Connect

    Tazzari, S.

    1988-01-01

    This book contains the following topics: The LEP project, Superconducting RF cavities for accelerator application, Commissioning of super-ACO, Pulsed high-power beams, RF Power sources, Astrid, A storage ring for ions and electrons, Linear collider studies in Europe.

  20. Acceleration and Mass

    NSDL National Science Digital Library

    Michael Horton

    2009-05-30

    Although this lab is not an inquiry activity, it is very important in learning about acceleration and mass. It is a deeply held misconception among students that objects of different masses fall at different rates. Simply explaining that this is not true

  1. Photon acceleration in vacuum

    E-print Network

    J. T. Mendonca; M. Marklund; P. K. Shukla; G. Brodin

    2006-08-16

    A new process associated with the nonlinear optical properties of the electromagnetic vacuum, as predicted by quantum electrodynamics, is described. This can be called photon acceleration in vacuum, and corresponds to the frequency shift that takes place when a given test photon interacts with an intense beam of background radiation.

  2. Electron cloud in accelerators

    NASA Astrophysics Data System (ADS)

    Cimino, Roberto; Demma, Theo

    2014-06-01

    Low energy electrons in accelerators are known to interact with the circulating beam, giving rise to the formation of a so-called e- cloud. Such e- cloud may induce detrimental effects on the accelerated beam quality and stability. Those effects have been observed in most accelerators of positively charged particles. A longstanding effort has been so far devoted to understand in detail the physical origin of such e- cloud, its build-up and its interaction with the circulating beam. We will first describe the origin and the basic features causing e- cloud formation in accelerators, then we review some of the theoretical work produced to simulate and analyze such phenomenon. In selected cases, theoretical expectations and experimental observations will be compared, to address the importance of benchmarking codes versus observations to reach the required predictive capability. To this scope, codes need realistic input parameters which correctly describe material and surface properties at the basis of such e- cloud formation and build-up. The experimental efforts, performed worldwide in many surface and material science laboratories, to measure such essential parameters will then be presented and critically reviewed. Finally, we will describe some of the e- cloud mitigation strategies adopted so far and draw some conclusions.

  3. Plasma based accelerators

    SciTech Connect

    Evans, R.G.

    1987-05-05

    A plasma medium can support a variety of wave motions which may be useful for accelerating charged particles. For highly relativistic beams the longitudinal electrostatic wave is most suitable and may be driven by laser or by particle beams. The basic principles, limitations and prospects for these devices are discussed.

  4. ACCELERATED CONSTRUCTION IN IOWA

    Microsoft Academic Search

    Ahmad Abu-Hawash; Norman L. McDonald; James S. Nelson

    2007-01-01

    Recent transportation legislation has emphasized the need for increasing safety and reducing congestion in the construction zone and has provided incentive funding to help state DOTs achieve these goals. One proven strategy is to shorten the construction duration by utilizing prefabricated elements. The Innovative Bridge Research and Construction program gave Iowa the opportunity to demonstrate construction acceleration on two projects,

  5. Two-beam accelerator

    SciTech Connect

    Selph, F.B.

    1984-09-01

    In the two-beam accelerator (TBA) concept, an electron linear accelerator structure is established in which two beams propagate. One is an intense low energy beam that is made to undergo free electron lasing to produce microwaves. These microwaves are then coupled to another part of the structure where they act to produce a high longitudinal electric gradient that is used to accelerate a second relatively low intensity electron beam to very high energies. The TBA was originally suggested by Sessler as a possible means for economically achieving linear collider energies of 100 GeV and above. Although still in a conceptual stage, the TBA is an inherently plausible concept that combines the free electron laser (FEL) with several well-known technologies - high current induction linacs, microwave waveguides, and traveling-wave linac structures - in a novel and interesting way. Two characteristics of the TBA that make it a particularly suitable candidate for achieving high energies are its ability to operate at higher frequencies than typical present-day linacs (say 30 GHz as compared with 3 GHz), and to be an efficient means for delivering power to a hitherto unattainable high-gradient structure (say 250 MV/m) that the higher frequency makes possible. These high accelerating gradients will permit much shorter linac structures for a given energy.

  6. Inductive Plasma Accelerator (IPA)

    NASA Astrophysics Data System (ADS)

    Ziemba, Timothy; Slough, John

    2005-10-01

    The Inductive Plasma Accelerator (IPA) is a plasma accelerator/interaction experiment currently under constuction at MSNW. The accelerator will be capable of launching a Field Reversed Configuration (FRC) plasmoid having a mass of up to 0.2 mg with a diameter no larger than about 10 cm. In addition, the accelerator will be designed to attain plasma/plasmoid velocities up to 300 km/s while maintaining high uniformity and purity. Two IPAs will be arranged on a test bed to perform FRC merging experiments. In addition, an interaction chamber will be constucted to produce and implode a plasma liner for enhanced compression experiments on the merged FRCs thus providing the first experimental test of the plasma liner fusion concept. 2D MHD simulations show expected densities of > 10^22 m-3 with ion temperatures in excess of 800 eV for the merging FRCs. The status of design and construction of the experiment and additional simulation results will be presented

  7. Electrodynamics of accelerated systems

    NASA Astrophysics Data System (ADS)

    Hauck, John Christian

    The standard theory for accelerated observers relies on the premise that measurements can be made instantaneously or, equivalently, over a time interval where the change in the observer's velocity is negligible i.e. the hypothesis of locality. This theory provides good agreement with experiment for most cases. However, for very large accelerations this local theory should diverge from experimental results. This work considers measurements of frequency where the velocity of the observer appreciably changes during the time of the measurement. This is done through a numerical Fourier analysis of a pulse of electromagnetic radiation. When this is done, the frequency spectra seen by these accelerated observers have a much more complex structure than under the standard theory. Also, in this work, the phenomenon of helicity-rotation coupling is considered and some of the observation consequences of the coupling of the spin of the particle with the rotation of a gravitational source will be examined. Although at present most experiments can not produce accelerations large enough to diverge from the standard theory, recent advances in laser technology, such as Chirped Pulse Amplification, may soon allow the non-standard theory to be tested. It is in expectation of this that this work has been done.

  8. [Accelerated titration design].

    PubMed

    Minami, H

    2000-09-01

    To reduce the number of patients treated at low and biologically inactive doses in phase I trials of anticancer agents, attempts to decrease the number of patients per dose level and to conduct a larger dose escalation have been made. Among them, accelerated titration designs were proposed and evaluated by simulation; designs 2 and 4 were reported to be acceptable (J Natl Cancer Inst 89: 1138-1147, 1997). Both designs 2 and 4 included only one patient per cohort during the initial accelerated phase. Dosage steps for the accelerated phase were defined using the modified Fibonacci method for design 2 and 100% escalation for design 4, respectively. The accelerated phase continued until one patient experienced dose-limiting toxicity or two patients experienced grade 2 toxicities. Dose escalation was conducted based on the information from the first course in design 2 and from the first three courses in design 4. In the simulation, both designs successfully reduced the total number of patients and the number of undertreated patients without increasing the number of overtreated patients. However, the safety of design 4 was assured as long as all patients received three courses of chemotherapy, which is unusual in phase I studies in Japan. Decision-making on dose escalation based on the information on toxicity in three courses might be cumbersome. Therefore, in Japan, design 2 would be recommended among the proposed accelerated designs. The performance of the design should be investigated by applying it to actual phase I studies and by evaluating the number of undertreated and overtreated patients. PMID:11016010

  9. Cyclic AMP-dependent protein kinase and Epac mediate cyclic AMP responses in pancreatic acini

    PubMed Central

    Chaudhuri, Anamika; Husain, Sohail Z.; Kolodecik, Thomas R.; Grant, Wayne M.; Gorelick, Fred S.

    2010-01-01

    The pancreatic acinar cell has several phenotypic responses to cAMP agonists. At physiological concentrations of the muscarinic agonist carbachol (1 ?M) or the CCK analog caerulein (100 pM), ligands that increase cytosolic Ca2+, cAMP acts synergistically to enhance secretion. Supraphysiological concentrations of carbachol (1 mM) or caerulein (100 nM) suppress secretion and cause intracellular zymogen activation; cAMP enhances both zymogen activation and reverses the suppression of secretion. In addition to stimulating cAMP-dependent protein kinase (PKA), recent studies using cAMP analogs that lack a PKA response have shown that cAMP can also act through the cAMP-binding protein, Epac (exchange protein directly activated by cyclic AMP). The roles of PKA and Epac in cAMP responses were examined in isolated pancreatic acini. The activation of both cAMP-dependent pathways or the selective activation of Epac was found to enhance amylase secretion induced by physiological and supraphysiological concentrations of the muscarinic agonist carbachol. Similarly, activation of both PKA or the specific activation of Epac enhanced carbachol-induced activation of trypsinogen and chymotrypsinogen. Disorganization of the apical actin cytoskeleton has been linked to the decreased secretion observed with supraphysiological concentrations of carbachol and caerulein. Although stimulation of PKA and Epac or Epac alone could largely overcome the decreased secretion observed with either supraphysiological carbachol or caerulein, stimulation of cAMP pathways did not reduce the disorganization of the apical cytoskeleton. These studies demonstrate that PKA and Epac pathways are coupled to both secretion and zymogen activation in the pancreatic acinar cell. PMID:17234888

  10. Constellation Acceleration Study December 18, 2008

    E-print Network

    Christian, Eric

    Constellation Acceleration Study Report December 18, 2008 #12;Constellation Acceleration Study ........................................................................................................... 31 #12;Constellation Acceleration Study Report 12/18/08 Executive Summary In 2004, the White House

  11. Timescale Correlation between Marine Atmospheric Exposure and Accelerated Corrosion Testing - Part 2

    NASA Technical Reports Server (NTRS)

    Montgomery, Eliza L.; Calle, Luz Marina; Curran, Jerome C.; Kolody, Mark R.

    2012-01-01

    Evaluation of metals to predict service life of metal-based structures in corrosive environments has long relied on atmospheric exposure test sites. Traditional accelerated corrosion testing relies on mimicking the exposure conditions, often incorporating salt spray and ultraviolet (UV) radiation, and exposing the metal to continuous or cyclic conditions similar to those of the corrosive environment. Their reliability to correlate to atmospheric exposure test results is often a concern when determining the timescale to which the accelerated tests can be related. Accelerated corrosion testing has yet to be universally accepted as a useful tool in predicting the long-term service life of a metal, despite its ability to rapidly induce corrosion. Although visual and mass loss methods of evaluating corrosion are the standard, and their use is crucial, a method that correlates timescales from accelerated testing to atmospheric exposure would be very valuable. This paper presents work that began with the characterization of the atmospheric environment at the Kennedy Space Center (KSC) Beachside Corrosion Test Site. The chemical changes that occur on low carbon steel, during atmospheric and accelerated corrosion conditions, were investigated using surface chemistry analytical methods. The corrosion rates and behaviors of panels subjected to long-term and accelerated corrosion conditions, involving neutral salt fog and alternating seawater spray, were compared to identify possible timescale correlations between accelerated and long-term corrosion performance. The results, as well as preliminary findings on the correlation investigation, are presented.

  12. Principles of Charged Particle Acceleration

    NSDL National Science Digital Library

    This learning resources comprise a healthy introduction to charged particle acceleration. The site, by Stanley Humphries, a professor of electrical and computer engineering at University of New Mexico, amounts to an online textbook (.pdf) introducing the theory of charged particle acceleration. The book's fifteen chapters (with bibliography) summarize "the principles underlying all particle accelerators" and provide "a reference collection of equations and material essential to accelerator development and beam applications."

  13. Particle Acceleration at Relativistic Shocks

    E-print Network

    Yves A. Gallant

    2002-01-15

    I review the current status of Fermi acceleration theory at relativistic shocks. I first discuss the relativistic shock jump conditions, then describe the non-relativistic Fermi mechanism and the differences introduced by relativistic flows. I present numerical calculations of the accelerated particle spectrum, and examine the maximum energy attainable by this process. I briefly consider the minimum energy for Fermi acceleration, and a possible electron pre-acceleration mechanism.

  14. Overview of accelerators in medicine

    SciTech Connect

    Lennox, A.J. [Fermi National Accelerator Lab., Batavia, IL (US)]|[Rush Univ., Chicago, IL (US)

    1993-06-01

    Accelerators used for medicine include synchrotrons, cyclotrons, betatrons, microtrons, and electron, proton, and light ion linacs. Some accelerators which were formerly found only at physics laboratories are now being considered for use in hospital-based treatment and diagnostic facilities. This paper presents typical operating parameters for medical accelerators and gives specific examples of clinical applications for each type of accelerator, with emphasis on recent developments in the field.

  15. A Strip-Yield Model for Predicting the Growth of Part-Through Cracks Under Cyclic Loading

    NASA Technical Reports Server (NTRS)

    Daniewicz, S. R.; Newman, J. C., Jr. (Technical Monitor)

    2000-01-01

    Flaws exist in aircraft structures due to manufacturing operations and material defects. Under variable amplitude cyclic loading, these flaws grow as part-through cracks reducing the residual strength of structural components. To meet damage tolerant design requirements, accurate flaw growth predictions are needed which account for continual changes in crack shape as well as crack growth retardation and acceleration. Predicting the growth of part-through cracks under cyclic loading using an innovative and computationally efficient model is the focus of the research summarized in this report. In this research effort, a slice synthesis methodology was developed and used to construct a modified strip-yield model for the part-through semi-elliptical surface flaw, enabling prediction of plasticity-induced closure along the crack front and subsequent fatigue crack growth under constant amplitude and variable amplitude loading. While modeling the plasticity-induced closure in a part-through flaw may be performed using three dimensional elastic-plastic finite element analysis, this type of effort is impractical from an engineering perspective. A modified strip-yield model similar to that used in FASTRAN for part-through flaws is a much needed engineering design tool, particularly when computational resources are limited.

  16. I Investigation of Pellet Acceleration

    E-print Network

    I Investigation of Pellet Acceleration by an Arc heated Gas Gun An Interim Report INVESTIGATION OP PELLET ACCELERATION BY AN ARC HEATED GAS GUN* An Interim Report on the Investigations carried above those obtained so far. An experimental setup designed for a study of acceleration of 3 mm0 pellets

  17. Evaluation of Cyclic Behavior of Aircraft Turbine Disk Alloys

    NASA Technical Reports Server (NTRS)

    Shahani, V.; Popp, H. G.

    1978-01-01

    An evaluation of the cyclic behavior of three aircraft engine turbine disk materials was conducted to compare their relative crack initiation and crack propagation resistance. The disk alloys investigated were Inconel 718, hot isostatically pressed and forged powder metallurgy Rene '95, and as-hot-isostatically pressed Rene '95. The objective was to compare the hot isostatically pressed powder metallurgy alloy forms with conventionally processed superalloys as represented by Inconel 718. Cyclic behavior was evaluated at 650 C both under continuously cycling and a fifteen minute tensile hold time cycle to simulate engine conditions. Analysis of the test data were made to evaluate the strain range partitioning and energy exhaustion concepts for predicting hold time effects on low cycle fatigue.

  18. [A case of successfully treated cyclic amegakaryocytic thrombocytopenic purpura].

    PubMed

    Telek, B; Kiss, A; Pecze, K; Ujhelyi, P; Rák, K

    1990-05-20

    The case of a patient with cyclic, acquired, periodically amegakaryocytic thrombocytopenia is described. On the base of a seemingly typical megakaryocytic thrombocytopenia ITP was diagnosed at first. He did not respond to steroid, therefore splenectomy was performed. He relapsed and thereafter severe thrombocytopenia was observed, periodically, for 8-10 days in every five-six weeks. During the cytopenic periods recognizable megakaryocytes and precursors were totally absent from the bone marrow. After the haemorrhagic periods platelet counts elevated to normal or even higher levels and the marrow was plenty of megakaryocytes. Vincristine was unsuccessful, but cyclosporine administration for a longer time was not without success. The patient has a normal platelet count since one year. No similar case of cyclic amegakaryocytic thrombocytopenia was found in the literature. PMID:2345648

  19. De novo designed cyclic-peptide heme complexes

    PubMed Central

    Rosenblatt, Michael M.; Wang, Jiangyun; Suslick, Kenneth S.

    2003-01-01

    The structural characterization of de novo designed metalloproteins together with determination of chemical reactivity can provide a detailed understanding of the relationship between protein structure and functional properties. Toward this goal, we have prepared a series of cyclic peptides that bind to water-soluble metalloporphyrins (FeIII and CoIII). Neutral and positively charged histidine-containing peptides bind with a high affinity, whereas anionic peptides bind only weakly to the negatively charged metalloporphyrin. Additionally, it was found that the peptide becomes helical only in the presence of the metalloporphyrin. CD experiments confirm that the metalloporphyrin binds specific cyclic peptides with high affinity and with isodichroic behavior. Thermal unfolding experiments show that the complex has ”native-like” properties. Finally, NMR spectroscopy produced well dispersed spectra and experimental restraints that provide a high-resolution solution structure of the complexed peptide. PMID:14595023

  20. Free products, cyclic homology, and the Gauss-Manin connection

    E-print Network

    Ginzburg, Victor

    2008-01-01

    We present a new approach to cyclic homology that does not involve the Connes differential and is based on a `noncommutative equivariant de Rham complex' of an associative algebra. The differential in that complex is a sum of the Karoubi-de Rham differential, which replaces the Connes differential, and another operation analogous to contraction with a vector field. As a byproduct, we give a simple explicit construction of the Gauss-Manin connection, introduced earlier by E. Getzler, on the relative cyclic homology of a flat family of associative algebras over a central base ring. We introduce and study `free-product deformations' of an associative algebra, a new type of deformations over a not necessarily commutative base ring. Natural examples of free-product deformations arise from preprojective algebras and group algebras for compact surface groups.

  1. Effects of cyclic stress distribution models on fatigue life predictions

    NASA Astrophysics Data System (ADS)

    Sutherland, H. J.; Veers, P. S.

    1994-10-01

    The fatigue analysis of a wind turbine component typically uses representative samples of cyclic loads to determine lifetime loads. In this paper, several techniques currently in use are compared to one another based on fatigue life analyses. The generalized Weibull fitting technique is used to remove the artificial truncation of large-amplitude cycles that is inherent in relatively short data sets. Using data from the Sandia/DOE 34-m Test Bed, the generalized Weibull file technique is shown to be excellent for matching the body of the distribution of cyclic loads and for extrapolating the tail of the distribution. However, the data also illustrate that the fitting technique is not a substitute for an adequate data base.

  2. Defensive alliances in spatial models of cyclical population interactions

    NASA Astrophysics Data System (ADS)

    Szabó, György; Czárán, Tamás

    2001-10-01

    As a generalization of the three-strategy Rock-Scissors-Paper game dynamics in space, cyclical interaction models of six mutating species are studied on a square lattice, in which each species is supposed to have two dominant, two subordinated, and a neutral interacting partner. Depending on their interaction topologies, all imaginable systems can be classified into four (isomorphic) groups exhibiting significantly different behaviors as a function of mutation rate. In three out of four cases three (or four) species form defensive alliances that maintain themselves in a self-organizing polydomain structure via cyclic invasions. Varying the mutation rate, this mechanism results in an ordering phenomenon analogous to that of magnetic Ising systems. The model explains a very basic mechanism of community organization, which might gain important applications in biology, economics, and sociology.

  3. Low severity coal liquefaction promoted by cyclic olefins

    SciTech Connect

    Curtis, C.W.

    1991-01-01

    The objective of this project is to evaluate the efficacy of low severity coal liquefaction in the presence of highly reactive hydrogen donors, cyclic olefins. The work that was performed this quarter involved performing a literature search in which different aspects of low severity coal liquefaction were examined. In addition, two new mater's graduate students learned the fundamental differences between high severity coal liquefaction and low severity coal liquefaction by examining the literature and reading texts on coal liquefaction. The literature review presented for the first quarter's work is a compilation of the material which we have found to data involving low severity coal liquefaction. Additional review of low severity liquefaction literature is being conducted this quarter and will be reported in the next quarterly report. In addition, a summary of the work involving the reactivity of cyclic olefins in the absence and presence of coal will be presented next quarter.

  4. Matrix cracking in laminated composites under monotonic and cyclic loadings

    NASA Technical Reports Server (NTRS)

    Allen, David H.; Lee, Jong-Won

    1991-01-01

    An analytical model based on the internal state variable (ISV) concept and the strain energy method is proposed for characterizing the monotonic and cyclic response of laminated composites containing matrix cracks. A modified constitution is formulated for angle-ply laminates under general in-plane mechanical loading and constant temperature change. A monotonic matrix cracking criterion is developed for predicting the crack density in cross-ply laminates as a function of the applied laminate axial stress. An initial formulation for a cyclic matrix cracking criterion for cross-ply laminates is also discussed. For the monotonic loading case, a number of experimental data and well-known models are compared with the present study for validating the practical applicability of the ISV approach.

  5. Raman spectroscopic studies of beta-turn-containing cyclic peptides

    NASA Astrophysics Data System (ADS)

    Seaton, B. A.

    Two cyclic nonapeptides, cyclo(glycine- S-benzyl- L-cysteine-glycine) 3 and cyclo(glycine- S-methoxybenzyl- L-cysteine- L-proline) 3, and a cyclic hexapeptide, cyclo( D-alanine- L-proline- D-alanine) 2, were studied by Raman spectroscopy to determine the effects of conformation on their amide frequencies. The first and third of these peptides are known to contain three repeating type-II beta turns in solution. The second is also known to contain three repeating turns, but the turn type has not been established. Depending upon solubility properties of individual peptides, amide assignments were made either through H?D exchange or by evaluating spectra of constituent amino acids. The results suggest that, at least in these systems, beta turn types may be distinguished more readily by amide III rather than amide I vibration frequencies.

  6. Cyclic stretching of soft substrates induces spreading and growth

    NASA Astrophysics Data System (ADS)

    Cui, Yidan; Hameed, Feroz M.; Yang, Bo; Lee, Kyunghee; Pan, Catherine Qiurong; Park, Sungsu; Sheetz, Michael

    2015-02-01

    In the body, soft tissues often undergo cycles of stretching and relaxation that may affect cell behaviour without changing matrix rigidity. To determine whether transient forces can substitute for a rigid matrix, we stretched soft pillar arrays. Surprisingly, 1–5% cyclic stretching over a frequency range of 0.01–10?Hz caused spreading and stress fibre formation (optimum 0.1?Hz) that persisted after 4?h of stretching. Similarly, stretching increased cell growth rates on soft pillars comparative to rigid substrates. Of possible factors linked to fibroblast growth, MRTF-A (myocardin-related transcription factor-A) moved to the nucleus in 2?h of cyclic stretching and reversed on cessation; but YAP (Yes-associated protein) moved much later. Knockdown of either MRTF-A or YAP blocked stretch-dependent growth. Thus, we suggest that the repeated pulling from a soft matrix can substitute for a stiff matrix in stimulating spreading, stress fibre formation and growth.

  7. A straightforward approach towards cyclic photoactivatable tubulysin derivatives.

    PubMed

    Hoffmann, Judith; Kazmaier, Uli

    2014-10-13

    The development of a new photolabile protecting group containing an additional allyl functionality allows the synthesis of cyclic photoactivatable natural products. Cyclization occurs between the allyl moiety in the protecting group and a second double bond in the target molecule by means of ring-closing metathesis. Cyclization should increase the metabolic stability towards proteases. On the other hand, the conformational change should cause diminished biological activity. As illustrated for tubulysin derivatives, cyclic and photoactivatable drug candidates can easily be obtained in only two steps from simple building blocks through Ugi reaction and ring-closing metathesis. The photolabile protecting group is introduced by means of the isocyanide component during the Ugi reaction. PMID:25196233

  8. Strain rate change transients during cyclic deformation of copper

    SciTech Connect

    Kaschner, G.C.; Gibeling, J.C. [Univ. of California, Davis, CA (United States). Div. of Materials Science and Engineering] [Univ. of California, Davis, CA (United States). Div. of Materials Science and Engineering

    1996-12-15

    In the present study, the authors have undertaken to apply the strain rate change method to mechanically probe the mechanisms of cyclic deformation in copper. The goals of this work were twofold: to carefully explore differences in results obtained under conventional displacement control with those recorded under plastic strain control and to apply the formalism for monotonic deformation described above to cyclic deformation. To achieve these goals, it has been necessary to utilize computed-variable servo-hydraulic control to develop a new test technique incorporating strain rate change tests performed during low cycle fatigue. Plastic strain is used as the control variable to ensure a constant plastic strain rate between pre-determined plastic strain limits.

  9. Synthesis and properties of some cyclic AMP alkyl phosphotriesters

    PubMed Central

    Gohil, R.N.; Gillen, R.G.; Nagyvary, J.

    1974-01-01

    Cyclic AMP was converted to its phosphotriesters according to the classical approach of phosphate activation with a sulfonyl chloride, followed by esterification with an alcohol. The methyl, ethyl, propyl, butyl and cetyl triesters were prepared, and some of their physical-chemical properties determined. Alkaline hydrolysis of these alkyl phosphotriesters resulted predominantly in ring opening. On the other hand, nucleophilic attack by thiourea led to the formation of cAMP as the main product. The conclusion can be drawn from these results that cAMP phosphotriesters could serve as suitable storage forms of cAMP, and cyclic triesters may be the best vehicle of transporting nucleotides through biological membranes. PMID:4375277

  10. Synthesis and properties of some cyclic AMP alkyl phosphotriesters.

    PubMed

    Gohil, R N; Gillen, R G; Nagyvary, J

    1974-12-01

    Cyclic AMP was converted to its phosphotriesters according to the classical approach of phosphate activation with a sulfonyl chloride, followed by esterification with an alcohol. The methyl, ethyl, propyl, butyl and cetyl triesters were prepared, and some of their physical-chemical properties determined. Alkaline hydrolysis of these alkyl phosphotriesters resulted predominantly in ring opening. On the other hand, nucleophilic attack by thiourea led to the formation of cAMP as the main product. The conclusion can be drawn from these results that cAMP phosphotriesters could serve as suitable storage forms of cAMP, and cyclic triesters may be the best vehicle of transporting nucleotides through biological membranes. PMID:4375277

  11. Pulsed electromagnetic gas acceleration

    NASA Technical Reports Server (NTRS)

    Jahn, R. G.; Vonjaskowsky, W. F.; Clark, K. E.

    1971-01-01

    Experimental data were combined with one-dimensional conservation relations to yield information on the energy deposition ratio in a parallel-plate accelerator, where the downstream flow was confined to a constant area channel. Approximately 70% of the total input power was detected in the exhaust flow, of which only about 20% appeared as directed kinetic energy, thus implying that a downstream expansion to convert chamber enthalpy into kinetic energy must be an important aspect of conventional high power MPD arcs. Spectroscopic experiments on a quasi-steady MPD argon accelerator verified the presence of A(III) and the absence of A(I), and indicated an azimuthal structure in the jet related to the mass injection locations. Measurements of pressure in the arc chamber and impact pressure in the exhaust jet using a piezocrystal backed by a Plexiglas rod were in good agreement with the electromagnetic thrust model.

  12. Accelerator research studies

    SciTech Connect

    Not Available

    1993-01-01

    The Accelerator Research Studies program at the University of Maryland, sponsored by the Department of Energy under grant number DE-FG05-91ER40642, is currently in the second year of a three-year funding cycle. The program consists of the following three tasks: TASK A, Study of Transport and Longitudinal Compression of Intense, High-Brightness Beams,'' (P.I., M. Reiser); TASK B, Study of Collective Ion Acceleration by Intense Electron Beams and Pseudospark Produced High Brightness Electron Beams,'' (Co-P.I.'s, W.W. Destler, M. Reiser, M.J. Rhee, and C.D. Striffler); TASK C, Study of a Gyroklystron High-Power Microwave Source for Linear Colliders,'' (Co-P.I.'s, V.L. Granatstein, W. Lawson, M. Reiser, and C.D. Striffler). In this report we document the progress that has been made during the past year for each of the three tasks.

  13. Adaptive control for accelerators

    DOEpatents

    Eaton, Lawrie E. (Los Alamos, NM); Jachim, Stephen P. (Los Alamos, NM); Natter, Eckard F. (Santa Fe, NM)

    1991-01-01

    An adaptive feedforward control loop is provided to stabilize accelerator beam loading of the radio frequency field in an accelerator cavity during successive pulses of the beam into the cavity. A digital signal processor enables an adaptive algorithm to generate a feedforward error correcting signal functionally determined by the feedback error obtained by a beam pulse loading the cavity after the previous correcting signal was applied to the cavity. Each cavity feedforward correcting signal is successively stored in the digital processor and modified by the feedback error resulting from its application to generate the next feedforward error correcting signal. A feedforward error correcting signal is generated by the digital processor in advance of the beam pulse to enable a composite correcting signal and the beam pulse to arrive concurrently at the cavity.

  14. Review of ion accelerators

    SciTech Connect

    Alonso, J.

    1990-06-01

    The field of ion acceleration to higher energies has grown rapidly in the last years. Many new facilities as well as substantial upgrades of existing facilities have extended the mass and energy range of available beams. Perhaps more significant for the long-term development of the field has been the expansion in the applications of these beams, and the building of facilities dedicated to areas outside of nuclear physics. This review will cover many of these new developments. Emphasis will be placed on accelerators with final energies above 50 MeV/amu. Facilities such as superconducting cyclotrons and storage rings are adequately covered in other review papers, and so will not be covered here.

  15. Pulsed Drift Tube Accelerator

    SciTech Connect

    Faltens, A.

    2004-10-25

    The pulsed drift-tube accelerator (DTA) concept was revived by Joe Kwan and John Staples and is being considered for the HEDP/WDM application. It could be used to reach the full energy or as an intermediate accelerator between the diode and a high gradient accelerator such as multi-beam r.f. In the earliest LBNL HIF proposals and conceptual drivers it was used as an extended injector to reach energies where an induction linac with magnetic quadrupoles is the best choice. For HEDP, because of the very short pulse duration, the DTA could provide an acceleration rate of about 1MV/m. This note is divided into two parts: the first, a design based on existing experience; the second, an optimistic extrapolation. The first accelerates 16 parallel K{sup +} beams at a constant line charge density of 0.25{micro} C/m per beam to 10 MeV; the second uses a stripper and charge selector at around 4MeV followed by further acceleration to reach 40 MeV. Both benefit from more compact sources than the present 2MV injector source, although that beam is the basis of the first design and is a viable option. A pulsed drift-tube accelerator was the first major HIF experiment at LBNL. It was designed to produce a 2{micro}s rectangular 1 Ampere C{sub s}{sup +} beam at 2MeV. It ran comfortably at 1.6MeV for several years, then at lower voltages and currents for other experiments, and remnants of that experiment are in use in present experiments, still running 25 years later. The 1A current, completely equivalent to 1.8A K{sup +}, was chosen to be intermediate between the beamlets appropriate for a multi-beam accelerator, and a single beam of, say, 10A, at injection energies. The original driver scenarios using one large beam on each side of the reactor rapidly fell out of favor because of the very high transverse and longitudinal fields from the beam space charge, circa 1MV/cm and 250 kV/cm respectively, near the chamber and because of aberrations in focusing a large diameter beam down to a 1mm radius spot at a distance of 10m. Almost all subsequent work and the present concept have invoked multiple beams. For HEDP the major differences are that the focal distance can be centimeters instead of meters, provided strong-enough lenses exist and they do, thereby allowing much higher transverse and longitudinal emittances than driver concepts, and focusing parallel small beams is easier than one big beam.

  16. D-2 acceleration characterization

    NASA Astrophysics Data System (ADS)

    Hamacher, Hans; Bluemel, U.

    1994-07-01

    During the second German Spacelab Mission D-2, extensive onboard measurements of the residual acceleration were performed. The payload was equipped with accelerometer packages distributed over the entire Spacelab module. The microgravity measurement assembly (MMA) was the core system comprising fixed mounted as well as mobile sensor packages. Additional autonomous accelerometer systems were mounted within the payload elements MEDEA and Werkstofflabor. On-board video recording has been performed to correlate the measured accelerations to mission events. The D-2 microgravity characterization program also included numerical calculations to predict low frequency effects due to atmospheric drag, tidal force, and spacecraft rotation. Results of characteristic quiet mission phases show that the microgravity level is essentially below the requirements defined for the space station. Other results of some other mission phases revealed that a wealth can be done by improving payload design and operation to improve the microgravity quality of Spacelab missions.

  17. NEW ACCELERATION METHODS

    SciTech Connect

    Sessler, A.M.

    1984-07-01

    But a glance at the Livingston chart, Fig. 1, of accelerator particle energy as a function of time shows that the energy has steadily, exponentially, increased. Equally significant is the fact that this increase is the envelope of diverse technologies. If one is to stay on, or even near, the Livingston curve in future years then new acceleration techniques need to be developed. What are the new acceleration methods? In these two lectures I would like to sketch some of these new ideas. I am well aware that they will probably not result in high energy accelerators within this or the next decade, but conversely, it is likely that these ideas will form the basis for the accelerators of the next century. Anyway, the ideas are stimulating and suffice to show that accelerator physicists are not just 'engineers', but genuine scientists deserving to be welcomed into the company of high energy physicists. I believe that outsiders will find this field surprisingly fertile and, certainly fun. To put it more personally, I very much enjoy working in this field and lecturing on it. There are a number of review articles which should be consulted for references to the original literature. In addition there are three books on the subject. Given this material, I feel free to not completely reference the material in the remainder of this article; consultation of the review articles and books will be adequate as an introduction to the literature for references abound (hundreds are given). At last, by way of introduction, I should like to quote from the end of Ref. 2 for I think the remarks made there are most germane. Remember that the talk was addressed to accelerator physicists: 'Finally, it is often said, I think by physicists who are not well-informed, that accelerator builders have used up their capital and now are bereft of ideas, and as a result, high energy physics will eventually--rather soon, in fact--come to a halt. After all, one can't build too many machines greater than 27 km, and soon one will run out of space or money (almost surely money before space). This argument seems terribly wrong to me, and worse than that possibly destructive, for it will have a serious effect if it causes, as it well might, young people to elect to go into fields other than high energy physics. The proper response, I believe, is to point--in considerable detail--to some of the new concepts which show by example that we are far from being out of new ideas. Some of these concepts shall, in my view, be, or lead to, the 'stocks in trade' of the next century, and thus they will allow high energy physics to be as exciting then as it is now. It is our job to make it all happen.

  18. Plasma wave accelerator. II

    SciTech Connect

    Mori, W.; Joshi, C.; Dawson, J.M.

    1982-01-01

    It was shown that the insertion of a cross magnetic field prevents the particles from getting out of phase with the electric field of the plasma wave in the beat wave accelerator scheme. Thus, using a CO/sub 2/ laser, n/sub c//n/sub e/ = (..omega../sub 0//..omega../sub p/)/sup 2/ approx. 35, and a 300 kG magnetic field, electrons can be (in principle) accelerated to 100 GeV in 2 meters. For comparison without the magnetic field, the same energies may be obtained in a n/sub c//n/sub e/ approx. 10/sup 5/ plasma over a distance of 100 meters.

  19. Hypervelocity plate acceleration

    SciTech Connect

    Marsh, S.P.; Tan, T.H.

    1991-01-01

    Shock tubes have been used to accelerate 1.5-mm-thick stainless steel plates to high velocity while retaining their integrity. The fast shock tubes are 5.1-cm-diameter, 15.2-cm-long cylinders of PBX-9501 explosive containing a 1.1-cm-diameter cylindrical core of low-density polystyrene foam. The plates have been placed directly in contact with one face of the explosive system. Plane-wave detonation was initiated on the opposite face. A Mach disk was formed in the imploding styrofoam core, which provided the impulse required to accelerate the metal plate to high velocity. Parametric studies were made on this system to find the effect of varying plate metal, plate thickness, foam properties, and addition of a barrel. A maximum plate velocity of 9.0 km/s has been observed. 6 refs., 17 figs.

  20. On the densest MIMO lattices from cyclic division algebras

    Microsoft Academic Search

    Camilla Hollanti; Jyrki T. Lahtonen; Kalle Ranto; Roope Vehkalahti

    2007-01-01

    It is shown why the discriminant of a maximal order within a cyclic division\\u000aalgebra must be minimized in order to get the densest possible matrix lattices\\u000awith a prescribed nonvanishing minimum determinant. Using results from class\\u000afield theory a lower bound to the minimum discriminant of a maximal order with\\u000aa given center and index (= the number of